Variability of stratification according to operation of the tidal power plant in Lake Sihwa, South Korea.

NASA Astrophysics Data System (ADS)

Woo, S. B.; Song, J. I.; Jang, T. H.; Park, C. J.; Kwon, H. K.

2017-12-01

Artificial forcing according to operation of the tidal power plant (TPP) affects the physical environmental changes near the power plant. Strong turbulence by generation is expected to change the stratification structure of the Lake Sihwa inside. In order to examine the stratification changes by the power plant operation, ship bottom mounted observation were performed for 13 hours using an acoustic Doppler current profiler (ADCP) and Conductivity-Temperature-Depth (CTD) in Lake Sihwa at near TPP. The strong stratification in Sihwa Lake is maintained before TPP operation. The absence of external forces and freshwater inflow from the land forms the stratification in the Lake. Strong winds in a stratification statement lead to two-layer circulation. After wind event, multi-layer velocity structure is formed which lasted for approximately 4 h. After TPP operation, the jet flow was observed in entire water column at the beginning of the power generation. Vortex is formed by strong jet flow and maintained throughout during power generation period. Strong turbulence flow is generated by the turbine blades, enhancing vertical mixing. External forces, which dominantly affect Lake Sihwa, have changed from the wind to the turbulent flow. The stratification was extinguished by strong turbulent flow and becomes fully-mixed state. Changes in stratification structure are expected to affect material transport and ecological environment change continuously.

An optimal tuning strategy for tidal turbines

PubMed Central

2016-01-01

Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This ‘impatient-tuning strategy’ results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing ‘patient-tuning strategy’ which maximizes the power output averaged over the tidal cycle. This paper presents a ‘smart patient tuning strategy’, which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine’s average power output. PMID:27956870

An optimal tuning strategy for tidal turbines

NASA Astrophysics Data System (ADS)

Vennell, Ross

2016-11-01

Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This `impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing `patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a `smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

An optimal tuning strategy for tidal turbines.

PubMed

Vennell, Ross

2016-11-01

Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This 'impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing 'patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a 'smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

Mobility power flow analysis of an L-shaped plate structure subjected to distributed loading

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.; Cimmerman, B.

1990-01-01

An analytical investigation based in the Mobility Power Flow (MPF) method is presented for the determination of the vibrational response and power flow for two coupled flat plate structures in an L-shaped configuration, subjected to distributed excitation. The principle of the MPF method consists of dividing the global structure into a series of subsystems coupled together using mobility functions. Each separate subsystem is analyzed independently to determine the structural mobility functions for the junction and excitation locations. The mobility functions, together with the characteristics of the junction between the subsystems, are then used to determine the response of the global structure and the MPF. In the considered coupled plate structure, MPF expressions are derived for distributed mechanical excitation which is independent of the structure response. However using a similar approach with some modifications excitation by an acoustic plane wave can be considered. Some modifications are required to deal with the latter case are necessary because the forces (acoustic pressure) acting on the structure are dependent on the response of the structure due to the presence of the scattered pressure.

Nano-composite insert in 1D waveguides for control of elastic power flow

NASA Astrophysics Data System (ADS)

Vignesh, P. S.; Mitra, Mira; Gopalakrishnan, S.

2007-01-01

In this paper, carbon nanotube embedded polymer composite/nano-composites are used to regulate power flow from its source to other parts of the structure. This is done by inserting nano-composite strips in the waveguides which are modelled here as isotropic Euler-Bernoulli beams with axial, transverse and rotational degrees of freedom. The power flow is due to wave propagation resulting from a high frequency broadband impulse load. The underlying concept is that the high stiffness of the insert reduces the wave transmission between different parts of the structures. The simulations are done using a wavelet based spectral finite element (WSFE) technique which is specially tailored for such high frequency wave propagation analysis. Numerical experiments are performed to illustrate the use of inserts in maintaining the power flow in a certain region of the structure below a given threshold value which may be specified depending on various applications. The effects of parameters such as the volume fraction of carbon nanotube (CNT) in the polymer, and the length and position of the inserts are also studied. These studies help in defining the optimal volume fraction of CNT and length of the insert for a specified structural configuration.

Effects of energetic coherent motions on the power and wake of an axial-flow turbine

NASA Astrophysics Data System (ADS)

Chamorro, L. P.; Hill, C.; Neary, V. S.; Gunawan, B.; Arndt, R. E. A.; Sotiropoulos, F.

2015-05-01

A laboratory experiment examined the effects of energetic coherent motions on the structure of the wake and power fluctuations generated by a model axial-flow hydrokinetic turbine. The model turbine was placed in an open-channel flow and operated under subcritical conditions. The incoming flow was locally perturbed with vertically oriented cylinders of various diameters. An array of three acoustic Doppler velocimeters aligned in the cross-stream direction and a torque transducer were used to collect high-resolution and synchronous measurements of the three-velocity components of the incoming and wake flow as well as the turbine power. A strong scale-to-scale interaction between the large-scale and broadband turbulence shed by the cylinders and the turbine power revealed how the turbulence structure modulates the turbine behavior. In particular, the response of the turbine to the distinctive von Kármán-type vortices shed from the cylinders highlighted this phenomenon. The mean and fluctuating characteristics of the turbine wake are shown to be very sensitive to the energetic motions present in the flow. Tip vortices were substantially dampened and the near-field mean wake recovery accelerated in the presence of energetic motions in the flow. Strong coherent motions are shown to be more effective than turbulence levels for triggering the break-up of the spiral structure of the tip-vortices.

Deformation of a Capsule in a Power-Law Shear Flow

PubMed Central

2016-01-01

An immersed boundary-lattice Boltzmann method is developed for fluid-structure interactions involving non-Newtonian fluids (e.g., power-law fluid). In this method, the flexible structure (e.g., capsule) dynamics and the fluid dynamics are coupled by using the immersed boundary method. The incompressible viscous power-law fluid motion is obtained by solving the lattice Boltzmann equation. The non-Newtonian rheology is achieved by using a shear rate-dependant relaxation time in the lattice Boltzmann method. The non-Newtonian flow solver is then validated by considering a power-law flow in a straight channel which is one of the benchmark problems to validate an in-house solver. The numerical results present a good agreement with the analytical solutions for various values of power-law index. Finally, we apply this method to study the deformation of a capsule in a power-law shear flow by varying the Reynolds number from 0.025 to 0.1, dimensionless shear rate from 0.004 to 0.1, and power-law index from 0.2 to 1.8. It is found that the deformation of the capsule increases with the power-law index for different Reynolds numbers and nondimensional shear rates. In addition, the Reynolds number does not have significant effect on the capsule deformation in the flow regime considered. Moreover, the power-law index effect is stronger for larger dimensionless shear rate compared to smaller values. PMID:27840656

Power flow as a complement to statistical energy analysis and finite element analysis

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.

1987-01-01

Present methods of analysis of the structural response and the structure-borne transmission of vibrational energy use either finite element (FE) techniques or statistical energy analysis (SEA) methods. The FE methods are a very useful tool at low frequencies where the number of resonances involved in the analysis is rather small. On the other hand SEA methods can predict with acceptable accuracy the response and energy transmission between coupled structures at relatively high frequencies where the structural modal density is high and a statistical approach is the appropriate solution. In the mid-frequency range, a relatively large number of resonances exist which make finite element method too costly. On the other hand SEA methods can only predict an average level form. In this mid-frequency range a possible alternative is to use power flow techniques, where the input and flow of vibrational energy to excited and coupled structural components can be expressed in terms of input and transfer mobilities. This power flow technique can be extended from low to high frequencies and this can be integrated with established FE models at low frequencies and SEA models at high frequencies to form a verification of the method. This method of structural analysis using power flo and mobility methods, and its integration with SEA and FE analysis is applied to the case of two thin beams joined together at right angles.

Simulation of cooling efficiency via miniaturised channels in multilayer LTCC for power electronics

NASA Astrophysics Data System (ADS)

Pietrikova, Alena; Girasek, Tomas; Lukacs, Peter; Welker, Tilo; Müller, Jens

2017-03-01

The aim of this paper is detailed investigation of thermal resistance, flow analysis and distribution of coolant as well as thermal distribution inside multilayer LTCC substrates with embedded channels for power electronic devices by simulation software. For this reason four various structures of internal channels in the multilayer LTCC substrates were designed and simulated. The impact of the volume flow, structures of channels, and power loss of chip was simulated, calculated and analyzed by using the simulation software Mentor Graphics FloEFDTM. The structure, size and location of channels have the significant impact on thermal resistance, pressure of coolant as well as the effectivity of cooling power components (chips) that can be placed on the top of LTCC substrate. The main contribution of this paper is thermal analyze, optimization and impact of 4 various cooling channels embedded in LTCC multilayer structure. Paper investigate, the effect of volume flow in cooling channels for achieving the least thermal resistance of LTCC substrate that is loaded by power thermal chips. Paper shows on the impact of the first chips thermal load on the second chip as well as. This possible new technology could ensure in the case of practical realization effective cooling and increasing reliability of high power modules.

Voltage collapse in complex power grids

PubMed Central

Simpson-Porco, John W.; Dörfler, Florian; Bullo, Francesco

2016-01-01

A large-scale power grid's ability to transfer energy from producers to consumers is constrained by both the network structure and the nonlinear physics of power flow. Violations of these constraints have been observed to result in voltage collapse blackouts, where nodal voltages slowly decline before precipitously falling. However, methods to test for voltage collapse are dominantly simulation-based, offering little theoretical insight into how grid structure influences stability margins. For a simplified power flow model, here we derive a closed-form condition under which a power network is safe from voltage collapse. The condition combines the complex structure of the network with the reactive power demands of loads to produce a node-by-node measure of grid stress, a prediction of the largest nodal voltage deviation, and an estimate of the distance to collapse. We extensively test our predictions on large-scale systems, highlighting how our condition can be leveraged to increase grid stability margins. PMID:26887284

Flow Energy Piezoelectric Bimorph Nozzle Harvester

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Lee, Hyeong Jae; Kim, Namhyo; Sun, Kai; Corbett, Gary; Walkemeyer, Phillip; Hasenoehrl, Jennifer; Hall, Jeffery L.; Colonius, Tim; Tosi, Luis Phillipe;

Flow energy piezoelectric bimorph nozzle harvester

NASA Astrophysics Data System (ADS)

Sherrit, Stewart; Lee, Hyeong Jae; Walkemeyer, Phillip; Hasenoehrl, Jennifer; Hall, Jeffrey L.; Colonius, Tim; Tosi, Luis Phillipe; Arrazola, Alvaro; Kim, Namhyo; Sun, Kai; Corbett, Gary

2014-04-01

There is a need for a long-life power generation scheme that could be used downhole in an oil well to produce 1 Watt average power. There are a variety of existing or proposed energy harvesting schemes that could be used in this environment but each of these has its own limitations. The vibrating piezoelectric structure is in principle capable of operating for very long lifetimes (decades) thereby possibly overcoming a principle limitation of existing technology based on rotating turbo-machinery. In order to determine the feasibility of using piezoelectrics to produce suitable flow energy harvesting, we surveyed experimentally a variety of nozzle configurations that could be used to excite a vibrating piezoelectric structure in such a way as to enable conversion of flow energy into useful amounts of electrical power. These included reed structures, spring mass-structures, drag and lift bluff bodies and a variety of nozzles with varying flow profiles. Although not an exhaustive survey we identified a spline nozzle/piezoelectric bimorph system that experimentally produced up to 3.4 mW per bimorph. This paper will discuss these results and present our initial analyses of the device using dimensional analysis and constitutive electromechanical modeling. The analysis suggests that an order-of-magnitude improvement in power generation from the current design is possible.

Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

NASA Astrophysics Data System (ADS)

Pan, Minqiang; Zhong, Yujian

2018-01-01

Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

Integrative energy-systems design: System structure from thermodynamic optimization

NASA Astrophysics Data System (ADS)

Ordonez, Juan Carlos

This thesis deals with the application of thermodynamic optimization to find optimal structure and operation conditions of energy systems. Chapter 1 outlines the thermodynamic optimization of a combined power and refrigeration system subject to constraints. It is shown that the thermodynamic optimum is reached by distributing optimally the heat exchanger inventory. Chapter 2 considers the maximization of power extraction from a hot stream in the presence of phase change. It shows that when the receiving (cold) stream boils in a counterflow heat exchanger, the thermodynamic optimization consists of locating the optimal capacity rate of the cold stream. Chapter 3 shows that the main architectural features of a counterflow heat exchanger can be determined based on thermodynamic optimization subject to volume constraint. Chapter 4 addresses two basic issues in the thermodynamic optimization of environmental control systems (ECS) for aircraft: realistic limits for the minimal power requirement, and design features that facilitate operation at minimal power consumption. Several models of the ECS-Cabin interaction are considered and it is shown that in all the models the temperature of the air stream that the ECS delivers to the cabin can be optimized for operation at minimal power. In chapter 5 it is shown that the sizes (weights) of heat and fluid flow systems that function on board vehicles such as aircraft can be derived from the maximization of overall (system level) performance. Chapter 6 develops analytically the optimal sizes (hydraulic diameters) of parallel channels that penetrate and cool a volume with uniformly distributed internal heat generation and Chapter 7 shows analytically and numerically how an originally uniform flow structure transforms itself into a nonuniform one when the objective is to minimize global flow losses. It is shown that flow maldistribution and the abandonment of symmetry are necessary for the development of flow structures with minimal resistance. In the second part of the chapter, the flow medium is continuous and permeated by Darcy flow. As flow systems become smaller and more compact, the flow systems themselves become "designed porous media".

Power laws and fragility in flow networks.

PubMed

Shore, Jesse; Chu, Catherine J; Bianchi, Matt T

2013-01-01

What makes economic and ecological networks so unlike other highly skewed networks in their tendency toward turbulence and collapse? Here, we explore the consequences of a defining feature of these networks: their nodes are tied together by flow. We show that flow networks tend to the power law degree distribution (PLDD) due to a self-reinforcing process involving position within the global network structure, and thus present the first random graph model for PLDDs that does not depend on a rich-get-richer function of nodal degree. We also show that in contrast to non-flow networks, PLDD flow networks are dramatically more vulnerable to catastrophic failure than non-PLDD flow networks, a finding with potential explanatory power in our age of resource- and financial-interdependence and turbulence.

Application of the mobility power flow approach to structural response from distributed loading

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.

1988-01-01

The problem of the vibration power flow through coupled substructures when one of the substructures is subjected to a distributed load is addressed. In all the work performed thus far, point force excitation was considered. However, in the case of the excitation of an aircraft fuselage, distributed loading on the whole surface of a panel can be as important as the excitation from directly applied forces at defined locations on the structures. Thus using a mobility power flow approach, expressions are developed for the transmission of vibrational power between two coupled plate substructures in an L configuration, with one of the surfaces of one of the plate substructures being subjected to a distributed load. The types of distributed loads that are considered are a force load with an arbitrary function in space and a distributed load similar to that from acoustic excitation.

Comparison of Comet Enflow and VA One Acoustic-to-Structure Power Flow Predictions

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Schiller, Noah H.; Cabell, Randolph H.

2010-01-01

Comet Enflow is a commercially available, high frequency vibroacoustic analysis software based on the Energy Finite Element Analysis (EFEA). In this method the same finite element mesh used for structural and acoustic analysis can be employed for the high frequency solutions. Comet Enflow is being validated for a floor-equipped composite cylinder by comparing the EFEA vibroacoustic response predictions with Statistical Energy Analysis (SEA) results from the commercial software program VA One from ESI Group. Early in this program a number of discrepancies became apparent in the Enflow predicted response for the power flow from an acoustic space to a structural subsystem. The power flow anomalies were studied for a simple cubic, a rectangular and a cylindrical structural model connected to an acoustic cavity. The current investigation focuses on three specific discrepancies between the Comet Enflow and the VA One predictions: the Enflow power transmission coefficient relative to the VA One coupling loss factor; the importance of the accuracy of the acoustic modal density formulation used within Enflow; and the recommended use of fast solvers in Comet Enflow. The frequency region of interest for this study covers the one-third octave bands with center frequencies from 16 Hz to 4000 Hz.

Comparison of control structures for a bidirectional high-frequency dc-dc converter

NASA Astrophysics Data System (ADS)

Himmelstoss, Felix A.; Kolar, Johann W.; Zach, Franz C.

1989-08-01

A system for dc-dc power conversion based on a buck-boost converter topology is presented. It makes power flow in both directions possible. The possibility of bidirectional power flow is useful for certain applications, such as uninterruptable power supplies. Starting from a structural diagram the transfer function of the system is derived. The controller for the converter is then designed. It is made up of a simple voltage controller, a voltage controller with an inner loop current controller (cascade control) and with two kinds of state space control. The transfer functions of the different system parts are derived and dimensioning guidelines for the controller sections are presented. The closed loop behavior of the bidirectional converter for the different control structures is analyzed based on simulation using duty cycle averaging. Bodediagrams and step responses are shown.

Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

NASA Astrophysics Data System (ADS)

Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

2016-09-01

An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

Intracycle angular velocity control of cross-flow turbines

NASA Astrophysics Data System (ADS)

Strom, Benjamin; Brunton, Steven L.; Polagye, Brian

2017-08-01

Cross-flow turbines, also known as vertical-axis turbines, are attractive for power generation from wind and water currents. Some cross-flow turbine designs optimize unsteady fluid forces and maximize power output by controlling blade kinematics within one rotation. One established method is to dynamically pitch the blades. Here we introduce a mechanically simpler alternative: optimize the turbine rotation rate as a function of angular blade position. We demonstrate experimentally that this approach results in a 59% increase in power output over standard control methods. Analysis of fluid forcing and blade kinematics suggest that power increase is achieved through modification of the local flow conditions and alignment of fluid force and rotation rate extrema. The result is a low-speed, structurally robust turbine that achieves high efficiency and could enable a new generation of environmentally benign turbines for renewable power generation.

Investigation of Blade Angle of an Open Cross-Flow Runner

NASA Astrophysics Data System (ADS)

Katayama, Yusuke; Iio, Shouichiro; Veerapun, Salisa; Uchiyama, Tomomi

2015-04-01

The aim of this study was to develop a nano-hydraulic turbine utilizing drop structure in irrigation channels or industrial waterways. This study was focused on an open-type cross-flow turbine without any attached equipment for cost reduction and easy maintenance. In this study, the authors used an artificial indoor waterfall as lab model. Test runner which is a simple structure of 20 circular arc-shaped blades sandwiched by two circular plates was used The optimum inlet blade angle and the relationship between the power performance and the flow rate approaching theoretically and experimentally were investigated. As a result, the optimum inlet blade angle due to the flow rate was changed. Additionally, allocation rate of power output in 1st stage and 2nd stage is changed by the blade inlet angle.

A Comparison of Hybrid Reynolds Averaged Navier Stokes/Large Eddy Simulation (RANS/LES) and Unsteady RANS Predictions of Separated Flow for a Variable Speed Power Turbine Blade Operating with Low Inlet Turbulence Levels

DTIC Science & Technology

2017-10-01

Facility is a large-scale cascade that allows detailed flow field surveys and blade surface measurements.10–12 The facility has a continuous run ...structured grids at 2 flow conditions, cruise and takeoff, of the VSPT blade . Computations were run in parallel on a Department of Defense...RANS/LES) and Unsteady RANS Predictions of Separated Flow for a Variable-Speed Power- Turbine Blade Operating with Low Inlet Turbulence Levels

Graphical models for optimal power flow

DOE PAGES

Dvijotham, Krishnamurthy; Chertkov, Michael; Van Hentenryck, Pascal; ...

2016-09-13

Optimal power flow (OPF) is the central optimization problem in electric power grids. Although solved routinely in the course of power grid operations, it is known to be strongly NP-hard in general, and weakly NP-hard over tree networks. In this paper, we formulate the optimal power flow problem over tree networks as an inference problem over a tree-structured graphical model where the nodal variables are low-dimensional vectors. We adapt the standard dynamic programming algorithm for inference over a tree-structured graphical model to the OPF problem. Combining this with an interval discretization of the nodal variables, we develop an approximation algorithmmore » for the OPF problem. Further, we use techniques from constraint programming (CP) to perform interval computations and adaptive bound propagation to obtain practically efficient algorithms. Compared to previous algorithms that solve OPF with optimality guarantees using convex relaxations, our approach is able to work for arbitrary tree-structured distribution networks and handle mixed-integer optimization problems. Further, it can be implemented in a distributed message-passing fashion that is scalable and is suitable for “smart grid” applications like control of distributed energy resources. In conclusion, numerical evaluations on several benchmark networks show that practical OPF problems can be solved effectively using this approach.« less

Flow-pattern identification and nonlinear dynamics of gas-liquid two-phase flow in complex networks.

PubMed

Gao, Zhongke; Jin, Ningde

2009-06-01

The identification of flow pattern is a basic and important issue in multiphase systems. Because of the complexity of phase interaction in gas-liquid two-phase flow, it is difficult to discern its flow pattern objectively. In this paper, we make a systematic study on the vertical upward gas-liquid two-phase flow using complex network. Three unique network construction methods are proposed to build three types of networks, i.e., flow pattern complex network (FPCN), fluid dynamic complex network (FDCN), and fluid structure complex network (FSCN). Through detecting the community structure of FPCN by the community-detection algorithm based on K -mean clustering, useful and interesting results are found which can be used for identifying five vertical upward gas-liquid two-phase flow patterns. To investigate the dynamic characteristics of gas-liquid two-phase flow, we construct 50 FDCNs under different flow conditions, and find that the power-law exponent and the network information entropy, which are sensitive to the flow pattern transition, can both characterize the nonlinear dynamics of gas-liquid two-phase flow. Furthermore, we construct FSCN and demonstrate how network statistic can be used to reveal the fluid structure of gas-liquid two-phase flow. In this paper, from a different perspective, we not only introduce complex network theory to the study of gas-liquid two-phase flow but also indicate that complex network may be a powerful tool for exploring nonlinear time series in practice.

Modeling of flowing gas diode pumped alkali lasers: dependence of the operation on the gas velocity and on the nature of the buffer gas.

PubMed

Barmashenko, B D; Rosenwaks, S

2012-09-01

A simple, semi-analytical model of flowing gas diode pumped alkali lasers (DPALs) is presented. The model takes into account the rise of temperature in the lasing medium with increasing pump power, resulting in decreasing pump absorption and slope efficiency. The model predicts the dependence of power on the flow velocity in flowing gas DPALs and checks the effect of using a buffer gas with high molar heat capacity and large relaxation rate constant between the 2P3/2 and 2P1/2 fine-structure levels of the alkali atom. It is found that the power strongly increases with flow velocity and that by replacing, e.g., ethane by propane as a buffer gas the power may be further increased by up to 30%. Eight kilowatt is achievable for 20 kW pump at flow velocity of 20  m/s.

Energy Harvesting from Fluid Flow in Water Pipelines for Smart Metering Applications

NASA Astrophysics Data System (ADS)

Hoffmann, D.; Willmann, A.; Göpfert, R.; Becker, P.; Folkmer, B.; Manoli, Y.

2013-12-01

In this paper a rotational, radial-flux energy harvester incorporating a three-phase generation principle is presented for converting energy from water flow in domestic water pipelines. The energy harvester together with a power management circuit and energy storage is used to power a smart metering system installed underground making it independent from external power supplies or depleting batteries. The design of the radial-flux energy harvester is adapted to the housing of a conventional mechanical water flow meter enabling the use of standard components such as housing and impeller. The energy harvester is able to generate up to 720 mW when using a flow rate of 20 l/min (fully opened water tab). A minimum flow rate of 3 l/min is required to get the harvester started. In this case a power output of 2 mW is achievable. By further design optimization of the mechanical structure including the impeller and magnetic circuit the threshold flow rate can be further reduced.

Fuel-Cell Structure Prevents Membrane Drying

NASA Technical Reports Server (NTRS)

Mcelroy, J.

1986-01-01

Embossed plates direct flows of reactants and coolant. Membrane-type fuel-cell battery has improved reactant flow and heat removal. Compact, lightweight battery produces high current and power without drying of membranes.

The Azimuth Structure of Nuclear Collisions — I

NASA Astrophysics Data System (ADS)

Trainor, Thomas A.; Kettler, David T.

We describe azimuth structure commonly associated with elliptic and directed flow in the context of 2D angular autocorrelations for the purpose of precise separation of so-called nonflow (mainly minijets) from flow. We extend the Fourier-transform description of azimuth structure to include power spectra and autocorrelations related by the Wiener-Khintchine theorem. We analyze several examples of conventional flow analysis in that context and question the relevance of reaction plane estimation to flow analysis. We introduce the 2D angular autocorrelation with examples from data analysis and describe a simulation exercise which demonstrates precise separation of flow and nonflow using the 2D autocorrelation method. We show that an alternative correlation measure based on Pearson's normalized covariance provides a more intuitive measure of azimuth structure.

Optimization of Cooling Water Flow Rate in Nuclear and Thermal Power Plants Based on a Mathematical Model of Cooling Systems{sup 1}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murav’ev, V. P., E-mail: murval1@mail.ru; Kochetkov, A. V.; Glazova, E. G.

A mathematical model and algorithms are proposed for automatic calculation of the optimum flow rate of cooling water in nuclear and thermal power plants with cooling systems of arbitrary complexity. An unlimited number of configuration and design variants are assumed with the possibility of obtaining a result for any computational time interval, from monthly to hourly. The structural solutions corresponding to an optimum cooling water flow rate can be used for subsequent engineering-economic evaluation of the best cooling system variant. The computerized mathematical model and algorithms make it possible to determine the availability and degree of structural changes for themore » cooling system in all stages of the life cycle of a plant.« less

Identification of spatially-localized initial conditions via sparse PCA

NASA Astrophysics Data System (ADS)

Dwivedi, Anubhav; Jovanovic, Mihailo

2017-11-01

Principal Component Analysis involves maximization of a quadratic form subject to a quadratic constraint on the initial flow perturbations and it is routinely used to identify the most energetic flow structures. For general flow configurations, principal components can be efficiently computed via power iteration of the forward and adjoint governing equations. However, the resulting flow structures typically have a large spatial support leading to a question of physical realizability. To obtain spatially-localized structures, we modify the quadratic constraint on the initial condition to include a convex combination with an additional regularization term which promotes sparsity in the physical domain. We formulate this constrained optimization problem as a nonlinear eigenvalue problem and employ an inverse power-iteration-based method to solve it. The resulting solution is guaranteed to converge to a nonlinear eigenvector which becomes increasingly localized as our emphasis on sparsity increases. We use several fluids examples to demonstrate that our method indeed identifies the most energetic initial perturbations that are spatially compact. This work was supported by Office of Naval Research through Grant Number N00014-15-1-2522.

Piezoelectric energy harvesting in internal fluid flow.

PubMed

Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim

2015-10-14

We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph's clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well.

Piezoelectric Energy Harvesting in Internal Fluid Flow

PubMed Central

Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim

2015-01-01

We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph’s clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well. PMID:26473879

Design and simulation of a novel high-efficiency cooling heat-sink structure using fluid-thermodynamics

NASA Astrophysics Data System (ADS)

Hongqi, Jing; Li, Zhong; Yuxi, Ni; Junjie, Zhang; Suping, Liu; Xiaoyu, Ma

2015-10-01

A novel high-efficiency cooling mini-channel heat-sink structure has been designed to meet the package technology demands of high power density laser diode array stacks. Thermal and water flowing characteristics have been simulated using the Ansys-Fluent software. Owing to the increased effective cooling area, this mini-channel heat-sink structure has a better cooling effect when compared with the traditional macro-channel heat-sinks. Owing to the lower flow velocity in this novel high efficient cooling structure, the chillers' water-pressure requirement is reduced. Meanwhile, the machining process of this high-efficiency cooling mini-channel heat-sink structure is simple and the cost is relatively low, it also has advantages in terms of high durability and long lifetime. This heat-sink is an ideal choice for the package of high power density laser diode array stacks. Project supported by the Defense Industrial Technology Development Program (No. B1320133033).

Flaw-induced plastic-flow dynamics in bulk metallic glasses under tension

PubMed Central

Chen, S. H.; Yue, T. M.; Tsui, C. P.; Chan, K. C.

2016-01-01

Inheriting amorphous atomic structures without crystalline lattices, bulk metallic glasses (BMGs) are known to have superior mechanical properties, such as high strength approaching the ideal value, but are susceptible to catastrophic failures. Understanding the plastic-flow dynamics of BMGs is important for achieving stable plastic flow in order to avoid catastrophic failures, especially under tension, where almost all BMGs demonstrate limited plastic flow with catastrophic failure. Previous findings have shown that the plastic flow of BMGs displays critical dynamics under compression tests, however, the plastic-flow dynamics under tension are still unknown. Here we report that power-law critical dynamics can also be achieved in the plastic flow of tensile BMGs by introducing flaws. Differing from the plastic flow under compression, the flaw-induced plastic flow under tension shows an upward trend in the amplitudes of the load drops with time, resulting in a stable plastic-flow stage with a power-law distribution of the load drop. We found that the flaw-induced plastic flow resulted from the stress gradients around the notch roots, and the stable plastic-flow stage increased with the increase of the stress concentration factor ahead of the notch root. The findings are potentially useful for predicting and avoiding the catastrophic failures in tensile BMGs by tailoring the complex stress fields in practical structural-applications. PMID:27779221

Theoretical modeling on the laser-induced phase deformation of liquid crystal optical phased shifter

NASA Astrophysics Data System (ADS)

Zhou, Zhuangqi; Wang, Xiangru; Zhuo, Rusheng; He, Xiaoxian; Wu, Liang; Wang, Xiaolin; Tan, Qinggui; Qiu, Qi

2018-03-01

To improve the working condition of liquid crystal phase shifter on incident laser power, a theoretical model on laser induced phase distortion is built on the physics of heat deposition and heat transfer. Four typical factors (absorption, heat sink structure, cooling fluid rate, and substrate) are analyzed to evaluate the influence of phase distortion when a relative high-power laser is pumped into the liquid crystal phase shifter. Flow rate of cooling fluid and heat sink structure are the most important two factors on improving the limit of incident laser power. Meanwhile, silicon wafer is suggested to replace the back glass contacting the heat sink, because of its higher heat transfer coefficient. If the device is fabricated on the conditions that: the total absorption is 5% and it has a strong heat sink structure with a flow rate of 0.01 m/s, when the incident laser power is 110W, the laser-induced phase deformation on the center is diminished to be less than 0.06, and the maximum temperature increase on the center is less than 1K degree.

Coordinated Voltage Control of Transformer Taps on account of Hierarchical Structure in Power System

NASA Astrophysics Data System (ADS)

Nakachi, Yoshiki; Kato, Satoshi; Ukai, Hiroyuki

Participation of distributed generators (DG), such as wind turbines, co-generation system etc., is natural trend from ecological point of view and will increase more and more. The outputs of these DGs mainly depend on weather condition but don't correspond to the changes of electrical load demand necessarily. On the other hand, due to the deregulation of electric power market, the power flow in power system will uncertainly vary with several power transactions. Thus, complex power flow by DGs or transactions will cause the voltage deviation. It will be difficult to sustain the voltage quality by using the conventional voltage/reactive power control in near future. In this paper, in order to avoid such a voltage deviation and to decrease the frequency of transformer tap actions, the coordinated voltage control scheme of transformer taps on account of hierarchical structure in power system is proposed. In the proposed scheme, integral of voltage deviation at each layer bus is applied to decide the timing of each transformer tap action. It is confirmed by some numerical simulations that the proposed scheme is able to respond to every conditions on voltage deviation.

Flow Solution for Advanced Separate Flow Nozzles Response A: Structured Grid Navier-Stokes Approach

NASA Technical Reports Server (NTRS)

Kenzakowski, D. C.; Shipman, J.; Dash, S. M.; Saiyed, Naseem (Technical Monitor)

2001-01-01

NASA Glenn Research Center funded a computational study to investigate the effect of chevrons and tabs on the exhaust plume from separate flow nozzles. Numerical studies were conducted at typical takeoff power with 0.28 M flight speed. Report provides numerical data and insights into the mechanisms responsible for increased mixing.

Bi-directional transition nets

NASA Astrophysics Data System (ADS)

Staines, Anthony Spiteri

2017-06-01

Ordinary Petri nets are forward directed transition systems. Modern transition systems events and event flows are reversible. Hence modeling structures that reflect this are important. The creation of a bi-directional Petri net extends the modeling power of Petri nets. This work presents the successful implementation of a bi-directional transition net. Some toy examples in comparison to Petri nets are given showing the increased modeling power in a compacted form. The results show some interesting findings on how the expressive power of these structures has been increased.

Numerical investigation of cavitation flow inside spool valve with large pressure drop

NASA Astrophysics Data System (ADS)

Deng, Jian; Pan, Dingyi; Xie, Fangfang; Shao, Xueming

2015-12-01

Spool valves play an important role in fluid power system. Cavitation phenomena happen frequently inside the spool valves, which cause structure damages, noise and lower down hydrodynamic performance. A numerical tools incorporating the cavitation model, are developed to predict the flow structure and cavitation pattern in the spool valve. Two major flow states in the spool valve chamber, i.e. flow-in and flow-out, are studies. The pressure distributions along the spool wall are first investigated, and the results agree well with the experimental data. For the flow-in cases, the local pressure at the throttling area drops much deeper than the pressure in flow-out cases. Meanwhile, the bubbles are more stable in flow-in cases than those in flow-out cases, which are ruptured and shed into the downstream.

Flow Energy Piezoelectric Bimorph Nozzle Harvester

NASA Technical Reports Server (NTRS)

Walkemeyer, Phillip E. (Inventor); Tosi, Phillipe (Inventor); Corbett, Thomas Gary (Inventor); Hall, Jeffrey L. (Inventor); Lee, Hyeong Jae (Inventor); Arrazola, Alvaro Jose (Inventor); Sherrit, Stewart (Inventor); Colonius, Tim (Inventor); Kim, Namhyo (Inventor); Sun, Kai (Inventor)

2016-01-01

A flow energy harvesting device having a harvester pipe includes a flow inlet that receives flow from a primary pipe, a flow outlet that returns the flow into the primary pipe, and a flow diverter within the harvester pipe having an inlet section coupled to the flow inlet, a flow constriction section coupled to the inlet section and positioned at a midpoint of the harvester pipe and having a spline shape with a substantially reduced flow opening size at a constriction point along the spline shape, and an outlet section coupled to the constriction section. The harvester pipe may further include a piezoelectric structure extending from the inlet section through the constriction section and point such that the fluid flow past the constriction point results in oscillatory pressure amplitude inducing vibrations in the piezoelectric structure sufficient to cause a direct piezoelectric effect and to generate electrical power for harvesting.

Traveling wave linear accelerator with RF power flow outside of accelerating cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgashev, Valery A.

A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities hasmore » a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.« less

Wind Farm Flow Modeling using an Input-Output Reduced-Order Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annoni, Jennifer; Gebraad, Pieter; Seiler, Peter

Wind turbines in a wind farm operate individually to maximize their own power regardless of the impact of aerodynamic interactions on neighboring turbines. There is the potential to increase power and reduce overall structural loads by properly coordinating turbines. To perform control design and analysis, a model needs to be of low computational cost, but retains the necessary dynamics seen in high-fidelity models. The objective of this work is to obtain a reduced-order model that represents the full-order flow computed using a high-fidelity model. A variety of methods, including proper orthogonal decomposition and dynamic mode decomposition, can be used tomore » extract the dominant flow structures and obtain a reduced-order model. In this paper, we combine proper orthogonal decomposition with a system identification technique to produce an input-output reduced-order model. This technique is used to construct a reduced-order model of the flow within a two-turbine array computed using a large-eddy simulation.« less

Damage Response in Fluid Flow Networks

NASA Astrophysics Data System (ADS)

Gavrilchenko, Tatyana; Katifori, Eleni

The networks found in biological fluid flow systems such as leaf venation and animal vasculature are characterized by hierarchically nested loops. This structure allows the system to be resilient against fluctuations in the flow of fluid and to be robust against damage. We analytically and computationally investigate how this loopy hierarchy determines the extent of disruption in fluid flow in the vicinity of a damage site. Perturbing the network with the removal of a single edge results in the differential flow as a function of distance from the perturbation decaying as a power law. The power law exponent is generally around -2 in 2D, but we find that it varies due to edge effects, initial edge conductivity, and local topology. We expect that these network flow findings, directly applicable to plant and animal veins, will have analogues in electrical grids, traffic flow and other transport networks.

APPLICATION OF STATISTICAL ENERGY ANALYSIS TO VIBRATIONS OF MULTI-PANEL STRUCTURES.

DTIC Science & Technology

cylindrical shell are compared with predictions obtained from statistical energy analysis . Generally good agreement is observed. The flow of mechanical...the coefficients of proportionality between power flow and average modal energy difference, which one must know in order to apply statistical energy analysis . No

Power and efficiency analysis of a flapping wing wind energy harvester

NASA Astrophysics Data System (ADS)

Bryant, Matthew; Shafer, Michael W.; Garcia, Ephrahim

2012-04-01

Energy harvesting from flowing fluids using flapping wings and fluttering aeroelastic structures has recently gained significant research attention as a possible alternative to traditional rotary turbines, especially at and below the centimeter scale. One promising approach uses an aeroelastic flutter instability to drive limit cycle oscillations of a flexible piezoelectric energy harvesting structure. Such a system is well suited to miniaturization and could be used to create self-powered wireless sensors wherever ambient flows are available. In this paper, we examine modeling of the aerodynamic forces, power extraction, and efficiency of such a flapping wing energy harvester at a low Reynolds number on the order of 1000. Two modeling approaches are considered, a quasi-steady method generalized from existing models of insect flight and a modified model that includes terms to account to the effects of dynamic stall. The modified model is shown to provide better agreement with CFD simulations of a flapping energy harvester.

Information flow and work productivity through integrated information technology

NASA Technical Reports Server (NTRS)

Wigand, R. T.

1985-01-01

The work environment surrounding integrated office systems is reviewed. The known effects of automated office technologies is synthesized and their known impact on work efficiency is reviewed. These effects are explored with regard to their impact on networks, work flow/processes, as well as organizational structure and power. Particular emphasis is given to structural changes due to the introduction of newer information technologies in organizations. The new information technologies have restructed the average organization's middle banks and, as a consequence, they have shrunk drastically. Organizational pyramids have flattened with fewer levels since executives have realized that they can get ahold of the needed information via the new technologies quicker and directly and do not have to rely on middle-level managers. Power shifts are typically accompanied with the introduction of these technologies resulting in the generation of a new form of organizational power.

Formation and structure of a current sheet in pulsed-power driven magnetic reconnection experiments

NASA Astrophysics Data System (ADS)

Hare, J. D.; Lebedev, S. V.; Suttle, L. G.; Loureiro, N. F.; Ciardi, A.; Burdiak, G. C.; Chittenden, J. P.; Clayson, T.; Eardley, S. J.; Garcia, C.; Halliday, J. W. D.; Niasse, N.; Robinson, T.; Smith, R. A.; Stuart, N.; Suzuki-Vidal, F.; Swadling, G. F.; Ma, J.; Wu, J.

2017-10-01

We describe magnetic reconnection experiments using a new, pulsed-power driven experimental platform in which the inflows are super-sonic but sub-Alfvénic. The intrinsically magnetised plasma flows are long lasting, producing a well-defined reconnection layer that persists over many hydrodynamic time scales. The layer is diagnosed using a suite of high resolution laser based diagnostics, which provide measurements of the electron density, reconnecting magnetic field, inflow and outflow velocities, and the electron and ion temperatures. Using these measurements, we observe a balance between the power flow into and out of the layer, and we find that the heating rates for the electrons and ions are significantly in excess of the classical predictions. The formation of plasmoids is observed in laser interferometry and optical self-emission, and the magnetic O-point structure of these plasmoids is confirmed using magnetic probes.

Self-regulating flow control device

DOEpatents

Humphreys, Duane A.

1984-01-01

A variable, self-regulating valve having a hydraulic loss coefficient proportional to a positive exponential power of the flow rate. The device includes two objects in a flow channel and structure which assures that the distance between the two objects is an increasing function of the flow rate. The range of spacing between the objects is such that the hydraulic resistance of the valve is an increasing function of the distance between the two objects so that the desired hydraulic loss coefficient as a function of flow rate is obtained without variation in the flow area.

Four cavity efficiency enhanced magnetically insulated line oscillator

DOEpatents

Lemke, Raymond W.; Clark, Miles C.; Calico, Steve E.

1998-04-21

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity (C4) portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor.

Four cavity efficiency enhanced magnetically insulated line oscillator

DOEpatents

Lemke, R.W.; Clark, M.C.; Calico, S.E.

1998-04-21

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode is disclosed. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor. 34 figs.

Grid tied PV/battery system architecture and power management for fast electric vehicle charging

NASA Astrophysics Data System (ADS)

Badawy, Mohamed O.

The prospective spread of Electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) arises the need for fast charging rates. Higher charging rates requirements lead to high power demands, which cant be always supported by the grid. Thus, the use of on-site sources alongside the electrical grid for EVs charging is a rising area of interest. In this dissertation, a photovoltaic (PV) source is used to support the high power EVs charging. However, the PV output power has an intermittent nature that is dependable on the weather conditions. Thus, battery storage are combined with the PV in a grid tied system, providing a steady source for on-site EVs use in a renewable energy based fast charging station. Verily, renewable energy based fast charging stations should be cost effective, efficient, and reliable to increase the penetration of EVs in the automotive market. Thus, this Dissertation proposes a novel power flow management topology that aims on decreasing the running cost along with innovative hardware solutions and control structures for the developed architecture. The developed power flow management topology operates the hybrid system at the minimum operating cost while extending the battery lifetime. An optimization problem is formulated and two stages of optimization, i.e online and offline stages, are adopted to optimize the batteries state of charge (SOC) scheduling and continuously compensate for the forecasting errors. The proposed power flow management topology is validated and tested with two metering systems, i.e unified and dual metering systems. The results suggested that minimal power flow is anticipated from the battery storage to the grid in the dual metering system. Thus, the power electronic interfacing system is designed accordingly. Interconnecting bi-directional DC/DC converters are analyzed, and a cascaded buck boost (CBB) converter is chosen and tested under 80 kW power flow rates. The need to perform power factor correction (PFC) on the grid power while supplying the battery storage and the DC loads inspired a novel dual switch control structure for the CBB AC/DC converter used in this dissertation. Thus, The CBB operates at a discontinuous capacitor voltage mode (DCVM) and the control structure enables for a non-distorted input current at overlapping output voltage levels. The PFC concept is validated and tested for a single phase rectifier and a 3 phase extension of the proposed concept is presented. Lastly, the PV source used in this study is required to supply power to both, the grid system, and to the DC loads, i.e the battery storage and the EVs. Thus, the PV panels used are connected in series to reach a desirable high voltage on the DC bus output of the PV system. Consequently, a novel differential power processing architecture is proposed in this dissertation. The proposed architecture enables each PV element to operate at its local maximum power point (MPP) while processing only a small portion of its total generated power through the distributed integrated converters. This leads to higher energy capture at an increased conversion efficiency while overcoming the difficulties associated with unmatched MPPs of the PV elements.

Lighting system with thermal management system

DOEpatents

Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Seeley, Charles Erklin; Kuenzler, Glenn Howard; Wolfe, Jr., Charles Franklin; Utturkar, Yogen Vishwas; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

2015-02-24

Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

Lighting system with thermal management system

DOEpatents

Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Seeley, Charles Erklin; Kuenzler, Glenn Howard; Wolfe, Jr., Charles Franklin; Utturkar, Yogen Vishwas; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

2015-08-25

Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

Lighting system with thermal management system

DOEpatents

Arik, Mehmet; Weaver, Stanton; Stecher, Thomas; Seeley, Charles; Kuenzler, Glenn; Wolfe, Jr., Charles; Utturkar, Yogen; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

2013-05-07

Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

Lighting system with thermal management system

DOEpatents

Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Seeley, Charles Erklin; Kuenzler, Glenn Howard; Wolfe, Jr, Charles Franklin; Utturkar, Yogen Vishwas; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

2016-10-11

Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

Mechanical energy flow models of rods and beams

NASA Technical Reports Server (NTRS)

Wohlever, J. C.; Bernhard, R. J.

1992-01-01

It has been proposed that the flow of mechanical energy through a structural/acoustic system may be modeled in a manner similar to that of flow of thermal energy/in a heat conduction problem. If this hypothesis is true, it would result in relatively efficient numerical models of structure-borne energy in large built-up structures. Fewer parameters are required to approximate the energy solution than are required to model the characteristic wave behavior of structural vibration by using traditional displacement formulations. The energy flow hypothesis is tested in this investigation for both longitudinal vibration in rods and transverse flexural vibrations of beams. The rod is shown to behave approximately according to the thermal energy flow analogy. However, the beam solutions behave significantly differently than predicted by the thermal analogy unless locally-space-averaged energy and power are considered. Several techniques for coupling dissimilar rods and beams are also discussed. Illustrations of the solution accuracy of the methods are included.

An open-structure sound insulator against low-frequency and wide-band acoustic waves

NASA Astrophysics Data System (ADS)

Chen, Zhe; Fan, Li; Zhang, Shu-yi; Zhang, Hui; Li, Xiao-juan; Ding, Jin

2015-10-01

To block sound, i.e., the vibration of air, most insulators are based on sealed structures and prevent the flow of the air. In this research, an acoustic metamaterial adopting side structures, loops, and labyrinths, arranged along a main tube, is presented. By combining the accurately designed side structures, an extremely wide forbidden band with a low cut-off frequency of 80 Hz is produced, which demonstrates a powerful low-frequency and wide-band sound insulation ability. Moreover, by virtue of the bypass arrangement, the metamaterial is based on an open structure, and thus air flow is allowed while acoustic waves can be insulated.

Development of energy-harvesting system using deformation of magnetic elastomer

NASA Astrophysics Data System (ADS)

Shinoda, Hayato; Tsumori, Fujio

2018-06-01

In this paper, we propose a power generation method using the deformation of a magnetic elastomer for vibration energy harvesting. The magnetic flux lines in the structure of the magnetic elastomer could be markedly changed if the properly designed structure was expanded and contracted in a static magnetic field. We set a coil on the magnetic elastomer to generate electricity by capturing this change in magnetic flux flow. We fabricated a centimeter-scale device and demonstrated that it generated 10.5 mV of maximum voltage by 10 Hz vibration. We also simulated the change in the magnetic flux flow using finite element analysis, and compared the result with the experimental data. Furthermore, we evaluated the power generation of a miniaturized device.

Development of the Technology of Vortex Diagnostics to Improve the Safety of Operation of Nuclear Reactors

NASA Astrophysics Data System (ADS)

Mitrofanova, O. V.; Ivlev, O. A.; Pozdeeva, I. G.; Urtenov, D. S.

2017-11-01

The results of studies are aimed at developing theoretical foundations and instrumentation system to ensure a technology of vortex diagnostics of the state of flows of fluids for nuclear power installations with power water reactors and fast neutrons reactors with liquid-metal coolants. The technology of vortex diagnostics is based on the study of acoustic, magneto-hydrodynamic and resonant effects related to the formation of stable vortex structures. For creation a system of monitoring and diagnostics of the crisis phenomena due to hydrodynamics of the flow, it is proposed to use acoustic method to record the radiation of elastic waves in the fluids caused by the dynamic local rearrangement of its structure.

Vortex flows with suspended separation regions and long-range untwisted central jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abramovich, G.N.; Trofimov, R.S.

1988-05-01

A study is made of possible physicoaerodynamic configurations of vortical flow with suspended separation regions and untwisted central jets. Such flows are encountered in power plants (heat exchangers, combustion chambers, and chemical reactors) and in nature (tornadoes). The basic configurations of several flows of this type are described, including the structure of a flow formed by coaxial cocurrent twisted jets, the flow in a conical swirl chamber with the formation of an untwisted long-range axial jet, the flow pattern in a gas turbine engine chamber, and some considerations regarding the aerodynamics of a tornado.

Towards uncovering the structure of power fluctuations of wind farms

NASA Astrophysics Data System (ADS)

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P.

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations ΦP exhibit a power-law decay proportional to f-5 /3 -2 in the region corresponding to the turbulence inertial subrange and at relatively large scales, ΦP˜f-2 . Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Towards uncovering the structure of power fluctuations of wind farms.

PubMed

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations Φ_{P} exhibit a power-law decay proportional to f^{-5/3-2} in the region corresponding to the turbulence inertial subrange and at relatively large scales, Φ_{P}∼f^{-2}. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Geometry of tracer trajectories in turbulent rotating convection

NASA Astrophysics Data System (ADS)

Alards, Kim; Rajaei, Hadi; Kunnen, Rudie; Toschi, Federico; Clercx, Herman

2016-11-01

In Rayleigh-Bénard convection rotation is known to cause transitions in flow structures and to change the level of anisotropy close to the horizontal plates. To analyze this effect of rotation, we collect curvature and torsion statistics of passive tracer trajectories in rotating Rayleigh-Bénard convection, using both experiments and direct numerical simulations. In previous studies, focusing on homogeneous isotropic turbulence (HIT), curvature and torsion PDFs are found to reveal pronounced power laws. In the center of the convection cell, where the flow is closest to HIT, we recover these power laws, regardless of the rotation rate. However, near the top plate, where we expect the flow to be anisotropic, the scaling of the PDFs deviates from the HIT prediction for lower rotation rates. This indicates that anisotropy clearly affects the geometry of tracer trajectories. Another effect of rotation is observed as a shift of curvature and torsion PDFs towards higher values. We expect this shift to be related to the length scale of typical flow structures. Using curvature and torsion statistics, we can characterize how these typical length scales evolve under rotation and moreover analyze the effect of rotation on more complicated flow characteristics, such as anisotropy.

The effect of dentinal fluid flow during loading in various directions--simulation of fluid-structure interaction.

PubMed

Su, Kuo-Chih; Chang, Chih-Han; Chuang, Shu-Fen; Ng, Eddie Yin-Kwee

2013-06-01

This study uses a fluid-structure interaction (FSI) simulation to evaluate the fluid flow in a dental intrapulpal chamber induced by the deformation of the tooth structure during loading in various directions. The FSI is used for the biomechanics simulation of dental intrapulpal responses with the force loading gradually increasing from 0 to 100N at 0°, 30°, 45°, 60°, and 90° on the tooth surface in 1s, respectively. The effect of stress or deformation on tooth and fluid flow changes in the pulp chamber are evaluated. A horizontal loading force on a tooth may induce tooth structure deformation, which increases fluid flow velocity in the coronal pulp. Thus, horizontal loading on a tooth may easily induce tooth pain. This study suggests that experiments to investigate the relationship between loading in various directions and dental pain should avoid measuring the bulk pulpal fluid flow from radicular pulp, but rather should measure the dentinal fluid flow in the dentinal tubules or coronal pulp. The FSI analysis used here could provide a powerful tool for investigating problems with coupled solid and fluid structures in dental biomechanics. Copyright © 2012 Elsevier Ltd. All rights reserved.

Global Qualitative Flow-Path Modeling for Local State Determination in Simulation and Analysis

NASA Technical Reports Server (NTRS)

Malin, Jane T. (Inventor); Fleming, Land D. (Inventor)

1998-01-01

For qualitative modeling and analysis, a general qualitative abstraction of power transmission variables (flow and effort) for elements of flow paths includes information on resistance, net flow, permissible directions of flow, and qualitative potential is discussed. Each type of component model has flow-related variables and an associated internal flow map, connected into an overall flow network of the system. For storage devices, the implicit power transfer to the environment is represented by "virtual" circuits that include an environmental junction. A heterogeneous aggregation method simplifies the path structure. A method determines global flow-path changes during dynamic simulation and analysis, and identifies corresponding local flow state changes that are effects of global configuration changes. Flow-path determination is triggered by any change in a flow-related device variable in a simulation or analysis. Components (path elements) that may be affected are identified, and flow-related attributes favoring flow in the two possible directions are collected for each of them. Next, flow-related attributes are determined for each affected path element, based on possibly conflicting indications of flow direction. Spurious qualitative ambiguities are minimized by using relative magnitudes and permissible directions of flow, and by favoring flow sources over effort sources when comparing flow tendencies. The results are output to local flow states of affected components.

Self-regulating valve

DOEpatents

Humphreys, D.A.

1982-07-20

A variable, self-regulating valve having a hydraulic loss coefficient proportional to a positive exponential power of the flow rate. The device includes two objects in a flow channel and structure which assures that the distance between the two objects is an increasing function of the flow rate. The range of spacing between the objects is such that the hydraulic resistance of the valve is an increasing function of the distance between the two objects so that the desired hydraulic loss coefficient as a function of flow rate is obtained without variation in the flow area.

An investigation of chaotic Kolmogorov flows

NASA Technical Reports Server (NTRS)

Platt, N.; Sirovich, L.; Fitzmaurice, N.

1990-01-01

A two dimensional flow governed by the incompressible Navier-Stokes equations with a steady spatially periodic forcing (known as the Kolmogorov flow) is numerically simulated. The behavior of the flow and its transition states as the Reynolds number (Re) varies is investigated in detail, as well as a number of the flow features. A sequence of bifurcations is shown to take place in the flow as Re varied. Two main regimes of the flow were observed: small and large scale structure regimes corresponding to different ranges of Re. Each of the regimes includes a number of quasiperiodic, chaotic, and relaminarization windows. In addition, each range contains a chaotic window with non-ergodic chaotic attractors. Spatially disordered, but temporally steady states were discovered in large scale structure regime. Features of the diverse cases are displayed in terms of the temporal power spectrum, Poincare sections and, where possible, Lyapunov exponents and Kaplan-Yorke dimension.

Application of process tomography in gas-solid fluidised beds in different scales and structures

NASA Astrophysics Data System (ADS)

Wang, H. G.; Che, H. Q.; Ye, J. M.; Tu, Q. Y.; Wu, Z. P.; Yang, W. Q.; Ocone, R.

2018-04-01

Gas-solid fluidised beds are commonly used in particle-related processes, e.g. for coal combustion and gasification in the power industry, and the coating and granulation process in the pharmaceutical industry. Because the operation efficiency depends on the gas-solid flow characteristics, it is necessary to investigate the flow behaviour. This paper is about the application of process tomography, including electrical capacitance tomography (ECT) and microwave tomography (MWT), in multi-scale gas-solid fluidisation processes in the pharmaceutical and power industries. This is the first time that both ECT and MWT have been applied for this purpose in multi-scale and complex structure. To evaluate the sensor design and image reconstruction and to investigate the effects of sensor structure and dimension on the image quality, a normalised sensitivity coefficient is introduced. In the meantime, computational fluid dynamic (CFD) analysis based on a computational particle fluid dynamic (CPFD) model and a two-phase fluid model (TFM) is used. Part of the CPFD-TFM simulation results are compared and validated by experimental results from ECT and/or MWT. By both simulation and experiment, the complex flow hydrodynamic behaviour in different scales is analysed. Time-series capacitance data are analysed both in time and frequency domains to reveal the flow characteristics.

Control of Vibratory Energy Harvesters in the Presence of Nonlinearities and Power-Flow Constraints

NASA Astrophysics Data System (ADS)

Cassidy, Ian L.

Over the past decade, a significant amount of research activity has been devoted to developing electromechanical systems that can convert ambient mechanical vibrations into usable electric power. Such systems, referred to as vibratory energy harvesters, have a number of useful of applications, ranging in scale from self-powered wireless sensors for structural health monitoring in bridges and buildings to energy harvesting from ocean waves. One of the most challenging aspects of this technology concerns the efficient extraction and transmission of power from transducer to storage. Maximizing the rate of power extraction from vibratory energy harvesters is further complicated by the stochastic nature of the disturbance. The primary purpose of this dissertation is to develop feedback control algorithms which optimize the average power generated from stochastically-excited vibratory energy harvesters. This dissertation will illustrate the performance of various controllers using two vibratory energy harvesting systems: an electromagnetic transducer embedded within a flexible structure, and a piezoelectric bimorph cantilever beam. Compared with piezoelectric systems, large-scale electromagnetic systems have received much less attention in the literature despite their ability to generate power at the watt--kilowatt scale. Motivated by this observation, the first part of this dissertation focuses on developing an experimentally validated predictive model of an actively controlled electromagnetic transducer. Following this experimental analysis, linear-quadratic-Gaussian control theory is used to compute unconstrained state feedback controllers for two ideal vibratory energy harvesting systems. This theory is then augmented to account for competing objectives, nonlinearities in the harvester dynamics, and non-quadratic transmission loss models in the electronics. In many vibratory energy harvesting applications, employing a bi-directional power electronic drive to actively control the harvester is infeasible due to the high levels of parasitic power required to operate the drive. For the case where a single-directional drive is used, a constraint on the directionality of power-flow is imposed on the system, which necessitates the use of nonlinear feedback. As such, a sub-optimal controller for power-flow-constrained vibratory energy harvesters is presented, which is analytically guaranteed to outperform the optimal static admittance controller. Finally, the last section of this dissertation explores a numerical approach to compute optimal discretized control manifolds for systems with power-flow constraints. Unlike the sub-optimal nonlinear controller, the numerical controller satisfies the necessary conditions for optimality by solving the stochastic Hamilton-Jacobi equation.

A Concept for Power Cycling the Electronics of CALICE-AHCAL with the Train Structure of ILC

NASA Astrophysics Data System (ADS)

Göottlicher, Peter; The Calice-Collaboration

Particle flow algorithm calorimetry requires high granularity three-dimensional readout. The tight power requirement of 40 μW/channel is reached by enabling readout ASIC currents only during beam delivery, corresponding to a 1% duty cycle. EMI noise caused by current switching needs to be minimized by the power system and this paper presents ideas, simulations and first measurements for minimizing disturbances. A carefully design of circuits, printed circuit boards, grounding scheme and use of floating supplies allows current loops to be closed locally, stabilized voltages and minimal currents in the metal structures.

Method and system to directly produce electrical power within the lithium blanket region of a magnetically confined, deuterium-tritium (DT) fueled, thermonuclear fusion reactor

DOEpatents

Woolley, Robert D.

1999-01-01

A method for integrating liquid metal magnetohydrodynamic power generation with fusion blanket technology to produce electrical power from a thermonuclear fusion reactor located within a confining magnetic field and within a toroidal structure. A hot liquid metal flows from a liquid metal blanket region into a pump duct of an electromagnetic pump which moves the liquid metal to a mixer where a gas of predetermined pressure is mixed with the pressurized liquid metal to form a Froth mixture. Electrical power is generated by flowing the Froth mixture between electrodes in a generator duct. When the Froth mixture exits the generator the gas is separated from the liquid metal and both are recycled.

Balancing the Power-to-Load Ratio for a Novel Variable Geometry Wave Energy Converter with Nonideal Power Take-Off in Regular Waves: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tom, Nathan M; Yu, Yi-Hsiang; Wright, Alan D

This work attempts to balance power absorption against structural loading for a novel variable geometry wave energy converter. The variable geometry consists of four identical flaps that will be opened in ascending order starting with the flap closest to the seafloor and moving to the free surface. The influence of a pitch motion constraint on power absorption when utilizing a nonideal power take-off (PTO) is examined and found to reduce the losses associated with bidirectional energy flow. The power-to-load ratio is evaluated using pseudo-spectral control to determine the optimum PTO torque based on a multiterm objective function. The pseudo-spectral optimalmore » control problem is extended to include load metrics in the objective function, which may now consist of competing terms. Separate penalty weights are attached to the surge-foundation force and PTO control torque to tune the optimizer performance to emphasize either power absorption or load shedding. PTO efficiency is not included in the objective function, but the penalty weights are utilized to limit the force and torque amplitudes, thereby reducing losses associated with bidirectional energy flow. Results from pseudo-spectral control demonstrate that shedding a portion of the available wave energy can provide greater reductions in structural loads and reactive power.« less

Network structure of subway passenger flows

NASA Astrophysics Data System (ADS)

Xu, Q.; Mao, B. H.; Bai, Y.

2016-03-01

The results of transportation infrastructure network analyses have been used to analyze complex networks in a topological context. However, most modeling approaches, including those based on complex network theory, do not fully account for real-life traffic patterns and may provide an incomplete view of network functions. This study utilizes trip data obtained from the Beijing Subway System to characterize individual passenger movement patterns. A directed weighted passenger flow network was constructed from the subway infrastructure network topology by incorporating trip data. The passenger flow networks exhibit several properties that can be characterized by power-law distributions based on flow size, and log-logistic distributions based on the fraction of boarding and departing passengers. The study also characterizes the temporal patterns of in-transit and waiting passengers and provides a hierarchical clustering structure for passenger flows. This hierarchical flow organization varies in the spatial domain. Ten cluster groups were identified, indicating a hierarchical urban polycentric structure composed of large concentrated flows at urban activity centers. These empirical findings provide insights regarding urban human mobility patterns within a large subway network.

Trash Diverter Orientation Angle Optimization at Run-Off River Type Hydro-power Plant using CFD

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Kamal, Ahmad; Shuaib, Norshah Hafeez; Yusoff, Mohd. Zamri; Hasini, Hasril; Rashid, Azri Zainol; Thangaraju, Savithry K.; Hamid, Hazha

2010-06-01

Tenom Pangi Hydro Power Station in Tenom, Sabah is suffering from poor river quality with a lot of suspended trashes. This problem necessitates the need for a trash diverter to divert the trash away from the intake region. Previously, a trash diverter (called Trash Diverter I) was installed at the site but managed to survived for a short period of time due to an impact with huge log as a results of a heavy flood. In the current project, a second trash diverter structure is designed (called Trash Diverter II) with improved features compared to Trash Diverter I. The Computational Fluid Dynamics (CFD) analysis is done to evaluate the river flow interaction onto the trash diverter from the fluid flow point of view, Computational Fluids Dynamics is a numerical approach to solve fluid flow profile for different inlet conditions. In this work, the river geometry is modeled using commercial CFD code, FLUENT®. The computational model consists of Reynolds Averaged Navier-Stokes (RANS) equations coupled with other related models using the properties of the fluids under investigation. The model is validated with site-measurements done at Tenom Pangi Hydro Power Station. Different operating condition of river flow rate and weir opening is also considered. The optimum angle is determined in this simulation to further use the data for 3D simulation and structural analysis.

Structural dimensions of knowledge-action networks for sustainability

Treesearch

Tischa A. Munoz; B.B. Cutts

2016-01-01

Research on the influence of social network structure over flows of knowledge in support of sustainability governance and action has recently flourished. These studies highlight three challenges to evaluating knowledge-action networks: first, defining boundaries; second, characterizing power distributions; and third, identifying obstacles to knowledge sharing and...

Concentration Measurements in Self-Excited Momentum Dominated Low-Density Gas Jets

NASA Technical Reports Server (NTRS)

Yildirim, B. S.; Pasumarthi, K. S.; Agrawal, A. K.

2004-01-01

Flow structure of self-excited, laminar, axisymmetric, momentum-dominated helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry technique. Measurements were obtained at temporal resolution of 1 ms and spatial resolution of 0.19 mm for two test cases with Richardson number of 0.034 and 0.018. Power spectra revealed that the oscillation frequency was independent of spatial coordinates, suggesting global oscillations in the flow. Abel inversion algorithm was used to reconstruct the concentration field of helium. Instantaneous concentration contours revealed changes in the flow field and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial locations provided detailed information about the instability in the flow field.

Dense Array Optimization of Cross-Flow Turbines

NASA Astrophysics Data System (ADS)

Scherl, Isabel; Strom, Benjamin; Brunton, Steven; Polagye, Brian

2017-11-01

Cross-flow turbines, where the axis of rotation is perpendicular to the freestream flow, can be used to convert the kinetic energy in wind or water currents to electrical power. By taking advantage of mean and time-resolved wake structures, the optimal density of an array of cross-flow turbines has the potential for higher power output per unit area of land or sea-floor than an equivalent array of axial-flow turbines. In addition, dense arrays in tidal or river channels may be able to further elevate efficiency by exploiting flow confinement and surface proximity. In this work, a two-turbine array is optimized experimentally in a recirculating water channel. The spacing between turbines, as well as individual and coordinated turbine control strategies are optimized. Array efficiency is found to exceed the maximum efficiency for a sparse array (i.e., no interaction between turbines) for stream-wise rotor spacing of less than two diameters. Results are discussed in the context of wake measurements made behind a single rotor.

Natural snowfall reveals large-scale flow structures in the wake of a 2.5-MW wind turbine.

PubMed

Hong, Jiarong; Toloui, Mostafa; Chamorro, Leonardo P; Guala, Michele; Howard, Kevin; Riley, Sean; Tucker, James; Sotiropoulos, Fotis

2014-06-24

To improve power production and structural reliability of wind turbines, there is a pressing need to understand how turbines interact with the atmospheric boundary layer. However, experimental techniques capable of quantifying or even qualitatively visualizing the large-scale turbulent flow structures around full-scale turbines do not exist today. Here we use snowflakes from a winter snowstorm as flow tracers to obtain velocity fields downwind of a 2.5-MW wind turbine in a sampling area of ~36 × 36 m(2). The spatial and temporal resolutions of the measurements are sufficiently high to quantify the evolution of blade-generated coherent motions, such as the tip and trailing sheet vortices, identify their instability mechanisms and correlate them with turbine operation, control and performance. Our experiment provides an unprecedented in situ characterization of flow structures around utility-scale turbines, and yields significant insights into the Reynolds number similarity issues presented in wind energy applications.

Hydro-power production and fish habitat suitability: Assessing impact and effectiveness of ecological flows at regional scale

NASA Astrophysics Data System (ADS)

Ceola, Serena; Pugliese, Alessio; Ventura, Matteo; Galeati, Giorgio; Montanari, Alberto; Castellarin, Attilio

2018-06-01

Anthropogenic activities along streams and rivers may be of major concern for fluvial ecosystems, e.g. abstraction and impoundment of surface water resources may profoundly alter natural streamflow regimes. An established approach aimed at preserving the behavior and distribution of fluvial species relies on the definition of ecological flows (e-flows) downstream of dams and diversion structures. E-flow prescriptions are usually set by basin authorities at regional scale, often without a proper assessment of their impact and effectiveness. On the contrary, we argue that e-flows should be identified on the basis of (i) regional and (ii) quantitative assessments. We focus on central Italy and evaluate the effects on habitat suitability of two near-threatened fish species (i.e. Barbel and Chub) and an existing hydro-power network when shifting from the current time-invariant e-flow policy to a tighter and seasonally-varying soon-to-be-enforced one. Our example clearly shows that: (a) quantitative regional scale assessments are viable even when streamflow observations are entirely missing at study sites; (b) aprioristic e-flows policies may impose releases that exceed natural streamflows for significantly long time intervals (weeks, or months); (c) unduly tightening e-flow policies may heavily impact regional hydro-power productivity (15% and 42% losses on annual and seasonal basis, respectively), yet resulting in either marginal or negligible improvements of fluvial ecosystem.

A nonlinear flow-induced energy harvester by considering effects of fictitious springs

NASA Astrophysics Data System (ADS)

Zhang, Guangcheng; Lin, Yueh-Jaw

2018-01-01

In this paper, a newly proposed energy harvesting approach involving nonlinear coupling effects is demonstrated by utilizing a pair of inducing bluff bodies that are put on both sides of the flag-shaped cantilever beam, and placed in a side-by-side configuration to harvest the energy of the flow. One patch of macro fiber composite is attached to the fixed end of the cantilever beam to facilitate converting the kinetic energy into electric power. It is the first time in recent literature that two fluid dynamic phenomena (i.e. the vortex shedding and the Bernoulli effect) are considered simultaneously in the flow-induced energy harvesting field. The fictitious springs are introduced to explain the nonlinear characteristics of the proposed structure. With the effect of the fictitious springs, the speed range of the flow-induced energy harvester is extended. The proposed structure not only improves the output of the induced-based energy harvester compared to one that has just one cylinder, but can also be utilized in an actual hostile ambient environment. The experimental results for the energy harvester prototype are also investigated. The output power of the energy harvester with two cylinders (D = 25 mm) is measured to be 1.12 μW when the flow speed is 0.325 m s-1 and the center-to-center transverse spacing is 45 mm. This research also delves into the geometric variations of the proposed structure and its optimization.

Study of Jet-Propulsion System Comprising Blower, Burner, and Nozzle

NASA Technical Reports Server (NTRS)

Hall, Eldon W

1944-01-01

A study was made of the performance of a jet-propulsion system composed of an engine-driven blower, a combustion chamber, and a discharge nozzle. A simplified analysis is made of this system for the purpose of showing in concise form the effect of the important design variables and operating conditions on jet thrust, thrust horsepower, and fuel consumption. Curves are presented that permit a rapid evaluation of the performance of this system for a range of operating conditions. The performance for an illustrative case of a power plant of the type under consideration id discussed in detail. It is shown that for a given airplane velocity the jet thrust horsepower depends mainly on the blower power and the amount of fuel burned in the jet; the higher the thrust horsepower is for a given blower power, the higher the fuel consumption per thrust horsepower. Within limits the amount of air pumped has only a secondary effect on the thrust horsepower and efficiency. A lower limit on air flow for a given fuel flow occurs where the combustion-chamber temperature becomes excessive on the basis of the strength of the structure. As the air-flow rate is increased, an upper limit is reached where, for a given blower power, fuel-flow rate, and combustion-chamber size, further increase in air flow causes a decrease in power and efficiency. This decrease in power is caused by excessive velocity through the combustion chamber, attended by an excessive pressure drop caused by momentum changes occurring during combustion.

Evaluation of the effectiveness of elastomeric mount using vibration power flow and transmissibility methods

NASA Astrophysics Data System (ADS)

Arib Rejab, M. N.; Shukor, S. A. Abdul; Sofian, M. R. Mohd; Inayat-Hussain, J. I.; Nazirah, A.; Asyraf, I.

2017-10-01

This paper presents the results of an experimental work to determine the dynamic stiffness and loss factor of elastomeric mounts. It also presents the results of theoretical analysis to determine the transmissibility and vibration power flow of these mounts, which are associated with their contribution to structure-borne noise. Four types of elastomeric mounts were considered, where three of them were made from green natural rubber material (SMR CV60, Ekoprena and Pureprena) and one made from petroleum based synthetic rubber (EPDM). In order to determine the dynamic stiffness and loss factor of these elastomeric mounts, dynamic tests were conducted using MTS 830 Elastomer Test System. Dynamic stiffness and loss factor of these mounts were measured for a range of frequency between 5 Hz and 150 Hz, and with a dynamic amplitude of 0.2 mm (p-p). The transmissibility and vibration power flow were determined based on a simple 2-Degree-of-Freedom model representing a vibration isolation system with a flexible receiver. This model reprsents the three main parts of a vehicle, which are the powertrain and engine mounting, the flexible structure and the floor of the vehicle. The results revealed that synthetic rubber (EPDM) was only effective at high frequency region. Natural rubber (Ekoprena), on the other hand, was found to be effective at both low and high frequency regions due to its low transmissibility at resonant frequency and its ability to damp the resonance. The estimated structure-borne noise emission showed that Ekoprena has a lower contribution to structure-borne noise as compared to the other types of elastomeric mounts.

New insights on the interaction between atmospheric flow and a full-scale 2.5 MW wind turbine

NASA Astrophysics Data System (ADS)

Chamorro, L. P.; Lee, S.; Olsen, D.; Milliren, C.; Marr, J.; Arndt, R.; Sotiropoulos, F.

2012-12-01

Power fluctuations and fatigue loads are among the most significant problems that wind turbines face throughout their lifetime. Atmospheric turbulence is the common driving mechanism that triggers instabilities on these quantities. Reducing the effects of the fluctuating flow on wind turbines is quite challenging due to the wide variety of length scales present in the boundary layer flow. Each group of these scales, which range from the order of a millimeter to kilometer and larger, plays a characteristic and distinctive role on the performance and structural reliability of wind turbines. This study seeks to contribute toward the understanding on the complex scale-to-scale interaction between wind turbine and flow turbulence. Novel insights into the physical mechanisms that govern the flow/turbine interaction will be discussed. To tackle the problem, we investigate the unsteady behavior of a full-scale 2.5 MW wind turbine under nearly neutral thermal stratification. The study is performed in the Eolos Wind Energy Research Field Station of the University of Minnesota. An instrumented 130 meter meteorological tower located upstream of a Clipper Liberty C96 wind turbine is used to characterize the turbulent flow and atmospheric conditions right upstream of the wind turbine. High resolution and synchronous measurements of the approach wind velocity at several heights, turbine power and strain at the tower foundation are used to determine the scale-to-scale interaction between flow and the wind turbine performance and its physical structure. The spectral distribution of the fluctuating turbine power and instantaneous stresses will be discussed in detail. Characteristic length scales playing a key role on the dynamics of the wind turbine as well as the distinctive effects of flow coherent motions and strong intermittent gusts will also be addressed. Funding was provided by the U.S. Department of Energy (DE-EE0002980) and Xcel Energy through the Renewable Development Fund (grant RD3-42).

Characterization of hydrofoil damping due to fluid-structure interaction using piezocomposite actuators

NASA Astrophysics Data System (ADS)

Seeley, Charles; Coutu, André; Monette, Christine; Nennemann, Bernd; Marmont, Hugues

2012-03-01

Hydroelectric power generation is an important non-fossil fuel power source to help meet the world’s energy needs. Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Although the effects of fluid mass loading are well documented, fluid damping is also a critical quantity that may limit vibration amplitudes during service, and therefore help to avoid premature failure of the turbines. However, fluid damping has received less attention in the literature. This paper presents an experimental investigation of damping due to FSI. Three hydrofoils were designed and built to investigate damping due to FSI. Piezoelectric actuation using macrofiber composites (MFCs) provided excitation to the hydrofoil test structure, independent of the flow conditions, to overcome the noisy environment. Natural frequency and damping estimates were experimentally obtained from sine sweep frequency response functions measured with a laser vibrometer through a window in the test section. The results indicate that, although the natural frequencies were not substantially affected by the flow, the damping ratios were observed to increase in a linear manner with respect to flow velocity.

Passive noise control by enhancing aeroacoustic interference due to structural discontinuities in close proximity

NASA Astrophysics Data System (ADS)

Leung, R. C. K.; So, R. M. C.; Tang, S. K.; Wang, X. Q.

2011-07-01

In-duct devices are commonly installed in flow ducts for various flow management purposes. The structural construction of these devices indispensably creates disruption to smooth flow through duct passages so they exist as structural discontinuities in duct flow. The presence of these discontinuities provides additional possibility of noise generation. In real practice, in-duct devices do not exist alone in any duct system. Even though each in-duct device would generate its own noise, it might be possible that these devices could be properly arranged so as to strengthen the interference between individual noise; thus giving rise to an overall reduction of noise radiation in the in-duct far field. This concept of passive noise control is investigated by considering different configurations of two structural discontinuities of simple form (i.e., a cavity) in tandem in an unconfined flow and in opposing setting within a flow duct. It is known that noise generated by a cavity in unconfined domain (unconfined cavity) is strongly dependent on flow-resonant behavior within the cavity so the interference it produces is merely aeroacoustic. The objective of the present study is to verify the concept of passive noise reduction through enhancement of aeroacoustic interference due to two cavities by considering laminar flow only. A two-dimensional approach is adopted for the direct aeroacoustic calculations using a direct numerical simulation (DNS) technique. The position and geometries of the cavities and the Mach number are varied; the resultant aeroacoustic behavior and acoustic power are calculated. The numerical results are compared with a single cavity case to highlight the effect of introducing additional cavities to the aeroacoustic problem. Resonant flow oscillations occur when two unconfined cavities are very close and the associated acoustic field is very intense with no noise reduction possible. However, for duct aeroacoustics, it is found that a 7.9 db reduction of acoustic power in the downstream side of the duct or a total reduction of ˜6 db is possible with opposing cavities having an offset of half a cavity length. In addition, the reduction is shown to be free from lock-on with trapped modes of the ducts with cavities.

Visualization of vortex structures and analysis of frequency of PVC

NASA Astrophysics Data System (ADS)

Gesheva, E. S.; Shtork, S. I.; Alekseenko, S. V.

2018-03-01

The paper presents the results of the study of large-scale vortex structures in a model chamber. Methods of forming quasi-stationary vortices of various shapes by changing the geometric parameters of the chamber have been proposed. In the model chamber with a tangential swirl of the flow, a rectilinear vortex, single helical and double helical vortices were obtained. The double helical structure of the vortex is unique due to its immovability around the axis of the chamber. The resulting structures slowly oscillate around their own axes, which is called the vortex core precession; while the oscillation frequency depends linearly on the liquid flow rate. The use of stationary vortex structures in power plants will increase the efficiency of combustion chambers and reduce slagging.

Emergence of power-law scalings in shock-driven mixing transition

NASA Astrophysics Data System (ADS)

Vorobieff, Peter; Wayne, Patrick; Olmstead, Dell; Simons, Dylan; Truman, C. Randall; Kumar, Sanjay

2016-11-01

We present an experimental study of transition to turbulence due to shock-driven instability evolving on an initially cylindrical, diffuse density interface between air and a mixture of sulfur hexafluoride (SF6) and acetone. The plane of the shock is at an initial angle θ with the axis of the heavy-gas cylinder. We present the cases of planar normal (θ = 0) and oblique (θ =20°) shock interaction with the initial conditions. Flow is visualized in two perpendicular planes with planar laser-induced fluorescence (PLIF) triggered in acetone with a pulsed ultraviolet laser. Statistics of the flow are characterized in terms of the second-order structure function of the PLIF intensity. As instabilities in the flow evolve, the structure functions begin to develop power-law scalings, at late times manifesting over a range of scales spanning more than two orders of magnitude. We discuss the effects of the initial conditions on the emergence of these scalings, comparing the fully three-dimensional case (oblique shock interaction) with the quasi-two-dimensional case (planar normal shock interaction). We also discuss the flow anisotropy apparent in statistical differences in data from the two visualization planes. This work is funded by NNSA Grant DE-NA0002913.

Dynamic power flow controllers

DOEpatents

Divan, Deepakraj M.; Prasai, Anish

2017-03-07

Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.

Using Delft3D to Simulate Current Energy Conversion

NASA Astrophysics Data System (ADS)

James, S. C.; Chartrand, C.; Roberts, J.

2015-12-01

As public concern with renewable energy increases, current energy conversion (CEC) technology is being developed to optimize energy output and minimize environmental impact. CEC turbines generate energy from tidal and current systems and create wakes that interact with turbines located downstream of a device. The placement of devices can greatly influence power generation and structural reliability. CECs can also alter the ecosystem process surrounding the turbines, such as flow regimes, sediment dynamics, and water quality. Software is needed to investigate specific CEC sites to simulate power generation and hydrodynamic responses of a flow through a CEC turbine array. This work validates Delft3D against several flume experiments by simulating the power generation and hydrodynamic response of flow through a turbine or actuator disc(s). Model parameters are then calibrated against these data sets to reproduce momentum removal and wake recovery data with 3-D flow simulations. Simulated wake profiles and turbulence intensities compare favorably to the experimental data and demonstrate the utility and accuracy of a fast-running tool for future siting and analysis of CEC arrays in complex domains.

Model-based reasoning for power system management using KATE and the SSM/PMAD

NASA Technical Reports Server (NTRS)

Morris, Robert A.; Gonzalez, Avelino J.; Carreira, Daniel J.; Mckenzie, F. D.; Gann, Brian

1993-01-01

The overall goal of this research effort has been the development of a software system which automates tasks related to monitoring and controlling electrical power distribution in spacecraft electrical power systems. The resulting software system is called the Intelligent Power Controller (IPC). The specific tasks performed by the IPC include continuous monitoring of the flow of power from a source to a set of loads, fast detection of anomalous behavior indicating a fault to one of the components of the distribution systems, generation of diagnosis (explanation) of anomalous behavior, isolation of faulty object from remainder of system, and maintenance of flow of power to critical loads and systems (e.g. life-support) despite fault conditions being present (recovery). The IPC system has evolved out of KATE (Knowledge-based Autonomous Test Engineer), developed at NASA-KSC. KATE consists of a set of software tools for developing and applying structure and behavior models to monitoring, diagnostic, and control applications.

Analysis of spatial and temporal spectra of liquid film surface in annular gas-liquid flow

NASA Astrophysics Data System (ADS)

Alekseenko, Sergey; Cherdantsev, Andrey; Heinz, Oksana; Kharlamov, Sergey; Markovich, Dmitriy

2013-09-01

Wavy structure of liquid film in annular gas-liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

Conversion of evanescent Lamb waves into propagating waves via a narrow aperture edge.

PubMed

Yan, Xiang; Yuan, Fuh-Gwo

2015-06-01

This paper presents a quantitative study of conversion of evanescent Lamb waves into propagating in isotropic plates. The conversion is substantiated by prescribing time-harmonic Lamb displacements/tractions through a narrow aperture at an edge of a semi-infinite plate. Complex-valued dispersion and group velocity curves are employed to characterize the conversion process. The amplitude coefficient of the propagating Lamb modes converted from evanescent is quantified based on the complex reciprocity theorem via a finite element analysis. The power flow generated into the plate can be separated into radiative and reactive parts made on the basis of propagating and evanescent Lamb waves, where propagating Lamb waves are theoretically proved to radiate pure real power flow, and evanescent Lamb waves carry reactive pure imaginary power flow. The propagating power conversion efficiency is then defined to quantitatively describe the conversion. The conversion efficiency is strongly frequency dependent and can be significant. With the converted propagating waves from evanescent, sensors at far-field can recapture some localized damage information that is generally possessed in evanescent waves and may have potential application in structural health monitoring.

Pressure Mapping and Efficiency Analysis of an EPPLER 857 Hydrokinetic Turbine

NASA Astrophysics Data System (ADS)

Clark, Tristan

A conceptual energy ship is presented to provide renewable energy. The ship, driven by the wind, drags a hydrokinetic turbine through the water. The power generated is used to run electrolysis on board, taking the resultant hydrogen back to shore to be used as an energy source. The basin efficiency (Power/thrust*velocity) of the Hydrokinetic Turbine (HTK) plays a vital role in this process. In order to extract the maximum allowable power from the flow, the blades need to be optimized. The structural analysis of the blade is important, as the blade will undergo high pressure loads from the water. A procedure for analysis of a preliminary Hydrokinetic Turbine blade design is developed. The blade was designed by a non-optimized Blade Element Momentum Theory (BEMT) code. Six simulations were run, with varying mesh resolution, turbulence models, and flow region size. The procedure was developed that provides detailed explanation for the entire process, from geometry and mesh generation to post-processing analysis tools. The efficiency results from the simulations are used to study the mesh resolution, flow region size, and turbulence models. The results are compared to the BEMT model design targets. Static pressure maps are created that can be used for structural analysis of the blades.

Compressible turbulent mixing: Effects of Schmidt number.

PubMed

Ni, Qionglin

2015-05-01

We investigated by numerical simulations the effects of Schmidt number on passive scalar transport in forced compressible turbulence. The range of Schmidt number (Sc) was 1/25∼25. In the inertial-convective range the scalar spectrum seemed to obey the k(-5/3) power law. For Sc≫1, there appeared a k(-1) power law in the viscous-convective range, while for Sc≪1, a k(-17/3) power law was identified in the inertial-diffusive range. The scaling constant computed by the mixed third-order structure function of the velocity-scalar increment showed that it grew over Sc, and the effect of compressibility made it smaller than the 4/3 value from incompressible turbulence. At small amplitudes, the probability distribution function (PDF) of scalar fluctuations collapsed to the Gaussian distribution whereas, at large amplitudes, it decayed more quickly than Gaussian. At large scales, the PDF of scalar increment behaved similarly to that of scalar fluctuation. In contrast, at small scales it resembled the PDF of scalar gradient. Furthermore, the scalar dissipation occurring at large magnitudes was found to grow with Sc. Due to low molecular diffusivity, in the Sc≫1 flow the scalar field rolled up and got mixed sufficiently. However, in the Sc≪1 flow the scalar field lost the small-scale structures by high molecular diffusivity and retained only the large-scale, cloudlike structures. The spectral analysis found that the spectral densities of scalar advection and dissipation in both Sc≫1 and Sc≪1 flows probably followed the k(-5/3) scaling. This indicated that in compressible turbulence the processes of advection and dissipation except that of scalar-dilatation coupling might deferring to the Kolmogorov picture. It then showed that at high wave numbers, the magnitudes of spectral coherency in both Sc≫1 and Sc≪1 flows decayed faster than the theoretical prediction of k(-2/3) for incompressible flows. Finally, the comparison with incompressible results showed that the scalar in compressible turbulence with Sc=1 lacked a conspicuous bump structure in its spectrum, but was more intermittent in the dissipative range.

Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

PubMed

Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

2017-05-10

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayakumar, M.; Nie, Zimin; Walter, Eric D.

Redox flow battery (RFB) is a promising candidate for energy storage component in designing resilient grid scale power supply due to the advantage of the separation of power and energy. However, poorly understood chemical and thermal stability issues of electrolytes currently limit the performance of RFB. Designing of high performance stable electrolytes requires comprehensive knowledge about the molecular level solvation structure and dynamics of their redox active species. The molecular level understanding of detrimental V2O5 precipitation process led to successful designing of mixed acid based electrolytes for vanadium redox flow batteries (VRFB). The higher stability of mixed acid based electrolytesmore » is attributed to the choice of hydrochloric acid as optimal co-solvent, which provides chloride anions for ligand exchange process in vanadium solvation structure. The role of chloride counter anion on solvation structure and dynamics of vanadium species were studied using combined magnetic resonance spectroscopy and DFT based theoretical methods. Finally, the solvation phenomenon of multiple vanadium species and their impact on VRFB electrolyte chemical stability were discussed.« less

Impact of Considering 110 kV Grid Structures on the Congestion Management in the German Transmission Grid

NASA Astrophysics Data System (ADS)

Hoffrichter, André; Barrios, Hans; Massmann, Janek; Venkataramanachar, Bhavasagar; Schnettler, Armin

2018-02-01

The structural changes in the European energy system lead to an increase of renewable energy sources that are primarily connected to the distribution grid. Hence the stationary analysis of the transmission grid and the regionalization of generation capacities are strongly influenced by subordinate grid structures. To quantify the impact on the congestion management in the German transmission grid, a 110 kV grid model is derived using publicly available data delivered by Open Street Map and integrated into an existing model of the European transmission grid. Power flow and redispatch simulations are performed for three different regionalization methods and grid configurations. The results show a significant impact of the 110 kV system and prove an overestimation of power flows in the transmission grid when neglecting subordinate grids. Thus, the redispatch volume in Germany to dissolve bottlenecks in case of N-1 contingencies decreases by 38 % when considering the 110 kV grid.

IR-drop analysis for validating power grids and standard cell architectures in sub-10nm node designs

NASA Astrophysics Data System (ADS)

Ban, Yongchan; Wang, Chenchen; Zeng, Jia; Kye, Jongwook

2017-03-01

Since chip performance and power are highly dependent on the operating voltage, the robust power distribution network (PDN) is of utmost importance in designs to provide with the reliable voltage without voltage (IR)-drop. However, rapid increase of parasitic resistance and capacitance (RC) in interconnects makes IR-drop much worse with technology scaling. This paper shows various IR-drop analyses in sub 10nm designs. The major objectives are to validate standard cell architectures, where different sizes of power/ground and metal tracks are validated, and to validate PDN architecture, where types of power hook-up approaches are evaluated with IR-drop calculation. To estimate IR-drops in 10nm and below technologies, we first prepare physically routed designs given standard cell libraries, where we use open RISC RTL, synthesize the CPU, and apply placement & routing with process-design kits (PDK). Then, static and dynamic IR-drop flows are set up with commercial tools. Using the IR-drop flow, we compare standard cell architectures, and analysis impacts on performance, power, and area (PPA) with the previous technology-node designs. With this IR-drop flow, we can optimize the best PDN structure against IR-drops as well as types of standard cell library.

Instabilities in rapid directional solidification under weak flow

NASA Astrophysics Data System (ADS)

Kowal, Katarzyna N.; Davis, Stephen H.; Voorhees, Peter W.

2017-12-01

We examine a rapidly solidifying binary alloy under directional solidification with nonequilibrium interfacial thermodynamics viz. the segregation coefficient and the liquidus slope are speed dependent and attachment-kinetic effects are present. Both of these effects alone give rise to (steady) cellular instabilities, mode S , and a pulsatile instability, mode P . We examine how weak imposed boundary-layer flow of magnitude |V | affects these instabilities. For small |V | , mode S becomes a traveling and the flow stabilizes (destabilizes) the interface for small (large) surface energies. For small |V | , mode P has a critical wave number that shifts from zero to nonzero giving spatial structure. The flow promotes this instability and the frequencies of the complex conjugate pairs each increase (decrease) with flow for large (small) wave numbers. These results are obtained by regular perturbation theory in powers of V far from the point where the neutral curves cross, but requires a modified expansion in powers of V1 /3 near the crossing. A uniform composite expansion is then obtained valid for all small |V | .

Pulsed electromagnetic gas acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1974-01-01

Detailed measurements of the axial velocity profile and electromagnetic structure of a high power, quasi-steady MPD discharge are used to formulate a gasdynamic model of the acceleration process. Conceptually dividing the accelerated plasma into an inner flow and an outer flow, it is found that more than two-thirds of the total power in the plasma is deposited in the inner flow, accelerating it to an exhaust velocity of 12.5 km/sec. The outer flow, which is accelerated to a velocity of only 6.2 km/sec, appears to provide a current conduction path between the inner flow and the anode. Related cathode studies have shown that the critical current for the onset of terminal voltage fluctuations, which was recently shown to be a function of the cathode area, appears to reach an asymptote for cathodes of very large surface area. Detailed floating potential measurements show that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance.

Liquid metal heat sink for high-power laser diodes

NASA Astrophysics Data System (ADS)

Vetrovec, John; Litt, Amardeep S.; Copeland, Drew A.; Junghans, Jeremy; Durkee, Roger

2013-02-01

We report on the development of a novel, ultra-low thermal resistance active heat sink (AHS) for thermal management of high-power laser diodes (HPLD) and other electronic and photonic components. AHS uses a liquid metal coolant flowing at high speed in a miniature closed and sealed loop. The liquid metal coolant receives waste heat from an HPLD at high flux and transfers it at much reduced flux to environment, primary coolant fluid, heat pipe, or structure. Liquid metal flow is maintained electromagnetically without any moving parts. Velocity of liquid metal flow can be controlled electronically, thus allowing for temperature control of HPLD wavelength. This feature also enables operation at a stable wavelength over a broad range of ambient conditions. Results from testing an HPLD cooled by AHS are presented.

Nature of convection-stabilized dc arcs in dual-flow nozzle geometry. I - The cold flow field and dc arc characteristics. II - Optical diagnostics and theory

NASA Astrophysics Data System (ADS)

Serbetci, Ilter; Nagamatsu, H. T.

1990-02-01

Steady-state low-current air arcs in a dual-flow nozzle system are studied experimentally. The cold flow field with no arc is investigated using a 12.7-mm diameter dual-flow nozzle in a steady-flow facility. Mach number and mass flux distributions are determined for various nozzle-pressure ratios and nozzle-gap spacing. It is found that the shock waves in the converging-diverging nozzles result in a decrease in overal resistance by about 15 percent. Also, Schlieren and differential interferometry techniques are used to visualize the density gradients within the arc plasma and thermal mantle. Both optical techniques reveal a laminar arc structure for a reservoir pressure of 1 atm at various current levels. Experimentally determined axial static pressure and cold-flow mass flux rate distributions and a channel-flow model with constant arc temperatre are used to solve the energy integral for the arc radius as a function of axial distance. The arc electric field strength, voltage, resistance, and power are determined with Ohm's law and the total heat transfer is related to arc power.

Intensified depolymerization of aqueous polyacrylamide solution using combined processes based on hydrodynamic cavitation, ozone, ultraviolet light and hydrogen peroxide.

PubMed

Prajapat, Amrutlal L; Gogate, Parag R

2016-07-01

The present work deals with intensification of depolymerization of polyacrylamide (PAM) solution using hydrodynamic cavitation (HC) reactors based on a combination with hydrogen peroxide (H2O2), ozone (O3) and ultraviolet (UV) irradiation. Effect of inlet pressure in hydrodynamic cavitation reactor and power dissipation in the case of UV irradiation on the extent of viscosity reduction has been investigated. The combined approaches such as HC+UV, HC+O3, HC+H2O2, UV+H2O2 and UV+O3 have been subsequently investigated and found to be more efficient as compared to individual approaches. For the approach based on HC+UV+H2O2, the extent of viscosity reduction under the optimized conditions of HC (3 bar inlet pressure)+UV (8 W power)+H2O2 (0.2% loading) was 97.27% in 180 min whereas individual operations of HC (3 bar inlet pressure) and UV (8 W power) resulted in about 35.38% and 40.83% intrinsic viscosity reduction in 180 min respectively. In the case of HC (3 bar inlet pressure)+UV (8 W power)+ozone (400 mg/h flow rate) approach, the extent of viscosity reduction was 89.06% whereas individual processes of only ozone (400 mg/h flow rate), ozone (400 mg/h flow rate)+HC (3 bar inlet pressure) and ozone (400 mg/h flow rate)+UV (8 W power) resulted in lower extent of viscosity reduction as 50.34%, 60.65% and 75.31% respectively. The chemical structure of the treated PAM by all approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant chemical structure changes were obtained during the treatment. Overall, it can be said that the combination of HC+UV+H2O2 is an efficient approach for the depolymerization of PAM solution. Copyright © 2016 Elsevier B.V. All rights reserved.

A computational fluid dynamics modeling study of guide walls for downstream fish passage

USGS Publications Warehouse

Mulligan, Kevin; Towler, Brett; Haro, Alexander J.; Ahlfeld, David P.

2017-01-01

A partial-depth, impermeable guidance structure (or guide wall) for downstream fish passage is typically constructed as a series of panels attached to a floating boom and anchored across a water body (e.g. river channel, reservoir, or power canal). The downstream terminus of the wall is generally located nearby to a fish bypass structure. If guidance is successful, the fish will avoid entrainment in a dangerous intake structure (i.e. turbine intakes) while passing from the headpond to the tailwater of a hydroelectric facility through a safer passage route (i.e. the bypass). The goal of this study is to determine the combination of guide wall design parameters that will most likely increase the chance of surface-oriented fish being successfully guided to the bypass. To evaluate the flow field immediately upstream of a guide wall, a parameterized computational fluid dynamics model of an idealized power canal was constructed in © ANSYS Fluent v 14.5 (ANSYS Inc., 2012). The design parameters investigated were the angle and depth of the guide wall and the average approach velocity in the power canal. Results call attention to the importance of the downward to sweeping flow ratio and demonstrate how a change in guide wall depth and angle can affect this important hydraulic cue to out-migrating fish. The key findings indicate that a guide wall set at a small angle (15° is the minimum in this study) and deep enough such that sweeping flow dominant conditions prevail within the expected vertical distribution of fish approaching the structure will produce hydraulic conditions that are more likely to result in effective passage.

Design and evaluation of a microgrid for PEV charging with flexible distribution of energy sources and storage

NASA Astrophysics Data System (ADS)

Pyne, Moinak

This thesis aspires to model and control, the flow of power in a DC microgrid. Specifically, the energy sources are a photovoltaic system and the utility grid, a lead acid battery based energy storage system and twenty PEV charging stations as the loads. Theoretical principles of large scale state space modeling are applied to model the considerable number of power electronic converters needed for controlling voltage and current thresholds. The energy storage system is developed using principles of neural networks to facilitate a stable and uncomplicated model of the lead acid battery. Power flow control is structured as a hierarchical problem with multiple interactions between individual components of the microgrid. The implementation is done using fuzzy logic with scheduling the maximum use of available solar energy and compensating demand or excess power with the energy storage system, and minimizing utility grid use, while providing multiple speeds of charging the PEVs.

Wind and solar powered turbine

NASA Technical Reports Server (NTRS)

Wells, I. D.; Koh, J. L.; Holmes, M. (Inventor)

1984-01-01

A power generating station having a generator driven by solar heat assisted ambient wind is described. A first plurality of radially extendng air passages direct ambient wind to a radial flow wind turbine disposed in a centrally located opening in a substantially disc-shaped structure. A solar radiation collecting surface having black bodies is disposed above the fist plurality of air passages and in communication with a second plurality of radial air passages. A cover plate enclosing the second plurality of radial air passages is transparent so as to permit solar radiation to effectively reach the black bodies. The second plurality of air passages direct ambient wind and thermal updrafts generated by the black bodies to an axial flow turbine. The rotating shaft of the turbines drive the generator. The solar and wind drien power generating system operates in electrical cogeneration mode with a fuel powered prime mover.

Capillarics: pre-programmed, self-powered microfluidic circuits built from capillary elements.

PubMed

Safavieh, Roozbeh; Juncker, David

2013-11-07

Microfluidic capillary systems employ surface tension effects to manipulate liquids, and are thus self-powered and self-regulated as liquid handling is structurally and chemically encoded in microscale conduits. However, capillary systems have been limited to perform simple fluidic operations. Here, we introduce complex capillary flow circuits that encode sequential flow of multiple liquids with distinct flow rates and flow reversal. We first introduce two novel microfluidic capillary elements including (i) retention burst valves and (ii) robust low aspect ratio trigger valves. These elements are combined with flow resistors, capillary retention valves, capillary pumps, and open and closed reservoirs to build a capillary circuit that, following sample addition, autonomously delivers a defined sequence of multiple chemicals according to a preprogrammed and predetermined flow rate and time. Such a circuit was used to measure the concentration of C-reactive protein. This work illustrates that as in electronics, complex capillary circuits may be built by combining simple capillary elements. We define such circuits as "capillarics", and introduce symbolic representations. We believe that more complex circuits will become possible by expanding the library of building elements and formulating abstract design rules.

Characterization of Flow Dynamics and Reduced-Order Description of Experimental Two-Phase Pipe Flow

NASA Astrophysics Data System (ADS)

Viggiano, Bianca; SkjæRaasen, Olaf; Tutkun, Murat; Cal, Raul Bayoan

2017-11-01

Multiphase pipe flow is investigated using proper orthogonal decomposition for tomographic X-ray data, where holdup, cross sectional phase distributions and phase interface characteristics are obtained. Instantaneous phase fractions of dispersed flow and slug flow are analyzed and a reduced order dynamical description is generated. The dispersed flow displays coherent structures in the first few modes near the horizontal center of the pipe, representing the liquid-liquid interface location while the slug flow case shows coherent structures that correspond to the cyclical formation and breakup of the slug in the first 10 modes. The reconstruction of the fields indicate that main features are observed in the low order dynamical descriptions utilizing less than 1 % of the full order model. POD temporal coefficients a1, a2 and a3 show interdependence for the slug flow case. The coefficients also describe the phase fraction holdup as a function of time for both dispersed and slug flow. These flows are highly applicable to petroleum transport pipelines, hydroelectric power and heat exchanger tubes to name a few. The mathematical representations obtained via proper orthogonal decomposition will deepen the understanding of fundamental multiphase flow characteristics.

Energy distributions in rods and beams

NASA Technical Reports Server (NTRS)

Wohlever, J. C.; Bernhard, R. J.

1989-01-01

A hypothesis proposed by Nefske and Sung (1987) that the mechanical energy flow in acoustic/structural systems can be modeled using a thermal energy flow analogy was tested for both longitudinal vibration in rods and transverse flexural vibrations in beams. It was found that the rod behaves according to the energy flow analogy. However, the beam solutions behaved significantly differently than predicted by the thermal analogy, unless spatially averaged energy and power flow were considered. Otherwise, the beam analysis is restricted to frequencies where the near-field terms in the displacement solution are negligible over most of the beam.

Thermal convection of liquid metal in the titanium reduction reactor

NASA Astrophysics Data System (ADS)

Teimurazov, A.; Frick, P.; Stefani, F.

2017-06-01

The structure of the convective flow of molten magnesium in a metallothermic titanium reduction reactor has been studied numerically in a three-dimensional non-stationary formulation with conjugated heat transfer between liquid magnesium and solids (steel walls of the cavity and titanium block). A nonuniform computational mesh with a total of 3.7 million grid points was used. The Large Eddy Simulation technique was applied to take into account the turbulence in the liquid phase. The instantaneous and average characteristics of the process and the velocity and temperature pulsation fields are analyzed. The simulations have been performed for three specific heating regimes: with furnace heaters operating at full power, with furnace heaters switched on at the bottom of the vessel only, and with switched-off furnace heaters. It is shown that the localization of the cooling zone can completely reorganize the structure of the large-scale flow. Therefore, by changing heating regimes, it is possible to influence the flow structure for the purpose of creating the most favorable conditions for the reaction. It is also shown that the presence of the titanium block strongly affects the flow structure.

Statistical assessment of optical phase fluctuations through turbulent mixing layers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.

1995-09-01

A lateral shearing interferometer is used to measure the slope of perturbed wavefronts after propagating through turbulent shear flows. This provides a two-dimensional flow visualization technique which is nonintrusive. The slope measurements are used to reconstruct the phase of the turbulence-corrupted wave front. Experiments were performed on a plane shear mixing layer of helium and nitrogen gas at fixed velocities, for five locations in the flow development. The two gases, having a density ratio of approximately seven, provide an effective means of simulating compressible shear layers. Statistical autocorrelation functions and structure functions are computed on the reconstructed phase maps. The autocorrelation function results indicate that the turbulence-induced phase fluctuations are not wide-sense stationary. The structure functions exhibit statistical homogeneity, indicating the phase fluctuation are stationary in first increments. However, the turbulence-corrupted phase is not isotropic. A five-thirds power law is shown to fit one-dimensional, orthogonal slices of the structure function, with scaling coefficients related to the location in the flow.

Power module assembly with reduced inductance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Terence G.; Stancu, Constantin C.; Jaksic, Marko

A power module assembly has a plurality of electrically conducting layers, including a first layer and a third layer. One or more electrically insulating layers are operatively connected to each of the plurality of electrically conducting layers. The electrically insulating layers include a second layer positioned between and configured to electrically isolate the first and the third layers. The first layer is configured to carry a first current flowing in a first direction. The third layer is configured to carry a second current flowing in a second direction opposite to the first direction, thereby reducing an inductance of the assembly.more » The electrically insulating layers may include a fourth layer positioned between and configured to electrically isolate the third layer and a fifth layer. The assembly results in a combined substrate and heat sink structure. The assembly eliminates the requirements for connections between separate substrate and heat sink structures.« less

Investigation of Structure/Fluid Interaction in Piping Systems Using an Intensity Measurement Approach.

DTIC Science & Technology

1987-07-01

of vibrational power flow had been considered by experiments in the area of statistical energy analysis (SEA)8, 9 using other measurement ipproaches...Constants in Statistical Energy Analysis of Structure," J. Acoust. Soc. Am. Vol. 52, No. 2, pp. 516-524 (1973) 9. Fahy, F. and R. Pierri, "Application of

Fault-tolerant continuous flow systems modelling

NASA Astrophysics Data System (ADS)

Tolbi, B.; Tebbikh, H.; Alla, H.

2017-01-01

This paper presents a structural modelling of faults with hybrid Petri nets (HPNs) for the analysis of a particular class of hybrid dynamic systems, continuous flow systems. HPNs are first used for the behavioural description of continuous flow systems without faults. Then, faults' modelling is considered using a structural method without having to rebuild the model to new. A translation method is given in hierarchical way, it gives a hybrid automata (HA) from an elementary HPN. This translation preserves the behavioural semantics (timed bisimilarity), and reflects the temporal behaviour by giving semantics for each model in terms of timed transition systems. Thus, advantages of the power modelling of HPNs and the analysis ability of HA are taken. A simple example is used to illustrate the ideas.

Measurement and Analysis of Structural Integrity of Reactor Core Support Structure in Pressurized Water Reactor (PWR) Plant

NASA Astrophysics Data System (ADS)

Ansari, Saleem A.; Haroon, Muhammad; Rashid, Atif; Kazmi, Zafar

2017-02-01

Extensive calculation and measurements of flow-induced vibrations (FIV) of reactor internals were made in a PWR plant to assess the structural integrity of reactor core support structure against coolant flow. The work was done to meet the requirements of the Fukushima Response Action Plan (FRAP) for enhancement of reactor safety, and the regulatory guide RG-1.20. For the core surveillance measurements the Reactor Internals Vibration Monitoring System (IVMS) has been developed based on detailed neutron noise analysis of the flux signals from the four ex-core neutron detectors. The natural frequencies, displacement and mode shapes of the reactor core barrel (CB) motion were determined with the help of IVMS. The random pressure fluctuations in reactor coolant flow due to turbulence force have been identified as the predominant cause of beam-mode deflection of CB. The dynamic FIV calculations were also made to supplement the core surveillance measurements. The calculational package employed the computational fluid dynamics, mode shape analysis, calculation of power spectral densities of flow & pressure fields and the structural response to random flow excitation forces. The dynamic loads and stiffness of the Hold-Down Spring that keeps the core structure in position against upward coolant thrust were also determined by noise measurements. Also, the boron concentration in primary coolant at any time of the core cycle has been determined with the IVMS.

Dynamic Response of an Energy Harvesting Device Under Realistic Flow Conditions

NASA Astrophysics Data System (ADS)

O'Connor, Joseph; Revell, Alistair

2017-11-01

The need for reliable, cost-efficient, green energy alternatives has led to increased research in the area of energy harvesting. One approach to energy harvesting is to take advantage of self-sustaining flow-induced vibrations. Through the use of a piezoelectric flag, the mechanical strain from the flapping motion can be converted into electrical energy. While such devices show a lot of promise, the fluid-structure-electrical interactions are highly nonlinear and their response to off-design variations in flow conditions, such as those likely to be encountered upon deployment, is relatively unexplored. The purpose of the present work is to examine how a representative energy harvesting device performs in realistic atmospheric flow conditions involving wind gusts with spatial and temporal variations. A recently developed lattice-Boltzmann-immersed boundary-finite element model is used to perform fully-coupled 3D simulations of the fluid-structure system. For a range of unsteady flow conditions the resulting flow features and structural motion are examined and key behaviour modes are mapped out. The findings of this work will be particularly relevant for self-powered remote sensing networks, which often require deployment in unpredictable and varied environments.

Automated structure and flow measurement - a promising tool in nailfold capillaroscopy.

PubMed

Berks, Michael; Dinsdale, Graham; Murray, Andrea; Moore, Tonia; Manning, Joanne; Taylor, Chris; Herrick, Ariane L

2018-07-01

Despite increasing interest in nailfold capillaroscopy, objective measures of capillary structure and blood flow have been little studied. We aimed to test the hypothesis that structural measurements, capillary flow, and a combined measure have the predictive power to separate patients with systemic sclerosis (SSc) from those with primary Raynaud's phenomenon (PRP) and healthy controls (HC). 50 patients with SSc, 12 with PRP, and 50 HC were imaged using a novel capillaroscopy system that generates high-quality nailfold images and provides fully-automated measurements of capillary structure and blood flow (capillary density, mean width, maximum width, shape score, derangement and mean flow velocity). Population statistics summarise the differences between the three groups. Areas under ROC curves (A Z ) were used to measure classification accuracy when assigning individuals to SSc and HC/PRP groups. Statistically significant differences in group means were found between patients with SSc and both HC and patients with PRP, for all measurements, e.g. mean width (μm) ± SE: 15.0 ± 0.71, 12.7 ± 0.74 and 11.8 ± 0.23 for SSc, PRP and HC respectively. Combining the five structural measurements gave better classification (A Z  = 0.919 ± 0.026) than the best single measurement (mean width, A Z  = 0.874 ± 0.043), whilst adding flow further improved classification (A Z  = 0.930 ± 0.024). Structural and blood flow measurements are both able to distinguish patients with SSc from those with PRP/HC. Importantly, these hold promise as clinical trial outcome measures for treatments aimed at improving finger blood flow or microvascular remodelling. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

An Investigation of Chaotic Kolmogorov Flows

DTIC Science & Technology

1990-08-01

plane for the Poincare sections used later. The choice of the constant D controls apparent positioning of the hyperplane in the phase...discovered in large scale structure regime. Features of the diverse cases are displayed in terms of the temporal power spectrum, Poincare sections and...examine in some detail the behavior of the flow and its transition states for a range of the bifurcation parameter Re. We use Poincare sections to

On the efficiency of jet production in FR II radio galaxies and quasars

NASA Astrophysics Data System (ADS)

Rusinek, Katarzyna; Sikora, Marek; Kozieł-Wierzbowska, Dorota; Godfrey, Leith

2017-04-01

Jet powers in many radio galaxies with extended radio structures appear to exceed their associated accretion luminosities. In systems with very low accretion rates, this is likely due to the very low accretion luminosities resulting from radiatively inefficient accretion flows. In systems with high accretion rates, the accretion flows are expected to be radiatively efficient, and the production of such powerful jets may require an accretion scenario, which involves magnetically arrested discs (MADs). However, numerical simulations of the MAD scenario indicate that jet production efficiency is large only for geometrically thick accretion flows and scales roughly with (H/R)2, where H is the disc height and R is the distance from the black hole. Using samples of FR II radio galaxies and quasars accreting at moderate accretion rates, we show that their jets are much more powerful than predicted by the MAD scenario. We discuss possible origins of this discrepancy, suggesting that it can be related to approximations adopted in magnetohydrodynamic simulations to treat optically thick accretion flow within the MAD zone, or may indicate that accretion discs are geometrically thicker than the standard theory predicts.

Heat transfer and oil flow studies on a single-stage-to-orbit control-configured winged entry vehicle

NASA Technical Reports Server (NTRS)

Helms, V. T., III; Bradley, P. F.

1984-01-01

Results are presented for oil flow and phase change paint heat transfer tests conducted on a 0.006 scale model of a proposed single stage to orbit control configured vehicle. The data were taken at angles of attack up to 40 deg at a free stream Mach number of 10 for Reynolds numbers based on model length of 0.5 x 10 to the 6th power, 1.0 x 10 to the 6th power and 2.0 x 10 to the 6th power. The magnitude and distribution of heating are characterized in terms of angle of attack and Reynolds number aided by an analysis of the flow data which are used to suggest the presence of various three dimensional flow structures that produce the observed heating patterns. Of particular interest are streak heating patterns that result in high localized heat transfer rates on the wing windward surface at low to moderate angles of attack. These streaks are caused by the bow-shock/wing-shock interaction and formation of the wing-shock. Embedded vorticity was found to be associated with these interactions.

Fundamental investigation of ARC interruption in gas flows

NASA Astrophysics Data System (ADS)

Benenson, D. M.; Frind, G.; Kinsinger, R. E.; Nagamatsu, H. T.; Noeske, H. O.; Sheer, R. E., Jr.

1980-07-01

Thermal recovery in gas blast interrupters is discussed. The thermal recovery process was investigated with physical and aerodynamic methods, typically using reduced size nozzles and short sinusoidal current pulses. Aerodynamic characterization of the cold flow fields in several different nozzle types included measurements of the pressure and flow fields, both steady-state and turbulent components, with special attention given to wakes and shock structures. Special schlieren techniques on DC arcs and high speed photography on arcs in orifice nozzles show that shock heating broadens the arc independent of turbulence effects and produces a poorly recovering downstream arc section. Measured recovery speeds in both orifice and convergent-divergent nozzles agree with predictions of several arc theories assuming turbulent power losses. However, data on post-zero currents and power loss show values much smaller than theoretical predictions. Hydrogen, deuterium, and methane were measured.

Diagnostic value of high-resolution B-mode and power-mode sonography in the follow-up of thyroid cancer.

PubMed

Görges, Rainer; Eising, E G; Fotescu, D; Renzing-Köhler, K; Frilling, A; Schmid, K W; Bockisch, A; Dirsch, O

2003-02-01

Ultrasonography is an established diagnostic modality in the follow-up of thyroid cancer. Color flow Doppler has been proposed by some authors as an additional tool for differentiating benign from malignant cervical lesions in various types of head and neck cancer. Over the last few years, a new generation of high-resolution ultrasound platforms with the "power-mode" feature has become available, that also enables the imaging of small vessel blood flow. The objective of our study was to find ways of optimizing the differentiation of benign and malignant cervical tumors in thyroid cancer follow-up by means of sonography. Hundred and twelve cervical lesions in 90 patients with thyroid cancer were evaluated by high-end ultrasonography (Sonoline Elegra, Siemens) using a small-part transducer (7.5 L 40, Siemens). B-mode sonography was performed at a frequency of 8 MHz. The Solbiati index (SI= ratio of largest to smallest diameter), configuration, echogenicity, intranodular structures, and margins were assessed. Perinodular and intranodular blood flow was evaluated by color flow Doppler (PRF 1250 Hz for conventional color flow Doppler, 868 Hz for power-mode Doppler). Possible malignancy was validated by histology, cytology, scintigraphy, and follow-up. Thirty five lesions were benign (diameter 0.4-3.0 cm) and 77 were malignant (0.4-5.4 cm). The patients were randomized into a test group and a learning group to determine the diagnostic value of various ultrasound criteria by means of statistical analysis. In the learning group, decision rules based on the dichotomized criteria were developed using a logistic regression model. Sensitivity and specificity of these decision rules were then evaluated in the test group. The presence of an echocomplex pattern or irregular hyperechoic small intranodular structures (criterion A) and the presence of an irregular diffuse intranodular blood flow (criterion B) are the best indicators of malignancy, whereas an SI >2 is highly indicative of benign changes. Color flow Doppler is a useful addition to B-mode scanning for distinguishing benign and malignant neoplasms in the follow-up of thyroid cancer. Power-mode Doppler sonography significantly improves imaging of perinodular and intranodular blood flow when compared with conventional color flow Doppler. We propose the following decision rules based on a combination of the criteria above: (A) and (B) fulfilled: malignant, if SI< or =4; (B) but not (A) fulfilled: malignant, if SI< or =3; (A) but not (B) fulfilled: malignant, if SI< or =2; neither (A) nor (B) fulfilled: malignant, if SI approximately equal to 1 (sensitivity: 90%; specificity: 82%; accuracy 88%).

Continuation Power Flow with Variable-Step Variable-Order Nonlinear Predictor

NASA Astrophysics Data System (ADS)

Kojima, Takayuki; Mori, Hiroyuki

This paper proposes a new continuation power flow calculation method for drawing a P-V curve in power systems. The continuation power flow calculation successively evaluates power flow solutions through changing a specified value of the power flow calculation. In recent years, power system operators are quite concerned with voltage instability due to the appearance of deregulated and competitive power markets. The continuation power flow calculation plays an important role to understand the load characteristics in a sense of static voltage instability. In this paper, a new continuation power flow with a variable-step variable-order (VSVO) nonlinear predictor is proposed. The proposed method evaluates optimal predicted points confirming with the feature of P-V curves. The proposed method is successfully applied to IEEE 118-bus and IEEE 300-bus systems.

On the Feedback Phenomenon of an Impinging Jet

DTIC Science & Technology

1979-09-01

the double-structured nature of turbulent flows: time dependent quasi- ordered large scale structures, and fine-scale random structures. Numerous ...downstream and upstream waves d Nozzle diameter f Frequency (Hz) Gf Normalized power si.c ,ur’ of i G ,(f) Normalized cr,- tr bee -en i(t) and J(t) I ,j xiv...1975) suggested that these quasi- ordered structures are deterministic, in the sense that they have a characteristic shape, size and convection motion

FLOWS AND WAVES IN BRAIDED SOLAR CORONAL MAGNETIC STRUCTURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pant, V.; Datta, A.; Banerjee, D., E-mail: vaibhav@iiap.res.in

We study the high frequency dynamics in the braided magnetic structure of an active region (AR 11520) moss as observed by the High-Resolution Coronal Imager (Hi-C). We detect quasi-periodic flows and waves in these structures. We search for high frequency dynamics while looking at power maps of the observed region. We find that shorter periodicities (30–60 s) are associated with small spatial scales which can be resolved by Hi-C only. We detect quasi-periodic flows with a wide range of velocities, from 13–185 km s{sup −1}, associated with braided regions. This can be interpreted as plasma outflows from reconnection sites. Wemore » also find short period and large amplitude transverse oscillations associated with the braided magnetic region. Such oscillations could be triggered by reconnection or such oscillations may trigger reconnection.« less

Industrial application of ultrasound based in-line rheometry: From stationary to pulsating pipe flow of chocolate suspension in precrystallization process

NASA Astrophysics Data System (ADS)

Ouriev, Boris; Windhab, Erich; Braun, Peter; Birkhofer, Beat

2004-10-01

In-line visualization and on-line characterization of nontransparent fluids becomes an important subject for process development in food and nonfood industries. In our work, a noninvasive Doppler ultrasound-based technique is introduced. Such a technique is applied for investigation of nonstationary flow in the chocolate precrystallization process. Unstable flow conditions were induced by abrupt flow interruption and were followed up by strong flow pulsations in the piping system. While relying on available process information, such as absolute pressures and temperatures, no analyses of flow conditions or characterization of suspension properties could possibly be done. It is obvious that chocolate flow properties are sensitive to flow boundary conditions. Therefore, it becomes essential to perform reliable structure state monitoring and particularly in application to nonstationary flow processes. Such flow instabilities in chocolate processing can often lead to failed product quality with interruption of the mainstream production. As will be discussed, a combination of flow velocity profiles, on-line fit into flow profiles, and pressure difference measurement are sufficient for reliable analyses of fluid properties and flow boundary conditions as well as monitoring of the flow state. Analyses of the flow state and flow properties of chocolate suspension are based on on-line measurement of one-dimensional velocity profiles across the flow channel and their on-line characterization with the power-law model. Conclusions about flow boundary conditions were drawn from a calculated velocity standard mean deviation, the parameters of power-law fit into velocity profiles, and volumetric flow rate information.

A review of progress and challenges in flapping foil power generation

NASA Astrophysics Data System (ADS)

Young, John; Lai, Joseph C. S.; Platzer, Max F.

2014-05-01

Power may be extracted from a flowing fluid in a variety of ways. Turbines using one or more oscillating foils are under increasingly active investigation, as an alternative to rotary wind turbines and river, oceanic and tidal current water turbines, although industrial development is at a very nascent stage. Such flapping foil turbines promise some key potential advantages, including lower foil velocities (and hence lower noise and wildlife impact), and more effective small-scale and shallow water operation. The role of a number of parameters is investigated, including foil kinematics (modes, frequencies, amplitudes and time histories of motion), foil and system geometry (shape, configuration and structural flexibility), and flow physics effects (Reynolds number and turbulence, shear flows and ground effect). Details of the kinematics are shown to have the single largest influence on power output and efficiency (measured as the ratio of power output to that available and accessible in the fluid stream). The highest levels of power and efficiency are associated with very large foil pitch angles (upwards of 70°) and angles of attack (30-40°), such that the flow is massively separated for much of the flapping cycle, in contrast to rotary turbines which rely on attached flow over as much of the rotor disk as possible. This leads to leading edge vortices comparable in size to the foil chord, and the evolution and interaction of these vortices with the foil as it moves play a central role in determining performance. The other parameters also influence the vortex behaviour, but in general to a lesser degree. Numerous gaps in the research literature and outstanding issues are highlighted.

Investigation on heat transfer analysis and its effect on a multi-mode, beam-wave interaction for a 140 GHz, MW-class gyrotron

NASA Astrophysics Data System (ADS)

Liu, Qiao; Liu, Yinghui; Chen, Zhaowei; Niu, Xinjian; Li, Hongfu; Xu, Jianhua

2018-04-01

The interaction cavity of a 140 GHz, 1 MW continuous wave gyrotron developed in UESTC will be loaded with a very large heat load in the inner surface during operation. In order to reduce the heat, the axial wedge grooves of the outside surface of the cavity are considered and employed as the heat radiation structure. Thermoanalysis and structural analysis were discussed in detail to obtain the effects of heat on the cavity. In thermoanalysis, the external coolant-flow rates ranging from 20 L/min to 50 L/min were considered, and the distribution of wall loading was loaded as the heat flux source. In structural analysis, the cavity's deformation caused by the loads of heat and pressure was calculated. Compared with a non-deformed cavity, the effects of deformation on the performance of a cavity were discussed. For a cold-cavity, the results show that the quality factor would be reduced by 72, 89, 99 and 171 at the flow rates of 50 L/min, 40 L/min, 30 L/min and 20 L/min, respectively. Correspondingly, the cold-cavity frequencies would be decreased by 0.13 GHz, 0.15 GHz, 0.19 GHz and 0.38 GHz, respectively. For a hot-cavity, the results demonstrate that the output port frequencies would be dropped down, but the offset would be gradually decreased with increasing coolant-flow rate. Meanwhile, the output powers would be reduced dramatically with decreasing coolant-flow rate. In addition, when the coolant-flow rate reaches 40 L/min, the output power and the frequency are just reduced by 30 kW and 0.151 GHz, respectively.

The harmonic oscillator and nuclear physics

NASA Technical Reports Server (NTRS)

Rowe, D. J.

1993-01-01

The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.

75 FR 20589 - City of Oberlin, OH; Free Flow Power Missouri 1, LLC; Notice of Competing Preliminary Permit...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-20

... chambers. Oberlin's proposed project would consist of: (1) A new 155-foot- wide, 71-foot-tall water intake structure; (2) a new 155-foot-wide, 189-foot-long powerhouse containing three turbine generating units with...) A new 225- foot-wide, 50-foot-long water intake structure equipped with trashracks, sluice gates...

Evidence of sublaminar drag naturally occurring in a curved pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noorani, A.; Schlatter, P., E-mail: pschlatt@mech.kth.se

Steady and unsteady flows in a mildly curved pipe for a wide range of Reynolds numbers are examined with direct numerical simulation. It is shown that in a range of Reynolds numbers in the vicinity of Re{sub b} ≈ 3400, based on bulk velocity and pipe diameter, a marginally turbulent flow is established in which the friction drag naturally reduces below the laminar solution at the same Reynolds number. The obtained values for friction drag for the laminar and turbulent (sublaminar) flows turn out to be in excellent agreement with experimental measurements in the literature. Our results are also inmore » agreement with Fukagata et al. [“On the lower bound of net driving power in controlled duct flows,” Phys. D 238, 1082 (2009)], as the lower bound of net power required to drive the flow, i.e., the pressure drop of the Stokes solution, is still lower than our marginally turbulent flow. A large-scale traveling structure that is thought to be responsible for that behaviour is identified in the instantaneous field. This mode could also be extracted using proper orthogonal decomposition. The effect of this mode is to redistribute the mean flow in the circular cross section which leads to lower gradients at the wall compared to the laminar flow.« less

Evidence of sublaminar drag naturally occurring in a curved pipe

NASA Astrophysics Data System (ADS)

Noorani, A.; Schlatter, P.

2015-03-01

Steady and unsteady flows in a mildly curved pipe for a wide range of Reynolds numbers are examined with direct numerical simulation. It is shown that in a range of Reynolds numbers in the vicinity of Reb ≈ 3400, based on bulk velocity and pipe diameter, a marginally turbulent flow is established in which the friction drag naturally reduces below the laminar solution at the same Reynolds number. The obtained values for friction drag for the laminar and turbulent (sublaminar) flows turn out to be in excellent agreement with experimental measurements in the literature. Our results are also in agreement with Fukagata et al. ["On the lower bound of net driving power in controlled duct flows," Phys. D 238, 1082 (2009)], as the lower bound of net power required to drive the flow, i.e., the pressure drop of the Stokes solution, is still lower than our marginally turbulent flow. A large-scale traveling structure that is thought to be responsible for that behaviour is identified in the instantaneous field. This mode could also be extracted using proper orthogonal decomposition. The effect of this mode is to redistribute the mean flow in the circular cross section which leads to lower gradients at the wall compared to the laminar flow.

Concentration Measurements in Self-Excited, Momentum-Dominated Helium Jets

NASA Technical Reports Server (NTRS)

Yildirim, Bekir Sedat

2004-01-01

Flow structure of momentum-dominated pure helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry (RSD) technique. Effects of the operating parameters, i.e., Reynolds number (Re) and Richardson number (Ri), on the oscillatory behavior of the flow were examined over a range of experimental conditions. To seek the individual effect of these parameters, one of them was fixed and the other was varied with certain constraints. Measurements revealed highly periodic oscillations in the laminar region as well as high regularity in transition and turbulent regions. Maximum spectral power profiles at different axial locations indicated the oscillation amplitude increasing until the breakdown of the jet in the turbulent regime. The transition from the laminar to turbulent flow was also investigated. Fast Fourier transform analysis performed in the transition regime showed that the flow oscillates at a unique frequency, which was the same in the upstream laminar flow region. Measured deflection angle data were used in Abel inversion algorithm to construct the helium concentration fields. Instantaneous helium concentration contours revealed changes in the flow structure and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial location showed repeatable oscillations at all axial and radial locations up to the turbulent regime. A cross-correlation technique, applied to find the spatial displacements of the vortical structures, provided correlation coefficient peaks between consecutive schlieren images. Results show that the vortical structure convected and accelerated only in the axial direction.

Multi-scale evaporator architectures for geothermal binary power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabau, Adrian S; Nejad, Ali; Klett, James William

2016-01-01

In this paper, novel geometries of heat exchanger architectures are proposed for evaporators that are used in Organic Rankine Cycles. A multi-scale heat exchanger concept was developed by employing successive plenums at several length-scale levels. Flow passages contain features at both macro-scale and micro-scale, which are designed from Constructal Theory principles. Aside from pumping power and overall thermal resistance, several factors were considered in order to fully assess the performance of the new heat exchangers, such as weight of metal structures, surface area per unit volume, and total footprint. Component simulations based on laminar flow correlations for supercritical R134a weremore » used to obtain performance indicators.« less

Experimental measurement of structural power flow on an aircraft fuselage

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.

1989-01-01

An experimental technique is used to measure the structural power flow through an aircraft fuselage with the excitation near the wing attachment location. Because of the large number of measurements required to analyze the whole of an aircraft fuselage, it is necessary that a balance be achieved between the number of measurement transducers, the mounting of these transducers, and the accuracy of the measurements. Using four transducers mounted on a bakelite platform, the structural intensity vectors at locations distributed throughout the fuselage are measured. To minimize the errors associated with using a four transducers technique the measurement positions are selected away from bulkheads and stiffeners. Because four separate transducers are used, with each transducer having its own drive and conditioning amplifiers, phase errors are introduced in the measurements that can be much greater than the phase differences associated with the measurements. To minimize these phase errors two sets of measurements are taken for each position with the orientation of the transducers rotated by 180 deg and an average taken between the two sets of measurements. Results are presented and discussed.

Method and apparatus for optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

DOEpatents

Nelson, John Stuart; Milner, Thomas Edward; Chen, Zhongping

1999-01-01

Optical Doppler tomography permits imaging of fluid flow velocity in highly scattering media. The tomography system combines Doppler velocimetry with high spatial resolution of partially coherent optical interferometry to measure fluid flow velocity at discrete spatial locations. Noninvasive in vivo imaging of blood flow dynamics and tissue structures with high spatial resolutions of the order of 2 to 10 microns is achieved in biological systems. The backscattered interference signals derived from the interferometer may be analyzed either through power spectrum determination to obtain the position and velocity of each particle in the fluid flow sample at each pixel, or the interference spectral density may be analyzed at each frequency in the spectrum to obtain the positions and velocities of the particles in a cross-section to which the interference spectral density corresponds. The realized resolutions of optical Doppler tomography allows noninvasive in vivo imaging of both blood microcirculation and tissue structure surrounding the vessel which has significance for biomedical research and clinical applications.

Self-organization, preferential flow and rainfall runoff behavior - is there a connection?

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Blume, Theresa; Kleidon, Axel; Ehret, Uwe; Scherer, Ulrike; Westhoff, Martijn

2013-04-01

In line with the studies of Kleidon et al. (2012) and Zehe et al. (2010) the proposed study analyzes mass flow related flows of free energy in open hydrological systems - hillslopes and small catchments - using thermodynamics methods. Why a thermodynamic treatment? A small part of the kinetic energy input from incoming rainfall is dissipated into heat and to break up soil aggregates. Depending on the partitioning of the incoming rainfall into overland flow and soil water, the remaining part of the incoming kinetic energy is partly transformed into potential energy of surface water and subsequently partly exported as kinetic energy of overland flow from the system; the rest is dissipated by frictional losses. The other part of rainfall infiltrates thereby increasing potential energy of soil water but depleting at the same time (gradients in) capillary binding energy of soil water, which again comprises energy dissipation into heat of immersion. Although, these mass fluxes are not associated with large heat fluxes, they reflect the overall conservation of energy as well as the second law of thermodynamics. They require thus a thermodynamic treatment, because tiny amounts of kinetic energy, surface energy and potential energy are dissipated into heat: this implies irreversibility and explains why water does not flow uphill. Soil hydraulic equilibrium (HE), arising from a balance in potential and capillary binding energy in soil, can be interpreted as a state of maximum entropy in soil. Soil water potential, defined as sum of matric potential and gravity potential, is in HE equal to zero along the soil profile. This corresponds to a state of maximum entropy due to a zero potential gradient, which implies due to Zehe et al. (2010) a state of minimum (Helmholtz) free energy. Our first main objective is to quantify to which extent connected preferential flow path, in our case vertical macropores and the river network enhance flow velocities at a given driving gradient and thus power in the associated mass fluxes. This implies either an enhanced export of free energy in form of kinetic energy in case of the river net, or an accelerated reduction of potential energy of infiltrating surface water which implies a reduction free energy in form of capillary binding energy of soil water. We hypothesize (H1) that network like structures act as dissipative structures "serving the purpose" of reducing the relaxation time to a state of lower "free" energy in the entire system. This is because they minimize dissipative losses of kinetic energy along their extent. This faster relaxation towards a state of smaller free energy is deemed to be favorable for mechanic stability of the entire hydrological system because a) mass flows perform due to the enhanced export of kinetic energy less work on the system itself and b) mechanical stress from ponded surface water is quickly reduced by fast infiltration and preferential flow. Our second main objective is, in line with the study of Zehe et al. (2010), the search for thermodynamic optimal hillslope architectures both with respect to the surface density of vertical macropores in soil and with respect to the spatial arrangement of soil types and macropores at the hillslope scale. In line with H1 we suggest (H2) that a hydro-geo-ecosystem is closer to a functional optimum than other possible configurations if it dissipates and exports more of the kinetic energy input from incoming rainfall by redistributing water against internal gradients and exporting water against macroscale geo-potential gradients. Note that H2 does not postulate that functionally optimal hillslope architectures necessarily exist, if they exist H2 implies however that they maximize entropy production and thus reduction of total free energy of the system at a "wisely" selected time scale. The surface density of apparent macropores does for instance control the tradeoff between Hortonian overland flow formation and infiltration, which implies a tradeoff between the amount of kinetic energy input from rainfall that is converted in to power associated with overland flow and power associated with soil water flows depleting gradients in soil water potential. Does this tradeoff imply an optimum surface density of macropores at the hillslope scale in the sense that power in soil water flow is maximized or reduction of free energy is maximized? In case such an optimum hillslope architecture existed, and in case that the evolution of the hydrological systems of interested was indeed in accordance with hypothesis H2, this optimal architecture should allow an acceptable uncalibrated simulation of the systems rainfall -runoff behavior (if the selected model structure can properly represent this architecture). We will address these questions and test the main implications of our hypotheses by means of numerical experiments with the physically based hydrological model CATFLOW. We use behavioral model structures as basic model setup, which have been shown to closely portray system behavior and its architecture in a sense that they reproduce distributed observations of soil moisture and catchment scale discharge and represent the observed structural and textural signatures of soils, flow networks and vegetation. Our test areas are the Weiherbach (Germany) and the Malalcahuello research headwaters (Chile), which are located in distinctly different hydro-climatic and hydro-pedological settings. Within the numerical experiments we will simulate the full concert of hydrological processes at the hillslope and headwater scales for meaningful perturbations of the behavioral model structure and compare them with respect to dynamics of free energy and production of power. These perturbations affect a) the river network and the geomorphology of the Weiherbach catchment, b) surface density of macropores in both catchments c) the spatial arrangement of soils and preferential pathways at the hillslope scale in the Weiherbach catchment. References: Kleidon, A., Zehe, E., Ehret, U., and Scherer, U.: Thermodynamics, maximum power, and the dynamics of preferential river flow structures on continents, Hydrol. Earth Syst. Sci. Discuss., 9, 7317-7378, 10.5194/hessd-9-7317-2012, 2012. Zehe, E., Blume, T., and Blöschl, G.: The principle of 'maximum energy dissipation': a novel thermodynamic perspective on rapid water flow in connected soil structures, Phil. Trans. R. Soc. B, 1-10, doi:10.1098/rstb.2009.0308, 2010.

Stirling Engine With Radial Flow Heat Exchangers

NASA Technical Reports Server (NTRS)

Vitale, N.; Yarr, George

1993-01-01

Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.

Flow through a very porous obstacle in a shallow channel.

PubMed

Creed, M J; Draper, S; Nishino, T; Borthwick, A G L

2017-04-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence.

A reliable ground bounce noise reduction technique for nanoscale CMOS circuits

NASA Astrophysics Data System (ADS)

Sharma, Vijay Kumar; Pattanaik, Manisha

2015-11-01

Power gating is the most effective method to reduce the standby leakage power by adding header/footer high-VTH sleep transistors between actual and virtual power/ground rails. When a power gating circuit transitions from sleep mode to active mode, a large instantaneous charge current flows through the sleep transistors. Ground bounce noise (GBN) is the high voltage fluctuation on real ground rail during sleep mode to active mode transitions of power gating circuits. GBN disturbs the logic states of internal nodes of circuits. A novel and reliable power gating structure is proposed in this article to reduce the problem of GBN. The proposed structure contains low-VTH transistors in place of high-VTH footer. The proposed power gating structure not only reduces the GBN but also improves other performance metrics. A large mitigation of leakage power in both modes eliminates the need of high-VTH transistors. A comprehensive and comparative evaluation of proposed technique is presented in this article for a chain of 5-CMOS inverters. The simulation results are compared to other well-known GBN reduction circuit techniques at 22 nm predictive technology model (PTM) bulk CMOS model using HSPICE tool. Robustness against process, voltage and temperature (PVT) variations is estimated through Monte-Carlo simulations.

Robust Fixed-Structure Control

DTIC Science & Technology

1994-10-30

Deterministic Foundation for Statistical Energy Analysis ," J. Sound Vibr., to appear. 1.96 D. S. Bernstein and S. P. Bhat, "Lyapunov Stability, Semistability...S. Bernstein, "Power Flow, Energy Balance, and Statistical Energy Analysis for Large Scale, Interconnected Systems," Proc. Amer. Contr. Conf., pp

Impact localization and energy quantification based on the power flow: A low-power requirement approach

NASA Astrophysics Data System (ADS)

Guyomar, Daniel; Lallart, Mickaël; Petit, Lionel; Wang, Xing-Jun

2011-06-01

The increasing use of composite materials has led to a dramatic change in the definition of safety standards. In particular, composite structures may be subjected to internal damages caused by external impacts that may not be detected by classical inspection methods. Additional constraints related to energy requirements may also be considered in order to make the system autonomous and possibly self-powered. The purpose of this paper is to present a low-cost impact detection and quantification scheme for thin plates or shells giving the whole history of the structure solicitation. Based on the analysis of the energy that has flown over a monitored area through the use of the elastic Poynting vector (that relates the mechanical power density of travelling waves), it is shown that this global energy balance may be linked in a simple way to the voltage output of piezoelectric elements in open-circuit condition. From this estimation, it is therefore possible to detect if an impact occurred inside the monitored area (in this case, the global energy balance would be positive) as well as its associated energy. If the impact occurs out of the frame, the global energy (and thus the obtained estimator) would be negative because of energy dissipation caused by internal losses and almost null. Thanks to this energy flow approach, the system is also independent from the boundary conditions of the structure. Experimental measurements aiming at validating the theoretical predictions showed that the technique permits detecting the impact area (inside/outside the frame) as well as an accurate estimation of the impact energy if the latter occurred inside the frame, both on a steel plate (with different boundary conditions) and an anisotropic composite structure.

Electrostatically frequency tunable micro-beam-based piezoelectric fluid flow energy harvester

NASA Astrophysics Data System (ADS)

Rezaee, Mousa; Sharafkhani, Naser

2017-07-01

This research investigates the dynamic behavior of a sandwich micro-beam based piezoelectric energy harvester with electrostatically adjustable resonance frequency. The system consists of a cantilever micro-beam immersed in a fluid domain and is subjected to the simultaneous action of cross fluid flow and nonlinear electrostatic force. Two parallel piezoelectric laminates are extended along the length of the micro-beam and connected to an external electric circuit which generates an output power as a result of the micro-beam oscillations. The fluid-coupled structure is modeled using Euler-Bernoulli beam theory and the equivalent force terms for the fluid flow. Fluid induced forces comprise the added inertia force which is evaluated using equivalent added mass and the drag and lift forces which are evaluated using relative velocity and Van der Pol equation. In addition to flow velocity and fluid density, the influence of several design parameters such as external electrical resistance, piezo layer position, and dc voltage on the generated power are investigated by using Galerkin and step by step linearization method. It is shown that for given flowing fluid parameters, i.e., density and velocity, one can adjust the applied dc voltage to tune resonance frequency so that the lock-in phenomenon with steady large amplitude oscillations happens, also by adjusting the harvester parameters including the mechanical and electrical ones, the maximal output power of the harvester becomes possible.

Recovery Act - Refinement of Cross Flow Turbine Airfoils

DOE Office of Scientific and Technical Information (OSTI.GOV)

McEntee, Jarlath

2013-08-30

Ocean Renewable Power Company, LLC (ORPC) is a global leader in hydrokinetic technology and project development. ORPC develops hydrokinetic power systems and eco-conscious projects that harness the power of oceans and rivers to create clean, predictable renewable energy. ORPC’s technology consists of a family of modular hydrokinetic power systems: the TidGen® Power System, for use at shallow to medium-depth tidal sites; the RivGen™ Power System, for use at river and estuary sites; and the OCGen® Power System, presently under development, for use at deep tidal and offshore ocean current sites. These power systems convert kinetic energy in moving water intomore » clean, renewable, grid-compatible electric power. The core technology component for all ORPC power systems is its patented turbine generator unit (TGU). The TGU uses proprietary advanced design cross flow (ADCF) turbines to drive an underwater permanent magnet generator mounted at the TGU’s center. It is a gearless, direct-drive system that has the potential for high reliability, requires no lubricants and releases no toxins that could contaminate the surrounding water. The hydrokinetic industry shows tremendous promise as a means of helping reduce the U.S.’s use of fossil fuels and dependence on foreign oil. To exploit this market opportunity, cross-flow hydrokinetic devices need to advance beyond the pre-commercial state and more systematic data about the structure and function of cross-flow hydrokinetic devices is required. This DOE STTR project, “Recovery Act - Refinement of Cross Flow Turbine Airfoils,” refined the cross-flow turbine design process to improve efficiency and performance and developed turbine manufacturing processes appropriate for volume production. The project proposed (1) to overcome the lack of data by extensively studying the properties of cross flow turbines, a particularly competitive design approach for extracting hydrokinetic energy and (2) to help ORPC mature its pre-commercial hydrokinetic technology into a commercially viable product over a three-year period by means of a design-for-manufacture process to be applied to the turbines which would result in a detail turbine design suitable for volume manufacture. In Phase I of the Project, ORPC systematically investigated performance of cross flow turbines by varying design parameters including solidity, foil profile, number of foils and foil toe angle using scale models of ORPC’s turbine design in a tow tank at the University of Maine (UMaine). Data collected provided information on interactions between design variables and helped ORPC improve turbine efficiency from 21% to greater than 35%. Analytical models were developed to better understand the physical phenomena at play in cross-flow turbines. In Phase II of the Project, ORPC expanded on data collected in Phase I to continue improving turbine efficiency, with a goal to optimally approach the Betz limit of 59.3%. Further tow tank testing and development of the analytical models and techniques was completed at UMaine and led to a deeper understanding of the flow phenomena involved. In addition, ORPC evaluated various designs, materials and manufacturing methods for full-scale turbine foils, and identified those most conducive to volume manufacture. Selected components of the turbine were structurally tested in a laboratory environment at UMaine. Performance and structural testing of the full scale turbine design was conducted as part of the field testing. The work funded by this project enabled the development of design tools for the rapid and efficient development of high performance cross-flow hydrokinetic turbine foils. The analytical tools are accurate and properly capture the underlying physical flow phenomena present in hydrokinetic cross-flow turbines. The ability to efficiently examine the design space provides substantial economic benefit to ORPC in that it allows for rapid design iteration at a low computational cost. The design-for-manufacture work enabled the delivery of a turbine design suitable for manufacture in intermediate to large quantity, lowering the unit cost of turbines and the levelized cost of electricity from ORPC hydrokinetic turbine. ORPC fielded the turbine design in a full scale application – the Cobscook Bay Tidal Energy Project which began operation off the coast of Eastport, Maine in September 2012. This is the first commercial, grid-connected tidal energy project in North America and the only ocean energy project not involving a dam which delivers power to a utility grid anywhere in the Americas. ORPC received a Federal Energy Regulatory Commission pilot project license to install and operate this project in February 2012. Construction of the TidGen® Power System began in March 2012, and the system was grid-connected on September 13, 2012. A 20-year commercial power purchase agreement to sell the power generated by the project was completed with Bangor Hydro Electric Company and is the first and only power purchase agreement for tidal energy. This is the first project in the U.S. to receive Renewable Energy Certificates for tidal energy production. The STTR project is a benefit to the public through its creation of jobs. ORPC’s recent deployment of the TidGen™ Power System is part of their larger project, the Maine Tidal Energy Project. According to ORPC’s report to the Maine Public Utilities Commission and the 20-year power purchase agreement, the Maine Tidal Energy Project will create and/or retain at least 80 direct full-time equivalent jobs in Maine during the development, construction and installation phase (2011 through 2016). In addition, the Maine Tidal Energy Project will create and/or retain at least 12 direct full-time equivalent jobs in Maine during the operating and maintenance phase (2016 through 2020). The STTR project has facilitated new and expanded services in manufacturing, fabrication and assembly, including major business growth for the composite technologies sector; creation of deepwater deployment, maintenance and retrieval services; and the expansion and formation of technical support services such as site assessment and design services, geotechnical services, underwater transmission services, and environmental monitoring services. The Maine Tidal Energy Project’s impact on workforce will enable other ocean energy projects – be they offshore wind, wave or additional tidal opportunities – to succeed in Maine. ORPC received a 2013 Tibbetts Award by the U.S. Small Business Administration.« less

PowerWheel - A new look at waterwheels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisman, R.N.; Broome, K.R.; Mayo, H.A.

1995-12-31

The PowerWheel is an advanced overshot water wheel, designed to generate electric power at drop structures on canals or on overflow spillways. Unlike the wheels of the 18th and 19th century which were designed to have maximum efficiency at a single flow rate, the current applications demand a wheel that can operate efficiently over a wide range of flows. The prototype PowerWheel will have a width to diameter ratio of 3 or more, in contrast to the wheels of the 19th century, which had large diameters and narrow widths. A model PowerWheel was built of plexiglass and delivered for testingmore » to the Imbt Hydraulics Laboratory at Lehigh University. The wheel has a diameter of 3.5 ft and is 16 in wide. The wheel contains 20 buckets and the bucket depth can be varied from a shallow depth of 4 in to a mid depth of 7 in to 10 in for the deep bucket. The blades have a rather simple geometry with a 4 in radius quarter circle at the outside of the wheel and then straight to the bottom of the bucket. The flume in which the wheel was tested has a width of 18 in. A hole was cut in the head box of the flume and a delivery chute was connected to the head box. The position of the chute can readily be moved up or down in relation to the wheel; for a fixed position of the chute on the head box, the slope of the chute can be changed because the chute was attached to the head box with a piano hinge. The laboratory flow system can deliver flow up to 6 cfs through a calibrated Venturi meter. The PowerWheel was subjected to flows ranging from 0.3 to 3.5 cfs.« less

PageRank versatility analysis of multilayer modality-based network for exploring the evolution of oil-water slug flow.

PubMed

Gao, Zhong-Ke; Dang, Wei-Dong; Li, Shan; Yang, Yu-Xuan; Wang, Hong-Tao; Sheng, Jing-Ran; Wang, Xiao-Fan

2017-07-14

Numerous irregular flow structures exist in the complicated multiphase flow and result in lots of disparate spatial dynamical flow behaviors. The vertical oil-water slug flow continually attracts plenty of research interests on account of its significant importance. Based on the spatial transient flow information acquired through our designed double-layer distributed-sector conductance sensor, we construct multilayer modality-based network to encode the intricate spatial flow behavior. Particularly, we calculate the PageRank versatility and multilayer weighted clustering coefficient to quantitatively explore the inferred multilayer modality-based networks. Our analysis allows characterizing the complicated evolution of oil-water slug flow, from the opening formation of oil slugs, to the succedent inter-collision and coalescence among oil slugs, and then to the dispersed oil bubbles. These properties render our developed method particularly powerful for mining the essential flow features from the multilayer sensor measurements.

Simultaneous Neutron and X-ray Tomography for Quantitative analysis of Geological Samples

NASA Astrophysics Data System (ADS)

LaManna, J.; Hussey, D. S.; Baltic, E.; Jacobson, D. L.

2016-12-01

Multiphase flow is a critical area of research for shale gas, oil recovery, underground CO2 sequestration, geothermal power, and aquifer management. It is critical to understand the porous structure of the geological formations in addition to the fluid/pore and fluid/fluid interactions. Difficulties for analyzing flow characteristics of rock cores are in obtaining 3D distribution information on the fluid flow and maintaining the cores in a state for other analysis methods. Two powerful non-destructive methods for obtaining 3D structural and compositional information are X-ray and neutron tomography. X-ray tomography produces information on density and structure while neutrons excel at acquiring the liquid phase and produces compositional information. These two methods can offer strong complementary information but are typically conducted at separate times and often at different facilities. This poses issues for obtaining dynamic and stochastic information as the sample will change between analysis modes. To address this, NIST has developed a system that allows for multimodal, simultaneous tomography using thermal neutrons and X-rays by placing a 90 keVp micro-focus X-ray tube 90° to the neutron beam. High pressure core holders that simulate underground conditions have been developed to facilitate simultaneous tomography. These cells allow for the control of confining pressure, axial load, temperature, and fluid flow through the core. This talk will give an overview the simultaneous neutron and x-ray tomography capabilities at NIST, the benefits of multimodal imaging, environmental equipment for geology studies, and several case studies that have been conducted at NIST.

Nonlinear Tollmien-Schlichting/vortex interaction in boundary layers

NASA Technical Reports Server (NTRS)

Hall, P.; Smith, F. T.

1988-01-01

The nonlinear reaction between two oblique 3-D Tollmein-Schlichting (TS) waves and their induced streamwise-vortex flow is considered theoretically for an imcompressible boundary layer. The same theory applies to the destabilization of an incident vortex motion by subharmonic TS waves, followed by interaction. The scales and flow structure involved are addressed for high Reynolds numbers. The nonlionear interaction is powerful, starting at quite low amplitudes with a triple-deck structure for the TS waves but a large-scale structure for the induced vortex, after which strong nonlinear amplification occurs. This includes nonparallel-flow effects. The nonlinear interaction is governed by a partial differential system for the vortex flow coupled with an ordinary-differential one for the TS pressure. The solution properties found sometimes produce a breakup within a finite distance and sometimes further downstream, depending on the input amplitudes upstream and on the wave angles, and that then leads to the second stages of interaction associated with higher amplitudes, the main second stages giving either long-scale phenomena significantly affected by nonparallelism or shorter quasi-parallel ones governed by the full nonlinear triple-deck response.

A Comprehensive Review of Travelling-Wave Tube Technology

DTIC Science & Technology

1979-11-01

drivers for crossed-field amplifiers. Coupled-cavity TWT interaction is similar to helix TWT interaction in one respect, that is, power flows along the...resulting in a similar improvement in tube efficiency. Also, an improvement in efficiency can be obtained in helix TWTs by increasing the circuit period...Impedance. Based on theory and measurement the helix is far superior to any other type of propagating structure. The low power helix TWT is still the

Numerical investigation of the air injection effect on the cavitating flow in Francis hydro turbine

NASA Astrophysics Data System (ADS)

Chirkov, D. V.; Shcherbakov, P. K.; Cherny, S. G.; Skorospelov, V. A.; Turuk, P. A.

2017-09-01

At full and over load operating points, some Francis turbines experience strong self-excited pressure and power oscillations. These oscillations are occuring due to the hydrodynamic instability of the cavitating fluid flow. In many cases, the amplitude of such pulsations may be reduced substantially during the turbine operation by the air injection/ admission below the runner. Such an effect is investigated numerically in the present work. To this end, the hybrid one-three-dimensional model of the flow of the mixture "liquid-vapor" in the duct of a hydroelectric power station, which was proposed previously by the present authors, is augmented by the second gaseous component — the noncondensable air. The boundary conditions and the numerical method for solving the equations of the model are described. To check the accuracy of computing the interface "liquid-gas", the numerical method was applied at first for solving the dam break problem. The algorithm was then used for modeling the flow in a hydraulic turbine with air injection below the runner. It is shown that with increasing flow rate of the injected air, the amplitude of pressure pulsations decreases. The mechanism of the flow structure alteration in the draft tube cone has been elucidated, which leads to flow stabilization at air injection.

POD Analysis of Jet-Plume/Afterbody-Wake Interaction

NASA Astrophysics Data System (ADS)

Murray, Nathan E.; Seiner, John M.; Jansen, Bernard J.; Gui, Lichuan; Sockwell, Shuan; Joachim, Matthew

2009-11-01

The understanding of the flow physics in the base region of a powered rocket is one of the keys to designing the next generation of reusable launchers. The base flow features affect the aerodynamics and the heat loading at the base of the vehicle. Recent efforts at the National Center for Physical Acoustics at the University of Mississippi have refurbished two models for studying jet-plume/afterbody-wake interactions in the NCPA's 1-foot Tri-Sonic Wind Tunnel Facility. Both models have a 2.5 inch outer diameter with a nominally 0.5 inch diameter centered exhaust nozzle. One of the models is capable of being powered with gaseous H2 and O2 to study the base flow in a fully combusting senario. The second model uses hi-pressure air to drive the exhaust providing an unheated representative flow field. This unheated model was used to acquire PIV data of the base flow. Subsequently, a POD analysis was performed to provide a first look at the large-scale structures present for the interaction between an axisymmetric jet and an axisymmetric afterbody wake. PIV and Schlieren data are presented for a single jet-exhaust to free-stream flow velocity along with the POD analysis of the base flow field.

Quantitative three-dimensional power Doppler angiography: a flow-free phantom experiment to evaluate the relationship between color gain, depth and signal artifact.

PubMed

Martins, W P; Raine-Fenning, N J; Ferriani, R A; Nastri, C O

2010-03-01

To evaluate the presence of false flow three-dimensional (3D) power Doppler signals in 'flow-free' models. 3D power Doppler datasets were acquired from three different flow-free phantoms (muscle, air and water) with two different transducers and Virtual Organ Computer-aided AnaLysis was used to generate a sphere that was serially applied through the 3D dataset. The vascularization flow index was used to compare artifactual signals at different depths (from 0 to 6 cm) within the different phantoms and at different gain and pulse repetition frequency (PRF) settings. Artifactual Doppler signals were seen in all phantoms despite these being flow-free. The pattern was very similar and the degree of artifact appeared to be dependent on the gain and distance from the transducer. False signals were more evident in the far field and increased as the gain was increased, with false signals first appearing with a gain of 1 dB in the air and muscle phantoms. False signals were seen at a lower gain with the water phantom (-15 dB) and these were associated with vertical lines of Doppler artifact that were related to PRF, and disappeared when reflections were attenuated. Artifactual Doppler signals are seen in flow-free phantoms and are related to the gain settings and the distance from the transducer. In the in-vivo situation, the lowest gain settings that allow the detection of blood flow and adequate definition of vessel architecture should be used, which invariably means using a setting near or below the middle of the range available. Additionally, observers should be aware of vertical lines when evaluating cystic or liquid-containing structures. (c) 2010 ISUOG. Published by John Wiley & Sons, Ltd.

GASCAN 2 payload integration

NASA Technical Reports Server (NTRS)

Brown, Henry B., Jr.; Buzby, Jared G.; Doyle, Barbara J.; Wibisono, Benedict C.

1994-01-01

This MQP is an ongoing part of the NASA Advanced Space Design Program which examines the integration of the WPI/MITRE Get Away Special Canister (GASCan 2). GASCan 2 contains the Ionospheric Properties and Propagation, Micro-Gravity Ignition, and Rotational Fluid Flow experiments, as well as the integrated support structure. The objectives this year were to finalize the power supply system, connections for experiments, mechanical design of the IPPE's antenna, and to update the structural and vibrational analysis of the integrated support structure.

Forced-flow once-through boilers. [structural design criteria/aerospace environments

NASA Technical Reports Server (NTRS)

Stone, J. R.; Gray, V. H.; Gutierrez, O. A.

1975-01-01

A compilation and review of NASA-sponsored research on boilers for use in spacecraft electrical power generation systems is presented. Emphasis is on the heat-transfer and fluid-flow problems. In addition to space applications, much of the boiler technology is applicable to terrestrial and marine uses such as vehicular power, electrical power generation, vapor generation, and heating and cooling. Related research areas are discussed such as condensation, cavitation, line and boiler dynamics, the SNAP-8 project (Mercury-Rankine cycle), and conventional terrestrial boilers (either supercritical or gravity-assisted liquid-vapor separation types). The research effort was directed at developing the technology for once-through compact boilers with high heat fluxes to generate dry vapor stably, without utilizing gravity for phase separations. A background section that discusses, tutorially, the complex aspects of the boiling process is presented. Discussions of tests on alkali metals are interspersed with those on water and other fluids on a phenomenological basis.

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods.

PubMed

Shen, Lu; Chen, Zong-Nan; Wen, Chihyung

2018-04-23

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is not well understood. The flow visualization technique is a promising non-intrusive method to illustrate the complex flow field spatially and temporally. A basic flow visualization setup consists of a high-powered laser and optic lenses to generate the laser sheet, a camera, a tracer particle generator, and a data processor. The wind tunnel setup, the specifications of devices involved, and the corresponding parameter settings are dependent on the flow features to be obtained. Normal smoke wire flow visualization uses a smoke wire to demonstrate the flow streaklines. However, the performance of this method is limited by poor spatial resolution when it is conducted in a complex flow field. Therefore, an improved smoke flow visualization technique has been developed. This technique illustrates the large-scale global LEV flow field and the small-scale shear layer flow structure at the same time, providing a valuable reference for later detailed particle image velocimetry (PIV) measurement. In this paper, the application of the improved smoke flow visualization and PIV measurement to study the unsteady flow phenomena over a delta wing is demonstrated. The procedure and cautions for conducting the experiment are listed, including wind tunnel setup, data acquisition, and data processing. The representative results show that these two flow visualization methods are effective techniques for investigating the three-dimensional flow field qualitatively and quantitatively.

8- by 6-Foot Supersonic Wind Tunnel's Original Design

NASA Image and Video Library

1949-07-21

Aerial view of the 8- by 6-Foot Supersonic Wind Tunnel in its original configuration at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. The 8- by 6 was the laboratory’s first large supersonic wind tunnel. It was also the NACA’s most powerful supersonic tunnel, and its first facility capable of running an engine at supersonic speeds. The 8- by 6-foot tunnel has been used to study inlets and exit nozzles, fuel injectors, flameholders, exit nozzles, and controls on ramjet and turbojet propulsion systems. The 8- by 6 was originally an open-throat and non-return tunnel. This meant that the supersonic air flow was blown through the test section and out the other end into the atmosphere. In this photograph, the three drive motors in the structure at the left supplied power to the seven-stage axial-flow compressor in the light-colored structure. The air flow passed through flexible walls which were bent to create the desired speed. The test article was located in the 8- by 6-foot stainless steel test section located inside the steel pressure chamber at the center of this photograph. The tunnel dimensions were then gradually increased to slow the air flow before it exited into the atmosphere. The large two-story building in front of the tunnel was used as office space for the researchers.

Reconstructing mantle flow and long-wavelength dynamic topography since the Jurassic Period (GD Division Outstanding ECS Award Lecture)

NASA Astrophysics Data System (ADS)

Flament, Nicolas

2017-04-01

Global tectonic reconstructions can be used as boundary conditions of forward mantle convection models to simulate past mantle flow and long-wavelength dynamic topography. The predictions of such models can be compared to seismic tomography, to estimates of residual topography and to geological indicators of past vertical motions. Here we present models that reproduce the present-day structure of the lower mantle, including two large structures that resemble the Pacific and African Large Low Shear Velocity Provinces (LLSVPs, ˜15,000 km in diameter) and a smaller structure that resembles the recently discovered Perm Anomaly (˜1,000 km in diameter). The match between predicted and seismically inferred lower mantle structure is quantified across a series of mantle flow and tomography models. In the models, the Perm-like anomaly forms in isolation within a closed and long-lived subduction network (East Asia, Northern Tethys and Mongol-Okhotsk) ˜22,000 km in circumference before migrating ˜1,500 km westward at an average rate of 1 cm yr-1 since 150 million years ago. These results indicate a greater mobility of deep mantle structures than previously recognized, and illustrate that the predictive power of mantle flow models has significantly increased over the last thirty years. We suggest that the mobile Perm Anomaly could be linked to the ˜258 Ma Emeishan volcanics, in contrast to the previously proposed ˜251 Ma Siberian Traps. We also compare the present-day dynamic topography predicted by forward mantle flow models to residual topography models, and show that radial and lateral viscosity variations significantly influence the distribution of power of predicted dynamic topography as a function of spherical harmonic degree. We finally show how past vertical motions preserved in the geological record and the present-day position of slabs in the mantle inferred from seismic tomography may be used to constrain tectonic reconstructions and mantle rheology, including examples focusing on the large-scale topographic asymmetry of the South Atlantic domain and on the uplift history of the eastern highlands of Australia.

76 FR 20971 - Free Flow Power Corporation; Notice of Intent To File License Application, Filing of Pre...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-14

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. P-13346-001] Free Flow...: February 18, 2011. d. Submitted By: Free Flow Power Corporation (Free Flow Power), on behalf of its... Officer, Free Flow Power Corporation, 239 Causeway Street, Boston, MA 02114-2130; or at (978) 283-2822. i...

Unscheduled load flow effect due to large variation in the distributed generation in a subtransmission network

NASA Astrophysics Data System (ADS)

Islam, Mujahidul

A sustainable energy delivery infrastructure implies the safe and reliable accommodation of large scale penetration of renewable sources in the power grid. In this dissertation it is assumed there will be no significant change in the power transmission and distribution structure currently in place; except in the operating strategy and regulatory policy. That is to say, with the same old structure, the path towards unveiling a high penetration of switching power converters in the power system will be challenging. Some of the dimensions of this challenge are power quality degradation, frequent false trips due to power system imbalance, and losses due to a large neutral current. The ultimate result is the reduced life of many power distribution components - transformers, switches and sophisticated loads. Numerous ancillary services are being developed and offered by the utility operators to mitigate these problems. These services will likely raise the system's operational cost, not only from the utility operators' end, but also reflected on the Independent System Operators and by the Regional Transmission Operators (RTO) due to an unforeseen backlash of frequent variation in the load-side generation or distributed generation. The North American transmission grid is an interconnected system similar to a large electrical circuit. This circuit was not planned but designed over 100 years. The natural laws of physics govern the power flow among loads and generators except where control mechanisms are installed. The control mechanism has not matured enough to withstand the high penetration of variable generators at uncontrolled distribution ends. Unlike a radial distribution system, mesh or loop networks can alleviate complex channels for real and reactive power flow. Significant variation in real power injection and absorption on the distribution side can emerge as a bias signal on the routing reactive power in some physical links or channels that are not distinguishable from the vast network. A path tracing methodology is developed to identify the power lines that are vulnerable to an unscheduled flow effect in the sub-transmission network. It is much harder to aggregate power system network sensitivity information or data from measuring load flow physically than to simulate in software. System dynamics is one of the key factors to determine an appropriate dynamic control mechanism at an optimum network location. Once a model of deterministic but variable power generator is used, the simulation can be meaningful in justifying this claim. The method used to model the variable generator is named the two-components phase distortion model. The model was validated from the high resolution data collected from three pilot photovoltaic sites in Florida - two in the city of St. Petersburg and one in the city of Tampa. The high resolution data was correlated with weather radar closest to the sites during the design stage of the model. Technically the deterministic model cannot replicate a stochastic model which is more realistically applicable for solar isolation and involves a Markov chain. The author justified the proposition based on the fact that for analysis of the response functions of different systems, the excitation function should be common for comparison. Moreover, there could be many possible simulation scenarios but fewer worst cases. Almost all commercial systems are protected against potential faults and contingencies to a certain extent. Hence, the proposed model for worst case studies was designed within a reasonable limit. The simulation includes steady state and transient mode using multiple software modules including MatlabRTM, PSCADRTM and Paladin Design BaseRTM. It is shown that by identifying vulnerable or sensitive branches in the network, the control mechanisms can be coordinated reliably. In the long run this can save money by preventing unscheduled power flow in the network and eventually stabilizing the energy market.

The Investigation and Development of Low Cost Hardware Components for Proton-Exchange Membrane Fuel Cells - Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

George A. Marchetti

1999-12-15

Proton exchange membrane (PEM) fuel cell components, which would have a low-cost structure in mass production, were fabricated and tested. A fuel cell electrode structure, comprising a thin layer of graphite (50 microns) and a front-loaded platinum catalyst layer (600 angstroms), was shown to produce significant power densities. In addition, a PEM bipolar plate, comprising flexible graphite, carbon cloth flow-fields and an integrated polymer gasket, was fabricated. Power densities of a two-cell unit using this inexpensive bipolar plate architecture were shown to be comparable to state-of-the-art bipolar plates.

Electron wind in strong wave guide fields

NASA Astrophysics Data System (ADS)

Krienen, F.

1985-03-01

The X-ray activity observed near highly powered waveguide structures is usually caused by local electric discharges originating from discontinuities such as couplers, tuners or bends. In traveling waves electrons move in the direction of the power flow. Seed electrons can multipactor in a traveling wave, the moving charge pattern is different from the multipactor in a resonant structure and is self-extinguishing. The charge density in the wave guide will modify impedance and propagation constant of the wave guide. The radiation level inside the output wave guide of the SLAC, 50 MW, S-band, klystron is estimated. Possible contributions of radiation to window failure are discussed.

Ecosystem Services Flows: Why Stakeholders' Power Relationships Matter.

PubMed

Felipe-Lucia, María R; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A

2015-01-01

The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the "cascade" framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders' interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders' ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services.

Ecosystem Services Flows: Why Stakeholders’ Power Relationships Matter

PubMed Central

Felipe-Lucia, María R.; Martín-López, Berta; Lavorel, Sandra; Berraquero-Díaz, Luis; Escalera-Reyes, Javier; Comín, Francisco A.

2015-01-01

The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the “cascade” framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders’ interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders’ ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services. PMID:26201000

77 FR 3761 - Free Flow Power Corporation, Northland Power Mississippi River LLC; Notice Announcing Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-25

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 12817-002, Project No. 14083-000] Free Flow Power Corporation, Northland Power Mississippi River LLC; Notice Announcing Filing... priority is as follows: 1. Free Flow Power Corporation; Project No. 12817-002. 2. Northland Power...

Hierarchical Velocity Structure in the Core of Abell 2597

NASA Technical Reports Server (NTRS)

Still, Martin; Mushotzky, Richard

2004-01-01

We present XMM-Newton RGS and EPIC data of the putative cooling flow cluster Abell 2597. Velocities of the low-ionization emission lines in the spectrum are blue shifted with respect to the high-ionization lines by 1320 (sup +660) (sub -210) kilometers per second, which is consistent with the difference in the two peaks of the galaxy velocity distribution and may be the signature of bulk turbulence, infall, rotation or damped oscillation in the cluster. A hierarchical velocity structure such as this could be the direct result of galaxy mergers in the cluster core, or the injection of power into the cluster gas from a central engine. The uniform X-ray morphology of the cluster, the absence of fine scale temperature structure and the random distribution of the the galaxy positions, independent of velocity, suggests that our line of sight is close to the direction of motion. These results have strong implications for cooling flow models of the cluster Abell 2597. They give impetus to those models which account for the observed temperature structure of some clusters using mergers instead of cooling flows.

The Shock and Vibration Digest, Volume 17, Number 8

DTIC Science & Technology

1985-08-01

ate, transmit, and radiate audible sound. dures are based on acoustic power flow, statistical energy analysis (SEA), and modal methods [22-283. A...modified partition area. features of the acoustic field. I.--1 85-1642 Statistical Energy Analysis , Structural Reso- nances, and Beam Networks BUILDING...energy methods, Structural resonance L.J. Lee Heriot-Watt Univ., Chambers St., Edinburgh The statistical energy analysis method is EHI 1HX, Scotland

Electronics for Piezoelectric Smart Structures

NASA Technical Reports Server (NTRS)

Warkentin, D. J.; Tani, J.

1997-01-01

This paper briefly presents work addressing some of the basic considerations for the electronic components used in smart structures incorporating piezoelectric elements. After general remarks on the application of piezoelectric elements to the problem of structural vibration control, three main topics are described. Work to date on the development of techniques for embedding electronic components within structural parts is presented, followed by a description of the power flow and dissipation requirements of those components. Finally current work on the development of electronic circuits for use in an 'active wall' for acoustic noise is introduced.

Multi-scale roughness spectra of Mount St. Helens debris flows

NASA Technical Reports Server (NTRS)

Austin, Richard T.; England, Anthony W.

1993-01-01

A roughness spectrum allows surface structure to be interpreted as a sum of sinusoidal components with differing wavelengths. Knowledge of the roughness spectrum gives insight into the mechanisms responsible for electromagnetic scattering at a given wavelength. Measured spectra from 10-year-old primary debris flow surfaces at Mount St. Helens conform to a power-law spectral model, suggesting that these surfaces are scaling over the measured range of spatial frequencies. Measured spectra from water-deposited surfaces deviate from this model.

Which catchment characteristics control the temporal dependence structure of daily river flows?

NASA Astrophysics Data System (ADS)

Chiverton, Andrew; Hannaford, Jamie; Holman, Ian; Corstanje, Ron; Prudhomme, Christel; Bloomfield, John; Hess, Tim

2014-05-01

A hydrological classification system would provide information about the dominant processes in the catchment enabling information to be transferred between catchments. Currently there is no widely-agreed upon system for classifying river catchments. This paper developed a novel approach to assess the influence that catchment characteristics have on the precipitation-to-flow relationship, using a catchment classification based on the average temporal dependence structure in daily river flow data over the period 1980 to 2010. Temporal dependence in river flow data is driven by the flow pathways, connectivity and storage within the catchment. Temporal dependence was analysed by creating temporally averaged semi-variograms for a set of 116 near-natural catchments (in order to prevent direct anthropogenic disturbances influencing the results) distributed throughout the UK. Cluster analysis, using the variogram, classified the catchments into four well defined clusters driven by the interaction of catchment characteristics, predominantly characteristics which influence the precipitation-to-flow relationship. Geology, depth to gleyed layer in soils, slope of the catchment and the percentage of arable land were significantly different between the clusters. These characteristics drive the temporal dependence structure by influencing the rate at which water moves through the catchment and / or the storage in the catchment. Arable land is correlated with several other variables, hence is a proxy indicating the residence time of the water in the catchment. Finally, quadratic discriminant analysis was used to show that a model with five catchment characteristics is able to predict the temporal dependence structure for un-gauged catchments. This work demonstrates that a variogram-based approach is a powerful and flexible methodology for grouping catchments based on the precipitation-to-flow relationship which could be applied to any set of catchments with a relatively complete daily river flow record.

Velocity mapping in the Lower Congo River: a first look at the unique bathymetry and hydrodynamics of Bulu Reach

USGS Publications Warehouse

Jackson, P. Ryan; Oberg, Kevin A.; Gardiner, Ned; Shelton, John

2009-01-01

The lower Congo River is one of the deepest, most powerful, and most biologically diverse stretches of river on Earth. The river’s 270 m decent from Malebo Pool though the gorges of the Crystal Mountains to the Atlantic Ocean (498 km downstream) is riddled with rapids, cataracts, and deep pools. Much of the lower Congo is a mystery from a hydraulics perspective. However, this stretch of the river is a hotbed for biologists who are documenting evolution in action within the diverse, but isolated, fish populations. Biologists theorize that isolation of fish populations within the lower Congo is due to barriers presented by flow structure and bathymetry. To investigate this theory, scientists from the U.S. Geological Survey and American Museum of Natural History teamed up with an expedition crew from National Geographic in 2008 to map flow velocity and bathymetry within target reaches in the lower Congo River using acoustic Doppler current profilers (ADCPs) and echo sounders. Simultaneous biological and water quality sampling was also completed. This paper presents some preliminary results from this expedition, specifically with regard to the velocity structure andbathymetry. Results show that the flow in the bedrock controlled Bulu reach of the lower Congo is highly energetic. Turbulent and secondary flow structures can span the full depth of flow (up to 165 m), while coherent bank-to-bank cross-channel flow structures are absent. Regions of flow separation near the banks are isolated from one another and from the opposite bank by high shear, high velocity zones with depth-averaged flow velocities that can exceed 4 m/s.

78 FR 33400 - Free Flow Power Corporation; Notice Soliciting Scoping Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-04

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [ Project No. 13346-003] Free Flow Power... Major License. b. Project No.: P-13346-003. c. Date filed: December 3, 2012. d. Applicant: Free Flow Power Corporation (Free Flow Power), on behalf of its subsidiary PayneBridge, LLC. e. Name of Project...

Numerical studies on the performance of a flow distributor in tank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Soo Jai, E-mail: shinsoojai@kaeri.re.kr; Kim, Young In; Ryu, Seungyeob

2015-03-10

Flow distributors are generally observed in several nuclear power plants. During core make-up tank (CMT) injection into the reactor, the condensation and thermal stratification are observed in the CMT, and rapid condensation disturbs the injection operation. To reduce the condensation phenomena in the tank, CMT was equipped with a flow distributor. The optimal design of the flow distributor is very important to ensure the structural integrity the CMT and its safe operation during certain transient or accident conditions. In the present study, we numerically investigated the performance of a flow distributor in tank with different shape factors such as themore » total number of holes, pitch-to-hole diameter ratios, diameter of the hole, and the area ratios. These data will contribute to a design of the flow distributor.« less

Exploring the Powerful Ionised Wind in the Seyfert Galaxy PG1211+143

NASA Astrophysics Data System (ADS)

Pounds, Ken

2013-10-01

Highly-ionised high-speed winds in AGN (UFOs) were first detected with XMM-Newton a decade ago, and are now established as a key factor in the study of SMBH accretion, and in the growth and metal enrichment of their host galaxies. However, information on the ionisation and dynamical structure, and the ultimate fate of UFOs remains very limited. We request a 600ks extended XMM-Newton study of the prototype UFO PG1211+143 in AO-13, to obtain high quality EPIC and RGS spectra, to map the flow structure and variability, while seeking evidence for the anticipated interaction with the ISM and possible conversion of the energetic wind to a momentum-driven flow.

Wave propagation and power flow in an acoustic metamaterial plate with lateral local resonance attachment

NASA Astrophysics Data System (ADS)

Wang, Ting; Sheng, Meiping; Ding, Xiaodong; Yan, Xiaowei

2018-03-01

This paper presents analysis on wave propagation and power flow in an acoustic metamaterial plate with lateral local resonance. The metamaterial is designed to have lateral local resonance systems attached to a homogeneous plate. Relevant theoretical analysis, numerical modelling and application prospect are presented. Results show that the metamaterial has two complete band gaps for flexural wave absorption and vibration attenuation. Damping can smooth and lower the metamaterial’s frequency responses in high frequency ranges at the expense of the band gap effect, and as an important factor to calculate the power flow is thoroughly investigated. Moreover, the effective mass density becomes negative and unbounded at specific frequencies. Simultaneously, power flow within band gaps are dramatically blocked from the power flow contour and power flow maps. Results from finite element modelling and power flow analysis reveal the working mechanism of the flexural wave attenuation and power flow blocked within the band gaps, where part of the flexural vibration is absorbed by the vertical resonator and the rest is transformed through four-link-mechanisms to the lateral resonators that oscillate and generate inertial forces indirectly to counterbalance the shear forces induced by the vibrational plate. The power flow is stored in the vertical and lateral local resonance, as well as in the connected plate.

Flow through a very porous obstacle in a shallow channel

PubMed Central

Draper, S.; Nishino, T.; Borthwick, A. G. L.

2017-01-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence. PMID:28484321

Renormalization-group flow of the effective action of cosmological large-scale structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Floerchinger, Stefan; Garny, Mathias; Tetradis, Nikolaos

Following an approach of Matarrese and Pietroni, we derive the functional renormalization group (RG) flow of the effective action of cosmological large-scale structures. Perturbative solutions of this RG flow equation are shown to be consistent with standard cosmological perturbation theory. Non-perturbative approximate solutions can be obtained by truncating the a priori infinite set of possible effective actions to a finite subspace. Using for the truncated effective action a form dictated by dissipative fluid dynamics, we derive RG flow equations for the scale dependence of the effective viscosity and sound velocity of non-interacting dark matter, and we solve them numerically. Physically,more » the effective viscosity and sound velocity account for the interactions of long-wavelength fluctuations with the spectrum of smaller-scale perturbations. We find that the RG flow exhibits an attractor behaviour in the IR that significantly reduces the dependence of the effective viscosity and sound velocity on the input values at the UV scale. This allows for a self-contained computation of matter and velocity power spectra for which the sensitivity to UV modes is under control.« less

Curvilinear immersed-boundary method for simulating unsteady flows in shallow natural streams with arbitrarily complex obstacles

NASA Astrophysics Data System (ADS)

Kang, Seokkoo; Borazjani, Iman; Sotiropoulos, Fotis

2008-11-01

Unsteady 3D simulations of flows in natural streams is a challenging task due to the complexity of the bathymetry, the shallowness of the flow, and the presence of multiple nature- and man-made obstacles. This work is motivated by the need to develop a powerful numerical method for simulating such flows using coherent-structure-resolving turbulence models. We employ the curvilinear immersed boundary method of Ge and Sotiropoulos (Journal of Computational Physics, 2007) and address the critical issue of numerical efficiency in large aspect ratio computational domains and grids such as those encountered in long and shallow open channels. We show that the matrix-free Newton-Krylov method for solving the momentum equations coupled with an algebraic multigrid method with incomplete LU preconditioner for solving the Poisson equation yield a robust and efficient procedure for obtaining time-accurate solutions in such problems. We demonstrate the potential of the numerical approach by carrying out a direct numerical simulation of flow in a long and shallow meandering stream with multiple hydraulic structures.

Propulsion efficiency and imposed flow fields of a copepod jump.

PubMed

Jiang, Houshuo; Kiørboe, Thomas

2011-02-01

Pelagic copepods jump to relocate, to attack prey and to escape predators. However, there is a price to be paid for these jumps in terms of their energy costs and the hydrodynamic signals they generate to rheotactic predators. Using observed kinematics of various types of jumps, we computed the imposed flow fields and associated energetics of jumps by means of computational fluid dynamics simulations by modeling the copepod as a self-propelled body. The computational fluid dynamics simulation was validated by particle image velocimetry data. The flow field generated by a repositioning jump quickly evolves into two counter-rotating viscous vortex rings that are near mirror image of one another, one in the wake and one around the body of the copepod; this near symmetrical flow may provide hydrodynamic camouflage because it contains no information about the position of the copepod prey within the flow structure. The flow field associated with an escape jump sequence also includes two dominant vortex structures: one leading wake vortex generated as a result of the first jump and one around the body, but between these two vortex structures is an elongated, long-lasting flow trail with flow velocity vectors pointing towards the copepod; such a flow field may inform the predator of the whereabouts of the escaping copepod prey. High Froude propulsion efficiency (0.94-0.98) was obtained for individual power stroke durations of all simulated jumps. This is unusual for small aquatic organisms but is caused by the rapidity and impulsiveness of the jump that allows only a low-cost viscous wake vortex to travel backwards.

Optimization of Vertical Double-Diffused Metal-Oxide Semiconductor (VDMOS) Power Transistor Structure for Use in High Frequencies and Medical Devices

PubMed Central

Farhadi, Rozita; Farhadi, Bita

2014-01-01

Power transistors, such as the vertical, double-diffused, metal-oxide semiconductor (VDMOS), are used extensively in the amplifier circuits of medical devices. The aim of this research was to construct a VDMOS power transistor with an optimized structure to enhance the operation of medical devices. First, boron was implanted in silicon by implanting unclamped inductive switching (UIS) and a Faraday shield. The Faraday shield was implanted in order to replace the gate-field parasitic capacitor on the entry part of the device. Also, implanting the UIS was used in order to decrease the effect of parasitic bipolar junction transistor (BJT) of the VDMOS power transistor. The research tool used in this study was Silvaco software. By decreasing the transistor entry resistance in the optimized VDMOS structure, power losses and noise at the entry of the transistor were decreased, and, by increasing the breakdown voltage, the lifetime of the VDMOS transistor lifetime was increased, which resulted in increasing drain flow and decreasing Ron. This consequently resulted in enhancing the operation of high-frequency medical devices that use transistors, such as Radio Frequency (RF) and electrocardiograph machines. PMID:25763152

Optimization of Vertical Double-Diffused Metal-Oxide Semiconductor (VDMOS) Power Transistor Structure for Use in High Frequencies and Medical Devices.

PubMed

Farhadi, Rozita; Farhadi, Bita

2014-01-01

Power transistors, such as the vertical, double-diffused, metal-oxide semiconductor (VDMOS), are used extensively in the amplifier circuits of medical devices. The aim of this research was to construct a VDMOS power transistor with an optimized structure to enhance the operation of medical devices. First, boron was implanted in silicon by implanting unclamped inductive switching (UIS) and a Faraday shield. The Faraday shield was implanted in order to replace the gate-field parasitic capacitor on the entry part of the device. Also, implanting the UIS was used in order to decrease the effect of parasitic bipolar junction transistor (BJT) of the VDMOS power transistor. The research tool used in this study was Silvaco software. By decreasing the transistor entry resistance in the optimized VDMOS structure, power losses and noise at the entry of the transistor were decreased, and, by increasing the breakdown voltage, the lifetime of the VDMOS transistor lifetime was increased, which resulted in increasing drain flow and decreasing Ron. This consequently resulted in enhancing the operation of high-frequency medical devices that use transistors, such as Radio Frequency (RF) and electrocardiograph machines.

Power flow controller with a fractionally rated back-to-back converter

DOEpatents

Divan, Deepakraj M.; Kandula, Rajendra Prasad; Prasai, Anish

2016-03-08

A power flow controller with a fractionally rated back-to-back (BTB) converter is provided. The power flow controller provide dynamic control of both active and reactive power of a power system. The power flow controller inserts a voltage with controllable magnitude and phase between two AC sources at the same frequency; thereby effecting control of active and reactive power flows between the two AC sources. A transformer may be augmented with a fractionally rated bi-directional Back to Back (BTB) converter. The fractionally rated BTB converter comprises a transformer side converter (TSC), a direct-current (DC) link, and a line side converter (LSC). By controlling the switches of the BTB converter, the effective phase angle between the two AC source voltages may be regulated, and the amplitude of the voltage inserted by the power flow controller may be adjusted with respect to the AC source voltages.

Laser speckle contrast imaging: monitoring blood flow dynamics and vascular structure of photodynamic therapy

NASA Astrophysics Data System (ADS)

Liu, Qian; Zhou, Sibo; Zhang, Zhihong; Luo, Qingming

2005-01-01

Laser speckle contrast imaging (LSCI) is a noninvasive optical image technique that has been developed for imaging in vivo blood flow dynamics and vascular structure with high spatial and temporal resolution. It records the full-field spatio-temporal characteristics of microcirculation in real time without the need of laser beam flying. In this paper applications of this technique for monitoring changes of blood flow and vascular structure following photodynamic therapy (PDT) in vivo model were demonstrated. In this study, an in vivo model of chick chorioallantoic membrane (CAM) at embryo age (EA) of 10~13 days, was observed following PDT irradiated by a power tunable laser diode (λ = 656.5 nm). Laser intensity incident on the treatment site was maintained at 40 mW/cm2 and photosensitizer of Pyropheophorbide Acid (Pyro-Acid) was used. CAM was adopted in PDT since it is a transparent in vivo model and the irradiated lights of laser can penetrate tumor with greater depth. The laser delivered through fiber bundle to the treatment site in PDT also acted as the coherent light source of LSCI. This study shows that LSCI can be used to assess the efficacy of peripheral vessels damage of tumor in PDT by monitoring changes of blood flow and vascular structure.

Study of electrode slice forming of bicycle dynamo hub power connector

NASA Astrophysics Data System (ADS)

Chen, Dyi-Cheng; Jao, Chih-Hsuan

2013-12-01

Taiwan's bicycle industry has been an international reputation as bicycle kingdom, but the problem in the world makes global warming green energy rise, the development of electrode slice of hub dynamo and power output connector to bring new hope to bike industry. In this study connector power output to gather public opinion related to patent, basis of collected documents as basis for design, structural components in least drawn to power output with simple connector. Power output of this study objectives connector hope at least cost, structure strongest, highest efficiency in output performance characteristics such as use of computer-aided drawing software Solid works to establish power output connector parts of 3D model, the overall portfolio should be considered part types including assembly ideas, weather resistance, water resistance, corrosion resistance to vibration and power flow stability. Moreover the 3D model import computer-aided finite element analysis software simulation of expected the power output of the connector parts manufacturing process. A series of simulation analyses, in which the variables relied on first stage and second stage forming, were run to examine the effective stress, effective strain, press speed, and die radial load distribution when forming electrode slice of bicycle dynamo hub.

Power systems and requirements for the integration of smart structures into aircraft

NASA Astrophysics Data System (ADS)

Lockyer, Allen J.; Martin, Christopher A.; Lindner, Douglas K.; Walia, Paramjit S.

2002-07-01

Electrical power distribution for recently developed smart actuators becomes an important air-vehicle challenge if projected smart actuation benefits are to be met. Among the items under development are variable shape inlets and control surfaces that utilize shape memory alloys (SMA); full span, chord-wise and span-wise contouring trailing control surfaces that use SMA or piezoelectric materials for actuation; and other strain-based actuators for buffet load alleviation, flutter suppression and flow control. At first glance, such technologies afford overall vehicle performance improvement, however, integration system impacts have yet to be determined or quantified. Power systems to support smart structures initiatives are the focus of the current paper. The paper has been organized into five main topics for further discussion: (1) air-vehicle power system architectures - standard and advanced distribution concepts for actuators, (2) smart wing actuator power requirements and results - highlighting wind tunnel power measurements from shape memory alloy and piezoelectric ultrasonic motor actuated control surfaces and different dynamic pressure and angle of attack; (3) vehicle electromagnetic effects (EME) issues, (4) power supply design considerations for smart actuators - featuring the aircraft power and actuator interface, and (5) summary and conclusions.

78 FR 71594 - Free Flow Power Missouri 2, LLC; Notice of Application Tendered for Filing With the Commission...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-29

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13703-002] Free Flow Power.... c. Date filed: November 13, 2013. d. Applicant: Free Flow Power Missouri 2, LLC. e. Name of Project... President of Project Development, Free Flow Power Corporation, 239 Causeway Street, Suite 300, Boston, MA...

78 FR 71596 - Free Flow Power Missouri 2, LLC; Notice of Application Tendered for Filing With the Commission...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-29

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13704-002] Free Flow Power.... c. Date Filed: November 13, 2013. d. Applicant: Free Flow Power Missouri 2, LLC. e. Name of Project... Feldman, Vice President of Project Development, Free Flow Power Corporation, 239 Causeway Street, Suite...

78 FR 71593 - Free Flow Power Missouri 2, LLC; Notice of Application Tendered for Filing With the Commission...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-29

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13702-002] Free Flow Power.... c. Date filed: November 13, 2013. d. Applicant: Free Flow Power Missouri 2, LLC. e. Name of Project... President of Project Development, Free Flow Power Corporation, 239 Causeway Street, Suite 300, Boston, MA...

78 FR 71592 - Free Flow Power Missouri 2, LLC; Notice of Application Tendered for Filing With the Commission...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-29

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13701-002] Free Flow Power.... c. Date filed: November 13, 2013. d. Applicant: Free Flow Power Missouri 2, LLC. e. Name of Project..., Vice President of Project Development, Free Flow Power Corporation, 239 Causeway Street, Suite 300...

Computational Investigations of Inboard Flow Separation and Mitigation Techniques on Multi-Megawatt Wind Turbines

NASA Astrophysics Data System (ADS)

Chow, Raymond

The aerodynamic characteristics of the NREL 5-MW rotor have been examined using a Reynolds-averaged Navier-Stokes method, OVERFLOW2. A comprehensive off-body grid independence study has been performed. A strong dependence on the size of the near-body wake grid has been found. Rapid diffusion of the wake appears to generate an overprediction of power and thrust. A large, continuous near-wake grid at minimum of two rotor diameters downstream of the rotor appears to be necessary for accurate predictions of near-body forces. The NREL 5-MW rotor demonstrates significant inboard flow separation up to 30% of span. This separation appears to be highly three-dimensional, with a significant amount of radial flow increasing the size of the separated region outboard. Both integrated aerodynamic coefficients and detailed wake structures for the baseline NREL 5-MW rotor are in excellent agreement with results by Riso at Uinfinity = 8 and 11 m/s. A simple, continuous full-chord fence was applied at the maximum chord location of the blade, within the region of separation. This non-optimized device reduced the boundary-layer cross-flow and resulting separation, and increased rotor power capture by 0.9% and 0.6% at U infinity = 8 and 11 m/s, respectively. Suction side only fences perform similarly in terms of power capture but reduce the increase in rotor thrust. Fence heights from 0.5% to 17.5% of the maximum chord all demonstrate some level of effectiveness, with fences (1-2.5%cmax) showing similar performance gains to taller fences with smaller penalties in thrust. Performance in terms of power capture is not very sensitive to spanwise location when placed within the separation region. Blunt trailing edge modifications to the inboard region of the blade showed a relatively significant effect on rotor power. Over a large range of trailing edge thicknesses from hTE = 10 to 25%c, power was found to increase by 1.4%. Thrust increased proportionally with the thicknesses examined, reaching a comparable increase of 1.4% by a trailing edge thickness of 15%c. Decreasing inboard twist only acted to increase thrust without increasing power capture any further at U infinity = 11 m/s. While increasing inboard blade twist decreased power, but decreased thrust at even a higher rate. Vortex generators were not successively configured to significantly improve power capture in this study. Two of the three configurations examined actually decreased power capture and increased the separation region. The results found in this study are not believed to be representative of a properly sized and located array of VGs. The presence of the nose cone and nacelle body at the hub of the rotor is found to have a minimal effect on the power and thrust of the overall rotor. The downstream wake structure however is changed by the nacelle, potentially useful for wake tailoring when turbines are closely spaced together.

Analyse et caracterisation d'interactions fluide-structure instationnaires en grands deplacements

NASA Astrophysics Data System (ADS)

Cori, Jean-Francois

Flapping wings for flying and oscillating fins for swimming stand out as the most complex yet efficient propulsion methods found in nature. Understanding the phenomena involved is a great challenge generating significant interests, especially in the growing field of Micro Air Vehicles. The thrust and lift are induced by oscillating foils thanks to a complex phenomenon of unsteady fluid-structure interaction (FSI). The aim of the dissertation is to develop an efficient CFD framework for simulating the FSI process involved in the propulsion or the power extraction of an oscillating flexible airfoil in a viscous incompressible flow. The numerical method relies on direct implicit monolithic formulation using high-order implicit time integrators. We use an Arbitrary Lagrangian Eulerian (ALE) formulation of the equations designed to satisfy the Geometric Conservation Law (GCL) and to guarantee that the high order temporal accuracy of the time integrators observed on fixed meshes is preserved on ALE deforming meshes. Hyperelastic structural Saint-Venant Kirchhoff model, viscous incompressible Navier-Stokes equations for the flow, Newton's law for the point mass and equilibrium equations at the interface form one large monolithic system. The fully implicit FSI approach uses coincidents nodes on the fluid-structure interface, so that loads, velocities and displacements are evaluated at the same location and at the same time. The problem is solved in an implicit manner using a Newton-Raphson pseudo-solid finite element approach. High-order implicit Runge-Kutta time integrators are implemented (up to 5th order) to improve the accuracy and reduce the computational cost. In this context of stiff interaction problems, the highly stable fully implicit one-step approach is an original alternative to traditional multistep or explicit one-step finite element approaches. The methodology has been verified with three different test-cases. Thorough time-step refinement studies for a rigid oscillating airfoil on deforming meshes, for flow induced vibrations of a flexible strip and for a self-propulsed flapping airfoil indicate that the stability of the proposed approach is always observed even with large time steps, spurious oscillations on the structure are avoided without any damping and the high order accuracy of the IRK schemes is maintained. We have applied our powerful FSI framework on three interesting applications, with a detailed dimensional analysis to obtain their characteristic parameters. Firstly, we have studied the vibrational characteristics of a well-documented fluid-structure interaction case : a flexible strip fixed behind a rigid square cylinder. Our results compare favorably with previous works. The accuracy of the IRK time integrators (even for the pressure field of incompressible flow), their unconditional stability and their non-dissipative nature produced results revealing new, never previously reported, higher frequency structural forces weakly coupled with the fluid. Secondly, we have explored the propulsive and power extraction characteristics of rigid and flexible flapping airfoils. For the power extraction, we found an excellent agreement with literature results. A parametric study indicates the optimal motion parameters to get high propulsive efficiencies. An optimal flexibility seems to improve power extraction efficiency. Finally, a survey on flapping propulsion has given initial results for a self-propulsed airfoil and has opened a new way of studying propulsive efficiency. (Abstract shortened by UMI.)

DISTRIBUTION OF THE TEMPERATURE IN THE ASH-GAS FLOW DURING KORYAKSKY VOLCANO ERUPTION IN 2009

NASA Astrophysics Data System (ADS)

Gordeev, E.; Droznin, V.

2009-12-01

The observations of the ash-gas plumes during the Koryaksky eruption in March 2009 by the high resolution thermovision camera allowed obtaining thermal distributions inside the ash-gas flows. The plume structure is formed by single emissions. They rise at the rate of 5.5-7 m/s. The plume structure in general is represented as 3 zones: 1. a zone of high heat exchange; 2. a zone of floating up; 3. a zone of lateral movement. The plume temperature within the zone of lateral movement exceeds the atmospheric temperature by 3-5 oC, within the zone of floating up it exceeds by 20 oC. Its rate within the zone of floating up comprises 5-7 m/s. At the boundary between the zones of high heat exchange and floating up where we know the plume section, from heat balance equation we can estimate steam rate and heat power of the fluid thermal flow. Power of the overheated steam was estimated as Q=35 kg/s. It forms the ash-gas plume from the eruption and has temperature equal to 450 oC. The total volume of water steam produced during 100 days of eruption was estimated 3*105 t, its energy - 109 MJ.

Continuous microwave flow synthesis of mesoporous hydroxyapatite.

PubMed

Akram, Muhammad; Alshemary, Ammar Z; Goh, Yi-Fan; Wan Ibrahim, Wan Aini; Lintang, Hendrik O; Hussain, Rafaqat

2015-11-01

We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Temporally resolved ozone distribution of a time modulated RF atmospheric pressure argon plasma jet: flow, chemical reaction, and transient vortex

NASA Astrophysics Data System (ADS)

Zhang, S.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P. J.

2015-08-01

The ozone density distribution in the effluent of a time modulated RF atmospheric pressure plasma jet (APPJ) is investigated by time and spatially resolved by UV absorption spectroscopy. The plasma jet is operated with an averaged dissipated power of 6.5 W and gas flow rate 2 slm argon  +2% O2. The modulation frequency of the RF power is 50 Hz with a duty cycle of 50%. To investigate the production and destruction mechanism of ozone in the plasma effluent, the atomic oxygen and gas temperature is also obtained by TALIF and Rayleigh scattering, respectively. A temporal increase in ozone density is observed close to the quartz tube exit when the plasma is switched off due to the decrease in O density and gas temperature. Ozone absorption at different axial positions indicates that the ozone distribution is dominated by the convection induced by the gas flow and allows estimating the on-axis local gas velocity in the jet effluent. Transient vortex structures occurring during the switch on and off of the RF power also significantly affect the ozone density in the far effluent.

Multifractal Modeling of Turbulent Mixing

NASA Astrophysics Data System (ADS)

Samiee, Mehdi; Zayernouri, Mohsen; Meerschaert, Mark M.

2017-11-01

Stochastic processes in random media are emerging as interesting tools for modeling anomalous transport phenomena. Applications include intermittent passive scalar transport with background noise in turbulent flows, which are observed in atmospheric boundary layers, turbulent mixing in reactive flows, and long-range dependent flow fields in disordered/fractal environments. In this work, we propose a nonlocal scalar transport equation involving the fractional Laplacian, where the corresponding fractional index is linked to the multifractal structure of the nonlinear passive scalar power spectrum. This work was supported by the AFOSR Young Investigator Program (YIP) award (FA9550-17-1-0150) and partially by MURI/ARO (W911NF-15-1-0562).

A Wave Power Device with Pendulum Based on Ocean Monitoring Buoy

NASA Astrophysics Data System (ADS)

Chai, Hui; Guan, Wanchun; Wan, Xiaozheng; Li, Xuanqun; Zhao, Qiang; Liu, Shixuan

2018-01-01

The ocean monitoring buoy usually exploits solar energy for power supply. In order to improve power supply capacity, this paper proposes a wave power device according to the structure and moving character of buoy. The wave power device composes of pendulum mechanism that converts wave energy into mechanical energy and energy storage mechanism where the mechanical energy is transferred quantitatively to generator. The hydrodynamic equation for the motion of buoy system with generator devise is established based on the potential flow theory, and then the characteristics of pendulum motion and energy conversion properties are analysed. The results of this research show that the proposed wave power devise is able to efficiently and periodically convert wave energy into power, and increasing the stiffness of energy storage spring is benefit for enhancing the power supply capacity of the buoy. This study provides a theory reference for the development of technology on wave power generator for ocean monitoring buoy.

Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistor and Its RF Power Efficiency Optimization with Source-Bridged Field-Plate Structure.

PubMed

Kwak, Hyeon-Tak; Chang, Seung-Bo; Jung, Hyun-Gu; Kim, Hyun-Seok

2018-09-01

In this study, we consider the relationship between the temperature in a two-dimensional electron gas (2-DEG) channel layer and the RF characteristics of an AlGaN/GaN high-electron-mobility transistor by changing the geometrical structure of the field-plate. The final goal is to achieve a high power efficiency by decreasing the channel layer temperature. First, simulations were performed to compare and contrast the experimental data of a conventional T-gate head structure. Then, a source-bridged field-plate (SBFP) structure was used to obtain the lower junction temperature in the 2-DEG channel layer. The peak electric field intensity was reduced, and a decrease in channel temperature resulted in an increase in electron mobility. Furthermore, the gate-to-source capacitance was increased by the SBFP structure. However, under the large current flow condition, the SBFP structure had a lower maximum temperature than the basic T-gate head structure, which improved the device electron mobility. Eventually, an optimum position of the SBFP was used, which led to higher frequency responses and improved the breakdown voltages. Hence, the optimized SBFP structure can be a promising candidate for high-power RF devices.

Cavitating behaviour analysis of Darrieus-type cross flow water turbines

NASA Astrophysics Data System (ADS)

Aumelas, V.; Pellone, C.; Maître, T.

2010-08-01

The aim of this paper is to study the cavitating behaviour of bare Darrieus-type turbines. For that, the RANS code CAVKA, has been used. Under non-cavitating conditions, the power coefficient and the thrusts calculated with CAVKA are compared to experimental values obtained in the LEGI hydrodynamic tunnel. Under cavitating conditions, for several cavitation numbers, the numerical power coefficients and vapour structures are compared to experimental ones. Different blade profiles and camber lines are also studied for non-cavitating and cavitating conditions.

Development of an outdoor MRI system for measuring flow in a living tree

NASA Astrophysics Data System (ADS)

Nagata, Akiyoshi; Kose, Katsumi; Terada, Yasuhiko

2016-04-01

An outdoor MRI system for noninvasive, long-term measurements of sap flow in a living tree in its natural environment has been developed. An open-access, 0.2 T permanent magnet with a 160 mm gap was combined with a radiofrequency probe, planar gradient coils, electromagnetic shielding, several electrical units, and a waterproofing box. Two-dimensional cross-sectional images were acquired for a ring-porous tree, and the anatomical structures, including xylem and phloem, were identified. The MRI flow measurements demonstrated the diurnal changes in flow velocity in the stem on a per-pixel basis. These results demonstrate that our outdoor MRI system is a powerful tool for studies of water transport in outdoor trees.

Mathematical modeling and optimization of flow structure in stage of francis turbine of micro gas turbine power plant

NASA Astrophysics Data System (ADS)

Kartashev, A. L.; Vaulin, S. D.; Kartasheva, M. A.; Martynov, A. A.; Safonov, E. V.

2016-06-01

This article presents information about the main distinguishing features of microturbine power plants. The justification of the use of Francis turbine in microturbine power plants with rated power of 100 kW is given. Initial analytical engineering calculations of the turbine (without using computational fluid dynamics) with appropriate calculation methods are considered. The parametric study of nozzle blade and whole turbine stage using ANSYS CFX is descripted. The calculations determined the optimal geometry on the criterion of maximizing efficiency at total pressure ratio. The calculation results are presented in graphical form, as well as the velocity and pressure fields at the interscapular channels of nozzle unit and the impeller.

Method of assembling an electric power

DOEpatents

Rinehart, Lawrence E [Lake Oswego, OR; Romero, Guillermo L [Phoenix, AZ

2007-05-03

A method of assembling and providing an electric power apparatus. The method uses a heat resistant housing having a structure adapted to accommodate and retain a power circuit card and also including a bracket adapted to accommodate and constrain a rigid conductive member. A power circuit card having an electrical terminal is placed into the housing and a rigid conductive member into the bracket. The rigid conductive member is flow soldered to the electrical terminal, thereby exposing the heat resistant housing to heat and creating a solder bond. Finally, the rigid conductive member is affirmatively connected to the housing. The bracket constrains the rigid conductive member so that the act of affirmatively connecting does not weaken the solder bond.

Numerical simulation of mechanical mixing in high solid anaerobic digester.

PubMed

Yu, Liang; Ma, Jingwei; Chen, Shulin

2011-01-01

Computational fluid dynamics (CFD) was employed to study mixing performance in high solid anaerobic digester (HSAD) with A-310 impeller and helical ribbon. A mathematical model was constructed to assess flow fields. Good agreement of the model results with experimental data was obtained for the A-310 impeller. A systematic comparison for the interrelationship of power number, flow number and Reynolds number was simulated in a digester with less than 5% TS and 10% TS (total solids). The simulation results suggested a great potential for using the helical ribbon mixer in the mixing of high solids digester. The results also provided quantitative confirmation for minimum power consumption in HSAD and the effect of share rate on bio-structure. Copyright © 2010 Elsevier Ltd. All rights reserved.

On the basically single-type excitation source of resonance in the wind tunnel and in the hydroturbine channel of a hydraulic power plant

NASA Astrophysics Data System (ADS)

Karavosov, R. K.; Prozorov, A. G.

2012-01-01

We have investigated the spectra of pressure pulsations in the near field of the open working section of the wind tunnel with a vortex flow behind the tunnel blower formed like the flow behind the hydroturbine of a hydraulic power plant. We have made a comparison between the measurement data for pressure pulsations and the air stream velocity in tunnels of the above type and in tunnels in which a large-scale vortex structure behind the blower is not formed. It has been established that the large-scale vortex formation in the incompressible medium behind the blade system in the wind tunnel is a source of narrow-band acoustic radiation capable of exciting resonance self-oscillations in the tunnel channel.

Gaseous-fuel nuclear reactor research for multimegawatt power in space

NASA Technical Reports Server (NTRS)

Thom, K.; Schneider, R. T.; Helmick, H. H.

1977-01-01

In the gaseous-fuel reactor concept, the fissile material is contained in a moderator-reflector cavity and exists in the form of a flowing gas or plasma separated from the cavity walls by means of fluid mechanical forces. Temperatures in excess of structural limitations are possible for low-specific-mass power and high-specific-impulse propulsion in space. Experiments have been conducted with a canister filled with enriched UF6 inserted into a beryllium-reflected cavity. A theoretically predicted critical mass of 6 kg was measured. The UF6 was also circulated through this cavity, demonstrating stable reactor operation with the fuel in motion. Because the flowing gaseous fuel can be continuously processed, the radioactive waste in this type of reactor can be kept small. Another potential of fissioning gases is the possibility of converting the kinetic energy of fission fragments directly into coherent electromagnetic radiation, the nuclear pumping of lasers. Numerous nuclear laser experiments indicate the possibility of transmitting power in space directly from fission energy. The estimated specific mass of a multimegawatt gaseous-fuel reactor power system is from 1 to 5 kg/kW while the companion laser-power receiver station would be much lower in specific mass.

Statistical scaling of pore-scale Lagrangian velocities in natural porous media.

PubMed

Siena, M; Guadagnini, A; Riva, M; Bijeljic, B; Pereira Nunes, J P; Blunt, M J

2014-08-01

We investigate the scaling behavior of sample statistics of pore-scale Lagrangian velocities in two different rock samples, Bentheimer sandstone and Estaillades limestone. The samples are imaged using x-ray computer tomography with micron-scale resolution. The scaling analysis relies on the study of the way qth-order sample structure functions (statistical moments of order q of absolute increments) of Lagrangian velocities depend on separation distances, or lags, traveled along the mean flow direction. In the sandstone block, sample structure functions of all orders exhibit a power-law scaling within a clearly identifiable intermediate range of lags. Sample structure functions associated with the limestone block display two diverse power-law regimes, which we infer to be related to two overlapping spatially correlated structures. In both rocks and for all orders q, we observe linear relationships between logarithmic structure functions of successive orders at all lags (a phenomenon that is typically known as extended power scaling, or extended self-similarity). The scaling behavior of Lagrangian velocities is compared with the one exhibited by porosity and specific surface area, which constitute two key pore-scale geometric observables. The statistical scaling of the local velocity field reflects the behavior of these geometric observables, with the occurrence of power-law-scaling regimes within the same range of lags for sample structure functions of Lagrangian velocity, porosity, and specific surface area.

Analysis and Down Select of Flow Passages for Thermal Hydraulic Testing of a SNAP Derived Reactor

NASA Technical Reports Server (NTRS)

Godfroy, T. J.; Sadasivan, P.; Masterson, S.

2007-01-01

As past of the Vision for Space Exploration, man will return to the moon. To enable safe and productive time on the lunar surface will require adequate power resources. To provide the needed power and to give mission planners all landing site possibilities, including a permanently dark crater, a nuclear reactor provides the most options. Designed to be l00kWt providing approx. 25kWe this power plants would be very effective in delivering dependable, site non-specific power to crews or robotic missions on the lunar surface. An affordable reference reactor based upon the successful SNAP program of the 1960's and early 1970's has been designed by Los Alamos National Laboratory that will meet such a requirement. Considering current funding, environmental, and schedule limitations this lunar surface power reactor will be tested using non-nuclear simulators to simulate the heat from fission reactions. Currently a 25kWe surface power SNAP derivative reactor is in the early process of design and testing with collaboration between Los Alamos National Laboratory, Idaho National Laboratory, Glenn Research Center, Marshall Space Flight Center, and Sandia National Laboratory to ensure that this new design is affordable and can be tested using non-nuclear methods as have proven so effective in the past. This paper will discuss the study and down selection of a flow passage concept for a approx. 25kWe lunar surface power reactor. Several different flow passages designs were evaluated using computational fluid dynamics to determine pressure drop and a structural assessment to consider thermal and stress of the passage walls. The reactor design basis conditions are discussed followed by passage problem setup and results for each concept. A recommendation for passage design is made with rationale for selection.

History, Structure and Agency in Global Health Governance

PubMed Central

Gill, Stephen; Benatar, Solomon R.

2017-01-01

Ilona Kickbusch’s thought provoking editorial is criticized in this commentary, partly because she fails to refer to previous critical work on the global conditions and policies that sustain inequality, poverty, poor health and damage to the biosphere and, as a result, she misreads global power and elides consideration of the fundamental historical structures of political and material power that shape agency in global health governance. We also doubt that global health can be improved through structures and processes of multilateralism that are premised on the continued reproduction of the ecologically myopic and socially unsustainable market civilization model of capitalist development that currently prevails in the world economy. This model drives net financial flows from poor to rich countries and from the poor to the affluent and super wealthy individuals. By contrast, we suggest that significant progress in global health requires a profound and socially just restructuring of global power, greater global solidarity and the "development of sustainability." PMID:28812808

Vacuum testing of a miniaturised switch mode amplifier powering an electrothermal plasma micro-thruster

NASA Astrophysics Data System (ADS)

Charles, Christine; Liang, Wei; Raymond, Luke; Rivas-Davila, Juan; Boswell, Roderick W.

2017-08-01

A structurally supportive miniaturised low-weight (≤150 g) radiofrequency switch mode amplifier developed to power the small diameter Pocket Rocket electrothermal plasma micro-thruster called MiniPR is tested in vacuum conditions representative of space to demonstrate its suitability for use on nano-satellites such as `CubeSats'. Argon plasma characterisation is carried out by measuring the optical emission signal seen through the plenum window versus frequency (12.8-13.8 MHz) and the plenum cavity pressure increase (indicative of thrust generation from volumetric gas heating in the plasma cavity) versus power (1-15 Watts) with the amplifier operating at atmospheric pressure and a constant flow rate of 20 sccm. Vacuum testing is subsequently performed by measuring the operational frequency range of the amplifier as a function of gas flow rate. The switch mode amplifier design is finely tuned to the input impedance of the thruster ˜16 pF) to provide a power efficiency of 88 % at the resonant frequency and a direct feed to a low-loss (˜ 10 %) impedance matching network. This system provides successful plasma coupling at 1.54 Watts for all investigated flow rates (10-130 sccm) for cryogenic pumping speeds of the order of 6000 l.s^{-1} and a vacuum pressure of the order of ˜ 2x10^{-5} Torr during operation. Interestingly, the frequency bandwidth for which a plasma can be coupled increases from 0.04 to 0.4 MHz when the gas flow rate is increased, probably as a result of changes in the plasma impedance.

Fine-Scale Analysis Reveals Cryptic Landscape Genetic Structure in Desert Tortoises

PubMed Central

Latch, Emily K.; Boarman, William I.; Walde, Andrew; Fleischer, Robert C.

2011-01-01

Characterizing the effects of landscape features on genetic variation is essential for understanding how landscapes shape patterns of gene flow and spatial genetic structure of populations. Most landscape genetics studies have focused on patterns of gene flow at a regional scale. However, the genetic structure of populations at a local scale may be influenced by a unique suite of landscape variables that have little bearing on connectivity patterns observed at broader spatial scales. We investigated fine-scale spatial patterns of genetic variation and gene flow in relation to features of the landscape in desert tortoise (Gopherus agassizii), using 859 tortoises genotyped at 16 microsatellite loci with associated data on geographic location, sex, elevation, slope, and soil type, and spatial relationship to putative barriers (power lines, roads). We used spatially explicit and non-explicit Bayesian clustering algorithms to partition the sample into discrete clusters, and characterize the relationships between genetic distance and ecological variables to identify factors with the greatest influence on gene flow at a local scale. Desert tortoises exhibit weak genetic structure at a local scale, and we identified two subpopulations across the study area. Although genetic differentiation between the subpopulations was low, our landscape genetic analysis identified both natural (slope) and anthropogenic (roads) landscape variables that have significantly influenced gene flow within this local population. We show that desert tortoise movements at a local scale are influenced by features of the landscape, and that these features are different than those that influence gene flow at larger scales. Our findings are important for desert tortoise conservation and management, particularly in light of recent translocation efforts in the region. More generally, our results indicate that recent landscape changes can affect gene flow at a local scale and that their effects can be detected almost immediately. PMID:22132143

Fine-scale analysis reveals cryptic landscape genetic structure in desert tortoises.

PubMed

Latch, Emily K; Boarman, William I; Walde, Andrew; Fleischer, Robert C

2011-01-01

Characterizing the effects of landscape features on genetic variation is essential for understanding how landscapes shape patterns of gene flow and spatial genetic structure of populations. Most landscape genetics studies have focused on patterns of gene flow at a regional scale. However, the genetic structure of populations at a local scale may be influenced by a unique suite of landscape variables that have little bearing on connectivity patterns observed at broader spatial scales. We investigated fine-scale spatial patterns of genetic variation and gene flow in relation to features of the landscape in desert tortoise (Gopherus agassizii), using 859 tortoises genotyped at 16 microsatellite loci with associated data on geographic location, sex, elevation, slope, and soil type, and spatial relationship to putative barriers (power lines, roads). We used spatially explicit and non-explicit Bayesian clustering algorithms to partition the sample into discrete clusters, and characterize the relationships between genetic distance and ecological variables to identify factors with the greatest influence on gene flow at a local scale. Desert tortoises exhibit weak genetic structure at a local scale, and we identified two subpopulations across the study area. Although genetic differentiation between the subpopulations was low, our landscape genetic analysis identified both natural (slope) and anthropogenic (roads) landscape variables that have significantly influenced gene flow within this local population. We show that desert tortoise movements at a local scale are influenced by features of the landscape, and that these features are different than those that influence gene flow at larger scales. Our findings are important for desert tortoise conservation and management, particularly in light of recent translocation efforts in the region. More generally, our results indicate that recent landscape changes can affect gene flow at a local scale and that their effects can be detected almost immediately.

Analysis of the power flow in nonlinear oscillators driven by random excitation using the first Wiener kernel

NASA Astrophysics Data System (ADS)

Hawes, D. H.; Langley, R. S.

2018-01-01

Random excitation of mechanical systems occurs in a wide variety of structures and, in some applications, calculation of the power dissipated by such a system will be of interest. In this paper, using the Wiener series, a general methodology is developed for calculating the power dissipated by a general nonlinear multi-degree-of freedom oscillatory system excited by random Gaussian base motion of any spectrum. The Wiener series method is most commonly applied to systems with white noise inputs, but can be extended to encompass a general non-white input. From the extended series a simple expression for the power dissipated can be derived in terms of the first term, or kernel, of the series and the spectrum of the input. Calculation of the first kernel can be performed either via numerical simulations or from experimental data and a useful property of the kernel, namely that the integral over its frequency domain representation is proportional to the oscillating mass, is derived. The resulting equations offer a simple conceptual analysis of the power flow in nonlinear randomly excited systems and hence assist the design of any system where power dissipation is a consideration. The results are validated both numerically and experimentally using a base-excited cantilever beam with a nonlinear restoring force produced by magnets.

Predicting vibratory stresses from aero-acoustic loads

NASA Astrophysics Data System (ADS)

Shaw, Matthew D.

Sonic fatigue has been a concern of jet aircraft engineers for many years. As engines become more powerful, structures become more lightly damped and complex, and materials become lighter, stiffer, and more complicated, the need to understand and predict structural response to aeroacoustic loads becomes more important. Despite decades of research, vibration in panels caused by random pressure loads, such as those found in a supersonic jet, is still difficult to predict. The work in this research improves on current prediction methods in several ways, in particular for the structural response due to wall pressures induced by supersonic turbulent flows. First, solutions are calculated using time-domain input pressure loads that include shock cells and their interaction with turbulent flow. The solutions include both mean (static) and oscillatory components. Second, the time series of stresses are required for many fatigue assessment counting algorithms. To do this, a method is developed to compute time-dependent solutions in the frequency domain. The method is first applied to a single-degree-of-freedom system. The equations of motion are derived and solved in both the frequency domain and the time domain. The pressure input is a random (broadband) signal representative of jet flow. The method is then applied to a simply-supported beam vibrating in flexure using a line of pressure inputs computed with computational fluid dynamics (CFD). A modal summation approach is used to compute structural response. The coupling between the pressure field and the structure, through the joint acceptance, is reviewed and discussed for its application to more complicated structures. Results from the new method and from a direct time domain method are compared for method verification. Because the match is good and the new frequency domain method is faster computationally, it is chosen for use in a more complicated structure. The vibration of a two-dimensional panel loaded by jet nozzle discharge flow is addressed. The surface pressures calculated at Pratt and Whitney using viscous and compressible CFD are analyzed and compared to surface pressure measurements made at the United Technologies Research Center (UTRC). A structural finite element model is constructed to represent a flexible panel also used in the UTRC setup. The mode shapes, resonance frequencies, modal loss factors, and surface pressures are input into the solution method. Displacement time series and power spectral densities are computed and compared to measurement and show good agreement. The concept of joint acceptance is further addressed for two-dimensional plates excited by supersonic jet flow. Static and alternating stresses in the panel are also computed, and the most highly stressed modes are identified. The surface pressures are further analyzed in the wavenumber domain for insight into the physics of sonic fatigue. Most of the energy in the wall pressure wavenumber-frequency spectrum at subsonic speeds is in turbulent structures near the convective wavenumber. In supersonic flow, however, the shock region dominates the spectrum at low frequencies, but convective behavior is still dominant at higher frequencies. When the forcing function wavenumber energy overlaps the modal wavenumbers, the acceptance of energy by the structure from the flow field is greatest. The wavenumber analysis suggests a means of designing structures to minimize overlap of excitation and structural wavenumber peaks to minimize vibration and sonic fatigue.

Power formula for open-channel flow resistance

USGS Publications Warehouse

Chen, Cheng-lung

1988-01-01

This paper evaluates various power formulas for flow resistance in open channels. Unlike the logarithmic resistance equation that can be theoretically derived either from Prandtl's mixing-length hypothesis or von Karman's similarity hypothesis, the power formula has long had an appearance of empiricism. Nevertheless, the simplicity in the form of the power formula has made it popular among the many possible forms of flow resistance formulas. This paper reexamines the concept and rationale of the power formulation, thereby addressing some critical issues in the modeling of flow resistance.

High power Nb-doped LiFePO4 Li-ion battery cathodes; pilot-scale synthesis and electrochemical properties

NASA Astrophysics Data System (ADS)

Johnson, Ian D.; Blagovidova, Ekaterina; Dingwall, Paul A.; Brett, Dan J. L.; Shearing, Paul R.; Darr, Jawwad A.

2016-09-01

High power, phase-pure Nb-doped LiFePO4 (LFP) nanoparticles are synthesised using a pilot-scale continuous hydrothermal flow synthesis process (production rate of 6 kg per day) in the range 0.01-2.00 at% Nb with respect to total transition metal content. EDS analysis suggests that Nb is homogeneously distributed throughout the structure. The addition of fructose as a reagent in the hydrothermal flow process, followed by a post synthesis heat-treatment, affords a continuous graphitic carbon coating on the particle surfaces. Electrochemical testing reveals that cycling performance improves with increasing dopant concentration, up to a maximum of 1.0 at% Nb, for which point a specific capacity of 110 mAh g-1 is obtained at 10 C (6 min for the charge or discharge). This is an excellent result for a high power cathode LFP based material, particularly when considering the synthesis was performed on a large pilot-scale apparatus.

Gas and plasma dynamics of RF discharge jet of low pressure in a vacuum chamber with flat electrodes and inside tube, influence of RF discharge on the steel surface parameters

NASA Astrophysics Data System (ADS)

Khristoliubova, V. I.; Kashapov, N. F.; Shaekhov, M. F.

2016-06-01

Researches results of the characteristics of the RF discharge jet of low pressure and the discharge influence on the surface modification of high speed and structural steels are introduced in the article. Gas dynamics, power and energy parameters of the RF low pressure discharge flow in the discharge chamber and the electrode gap are studied in the presence of the materials. Plasma flow rate, discharge power, the concentration of electrons, the density of RF power, the ion current density, and the energy of the ions bombarding the surface materials are considered for the definition of basic properties crucial for the process of surface modification of materials as they were put in the plasma jet. The influence of the workpiece and effect of products complex configuration on the RF discharge jet of low pressure is defined. The correlation of the input parameters of the plasma unit on the characteristics of the discharge is established.

A 400-kWe high-efficiency steam turbine for industrial cogeneration

NASA Technical Reports Server (NTRS)

Leibowitz, H. M.

1982-01-01

An advanced state-of-the-art steam turbine-generator developed to serve as the power conversion subsystem for the Department of Energy's Sandia National Laboratories' Solar Total-Energy Project (STEP) is described. The turbine-generator, which is designed to provide 400-kW of net electrical power, represents the largest turbine-generator built specifically for commercial solar-powered cogeneration. The controls for the turbine-generator incorporate a multiple, partial-arc entry to provide efficient off-design performance, as well as an extraction control scheme to permit extraction flow regulation while maintaining 110-spsig pressure. Normal turbine operation is achieved while synchronized to a local utility and in a stand-alone mode. In both cases, the turbine-generator features automatic load control as well as remote start-up and shutdown capability. Tests totaling 200 hours were conducted to confirm the integrity of the turbine's mechanical structure and control function. Performance tests resulted in a measured inlet throttle flow of 8,450 pounds per hour, which was near design conditions.

Structure of S-shaped growth in innovation diffusion

NASA Astrophysics Data System (ADS)

Shimogawa, Shinsuke; Shinno, Miyuki; Saito, Hiroshi

2012-05-01

A basic question on innovation diffusion is why the growth curve of the adopter population in a large society is often S shaped. From macroscopic, microscopic, and mesoscopic viewpoints, the growth of the adopter population is observed as the growth curve, individual adoptions, and differences among individual adoptions, respectively. The S shape can be explained if an empirical model of the growth curve can be deduced from models of microscopic and mesoscopic structures. However, even the structure of growth curve has not been revealed yet because long-term extrapolations by proposed models of S-shaped curves are unstable and it has been very difficult to predict the long-term growth and final adopter population. This paper studies the S-shaped growth from the viewpoint of social regularities. Simple methods to analyze power laws enable us to extract the structure of the growth curve directly from the growth data of recent basic telecommunication services. This empirical model of growth curve is singular at the inflection point and a logarithmic function of time after this point, which explains the unstable extrapolations obtained using previously proposed models and the difficulty in predicting the final adopter population. Because the empirical S curve can be expressed in terms of two power laws of the regularity found in social performances of individuals, we propose the hypothesis that the S shape represents the heterogeneity of the adopter population, and the heterogeneity parameter is distributed under the regularity in social performances of individuals. This hypothesis is so powerful as to yield models of microscopic and mesoscopic structures. In the microscopic model, each potential adopter adopts the innovation when the information accumulated by the learning about the innovation exceeds a threshold. The accumulation rate of information is heterogeneous among the adopter population, whereas the threshold is a constant, which is the opposite of previously proposed models. In the mesoscopic model, flows of innovation information incoming to individuals are organized as dimorphic and partially clustered. These microscopic and mesoscopic models yield the empirical model of the S curve and explain the S shape as representing the regularities of information flows generated through a social self-organization. To demonstrate the validity and importance of the hypothesis, the models of three level structures are applied to reveal the mechanism determining and differentiating diffusion speeds. The empirical model of S curves implies that the coefficient of variation of the flow rates determines the diffusion speed for later adopters. Based on this property, a model describing the inside of information flow clusters can be given, which provides a formula interconnecting the diffusion speed, cluster populations, and a network topological parameter of the flow clusters. For two recent basic telecommunication services in Japan, the formula represents the variety of speeds in different areas and enables us to explain speed gaps between urban and rural areas and between the two services. Furthermore, the formula provides a method to estimate the final adopter population.

Stationary zonal flows during the formation of the edge transport barrier in the JET tokamak

DOE PAGES

Hillesheim, J. C.; Meyer, H.; Maggi, C. F.; ...

2016-02-10

In this study, high spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge E r. We observe fine-scale spatial structures in the edge E r well with a wave number k rρi ≈ 0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E x B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-modemore » transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.« less

Relationship between microscopic dynamics in traffic flow and complexity in networks.

PubMed

Li, Xin-Gang; Gao, Zi-You; Li, Ke-Ping; Zhao, Xiao-Mei

2007-07-01

Complex networks are constructed in the evolution process of traffic flow, and the states of traffic flow are represented by nodes in the network. The traffic dynamics can then be studied by investigating the statistical properties of those networks. According to Kerner's three-phase theory, there are two different phases in congested traffic, synchronized flow and wide moving jam. In the framework of this theory, we study different properties of synchronized flow and moving jam in relation to complex network. Scale-free network is constructed in stop-and-go traffic, i.e., a sequence of moving jams [Chin. Phys. Lett. 10, 2711 (2005)]. In this work, the networks generated in synchronized flow are investigated in detail. Simulation results show that the degree distribution of the networks constructed in synchronized flow has two power law regions, so the distinction in topological structure can really reflect the different dynamics in traffic flow. Furthermore, the real traffic data are investigated by this method, and the results are consistent with the simulations.

Computational Study on the Effect of Shroud Shape on the Efficiency of the Gas Turbine Stage

NASA Astrophysics Data System (ADS)

Afanas'ev, I. V.; Granovskii, A. V.

2018-03-01

The last stages of powerful power gas turbines play an important role in the development of power and efficiency of the whole unit as well as in the distribution of the flow parameters behind the last stage, which determines the efficient operation of the exhaust diffusers. Therefore, much attention is paid to improving the efficiency of the last stages of gas turbines as well as the distribution of flow parameters. Since the long blades of the last stages of multistage high-power gas turbines could fall into the resonance frequency range in the course of operation, which results in the destruction of the blades, damping wires or damping bolts are used for turning out of resonance frequencies. However, these damping elements cause additional energy losses leading to a reduction in the efficiency of the stage. To minimize these losses, dampening shrouds are used instead of wires and bolts at the periphery of the working blades. However, because of the strength problems, designers have to use, instead of the most efficient full shrouds, partial shrouds that do not provide for significantly reducing the losses in the tip clearance between the blade and the turbine housing. In this paper, a computational study is performed concerning an effect that the design of the shroud of the turbine-working blade exerted on the flow structure in the vicinity of the shroud and on the efficiency of the stage as a whole. The analysis of the flow structure has shown that a significant part of the losses under using the shrouds is associated with the formation of vortex zones in the cavities on the turbine housing before the shrouds, between the ribs of the shrouds, and in the cavities at the outlet behind the shrouds. All the investigated variants of a partial shrouding are inferior in efficiency to the stages with shrouds that completely cover the tip section of the working blade. The stage with a unshrouded working blade was most efficient at the values of the relative tip clearance less than 0.9%.

Analysis and experimental verification of new power flow control for grid-connected inverter with LCL filter in microgrid.

PubMed

Gu, Herong; Guan, Yajuan; Wang, Huaibao; Wei, Baoze; Guo, Xiaoqiang

2014-01-01

Microgrid is an effective way to integrate the distributed energy resources into the utility networks. One of the most important issues is the power flow control of grid-connected voltage-source inverter in microgrid. In this paper, the small-signal model of the power flow control for the grid-connected inverter is established, from which it can be observed that the conventional power flow control may suffer from the poor damping and slow transient response. While the new power flow control can mitigate these problems without affecting the steady-state power flow regulation. Results of continuous-domain simulations in MATLAB and digital control experiments based on a 32-bit fixed-point TMS320F2812 DSP are in good agreement, which verify the small signal model analysis and effectiveness of the proposed method.

In-space research, technology and engineering experiments and Space Station

NASA Technical Reports Server (NTRS)

Tyson, Richard; Gartrell, Charles F.

1988-01-01

The NASA Space Station will serve as a technology research laboratory, a payload-servicing facility, and a large structure fabrication and assembly facility. Space structures research will encompass advanced structural concepts and their dynamics, advanced control concepts, sensors, and actuators. Experiments dealing with fluid management will gather data on such fundamentals as multiphase flow phenomena. As requirements for power systems and thermal management grow, experiments quantifying the performance of energy systems and thermal management concepts will be undertaken, together with expanded efforts in the fields of information systems, automation, and robotics.

MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

MIDDLE GORGE POWER PLANT, OWENS RIVER STREAM FLOWING OVER TAIL RACE OF POWER PLANT AND PENSTOCK HEADGATE TO LOWER GORGE CONTROL PLANT. A MINIMAL FLOW OF RIVER WATER IS REQUIRED TO MAINTAIN FISH LIFE - Los Angeles Aqueduct, Middle Gorge Power Plant, Los Angeles, Los Angeles County, CA

Multi-port power router and its impact on resilient power grid systems

NASA Astrophysics Data System (ADS)

Kado, Yuichi; Iwatsuki, Katsumi; Wada, Keiji

2016-02-01

We propose a Y-configuration power router as a unit cell to easily construct a power delivery system that can meet many types of user requirements. The Y-configuration power router controls the direction and magnitude of power flow among three ports regardless of DC and AC. We constructed a prototype three-way isolated DC/DC converter that is the core unit of the Y-configuration power router and tested the power flow control operation. Experimental results revealed that our methodology based on the governing equation was appropriate for the power flow control of the three-way DC/DC converter. In addition, the hexagonal distribution network composed of the power routers has the ability to easily interchange electric power between autonomous microgrid cells. We also explored the requirements for communication between energy routers to achieve dynamic adjustments of energy flow in a coordinated manner and its impact on resilient power grid systems.

Studies on spectral analysis of randomly sampled signals: Application to laser velocimetry data

NASA Technical Reports Server (NTRS)

Sree, David

1992-01-01

Spectral analysis is very useful in determining the frequency characteristics of many turbulent flows, for example, vortex flows, tail buffeting, and other pulsating flows. It is also used for obtaining turbulence spectra from which the time and length scales associated with the turbulence structure can be estimated. These estimates, in turn, can be helpful for validation of theoretical/numerical flow turbulence models. Laser velocimetry (LV) is being extensively used in the experimental investigation of different types of flows, because of its inherent advantages; nonintrusive probing, high frequency response, no calibration requirements, etc. Typically, the output of an individual realization laser velocimeter is a set of randomly sampled velocity data. Spectral analysis of such data requires special techniques to obtain reliable estimates of correlation and power spectral density functions that describe the flow characteristics. FORTRAN codes for obtaining the autocorrelation and power spectral density estimates using the correlation-based slotting technique were developed. Extensive studies have been conducted on simulated first-order spectrum and sine signals to improve the spectral estimates. A first-order spectrum was chosen because it represents the characteristics of a typical one-dimensional turbulence spectrum. Digital prefiltering techniques, to improve the spectral estimates from randomly sampled data were applied. Studies show that the spectral estimates can be increased up to about five times the mean sampling rate.

Optimality and Conductivity for Water Flow: From Landscapes, to Unsaturated Soils, to Plant Leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H.H.

2012-02-23

Optimality principles have been widely used in many areas. Based on an optimality principle that any flow field will tend toward a minimum in the energy dissipation rate, this work shows that there exists a unified form of conductivity relationship for three different flow systems: landscapes, unsaturated soils and plant leaves. The conductivity, the ratio of water flux to energy gradient, is a power function of water flux although the power value is system dependent. This relationship indicates that to minimize energy dissipation rate for a whole system, water flow has a small resistance (or a large conductivity) at amore » location of large water flux. Empirical evidence supports validity of the relationship for landscape and unsaturated soils (under gravity dominated conditions). Numerical simulation results also show that the relationship can capture the key features of hydraulic structure for a plant leaf, although more studies are needed to further confirm its validity. Especially, it is of interest that according to this relationship, hydraulic conductivity for gravity-dominated unsaturated flow, unlike that defined in the classic theories, depends on not only capillary pressure (or saturation), but also the water flux. Use of the optimality principle allows for determining useful results that are applicable to a broad range of areas involving highly non-linear processes and may not be possible to obtain from classic theories describing water flow processes.« less

Optimal design of high damping force engine mount featuring MR valve structure with both annular and radial flow paths

NASA Astrophysics Data System (ADS)

Nguyen, Q. H.; Choi, S. B.; Lee, Y. S.; Han, M. S.

2013-11-01

This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption.

Simultaneous visualization of transonic buffet on a rocket faring model using unsteady PSP measurement and Schlieren method

NASA Astrophysics Data System (ADS)

Nakakita, K.

2017-02-01

Simultaneous visualization technique of the combination of the unsteady Pressure-Sensitive Paint and the Schlieren measurement was introduced. It was applied to a wind tunnel test of a rocket faring model at the JAXA 2mx2m transonic wind tunnel. Quantitative unsteady pressure field was acquired by the unsteady PSP measurement, which consisted of a high-speed camera, high-power laser diode, and so on. Qualitative flow structure was acquired by the Schlieren measurement using a high-speed camera and Xenon lamp with a blue optical filter. Simultaneous visualization was achieved 1.6 kfps frame rate and it gave the detailed structure of unsteady flow fields caused by the unsteady shock wave oscillation due to shock-wave/boundary-layer interaction around the juncture between cone and cylinder on the model. Simultaneous measurement results were merged into a movie including surface pressure distribution on the rocket faring and spatial structure of shock wave system concerning to transonic buffet. Constructed movie gave a timeseries and global information of transonic buffet flow field on the rocket faring model visually.

Propagation of stationary Rossby waves in the Martian lower atmosphere

NASA Astrophysics Data System (ADS)

Ghosh, Priyanka; Thokuluwa, Ramkumar

The Martian lower atmospheric (-1.5 km to 29.3 km) temperature, measured by radio occultation technique during the Mars Global Surveyor (MGS) mission launched by US in November 1996, at the Northern winter hemispheric latitude of about 63(°) N clearly shows a statistically significant (above 95 percent confidential level white noise) and strong 3.5-day oscillation during 1-10 January 2006. This strong signal occurs in the longitudinal sectors of 0-30(°) E and 190-230(°) E but statistically insignificant in almost all the other longitudes. This 180 degree separation between the two peaks of occurrence of strong 3.5 day oscillation indicates that this may be associated with zonal wave number 2 structure global scale wave. At the lowest height of -1.5 km, the power observed in the longitude of 0-30(°) E is 50 K (2) and it increased gradually to the maximum power of 130 K (2) at the height of 0.8 - 1.7 km. Above this height, the power decreased monotonously and gradually to insignificant level at the height of 3.7 km (20 K (2) ). This gradual decrease of power above the height of 1.7 km indicates that radiative damping (infra red cooling due to large abundance of CO _{2} molecules and dust particles) would have played an important role in the dissipation of waves. The height and longitudinal profiles of phase of the 3.5-day wave indicate that this wave is a vertically standing and eastward propagating planetary wave respectively. Since the statistically significant spectral amplitude occurs near the high topography structures, it seems that the wave is generated by flows over the topography. In the Northern winter, it is possible that the large gradient of temperature between the low and high latitudes would lead to flow of winds from the tropical to polar latitudes. Due to the Coriolis effect, this flow would in turn move towards the right and incite wave generation when the air flows over the high topographic structures. This lead to speculate that the observed 3.5-day wave may be associated with topography-related zonal wave number 2 baroclinic Rossby wave. Similar analyses for January and February 2005 show significant 15-day oscillation for almost all the longitude sectors, indicating that this oscillation may be associated with barotropic waves generated by the geostrophic adjustment of planetary scale flows at the higher latitudes. The sharp contrast between the characteristics of atmospheric waves occurred in 2005 (summer) and 2006 (winter) indicates that there is a strong seasonal variation over the Mars. A detailed investigation will be presented about the various other characteristics of atmospheric waves observed for different years by various Mars missions.

Oscillating fluid power generator

DOEpatents

Morris, David C

2014-02-25

A system and method for harvesting the kinetic energy of a fluid flow for power generation with a vertically oriented, aerodynamic wing structure comprising one or more airfoil elements pivotably attached to a mast. When activated by the moving fluid stream, the wing structure oscillates back and forth, generating lift first in one direction then in the opposite direction. This oscillating movement is converted to unidirectional rotational movement in order to provide motive power to an electricity generator. Unlike other oscillating devices, this device is designed to harvest the maximum aerodynamic lift forces available for a given oscillation cycle. Because the system is not subjected to the same intense forces and stresses as turbine systems, it can be constructed less expensively, reducing the cost of electricity generation. The system can be grouped in more compact clusters, be less evident in the landscape, and present reduced risk to avian species.

Power generation systems and methods

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor); Chao, Yi (Inventor)

2011-01-01

A power generation system includes a plurality of submerged mechanical devices. Each device includes a pump that can be powered, in operation, by mechanical energy to output a pressurized output liquid flow in a conduit. Main output conduits are connected with the device conduits to combine pressurized output flows output from the submerged mechanical devices into a lower number of pressurized flows. These flows are delivered to a location remote of the submerged mechanical devices for power generation.

Vibration Power Flow In A Constrained Layer Damping Cylindrical Shell

NASA Astrophysics Data System (ADS)

Wang, Yun; Zheng, Gangtie

2012-07-01

In this paper, the vibration power flow in a constrained layer damping (CLD) cylindrical shell using wave propagation approach is investigated. The dynamic equations of the shell are derived with the Hamilton principle in conjunction with the Donnell shell assumption. With these equations, the dynamic responses of the system under a line circumferential cosine harmonic exciting force is obtained by employing the Fourier transform and the residue theorem. The vibration power flows inputted to the system and transmitted along the shell axial direction are both studied. The results show that input power flow varies with driving frequency and circumferential mode order, and the constrained damping layer can obviously restrict the exciting force from inputting power flow into the base shell especially for a thicker viscoelastic layer, a thicker or stiffer constraining layer (CL), and a higher circumferential mode order, can rapidly attenuate the vibration power flow transmitted along the base shell axial direction.

Analysis and Experimental Verification of New Power Flow Control for Grid-Connected Inverter with LCL Filter in Microgrid

PubMed Central

Gu, Herong; Guan, Yajuan; Wang, Huaibao; Wei, Baoze; Guo, Xiaoqiang

2014-01-01

Microgrid is an effective way to integrate the distributed energy resources into the utility networks. One of the most important issues is the power flow control of grid-connected voltage-source inverter in microgrid. In this paper, the small-signal model of the power flow control for the grid-connected inverter is established, from which it can be observed that the conventional power flow control may suffer from the poor damping and slow transient response. While the new power flow control can mitigate these problems without affecting the steady-state power flow regulation. Results of continuous-domain simulations in MATLAB and digital control experiments based on a 32-bit fixed-point TMS320F2812 DSP are in good agreement, which verify the small signal model analysis and effectiveness of the proposed method. PMID:24672304

Mechanical energy and power flow of the upper extremity in manual wheelchair propulsion.

PubMed

Guo, Lan-Yuen; Su, Fong-Chin; Wu, Hong-Wen; An, Kai-Nan

2003-02-01

To investigate the characteristics of mechanical energy and power flow of the upper limb during wheelchair propulsion. Mechanical energy and power flow of segments were calculated. Very few studies have taken into account the mechanical energy and power flow of the musculoskeletal system during wheelchair propulsion. Mechanical energy and power flow have proven to be useful tools for investigating locomotion disorders during human gait. Twelve healthy male adults (mean age, 23.5 years) were recruited for this study. Three-dimensional kinematic and kinetic data of the upper extremity were collected during wheelchair propulsion using a Hi-Res Expert Vision system and an instrumented wheel, respectively. During the initiation of the propulsion phase, joint power is generated in the upper arm or is transferred from the trunk downward to the forearm and hand to propel the wheel forward. During terminal propulsion, joint power is transferred upward to the trunk from the forearm and upper arm. The rate of change of mechanical energy and power flow for the forearm and hand have similar patterns, but the upper arm values differ. Joint power plays an important role in energy transfer as well as the energy generated and absorbed by muscles spanning the joints during wheelchair propulsion. Energy and power flow information during wheelchair propulsion allows us to gain a better understanding of the coordination of the movement by the musculoskeletal system.

Rheotaxis of elongated platinum-gold nanoswimmers

NASA Astrophysics Data System (ADS)

Brosseau, Quentin; Wu, Yang; Ristroph, Leif; Zhang, Jun; Ward, Michael; Shelley, Michael

2017-11-01

Directed motion of self-propelled colloids has attracted much attention as a possible means to transport microscopic cargo to desired locations. However, active colloids, such as our gold-platinum (Au-Pt) bi-metallic motors ( 2 micrometers) that are powered by hydrogen peroxide (H2O2), are subjected to Brownian motion and move diffusively. These swimmers can be directed via interactions with structured substrates, e.g. within an array of asymmetric pillars. Our current study focuses on realizing the directed motion in an imposed open flow, of these active nanorods. This dynamic response, often referred to as ``rheotaxis'', is found in many marine organisms. The effect of flow geometry and flow characteristics will be discussed in more details.

Hemodynamic flow visualization of early embryonic great vessels using μPIV.

PubMed

Goktas, Selda; Chen, Chia-Yuan; Kowalski, William J; Pekkan, Kerem

2015-01-01

Microparticle image velocimetry (μPIV) is an evolving quantitative methodology to closely and accurately monitor the cardiac flow dynamics and mechanotransduction during vascular morphogenesis. While PIV technique has a long history, contemporary developments in advanced microscopy have significantly expanded its power. This chapter includes three new methods for μPIV acquisition in selected embryonic structures achieved through advanced optical imaging: (1) high-speed confocal scanning of transgenic zebrafish embryos, where the transgenic erythrocytes act as the tracing particles; (2) microinjection of artificial seeding particles in chick embryos visualized with stereomicroscopy; and (3) real-time, time-resolved optical coherence tomography acquisition of vitelline vessel flow profiles in chick embryos, tracking the erythrocytes.

Multiple feed powder splitter

DOEpatents

Lewis, Gary K.; Less, Richard M.

2001-01-01

A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

Multiple feed powder splitter

DOEpatents

Lewis, Gary K.; Less, Richard M.

2002-01-01

A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

Flow in Atherosclerotic Blood Vessels

NASA Astrophysics Data System (ADS)

Berger, Stanley A.; Stroud, Jenn S.

2000-11-01

Atherosclerotic lesions occur in arteries where there are major changes in flow structure, e.g. bifurcations and junctions. The reduction of vessel lumen alters the flow, including the mechanical forces on the walls. We have examined the flow in carotid artery bifurcations with realistic plaque contours. The unsteady, incompressible, Navier-Stokes equations are solved in finite-volume form. Steady and pulsatile flows have been analyzed for laminar and turbulent flows, using for the latter a low-Reynolds number k- ɛ model and a k-ω model. Non-Newtonian viscosity is also considered using a power-law model. In general the very irregular contours of the vessels lead to recirculating regions, strong spatial variations of wall shear stresses, and in some cases, vortex shedding. Even steady inlet flow exhibits fluctuating, unsteady behavior. Neither turbulence models captures all the physics of the flow. The flow, in fact, appears to be transitional and not fully turbulent. For unsteady flow, there are also strong temporal variations of normal and shear stresses, which together with the strong spatial variations, has important implications for the onset and progression of atherosclerotic disease.

Comparison of measured and computed Strehl ratios for light propagated through a channel flow of a He N 2 mixing layer at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1997-04-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after they propagated through a He N 2 mixing layer in a rectangular channel. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Phase structure functions, computed from the reconstructed phase surfaces, were stationary in first increments. A five-thirds power law is shown to fit streamwise and cross-stream slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence, which describes the structure function with a single parameter. Strehl ratios were computed from the phase structure functions and compared with a measured experiment obtained from simultaneous point-spread function measurements. Two additional Strehl ratios were calculated by using classical estimates that assume statistical isotropy throughout the flow. The isotropic models are a reasonable estimate of the optical degradation only within a few centimeters of the initial mixing, where the Reynolds number is low. At higher Reynolds numbers, Strehl ratios calculated from the structure functions match the experiment much better than Strehl ratio calculations that assume isotropic flow.

Coherent structures in a supersonic complex nozzle

NASA Astrophysics Data System (ADS)

Magstadt, Andrew; Berry, Matthew; Glauser, Mark

2016-11-01

The jet flow from a complex supersonic nozzle is studied through experimental measurements. The nozzle's geometry is motivated by future engine designs for high-performance civilian and military aircraft. This rectangular jet has a single plane of symmetry, an additional shear layer (referred to as a wall jet), and an aft deck representative of airframe integration. The core flow operates at a Mach number of Mj , c = 1 . 6 , and the wall jet is choked (Mj , w = 1 . 0). This high Reynolds number jet flow is comprised of intense turbulence levels, an intricate shock structure, shear and boundary layers, and powerful corner vortices. In the present study, stereo PIV measurements are simultaneously sampled with high-speed pressure measurements, which are embedded in the aft deck, and far-field acoustics in the anechoic chamber at Syracuse University. Time-resolved schlieren measurements have indicated the existence of strong flow events at high frequencies, at a Strouhal number of St = 3 . 4 . These appear to result from von Kàrmàn vortex shedding within the nozzle and pervade the entire flow and acoustic domain. Proper orthogonal decomposition is applied on the current data to identify coherent structures in the jet and study the influence of this vortex street. AFOSR Turbulence and Transition Program (Grant No. FA9550-15-1-0435) with program managers Dr. I. Leyva and Dr. R. Ponnappan.

Comparative 1D and 3D numerical investigation of open-channel junction flows and energy losses

NASA Astrophysics Data System (ADS)

Luo, Hao; Fytanidis, Dimitrios K.; Schmidt, Arthur R.; García, Marcelo H.

2018-07-01

The complexity of open channel confluences stems from flow mixing, secondary circulation, post-confluence flow separation, contraction and backwater effects. These effects in turn result in a large number of parameters required to adequately quantify the junction induced hydraulic resistance and describe mean flow pattern and turbulent flow structures due to flow merging. The recent development in computing power advances the application of 3D Computational Fluid Dynamics (CFD) codes to visualize and understand the Confluence Hydrodynamic Zone (CHZ). Nevertheless, 1D approaches remain the mainstay in large drainage network or waterway system modeling considering computational efficiency and data availability. This paper presents (i) a modified 1D nonlinear dynamic model; (ii) a fully 3D non-hydrostatic, Reynolds-averaged Navier-Stokes Equations (RANS)-based, Computational Fluid Dynamics (CFD) model; (iii) an analysis of changing confluence hydrodynamics and 3D turbulent flow structure under various controls; (iv) a comparison of flow features (i.e. upstream water depths, energy losses and post-confluence contraction) predicted by 1D and 3D models; and (v) parameterization of 3D flow characteristics in 1D modeling through the computation of correction coefficients associated with contraction, energy and momentum. The present comprehensive 3D numerical investigation highlights the driving mechanisms for junction induced energy losses. Moreover, the comparative 1D and 3D study quantifies the deviation of 1D approximations and associated underlying assumptions from the 'true' resultant flow field. The study may also shed light on improving the accuracy of the 1D large network modeling through the parameterization of the complex 3D feature of the flow field and correction of interior boundary conditions at junctions of larger angles and/or with substantial lateral inflows. Moreover, the enclosed numerical investigations may enhance the understanding of the primary mechanisms contributing to hydraulic structure induced turbulent flow behavior and increased hydraulic resistance.

Freeform Fluidics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Love, Lonnie J; Richardson, Bradley S; Lind, Randall F

This work explores the integration of miniaturized fluid power and additive manufacturing. Oak Ridge National Laboratory (ORNL) has been developing an approach to miniaturized fluidic actuation and control that enables high dexterity, low cost and a pathway towards energy efficiency. Previous work focused on mesoscale digital control valves (high pressure, low flow) and the integration of actuation and fluid passages directly with the structure. The primary application being fluid powered robotics. The fundamental challenge was part complexity. Additive manufacturing technologies (E-Beam, Laser and Ultrasonic deposition) enable freeform manufacturing using conventional metal alloys with excellent mechanical properties. The combination of thesemore » two technologies (miniaturized fluid power and additive manufacturing) can enable a paradigm shift in fluid power, increasing efficiency while simultaneously reducing weight, size, complexity and cost.« less

Effect of sputtering power on MgF2 thin films deposited by sputtering technique under fluorine trapping

NASA Astrophysics Data System (ADS)

De, Rajnarayan; Haque, S. Maidul; Tripathi, S.; Prathap, C.; Rao, K. Divakar; Sahoo, N. K.

2016-05-01

A non-conventional magnetron sputtering technique was explored to deposit magnesium fluoride thin films using the concept of fluorine gas trapping without the introduction of additional fluorine gas flow inside the chamber. The effect of magnetron power from 50 W to 250 W has been explored on structural, optical and physical properties of the samples. Polycrystalline nature with tetragonal crystallinity of the films has been confirmed by GIXRD measurements along with thickness dependency. Monotonic increase of attenuation coefficient (k) with RF power has been explained in terms of target compound dissociation probability. In conclusion, with fluorine trapping method, the samples deposited at lower RF powers (<100 W) are found to be more suitable for optical applications.

Fluctuating pressures in flow fields of jets

NASA Technical Reports Server (NTRS)

Schroeder, J. C.; Haviland, J. K.

1976-01-01

The powered lift configurations under present development for STOL aircraft are the externally blown flap (EBF), involving direct jet impingement on the aircraft flaps, and the upper surface blown (USB), where the jet flow is attached on the upper surface of the wing and directed downwards. Towards the goal of developing scaling laws to predict unsteady loads imposed on the structural components of these STOL aircraft from small model tests, the near field fluctuating pressure behavior for the simplified cases of a round free cold jet and the same jet impinging on a flat plate was investigated. Examples are given of coherences, phase lags (giving convection velocities), and overall fluctuating pressure levels measured. The fluctuating pressure levels measured on the flat plate are compared to surface fluctuating pressure levels measured on full-scale powered-lift configuration models.

Pulsed electromagnetic gas acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1971-01-01

Experimental data were combined with one-dimensional conservation relations to yield information on the energy deposition ratio in a parallel-plate accelerator, where the downstream flow was confined to a constant area channel. Approximately 70% of the total input power was detected in the exhaust flow, of which only about 20% appeared as directed kinetic energy, thus implying that a downstream expansion to convert chamber enthalpy into kinetic energy must be an important aspect of conventional high power MPD arcs. Spectroscopic experiments on a quasi-steady MPD argon accelerator verified the presence of A(III) and the absence of A(I), and indicated an azimuthal structure in the jet related to the mass injection locations. Measurements of pressure in the arc chamber and impact pressure in the exhaust jet using a piezocrystal backed by a Plexiglas rod were in good agreement with the electromagnetic thrust model.

Characterising the structure of quasi-periodic mixing events in stratified turbulent Taylor-Couette flow

NASA Astrophysics Data System (ADS)

Singh, Kanwar Nain; Partridge, Jamie; Dalziel, Stuart; Caulfield, C. P.; Mathematical Underpinnings of Stratified Turbulence (MUST) Team

2017-11-01

We present results from experiments conducted to study mixing in a two-layer stably-stratified turbulent Taylor-Couette flow. It has previously been observed that there is a quasi-periodic mixing event located at the interface separating the layers. We observe, through conductivity probe measurements, that the power of the mixing event in the frequency spectrum of the density data at the interface is higher when measured near the inner cylinder than in the middle of the annular gap. This is consistent with Oglethorpe's (2014) hypothesis that the mixing structure is triggered near the inner cylinder, and then advects and decays or disperses radially. We also observe that at Ri =g/'Ro (RiΩi)2 7 , where Ri, Ro are the inner and outer cylinder radius, respectively, g ' the reduced gravity characterising the density jump between the layers and Ωi is the rotation rate of the inner cylinder, the power drops significantly at all radial locations, which is reminiscent of the onset of the enhanced flux regime as observed by Oglethorpe et al. (2013). We perform experiments to characterise the spatial extent and dynamics of this mixing structure using particle image velocimetry (PIV) giving further insights into this important mixing process. EPSRC programme Grant EP/K034529/1 & SGPC-CCT Scholarship.

Multi-functional metal-dielectric photonic structures

NASA Astrophysics Data System (ADS)

Smith, Kyle J.

In RF circuits and integrated photonics, it is important to effectively control an electromagnetic signal. This includes protecting of the network from high power and/or undesired signal flow, which is achieved with device functionalities such as isolation, circulation, switching, and limiting. In an attempt to develop light-weight, small-footprint, better protection devices, new designs have been sought utilizing materials that have been otherwise avoided due to some primary downside. For example, ferromagnetic metals like Iron and Cobalt, despite being powerful magnets, have been completely shunned for uses in nonreciprocal devices due to their overwhelming electric losses and high reflectivity. How could we utilize lossy materials in electromagnetic applications? In this thesis research, we design and fabricate metal-dielectric photonic structures in which metal can be highly transmissive, while the desired response (e.g., magneto-photonic response) is strongly enhanced. Moreover, the metal-dielectric structures can be designed to exhibit a sharp transition from the induced transmission to broadband opacity for oblique incidence and/or due to a tiny alteration of the photonic structure (e.g., because of nonlinearity). Thus, the photonic structures can be tailored to produce collimation and power-limiting effects. In the case of ferromagnetic metals, the metal-dielectric structure can be realized as an omnidirectional isolator passing radiation in a single direction and for a single frequency. The effectiveness of such structures will be verified in microwave measurements. Additionally, metal-dielectric structures including a nonlinear component will be shown to function as a reflective power limiter, thus providing a far superior alternative to absorptive, and often sacrificial, limiters.

A Concept of Cross-Ferroic Plasma Turbulence

PubMed Central

Inagaki, S.; Kobayashi, T.; Kosuga, Y.; Itoh, S.-I.; Mitsuzono, T.; Nagashima, Y.; Arakawa, H.; Yamada, T.; Miwa, Y.; Kasuya, N.; Sasaki, M.; Lesur, M.; Fujisawa, A.; Itoh, K.

2016-01-01

The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux. PMID:26917218

Experimental vibration damping characteristics of the third-stage rotor of a three-stage transonic axial-flow compressor

NASA Technical Reports Server (NTRS)

Newman, Frederick A.

1988-01-01

Rotor blade aerodynamic damping is experimentally determined in a three-stage transonic axial flow compressor having design aerodynamic performance goals of 4.5:1 pressure ratio and 65.5 lbm/sec weight flow. The combined damping associated with each mode is determined by a least squares fit of a single degree of freedom system transfer function to the nonsynchronous portion of the rotor blade strain gage output power spectra. The combined damping consists of the aerodynanmic damping and the structural and mechanical damping. The aerodynamic damping varies linearly with the inlet total pressure for a given corrected speed, weight flow, and pressure ratio while the structural and mechanical damping is assumed to remain constant. The combined damping is determined at three inlet total pressure levels to obtain the aerodynamic damping. The third-stage rotor blade aerodynamic damping is presented and discussed for the design equivalent speed with the stator blades reset for maximum efficiency. The compressor overall performance and experimental Campbell diagrams for the third-stage rotor blade row are also presented.

Experimental Determination of Aerodynamic Damping in a Three-Stage Transonic Axial-Flow Compressor. Degree awarded by Case Western Reserve Univ.

NASA Technical Reports Server (NTRS)

Newman, Frederick A.

1988-01-01

Rotor blade aerodynamic damping is experimentally determined in a three-stage transonic axial flow compressor having design aerodynamic performance goals of 4.5:1 pressure ratio and 65.5 lbm/sec weight flow. The combined damping associated with each mode is determined by a least squares fit of a single degree of freedom system transfer function to the nonsynchronous portion of the rotor blade strain gauge output power spectra. The combined damping consists of aerodynamic and structural and mechanical damping. The aerodynamic damping varies linearly with the inlet total pressure for a given equivalent speed, equivalent mass flow, and pressure ratio while structural and mechanical damping are assumed to be constant. The combined damping is determined at three inlet total pressure levels to obtain the aerodynamic damping. The third stage rotor blade aerodynamic damping is presented and discussed for 70, 80, 90, and 100 percent design equivalent speed. The compressor overall performance and experimental Campbell diagrams for the third stage rotor blade row are also presented.

Experimental Vibration Damping Characteristics of the Third-stage Rotor of a Three-stage Transonic Axial-flow Compressor

NASA Technical Reports Server (NTRS)

Newman, Frederick A.

1988-01-01

Rotor blade aerodynamic damping is experimentally determined in a three-stage transonic axial flow compressor having design aerodynamic performance goals of 4.5:1 pressure ratio and 65.5 lbm/sec weight flow. The combined damping associated with each mode is determined by a least squares fit of a single degree of freedom system transfer function to the nonsynchronous portion of the rotor blade strain gage output power spectra. The combined damping consists of the aerodynamic damping and the structural and mechanical damping. The aerodynamic damping varies linearly with the inlet total pressure for a given corrected speed, weight flow, and pressure ratio while the structural and mechanical damping is assumed to remain constant. The combined damping is determined at three inlet total pressure levels to obtain the aerodynamic damping. The third-stage rotor blade aerodynamic damping is presented and discussed for the design equivalent speed with the stator blades reset for maximum efficiency. The compressor overall preformance and experimental Campbell diagrams for the third-stage rotor blade row are also presented.

Statistical analysis of kinetic energy entrainment in a model wind turbine array boundary layer

NASA Astrophysics Data System (ADS)

Cal, Raul Bayoan; Hamilton, Nicholas; Kang, Hyung-Suk; Meneveau, Charles

2012-11-01

For large wind farms, kinetic energy must be entrained from the flow above the wind turbines to replenish wakes and enable power extraction in the array. Various statistical features of turbulence causing vertical entrainment of mean-flow kinetic energy are studied using hot-wire velocimetry data taken in a model wind farm in a scaled wind tunnel experiment. Conditional statistics and spectral decompositions are employed to characterize the most relevant turbulent flow structures and determine their length-scales. Sweep and ejection events are shown to be the largest contributors to the vertical kinetic energy flux, although their relative contribution depends upon the location in the wake. Sweeps are shown to be dominant in the region above the wind turbine array. A spectral analysis of the data shows that large scales of the flow, about the size of the rotor diameter in length or larger, dominate the vertical entrainment. The flow is more incoherent below the array, causing decreased vertical fluxes there. The results show that improving the rate of vertical kinetic energy entrainment into wind turbine arrays is a standing challenge and would require modifying the large-scale structures of the flow. This work was funded in part by the National Science Foundation (CBET-0730922, CBET-1133800 and CBET-0953053).

Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity

NASA Astrophysics Data System (ADS)

Bian, Shiyao; Driscoll, James F.; Elbing, Brian R.; Ceccio, Steven L.

2011-07-01

High Reynolds number, low Mach number, turbulent shear flow past a rectangular, shallow cavity has been experimentally investigated with the use of dual-camera cinematographic particle image velocimetry (CPIV). The CPIV had a 3 kHz sampling rate, which was sufficient to monitor the time evolution of large-scale vortices as they formed, evolved downstream and impinged on the downstream cavity wall. The time-averaged flow properties (velocity and vorticity fields, streamwise velocity profiles and momentum and vorticity thickness) were in agreement with previous cavity flow studies under similar operating conditions. The time-resolved results show that the separated shear layer quickly rolled-up and formed eddies immediately downstream of the separation point. The vortices convect downstream at approximately half the free-stream speed. Vorticity strength intermittency as the structures approach the downstream edge suggests an increase in the three-dimensionality of the flow. Time-resolved correlations reveal that the in-plane coherence of the vortices decays within 2-3 structure diameters, and quasi-periodic flow features are present with a vortex passage frequency of ~1 kHz. The power spectra of the vertical velocity fluctuations within the shear layer revealed a peak at a non-dimensional frequency corresponding to that predicted using linear, inviscid instability theory.

Evaluation of the effect of reactant gases mass flow rates on power density in a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Kahveci, E. E.; Taymaz, I.

2018-03-01

In this study it was experimentally investigated the effect of mass flow rates of reactant gases which is one of the most important operational parameters of polymer electrolyte membrane (PEM) fuel cell on power density. The channel type is serpentine and single PEM fuel cell has an active area of 25 cm2. Design-Expert 8.0 (trial version) was used with four variables to investigate the effect of variables on the response using. Cell temperature, hydrogen mass flow rate, oxygen mass flow rate and humidification temperature were selected as independent variables. In addition, the power density was used as response to determine the combined effects of these variables. It was kept constant cell and humidification temperatures while changing mass flow rates of reactant gases. From the results an increase occurred in power density with increasing the hydrogen flow rates. But oxygen flow rate does not have a significant effect on power density within determined mass flow rates.

Specific features of the flow structure in a reactive type turbine stage

NASA Astrophysics Data System (ADS)

Chernikov, V. A.; Semakina, E. Yu.

2017-04-01

The results of experimental studies of the gas dynamics for a reactive type turbine stage are presented. The objective of the studies is the measurement of the 3D flow fields in reference cross sections, experimental determination of the stage characteristics, and analysis of the flow structure for detecting the sources of kinetic energy losses. The integral characteristics of the studied stage are obtained by averaging the results of traversing the 3D flow over the area of the reference cross sections before and behind the stage. The averaging is performed using the conservation equations for mass, total energy flux, angular momentum with respect to the axis z of the turbine, entropy flow, and the radial projection of the momentum flux equation. The flow parameter distributions along the channel height behind the stage are obtained in the same way. More thorough analysis of the flow structure is performed after interpolation of the experimentally measured point parameter values and 3D flow velocities behind the stage. The obtained continuous velocity distributions in the absolute and relative coordinate systems are presented in the form of vector fields. The coordinates of the centers and the vectors of secondary vortices are determined using the results of point measurements of velocity vectors in the cross section behind the turbine stage and their subsequent interpolation. The approach to analysis of experimental data on aerodynamics of the turbine stage applied in this study allows one to find the detailed space structure of the working medium flow, including secondary coherent vortices at the root and peripheral regions of the air-gas part of the stage. The measured 3D flow parameter fields and their interpolation, on the one hand, point to possible sources of increased power losses, and, on the other hand, may serve as the basis for detailed testing of CFD models of the flow using both integral and local characteristics. The comparison of the numerical and experimental results, as regards local characteristics, using statistical methods yields the quantitative estimate of their agreement.

Pneumatic Proboscis Heat-Flow Probe

NASA Technical Reports Server (NTRS)

Zacny, Kris; Hedlund, Magnus; Mumm, Eric; Shasho, Jeffrey; Chu, Philip; Kumar, Nishant

2013-01-01

Heat flow is a fundamental property of a planet, and provides significant constraints on the abundance of radiogenic isotopes, the thermal evolution and differentiation history, and the mechanical properties of the lithosphere. Heat-flow measurements are also essential in achieving at least four of the goals set out by the National Research Council for future lunar exploration. The heat-flow probe therefore directly addresses the goal of the Lunar Geophysical Network, which is to understand the interior structure and composition of the Moon. A key challenge for heat flow measurement is to install thermal sensors to the depths approximately equal to 3 m that are not influenced by the diurnal, annual, and longer-term fluctuations of the surface thermal environment. In addition, once deployed, the heat flow probe should cause little disturbance to the thermal regime of the surrounding regolith. A heat-flow probe system was developed that has two novel features: (1) it utilizes a pneumatic (gas) approach, excavates a hole by lofting the lunar soil out of the hole, and (2) deploys the heat flow probe, which utilizes a coiled up tape as a thermal probe to reach greater than 3-meter depth. The system is a game-changer for small lunar landers as it exhibits extremely low mass, volume, and simple deployment. The pneumatic system takes advantage of the helium gas used for pressurizing liquid propellant of the lander. Normally, helium is vented once the lander is on the surface, but it can be utilized for powering pneumatic systems. Should sufficient helium not be available, a simple gas delivery system may be taken specifically for the heat flow probe. Either way, the pneumatic heat flow probe system would be much lighter than other systems that entirely rely on the electrical power of the lander.

Experimental Hydro-Mechanical Characterization of Full Load Pressure Surge in Francis Turbines

NASA Astrophysics Data System (ADS)

Müller, A.; Favrel, A.; Landry, C.; Yamamoto, K.; Avellan, F.

2017-04-01

Full load pressure surge limits the operating range of hydro-electric generating units by causing significant power output swings and by compromising the safety of the plant. It appears during the off-design operation of hydraulic machines, which is increasingly required to regulate the broad integration of volatile renewable energy sources into the existing power network. The underlying causes and governing physical mechanisms of this instability were investigated in the frame of a large European research project and this paper documents the main findings from two experimental campaigns on a reduced scale model of a Francis turbine. The multi-phase flow in the draft tube is characterized by Particle Image Velocimetry, Laser Doppler Velocimetry and high-speed visualizations, along with synchronized measurements of the relevant hydro-mechanical quantities. The final result is a comprehensive overview of how the unsteady draft tube flow and the mechanical torque on the runner shaft behave during one mean period of the pressure oscillation, thus defining the unstable fluid-structure interaction responsible for the power swings. A discussion of the root cause is initiated, based on the state of the art. Finally, the latest results will enable a validation of recent RANS flow simulations used for determining the key parameters of hydro-acoustic stability models.

The influence and analysis of natural crosswind on cooling characteristics of the high level water collecting natural draft wet cooling tower

NASA Astrophysics Data System (ADS)

Ma, Libin; Ren, Jianxing

2018-01-01

Large capacity and super large capacity thermal power is becoming the main force of energy and power industry in our country. The performance of cooling tower is related to the water temperature of circulating water, which has an important influence on the efficiency of power plant. The natural draft counter flow wet cooling tower is the most widely used cooling tower type at present, and the high cooling tower is a new cooling tower based on the natural ventilation counter flow wet cooling tower. In this paper, for high cooling tower, the application background of high cooling tower is briefly explained, and then the structure principle of conventional cooling tower and high cooling tower are introduced, and the difference between them is simply compared. Then, the influence of crosswind on cooling performance of high cooling tower under different wind speeds is introduced in detail. Through analysis and research, wind speed, wind cooling had little impact on the performance of high cooling tower; wind velocity, wind will destroy the tower inside and outside air flow, reducing the cooling performance of high cooling tower; Wind speed, high cooling performance of cooling tower has increased, but still lower than the wind speed.

Physical modeling of the atmospheric boundary layer in the UNH Flow Physics Facility

NASA Astrophysics Data System (ADS)

Taylor-Power, Gregory; Gilooly, Stephanie; Wosnik, Martin; Klewicki, Joe; Turner, John

2016-11-01

The Flow Physics Facility (FPF) at UNH has test section dimensions W =6.0m, H =2.7m, L =72m. It can achieve high Reynolds number boundary layers, enabling turbulent boundary layer, wind energy and wind engineering research with exceptional spatial and temporal instrument resolution. We examined the FPF's ability to experimentally simulate different types of the atmospheric boundary layer (ABL) using upstream roughness arrays. The American Society for Civil Engineers defines standards for simulating ABLs for different terrain types, from open sea to dense city areas (ASCE 49-12). The standards require the boundary layer to match a power law shape, roughness height, and power spectral density criteria. Each boundary layer type has a corresponding power law exponent and roughness height. The exponent and roughness height both increase with increasing roughness. A suburban boundary layer was chosen for simulation and a roughness element fetch was created. Several fetch lengths were experimented with and the resulting boundary layers were measured and compared to standards in ASCE 49-12: Wind Tunnel Testing for Buildings and Other Structures. Pitot tube and hot wire anemometers were used to measure average and fluctuating flow characteristics. Velocity profiles, turbulence intensity and velocity spectra were found to compare favorably.

In vitro evaluation of forward and reverse volumetric flow across a regurgitant aortic valve using Doppler power-weighted mean velocities.

PubMed

Minich, L L; Tani, L Y; Pantalos, G M

1997-01-01

To determine the accuracy of using power-weighted mean velocities for quantitating volumetric flow across a cardiac valve, we equipped pulsatile flow-tank systems with a 25 mm porcine or a 27 mm mechanical valve with various sizes of regurgitant orifices. Forward and reverse volumetric flows were measured over a range of hemodynamic conditions using two insonating angles (0 and 45 degrees). Pulsed Doppler power-weighted mean velocity measurements were obtained simultaneously with electromagnetic or ultrasonic transit-time probe measurements. For the porcine valve, Doppler measurements correlated well with electromagnetic flow measurements for all (r = 0.75 to 0.97, p < 0.05) except the smallest (2.7 mm) orifice (r = 0.19). For the mechanical valve, power-weighted mean velocity measurements correlated well with ultrasonic transit-time measurements for each hemodynamic condition defined by pulse rate, mean arterial pressure, and insonating angle (r = 0.93 to 0.99, p < 0.01), but equations varied unpredictably. Thus, although power-weighted mean velocity volumetric flow measurements correlate well with flow probe measurements, equations vary widely as hemodynamic conditions change. Because of this variation, power-weighted mean velocity data are not useful for quantitation of volumetric flow across a cardiac valve at this time. Further investigation may show how different hemodynamic conditions affect power-weighted mean velocity measurements of volumetric flow.

Methods of computing steady-state voltage stability margins of power systems

DOEpatents

Chow, Joe Hong; Ghiocel, Scott Gordon

2018-03-20

In steady-state voltage stability analysis, as load increases toward a maximum, conventional Newton-Raphson power flow Jacobian matrix becomes increasingly ill-conditioned so power flow fails to converge before reaching maximum loading. A method to directly eliminate this singularity reformulates the power flow problem by introducing an AQ bus with specified bus angle and reactive power consumption of a load bus. For steady-state voltage stability analysis, the angle separation between the swing bus and AQ bus can be varied to control power transfer to the load, rather than specifying the load power itself. For an AQ bus, the power flow formulation is only made up of a reactive power equation, thus reducing the size of the Jacobian matrix by one. This reduced Jacobian matrix is nonsingular at the critical voltage point, eliminating a major difficulty in voltage stability analysis for power system operations.

Structure and flow-induced variability of the subtidal salinity field in northern San Francisco Bay

USGS Publications Warehouse

Monismith, Stephen G.; Kimmerer, W.; Burau, J.R.; Stacey, M.T.

2002-01-01

The structure of the salinity field in northern San Francisco Bay and how it is affected by freshwater flow are discussed. Two datasets are examined: the first is 23 years of daily salinity data taken by the U.S. Bureau of Reclamation along the axis of northern San Francisco Bay: the second is a set of salinity transects taken by the U.S. Geological Survey between 1988 and 1993. Central to this paper is a measure of salinity intrusion. X2: the distance from the Golden Gate Bridge to where the bottom salinity is 2 psu. Using X2 to scale distance, the authors find that for most flow conditions, the mean salinity distribution of the estuary is nearly self-similar with a salinity gradient in the center 70% of the region between the Golden Gate and X2 that is proportional to X2-1. Analysis of covariability of Q and X2 showed a characteristics timescale of adjustment of the salinity field of approximately 2 weeks. The steady-state response deduced from the X2 time series implies that X2 is proportional to riverflow to the 1/7 power. This relation, which differs from the standard 1/3 power dependence that is derived theoretically assuming constant exchange coefficients, shows that the upstream salt flux associated with gravitational circulation is more sensitive to the longitudinal salinity gradient than theory supposes. This is attributed to the strengthening of stratification caused by the stronger longitudinal salinity gradient that accompanies larger river flows.

Wave structure and flow amplitude-frequency characteristics in the turbine nozzle lattice in the presence of phase transition

NASA Astrophysics Data System (ADS)

Gribin, V. G.; Gavrilov, I. Yu.; Tishchenko, A. A.; Tishchenko, V. A.; Alekseev, R. A.

2017-05-01

This paper is devoted to the wave structure of a flow at its near- and supersonic velocities in a flat turbine cascade of profiles in the zone of phase transitions. The main task was investigation of the mechanics of interaction of the condensation jump with the adiabatic jumps of packing in a change of the initial condition of the flow. The obtained results are necessary for verification of the calculation models of the moisture-steam flow in the elements of lotic parts of the steam turbines. The experimental tests were made on a stand of the wet steam contour (WSC-2) in the Moscow Power Engineering Institute (MPEI, National Research University) at various initial states of steam in a wide range of Mach numbers. In the investigation of the wave structure, use was made of an instrument based on the Schlieren-method principle. The amplitude-frequency characteristics of the flow was found by measurement of static pressure pulsations by means of the piezo resistive sensors established on a bandage plate along the bevel cut of the cascade. It is shown that appearance of phase transitions in the bevel cut of the nozzle turbine cascade leads to a change in the wave structure of the flow. In case of condensation jump, the system of adiabatic jumps in the bevel cut of the cascade becomes nonstationary, and the amplitude-frequency characteristics of static pressure pulsations are restructured. In this, a change in the frequency pulsations of pressure and amplitude takes place. It is noted that, at near-sonic speeds of the flow and the state of saturation at the input, the low-frequency pulsations of static pressure appear that lead to periodic disappearance of the condensation jump and of the adiabatic jump. As a result, in this mode, the flow discharge variations take place.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lagier, B.; Rousset, B.; Hoa, C.

Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and themore » refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.« less

Wavelet analysis methods for radiography of multidimensional growth of planar mixing layers

DOE PAGES

Merritt, Elizabeth Catherine; Doss, Forrest William

2016-07-06

The counter-propagating shear campaign is examining instability growth and its transition to turbulence in the high-energy-density physics regime using a laser-driven counter-propagating flow platform. In these experiments, we observe consistent complex break-up of and structure growth in a tracer layer placed at the shear flow interface during the instability growth phase. We present a wavelet-transform based analysis technique capable of characterizing the scale- and directionality-resolved average intensity perturbations in static radiographs of the experiment. This technique uses the complete spatial information available in each radiograph to describe the structure evolution. We designed this analysis technique to generate a two-dimensional powermore » spectrum for each radiograph from which we can recover information about structure widths, amplitudes, and orientations. Lastly, the evolution of the distribution of power in the spectra for an experimental series is a potential metric for quantifying the structure size evolution as well as a system’s evolution towards isotropy.« less

CFD simulation of flow through heart: a perspective review.

PubMed

Khalafvand, S S; Ng, E Y K; Zhong, L

2011-01-01

The heart is an organ which pumps blood around the body by contraction of muscular wall. There is a coupled system in the heart containing the motion of wall and the motion of blood fluid; both motions must be computed simultaneously, which make biological computational fluid dynamics (CFD) difficult. The wall of the heart is not rigid and hence proper boundary conditions are essential for CFD modelling. Fluid-wall interaction is very important for real CFD modelling. There are many assumptions for CFD simulation of the heart that make it far from a real model. A realistic fluid-structure interaction modelling the structure by the finite element method and the fluid flow by CFD use more realistic coupling algorithms. This type of method is very powerful to solve the complex properties of the cardiac structure and the sensitive interaction of fluid and structure. The final goal of heart modelling is to simulate the total heart function by integrating cardiac anatomy, electrical activation, mechanics, metabolism and fluid mechanics together, as in the computational framework.

Wavelet analysis methods for radiography of multidimensional growth of planar mixing layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merritt, E. C., E-mail: emerritt@lanl.gov; Doss, F. W.

2016-07-15

The counter-propagating shear campaign is examining instability growth and its transition to turbulence in the high-energy-density physics regime using a laser-driven counter-propagating flow platform. In these experiments, we observe consistent complex break-up of and structure growth in a tracer layer placed at the shear flow interface during the instability growth phase. We present a wavelet-transform based analysis technique capable of characterizing the scale- and directionality-resolved average intensity perturbations in static radiographs of the experiment. This technique uses the complete spatial information available in each radiograph to describe the structure evolution. We designed this analysis technique to generate a two-dimensional powermore » spectrum for each radiograph from which we can recover information about structure widths, amplitudes, and orientations. The evolution of the distribution of power in the spectra for an experimental series is a potential metric for quantifying the structure size evolution as well as a system’s evolution towards isotropy.« less

New Methodology for Evaluating Optimal Pricing for Primary Regulation of Deregulated Power Systems under Steady State Condition

NASA Astrophysics Data System (ADS)

Satyaramesh, P. V.; RadhaKrishna, C.

2013-06-01

A generalized pricing structure for procurement of power under frequency ancillary service is developed in this paper. It is a frequency linked-price model and suitable for deregulation market environment. This model takes into consideration: governor characteristics and frequency characteristics of generator as additional parameters in load flow method. The main objective of the new approach proposed in this paper is to establish bidding price structure for frequency regulation services in competitive ancillary electrical markets under steady state condition. Lot of literatures are available for calculating the frequency deviations with respect to load changes by using dynamic simulation methods. But in this paper, the model computes the frequency deviations for additional requirements of power under steady state with considering power system network topology. An attempt is also made in this paper to develop optimal bidding price structure for the frequency-regulated systems. It gives a signal to traders or bidders that the power demand can be assessed more accurately much closer to real time and helps participants bid more accurate quantities on day-ahead market. The recent trends of frequency linked-price model existing in Indian power systems issues required for attention are also dealt in this paper. Test calculations have been performed on 30-bus system. The paper also explains adoptability of 33 this model to practical Indian power system. The results presented are analyzed and useful conclusions are drawn.

Honeycomb-Fin Heat Sink

NASA Technical Reports Server (NTRS)

Rippel, Wally E.

1989-01-01

Improved finned heat sink for electronic components more lightweight, inexpensive, and efficient. Designed for use with forced air, easily scaled up to dissipate power up to few hundred watts. Fins are internal walls of aluminum honeycomb structure. Cell structure gives strength to thin aluminum foil. Length of channels chosen for thermodynamic efficency; columns of cells combined in any reasonable number because flowing air distributed to all. Heat sink cools nearly as effectively at ends as near its center, no matter how many columns of cells combined.

n+ GaAs/AuGeNi-Au Thermocouple-Type RF MEMS Power Sensors Based on Dual Thermal Flow Paths in GaAs MMIC

PubMed Central

Zhang, Zhiqiang; Liao, Xiaoping

2017-01-01

To achieve radio frequency (RF) power detection, gain control, and circuit protection, this paper presents n+ GaAs/AuGeNi-Au thermocouple-type RF microelectromechanical system (MEMS) power sensors based on dual thermal flow paths. The sensors utilize a conversion principle of RF power-heat-voltage, where a thermovoltage is obtained as the RF power changes. To improve the heat transfer efficiency and the sensitivity, structures of two heat conduction paths are designed: one in which a thermal slug of Au is placed between two load resistors and hot junctions of the thermocouples, and one in which a back cavity is fabricated by the MEMS technology to form a substrate membrane underneath the resistors and the hot junctions. The improved sensors were fabricated by a GaAs monolithic microwave integrated circuit (MMIC) process. Experiments show that these sensors have reflection losses of less than −17 dB up to 12 GHz. At 1, 5, and 10 GHz, measured sensitivities are about 63.45, 53.97, and 44.14 µV/mW for the sensor with the thermal slug, and about 111.03, 94.79, and 79.04 µV/mW for the sensor with the thermal slug and the back cavity, respectively. PMID:28629144

n⁺ GaAs/AuGeNi-Au Thermocouple-Type RF MEMS Power Sensors Based on Dual Thermal Flow Paths in GaAs MMIC.

PubMed

Zhang, Zhiqiang; Liao, Xiaoping

2017-06-17

To achieve radio frequency (RF) power detection, gain control, and circuit protection, this paper presents n⁺ GaAs/AuGeNi-Au thermocouple-type RF microelectromechanical system (MEMS) power sensors based on dual thermal flow paths. The sensors utilize a conversion principle of RF power-heat-voltage, where a thermovoltage is obtained as the RF power changes. To improve the heat transfer efficiency and the sensitivity, structures of two heat conduction paths are designed: one in which a thermal slug of Au is placed between two load resistors and hot junctions of the thermocouples, and one in which a back cavity is fabricated by the MEMS technology to form a substrate membrane underneath the resistors and the hot junctions. The improved sensors were fabricated by a GaAs monolithic microwave integrated circuit (MMIC) process. Experiments show that these sensors have reflection losses of less than -17 dB up to 12 GHz. At 1, 5, and 10 GHz, measured sensitivities are about 63.45, 53.97, and 44.14 µ V/mW for the sensor with the thermal slug, and about 111.03, 94.79, and 79.04 µ V/mW for the sensor with the thermal slug and the back cavity, respectively.

Multiport power router and its impact on future smart grids

NASA Astrophysics Data System (ADS)

Kado, Yuichi; Shichijo, Daiki; Wada, Keiji; Iwatsuki, Katsumi

2016-07-01

We propose a Y configuration power router as a unit cell to easily construct a power delivery system that can meet many types of user requirements. The Y configuration power router controls the direction and magnitude of power flows between three ports regardless of DC or AC. We constructed a prototype three-way isolated DC/DC converter that is the core unit of the Y configuration power router. The electrical insulation between three ports assures safety and reliability for power network systems. We then tested the operation of power flow control. The experimental results revealed that our methodology based on a governing equation was appropriate to control the power flow of the three-way DC/DC converter. In addition, a distribution network composed of power routers had the ability to easily enable interchanges of electrical power between autonomous microgrid cells. We also explored the requirements for communication between energy routers to achieve dynamic adjustments of energy flows in a coordinated manner and their impact on resilient power grid systems.

Study on a high capacity two-stage free piston Stirling cryocooler working around 30 K

NASA Astrophysics Data System (ADS)

Wang, Xiaotao; Zhu, Jian; Chen, Shuai; Dai, Wei; Li, Ke; Pang, Xiaomin; Yu, Guoyao; Luo, Ercang

2016-12-01

This paper presents a two-stage high-capacity free-piston Stirling cryocooler driven by a linear compressor to meet the requirement of the high temperature superconductor (HTS) motor applications. The cryocooler system comprises a single piston linear compressor, a two-stage free piston Stirling cryocooler and a passive oscillator. A single stepped displacer configuration was adopted. A numerical model based on the thermoacoustic theory was used to optimize the system operating and structure parameters. Distributions of pressure wave, phase differences between the pressure wave and the volume flow rate and different energy flows are presented for a better understanding of the system. Some characterizing experimental results are presented. Thus far, the cryocooler has reached a lowest cold-head temperature of 27.6 K and achieved a cooling power of 78 W at 40 K with an input electric power of 3.2 kW, which indicates a relative Carnot efficiency of 14.8%. When the cold-head temperature increased to 77 K, the cooling power reached 284 W with a relative Carnot efficiency of 25.9%. The influences of different parameters such as mean pressure, input electric power and cold-head temperature are also investigated.

CFD Analysis of Upper Plenum Flow for a Sodium-Cooled Small Modular Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraus, A.; Hu, R.

2015-01-01

Upper plenum flow behavior is important for many operational and safety issues in sodium fast reactors. The Prototype Gen-IV Sodium Fast Reactor (PGSFR), a pool-type, 150 MWe output power design, was used as a reference case for a detailed characterization of upper plenum flow for normal operating conditions. Computational Fluid Dynamics (CFD) simulation was utilized with detailed geometric modeling of major structures. Core outlet conditions based on prior system-level calculations were mapped to approximate the outlet temperatures and flow rates for each core assembly. Core outlet flow was found to largely bypass the Upper Internal Structures (UIS). Flow curves overmore » the shield and circulates within the pool before exiting the plenum. Cross-flows and temperatures were evaluated near the core outlet, leading to a proposed height for the core outlet thermocouples to ensure accurate assembly-specific temperature readings. A passive scalar was used to evaluate fluid residence time from core outlet to IHX inlet, which can be used to assess the applicability of various methods for monitoring fuel failure. Additionally, the gas entrainment likelihood was assessed based on the CFD simulation results. Based on the evaluation of velocity gradients and turbulent kinetic energies and the available gas entrainment criteria in the literature, it was concluded that significant gas entrainment is unlikely for the current PGSFR design.« less

High-frequency Ultrasound Imaging of Mouse Cervical Lymph Nodes.

PubMed

Walk, Elyse L; McLaughlin, Sarah L; Weed, Scott A

2015-07-25

High-frequency ultrasound (HFUS) is widely employed as a non-invasive method for imaging internal anatomic structures in experimental small animal systems. HFUS has the ability to detect structures as small as 30 µm, a property that has been utilized for visualizing superficial lymph nodes in rodents in brightness (B)-mode. Combining power Doppler with B-mode imaging allows for measuring circulatory blood flow within lymph nodes and other organs. While HFUS has been utilized for lymph node imaging in a number of mouse  model systems, a detailed protocol describing HFUS imaging and characterization of the cervical lymph nodes in mice has not been reported. Here, we show that HFUS can be adapted to detect and characterize cervical lymph nodes in mice. Combined B-mode and power Doppler imaging can be used to detect increases in blood flow in immunologically-enlarged cervical nodes. We also describe the use of B-mode imaging to conduct fine needle biopsies of cervical lymph nodes to retrieve lymph tissue for histological  analysis. Finally, software-aided steps are described to calculate changes in lymph node volume and to visualize changes in lymph node morphology following image reconstruction. The ability to visually monitor changes in cervical lymph node biology over time provides a simple and powerful technique for the non-invasive monitoring of cervical lymph node alterations in preclinical mouse models of oral cavity disease.

Application of wavelet analysis for monitoring the hydrologic effects of dam operation: Glen canyon dam and the Colorado River at lees ferry, Arizona

USGS Publications Warehouse

White, M.A.; Schmidt, J.C.; Topping, D.J.

2005-01-01

Wavelet analysis is a powerful tool with which to analyse the hydrologic effects of dam construction and operation on river systems. Using continuous records of instantaneous discharge from the Lees Ferry gauging station and records of daily mean discharge from upstream tributaries, we conducted wavelet analyses of the hydrologic structure of the Colorado River in Grand Canyon. The wavelet power spectrum (WPS) of daily mean discharge provided a highly compressed and integrative picture of the post-dam elimination of pronounced annual and sub-annual flow features. The WPS of the continuous record showed the influence of diurnal and weekly power generation cycles, shifts in discharge management, and the 1996 experimental flood in the post-dam period. Normalization of the WPS by local wavelet spectra revealed the fine structure of modulation in discharge scale and amplitude and provides an extremely efficient tool with which to assess the relationships among hydrologic cycles and ecological and geomorphic systems. We extended our analysis to sections of the Snake River and showed how wavelet analysis can be used as a data mining technique. The wavelet approach is an especially promising tool with which to assess dam operation in less well-studied regions and to evaluate management attempts to reconstruct desired flow characteristics. Copyright ?? 2005 John Wiley & Sons, Ltd.

Non-Flow-Through Fuel Cell System Test Results and Demonstration on the SCARAB Rover

NASA Technical Reports Server (NTRS)

Scheidegger, Brianne; Burke, Kenneth; Jakupca, Ian

2012-01-01

This presentation describes the results of the demonstration of a non-flow-through PEM fuel cell as part of a power system on the SCARAB rover at the NASA Glenn Research Center. A 16-cell non-flow-through fuel cell stack from Infinity Fuel Cell and Hydrogen, Inc. was incorporated into a power system designed to act as a range extender by providing power to the SCARAB rover s hotel loads. The power system, including the non-flow-through fuel cell technology, successfully demonstrated its goal as a range extender by powering hotel loads on the SCARAB rover, making this demonstration the first to use the non-flow-through fuel cell technology on a mobile platform.

Network, system, and status software enhancements for the autonomously managed electrical power system breadboard. Volume 2: Protocol specification

NASA Technical Reports Server (NTRS)

Mckee, James W.

1990-01-01

This volume (2 of 4) contains the specification, structured flow charts, and code listing for the protocol. The purpose of an autonomous power system on a spacecraft is to relieve humans from having to continuously monitor and control the generation, storage, and distribution of power in the craft. This implies that algorithms will have been developed to monitor and control the power system. The power system will contain computers on which the algorithms run. There should be one control computer system that makes the high level decisions and sends commands to and receive data from the other distributed computers. This will require a communications network and an efficient protocol by which the computers will communicate. One of the major requirements on the protocol is that it be real time because of the need to control the power elements.

Numerical model of solar dynamic radiator for parametric analysis

NASA Technical Reports Server (NTRS)

Rhatigan, Jennifer L.

1989-01-01

Growth power requirements for Space Station Freedom will be met through addition of 25 kW solar dynamic (SD) power modules. The SD module rejects waste heat from the power conversion cycle to space through a pumped-loop, multi-panel, deployable radiator. The baseline radiator configuration was defined during the Space Station conceptual design phase and is a function of the state point and heat rejection requirements of the power conversion unit. Requirements determined by the overall station design such as mass, system redundancy, micrometeoroid and space debris impact survivability, launch packaging, costs, and thermal and structural interaction with other station components have also been design drivers for the radiator configuration. Extensive thermal and power cycle modeling capabilities have been developed which are powerful tools in Station design and analysis, but which prove cumbersome and costly for simple component preliminary design studies. In order to aid in refining the SD radiator to the mature design stage, a simple and flexible numerical model was developed. The model simulates heat transfer and fluid flow performance of the radiator and calculates area mass and impact survivability for many combinations of flow tube and panel configurations, fluid and material properties, and environmental and cycle variations. A brief description and discussion of the numerical model, it's capabilities and limitations, and results of the parametric studies performed is presented.

Strain-rate/temperature behavior of high density polyethylene in compression

NASA Technical Reports Server (NTRS)

Clements, L. L.; Sherby, O. D.

1978-01-01

The compressive strain rate/temperature behavior of highly linear, high density polyethylene was analyzed in terms of the predictive relations developed for metals and other crystalline materials. For strains of 5 percent and above, the relationship between applied strain rate, dotted epsilon, and resulting flow stress, sigma, was found to be: dotted epsilon exp times (Q sub f/RT) = k'(sigma/sigma sub c) to the nth power; the left-hand side is the activation-energy-compensated strain rate, where Q sub f is activation energy for flow, R is gas constant, and T is temperature; k is a constant, n is temperature-independent stress exponent, and sigma/sigma sub c is structure-compensated stress. A master curve resulted from a logarithmic plot of activation-energy-compensated strain rate versus structure-compensated stress.

On the formalization of multi-scale and multi-science processes for integrative biology

PubMed Central

Díaz-Zuccarini, Vanessa; Pichardo-Almarza, César

2011-01-01

The aim of this work is to introduce the general concept of ‘Bond Graph’ (BG) techniques applied in the context of multi-physics and multi-scale processes. BG modelling has a natural place in these developments. BGs are inherently coherent as the relationships defined between the ‘elements’ of the graph are strictly defined by causality rules and power (energy) conservation. BGs clearly show how power flows between components of the systems they represent. The ‘effort’ and ‘flow’ variables enable bidirectional information flow in the BG model. When the power level of a system is low, BGs degenerate into signal flow graphs in which information is mainly one-dimensional and power is minimal, i.e. they find a natural limitation when dealing with populations of individuals or purely kinetic models, as the concept of energy conservation in these systems is no longer relevant. The aim of this work is twofold: on the one hand, we will introduce the general concept of BG techniques applied in the context of multi-science and multi-scale models and, on the other hand, we will highlight some of the most promising features in the BG methodology by comparing with examples developed using well-established modelling techniques/software that could suggest developments or refinements to the current state-of-the-art tools, by providing a consistent framework from a structural and energetic point of view. PMID:22670211

On the development of co-axial miniature pulse tube coolers for space applications

NASA Astrophysics Data System (ADS)

Zhou, Y.; Liang, J. T.; Zhu, W. Q.; Cai, J. H.; Ju, Y. L.

2002-05-01

Cryocoolers for cooling infrared sensors in space applications require high reliability, long lifetime, low power and minimum weight. In this paper we report work on a miniature pulse tube cooler specifically designed for such applications. A series of engineering model co-axial miniature pulse tube coolers with a flexure bearing linear compressor of 1 cc swept volume have been designed and fabricated in our laboratory. A theoretical model is established based on the analyses of thermodynamic and hydrodynamic behaviors of oscillatory flows in regenerator, for performance prediction, optimization and as a rough guide in the early stages of system design. An experimental apparatus, including a hot wire anemometer, has been set up to study the flow resistance of regenerators under oscillatory flow conditions. The co-axial, multi-bypass, and symmetric nozzle structure has been used in the coolers. We will present here the performance of two sizes of coolers with 9 mm and 8 mm diameter of cold fingers. The 9 mm cooler currently provides 500 mW net cooling power at 80 K with input power of 47 W, and the 8 mm cooler, provides 450 mW at 80 K with 51 W input power with a 65% efficient compressor. The cold fingers of our co-axial pulse tube coolers have the similar size of miniature Stirling coolers and are the only one that could meet the geometry specifications of the Standard Advance Dewar Assembly (SADA) for thermal imaging systems in most military applications.

Wide-Area Situational Awareness of Power Grids with Limited Phasor Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Huang, Zhenyu; Nieplocha, Jarek

Lack of situational awareness has been identified as one of root causes for the August 14, 2003 Northeast Blackout in North America. To improve situational awareness, the Department of Energy (DOE) launched several projects to deploy Wide Area Measurement Systems (WAMS) in different interconnections. Compared to the tens of thousands of buses, the number of Phasor Measurement Units (PMUs) is quite limited and not enough to achieve the observability for the whole interconnections. To utilize the limited number of PMU measurements to improve situational awareness, this paper proposes to combine PMU measurement data and power flow equations to form amore » hybrid power flow model. Technically, a model which combines the concept of observable islands and modeling of power flow conditions, is proposed. The model is called a Hybrid Power Flow Model as it has both PMU measurements and simulation assumptions, which describes prior knowledge available about whole power systems. By solving the hybrid power flow equations, the proposed method can be used to derive power system states to improve the situational awareness of a power grid.« less

Effect of Er,Cr:YSGG laser on human dentin fluid flow.

PubMed

Al-Omari, Wael M; Palamara, Joseph E

2013-11-01

The aim of the current investigation was to assess the rate and magnitude of dentin fluid flow of dentinal surfaces irradiated with Er,Cr:YSGG laser. Twenty extracted third molars were sectioned, mounted, and irradiated with Er,Cr:YSGG laser at 3.5 and 4.5 W power settings. Specimens were connected to an automated fluid flow measurement apparatus (Flodec). The rate, magnitude, and direction of dentin fluid flow were recorded at baseline and after irradiation. Nonparametric Wilcoxon signed ranks repeated measure t test revealed a statistically significant reduction in fluid flow for all the power settings. The 4.5-W power output reduced the flow significantly more than the 3.5 W. The samples showed a baseline outward flow followed by inward flow due to irradiation then followed by decreased outward flow. It was concluded that Er,Cr:YSGG laser irradiation at 3.5 and 4.5 W significantly reduced dentinal fluid flow rate. The reduction was directly proportional to power output.

In silico designing of power conversion efficient organic lead dyes for solar cells using todays innovative approaches to assure renewable energy for future

NASA Astrophysics Data System (ADS)

Kar, Supratik; Roy, Juganta K.; Leszczynski, Jerzy

2017-06-01

Advances in solar cell technology require designing of new organic dye sensitizers for dye-sensitized solar cells with high power conversion efficiency to circumvent the disadvantages of silicon-based solar cells. In silico studies including quantitative structure-property relationship analysis combined with quantum chemical analysis were employed to understand the primary electron transfer mechanism and photo-physical properties of 273 arylamine organic dyes from 11 diverse chemical families explicit to iodine electrolyte. The direct quantitative structure-property relationship models enable identification of the essential electronic and structural attributes necessary for quantifying the molecular prerequisites of 11 classes of arylamine organic dyes, responsible for high power conversion efficiency of dye-sensitized solar cells. Tetrahydroquinoline, N,N'-dialkylaniline and indoline have been least explored classes under arylamine organic dyes for dye-sensitized solar cells. Therefore, the identified properties from the corresponding quantitative structure-property relationship models of the mentioned classes were employed in designing of "lead dyes". Followed by, a series of electrochemical and photo-physical parameters were computed for designed dyes to check the required variables for electron flow of dye-sensitized solar cells. The combined computational techniques yielded seven promising lead dyes each for all three chemical classes considered. Significant (130, 183, and 46%) increment in predicted %power conversion efficiency was observed comparing with the existing dye with highest experimental %power conversion efficiency value for tetrahydroquinoline, N,N'-dialkylaniline and indoline, respectively maintaining required electrochemical parameters.

Electrochromic Properties of Tungsten Oxide Films Prepared by Reactive Sputtering

NASA Astrophysics Data System (ADS)

Kim, Min Hong; Kang, Tai Young; Jung, Yu Sup; Kim, Kyung Hwan

2013-05-01

WO3-x thin films were deposited on induim tin oxide (ITO) glass substrates with various oxygen flow ratios from 0.55 to 0.7 by the reactive facing-target sputtering method, at a power density of 4 W/cm2 and room temperature. The structural properties of the WO3-x thin films were measured by X-ray diffractometry and Raman spectral analysis. As-deposited WO3-x thin films had an amorphous structure. In the Raman spectra, WO3-x thin films exhibited two strong peaks at 770 and 950 cm-1 attributed to the vibrations of W6+-O and W6+=O bonds, respectively. The electrochemical and optical properties of WO3-x thin films were measured by cyclic voltammetry and UV/vis spectrometry. The results showed the highest charge density at an oxygen flow ratio of 0.7 and the highest transmittance in the visible range. The maximum coloration efficiency was 30.82 cm2/C at an oxygen flow ratio of 0.7.

Structural characterization and numerical simulations of flow properties of standard and reservoir carbonate rocks using micro-tomography

NASA Astrophysics Data System (ADS)

Islam, Amina; Chevalier, Sylvie; Sassi, Mohamed

2018-04-01

With advances in imaging techniques and computational power, Digital Rock Physics (DRP) is becoming an increasingly popular tool to characterize reservoir samples and determine their internal structure and flow properties. In this work, we present the details for imaging, segmentation, as well as numerical simulation of single-phase flow through a standard homogenous Silurian dolomite core plug sample as well as a heterogeneous sample from a carbonate reservoir. We develop a procedure that integrates experimental results into the segmentation step to calibrate the porosity. We also look into using two different numerical tools for the simulation; namely Avizo Fire Xlab Hydro that solves the Stokes' equations via the finite volume method and Palabos that solves the same equations using the Lattice Boltzmann Method. Representative Elementary Volume (REV) and isotropy studies are conducted on the two samples and we show how DRP can be a useful tool to characterize rock properties that are time consuming and costly to obtain experimentally.

Computational Study of the Impact of Unsteadiness on the Aerodynamic Performance of a Variable- Speed Power Turbine

NASA Technical Reports Server (NTRS)

Welch, Gerard E.

2012-01-01

The design-point and off-design performance of an embedded 1.5-stage portion of a variable-speed power turbine (VSPT) was assessed using Reynolds-Averaged Navier-Stokes (RANS) analyses with mixing-planes and sector-periodic, unsteady RANS analyses. The VSPT provides one means by which to effect the nearly 50 percent main-rotor speed change required for the NASA Large Civil Tilt-Rotor (LCTR) application. The change in VSPT shaft-speed during the LCTR mission results in blade-row incidence angle changes of as high as 55 . Negative incidence levels of this magnitude at takeoff operation give rise to a vortical flow structure in the pressure-side cove of a high-turn rotor that transports low-momentum flow toward the casing endwall. The intent of the effort was to assess the impact of unsteadiness of blade-row interaction on the time-mean flow and, specifically, to identify potential departure from the predicted trend of efficiency with shaft-speed change of meanline and 3-D RANS/mixing-plane analyses used for design.

Power Grid Maintenance Scheduling Intelligence Arrangement Supporting System Based on Power Flow Forecasting

NASA Astrophysics Data System (ADS)

Xie, Chang; Wen, Jing; Liu, Wenying; Wang, Jiaming

With the development of intelligent dispatching, the intelligence level of network control center full-service urgent need to raise. As an important daily work of network control center, the application of maintenance scheduling intelligent arrangement to achieve high-quality and safety operation of power grid is very important. By analyzing the shortages of the traditional maintenance scheduling software, this paper designs a power grid maintenance scheduling intelligence arrangement supporting system based on power flow forecasting, which uses the advanced technologies in maintenance scheduling, such as artificial intelligence, online security checking, intelligent visualization techniques. It implements the online security checking of maintenance scheduling based on power flow forecasting and power flow adjusting based on visualization, in order to make the maintenance scheduling arrangement moreintelligent and visual.

Modeling sediment concentration of rill flow

NASA Astrophysics Data System (ADS)

Yang, Daming; Gao, Peiling; Zhao, Yadong; Zhang, Yuhang; Liu, Xiaoyuan; Zhang, Qingwen

2018-06-01

Accurate estimation of sediment concentration is essential to establish physically-based erosion models. The objectives of this study were to evaluate the effects of flow discharge (Q), slope gradient (S), flow velocity (V), shear stress (τ), stream power (ω) and unit stream power (U) on sediment concentration. Laboratory experiments were conducted using a 10 × 0.1 m rill flume under four flow discharges (2, 4, 8 and 16 L min-1), and five slope gradients (5°, 10°, 15°, 20° and 25°). The results showed that the measured sediment concentration varied from 87.08 to 620.80 kg m-3 with a mean value of 343.13 kg m-3. Sediment concentration increased as a power function with flow discharge and slope gradient, with R2 = 0.975 and NSE = 0.945. The sediment concentration was more sensitive to slope gradient than to flow discharge. The sediment concentration was well predicted by unit stream power (R2 = 0.937, NSE = 0.865), whereas less satisfactorily by flow velocity (R2 = 0.470, NSE = 0.539) and stream power (R2 = 0.773, NSE = 0.732). In addition, using the equations to simulate the measured sediment concentration of other studies, the result further indicated that slope gradient, flow discharge and unit stream power were good predictors of sediment concentration. In general, slope gradient, flow discharge and unit stream power seem to be the preferred predictors for estimating sediment concentration.

Multifield analysis of a piezoelectric valveless micropump: effects of actuation frequency and electric potential

NASA Astrophysics Data System (ADS)

Sayar, Ersin; Farouk, Bakhtier

2012-07-01

Coupled multifield analysis of a piezoelectrically actuated valveless micropump device is carried out for liquid (water) transport applications. The valveless micropump consists of two diffuser/nozzle elements; the pump chamber, a thin structural layer (silicon), and a piezoelectric layer, PZT-5A as the actuator. We consider two-way coupling of forces between solid and liquid domains in the systems where actuator deflection causes fluid flow and vice versa. Flow contraction and expansion (through the nozzle and the diffuser respectively) generate net fluid flow. Both structural and flow field analysis of the microfluidic device are considered. The effect of the driving power (voltage) and actuation frequency on silicon-PZT-5A bi-layer membrane deflection and flow rate is investigated. For the compressible flow formulation, an isothermal equation of state for the working fluid is employed. The governing equations for the flow fields and the silicon-PZT-5A bi-layer membrane motions are solved numerically. At frequencies below 5000 Hz, the predicted flow rate increases with actuation frequency. The fluid-solid system shows a resonance at 5000 Hz due to the combined effect of mechanical and fluidic capacitances, inductances, and damping. Time-averaged flow rate starts to drop with increase of actuation frequency above (5000 Hz). The velocity profile in the pump chamber becomes relatively flat or plug-like, if the frequency of pulsations is sufficiently large (high Womersley number). The pressure, velocity, and flow rate prediction models developed in the present study can be utilized to optimize the design of MEMS based micropumps.

The shear flow processing of controlled DNA tethering and stretching for organic molecular electronics.

PubMed

Yu, Guihua; Kushwaha, Amit; Lee, Jungkyu K; Shaqfeh, Eric S G; Bao, Zhenan

2011-01-25

DNA has been recently explored as a powerful tool for developing molecular scaffolds for making reproducible and reliable metal contacts to single organic semiconducting molecules. A critical step in the process of exploiting DNA-organic molecule-DNA (DOD) array structures is the controlled tethering and stretching of DNA molecules. Here we report the development of reproducible surface chemistry for tethering DNA molecules at tunable density and demonstrate shear flow processing as a rationally controlled approach for stretching/aligning DNA molecules of various lengths. Through enzymatic cleavage of λ-phage DNA to yield a series of DNA chains of various lengths from 17.3 μm down to 4.2 μm, we have investigated the flow/extension behavior of these tethered DNA molecules under different flow strengths in the flow-gradient plane. We compared Brownian dynamic simulations for the flow dynamics of tethered λ-DNA in shear, and found our flow-gradient plane experimental results matched well with our bead-spring simulations. The shear flow processing demonstrated in our studies represents a controllable approach for tethering and stretching DNA molecules of various lengths. Together with further metallization of DNA chains within DOD structures, this bottom-up approach can potentially enable efficient and reliable fabrication of large-scale nanoelectronic devices based on single organic molecules, therefore opening opportunities in both fundamental understanding of charge transport at the single molecular level and many exciting applications for ever-shrinking molecular circuits.

Preliminary study of high energy density Zn/Ni flow batteries

NASA Astrophysics Data System (ADS)

Liu, Jin; Wang, Yan

2015-10-01

The escalation of power system promotes the development of energy storage technologies (ESTs). Among all of ESTs, battery technologies develop quickly and diversely because of its huge application market. Aqueous redox flow batteries (RFBs) are very attractive to customers in the energy grid system, and their noticeable technological innovations in past decades are driving them to gradually replace the conventional ESTs under certain circumstance. Here, the first fully-flow-able zinc-nickel flow battery (ZNFB) is preliminary reported in this paper, and its superior performance is supposed to be suitable for both large-scale storage need and carry-on powertrain in cars. Through using semi-solid fuel cell (SSFC) technology, we incorporates the beneficial features of Zn/Ni chemistry (essentially sustainable, eco-friendly and deposit-abundant) into RFB structure to make a ;hybrid; flow battery system, which can take the advantage of both. The relationship between carbon loading and suspension conductivity is determined. Electrochemical properties of ZNFB as static test, cycling test, and fully flowing test are studied to demonstrate our design.

Detailed Studies on the Structure and Dynamics of Reacting Dusty Flows at Normal and Microgravity

NASA Technical Reports Server (NTRS)

Egolfopoulos, Fokion N.; Campbell, Charles S.

1997-01-01

Two-phase reacting flows are substantially less understood compared to gas phase flows. While extensive work has been done on sprays, less attention has been given to the details of dusty reacting flows. Dusty flows are of particular interest for a wide range of applications. Particles can be present in a gas intentionally or unintentionally, and they can be inert or reacting. Inert particles can be also present in an otherwise reacting gas flow, and that can lead to flame cooling and modification of the extinction limits of a combustible mixture. Reacting solid particles can release substantial amounts of heat upon oxidation, and can be used either for propulsion (e.g. Al, B, Mg) or power generation (coal). Furthermore, accidents can occur when a reacting dust accumulates in air and which, in the presence of an ignition source, can cause explosion. Such explosions can occur during lumber milling, in grain elevators, and in mine galleries.

Hybrid Manipulation of Streamwise Vorticity in a Diffuser Boundary Layer

NASA Astrophysics Data System (ADS)

Gissen, Abraham; Vukasinovic, Bojan; Culp, John; Glezer, Ari

2010-11-01

The formation of streamwise vorticity concentrations by exploiting the interaction of surface-mounted passive (micro-vanes) and active (synthetic jets) flow control elements with the cross flow is investigated experimentally in a small-scale serpentine duct at high subsonic speeds (up to M = 0.6). Streamwise vortices can be a key element in the mitigation of the adverse effects on pressure recovery and distortion caused by the naturally occurring secondary flows in embedded propulsion systems with complex inlet geometries. Counter rotating and single-sense vortices are formed using conventional passive micro-vanes and active high-power synthetic jet actuators. Interaction of the flow control elements is examined through a hybrid actuation scheme whereby synthetic jet actuation augments the primary vanes' vortices resulting in dynamic enhancement of their strength. It is shown that such sub-boundary layer individual vortices can merge and evolve into duct-scale vortical structures that counteract the inherent secondary flow and mitigates global flow distortion.

PIC simulation of the vacuum power flow for a 5 terawatt, 5 MV, 1 MA pulsed power system

NASA Astrophysics Data System (ADS)

Liu, Laqun; Zou, Wenkang; Liu, Dagang; Guo, Fan; Wang, Huihui; Chen, Lin

2018-03-01

In this paper, a 5 Terawatt, 5 MV, 1 MA pulsed power system based on vacuum magnetic insulation is simulated by the particle-in-cell (PIC) simulation method. The system consists of 50 100-kV linear transformer drive (LTD) cavities in series, using magnetically insulated induction voltage adder (MIVA) technology for pulsed power addition and transmission. The pulsed power formation and the vacuum power flow are simulated when the system works in self-limited flow and load-limited flow. When the pulsed power system isn't connected to the load, the downstream magnetically insulated transmission line (MITL) works in the self-limited flow, the maximum of output current is 1.14 MA and the amplitude of voltage is 4.63 MV. The ratio of the electron current to the total current is 67.5%, when the output current reached the peak value. When the impedance of the load is 3.0 Ω, the downstream MITL works in the self-limited flow, the maximums of output current and the amplitude of voltage are 1.28 MA and 3.96 MV, and the ratio of the electron current to the total current is 11.7% when the output current reached the peak value. In addition, when the switches are triggered in synchronism with the passage of the pulse power flow, it effectively reduces the rise time of the pulse current.

Estimating the vibration level of an L-shaped beam using power flow techniques

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.; Mccollum, M.; Rassineux, J. L.; Gilbert, T.

1986-01-01

The response of one component of an L-shaped beam, with point force excitation on the other component, is estimated using the power flow method. The transmitted power from the source component to the receiver component is expressed in terms of the transfer and input mobilities at the excitation point and the joint. The response is estimated both in narrow frequency bands, using the exact geometry of the beams, and as a frequency averaged response using infinite beam models. The results using this power flow technique are compared to the results obtained using finite element analysis (FEA) of the L-shaped beam for the low frequency response and to results obtained using statistical energy analysis (SEA) for the high frequencies. The agreement between the FEA results and the power flow method results at low frequencies is very good. SEA results are in terms of frequency averaged levels and these are in perfect agreement with the results obtained using the infinite beam models in the power flow method. The narrow frequency band results from the power flow method also converge to the SEA results at high frequencies. The advantage of the power flow method is that detail of the response can be retained while reducing computation time, which will allow the narrow frequency band analysis of the response to be extended to higher frequencies.

VIPR III VADR SPIDER Structural Design and Analysis

NASA Technical Reports Server (NTRS)

Li, Wesley; Chen, Tony

2016-01-01

In support of the National Aeronautics and Space Administration (NASA) Vehicle Integrated Propulsion Research (VIPR) Phase III team to evaluate the volcanic ash environment effects on the Pratt & Whitney F117-PW-100 turbofan engine, NASA Armstrong Flight Research Center has successfully performed structural design and analysis on the Volcanic Ash Distribution Rig (VADR) and the Structural Particulate Integration Device for Engine Research (SPIDER) for the ash ingestion test. Static and dynamic load analyses were performed to ensure no structural failure would occur during the test. Modal analysis was conducted, and the results were used to develop engine power setting avoidance zones. These engine power setting avoidance zones were defined to minimize the dwell time when the natural frequencies of the VADR/SPIDER system coincided with the excitation frequencies of the engine which was operating at various revolutions per minute. Vortex-induced vibration due to engine suction air flow during the ingestion test was also evaluated, but was not a concern.

American Recovery and Reinvestment Act: North Fork Skokomish Powerhouse at Cushman No. 2 Dam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, Steve; McCarty, Patrick

2013-09-30

The objective of this project was to add generating capacity on an in-stream flow release at Tacoma Power's Cushman hydroelectric project, Cushman No. 2 Dam, FERC Project P-460. The flow that is being used to generate additional electricity was being discharged from a valve at the base of the dam without recovery of the energy. A second objective to the project was to incorporate upstream fish passage by use of a fish collection structure attached to the draft tubes of the hydroelectric units. This will enable reintroduction of native anadromous fish above the dams which have blocked fish passage sincemore » the late 1920's. The project was funded in part by the American Recovery and Reinvestment Act through the Department of Energy, Office of Energy, Efficiency and Renewable Energy, Wind and Water Power Program.« less

Experimental tests of truncated diffusion in fault damage zones

NASA Astrophysics Data System (ADS)

Suzuki, Anna; Hashida, Toshiyuki; Li, Kewen; Horne, Roland N.

2016-11-01

Fault zones affect the flow paths of fluids in groundwater aquifers and geological reservoirs. Fault-related fracture damage decreases to background levels with increasing distance from the fault core according to a power law. This study investigated mass transport in such a fault-related structure using nonlocal models. A column flow experiment is conducted to create a permeability distribution that varies with distance from a main conduit. The experimental tracer response curve is preasymptotic and implies subdiffusive transport, which is slower than the normal Fickian diffusion. If the surrounding area is a finite domain, an upper truncated behavior in tracer response (i.e., exponential decline at late times) is observed. The tempered anomalous diffusion (TAD) model captures the transition from subdiffusive to Fickian transport, which is characterized by a smooth transition from power-law to an exponential decline in the late-time breakthrough curves.

Effect of inlet conditions for numerical modelling of the urban boundary layer

NASA Astrophysics Data System (ADS)

Gnatowska, Renata

2018-01-01

The paper presents the numerical results obtained with the use of the ANSYS FLUENT commercial code for analysing the flow structure around two rectangular inline surface-mounted bluff bodies immersed in a boundary layer. The effects of the inflow boundary layer for the accuracy of the numerical modelling of the flow field around a simple system of objects are described. The analysis was performed for two concepts. In the former case, the inlet velocity profile was defined using the power law, whereas the kinetic and dissipation energy was defined from the equations according to Richards and Hoxey [1]. In the latter case, the inlet conditions were calculated for the flow over the rough area composed of the rectangular components.

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2010-06-14

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Can standard cosmological models explain the observed Abell cluster bulk flow?

NASA Technical Reports Server (NTRS)

Strauss, Michael A.; Cen, Renyue; Ostriker, Jeremiah P.; Laure, Tod R.; Postman, Marc

1995-01-01

Lauer and Postman (LP) observed that all Abell clusters with redshifts less than 15,000 km/s appear to be participating in a bulk flow of 689 km/s with respect to the cosmic microwave background. We find this result difficult to reconcile with all popular models for large-scale structure formation that assume Gaussian initial conditions. This conclusion is based on Monte Carlo realizations of the LP data, drawn from large particle-mesh N-body simulations for six different models of the initial power spectrum (standard, tilted, and Omega(sub 0) = 0.3 cold dark matter, and two variants of the primordial baryon isocurvature model). We have taken special care to treat properly the longest-wavelength components of the power spectra. The simulations are sampled, 'observed,' and analyzed as identically as possible to the LP cluster sample. Large-scale bulk flows as measured from clusters in the simulations are in excellent agreement with those measured from the grid: the clusters do not exhibit any strong velocity bias on large scales. Bulk flows with amplitude as large as that reported by LP are not uncommon in the Monte Carlo data stes; the distribution of measured bulk flows before error bias subtraction is rougly Maxwellian, with a peak around 400 km/s. However the chi squared of the observed bulk flow, taking into account the anisotropy of the error ellipsoid, is much more difficult to match in the simulations. The models examined are ruled out at confidence levels between 94% and 98%.

Nested high-resolution large-eddy simulations in WRF to support wind power

NASA Astrophysics Data System (ADS)

Mirocha, J.; Kirkil, G.; Kosovic, B.; Lundquist, J. K.

2009-12-01

The WRF model’s grid nesting capability provides a potentially powerful framework for simulating flow over a wide range of scales. One such application is computation of realistic inflow boundary conditions for large eddy simulations (LES) by nesting LES domains within mesoscale domains. While nesting has been widely and successfully applied at GCM to mesoscale resolutions, the WRF model’s nesting behavior at the high-resolution (Δx < 1000m) end of the spectrum is less well understood. Nesting LES within msoscale domains can significantly improve turbulent flow prediction at the scale of a wind park, providing a basis for superior site characterization, or for improved simulation of turbulent inflows encountered by turbines. We investigate WRF’s grid nesting capability at high mesh resolutions using nested mesoscale and large-eddy simulations. We examine the spatial scales required for flow structures to equilibrate to the finer mesh as flow enters a nest, and how the process depends on several parameters, including grid resolution, turbulence subfilter stress models, relaxation zones at nest interfaces, flow velocities, surface roughnesses, terrain complexity and atmospheric stability. Guidance on appropriate domain sizes and turbulence models for LES in light of these results is provided This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 LLNL-ABS-416482

Study of Hydrokinetic Turbine Arrays with Large Eddy Simulation

NASA Astrophysics Data System (ADS)

Sale, Danny; Aliseda, Alberto

2014-11-01

Marine renewable energy is advancing towards commercialization, including electrical power generation from ocean, river, and tidal currents. The focus of this work is to develop numerical simulations capable of predicting the power generation potential of hydrokinetic turbine arrays-this includes analysis of unsteady and averaged flow fields, turbulence statistics, and unsteady loadings on turbine rotors and support structures due to interaction with rotor wakes and ambient turbulence. The governing equations of large-eddy-simulation (LES) are solved using a finite-volume method, and the presence of turbine blades are approximated by the actuator-line method in which hydrodynamic forces are projected to the flow field as a body force. The actuator-line approach captures helical wake formation including vortex shedding from individual blades, and the effects of drag and vorticity generation from the rough seabed surface are accounted for by wall-models. This LES framework was used to replicate a previous flume experiment consisting of three hydrokinetic turbines tested under various operating conditions and array layouts. Predictions of the power generation, velocity deficit and turbulence statistics in the wakes are compared between the LES and experimental datasets.

Turbulence effects on a full-scale 2.5 MW horizontal axis wind turbine

NASA Astrophysics Data System (ADS)

Chamorro, Leonardo; Lee, Seung-Jae; Olsen, David; Milliren, Chris; Marr, Jeff; Arndt, Roger; Sotiropoulos, Fotis

2012-11-01

Power fluctuations and fatigue loads are among the most significant problems that wind turbines face throughout their lifetime. Turbulence is the common driving mechanism that triggers instabilities on these quantities. We investigate the complex response of a full-scale 2.5 MW wind turbine under nearly neutral thermal stratification. The study is performed in the EOLOS Wind Energy Research Field Station of the University of Minnesota. An instrumented 130 meter meteorological tower located upstream of a Clipper Liberty C96 wind turbine is used to characterize the turbulent flow and atmospheric conditions right upstream of the wind turbine. High resolution and synchronous measurements of the wind velocity, turbine power and strain at the tower foundation are used to determine the scale-to-scale interaction between flow and the wind turbine. The structure of the fluctuating turbine power and instantaneous stresses are studied in detail. Important insights about the role of turbulent and coherent motions as well as strong intermittent gusts will be discussed. Funding was provided by Department of Energy DOE (DE-EE0002980) and Xcel Energy through the Renewable Development Fund (grant RD3-42).

Efficient Hardware Implementation of the Horn-Schunck Algorithm for High-Resolution Real-Time Dense Optical Flow Sensor

PubMed Central

Komorkiewicz, Mateusz; Kryjak, Tomasz; Gorgon, Marek

2014-01-01

This article presents an efficient hardware implementation of the Horn-Schunck algorithm that can be used in an embedded optical flow sensor. An architecture is proposed, that realises the iterative Horn-Schunck algorithm in a pipelined manner. This modification allows to achieve data throughput of 175 MPixels/s and makes processing of Full HD video stream (1, 920 × 1, 080 @ 60 fps) possible. The structure of the optical flow module as well as pre- and post-filtering blocks and a flow reliability computation unit is described in details. Three versions of optical flow modules, with different numerical precision, working frequency and obtained results accuracy are proposed. The errors caused by switching from floating- to fixed-point computations are also evaluated. The described architecture was tested on popular sequences from an optical flow dataset of the Middlebury University. It achieves state-of-the-art results among hardware implementations of single scale methods. The designed fixed-point architecture achieves performance of 418 GOPS with power efficiency of 34 GOPS/W. The proposed floating-point module achieves 103 GFLOPS, with power efficiency of 24 GFLOPS/W. Moreover, a 100 times speedup compared to a modern CPU with SIMD support is reported. A complete, working vision system realized on Xilinx VC707 evaluation board is also presented. It is able to compute optical flow for Full HD video stream received from an HDMI camera in real-time. The obtained results prove that FPGA devices are an ideal platform for embedded vision systems. PMID:24526303

Efficient hardware implementation of the Horn-Schunck algorithm for high-resolution real-time dense optical flow sensor.

PubMed

Komorkiewicz, Mateusz; Kryjak, Tomasz; Gorgon, Marek

2014-02-12

This article presents an efficient hardware implementation of the Horn-Schunck algorithm that can be used in an embedded optical flow sensor. An architecture is proposed, that realises the iterative Horn-Schunck algorithm in a pipelined manner. This modification allows to achieve data throughput of 175 MPixels/s and makes processing of Full HD video stream (1; 920 × 1; 080 @ 60 fps) possible. The structure of the optical flow module as well as pre- and post-filtering blocks and a flow reliability computation unit is described in details. Three versions of optical flow modules, with different numerical precision, working frequency and obtained results accuracy are proposed. The errors caused by switching from floating- to fixed-point computations are also evaluated. The described architecture was tested on popular sequences from an optical flow dataset of the Middlebury University. It achieves state-of-the-art results among hardware implementations of single scale methods. The designed fixed-point architecture achieves performance of 418 GOPS with power efficiency of 34 GOPS/W. The proposed floating-point module achieves 103 GFLOPS, with power efficiency of 24 GFLOPS/W. Moreover, a 100 times speedup compared to a modern CPU with SIMD support is reported. A complete, working vision system realized on Xilinx VC707 evaluation board is also presented. It is able to compute optical flow for Full HD video stream received from an HDMI camera in real-time. The obtained results prove that FPGA devices are an ideal platform for embedded vision systems.

Balancing Power Absorption Against Structural Loads With Viscous Drag and Power-Takeoff Efficiency Considerations

DOE PAGES

Tom, Nathan; Yu, Yi-Hsiang; Wright, Alan; ...

2017-11-17

The focus of this paper is to balance power absorption against structural loading for a novel fixed-bottom oscillating surge wave energy converter in both regular and irregular wave environments. The power-to-load ratio will be evaluated using pseudospectral control (PSC) to determine the optimum power-takeoff (PTO) torque based on a multiterm objective function. This paper extends the pseudospectral optimal control problem to not just maximize the time-averaged absorbed power but also include measures for the surge-foundation force and PTO torque in the optimization. The objective function may now potentially include three competing terms that the optimizer must balance. Separate weighting factorsmore » are attached to the surge-foundation force and PTO control torque that can be used to tune the optimizer performance to emphasize either power absorption or load shedding. To correct the pitch equation of motion, derived from linear hydrodynamic theory, a quadratic-viscous-drag torque has been included in the system dynamics; however, to continue the use of quadratic programming solvers, an iteratively obtained linearized drag coefficient was utilized that provided good accuracy in the predicted pitch motion. Furthermore, the analysis considers the use of a nonideal PTO unit to more accurately evaluate controller performance. The PTO efficiency is not directly included in the objective function but rather the weighting factors are utilized to limit the PTO torque amplitudes, thereby reducing the losses resulting from the bidirectional energy flow through a nonideal PTO. Results from PSC show that shedding a portion of the available wave energy can lead to greater reductions in structural loads, peak-to-average power ratio, and reactive power requirement.« less

Freeform Fluidics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dehoff, Ryan R; Love, Lonnie J; Lind, Randall F

This work explores the integration of miniaturized fluid power and additive manufacturing. Oak Ridge National Laboratory (ORNL) has been developing an approach to miniaturized fluidic actuation and control that enables high dexterity, low cost and a pathway towards energy efficiency. Previous work focused on mesoscale digital control valves (high pressure, low flow) and the integration of actuation and fluid passages directly with the structure, the primary application being fluid powered robotics. The fundamental challenge was part complexity. ORNL s new additive manufacturing technologies (e-beam, laser and ultrasonic deposition) enables freeform manufacturing using conventional metal alloys with excellent mechanical properties. Themore » combination of these two technologies, miniaturized fluid power and additive manufacturing, can enable a paradigm shift in fluid power, increasing efficiency while simultaneously reducing weight, size, complexity and cost. This paper focuses on the impact additive manufacturing can have on new forms of fluid power components and systems. We begin with a description of additive manufacturing processes, highlighting the strengths and weaknesses of each technology. Next we describe fundamental results of material characterization to understand the design and mechanical limits of parts made with the e-beam process. A novel design approach is introduced that enables integration of fluid powered actuation with mechanical structure. Finally, we describe a proof-of-principle demonstration: an anthropomorphic (human-like) hydraulically powered hand with integrated power supply and actuation.« less

Effect of flow rate and concentration difference on reverse electrodialysis system

NASA Astrophysics Data System (ADS)

Kwon, Kilsugn; Han, Jaesuk; Kim, Daejoong

2013-11-01

Various energy conversion technologies have been developed to reduce dependency on limited fossil fuels, including wind power, solar power, hydropower, ocean power, and geothermal power. Among them, reverse electrodialysis (RED), which is one type of salinity gradient power (SGP), has received much attention due to high reliability and simplicity without moving parts. Here, we experimentally evaluated the RED performance with several parameters like flow rate of concentrated and dilute solution, concentration difference, and temperature. RED was composed of endplates, electrodes, spacers, anion exchange membrane, and cation exchange membrane. Endplates are made by a polypropylene. It included the electrodes, flow field for the electrode rinse solution, and path to supply a concentrated and dilute solution. Titanium coated by iridium and ruthenium was used as the electrode. The electrode rinse solution based on hexacyanoferrate system is used to reduce the power loss generated by conversion process form ionic current to electric current. Maximum power monotonously increases as increasing flow rate and concentration difference. Net power has optimal point because pumping power consumption increases with flow rate. This work was supported by Basic Science Research Program (Grat No. NRF-2011-0009993) through the National Research Foundation of Korea.

Radiation beam calorimetric power measurement system

DOEpatents

Baker, John; Collins, Leland F.; Kuklo, Thomas C.; Micali, James V.

1992-01-01

A radiation beam calorimetric power measurement system for measuring the average power of a beam such as a laser beam, including a calorimeter configured to operate over a wide range of coolant flow rates and being cooled by continuously flowing coolant for absorbing light from a laser beam to convert the laser beam energy into heat. The system further includes a flow meter for measuring the coolant flow in the calorimeter and a pair of thermistors for measuring the temperature difference between the coolant inputs and outputs to the calorimeter. The system also includes a microprocessor for processing the measured coolant flow rate and the measured temperature difference to determine the average power of the laser beam.

Dispersion of ferrofluid aggregates in steady flows

NASA Astrophysics Data System (ADS)

Williams, Alicia M.; Vlachos, Pavlos P.

2011-12-01

Using focused shadowgraphs, we investigate steady flows of a magnetically non-susceptible fluid interacting with ferrofluid aggregates comprised of superparamagnetic nanoparticles. The ferrofluid aggregate is retained at a specific site within the flow channel using two different applied magnetic fields. The bulk flow induces shear stresses on the aggregate, which give rise to the development of interfacial disturbances, leading to Kelvin-Helmholtz (K-H) instabilities and shedding of ferrofluid structures. Herein, the effects of bulk Reynolds number, ranging from 100 to 1000, and maximum applied magnetic fields of 1.2 × 105 and 2.4 × 105 A/m are investigated in the context of their impact on dispersion or removal of material from the core aggregate. The aggregate interaction with steady bulk flow reveals three regimes of aggregate dynamics over the span of Reynolds numbers studied: stable, transitional, and shedding. The first regime is characterized by slight aggregate stretching for low Reynolds numbers, with full aggregate retention. As the Reynolds number increases, the aggregate is in-transition between stable and shedding states. This second regime is characterized by significant initial stretching that gives way to small amplitude Kelvin-Helmholtz waves. Higher Reynolds numbers result in ferrofluid shedding, with Strouhal numbers initially between 0.2 and 0.3, wherein large vortical structures are shed from the main aggregate accompanied by precipitous decay of the accumulated ferrofluid aggregate. These behaviors are apparent for both magnetic field strengths, although the transitional Reynolds numbers are different between the cases, as are the characteristic shedding frequencies relative to the same Reynolds number. In the final step of this study, relevant parameters were extracted from the time series dispersion data to comprehensively quantify aggregate mechanics. The aggregate half-life is found to decrease as a function of the Reynolds number following a power law curve and can be scaled for different magnetic fields using the magnetic induction at the inner wall of the vessel. In addition, the decay rate of the ferrofluid is shown to be proportional to the wall shear rate. Finally, a dimensionless parameter, which scales the inertia-driven flow pressures, relative to the applied magnetic pressures, reveals a power law decay relationship with respect to the incident bulk flow.

Landscape genetics of a pollinator longhorn beetle [Typocerus v. velutinus (Olivier)] on a continuous habitat surface.

PubMed

Abdel Moniem, H E M; Schemerhorn, B J; DeWoody, J A; Holland, J D

2016-10-01

Landscape connectivity, the degree to which the landscape structure facilitates or impedes organismal movement and gene flow, is increasingly important to conservationists and land managers. Metrics for describing the undulating shape of continuous habitat surfaces can expand the usefulness of continuous gradient surfaces that describe habitat and predict the flow of organisms and genes. We adopted a landscape gradient model of habitat and used surface metrics of connectivity to model the genetic continuity between populations of the banded longhorn beetle [Typocerus v. velutinus (Olivier)] collected at 17 sites across a fragmentation gradient in Indiana, USA. We tested the hypothesis that greater habitat connectivity facilitates gene flow between beetle populations against a null model of isolation by distance (IBD). We used next-generation sequencing to develop 10 polymorphic microsatellite loci and genotype the individual beetles to assess the population genetic structure. Isolation by distance did not explain the population genetic structure. The surface metrics model of habitat connectivity explained the variance in genetic dissimilarities 30 times better than the IBD model. We conclude that surface metrology of habitat maps is a powerful extension of landscape genetics in heterogeneous landscapes. © 2016 John Wiley & Sons Ltd.

Structure of jammed configurations and their relation to unjamming times

NASA Astrophysics Data System (ADS)

Birwa, Sumit Kumar; Merrigan, Carl; Chakraborty, Bulbul; Tewari, Shubha

The distribution of the times for the cessation of flow of grains falling under gravity in a vertical hopper is known to be exponential. Recent experiments have shown, however, that the time lapse between avalanches follows a power-law distribution when the hopper is unjammed using periodic vertical vibrations. The reasons for this distribution of the unjamming times, which indicates the time needed for an applied continuous perturbation to induce another avalanche, are not well understood. We report on a numerical simulation of granular hopper flow using LAMMPS in which we seek to understand the origin and scope of this behavior. We find that cessation of flow is related to the formation of a stable arch that spans the system. However, the actual structure of the jammed configuration varies and is closely related to the unjamming time. We find that the symmetry of the arches is an important parameter in determining the strength of the jammed configurations. Using different force thresholds, we have characterized the contact networks around the arches which provides stability to the packed structure and analyzed the strength of various jammed configurations. Supported by NSF Grant DMR1409093 and DGE1068620.

Application of laminar flow control to supersonic transport configurations

NASA Technical Reports Server (NTRS)

Parikh, P. G.; Nagel, A. L.

1990-01-01

The feasibility and impact of implementing a laminar flow control system on a supersonic transport configuration were investigated. A hybrid laminar flow control scheme consisting of suction controlled and natural laminar flow was developed for a double-delta type wing planform. The required suction flow rates were determined from boundary layer stability analyses using representative wing pressure distributions. A preliminary design of structural modifications needed to accommodate suction through a perforated titanium skin was carried out together with the ducting and systems needed to collect, compress and discharge the suction air. The benefits of reduced aerodynamic drag were weighed against the weight, volume and power requirement penalties of suction system installation in a mission performance and sizing program to assess the net benefits. The study showed a feasibility of achieving significant laminarization of the wing surface by use of a hybrid scheme, leading to an 8.2 percent reduction in the cruise drag. This resulted in an 8.5 percent reduction in the maximum takeoff weight and a 12 percent reduction in the fuel burn after the inclusion of the LFC system installation penalties. Several research needs were identified for a resolution of aerodynamics, structural and systems issues before these potential benefits could be realized in a practical system.

Hydroelectric power plant with variable flow on drinking water adduction

NASA Astrophysics Data System (ADS)

Deaconu, S. I.; Babău, R.; Popa, G. N.; Gherman, P. L.

2018-01-01

The water feeding system of the urban and rural localities is mainly collected with feed pipes which can have different lengths and different levels. Before using, water must be treated. Since the treatment take place in the tanks, the pressure in the inlet of the station must be diminished. Many times the pressure must be reduced with 5-15 Barr and this is possible using valves, cavils, and so on. The flow capacity of the water consumption is highly fluctuating during one day, depending on the season, etc. This paper presents a method to use the hydroelectric potential of the feed pipes using a hydraulic turbine instead of the classical methods for decreasing the pressure. To avoid the dissipation of water and a good behavior of the power parameters it is used an asynchronous generator (AG) which is coupled at the electrical distribution network through a static frequency converter (SFC). The turbine has a simple structure without the classical devices (used to regulate the turbine blades). The speed of rotation is variable, depending on the necessary flow capacity in the outlet of the treatment station. The most important element of the automation is the static frequency converter (SFC) which allows speeds between 0 and 1.5 of the rated speed of rotation and the flow capacity varies accordingly with it.

A theory of self-organized zonal flow with fine radial structure in tokamak

NASA Astrophysics Data System (ADS)

Zhang, Y. Z.; Liu, Z. Y.; Xie, T.; Mahajan, S. M.; Liu, J.

2017-12-01

The (low frequency) zonal flow-ion temperature gradient (ITG) wave system, constructed on Braginskii's fluid model in tokamak, is shown to be a reaction-diffusion-advection system; it is derived by making use of a multiple spatiotemporal scale technique and two-dimensional (2D) ballooning theory. For real regular group velocities of ITG waves, two distinct temporal processes, sharing a very similar meso-scale radial structure, are identified in the nonlinear self-organized stage. The stationary and quasi-stationary structures reflect a particular feature of the poloidal group velocity. The equation set posed to be an initial value problem is numerically solved for JET low mode parameters; the results are presented in several figures and two movies that show the spatiotemporal evolutions as well as the spectrum analysis—frequency-wave number spectrum, auto power spectrum, and Lissajous diagram. This approach reveals that the zonal flow in tokamak is a local traveling wave. For the quasi-stationary process, the cycle of ITG wave energy is composed of two consecutive phases in distinct spatiotemporal structures: a pair of Cavitons growing and breathing slowly without long range propagation, followed by a sudden decay into many Instantons that carry negative wave energy rapidly into infinity. A spotlight onto the motion of Instantons for a given radial position reproduces a Blob-Hole temporal structure; the occurrence as well as the rapid decay of Caviton into Instantons is triggered by zero-crossing of radial group velocity. A sample of the radial profile of zonal flow contributed from 31 nonlinearly coupled rational surfaces near plasma edge is found to be very similar to that observed in the JET Ohmic phase [J. C. Hillesheim et al., Phys. Rev. Lett. 116, 165002 (2016)]. The theory predicts an interior asymmetric dipole structure associated with the zonal flow that is driven by the gradients of ITG turbulence intensity.

Locational Marginal Pricing in the Campus Power System at the Power Distribution Level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, Jun; Gu, Yi; Zhang, Yingchen

2016-11-14

In the development of smart grid at distribution level, the realization of real-time nodal pricing is one of the key challenges. The research work in this paper implements and studies the methodology of locational marginal pricing at distribution level based on a real-world distribution power system. The pricing mechanism utilizes optimal power flow to calculate the corresponding distributional nodal prices. Both Direct Current Optimal Power Flow and Alternate Current Optimal Power Flow are utilized to calculate and analyze the nodal prices. The University of Denver campus power grid is used as the power distribution system test bed to demonstrate themore » pricing methodology.« less

The logarithmic and power law behaviors of the accelerating, turbulent thermal boundary layer

NASA Astrophysics Data System (ADS)

Castillo, Luciano; Hussain, Fazle

2017-02-01

Direct numerical simulation of spatially evolving thermal turbulent boundary layers with strong favorable pressure gradient (FPG) shows that the thermal fluctuation intensity, θ' + and the Reynolds shear stress, u'v'¯+ exhibit a logarithmic behavior spanning the meso-layer (e.g., 50 ≤y+≤170 ). However, the mean thermal profile is not logarithmic even in the zero pressure gradient (ZPG) region; instead, it follows a power law. The maxima of u' 2 ¯+ and v'θ'¯+ change little with the strength of acceleration, while v'+, w'+, and u'v'¯+ continue to decay in the flow direction. Furthermore, θ'+ and u'θ'¯+ surprisingly experience changes from constants in ZPG to sharp rises in the FPG region. Such behavior appears to be due to squashing of the streaks which decreases the streak flank angle below the critical value for "transient growth" generation of streamwise vortices, shutting down production [W. Schoppa and F. Hussain, "Coherent structure generation near-wall turbulence," J. Fluid Mech. 453, 57-108 (2002)]. The streamwise vortices near the wall, although shrink because of stretching, simultaneously, also become weaker as the structures are progressively pushed farther down to the more viscous region near the wall. While the vortical structures decay rapidly in accelerating flows, the thermal field does not—nullifying the myth that both the thermal and velocity fields are similar.

Quasi-passive heat sink for high-power laser diodes

NASA Astrophysics Data System (ADS)

Vetrovec, John

2009-02-01

We report on a novel heat sink for high-power laser diodes offering unparalleled capacity in high-heat flux handling and temperature control. The heat sink uses a liquid coolant flowing at high speed in a miniature closed and sealed loop. Diode waste heat is received at high flux and transferred to environment, coolant fluid, heat pipe, or structure at a reduced flux. When pumping solid-state or alkali vapor lasers, diode wavelength can be electronically tuned to the absorption features of the laser gain medium. This paper presents the heat sink physics, engineering design, performance modeling, and configurations.

Estimating Vibrational Powers Of Parts In Fluid Machinery

NASA Technical Reports Server (NTRS)

Harvey, S. A.; Kwok, L. C.

1995-01-01

In new method of estimating vibrational power associated with component of fluid-machinery system, physics of flow through (or in vicinity of) component regarded as governing vibrations. Devised to generate scaling estimates for design of new parts of rocket engines (e.g., pumps, combustors, nozzles) but applicable to terrestrial pumps, turbines, and other machinery in which turbulent flows and vibrations caused by such flows are significant. Validity of method depends on assumption that fluid flows quasi-steadily and that flow gives rise to uncorrelated acoustic powers in different parts of pump.

Asymmetrical booster ascent guidance and control system design study. Volume 5: Space shuttle powered explicit guidance. [space shuttle development

NASA Technical Reports Server (NTRS)

Jaggers, R. F.

1974-01-01

An optimum powered explicit guidance algorithm capable of handling all space shuttle exoatospheric maneuvers is presented. The theoretical and practical basis for the currently baselined space shuttle powered flight guidance equations and logic is documented. Detailed flow diagrams for implementing the steering computations for all shuttle phases, including powered return to launch site (RTLS) abort, are also presented. Derivation of the powered RTLS algorithm is provided, as well as detailed flow diagrams for implementing the option. The flow diagrams and equations are compatible with the current powered flight documentation.

SOL effects on the pedestal structure in DIII-D discharges

DOE PAGES

Sontag, Aaron C.; Chen, Xi; Canik, John; ...

2017-05-24

SOLPS analysis explains the differences in pedestal structure associated with different ion ∇B drift directions in DIII-D. Core transport models predict that fusion power scales roughly as the square of the pressure at the top of the pedestal, so understanding the effects that determine pedestal structure in steady-state operational scenarios is important to projecting scenarios developed in DIII-D to ITER and other devices. Both experiments and modeling indicate that scrape off layer (SOL) conditions are important in optimizing the pedestal structure for high-beta steady-state scenarios. The SOLPS code is used to provide interpretive analysis of the pedestal and SOL tomore » examine the nature of flows and fueling on the pedestal structure including the effects of drifts in the fluid model. This analysis shows that flows driven by the ion ∇B drift are outward when this drift is toward the x-point in a single-null divertor configuration (favorable ∇B direction for reduced H-mode power threshold), and inward when the drift is away from the x-point (unfavorable ∇B direction). It is hypothesized that these flows decrease the density gradient in the pedestal in the favorable direction, thereby stabilizing the kinetic ballooning mode (KBM) and increasing the pedestal width. Comparisons of pedestal structures in similarly shaped DIII-D steady-state plasmas confirm this change, showing increased density pedestal width and lower peak density and lower separatrix density with the favorable drift direction. The pedestal temperature is higher in the lower density case, resulting in an increased pedestal pressure, which indicates that the increased particle flux does not significantly degrade energy confinement. Modeling of cases with constant ∇B drift direction but changing between the more open lower divertor and more closed upper divertor show that there is increased fueling inside the pedestal with the more open geometry. As a result, the pedestal fueling rate for both attached and detached cases is always lower with more closed divertor geometry than in any cases with more open geometry.« less

SOL effects on the pedestal structure in DIII-D discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sontag, Aaron C.; Chen, Xi; Canik, John

SOLPS analysis explains the differences in pedestal structure associated with different ion ∇B drift directions in DIII-D. Core transport models predict that fusion power scales roughly as the square of the pressure at the top of the pedestal, so understanding the effects that determine pedestal structure in steady-state operational scenarios is important to projecting scenarios developed in DIII-D to ITER and other devices. Both experiments and modeling indicate that scrape off layer (SOL) conditions are important in optimizing the pedestal structure for high-beta steady-state scenarios. The SOLPS code is used to provide interpretive analysis of the pedestal and SOL tomore » examine the nature of flows and fueling on the pedestal structure including the effects of drifts in the fluid model. This analysis shows that flows driven by the ion ∇B drift are outward when this drift is toward the x-point in a single-null divertor configuration (favorable ∇B direction for reduced H-mode power threshold), and inward when the drift is away from the x-point (unfavorable ∇B direction). It is hypothesized that these flows decrease the density gradient in the pedestal in the favorable direction, thereby stabilizing the kinetic ballooning mode (KBM) and increasing the pedestal width. Comparisons of pedestal structures in similarly shaped DIII-D steady-state plasmas confirm this change, showing increased density pedestal width and lower peak density and lower separatrix density with the favorable drift direction. The pedestal temperature is higher in the lower density case, resulting in an increased pedestal pressure, which indicates that the increased particle flux does not significantly degrade energy confinement. Modeling of cases with constant ∇B drift direction but changing between the more open lower divertor and more closed upper divertor show that there is increased fueling inside the pedestal with the more open geometry. As a result, the pedestal fueling rate for both attached and detached cases is always lower with more closed divertor geometry than in any cases with more open geometry.« less

Model calculations of kinetic and fluid dynamic processes in diode pumped alkali lasers

NASA Astrophysics Data System (ADS)

Barmashenko, Boris D.; Rosenwaks, Salman; Waichman, Karol

2013-10-01

Kinetic and fluid dynamic processes in diode pumped alkali lasers (DPALs) are analyzed in detail using a semianalytical model, applicable to both static and flowing-gas devices. The model takes into account effects of temperature rise, excitation of neutral alkali atoms to high lying electronic states and their losses due to ionization and chemical reactions, resulting in a decrease of the pump absorption, slope efficiency and lasing power. Effects of natural convection in static DPALs are also taken into account. The model is applied to Cs DPALs and the results are in good agreement with measurements in a static [B.V. Zhdanov, J. Sell and R.J. Knize, Electron. Lett. 44, 582 (2008)] and 1-kW flowing-gas [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] DPALs. It predicts the dependence of power on the flow velocity in flowing-gas DPALs and on the buffer gas composition. The maximum values of the laser power can be substantially increased by optimization of the flowing-gas DPAL parameters. In particular for the aforementioned 1 kW DPAL, 6 kW maximum power is achievable just by increasing the pump power and the temperature of the wall and the gas at the flow inlet (resulting in increase of the alkali saturated vapor density). Dependence of the lasing power on the pump power is non-monotonic: the power first increases, achieves its maximum and then decreases. The decrease of the lasing power with increasing pump power at large values of the latter is due to the rise of the aforementioned losses of the alkali atoms as a result of ionization. Work in progress applying two-dimensional computational fluid dynamics modeling of flowing-gas DPALs is also reported.

KSC-98pc458

NASA Image and Video Library

1998-04-06

KENNEDY SPACE CENTER, FLA. -- The Long Spacer, a component of the International Space Station, arrives and is moved to its test stand in the northeast corner of the high bay in KSC's Space Station Processing Facility. The Long Spacer provides structural support for the outboard Photovoltaic Modules that supply power to the station. Now just a structure, the Long Spacer will have attached to it as part of processing a heat dissipation radiator and two Pump and Flow Control subassemblies that circulate ammonia to cool the solar array electronics. Also to be mounted are ammonia fluid lines as part of the cooling system and the cabling necessary for power and control of the station. The Long Spacer becomes an integral part of a station truss segment when it is mated with the Integrated Equipment Assembly, which stores the electrical power generated by the solar arrays for use by the station modules. The Long Spacer is being processed in preparation for STS-97, currently planned for launch aboard Discovery in April 1999

KSC-98pc456

NASA Image and Video Library

1998-04-06

KENNEDY SPACE CENTER, FLA. -- The Long Spacer, a component of the International Space Station, arrives and is moved to its test stand in the northeast corner of the high bay in KSC's Space Station Processing Facility. The Long Spacer provides structural support for the outboard Photovoltaic Modules that supply power to the station. Now just a structure, the Long Spacer will have attached to it as part of processing a heat dissipation radiator and two Pump and Flow Control subassemblies that circulate ammonia to cool the solar array electronics. Also to be mounted are ammonia fluid lines as part of the cooling system and the cabling necessary for power and control of the station. The Long Spacer becomes an integral part of a station truss segment when it is mated with the Integrated Equipment Assembly, which stores the electrical power generated by the solar arrays for use by the station modules. The Long Spacer is being processed in preparation for STS-97, currently planned for launch aboard Discovery in April 1999

KSC-98pc459

NASA Image and Video Library

1998-04-06

KENNEDY SPACE CENTER, FLA. -- The Long Spacer, a component of the International Space Station, arrives and is moved to its test stand in the northeast corner of the high bay in KSC's Space Station Processing Facility. The Long Spacer provides structural support for the outboard Photovoltaic Modules that supply power to the station. Now just a structure, the Long Spacer will have attached to it as part of processing a heat dissipation radiator and two Pump and Flow Control subassemblies that circulate ammonia to cool the solar array electronics. Also to be mounted are ammonia fluid lines as part of the cooling system and the cabling necessary for power and control of the station. The Long Spacer becomes an integral part of a station truss segment when it is mated with the Integrated Equipment Assembly, which stores the electrical power generated by the solar arrays for use by the station modules. The Long Spacer is being processed in preparation for STS-97, currently planned for launch aboard Discovery in April 1999

KSC-98pc457

NASA Image and Video Library

1998-04-06

KENNEDY SPACE CENTER, FLA. -- The Long Spacer, a component of the International Space Station, arrives and is moved to its test stand in the northeast corner of the high bay in KSC's Space Station Processing Facility. The Long Spacer provides structural support for the outboard Photovoltaic Modules that supply power to the station. Now just a structure, the Long Spacer will have attached to it as part of processing a heat dissipation radiator and two Pump and Flow Control subassemblies that circulate ammonia to cool the solar array electronics. Also to be mounted are ammonia fluid lines as part of the cooling system and the cabling necessary for power and control of the station. The Long Spacer becomes an integral part of a station truss segment when it is mated with the Integrated Equipment Assembly, which stores the electrical power generated by the solar arrays for use by the station modules. The Long Spacer is being processed in preparation for STS-97, currently planned for launch aboard Discovery in April 1999

Critiquing ';pore connectivity' as basis for in situ flow in geothermal systems

NASA Astrophysics Data System (ADS)

Kenedi, C. L.; Leary, P.; Malin, P.

2013-12-01

Geothermal system in situ flow systematics derived from detailed examination of grain-scale structures, fabrics, mineral alteration, and pore connectivity may be extremely misleading if/when extrapolated to reservoir-scale flow structure. In oil/gas field clastic reservoir operations, it is standard to assume that small scale studies of flow fabric - notably the Kozeny-Carman and Archie's Law treatments at the grain-scale and well-log/well-bore sampling of formations/reservoirs at the cm-m scale - are adequate to define the reservoir-scale flow properties. In the case of clastic reservoirs, however, a wide range of reservoir-scale data wholly discredits this extrapolation: Well-log data show that grain-scale fracture density fluctuation power scales inversely with spatial frequency k, S(k) ~ 1/k^β, 1.0 < β < 1.2, 1cycle/km < k < 1cycle/cm; the scaling is a ';universal' feature of well-logs (neutron porosity, sonic velocity, chemical abundance, mass density, resistivity, in many forms of clastic rock and instances of shale bodies, for both horizontal and vertical wells). Grain-scale fracture density correlates with in situ porosity; spatial fluctuations of porosity φ in well-core correlate with spatial fluctuations in the logarithm of well-core permeability, δφ ~ δlog(κ) with typical correlation coefficient ~ 85%; a similar relation is observed in consolidating sediments/clays, indicating a generic coupling between fluid pressure and solid deformation at pore sites. In situ macroscopic flow systems are lognormally distributed according to κ ~ κ0 exp(α(φ-φ0)), α >>1 an empirical parameter for degree of in situ fracture connectivity; the lognormal distribution applies to well-productivities in US oil fields and NZ geothermal fields, ';frack productivity' in oil/gas shale body reservoirs, ore grade distributions, and trace element abundances. Although presently available evidence for these properties in geothermal reservoirs is limited, there are indications that geothermal system flow essentially obeys the same ';universal' in situ flow rules as does clastic rock: Well-log data from Los Azufres, MX, show power-law scaling S(k) ~ 1/k^β, 1.2 < β < 1.4, for spatial frequency range 2cycles/km to 0.5cycle/m; higher β-values are likely due to the relatively fresh nature of geothermal systems; Well-core at Bulalo (PH) and Ohaaki (NZ) show statistically significant spatial correlation, δφ ~ δlog(κ) Well productivity at Ohaaki/Ngawha (NZ) and in geothermal systems elsewhere are lognormally distributed; K/Th/U abundances lognormally distributed in Los Azufres well-logs We therefore caution that small-scale evidence for in situ flow fabric in geothermal systems that is interpreted in terms of ';pore connectivity' may in fact not reflect how small-scale chemical processes are integrated into a large-scale geothermal flow structure. Rather such small scale studies should (perhaps) be considered in term of the above flow rules. These flow rules are easily incorporated into standard flow simulation codes, in particular the OPM = Open Porous Media open-source industry-standard flow code. Geochemical transport data relevant to geothermal systems can thus be expected to be well modeled by OPM or equivalent (e.g., INL/LANL) codes.

Statistical features of rapidly rotating decaying turbulence: Enstrophy and energy spectra and coherent structures

NASA Astrophysics Data System (ADS)

Sharma, Manohar K.; Kumar, Abhishek; Verma, Mahendra K.; Chakraborty, Sagar

2018-04-01

In this paper, we investigate the properties of rapidly rotating decaying turbulence using numerical simulations and phenomenological modeling. We find that as the turbulent flow evolves in time, the Rossby number decreases to ˜10-3, and the flow becomes quasi-two-dimensional with strong coherent columnar structures arising due to the inverse cascade of energy. We establish that a major fraction of energy is confined in Fourier modes (±1, 0, 0) and (0, ±1, 0) that correspond to the largest columnar structure in the flow. For wavenumbers (k) greater than the enstrophy dissipation wavenumber (kd), our phenomenological arguments and numerical study show that the enstrophy flux and spectrum of a horizontal cross section perpendicular to the axis of rotation are given by ɛω⁡exp (-C (k/kd ) 2 ) and C ɛω2 /3k-1⁡exp (-C (k/kd ) 2 ) , respectively; for this 2D flow, ɛω is the enstrophy dissipation rate, and C is a constant. Using these results, we propose a new form for the energy spectrum of rapidly rotating decaying turbulence: E (k ) =C ɛω2 /3k-3⁡exp (-C (k/kd ) 2 ) . This model of the energy spectrum is based on wavenumber-dependent enstrophy flux, and it deviates significantly from power law energy spectrum reported earlier.

ACCELEROMETERS IN FLOW FIELDS: A STRUCTURAL ANALYSIS OF THE CHOPPED DUMMY INPILE TUBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, T. K.; Marcum, W. R.; Latimer, G. D.

2016-06-01

Four tests characterizing the structural response of the Chopped-Dummy In-Pile tube (CDIPT) experiment design were measured in the Hydro-Mechanical Fuel Test Facility (HMFTF). Four different test configurations were tried. These configurations tested the pressure drop and flow impact of various plate configurations and flow control orifices to be used later at different reactor power levels. Accelerometers were placed on the test vehicle and flow simulation housing. A total of five accelerometers were used with one on the top and bottom of the flow simulator and vehicle, and one on the outside of the flow simulator. Data were collected at amore » series of flow rates for 5 seconds each at an acquisition rate of 2 kHz for a Nyquist frequency of 1 kHz. The data were then analyzed using a Fast Fourier Transform (FFT) algorithm. The results show very coherent vibrations of the CDIPT experiment on the order of 50 Hz in frequency and 0.01 m/s2 in magnitude. The coherent vibrations, although small in magnitude pose a potential design problem if the frequencies coincide with the natural frequency of the fueled plates or test vehicle. The accelerometer data was integrated and combined to create a 3D trace of the experiment during the test. The merits of this data as well as further anomalies and artifacts are also discussed as well as their relation to the instrumentation and experiment design.« less

Three-phase Power Flow Calculation of Low Voltage Distribution Network Considering Characteristics of Residents Load

NASA Astrophysics Data System (ADS)

Wang, Yaping; Lin, Shunjiang; Yang, Zhibin

2017-05-01

In the traditional three-phase power flow calculation of the low voltage distribution network, the load model is described as constant power. Since this model cannot reflect the characteristics of actual loads, the result of the traditional calculation is always different from the actual situation. In this paper, the load model in which dynamic load represented by air conditioners parallel with static load represented by lighting loads is used to describe characteristics of residents load, and the three-phase power flow calculation model is proposed. The power flow calculation model includes the power balance equations of three-phase (A,B,C), the current balance equations of phase 0, and the torque balancing equations of induction motors in air conditioners. And then an alternating iterative algorithm of induction motor torque balance equations with each node balance equations is proposed to solve the three-phase power flow model. This method is applied to an actual low voltage distribution network of residents load, and by the calculation of three different operating states of air conditioners, the result demonstrates the effectiveness of the proposed model and the algorithm.

Macro- and micro- geodynamic of Terebliya-Riksk geodetic man-caused polygon of Ukrainian Carpathians influenced by specificities of structure-geological and hydro-geological conditions

NASA Astrophysics Data System (ADS)

Kulchyzkyy, A.; Serebryannyy, Y.; Tretyak, K.; Trevogo, I.; Zadoroznnyy, V.

2009-04-01

Terebliya-Riksk diversion power station is located on two levels ( with difference of 180m ) of south mountainside of Ukrainian Carpathians and separate parts of this power station lie inside rock. Therefore influential parameters of it's stability are geological, tectonic and hydrogeological conditions in complex. Monitoring of intensity and nature of displacements of flow ( pressure) pipe and other objects of power station with geoditic methods indicates that fluctuations of water-level in reservoir caused bouth by natural and artificial efects are of great influence on objects mentioned. Based on geodetical high-precision observations made by LeicaTPS 1201 robotic total station short-periodic components of fundamental vibrations which result in their destructive deformation were determined. Mathematical apparatus ( which uses function of Fourie series and theory of cinematic coefficients ) for displacements determinations of pressure pipe was disigned. Complex of engineering-geological surveys gave an opportunity to define the origin of macro- and micro- geodynamics movements of Terebliya-Riksk diversion power station region. Engineering-geological conditions which influence on power station structure most of all were determined as following : small foldings and cleavage areas appearances, also fluctuations of level of underground water (refered to hydrogeological conditions). Periodic micro-displacemets appearances ( which operate on reducing-stretching scheme) fixed on power station structure are turned to be in direct relation on to what exend reservoir is filled up. Permanent macro- displacements appearances ( which operates in north-west direction ) fixed on pressure pipe are the result sum of residual micro-displacements caused by return periodic movements and are determined by structure-geological, engineering-geological and tectonic conditions.

Research on a new wave energy absorption device

NASA Astrophysics Data System (ADS)

Lu, Zhongyue; Shang, Jianzhong; Luo, Zirong; Sun, Chongfei; Zhu, Yiming

2018-01-01

To reduce impact of global warming and the energy crisis problems caused by pollution of energy combustion, the research on renewable and clean energies becomes more and more important. This paper designed a new wave absorption device, and also gave an introduction on its mechanical structure. The flow tube model is analyzed, and presented the formulation of the proposed method. To verify the principle of wave absorbing device, an experiment was carried out in a laboratory environment, and the results of the experiment can be applied for optimizing the structure design of output power.

Aircraft interior noise models - Sidewall trim, stiffened structures, and cabin acoustics with floor partition

NASA Technical Reports Server (NTRS)

Pope, L. D.; Wilby, E. G.; Willis, C. M.; Mayes, W. H.

1983-01-01

As part of the continuing development of an aircraft interior noise prediction model, in which a discrete modal representation and power flow analysis are used, theoretical results are considered for inclusion of sidewall trim, stiffened structures, and cabin acoustics with floor partition. For validation purposes, predictions of the noise reductions for three test articles (a bare ring-stringer stiffened cylinder, an unstiffened cylinder with floor and insulation, and a ring-stringer stiffened cylinder with floor and sidewall trim) are compared with measurements.

Numerical Simulation of Tethered Underwater Kites for Power Generation

NASA Astrophysics Data System (ADS)

Ghasemi, Amirmahdi; Olinger, David; Tryggvason, Gretar

2015-11-01

An emerging renewable energy technology, tethered undersea kites (TUSK), which is used to extract hydrokinetic energy from ocean and tidal currents, is studied. TUSK systems consist of a rigid-winged ``kite,'' or glider, moving in an ocean current which is connected by tethers to a floating buoy on the ocean surface. The TUSK kite is a current speed enhancement device since the kite can move in high-speed, cross-current motion at 4-6 times the current velocity, thus producing more power than conventional marine turbines. A computational simulation is developed to simulate the dynamic motion of an underwater kite and extendable tether. A two-step projection method within a finite volume formulation, along with an Open MP acceleration method, is employed to solve the Navier-Stokes equations. An immersed boundary method is incorporated to model the fluid-structure interaction of the rigid kite (with NACA 0012 airfoil shape in 2D and NACA 0021 airfoil shape in 3D simulations) and the fluid flow. PID control methods are used to adjust the kite angle of attack during power (tether reel-out) and retraction (reel-in) phases. Two baseline simulations (for kite motions in two and three dimensions) are studied, and system power output, flow field vorticity, tether tension, and hydrodynamic coefficients (lift and drag) for the kite are determined. The simulated power output shows good agreement with established theoretical results for a kite moving in two-dimensions.

Forum on unsteady flow - 1985; Proceedings of the Winter Annual Meeting, Miami Beach, FL, November 17-22, 1985

NASA Astrophysics Data System (ADS)

Rothe, P. H.

The conference includes such topics as the reduction of fluid transient pressures by minimax optimization, modeling blockage in unsteady slurry flow in conduits, roles of vacuum breaker and air release devices in reducing waterhammer forces, and an analysis of laminar fluid transients in conduits of unconventional shape. Papers are presented on modulation systems for high speed water jets, water hammer analysis needs in nuclear power plant design, tail profile effects on unsteady large scale flow structure in the wing and plate junction, and a numerical study of pressure transients in a borehole due to pipe movement. Consideration is also given to boundary layer growth near a stagnation point, calculation of unsteady mixing in two-dimensional flows, the trailing edge of a pitching airfoil at high reduced frequencies, and a numerical study of instability-wave control through periodic wall suction/blowing.

Forced underwater laminar flows with active magnetohydrodynamic metamaterials

NASA Astrophysics Data System (ADS)

Culver, Dean; Urzhumov, Yaroslav

2017-12-01

Theory and practical implementations for wake-free propulsion systems are proposed and proven with computational fluid dynamic modeling. Introduced earlier, the concept of active hydrodynamic metamaterials is advanced by introducing magnetohydrodynamic metamaterials, structures with custom-designed volumetric distribution of Lorentz forces acting on a conducting fluid. Distributions of volume forces leading to wake-free, laminar flows are designed using multivariate optimization. Theoretical indications are presented that such flows can be sustained at arbitrarily high Reynolds numbers. Moreover, it is shown that in the limit Re ≫102 , a fixed volume force distribution may lead to a forced laminar flow across a wide range of Re numbers, without the need to reconfigure the force-generating metamaterial. Power requirements for such a device are studied as a function of the fluid conductivity. Implications to the design of distributed propulsion systems underwater and in space are discussed.

Detecting seasonal and cyclical trends in agricultural runoff water quality-hypothesis tests and block bootstrap power analysis.

PubMed

Uddameri, Venkatesh; Singaraju, Sreeram; Hernandez, E Annette

2018-02-21

Seasonal and cyclic trends in nutrient concentrations at four agricultural drainage ditches were assessed using a dataset generated from a multivariate, multiscale, multiyear water quality monitoring effort in the agriculturally dominant Lower Rio Grande Valley (LRGV) River Watershed in South Texas. An innovative bootstrap sampling-based power analysis procedure was developed to evaluate the ability of Mann-Whitney and Noether tests to discern trends and to guide future monitoring efforts. The Mann-Whitney U test was able to detect significant changes between summer and winter nutrient concentrations at sites with lower depths and unimpeded flows. Pollutant dilution, non-agricultural loadings, and in-channel flow structures (weirs) masked the effects of seasonality. The detection of cyclical trends using the Noether test was highest in the presence of vegetation mainly for total phosphorus and oxidized nitrogen (nitrite + nitrate) compared to dissolved phosphorus and reduced nitrogen (total Kjeldahl nitrogen-TKN). Prospective power analysis indicated that while increased monitoring can lead to higher statistical power, the effect size (i.e., the total number of trend sequences within a time-series) had a greater influence on the Noether test. Both Mann-Whitney and Noether tests provide complementary information on seasonal and cyclic behavior of pollutant concentrations and are affected by different processes. The results from these statistical tests when evaluated in the context of flow, vegetation, and in-channel hydraulic alterations can help guide future data collection and monitoring efforts. The study highlights the need for long-term monitoring of agricultural drainage ditches to properly discern seasonal and cyclical trends.

Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

NASA Astrophysics Data System (ADS)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2011-12-01

During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a transient evolution of the radiated heat flux closely related to the variations of the flow area. The study of experiments with time-variable effusion rates finally gives first leads on the inertia of the thermal surface structure. This is to be related to the time-period over which the thermal proxy averages the actual effusion rate, hence to the acquisition frequency appropriate for a thermal monitoring of effusive volcanic eruptions.

Habit, custom, and power: a multi-level theory of population health.

PubMed

Zimmerman, Frederick J

2013-03-01

In multi-level theory, individual behavior flows from cognitive habits, either directly through social referencing, rules of thumb, or automatic behaviors; or indirectly through the shaping of rationality itself by framing or heuristics. Although behavior does not arise from individually rational optimization, it generally appears to be rational, because the cognitive habits that guide behavior evolve toward optimality. However, power imbalances shaped by particular social, political, and economic structures can distort this evolution, leading to individual behavior that fails to maximize individual or social well-being. Replacing the dominant rational-choice paradigm with a multi-level theoretical paradigm involving habit, custom, and power will enable public health to engage in rigorous new areas of research. Copyright © 2013 Elsevier Ltd. All rights reserved.

Integrated control system and method

DOEpatents

Wang, Paul Sai Keat; Baldwin, Darryl; Kim, Myoungjin

2013-10-29

An integrated control system for use with an engine connected to a generator providing electrical power to a switchgear is disclosed. The engine receives gas produced by a gasifier. The control system includes an electronic controller associated with the gasifier, engine, generator, and switchgear. A gas flow sensor monitors a gas flow from the gasifier to the engine through an engine gas control valve and provides a gas flow signal to the electronic controller. A gas oversupply sensor monitors a gas oversupply from the gasifier and provides an oversupply signal indicative of gas not provided to the engine. A power output sensor monitors a power output of the switchgear and provide a power output signal. The electronic controller changes gas production of the gasifier and the power output rating of the switchgear based on the gas flow signal, the oversupply signal, and the power output signal.

Reactive Power Pricing Model Considering the Randomness of Wind Power Output

NASA Astrophysics Data System (ADS)

Dai, Zhong; Wu, Zhou

2018-01-01

With the increase of wind power capacity integrated into grid, the influence of the randomness of wind power output on the reactive power distribution of grid is gradually highlighted. Meanwhile, the power market reform puts forward higher requirements for reasonable pricing of reactive power service. Based on it, the article combined the optimal power flow model considering wind power randomness with integrated cost allocation method to price reactive power. Meanwhile, considering the advantages and disadvantages of the present cost allocation method and marginal cost pricing, an integrated cost allocation method based on optimal power flow tracing is proposed. The model realized the optimal power flow distribution of reactive power with the minimal integrated cost and wind power integration, under the premise of guaranteeing the balance of reactive power pricing. Finally, through the analysis of multi-scenario calculation examples and the stochastic simulation of wind power outputs, the article compared the results of the model pricing and the marginal cost pricing, which proved that the model is accurate and effective.

Wirelessly powered micro-tracer enabled by miniaturized antenna and microfluidic channel

NASA Astrophysics Data System (ADS)

Duan, G.; Zhao, X.; Seren, H. R.; Chen, C.; Zhang, X.

2015-12-01

A miniaturized antenna, 380μm by 380μm in size, was fabricated and integrated with a commercialized passive RFID chip to form a micro-tracer, whose size was 2mm by 1mm in total. The micro-tracer was wirelessly powered and interrogated by a single layer spiral reader antenna through near field coupling. To maximize the working distance, the resonant frequency of micro-tracer and reader antenna were matched at 840MHz. Due to the ultra small size of the tracer antenna, power transfer efficiency decreased dramatically as the distance between tracer antenna and reader antenna increased, thus the working distance of the microtracer was limited within 1mm. To achieve massive operation of the micro-tracer, a microfluidic platform was fabricated with in channel focusing and separation. Acrylic sheets were laser cut to define the channel and cover structure, then bonded together layer by layer with a glass substrate, on which reader antenna was integrated. Pump oil was used as the fluidic media carrying the micro-tracer flowing inside the microfluidic channel. The wireless power transfer and real-time communication was demonstrated with the micro-tracer flowing above the reader antenna, as the ID of the micro-tracer was retrieved and displayed on a computer screen.

A Compendium of Brazed Microstructures For Fission Power Systems Applications

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Bowman, Cheryl L.

2012-01-01

NASA has been supporting design studies and technology development for fission-based power systems that could provide power to an outpost on the Moon, Mars, or an asteroid. Technology development efforts have included fabrication and evaluation of components used in a Stirling engine power conversion system. This investigation is part of the development of several braze joints crucial for the heat exchanger transfer path from a hot-side heat exchanger to a Stirling engine heat acceptor. Dissimilar metal joints are required to impart both mechanical strength and thermal path integrity for a heater head of interest. Preliminary design work for the heat exchanger involved joints between low carbon stainless steel to Inconel 718, where the 316L stainless steel would contain flowing liquid metal NaK while Inconel 718, a stronger alloy, would be used as structural reinforcement. This paper addressed the long-term microstructural stability of various braze alloys used to join 316L stainless steel heater head to the high conductivity oxygen-free copper acceptor to ensure the endurance of the critical metallic components of this sophisticated heat exchanger. The bonding of the 316L stainless steel heater head material to a copper heat acceptor is required to increase the heat-transfer surface area in contact with flowing He, which is the Stirling engine working fluid.

Mechanical energy and power flow analysis of wheelchair use with different camber settings.

PubMed

Huang, Yueh-Chu; Guo, Lan-Yuen; Tsai, Chung-Ying; Su, Fong-Chin

2013-04-01

It has been suggested that minimisation of energy cost is one of the primary determinants of wheelchair designs. Wheel camber is one important parameter related to wheelchair design and its angle may affect usability during manual propulsion. However, there is little available literature addressing the effect of wheel camber on the mechanical energy or power flow involved in manual wheelchair propulsion. Twelve normal subjects (mean age, 22.3 years; SD, 1.6 years) participated in this study. A video-tracking system and an instrumented wheel were used to collect 3D kinematic and kinetic data. Wheel camber of 0° and 15° was chosen to examine the difference between mechanical power and power flow of the upper extremity during manual wheelchair propulsion. The work calculated from power flow and the discrepancy between the mechanical work and power flow work of upper extremity had significantly greater values with increased camber. The upper arm had a larger active muscle power compared with that in the forearm and hand segments. While propelling the increased camber, the magnitude of both the proximal and distal joint power and proximal muscle power was increased in all three segments. While the propelling wheel with camber not only needs a greater energy cost but also there is greater energy loss.

Coordinated Control of Cross-Flow Turbines

NASA Astrophysics Data System (ADS)

Strom, Benjamin; Brunton, Steven; Polagye, Brian

2016-11-01

Cross-flow turbines, also known as vertical-axis turbines, have several advantages over axial-flow turbines for a number of applications including urban wind power, high-density arrays, and marine or fluvial currents. By controlling the angular velocity applied to the turbine as a function of angular blade position, we have demonstrated a 79 percent increase in cross-flow turbine efficiency over constant-velocity control. This strategy uses the downhill simplex method to optimize control parameter profiles during operation of a model turbine in a recirculating water flume. This optimization method is extended to a set of two turbines, where the blade motions and position of the downstream turbine are optimized to beneficially interact with the coherent structures in the wake of the upstream turbine. This control scheme has the potential to enable high-density arrays of cross-flow turbines to operate at cost-effective efficiency. Turbine wake and force measurements are analyzed for insight into the effect of a coordinated control strategy.

The relationship between dynamic and average flow rates of the coolant in the channels of complex shape

NASA Astrophysics Data System (ADS)

Fedoseev, V. N.; Pisarevsky, M. I.; Balberkina, Y. N.

2018-01-01

This paper presents interconnection of dynamic and average flow rates of the coolant in a channel of complex geometry that is a basis for a generalization model of experimental data on heat transfer in various porous structures. Formulas for calculation of heat transfer of fuel rods in transversal fluid flow are acquired with the use of the abovementioned model. It is shown that the model describes a marginal case of separated flows in twisting channels where coolant constantly changes its flow direction and mixes in the communicating channels with large intensity. Dynamic speed is suggested to be identified by power for pumping. The coefficient of proportionality in general case depends on the geometry of the channel and the Reynolds number (Re). A calculation formula of the coefficient of proportionality for the narrow line rod packages is provided. The paper presents a comparison of experimental data and calculated values, which shows usability of the suggested models and calculation formulas.

Diaphragm Pump With Resonant Piezoelectric Drive

NASA Technical Reports Server (NTRS)

Izenson, Michael G.; Kline-Schoder, Robert J.; Shimko, Martin A.

2007-01-01

A diaphragm pump driven by a piezoelectric actuator is undergoing development. This pump is intended to be a prototype of lightweight, highly reliable pumps for circulating cooling liquids in protective garments and high-power electronic circuits, and perhaps for some medical applications. The pump would be highly reliable because it would contain no sliding seals or bearings that could wear, the only parts subject to wear would be two check valves, and the diaphragm and other flexing parts could be designed, by use of proven methods, for extremely long life. Because the pump would be capable of a large volumetric flow rate and would have only a small dead volume, its operation would not be disrupted by ingestion of gas, and it could be started reliably under all conditions. The prior art includes a number piezoelectrically actuated diaphragm pumps. Because of the smallness of the motions of piezoelectric actuators (typical maximum strains only about 0.001), the volumetric flow rates of those pumps are much too small for typical cooling applications. In the pump now undergoing development, mechanical resonance would be utilized to amplify the motion generated by the piezoelectric actuator and thereby multiply the volumetric flow rate. The prime mover in this pump would be a stack of piezoelectric ceramic actuators, one end of which would be connected to a spring that would be part of a spring-and-mass resonator structure. The mass part of the resonator structure would include the pump diaphragm (see Figure 1). Contraction of the spring would draw the diaphragm to the left, causing the volume of the fluid chamber to increase and thereby causing fluid to flow into the chamber. Subsequent expansion of the spring would push the diaphragm to the right, causing the volume of the fluid chamber to decrease, and thereby expelling fluid from the chamber. The fluid would enter and leave the chamber through check valves. The piezoelectric stack would be driven electrically to make it oscillate at the resonance frequency of the spring and- mass structure. This frequency could be made high enough (of the order of 400 Hz) that the masses of all components could be made conveniently small. The resonance would amplify the relatively small motion of the piezoelectric stack (a stroke of the order of 10 m) to a diaphragm stroke of the order of 0.5 mm. The exact amplification factor would depend on the rate of damping of oscillations; this, in turn, would depend on details of design and operation, including (but not limited to) the desired pressure rise and volumetric flow rate. In order to obtain resonance with large displacement, the damping rate must be low enough that the energy imparted to the pumped fluid on each stroke is much less than the kinetic and potential energy exchanged between the mass and spring during each cycle of oscillation. To minimize the power demand of the pump, a highly efficient drive circuit would be used to excite the piezoelectric stack. This circuit (see Figure 2) would amount to a special-purpose regenerative, switching power supply that would operate in a power-source mode during the part of an oscillation cycle when the excitation waveform was positive and in a power-recovery mode during the part of the cycle when the excitation waveform was negative. The circuit would include a voltage-boosting dc-to-dc converter that would convert between a supply potential of 24 Vdc and the high voltage needed to drive the piezoelectric stack. Because of the power-recovery feature, the circuit would consume little power. It should be possible to build the circuit as a compact unit, using readily available components.

77 FR 63811 - FFP Solia 6 Hydroelectric, LLC; Notice of Intent To File License Application, Filing of Pre...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-17

...: August 17, 2012. d. Submitted By: Free Flow Power Corporation on behalf of its subsidiary limited... River in Beaver County, Pennsylvania. The project would occupy United States lands administered by the U..., Boston, MA 02114-2130; (978) 283-2822; or email at flow-power.com ">[email protected] flow-power.com . i...

Research on energy conversion mechanism of rotodynamic pump and design of non-overload centrifugal pump

NASA Astrophysics Data System (ADS)

Zhang, X. L.; Hu, S. B.; Shen, Z. Z.; Wu, S. P.; Li, K.

2016-05-01

In this paper, an attempt has been made for the calculation of an expression for the intrinsic law of input power which has not yet been given by current theory of Rotodynamic pump. By adequate recognition of the characteristics of non-inertial system within the rotating impeller, it is concluded that the input power consists of two power components, the first power component, whose magnitude increases with the increase of the flow rate, corresponds to radial velocity component, and the second power component, whose magnitude decreases with the increase of the flow rate, corresponds to tangential velocity component, therefore, the law of rise, basic levelness and drop of input power curves of centrifugal pump, mixed-flow pump and axial-flow pump can be explained reasonably. Through further analysis, the main ways for realizing non-overload of centrifugal pump are obtained, and its equivalent design factor is found out, the factor correlates with the outlet angle of leading face and back face of the blade, wrap angle, number of blades, outlet width, area ratio, and the ratio of operating flow rate to specified flow rate and so on. These are verified with actual example.

Experimental chaotic quantification in bistable vortex induced vibration systems

NASA Astrophysics Data System (ADS)

Huynh, B. H.; Tjahjowidodo, T.

2017-02-01

The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand. In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear out the regularity of periodic responses. For this purpose, a surrogate data test is used in order to check the hypotheses for the presence of chaotic behavior. The analyses from the experimental results support the hypothesis from simulation that chaotic response is likely occur on the real system.

Optimal structural design of a 5-kW CPV tracking system by considering the ISO 4017/4762 standard through structure and flow simulations

NASA Astrophysics Data System (ADS)

Lee, Hyo Geun; Kim, Sang Suk; Kim, Sung Jo; Park, Su-Jin; Yun, Chang-wuk; Im, Gil-pyeong

2015-09-01

Photovoltaic generation systems have disadvantage in that they are usually installed outdoors and are exposed to extreme environments such as wind, snow and rain loadings. The structure of a photovoltaic generation system should be designed to have sufficient stiffness and strength against such loads. Especially, electric power generation by a concentrator photovoltaic(CPV) system can produce enough power if a right angle is main fained between the solar and the CPV panel within 90° ± 1°. To make the CPV tracking system in this study, we designed the structure by calculating the variations in and the strees applied to the structure by the wind load when the CPV tracking was influenced by the wind load. In this study, a 5-kW CPV tracking structure was designed through a structural analysis and a finiteelement analysis for a wind speed of 65 m/s by using ANSYS. The simulation of the structural design showed that the, structure of the 5-kW CPV tracking system corresponded with the ISO4017/ISO4762 standard. Based on this research, we will produce a 5-kW CPV tracking system and proceed to field test.

A Minicomputer Based Scheme for Turbulence Measurements with Pulsed Doppler Ultrasound

PubMed Central

Craig, J. I.; Saxena, Vijay; Giddens, D. P.

1979-01-01

The present paper describes the design and performance of a digital-based Doppler signal processing system that is currently being used in hemodynamics research on arteriosclerosis. The major emphasis is on the development of the digital signal processing technique and its implementation in a small but powerful minicomputer. The work reported on here is part of a larger ongoing effort that the authors are undertaking to study the structure of turbulence in blood flow and its relation to arteriosclerosis. Some of the techniques and instruments developed are felt to have a broad applicability to fluid mechanics and especially to pipe flow fluid mechanics.

Analysis on Voltage Profile of Distribution Network with Distributed Generation

NASA Astrophysics Data System (ADS)

Shao, Hua; Shi, Yujie; Yuan, Jianpu; An, Jiakun; Yang, Jianhua

2018-02-01

Penetration of distributed generation has some impacts on a distribution network in load flow, voltage profile, reliability, power loss and so on. After the impacts and the typical structures of the grid-connected distributed generation are analyzed, the back/forward sweep method of the load flow calculation of the distribution network is modelled including distributed generation. The voltage profiles of the distribution network affected by the installation location and the capacity of distributed generation are thoroughly investigated and simulated. The impacts on the voltage profiles are summarized and some suggestions to the installation location and the capacity of distributed generation are given correspondingly.

Power of Your Pancreas: Keep Your Digestive Juices Flowing

MedlinePlus

... Issues Subscribe February 2017 Print this issue The Power of Your Pancreas Keep Your Digestive Juices Flowing ... your entire digestive system working properly. Related Stories Power to the Pelvis Battling a Bulging Hernia Keeping ...

A numerical investigation of flow around octopus-like arms: near-wake vortex patterns and force development.

PubMed

Kazakidi, A; Vavourakis, V; Tsakiris, D P; Ekaterinaris, J A

2015-01-01

The fluid dynamics of cephalopods has so far received little attention in the literature, due to their complexity in structure and locomotion. The flow around octopuses, in particular, can be complicated due to their agile and dexterous arms, which frequently display some of the most diverse mechanisms of motion. The study of this flow amounts to a specific instance of the hydrodynamics problem for rough tapered cylinder geometries. The outstanding manipulative and locomotor skills of octopuses could inspire the development of advanced robotic arms, able to operate in fluid environments. Our primary aim was to study the hydrodynamic characteristics of such bio-inspired robotic models and to derive the hydrodynamic force coefficients as a concise description of the vortical flow effects. Utilizing computational fluid dynamic methods, the coefficients were computed on realistic morphologies of octopus-like arm models undergoing prescribed solid-body movements; such motions occur in nature for short durations in time, e.g. during reaching movements and exploratory behaviors. Numerical simulations were performed on translating, impulsively rotating, and maneuvering arms, around which the flow field structures were investigated. The results reveal in detail the generation of complex vortical flow structures around the moving arms. Hydrodynamic forces acting on a translating arm depend on the angle of incidence; forces generated during impulsive rotations of the arms are independent of their exact morphology and the angle of rotation; periodic motions based on a slow recovery and a fast power stroke are able to produce considerable propulsive thrust while harmonic motions are not. Parts of these results have been employed in bio-inspired models of underwater robotic mechanisms. This investigation may further assist elucidating the hydrodynamics underlying aspects of octopus locomotion and exploratory behaviors.

Electricity market pricing, risk hedging and modeling

NASA Astrophysics Data System (ADS)

Cheng, Xu

In this dissertation, we investigate the pricing, price risk hedging/arbitrage, and simplified system modeling for a centralized LMP-based electricity market. In an LMP-based market model, the full AC power flow model and the DC power flow model are most widely used to represent the transmission system. We investigate the differences of dispatching results, congestion pattern, and LMPs for the two power flow models. An appropriate LMP decomposition scheme to quantify the marginal costs of the congestion and real power losses is critical for the implementation of financial risk hedging markets. However, the traditional LMP decomposition heavily depends on the slack bus selection. In this dissertation we propose a slack-independent scheme to break LMP down into energy, congestion, and marginal loss components by analyzing the actual marginal cost of each bus at the optimal solution point. The physical and economic meanings of the marginal effect at each bus provide accurate price information for both congestion and losses, and thus the slack-dependency of the traditional scheme is eliminated. With electricity priced at the margin instead of the average value, the market operator typically collects more revenue from power sellers than that paid to power buyers. According to the LMP decomposition results, the revenue surplus is then divided into two parts: congestion charge surplus and marginal loss revenue surplus. We apply the LMP decomposition results to the financial tools, such as financial transmission right (FTR) and loss hedging right (LHR), which have been introduced to hedge against price risks associated to congestion and losses, to construct a full price risk hedging portfolio. The two-settlement market structure and the introduction of financial tools inevitably create market manipulation opportunities. We investigate several possible market manipulation behaviors by virtual bidding and propose a market monitor approach to identify and quantify such behavior. Finally, the complexity of the power market and size of the transmission grid make it difficult for market participants to efficiently analyze the long-term market behavior. We propose a simplified power system commercial model by simulating the PTDFs of critical transmission bottlenecks of the original system.

A liquid metal-based structurally embedded vascular antenna: I. Concept and multiphysical modeling

NASA Astrophysics Data System (ADS)

Hartl, D. J.; Frank, G. J.; Huff, G. H.; Baur, J. W.

2017-02-01

This work proposes a new concept for a reconfigurable structurally embedded vascular antenna (SEVA). The work builds on ongoing research of structurally embedded microvascular systems in laminated structures for thermal transport and self-healing and on studies of non-toxic liquid metals for reconfigurable electronics. In the example design, liquid metal-filled channels in a laminated composite act as radiating elements for a high-power planar zig-zag wire log periodic dipole antenna. Flow of liquid metal through the channels is used to limit the temperature of the composite in which the antenna is embedded. A multiphysics engineering model of the transmitting antenna is formulated that couples the electromagnetic, fluid, thermal, and mechanical responses. In part 1 of this two-part work, it is shown that the liquid metal antenna is highly reconfigurable in terms of its electromagnetic response and that dissipated thermal energy generated during high power operation can be offset by the action of circulating or cyclically replacing the liquid metal such that heat is continuously removed from the system. In fact, the SEVA can potentially outperform traditional copper-based antennas in high-power operational configurations. The coupled engineering model is implemented in an automated framework and a design of experiment study is performed to quantify first-order design trade-offs in this multifunctional structure. More rigorous design optimization is addressed in part 2.

A novel HTS SMES application in combination with a permanent magnet synchronous generator type wind power generation system

NASA Astrophysics Data System (ADS)

Kim, G. H.; Kim, A. R.; Kim, S.; Park, M.; Yu, I. K.; Seong, K. C.; Won, Y. J.

2011-11-01

Superconducting magnetic energy storage (SMES) system is a DC current driven device and can be utilized to improve power quality particularly in connection with renewable energy sources due to higher efficiency and faster response than other devices. This paper suggests a novel connection topology of SMES which can smoothen the output power flow of the wind power generation system (WPGS). The structure of the proposed system is cost-effective because it reduces a power converter in comparison with a conventional application of SMES. One more advantage of SMES in the proposed system is to improve the capability of low voltage ride through (LVRT) for the permanent magnet synchronous generator (PMSG) type WPGS. The proposed system including a SMES has been modeled and analyzed by a PSCAD/EMTDC. The simulation results show the effectiveness of the novel SMES application strategy to not only mitigate the output power of the PMSG but also improve the capability of LVRT for PMSG type WPGS.

Modeling and simulation of large scale stirred tank

NASA Astrophysics Data System (ADS)

Neuville, John R.

The purpose of this dissertation is to provide a written record of the evaluation performed on the DWPF mixing process by the construction of numerical models that resemble the geometry of this process. There were seven numerical models constructed to evaluate the DWPF mixing process and four pilot plants. The models were developed with Fluent software and the results from these models were used to evaluate the structure of the flow field and the power demand of the agitator. The results from the numerical models were compared with empirical data collected from these pilot plants that had been operated at an earlier date. Mixing is commonly used in a variety ways throughout industry to blend miscible liquids, disperse gas through liquid, form emulsions, promote heat transfer and, suspend solid particles. The DOE Sites at Hanford in Richland Washington, West Valley in New York, and Savannah River Site in Aiken South Carolina have developed a process that immobilizes highly radioactive liquid waste. The radioactive liquid waste at DWPF is an opaque sludge that is mixed in a stirred tank with glass frit particles and water to form slurry of specified proportions. The DWPF mixing process is composed of a flat bottom cylindrical mixing vessel with a centrally located helical coil, and agitator. The helical coil is used to heat and cool the contents of the tank and can improve flow circulation. The agitator shaft has two impellers; a radial blade and a hydrofoil blade. The hydrofoil is used to circulate the mixture between the top region and bottom region of the tank. The radial blade sweeps the bottom of the tank and pushes the fluid in the outward radial direction. The full scale vessel contains about 9500 gallons of slurry with flow behavior characterized as a Bingham Plastic. Particles in the mixture have an abrasive characteristic that cause excessive erosion to internal vessel components at higher impeller speeds. The desire for this mixing process is to ensure the agitation of the vessel is adequate to produce a homogenous mixture but not so high that it produces excessive erosion to internal components. The main findings reported by this study were: (1) Careful consideration of the fluid yield stress characteristic is required to make predictions of fluid flow behavior. Laminar Models can predict flow patterns and stagnant regions in the tank until full movement of the flow field occurs. Power Curves and flow patterns were developed for the full scale mixing model to show the differences in expected performance of the mixing process for a broad range of fluids that exhibit Herschel--Bulkley and Bingham Plastic flow behavior. (2) The impeller power demand is independent of the flow model selection for turbulent flow fields in the region of the impeller. The laminar models slightly over predicted the agitator impeller power demand produced by turbulent models. (3) The CFD results show that the power number produced by the mixing system is independent of size. The 40 gallon model produced the same power number results as the 9300 gallon model for the same process conditions. (4) CFD Results show that the Scale-Up of fluid motion in a 40 gallon tank should compare with fluid motion at full scale, 9300 gallons by maintaining constant impeller Tip Speed.

X-RAY EMISSION LINE PROFILES FROM WIND CLUMP BOW SHOCKS IN MASSIVE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ignace, R.; Waldron, W. L.; Cassinelli, J. P.

2012-05-01

The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two-component flow structure of wind and clumps using two 'beta' velocity laws. While individual bow shocks tend to generate double-horned emission line profiles,more » a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution is broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted for in modeling X-ray line profile shapes for massive stars.« less

Computational and experimental aftbody flow fields for hypersonic, airbreathing configurations with scramjet exhaust flow simulation

NASA Technical Reports Server (NTRS)

Huebner, Lawrence D.; Tatum, Kenneth E.

1991-01-01

Computational results are presented for three issues pertinent to hypersonic, airbreathing vehicles employing scramjet exhaust flow simulation. The first issue consists of a comparison of schlieren photographs obtained on the aftbody of a cruise missile configuration under powered conditions with two-dimensional computational solutions. The second issue presents the powered aftbody effects of modeling the inlet with a fairing to divert the external flow as compared to an operating flow-through inlet on a generic hypersonic vehicle. Finally, a comparison of solutions examining the potential of testing powered configurations in a wind-off, instead of a wind-on, environment, indicate that, depending on the extent of the three-dimensional plume, it may be possible to test aftbody powered hypersonic, airbreathing configurations in a wind-off environment.

Flow reversal power limit for the HFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Lap Y.; Tichler, P.R.

The High Flux Beam Reactor (HFBR) undergoes a buoyancy-driven reversal of flow in the reactor core following certain postulated accidents. Uncertainties about the afterheat removal capability during the flow reversal has limited the reactor operating power to 30 MW. An experimental and analytical program to address these uncertainties is described in this report. The experiments were single channel flow reversal tests under a range of conditions. The analytical phase involved simulations of the tests to benchmark the physical models and development of a criterion for dryout. The criterion is then used in simulations of reactor accidents to determine a safemore » operating power level. It is concluded that the limit on the HFBR operating power with respect to the issue of flow reversal is in excess of 60 MW.« less

Mass-Mobility Characterization of Flame-made ZrO2 Aerosols: Primary Particle Diameter & Extent of Aggregation

PubMed Central

Eggersdorfer, M.L.; Gröhn, A.J.; Sorensen, C.M.; McMurry, P.H.; Pratsinis, S.E.

2013-01-01

Gas-borne nanoparticles undergoing coagulation and sintering form irregular or fractal-like structures affecting their transport, light scattering, effective surface area and density. Here, zirconia (ZrO2) nanoparticles are generated by scalable spray combustion, and their mobility diameter and mass are obtained nearly in-situ by differential mobility analyzer (DMA) and aerosol particle mass (APM) measurements. Using these data, the density of ZrO2 and a power law between mobility and primary particle diameters, the structure of fractal-like particles is determined (mass-mobility exponent, prefactor and average number and surface area mean diameter of primary particles, dva). The dva determined by DMA-APM measurements and this power law is in good agreement with the dva obtained by ex-situ nitrogen adsorption and microscopic analysis. Using this combination of measurements and above power law, the effect of flame spray process parameters (e.g. precursor solution and oxygen flow rate as well as zirconium concentration) on fractal-like particle structure characteristics is investigated in detail. This reveals that predominantly agglomerates (physically-bonded particles) and aggregates (chemically- or sinter-bonded particles) of nanoparticles are formed at low and high particle concentrations, respectively. PMID:22959835

U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities

NASA Technical Reports Server (NTRS)

Schmit, Ryan

2010-01-01

To develop New Flow Control Techniques: a) Knowledge of the Flow Physics with and without control. b) How does Flow Control Effect Flow Physics (What Works to Optimize the Design?). c) Energy or Work Efficiency of the Control Technique (Cost - Risk - Benefit Analysis). d) Supportability, e.g. (size of equipment, computational power, power supply) (Allows Designer to include Flow Control in Plans).

A Low-Power Thermal-Based Sensor System for Low Air Flow Detection

PubMed Central

Arifuzzman, AKM; Haider, Mohammad Rafiqul; Allison, David B.

2016-01-01

Being able to rapidly detect a low air flow rate with high accuracy is essential for various applications in the automotive and biomedical industries. We have developed a thermal-based low air flow sensor with a low-power sensor readout for biomedical applications. The thermal-based air flow sensor comprises a heater and three pairs of temperature sensors that sense temperature differences due to laminar air flow. The thermal-based flow sensor was designed and simulated by using laminar flow, heat transfer in solids and fluids physics in COMSOL MultiPhysics software. The proposed sensor can detect air flow as low as 0.0064 m/sec. The readout circuit is based on a current- controlled ring oscillator in which the output frequency of the ring oscillator is proportional to the temperature differences of the sensors. The entire readout circuit was designed and simulated by using a 130-nm standard CMOS process. The sensor circuit features a small area and low-power consumption of about 22.6 µW with an 800 mV power supply. In the simulation, the output frequency of the ring oscillator and the change in thermistor resistance showed a high linearity with an R2 value of 0.9987. The low-power dissipation, high linearity and small dimensions of the proposed flow sensor and circuit make the system highly suitable for biomedical applications. PMID:28435186

Mean flow produced by small-amplitude vibrations of a liquid bridge with its free surface covered with an insoluble surfactant

NASA Astrophysics Data System (ADS)

Carrión, Luis M.; Herrada, Miguel A.; Montanero, José M.; Vega, José M.

2017-09-01

As is well known, confined fluid systems subject to forced vibrations produce mean flows, called in this context streaming flows. These mean flows promote an overall mass transport in the fluid that has consequences in the transport of passive scalars and surfactants, when these are present in a fluid interface. Such transport causes surfactant concentration inhomogeneities that are to be counterbalanced by Marangoni elasticity. Therefore, the interaction of streaming flows and Marangoni convection is expected to produce new flow structures that are different from those resulting when only one of these effects is present. The present paper focuses on this interaction using the liquid bridge geometry as a paradigmatic system for the analysis. Such analysis is based on an appropriate post-processing of the results obtained via direct numerical simulation of the system for moderately small viscosity, a condition consistent with typical experiments of vibrated millimetric liquid bridges. It is seen that the flow patterns show a nonmonotone behavior as the Marangoni number is increased. In addition, the strength of the mean flow at the free surface exhibits two well-defined regimes as the forcing amplitude increases. These regimes show fairly universal power-law behaviors.

Three-dimensional numerical investigation of the separation process in a vortex tube at different operating conditions

NASA Astrophysics Data System (ADS)

Rafiee, Seyed Ehsan; Sadeghiazad, M. M.

2016-06-01

Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process inside a Ranque-Hilsch vortex tube cleaning (cooling) system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-ɛ turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows inside the air separators. Results present a comprehensive and practical solution for use in future numerical studies.

A lab-in-a-droplet bioassay strategy for centrifugal microfluidics with density difference pumping, power to disc and bidirectional flow control.

PubMed

Wang, Guanghui; Ho, Ho-Pui; Chen, Qiulan; Yang, Alice Kar-Lai; Kwok, Ho-Chin; Wu, Shu-Yuen; Kong, Siu-Kai; Kwan, Yiu-Wa; Zhang, Xuping

2013-09-21

In this paper, we present a lab-in-a-droplet bioassay strategy for a centrifugal microfluidics or lab-on-a-disc (LOAD) platform with three important advancements including density difference pumping, power to disc and bidirectional flow control. First, with the water based bioassay droplets trapped in a micro-channel filled with mineral oil, centrifugal force due to the density difference between the water and oil phases actuates droplet movement while the oil based medium remains stationary. Second, electricity is coupled to the rotating disc through a split-core transformer, thus enabling on-chip real-time heating in selected areas as desired and wireless programmable functionality. Third, an inertial mechanical structure is proposed to achieve bidirectional flow control within the spinning disc. The droplets can move back and forth between two heaters upon changing the rotational speed. Our platform is an essential and versatile solution for bioassays such as those involving DNA amplification, where localized temperature cycling is required. Finally, without the loss of generality, we demonstrate the functionality of our platform by performing real-time polymerase chain reaction (RT-PCR) in a linear microchannel made with PTFE (Teflon) micro-tubing.

Towards Large Eddy Simulation of gas turbine compressors

NASA Astrophysics Data System (ADS)

McMullan, W. A.; Page, G. J.

2012-07-01

With increasing computing power, Large Eddy Simulation could be a useful simulation tool for gas turbine axial compressor design. This paper outlines a series of simulations performed on compressor geometries, ranging from a Controlled Diffusion Cascade stator blade to the periodic sector of a stage in a 3.5 stage axial compressor. The simulation results show that LES may offer advantages over traditional RANS methods when off-design conditions are considered - flow regimes where RANS models often fail to converge. The time-dependent nature of LES permits the resolution of transient flow structures, and can elucidate new mechanisms of vorticity generation on blade surfaces. It is shown that accurate LES is heavily reliant on both the near-wall mesh fidelity and the ability of the imposed inflow condition to recreate the conditions found in the reference experiment. For components embedded in a compressor this requires the generation of turbulence fluctuations at the inlet plane. A recycling method is developed that improves the quality of the flow in a single stage calculation of an axial compressor, and indicates that future developments in both the recycling technique and computing power will bring simulations of axial compressors within reach of industry in the coming years.

Power Generation Evaluated on a Bismuth Telluride Unicouple Module

NASA Astrophysics Data System (ADS)

Hu, Xiaokai; Nagase, Kazuo; Jood, Priyanka; Ohta, Michihiro; Yamamoto, Atsushi

2015-06-01

The power generated by a thermoelectric unicouple module made of Bi2Te3 alloy was evaluated by use of a newly developed instrument. An electrical load was connected to the module, and the terminal voltage and output power of the module were obtained by altering electric current. Water flow was used to cool the cold side of the module and for heat flow measurement, by monitoring inlet and outlet temperatures. When the electric current was increased, heat flow was enhanced as a result of the Peltier effect and Joule heating. Voltage, power, heat flow, and efficiency as functions of current were determined for hot-side temperatures from 50 to 220°C. Maximum power output and peak conversion efficiency could thus be easily derived for each temperature.

Numerical prediction of micro-channel LD heat sink operated with antifreeze based on CFD method

NASA Astrophysics Data System (ADS)

Liu, Gang; Liu, Yang; Wang, Chao; Wang, Wentao; Wang, Gang; Tang, Xiaojun

2014-12-01

To theoretically study the feasibility of antifreeze coolants applied as cooling fluids for high power LD heat sink, detailed Computational Fluid Dynamics (CFD) analysis of liquid cooled micro-channels heat sinks is presented. The performance operated with antifreeze coolant (ethylene glycol aqueous solution) compared with pure water are numerical calculated for the heat sinks with the same micro-channels structures. The maximum thermal resistance, total pressure loss (flow resistance), thermal resistance vs. flow-rate, and pressure loss vs. flow-rate etc. characteristics are numerical calculated. The results indicate that the type and temperature of coolants plays an important role on the performance of heat sinks. The whole thermal resistance and pressure loss of heat sinks increase significantly with antifreeze coolants compared with pure water mainly due to its relatively lower thermal conductivity and higher fluid viscosity. The thermal resistance and pressure loss are functions of the flow rate and operation temperature. Increasing of the coolant flow rate can reduce the thermal resistance of heat sinks; meanwhile increase the pressure loss significantly. The thermal resistance tends to a limit with increasing flow rate, while the pressure loss tends to increase exponentially with increasing flow rate. Low operation temperature chiefly increases the pressure loss rather than thermal resistance due to the remarkable increasing of fluid viscosity. The actual working point of the cooling circulation system can be determined on the basis of the pressure drop vs. flow rate curve for the micro-channel heat sink and that for the circulation system. In the same system, if the type or/and temperature of the coolant is changed, the working point is accordingly influenced, that is, working flow rate and pressure is changed simultaneously, due to which the heat sink performance is influenced. According to the numerical simulation results, if ethylene glycol aqueous solution is applied instead of pure water as the coolant under the same or a higher working temperature, the available output of optical power will decrease due to the worse heat sink performance; if applied under a lower working temperature(0 °C, －20 °C), although the heat sink performance become worse, however the temperature difference of heat transfer rises more significantly, the available output of optical power will increase on the contrary.

Regulation of Renewable Energy Sources to Optimal Power Flow Solutions Using ADMM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dall-Anese, Emiliano; Zhang, Yijian; Hong, Mingyi

This paper considers power distribution systems featuring renewable energy sources (RESs), and develops a distributed optimization method to steer the RES output powers to solutions of AC optimal power flow (OPF) problems. The design of the proposed method leverages suitable linear approximations of the AC-power flow equations, and is based on the Alternating Direction Method of Multipliers (ADMM). Convergence of the RES-inverter output powers to solutions of the OPF problem is established under suitable conditions on the stepsize as well as mismatches between the commanded setpoints and actual RES output powers. In a broad sense, the methods and results proposedmore » here are also applicable to other distributed optimization problem setups with ADMM and inexact dual updates.« less

Industrial application of ultrasound based in-line rheometry: Visualization of steady shear pipe flow of chocolate suspension in pre-crystallization process

NASA Astrophysics Data System (ADS)

Ouriev, Boris; Windhab, Erich; Braun, Peter; Zeng, Yuantong; Birkhofer, Beat

2003-12-01

In the present work an in-line ultrasonic method for investigation of the rheological flow behavior of concentrated suspensions was created. It is based on a nondestructive rheological measuring technique for pilot plant and industrial scale applications. Elsewhere the author discusses a tremendous need for in-line rheological characterization of highly concentrated suspensions exposed to pressure driven shear flow conditions. Most existing on-line methods are based on destructive macro actuators, which are not suitable for materials with sensitive to applied deformation structure. Since the process of our basic interest influences the structure of suspension it would be difficult to separate the effects of rheometric measurement and weakly pronounced structural changes arising from a fine adjustment of the process parameters. The magnitude of these effects is usually associated with the complex flow dynamics of structured liquids and is sensitive to density or temperature fluctuations around the moving rheometric actuator. Interpretation of the results of such measurements can be hindered by process parameter influences on liquid product structure. Therefore, the author introduces an in-line noninvasive rheometric method, which is implemented in a pre-crystallization process of chocolate suspension. Use of ultrasound velocity profile pressure difference (UVP-PD) technique enabled process monitoring of the chocolate pre-crystallization process. Influence of seeded crystals on Rheology of chocolate suspension was recorded and monitored on line. It was shown that even slight velocity pulsations in chocolate mainstream can strongly influence rheological properties besides influencing flow velocity profiles. Based on calculations of power law fit in raw velocity profiles and calculation of wall shear stress from pressure difference measurement, a viscosity function was calculated and monitored on line. On-line results were found to be in a good agreement with off-line data. The results of the industrial test of the UVP-PD system brought practical knowledge and stipulated further development of a Smart UVP-PD noninventive on-line rheometer.

77 FR 34032 - FFP Project 70, LLC; Notice of Intent To File License Application, Filing of Pre-Application...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-08

...: April 3, 2012. d. Submitted By: Free Flow Power Corporation on behalf of FFP Project 70, LLC (FFP), a wholly-owned subsidiary of Free Flow Power, LLC. e. Name of Project: Mississippi Lock and Dam 19 Water..., Free Flow Power Corporation, 239 Causeway Street, Suite 300, Boston, MA 02114; (978) 283-2822; or email...

Novel flat datacenter network architecture based on scalable and flow-controlled optical switch system.

PubMed

Miao, Wang; Luo, Jun; Di Lucente, Stefano; Dorren, Harm; Calabretta, Nicola

2014-02-10

We propose and demonstrate an optical flat datacenter network based on scalable optical switch system with optical flow control. Modular structure with distributed control results in port-count independent optical switch reconfiguration time. RF tone in-band labeling technique allowing parallel processing of the label bits ensures the low latency operation regardless of the switch port-count. Hardware flow control is conducted at optical level by re-using the label wavelength without occupying extra bandwidth, space, and network resources which further improves the performance of latency within a simple structure. Dynamic switching including multicasting operation is validated for a 4 x 4 system. Error free operation of 40 Gb/s data packets has been achieved with only 1 dB penalty. The system could handle an input load up to 0.5 providing a packet loss lower that 10(-5) and an average latency less that 500 ns when a buffer size of 16 packets is employed. Investigation on scalability also indicates that the proposed system could potentially scale up to large port count with limited power penalty.

Meridional Flow Measurements: Comparisons Between Ring Diagram Analysis and Fourier-Hankel Analysis

NASA Astrophysics Data System (ADS)

Zaatri, A.; Roth, M.

2008-09-01

The meridional circulation is a weak flow with amplitude in the order of 10 m/s on the solar surface. As this flow could be responsible for the transport of magnetic flux during the solar cycle it has become a crucial ingredient in some dynamo models. However, only less is known about the overall structure of the meridional circulation. Helioseismology is able to provide information on the structure of this flow in the solar interior. One widely used helioseismic technique for measuring frequency shifts due to horizontal flows in the subsurface layers of the sun is the ring diagram analyis (Corbard et al. 2003). It is based on the analysis of frequency shifts in the solar oscillation power spectrum as a function of the orientation of the wave vector. This then allows drawing conclusions on the strength of meridional flow, too. Ring diagram analysis is currently limited to the analysis of the wave field in only a small region on the solar surface. Consequently, information on the solar interior can only be inferred down to a depth of about 16 Mm. Another helioseismology method that promises to estimate the meridional flow strength down to greater depths is the Fourier-Hankel analysis (Krieger et al. 2007). This technique is based on a decomposition of the wave field in poleward and equatorward propagating waves. A possible frequency shift between them is then due to the meridional flow. We have been motivated for carrying out a comparative study between the two techniques to measure the meridional flow. We investigate the degree of coherence between the two methods by analyzing the same data sets recorded by the SOHO-MDI and GONG instruments.

Piezoelectric axial flow microvalve

DOEpatents

Gemmen, Randall; Thornton, Jimmy; Vipperman, Jeffrey S.; Clark, William W.

2007-01-09

This invention is directed to a fuel cell operable with a quantity of fuel and a quantity of an oxidizer to produce electrical power, the fuel cell including a fuel cell body including a labyrinth system structured to permit the fuel and the oxidizer to flow therethrough; at least a first catalyst in fluid communication with the labyrinth; and at least a first microvalve operably disposed within at least a portion of the labyrinth. The microvalve utilizes a deflectable member operable upon the application of a voltage from a voltage source. The microvalve includes an elongated flow channel formed therein and extending substantially longitudinally between the first and second ends to permit substantially longitudinal flow of the fluid therethrough and between the first and second ends; and the deflectable member disposed on the valve body, the deflectable member including at least a first piezoelectric portion that is piezoelectrically operable to deflect the deflectable member between an open position and a closed position upon the application of a voltage, the deflectable member in the closed position being operable to resist the flow of the fluid through the flow channel.

Microgrid Enabled Distributed Energy Solutions (MEDES) Fort Bliss Military Reservation

DTIC Science & Technology

2014-02-01

Logic Controller PF Power Factor PO Performance Objectives PPA Power Purchase Agreements PV Photovoltaic R&D Research and Development RDSI...controller, algorithms perform power flow analysis, short term optimization, and long-term forecasted planning. The power flow analysis ensures...renewable photovoltaic power and energy storage in this microgrid configuration, the available mission operational time of the backup generator can be

Identification of Characterization Factor for Power System Oscillation Based on Multiple Synchronized Phasor Measurements

NASA Astrophysics Data System (ADS)

Hashiguchi, Takuhei; Watanabe, Masayuki; Matsushita, Akihiro; Mitani, Yasunori; Saeki, Osamu; Tsuji, Kiichiro; Hojo, Masahide; Ukai, Hiroyuki

Electric power systems in Japan are composed of remote and distributed location of generators and loads mainly concentrated in large demand areas. The structures having long distance transmission tend to produce heavy power flow with increasing electric power demand. In addition, some independent power producers (IPP) and power producer and suppliers (PPS) are participating in the power generation business, which makes power system dynamics more complex. However, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand side outlets. Phasor Measurement Units (PMU) are synchronized based on the global positioning system (GPS). The purpose of this paper is to show oscillation characteristics and methods for processing original data obtained from PMU after certain power system disturbances triggered by some accidents. This analysis resulted in the observation of the lowest and the second lowest frequency mode. The derivation of eigenvalue with two degree of freedom model brings a monitoring of two oscillation modes. Signal processing based on Wavelet analysis and simulation studies to illustrate the obtained phenomena are demonstrated in detail.

A study of GaN-based LED structure etching using inductively coupled plasma

NASA Astrophysics Data System (ADS)

Wang, Pei; Cao, Bin; Gan, Zhiyin; Liu, Sheng

2011-02-01

GaN as a wide band gap semiconductor has been employed to fabricate optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes (LDs). Recently several different dry etching techniques for GaN-based materials have been developed. ICP etching is attractive because of its superior plasma uniformity and strong controllability. Most previous reports emphasized on the ICP etching characteristics of single GaN film. In this study dry etching of GaN-based LED structure was performed by inductively coupled plasmas (ICP) etching with Cl2 as the base gas and BCl3 as the additive gas. The effects of the key process parameters such as etching gases flow rate, ICP power, RF power and chamber pressure on the etching properties of GaN-based LED structure including etching rate, selectivity, etched surface morphology and sidewall was investigated. Etch depths were measured using a depth profilometer and used to calculate the etch rates. The etch profiles were observed with a scanning electron microscope (SEM).

Parallel processing methods for space based power systems

NASA Technical Reports Server (NTRS)

Berry, F. C.

1993-01-01

This report presents a method for doing load-flow analysis of a power system by using a decomposition approach. The power system for the Space Shuttle is used as a basis to build a model for the load-flow analysis. To test the decomposition method for doing load-flow analysis, simulations were performed on power systems of 16, 25, 34, 43, 52, 61, 70, and 79 nodes. Each of the power systems was divided into subsystems and simulated under steady-state conditions. The results from these tests have been found to be as accurate as tests performed using a standard serial simulator. The division of the power systems into different subsystems was done by assigning a processor to each area. There were 13 transputers available, therefore, up to 13 different subsystems could be simulated at the same time. This report has preliminary results for a load-flow analysis using a decomposition principal. The report shows that the decomposition algorithm for load-flow analysis is well suited for parallel processing and provides increases in the speed of execution.

The mechanism performance of improved oil pump with micro-structured vanes

NASA Astrophysics Data System (ADS)

Li, Ping; Xie, Jin; Qi, Dongtao; Li, Houbu

2017-09-01

The wear of oil pump vanes easily leads to the noise and vibration, even results the decrease of volume efficiency and total efficiency. In order to reduce the friction and improve the lubrication between the vane and the pump inner wall, the micro-machining of micro-structure on the oil pump vanes is proposed. First, the micro-V-grooves with the depth ranging from 500μm to 50μm were micro-grinding on the top of the vanes by a diamond grinding wheel. Secondly, the experiments were conducted to test the actual flow rate, the output power and the overall efficiency of the oil pump with and without the micro-groove vanes. Then, the computational fluid dynamics (CFD) method was adopted to simulate the pump internal flow field. Finally, the micro-flow field between the internal wall of the oil pump and the top of micro-grooved vanes was analyzed. The results shows that the pump overall efficiency increased as the decrease of micro-groove depth from 500 μm to 50μm and not be affected by the rotate speed and working frequency of the pump rotator. Especially the micro-groove with depth of 50μm, the actual flow rate, the output power and the overall efficiency reached to the maximum. From CFD simulation, the velocity of the micro-flow between the surfaces of the vane and inner wall was larger than the pump linear velocity when the microstructure depth is larger than 50μm, leading to an internal leakage. When the micro-groove depth is between10-50μm, the velocity of the micro-flow was less than the pump linear velocity and no internal leakage was found, but the oil film thickness is too small to be beneficial to lubrication according to the fluid dynamic characteristics. Thus, for the oil pump equipping with micro-grooved vane with the depth of 50 μm, the internal leakage not only is avoided but the lubrication efficiency is improved and the oil pump efficiency is also enhanced.

Precision control of high temperature furnaces using an auxiliary power supply and charged practice current flow

DOEpatents

Pollock, George G.

1997-01-01

Two power supplies are combined to control a furnace. A main power supply heats the furnace in the traditional manner, while the power from the auxiliary supply is introduced as a current flow through charged particles existing due to ionized gas or thermionic emission. The main power supply provides the bulk heating power and the auxiliary supply provides a precise and fast power source such that the precision of the total power delivered to the furnace is improved.

Integrated support structure for GASCAN 2

NASA Technical Reports Server (NTRS)

1990-01-01

The focus of the Worcester Polytechnic Institute (WPI) Advanced Space Design Program was the preliminary design of the Integrated Support Structure for GASCAN II, a Get Away Special canister donated by the MITRE Corporation. Two teams of three students each worked on the support structure. There was a structural design team and a thermal design team. The structure will carry three experiments also undergoing preliminary design this year, the mu-gravity Ignition Experiment, the Rotational Flow in Low Gravity Experiment, and the Ionospheric Properties and Propagation Experiment. The structural design team was responsible for the layout of the GASCAN and the preliminary design of the structure itself. They produced the physical interface specifications defining the baseline weights and volumes for the equipment and produced layout drawings of the system. The team produced static and modal finite element analysis of the structure using ANSYS. The thermal design team was responsible for the power and timing requirements of the payload and for the identification and preliminary analysis of potential thermal problems. The team produced the power, timing, and energy interface specifications and assisted in the development of the specification of the battery pack. The thermal parameters of each experiment were cataloged and the experiments were subjected to worst case heat transfer scenarios.

Dynamics of comb-of-comb-network polymers in random layered flows

NASA Astrophysics Data System (ADS)

Katyal, Divya; Kant, Rama

2016-12-01

We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength Wα. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν =2 -α /2 . Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t-α /2. We show that the network with greater total mass moves faster.

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth

PubMed Central

Johansson, L. Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

2013-01-01

The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals. PMID:24253180

Phase Synchronization and Desynchronization of Structural Response Induced by Turbulent and External Sound

NASA Technical Reports Server (NTRS)

Maestrello, Lucio

2002-01-01

Acoustic and turbulent boundary layer flow loadings over a flexible structure are used to study the spatial-temporal dynamics of the response of the structure. The stability of the spatial synchronization and desynchronization by an active external force is investigated with an array of coupled transducers on the structure. In the synchronous state, the structural phase is locked, which leads to the formation of spatial patterns while the amplitude peaks exhibit chaotic behaviors. Large amplitude, spatially symmetric loading is superimposed on broadband, but in the desynchronized state, the spectrum broadens and the phase space is lost. The resulting pattern bears a striking resemblance to phase turbulence. The transition is achieved by using a low power external actuator to trigger broadband behaviors from the knowledge of the external acoustic load inducing synchronization. The changes are made favorably and efficiently to alter the frequency distribution of power, not the total power level. Before synchronization effects are seen, the panel response to the turbulent boundary layer loading is discontinuously spatio-temporally correlated. The stability develops from different competing wavelengths; the spatial scale is significantly shorter than when forced with the superimposed external sound. When the external sound level decreases and the synchronized phases are lost, changes in the character of the spectra can be linked to the occurrence of spatial phase transition. These changes can develop broadband response. Synchronized responses of fuselage structure panels have been observed in subsonic and supersonic aircraft; results from two flights tests are discussed.

Quantitative description on structure-property relationships of Li-ion battery materials for high-throughput computations

NASA Astrophysics Data System (ADS)

Wang, Youwei; Zhang, Wenqing; Chen, Lidong; Shi, Siqi; Liu, Jianjun

2017-12-01

Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure-property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure-property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure-property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials.

Quantitative description on structure-property relationships of Li-ion battery materials for high-throughput computations.

PubMed

Wang, Youwei; Zhang, Wenqing; Chen, Lidong; Shi, Siqi; Liu, Jianjun

2017-01-01

Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure-property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure-property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure-property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials.

A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

PubMed

Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

2016-03-01

Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

New strategies for SHM based on a multichannel wireless AE node

NASA Astrophysics Data System (ADS)

Godinez-Azcuaga, Valery; Ley, Obdulia

2014-03-01

This paper discusses the development of an Acoustic Emission (AE) wireless node and its application for SHM (Structural Health Monitoring). The instrument development was planned for applications monitoring steel and concrete bridges components. The final product, now commercially available, is a sensor node which includes multiple sensing elements, on board signal processing and analysis capabilities, signal conditioning electronics, power management circuits, wireless data transmission element and energy harvesting unit. The sensing elements are capable of functioning in both passive and active modes, while the multiple parametric inputs are available for connecting various sensor types to measure external characteristics affecting the performance of the structure under monitoring. The output of all these sensors are combined and analyzed at the node in order to minimize the data transmission rate, which consumes significant amount of power. Power management circuits are used to reduce the data collection intervals through selective data acquisition strategies and minimize the sensor node power consumption. This instrument, known as the 1284, is an excellent platform to deploy SHM in the original bridge applications, but initial prototypes has shown significant potential in monitoring composite wind turbine blades and composites mockups of Unmanned Autonomous Vehicles (UAV) components; currently we are working to extend the use of this system to fields such as coal flow, power transformer, and off-shore platform monitoring.

The Advantages of Non-Flow-Through Fuel Cell Power Systems for Aerospace Applications

NASA Technical Reports Server (NTRS)

Hoberecht, Mark; Burke, Kenneth; Jakupca, Ian

2011-01-01

NASA has been developing proton-exchange-membrane (PEM) fuel cell power systems for the past decade, as an upgraded technology to the alkaline fuel cells which presently provide power for the Shuttle Orbiter. All fuel cell power systems consist of one or more fuel cell stacks in combination with appropriate balance-of-plant hardware. Traditional PEM fuel cells are characterized as flow-through, in which recirculating reactant streams remove product water from the fuel cell stack. NASA recently embarked on the development of non-flow-through fuel cell systems, in which reactants are dead-ended into the fuel cell stack and product water is removed by internal wicks. This simplifies the fuel cell power system by eliminating the need for pumps to provide reactant circulation, and mechanical water separators to remove the product water from the recirculating reactant streams. By eliminating these mechanical components, the resulting fuel cell power system has lower mass, volume, and parasitic power requirements, along with higher reliability and longer life. These improved non-flow-through fuel cell power systems therefore offer significant advantages for many aerospace applications.

Active micromachines: Microfluidics powered by mesoscale turbulence

PubMed Central

Thampi, Sumesh P.; Doostmohammadi, Amin; Shendruk, Tyler N.; Golestanian, Ramin; Yeomans, Julia M.

2016-01-01

Dense active matter, from bacterial suspensions and microtubule bundles driven by motor proteins to cellular monolayers and synthetic Janus particles, is characterized by mesoscale turbulence, which is the emergence of chaotic flow structures. By immersing an ordered array of symmetric rotors in an active fluid, we introduce a microfluidic system that exploits spontaneous symmetry breaking in mesoscale turbulence to generate work. The lattice of rotors self-organizes into a spin state where neighboring discs continuously rotate in permanent alternating directions due to combined hydrodynamic and elastic effects. Our virtual prototype demonstrates a new research direction for the design of micromachines powered by the nematohydrodynamic properties of active turbulence. PMID:27419229

Parallel plate radiofrequency ion thruster

NASA Technical Reports Server (NTRS)

Nakanishi, S.

1982-01-01

An 8-cm-diam. argon ion thruster is described. It is operated by applying 100 to 160 Mhz rf power across a thin plasma volume in a strongly divergent static magnetic field. No cathode or electron emitter is required to sustain a continuous wave plasma discharge over a broad range of propellant gas flow. Preliminary results indicate that a large fraction of the incident power is being reflected by impedance mismatching in the coupling structure. Resonance effects due to plasma thickness, magnetic field strength, and distribution are presented. Typical discharge losses obtained to date are 500 to 600 W per beam ampere at extracted beam currents up to 60 mA.

SNAP 19 Pioneer F and G. Final Report

DOE R&D Accomplishments Database

1973-06-01

The generator developed for the Pioneer mission evolved from the SNAP 19 RTG`s launched aboard the NIMBUS III spacecraft. In order to satisfy the power requirements and environment of earth escape trajectory, significant modifications were made to the thermoelectric converter, heat source, and structural configuration. Specifically, a TAGS 2N thermoelectric couple was designed to provide higher efficiency and improved long term power performance, and the electrical circuitry was modified to yield very low magnetic field from current flow in the RTG. A new heat source was employed to satisfy operational requirements and its integration with the generator required alteration to the method of providing support to the fuel capsule.

Multi-mode evaluation of power-maximizing cross-flow turbine controllers

DOE PAGES

Forbush, Dominic; Cavagnaro, Robert J.; Donegan, James; ...

2017-09-21

A general method for predicting and evaluating the performance of three candidate cross-flow turbine power-maximizing controllers is presented in this paper using low-order dynamic simulation, scaled laboratory experiments, and full-scale field testing. For each testing mode and candidate controller, performance metrics quantifying energy capture (ability of a controller to maximize power), variation in torque and rotation rate (related to drive train fatigue), and variation in thrust loads (related to structural fatigue) are quantified for two purposes. First, for metrics that could be evaluated across all testing modes, we considered the accuracy with which simulation or laboratory experiments could predict performancemore » at full scale. Second, we explored the utility of these metrics to contrast candidate controller performance. For these turbines and set of candidate controllers, energy capture was found to only differentiate controller performance in simulation, while the other explored metrics were able to predict performance of the full-scale turbine in the field with various degrees of success. Finally, effects of scale between laboratory and full-scale testing are considered, along with recommendations for future improvements to dynamic simulations and controller evaluation.« less

Multi-mode evaluation of power-maximizing cross-flow turbine controllers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forbush, Dominic; Cavagnaro, Robert J.; Donegan, James

A general method for predicting and evaluating the performance of three candidate cross-flow turbine power-maximizing controllers is presented in this paper using low-order dynamic simulation, scaled laboratory experiments, and full-scale field testing. For each testing mode and candidate controller, performance metrics quantifying energy capture (ability of a controller to maximize power), variation in torque and rotation rate (related to drive train fatigue), and variation in thrust loads (related to structural fatigue) are quantified for two purposes. First, for metrics that could be evaluated across all testing modes, we considered the accuracy with which simulation or laboratory experiments could predict performancemore » at full scale. Second, we explored the utility of these metrics to contrast candidate controller performance. For these turbines and set of candidate controllers, energy capture was found to only differentiate controller performance in simulation, while the other explored metrics were able to predict performance of the full-scale turbine in the field with various degrees of success. Finally, effects of scale between laboratory and full-scale testing are considered, along with recommendations for future improvements to dynamic simulations and controller evaluation.« less

Energy harvesting concepts for small electric unmanned systems

NASA Astrophysics Data System (ADS)

Qidwai, Muhammad A.; Thomas, James P.; Kellogg, James C.; Baucom, Jared N.

2004-07-01

In this study, we identify and survey energy harvesting technologies for small electrically powered unmanned systems designed for long-term (>1 day) time-on-station missions. An environmental energy harvesting scheme will provide long-term, energy additions to the on-board energy source. We have identified four technologies that cover a broad array of available energy sources: solar, kinetic (wind) flow, autophagous structure-power (both combustible and metal air-battery systems) and electromagnetic (EM) energy scavenging. We present existing conceptual designs, critical system components, performance, constraints and state-of-readiness for each technology. We have concluded that the solar and autophagous technologies are relatively matured for small-scale applications and are capable of moderate power output levels (>1 W). We have identified key components and possible multifunctionalities in each technology. The kinetic flow and EM energy scavenging technologies will require more in-depth study before they can be considered for implementation. We have also realized that all of the harvesting systems require design and integration of various electrical, mechanical and chemical components, which will require modeling and optimization using hybrid mechatronics-circuit simulation tools. This study provides a starting point for detailed investigation into the proposed technologies for unmanned system applications under current development.

Soap film flows: Statistics of two-dimensional turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorobieff, P.; Rivera, M.; Ecke, R.E.

1999-08-01

Soap film flows provide a very convenient laboratory model for studies of two-dimensional (2-D) hydrodynamics including turbulence. For a gravity-driven soap film channel with a grid of equally spaced cylinders inserted in the flow, we have measured the simultaneous velocity and thickness fields in the irregular flow downstream from the cylinders. The velocity field is determined by a modified digital particle image velocimetry method and the thickness from the light scattered by the particles in the film. From these measurements, we compute the decay of mean energy, enstrophy, and thickness fluctuations with downstream distance, and the structure functions of velocity,more » vorticity, thickness fluctuation, and vorticity flux. From these quantities we determine the microscale Reynolds number of the flow R{sub {lambda}}{approx}100 and the integral and dissipation scales of 2D turbulence. We also obtain quantitative measures of the degree to which our flow can be considered incompressible and isotropic as a function of downstream distance. We find coarsening of characteristic spatial scales, qualitative correspondence of the decay of energy and enstrophy with the Batchelor model, scaling of energy in {ital k} space consistent with the k{sup {minus}3} spectrum of the Kraichnan{endash}Batchelor enstrophy-scaling picture, and power-law scalings of the structure functions of velocity, vorticity, vorticity flux, and thickness. These results are compared with models of 2-D turbulence and with numerical simulations. {copyright} {ital 1999 American Institute of Physics.}« less

Speckle variance optical coherence tomography of blood flow in the beating mouse embryonic heart.

PubMed

Grishina, Olga A; Wang, Shang; Larina, Irina V

2017-05-01

Efficient separation of blood and cardiac wall in the beating embryonic heart is essential and critical for experiment-based computational modelling and analysis of early-stage cardiac biomechanics. Although speckle variance optical coherence tomography (SV-OCT) relying on calculation of intensity variance over consecutively acquired frames is a powerful approach for segmentation of fluid flow from static tissue, application of this method in the beating embryonic heart remains challenging because moving structures generate SV signal indistinguishable from the blood. Here, we demonstrate a modified four-dimensional SV-OCT approach that effectively separates the blood flow from the dynamic heart wall in the beating mouse embryonic heart. The method takes advantage of the periodic motion of the cardiac wall and is based on calculation of the SV signal over the frames corresponding to the same phase of the heartbeat cycle. Through comparison with Doppler OCT imaging, we validate this speckle-based approach and show advantages in its insensitiveness to the flow direction and velocity as well as reduced influence from the heart wall movement. This approach has a potential in variety of applications relying on visualization and segmentation of blood flow in periodically moving structures, such as mechanical simulation studies and finite element modelling. Picture: Four-dimensional speckle variance OCT imaging shows the blood flow inside the beating heart of an E8.5 mouse embryo. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion Heating and Flows in a High Power Helicon Source

NASA Astrophysics Data System (ADS)

Scime, Earl; Agnello, Riccardo; Furno, Ivo; Howling, Alan; Jacquier, Remy; Plyushchev, Gennady; Thompson, Derek

2017-10-01

We report experimental measurements of ion temperatures and flows in a high power, linear, magnetized, helicon plasma device, the Resonant Antenna Ion Device (RAID). RAID is equipped with a high power helicon source. Parallel and perpendicular ion temperatures on the order of 0.6 eV are observed for an rf power of 4 kW, suggesting that higher power helicon sources should attain ion temperatures in excess of 1 eV. The unique RAID antenna design produces broad, uniform plasma density and perpendicular ion temperature radial profiles. Measurements of the azimuthal flow indicate rigid body rotation of the plasma column of a few kHz. When configured with an expanding magnetic field, modest parallel ion flows are observed in the expansion region. The ion flows and temperatures are derived from laser induced fluorescence measurements of the Doppler resolved velocity distribution functions of argon ions. This work supported by U.S. National Science Foundation Grant No. PHY-1360278.

JPRS Report, Nuclear Developments

DTIC Science & Technology

1991-04-23

East countries. Bush once expressed Taishan. the hope of reducing arms sales to the Middle East but has never taken effective measures to weaken the flow...structure containing sand armament will bring enormous effects in strategic envi- 350 meters to 500 meters below the surface and then ronment in Northeast...underestimation of its consequences may have some Kozloduy Nuclear Power Plant which results in radioac- tragic effects on Bulgaria’s population which

In-cylinder flows of a motored four-stroke engine with flat-crown and slightly concave-crown pistons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, R.F.; Yang, H.S.; Yeh, C.-N.

2008-04-15

The temporal and spatial evolution processes of the in-cylinder flow structures and turbulence intensities in the symmetry and offset planes of a motored four-valve, four-stroke engine during the intake and compression strokes are diagnosed by using a particle image velocimeter. Two pistons of different crown shapes (flat-crown and slightly concave-crown pistons) are studied. The inception, establishment, and evolution of the tumbling vortical flow structures during the intake and compression strokes are clearly depicted. Quantitative strengths of the rotating vortical flow motions are presented by a dimensionless parameter, the tumble ratio, which can represent the mean angular velocity of the vorticesmore » in the target plane. The turbulence intensity of the in-cylinder flow is also calculated by using the measured time-varying velocity data. The results show that the flat-crown piston induces higher bulk-averaged tumble ratio and turbulence intensity than the slightly concave-crown piston does because the tumble ratio and turbulence generated by the flat-crown piston in the offset planes during the compression stroke are particularly large. The engine with the flat-crown piston also presents larger torque and power outputs and lower hydrocarbon emission than that with the slightly concave-crown piston. This might be caused by the enhanced combustion in the engine cylinder due to the stronger tumble ratio and turbulence intensity. (author)« less

Ion heating and flows in a high power helicon source

NASA Astrophysics Data System (ADS)

Thompson, Derek S.; Agnello, Riccardo; Furno, Ivo; Howling, Alan; Jacquier, Rémy; Plyushchev, Gennady; Scime, Earl E.

2017-06-01

We report experimental measurements of ion temperatures and flows in a high power, linear, magnetized, helicon plasma device, the Resonant Antenna Ion Device (RAID). Parallel and perpendicular ion temperatures on the order of 0.6 eV are observed for an rf power of 4 kW, suggesting that higher power helicon sources should attain ion temperatures in excess of 1 eV. The unique RAID antenna design produces broad, uniform plasma density and perpendicular ion temperature radial profiles. Measurements of the azimuthal flow indicate rigid body rotation of the plasma column of a few kHz. When configured with an expanding magnetic field, modest parallel ion flows are observed in the expansion region. The ion flows and temperatures are derived from laser induced fluorescence measurements of the Doppler resolved velocity distribution functions of argon ions.

Transport on percolation clusters with power-law distributed bond strengths.

PubMed

Alava, Mikko; Moukarzel, Cristian F

2003-05-01

The simplest transport problem, namely finding the maximum flow of current, or maxflow, is investigated on critical percolation clusters in two and three dimensions, using a combination of extremal statistics arguments and exact numerical computations, for power-law distributed bond strengths of the type P(sigma) approximately sigma(-alpha). Assuming that only cutting bonds determine the flow, the maxflow critical exponent v is found to be v(alpha)=(d-1)nu+1/(1-alpha). This prediction is confirmed with excellent accuracy using large-scale numerical simulation in two and three dimensions. However, in the region of anomalous bond capacity distributions (0< or =alpha< or =1) we demonstrate that, due to cluster-structure fluctuations, it is not the cutting bonds but the blobs that set the transport properties of the backbone. This "blob dominance" avoids a crossover to a regime where structural details, the distribution of the number of red or cutting bonds, would set the scaling. The restored scaling exponents, however, still follow the simplistic red bond estimate. This is argued to be due to the existence of a hierarchy of so-called minimum cut configurations, for which cutting bonds form the lowest level, and whose transport properties scale all in the same way. We point out the relevance of our findings to other scalar transport problems (i.e., conductivity).

Experimental and analytical study of loss-of-flow transients in EBR-II occurring at decay power levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, L.K.; Mohr, D.; Feldman, E.E.

A series of eight loss-of-flow (LOF) tests have been conducted in EBR-II to study the transition between forced and natural convective flows following a variety of loss-of-primary-pumping power conditions from decay heat levels. Comparisons of measurements and pretest/posttest predictions were made on a selected test. Good agreements between measurements and predictions was found prior to and just after the flow reaching its minimum, but the agreement is not as good after that point. The temperatures are consistent with the flow response and the assumed decay power. The measured results indicate that the flows of driver and the instrumented subassemblies aremore » too much in the analytical model in the natural convective region. Although a parametric study on secondary flow, turbulent-laminar flow transition, heat transfer ability of the intermediate heat exchange at low flow and flow mixing in the primary tank has been performed to determine their effects on the flow, the cause of the discrepancy at very low flow level is still unknown.« less

Exhumation rates of high pressure metamorphic rocks in subduction channels: The effect of Rheology

NASA Astrophysics Data System (ADS)

Gerya, T. V.; Stöckhert, B.

2002-04-01

Exhumation of high-pressure metamorphic rocks can take place with typical plate velocities of cm/year. This is consistent with a model of forced flow in a subduction channel. The (micro)structural record of exhumed metamorphic rocks indicates that stresses are generally too low to drive deformation of the bulk material by dislocation creep, according to a power-law rheology. Instead deformation appears to be localized in low-strength shear zones, and is dominated by dissolution precipitation creep or fluid assisted granular flow, implying a Newtonian rheology. 1D modeling shows that the effective rheology of the material in the subduction channel has a significant influence on the rate of exhumation. When the subduction flux either equals or exceeds the return flux, the maximum exhumation rate for Newtonian behavior of the material is at least twice as high (~1/3 of the subduction burial rate) compared to that for power-law creep (~1/6 of the subduction burial rate).

A study of phase explosion of metal using high power Nd:YAG laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoh, Jack J.; Lee, H. H.; Choi, J. H.

2007-12-12

The interaction of high-power pulsed-laser beam with metal targets in air from 1.06 {mu}m, 5 ns, 3 J/pulse max, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported detonation (LSD) wave and multi-material reactive Euler equations. The high speed blast wave generated by the laser ablation of metal reaches maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations of motion for energetic materials and to understand the explosive behavior of metal vaporization upon laser ablation. The characteristic time at which planar tomore » spherical wave transition occurs is confirmed at low (20 mJ/pulse) to higher (200 mJ/pulse) beam intensities. The flow structure behind the leading shock wave during the early planar shock state is confirmed by the high-resolution multi-material hydrocode originally developed for shock compression of condensed matter.« less

Sharing the opportunity cost among power companies to support hydropower-to-environment water transfers

NASA Astrophysics Data System (ADS)

Tilmant, Amaury; Marques, Guilherme

2016-04-01

Among the environmental impacts caused by dams, the alteration of flow regimes is one of the most critical to river ecosystems given its influence in long river reaches and its continuous pattern. Provided it is technically feasible, the reoperation of hydroelectric reservoir systems can, in principle, mitigate the impacts on degraded freshwater ecosystems by recovering some of the natural flow regime. The typical approach to implement hydropower-to-environment water transfers focuses on the reoperation of the dam located immediately upstream of the environmentally sensitive area, meaning that only one power station will bear the brunt of the benefits forgone for the power sector. By ignoring the contribution of upstream infrastructures to the alteration of the flow regime, the opportunity cost associated with the restoration of a flow regime is not equitably distributed among the power companies in the river basin, therefore slowing the establishment of environmental flow programs. Yet, there is no criterion, nor institutional mechanisms, to ensure a fair distribution of the opportunity cost among power stations. This paper addresses this issue by comparing four rules to redistribute the costs faced by the power sector when environmental flows must be implemented in a multireservoir system. The rules are based on the the installed capacity of the power plants, the live storage capacity of the reservoirs, the ratio between the incremental flows and the live storage capacity, and the extent of the storage services; that is, the volume of water effectively transferred by each reservoir. The analysis is carried out using the Parana River Basin (Brazil) as a case study.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Xiao; Blazek, Jonathan A.; McEwen, Joseph E.

Cosmological perturbation theory is a powerful tool to predict the statistics of large-scale structure in the weakly non-linear regime, but even at 1-loop order it results in computationally expensive mode-coupling integrals. Here we present a fast algorithm for computing 1-loop power spectra of quantities that depend on the observer's orientation, thereby generalizing the FAST-PT framework (McEwen et al., 2016) that was originally developed for scalars such as the matter density. This algorithm works for an arbitrary input power spectrum and substantially reduces the time required for numerical evaluation. We apply the algorithm to four examples: intrinsic alignments of galaxies inmore » the tidal torque model; the Ostriker-Vishniac effect; the secondary CMB polarization due to baryon flows; and the 1-loop matter power spectrum in redshift space. Code implementing this algorithm and these applications is publicly available at https://github.com/JoeMcEwen/FAST-PT.« less

Thermal margin protection system for a nuclear reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musick, C.R.

1974-02-12

A thermal margin protection system for a nuclear reactor is described where the coolant flow flow trip point and the calculated thermal margin trip point are switched simultaneously and the thermal limit locus is made more restrictive as the allowable flow rate is decreased. The invention is characterized by calculation of the thermal limit Locus in response to applied signals which accurately represent reactor cold leg temperature and core power; cold leg temperature being corrected for stratification before being utilized and reactor power signals commensurate with power as a function of measured neutron flux and thermal energy added to themore » coolant being auctioneered to select the more conservative measure of power. The invention further comprises the compensation of the selected core power signal for the effects of core radial peaking factor under maximum coolant flow conditions. (Official Oazette)« less

Packing microstructure and local density variations of experimental and computational pebble beds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auwerda, G. J.; Kloosterman, J. L.; Lathouwers, D.

2012-07-01

In pebble bed type nuclear reactors the fuel is contained in graphite pebbles, which form a randomly stacked bed with a non-uniform packing density. These variations can influence local coolant flow and power density and are a possible cause of hotspots. To analyse local density variations computational methods are needed that can generate randomly stacked pebble beds with a realistic packing structure on a pebble-to-pebble level. We first compare various properties of the local packing structure of a computed bed with those of an image made using computer aided X-ray tomography, looking at properties in the bulk of the bedmore » and near the wall separately. Especially for the bulk of the bed, properties of the computed bed show good comparison with the scanned bed and with literature, giving confidence our method generates beds with realistic packing microstructure. Results also show the packing structure is different near the wall than in the bulk of the bed, with pebbles near the wall forming ordered layers similar to hexagonal close packing. Next, variations in the local packing density are investigated by comparing probability density functions of the packing fraction of small clusters of pebbles throughout the bed. Especially near the wall large variations in local packing fractions exists, with a higher probability for both clusters of pebbles with low (<0.6) and high (>0.65) packing fraction, which could significantly affect flow rates and, together with higher power densities, could result in hotspots. (authors)« less

Automated flow quantification in valvular heart disease based on backscattered Doppler power analysis: implementation on matrix-array ultrasound imaging systems.

PubMed

Buck, Thomas; Hwang, Shawn M; Plicht, Björn; Mucci, Ronald A; Hunold, Peter; Erbel, Raimund; Levine, Robert A

2008-06-01

Cardiac ultrasound imaging systems are limited in the noninvasive quantification of valvular regurgitation due to indirect measurements and inaccurate hemodynamic assumptions. We recently demonstrated that the principle of integration of backscattered acoustic Doppler power times velocity can be used for flow quantification in valvular regurgitation directly at the vena contracta of a regurgitant flow jet. We now aimed to accomplish implementation of automated Doppler power flow analysis software on a standard cardiac ultrasound system utilizing novel matrix-array transducer technology with detailed description of system requirements, components and software contributing to the system. This system based on a 3.5 MHz, matrix-array cardiac ultrasound scanner (Sonos 5500, Philips Medical Systems) was validated by means of comprehensive experimental signal generator trials, in vitro flow phantom trials and in vivo testing in 48 patients with mitral regurgitation of different severity and etiology using magnetic resonance imaging (MRI) for reference. All measurements displayed good correlation to the reference values, indicating successful implementation of automated Doppler power flow analysis on a matrix-array ultrasound imaging system. Systematic underestimation of effective regurgitant orifice areas >0.65 cm(2) and volumes >40 ml was found due to currently limited Doppler beam width that could be readily overcome by the use of new generation 2D matrix-array technology. Automated flow quantification in valvular heart disease based on backscattered Doppler power can be fully implemented on board a routinely used matrix-array ultrasound imaging systems. Such automated Doppler power flow analysis of valvular regurgitant flow directly, noninvasively, and user independent overcomes the practical limitations of current techniques.

High power gas laser - Applications and future developments

NASA Technical Reports Server (NTRS)

Hertzberg, A.

1977-01-01

Fast flow can be used to create the population inversion required for lasing action, or can be used to improve laser operation, for example by the removal of waste heat. It is pointed out that at the present time all lasers which are capable of continuous high-average power employ flow as an indispensable aspect of operation. High power laser systems are discussed, taking into account the gasdynamic laser, the HF supersonic diffusion laser, and electric discharge lasers. Aerodynamics and high power lasers are considered, giving attention to flow effects in high-power gas lasers, aerodynamic windows and beam manipulation, and the Venus machine. Applications of high-power laser technology reported are related to laser material working, the employment of the laser in controlled fusion machines, laser isotope separation and photochemistry, and laser power transmission.

Energy harvesting for self-powered aerostructure actuation

NASA Astrophysics Data System (ADS)

Bryant, Matthew; Pizzonia, Matthew; Mehallow, Michael; Garcia, Ephrahim

2014-04-01

This paper proposes and experimentally investigates applying piezoelectric energy harvesting devices driven by flow induced vibrations to create self-powered actuation of aerostructure surfaces such as tabs, flaps, spoilers, or morphing devices. Recently, we have investigated flow-induced vibrations and limit cycle oscillations due to aeroelastic flutter phenomena in piezoelectric structures as a mechanism to harvest energy from an ambient fluid flow. We will describe how our experimental investigations in a wind tunnel have demonstrated that this harvested energy can be stored and used on-demand to actuate a control surface such as a trailing edge flap in the airflow. This actuated control surface could take the form of a separate and discrete actuated flap, or could constitute rotating or deflecting the oscillating energy harvester itself to produce a non-zero mean angle of attack. Such a rotation of the energy harvester and the associated change in aerodynamic force is shown to influence the operating wind speed range of the device, its limit cycle oscillation (LCO) amplitude, and its harvested power output; hence creating a coupling between the device's performance as an energy harvester and as a control surface. Finally, the induced changes in the lift, pitching moment, and drag acting on a wing model are quantified and compared for a control surface equipped with an oscillating energy harvester and a traditional, static control surface of the same geometry. The results show that when operated in small amplitude LCO the energy harvester adds negligible aerodynamic drag.

Thermal structure of the crust in Inner East Anatolia from aeromagnetic and gravity data

NASA Astrophysics Data System (ADS)

Bektaş, Özcan

2013-08-01

Inner East Anatolia has many hot spring outcomes. In this study, the relationship between the thermal structure and hot spring outcomes is investigated. The residual aeromagnetic and gravity anomalies of the Inner East Anatolia, surveyed by the Mineral Research and Exploration (MTA) of Turkey, show complexities. The magnetic data were analyzed to produce Curie point depth estimates. The depth of magnetic dipole was calculated by azimuthally averaged power spectrum method for the whole area. The Curie point depth (CPD) map covering the Inner East Anatolia has been produced. The Curie point depths of the region between Sivas and Malatya vary from 16.5 to 18.7 km. Values of heat flow were calculated according to continental geotherm from the model. The heat flow values vary between 89 and 99 mW m-2. Heat flow values are incorporated with surface heat flow values. Gravity anomalies were modeled by means of a three-dimensional method. The deepest part of the basin (12-14 km), determined from the 3D model, are located below the settlement of Hafik and to the south of Zara towns. Two-dimensional cross sections produced from the basin depths, Curie values and MOHO depths. Based on the analysis of magnetic, gravity anomalies, thermal structures and geology, it seems likely that the hot springs are not related to rising asthenosphere, in the regions of shallow CPDs (∼16.5 km), and mostly hot springs are related to faulting systems in Inner East Anatolia.

The Impact of Unsteady Reconfiguration on Turbulence Structure within a Flexible Canopy: Large-Eddy Simulation Study of a Cornfield

NASA Astrophysics Data System (ADS)

Chamecki, M.; Pan, Y.; Nepf, H. M.; Follett, E.

2014-12-01

Flexible plants bend in response to fluid motion and this reconfiguration mechanism allows plants to minimize the increase of drag force with increasing velocity, ensuring survival in flow-dominated habitats. The effect of reconfiguration on the flow field can be modeled by introducing a drag coefficient that decreases with increasing velocity. Typically, a power-law decrease of the drag coefficient with increasing velocity is used, and the negative exponent is known as the Vogel number. In practice, the Vogel number is a function of canopy rigidity and flow conditions. In this work we show that accounting for the effect of reconfiguration is required for large-eddy simulation (LES) models to reproduce the skewness of the streamwise and vertical velocity components and the distribution of sweeps and ejections observed in a large cornfield. Additional LES runs are conducted to investigate the structure of turbulence in different reconfiguration regimes, with mean vertical momentum flux constrained by measurements. The change of the Vogel number has negligible effects on LES predictions of the total vertical momentum flux and the components of turbulent kinetic energy, but produces profound changes in the mechanisms of momentum transport. This work demonstrates the necessity to model the effect of reconfiguration in LES studies of canopy flows. It also highlights the impacts of reconfiguration on the structure of turbulence and the dynamics of momentum fluxes, as well as any other process that depends on velocity fluctuations above and within the canopy region.

Micro-Organ Devices

NASA Technical Reports Server (NTRS)

Gonda, Steven R.; Leslie, Julia; Chang, Robert C.; Starly, Binil; Sun, Wei; Culbertson, Christopher; Holtorf, Heidi

2009-01-01

Micro-organ devices (MODs) are being developed to satisfy an emerging need for small, lightweight, reproducible, biological-experimentati on apparatuses that are amenable to automated operation and that imp ose minimal demands for resources (principally, power and fluids). I n simplest terms, a MOD is a microfluidic device containing a variety of microstructures and assemblies of cells, all designed to mimic a complex in vivo microenvironment by replicating one or more in vivo micro-organ structures, the architectures and composition of the extr acellular matrices in the organs of interest, and the in vivo fluid flows. In addition to microscopic flow channels, a MOD contains one or more micro-organ wells containing cells residing in microscopic e xtracellular matrices and/or scaffolds, the shapes and compositions o f which enable replication of the corresponding in vivo cell assembl ies and flows.

Numerical simulation of a shear-thinning fluid through packed spheres

NASA Astrophysics Data System (ADS)

Liu, Hai Long; Moon, Jong Sin; Hwang, Wook Ryol

2012-12-01

Flow behaviors of a non-Newtonian fluid in spherical microstructures have been studied by a direct numerical simulation. A shear-thinning (power-law) fluid through both regular and randomly packed spheres has been numerically investigated in a representative unit cell with the tri-periodic boundary condition, employing a rigorous three-dimensional finite-element scheme combined with fictitious-domain mortar-element methods. The present scheme has been validated for the classical spherical packing problems with literatures. The flow mobility of regular packing structures, including simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC), as well as randomly packed spheres, has been investigated quantitatively by considering the amount of shear-thinning, the pressure gradient and the porosity as parameters. Furthermore, the mechanism leading to the main flow path in a highly shear-thinning fluid through randomly packed spheres has been discussed.

F-actin and microtubule suspensions as indeterminate fluids.

PubMed

Buxbaum, R E; Dennerll, T; Weiss, S; Heidemann, S R

1987-03-20

The viscosity of F-actin and microtubule suspensions has been measured as a function of shear rate with a Weissenberg rheogoniometer. At shear rates of less than 1.0 per second the viscosity of suspensions of these two structural proteins is inversely proportional to shear rate. These results are consistent with previous in vivo measurements of the viscosity of cytoplasm. This power law implies that shear stress is independent of shear rate; that is, shear stress is a constant at all shear rates less than 1.0 per second. Thus the flow profile of these fluids is indeterminate, or nearly so. This flow property may explain several aspects of intracellular motility in living cells. Possible explanations for this flow property are based on a recent model for semidilute suspensions of rigid rods or a classical friction model for liquid crystals.

Turbulent Flow and Sand Dune Dynamics: Identifying Controls on Aeolian Sediment Transport

NASA Astrophysics Data System (ADS)

Weaver, C. M.; Wiggs, G.

2007-12-01

Sediment transport models are founded on cubic power relationships between the transport rate and time averaged flow parameters. These models have achieved limited success and recent aeolian and fluvial research has focused on the modelling and measurement of sediment transport by temporally varying flow conditions. Studies have recognised turbulence as a driving force in sediment transport and have highlighted the importance of coherent flow structures in sediment transport systems. However, the exact mechanisms are still unclear. Furthermore, research in the fluvial environment has identified the significance of turbulent structures for bedform morphology and spacing. However, equivalent research in the aeolian domain is absent. This paper reports the findings of research carried out to characterise the importance of turbulent flow parameters in aeolian sediment transport and determine how turbulent energy and turbulent structures change in response to dune morphology. The relative importance of mean and turbulent wind parameters on aeolian sediment flux was examined in the Skeleton Coast, Namibia. Measurements of wind velocity (using sonic anemometers) and sand transport (using grain impact sensors) at a sampling frequency of 10 Hz were made across a flat surface and along transects on a 9 m high barchan dune. Mean wind parameters and mass sand flux were measured using cup anemometers and wedge-shaped sand traps respectively. Vertical profile data from the sonic anemometers were used to compute turbulence and turbulent stress (Reynolds stress; instantaneous horizontal and vertical fluctuations; coherent flow structures) and their relationship with respect to sand transport and evolving dune morphology. On the flat surface time-averaged parameters generally fail to characterise sand transport dynamics, particularly as the averaging interval is reduced. However, horizontal wind speed correlates well with sand transport even with short averaging times. Quadrant analysis revealed that turbulent events with a positive horizontal component, such as sweeps and outward interactions, were responsible for the majority of sand transport. On the dune surface results demonstrate the development and modification of turbulence and sediment flux in key regions: toe, crest and brink. Analysis suggests that these modifications are directly controlled by streamline curvature and flow acceleration. Conflicting models of dune development, morphology and stability arise when based upon either the dynamics of measured turbulent flow or mean flow.

Debris Flow Process and Climate Controls on Steepland Valley Form and Evolution

NASA Astrophysics Data System (ADS)

Struble, W.; Roering, J. J.

2017-12-01

In unglaciated mountain ranges, steepland bedrock valleys often dominate relief structure and dictate landscape response to perturbations in tectonics or climate; drainage divides have been shown to be dynamic and drainage capture is common. Landscape evolution models often use the stream power model to simulate morphologic changes, but steepland valley networks exhibit trends that deviate from predictions of this model. The prevalence of debris flows in steep channels has motivated approaches that account for commonly observed curvature of slope-area data at small drainage areas. Debris flow deposits correspond with observed curvature in slope-area data, wherein slope increases slowly as drainage area decreases; debris flow incision is implied upstream of deposits. In addition, shallow landslides and in-channel sediment entrainment in humid and arid regions, respectively, have been identified as likely debris flow triggering mechanisms, but the extent to which they set the slope of steep channels is unclear. While an untested model exists for humid landscape debris flows, field observations and models are lacking for regions with lower mean annual precipitation. The Oregon Coastal Ranges are an ideal humid setting for observing how shallow landslide-initiated debris flows abrade channel beds and/or drive exposure-driven weathering. Preliminary field observations in the Lost River Range and the eastern Sierra Nevada - semi-arid and unglaciated environments - suggest that debris flows are pervasive in steep reaches. Evidence for fluvial incision is lacking and the presence of downstream debris flow deposits and a curved morphologic signature in slope-area space suggests stream power models are insufficient for predicting and interpreting landscape dynamics. Investigation of debris flow processes in both humid and arid sites such as these seeks to identify the linkage between sediment transport and the characteristic form of steepland valleys. Bedrock weathering, fracture density, recurrence interval, bulking, and grain size may determine process-form linkages in humid and arid settings. Evaluation of debris flow processes in sites of varying climate presents the opportunity to quantify the role of debris flow incision in the evolution of steepland valleys and improve landscape evolution models.

Divergence instability of pipes conveying fluid with uncertain flow velocity

NASA Astrophysics Data System (ADS)

Rahmati, Mehdi; Mirdamadi, Hamid Reza; Goli, Sareh

2018-02-01

This article deals with investigation of probabilistic stability of pipes conveying fluid with stochastic flow velocity in time domain. As a matter of fact, this study has focused on the randomness effects of flow velocity on stability of pipes conveying fluid while most of research efforts have only focused on the influences of deterministic parameters on the system stability. The Euler-Bernoulli beam and plug flow theory are employed to model pipe structure and internal flow, respectively. In addition, flow velocity is considered as a stationary random process with Gaussian distribution. Afterwards, the stochastic averaging method and Routh's stability criterion are used so as to investigate the stability conditions of system. Consequently, the effects of boundary conditions, viscoelastic damping, mass ratio, and elastic foundation on the stability regions are discussed. Results delineate that the critical mean flow velocity decreases by increasing power spectral density (PSD) of the random velocity. Moreover, by increasing PSD from zero, the type effects of boundary condition and presence of elastic foundation are diminished, while the influences of viscoelastic damping and mass ratio could increase. Finally, to have a more applicable study, regression analysis is utilized to develop design equations and facilitate further analyses for design purposes.

Velocity Profile measurements in two-phase flow using multi-wave sensors

NASA Astrophysics Data System (ADS)

Biddinika, M. K.; Ito, D.; Takahashi, H.; Kikura, H.; Aritomi, M.

2009-02-01

Two-phase flow has been recognized as one of the most important phenomena in fluid dynamics. In addition, gas-liquid two-phase flow appears in various industrial fields such as chemical industries and power generations. In order to clarify the flow structure, some flow parameters have been measured by using many effective measurement techniques. The velocity profile as one of the important flow parameter, has been measured by using ultrasonic velocity profile (UVP) technique. This technique can measure velocity distributions along a measuring line, which is a beam formed by pulse ultrasounds. Furthermore, a multi-wave sensor can measure the velocity profiles of both gas and liquid phase using UVP method. In this study, two types of multi-wave sensors are used. A sensor has cylindrical shape, and another one has square shape. The piezoelectric elements of each sensor have basic frequencies of 8 MHz for liquid phase and 2 MHz for gas phase, separately. The velocity profiles of air-water bubbly flow in a vertical rectangular channel were measured by using these multi-wave sensors, and the validation of the measuring accuracy was performed by the comparison between the velocity profiles measured by two multi-wave sensors.

Experimental investigation of the draft tube inlet flow of a bulb turbine

NASA Astrophysics Data System (ADS)

Vuillemard, J.; Aeschlimann, V.; Fraser, R.; Lemay, S.; Deschênes, C.

2014-03-01

In the BulbT project framework, a bulb turbine model was studied with a strongly diverging draft tube. At high discharge, flow separation occurs in the draft tube correlated to significant efficiency and power drops. In this context, a focus was put on the draft tube inlet flow conditions. Actually, a precise inlet flow velocity field is required for comparison and validation purposes with CFD simulation. This paper presents different laser Doppler velocimetry (LDV) measurements at the draft tube inlet and their analysis. The LDV was setup to measure the axial and circumferential velocity on a radius under the runner and a diameter under the hub. A method was developed to perform indirect measurement of the mean radial velocity component. Five operating conditions were studied to correlate the inlet flow to the separation in the draft tube. Mean velocities, fluctuations and frequencies allowed characterizing the flow. Using this experimental database, the flow structure was characterized. Phase averaged velocities based on the runner position allowed detecting the runner blade wakes. The velocity gradients induced by the blade tip vortices were captured. The guide vane wakes was also detected at the draft tube inlet. The recirculation in the hub wake was observed.

Imaging the 3D flow around swimming Chlamydomonas reinhardtii using digital inline holographic microscopy

NASA Astrophysics Data System (ADS)

Welch, Kyle; Kumar, Santosh; Hong, Jiarong; Cheng, Xiang

2017-11-01

Understanding the 3D flow induced by microswimmers is paramount to revealing how they interact with each other and their environment. While many studies have measured 2D projections of flow fields around single microorganisms, reliable 3D measurement remains elusive due to the difficulty in imaging fast 3D fluid flows at submicron spatial and millisecond temporal scales. Here, we present a precision measurement of the 3D flow field induced by motile planktonic algae cells, Chlamydomonas reinhardtii. We manually capture and hold stationary a single alga using a micropipette, while still allowing it to beat its flagella in the breastroke pattern characteristic to C. reinhardtii. The 3D flow field around the alga is then tracked by employing fast holographic imaging on 1 um tracer particles, which leads to a spatial resolution of 100 nm along the optical axis and 40 nm in the imaging plane normal to the optical axis. We image the flow around a single alga continuously through thousands of flagellar beat cycles and aggregate that data into a complete 3D flow field. Our study demonstrates the power of holography in imaging fast complex microscopic flow structures and provides crucial information for understanding the detailed locomotion of swimming microorganisms.

Simulation and Experimental Study of Bipolar Plate on the Performance PEM Fuel cell

NASA Astrophysics Data System (ADS)

Chinnasa, Pornchai; Khamsuk, Pattama; Seechalee, Sarunya; Swatsitang, Ekaphan

2017-09-01

This research is a simulated and experimental study on effects of bipolar electrodes of a PEM fuel cell on its power conversion efficiency. The PEM fuel cell structure consists of bipolar electrodes, proton exchange membrane with catalysts, flow channels of gases. This research used fuel cell of 49 cm2 in active area as a research sample and the Comsol 4.4 was employed to simulate flow channels which are serpentine pattern for anode and parallel pattern for cathode. The parameters used were calculated effects of such parameters using Comsol 4.4. After the calculation has been completed, the prototype of the PEM fuel cell were fabricated using graphite plate as electrodes which had the channel height of 0.20 cm, proton exchange membrane using carbon-platinum catalyst. Finally, further it was found that the effect of temperature on the power conversion efficiency is not severely. And for anode, the concentration of hydrogen gas was reduced 64 wt% due to the reaction whereas in parallel channel of cathode the oxygen concentration was reduced by only 6 wt% from 23 wt% at the entrance to 17 wt% at the end. The maximum power output of the prototype operated under such condition was 0.28 W/cm2 calculated from maximum power output voltage (Vmp) of 0.70 V and maximum power output current density of 0.42 A/cm2 which was in good agreement with that simulated using Comsol 4.4 which revealed the power output of 0.29 W/cm2.

AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XXI, MICHIGAN/CLARK TRANSMISSION--COMPLETE POWER TRAIN.

ERIC Educational Resources Information Center

Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

THIS MOSULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF A SPECIFIC POWER TRAIN SYSTEM USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE EXAMINING THE POWER FLOW, UNIT OIL FLOW, AND OIL PRESSURE IN THE CONVERTER AND TRANSMISSION SYSTEM. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL PROGRAM TRAINING FILM "UNDERSTANDING THE…

Wind tunnel study of the wind turbine interaction with a boundary-layer flow: Upwind region, turbine performance, and wake region

NASA Astrophysics Data System (ADS)

Bastankhah, M.; Porté-Agel, F.

2017-06-01

Comprehensive wind tunnel experiments were carried out to study the interaction of a turbulent boundary layer with a wind turbine operating under different tip-speed ratios and yaw angles. Force and power measurements were performed to characterize the variation of thrust force (both magnitude and direction) and generated power of the wind turbine under different operating conditions. Moreover, flow measurements, collected using high-resolution particle-image velocimetry as well as hot-wire anemometry, were employed to systematically study the flow in the upwind, near-wake, and far-wake regions. These measurements provide new insights into the effect of turbine operating conditions on flow characteristics in these regions. For the upwind region, the results show a strong lateral asymmetry under yawed conditions. For the near-wake region, the evolution of tip and root vortices was studied with the use of both instantaneous and phase-averaged vorticity fields. The results suggest that the vortex breakdown position cannot be determined based on phase-averaged statistics, particularly for tip vortices under turbulent inflow conditions. Moreover, the measurements in the near-wake region indicate a complex velocity distribution with a speed-up region in the wake center, especially for higher tip-speed ratios. In order to elucidate the meandering tendency of far wakes, particular focus was placed on studying the characteristics of large turbulent structures in the boundary layer and their interaction with wind turbines. Although these structures are elongated in the streamwise direction, their cross sections are found to have a size comparable to the rotor area, so that they can be affected by the presence of the turbine. In addition, the study of spatial coherence in turbine wakes reveals that any statistics based on streamwise velocity fluctuations cannot provide reliable information about the size of large turbulent structures in turbine wakes due to the effect of wake meandering. The results also suggest that the magnitude of wake meandering does not depend on turbine-operating conditions. Finally, the suitability of the proper orthogonal decomposition for studying wake meandering is examined.

78 FR 58301 - Go With the Flow Hydro Power, LLC; Notice of Preliminary Permit Application Accepted for Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-23

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 14538-000] Go With the Flow..., Motions To Intervene, and Competing Applications On July 22, 2013, Go with the Flow Hydro Power, LLC...), proposing to study the feasibility of the Go with the Flow Hydroelectric Project (project) to be located on...

The Evolution of the Large-Scale ISM: Bubbles, Superbubbles and Non-Equilibrium Ionization

NASA Astrophysics Data System (ADS)

de Avillez, M. A.; Breitschwerdt, D.

2010-12-01

The ISM, powered by SNe, is turbulent and permeated by a magnetic field (with a mean and a turbulent component). It constitutes a frothy medium that is mostly out of equilibrium and is ram pressure dominated on most of the temperature ranges, except for T < 200 K and T > 106K, where magnetic and thermal pressures dominate, respectively. Such lack of equilibrium is also imposed by the feedback of the radiative processes into the ISM flow. Many models of the ISM or isolated phenomena, such as bubbles, superbubbles, clouds evolution, etc., take for granted that the flow is in the so-called collisional ionization equilibrium (CIE). However, recombination time scales of most of the ions below 106 K are longer than the cooling time scale. This implies that the recombination lags behind and the plasma is overionized while it cools. As a consequence cooling deviates from CIE. This has severe implications on the evolution of the ISM flow and its ionization structure. Here, besides reviewing several models of the ISM, including bubbles and superbubbles, the validity of the CIE approximation is discussed, and a presentation of recent developments in modeling the ISM by taking into account the time-dependent ionization structure of the flow in a full-blown numerical 3D high resolution simulation is presented.

Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications

PubMed Central

Ward, Jonathan M.; Yang, Yong; Nic Chormaic, Síle

2016-01-01

We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated. PMID:27121151

Precision control of high temperature furnaces using an auxiliary power supply and charged particle current flow

DOEpatents

Pollock, G.G.

1997-01-28

Two power supplies are combined to control a furnace. A main power supply heats the furnace in the traditional manner, while the power from the auxiliary supply is introduced as a current flow through charged particles existing due to ionized gas or thermionic emission. The main power supply provides the bulk heating power and the auxiliary supply provides a precise and fast power source such that the precision of the total power delivered to the furnace is improved. 5 figs.

Assessment of Power Potential of Tidal Currents and Impacts of Power Extraction on Flow Speeds in Indonesia

NASA Astrophysics Data System (ADS)

Orhan, K.; Mayerle, R.

2016-12-01

A methodology comprising of the estimates of power yield, evaluation of the effects of power extraction on flow conditions, and near-field investigations to deliver wake characteritics, recovery and interactions is described and applied to several straits in Indonesia. Site selection is done with high-resolution, three-dimensional flow models providing sufficient spatiotemporal coverage. Much attention has been given to the meteorological forcing, and conditions at the open sea boundaries to adequately capture the density gradients and flow fields. Model verification using tidal records shows excellent agreement. Sites with adequate depth for the energy conversion using horizontal axis tidal turbines, average kinetic power density greater than 0.5 kW/m2, and surface area larger than 0.5km2 are defined as energy hotspots. Spatial variation of the average extractable electric power is determined, and annual tidal energy resource is estimated for the straits in question. The results showed that the potential for tidal power generation in Indonesia is likely to exceed previous predictions reaching around 4,800MW. To assess the impact of the devices, flexible mesh models with higher resolutions have been developed. Effects on flow conditions, and near-field turbine wakes are resolved in greater detail with triangular horizontal grids. The energy is assumed to be removed uniformly by sub-grid scale arrays of turbines, and calculations are made based on velocities at the hub heights of the devices. An additional drag force resulting in dissipation of the pre-existing kinetic power from %10 to %60 within a flow cross-section is introduced to capture the impacts. It was found that the effect of power extraction on water levels and flow speeds in adjacent areas is not significant. Results show the effectivess of the method to capture wake characteritics and recovery reasonably well with low computational cost.

Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part II: programmed operation.

PubMed

Williams, P Stephen

2017-01-01

Asymmetrical flow field-flow fractionation (As-FlFFF) is a widely used technique for analyzing polydisperse nanoparticle and macromolecular samples. The programmed decay of cross flow rate is often employed. The interdependence of the cross flow rate through the membrane and the fluid flow along the channel length complicates the prediction of elution time and fractionating power. The theory for their calculation is presented. It is also confirmed for examples of exponential decay of cross flow rate with constant channel outlet flow rate that the residual sample polydispersity at the channel outlet is quite well approximated by the reciprocal of four times the fractionating power. Residual polydispersity is of importance when online MALS or DLS detection are used to extract quantitative information on particle size or molecular weight. The theory presented here provides a firm basis for the optimization of programmed flow conditions in As-FlFFF. Graphical abstract Channel outlet polydispersity remains significant following fractionation by As-FlFFF under conditions of programmed decay of cross flow rate.

Non-Newtonian fluid flow in 2D fracture networks

NASA Astrophysics Data System (ADS)

Zou, L.; Håkansson, U.; Cvetkovic, V.

2017-12-01

Modeling of non-Newtonian fluid (e.g., drilling fluids and cement grouts) flow in fractured rocks is of interest in many geophysical and industrial practices, such as drilling operations, enhanced oil recovery and rock grouting. In fractured rock masses, the flow paths are dominated by fractures, which are often represented as discrete fracture networks (DFN). In the literature, many studies have been devoted to Newtonian fluid (e.g., groundwater) flow in fractured rock using the DFN concept, but few works are dedicated to non-Newtonian fluids.In this study, a generalized flow equation for common non-Newtonian fluids (such as Bingham, power-law and Herschel-Bulkley) in a single fracture is obtained from the analytical solutions for non-Newtonian fluid discharge between smooth parallel plates. Using Monte Carlo sampling based on site characterization data for the distribution of geometrical features (e.g., density, length, aperture and orientations) in crystalline fractured rock, a two dimensional (2D) DFN model is constructed for generic flow simulations. Due to complex properties of non-Newtonian fluids, the relationship between fluid discharge and the pressure gradient is nonlinear. A Galerkin finite element method solver is developed to iteratively solve the obtained nonlinear governing equations for the 2D DFN model. Using DFN realizations, simulation results for different geometrical distributions of the fracture network and different non-Newtonian fluid properties are presented to illustrate the spatial discharge distributions. The impact of geometrical structures and the fluid properties on the non-Newtonian fluid flow in 2D DFN is examined statistically. The results generally show that modeling non-Newtonian fluid flow in fractured rock as a DFN is feasible, and that the discharge distribution may be significantly affected by the geometrical structures as well as by the fluid constitutive properties.

CFD research on runaway transient of pumped storage power station caused by pumping power failure

NASA Astrophysics Data System (ADS)

Zhang, L. G.; Zhou, D. Q.

2013-12-01

To study runaway transient of pumped storage power station caused by pumping power failure, three dimensional unsteady numerical simulations were executed on geometrical model of the whole flow system. Through numerical calculation, the changeable flow configuration and variation law of some parameters such as unit rotate speed,flow rate and static pressure of measurement points were obtained and compared with experimental data. Numerical results show that runaway speed agrees well with experimental date and its error was 3.7%. The unit undergoes pump condition, brake condition, turbine condition and runaway condition with flow characteristic changing violently. In runaway condition, static pressure in passage pulses very strongly which frequency is related to runaway speed.

Panel acoustic contribution analysis.

PubMed

Wu, Sean F; Natarajan, Logesh Kumar

2013-02-01

Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated.

Mantle plumes - A boundary layer approach for Newtonian and non-Newtonian temperature-dependent rheologies. [modeling for island chains and oceanic aseismic ridges

NASA Technical Reports Server (NTRS)

Yuen, D. A.; Schubert, G.

1976-01-01

Stress is placed on the temperature dependence of both a linear Newtonian rheology and a nonlinear olivine rheology in accounting for narrow mantle flow structures. The boundary-layer theory developed incorporates an arbitrary temperature-dependent power-law rheology for the medium, in order to facilitate the study of mantle plume dynamics under real conditions. Thermal, kinematic, and dynamic structures of mantle plumes are modelled by a two-dimensional natural-convection boundary layer rising in a fluid with a temperature-dependent power-law relationship between shear stress and strain rate. An analytic similarity solution is arrived at for upwelling adjacent to a vertical isothermal stress-free plane. Newtonian creep as a deformation mechanism, thermal anomalies resulting from chemical heterogeneity, the behavior of plumes in non-Newtonian (olivine) mantles, and differences in the dynamics of wet and dry olivine are discussed.

Research and investigation of a communication chain on optical fiber with a Fabry-Perot power diode for the automotive industry

NASA Astrophysics Data System (ADS)

Bacis, Irina Bristena; Vasile, Alexandru; Ionescu, Ciprian; Marghescu, Cristina

2016-12-01

The purpose of this paper is to analyze different power devices - emitters of optical flow, from the point of view of optical coupling, emitted optical powers, optical fiber losses and receiver. The research and characterization of the transmission through a power optical system is done using a computer system specialized for the automotive industry. This system/platform can deliver current pulses that are controlled by a computer through a software (it is possible to set different parameters such as pulse repetition frequency, duty cycle, and current intensity). For the experiments a power Fabry Perot 1035 laser diode operating in pulse with μφ 1055 nm, Ith = 40 mA, and Iop =750 mA was used with a single-mode SFM 128 optical fiber and an EM type optical coupler connected through alignment. Two types of measurements were conducted to demonstrate the usefulness of the experimental structure. In the first case the amplitude of the voltage pulses was measured at the output of an optical detector with receiving diode in a built-in amplifier with a 50 kΩ load resistance. In the second stage measurements were conducted to determine the optical power injected in the optical fiber and received at the reception cell of a power meter. Another parameter of optical coupling that can be measured using the experimental structure is irradiation. This parameter is very important to determine the optimum cutting angle of the fiber for continuity welding.

Power flow control based solely on slow feedback loop for heart pump applications.

PubMed

Wang, Bob; Hu, Aiguo Patrick; Budgett, David

2012-06-01

This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz.

Flow induced/ refined solution crystallization of a semiconducting polymer

NASA Astrophysics Data System (ADS)

Nguyen, Ngoc A.

Organic photovoltaics, a new generation of solar cells, has gained scientific and economic interests due to the ability of solution-processing and potentially low-cost power production. Though, the low power conversion efficiency of organic/ plastic solar cells is one of the most pertinent challenges that has appealed to research communities from many different fields including materials science and engineering, electrical engineering, chemical engineering, physics and chemistry. This thesis focuses on investigating and controlling the morphology of a semi-conducting, semi-crystalline polymer formed under shear-flow. Molecular structures and processing techniques are critical factors that significantly affect the morphology formation in the plastic solar cells, thus influencing device performance. In this study, flow-induced solution crystallization of poly (3-hexylthiophene) (P3HT) in a poor solvent, 2-ethylnapthalene (2-EN) was utilized to make a paint-like, structural liquid. The polymer crystals observed in this structured paint are micrometers long, nanometers in cross section and have a structure similar to that formed under quiescent conditions. There is pi-pi stacking order along the fibril axis, while polymer chain folding occurs along the fibril width and the order of the side-chain stacking is along fibril height. It was revealed that shear-flow not only induces P3HT crystallization from solution, but also refines and perfects the P3HT crystals. Thus, a general strategy to refine the semiconducting polymer crystals from solution under shear-flow has been developed and employed by simply tuning the processing (shearing) conditions with respect to the dissolution temperature of P3HT in 2-EN. The experimental results demonstrated that shear removes defects and allows more perfect crystals to be formed. There is no glass transition temperature observed in the crystals formed using the flow-induced crystallization indicating a significantly different morphology formation in comparison to that of the pristine (as-received) P3HT. As a result, single P3HT crystals with high surface energy chain folds were analyzed and determined. Previous reported results of infinite melting enthalpy of extended chain P3HT crystals are much higher than the result discovered in this study. The findings in this study revealed that the infinite melting enthalpy of chain-folded P3HT crystals is considerably decreased due to the presence of this P3HT chain-folded surface energy. In this study, the kinetics and mechanism of P3HT crystallization under shear-flow was thoroughly investigated as well. A homogeneous nucleation of P3HT was observed that allows one dimensional fibril crystal growth. The micrometer long P3HT crystals are formed and limited by the contact time between the P3HT molecules. Furthermore, it was found that phenyl-C61-butyric acid methyl ester (PCBM) nanoparticles inhibit the crystallization of P3HT under shear. However, the shear-flow leads to nanophase agglomeration of PCBM and creates percolation of P3HT fibril crystal networks and the PCBM phase separated domains that apparently present better pathways for transporting electrons and holes. Interestingly, the structured liquid was simply applied onto substrates with a paintbrush resulting in similar device performance to those made with current techniques in which the morphology is commonly formed during application or post-processing steps. These detailed findings are given and discussed in the thesis.

Decision-making in irrigation networks: Selecting appropriate canal structures using multi-attribute decision analysis.

PubMed

Hosseinzade, Zeinab; Pagsuyoin, Sheree A; Ponnambalam, Kumaraswamy; Monem, Mohammad J

2017-12-01

The stiff competition for water between agriculture and non-agricultural production sectors makes it necessary to have effective management of irrigation networks in farms. However, the process of selecting flow control structures in irrigation networks is highly complex and involves different levels of decision makers. In this paper, we apply multi-attribute decision making (MADM) methodology to develop a decision analysis (DA) framework for evaluating, ranking and selecting check and intake structures for irrigation canals. The DA framework consists of identifying relevant attributes for canal structures, developing a robust scoring system for alternatives, identifying a procedure for data quality control, and identifying a MADM model for the decision analysis. An application is illustrated through an analysis for automation purposes of the Qazvin irrigation network, one of the oldest and most complex irrigation networks in Iran. A survey questionnaire designed based on the decision framework was distributed to experts, managers, and operators of the Qazvin network and to experts from the Ministry of Power in Iran. Five check structures and four intake structures were evaluated. A decision matrix was generated from the average scores collected from the survey, and was subsequently solved using TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) method. To identify the most critical structure attributes for the selection process, optimal attribute weights were calculated using Entropy method. For check structures, results show that the duckbill weir is the preferred structure while the pivot weir is the least preferred. Use of the duckbill weir can potentially address the problem with existing Amil gates where manual intervention is required to regulate water levels during periods of flow extremes. For intake structures, the Neyrpic® gate and constant head orifice are the most and least preferred alternatives, respectively. Some advantages of the Neyrpic® gate are ease of operation and capacity to measure discharge flows. Overall, the application to the Qazvin irrigation network demonstrates the utility of the proposed DA framework in selecting appropriate structures for regulating water flows in irrigation canals. This framework systematically aids the decision process by capturing decisions made at various levels (individual farmers to high-level management). It can be applied to other cases where a new irrigation network is being designed, or where changes in irrigation structures need to be identified to improve flow control in existing networks. Copyright © 2017 Elsevier B.V. All rights reserved.

What Supergranule Flow Models Tell Us About the Sun's Surface Shear Layer and Magnetic Flux Transport

NASA Technical Reports Server (NTRS)

Hathaway, David

2011-01-01

Models of the photospheric flows due to supergranulation are generated using an evolving spectrum of vector spherical harmonics up to spherical harmonic wavenumber l1500. Doppler velocity data generated from these models are compared to direct Doppler observations from SOHO/MDI and SDO/HMI. The models are adjusted to match the observed spatial power spectrum as well as the wavenumber dependence of the cell lifetimes, differential rotation velocities, meridional flow velocities, and relative strength of radial vs. horizontal flows. The equatorial rotation rate as a function of wavelength matches the rotation rate as a function of depth as determined by global helioseismology. This leads to the conclusions that the cellular structures are anchored at depths equal to their widths, that the surface shear layer extends to at least 70 degrees latitude, and that the poleward meridional flow decreases in amplitude and reverses direction at the base of the surface shear layer (approx.35 Mm below the surface). Using the modeled flows to passively transport magnetic flux indicates that the observed differential rotation and meridional flow of the magnetic elements are directly related to the differential rotation and meridional flow of the convective pattern itself. The magnetic elements are transported by the evolving boundaries of the supergranule pattern (where the convective flows converge) and are unaffected by the weaker flows associated with the differential rotation or meridional flow of the photospheric plasma.

Computing the Feasible Spaces of Optimal Power Flow Problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molzahn, Daniel K.

The solution to an optimal power flow (OPF) problem provides a minimum cost operating point for an electric power system. The performance of OPF solution techniques strongly depends on the problem’s feasible space. This paper presents an algorithm that is guaranteed to compute the entire feasible spaces of small OPF problems to within a specified discretization tolerance. Specifically, the feasible space is computed by discretizing certain of the OPF problem’s inequality constraints to obtain a set of power flow equations. All solutions to the power flow equations at each discretization point are obtained using the Numerical Polynomial Homotopy Continuation (NPHC)more » algorithm. To improve computational tractability, “bound tightening” and “grid pruning” algorithms use convex relaxations to preclude consideration of many discretization points that are infeasible for the OPF problem. Here, the proposed algorithm is used to generate the feasible spaces of two small test cases.« less

Computing the Feasible Spaces of Optimal Power Flow Problems

DOE PAGES

Molzahn, Daniel K.

2017-03-15

The solution to an optimal power flow (OPF) problem provides a minimum cost operating point for an electric power system. The performance of OPF solution techniques strongly depends on the problem’s feasible space. This paper presents an algorithm that is guaranteed to compute the entire feasible spaces of small OPF problems to within a specified discretization tolerance. Specifically, the feasible space is computed by discretizing certain of the OPF problem’s inequality constraints to obtain a set of power flow equations. All solutions to the power flow equations at each discretization point are obtained using the Numerical Polynomial Homotopy Continuation (NPHC)more » algorithm. To improve computational tractability, “bound tightening” and “grid pruning” algorithms use convex relaxations to preclude consideration of many discretization points that are infeasible for the OPF problem. Here, the proposed algorithm is used to generate the feasible spaces of two small test cases.« less

Pressure and heat-transfer distributions in a simulated wing-elevon cove with variable leakage at a free-stream Mach number of 6.9

NASA Technical Reports Server (NTRS)

Deveikis, W. D.; Bartlett, W.

1978-01-01

An experimental aerodynamic heating investigation was conducted to determine effects of hot boundary-layer ingestion into the cove on the windward surface between a wing and elevon for cove seal leak areas nominally between 0 and 100 percent of cove entrance area. Pressure and heating-rate distributions were obtained on the wing and elevon surfaces and on the cove walls of a full-scale model that represented a section of the cove region on the space shuttle orbiter. Data were obtained for both attached and separated turbulent boundary layers upstream of the unswept cove entrance. Average free-stream Mach number was 6.9, average free-stream unit Reynolds numbers were 1.31 x 10 to the 6th power and 4.40 x 10 to the 6th power per meter (0.40 x 10 to the 6th power and 1.34 x 10 to the 6th power per foot), and average total temperature was 1888 K (3400 R). Cove pressures and heating rates varied as a function of seal leak area independent of leak aspect ratio. Although cove heating rates for attached flow did not appear intolerable, it was postulated that convective heating in the cove may increase with time. For separated flow, the cove environment was considered too severe for unprotected interior structures of control surfaces.

Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

NASA Astrophysics Data System (ADS)

Mateo, Cherry May R.; Yamazaki, Dai; Kim, Hyungjun; Champathong, Adisorn; Vaze, Jai; Oki, Taikan

2017-10-01

Global-scale river models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representations of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC) is assumed, simulation results deteriorate with finer spatial resolution; Nash-Sutcliffe efficiency coefficients decreased by more than 50 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC) is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions at finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings should be universal and may have significant impacts on large- to global-scale simulations, especially in regions where mega deltas exist.These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

Theoretical Investigation For The Effect of Fuel Quality on Gas Turbine Power Plants

NASA Astrophysics Data System (ADS)

AbdulRazzak khudair, Omar; Alwan Abass, Khetam; Saadi Abed, Noor; Hussain Ali, Khalid; AbdulAziz, Saad; Chlaib Shaboot, Ali

2018-05-01

Gas turbine engine power generation is declined dramatically because of the reduction in thermodynamic parameters as a work of turbine, compressor ratio, compressor work, and air mass flow rate and fuel consumption. There are two main objectives of this work, the first is related with the effect of fuel kinds and their quality on the operation of fuel flow divider and its performance specifically gear pump displacement and fuel flow rate to the combustion chambers of gas power plant. AL-DORA gas turbine power plant 35MW was chosen to predict these effects on its performance MATLAB Software program is used to perform thermodynamic calculations. Fuel distribution stage before the process of combustion and as a result of the kind and its quality, chemical reaction will occur between the fuel and the parts of the gear system of each pump of the flow divider, which causes the erosion of the internal pump wall and the teeth of the gear system, thus hampering the pump operation in terms of fuel discharge. The discharge of fuel form the eight external gates of flow divider is decreased and varied when going to the combustion chambers, so that, flow divider does not give reliable mass flow rate due to absence of accurate pressure in each of eight exit pipes. The second objective deals with the stage of fuel combustion process inside the combustion chamber. A comparative study based upon performance parameters, such as specific fuel consumption for gas and gasoil and power generation. Fuel poor quality causes incomplete combustion and increased its consumption, so that combustion products are interacted with the surface of the turbine blades, causing the erosion and create surface roughness of the blade and disruption of gas flow. As a result of this situation, turbulence flow of these gases will increase causing the separation of gas boundary layers over the suction surface of the blade. Therefore the amount of extracted gas will decrease causing retreat work done by turbine, as a result decline of power and gas turbine power plant efficiency causing the drop in the level of electric generation. The fuel quality is found to be a strong function of specific fuel consumption and its effects on the power generation and the efficiency of the gas turbine power plants and hence, the cycle performance shifts towards favorable conditions.

Oscillatory lower body negative pressure impairs working memory task-related functional hyperemia in healthy volunteers.

PubMed

Merchant, Sana; Medow, Marvin S; Visintainer, Paul; Terilli, Courtney; Stewart, Julian M

2017-04-01

Neurovascular coupling (NVC) describes the link between an increase in task-related neural activity and increased cerebral blood flow denoted "functional hyperemia." We previously showed induced cerebral blood flow oscillations suppressed functional hyperemia; conversely functional hyperemia also suppressed cerebral blood flow oscillations. We used lower body negative pressure (OLBNP) oscillations to force oscillations in middle cerebral artery cerebral blood flow velocity (CBFv). Here, we used N-back testing, an intellectual memory challenge as a neural activation task, to test the hypothesis that OLBNP-induced oscillatory cerebral blood flow can reduce functional hyperemia and NVC produced by a working memory task and can interfere with working memory. We used OLBNP (-30 mmHg) at 0.03, 0.05, and 0.10 Hz and measured spectral power of CBFv at all frequencies. Neither OLBNP nor N-back, alone or combined, affected hemodynamic parameters. 2-Back power and OLBNP individually were compared with 2-back power during OLBNP. 2-Back alone produced a narrow band increase in oscillatory arterial pressure (OAP) and oscillatory cerebral blood flow power centered at 0.0083 Hz. Functional hyperemia in response to 2-back was reduced to near baseline and 2-back memory performance was decreased by 0.03-, 0.05-, and 0.10-Hz OLBNP. OLBNP alone produced increased oscillatory power at frequencies of oscillation not suppressed by added 2-back. However, 2-back preceding OLBNP suppressed OLBNP power. OLBNP-driven oscillatory CBFv blunts NVC and memory performance, while memory task reciprocally interfered with forced CBFv oscillations. This shows that induced cerebral blood flow oscillations suppress functional hyperemia and functional hyperemia suppresses cerebral blood flow oscillations. NEW & NOTEWORTHY We show that induced cerebral blood flow oscillations suppress functional hyperemia produced by a working memory task as well as memory task performance. We conclude that oscillatory cerebral blood flow produces causal reductions of memory task neurovascular coupling and memory task performance. Reductions of functional hyperemia are constrained by autoregulation. Copyright © 2017 the American Physiological Society.

Non-Flow-Through Fuel Cell System Test Results and Demonstration on the SCARAB Rover

NASA Technical Reports Server (NTRS)

Scheidegger, Brianne, T.; Burke, Kenneth A.; Jakupca, Ian J.

2012-01-01

This paper describes the results of the demonstration of a non-flow-through PEM fuel cell as part of a power system on the SCARAB rover. A 16-cell non-flow-through fuel cell stack from Infinity Fuel Cell and Hydrogen, Inc. was incorporated into a power system designed to act as a range extender by providing power to the rover s hotel loads. This work represents the first attempt at a ground demonstration of this new technology aboard a mobile test platform. Development and demonstration were supported by the Office of the Chief Technologist s Space Power Systems Project and the Advanced Exploration System Modular Power Systems Project.

76 FR 35209 - FFP Qualified Hydro 14 LLC; Notice of Intent To File License Application, Filing of Pre...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-16

...: April 4, 2011. d. Submitted by: Free Flow Power Qualified Hydro 14 LLC (Qualified Power 14 LLC), a subsidiary of Free Flow Power Corporation. e. Name of Project: Saylorville Dam Water Power Project. f... County, Iowa. The project would occupy 1.5 acres of United States lands administered by Corps' Rock...

Electrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow conditions

NASA Astrophysics Data System (ADS)

Ren, Lijiao; Ahn, Yongtae; Hou, Huijie; Zhang, Fang; Logan, Bruce E.

2014-07-01

Power production of four hydraulically connected microbial fuel cells (MFCs) was compared with the reactors operated using individual electrical circuits (individual), and when four anodes were wired together and connected to four cathodes all wired together (combined), in fed-batch or continuous flow conditions. Power production under these different conditions could not be made based on a single resistance, but instead required polarization tests to assess individual performance relative to the combined MFCs. Based on the power curves, power produced by the combined MFCs (2.12 ± 0.03 mW, 200 Ω) was the same as the summed power (2.13 mW, 50 Ω) produced by the four individual reactors in fed-batch mode. With continuous flow through the four MFCs, the maximum power (0.59 ± 0.01 mW) produced by the combined MFCs was slightly lower than the summed maximum power of the four individual reactors (0.68 ± 0.02 mW). There was a small parasitic current flow from adjacent anodes and cathodes, but overall performance was relatively unaffected. These findings demonstrate that optimal power production by reactors hydraulically and electrically connected can be predicted from performance by individual reactors.

Predicting Rediated Noise With Power Flow Finite Element Analysis

DTIC Science & Technology

2007-02-01

Defence R&D Canada – Atlantic DEFENCE DÉFENSE & Predicting Rediated Noise With Power Flow Finite Element Analysis D. Brennan T.S. Koko L. Jiang J...PREDICTING RADIATED NOISE WITH POWER FLOW FINITE ELEMENT ANALYSIS D.P. Brennan T.S. Koko L. Jiang J.C. Wallace Martec Limited Martec Limited...model- or full-scale data before it is available for general use. Brennan, D.P., Koko , T.S., Jiang, L., Wallace, J.C. 2007. Predicting Radiated

Flow tests of a single fuel element coolant channel for a compact fast reactor for space power

NASA Technical Reports Server (NTRS)

Springborn, R. H.

1971-01-01

Water flow tests were conducted on a single-fuel-element cooling channel for a nuclear concept to be used for space power. The tests established a method for measuring coolant flow rate which is applicable to water flow testing of a complete mockup of the reference reactor. The inlet plenum-to-outlet plenum pressure drop, which approximates the overall core pressure drop, was measured and correlated with flow rate. This information can be used for reactor coolant flow and heat transfer calculations. An analytical study of the flow characteristics was also conducted.

Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

NASA Astrophysics Data System (ADS)

Kern, J.; Characklis, G. W.

2012-12-01

Conventional hydropower can be turned on and off quicker and less expensively than thermal generation (coal, nuclear, or natural gas). These advantages enable hydropower utilities to respond to rapid fluctuations in energy supply and demand. More recently, a growing renewable energy sector has underlined the need for flexible generation capacity that can complement intermittent renewable resources such as wind power. While wind power entails lower variable costs than other types of generation, incorporating it into electric power systems can be problematic. Due to variable and unpredictable wind speeds, wind power is difficult to schedule and must be used when available. As a result, integrating large amounts of wind power into the grid may result in atypical, swiftly changing demand patterns for other forms of generation, placing a premium on sources that can be rapidly ramped up and down. Moreover, uncertainty in wind power forecasts will stipulate increased levels of 'reserve' generation capacity that can respond quickly if real-time wind supply is less than expected. These changes could create new hourly price dynamics for energy and reserves, altering the short-term financial signals that hydroelectric dam operators use to schedule water releases. Traditionally, hourly stream flow patterns below hydropower dams have corresponded in a very predictable manner to electricity demand, whose primary factors are weather (hourly temperature) and economic activity (workday hours). Wind power integration has the potential to yield more variable, less predictable flows at hydro dams, flows that at times could resemble reciprocal wind patterns. An existing body of research explores the impacts of standard, demand-following hydroelectric dams on downstream ecological flows; but weighing the benefits of increased reliance on wind power against further impacts to ecological flows may be a novel challenge for the environmental community. As a preliminary step in meeting this challenge, the following study was designed to investigate the potential for wind power integration to alter riparian flow regimes below hydroelectric dams. A hydrological model of a three-dam cascade in the Roanoke River basin (Virginia, USA) is interfaced with a simulated electricity market (i.e. a unit commitment problem) representing the Dominion Zone of PJM Interconnection. Incorporating forecasts of electricity demand, hydro capacity and wind availability, a mixed-integer optimization program minimizes the system cost of meeting hourly demand and reserve requirements by means of a diverse generation portfolio (e.g. nuclear, fossil, hydro, and biomass). A secondary 'balancing' energy market is executed if real-time wind generation is less than the day-ahead forecast, calling upon reserved generation resources to meet the supply shortfall. Hydropower release schedules are determined across a range of wind development scenarios (varying wind's fraction of total installed generating capacity, as well as its geographical source region). Flow regimes for each wind development scenario are compared against both historical and simulated flows under current operations (negligible wind power), as well as simulated natural flows (dam removal), in terms of ecologically relevant flow metrics. Results quantify the ability of wind power development to alter within-week stream flows downstream from hydropower dams.

Combustion and Magnetohydrodynamic Processes in Advanced Pulse Detonation Rocket Engines

DTIC Science & Technology

2012-10-01

use of high-order numerical methods can also be a powerful tool in the analysis of such complex flows, but we need to understand the interaction of...computational physics, 43(2):357372, 1981. [47] B. Einfeldt. On godunov-type methods for gas dynamics . SIAM Journal on Numerical Analysis , pages 294...dimensional effects with complex reaction kinetics, the simple one-dimensional detonation structure provides a rich spectrum of dynamical features which are

A Mechanical Power Flow Capability for the Finite Element Code NASTRAN

DTIC Science & Technology

1989-07-01

perimental methods. statistical energy analysis , the finite element method, and a finite element analog-,y using heat conduction equations. Experimental...weights and inertias of the transducers attached to an experimental structure may produce accuracy problems. Statistical energy analysis (SEA) is a...405-422 (1987). 8. Lyon, R.L., Statistical Energy Analysis of Dynamical Sistems, The M.I.T. Press, (1975). 9. Mickol, J.D., and R.J. Bernhard, "An

FOREIGN AFFAIRS: Perspectives on Foreign Affairs Programs and Structures

DTIC Science & Technology

1996-11-01

would end. One participant cited Egypt as a case where large amounts of aid have had negligible effect. Another participant, however, pointed out...within the country, but this has not always been the case . As one participant noted, it has not been within the Secretary of State’s power to direct...particular, Indonesia, Malaysia , Chile, Argentina, and Brazil—private sector trade and capital flows are occurring to support development. It was

Publications | Grid Modernization | NREL

Science.gov Websites

Photovoltaics: Trajectories and Challenges Cover of Efficient Relaxations for Joint Chance Constrained AC Optimal Power Flow publication Efficient Relaxations for Joint Chance Constrained AC Optimal Power Flow

Numerical Investigation of Oxygenated and Deoxygenated Blood Flow through a Tapered Stenosed Arteries in Magnetic Field.

PubMed

Abdollahzadeh Jamalabadi, M Y; Akbari Bidokhti, Amin Ali; Khak Rah, Hamid; Vaezi, Siavash; Hooshmand, Payam

2016-01-01

Current paper is focused on transient modeling of blood flow through a tapered stenosed arteries surrounded a by solenoid under the presence of heat transfer. The oxygenated and deoxygenated blood are considered here by the Newtonian and Non-Newtonian fluid (power law and Carreau-Yasuda) models. The governing equations of bio magnetic fluid flow for an incompressible, laminar, homogeneous, non-Newtonian are solved by finite volume method with SIMPLE algorithm for structured grid. Both magnetization and electric current source terms are well thought-out in momentum and energy equations. The effects of fluid viscosity model, Hartmann number, and magnetic number on wall shear stress, shearing stress at the stenosis throat and maximum temperature of the system are investigated and are optimized. The current study results are in agreement with some of the existing findings in the literature and are useful in thermal and mechanical design of spatially varying magnets to control the drug delivery and biomagnetic fluid flows through tapered arteries.

Nobody knew turbulent transition could be so complicated

NASA Astrophysics Data System (ADS)

Barkley, Dwight

2017-11-01

Explaining the route to turbulence in wall-bounded shear flows has been a long and tortuous journey. After years of missteps, controversies, and uncertainties, we are at last converging on a unified and fascinating picture of transition in flows such as pipes, channels, and ducts. Classically, subcritical transition (such as in a pipe), was thought to imply a discontinuous route to turbulence. We now know that this is not the case - subcritical shear flows may, and often do, exhibit continuous transition. I will discuss recent developments in experiments, simulations, and theory that have established a deep connection between transition in subcritical shear flows and a class of non-equilibrium statistical phase transitions known as directed percolation. From this we understand how to define precise critical points for systems without linear instabilities and how to characterize the onset of turbulence in terms of non-trivial, but universal power laws. I will discuss the physics responsible for the complex turbulent structures ubiquitously observed near transition and end with thoughts on outstanding open questions.

Unsteady flow of a thixotropic or antithixotropic fluid

NASA Astrophysics Data System (ADS)

Wilson, Stephen; Pritchard, David; Croudace, Andrew

2016-11-01

We describe a general formulation of the governing equations for the unsteady, axisymmetric flow of a thixotropic or antithixotropic fluid in a channel of slowly varying width. These equations are equivalent to the equations of classical lubrication theory for a Newtonian fluid, but incorporate the evolving microstructure of the fluid, described in terms of a scalar structure parameter; they extend and generalise the corresponding results for steady, two-dimensional flow obtained recently by Pritchard, Wilson and McArdle. The magnitudes of temporal and advective thixotropic effects are gauged by naturally defined temporal and advective Deborah numbers. To gain insight into the complicated behaviour of the flow, we explore regimes in which these thixotropic effects first appear at first order in powers of the small aspect ratio. We present illustrative analytical and semi-analytical solutions for particular choices of the constitutive and kinetic laws, including a purely viscous Moore-Mewis-Wagner model and a regularised viscoplastic Hou\\vska model. Partly supported by a United Kingdom EPSRC DTA Studentship and Leverhulme Trust Research Fellowship RF-2013-355.

Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

NASA Technical Reports Server (NTRS)

Baum, S. A.; O'Dea, C. P.

1991-01-01

Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

Chemical preconcentrator with integral thermal flow sensor

DOEpatents

Manginell, Ronald P.; Frye-Mason, Gregory C.

2003-01-01

A chemical preconcentrator with integral thermal flow sensor can be used to accurately measure fluid flow rate in a microanalytical system. The thermal flow sensor can be operated in either constant temperature or constant power mode and variants thereof. The chemical preconcentrator with integral thermal flow sensor can be fabricated with the same MEMS technology as the rest of the microanlaytical system. Because of its low heat capacity, low-loss, and small size, the chemical preconcentrator with integral thermal flow sensor is fast and efficient enough to be used in battery-powered, portable microanalytical systems.

A water-powered Energy Harvesting system with Bluetooth Low Energy interface

NASA Astrophysics Data System (ADS)

Kroener, M.; Allinger, K.; Berger, M.; Grether, E.; Wieland, F.; Heller, S.; Woias, P.

2016-11-01

This paper reports the design, and testing of a water turbine generator system for typical flow rates in domestic applications, with an integrated power management and a Bluetooth low energy (BLE) based RF data transmission interface. It is based on a commercially available low cost hydro generator. The generator is built into a housing with optimized reduced fluidic resistance to enable operation with flow rates as low as 6 l/min. The power management combines rectification, buffering, defined start-up, and circuit protection. An MSP430FR5949 microcontroller is used for data acquisition and processing. The data are transmitted via RF, using a Bluegiga BLE112 module in advertisement mode, to a PC where the measured flow rate is stored and displayed. The transmission rate of the wireless sensor node (WSN) is set to 1 Hz if enough power is available, which is the case for flow rates above 5.5 l/min. The electronics power demand is calculated to be 340 μW in average, while the generator is capable of delivering more than 200 mW for flow rates above 15 l/min.

Analysis and Improvement of Aerodynamic Performance of Straight Bladed Vertical Axis Wind Turbines

NASA Astrophysics Data System (ADS)

Ahmadi-Baloutaki, Mojtaba

Vertical axis wind turbines (VAWTs) with straight blades are attractive for their relatively simple structure and aerodynamic performance. Their commercialization, however, still encounters many challenges. A series of studies were conducted in the current research to improve the VAWTs design and enhance their aerodynamic performance. First, an efficient design methodology built on an existing analytical approach is presented to formulate the design parameters influencing a straight bladed-VAWT (SB-VAWT) aerodynamic performance and determine the optimal range of these parameters for prototype construction. This work was followed by a series of studies to collectively investigate the role of external turbulence on the SB-VAWTs operation. The external free-stream turbulence is known as one of the most important factors influencing VAWTs since this type of turbines is mainly considered for urban applications where the wind turbulence is of great significance. Initially, two sets of wind tunnel testing were conducted to study the variation of aerodynamic performance of a SB-VAWT's blade under turbulent flows, in two major stationary configurations, namely two- and three-dimensional flows. Turbulent flows generated in the wind tunnel were quasi-isotropic having uniform mean flow profiles, free of any wind shear effects. Aerodynamic force measurements demonstrated that the free-stream turbulence improves the blade aerodynamic performance in stall and post-stall regions by delaying the stall and increasing the lift-to-drag ratio. After these studies, a SB-VAWT model was tested in the wind tunnel under the same type of turbulent flows. The turbine power output was substantially increased in the presence of the grid turbulence at the same wind speeds, while the increase in turbine power coefficient due to the effect of grid turbulence was small at the same tip speed ratios. The final section presents an experimental study on the aerodynamic interaction of VAWTs in arrays configurations. Under controlled flow conditions in a wind tunnel, the counter-rotating configuration resulted in a slight improvement in the aerodynamic performance of each turbine compared to the isolated installation. Moreover, the counter-rotating pair improved the power generation of a turbine located downstream of the pair substantially.

Optimized open-flow mixing: insights from microbubble streaming

NASA Astrophysics Data System (ADS)

Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

2015-11-01

Microbubble streaming has been developed into a robust and powerful flow actuation technique in microfluidics. Here, we study it as a paradigmatic system for microfluidic mixing under a continuous throughput of fluid (open-flow mixing), providing a systematic optimization of the device parameters in this practically important situation. Focusing on two-dimensional advective stirring (neglecting diffusion), we show through numerical simulation and analytical theory that mixing in steady streaming vortices becomes ineffective beyond a characteristic time scale, necessitating the introduction of unsteadiness. By duty cycling the streaming, such unsteadiness is introduced in a controlled fashion, leading to exponential refinement of the advection structures. The rate of refinement is then optimized for particular parameters of the time modulation, i.e. a particular combination of times for which the streaming is turned ``on'' and ``off''. The optimized protocol can be understood theoretically using the properties of the streaming vortices and the throughput Poiseuille flow. We can thus infer simple design principles for practical open flow micromixing applications, consistent with experiments. Current Address: Mechanical and Aerospace Engineering, Princeton University.

Comparison of Models for Spacer Grid Pressure Loss in Nuclear Fuel Bundles for One and Two-Phase Flows

NASA Astrophysics Data System (ADS)

Maskal, Alan B.

Spacer grids maintain the structural integrity of the fuel rods within fuel bundles of nuclear power plants. They can also improve flow characteristics within the nuclear reactor core. However, spacer grids add reactor coolant pressure losses, which require estimation and engineering into the design. Several mathematical models and computer codes were developed over decades to predict spacer grid pressure loss. Most models use generalized characteristics, measured by older, less precise equipment. The study of OECD/US-NRC BWR Full-Size Fine Mesh Bundle Tests (BFBT) provides updated and detailed experimental single and two-phase results, using technically advanced flow measurements for a wide range of boundary conditions. This thesis compares the predictions from the mathematical models to the BFBT experimental data by utilizing statistical formulae for accuracy and precision. This thesis also analyzes the effects of BFBT flow characteristics on spacer grids. No single model has been identified as valid for all flow conditions. However, some models' predictions perform better than others within a range of flow conditions, based on the accuracy and precision of the models' predictions. This study also demonstrates that pressure and flow quality have a significant effect on two-phase flow spacer grid models' biases.

On the aeroacoustic and flow structures developed on a flat plate with a serrated sawtooth trailing edge

NASA Astrophysics Data System (ADS)

Chong, Tze Pei; Vathylakis, Alexandros

2015-10-01

Results of an experimental study on turbulent flow over a flat plate with a serrated sawtooth trailing edge are presented in this paper. After tripping the boundary layer to become turbulent, the broadband noise sources at the sawtooth serrated trailing edge is studied by several experimental techniques. Broadband noise reduction by the serrated sawtooth trailing edge can be realistically achieved in the flat plate configuration. The variations of wall pressure power spectral density and the spanwise coherence (which relates to the spanwise correlation length) in a sawtooth trailing edge play a minor role in the mechanisms underpinning the reduction of self noise radiation. Conditional-averaging technique was applied in the boundary layer data where a pair of pressure-driven oblique vortical structures near the sawtooth side edges is identified. In the current flat plate configuration, the interaction between the vortical structures and the local turbulent boundary layer results in a redistribution of the momentum transport and turbulent shear stress near the sawtooth side edges as well as the sawtooth tip, thus affecting the efficiency of self noise radiation.

Allocation of Transaction Cost to Market Participants Using an Analytical Method in Deregulated Market

NASA Astrophysics Data System (ADS)

Jeyasankari, S.; Jeslin Drusila Nesamalar, J.; Charles Raja, S.; Venkatesh, P.

2014-04-01

Transmission cost allocation is one of the major challenges in transmission open access faced by the electric power sector. The purpose of this work is to provide an analytical method for allocating transmission transaction cost in deregulated market. This research work provides a usage based transaction cost allocation method based on line-flow impact factor (LIF) which relates the power flow in each line with respect to transacted power for the given transaction. This method provides the impact of line flows without running iterative power flow solution and is well suited for real time applications. The proposed method is compared with the Newton-Raphson (NR) method of cost allocation on sample six bus and practical Indian utility 69 bus systems by considering multilateral transaction.

Automatic-Control System for Safer Brazing

NASA Technical Reports Server (NTRS)

Stein, J. A.; Vanasse, M. A.

1986-01-01

Automatic-control system for radio-frequency (RF) induction brazing of metal tubing reduces probability of operator errors, increases safety, and ensures high-quality brazed joints. Unit combines functions of gas control and electric-power control. Minimizes unnecessary flow of argon gas into work area and prevents electrical shocks from RF terminals. Controller will not allow power to flow from RF generator to brazing head unless work has been firmly attached to head and has actuated micro-switch. Potential shock hazard eliminated. Flow of argon for purging and cooling must be turned on and adjusted before brazing power applied. Provision ensures power not applied prematurely, causing damaged work or poor-quality joints. Controller automatically turns off argon flow at conclusion of brazing so potentially suffocating gas does not accumulate in confined areas.

Developing a Procedure for Segmenting Meshed Heat Networks of Heat Supply Systems without Outflows

NASA Astrophysics Data System (ADS)

Tokarev, V. V.

2018-06-01

The heat supply systems of cities have, as a rule, a ring structure with the possibility of redistributing the flows. Despite the fact that a ring structure is more reliable than a radial one, the operators of heat networks prefer to use them in normal modes according to the scheme without overflows of the heat carrier between the heat mains. With such a scheme, it is easier to adjust the networks and to detect and locate faults in them. The article proposes a formulation of the heat network segmenting problem. The problem is set in terms of optimization with the heat supply system's excessive hydraulic power used as the optimization criterion. The heat supply system computer model has a hierarchically interconnected multilevel structure. Since iterative calculations are only carried out for the level of trunk heat networks, decomposing the entire system into levels allows the dimensionality of the solved subproblems to be reduced by an order of magnitude. An attempt to solve the problem by fully enumerating possible segmentation versions does not seem to be feasible for systems of really existing sizes. The article suggests a procedure for searching rational segmentation of heat supply networks with limiting the search to versions of dividing the system into segments near the flow convergence nodes with subsequent refining of the solution. The refinement is performed in two stages according to the total excess hydraulic power criterion. At the first stage, the loads are redistributed among the sources. After that, the heat networks are divided into independent fragments, and the possibility of increasing the excess hydraulic power in the obtained fragments is checked by shifting the division places inside a fragment. The proposed procedure has been approbated taking as an example a municipal heat supply system involving six heat mains fed from a common source, 24 loops within the feeding mains plane, and more than 5000 consumers. Application of the proposed segmentation procedure made it possible to find a version with required hydraulic power in the heat supply system on 3% less than the one found using the simultaneous segmentation method.

33 CFR 207.310 - Mississippi River at Keokuk, Iowa; operation of power dam by Mississippi River Power Co.

Code of Federal Regulations, 2011 CFR

2011-07-01

... when the natural flow of the Mississippi River is falling or when such natural flow is less than... maintained by the power company, such river and pool gages as may be advisable, and make from time to time...

Application of PSAT to Load Flow Analysis with STATCOM under Load Increase Scenario and Line Contingencies

NASA Astrophysics Data System (ADS)

Telang, Aparna S.; Bedekar, P. P.

2017-09-01

Load flow analysis is the initial and essential step for any power system computation. It is required for choosing better options for power system expansion to meet with ever increasing load demand. Implementation of Flexible AC Transmission System (FACTS) device like STATCOM, in the load flow, which is having fast and very flexible control, is one of the important tasks for power system researchers. This paper presents a simple and systematic approach for steady state power flow calculations with FACTS controller, static synchronous compensator (STATCOM) using command line usage of MATLAB tool-power system analysis toolbox (PSAT). The complexity of MATLAB language programming increases due to incorporation of STATCOM in an existing Newton-Raphson load flow algorithm. Thus, the main contribution of this paper is to show how command line usage of user friendly MATLAB tool, PSAT, can extensively be used for quicker and wider interpretation of the results of load flow with STATCOM. The novelty of this paper lies in the method of applying the load increase pattern, where the active and reactive loads have been changed simultaneously at all the load buses under consideration for creating stressed conditions for load flow analysis with STATCOM. The performance have been evaluated on many standard IEEE test systems and the results for standard IEEE-30 bus system, IEEE-57 bus system, and IEEE-118 bus system are presented.