The Jungle Universe: coupled cosmological models in a Lotka-Volterra framework

NASA Astrophysics Data System (ADS)

Perez, Jérôme; Füzfa, André; Carletti, Timoteo; Mélot, Laurence; Guedezounme, Lazare

2014-06-01

In this paper, we exploit the fact that the dynamics of homogeneous and isotropic Friedmann-Lemaître universes is a special case of generalized Lotka-Volterra system where the competitive species are the barotropic fluids filling the Universe. Without coupling between those fluids, Lotka-Volterra formulation offers a pedagogical and simple way to interpret usual Friedmann-Lemaître cosmological dynamics. A natural and physical coupling between cosmological fluids is proposed which preserves the structure of the dynamical equations. Using the standard tools of Lotka-Volterra dynamics, we obtain the general Lyapunov function of the system when one of the fluids is coupled to dark energy. This provides in a rigorous form a generic asymptotic behavior for cosmic expansion in presence of coupled species, beyond the standard de Sitter, Einstein-de Sitter and Milne cosmologies. Finally, we conjecture that chaos can appear for at least four interacting fluids.

An Innovative Improvement of Engineering Learning System Using Computational Fluid Dynamics Concept

ERIC Educational Resources Information Center

Hung, T. C.; Wang, S. K.; Tai, S. W.; Hung, C. T.

2007-01-01

An innovative concept of an electronic learning system has been established in an attempt to achieve a technology that provides engineering students with an instructive and affordable framework for learning engineering-related courses. This system utilizes an existing Computational Fluid Dynamics (CFD) package, Active Server Pages programming,…

System and method for reducing combustion dynamics in a combustor

DOEpatents

Uhm, Jong Ho; Ziminsky, Willy Steve; Johnson, Thomas Edward; Srinivasan, Shiva; York, William David

2016-11-29

A system for reducing combustion dynamics in a combustor includes an end cap that extends radially across the combustor and includes an upstream surface axially separated from a downstream surface. A combustion chamber is downstream of the end cap, and tubes extend from the upstream surface through the downstream surface. Each tube provides fluid communication through the end cap to the combustion chamber. The system further includes means for reducing combustion dynamics in the combustor. A method for reducing combustion dynamics in a combustor includes flowing a working fluid through tubes that extend axially through an end cap that extends radially across the combustor and obstructing at least a portion of the working fluid flowing through a first set of the tubes.

Comments on Frequency Swept Rotating Input Perturbation Techniques and Identification of the Fluid Force Models in Rotor/bearing/seal Systems and Fluid Handling Machines

NASA Technical Reports Server (NTRS)

Muszynska, Agnes; Bently, Donald E.

1991-01-01

Perturbation techniques used for identification of rotating system dynamic characteristics are described. A comparison between two periodic frequency-swept perturbation methods applied in identification of fluid forces of rotating machines is presented. The description of the fluid force model identified by inputting circular periodic frequency-swept force is given. This model is based on the existence and strength of the circumferential flow, most often generated by the shaft rotation. The application of the fluid force model in rotor dynamic analysis is presented. It is shown that the rotor stability is an entire rotating system property. Some areas for further research are discussed.

Research Summary 3-D Computational Fluid Dynamics (CFD) Model Of The Human Respiratory System

EPA Science Inventory

The U.S. EPA’s Office of Research and Development (ORD) has developed a 3-D computational fluid dynamics (CFD) model of the human respiratory system that allows for the simulation of particulate based contaminant deposition and clearance, while being adaptable for age, ethnicity,...

General dynamical density functional theory for classical fluids.

PubMed

Goddard, Benjamin D; Nold, Andreas; Savva, Nikos; Pavliotis, Grigorios A; Kalliadasis, Serafim

2012-09-21

We study the dynamics of a colloidal fluid including inertia and hydrodynamic interactions, two effects which strongly influence the nonequilibrium properties of the system. We derive a general dynamical density functional theory which shows very good agreement with full Langevin dynamics. In suitable limits, we recover existing dynamical density functional theories and a Navier-Stokes-like equation with additional nonlocal terms.

The fluid dynamics of atmospheric clouds

NASA Astrophysics Data System (ADS)

Randall, David A.

2017-11-01

Clouds of many types are of leading-order importance for Earth's weather and climate. This importance is most often discussed in terms of the effects of clouds on radiative transfer, but the fluid dynamics of clouds are at least equally significant. Some very small-scale cloud fluid-dynamical processes have significant consequences on the global scale. These include viscous dissipation near falling rain drops, and ``buoyancy reversal'' associated with the evaporation of liquid water. Major medium-scale cloud fluid-dynamical processes include cumulus convection and convective aggregation. Planetary-scale processes that depend in an essential way on cloud fluid dynamics include the Madden-Julian Oscillation, which is one of the largest and most consequential weather systems on Earth. I will attempt to give a coherent introductory overview of this broad range of phenomena.

Multidisciplinary Design Optimization Techniques: Implications and Opportunities for Fluid Dynamics Research

NASA Technical Reports Server (NTRS)

Zang, Thomas A.; Green, Lawrence L.

1999-01-01

A challenge for the fluid dynamics community is to adapt to and exploit the trend towards greater multidisciplinary focus in research and technology. The past decade has witnessed substantial growth in the research field of Multidisciplinary Design Optimization (MDO). MDO is a methodology for the design of complex engineering systems and subsystems that coherently exploits the synergism of mutually interacting phenomena. As evidenced by the papers, which appear in the biannual AIAA/USAF/NASA/ISSMO Symposia on Multidisciplinary Analysis and Optimization, the MDO technical community focuses on vehicle and system design issues. This paper provides an overview of the MDO technology field from a fluid dynamics perspective, giving emphasis to suggestions of specific applications of recent MDO technologies that can enhance fluid dynamics research itself across the spectrum, from basic flow physics to full configuration aerodynamics.

Amplification without instability: applying fluid dynamical insights in chemistry and biology

NASA Astrophysics Data System (ADS)

McCoy, Jonathan H.

2013-11-01

While amplification of small perturbations often arises from instability, transient amplification is possible locally even in asymptotically stable systems. That is, knowledge of a system's stability properties can mislead one's intuition for its transient behaviors. This insight, which has an interesting history in fluid dynamics, has more recently been rediscovered in ecology. Surprisingly, many nonlinear fluid dynamical and ecological systems share linear features associated with transient amplification of noise. This paper aims to establish that these features are widespread in many other disciplines concerned with noisy systems, especially chemistry, cell biology and molecular biology. Here, using classic nonlinear systems and the graphical language of network science, we explore how the noise amplification problem can be reframed in terms of activatory and inhibitory interactions between dynamical variables. The interaction patterns considered here are found in a great variety of systems, ranging from autocatalytic reactions and activator-inhibitor systems to influential models of nerve conduction, glycolysis, cell signaling and circadian rhythms.

Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

NASA Technical Reports Server (NTRS)

Groves, Curtis; Ilie, Marcel; Schallhorn, Paul

2014-01-01

Spacecraft components may be damaged due to airflow produced by Environmental Control Systems (ECS). There are uncertainties and errors associated with using Computational Fluid Dynamics (CFD) to predict the flow field around a spacecraft from the ECS System. This paper describes an approach to estimate the uncertainty in using CFD to predict the airflow speeds around an encapsulated spacecraft.

Immersed Boundary Simulations of Active Fluid Droplets

PubMed Central

Hawkins, Rhoda J.

2016-01-01

We present numerical simulations of active fluid droplets immersed in an external fluid in 2-dimensions using an Immersed Boundary method to simulate the fluid droplet interface as a Lagrangian mesh. We present results from two example systems, firstly an active isotropic fluid boundary consisting of particles that can bind and unbind from the interface and generate surface tension gradients through active contractility. Secondly, a droplet filled with an active polar fluid with homeotropic anchoring at the droplet interface. These two systems demonstrate spontaneous symmetry breaking and steady state dynamics resembling cell motility and division and show complex feedback mechanisms with minimal degrees of freedom. The simulations outlined here will be useful for quantifying the wide range of dynamics observable in these active systems and modelling the effects of confinement in a consistent and adaptable way. PMID:27606609

Geophysical Fluid Dynamics Outreach Films

NASA Astrophysics Data System (ADS)

Aurnou, J. M.; Schwarz, J. W.; Noguez, G.

2012-12-01

Here we will present high definition films of laboratory experiments demonstrating basic fluid motions similar to those occurring in atmospheres and oceans. In these experiments, we use water to simulate the fluid dynamics of both the liquid (oceans) and gaseous (atmospheric) envelopes. To simulate the spinning of the earth, we carry out the experiments on a rotating table. For each experiment, we begin by looking at our system first without the effects of rotation. Then, we include rotation to see how the behavior of the fluid changes due to the Coriolis accelerations. Our hope is that by viewing these experiments one will develop a sense for how fluids behave both in rotating and non-rotating systems. By noting the differences between the experiments, it should then be possible to establish a basis to think about large-scale fluid motions that exist in Earth's oceans and atmospheres as well as on planets other than Earth.Plan view image of vortices in a rotating tank of fluid. Movies of such flows make accessible the often difficult to comprehend fluid dynamical processes that occur in planetary atmospheres and oceans.

The Borexino Thermal Monitoring & Management System and simulations of the fluid-dynamics of the Borexino detector under asymmetrical, changing boundary conditions

NASA Astrophysics Data System (ADS)

Bravo-Berguño, D.; Mereu, R.; Cavalcante, P.; Carlini, M.; Ianni, A.; Goretti, A.; Gabriele, F.; Wright, T.; Yokley, Z.; Vogelaar, R. B.; Calaprice, F.; Inzoli, F.

2018-03-01

A comprehensive monitoring system for the thermal environment inside the Borexino neutrino detector was developed and installed in order to reduce uncertainties in determining temperatures throughout the detector. A complementary thermal management system limits undesirable thermal couplings between the environment and Borexino's active sections. This strategy is bringing improved radioactive background conditions to the region of interest for the physics signal thanks to reduced fluid mixing induced in the liquid scintillator. Although fluid-dynamical equilibrium has not yet been fully reached, and thermal fine-tuning is possible, the system has proven extremely effective at stabilizing the detector's thermal conditions while offering precise insights into its mechanisms of internal thermal transport. Furthermore, a Computational Fluid-Dynamics analysis has been performed, based on the empirical measurements provided by the thermal monitoring system, and providing information into present and future thermal trends. A two-dimensional modeling approach was implemented in order to achieve a proper understanding of the thermal and fluid-dynamics in Borexino. It was optimized for different regions and periods of interest, focusing on the most critical effects that were identified as influencing background concentrations. Literature experimental case studies were reproduced to benchmark the method and settings, and a Borexino-specific benchmark was implemented in order to validate the modeling approach for thermal transport. Finally, fully-convective models were applied to understand general and specific fluid motions impacting the detector's Active Volume.

The WCA reference system for four- and five-dimensional Lennard-Jones fluids

NASA Astrophysics Data System (ADS)

Bishop, Marvin

1988-05-01

The WCA reference system is investigated for four- and five-dimensional Lennard-Jones fluids by molecular dynamics simulations. It is found that the WCA prescription for the scaling of the reference system to a hard hypersphere one is a very good approximation in the fluid region.

The nonlinear dynamics of a spacecraft coupled to the vibration of a contained fluid

NASA Technical Reports Server (NTRS)

Peterson, Lee D.; Crawley, Edward F.; Hansman, R. John

1988-01-01

The dynamics of a linear spacecraft mode coupled to a nonlinear low gravity slosh of a fluid in a cylindrical tank is investigated. Coupled, nonlinear equations of motion for the fluid-spacecraft dynamics are derived through an assumed mode Lagrangian method. Unlike linear fluid slosh models, this nonlinear slosh model retains two fundamental slosh modes and three secondary modes. An approximate perturbation solution of the equations of motion indicates that the nonlinear coupled system response involves fluid-spacecraft modal resonances not predicted by either a linear, or a nonlinear, uncoupled slosh analysis. Experimental results substantiate the analytical predictions.

Dynamic behavior of microscale particles controlled by standing bulk acoustic waves

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

Greenhall, J.; Raeymaekers, B., E-mail: bart.raeymaekers@utah.edu; Guevara Vasquez, F.

2014-10-06

We analyze the dynamic behavior of a spherical microparticle submerged in a fluid medium, driven to the node of a standing bulk acoustic wave created by two opposing transducers. We derive the dynamics of the fluid-particle system taking into account the acoustic radiation force and the time-dependent and time-independent drag force acting on the particle. Using this dynamic model, we characterize the transient and steady-state behavior of the fluid-particle system as a function of the particle and fluid properties and the transducer operating parameters. The results show that the settling time and percent overshoot of the particle trajectory are dependentmore » on the ratio of the acoustic radiation force and time-independent damping force. In addition, we show that the particle oscillates around the node of the standing wave with an amplitude that depends on the ratio of the time-dependent drag forces and the particle inertia.« less

The Direction of Fluid Dynamics for Liquid Propulsion at NASA Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Griffin, Lisa W.

2012-01-01

Marshall Space Flight Center (MSFC) is the National Aeronautics and Space Administration (NASA)-designated center for the development of space launch systems. MSFC is particularly known for propulsion system development. Many engineering skills and technical disciplines are needed to accomplish this mission. This presentation will focus on the work of the Fluid Dynamics Branch (ER42). ER42 resides in the Propulsion Systems Department at MSFC. The branch is responsible for all aspects of the discipline of fluid dynamics applied to propulsion or propulsion-induced loads and environments. This work begins with design trades and parametric studies, and continues through development, risk assessment, anomaly investigation and resolution, and failure investigations. Applications include the propellant delivery system including the main propulsion system (MPS) and turbomachinery; combustion devices for liquid engines and solid rocket motors; coupled systems; and launch environments. An advantage of the branch is that it is neither analysis nor test centric, but discipline centric. Fluid dynamics assessments are made by analysis, from lumped parameter modeling through unsteady computational fluid dynamics (CFD); testing, which can be cold flow or hot fire; or a combination of analysis and testing. Integration of all discipline methods into one branch enables efficient and accurate support to the projects. To accomplish this work, the branch currently employs approximately fifty engineers divided into four teams -- Propellant Delivery CFD, Combustion Driven Flows CFD, Unsteady and Experimental Flows, and Acoustics and Stability. This discussion will highlight some of the work performed in the branch and the direction in which the branch is headed.

Energy dissipation in flows through curved spaces.

PubMed

Debus, J-D; Mendoza, M; Succi, S; Herrmann, H J

2017-02-14

Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space. We find that local sources of curvature generate viscous stresses as a result of the inertial forces. The curvature- induced viscous forces are shown to cause hitherto unnoticed and yet appreciable energy dissipation, which might play a significant role for a variety of physical systems involving fluid dynamics in curved spaces.

Modeling the relaxation dynamics of fluids in nanoporous materials

NASA Astrophysics Data System (ADS)

Edison, John R.

Mesoporous materials are being widely used in the chemical industry in various environmentally friendly separation processes and as catalysts. Our research can be broadly described as an effort to understand the behavior of fluids confined in such materials. More specifically we try to understand the influence of state variables like temperature and pore variables like size, shape, connectivity and structural heterogeneity on both the dynamic and equilibrium behavior of confined fluids. The dynamic processes associated with the approach to equilibrium are largely unexplored. It is important to look into the dynamic behavior for two reasons. First, confined fluids experience enhanced metastabilities and large equilibration times in certain classes of mesoporous materials, and the approach to the metastable/stable equilibrium is of tremendous interest. Secondly, understanding the transport resistances in a microscopic scale will help better engineer heterogeneous catalysts and separation processes. Here we present some of our preliminary studies on dynamics of fluids in ideal pore geometries. The tool that we have used extensively to investigate the relaxation dynamics of fluids in pores is the dynamic mean field theory (DMFT) as developed by Monson [P. A. Monson, J. Chem. Phys., 128, 084701 (2008)]. The theory is based on a lattice gas model of the system and can be viewed as a highly computationally efficient approximation to the dynamics averaged over an ensemble of Kawasaki dynamics Monte Carlo trajectories of the system. It provides a theory of the dynamics of the system consistent with the thermodynamics in mean field theory. The nucleation mechanisms associated with confined fluid phase transitions are emergent features in the calculations. We begin by describing the details of the theory and then present several applications of DMFT. First we present applications to three model pore networks (a) a network of slit pores with a single pore width; (b) a network of slit pores with two pore widths arranged in intersecting channels with a single pore width in each channel; (c) a network of slit pores with two pore widths forming an array of ink-bottles. The results illustrate the effects of pore connectivity upon the dynamics of vapor liquid phase transformations as well as on the mass transfer resistances to equilibration. We then present an application to a case where the solid-fluid interactions lead to partial wetting on a planar surface. The pore filling process in such systems features an asymmetric density distribution where a liquid droplet appears on one of the walls. We also present studies on systems where there is partial drying or drying associated with weakly attractive or repulsive interactions between the fluid and the pore walls. We describe the symmetries exhibited by the lattice model between pore filling for wetting states and pore emptying for drying states, for both the thermodynamics and dynamics. We then present an extension of DMFT to mixtures and present some examples that illustrate the utility of the approach. Finally we present an assessment the accuracy of the DMFT through comparisons with a higher order approximation based on the path probability method as well as Kawasaki dynamics.

Experimental Observations of Multiscale Dynamics of Viscous Fluid Behavior: Implications in Volcanic Systems

NASA Astrophysics Data System (ADS)

Arciniega-Ceballos, A.; Spina, L.; Scheu, B.; Dingwell, D. B.

2015-12-01

We have investigated the dynamics of Newtonian fluids with viscosities (10-1000 Pa s; corresponding to mafic to intermediate silicate melts) during slow decompression, in a Plexiglas shock tube. As an analogue fluid we used silicon oil saturated with Argon gas for 72 hours. Slow decompression, dropping from 10 MPa to ambient pressure, acts as the excitation mechanism, initiating several processes with their own distinct timescales. The evolution of this multi-timescale phenomenon generates complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit. Correlation analysis of these time series with the associated high-speed imaging enables characterization of distinct phases of the dynamics of these viscous fluids and the extraction of the time and the frequency characteristics of the individual processes. We have identified fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution in space. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the system. Our observations point to the great potential of this experimental approach in the understanding of volcanic processes and volcanic seismicity.

A Textbook for a First Course in Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Zingg, D. W.; Pulliam, T. H.; Nixon, David (Technical Monitor)

1999-01-01

This paper describes and discusses the textbook, Fundamentals of Computational Fluid Dynamics by Lomax, Pulliam, and Zingg, which is intended for a graduate level first course in computational fluid dynamics. This textbook emphasizes fundamental concepts in developing, analyzing, and understanding numerical methods for the partial differential equations governing the physics of fluid flow. Its underlying philosophy is that the theory of linear algebra and the attendant eigenanalysis of linear systems provides a mathematical framework to describe and unify most numerical methods in common use in the field of fluid dynamics. Two linear model equations, the linear convection and diffusion equations, are used to illustrate concepts throughout. Emphasis is on the semi-discrete approach, in which the governing partial differential equations (PDE's) are reduced to systems of ordinary differential equations (ODE's) through a discretization of the spatial derivatives. The ordinary differential equations are then reduced to ordinary difference equations (O(Delta)E's) using a time-marching method. This methodology, using the progression from PDE through ODE's to O(Delta)E's, together with the use of the eigensystems of tridiagonal matrices and the theory of O(Delta)E's, gives the book its distinctiveness and provides a sound basis for a deep understanding of fundamental concepts in computational fluid dynamics.

The Interplay Between Saline Fluid Flow and Dynamic Permeability in Magmatic-Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Weis, P.

2014-12-01

Magmatic-hydrothermal ore deposits document the interplay between saline fluid flow and rock permeability. Numerical simulations of multi-phase flow of variably miscible, compressible H20-NaCl fluids in concert with a dynamic permeability model can reproduce characteristics of porphyry copper and epithermal gold systems. This dynamic permeability model incorporates depth-dependent permeability profiles characteristic for tectonically active crust as well as pressure- and temperature-dependent relationships describing hydraulic fracturing and the transition from brittle to ductile rock behavior. In response to focused expulsion of magmatic fluids from a crystallizing upper crustal magma chamber, the hydrothermal system self-organizes into a hydrological divide, separating an inner part dominated by ascending magmatic fluids under near-lithostatic pressures from a surrounding outer part dominated by convection of colder meteoric fluids under near-hydrostatic pressures. This hydrological divide also provides a mechanism to transport magmatic salt through the crust, and prevents the hydrothermal system to become "clogged" by precipitation of solid halite due to depressurization of saline, high-temperature magmatic fluids. The same physical processes at similar permeability ranges, crustal depths and flow rates are relevant for a number of active systems, including geothermal resources and excess degassing at volcanos. The simulations further suggest that the described mechanism can separate the base of free convection in high-enthalpy geothermal systems from the magma chamber as a driving heat source by several kilometers in the vertical direction in tectonic settings with hydrous magmatism. This hydrology would be in contrast to settings with anhydrous magmatism, where the base of the geothermal systems may be closer to the magma chamber.

Visualization of Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Gerald-Yamasaki, Michael; Hultquist, Jeff; Bryson, Steve; Kenwright, David; Lane, David; Walatka, Pamela; Clucas, Jean; Watson, Velvin; Lasinski, T. A. (Technical Monitor)

1995-01-01

Scientific visualization serves the dual purpose of exploration and exposition of the results of numerical simulations of fluid flow. Along with the basic visualization process which transforms source data into images, there are four additional components to a complete visualization system: Source Data Processing, User Interface and Control, Presentation, and Information Management. The requirements imposed by the desired mode of operation (i.e. real-time, interactive, or batch) and the source data have their effect on each of these visualization system components. The special requirements imposed by the wide variety and size of the source data provided by the numerical simulation of fluid flow presents an enormous challenge to the visualization system designer. We describe the visualization system components including specific visualization techniques and how the mode of operation and source data requirements effect the construction of computational fluid dynamics visualization systems.

Study on heat transfer coefficients during cooling of PET bottles for food beverages

NASA Astrophysics Data System (ADS)

Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco

2016-08-01

The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.

On the Unsteady Shock Wave Interaction with a Backward-Facing Step: Viscous Analysis

NASA Astrophysics Data System (ADS)

Mendoza, N.; Bowersox, R. D. W.

Unsteady shock propagation through ducts with varying cross-sectional area occurs in many engineering applications, such as explosions in underground tunnels, blast shelter design, engine exhaust systems, and high-speed propulsion systems. These complex, transient flows are rich in fundamental fluid-dynamic phenomena and are excellent testbeds for improving our understanding of unsteady fluid dynamics

Dynamical Systems Analysis Of Transport In Flows Defined As Data Sets: Contaminant Control On The Coast Of Florida And Criteria For Warm Rings In The North Atlantic

NASA Astrophysics Data System (ADS)

Lekien, F.; Coulliette, C.

In this talk we will briefly describe the dynamical systems framework for Lagrangian transport. In particular, we will show how dynamical systems theory can now be uti- lized in the context of "real" problems, such as those derived from remote sensing observations or the input of a large scale numerical model. We will illustrate these ideas by two examples. Study of fluid transport near the Atlantic coast of Florida us- ing a velocity field observed experimentally from high frequency radar measurements reveals that dynamical systems theory can be used to reduce contaminant density in coastal areas. We also study intergyre transport in a quasigeostrophic model of the North Atlantic. We investigate the structure of eddies detaching from the Gulf Stream and prove that in a double gyre structure cyclonic rings cannot contain fluid from the other gyre. Only anticyclonic rings can contain "foreign" fluid coming from another gyre. This explains many phenomenons, such as why counter-clockwise rings South of the Gulf Stream contain colder fluid advected directly from the northern gyre, which has been illustrated in many observational studies.

Dynamical modeling and free vibration analysis of spinning pipes conveying fluid with axial deployment

NASA Astrophysics Data System (ADS)

Liang, Feng; Yang, Xiao-Dong; Zhang, Wei; Qian, Ying-Jing

2018-03-01

In this paper, a dynamical model of simply-supported spinning pipes conveying fluid with axial deployment is proposed and the transverse free vibration and stability for such a doubly gyroscopic system involving time-dependent parameters are investigated. The partial differential equations of motion are derived by the extended Hamilton principle and then truncated by the Galerkin technique. The time-variant frequencies, mode shapes and responses to initial conditions are comprehensively investigated to reveal the dynamical essence of the system. It is indicated that the qualitative stability evolution of the system mainly depends on the effect of fluid-structure interaction (FSI), while the spinning motion will enhance the pipe rigidity and eliminate the buckling instability. The dynamical evolution of a retracting pipe is almost inverse to that of the deploying one. The pipe possesses different mode configurations of spatial curves as the pipe length increases and some modal and response characteristics of the present system are found rather distinct from those of deploying cantilevered structures.

Review article: closed-loop systems in anesthesia: is there a potential for closed-loop fluid management and hemodynamic optimization?

PubMed

Rinehart, Joseph; Liu, Ngai; Alexander, Brenton; Cannesson, Maxime

2012-01-01

Closed-loop (automated) controllers are encountered in all aspects of modern life in applications ranging from air-conditioning to spaceflight. Although these systems are virtually ubiquitous, they are infrequently used in anesthesiology because of the complexity of physiologic systems and the difficulty in obtaining reliable and valid feedback data from the patient. Despite these challenges, closed-loop systems are being increasingly studied and improved for medical use. Two recent developments have made fluid administration a candidate for closed-loop control. First, the further description and development of dynamic predictors of fluid responsiveness provides a strong parameter for use as a control variable to guide fluid administration. Second, rapid advances in noninvasive monitoring of cardiac output and other hemodynamic variables make goal-directed therapy applicable for a wide range of patients in a variety of clinical care settings. In this article, we review the history of closed-loop controllers in clinical care, discuss the current understanding and limitations of the dynamic predictors of fluid responsiveness, and examine how these variables might be incorporated into a closed-loop fluid administration system.

Fluid technology (selected components, devices, and systems): A compilation

NASA Technical Reports Server (NTRS)

1974-01-01

Developments in fluid technology and hydraulic equipment are presented. The subjects considered are: (1) the use of fluids in the operation of switches, amplifiers, and servo devices, (2) devices and data for laboratory use in the study of fluid dynamics, and (3) the use of fluids as controls and certain methods of controlling fluids.

Cellular fluid mechanics.

PubMed

Kamm, Roger D

2002-01-01

The coupling of fluid dynamics and biology at the level of the cell is an intensive area of investigation because of its critical role in normal physiology and disease. Microcirculatory flow has been a focus for years, owing to the complexity of cell-cell or cell-glycocalyx interactions. Noncirculating cells, particularly those that comprise the walls of the circulatory system, experience and respond biologically to fluid dynamic stresses. In this article, we review the more recent studies of circulating cells, with an emphasis on the role of the glycocalyx on red-cell motion in small capillaries and on the deformation of leukocytes passing through the microcirculation. We also discuss flows in the vicinity of noncirculating cells, the influence of fluid dynamic shear stress on cell biology, and diffusion in the lipid bi-layer, all in the context of the important fluid-dynamic phenomena.

Tracking interface and common curve dynamics for two-fluid flow in porous media

DOE PAGES

Mcclure, James E.; Miller, Cass T.; Gray, W. G.; ...

2016-04-29

Pore-scale studies of multiphase flow in porous medium systems can be used to understand transport mechanisms and quantitatively determine closure relations that better incorporate microscale physics into macroscale models. Multiphase flow simulators constructed using the lattice Boltzmann method provide a means to conduct such studies, including both the equilibrium and dynamic aspects. Moving, storing, and analyzing the large state space presents a computational challenge when highly-resolved models are applied. We present an approach to simulate multiphase flow processes in which in-situ analysis is applied to track multiphase flow dynamics at high temporal resolution. We compute a comprehensive set of measuresmore » of the phase distributions and the system dynamics, which can be used to aid fundamental understanding and inform closure relations for macroscale models. The measures computed include microscale point representations and macroscale averages of fluid saturations, the pressure and velocity of the fluid phases, interfacial areas, interfacial curvatures, interface and common curve velocities, interfacial orientation tensors, phase velocities and the contact angle between the fluid-fluid interface and the solid surface. Test cases are studied to validate the approach and illustrate how measures of system state can be obtained and used to inform macroscopic theory.« less

Environmental Fluid Dynamics Code

EPA Science Inventory

The Environmental Fluid Dynamics Code (EFDC)is a state-of-the-art hydrodynamic model that can be used to simulate aquatic systems in one, two, and three dimensions. It has evolved over the past two decades to become one of the most widely used and technically defensible hydrodyn...

Renewable fluid dynamic energy derived from aquatic animal locomotion.

PubMed

Dabiri, John O

2007-09-01

Aquatic animals swimming in isolation and in groups are known to extract energy from the vortices in environmental flows, significantly reducing muscle activity required for locomotion. A model for the vortex dynamics associated with this phenomenon is developed, showing that the energy extraction mechanism can be described by simple criteria governing the kinematics of the vortices relative to the body in the flow. In this way, we need not make direct appeal to the fluid dynamics, which can be more difficult to evaluate than the kinematics. Examples of these principles as exhibited in swimming fish and existing energy conversion devices are described. A benefit of the developed framework is that the potentially infinite-dimensional parameter space of the fluid-structure interaction is reduced to a maximum of eight combinations of three parameters. The model may potentially aid in the design and evaluation of unsteady aero- and hydrodynamic energy conversion systems that surpass the Betz efficiency limit of steady fluid dynamic energy conversion systems.

SPAR improved structure/fluid dynamic analysis capability

NASA Technical Reports Server (NTRS)

Oden, J. T.; Pearson, M. L.

1983-01-01

The capability of analyzing a coupled dynamic system of flowing fluid and elastic structure was added to the SPAR computer code. A method, developed and adopted for use in SPAR utilizes the existing assumed stress hybrid plan element in SPAR. An operational mode was incorporated in SPAR which provides the capability for analyzing the flaw of a two dimensional, incompressible, viscous fluid within rigid boundaries. Equations were developed to provide for the eventual analysis of the interaction of such fluids with an elastic solid.

Using LEGO Kits to Teach Higher Level Problem Solving Skills in System Dynamics: A Case Study

ERIC Educational Resources Information Center

Wu, Yi; de Vries, Charlotte; Dunsworth, Qi

2018-01-01

System Dynamics is a required course offered to junior Mechanical Engineering students at Penn State Erie, the Behrend College. It addresses the intercoupling dynamics of a wide range of dynamic systems: including mechanical, electrical, fluid, hydraulic, electromechanical, and biomedical systems. This course is challenging for students due to the…

SPAR improved structure-fluid dynamic analysis capability, phase 2

NASA Technical Reports Server (NTRS)

Pearson, M. L.

1984-01-01

An efficient and general method of analyzing a coupled dynamic system of fluid flow and elastic structures is investigated. The improvement of Structural Performance Analysis and Redesign (SPAR) code is summarized. All error codes are documented and the SPAR processor/subroutine cross reference is included.

Attractors of equations of non-Newtonian fluid dynamics

NASA Astrophysics Data System (ADS)

Zvyagin, V. G.; Kondrat'ev, S. K.

2014-10-01

This survey describes a version of the trajectory-attractor method, which is applied to study the limit asymptotic behaviour of solutions of equations of non-Newtonian fluid dynamics. The trajectory-attractor method emerged in papers of the Russian mathematicians Vishik and Chepyzhov and the American mathematician Sell under the condition that the corresponding trajectory spaces be invariant under the translation semigroup. The need for such an approach was caused by the fact that for many equations of mathematical physics for which the Cauchy initial-value problem has a global (weak) solution with respect to the time, the uniqueness of such a solution has either not been established or does not hold. In particular, this is the case for equations of fluid dynamics. At the same time, trajectory spaces invariant under the translation semigroup could not be constructed for many equations of non-Newtonian fluid dynamics. In this connection, a different approach to the construction of trajectory attractors for dissipative systems was proposed in papers of Zvyagin and Vorotnikov without using invariance of trajectory spaces under the translation semigroup and is based on the topological lemma of Shura-Bura. This paper presents examples of equations of non-Newtonian fluid dynamics (the Jeffreys system describing movement of the Earth's crust, the model of motion of weak aqueous solutions of polymers, a system with memory) for which the aforementioned construction is used to prove the existence of attractors in both the autonomous and the non-autonomous cases. At the beginning of the paper there is also a brief exposition of the results of Ladyzhenskaya on the existence of attractors of the two-dimensional Navier-Stokes system and the result of Vishik and Chepyzhov for the case of attractors of the three-dimensional Navier-Stokes system. Bibliography: 34 titles.

Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsions - 2

NASA Technical Reports Server (NTRS)

Furst, Eric M.; Gast, Alice P.

2008-01-01

Particle dynamics of magnetorheological fluids (fluids that change properties in response to magnetic fields) are studied to help understand adaptable new fluids for use in such applications as brake systems and robotics.

Finite Element Modeling of Non-linear Coupled Interacting Fault System

NASA Astrophysics Data System (ADS)

Xing, H. L.; Zhang, J.; Wyborn, D.

2009-04-01

PANDAS - Parallel Adaptive static/dynamic Nonlinear Deformation Analysis System - a novel supercomputer simulation tool is developed for simulating the highly non-linear coupled geomechanical-fluid flow-thermal systems involving heterogeneously fractured geomaterials. PANDAS includes the following key components: Pandas/Pre, ESyS_Crustal, Pandas/Thermo, Pandas/Fluid and Pandas/Post as detailed in the following: • Pandas/Pre is developed to visualise the microseismicity events recorded during the hydraulic stimulation process to further evaluate the fracture location and evolution and geological setting of a certain reservoir, and then generate the mesh by it and/or other commercial graphics software (such as Patran) for the further finite element analysis of various cases; The Delaunay algorithm is applied as a suitable method for mesh generation using such a point set; • ESyS_Crustal is a finite element code developed for the interacting fault system simulation, which employs the adaptive static/dynamic algorithm to simulate the dynamics and evolution of interacting fault systems and processes that are relevant on short to mediate time scales in which several dynamic phenomena related with stick-slip instability along the faults need to be taken into account, i.e. (a). slow quasi-static stress accumulation, (b) rapid dynamic rupture, (c) wave propagation and (d) corresponding stress redistribution due to the energy release along the multiple fault boundaries; those are needed to better describe ruputure/microseimicity/earthquake related phenomena with applications in earthquake forecasting, hazard quantification, exploration, and environmental problems. It has been verified with various available experimental results[1-3]; • Pandas/Thermo is a finite element method based module for the thermal analysis of the fractured porous media; the temperature distribution is calculated from the heat transfer induced by the thermal boundary conditions without/with the coupled fluid effects and the geomechanical energy conversion for the pure/coupled thermal analysis. • Pandas/Fluid is a finite element method based module for simulating the fluid flow in the fractured porous media; the fluid flow velocity and pressure are calculated from energy equilibrium equations without/together with the coupling effects of the thermal and solid rock deformation for an independent/coupled fluid flow analysis; • Pandas/Post is to visualise the simulation results through the integration of VTK and/or Patran. All the above modules can be used independently/together to simulate individual/coupled phenomena (such as interacting fault system dynamics, heat flow and fluid flow) without/with coupling effects. PANDAS has been applied to the following issues: • visualisation of the microseismic events to monitor and determine where/how the underground rupture proceeds during a hydraulic stimulation, to generate the mesh using the recorded data for determining the domain of the ruptured zone and to evaluate the material parameters (i.e. the permeability) for the further numerical analysis; • interacting fault system simulation to determine the relevant complicated dynamic rupture process. • geomechanical-fluid flow coupling analysis to investigate the interactions between fluid flow and deformation in the fractured porous media under different loading conditions. • thermo-fluid flow coupling analysis of a fractured geothermal reservoir system. PANDAS will be further developed for a multiscale simulation of multiphase dynamic behaviour for a certain fractured geothermal reservoir. More details and additional application examples will be given during the presentation. References [1] Xing, H. L., Makinouchi, A. and Mora, P. (2007). Finite element modeling of interacting fault system, Physics of the Earth and Planetary Interiors, 163, 106-121.doi:10.1016/j.pepi.2007.05.006 [2] Xing, H. L., Mora, P., Makinouchi, A. (2006). An unified friction description and its application to simulation of frictional instability using finite element method. Philosophy Magazine, 86, 3453-3475 [3] Xing, H. L., Mora, P.(2006). Construction of an intraplate fault system model of South Australia, and simulation tool for the iSERVO institute seed project.. Pure and Applied Geophysics. 163, 2297-2316. DOI 10.1007/s00024-006-0127-x

14 CFR 1201.200 - General.

Code of Federal Regulations, 2013 CFR

2013-01-01

... development in astrophysics, life sciences, Earth sciences and applications, solar system exploration, space physics, communications, microgravity science and applications, and communications and information systems... computational and experimental fluid dynamics and aerodynamics; fluid and thermal physics; rotorcraft, powered...

14 CFR § 1201.200 - General.

Code of Federal Regulations, 2014 CFR

2014-01-01

... development in astrophysics, life sciences, Earth sciences and applications, solar system exploration, space physics, communications, microgravity science and applications, and communications and information systems... computational and experimental fluid dynamics and aerodynamics; fluid and thermal physics; rotorcraft, powered...

14 CFR 1201.200 - General.

Code of Federal Regulations, 2012 CFR

2012-01-01

... development in astrophysics, life sciences, Earth sciences and applications, solar system exploration, space physics, communications, microgravity science and applications, and communications and information systems... computational and experimental fluid dynamics and aerodynamics; fluid and thermal physics; rotorcraft, powered...

Effect of fluid compressibility on journal bearing performance

NASA Technical Reports Server (NTRS)

Dimofte, Florin

1993-01-01

An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

Incubation under fluid dynamic conditions markedly improves the structural preservation in vitro of explanted skeletal muscles.

PubMed

Carton, Flavia; Calderan, Laura; Malatesta, Manuela

2017-11-28

Explanted organs and tissues represent suitable experimental systems mimicking the functional and structural complexity of the living organism, with positive ethical and economic impact on research activities. However, their preservation in culture is generally limited, thus hindering their application as experimental models for biomedical research. In the present study, we investigated the potential of an innovative fluid dynamic culture system to improve the structural preservation in vitro of explanted mouse skeletal muscles (soleus). We used light and transmission electron microscopy to compare the morphological features of muscles maintained either in multiwell plates under conventional conditions or in a bioreactor mimicking the flow of physiological fluids. Our results demonstrate that fluid dynamic conditions markedly slowed the progressive structural deterioration of the muscle tissue occurring during the permanence in the culture medium, prolonging the preservation of some organelles such as mitochondria up to 48 h.

Incubation under fluid dynamic conditions markedly improves the structural preservation in vitro of explanted skeletal muscles

PubMed Central

Carton, Flavia; Calderan, Laura; Malatesta, Manuela

2017-01-01

Explanted organs and tissues represent suitable experimental systems mimicking the functional and structural complexity of the living organism, with positive ethical and economic impact on research activities. However, their preservation in culture is generally limited, thus hindering their application as experimental models for biomedical research. In the present study, we investigated the potential of an innovative fluid dynamic culture system to improve the structural preservation in vitro of explanted mouse skeletal muscles (soleus). We used light and transmission electron microscopy to compare the morphological features of muscles maintained either in multiwell plates under conventional conditions or in a bioreactor mimicking the flow of physiological fluids. Our results demonstrate that fluid dynamic conditions markedly slowed the progressive structural deterioration of the muscle tissue occurring during the permanence in the culture medium, prolonging the preservation of some organelles such as mitochondria up to 48 h. PMID:29313601

Software Surface Modeling and Grid Generation Steering Committee

NASA Technical Reports Server (NTRS)

Smith, Robert E. (Editor)

1992-01-01

It is a NASA objective to promote improvements in the capability and efficiency of computational fluid dynamics. Grid generation, the creation of a discrete representation of the solution domain, is an essential part of computational fluid dynamics. However, grid generation about complex boundaries requires sophisticated surface-model descriptions of the boundaries. The surface modeling and the associated computation of surface grids consume an extremely large percentage of the total time required for volume grid generation. Efficient and user friendly software systems for surface modeling and grid generation are critical for computational fluid dynamics to reach its potential. The papers presented here represent the state-of-the-art in software systems for surface modeling and grid generation. Several papers describe improved techniques for grid generation.

A FRAMEWORK FOR FINE-SCALE COMPUTATIONAL FLUID DYNAMICS AIR QUALITY MODELING AND ANALYSIS

EPA Science Inventory

This paper discusses a framework for fine-scale CFD modeling that may be developed to complement the present Community Multi-scale Air Quality (CMAQ) modeling system which itself is a computational fluid dynamics model. A goal of this presentation is to stimulate discussions on w...

Thermal Protection System Cavity Heating for Simplified and Actual Geometries Using Computational Fluid Dynamics Simulations with Unstructured Grids

NASA Technical Reports Server (NTRS)

McCloud, Peter L.

2010-01-01

Thermal Protection System (TPS) Cavity Heating is predicted using Computational Fluid Dynamics (CFD) on unstructured grids for both simplified cavities and actual cavity geometries. Validation was performed using comparisons to wind tunnel experimental results and CFD predictions using structured grids. Full-scale predictions were made for simplified and actual geometry configurations on the Space Shuttle Orbiter in a mission support timeframe.

Verification of Modelica-Based Models with Analytical Solutions for Tritium Diffusion

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

Rader, Jordan D.; Greenwood, Michael Scott; Humrickhouse, Paul W.

Here, tritium transport in metal and molten salt fluids combined with diffusion through high-temperature structural materials is an important phenomenon in both magnetic confinement fusion (MCF) and molten salt reactor (MSR) applications. For MCF, tritium is desirable to capture for fusion fuel. For MSRs, uncaptured tritium potentially can be released to the environment. In either application, quantifying the time- and space-dependent tritium concentration in the working fluid(s) and structural components is necessary.Whereas capability exists specifically for calculating tritium transport in such systems (e.g., using TMAP for fusion reactors), it is desirable to unify the calculation of tritium transport with othermore » system variables such as dynamic fluid and structure temperature combined with control systems such as those that might be found in a system code. Some capability for radioactive trace substance transport exists in thermal-hydraulic systems codes (e.g., RELAP5-3D); however, this capability is not coupled to species diffusion through solids. Combined calculations of tritium transport and thermal-hydraulic solution have been demonstrated with TRIDENT but only for a specific type of MSR.Researchers at Oak Ridge National Laboratory have developed a set of Modelica-based dynamic system modeling tools called TRANsient Simulation Framework Of Reconfigurable Models (TRANSFORM) that were used previously to model advanced fission reactors and associated systems. In this system, the augmented TRANSFORM library includes dynamically coupled fluid and solid trace substance transport and diffusion. Results from simulations are compared against analytical solutions for verification.« less

Verification of Modelica-Based Models with Analytical Solutions for Tritium Diffusion

DOE PAGES

Rader, Jordan D.; Greenwood, Michael Scott; Humrickhouse, Paul W.

2018-03-20

Here, tritium transport in metal and molten salt fluids combined with diffusion through high-temperature structural materials is an important phenomenon in both magnetic confinement fusion (MCF) and molten salt reactor (MSR) applications. For MCF, tritium is desirable to capture for fusion fuel. For MSRs, uncaptured tritium potentially can be released to the environment. In either application, quantifying the time- and space-dependent tritium concentration in the working fluid(s) and structural components is necessary.Whereas capability exists specifically for calculating tritium transport in such systems (e.g., using TMAP for fusion reactors), it is desirable to unify the calculation of tritium transport with othermore » system variables such as dynamic fluid and structure temperature combined with control systems such as those that might be found in a system code. Some capability for radioactive trace substance transport exists in thermal-hydraulic systems codes (e.g., RELAP5-3D); however, this capability is not coupled to species diffusion through solids. Combined calculations of tritium transport and thermal-hydraulic solution have been demonstrated with TRIDENT but only for a specific type of MSR.Researchers at Oak Ridge National Laboratory have developed a set of Modelica-based dynamic system modeling tools called TRANsient Simulation Framework Of Reconfigurable Models (TRANSFORM) that were used previously to model advanced fission reactors and associated systems. In this system, the augmented TRANSFORM library includes dynamically coupled fluid and solid trace substance transport and diffusion. Results from simulations are compared against analytical solutions for verification.« less

Improved Pyrolysis Micro reactor Design via Computational Fluid Dynamics Simulations

DTIC Science & Technology

2017-05-23

Dynamics Simulations Ghanshyam L. Vaghjiani Air Force Research Laboratory (AFMC) AFRL/RQRS 1 Ara Drive Edwards AFB, CA 93524-7013 Air Force...Aerospace Systems Directorate Air Force Research Laboratory AFRL/RQRS 1 Ara Road Edwards AFB, CA 93524 *Email: ghanshyam.vaghjiani@us.af.mil IMPROVED...PYROLYSIS MICRO-REACTOR DESIGN VIA COMPUTATIONAL FLUID DYNAMICS SIMULATIONS Ghanshyam L. Vaghjiani* DISTRIBUTION A: Approved for public release

Modeling Tools Predict Flow in Fluid Dynamics

NASA Technical Reports Server (NTRS)

2010-01-01

"Because rocket engines operate under extreme temperature and pressure, they present a unique challenge to designers who must test and simulate the technology. To this end, CRAFT Tech Inc., of Pipersville, Pennsylvania, won Small Business Innovation Research (SBIR) contracts from Marshall Space Flight Center to develop software to simulate cryogenic fluid flows and related phenomena. CRAFT Tech enhanced its CRUNCH CFD (computational fluid dynamics) software to simulate phenomena in various liquid propulsion components and systems. Today, both government and industry clients in the aerospace, utilities, and petrochemical industries use the software for analyzing existing systems as well as designing new ones."

Enhancing power cycle efficiency for a supercritical Brayton cycle power system using tunable supercritical gas mixtures

DOEpatents

Wright, Steven A.; Pickard, Paul S.; Vernon, Milton E.; Radel, Ross F.

2017-08-29

Various technologies pertaining to tuning composition of a fluid mixture in a supercritical Brayton cycle power generation system are described herein. Compounds, such as Alkanes, are selectively added or removed from an operating fluid of the supercritical Brayton cycle power generation system to cause the critical temperature of the fluid to move up or down, depending upon environmental conditions. As efficiency of the supercritical Brayton cycle power generation system is substantially optimized when heat is rejected near the critical temperature of the fluid, dynamically modifying the critical temperature of the fluid based upon sensed environmental conditions improves efficiency of such a system.

Workshop on Computational Turbulence Modeling

NASA Technical Reports Server (NTRS)

1993-01-01

This document contains presentations given at Workshop on Computational Turbulence Modeling held 15-16 Sep. 1993. The purpose of the meeting was to discuss the current status and future development of turbulence modeling in computational fluid dynamics for aerospace propulsion systems. Papers cover the following topics: turbulence modeling activities at the Center for Modeling of Turbulence and Transition (CMOTT); heat transfer and turbomachinery flow physics; aerothermochemistry and computational methods for space systems; computational fluid dynamics and the k-epsilon turbulence model; propulsion systems; and inlet, duct, and nozzle flow.

Brake Fluid Compatibility Studies with Advanced Brake Systems

DTIC Science & Technology

2016-01-16

and chemical characterization tests. Increased wear seen with the silicone brake fluid on brake system parts was substantiated by laboratory bench...tests and dynamic seal tests, followed by a series of physical and chemical characterization tests on used silicone brake fluid and hydraulic...elastomers with silicone brake fluid was conducted at ambient and 40 °C, primarily to determine using GC-MS, if the chemical constituents in the

Low-cost digital dynamic visualization system

NASA Astrophysics Data System (ADS)

Asundi, Anand K.; Sajan, M. R.

1995-05-01

High speed photographic systems like the image rotation camera, the Cranz Schardin camera and the drum camera are typically used for recording and visualization of dynamic events in stress analysis, fluid mechanics, etc. All these systems are fairly expensive and generally not simple to use. Furthermore they are all based on photographic film recording systems requiring time consuming and tedious wet processing of the films. Currently digital cameras are replacing to certain extent the conventional cameras for static experiments. Recently, there is lot of interest in developing and modifying CCD architectures and recording arrangements for dynamic scene analysis. Herein we report the use of a CCD camera operating in the Time Delay and Integration (TDI) mode for digitally recording dynamic scenes. Applications in solid as well as fluid impact problems are presented.

The Influence of Dynamic Contact Angle on Wetting Dynamics

NASA Technical Reports Server (NTRS)

Rame, Enrique; Garoff, Steven

2005-01-01

When surface tension forces dominate, and regardless of whether the situation is static or dynamic, the contact angle (the angle the interface between two immiscible fluids makes when it contacts a solid) is the key parameter that determines the shape of a fluid-fluid interface. The static contact angle is easy to measure and implement in models predicting static capillary surface shapes and such associated quantities as pressure drops. By contrast, when the interface moves relative to the solid (as in dynamic wetting processes) the dynamic contact angle is not identified unambiguously because it depends on the geometry of the system Consequently, its determination becomes problematic and measurements in one geometry cannot be applied in another for prediction purposes. However, knowing how to measure and use the dynamic contact angle is crucial to determine such dynamics as a microsystem throughput reliably. In this talk we will present experimental and analytical efforts aimed at resolving modeling issues present in dynamic wetting. We will review experiments that show the inadequacy of the usual hydrodynamic model when a fluid-fluid meniscus moves over a solid surface such as the wall of a small tube or duct. We will then present analytical results that show how to parametrize these problems in a predictive manner. We will illustrate these ideas by showing how to implement the method in numerical fluid mechanical calculations.

Cerebrospinal Fluid Mechanics and Its Coupling to Cerebrovascular Dynamics

NASA Astrophysics Data System (ADS)

Linninger, Andreas A.; Tangen, Kevin; Hsu, Chih-Yang; Frim, David

2016-01-01

Cerebrospinal fluid (CSF) is not stagnant but displays fascinating oscillatory flow patterns inside the ventricular system and reversing fluid exchange between the cranial vault and spinal compartment. This review provides an overview of the current knowledge of pulsatile CSF motion. Observations contradicting classical views about its bulk production and clearance are highlighted. A clinical account of diseases of abnormal CSF flow dynamics, including hydrocephalus, syringomyelia, Chiari malformation type 1, and pseudotumor cerebri, is also given. We survey medical imaging modalities used to observe intracranial dynamics in vivo. Additionally, we assess the state of the art in predictive models of CSF dynamics. The discussion addresses open questions regarding CSF dynamics as they relate to the understanding and management of diseases.

Fluid Dynamical Profiles and Constants of Motionfrom d-Branes

NASA Astrophysics Data System (ADS)

Jackiw, R.; Polychronakos, A. P.

Various fluid mechanical systems enjoy a hidden, higher-dimensional dynamical Poincaré symmetry, which arises owing to their descent from a Nambu-Goto action. Also, for the same reason, there are equivalence transformations between different models. These interconnections, summarized by the diagram below, are discussed in our paper.

Parallel computational fluid dynamics '91; Conference Proceedings, Stuttgart, Germany, Jun. 10-12, 1991

NASA Technical Reports Server (NTRS)

Reinsch, K. G. (Editor); Schmidt, W. (Editor); Ecer, A. (Editor); Haeuser, Jochem (Editor); Periaux, J. (Editor)

1992-01-01

A conference was held on parallel computational fluid dynamics and produced related papers. Topics discussed in these papers include: parallel implicit and explicit solvers for compressible flow, parallel computational techniques for Euler and Navier-Stokes equations, grid generation techniques for parallel computers, and aerodynamic simulation om massively parallel systems.

Marangoni-driven chemotaxis, chemotactic collapse, and the Keller-Segel equation

NASA Astrophysics Data System (ADS)

Shelley, Michael; Masoud, Hassan

2013-11-01

Almost by definition, chemotaxis involves the biased motion of motile particles along gradients of a chemical concentration field. Perhaps the most famous model for collective chemotaxis in mathematical biology is the Keller-Segel model, conceived to describe collective aggregation of slime mold colonies in response to an intrinsically produced, and diffusing, chemo-attractant. Heavily studied, particularly in 2D where the system is ``super-critical'', it has been proved that the KS model can develop finite-time singularities - so-called chemotactic collapse - of delta-function type. Here, we study the collective dynamics of immotile particles bound to a 2D interface above a 3D fluid. These particles are chemically active and produce a diffusing field that creates surface-tension gradients along the surface. The resultant Marangoni stresses create flows that carry the particles, possibly concentrating them. Remarkably, we show that this system involving 3D diffusion and fluid dynamics, exactly yields the 2D Keller-Segel model for the surface-flow of active particles. We discuss the consequences of collapse on the 3D fluid dynamics, and generalizations of the fluid-dynamical model.

Rotor-Bearing Dynamics Technology Design Guide. Part 8. A computerized Data Retrieval System for Fluid Film Bearings

DTIC Science & Technology

1980-10-01

AFAPL-TR-78-6 ’: Part Vill (U ROTOR -BEARING DYNAMICS - TECHNOLOGY DESIGN GUIDE ¢ Part Vil A Comput eri eval Syteftor Fluid Film Bearings SHAKER...Protection," Task 304806, "Aerospace Lubrication," Work Unit 30480685, " Rotor -Bearing Dynamics Design." The work reported herein was performed during the...the previous issue of the Rotor -Bearing Dynamics Technology Design Guide, - one volume dealt with the calculation of performance parameters and pertur

Burning invariant manifolds for reaction fronts in three-dimensional fluid flows

NASA Astrophysics Data System (ADS)

Mitchell, Kevin; Solomon, Tom

2017-11-01

The geometry of reaction fronts that propagate in fully three-dimensional (3D) fluid flows is studied using the tools of dynamical systems theory. The evolution of an infinitesimal front element is modeled as a six-dimensional ODE-three dimensions for the position of the front element and three for the orientation of its unit normal. This generalizes an earlier approach to understanding front propagation in two-dimensional (2D) fluid flows. As in 2D, the 3D system exhibits prominent burning invariant manifolds (BIMs). In 3D, BIMs are two-dimensional dynamically defined surfaces that form one-way barriers to the propagation of reaction fronts within the fluid. Due to the third dimension, BIMs in 3D exhibit a richer topology than their cousins in 2D. In particular, whereas BIMs in both 2D and 3D can originate from fixed points of the dynamics, BIMs in 3D can also originate from limit cycles. Such BIMs form robust tube-like channels that guide and constrain the evolution of the front within the bulk of the fluid. Supported by NSF Grant CMMI-1201236.

Vibration Propagation of Gear Dynamics in a Gear-Bearing-Housing System Using Mathematical Modeling and Finite Element Analysis

NASA Technical Reports Server (NTRS)

Parker, Robert G.; Guo, Yi; Eritenel, Tugan; Ericson, Tristan M.

2012-01-01

Vibration and noise caused by gear dynamics at the meshing teeth propagate through power transmission components to the surrounding environment. This study is devoted to developing computational tools to investigate the vibro-acoustic propagation of gear dynamics through a gearbox using different bearings. Detailed finite element/contact mechanics and boundary element models of the gear/bearing/housing system are established to compute the system vibration and noise propagation. Both vibration and acoustic models are validated by experiments including the vibration modal testing and sound field measurements. The effectiveness of each bearing type to disrupt vibration propagation is speed-dependent. Housing plays an important role in noise radiation .It, however, has limited effects on gear dynamics. Bearings are critical components in drivetrains. Accurate modeling of rolling element bearings is essential to assess vibration and noise of drivetrain systems. This study also seeks to fully describe the vibro-acoustic propagation of gear dynamics through a power-transmission system using rolling element and fluid film wave bearings. Fluid film wave bearings, which have higher damping than rolling element bearings, could offer an energy dissipation mechanism that reduces the gearbox noise. The effectiveness of each bearing type to disrupt vibration propagation in explored using multi-body computational models. These models include gears, shafts, rolling element and fluid film wave bearings, and the housing. Radiated noise is mapped from the gearbox surface to surrounding environment. The effectiveness of rolling element and fluid film wave bearings in breaking the vibro-acoustic propagation path from the gear to the housing is investigated.

A preliminary investigation of the growth of an aneurysm with a multiscale monolithic Fluid-Structure interaction solver

NASA Astrophysics Data System (ADS)

Cerroni, D.; Manservisi, S.; Pozzetti, G.

2015-11-01

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

The dynamic two-fluid model OLGA; Theory and application

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

Bendiksen, K.H.; Maines, D.; Moe, R.

1991-05-01

Dynamic two-fluid models have found a wide range of application in the simulation of two-phase-flow systems, particularly for the analysis of steam/water flow in the core of a nuclear reactor. Until quite recently, however, very few attempts have been made to use such models in the simulation of two-phase oil and gas flow in pipelines. This paper presents a dynamic two-fluid model, OLGA, in detail, stressing the basic equations and the two-fluid models applied. Predictions of steady-state pressure drop, liquid hold-up, and flow-regime transitions are compared with data from the SINTEF Two-Phase Flow Laboratory and from the literature. Comparisons withmore » evaluated field data are also presented.« less

An Unstructured Finite Volume Approach for Structural Dynamics in Response to Fluid Motions.

PubMed

Xia, Guohua; Lin, Ching-Long

2008-04-01

A new cell-vortex unstructured finite volume method for structural dynamics is assessed for simulations of structural dynamics in response to fluid motions. A robust implicit dual-time stepping method is employed to obtain time accurate solutions. The resulting system of algebraic equations is matrix-free and allows solid elements to include structure thickness, inertia, and structural stresses for accurate predictions of structural responses and stress distributions. The method is coupled with a fluid dynamics solver for fluid-structure interaction, providing a viable alternative to the finite element method for structural dynamics calculations. A mesh sensitivity test indicates that the finite volume method is at least of second-order accuracy. The method is validated by the problem of vortex-induced vibration of an elastic plate with different initial conditions and material properties. The results are in good agreement with existing numerical data and analytical solutions. The method is then applied to simulate a channel flow with an elastic wall. The effects of wall inertia and structural stresses on the fluid flow are investigated.

Cellular Biotechnology Operations Support System Fluid Dynamics Investigation

NASA Technical Reports Server (NTRS)

2003-01-01

Aboard the International Space Station (ISS), the Tissue Culture Medium (TCM) is the bioreactor vessel in which cell cultures are grown. With its two syringe ports, it is much like a bag used to administer intravenous fluid, except it allows gas exchange needed for life. The TCM contains cell culture medium, and when frozen cells are flown to the ISS, they are thawed and introduced to the TCM through the syringe ports. In the Cellular Biotechnology Operations Support System-Fluid Dynamics Investigation (CBOSS-FDI) experiment, several mixing procedures are being assessed to determine which method achieves the most uniform mixing of growing cells and culture medium.

From viscous to elastic sheets: Dynamics of smectic freely floating films

NASA Astrophysics Data System (ADS)

Harth, Kirsten; May, Kathrin; Trittel, Torsten; Stannarius, Ralf

2015-03-01

Oscillations and rupture of bubbles, composed of an inner fluid separated from an outer fluid by a membrane, represent an old but still immensely active field of research. Membrane properties except surface tension are often neglected for simple fluid films (e.g. soap bubbles), whereas they govern the dynamics in systems with more complex membranes (e.g. vesicles). Due to their layered phase structure, smectic liquid crystals can form stable, uniform and easy-to handle fluid films of immense aspect ratios. Recently, freely floating bubbles detached from a support were prepared. We analyze the relaxation from strongly non-spherical shapes and the rupture dynamics of such bubbles using high-speed video recordings. Peculiar dynamics intermediate between those of simple viscous fluid films and an elastic response emerge: Oscillations, slowed relaxation and even the formation of wrinkles and extrusions. We characterize these phenomena and propose explanations. We acknowledge funding by the German Aerospace Center DLR within Project OASIS-CO and German Science Foundation Project STA 425-28.

Resealable, optically accessible, PDMS-free fluidic platform for ex vivo interrogation of pancreatic islets.

PubMed

Lenguito, Giovanni; Chaimov, Deborah; Weitz, Jonathan R; Rodriguez-Diaz, Rayner; Rawal, Siddarth A K; Tamayo-Garcia, Alejandro; Caicedo, Alejandro; Stabler, Cherie L; Buchwald, Peter; Agarwal, Ashutosh

2017-02-28

We report the design and fabrication of a robust fluidic platform built out of inert plastic materials and micromachined features that promote optimized convective fluid transport. The platform is tested for perfusion interrogation of rodent and human pancreatic islets, dynamic secretion of hormones, concomitant live-cell imaging, and optogenetic stimulation of genetically engineered islets. A coupled quantitative fluid dynamics computational model of glucose stimulated insulin secretion and fluid dynamics was first utilized to design device geometries that are optimal for complete perfusion of three-dimensional islets, effective collection of secreted insulin, and minimization of system volumes and associated delays. Fluidic devices were then fabricated through rapid prototyping techniques, such as micromilling and laser engraving, as two interlocking parts from materials that are non-absorbent and inert. Finally, the assembly was tested for performance using both rodent and human islets with multiple assays conducted in parallel, such as dynamic perfusion, staining and optogenetics on standard microscopes, as well as for integration with commercial perfusion machines. The optimized design of convective fluid flows, use of bio-inert and non-absorbent materials, reversible assembly, manual access for loading and unloading of islets, and straightforward integration with commercial imaging and fluid handling systems proved to be critical for perfusion assay, and particularly suited for time-resolved optogenetics studies.

Fluid Dynamics of the Heart and its Valves

NASA Astrophysics Data System (ADS)

Peskin, Charles S.

1997-11-01

The fluid dynamics of the heart involve the interaction of blood, a viscous incompressible fluid, with the flexible, elastic, fiber-reinforced heart valve leaflets that are immersed in that fluid. Neither the fluid motion nor the valve leaflet motion are known in advance: both must be computed simultaneously by solving their coupled equations of motion. This can be done by the immersed boundary method(Peskin CS and McQueen DM: A general method for the computer simulation of biological systems interacting with fluids. In: Biological Fluid Dynamics (Ellington CP and Pedley TJ, eds.), The Company of Biologists Limited, Cambridge UK, 1995, pp. 265-276.), which can be extended to incorporate the contractile fiber architecture of the muscular heart walls as well as the valve leaflets and the blood. In this way we arrive at a three-dimensional computer model of the heart(Peskin CS and McQueen DM: Fluid dynamics of the heart and its valves. In: Case Studies in Mathematical Modeling: Ecology, Physiology, and Cell Biology (Othmer HG, Adler FR, Lewis MA, and Dallon JC, eds.), Prentice-Hall, Englewood Cliffs NJ, 1996, pp. 309-337.), which can be used as a test chamber for the design of prosthetic cardiac valves, and also to study the function of the heart in health and in disease. Numerical solutions of the equations of cardiac fluid dynamics obtained by the immersed boundary method will be presented in the form of a video animation of the beating heart.

Time-nonlocal kinetic equations, jerk and hyperjerk in plasmas and solar physics

NASA Astrophysics Data System (ADS)

El-Nabulsi, Rami Ahmad

2018-06-01

The simulation and analysis of nonlocal effects in fluids and plasmas is an inherently complicated problem due to the massive breadth of physics required to describe the nonlocal dynamics. This is a multi-physics problem that draws upon various miscellaneous fields, such as electromagnetism and statistical mechanics. In this paper we strive to focus on one narrow but motivating mathematical way: the derivation of nonlocal plasma-fluid equations from a generalized nonlocal Liouville derivative operator motivated from Suykens's nonlocal arguments. The paper aims to provide a guideline toward modeling nonlocal effects occurring in plasma-fluid systems by means of a generalized nonlocal Boltzmann equation. The generalized nonlocal equations of fluid dynamics are derived and their implications in plasma-fluid systems are addressed, discussed and analyzed. Three main topics were discussed: Landau damping in plasma electrodynamics, ideal MHD and solar wind. A number of features were revealed, analyzed and confronted with recent research results and observations.

Microfabrication of hybrid fluid membrane for microengines

NASA Astrophysics Data System (ADS)

Chutani, R.; Formosa, F.; de Labachelerie, M.; Badel, A.; Lanzetta, F.

2015-12-01

This paper describes the microfabrication and dynamic characterization of thick membranes providing a technological solution for microengines. The studied membranes are called hybrid fluid-membrane (HFM) and consist of two thin membranes that encapsulate an incompressible fluid. This work details the microelectromechanical system (MEMS) scalable fabrication and characterization of HFMs. The membranes are composite structures based on Silicon spiral springs embedded in a polymer (RTV silicone). The anodic bonding of multiple stacks of Si/glass structures, the fluid filling and the sealing have been demonstrated. Various HFMs were successfully fabricated and their dynamic characterization demonstrates the agreement between experimental and theoretical results.

Off-shell hydrodynamics from holography

DOE PAGES

Crossley, Michael; Glorioso, Paolo; Liu, Hong; ...

2016-02-18

In this article, we outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual. As a first step, in this paper we restrict to systems with a non-dissipative horizon. By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces. At zeroth order, this action reduces tomore » that proposed by Dubovsky et al. as an off-shell formulation of ideal fluid dynamics.« less

The development of an intelligent interface to a computational fluid dynamics flow-solver code

NASA Technical Reports Server (NTRS)

Williams, Anthony D.

1988-01-01

Researchers at NASA Lewis are currently developing an 'intelligent' interface to aid in the development and use of large, computational fluid dynamics flow-solver codes for studying the internal fluid behavior of aerospace propulsion systems. This paper discusses the requirements, design, and implementation of an intelligent interface to Proteus, a general purpose, 3-D, Navier-Stokes flow solver. The interface is called PROTAIS to denote its introduction of artificial intelligence (AI) concepts to the Proteus code.

The development of an intelligent interface to a computational fluid dynamics flow-solver code

NASA Technical Reports Server (NTRS)

Williams, Anthony D.

1988-01-01

Researchers at NASA Lewis are currently developing an 'intelligent' interface to aid in the development and use of large, computational fluid dynamics flow-solver codes for studying the internal fluid behavior of aerospace propulsion systems. This paper discusses the requirements, design, and implementation of an intelligent interface to Proteus, a general purpose, three-dimensional, Navier-Stokes flow solver. The interface is called PROTAIS to denote its introduction of artificial intelligence (AI) concepts to the Proteus code.

Interfacial fluid instabilities and Kapitsa pendula.

PubMed

Krieger, Madison S

2017-07-01

The onset and development of instabilities is one of the central problems in fluid mechanics. Here we develop a connection between instabilities of free fluid interfaces and inverted pendula. When acted upon solely by the gravitational force, the inverted pendulum is unstable. This position can be stabilized by the Kapitsa phenomenon, in which high-frequency low-amplitude vertical vibrations of the base creates a fictitious force which opposes the gravitational force. By transforming the dynamical equations governing a fluid interface into an appropriate pendulum-type equation, we demonstrate how stability can be induced in fluid systems by properly tuned vibrations. We construct a "dictionary"-type relationship between various pendula and the classical Rayleigh-Taylor, Kelvin-Helmholtz, Rayleigh-Plateau and the self-gravitational instabilities. This makes several results in control theory and dynamical systems directly applicable to the study of tunable fluid instabilities, where the critical wavelength depends on the external forces or the instability is suppressed entirely. We suggest some applications and instances of the effect ranging in scale from microns to the radius of a galaxy.

FDNS CFD Code Benchmark for RBCC Ejector Mode Operation

NASA Technical Reports Server (NTRS)

Holt, James B.; Ruf, Joe

1999-01-01

Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi-dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for both Diffusion and Afterburning (DAB) and Simultaneous Mixing and Combustion (SMC) test conditions. Results from both the 2D and the 3D models are presented.

Dynamic Mesh CFD Simulations of Orion Parachute Pendulum Motion During Atmospheric Entry

NASA Technical Reports Server (NTRS)

Halstrom, Logan D.; Schwing, Alan M.; Robinson, Stephen K.

2016-01-01

This paper demonstrates the usage of computational fluid dynamics to study the effects of pendulum motion dynamics of the NASAs Orion Multi-Purpose Crew Vehicle parachute system on the stability of the vehicles atmospheric entry and decent. Significant computational fluid dynamics testing has already been performed at NASAs Johnson Space Center, but this study sought to investigate the effect of bulk motion of the parachute, such as pitching, on the induced aerodynamic forces. Simulations were performed with a moving grid geometry oscillating according to the parameters observed in flight tests. As with the previous simulations, OVERFLOW computational fluid dynamics tool is used with the assumption of rigid, non-permeable geometry. Comparison to parachute wind tunnel tests is included for a preliminary validation of the dynamic mesh model. Results show qualitative differences in the flow fields of the static and dynamic simulations and quantitative differences in the induced aerodynamic forces, suggesting that dynamic mesh modeling of the parachute pendulum motion may uncover additional dynamic effects.

Research and Technology 1990

NASA Technical Reports Server (NTRS)

1990-01-01

A brief but comprehensive review is given of the technical accomplishments of the NASA Lewis Research Center during the past year. Topics covered include instrumentation and controls technology; internal fluid dynamics; aerospace materials, structures, propulsion, and electronics; space flight systems; cryogenic fluids; Space Station Freedom systems engineering, photovoltaic power module, electrical systems, and operations; and engineering and computational support.

Modeling and control of magnetorheological fluid dampers using neural networks

NASA Astrophysics Data System (ADS)

Wang, D. H.; Liao, W. H.

2005-02-01

Due to the inherent nonlinear nature of magnetorheological (MR) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the direct identification and inverse dynamic modeling for MR fluid dampers using feedforward and recurrent neural networks are studied. The trained direct identification neural network model can be used to predict the damping force of the MR fluid damper on line, on the basis of the dynamic responses across the MR fluid damper and the command voltage, and the inverse dynamic neural network model can be used to generate the command voltage according to the desired damping force through supervised learning. The architectures and the learning methods of the dynamic neural network models and inverse neural network models for MR fluid dampers are presented, and some simulation results are discussed. Finally, the trained neural network models are applied to predict and control the damping force of the MR fluid damper. Moreover, validation methods for the neural network models developed are proposed and used to evaluate their performance. Validation results with different data sets indicate that the proposed direct identification dynamic model using the recurrent neural network can be used to predict the damping force accurately and the inverse identification dynamic model using the recurrent neural network can act as a damper controller to generate the command voltage when the MR fluid damper is used in a semi-active mode.

Dynamic modeling method for infrared smoke based on enhanced discrete phase model

NASA Astrophysics Data System (ADS)

Zhang, Zhendong; Yang, Chunling; Zhang, Yan; Zhu, Hongbo

2018-03-01

The dynamic modeling of infrared (IR) smoke plays an important role in IR scene simulation systems and its accuracy directly influences the system veracity. However, current IR smoke models cannot provide high veracity, because certain physical characteristics are frequently ignored in fluid simulation; simplifying the discrete phase as a continuous phase and ignoring the IR decoy missile-body spinning. To address this defect, this paper proposes a dynamic modeling method for IR smoke, based on an enhanced discrete phase model (DPM). A mathematical simulation model based on an enhanced DPM is built and a dynamic computing fluid mesh is generated. The dynamic model of IR smoke is then established using an extended equivalent-blackbody-molecule model. Experiments demonstrate that this model realizes a dynamic method for modeling IR smoke with higher veracity.

Fluid elasticity and the transition to chaos in thermal convection

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

Khayat, R.E.

1995-01-01

The influence of fluid elasticity on the onset of aperiodic or chaotic motion of an upper-convected Maxwellian fluid is examined in the context of the Rayleigh-Benard thermal convection problem. A truncated Fourier representation of the flow and temperature fields leads to a four-dimensional dynamical system that constitutes a generalization of the classical Lorenz system for Newtonian fluids. It is found that, to the order of the present truncation and above a critical value of the Deborah number De[sup [ital c

Applied Nonlinear Dynamics and Stochastic Systems Near The Millenium. Proceedings

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

Kadtke, J.B.; Bulsara, A.

These proceedings represent papers presented at the Applied Nonlinear Dynamics and Stochastic Systems conference held in San Diego, California in July 1997. The conference emphasized the applications of nonlinear dynamical systems theory in fields as diverse as neuroscience and biomedical engineering, fluid dynamics, chaos control, nonlinear signal/image processing, stochastic resonance, devices and nonlinear dynamics in socio{minus}economic systems. There were 56 papers presented at the conference and 5 have been abstracted for the Energy Science and Technology database.(AIP)

Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics

NASA Astrophysics Data System (ADS)

Dawson, Scott T. M.

This thesis focuses on two major themes: modeling and understanding the dynamics of rapidly pitching airfoils, and developing methods that can be used to extract models and pertinent features from datasets obtained in the study of these and other systems in fluid mechanics and aerodynamics. Much of the work utilizes in some capacity dynamic mode decomposition (DMD), a recently developed method to extract dynamical features and models from data. The investigation of pitching airfoils includes both wind tunnel experiments and direct numerical simulations. Experiments are performed on a NACA 0012 airfoil undergoing rapid pitching motion, with the focus on developing a switched linear modeling framework that can accurately predict unsteady aerodynamic forces and pressure distributions throughout arbitrary pitching motions. Numerical simulations are used to study the behavior of sinusoidally pitching airfoils. By systematically varying the amplitude, frequency, mean angle and axis of pitching, a comprehensive database of results is acquired, from which interesting regions in parameter space are identified and studied. Attention is given to pitching at "preferred" frequencies, where vortex shedding in the wake is excited or amplified, leading to larger lift forces. More generally, the ability to extract nonlinear models that describe the behavior of complex fluids systems can assist in not only understanding the dominant features of such systems, but also to achieve accurate prediction and control. One potential avenue to achieve this objective is through numerical approximation of the Koopman operator, an infinite-dimensional linear operator capable of describing finite-dimensional nonlinear systems, such as those that might describe the dominant dynamics of fluids systems. This idea is explored by showing that algorithms designed to approximate the Koopman operator can indeed be utilized to accurately model nonlinear fluids systems, even when the data available is limited or noisy. Data-driven algorithms can be adversely affected by noisy data. Focusing on DMD, it is shown analytically that the algorithm is biased to sensor noise, which explains a previously observed sensitivity to noisy data. Using this finding, a number of modifications to DMD are proposed, which all give better approximations of the true dynamics using noise-corrupted data.

Fluid Dynamics Assessment of the VPCAR Water Recovery System in Partial and Microgravity

NASA Technical Reports Server (NTRS)

Niederhaus, Charles; Nahra, Henry; Flynn, Michael

2006-01-01

The Vapor Phase Catalytic Ammonia Removal (VPCAR) system is being developed to recycle water for future NASA Exploration Missions. Testing was recently conducted on NASA s C-9B Reduced Gravity Aircraft to determine the microgravity performance of a key component of the VPCAR water recovery system. Six flights were conducted to evaluate the fluid dynamics of the Wiped-Film Rotating Disk (WFRD) distillation component of the VPCAR system in microgravity, focusing on the water delivery method. The experiments utilized a simplified system to study the process of forming a thin film on a disk similar to that in the evaporator section of VPCAR. Fluid issues are present with the current configuration, and the initial alternative configurations were only partial successful in microgravity operation. The underlying causes of these issues are understood, and new alternatives are being designed to rectify the problems.

Dynamics of two-phase interfaces and surface tensions: A density-functional theory perspective

NASA Astrophysics Data System (ADS)

Yatsyshin, Petr; Sibley, David N.; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim

2016-11-01

Classical density functional theory (DFT) is a statistical mechanical framework for the description of fluids at the nanoscale, where the inhomogeneity of the fluid structure needs to be carefully accounted for. By expressing the grand free-energy of the fluid as a functional of the one-body density, DFT offers a theoretically consistent and computationally accessible way to obtain two-phase interfaces and respective interfacial tensions in a ternary solid-liquid-gas system. The dynamic version of DFT (DDFT) can be rigorously derived from the Smoluchowsky picture of the dynamics of colloidal particles in a solvent. It is generally agreed that DDFT can capture the diffusion-driven evolution of many soft-matter systems. In this context, we use DDFT to investigate the dynamic behaviour of two-phase interfaces in both equilibrium and dynamic wetting and discuss the possibility of defining a time-dependent surface tension, which still remains in debate. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from the Engineering and Physical Sciences Research Council of the UK via Grants No. EP/L027186 and EP/L020564.

Bursting dynamics in Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Dan, Surajit; Ghosh, Manojit; Nandukumar, Yada; Dana, Syamal K.; Pal, Pinaki

2017-06-01

We report bursting dynamics in a parametrically driven Rayleigh-Bénard convection (RBC) model of low Prandtl-number fluids with free-slip boundary conditions. A four dimensional RBC model [P. Pal, K. Kumar, P. Maity, S.K. Dana, Phys. Rev. E 87, 023001 (2013)] is used for this study. The dynamical system shows pitchfork, Hopf and gluing bifurcations near the onset of RBC of low Prandtl-number fluids. Around the bifurcation points, when the Rayleigh number of the system is slowly modulated periodically, two unknown kinds of bursting appears, namely, Hopf/Hopf via pitchfork bifurcation and Hopf/Hopf via gluing bifurcation besides the conventional Hopf/Hopf (elliptical) and pitchfork/pitchfork bursting.

Quantum trajectory analysis of multimode subsystem-bath dynamics.

PubMed

Wyatt, Robert E; Na, Kyungsun

2002-01-01

The dynamics of a swarm of quantum trajectories is investigated for systems involving the interaction of an active mode (the subsystem) with an M-mode harmonic reservoir (the bath). Equations of motion for the position, velocity, and action function for elements of the probability fluid are integrated in the Lagrangian (moving with the fluid) picture of quantum hydrodynamics. These fluid elements are coupled through the Bohm quantum potential and as a result evolve as a correlated ensemble. Wave function synthesis along the trajectories permits an exact description of the quantum dynamics for the evolving probability fluid. The approach is fully quantum mechanical and does not involve classical or semiclassical approximations. Computational results are presented for three systems involving the interaction on an active mode with M=1, 10, and 15 bath modes. These results include configuration space trajectory evolution, flux analysis of the evolving ensemble, wave function synthesis along trajectories, and energy partitioning along specific trajectories. These results demonstrate the feasibility of using a small number of quantum trajectories to obtain accurate quantum results on some types of open quantum systems that are not amenable to standard quantum approaches involving basis set expansions or Eulerian space-fixed grids.

ER fluid applications to vibration control devices and an adaptive neural-net controller

NASA Astrophysics Data System (ADS)

Morishita, Shin; Ura, Tamaki

1993-07-01

Four applications of electrorheological (ER) fluid to vibration control actuators and an adaptive neural-net control system suitable for the controller of ER actuators are described: a shock absorber system for automobiles, a squeeze film damper bearing for rotational machines, a dynamic damper for multidegree-of-freedom structures, and a vibration isolator. An adaptive neural-net control system composed of a forward model network for structural identification and a controller network is introduced for the control system of these ER actuators. As an example study of intelligent vibration control systems, an experiment was performed in which the ER dynamic damper was attached to a beam structure and controlled by the present neural-net controller so that the vibration in several modes of the beam was reduced with a single dynamic damper.

Numerical simulations (2D) on the influence of pre-existing local structures and seismic source characteristics in earthquake-volcano interactions

NASA Astrophysics Data System (ADS)

Farías, Cristian; Galván, Boris; Miller, Stephen A.

2017-09-01

Earthquake triggering of hydrothermal and volcanic systems is ubiquitous, but the underlying processes driving these systems are not well-understood. We numerically investigate the influence of seismic wave interaction with volcanic systems simulated as a trapped, high-pressure fluid reservoir connected to a fluid-filled fault system in a 2-D poroelastic medium. Different orientations and earthquake magnitudes are studied to quantify dynamic and static stress, and pore pressure changes induced by a seismic event. Results show that although the response of the system is mainly dominated by characteristics of the radiated seismic waves, local structures can also play an important role on the system dynamics. The fluid reservoir affects the seismic wave front, distorts the static overpressure pattern induced by the earthquake, and concentrates the kinetic energy of the incoming wave on its boundaries. The static volumetric stress pattern inside the fault system is also affected by the local structures. Our results show that local faults play an important role in earthquake-volcanic systems dynamics by concentrating kinetic energy inside and acting as wave-guides that have a breakwater-like behavior. This generates sudden changes in pore pressure, volumetric expansion, and stress gradients. Local structures also influence the regional Coulomb yield function. Our results show that local structures affect the dynamics of volcanic and hydrothermal systems, and should be taken into account when investigating triggering of these systems from nearby or distant earthquakes.

A variational approach to the strongly nonlinear regime of the Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Yoshikawa, Toshio

The Rayleigh-Taylor instability is the instability of the interface between two fluids of different densities. When a heavy fluid is superposed over a light fluid. small disturbances on the interface develop into a complex form with heavy fluid ``fingers'' and light fluid ``bubbles.'' We propose a variational method for the description of the evolution of the fingers and bubbles in the late stage of the instability. In this method, the fluid region is represented as the image of a time-dependent conformal mapping; the dynamics of the mapping is determined by the least action principle for the Lagrangian. i.e., the kinetic energy minus the potential energy. The evolution of a single finger and bubble is investigated by this method. We first consider a symmetric finger and bubble in a zero gravitational field. We derive an integrable Hamiltonian system with two degrees of freedom that governs the dynamics of the symmetric finger and bubble. We present a general solution of the system. The solution predicts the linear growth of the finger and the saturation of the bubble growth. It is shown that this solution is asymptotically exact. We consider a symmetric finger and bubble with perturbations. We show that the dynamics of the finger and bubble and that of the perturbations are decoupled. We next consider an inclined finger and bubble in a zero gravitational field. We derive a Hamiltonian system with four degrees of freedom that governs the dynamics of the inclined finger and bubble. The system has four integrals of motion, one of them depends on time explicitly. When there is no lateral motion, the system reduces to an integrable Hamiltonian system with three degrees of freedom. A general solution of the system is presented. The solution predicts the linear growth of the finger toward a direction and the saturation of the bubble growth. Finally, we consider a symmetric finger and bubble in a uniform gravitational field. We derive a Hamiltonian system with two degrees of freedom that governs the dynamics of the symmetric finger and bubble. Since the system includes a potential energy term, it is not integrable in general. However, we present a general solution in the case of the total energy being zero. This case corresponds to an interesting case where the evolution starts from a flat surface. The solution predicts that the finger grows as the square of time, and the bubble as the square root of time.

Magnetofluid dynamics in curved spacetime

NASA Astrophysics Data System (ADS)

Bhattacharjee, Chinmoy; Das, Rupam; Mahajan, S. M.

2015-03-01

A grand unified field Mμ ν is constructed from Maxwell's field tensor and an appropriately modified flow field, both nonminimally coupled to gravity, to analyze the dynamics of hot charged fluids in curved background space-time. With a suitable 3 +1 decomposition, this new formalism of the hot fluid is then applied to investigate the vortical dynamics of the system. Finally, the equilibrium state for plasma with nonminimal coupling through Ricci scalar R to gravity is investigated to derive a double Beltrami equation in curved space-time.

Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

NASA Technical Reports Server (NTRS)

Nance, Donald K.; Liever, Peter A.

2015-01-01

The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test (SMAT), conducted at Marshall Space Flight Center (MSFC). The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

NASA Technical Reports Server (NTRS)

Nance, Donald; Liever, Peter; Nielsen, Tanner

2015-01-01

The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test, conducted at Marshall Space Flight Center. The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed.

Static and dynamic properties of smoothed dissipative particle dynamics

NASA Astrophysics Data System (ADS)

Alizadehrad, Davod; Fedosov, Dmitry A.

2018-03-01

In this paper, static and dynamic properties of the smoothed dissipative particle dynamics (SDPD) method are investigated. We study the effect of method parameters on SDPD fluid properties, such as structure, speed of sound, and transport coefficients, and show that a proper choice of parameters leads to a well-behaved and accurate fluid model. In particular, the speed of sound, the radial distribution function (RDF), shear-thinning of viscosity, the mean-squared displacement (〈R2 〉 ∝ t), and the Schmidt number (Sc ∼ O (103) - O (104)) can be controlled, such that the model exhibits a fluid-like behavior for a wide range of temperatures in simulations. Furthermore, in addition to the consideration of fluid density variations for fluid compressibility, a more challenging test of incompressibility is performed by considering the Poisson ratio and divergence of velocity field in an elongational flow. Finally, as an example of complex-fluid flow, we present the applicability and validity of the SDPD method with an appropriate choice of parameters for the simulation of cellular blood flow in irregular geometries. In conclusion, the results demonstrate that the SDPD method is able to approximate well a nearly incompressible fluid behavior, which includes hydrodynamic interactions and consistent thermal fluctuations, thereby providing, a powerful approach for simulations of complex mesoscopic systems.

Hydraulics of sprinkler and microirrigation systems

USDA-ARS?s Scientific Manuscript database

The fluid dynamics of sprinkler and microirrigation systems are complex. Water moves dynamically from the water source through the pump into the pipe network. Water often goes through a series of screens and filters depending on the source and type of irrigation system. From the pipe network, water ...

46 CFR 56.15-5 - Fluid-conditioner fittings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Class I, I-L, and II-L systems receiving ship motion dynamic analysis and nondestructive examination. For Class I, I-L, or II-L systems not receiving ship motion dynamic analysis and nondestructive... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND...

Parallel Three-Dimensional Computation of Fluid Dynamics and Fluid-Structure Interactions of Ram-Air Parachutes

NASA Technical Reports Server (NTRS)

Tezduyar, Tayfun E.

1998-01-01

This is a final report as far as our work at University of Minnesota is concerned. The report describes our research progress and accomplishments in development of high performance computing methods and tools for 3D finite element computation of aerodynamic characteristics and fluid-structure interactions (FSI) arising in airdrop systems, namely ram-air parachutes and round parachutes. This class of simulations involves complex geometries, flexible structural components, deforming fluid domains, and unsteady flow patterns. The key components of our simulation toolkit are a stabilized finite element flow solver, a nonlinear structural dynamics solver, an automatic mesh moving scheme, and an interface between the fluid and structural solvers; all of these have been developed within a parallel message-passing paradigm.

Results of the Workshop on Two-Phase Flow, Fluid Stability and Dynamics: Issues in Power, Propulsion, and Advanced Life Support Systems

NASA Technical Reports Server (NTRS)

McQuillen, John; Rame, Enrique; Kassemi, Mohammad; Singh, Bhim; Motil, Brian

2003-01-01

The Two-phase Flow, Fluid Stability and Dynamics Workshop was held on May 15, 2003 in Cleveland, Ohio to define a coherent scientific research plan and roadmap that addresses the multiphase fluid problems associated with NASA s technology development program. The workshop participants, from academia, industry and government, prioritized various multiphase issues and generated a research plan and roadmap to resolve them. This report presents a prioritization of the various multiphase flow and fluid stability phenomena related primarily to power, propulsion, fluid and thermal management and advanced life support; and a plan to address these issues in a logical and timely fashion using analysis, ground-based and space-flight experiments.

Natural frequency and stability analysis of a pipe conveying fluid with axially moving supports immersed in fluid

NASA Astrophysics Data System (ADS)

Ni, Qiao; Luo, Yangyang; Li, Mingwu; Yan, Hao

2017-09-01

Structural model for a slender and uniform pipe conveying fluid, with axially moving supports on both ends, immersed in an incompressible fluid, is formulated. Free vibration and stability of the system are studied through numerical calculation. First, the equations of motion of the system are derived in an absolute coordinate system. An "axial added mass coefficient" is adopted to amend the forces caused by the external fluid. Boundary conditions are fixed by using coordinated conversion. Then, numerical results of the natural frequency are obtained via the Galerkin method, both for pinned-pinned and clamped-clamped supports. The critical speeds of supports and several instability types are discussed. Last, the effects of the system parameters on the dynamics and instability of the system are investigated.

Microgravity fluid management requirements of advanced solar dynamic power systems

NASA Technical Reports Server (NTRS)

Migra, Robert P.

1987-01-01

The advanced solar dynamic system (ASDS) program is aimed at developing the technology for highly efficient, lightweight space power systems. The approach is to evaluate Stirling, Brayton and liquid metal Rankine power conversion systems (PCS) over the temperature range of 1025 to 1400K, identify the critical technologies and develop these technologies. Microgravity fluid management technology is required in several areas of this program, namely, thermal energy storage (TES), heat pipe applications and liquid metal, two phase flow Rankine systems. Utilization of the heat of fusion of phase change materials offers potential for smaller, lighter TES systems. The candidate TES materials exhibit large volume change with the phase change. The heat pipe is an energy dense heat transfer device. A high temperature application may transfer heat from the solar receiver to the PCS working fluid and/or TES. A low temperature application may transfer waste heat from the PCS to the radiator. The liquid metal Rankine PCS requires management of the boiling/condensing process typical of two phase flow systems.

On the coupling of fluid dynamics and electromagnetism at the top of the earth's core

NASA Technical Reports Server (NTRS)

Benton, E. R.

1985-01-01

A kinematic approach to short-term geomagnetism has recently been based upon pre-Maxwell frozen-flux electromagnetism. A complete dynamic theory requires coupling fluid dynamics to electromagnetism. A geophysically plausible simplifying assumption for the vertical vorticity balance, namely that the vertical Lorentz torque is negligible, is introduced and its consequences are developed. The simplified coupled magnetohydrodynamic system is shown to conserve a variety of magnetic and vorticity flux integrals. These provide constraints on eligible models for the geomagnetic main field, its secular variation, and the horizontal fluid motions at the top of the core, and so permit a number of tests of the underlying assumptions.

Nanoscale hydrodynamics near solids

NASA Astrophysics Data System (ADS)

Camargo, Diego; de la Torre, J. A.; Duque-Zumajo, D.; Español, Pep; Delgado-Buscalioni, Rafael; Chejne, Farid

2018-02-01

Density Functional Theory (DFT) is a successful and well-established theory for the study of the structure of simple and complex fluids at equilibrium. The theory has been generalized to dynamical situations when the underlying dynamics is diffusive as in, for example, colloidal systems. However, there is no such a clear foundation for Dynamic DFT (DDFT) for the case of simple fluids in contact with solid walls. In this work, we derive DDFT for simple fluids by including not only the mass density field but also the momentum density field of the fluid. The standard projection operator method based on the Kawasaki-Gunton operator is used for deriving the equations for the average value of these fields. The solid is described as featureless under the assumption that all the internal degrees of freedom of the solid relax much faster than those of the fluid (solid elasticity is irrelevant). The fluid moves according to a set of non-local hydrodynamic equations that include explicitly the forces due to the solid. These forces are of two types, reversible forces emerging from the free energy density functional, and accounting for impenetrability of the solid, and irreversible forces that involve the velocity of both the fluid and the solid. These forces are localized in the vicinity of the solid surface. The resulting hydrodynamic equations should allow one to study dynamical regimes of simple fluids in contact with solid objects in isothermal situations.

Study of toluene stability for an Organic Rankine Cycle (ORC) space-based power system

NASA Technical Reports Server (NTRS)

Havens, Vance; Ragaller, Dana

1988-01-01

The design, fabrication, assembly, and endurance operation of a dynamic test loop, built to evaluate the thermal stability of a proposed Organic Rankine Cycle (ORC) working fluid, is discussed. The test fluid, toluene, was circulated through a heater, simulated turbine, regenerator, condenser and pump to duplicate an actual ORC system. The maximum nominal fluid temperature, 750 F, was at the turbine simulator inlet. Samples of noncondensible gases and liquid toluene were taken periodically during the test. The samples were analyzed to identify the degradation products formed and the quantity of these products. From these data it was possible to determine the degradation rate of the working fluid and the generation rate of noncondensible gases. A further goal of this work was to relate the degradation observed in the dynamic operating loop to degradation obtained in isothermal capsule tests. This relationship was the basis for estimating the power loop degradation in the Space Station Organic Rankine Cycle system.

Periodic orbit analysis of a system with continuous symmetry--A tutorial.

PubMed

Budanur, Nazmi Burak; Borrero-Echeverry, Daniel; Cvitanović, Predrag

2015-07-01

Dynamical systems with translational or rotational symmetry arise frequently in studies of spatially extended physical systems, such as Navier-Stokes flows on periodic domains. In these cases, it is natural to express the state of the fluid in terms of a Fourier series truncated to a finite number of modes. Here, we study a 4-dimensional model with chaotic dynamics and SO(2) symmetry similar to those that appear in fluid dynamics problems. A crucial step in the analysis of such a system is symmetry reduction. We use the model to illustrate different symmetry-reduction techniques. The system's relative equilibria are conveniently determined by rewriting the dynamics in terms of a symmetry-invariant polynomial basis. However, for the analysis of its chaotic dynamics, the "method of slices," which is applicable to very high-dimensional problems, is preferable. We show that a Poincaré section taken on the "slice" can be used to further reduce this flow to what is for all practical purposes a unimodal map. This enables us to systematically determine all relative periodic orbits and their symbolic dynamics up to any desired period. We then present cycle averaging formulas adequate for systems with continuous symmetry and use them to compute dynamical averages using relative periodic orbits. The convergence of such computations is discussed.

Analytical structure, dynamics, and coarse graining of a kinetic model of an active fluid

NASA Astrophysics Data System (ADS)

Gao, Tong; Betterton, Meredith D.; Jhang, An-Sheng; Shelley, Michael J.

2017-09-01

We analyze one of the simplest active suspensions with complex dynamics: a suspension of immotile "extensor" particles that exert active extensile dipolar stresses on the fluid in which they are immersed. This is relevant to several experimental systems, such as recently studied tripartite rods that create extensile flows by consuming a chemical fuel. We first describe the system through a Doi-Onsager kinetic theory based on microscopic modeling. This theory captures the active stresses produced by the particles that can drive hydrodynamic instabilities, as well as the steric interactions of rodlike particles that lead to nematic alignment. This active nematic system yields complex flows and disclination defect dynamics very similar to phenomenological Landau-deGennes Q -tensor theories for active nematic fluids, as well as by more complex Doi-Onsager theories for polar microtubule-motor-protein systems. We apply the quasiequilibrium Bingham closure, used to study suspensions of passive microscopic rods, to develop a nonstandard Q -tensor theory. We demonstrate through simulation that this B Q -tensor theory gives an excellent analytical and statistical accounting of the suspension's complex dynamics, at a far reduced computational cost. Finally, we apply the B Q -tensor model to study the dynamics of extensor suspensions in circular and biconcave domains. In circular domains, we reproduce previous results for systems with weak nematic alignment, but for strong alignment we find unusual dynamics with activity-controlled defect production and absorption at the boundaries of the domain. In biconcave domains, a Fredericks-like transition occurs as the width of the neck connecting the two disks is varied.

Flocking from a quantum analogy: spin-orbit coupling in an active fluid

NASA Astrophysics Data System (ADS)

Loewe, Benjamin; Souslov, Anton; Goldbart, Paul M.

2018-01-01

Systems composed of strongly interacting self-propelled particles can form a spontaneously flowing polar active fluid. The study of the connection between the microscopic dynamics of a single such particle and the macroscopic dynamics of the fluid can yield insights into experimentally realizable active flows, but this connection is well understood in only a few select cases. We introduce a model of self-propelled particles based on an analogy with the motion of electrons that have strong spin-orbit coupling. We find that, within our model, self-propelled particles are subject to an analog of the Heisenberg uncertainty principle that relates translational and rotational noise. Furthermore, by coarse-graining this microscopic model, we establish expressions for the coefficients of the Toner-Tu equations—the hydrodynamic equations that describe an active fluid composed of these ‘active spins.’ The connection between stochastic self-propelled particles and quantum particles with spin may help realize exotic phases of matter using active fluids via analogies with systems composed of strongly correlated electrons.

Grain scale observations of stick-slip dynamics in fluid saturated granular fault gouge

NASA Astrophysics Data System (ADS)

Johnson, P. A.; Dorostkar, O.; Guyer, R. A.; Marone, C.; Carmeliet, J.

2017-12-01

We are studying granular mechanics during slip. In the present work, we conduct coupled computational fluid dynamics (CFD) and discrete element method (DEM) simulations to study grain scale characteristics of slip instabilities in fluid saturated granular fault gouge. The granular sample is confined with constant normal load (10 MPa), and sheared with constant velocity (0.6 mm/s). This loading configuration is chosen to promote stick-slip dynamics, based on a phase-space study. Fluid is introduced in the beginning of stick phase and characteristics of slip events i.e. macroscopic friction coefficient, kinetic energy and layer thickness are monitored. At the grain scale, we monitor particle coordination number, fluid-particle interaction forces as well as particle and fluid kinetic energy. Our observations show that presence of fluids in a drained granular fault gouge stabilizes the layer in the stick phase and increases the recurrence time. In saturated model, we observe that average particle coordination number reaches higher values compared to dry granular gouge. Upon slip, we observe that a larger portion of the granular sample is mobilized in saturated gouge compared to dry system. We also observe that regions with high particle kinetic energy are correlated with zones of high fluid motion. Our observations highlight that spatiotemporal profile of fluid dynamic pressure affects the characteristics of slip instabilities, increasing macroscopic friction coefficient drop, kinetic energy release and granular layer compaction. We show that numerical simulations help characterize the micromechanics of fault mechanics.

Coupling fast fluid dynamics and multizone airflow models in Modelica Buildings library to simulate the dynamics of HVAC systems

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

Tian, Wei; Sevilla, Thomas Alonso; Zuo, Wangda

Historically, multizone models are widely used in building airflow and energy performance simulations due to their fast computing speed. However, multizone models assume that the air in a room is well mixed, consequently limiting their application. In specific rooms where this assumption fails, the use of computational fluid dynamics (CFD) models may be an alternative option. Previous research has mainly focused on coupling CFD models and multizone models to study airflow in large spaces. While significant, most of these analyses did not consider the coupled simulation of the building airflow with the building's Heating, Ventilation, and Air-Conditioning (HVAC) systems. Thismore » paper tries to fill the gap by integrating the models for HVAC systems with coupled multizone and CFD simulations for airflows, using the Modelica simul ation platform. To improve the computational efficiency, we incorporated a simplified CFD model named fast fluid dynamics (FFD). We first introduce the data synchronization strategy and implementation in Modelica. Then, we verify the implementation using two case studies involving an isothermal and a non-isothermal flow by comparing model simulations to experiment data. Afterward, we study another three cases that are deemed more realistic. This is done by attaching a variable air volume (VAV) terminal box and a VAV system to previous flows to assess the capability of the models in studying the dynamic control of HVAC systems. Finally, we discuss further research needs on the coupled simulation using the models.« less

Liquid phase fluid dynamic (methanol) run in the LaPorte alternative fuels development unit

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

Bharat L. Bhatt

1997-05-01

A fluid dynamic study was successfully completed in a bubble column at DOE's Alternative Fuels Development Unit (AFDU) in LaPorte, Texas. Significant fluid dynamic information was gathered at pilot scale during three weeks of Liquid Phase Methanol (LPMEOJP) operations in June 1995. In addition to the usual nuclear density and temperature measurements, unique differential pressure data were collected using Sandia's high-speed data acquisition system to gain insight on flow regime characteristics and bubble size distribution. Statistical analysis of the fluctuations in the pressure data suggests that the column was being operated in the churn turbulent regime at most of themore » velocities considered. Dynamic gas disengagement experiments showed a different behavior than seen in low-pressure, cold-flow work. Operation with a superficial gas velocity of 1.2 ft/sec was achieved during this run, with stable fluid dynamics and catalyst performance. Improvements included for catalyst activation in the design of the Clean Coal III LPMEOH{trademark} plant at Kingsport, Tennessee, were also confirmed. In addition, an alternate catalyst was demonstrated for LPMEOH{trademark}.« less

The solar dynamic radiator with a historical perspective

NASA Technical Reports Server (NTRS)

Mclallin, K. L.; Fleming, M. L.; Hoehn, F. W.; Howerton, R. L.

1988-01-01

A historical perspective on pumped-fluid loop space radiators provides a basis for the design of the Space Station Solar Dynamic (SD) power module radiator. SD power modules, capable of generating 25 kW (electrical) each, are planned for growth in Station power requirements. The Brayton cycle SD module configuration incorporates a pumped-fluid loop radiator that must reject up to 99 kW (thermal). The thermal/hydraulic design conditions in combination with required radiator orientation and packaging envelope form a unique set of constraints as compared to previous pumped-fluid loop radiator systems. Nevertheless, past program successes have demonstrated a technology base that can be applied to the SD radiator development program to ensure a low risk, low cost system.

Overview of Fluid Dynamics Activities at the Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Garcia, Roberto; Griffin, Lisa W.; Wang, Ten-See

1999-01-01

Since its inception 40 years ago, Marshall Space Flight Center (MSFC) has had the need to maintain and advance state-of-the-art flow analysis and cold-flow testing capability to support its roles and missions. This overview discusses the recent organizational changes that have occurred at MSFC with emphasis on the resulting three groups that form the core of fluid dynamics expertise at MSFC: the Fluid Physics and Dynamics Group, the Applied Fluid Dynamics Analysis Group, and the Experimental Fluid Dynamics Group. Recently completed activities discussed include the analysis and flow testing in support of the Fastrac engine design, the X-33 vehicle design, and the X34 propulsion system design. Ongoing activities include support of the RLV vehicle design, Liquid Fly Back Booster aerodynamic configuration definition, and RLV focused technologies development. Other ongoing activities discussed are efforts sponsored by the Center Director's Discretionary Fund (CDDF) to develop an advanced incompressible flow code and to develop optimization techniques. Recently initiated programs and their anticipated required fluid dynamics support are discussed. Based on recent experiences and on the anticipated program needs, required analytical and experimental technique improvements are presented. Due to anticipated budgetary constraints, there is a strong need to leverage activities and to pursue teaming arrangements in order to advance the state-of-the-art and to adequately support concept development. Throughout this overview there is discussion of the lessons learned and of the capabilities demonstrated and established in support of the hardware development programs.

FDNS CFD Code Benchmark for RBCC Ejector Mode Operation: Continuing Toward Dual Rocket Effects

NASA Technical Reports Server (NTRS)

West, Jeff; Ruf, Joseph H.; Turner, James E. (Technical Monitor)

2000-01-01

Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi -dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code [2] was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for the Diffusion and Afterburning (DAB) test conditions at the 200-psia thruster operation point, Results with and without downstream fuel injection are presented.

PREFACE: Complex dynamics of fluids in disordered and crowded environments Complex dynamics of fluids in disordered and crowded environments

NASA Astrophysics Data System (ADS)

Coslovich, Daniele; Kahl, Gerhard; Krakoviack, Vincent

2011-06-01

Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized. In fact, theory and simulations were recently able to predict new and surprising dynamical features, such as the occurrence of sub-diffusive laws, which result from the trapping due to the geometric and topological constraints and/or quenched disorder, the presence of both continuous and discontinuous glass transitions, and diffusion-localization transitions. Together, theory and simulations are thus able to contribute to a deeper insight into the complex dynamical behaviour of fluids in disordered confinement. Still, many yet unsolved problems remain. The fact that theoretical and simulation approaches have caught up with experimental investigations, has motivated us to organize a workshop on the dynamics of fluids confined in disordered environments, so as to bring together the different communities working in this field: theory and simulations, with their recent developments based on the mode-coupling theory of the glass transition, and experiments, with particular emphasis on colloidal systems and novel techniques. In an effort to give credit to recent developments in related problems of biophysical relevance, an entire session of the programme was dedicated to anomalous diffusion in crowded environments. The workshop was thus aimed at providing a deeper understanding of the complex dynamics of fluids in confinement as well as up-to-date perspectives on the interdisciplinary applications of this field of research. We are proud to say that all 32 contacted speakers accepted our invitation. Additional participants were attracted by our scientific programme, contributing poster presentations to the workshop. In total, close to 50 participants were registered, arriving from 11 different countries (including the US, Japan, and Mexico). Thus we conclude that the workshop indeed addressed a highly topical scientific field. From the scientific point of view a broad range of problems was covered, ranging from biophysics over soft matter to fermion systems. From the vivid discussions it became evident that the close scientific contact between theory, simulation and experiment brought along a fruitful and mutually inspiring atmosphere. On the theoretical side, these discussions have allowed clarification of several connections between the dynamics of models of fluids in porous media (quenched-annealed, pinned particles models), those of well-known limiting cases (Lorentz gas), of realistic models of liquids with strong dynamic asymmetry (asymmetric size and mass mixtures, sodium silicates, polymers blends) and even of bulk glass-formers. On the experimental side, it appeared that soft matter systems may provide an excellent test-bed to verify the theoretical predictions. From the concluding discussion it was also clear that addressing related issues relevant to biology still remains an open challenge for the future. In view of all this, it was concluded that within a short time period a workshop with analogous scope should be organized to address the progress made on both fundamental and interdisciplinary aspects. The realization of this workshop was made possible by generous financial support from CECAM, Centre Blaise Pascal-ENS de Lyon, and the ESF network 'Molecular Simulations in Biosystems and Material Science' (SimBioMa). Complex dynamics of fluids in disordered and crowded environments contents Phonon dispersions of cluster crystals Tim Neuhaus and Christos N Likos Challenges in determining anomalous diffusion in crowded fluids Marcel Hellmann, Joseph Klafter, Dieter W Heermann and Matthias Weiss Diffusion of active tracers in fluctuating fields David S Dean and Vincent Démery Self-diffusion of non-interacting hard spheres in particle gels Jean-Christophe Gimel and Taco Nicolai Probing glassy states in binary mixtures of soft interpenetrable colloids E Stiakakis, B M Erwin, D Vlassopoulos, M Cloitre, A Munam, M Gauthier, H Iatrou and N Hadjichristidis Fluids with quenched disorder: scaling of the free energy barrier near critical points T Fischer and R L C Vink Lennard-Jones binary mixture in disordered matrices: exploring the mode coupling scenario at increasing confinement P Gallo and M Rovere Static and dynamic contributions to anomalous chain dynamics in polymer blends Marco Bernabei, Angel J Moreno and J Colmenero Anomalous transport of a tracer on percolating clusters Markus Spanner, Felix Höfling, Gerd E Schröder-Turk, Klaus Mecke and Thomas Franosch Long-wavelength anomalies in the asymptotic behavior of mode-coupling theory S K Schnyder, F Höfling, T Franosch and Th Voigtmann Dynamic arrest of colloids in porous environments: disentangling crowding and confinement Jan Kurzidim, Daniele Coslovich and Gerhard Kahl Slow dynamics, dynamic heterogeneities, and fragility of supercooled liquids confined in random media Kang Kim, Kunimasa Miyazaki and Shinji Saito

Statistical Decoupling of a Lagrangian Fluid Parcel in Newtonian Cosmology

NASA Astrophysics Data System (ADS)

Wang, Xin; Szalay, Alex

2016-03-01

The Lagrangian dynamics of a single fluid element within a self-gravitational matter field is intrinsically non-local due to the presence of the tidal force. This complicates the theoretical investigation of the nonlinear evolution of various cosmic objects, e.g., dark matter halos, in the context of Lagrangian fluid dynamics, since fluid parcels with given initial density and shape may evolve differently depending on their environments. In this paper, we provide a statistical solution that could decouple this environmental dependence. After deriving the evolution equation for the probability distribution of the matter field, our method produces a set of closed ordinary differential equations whose solution is uniquely determined by the initial condition of the fluid element. Mathematically, it corresponds to the projected characteristic curve of the transport equation of the density-weighted probability density function (ρPDF). Consequently it is guaranteed that the one-point ρPDF would be preserved by evolving these local, yet nonlinear, curves with the same set of initial data as the real system. Physically, these trajectories describe the mean evolution averaged over all environments by substituting the tidal tensor with its conditional average. For Gaussian distributed dynamical variables, this mean tidal tensor is simply proportional to the velocity shear tensor, and the dynamical system would recover the prediction of the Zel’dovich approximation (ZA) with the further assumption of the linearized continuity equation. For a weakly non-Gaussian field, the averaged tidal tensor could be expanded perturbatively as a function of all relevant dynamical variables whose coefficients are determined by the statistics of the field.

STATISTICAL DECOUPLING OF A LAGRANGIAN FLUID PARCEL IN NEWTONIAN COSMOLOGY

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

Wang, Xin; Szalay, Alex, E-mail: xwang@cita.utoronto.ca

The Lagrangian dynamics of a single fluid element within a self-gravitational matter field is intrinsically non-local due to the presence of the tidal force. This complicates the theoretical investigation of the nonlinear evolution of various cosmic objects, e.g., dark matter halos, in the context of Lagrangian fluid dynamics, since fluid parcels with given initial density and shape may evolve differently depending on their environments. In this paper, we provide a statistical solution that could decouple this environmental dependence. After deriving the evolution equation for the probability distribution of the matter field, our method produces a set of closed ordinary differentialmore » equations whose solution is uniquely determined by the initial condition of the fluid element. Mathematically, it corresponds to the projected characteristic curve of the transport equation of the density-weighted probability density function (ρPDF). Consequently it is guaranteed that the one-point ρPDF would be preserved by evolving these local, yet nonlinear, curves with the same set of initial data as the real system. Physically, these trajectories describe the mean evolution averaged over all environments by substituting the tidal tensor with its conditional average. For Gaussian distributed dynamical variables, this mean tidal tensor is simply proportional to the velocity shear tensor, and the dynamical system would recover the prediction of the Zel’dovich approximation (ZA) with the further assumption of the linearized continuity equation. For a weakly non-Gaussian field, the averaged tidal tensor could be expanded perturbatively as a function of all relevant dynamical variables whose coefficients are determined by the statistics of the field.« less

Effects of Acoustic and Fluid Dynamic Interactions in Resonators: Applications in Thermoacoustic Refrigeration

NASA Astrophysics Data System (ADS)

Antao, Dion Savio

Thermoacoustic refrigeration systems have gained increased importance in cryogenic cooling technologies and improvements are needed to increase the efficiency and effectiveness of the current cryogenic refrigeration devices. These improvements in performance require a re-examination of the fundamental acoustic and fluid dynamic interactions in the acoustic resonators that comprise a thermoacoustic refrigerator. A comprehensive research program of the pulse tube thermoacoustic refrigerator (PTR) and arbitrarily shaped, circular cross-section acoustic resonators was undertaken to develop robust computational models to design and predict the transport processes in these systems. This effort was divided into three main focus areas: (a) studying the acoustic and fluid dynamic interactions in consonant and dissonant acoustic resonators, (b) experimentally investigating thermoacoustic refrigeration systems attaining cryogenic levels and (c) computationally studying the transport processes and energy conversion through fluid-solid interactions in thermoacoustic pulse tube refrigeration devices. To investigate acoustic-fluid dynamic interactions in resonators, a high fidelity computational fluid dynamic model was developed and used to simulate the flow, pressure and temperature fields generated in consonant cylindrical and dissonant conical resonators. Excitation of the acoustic resonators produced high-amplitude standing waves in the conical resonator. The generated peak acoustic overpressures exceeded the initial undisturbed pressure by two to three times. The harmonic response in the conical resonator system was observed to be dependent on the piston amplitude. The resultant strong acoustic streaming structures in the cone resonator highlighted its potential over a cylindrical resonator as an efficient mixer. Two pulse tube cryogenic refrigeration (PTR) devices driven by a linear motor (a pressure wave generator) were designed, fabricated and tested. The characterization of the systems over a wide range of operating conditions helped to better understand the factors that govern and affect the performance of the PTR. The operating frequency of the linear motor driving the PTR affected the systems' performance the most. Other parameters that resulted in performance variations were the mean operating pressure, the pressure amplitude output from the linear motor, and the geometry of the inertance tube. The effect of the inertance tube's geometry was controlled by a single parameter labeled the "inertance". External/ambient conditions affected the performance of the cryocoolers too. To prevent the influence of the ambient conditions on the performance, a vacuum chamber was fabricated to isolate the low temperature regions of the PTR from the variable ambient atmosphere. The experiments provided important information and guidelines for the simulation studies of the PTR that were carried out concurrently. A time-dependent high fidelity computational fluid dynamic model of the entire PTR system was developed to gain a better understanding of internal interactions between the refrigerant fluid and the porous heat-exchangers in its various components and to facilitate better design of PTR systems based on the knowledge gained. The compressible forms of the conservation of mass, momentum and energy equations are solved in the gas and porous media (appropriate estimation of fluid dynamics in heat-exchangers) regions. The heat transfer in the porous regions is governed by a thermal non-equilibrium heat transfer model that calculates a separate gas and solid temperature and accounts for heat transfer between the two. The numerical model was validated using both temporal and quasi-steady state results obtained from the experimental studies. The validated model was applied to study the effects of different operating parameters (frequency, pressure and geometry of the components) on the PTR's performance. The simulations revealed interesting steady-periodic flow patterns that develop in the pulse tube due to the fluctuations caused by the piston and the presence of the inertance tube. Similar to the experiments, the simulations provided important information that help guide the design of efficient PTR systems.

Numerical modeling of multidimensional flow in seals and bearings used in rotating machinery

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Tam, L. T.; Przekwas, A.; Muszynska, A.; Braun, M. J.; Mullen, R. L.

1988-01-01

The rotordynamic behavior of turbomachinery is critically dependent on fluid dynamic rotor forces developed by various types of seals and bearings. The occurrence of self-excited vibrations often depends on the rotor speed and load. Misalignment and rotor wobbling motion associated with differential clearance were often attributed to stability problems. In general, the rotative character of the flowfield is a complex three dimensional system with secondary flow patterns that significantly alter the average fluid circumferential velocity. A multidimensional, nonorthogonal, body-fitted-grid fluid flow model is presented that describes the fluid dynamic forces and the secondary flow pattern development in seals and bearings. Several numerical experiments were carried out to demonstrate the characteristics of this complex flowfield. Analyses were performed by solving a conservation form of the three dimensional Navier-Stokes equations transformed to those for a rotating observer and using the general-purpose computer code PHOENICS with the assumptions that the rotor orbit is circular and that static eccentricity is zero. These assumptions have enabled a precise steady-state analysis to be used. Fluid injection from ports near the seal or bearing center increased fluid-film direct dynamic stiffness and, in some cases, significantly increased quadrature dynamic stiffness. Injection angle and velocity could be used for active rotordynamic control; for example, injection, when compared with no injection, increased direct dynamic stiffness, which is an important factor for hydrostatic bearings.

Potential pressurized payloads: Fluid and thermal experiments

NASA Technical Reports Server (NTRS)

Swanson, Theodore D.

1992-01-01

Space Station Freedom (SSF) presents the opportunity to perform long term fluid and thermal experiments in a microgravity environment. This presentation provides perspective on the need for fluids/thermal experimentation in a microgravity environment, addresses previous efforts, identifies possible experiments, and discusses the capabilities of a proposed fluid physics/dynamics test facility. Numerous spacecraft systems use fluids for their operation. Thermal control, propulsion, waste management, and various operational processes are examples of such systems. However, effective ground testing is very difficult. This is because the effect of gravity induced phenomena, such as hydrostatic pressure, buoyant convection, and stratification, overcome such forces as surface tension, diffusion, electric potential, etc., which normally dominate in a microgravity environment. Hence, space experimentation is necessary to develop and validate a new fluid based technology. Two broad types of experiments may be performed on SSF: basic research and applied research. Basic research might include experiments focusing on capillary phenomena (with or without thermal and/or solutal gradients), thermal/solutal convection, phase transitions, and multiphase flow. Representative examples of applied research might include two-phase pressure drop, two-phase flow instabilities, heat transfer coefficients, fluid tank fill/drain, tank slosh dynamics, condensate removal enhancement, and void formation within thermal energy storage materials. In order to better support such fluid/thermal experiments on board SSF, OSSA has developed a conceptual design for a proposed Fluid Physics/Dynamics Facility (FP/DF). The proposed facility consists of one facility rack permanently located on SSF and one experimenter rack which is changed out as needed to support specific experiments. This approach will minimize the on-board integration/deintegration required for specific experiments. The FP/DF will have acceleration/vibration compensation, power and thermal interfaces, computer command/data collection, a video imaging system, and a portable glove box for operations. This facility will allow real-time astronaut interaction with the testing.

A topological classification of the Chaplygin systems in the dynamics of a rigid body in a fluid

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

Nikolaenko, S S

2014-02-28

The paper is concerned with the topological analysis of the Chaplygin integrable case in the dynamics of a rigid body in a fluid. A full list of the topological types of Chaplygin systems in their dependence on the energy level is compiled on the basis of the Fomenko-Zieschang theory. An effective description of the topology of the Liouville foliation in terms of natural coordinate variables is also presented, which opens a direct way to calculating topological invariants. It turns out that on all nonsingular energy levels Chaplygin systems are Liouville equivalent to the well-known Euler case in the dynamics of a rigid body withmore » fixed point. Bibliography: 23 titles.« less

Modeling meniscus rise in capillary tubes using fluid in rigid-body motion approach

NASA Astrophysics Data System (ADS)

Hamdan, Mohammad O.; Abu-Nabah, Bassam A.

2018-04-01

In this study, a new term representing net flux rate of linear momentum is introduced to Lucas-Washburn equation. Following a fluid in rigid-body motion in modeling the meniscus rise in vertical capillary tubes transforms the nonlinear Lucas-Washburn equation to a linear mass-spring-damper system. The linear nature of mass-spring-damper system with constant coefficients offers a nondimensional analytical solution where meniscus dynamics are dictated by two parameters, namely the system damping ratio and its natural frequency. This connects the numerous fluid-surface interaction physical and geometrical properties to rather two nondimensional parameters, which capture the underlying physics of meniscus dynamics in three distinct cases, namely overdamped, critically damped, and underdamped systems. Based on experimental data available in the literature and the understanding meniscus dynamics, the proposed model brings a new approach of understanding the system initial conditions. Accordingly, a closed form relation is produced for the imbibition velocity, which equals half of the Bosanquet velocity divided by the damping ratio. The proposed general analytical model is ideal for overdamped and critically damped systems. While for underdamped systems, the solution shows fair agreement with experimental measurements once the effective viscosity is determined. Moreover, the presented model shows meniscus oscillations around equilibrium height occur if the damping ratio is less than one.

On Flexible Tubes Conveying Fluid: Geometric Nonlinear Theory, Stability and Dynamics

NASA Astrophysics Data System (ADS)

Gay-Balmaz, François; Putkaradze, Vakhtang

2015-08-01

We derive a fully three-dimensional, geometrically exact theory for flexible tubes conveying fluid. The theory also incorporates the change of the cross section available to the fluid motion during the dynamics. Our approach is based on the symmetry-reduced, exact geometric description for elastic rods, coupled with the fluid transport and subject to the volume conservation constraint for the fluid. We first derive the equations of motion directly, by using an Euler-Poincaré variational principle. We then justify this derivation with a more general theory elucidating the interesting mathematical concepts appearing in this problem, such as partial left (elastic) and right (fluid) invariance of the system, with the added holonomic constraint (volume). We analyze the fully nonlinear behavior of the model when the axis of the tube remains straight. We then proceed to the linear stability analysis and show that our theory introduces important corrections to previously derived results, both in the consistency at all wavelength and in the effects arising from the dynamical change of the cross section. Finally, we derive and analyze several analytical, fully nonlinear solutions of traveling wave type in two dimensions.

Smoothed-particle hydrodynamics and nonequilibrium molecular dynamics

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

Hoover, W. G.; Hoover, C. G.

1993-08-01

Gingold, Lucy, and Monaghan invented a grid-free version of continuum mechanics ``smoothed-particle hydrodynamics,`` in 1977. It is a likely contributor to ``hybrid`` simulations combining atomistic and continuum simulations. We describe applications of this particle-based continuum technique from the closely-related standpoint of nonequilibrium molecular dynamics. We compare chaotic Lyapunov spectra for atomistic solids and fluids with those which characterize a two-dimensional smoothed-particle fluid system.

Fluid Dynamic Analysis of Volcanic Tremor,

DTIC Science & Technology

1982-10-01

information regarding the fluid system Fiske (1969) Kilauea volcano : The 1967-68 summit configuration, tremor magnitudes and source loca- eruption...Koyanagi (1981) Deep volcanic tremor logicalSociety of America, vol. 40, p. 175-194. and magma ascent mechanism under Kilauea , Hawaii . Omori, F...dynamics Seismology Tremors Volcanoes 40 M\\ TlACT (amhue ai revers if5 neeeeiy md ide~Wify by block number) Low-frequency (< 10 Hz) volcanic earthquakes

Implementation of Finite Volume based Navier Stokes Algorithm Within General Purpose Flow Network Code

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Majumdar, Alok

2012-01-01

This paper describes a finite volume based numerical algorithm that allows multi-dimensional computation of fluid flow within a system level network flow analysis. There are several thermo-fluid engineering problems where higher fidelity solutions are needed that are not within the capacity of system level codes. The proposed algorithm will allow NASA's Generalized Fluid System Simulation Program (GFSSP) to perform multi-dimensional flow calculation within the framework of GFSSP s typical system level flow network consisting of fluid nodes and branches. The paper presents several classical two-dimensional fluid dynamics problems that have been solved by GFSSP's multi-dimensional flow solver. The numerical solutions are compared with the analytical and benchmark solution of Poiseulle, Couette and flow in a driven cavity.

The Stokesian hydrodynamics of flexing, stretching filaments

NASA Astrophysics Data System (ADS)

Shelley, Michael J.; Ueda, Tetsuji

2000-11-01

A central element of many fundamental problems in physics and biology lies in the interaction of a viscous fluid with slender, elastic filaments. Examples arise in the dynamics of biological fibers, the motility of microscopic organisms, and in phase transitions of liquid crystals. When considering the dynamics on the scale of a single filament, the surrounding fluid can often be assumed to be inertialess and hence governed by the Stokes’ equations. A typical simplification then is to assume a local relation, along the filament, between the force per unit length exerted by the filament upon the fluid and the velocity of the filament. While this assumption can be justified through slender-body theory as the leading-order effect, this approximation is only logarithmically separated (in aspect ratio) from the next-order contribution capturing the first effects of non-local interactions mediated by the surrounding fluid; non-local interactions become increasingly important as a filament comes within proximity to itself, or another filament. Motivated by a pattern forming system in isotropic to smectic-A phase transitions, we consider the non-local Stokesian dynamics of a growing elastica immersed in a fluid. The non-local interactions of the filament with itself are included using a modification of the slender-body theory of Keller and Rubinow. This modification is asymptotically equivalent, and removes an instability of their formulation at small, unphysical length-scales. Within this system, the filament lives on a marginal stability boundary, driven by a continual process of growth and buckling. Repeated bucklings result in filament flex, which, coupled to the non-local interactions and mediated by elastic response, leads to the development of space-filling patterns. We develop numerical methods to solve this system accurately and efficiently, even in the presence of temporal stiffness and the close self-approach of the filament. While we have ignored many of the thermodynamic aspects of this system, our simulations show good qualitative agreement with experimental observations. Our results also suggest that non-locality, induced by the surrounding fluid, will be important to understanding the dynamics of related filament systems.

Geophysical fluid dynamics: whence, whither and why?

PubMed Central

2016-01-01

This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena—the Gulf Stream, for example—something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future. PMID:27616918

A cyber-physical approach to experimental fluid mechanics

NASA Astrophysics Data System (ADS)

Mackowski, Andrew Williams

This Thesis documents the design, implementation, and use of a novel type of experimental apparatus, termed Cyber-Physical Fluid Dynamics (CPFD). Unlike traditional fluid mechanics experiments, CPFD is a general-purpose technique that allows one to impose arbitrary forces on an object submerged in a fluid. By combining fluid mechanics with robotics, we can perform experiments that would otherwise be incredibly difficult or time-consuming. More generally, CPFD allows a high degree of automation and control of the experimental process, allowing for much more efficient use of experimental facilities. Examples of CPFD's capabilites include imposing a gravitational force in the horizontal direction (allowing a test object to "fall" sideways in a water channel), simulating nonlinear springs for a vibrating fluid-structure system, or allowing a self-propelled body to move forward under its own force. Because experimental parameters (including forces and even the mass of the test object) are defined in software, one can define entire ensembles of experiments to run autonomously. CPFD additionally integrates related systems such as water channel speed control, LDV flow speed measurements, and PIV flowfield measurements. The end result is a general-purpose experimental system that opens the door to a vast array of fluid-structure interaction problems. We begin by describing the design and implementation of CPFD, the heart of which is a high-performance force-feedback control system. Precise measurement of time-varying forces (including removing effects of the test object's inertia) is more critical here than in typical robotic force-feedback applications. CPFD is based on an integration of ideas from control theory, fluid dynamics, computer science, electrical engineering, and solid mechanics. We also describe experiments using the CPFD experimental apparatus to study vortex-induced vibration (VIV) and oscillating-airfoil propulsion. We show how CPFD can be used to simulate a hypothetical VIV energy harvesting device. By replacing standard linear springs with nonlinear ones, we can broaden the system's frequency response. Next, we transition from bluff bodies to unsteady airfoils, where we begin by measuring the thrust and efficiency of an airfoil pitching about its quarter-chord point. Finally, we examine how the propulsive performance of an oscillating airfoil is improved by the addition of passive dynamics.

Viscoinertial regime of immersed granular flows

NASA Astrophysics Data System (ADS)

Amarsid, L.; Delenne, J.-Y.; Mutabaruka, P.; Monerie, Y.; Perales, F.; Radjai, F.

2017-07-01

By means of extensive coupled molecular dynamics-lattice Boltzmann simulations, accounting for grain dynamics and subparticle resolution of the fluid phase, we analyze steady inertial granular flows sheared by a viscous fluid. We show that, for a broad range of system parameters (shear rate, confining stress, fluid viscosity, and relative fluid-grain density), the frictional strength and packing fraction can be described by a modified inertial number incorporating the fluid effect. In a dual viscous description, the effective viscosity diverges as the inverse square of the difference between the packing fraction and its jamming value, as observed in experiments. We also find that the fabric and force anisotropies extracted from the contact network are well described by the modified inertial number, thus providing clear evidence for the role of these key structural parameters in dense suspensions.

Shuttle rocket booster computational fluid dynamics

NASA Technical Reports Server (NTRS)

Chung, T. J.; Park, O. Y.

1988-01-01

Additional results and a revised and improved computer program listing from the shuttle rocket booster computational fluid dynamics formulations are presented. Numerical calculations for the flame zone of solid propellants are carried out using the Galerkin finite elements, with perturbations expanded to the zeroth, first, and second orders. The results indicate that amplification of oscillatory motions does indeed prevail in high frequency regions. For the second order system, the trend is similar to the first order system for low frequencies, but instabilities may appear at frequencies lower than those of the first order system. The most significant effect of the second order system is that the admittance is extremely oscillatory between moderately high frequency ranges.

Artificial Intelligence In Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Vogel, Alison Andrews

1991-01-01

Paper compares four first-generation artificial-intelligence (Al) software systems for computational fluid dynamics. Includes: Expert Cooling Fan Design System (EXFAN), PAN AIR Knowledge System (PAKS), grid-adaptation program MITOSIS, and Expert Zonal Grid Generation (EZGrid). Focuses on knowledge-based ("expert") software systems. Analyzes intended tasks, kinds of knowledge possessed, magnitude of effort required to codify knowledge, how quickly constructed, performances, and return on investment. On basis of comparison, concludes Al most successful when applied to well-formulated problems solved by classifying or selecting preenumerated solutions. In contrast, application of Al to poorly understood or poorly formulated problems generally results in long development time and large investment of effort, with no guarantee of success.

A study analysis of cable-body systems totally immersed in a fluid stream

NASA Technical Reports Server (NTRS)

Delaurier, J. D.

1972-01-01

A general stability analysis of a cable-body system immersed in a fluid stream is presented. The analytical portion of this analysis treats the system as being essentially a cable problem, with the body dynamics giving the end conditions. The mathematical form of the analysis consists of partial differential wave equations, with the end and auxiliary conditions being determined from the body equations of motion. The equations uncouple to give a lateral problem and a longitudinal problem as in first order airplane dynamics. A series of tests on a tethered wind tunnel model provide a comparison of the theory with experiment.

From viscous to elastic sheets: Dynamics of smectic bubbles

NASA Astrophysics Data System (ADS)

Harth, Kirsten; Trittel, Torsten; van der Meer, Devaraj; Stannarius, Ralf

2015-11-01

Oscillations and rupture of bubbles composed of an inner fluid separated from an outer fluid by a membrane, represent an old but still immensely active field of research. Membrane properties apart from surface tension are often neglected for fluids (e.g. soap bubbles), whereas they govern the dynamics in systems with a rigid membrane (e.g. vesicles). Due to their layered phase structure, smectic liquid crystals can form stable, uniform and easy-to-handle fluid films of immense aspect ratios. Only recently, freely floating bubbles detached from a support could be prepared. We analyze their relaxation from strongly non-spherical shapes and the rupture using high-speed video recordings. Peculiar dynamics intermediate between simple viscous fluid films and an elastic response are observed: Fast oscillations, slowed relaxation and even the reversible formation of wrinkles and extrusions. Bubble rupture deviates qualitatively from previously observed behavior of simple Newtonian and other complex fluids. It becomes retarded by at least two orders of magnitude compared to the predictions of Taylor and Culick. A transition between fluid-like and elastic behavior is seen with increasing thickness. We give experimental results, an intuitive explanation and a novel hydrodynamic description.

Dynamic analysis of a 5-MW tripod offshore wind turbine by considering fluid-structure interaction

NASA Astrophysics Data System (ADS)

Zhang, Li-wei; Li, Xin

2017-10-01

Fixed offshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod offshore wind turbine considering the pile-soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of offshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of offshore wind turbines fixed in deep seawater.

Self-regulation in self-propelled nematic fluids.

PubMed

Baskaran, A; Marchetti, M C

2012-09-01

We consider the hydrodynamic theory of an active fluid of self-propelled particles with nematic aligning interactions. This class of materials has polar symmetry at the microscopic level, but forms macrostates of nematic symmetry. We highlight three key features of the dynamics. First, as in polar active fluids, the control parameter for the order-disorder transition, namely the density, is dynamically convected by the order parameter via active currents. The resulting dynamical self-regulation of the order parameter is a generic property of active fluids and destabilizes the uniform nematic state near the mean-field transition. Secondly, curvature-driven currents render the system unstable deep in the nematic state, as found previously. Finally, and unique to self-propelled nematics, nematic order induces local polar order that in turn leads to the growth of density fluctuations. We propose this as a possible mechanism for the smectic order of polar clusters seen in numerical simulations.

Education and research in fluid dynamics

NASA Astrophysics Data System (ADS)

López González-Nieto, P.; Redondo, J. M.; Cano, J. L.

2009-04-01

Fluid dynamics constitutes an essential subject for engineering, since auronautic engineers (airship flights in PBL, flight processes), industrial engineers (fluid transportation), naval engineers (ship/vessel building) up to agricultural engineers (influence of the weather conditions on crops/farming). All the above-mentioned examples possess a high social and economic impact on mankind. Therefore, the fluid dynamics education of engineers is very important, and, at the same time, this subject gives us an interesting methodology based on a cycle relation among theory, experiments and numerical simulation. The study of turbulent plumes -a very important convective flow- is a good example because their theoretical governing equations are simple; it is possible to make experimental plumes in an aesy way and to carry out the corresponding numerical simulatons to verify experimental and theoretical results. Moreover, it is possible to get all these aims in the educational system (engineering schools or institutions) using a basic laboratory and the "Modellus" software.

Implementing a Loosely Coupled Fluid Structure Interaction Finite Element Model in PHASTA

NASA Astrophysics Data System (ADS)

Pope, David

Fluid Structure Interaction problems are an important multi-physics phenomenon in the design of aerospace vehicles and other engineering applications. A variety of computational fluid dynamics solvers capable of resolving the fluid dynamics exist. PHASTA is one such computational fluid dynamics solver. Enhancing the capability of PHASTA to resolve Fluid-Structure Interaction first requires implementing a structural dynamics solver. The implementation also requires a correction of the mesh used to solve the fluid equations to account for the deformation of the structure. This results in mesh motion and causes the need for an Arbitrary Lagrangian-Eulerian modification to the fluid dynamics equations currently implemented in PHASTA. With the implementation of both structural dynamics physics, mesh correction, and the Arbitrary Lagrangian-Eulerian modification of the fluid dynamics equations, PHASTA is made capable of solving Fluid-Structure Interaction problems.

Viscous-elastic dynamics of power-law fluids within an elastic cylinder

NASA Astrophysics Data System (ADS)

Boyko, Evgeniy; Bercovici, Moran; Gat, Amir D.

2017-07-01

In a wide range of applications, microfluidic channels are implemented in soft substrates. In such configurations, where fluidic inertia and compressibility are negligible, the propagation of fluids in channels is governed by a balance between fluid viscosity and elasticity of the surrounding solid. The viscous-elastic interactions between elastic substrates and non-Newtonian fluids are particularly of interest due to the dependence of viscosity on the state of the system. In this work, we study the fluid-structure interaction dynamics between an incompressible non-Newtonian fluid and a slender linearly elastic cylinder under the creeping flow regime. Considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a nonhomogeneous p-Laplacian equation governing the viscous-elastic dynamics. We present exact solutions for the pressure and deformation fields for various initial and boundary conditions for both shear-thinning and shear-thickening fluids. We show that in contrast to Stokes' problem where a compactly supported front is obtained for shear-thickening fluids, here the role of viscosity is inversed and such fronts are obtained for shear-thinning fluids. Furthermore, we demonstrate that for the case of a step in inlet pressure, the propagation rate of the front has a tn/n +1 dependence on time (t ), suggesting the ability to indirectly measure the power-law index (n ) of shear-thinning liquids through measurements of elastic deformation.

Assessment of Fluid Balance and the Approach to Fluid Therapy in the Perioperative Patient.

PubMed

Boller, Elise; Boller, Manuel

2015-09-01

Perioperative patients can be highly dynamic and have various metabolic, physiologic, and organ system derangements that necessitate smart monitoring strategies and careful fluid therapy. The interplay between changing patient status, therapeutic interventions, and patient response makes effective monitoring crucial to successful treatment. Monitoring the perioperative patient and an approach to fluid therapy are discussed in this text. Copyright © 2015 Elsevier Inc. All rights reserved.

Multi-fluid CFD analysis in Process Engineering

NASA Astrophysics Data System (ADS)

Hjertager, B. H.

2017-12-01

An overview of modelling and simulation of flow processes in gas/particle and gas/liquid systems are presented. Particular emphasis is given to computational fluid dynamics (CFD) models that use the multi-dimensional multi-fluid techniques. Turbulence modelling strategies for gas/particle flows based on the kinetic theory for granular flows are given. Sub models for the interfacial transfer processes and chemical kinetics modelling are presented. Examples are shown for some gas/particle systems including flow and chemical reaction in risers as well as gas/liquid systems including bubble columns and stirred tanks.

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids.

PubMed

Dahlberg, Jerry; Tkacik, Peter T; Mullany, Brigid; Fleischhauer, Eric; Shahinian, Hossein; Azimi, Farzad; Navare, Jayesh; Owen, Spencer; Bisel, Tucker; Martin, Tony; Sholar, Jodie; Keanini, Russell G

2017-12-04

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are highlighted. The proposed technique provides a relatively straightforward alternative to photonic and neutron beam scattering methods traditionally used in molecular hydrodynamic studies.

Numerical Modeling of Multiphase Fluid Flow in Ore-Forming Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Weis, P.; Driesner, T.; Coumou, D.; Heinrich, C. A.

2007-12-01

Two coexisting fluid phases - a variably saline liquid and a vapor phase - are ubiquitous in ore-forming and other hydrothermal systems. Understanding the dynamics of phase separation and the distinct physical and chemical evolution of the two fluids probably plays a key role in generating different ore deposit types, e.g. porphyry type, high and low sulfidation Cu-Mo-Au deposits. To this end, processes within hydrothermal systems have been studied with a refined numerical model describing fluid flow in transient porous media (CSP~5.0). The model is formulated on a mass, energy and momentum conserving finite-element-finite-volume (FEFV) scheme and is capable of simulating multiphase flow of NaCl-H20 fluids. Fluid properties are computed from an improved equation of state (SOWAT~2.0). It covers conditions with temperatures of up to 1000 degrees~C, pressures of up to 500 MPa, and fluid salinities of 0~to 100%~NaCl. In particular, the new set-up allows for a more accurate description of fluid phase separation during boiling of hydrothermal fluids into a vapor and a brine phase. The geometric flexibility of the FEFV-meshes allows for investigations of a large variety of geological settings, ranging from ore-forming processes in magmatic hydrothermal system to the dynamics of black smokers at mid-ocean ridges. Simulations demonstrated that hydrothermal convection patterns above cooling plutons are primarily controlled by the system-scale permeability structure. In porphyry systems, high fluid pressures develop in a stock rising from the magma chamber which can lead to rock failure and, eventually, an increase in permeability due to hydrofracturing. Comparisons of the thermal evolution as inferred from modeling studies with data from fluid inclusion studies of the Pb-Zn deposits of Madan, Bulgaria are in a strikingly good agreement. This indicates that cross-comparisons of field observations, analytical data and numerical simulations will become a powerful tool towards a more thorough understanding of hydrothermal fluid processes. One such attempt will incorporate geometric data of veins in the Bingham porphyry Cu-Mo-Au deposit into our numerical model. The presentation will introduce the numerical model and show examples and first results of the aforementioned applications.

Satellite Gravity and the Geosphere: Contributions to the Study of the Solid Earth and Its Fluid Earth

NASA Technical Reports Server (NTRS)

Dickey, J. O.; Bentley, C. R.; Bilham, R.; Carton, J. A.; Eanes, R. J.; Herring, T. A.; Kaula, W. M.; Lagerloef, G. S. E.; Rojstaczer, S.; Smith, W. H. F.;

Waving of filaments induced by molecular motors

NASA Astrophysics Data System (ADS)

de Canio, Gabriele; Lauga, Eric; Goldstein, Raymond E.

2017-11-01

In many cellular phenomena, for example cytoplasmic streaming, molecular motors translocate along microtubules carrying cargoes which entrain fluid. The piconewton forces that motors produce can be sufficient to bend or buckle the filaments. When large numbers of such forced filaments interact through the surrounding fluid, as in particular stages of oocyte development in Drosophila melanogaster, complex dynamics are observed, but the mechanism underlying them has remained unclear. By using a combination of theory and numerical simulations, we study a simplified microtubules-molecular motor system in a viscous fluid and show that it can capture the wave-like filament motion dynamics observed in experiments.

Dynamic Pressure Calibration Standard

NASA Technical Reports Server (NTRS)

Schutte, P. C.; Cate, K. H.; Young, S. D.

1986-01-01

Vibrating columns of fluid used to calibrate transducers. Dynamic pressure calibration standard developed for calibrating flush diaphragm-mounted pressure transducers. Pressures up to 20 kPa (3 psi) accurately generated over frequency range of 50 to 1,800 Hz. System includes two conically shaped aluminum columns one 5 cm (2 in.) high for low pressures and another 11 cm (4.3 in.) high for higher pressures, each filled with viscous fluid. Each column mounted on armature of vibration exciter, which imparts sinusoidally varying acceleration to fluid column. Signal noise low, and waveform highly dependent on quality of drive signal in vibration exciter.

Physics through the 1990s: Plasmas and fluids

NASA Technical Reports Server (NTRS)

1986-01-01

The volume contains recommendations for programs in, and government support of, plasma and fluid physics. Four broad areas are covered: the physics of fluids, general plasma physics, fusion, and space and astrophysical plasmas. In the first section, the accomplishments of fluid physics and a detailed review of its sub-fields, such as combustion, non-Newtonian fluids, turbulence, aerodynamics, and geophysical fluid dynamics, are described. The general plasma physics section deals with the wide scope of the theoretical concepts involved in plasma research, and with the machines; intense beam systems, collective and laser-driven accelerators, and the associated diagnostics. The section on the fusion plasma research program examines confinement and heating systems, such as Tokamaks, magnetic mirrors, and inertial-confinement systems, and several others. Finally, theory and experiment in space and astrophysical plasma research is detailed, ranging from the laboratory to the solar system and beyond. A glossary is included.

An experimental study of dynamic characteristics of labyrinth seal

NASA Technical Reports Server (NTRS)

Iwatsubo, Takuzo; Fukumoto, Koji; Mochida, Hideyuki

1994-01-01

The fluid force due to labyrinth seal sometimes makes the turbomachineries unstable under higher rotating speed, higher pressure and higher power. Therefore, it is important to predict the magnitude and the direction of the fluid force and to evaluate the stability of the rotor system in design process. This paper shows the experimental results of the fluid force induced by a straight labyrinth seal and the rotordynamic coefficients calculated from the fluid force. Influences of the number of fins under the rotating speed, whirling speed, inlet pressure, and inlet tangential velocity are mainly investigated on a stability of the rotor system. The results show that increase of the number of fins makes the fluid force small and the rotor system stable, an increase of inlet pressure makes the fluid forces large and an increase of inlet tangential velocity makes the rotor system unstable.

High frequency flow-structural interaction in dense subsonic fluids

NASA Technical Reports Server (NTRS)

Liu, Baw-Lin; Ofarrell, J. M.

1995-01-01

Prediction of the detailed dynamic behavior in rocket propellant feed systems and engines and other such high-energy fluid systems requires precise analysis to assure structural performance. Designs sometimes require placement of bluff bodies in a flow passage. Additionally, there are flexibilities in ducts, liners, and piping systems. A design handbook and interactive data base have been developed for assessing flow/structural interactions to be used as a tool in design and development, to evaluate applicable geometries before problems develop, or to eliminate or minimize problems with existing hardware. This is a compilation of analytical/empirical data and techniques to evaluate detailed dynamic characteristics of both the fluid and structures. These techniques have direct applicability to rocket engine internal flow passages, hot gas drive systems, and vehicle propellant feed systems. Organization of the handbook is by basic geometries for estimating Strouhal numbers, added mass effects, mode shapes for various end constraints, critical onset flow conditions, and possible structural response amplitudes. Emphasis is on dense fluids and high structural loading potential for fatigue at low subsonic flow speeds where high-frequency excitations are possible. Avoidance and corrective measure illustrations are presented together with analytical curve fits for predictions compiled from a comprehensive data base.

Restricted Euler dynamics along trajectories of small inertial particles in turbulence

NASA Astrophysics Data System (ADS)

Johnson, Perry; Meneveau, Charles

2016-11-01

The fate of small particles in turbulent flows depends strongly on the surrounding fluid's velocity gradient properties such as rotation and strain-rates. For non-inertial (fluid) particles, the Restricted Euler model provides a simple, low-dimensional dynamical system representation of Lagrangian evolution of velocity gradients in fluid turbulence, at least for short times. Here we derive a new restricted Euler dynamical system for the velocity gradient evolution of inertial particles such as solid particles in a gas or droplets and bubbles in turbulent liquid flows. The model is derived in the limit of small (sub Kolmogorov scale) particles and low Stokes number. The system exhibits interesting fixed points, stability and invariant properties. Comparisons with data from Direct Numerical Simulations show that the model predicts realistic trends such as the tendency of increased straining over rotation along heavy particle trajectories and, for light particles such as bubbles, the tendency of severely reduced self-stretching of strain-rate. Supported by a National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1232825 and by a Grant from The Gulf of Mexico Research Initiative.

Statistical mechanics of homogeneous partly pinned fluid systems.

PubMed

Krakoviack, Vincent

2010-12-01

The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.

Study on fluid-structure interaction in liquid oxygen feeding pipe systems using finite volume method

NASA Astrophysics Data System (ADS)

Wei, Xin; Sun, Bing

2011-10-01

The fluid-structure interaction may occur in space launch vehicles, which would lead to bad performance of vehicles, damage equipments on vehicles, or even affect astronauts' health. In this paper, analysis on dynamic behavior of liquid oxygen (LOX) feeding pipe system in a large scale launch vehicle is performed, with the effect of fluid-structure interaction (FSI) taken into consideration. The pipe system is simplified as a planar FSI model with Poisson coupling and junction coupling. Numerical tests on pipes between the tank and the pump are solved by the finite volume method. Results show that restrictions weaken the interaction between axial and lateral vibrations. The reasonable results regarding frequencies and modes indicate that the FSI affects substantially the dynamic analysis, and thus highlight the usefulness of the proposed model. This study would provide a reference to the pipe test, as well as facilitate further studies on oscillation suppression.

Least-squares finite element method for fluid dynamics

NASA Technical Reports Server (NTRS)

Jiang, Bo-Nan; Povinelli, Louis A.

1989-01-01

An overview is given of new developments of the least squares finite element method (LSFEM) in fluid dynamics. Special emphasis is placed on the universality of LSFEM; the symmetry and positiveness of the algebraic systems obtained from LSFEM; the accommodation of LSFEM to equal order interpolations for incompressible viscous flows; and the natural numerical dissipation of LSFEM for convective transport problems and high speed compressible flows. The performance of LSFEM is illustrated by numerical examples.

FAST: A multi-processed environment for visualization of computational fluid dynamics

NASA Technical Reports Server (NTRS)

Bancroft, Gordon V.; Merritt, Fergus J.; Plessel, Todd C.; Kelaita, Paul G.; Mccabe, R. Kevin

1991-01-01

Three-dimensional, unsteady, multi-zoned fluid dynamics simulations over full scale aircraft are typical of the problems being investigated at NASA Ames' Numerical Aerodynamic Simulation (NAS) facility on CRAY2 and CRAY-YMP supercomputers. With multiple processor workstations available in the 10-30 Mflop range, we feel that these new developments in scientific computing warrant a new approach to the design and implementation of analysis tools. These larger, more complex problems create a need for new visualization techniques not possible with the existing software or systems available as of this writing. The visualization techniques will change as the supercomputing environment, and hence the scientific methods employed, evolves even further. The Flow Analysis Software Toolkit (FAST), an implementation of a software system for fluid mechanics analysis, is discussed.

Periodic orbit analysis of a system with continuous symmetry—A tutorial

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

Budanur, Nazmi Burak, E-mail: budanur3@gatech.edu; Cvitanović, Predrag; Borrero-Echeverry, Daniel

2015-07-15

Dynamical systems with translational or rotational symmetry arise frequently in studies of spatially extended physical systems, such as Navier-Stokes flows on periodic domains. In these cases, it is natural to express the state of the fluid in terms of a Fourier series truncated to a finite number of modes. Here, we study a 4-dimensional model with chaotic dynamics and SO(2) symmetry similar to those that appear in fluid dynamics problems. A crucial step in the analysis of such a system is symmetry reduction. We use the model to illustrate different symmetry-reduction techniques. The system's relative equilibria are conveniently determined bymore » rewriting the dynamics in terms of a symmetry-invariant polynomial basis. However, for the analysis of its chaotic dynamics, the “method of slices,” which is applicable to very high-dimensional problems, is preferable. We show that a Poincaré section taken on the 'slice' can be used to further reduce this flow to what is for all practical purposes a unimodal map. This enables us to systematically determine all relative periodic orbits and their symbolic dynamics up to any desired period. We then present cycle averaging formulas adequate for systems with continuous symmetry and use them to compute dynamical averages using relative periodic orbits. The convergence of such computations is discussed.« less

Differential Geometry Based Multiscale Models

PubMed Central

Wei, Guo-Wei

2010-01-01

Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atom-istic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier–Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson–Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson–Nernst–Planck equations that are coupled to generalized Navier–Stokes equations for fluid dynamics, Newton's equation for molecular dynamics, and potential and surface driving geometric flows for the micro-macro interface. For excessively large aqueous macromolecular complexes in chemistry and biology, we further develop differential geometry based multiscale fluid-electro-elastic models to replace the expensive molecular dynamics description with an alternative elasticity formulation. PMID:20169418

Nonlinear ship waves and computational fluid dynamics

PubMed Central

MIYATA, Hideaki; ORIHARA, Hideo; SATO, Yohei

2014-01-01

Research works undertaken in the first author’s laboratory at the University of Tokyo over the past 30 years are highlighted. Finding of the occurrence of nonlinear waves (named Free-Surface Shock Waves) in the vicinity of a ship advancing at constant speed provided the start-line for the progress of innovative technologies in the ship hull-form design. Based on these findings, a multitude of the Computational Fluid Dynamic (CFD) techniques have been developed over this period, and are highlighted in this paper. The TUMMAC code has been developed for wave problems, based on a rectangular grid system, while the WISDAM code treats both wave and viscous flow problems in the framework of a boundary-fitted grid system. These two techniques are able to cope with almost all fluid dynamical problems relating to ships, including the resistance, ship’s motion and ride-comfort issues. Consequently, the two codes have contributed significantly to the progress in the technology of ship design, and now form an integral part of the ship-designing process. PMID:25311139

Design of a pulsatile flow facility to evaluate thrombogenic potential of implantable cardiac devices.

PubMed

Arjunon, Sivakkumar; Ardana, Pablo Hidalgo; Saikrishnan, Neelakantan; Madhani, Shalv; Foster, Brent; Glezer, Ari; Yoganathan, Ajit P

2015-04-01

Due to expensive nature of clinical trials, implantable cardiac devices should first be extensively characterized in vitro. Prosthetic heart valves (PHVs), an important class of these devices, have been shown to be associated with thromboembolic complications. Although various in vitro systems have been designed to quantify blood-cell damage and platelet activation caused by nonphysiological hemodynamic shear stresses in these PHVs, very few systems attempt to characterize both blood damage and fluid dynamics aspects of PHVs in the same test system. Various numerical modeling methodologies are also evolving to simulate the structural mechanics, fluid mechanics, and blood damage aspects of these devices. This article presents a completely hemocompatible small-volume test-platform that can be used for thrombogenicity studies and experimental fluid mechanics characterization. Using a programmable piston pump to drive freshly drawn human blood inside a cylindrical column, the presented system can simulate various physiological and pathophysiological conditions in testing PHVs. The system includes a modular device-mounting chamber, and in this presented case, a 23 mm St. Jude Medical (SJM) Regents® mechanical heart valve (MHV) in aortic position was used as the test device. The system was validated for its capability to quantify blood damage by measuring blood damage induced by the tester itself (using freshly drawn whole human blood). Blood damage levels were ascertained through clinically relevant assays on human blood while fluid dynamics were characterized using time-resolved particle image velocimetry (PIV) using a blood-mimicking fluid. Blood damage induced by the tester itself, assessed through Thrombin-anti-Thrombin (TAT), Prothrombin factor 1.2 (PF1.2), and hemolysis (Drabkins assay), was within clinically accepted levels. The hydrodynamic performance of the tester showed consistent, repeatable physiological pressure and flow conditions. In addition, the system contains proximity sensors to accurately capture leaflet motion during the entire cardiac cycle. The PIV results showed skewing of the leakage jet, caused by the asymmetric closing of the two leaflets. All these results are critical to characterizing the blood damage and fluid dynamics characteristics of the SJM Regents® MHV, proving the utility of this tester as a precise system for assessing the hemodynamics and thrombogenicity for various PHVs.

Fluid management systems technology summaries

NASA Technical Reports Server (NTRS)

Stark, J. A.; Blatt, M. H.; Bennett, F. O., Jr.; Campbell, B. J.

1974-01-01

A summarization and categorization of the pertinent literature associated with fluid management systems technology having potential application to in-orbit fluid transfer and/or associated storage are presented. A literature search was conducted to obtain pertinent documents for review. Reports determined to be of primary significance were summarized in the following manner: (1) report identification, (2) objective(s) of the work, (3) description of pertinent work performed, (4) major results, and (5) comments of the reviewer. Pertinent figures are presented on a single facing page separate from the text. Specific areas covered are: fluid line dynamics and thermodynamics, low-g mass gauging, other instrumentation, stratification/pressurization, low-g vent systems, fluid mixing refrigeration and reliquefaction, and low-g interface control and liquid acquisition systems. Reports which were reviewed and not summarized, along with reasons for not summarizing, are also listed.

Use of computational fluid dynamics in respiratory medicine.

PubMed

Fernández Tena, Ana; Casan Clarà, Pere

2015-06-01

Computational Fluid Dynamics (CFD) is a computer-based tool for simulating fluid movement. The main advantages of CFD over other fluid mechanics studies include: substantial savings in time and cost, the analysis of systems or conditions that are very difficult to simulate experimentally (as is the case of the airways), and a practically unlimited level of detail. We used the Ansys-Fluent CFD program to develop a conducting airway model to simulate different inspiratory flow rates and the deposition of inhaled particles of varying diameters, obtaining results consistent with those reported in the literature using other procedures. We hope this approach will enable clinicians to further individualize the treatment of different respiratory diseases. Copyright © 2014 SEPAR. Published by Elsevier Espana. All rights reserved.

Dynamic modelling and simulation of CSP plant based on supercritical carbon dioxide closed Brayton cycle

NASA Astrophysics Data System (ADS)

Hakkarainen, Elina; Sihvonen, Teemu; Lappalainen, Jari

2017-06-01

Supercritical carbon dioxide (sCO2) has recently gained a lot of interest as a working fluid in different power generation applications. For concentrated solar power (CSP) applications, sCO2 provides especially interesting option if it could be used both as the heat transfer fluid (HTF) in the solar field and as the working fluid in the power conversion unit. This work presents development of a dynamic model of CSP plant concept, in which sCO2 is used for extracting the solar heat in Linear Fresnel collector field, and directly applied as the working fluid in the recuperative Brayton cycle; these both in a single flow loop. We consider the dynamic model is capable to predict the system behavior in typical operational transients in a physically plausible way. The novel concept was tested through simulation cases under different weather conditions. The results suggest that the concept can be successfully controlled and operated in the supercritical region to generate electric power during the daytime, and perform start-up and shut down procedures in order to stay overnight in sub-critical conditions. Besides the normal daily operation, the control system was demonstrated to manage disturbances due to sudden irradiance changes.

Volcano electrical tomography unveils edifice collapse hazard linked to hydrothermal system structure and dynamics

NASA Astrophysics Data System (ADS)

Rosas-Carbajal, Marina; Komorowski, Jean-Christophe; Nicollin, Florence; Gibert, Dominique

2016-07-01

Catastrophic collapses of the flanks of stratovolcanoes constitute a major hazard threatening numerous lives in many countries. Although many such collapses occurred following the ascent of magma to the surface, many are not associated with magmatic reawakening but are triggered by a combination of forcing agents such as pore-fluid pressurization and/or mechanical weakening of the volcanic edifice often located above a low-strength detachment plane. The volume of altered rock available for collapse, the dynamics of the hydrothermal fluid reservoir and the geometry of incipient collapse failure planes are key parameters for edifice stability analysis and modelling that remain essentially hidden to current volcano monitoring techniques. Here we derive a high-resolution, three-dimensional electrical conductivity model of the La Soufrière de Guadeloupe volcano from extensive electrical tomography data. We identify several highly conductive regions in the lava dome that are associated to fluid saturated host-rock and preferential flow of highly acid hot fluids within the dome. We interpret this model together with the existing wealth of geological and geochemical data on the volcano to demonstrate the influence of the hydrothermal system dynamics on the hazards associated to collapse-prone altered volcanic edifices.

Volcano electrical tomography unveils edifice collapse hazard linked to hydrothermal system structure and dynamics

PubMed Central

Rosas-Carbajal, Marina; Komorowski, Jean-Christophe; Nicollin, Florence; Gibert, Dominique

2016-01-01

Catastrophic collapses of the flanks of stratovolcanoes constitute a major hazard threatening numerous lives in many countries. Although many such collapses occurred following the ascent of magma to the surface, many are not associated with magmatic reawakening but are triggered by a combination of forcing agents such as pore-fluid pressurization and/or mechanical weakening of the volcanic edifice often located above a low-strength detachment plane. The volume of altered rock available for collapse, the dynamics of the hydrothermal fluid reservoir and the geometry of incipient collapse failure planes are key parameters for edifice stability analysis and modelling that remain essentially hidden to current volcano monitoring techniques. Here we derive a high-resolution, three-dimensional electrical conductivity model of the La Soufrière de Guadeloupe volcano from extensive electrical tomography data. We identify several highly conductive regions in the lava dome that are associated to fluid saturated host-rock and preferential flow of highly acid hot fluids within the dome. We interpret this model together with the existing wealth of geological and geochemical data on the volcano to demonstrate the influence of the hydrothermal system dynamics on the hazards associated to collapse-prone altered volcanic edifices. PMID:27457494

Volcano electrical tomography unveils edifice collapse hazard linked to hydrothermal system structure and dynamics.

PubMed

Rosas-Carbajal, Marina; Komorowski, Jean-Christophe; Nicollin, Florence; Gibert, Dominique

2016-07-26

Catastrophic collapses of the flanks of stratovolcanoes constitute a major hazard threatening numerous lives in many countries. Although many such collapses occurred following the ascent of magma to the surface, many are not associated with magmatic reawakening but are triggered by a combination of forcing agents such as pore-fluid pressurization and/or mechanical weakening of the volcanic edifice often located above a low-strength detachment plane. The volume of altered rock available for collapse, the dynamics of the hydrothermal fluid reservoir and the geometry of incipient collapse failure planes are key parameters for edifice stability analysis and modelling that remain essentially hidden to current volcano monitoring techniques. Here we derive a high-resolution, three-dimensional electrical conductivity model of the La Soufrière de Guadeloupe volcano from extensive electrical tomography data. We identify several highly conductive regions in the lava dome that are associated to fluid saturated host-rock and preferential flow of highly acid hot fluids within the dome. We interpret this model together with the existing wealth of geological and geochemical data on the volcano to demonstrate the influence of the hydrothermal system dynamics on the hazards associated to collapse-prone altered volcanic edifices.

Strongly Coupled Fluid-Body Dynamics in the Immersed Boundary Projection Method

NASA Astrophysics Data System (ADS)

Wang, Chengjie; Eldredge, Jeff D.

2014-11-01

A computational algorithm is developed to simulate dynamically coupled interaction between fluid and rigid bodies. The basic computational framework is built upon a multi-domain immersed boundary method library, whirl, developed in previous work. In this library, the Navier-Stokes equations for incompressible flow are solved on a uniform Cartesian grid by the vorticity-based immersed boundary projection method of Colonius and Taira. A solver for the dynamics of rigid-body systems is also included. The fluid and rigid-body solvers are strongly coupled with an iterative approach based on the block Gauss-Seidel method. Interfacial force, with its intimate connection with the Lagrange multipliers used in the fluid solver, is used as the primary iteration variable. Relaxation, developed from a stability analysis of the iterative scheme, is used to achieve convergence in only 2-4 iterations per time step. Several two- and three-dimensional numerical tests are conducted to validate and demonstrate the method, including flapping of flexible wings, self-excited oscillations of a system of linked plates and three-dimensional propulsion of flexible fluked tail. This work has been supported by AFOSR, under Award FA9550-11-1-0098.

14 CFR 1201.200 - General.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true General. 1201.200 Section 1201.200... assignments; maintains and upgrades the design of ground and flight systems throughout the operational period... computational and experimental fluid dynamics and aerodynamics; fluid and thermal physics; rotorcraft, powered...

Viscous fingering with partially miscible fluids

NASA Astrophysics Data System (ADS)

Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

2017-10-01

Viscous fingering—the fluid-mechanical instability that takes place when a low-viscosity fluid displaces a high-viscosity fluid—has traditionally been studied under either fully miscible or fully immiscible fluid systems. Here we study the impact of partial miscibility (a common occurrence in practice) on the fingering dynamics. Through a careful design of the thermodynamic free energy of a binary mixture, we develop a phase-field model of fluid-fluid displacements in a Hele-Shaw cell for the general case in which the two fluids have limited (but nonzero) solubility into one another. We show, by means of high-resolution numerical simulations, that partial miscibility exerts a powerful control on the degree of fingering: fluid dissolution hinders fingering while fluid exsolution enhances fingering. We also show that, as a result of the interplay between compositional exchange and the hydrodynamic pattern-forming process, stronger fingering promotes the system to approach thermodynamic equilibrium more quickly.

Bifurcation and response analysis of a nonlinear flexible rotating disc immersed in bounded compressible fluid

NASA Astrophysics Data System (ADS)

Remigius, W. Dheelibun; Sarkar, Sunetra; Gupta, Sayan

2017-03-01

Use of heavy gases in centrifugal compressors for enhanced oil extraction have made the impellers susceptible to failures through acousto-elastic instabilities. This study focusses on understanding the dynamical behavior of such systems by considering the effects of the bounded fluid housed in a casing on a rotating disc. First, a mathematical model is developed that incorporates the interaction between the rotating impeller - modelled as a flexible disc - and the bounded compressible fluid medium in which it is immersed. The nonlinear effects arising due to large deformations of the disc have been included in the formulation so as to capture the post flutter behavior. A bifurcation analysis is carried out with the disc rotational speed as the bifurcation parameter to investigate the dynamical behavior of the coupled system and estimate the stability boundaries. Parametric studies reveal that the relative strengths of the various dissipation mechanisms in the coupled system play a significant role that affect the bifurcation route and the post flutter behavior in the acousto-elastic system.

Automating the parallel processing of fluid and structural dynamics calculations

NASA Technical Reports Server (NTRS)

Arpasi, Dale J.; Cole, Gary L.

1987-01-01

The NASA Lewis Research Center is actively involved in the development of expert system technology to assist users in applying parallel processing to computational fluid and structural dynamic analysis. The goal of this effort is to eliminate the necessity for the physical scientist to become a computer scientist in order to effectively use the computer as a research tool. Programming and operating software utilities have previously been developed to solve systems of ordinary nonlinear differential equations on parallel scalar processors. Current efforts are aimed at extending these capabilities to systems of partial differential equations, that describe the complex behavior of fluids and structures within aerospace propulsion systems. This paper presents some important considerations in the redesign, in particular, the need for algorithms and software utilities that can automatically identify data flow patterns in the application program and partition and allocate calculations to the parallel processors. A library-oriented multiprocessing concept for integrating the hardware and software functions is described.

Navier-Stokes-Voigt Equations with Memory in 3D Lacking Instantaneous Kinematic Viscosity

NASA Astrophysics Data System (ADS)

Di Plinio, Francesco; Giorgini, Andrea; Pata, Vittorino; Temam, Roger

2018-04-01

We consider a Navier-Stokes-Voigt fluid model where the instantaneous kinematic viscosity has been completely replaced by a memory term incorporating hereditary effects, in presence of Ekman damping. Unlike the classical Navier-Stokes-Voigt system, the energy balance involves the spatial gradient of the past history of the velocity rather than providing an instantaneous control on the high modes. In spite of this difficulty, we show that our system is dissipative in the dynamical systems sense and even possesses regular global and exponential attractors of finite fractal dimension. Such features of asymptotic well-posedness in absence of instantaneous high modes dissipation appear to be unique within the realm of dynamical systems arising from fluid models.

Electro-elastoviscous response of polyaniline functionalized nano-porous zeolite based colloidal dispersions.

PubMed

Chattopadhyay, Ankur; Rani, Poonam; Srivastava, Rajendra; Dhar, Purbarun

2018-06-01

The present article discusses the typical influence of grafted conducting polymers in the mesoscale pores of dielectric particles on the static and dynamic electrorheology and electro-viscoelastic behavior of corresponding colloids. Nanocrystalline meso-nanoporous zeolite has been prepared by chemical synthesis and subsequently polyaniline (PANI) coating has been implemented. Electrorheological (ER) suspensions have been formed by dispersing the nanoparticles in silicone oil and their viscoelastic behaviors are examined to understand the nature of such complex colloidal systems under electric fields. PANI-Zeolite ER fluids demonstrate higher static electroviscous effects and yield stress potential than untreated Zeolite, typically studied in literature. Transient electro-viscous characterizations show a stable and negligible hysteresis behavior when both the fluids are exposed to constant as well as time varying electric field intensities. Further oscillatory shear experiments of frequency and strain sweeps exhibit predominant elastic behavior in case of Zeolite based ER suspensions as compared to PANI systems. Detailed investigations reveal Zeolite based ER suspensions display enhanced relative yielding as well as electro-viscoelastic stability than the PANI-Zeolite. The steady state viscous behaviors are scaled against the non-dimensional Mason number to model the system behavior for both fluids. Experimental data of flow behaviors of both the ER fluids are compared with semi-classical models and it is found that the CCJ model possesses a closer proximity than traditional Bingham model, thereby revealing the fluids to be generic pseudo-linear fluids. The present article reveals that while the PANI based fluids are typically hailed superior in literature, it is only restricted to steady shear utilities. In case of dynamic and oscillatory systems, the traditional Zeolite based fluids exhibit superior ER caliber. Copyright © 2018 Elsevier Inc. All rights reserved.

Computational Fluid Dynamics. [numerical methods and algorithm development

NASA Technical Reports Server (NTRS)

1992-01-01

This collection of papers was presented at the Computational Fluid Dynamics (CFD) Conference held at Ames Research Center in California on March 12 through 14, 1991. It is an overview of CFD activities at NASA Lewis Research Center. The main thrust of computational work at Lewis is aimed at propulsion systems. Specific issues related to propulsion CFD and associated modeling will also be presented. Examples of results obtained with the most recent algorithm development will also be presented.

An analysis of dynamic stability for a flexible rotor filled with liquid

NASA Astrophysics Data System (ADS)

Wang, Guangding; Yuan, Huiqun

2018-03-01

The investigation of dynamic stability for a flexible rotor completely filled with liquid is carried out. The perturbation differential equations of infinitesimal fluid are established on the basis of three-dimensional flow analysis in the rotor cavity. The analytical expression of the hydrodynamic force exerted on the rotor inner wall is obtained by using the Fourier series expansion. Assuming that both ends of the rotor are simply supported and the fluid motion is axially symmetric, the nondimensional whirling frequency equation of the system is derived. According to the obtained frequency equation, the system stability is analyzed and the results are compared with a rigid rotor system. Moreover, the effects of the mass ratio and system parameter on the stability of a flexible liquid-filled rotor system are discussed.

Nonequilibrium Langevin dynamics: A demonstration study of shear flow fluctuations in a simple fluid

NASA Astrophysics Data System (ADS)

Belousov, Roman; Cohen, E. G. D.; Rondoni, Lamberto

2017-08-01

The present paper is based on a recent success of the second-order stochastic fluctuation theory in describing time autocorrelations of equilibrium and nonequilibrium physical systems. In particular, it was shown to yield values of the related deterministic parameters of the Langevin equation for a Couette flow in a microscopic molecular dynamics model of a simple fluid. In this paper we find all the remaining constants of the stochastic dynamics, which then is simulated numerically and compared directly with the original physical system. By using these data, we study in detail the accuracy and precision of a second-order Langevin model for nonequilibrium physical systems theoretically and computationally. We find an intriguing relation between an applied external force and cumulants of the resulting flow fluctuations. This is characterized by a linear dependence of an athermal cumulant ratio, an apposite quantity introduced here. In addition, we discuss how the order of a given Langevin dynamics can be raised systematically by introducing colored noise.

Axisymmetric Lattice Boltzmann Model of Droplet Impact on Solid Surfaces

NASA Astrophysics Data System (ADS)

Dalgamoni, Hussein; Yong, Xin

2017-11-01

Droplet impact is a ubiquitous fluid phenomena encountered in scientific and engineering applications such as ink-jet printing, coating, electronics manufacturing, and many others. It is of great technological importance to understand the detailed dynamics of drop impact on various surfaces. The lattice Boltzmann method (LBM) emerges as an efficient method for modeling complex fluid systems involving rapidly evolving fluid-fluid and fluid-solid interfaces with complex geometries. In this work, we model droplet impact on flat solid substrates with well-defined wetting behavior using a two-phase axisymmetric LBM with high density and viscosity contrasts. We extend the two-dimensional Lee and Liu model to capture axisymmetric effect in the normal impact. First we compare the 2D axisymmetric results with the 2D and 3D results reported by Lee and Liu to probe the effect of axisymmetric terms. Then, we explore the effects of Weber number, Ohnesorge number, and droplet-surface equilibrium contact angle on the impact. The dynamic contact angle and spreading factor of the droplet during impact are investigated to qualitatively characterize the impact dynamics.

An Artificial Intelligence Approach for Modeling and Prediction of Water Diffusion Inside a Carbon Nanotube

PubMed Central

2009-01-01

Modeling of water flow in carbon nanotubes is still a challenge for the classic models of fluid dynamics. In this investigation, an adaptive-network-based fuzzy inference system (ANFIS) is presented to solve this problem. The proposed ANFIS approach can construct an input–output mapping based on both human knowledge in the form of fuzzy if-then rules and stipulated input–output data pairs. Good performance of the designed ANFIS ensures its capability as a promising tool for modeling and prediction of fluid flow at nanoscale where the continuum models of fluid dynamics tend to break down. PMID:20596382

An Artificial Intelligence Approach for Modeling and Prediction of Water Diffusion Inside a Carbon Nanotube.

PubMed

Ahadian, Samad; Kawazoe, Yoshiyuki

2009-06-04

Modeling of water flow in carbon nanotubes is still a challenge for the classic models of fluid dynamics. In this investigation, an adaptive-network-based fuzzy inference system (ANFIS) is presented to solve this problem. The proposed ANFIS approach can construct an input-output mapping based on both human knowledge in the form of fuzzy if-then rules and stipulated input-output data pairs. Good performance of the designed ANFIS ensures its capability as a promising tool for modeling and prediction of fluid flow at nanoscale where the continuum models of fluid dynamics tend to break down.

Multiscale Behavior of Viscous Fluids Dynamics: Experimental Observations

NASA Astrophysics Data System (ADS)

Arciniega-Ceballos, Alejandra; Spina, Laura; Scheu, Bettina; Dingwell, Donald B.

2016-04-01

The dynamics of Newtonian fluids with viscosities of mafic to intermediate silicate melts (10-1000 Pa s) during slow decompression present multi-time scale processes. To observe these processes we have performed several experiments on silicon oil saturated with Argon gas for 72 hours, in a Plexiglas autoclave. The slow decompression, dropping from 10 MPa to ambient pressure, acting as the excitation mechanism, triggered several processes with their own distinct timescales. These processes generate complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit flanked by high-speed video recordings. The analysis in time and frequency of these time series and their correlation with the associated high-speed imaging enables the characterization of distinct phases and the extraction of the individual processes during the evolution of decompression of these viscous fluids. We have observed fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution along the conduit. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the conduit system. Our observations point to the great potential of this experimental approach in the understanding of volcanic conduit dynamics and volcanic seismicity.

Molecular mechanics and structure of the fluid-solid interface in simple fluids

NASA Astrophysics Data System (ADS)

Wang, Gerald J.; Hadjiconstantinou, Nicolas G.

2017-09-01

Near a fluid-solid interface, the fluid spatial density profile is highly nonuniform at the molecular scale. This nonuniformity can have profound effects on the dynamical behavior of the fluid and has been shown to play an especially important role when modeling a wide variety of nanoscale heat and momentum transfer phenomena. We use molecular-mechanics arguments and molecular-dynamics (MD) simulations to develop a better understanding of the structure of the first fluid layer directly adjacent to the solid in the layering regime, as delineated by a nondimensional number that compares the effects of wall-fluid interaction to thermal energy. Using asymptotic analysis of the Nernst-Planck equation, we show that features of the fluid density profile close to the wall, such as the areal density of the first layer ΣFL (defined as the number of atoms in this layer per unit of fluid-solid interfacial area), can be expressed as polynomial functions of the fluid average density ρave. This is found to be in agreement with MD simulations, which also show that the width of the first layer hFL is a linear function of the average density and only a weak function of the temperature T . These results can be combined to show that, for system average densities corresponding to a dense fluid (ρave≥0.7 ), the ratio C ≡ΣFLρavehFL, representing a density enhancement with respect to the bulk fluid, depends only weakly on temperature and is essentially independent of density. Further MD simulations suggest that the above results, nominally valid for large systems (solid in contact with semi-infinite fluid), also describe fluid-solid interfaces under considerable nanoconfinement, provided ρave is appropriately defined.

Methodology for extracting local constants from petroleum cracking flows

DOEpatents

Chang, Shen-Lin; Lottes, Steven A.; Zhou, Chenn Q.

2000-01-01

A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.

Design of a Magnetostrictive-Hydraulic Actuator Considering Nonlinear System Dynamics and Fluid-Structure Coupling

NASA Astrophysics Data System (ADS)

Larson, John Philip

Smart material electro-hydraulic actuators (EHAs) utilize fluid rectification via one-way check valves to amplify the small, high-frequency vibrations of certain smart materials into large motions of a hydraulic cylinder. Although the concept has been demonstrated in previously, the operating frequency of smart material EHA systems has been limited to a small fraction of the available bandwidth of the driver materials. The focus of this work is to characterize and model the mechanical performance of a magnetostrictive EHA considering key system components: rectification valves, smart material driver, and fluid-system components, leading to an improved actuator design relative to prior work. The one-way valves were modeled using 3-D finite element analysis, and their behavior was characterized experimentally by static and dynamic experimental measurement. Taking into account the effect of the fluid and mechanical conditions applied to the valves within the pump, the dynamic response of the valve was quantified and applied to determine rectification bandwidth of different valve configurations. A novel miniature reed valve, designed for a frequency response above 10~kHz, was fabricated and tested within a magnetostrictive EHA. The nonlinear response of the magnetostrictive driver, including saturation and hysteresis effects, was modeled using the Jiles-Atherton approach to calculate the magnetization and the resulting magnetostriction based on the applied field calculated within the rod from Maxwell's equations. The dynamic pressure response of the fluid system components (pumping chamber, hydraulic cylinder, and connecting passages) was measured over a range of input frequencies. For the magnetostrictive EHA tested, the peak performance frequency was found to be limited by the fluid resonances within the system. A lumped-parameter modeling approach was applied to model the overall behavior of a magnetostrictive EHA, incorporating models for the reed valve response, nonlinear magnetostrictive behavior, and fluid behavior (including inertia and compliance). This model was validated by experimental study of a magnetostrictive EHA with a reduced volume manifold. The model was subsequently applied to design a compact magnetostrictive EHA for aircraft applications. Testing of the system shows that the output performance increases with frequency up to a peak unloaded flow rate of 100 cm3/s (6.4 cu in/s) at 1200 Hz, which is a 100% to 500% increase over previous state-of-the-art systems. A blocked differential pressure of 12.1 MPa (1750 psi) was measured, resulting in a power capacity of 310 W, more than 100 W higher than previously reported values. The design and modeling approach used to scale up the performance to create a compact aircraft EHA can also be applied to reduce the size and weight of smart material EHAs for lower power level applications.

Phase behavior of charged colloids at a fluid interface

NASA Astrophysics Data System (ADS)

Kelleher, Colm P.; Guerra, Rodrigo E.; Hollingsworth, Andrew D.; Chaikin, Paul M.

2017-02-01

We study the phase behavior of a system of charged colloidal particles that are electrostatically bound to an almost flat interface between two fluids. We show that, despite the fact that our experimental system consists of only 103-104 particles, the phase behavior is consistent with the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson, and Young. Using spatial and temporal correlations of the bond-orientational order parameter, we classify our samples into solid, isotropic fluid, and hexatic phases. We demonstrate that the topological defect structure we observe in each phase corresponds to the predictions of Kosterlitz-Thouless-Halperin-Nelson-Young theory. By measuring the dynamic Lindemann parameter γL(τ ) and the non-Gaussian parameter α2(τ ) of the displacements of the particles relative to their neighbors, we show that each of the phases displays distinctive dynamical behavior.

On the effect of gyroscopic forces on the instability of certain fluid-elastic systems. Part 1: Definitions

NASA Astrophysics Data System (ADS)

Kornecki, A.

1983-09-01

This study was motivated by work on the stability of nonconservative elastic systems and flutter of certain fluid-elastic systems. A literature review revealed that the concepts of conservative forces (and systems) and gyroscopic forces (and systems) need clarifications, and the definitions formulated by different authors for the forces and systems are sometimes conflicting. In this report, these controversies are thoroughly discussed and conservative and gyroscopic systems are redefined within the framework of the classical dynamics of a system of particles.

Self-Propulsion of a Flapping Airfoil Using Cyber-Physical Fluid Dynamics

NASA Astrophysics Data System (ADS)

Young, Jay; Asselin, Daniel; Williamson, C. H. K.

2017-11-01

The fluid dynamics of biologically-inspired flapping propulsion provides a fertile testing ground for the field of unsteady aerodynamics, serving as important groundwork for the design and development of underwater vehicles and micro air vehicles (MAVs). These technologies can provide low cost, compact, and maneuverable means for terrain mapping, search and rescue operations, and reconnaissance. However, most laboratory experiments and simulations have been conducted using tethered airfoils with an imposed freestream velocity, which does not necessarily reflect the conditions under which an airfoil employed as a propulsor would operate. Using a closed-loop force-feedback control system, defined as Cyber-Physical Fluid Dynamics, or CPFD (Mackowski & Williamson 2011, 2015, & 2016), we allow a flapping airfoil to fly forward freely, achieving an equilibrium velocity at which thrust and drag are balanced. We study a combination of actively and passively controlled pitching and heaving dynamics in order to find motions that minimize the energy expended per distance traveled by the propulsion system. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research Grant No. FA9550-15-1-0243, monitored by Dr. Douglas Smith.

Active Polar Two-Fluid Macroscopic Dynamics

NASA Astrophysics Data System (ADS)

Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.

2014-03-01

We study the dynamics of systems with a polar dynamic preferred direction. Examples include the pattern-forming growth of bacteria (in a solvent, shoals of fish (moving in water currents), flocks of birds and migrating insects (flying in windy air). Because the preferred direction only exists dynamically, but not statically, the macroscopic variable of choice is the macroscopic velocity associated with the motion of the active units. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this second velocity. We find a normal mode structure quite different compared to the static descriptions, as well as linear couplings between (active) flow and e.g. densities and concentrations due to the genuine two-fluid transport derivatives. On the other hand, we get, quite similar to the static case, a direct linear relation between the stress tensor and the structure tensor. This prominent ``active'' term is responsible for many active effects, meaning that our approach can describe those effects as well. In addition, we also deal with explicitly chiral systems, which are important for many active systems. In particular, we find an active flow-induced heat current specific for the dynamic chiral polar order.

Particles size distribution in diluted magnetic fluids

NASA Astrophysics Data System (ADS)

Yerin, Constantine V.

2017-06-01

Changes in particles and aggregates size distribution in diluted kerosene based magnetic fluids is studied by dynamic light scattering method. It has been found that immediately after dilution in magnetic fluids the system of aggregates with sizes ranging from 100 to 250-1000 nm is formed. In 50-100 h after dilution large aggregates are peptized and in the sample stationary particles and aggregates size distribution is fixed.

Closed-loop feedback control for microfluidic systems through automated capacitive fluid height sensing.

PubMed

Soenksen, L R; Kassis, T; Noh, M; Griffith, L G; Trumper, D L

2018-03-13

Precise fluid height sensing in open-channel microfluidics has long been a desirable feature for a wide range of applications. However, performing accurate measurements of the fluid level in small-scale reservoirs (<1 mL) has proven to be an elusive goal, especially if direct fluid-sensor contact needs to be avoided. In particular, gravity-driven systems used in several microfluidic applications to establish pressure gradients and impose flow remain open-loop and largely unmonitored due to these sensing limitations. Here we present an optimized self-shielded coplanar capacitive sensor design and automated control system to provide submillimeter fluid-height resolution (∼250 μm) and control of small-scale open reservoirs without the need for direct fluid contact. Results from testing and validation of our optimized sensor and system also suggest that accurate fluid height information can be used to robustly characterize, calibrate and dynamically control a range of microfluidic systems with complex pumping mechanisms, even in cell culture conditions. Capacitive sensing technology provides a scalable and cost-effective way to enable continuous monitoring and closed-loop feedback control of fluid volumes in small-scale gravity-dominated wells in a variety of microfluidic applications.

Effects of magnetic-fluid flow on structural instability of a carbon nanotube conveying nanoflow under a longitudinal magnetic field

NASA Astrophysics Data System (ADS)

Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

2017-09-01

In drug delivery systems, carbon nanotubes (CNTs) can be used to deliver anticancer drugs into target site to kill metastatic cancer cells under the magnetic field guidance. Deep understanding of dynamic behavior of CNTs in drug delivery systems may enable more efficient use of the drugs while reducing systemic side effects. In this paper, we study the effect of magnetic-fluid flow on the structural instability of a CNT conveying nanoflow under a longitudinal magnetic field. The Navier-Stokes equation of magnetic-fluid flow is coupled with Euler-Bernoulli beam theory for modeling fluid structure interaction (FSI). Size effects of the magnetic fluid and the CNT are addressed through small-scale parameters including the Knudsen number (Kn) and the nonlocal parameter. Results show the positive role of magnetic properties of fluid flow on the structural stability of CNT. Specifically, magnetic force applied to the fluid flow has an effect of decreasing the structural stiffness of system while increasing the critical flow velocity. Furthermore, we discover that the nanoscale effects of CNT and fluid flow tend to amplify the influence of magnetic field on the vibrational behavior of the system.

Nonlinear Oscillators in Space Physics

NASA Technical Reports Server (NTRS)

Lester,Daniel; Thronson, Harley

2011-01-01

We discuss dynamical systems that produce an oscillation without an external time dependent source. Numerical results are presented for nonlinear oscillators in the Em1h's atmosphere, foremost the quasi-biennial oscillation (QBOl. These fluid dynamical oscillators, like the solar dynamo, have in common that one of the variables in a governing equation is strongly nonlinear and that the nonlinearity, to first order, has particular form. of 3rd or odd power. It is shown that this form of nonlinearity can produce the fundamental li'equency of the internal oscillation. which has a period that is favored by the dynamical condition of the fluid. The fundamental frequency maintains the oscillation, with no energy input to the system at that particular frequency. Nonlinearities of 2nd or even power could not maintain the oscillation.

Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

DOEpatents

Battiste, Richard L.

2007-12-25

Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into the mold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with the fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a temperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into the mold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

DOEpatents

Battiste, Richard L

2013-12-31

Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into th emold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with a fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a termperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into th emold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

Fluid Mechanics of Blood Clot Formation.

PubMed

Fogelson, Aaron L; Neeves, Keith B

2015-01-01

Intravascular blood clots form in an environment in which hydrodynamic forces dominate and in which fluid-mediated transport is the primary means of moving material. The clotting system has evolved to exploit fluid dynamic mechanisms and to overcome fluid dynamic challenges to ensure that clots that preserve vascular integrity can form over the wide range of flow conditions found in the circulation. Fluid-mediated interactions between the many large deformable red blood cells and the few small rigid platelets lead to high platelet concentrations near vessel walls where platelets contribute to clotting. Receptor-ligand pairs with diverse kinetic and mechanical characteristics work synergistically to arrest rapidly flowing cells on an injured vessel. Variations in hydrodynamic stresses switch on and off the function of key clotting polymers. Protein transport to, from, and within a developing clot determines whether and how fast it grows. We review ongoing experimental and modeling research to understand these and related phenomena.

Fluid Mechanics of Blood Clot Formation

NASA Astrophysics Data System (ADS)

Fogelson, Aaron L.; Neeves, Keith B.

2015-01-01

Intravascular blood clots form in an environment in which hydrodynamic forces dominate and in which fluid-mediated transport is the primary means of moving material. The clotting system has evolved to exploit fluid dynamic mechanisms and to overcome fluid dynamic challenges to ensure that clots that preserve vascular integrity can form over the wide range of flow conditions found in the circulation. Fluid-mediated interactions between the many large deformable red blood cells and the few small rigid platelets lead to high platelet concentrations near vessel walls where platelets contribute to clotting. Receptor-ligand pairs with diverse kinetic and mechanical characteristics work synergistically to arrest rapidly flowing cells on an injured vessel. Variations in hydrodynamic stresses switch on and off the function of key clotting polymers. Protein transport to, from, and within a developing clot determines whether and how fast it grows. We review ongoing experimental and modeling research to understand these and related phenomena.

Locomotion at Low Reynolds Number: Dynamics in Newtonian and Non-Newtonian Systems with Biomedical Applications

NASA Astrophysics Data System (ADS)

Gagnon, David A.

Swimming microorganisms such as bacteria, spermatozoa, algae, and nematodes are critical to ubiquitous biological phenomena such as disease and infection, ecosystem dynamics, and mammalian fertilization. While there has been much scientific and practical interest in studying these swimmers in Newtonian (water-like) fluids, there are fewer systematic experimental studies on swimming through non-Newtonian (non-water-like) fluids with biologically-relevant mechanical properties. These organisms commonly swim through viscoelastic, structured, or shear-rate-dependent fluids, such as blood, mucus, and living tissues. Furthermore, the small length scales of these organisms dictate that their motion is dominated by viscous forces and inertia is negligible. Using rheology, microscopy, particle tracking, and image processing techniques, we examine the interaction of low Reynolds number swimmers and non-Newtonian fluids including viscoelastic, locally-anisotropic, and shear-thinning fluids. We then apply our understanding of locomotion to the study of the genetic disease Spinal Muscular Atrophy.

Instabilities and diffusion in a hydrodynamic model of a fluid membrane coupled to a thin active fluid layer.

PubMed

Sarkar, N; Basu, A

2012-11-01

We construct a coarse-grained effective two-dimensional (2d hydrodynamic theory as a theoretical model for a coupled system of a fluid membrane and a thin layer of a polar active fluid in its ordered state that is anchored to the membrane. We show that such a system is prone to generic instabilities through the interplay of nonequilibrium drive, polar order and membrane fluctuation. We use our model equations to calculate diffusion coefficients of an inclusion in the membrane and show that their values depend strongly on the system size, in contrast to their equilibrium values. Our work extends the work of S. Sankararaman and S. Ramaswamy (Phys. Rev. Lett., 102, 118107 (2009)) to a coupled system of a fluid membrane and an ordered active fluid layer. Our model is broadly inspired by and should be useful as a starting point for theoretical descriptions of the coupled dynamics of a cell membrane and a cortical actin layer anchored to it.

CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

NASA Technical Reports Server (NTRS)

Sances, Dillon J.; Gangadharan, Sathya N.; Sudermann, James E.; Marsell, Brandon

2010-01-01

Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response.

A dynamic human water and electrolyte balance model for verification and optimization of life support systems in space flight applications

NASA Astrophysics Data System (ADS)

Hager, P.; Czupalla, M.; Walter, U.

2010-11-01

In this paper we report on the development of a dynamic MATLAB SIMULINK® model for the water and electrolyte balance inside the human body. This model is part of an environmentally sensitive dynamic human model for the optimization and verification of environmental control and life support systems (ECLSS) in space flight applications. An ECLSS provides all vital supplies for supporting human life on board a spacecraft. As human space flight today focuses on medium- to long-term missions, the strategy in ECLSS is shifting to closed loop systems. For these systems the dynamic stability and function over long duration are essential. However, the only evaluation and rating methods for ECLSS up to now are either expensive trial and error breadboarding strategies or static and semi-dynamic simulations. In order to overcome this mismatch the Exploration Group at Technische Universität München (TUM) is developing a dynamic environmental simulation, the "Virtual Habitat" (V-HAB). The central element of this simulation is the dynamic and environmentally sensitive human model. The water subsystem simulation of the human model discussed in this paper is of vital importance for the efficiency of possible ECLSS optimizations, as an over- or under-scaled water subsystem would have an adverse effect on the overall mass budget. On the other hand water has a pivotal role in the human organism. Water accounts for about 60% of the total body mass and is educt and product of numerous metabolic reactions. It is a transport medium for solutes and, due to its high evaporation enthalpy, provides the most potent medium for heat load dissipation. In a system engineering approach the human water balance was worked out by simulating the human body's subsystems and their interactions. The body fluids were assumed to reside in three compartments: blood plasma, interstitial fluid and intracellular fluid. In addition, the active and passive transport of water and solutes between those compartments was modeled dynamically. A kidney model regulates the electrolyte concentration in body fluids (osmolality) in narrow confines and a thirst mechanism models the urge to ingest water. A controlled exchange of water and electrolytes with other human subsystems, as well as with the environment, is implemented. Finally, the changes in body composition due to muscle growth are accounted for. The outcome of this is a dynamic water and electrolyte balance, which is capable of representing body reactions like thirst and headaches, as well as heat stroke and collapse, as a response to its work load and environment.

Hydrodynamics of confined colloidal fluids in two dimensions

NASA Astrophysics Data System (ADS)

Sané, Jimaan; Padding, Johan T.; Louis, Ard A.

2009-05-01

We apply a hybrid molecular dynamics and mesoscopic simulation technique to study the dynamics of two-dimensional colloidal disks in confined geometries. We calculate the velocity autocorrelation functions and observe the predicted t-1 long-time hydrodynamic tail that characterizes unconfined fluids, as well as more complex oscillating behavior and negative tails for strongly confined geometries. Because the t-1 tail of the velocity autocorrelation function is cut off for longer times in finite systems, the related diffusion coefficient does not diverge but instead depends logarithmically on the overall size of the system. The Langevin equation gives a poor approximation to the velocity autocorrelation function at both short and long times.

Discovering governing equations from data by sparse identification of nonlinear dynamical systems

PubMed Central

Brunton, Steven L.; Proctor, Joshua L.; Kutz, J. Nathan

2016-01-01

Extracting governing equations from data is a central challenge in many diverse areas of science and engineering. Data are abundant whereas models often remain elusive, as in climate science, neuroscience, ecology, finance, and epidemiology, to name only a few examples. In this work, we combine sparsity-promoting techniques and machine learning with nonlinear dynamical systems to discover governing equations from noisy measurement data. The only assumption about the structure of the model is that there are only a few important terms that govern the dynamics, so that the equations are sparse in the space of possible functions; this assumption holds for many physical systems in an appropriate basis. In particular, we use sparse regression to determine the fewest terms in the dynamic governing equations required to accurately represent the data. This results in parsimonious models that balance accuracy with model complexity to avoid overfitting. We demonstrate the algorithm on a wide range of problems, from simple canonical systems, including linear and nonlinear oscillators and the chaotic Lorenz system, to the fluid vortex shedding behind an obstacle. The fluid example illustrates the ability of this method to discover the underlying dynamics of a system that took experts in the community nearly 30 years to resolve. We also show that this method generalizes to parameterized systems and systems that are time-varying or have external forcing. PMID:27035946

Discovering governing equations from data by sparse identification of nonlinear dynamical systems.

PubMed

Brunton, Steven L; Proctor, Joshua L; Kutz, J Nathan

2016-04-12

Extracting governing equations from data is a central challenge in many diverse areas of science and engineering. Data are abundant whereas models often remain elusive, as in climate science, neuroscience, ecology, finance, and epidemiology, to name only a few examples. In this work, we combine sparsity-promoting techniques and machine learning with nonlinear dynamical systems to discover governing equations from noisy measurement data. The only assumption about the structure of the model is that there are only a few important terms that govern the dynamics, so that the equations are sparse in the space of possible functions; this assumption holds for many physical systems in an appropriate basis. In particular, we use sparse regression to determine the fewest terms in the dynamic governing equations required to accurately represent the data. This results in parsimonious models that balance accuracy with model complexity to avoid overfitting. We demonstrate the algorithm on a wide range of problems, from simple canonical systems, including linear and nonlinear oscillators and the chaotic Lorenz system, to the fluid vortex shedding behind an obstacle. The fluid example illustrates the ability of this method to discover the underlying dynamics of a system that took experts in the community nearly 30 years to resolve. We also show that this method generalizes to parameterized systems and systems that are time-varying or have external forcing.

Molecular dynamics simulation of a needle-sphere binary mixture

NASA Astrophysics Data System (ADS)

Raghavan, Karthik

This paper investigates the dynamic behaviour of a hard needle-sphere binary system using a novel numerical technique called the Newton homotopy continuation (NHC) method. This mixture is representative of a polymer melt where both long chain molecules and monomers coexist. Since the intermolecular forces are generated from hard body interactions, the consequence of missed collisions or incorrect collision sequences have a significant bearing on the dynamic properties of the fluid. To overcome this problem, in earlier work NHC was chosen over traditional Newton-Raphson methods to solve the hard body dynamics of a needle fluid in random media composed of overlapping spheres. Furthermore, the simplicity of interactions and dynamics allows us to focus our research directly on the effects of particle shape and density on the transport behaviour of the mixture. These studies are also compared with earlier works that examined molecular chains in porous media primarily to understand the differences in molecular transport in the bulk versus porous systems.

Integrating aerodynamic surface modeling for computational fluid dynamics with computer aided structural analysis, design, and manufacturing

NASA Technical Reports Server (NTRS)

Thorp, Scott A.

1992-01-01

This presentation will discuss the development of a NASA Geometry Exchange Specification for transferring aerodynamic surface geometry between LeRC systems and grid generation software used for computational fluid dynamics research. The proposed specification is based on a subset of the Initial Graphics Exchange Specification (IGES). The presentation will include discussion of how the NASA-IGES standard will accommodate improved computer aided design inspection methods and reverse engineering techniques currently being developed. The presentation is in viewgraph format.

Computer-aided-engineering system for modeling and analysis of ECLSS integration testing

NASA Technical Reports Server (NTRS)

Sepahban, Sonbol

1987-01-01

The accurate modeling and analysis of two-phase fluid networks found in environmental control and life support systems is presently undertaken by computer-aided engineering (CAE) techniques whose generalized fluid dynamics package can solve arbitrary flow networks. The CAE system for integrated test bed modeling and analysis will also furnish interfaces and subsystem/test-article mathematical models. Three-dimensional diagrams of the test bed are generated by the system after performing the requisite simulation and analysis.

Super energy saver heat pump with dynamic hybrid phase change material

DOEpatents

Ally, Moonis Raza [Oak Ridge, TN; Tomlinson, John Jager [Knoxville, TN; Rice, Clifford Keith [Clinton, TN

2010-07-20

A heat pump has a refrigerant loop, a compressor in fluid communication with the refrigerant loop, at least one indoor heat exchanger in fluid communication with the refrigerant loop, and at least one outdoor heat exchanger in fluid communication with the refrigerant loop. The at least one outdoor heat exchanger has a phase change material in thermal communication with the refrigerant loop and in fluid communication with an outdoor environment. Other systems, devices, and methods are described.

Lymphatic System Flows

NASA Astrophysics Data System (ADS)

Moore, James E., Jr.; Bertram, Christopher D.

2018-01-01

The supply of oxygen and nutrients to tissues is performed by the blood system and involves a net leakage of fluid outward at the capillary level. One of the principal functions of the lymphatic system is to gather this fluid and return it to the blood system to maintain overall fluid balance. Fluid in the interstitial spaces is often at subatmospheric pressure, and the return points into the venous system are at pressures of approximately 20 cmH2O. This adverse pressure difference is overcome by the active pumping of collecting lymphatic vessels, which feature closely spaced one-way valves and contractile muscle cells in their walls. Passive vessel squeezing causes further pumping. The dynamics of lymphatic pumping have been investigated experimentally and mathematically, revealing complex behaviors that indicate that the system performance is robust against minor perturbations in pressure and flow. More serious disruptions can lead to incurable swelling of tissues called lymphedema.

Silverton Conference on Applications of the Zero Gravity Space Shuttle Environment to Problems in Fluid Dynamics

NASA Technical Reports Server (NTRS)

Eisner, M. (Editor)

1974-01-01

The possible utilization of the zero gravity resource for studies in a variety of fluid dynamics and fluid-dynamic related problems was investigated. A group of experiments are discussed and described in detail; these include experiments in the areas of geophysical fluid models, fluid dynamics, mass transfer processes, electrokinetic separation of large particles, and biophysical and physiological areas.

Holographic microscopy studies of emulsions

NASA Technical Reports Server (NTRS)

Witherow, W. K.

1981-01-01

A holographic microscopy system that records and observes the dynamic properties of separation of dispersed immiscible fluids is described. The holographic construction system and reconstruction system that were used to obtain particle size and distribution information from the holograms are discussed. The holographic microscopy system is used to observed the phase separating processes in immiscible fluids that were isothermally cooled into the two phase region. Nucleation, growth rates, coalescence, and particle motion are successfully demonstrated with this system. Thus a holographic particle sizing system with a resolution of 2 micrometers and a field of view of 100 cu cm was developed that provides the capability of testing the theories of separating immiscible fluids for particle number densities in the range of 10 to 10 to the 7th power particles.

High Performance Parallel Processing (HPPP) Finite Element Simulation of Fluid Structure Interactions Final Report CRADA No. TC-0824-94-A

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

Couch, R.; Ziegler, D. P.

This project was a muki-partner CRADA. This was a partnership between Alcoa and LLNL. AIcoa developed a system of numerical simulation modules that provided accurate and efficient threedimensional modeling of combined fluid dynamics and structural response.

Liquid Oxygen/Liquid Methane Integrated Propulsion System Test Bed

NASA Technical Reports Server (NTRS)

Flynn, Howard; Lusby, Brian; Villemarette, Mark

2011-01-01

In support of NASA?s Propulsion and Cryogenic Advanced Development (PCAD) project, a liquid oxygen (LO2)/liquid methane (LCH4) Integrated Propulsion System Test Bed (IPSTB) was designed and advanced to the Critical Design Review (CDR) stage at the Johnson Space Center. The IPSTB?s primary objectives are to study LO2/LCH4 propulsion system steady state and transient performance, operational characteristics and to validate fluid and thermal models of a LO2/LCH4 propulsion system for use in future flight design work. Two phase thermal and dynamic fluid flow models of the IPSTB were built to predict the system performance characteristics under a variety of operating modes and to aid in the overall system design work. While at ambient temperature and simulated altitude conditions at the White Sands Test Facility, the IPSTB and its approximately 600 channels of system instrumentation would be operated to perform a variety of integrated main engine and reaction control engine hot fire tests. The pressure, temperature, and flow rate data collected during this testing would then be used to validate the analytical models of the IPSTB?s thermal and dynamic fluid flow performance. An overview of the IPSTB design and analytical model development will be presented.

Design approach of an aquaculture cage system for deployment in the constructed channel flow environments of a power plant

PubMed Central

Lee, Jihoon; Fredriksson, David W.; DeCew, Judson; Drach, Andrew; Yim, Solomon C.

2018-01-01

This study provides an engineering approach for designing an aquaculture cage system for use in constructed channel flow environments. As sustainable aquaculture has grown globally, many novel techniques have been introduced such as those implemented in the global Atlantic salmon industry. The advent of several highly sophisticated analysis software systems enables the development of such novel engineering techniques. These software systems commonly include three-dimensional (3D) drafting, computational fluid dynamics, and finite element analysis. In this study, a combination of these analysis tools is applied to evaluate a conceptual aquaculture system for potential deployment in a power plant effluent channel. The channel is supposedly clean; however, it includes elevated water temperatures and strong currents. The first portion of the analysis includes the design of a fish cage system with specific net solidities using 3D drafting techniques. Computational fluid dynamics is then applied to evaluate the flow reduction through the system from the previously generated solid models. Implementing the same solid models, a finite element analysis is performed on the critical components to assess the material stresses produced by the drag force loads that are calculated from the fluid velocities. PMID:29897954

Data-Driven Model Reduction and Transfer Operator Approximation

NASA Astrophysics Data System (ADS)

Klus, Stefan; Nüske, Feliks; Koltai, Péter; Wu, Hao; Kevrekidis, Ioannis; Schütte, Christof; Noé, Frank

2018-06-01

In this review paper, we will present different data-driven dimension reduction techniques for dynamical systems that are based on transfer operator theory as well as methods to approximate transfer operators and their eigenvalues, eigenfunctions, and eigenmodes. The goal is to point out similarities and differences between methods developed independently by the dynamical systems, fluid dynamics, and molecular dynamics communities such as time-lagged independent component analysis, dynamic mode decomposition, and their respective generalizations. As a result, extensions and best practices developed for one particular method can be carried over to other related methods.

Computational aerodynamics and artificial intelligence

NASA Technical Reports Server (NTRS)

Mehta, U. B.; Kutler, P.

1984-01-01

The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

From Lattice Boltzmann to hydrodynamics in dissipative relativistic fluids

NASA Astrophysics Data System (ADS)

Gabbana, Alessandro; Mendoza, Miller; Succi, Sauro; Tripiccione, Raffaele

2017-11-01

Relativistic fluid dynamics is currently applied to several fields of modern physics, covering many physical scales, from astrophysics, to atomic scales (e.g. in the study of effective 2D systems such as graphene) and further down to subnuclear scales (e.g. quark-gluon plasmas). This talk focuses on recent progress in the largely debated connection between kinetic transport coefficients and macroscopic hydrodynamic parameters in dissipative relativistic fluid dynamics. We use a new relativistic Lattice Boltzmann method (RLBM), able to handle from ultra-relativistic to almost non-relativistic flows, and obtain strong evidence that the Chapman-Enskog expansion provides the correct pathway from kinetic theory to hydrodynamics. This analysis confirms recently obtained theoretical results, which can be used to obtain accurate calibrations for RLBM methods applied to realistic physics systems in the relativistic regime. Using this calibration methodology, RLBM methods are able to deliver improved physical accuracy in the simulation of the physical systems described above. European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 642069.

High bulk modulus of ionic liquid and effects on performance of hydraulic system.

PubMed

Kambic, Milan; Kalb, Roland; Tasner, Tadej; Lovrec, Darko

2014-01-01

Over recent years ionic liquids have gained in importance, causing a growing number of scientists and engineers to investigate possible applications for these liquids because of their unique physical and chemical properties. Their outstanding advantages such as nonflammable liquid within a broad liquid range, high thermal, mechanical, and chemical stabilities, low solubility for gases, attractive tribological properties (lubrication), and very low compressibility, and so forth, make them more interesting for applications in mechanical engineering, offering great potential for new innovative processes, and also as a novel hydraulic fluid. This paper focuses on the outstanding compressibility properties of ionic liquid EMIM-EtSO4, a very important physical chemically property when IL is used as a hydraulic fluid. This very low compressibility (respectively, very high Bulk modulus), compared to the classical hydraulic mineral oils or the non-flammable HFDU type of hydraulic fluids, opens up new possibilities regarding its usage within hydraulic systems with increased dynamics, respectively, systems' dynamic responses.

Beyond Our Boundaries: Research and Technology

NASA Technical Reports Server (NTRS)

1996-01-01

Topics considered include: Propulsion and Fluid Management; Structures and Dynamics; Materials and Manufacturing Processes; Sensor Technology; Software Technology; Optical Systems; Microgravity Science; Earth System Science; Astrophysics; Solar Physics; and Technology Transfer.

Laboratory and numerical investigations of kinetic interface sensitive tracers transport for immiscible two-phase flow porous media systems

NASA Astrophysics Data System (ADS)

Tatomir, Alexandru Bogdan A. C.; Sauter, Martin

2017-04-01

A number of theoretical approaches estimating the interfacial area between two fluid phases are available (Schaffer et al.,2013). Kinetic interface sensitive (KIS) tracers are used to describe the evolution of fluid-fluid interfaces advancing in two phase porous media systems (Tatomir et al., 2015). Initially developed to offer answers about the supercritical (sc)CO2 plume movement and the efficiency of trapping in geological carbon storage reservoirs, KIS tracers are tested in dynamic controlled laboratory conditions. N-octane and water, analogue to a scCO2 - brine system, are used. The KIS tracer is dissolved in n-octane, which is injected as the non-wetting phase in a fully water saturated porous media column. The porous system is made up of spherical glass beads with sizes of 100-250 μm. Subsequently, the KIS tracer follows a hydrolysis reaction over the n-octane - water interface resulting in an acid and phenol which are both water soluble. The fluid-fluid interfacial area is described numerically with the help of constitutive-relationships derived from the Brooks-Corey model. The specific interfacial area is determined numerically from pore scale calculations, or from different literature sources making use of pore network model calculations (Joekar-Niasar et al., 2008). This research describes the design of the laboratory setup and compares the break-through curves obtained with the forward model and in the laboratory experiment. Furthermore, first results are shown in the attempt to validate the immiscible two phase flow reactive transport numerical model with dynamic laboratory column experiments. Keywords: Fluid-fluid interfacial area, KIS tracers, model validation, CCS, geological storage of CO2

Sloshing dynamics on rotating helium dewar tank

NASA Technical Reports Server (NTRS)

Hung, R. J.

1993-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics were based on the non-inertia frame spacecraft bound coordinate, and solve time dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers were derived. Results were widely published in the open journals.

The Mochi project: a field theory approach to plasma dynamics and self-organization

NASA Astrophysics Data System (ADS)

You, Setthivoine; von der Linden, Jens; Lavine, Eric Sander; Card, Alexander; Carroll, Evan

2016-10-01

The Mochi project is designed to study the interaction between plasma flows and magnetic fields from the point-of-view of canonical flux tubes. The Mochi Labjet experiment is being commissioned after achieving first plasma. Analytical and numerical tools are being developed to visualize canonical flux tubes. One analytical tool described here is a field theory approach to plasma dynamics and self-organization. A redefinition of the Lagrangian of a multi-particle system in fields reformulates the single-particle, kinetic, and fluid equations governing fluid and plasma dynamics as a single set of generalized Maxwell's equations and Ohm's law for canonical force-fields. The Lagrangian includes new terms representing the coupling between the motion of particle distributions, between distributions and electromagnetic fields, with relativistic contributions. The formulation shows that the concepts of self-organization and canonical helicity transport are applicable across single-particle, kinetic, and fluid regimes, at classical and relativistic scales. The theory gives the basis for comparing canonical helicity change to energy change in general systems. This work is supported by by US DOE Grant DE-SC0010340.

Fish robotics and hydrodynamics

NASA Astrophysics Data System (ADS)

Lauder, George

2010-11-01

Studying the fluid dynamics of locomotion in freely-swimming fishes is challenging due to difficulties in controlling fish behavior. To provide better control over fish-like propulsive systems we have constructed a variety of fish-like robotic test platforms that range from highly biomimetic models of fins, to simple physical models of body movements during aquatic locomotion. First, we have constructed a series of biorobotic models of fish pectoral fins with 5 fin rays that allow detailed study of fin motion, forces, and fluid dynamics associated with fin-based locomotion. We find that by tuning fin ray stiffness and the imposed motion program we can produce thrust both on the fin outstroke and instroke. Second, we are using a robotic flapping foil system to study the self-propulsion of flexible plastic foils of varying stiffness, length, and trailing edge shape as a means of investigating the fluid dynamic effect of simple changes in the properties of undulating bodies moving through water. We find unexpected non-linear stiffness-dependent effects of changing foil length on self-propelled speed, and as well as significant effects of trailing edge shape on foil swimming speed.

Shock Dynamics for particle-laden thin film

NASA Astrophysics Data System (ADS)

Wang, Li; Bertozzi, Andrea

2013-11-01

We study the shock dynamics for a recently proposed system of conservation laws (Murisic et al. [J. Fluid Mech. 2013]) describing gravity-driven thin film flow of a suspension of particles down an incline. When the particle concentration is above a critical value, singular shock solutions can occur. We analyze the Hugoniot topology associated with the Riemann problem for this system, describing in detail how the transition from a double shock to a singular shock happen. We also derive the singular shock speed based on a key observation that the particles pilling up at the maximum packing fraction near the contact line. These results are further applied to constant volume case to generate a rarefaction-singular shock solution. The particle/fluid front are shown to move linearly to the leading order with time to the one-third power as predicted by the Huppert solution for clear fluid.

Data Point Averaging for Computational Fluid Dynamics Data

NASA Technical Reports Server (NTRS)

Norman, Jr., David (Inventor)

2016-01-01

A system and method for generating fluid flow parameter data for use in aerodynamic heating analysis. Computational fluid dynamics data is generated for a number of points in an area on a surface to be analyzed. Sub-areas corresponding to areas of the surface for which an aerodynamic heating analysis is to be performed are identified. A computer system automatically determines a sub-set of the number of points corresponding to each of the number of sub-areas and determines a value for each of the number of sub-areas using the data for the sub-set of points corresponding to each of the number of sub-areas. The value is determined as an average of the data for the sub-set of points corresponding to each of the number of sub-areas. The resulting parameter values then may be used to perform an aerodynamic heating analysis.

Data Point Averaging for Computational Fluid Dynamics Data

NASA Technical Reports Server (NTRS)

Norman, David, Jr. (Inventor)

2014-01-01

A system and method for generating fluid flow parameter data for use in aerodynamic heating analysis. Computational fluid dynamics data is generated for a number of points in an area on a surface to be analyzed. Sub-areas corresponding to areas of the surface for which an aerodynamic heating analysis is to be performed are identified. A computer system automatically determines a sub-set of the number of points corresponding to each of the number of sub-areas and determines a value for each of the number of sub-areas using the data for the sub-set of points corresponding to each of the number of sub-areas. The value is determined as an average of the data for the sub-set of points corresponding to each of the number of sub-areas. The resulting parameter values then may be used to perform an aerodynamic heating analysis.

Uncertainty Quantification in Aeroelasticity

NASA Astrophysics Data System (ADS)

Beran, Philip; Stanford, Bret; Schrock, Christopher

2017-01-01

Physical interactions between a fluid and structure, potentially manifested as self-sustained or divergent oscillations, can be sensitive to many parameters whose values are uncertain. Of interest here are aircraft aeroelastic interactions, which must be accounted for in aircraft certification and design. Deterministic prediction of these aeroelastic behaviors can be difficult owing to physical and computational complexity. New challenges are introduced when physical parameters and elements of the modeling process are uncertain. By viewing aeroelasticity through a nondeterministic prism, where key quantities are assumed stochastic, one may gain insights into how to reduce system uncertainty, increase system robustness, and maintain aeroelastic safety. This article reviews uncertainty quantification in aeroelasticity using traditional analytical techniques not reliant on computational fluid dynamics; compares and contrasts this work with emerging methods based on computational fluid dynamics, which target richer physics; and reviews the state of the art in aeroelastic optimization under uncertainty. Barriers to continued progress, for example, the so-called curse of dimensionality, are discussed.

Dynamics of Active Microfilaments

NASA Astrophysics Data System (ADS)

Ling, Feng; Guo, Hanliang; Kanso, Eva

2017-11-01

Soft elastic filaments are ubiquitous in natural and artificial systems at various length scales, and their interactions within and between filaments and their environments provide a persistent source of curiosity due to both the complexity of their behaviors and the relative mathematical simplicity of their structures. Specifically, a deeper understanding of the dynamic characteristics of microscopic filaments in viscous fluids is relevant to many biophysical and physiological processes. Here we start with the Cosserat model that allows all six possible modes of deformation for an elastic rod, and focus on the case of inextensible filaments submerged in viscous fluids by ignoring inertial effects and using local resistive force theory for fluid-filament interactions. We verify our simulations against special analytic solutions and present some results on the active internal control of cilia and flagella motion. We conclude by commenting on the utility of this general framework for studying other cellular and sub-cellular physical processes such as systems involving protein filaments.

Proceedings of the International Symposium on Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances

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

Faybishenko, B.

1999-02-01

This publication contains extended abstracts of papers presented at the International Symposium ''Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances'' held at Ernest Orlando Lawrence Berkeley National Laboratory on February 10-12, 1999. This Symposium is organized in Honor of the 80th Birthday of Paul A. Witherspoon, who initiated some of the early investigations on flow and transport in fractured rocks at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory. He is a key figure in the development of basic concepts, modeling, and field measurements of fluid flow and contaminant transport in fractured rock systems. Themore » technical problems of assessing fluid flow, radionuclide transport, site characterization, modeling, and performance assessment in fractured rocks remain the most challenging aspects of subsurface flow and transport investigations. An understanding of these important aspects of hydrogeology is needed to assess disposal of nu clear wastes, development of geothermal resources, production of oil and gas resources, and remediation of contaminated sites. These Proceedings of more than 100 papers from 12 countries discuss recent scientific and practical developments and the status of our understanding of fluid flow and radionuclide transport in fractured rocks. The main topics of the papers are: Theoretical studies of fluid flow in fractured rocks; Multi-phase flow and reactive chemical transport in fractured rocks; Fracture/matrix interactions; Hydrogeological and transport testing; Fracture flow models; Vadose zone studies; Isotopic studies of flow in fractured systems; Fractures in geothermal systems; Remediation and colloid transport in fractured systems; and Nuclear waste disposal in fractured rocks.« less

A phase-field method to analyze the dynamics of immiscible fluids in porous media

NASA Astrophysics Data System (ADS)

de Paoli, Marco; Roccon, Alessio; Zonta, Francesco; Soldati, Alfredo

2017-11-01

Liquid carbon dioxide (CO2) injected into geological formations (filled with brine) is not completely soluble in the surrounding fluid. For this reason, complex transport phenomena may occur across the interface that separates the two phases (CO2+brine and brine). Inspired by this geophysical instance, we used a Phase-Field Method (PFM) to describe the dynamics of two immiscible fluids in satured porous media. The basic idea of the PFM is to introduce an order parameter (ϕ) that varies continuously across the interfacial layer between the phases and is uniform in the bulk. The equation that describes the distribution of ϕ is the Cahn-Hilliard (CH) equation, which is coupled with the Darcy equation (to evaluate fluid velocity) through the buoyancy and Korteweg stress terms. The governing equations are solved through a pseudo-spectral technique (Fourier-Chebyshev). Our results show that the value of the surface tension between the two phases strongly influences the initial and the long term dynamics of the system. We believe that the proposed numerical approach, which grants an accurate evaluation of the interfacial fluxes of momentum/energy/species, is attractive to describe the transfer mechanism and the overall dynamics of immiscible and partially miscible phases.

On the kinetics of the capillary imbibition of a simple fluid through a designed nanochannel using the molecular dynamics simulation approach.

PubMed

Ahadian, Samad; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

2010-12-15

A molecular dynamics (MD) approach was employed to simulate the imbibition of a designed nanopore by a simple fluid (i.e., a Lennard-Jones (LJ) fluid). The length of imbibition as a function of time for various interactions between the LJ fluid and the pore wall was recorded for this system (i.e., the LJ fluid and the nanopore). By and large, the kinetics of imbibition was successfully described by the Lucas-Washburn (LW) equation, although deviation from it was observed in some cases. This lack of agreement is due to the neglect of the dynamic contact angle (DCA) in the LW equation. Two commonly used models (i.e., hydrodynamic and molecular-kinetic (MK) models) were thus employed to calculate the DCA. It is demonstrated that the MK model is able to justify the simulation results in which are not in good agreement with the simple LW equation. However, the hydrodynamic model is not capable of doing that. Further investigation of the MD simulation data revealed an interesting fact that there is a direct relationship between the wall-fluid interaction and the speed of the capillary imbibition. More evidence to support this claim is presented. Copyright © 2010 Elsevier Inc. All rights reserved.

Local equilibrium solutions in simple anisotropic cosmological models, as described by relativistic fluid dynamics

NASA Astrophysics Data System (ADS)

Shogin, Dmitry; Amund Amundsen, Per

2016-10-01

We test the physical relevance of the full and the truncated versions of the Israel-Stewart (IS) theory of irreversible thermodynamics in a cosmological setting. Using a dynamical systems method, we determine the asymptotic future of plane symmetric Bianchi type I spacetimes with a viscous mathematical fluid, keeping track of the magnitude of the relative dissipative fluxes, which determines the applicability of the IS theory. We consider the situations where the dissipative mechanisms of shear and bulk viscosity are involved separately and simultaneously. It is demonstrated that the only case in the given model when the fluid asymptotically approaches local thermal equilibrium, and the underlying assumptions of the IS theory are therefore not violated, is that of a dissipative fluid with vanishing bulk viscosity. The truncated IS equations for shear viscosity are found to produce solutions which manifest pathological dynamical features and, in addition, to be strongly sensitive to the choice of initial conditions. Since these features are observed already in the case of an oversimplified mathematical fluid model, we have no reason to assume that the truncation of the IS transport equations will produce relevant results for physically more realistic fluids. The possible role of bulk and shear viscosity in cosmological evolution is also discussed.

The Effect of the Density Ratio on the Nonlinear Dynamics of the Unstable Fluid Interface

NASA Technical Reports Server (NTRS)

Abarzhi, S. I.

2003-01-01

Here we report multiple harmonic theoretical solutions for a complete system of conservation laws, which describe the large-scale coherent dynamics in RTI and RMI for fluids with a finite density ratio in the general three-dimensional case. The analysis yields new properties of the bubble front dynamics. In either RTI or RMI, the obtained dependencies of the bubble velocity and curvature on the density ratio differ qualitatively and quantitatively from those suggested by the models of Sharp (1984), Oron et al. (2001), and Goncharov (2002). We show explicitly that these models violate the conservation laws. For the first time, our theory reveals an important qualitative distinction between the dynamics of the RT and RM bubbles.

Optimum periodicity of repeated contractile actions applied in mass transport

NASA Astrophysics Data System (ADS)

Ahn, Sungsook; Lee, Sang Joon

2015-01-01

Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices, and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications.

Microgravity Combustion Science and Fluid Physics Experiments and Facilities for the ISS

NASA Technical Reports Server (NTRS)

Lauver, Richard W.; Kohl, Fred J.; Weiland, Karen J.; Zurawski, Robert L.; Hill, Myron E.; Corban, Robert R.

2001-01-01

At the NASA Glenn Research Center, the Microgravity Science Program supports both ground-based and flight experiment research in the disciplines of Combustion Science and Fluid Physics. Combustion Science research includes the areas of gas jet diffusion flames, laminar flames, burning of droplets and misting fuels, solids and materials flammability, fire and fire suppressants, turbulent combustion, reaction kinetics, materials synthesis, and other combustion systems. The Fluid Physics discipline includes the areas of complex fluids (colloids, gels, foams, magneto-rheological fluids, non-Newtonian fluids, suspensions, granular materials), dynamics and instabilities (bubble and drop dynamics, magneto/electrohydrodynamics, electrochemical transport, geophysical flows), interfacial phenomena (wetting, capillarity, contact line hydrodynamics), and multiphase flows and phase changes (boiling and condensation, heat transfer, flow instabilities). A specialized International Space Station (ISS) facility that provides sophisticated research capabilities for these disciplines is the Fluids and Combustion Facility (FCF). The FCF consists of the Combustion Integrated Rack (CIR), the Fluids Integrated Rack (FIR) and the Shared Accommodations Rack and is designed to accomplish a large number of science investigations over the life of the ISS. The modular, multiuser facility is designed to optimize the science return within the available resources of on-orbit power, uplink/downlink capacity, crew time, upmass/downmass, volume, etc. A suite of diagnostics capabilities, with emphasis on optical techniques, will be provided to complement the capabilities of the subsystem multiuser or principal investigator-specific experiment modules. The paper will discuss the systems concept, technical capabilities, functionality, and the initial science investigations in each discipline.

Numerical study of Tallinn storm-water system flooding conditions using CFD simulations of multi-phase flow in a large-scale inverted siphon

NASA Astrophysics Data System (ADS)

Kaur, K.; Laanearu, J.; Annus, I.

2017-10-01

The numerical experiments are carried out for qualitative and quantitative interpretation of a multi-phase flow processes associated with malfunctioning of the Tallinn storm-water system during rain storms. The investigations are focused on the single-line inverted siphon, which is used as under-road connection of pipes of the storm-water system under interest. A multi-phase flow solver of Computational Fluid Dynamics software OpenFOAM is used for simulating the three-phase flow dynamics in the hydraulic system. The CFD simulations are performed with different inflow rates under same initial conditions. The computational results are compared essentially in two cases 1) design flow rate and 2) larger flow rate, for emptying the initially filled inverted siphon from a slurry-fluid. The larger flow-rate situations are under particular interest to detected possible flooding. In this regard, it is anticipated that the CFD solutions provide an important insight to functioning of inverted siphon under a restricted water-flow conditions at simultaneous presence of air and slurry-fluid.

Granular materials flow like complex fluids

NASA Astrophysics Data System (ADS)

Kou, Binquan; Cao, Yixin; Li, Jindong; Xia, Chengjie; Li, Zhifeng; Dong, Haipeng; Zhang, Ang; Zhang, Jie; Kob, Walter; Wang, Yujie

2017-11-01

Granular materials such as sand, powders and foams are ubiquitous in daily life and in industrial and geotechnical applications. These disordered systems form stable structures when unperturbed, but in the presence of external influences such as tapping or shear they `relax', becoming fluid in nature. It is often assumed that the relaxation dynamics of granular systems is similar to that of thermal glass-forming systems. However, so far it has not been possible to determine experimentally the dynamic properties of three-dimensional granular systems at the particle level. This lack of experimental data, combined with the fact that the motion of granular particles involves friction (whereas the motion of particles in thermal glass-forming systems does not), means that an accurate description of the relaxation dynamics of granular materials is lacking. Here we use X-ray tomography to determine the microscale relaxation dynamics of hard granular ellipsoids subject to an oscillatory shear. We find that the distribution of the displacements of the ellipsoids is well described by a Gumbel law (which is similar to a Gaussian distribution for small displacements but has a heavier tail for larger displacements), with a shape parameter that is independent of the amplitude of the shear strain and of the time. Despite this universality, the mean squared displacement of an individual ellipsoid follows a power law as a function of time, with an exponent that does depend on the strain amplitude and time. We argue that these results are related to microscale relaxation mechanisms that involve friction and memory effects (whereby the motion of an ellipsoid at a given point in time depends on its previous motion). Our observations demonstrate that, at the particle level, the dynamic behaviour of granular systems is qualitatively different from that of thermal glass-forming systems, and is instead more similar to that of complex fluids. We conclude that granular materials can relax even when the driving strain is weak.

Integration of Extended MHD and Kinetic Effects in Global Magnetosphere Models

NASA Astrophysics Data System (ADS)

Germaschewski, K.; Wang, L.; Maynard, K. R. M.; Raeder, J.; Bhattacharjee, A.

2015-12-01

Computational models of Earth's geospace environment are an important tool to investigate the science of the coupled solar-wind -- magnetosphere -- ionosphere system, complementing satellite and ground observations with a global perspective. They are also crucial in understanding and predicting space weather, in particular under extreme conditions. Traditionally, global models have employed the one-fluid MHD approximation, which captures large-scale dynamics quite well. However, in Earth's nearly collisionless plasma environment it breaks down on small scales, where ion and electron dynamics and kinetic effects become important, and greatly change the reconnection dynamics. A number of approaches have recently been taken to advance global modeling, e.g., including multiple ion species, adding Hall physics in a Generalized Ohm's Law, embedding local PIC simulations into a larger fluid domain and also some work on simulating the entire system with hybrid or fully kinetic models, the latter however being to computationally expensive to be run at realistic parameters. We will present an alternate approach, ie., a multi-fluid moment model that is derived rigorously from the Vlasov-Maxwell system. The advantage is that the computational cost remains managable, as we are still solving fluid equations. While the evolution equation for each moment is exact, it depends on the next higher-order moment, so that truncating the hiearchy and closing the system to capture the essential kinetic physics is crucial. We implement 5-moment (density, momentum, scalar pressure) and 10-moment (includes pressure tensor) versions of the model, and use local approximations for the heat flux to close the system. We test these closures by local simulations where we can compare directly to PIC / hybrid codes, and employ them in global simulations using the next-generation OpenGGCM to contrast them to MHD / Hall-MHD results and compare with observations.

Fluid dynamics: The subtle art of blowing bubbles

NASA Astrophysics Data System (ADS)

Witelski, Thomas P.

2009-05-01

Careful study of the moments leading up to pinch-off of air bubbles in water reveals rich and intricate dynamics controlling their evolution, and could spark re-examination of assumptions about the nature of the formation of singularities in many physical systems.

Bäcklund transformation and soliton solutions in terms of the Wronskian for the Kadomtsev-Petviashvili-based system in fluid dynamics

NASA Astrophysics Data System (ADS)

Du, Zhong; Tian, Bo; Xie, Xi-Yang; Chai, Jun; Wu, Xiao-Yu

2018-04-01

In this paper, investigation is made on a Kadomtsev-Petviashvili-based system, which can be seen in fluid dynamics, biology and plasma physics. Based on the Hirota method, bilinear form and Bäcklund transformation (BT) are derived. N-soliton solutions in terms of the Wronskian are constructed, and it can be verified that the N-soliton solutions in terms of the Wronskian satisfy the bilinear form and Bäcklund transformation. Through the N-soliton solutions in terms of the Wronskian, we graphically obtain the kink-dark-like solitons and parallel solitons, which keep their shapes and velocities unchanged during the propagation.

Coarse-grained forms for equations describing the microscopic motion of particles in a fluid.

PubMed

Das, Shankar P; Yoshimori, Akira

2013-10-01

Exact equations of motion for the microscopically defined collective density ρ(x,t) and the momentum density ĝ(x,t) of a fluid have been obtained in the past starting from the corresponding Langevin equations representing the dynamics of the fluid particles. In the present work we average these exact equations of microscopic dynamics over the local equilibrium distribution to obtain stochastic partial differential equations for the coarse-grained densities with smooth spatial and temporal dependence. In particular, we consider Dean's exact balance equation for the microscopic density of a system of interacting Brownian particles to obtain the basic equation of the dynamic density functional theory with noise. Our analysis demonstrates that on thermal averaging the dependence of the exact equations on the bare interaction potential is converted to dependence on the corresponding thermodynamic direct correlation functions in the coarse-grained equations.

Collective Surfing of Chemically Active Particles

NASA Astrophysics Data System (ADS)

Masoud, Hassan; Shelley, Michael J.

2014-03-01

We study theoretically the collective dynamics of immotile particles bound to a 2D surface atop a 3D fluid layer. These particles are chemically active and produce a chemical concentration field that creates surface-tension gradients along the surface. The resultant Marangoni stresses create flows that carry the particles, possibly concentrating them. For a 3D diffusion-dominated concentration field and Stokesian fluid we show that the surface dynamics of active particle density can be determined using nonlocal 2D surface operators. Remarkably, we also show that for both deep or shallow fluid layers this surface dynamics reduces to the 2D Keller-Segel model for the collective chemotactic aggregation of slime mold colonies. Mathematical analysis has established that the Keller-Segel model can yield finite-time, finite-mass concentration singularities. We show that such singular behavior occurs in our finite-depth system, and study the associated 3D flow structures.

Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

PubMed

Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

2014-07-04

Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. Copyright © 2014, American Association for the Advancement of Science.

Kinetic and dynamic probability-density-function descriptions of disperse turbulent two-phase flows

NASA Astrophysics Data System (ADS)

Minier, Jean-Pierre; Profeta, Christophe

2015-11-01

This article analyzes the status of two classical one-particle probability density function (PDF) descriptions of the dynamics of discrete particles dispersed in turbulent flows. The first PDF formulation considers only the process made up by particle position and velocity Zp=(xp,Up) and is represented by its PDF p (t ;yp,Vp) which is the solution of a kinetic PDF equation obtained through a flux closure based on the Furutsu-Novikov theorem. The second PDF formulation includes fluid variables into the particle state vector, for example, the fluid velocity seen by particles Zp=(xp,Up,Us) , and, consequently, handles an extended PDF p (t ;yp,Vp,Vs) which is the solution of a dynamic PDF equation. For high-Reynolds-number fluid flows, a typical formulation of the latter category relies on a Langevin model for the trajectories of the fluid seen or, conversely, on a Fokker-Planck equation for the extended PDF. In the present work, a new derivation of the kinetic PDF equation is worked out and new physical expressions of the dispersion tensors entering the kinetic PDF equation are obtained by starting from the extended PDF and integrating over the fluid seen. This demonstrates that, under the same assumption of a Gaussian colored noise and irrespective of the specific stochastic model chosen for the fluid seen, the kinetic PDF description is the marginal of a dynamic PDF one. However, a detailed analysis reveals that kinetic PDF models of particle dynamics in turbulent flows described by statistical correlations constitute incomplete stand-alone PDF descriptions and, moreover, that present kinetic-PDF equations are mathematically ill posed. This is shown to be the consequence of the non-Markovian characteristic of the stochastic process retained to describe the system and the use of an external colored noise. Furthermore, developments bring out that well-posed PDF descriptions are essentially due to a proper choice of the variables selected to describe physical systems and guidelines are formulated to emphasize the key role played by the notion of slow and fast variables.

Stabilising falling liquid film flows using feedback control

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

Thompson, Alice B., E-mail: alice.thompson1@imperial.ac.uk; Gomes, Susana N.; Pavliotis, Grigorios A.

2016-01-15

Falling liquid films become unstable due to inertial effects when the fluid layer is sufficiently thick or the slope sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and heat transfer, which benefit from smooth and wavy interfaces, respectively. Here, we discuss how the dynamics of the system are altered by feedback controls based on observations of the interface height, and supplied to the system via the perpendicular injection and suction of fluid through the wall. In this study, we model the system using both Benney and weighted-residual models that account for themore » fluid injection through the wall. We find that feedback using injection and suction is a remarkably effective control mechanism: the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the qualitative effects are independent of the details of the flow modelling. Furthermore, we show that the system can still be successfully controlled when the feedback is applied via a set of localised actuators and only a small number of system observations are available, and that this is possible using both static (where the controls are based on only the most recent set of observations) and dynamic (where the controls are based on an approximation of the system which evolves over time) control schemes. This study thus provides a solid theoretical foundation for future experimental realisations of the active feedback control of falling liquid films.« less

ISM simulations: an overview of models

NASA Astrophysics Data System (ADS)

de Avillez, M. A.; Breitschwerdt, D.; Asgekar, A.; Spitoni, E.

2015-03-01

Until recently the dynamical evolution of the interstellar medium (ISM) was simulated using collisional ionization equilibrium (CIE) conditions. However, the ISM is a dynamical system, in which the plasma is naturally driven out of equilibrium due to atomic and dynamic processes operating on different timescales. A step forward in the field comprises a multi-fluid approach taking into account the joint thermal and dynamical evolutions of the ISM gas.

A Versatile Nonlinear Method for Predictive Modeling

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Yao, Weigang

2015-01-01

As computational fluid dynamics techniques and tools become widely accepted for realworld practice today, it is intriguing to ask: what areas can it be utilized to its potential in the future. Some promising areas include design optimization and exploration of fluid dynamics phenomena (the concept of numerical wind tunnel), in which both have the common feature where some parameters are varied repeatedly and the computation can be costly. We are especially interested in the need for an accurate and efficient approach for handling these applications: (1) capturing complex nonlinear dynamics inherent in a system under consideration and (2) versatility (robustness) to encompass a range of parametric variations. In our previous paper, we proposed to use first-order Taylor expansion collected at numerous sampling points along a trajectory and assembled together via nonlinear weighting functions. The validity and performance of this approach was demonstrated for a number of problems with a vastly different input functions. In this study, we are especially interested in enhancing the method's accuracy; we extend it to include the second-orer Taylor expansion, which however requires a complicated evaluation of Hessian matrices for a system of equations, like in fluid dynamics. We propose a method to avoid these Hessian matrices, while maintaining the accuracy. Results based on the method are presented to confirm its validity.

Multiscale Modeling of Multiphase Fluid Flow

DTIC Science & Technology

2016-08-01

the disparate time and length scales involved in modeling fluid flow and heat transfer. Molecular dynamics simulations were carried out to provide a...fluid dynamics methods were used to investigate the heat transfer process in open-cell micro-foam with phase change material; enhancement of natural...Computational fluid dynamics, Heat transfer, Phase change material in Micro-foam, Molecular Dynamics, Multiphase flow, Multiscale modeling, Natural

Overview af MSFC's Applied Fluid Dynamics Analysis Group Activities

NASA Technical Reports Server (NTRS)

Garcia, Roberto; Griffin, Lisa; Williams, Robert

2004-01-01

This paper presents viewgraphs on NASA Marshall Space Flight Center's Applied Fluid Dynamics Analysis Group Activities. The topics include: 1) Status of programs at MSFC; 2) Fluid Mechanics at MSFC; 3) Relevant Fluid Dynamics Activities at MSFC; and 4) Shuttle Return to Flight.

Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

DOE PAGES

Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

2015-08-10

We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Re x < 300,000, 357 < Re δ2 < 813, and 0.02 < Gr/Re 2 < 0.232.

Three-dimensional user interfaces for scientific visualization

NASA Technical Reports Server (NTRS)

Vandam, Andries

1995-01-01

The main goal of this project is to develop novel and productive user interface techniques for creating and managing visualizations of computational fluid dynamics (CFD) datasets. We have implemented an application framework in which we can visualize computational fluid dynamics user interfaces. This UI technology allows users to interactively place visualization probes in a dataset and modify some of their parameters. We have also implemented a time-critical scheduling system which strives to maintain a constant frame-rate regardless of the number of visualization techniques. In the past year, we have published parts of this research at two conferences, the research annotation system at Visualization 1994, and the 3D user interface at UIST 1994. The real-time scheduling system has been submitted to SIGGRAPH 1995 conference. Copies of these documents are included with this report.

Optimization analysis of thermal management system for electric vehicle battery pack

NASA Astrophysics Data System (ADS)

Gong, Huiqi; Zheng, Minxin; Jin, Peng; Feng, Dong

2018-04-01

Electric vehicle battery pack can increase the temperature to affect the power battery system cycle life, charge-ability, power, energy, security and reliability. The Computational Fluid Dynamics simulation and experiment of the charging and discharging process of the battery pack were carried out for the thermal management system of the battery pack under the continuous charging of the battery. The simulation result and the experimental data were used to verify the rationality of the Computational Fluid Dynamics calculation model. In view of the large temperature difference of the battery module in high temperature environment, three optimization methods of the existing thermal management system of the battery pack were put forward: adjusting the installation position of the fan, optimizing the arrangement of the battery pack and reducing the fan opening temperature threshold. The feasibility of the optimization method is proved by simulation and experiment of the thermal management system of the optimized battery pack.

Supercomputing in Aerospace

NASA Technical Reports Server (NTRS)

Kutler, Paul; Yee, Helen

1987-01-01

Topics addressed include: numerical aerodynamic simulation; computational mechanics; supercomputers; aerospace propulsion systems; computational modeling in ballistics; turbulence modeling; computational chemistry; computational fluid dynamics; and computational astrophysics.

Stratified rotating Boussinesq equations in geophysical fluid dynamics: Dynamic bifurcation and periodic solutions

NASA Astrophysics Data System (ADS)

Hsia, Chun-Hsiung; Ma, Tian; Wang, Shouhong

2007-06-01

The main objective of this article is to study the dynamics of the stratified rotating Boussinesq equations, which are a basic model in geophysical fluid dynamics. First, for the case where the Prandtl number is greater than 1, a complete stability and bifurcation analysis near the first critical Rayleigh number is carried out. Second, for the case where the Prandtl number is smaller than 1, the onset of the Hopf bifurcation near the first critical Rayleigh number is established, leading to the existence of nontrivial periodic solutions. The analysis is based on a newly developed bifurcation and stability theory for nonlinear dynamical systems (both finite and infinite dimensional) by two of the authors [T. Ma and S. Wang, Bifurcation Theory and Applications, World Scientific Series on Nonlinear Sciences Vol. 53 (World Scientific, Singapore, 2005)].

Spherical accretion of matter by charged black holes on f(T) Gravity

NASA Astrophysics Data System (ADS)

Rodrigues, M. E.; Junior, E. L. B.

2018-03-01

We studied the spherical accretion of matter by charged black holes on f(T) Gravity. Considering the accretion model of a isentropic perfect fluid we obtain the general form of the Hamiltonian and the dynamic system for the fluid. We have analysed the movements of an isothermal fluid model with p=ω e and where p is the pressure and e the total energy density. The analysis of the cases shows the possibility of spherical accretion of fluid by black holes, revealing new phenomena as cyclical movement inside the event horizon.

The physical hydrogeology of ore deposits

USGS Publications Warehouse

Ingebritsen, Steven E.; Appold, M.S.

2012-01-01

Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux that is hydrogeologically unusual. From the hydrogeologic perspective, hydrothermal ore deposition represents a complex coupled-flow problem—sufficiently complex that physically rigorous description of the coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes (THMC modeling) continues to challenge our computational ability. Though research into these coupled behaviors has found only a limited subset to be quantitatively tractable, it has yielded valuable insights into the workings of hydrothermal systems in a wide range of geologic environments including sedimentary, metamorphic, and magmatic. Examples of these insights include the quantification of likely driving mechanisms, rates and paths of fluid flow, ore-mineral precipitation mechanisms, longevity of hydrothermal systems, mechanisms by which hydrothermal fluids acquire their temperature and composition, and the controlling influence of permeability and other rock properties on hydrothermal fluid behavior. In this communication we review some of the fundamental theory needed to characterize the physical hydrogeology of hydrothermal systems and discuss how this theory has been applied in studies of Mississippi Valley-type, tabular uranium, porphyry, epithermal, and mid-ocean ridge ore-forming systems. A key limitation in the computational state-of-the-art is the inability to describe fluid flow and transport fully in the many ore systems that show evidence of repeated shear or tensional failure with associated dynamic variations in permeability. However, we discuss global-scale compilations that suggest some numerical constraints on both mean and dynamically enhanced crustal permeability. Principles of physical hydrogeology can be powerful tools for investigating hydrothermal ore formation and are becoming increasingly accessible with ongoing advances in modeling software.

Microbial Fouling and Its Effect on Power Generation.

DTIC Science & Technology

1982-09-01

Bryers, J. D. (1980) " Dynamics of Early Biof’dm Formation in a Turbulent Flow System." Ph.D. dissertation, Rice University. Trulear, M. G. (1980...studies to date have avoided addressing fundamental questions concerning fouling in fluid flow and heat transfer systems and their effect on fluid...34clean" surface exposed to turbulent flow of a tuid con- taining dispersed microorganisms, nutrient, and organic macromolecules. Adsorption of an organic

3D MR flow analysis in realistic rapid-prototyping model systems of the thoracic aorta: comparison with in vivo data and computational fluid dynamics in identical vessel geometries.

PubMed

Canstein, C; Cachot, P; Faust, A; Stalder, A F; Bock, J; Frydrychowicz, A; Küffer, J; Hennig, J; Markl, M

2008-03-01

The knowledge of local vascular anatomy and function in the human body is of high interest for the diagnosis and treatment of cardiovascular disease. A comprehensive analysis of the hemodynamics in the thoracic aorta is presented based on the integration of flow-sensitive 4D MRI with state-of-the-art rapid prototyping technology and computational fluid dynamics (CFD). Rapid prototyping was used to transform aortic geometries as measured by contrast-enhanced MR angiography into realistic vascular models with large anatomical coverage. Integration into a flow circuit with patient-specific pulsatile in-flow conditions and application of flow-sensitive 4D MRI permitted detailed analysis of local and global 3D flow dynamics in a realistic vascular geometry. Visualization of characteristic 3D flow patterns and quantitative comparisons of the in vitro experiments with in vivo data and CFD simulations in identical vascular geometries were performed to evaluate the accuracy of vascular model systems. The results indicate the potential of such patient-specific model systems for detailed experimental simulation of realistic vascular hemodynamics. Further studies are warranted to examine the influence of refined boundary conditions of the human circulatory system such as fluid-wall interaction and their effect on normal and pathological blood flow characteristics associated with vascular geometry. (c) 2008 Wiley-Liss, Inc.

Deterministic and stochastic algorithms for resolving the flow fields in ducts and networks using energy minimization

NASA Astrophysics Data System (ADS)

Sochi, Taha

2016-09-01

Several deterministic and stochastic multi-variable global optimization algorithms (Conjugate Gradient, Nelder-Mead, Quasi-Newton and global) are investigated in conjunction with energy minimization principle to resolve the pressure and volumetric flow rate fields in single ducts and networks of interconnected ducts. The algorithms are tested with seven types of fluid: Newtonian, power law, Bingham, Herschel-Bulkley, Ellis, Ree-Eyring and Casson. The results obtained from all those algorithms for all these types of fluid agree very well with the analytically derived solutions as obtained from the traditional methods which are based on the conservation principles and fluid constitutive relations. The results confirm and generalize the findings of our previous investigations that the energy minimization principle is at the heart of the flow dynamics systems. The investigation also enriches the methods of computational fluid dynamics for solving the flow fields in tubes and networks for various types of Newtonian and non-Newtonian fluids.

Decoupled 1D/3D analysis of a hydraulic valve

NASA Astrophysics Data System (ADS)

Mehring, Carsten; Zopeya, Ashok; Latham, Matt; Ihde, Thomas; Massie, Dan

2014-10-01

Analysis approaches during product development of fluid valves and other aircraft fluid delivery components vary greatly depending on the development stage. Traditionally, empirical or simplistic one-dimensional tools are being deployed during preliminary design, whereas detailed analysis such as CFD (Computational Fluid Dynamics) tools are used to refine a selected design during the detailed design stage. In recent years, combined 1D/3D co-simulation has been deployed specifically for system level simulations requiring an increased level of analysis detail for one or more components. The present paper presents a decoupled 1D/3D analysis approach where 3D CFD analysis results are utilized to enhance the fidelity of a dynamic 1D modelin context of an aircraft fuel valve.

Gas-liquid phase coexistence in quasi-two-dimensional Stockmayer fluids: A molecular dynamics study.

PubMed

Ouyang, Wen-Ze; Xu, Sheng-Hua; Sun, Zhi-Wei

2011-01-07

The Maxwell construction together with molecular dynamics simulation is used to study the gas-liquid phase coexistence of quasi-two-dimensional Stockmayer fluids. The phase coexistence curves and corresponding critical points under different dipole strength are obtained, and the critical properties are calculated. We investigate the dependence of the critical point and critical properties on the dipole strength. When the dipole strength is increased, the abrupt disappearance of the gas-liquid phase coexistence in quasi-two-dimensional Stockmayer fluids is not found. However, if the dipole strength is large enough, it does lead to the formation of very long reversible chains which makes the relaxation of the system very slow and the observation of phase coexistence rather difficult or even impossible.

Pilot-Wave Hydrodynamics

NASA Astrophysics Data System (ADS)

Bush, John W. M.

2015-01-01

Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article reviews experimental evidence indicating that the walking droplets exhibit certain features previously thought to be exclusive to the microscopic, quantum realm. It then reviews theoretical descriptions of this hydrodynamic pilot-wave system that yield insight into the origins of its quantum-like behavior. Quantization arises from the dynamic constraint imposed on the droplet by its pilot-wave field, and multimodal statistics appear to be a feature of chaotic pilot-wave dynamics. I attempt to assess the potential and limitations of this hydrodynamic system as a quantum analog. This fluid system is compared to quantum pilot-wave theories, shown to be markedly different from Bohmian mechanics and more closely related to de Broglie's original conception of quantum dynamics, his double-solution theory, and its relatively recent extensions through researchers in stochastic electrodynamics.

Quantification and Control of Wall Effects in Porous Media Experiments

NASA Astrophysics Data System (ADS)

Roth, E. J.; Mays, D. C.; Neupauer, R.; Crimaldi, J. P.

2017-12-01

Fluid flow dynamics in porous media are dominated by media heterogeneity. This heterogeneity can create preferential pathways in which local seepage velocities dwarf system seepage velocities, further complicating an already incomplete understanding of dispersive processes. In physical models of porous media flows, apparatus walls introduce preferential flow paths (i.e., wall effects) that may overwhelm other naturally occurring preferential pathways within the apparatus, leading to deceptive results. We used planar laser-induced fluorescence (PLIF) in conjunction with refractive index matched (RIM) porous media and pore fluid to observe fluid dynamics in the porous media, with particular attention to the region near the apparatus walls in a 17 cm x 8 cm x 7 cm uniform flow cell. Hexagonal close packed spheres were used to create an isotropic, homogenous porous media field in the interior of the apparatus. Visualization of the movement of a fluorescent dye revealed the influence of the wall in creating higher permeability preferential flow paths in an otherwise homogenous media packing. These preferential flow paths extended approximately one half of one sphere diameter from the wall for homogenously packed regions, with a quickly diminishing effect on flow dynamics for homogenous media adjacent to the preferential pathway, but with major influence on flow dynamics for adjoining heterogeneous regions. Multiple approaches to mitigate wall effects were investigated, and a modified wall was created such that the fluid dynamics near the wall mimics the fluid dynamics within the homogenous porous media. This research supports the design of a two-dimensional experimental apparatus that will simulate engineered pumping schemes for use in contaminant remediation. However, this research could benefit the design of fixed bed reactors or other engineering challenges in which vessel walls contribute to unwanted preferential flow.

Superfluid helium sloshing dynamics induced oscillations and fluctuations of angular momentum, force and moment actuated on spacecraft driven by gravity gradient or jitter acceleration associated with slew motion

NASA Technical Reports Server (NTRS)

Hung, R. J.

1994-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by the gravity gradient and jitter accelerations associated with slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) for slew motion which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid-vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers have also been derived. Examples are also given for cases applicable to the AXAF-S spacecraft sloshing dynamics associated with slew motion.

The numerical dynamic for highly nonlinear partial differential equations

NASA Technical Reports Server (NTRS)

Lafon, A.; Yee, H. C.

1992-01-01

Problems associated with the numerical computation of highly nonlinear equations in computational fluid dynamics are set forth and analyzed in terms of the potential ranges of spurious behaviors. A reaction-convection equation with a nonlinear source term is employed to evaluate the effects related to spatial and temporal discretizations. The discretization of the source term is described according to several methods, and the various techniques are shown to have a significant effect on the stability of the spurious solutions. Traditional linearized stability analyses cannot provide the level of confidence required for accurate fluid dynamics computations, and the incorporation of nonlinear analysis is proposed. Nonlinear analysis based on nonlinear dynamical systems complements the conventional linear approach and is valuable in the analysis of hypersonic aerodynamics and combustion phenomena.

Data-driven sensor placement from coherent fluid structures

NASA Astrophysics Data System (ADS)

Manohar, Krithika; Kaiser, Eurika; Brunton, Bingni W.; Kutz, J. Nathan; Brunton, Steven L.

2017-11-01

Optimal sensor placement is a central challenge in the prediction, estimation and control of fluid flows. We reinterpret sensor placement as optimizing discrete samples of coherent fluid structures for full state reconstruction. This permits a drastic reduction in the number of sensors required for faithful reconstruction, since complex fluid interactions can often be described by a small number of coherent structures. Our work optimizes point sensors using the pivoted matrix QR factorization to sample coherent structures directly computed from flow data. We apply this sampling technique in conjunction with various data-driven modal identification methods, including the proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). In contrast to POD-based sensors, DMD demonstrably enables the optimization of sensors for prediction in systems exhibiting multiple scales of dynamics. Finally, reconstruction accuracy from pivot sensors is shown to be competitive with sensors obtained using traditional computationally prohibitive optimization methods.

The pressure is all in your head: A cilia-driven high-pressure pump in the head of a deep-sea animal

NASA Astrophysics Data System (ADS)

Nawroth, Janna; Katija, Kakani; Shelley, Michael; Kanso, Eva

2017-11-01

Motile cilia are microscopic, hair-like structures on the cell surface that can sense and propel the extracellular fluid environment. In many ciliated systems found in nature, such as the mammalian airways and marine sponges, the organization and collective behavior of the cilia favors the pumping of fluids at low pressures and high volumes. We recently discovered an alternate design located in the head of a deep-sea animal called Larvacean. Here, cilia morphology, kinematics and flow indicate a role in maintaining the hydrostatic skeleton of the animal by generating a high-pressure flow. We describe our empirical and computational approaches toward understanding the design principles and dynamic range of this newly discovered pumping mechanism. In ongoing work, we further explore the fluid dynamic constraints on the morphological diversity of cilia and the resulting categories of fluid transport functions.

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

PubMed Central

Cao, Bing-Yang; Sun, Jun; Chen, Min; Guo, Zeng-Yuan

2009-01-01

This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4. PMID:20087458

Detecting Rotational Superradiance in Fluid Laboratories

NASA Astrophysics Data System (ADS)

Cardoso, Vitor; Coutant, Antonin; Richartz, Mauricio; Weinfurtner, Silke

2016-12-01

Rotational superradiance was predicted theoretically decades ago, and is chiefly responsible for a number of important effects and phenomenology in black-hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behavior of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. Two types of instabilities are studied: one sets in whenever superradiant modes are confined near the rotating cylinder and the other, which does not rely on confinement, corresponds to a local excitation of the cylinder. Our findings are experimentally testable in existing fluid laboratories and, hence, offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems.

Fluid flow dynamics in MAS systems

NASA Astrophysics Data System (ADS)

Wilhelm, Dirk; Purea, Armin; Engelke, Frank

2015-08-01

The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3 mm-rotor diameter has been analyzed for spinning rates up to 67 kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3 mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7 mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.

Crossover in growth laws for phase-separating binary fluids: molecular dynamics simulations.

PubMed

Ahmad, Shaista; Das, Subir K; Puri, Sanjay

2012-03-01

Pattern and dynamics during phase separation in a symmetrical binary (A+B) Lennard-Jones fluid are studied via molecular dynamics simulations after quenching homogeneously mixed critical (50:50) systems to temperatures below the critical one. The morphology of the domains, rich in A or B particles, is observed to be bicontinuous. The early-time growth of the average domain size is found to be consistent with the Lifshitz-Slyozov law for diffusive domain coarsening. After a characteristic time, dependent on the temperature, we find a clear crossover to an extended viscous hydrodynamic regime where the domains grow linearly with time. Pattern formation in the present system is compared with that in solid binary mixtures, as a function of temperature. Important results for the finite-size and temperature effects on the small-wave-vector behavior of the scattering function are also presented.

System and method for reducing combustion dynamics in a combustor

DOEpatents

Uhm, Jong Ho; Johnson, Thomas Edward; Zuo, Baifang; York, William David

2013-08-20

A system for reducing combustion dynamics in a combustor includes an end cap having an upstream surface axially separated from a downstream surface, and tube bundles extend through the end cap. A diluent supply in fluid communication with the end cap provides diluent flow to the end cap. Diluent distributors circumferentially arranged inside at least one tube bundle extend downstream from the downstream surface and provide fluid communication for the diluent flow through the end cap. A method for reducing combustion dynamics in a combustor includes flowing fuel through tube bundles that extend axially through an end cap, flowing a diluent through diluent distributors into a combustion chamber, wherein the diluent distributors are circumferentially arranged inside at least one tube bundle and each diluent distributor extends downstream from the end cap, and forming a diluent barrier in the combustion chamber between at least one pair of adjacent tube bundles.

Image-based computational fluid dynamics in the lung: virtual reality or new clinical practice?

PubMed

Burrowes, Kelly S; De Backer, Jan; Kumar, Haribalan

2017-11-01

The development and implementation of personalized medicine is paramount to improving the efficiency and efficacy of patient care. In the respiratory system, function is largely dictated by the choreographed movement of air and blood to the gas exchange surface. The passage of air begins in the upper airways, either via the mouth or nose, and terminates at the alveolar interface, while blood flows from the heart to the alveoli and back again. Computational fluid dynamics (CFD) is a well-established tool for predicting fluid flows and pressure distributions within complex systems. Traditionally CFD has been used to aid in the effective or improved design of a system or device; however, it has become increasingly exploited in biological and medical-based applications further broadening the scope of this computational technique. In this review, we discuss the advancement in application of CFD to the respiratory system and the contributions CFD is currently making toward improving precision medicine. The key areas CFD has been applied to in the pulmonary system are in predicting fluid transport and aerosol distribution within the airways. Here we focus our discussion on fluid flows and in particular on image-based clinically focused CFD in the ventilatory system. We discuss studies spanning from the paranasal sinuses through the conducting airways down to the level of the alveolar airways. The combination of imaging and CFD is enabling improved device design in aerosol transport, improved biomarkers of lung function in clinical trials, and improved predictions and assessment of surgical interventions in the nasal sinuses. WIREs Syst Biol Med 2017, 9:e1392. doi: 10.1002/wsbm.1392 For further resources related to this article, please visit the WIREs website. © 2017 Wiley Periodicals, Inc.

Data-driven discovery of Koopman eigenfunctions using deep learning

NASA Astrophysics Data System (ADS)

Lusch, Bethany; Brunton, Steven L.; Kutz, J. Nathan

2017-11-01

Koopman operator theory transforms any autonomous non-linear dynamical system into an infinite-dimensional linear system. Since linear systems are well-understood, a mapping of non-linear dynamics to linear dynamics provides a powerful approach to understanding and controlling fluid flows. However, finding the correct change of variables remains an open challenge. We present a strategy to discover an approximate mapping using deep learning. Our neural networks find this change of variables, its inverse, and a finite-dimensional linear dynamical system defined on the new variables. Our method is completely data-driven and only requires measurements of the system, i.e. it does not require derivatives or knowledge of the governing equations. We find a minimal set of approximate Koopman eigenfunctions that are sufficient to reconstruct and advance the system to future states. We demonstrate the method on several dynamical systems.

Metagenomic Assessment of a Dynamic Microbial Population from Subseafloor Aquifer Fluids in the Cold, Oxygenated Crust

NASA Astrophysics Data System (ADS)

Tully, B. J.; Heidelberg, J. F.; Kraft, B.; Girguis, P. R.; Huber, J. A.

2016-12-01

The oceanic crust contains the largest aquifer on Earth with a volume approximately 2% of the global ocean. Ongoing research at the North Pond (NP) site, west of the Mid-Atlantic Ridge, provides an environment representative of oxygenated crustal aquifers beneath oligotrophic surface waters. Using subseafloor CORK observatories for multiple sampling depths beneath the seafloor, crustal fluids were sampled along the predicted aquifer fluid flow path over a two-year period. DNA was extracted and sequenced for metagenomic analysis from 22 crustal fluid samples, along with the overlying bottom. At broad taxonomic groupings, the aquifer system is highly dynamic over time and space, with shifts in dominant taxa and "blooms" of transient groups that appear at discreet time points and sample depths. We were able to reconstruct 194 high-quality, low-contamination bacterial and archaeal metagenomic-assembled genomes (MAGs) with estimated completeness >50% (429 MAGs >20% complete). Environmental genomes were assigned to phylogenies from the major bacterial phyla, putative novel groups, and poorly sampled phylogenetic groups, including the Marinimicrobia, Candidate Phyla Radiation, and Planctomycetes. Biogeochemically relevant processes were assigned to MAGs, including denitrification, dissimilatory sulfur and hydrogen cycling, and carbon fixation. Collectively, the oxic NP aquifer system represents a diverse, dynamic microbial habitat with the metabolic potential to impact multiple globally relevant biogeochemical cycles, including nitrogen, sulfur, and carbon.

Vein mineralizations - archives of paleo-fluid systems in the Thuringian basin (Germany)

NASA Astrophysics Data System (ADS)

Abratis, M.; Brey, M.; Fritsch, S.; Majzlan, J.; Viereck-Götte, L.

2012-04-01

We investigate vein mineralizations within and around the Thuringian basin (Germany) in order to characterize paleo-fluid systems that have been active in the basin. By investigating the composition, temperature, origin, age and evolution of paleo-fluids in the Thuringian basin as a model case, we aim for comprehensive understanding of the character of mineralized fluid systems in sedimentary basins in general and their evolution over geological time scales. Mineralizations along faults are archives for the composition of fluids which intruded the basin and circulated within it millions of years ago. These mineralizations give information on the physical and chemical characteristics of the related fluids as well as on their evolution with time during basin evolution. Mapping of mineralizations in space and time and comparison with the present-day fluid circulation system allows for recognition of the paleo-fluid dynamics and high temperature fluid influx pathways. The chemical characteristics of vein-related mineralizations are proxies for the paleo-fluid sources and their solution load. Methods implied comprise bulk rock analyses (petrography, XRD, XRF, ICP-MS), mineral analyses (EPMA, LA-ICP-MS), fluid inclusion measurements (microthermometry, Raman spectroscopy, ion chromatography) and isotope studies (O, H, C, S, Sr). Vein-related mineralizations within the Mesozoic sediments of the basin occur predominantly along WNW-ESE trending fault systems and comprise mainly carbonates and sulfates. Mineralizations within the basin-confining uplifted Variscan basement rocks and lowermost sedimentary units (Zechstein) show also (Fe-, Cu-, Zn-, As-, Sb-) sulfides, (Fe-, Mn-) oxides, fluorite and barite. The present study is part of INFLUINS, a BMBF-funded project bundle which is dedicated to comprehensive description and understanding of the fluid systems within the Thuringian basin in time and space.

Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions.

PubMed

Takahashi, Hirohide; Miyagi, Atsushi; Redondo-Morata, Lorena; Scheuring, Simon

2016-11-01

With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca 2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Current Results and Proposed Activities in Microgravity Fluid Dynamics

NASA Technical Reports Server (NTRS)

Polezhaev, V. I.

1996-01-01

The Institute for Problems in Mechanics' Laboratory work in mathematical and physical modelling of fluid mechanics develops models, methods, and software for analysis of fluid flow, instability analysis, direct numerical modelling and semi-empirical models of turbulence, as well as experimental research and verification of these models and their applications in technological fluid dynamics, microgravity fluid mechanics, geophysics, and a number of engineering problems. This paper presents an overview of the results in microgravity fluid dynamics research during the last two years. Nonlinear problems of weakly compressible and compressible fluid flows are discussed.

Fluid absorption solar energy receiver

NASA Technical Reports Server (NTRS)

Bair, Edward J.

1993-01-01

A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

Astrophysical Flows

NASA Astrophysics Data System (ADS)

Pringle, James E.; King, Andrew

2003-07-01

Almost all conventional matter in the Universe is fluid, and fluid dynamics plays a crucial role in astrophysics. This new graduate textbook provides a basic understanding of the fluid dynamical processes relevant to astrophysics. The mathematics used to describe these processes is simplified to bring out the underlying physics. The authors cover many topics, including wave propagation, shocks, spherical flows, stellar oscillations, the instabilities caused by effects such as magnetic fields, thermal driving, gravity, shear flows, and the basic concepts of compressible fluid dynamics and magnetohydrodynamics. The authors are Directors of the UK Astrophysical Fluids Facility (UKAFF) at the University of Leicester, and editors of the Cambridge Astrophysics Series. This book has been developed from a course in astrophysical fluid dynamics taught at the University of Cambridge. It is suitable for graduate students in astrophysics, physics and applied mathematics, and requires only a basic familiarity with fluid dynamics.• Provides coverage of the fundamental fluid dynamical processes an astrophysical theorist needs to know • Introduces new mathematical theory and techniques in a straightforward manner • Includes end-of-chapter problems to illustrate the course and introduce additional ideas

Fluid dynamics of the magnetic field dependent thermosolutal convection and viscosity between coaxial contracting discs

NASA Astrophysics Data System (ADS)

Khan, Aamir; Shah, Rehan Ali; Shuaib, Muhammad; Ali, Amjad

2018-06-01

The effects of magnetic field dependent (MFD) thermosolutal convection and MFD viscosity of the fluid dynamics are investigated between squeezing discs rotating with different velocities. The unsteady constitutive expressions of mass conservation, modified Navier-Stokes, Maxwell and MFD thermosolutal convection are coupled as a system of ordinary differential equations. The corresponding solutions for the transformed radial and azimuthal momentum as well as solutions for the azimuthal and axial induced magnetic field equations are determined, also the MHD pressure and torque which the fluid exerts on the upper disc is derived and discussed in details. In the case of smooth discs the self-similar equations are solved using Homotopy Analysis Method (HAM) with appropriate initial guesses and auxiliary parameters to produce an algorithm with an accelerated and assured convergence. The validity and accuracy of HAM results is proved by comparison of the HAM solutions with numerical solver package BVP4c. It has been shown that magnetic Reynolds number causes to decrease magnetic field distributions, fluid temperature, axial and tangential velocity. Also azimuthal and axial components of magnetic field have opposite behavior with increase in MFD viscosity. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems, heating up or cooling processes, biological sensor systems and biological prosthetic etc.

Numerical studies of the surface tension effect of cryogenic liquid helium

NASA Technical Reports Server (NTRS)

Hung, R. J.

1994-01-01

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose of performing scientific observation during the normal spacecraft operation is investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics has been based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers, have been derived.

Is the boundary layer of an ionic liquid equally lubricating at higher temperature?

PubMed

Hjalmarsson, Nicklas; Atkin, Rob; Rutland, Mark W

2016-04-07

Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.

A Spalart-Allmaras local correlation-based transition model for Thermo-fuid dynamics

NASA Astrophysics Data System (ADS)

D'Alessandro, V.; Garbuglia, F.; Montelpare, S.; Zoppi, A.

2017-11-01

The study of innovative energy systems often involves complex fluid flows problems and the Computational Fluid-Dynamics (CFD) is one of the main tools of analysis. It is important to put in evidence that in several energy systems the flow field experiences the laminar-to-turbulent transition. Direct Numerical Simulations (DNS) or Large Eddy Simulation (LES) are able to predict the flow transition but they are still inapplicable to the study of real problems due to the significant computational resources requirements. Differently standard Reynolds Averaged Navier Stokes (RANS) approaches are not always reliable since they assume a fully turbulent regime. In order to overcome this drawback in the recent years some locally formulated transition RANS models have been developed. In this work, we present a local correlation-based transition approach adding two equations that control the laminar-toturbulent transition process -γ and \\[\\overset{}{\\mathop{{{\\operatorname{Re}}θ, \\text{t}}}} \\] - to the well-known Spalart-Allmaras (SA) turbulence model. The new model was implemented within OpenFOAM code. The energy equation is also implemented in order to evaluate the model performance in thermal-fluid dynamics applications. In all the considered cases a very good agreement between numerical and experimental data was observed.

Running interfacial waves in a two-layer fluid system subject to longitudinal vibrations.

PubMed

Goldobin, D S; Pimenova, A V; Kovalevskaya, K V; Lyubimov, D V; Lyubimova, T P

2015-05-01

We study the waves at the interface between two thin horizontal layers of immiscible fluids subject to high-frequency horizontal vibrations. Previously, the variational principle for energy functional, which can be adopted for treatment of quasistationary states of free interface in fluid dynamical systems subject to vibrations, revealed the existence of standing periodic waves and solitons in this system. However, this approach does not provide regular means for dealing with evolutionary problems: neither stability problems nor ones associated with propagating waves. In this work, we rigorously derive the evolution equations for long waves in the system, which turn out to be identical to the plus (or good) Boussinesq equation. With these equations one can find all the time-independent-profile solitary waves (standing solitons are a specific case of these propagating waves), which exist below the linear instability threshold; the standing and slow solitons are always unstable while fast solitons are stable. Depending on initial perturbations, unstable solitons either grow in an explosive manner, which means layer rupture in a finite time, or falls apart into stable solitons. The results are derived within the long-wave approximation as the linear stability analysis for the flat-interface state [D.V. Lyubimov and A.A. Cherepanov, Fluid Dynamics 21, 849 (1986)] reveals the instabilities of thin layers to be long wavelength.

Nature of local magma storage zones and geometry of conduit systems below balsatic eruption sites - Pu'u 'O'o, Kilauea East Rift, Hawaii, example

NASA Technical Reports Server (NTRS)

Wilson, Lionel; Head, James W., III

1988-01-01

The fluid dynamics of the well-documented eruptive episodes at Pu'u 'O'o, Kilauea are used to investigate quantitatively the size and shape of the shallow conduit system beneath the vent. The possible geometry of this region is considered. The dynamics of the eruptive episodes is used to place restrictions on the size and shape of the region and thermal calculations are used to show that the geometry is consistent with the region being the fluid residue of the partially cooled, major preepisode 1 dike. The Pu'u 'O'o example is used to illustrate some general properties of shallow magma storage zones.

GAS payload no. G-025: Study of liquid sloshing behaviour in microgravity

NASA Technical Reports Server (NTRS)

Gilbert, C. R.

1986-01-01

The Get Away Special (GAS) G-025, which flew on shuttle Mission 51-G, examined the behavior of a liquid in a tank under microgravity conditions. The experiment is representative of phenomena occurring in satellite tanks with liquid propellants. A reference fluid in a hemispherical model tank will be subjected to linear acceleration inputs of known levels and frequencies, and the dynamic response of the tank liquid system was recorded. Preliminary analysis of the flight data indicates that the experiment functioned perfectly. The results will validate and refine mathematical models describing the dynamic characteristics of tank-fluid systems. This will in turn support the development of future spacecraft tanks, in particular the design of propellant management devices for surface tension tanks.

Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

NASA Astrophysics Data System (ADS)

Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

2016-04-01

Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D., & Gomez-Rivas, E. (2015). Transport efficiency and dynamics of hydraulic fracture networks. Frontiers in Physics, 3.

A computational model of amoeboid cell swimming in unbounded medium and through obstacles

NASA Astrophysics Data System (ADS)

Campbell, Eric; Bagchi, Prosenjit

2017-11-01

Pseudopod-driven motility is commonly observed in eukaryotic cells. Pseudopodia are actin-rich protrusions of the cellular membrane which extend, bifurcate, and retract in cycles resulting in amoeboid locomotion. While actin-myosin interactions are responsible for pseudopod generation, cell deformability is crucial concerning pseudopod dynamics. Because pseudopodia are highly dynamic, cells are capable of deforming into complex shapes over time. Pseudopod-driven motility represents a multiscale and complex process, coupling cell deformation, protein biochemistry, and cytoplasmic and extracellular fluid motion. In this work, we present a 3D computational model of amoeboid cell swimming in an extracellular medium (ECM). The ECM is represented as a fluid medium with or without obstacles. The model integrates full cell deformation, a coarse-grain reaction-diffusion system for protein dynamics, and fluid interaction. Our model generates pseudopodia which bifurcate and retract, showing remarkable similarity to experimental observations. Influence of cell deformation, protein diffusivity and cytoplasmic viscosity on the swimming speed is analyzed in terms of altered pseudopod dynamics. Insights into the role of matrix porosity and obstacle size on cell motility are also provided. Funded by NSF CBET 1438255.

Dynamical Heterogeneity in Granular Fluids and Structural Glasses

NASA Astrophysics Data System (ADS)

Avila, Karina E.

Our current understanding of the dynamics of supercooled liquids and other similar slowly evolving (glassy) systems is rather limited. One aspect that is particularly poorly understood is the origin and behavior of the strong non trivial fluctuations that appear in the relaxation process toward equilibrium. Glassy systems and granular systems both present regions of particles moving cooperatively and at different rates from other regions. This phenomenon is known as spatially heterogeneous dynamics. A detailed explanation of this phenomenon may lead to a better understanding of the slow relaxation process, and perhaps it could even help to explain the presence of the glass transition. This dissertation concentrates on studying dynamical heterogeneity by analyzing simulation data for models of granular materials and structural glasses. For dissipative granular fluids, the growing behavior of dynamical heterogeneities is studied for different densities and different degrees of inelasticity in the particle collisions. The correlated regions are found to grow rapidly as the system approaches dynamical arrest. Their geometry is conserved even when probing at different cutoff length in the correlation function or when the energy dissipation in the system is increased. For structural glasses, I test a theoretical framework that models dynamical heterogeneity as originated in the presence of Goldstone modes, which emerge from a broken continuous time reparametrization symmetry. This analysis is based on quantifying the size and the spatial correlations of fluctuations in the time variable and of other kinds of fluctuations. The results obtained here agree with the predictions of the hypothesis. In particular, the fluctuations associated to the time reparametrization invariance become stronger for low temperatures, long timescales, and large coarse graining lengths. Overall, this research points to dynamical heterogeneity to be described for granular systems similarly than for other glassy systems and it provides evidence in favor of a particular theory for the origin of dynamical heterogeneity.

Dynamics of pleural fluid effusion and chylothorax in the fetus and newborn: role of the lymphatic system.

PubMed

Bellini, C; Ergaz, Z; Boccardo, F; Bellini, T; Campisi, C C; Bonioli, E; Ramenghi, L A

2013-06-01

Pleural fluid effusion particularly chylothorax is a relatively rare occurrence in the newborn, but when it occurs it is often life-threatening. In this article, we describe and illustrate the morphologic features of the visceral and parietal pleura including pleural lymphatics and the physiology and pathophysiology of pleural fluid balance. The role and function of the lymphatic system in controlling the volume and composition of pleural liquid are detailed and a conceptual scheme presented. Finally, the crucial role of inadequate lymphatic drainage (either functional overload from an imbalance in Starling forces or mechanical insufficiency from lymphatic dysplasia) is emphasized.

Continuous variable transmission and regenerative braking devices in bicycles utilizing magnetorheological fluids

NASA Astrophysics Data System (ADS)

Cheung, Wai Ming; Liao, Wei-Hsin

2013-04-01

The use of magnetorheological (MR) fluids in vehicles has been gaining popular recently due to its controllable nature, which gives automotive designers more dimensions of freedom in functional designs. However, not much attention has been paid to apply it to bicycles. This paper is aimed to study the feasibility of applying MR fluids in different dynamic parts of a bicycle such as the transmission and braking systems. MR continuous variable transmission (CVT) and power generator assisted in braking systems were designed and analyzed. Both prototypes were fabricated and tested to evaluate their performances. Experimental results showed that the proposed designs are promising to be used in bicycles.

Effects of surface properties on droplet formation inside a microfluidic device

NASA Astrophysics Data System (ADS)

Steinhaus, Ben; Shen, Amy

2004-11-01

Micro-fluidic devices offer a unique method of creating and controlling droplets on small length scales. A microfluidic device is used to study the effects of surface properties on droplet formation of a 2-phase flow system. Four phase diagrams are generated to compare the dynamics of the 2 immiscible fluid system (silicone oil and water) inside microchannels with different surface properties. Results show that the channel surface plays an important role in determining the flow patterns and the droplet formation of the 2-phase fluid system.

Development of a cyber physical apparatus for investigating fluid structure interaction on leading edge vortex evolution

NASA Astrophysics Data System (ADS)

Raghu Gowda, Belagumba Venkatachalaiah

This dissertation examines how simple structural compliance impacts a specific transient vortex phenomenon that occurs on high angle of attack lifting surfaces termed dynamic stall. In many Fluid structure interaction (FSI) research efforts, a purely physical or purely computational approach is taken. In this work a low cost cyber-physical (CPFD) system is designed and developed for representing the FSI in the leading edge vortex (LEV) development problem. The leading edge compliance appears to be favorable in a specific spring constant range for a given wing. When the leading edge compliance prescribed via CPFD system is too low compared with the moment due to dynamic pressure or fluid unsteady effect, the LEV behavior is similar to that of a rigid wing system. When the leading edge compliance is too high, excessive compliance is introduced into the wing system and the leading edge vortex evolution is affected by the large change in wing angle. At moderate leading edge compliance, a balance appears to be achieved in which the leading edge vorticity shedding rate supports the long term evolution of the leading edge vortex. Further investigation is required to determine specific parameters governing these leading edge compliance ranges.

Time-dependent and outflow boundary conditions for Dissipative Particle Dynamics

PubMed Central

Lei, Huan; Fedosov, Dmitry A.; Karniadakis, George Em

2011-01-01

We propose a simple method to impose both no-slip boundary conditions at fluid-wall interfaces and at outflow boundaries in fully developed regions for Dissipative Particle Dynamics (DPD) fluid systems. The procedure to enforce the no-slip condition is based on a velocity-dependent shear force, which is a generalized force to represent the presence of the solid-wall particles and to maintain locally thermodynamic consistency. We show that this method can be implemented in both steady and time-dependent fluid systems and compare the DPD results with the continuum limit (Navier-Stokes) results. We also develop a force-adaptive method to impose the outflow boundary conditions for fully developed flow with unspecified outflow velocity profile or pressure value. We study flows over the backward-facing step and in idealized arterial bifurcations using a combination of the two new boundary methods with different flow rates. Finally, we explore the applicability of the outflow method in time-dependent flow systems. The outflow boundary method works well for systems with Womersley number of O(1), i.e., when the pressure and flowrate at the outflow are approximately in-phase. PMID:21499548

Smoothed dissipative particle dynamics with angular momentum conservation

NASA Astrophysics Data System (ADS)

Müller, Kathrin; Fedosov, Dmitry A.; Gompper, Gerhard

2015-01-01

Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier-Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor-Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.

Andreas Acrivos Dissertation Award: Onset of Dynamic Wetting Failure - The Mechanics of High-Speed Fluid Displacement

NASA Astrophysics Data System (ADS)

Vandre, Eric

2014-11-01

Dynamic wetting is crucial to processes where a liquid displaces another fluid along a solid surface, such as the deposition of a coating liquid onto a moving substrate. Dynamic wetting fails when process speed exceeds some critical value, leading to incomplete fluid displacement and transient phenomena that impact a variety of applications, such as microfluidic devices, oil-recovery systems, and splashing droplets. Liquid coating processes are particularly sensitive to wetting failure, which can induce air entrainment and other catastrophic coating defects. Despite the industrial incentives for careful control of wetting behavior, the hydrodynamic factors that influence the transition to wetting failure remain poorly understood from empirical and theoretical perspectives. This work investigates the fundamentals of wetting failure in a variety of systems that are relevant to industrial coating flows. A hydrodynamic model is developed where an advancing fluid displaces a receding fluid along a smooth, moving substrate. Numerical solutions predict the onset of wetting failure at a critical substrate speed, which coincides with a turning point in the steady-state solution path for a given set of system parameters. Flow-field analysis reveals a physical mechanism where wetting failure results when capillary forces can no longer support the pressure gradients necessary to steadily displace the receding fluid. Novel experimental systems are used to measure the substrate speeds and meniscus shapes associated with the onset of air entrainment during wetting failure. Using high-speed visualization techniques, air entrainment is identified by the elongation of triangular air films with system-dependent size. Air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Meniscus confinement in a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a variety of water/glycerol solutions. In addition, liquid pressurization (relative to ambient air) further postpones air entrainment when the meniscus is located near a sharp corner along the plate. Recorded critical speeds compare well to predictions from the model, supporting the hydrodynamic mechanism for the onset of wetting failure. Lastly, the industrial practice of curtain coating is investigated using the hydrodynamic model. Due to the complexity of this system, a new computational approach is developed combining a finite element method and lubrication theory in order to improve the efficiency of the numerical analysis. Results show that the onset of wetting failure varies strongly with the operating conditions of this system. In addition, stresses from the air flow dramatically affect the steady wetting behavior of curtain coating. Ultimately, these findings emphasize the important role of two-fluid displacement mechanics in high-speed wetting systems.

Thermal and fluid-dynamics behavior of circulating systems in the case of pressure relief

NASA Astrophysics Data System (ADS)

Moeller, L.

Aspects of safety in the case of large-scale installations with operational high-pressure conditions must be an important consideration already during the design of such installations, taking into account all conceivable disturbances. Within an analysis of such disturbances, studies related to pressure relief processes will have to occupy a central position. For such studies, it is convenient to combine experiments involving small-scale models of the actual installation with suitable computational programs. The experiments can be carried out at lower pressures and temperatures if the actual fluid is replaced by another medium, such as, for instance, a refrigerant. This approach has been used in the present investigation. The obtained experimental data are employed as a basis for a verification of the results provided by the computational model 'Frelap-UK' which has been expressly developed for the analysis of system behavior in the case of pressure relief. It is found that the computer fluid-dynamics characteristics agree with the experimental results.

Over-damped elastic `snap-through'

NASA Astrophysics Data System (ADS)

Gomez, Michael; Moulton, Derek E.; Vella, Dominic

Elastic `snap-through' occurs when a system is in an equilibrium state that either disappears or becomes unstable as a control parameter varies. The switch from one state to another is generally rapid and hence is used to generate fast motions in biology and engineering. While the conditions under which simple elastic objects undergo snap-through have been reasonably well studied, how fast snapping happens is much less well understood. Recently, it has been shown that snap-through can be subject to critical slowing down near the snapping transition, so that the dynamics may be slow even in the absence of viscous damping. Here, we study the interaction of snap-through with the flow of a viscous fluid. We begin by showing how snap-through may be used to create a channel whose hydraulic conductivity changes discontinuously in response to fluid flow. We then study the dynamics of snap-through for an elastic element embedded in a viscous fluid, which is typical of pull-in instabilities in micro-electromechanical systems (MEMS).

Dynamic fluid sloshing in a one-dimensional array of coupled vessels

NASA Astrophysics Data System (ADS)

Huang, Y. H.; Turner, M. R.

2017-12-01

This paper investigates the coupled motion between the dynamics of N vessels coupled together in a one-dimensional array by springs and the motion of the inviscid fluid sloshing within each vessel. We develop a fully nonlinear model for the system relative to a moving frame such that the fluid in each vessel is governed by the Euler equations and the motion of each vessel is modeled by a forced spring equation. By considering a linearization of the model, the characteristic equation for the natural frequencies of the system is derived and analyzed for a variety of nondimensional parameter regimes. It is found that the problem can exhibit a variety of resonance situations from the 1 :1 resonance to (N +1 ) -fold 1 :⋯:1 resonance, as well as more general r :s :⋯:t resonances for natural numbers r ,s ,t . This paper focuses in particular on determining the existence of regions of parameter space where the (N +1 ) -fold 1 :⋯:1 resonance can be found.

Evaluation of Computational Fluid Dynamics and Coupled Fluid-Solid Modeling for a Direct Transfer Preswirl System.

PubMed

Javiya, Umesh; Chew, John; Hills, Nick; Dullenkopf, Klaus; Scanlon, Timothy

2013-05-01

The prediction of the preswirl cooling air delivery and disk metal temperature are important for the cooling system performance and the rotor disk thermal stresses and life assessment. In this paper, standalone 3D steady and unsteady computation fluid dynamics (CFD), and coupled FE-CFD calculations are presented for prediction of these temperatures. CFD results are compared with previous measurements from a direct transfer preswirl test rig. The predicted cooling air temperatures agree well with the measurement, but the nozzle discharge coefficients are under predicted. Results from the coupled FE-CFD analyses are compared directly with thermocouple temperature measurements and with heat transfer coefficients on the rotor disk previously obtained from a rotor disk heat conduction solution. Considering the modeling limitations, the coupled approach predicted the solid metal temperatures well. Heat transfer coefficients on the rotor disk from CFD show some effect of the temperature variations on the heat transfer coefficients. Reasonable agreement is obtained with values deduced from the previous heat conduction solution.

Coupling of electromagnetics and structural/fluid dynamics - application to the dual coolant blanket subjected to plasma disruptions

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

Jordan, T.

Some aspects concerning the coupling of quasi-stationary electromagnetics and the dynamics of structure and fluid are investigated. The necessary equations are given in a dimensionless form. The dimensionless parameters in these equations are used to evaluate the importance of the different coupling effects. A finite element formulation of the eddy-current damping in solid structures is developed. With this formulation, an existing finite element method (FEM) structural dynamics code is extended and coupled to an FEM eddy-current code. With this program system, the influence of the eddy-current damping on the dynamic loading of the dual coolant blanket during a centered plasmamore » disruption is determined. The analysis proves that only in loosely fixed or soft structures will eddy-current damping considerably reduce the resulting stresses. Additionally, the dynamic behavior of the liquid metal in the blankets` poloidal channels is described with a simple two-dimensional magnetohydrodynamic approach. The analysis of the dimensionless parameters shows that for small-scale experiments, which are designed to model the coupled electromagnetic and structural/fluid dynamic effects in such a blanket, the same magnetic fields must be applied as in the real fusion device. This will be the easiest way to design experiments that produce transferable results. 10 refs., 7 figs.« less

Conservation form of the equations of fluid dynamics in general nonsteady coordinates

NASA Astrophysics Data System (ADS)

Zhang, H.; Camarero, R.; Kahawita, R.

1985-11-01

Many of the differential equations arising in fluid dynamics may be stated in conservation-law form. A number of investigations have been conducted with the aim to derive the conservation-law form of the Navier-Stokes equations in general nonsteady coordinate systems. The present note has the objective to illustrate a mathematical methodology with which such forms of the equations may be derived in an easier and more general fashion. For numerical applications, the scalar form of the equations is eventually provided. Attention is given to the conservation form of equations in curvilinear coordinates and numerical considerations.

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

Antonelli, Perry Edward

A low-level model-to-model interface is presented that will enable independent models to be linked into an integrated system of models. The interface is based on a standard set of functions that contain appropriate export and import schemas that enable models to be linked with no changes to the models themselves. These ideas are presented in the context of a specific multiscale material problem that couples atomistic-based molecular dynamics calculations to continuum calculations of fluid ow. These simulations will be used to examine the influence of interactions of the fluid with an adjacent solid on the fluid ow. The interface willmore » also be examined by adding it to an already existing modeling code, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) and comparing it with our own molecular dynamics code.« less

Effect of water chemistry upsets on the dynamics of corrective reagent dosing systems at thermal power stations

NASA Astrophysics Data System (ADS)

Voronov, V. N.; Yegoshina, O. V.; Bolshakova, N. A.; Yarovoi, V. O.; Latt, Aie Min

2016-12-01

Typical disturbances in the dynamics of a corrective reagent dosing system under unsteady-state conditions during the unsatisfactory operation of a chemical control system with some water chemistry upsets at thermal and nuclear power stations are considered. An experimental setup representing a physical model for the water chemistry control system is described. The two disturbances, which are most frequently encountered in water chemistry control practice, such as a breakdown or shutdown of temperature compensation during pH measurement and an increase in the heat-transfer fluid flow rate, have been modeled in the process of study. The study of the effect produced by the response characteristics of chemical control analyzers on the operation of a reagent dosing system under unsteady-state conditions is important for the operative control of a water chemistry regime state. The effect of temperature compensation during pH measurement on the dynamics of an ammonia-dosing system in the manual and automatic cycle chemistry control modes has been studied. It has been demonstrated that the reading settling time of a pH meter in the manual ammonia- dosing mode grows with a breakdown in temperature compensation and a simultaneous increase in the temperature of a heat-transfer fluid sample. To improve the efficiency of water chemistry control, some systems for the quality control of a heat-transfer fluid by a chemical parameter with the obligatory compensation of a disturbance in its flow rate have been proposed for use. Experimental results will possibly differ from industrial data due to a great length of sampling lines. For this reason, corrective reagent dosing systems must be adapted to the conditions of a certain power-generating unit in the process of their implementation.

Microfluidic enhancement of intramedullary pressure increases interstitial fluid flow and inhibits bone loss in hindlimb suspended mice.

PubMed

Kwon, Ronald Y; Meays, Diana R; Tang, W Joyce; Frangos, John A

2010-08-01

Interstitial fluid flow (IFF) has been widely hypothesized to mediate skeletal adaptation to mechanical loading. Although a large body of in vitro evidence has demonstrated that fluid flow stimulates osteogenic and antiresorptive responses in bone cells, there is much less in vivo evidence that IFF mediates loading-induced skeletal adaptation. This is due in large part to the challenges associated with decoupling IFF from matrix strain. In this study we describe a novel microfluidic system for generating dynamic intramedullary pressure (ImP) and IFF within the femurs of alert mice. By quantifying fluorescence recovery after photobleaching (FRAP) within individual lacunae, we show that microfluidic generation of dynamic ImP significantly increases IFF within the lacunocanalicular system. In addition, we demonstrate that dynamic pressure loading of the intramedullary compartment for 3 minutes per day significantly eliminates losses in trabecular and cortical bone mineral density in hindlimb suspended mice, enhances trabecular and cortical structural integrity, and increases endosteal bone formation rate. Unlike previously developed modalities for enhancing IFF in vivo, this is the first model that allows direct and dynamic modulation of ImP and skeletal IFF within mice. Given the large number of genetic tools for manipulating the mouse genome, this model is expected to serve as a powerful investigative tool in elucidating the role of IFF in skeletal adaptation to mechanical loading and molecular mechanisms mediating this process.

Parallel Multiscale Algorithms for Astrophysical Fluid Dynamics Simulations

NASA Technical Reports Server (NTRS)

Norman, Michael L.

1997-01-01

Our goal is to develop software libraries and applications for astrophysical fluid dynamics simulations in multidimensions that will enable us to resolve the large spatial and temporal variations that inevitably arise due to gravity, fronts and microphysical phenomena. The software must run efficiently on parallel computers and be general enough to allow the incorporation of a wide variety of physics. Cosmological structure formation with realistic gas physics is the primary application driver in this work. Accurate simulations of e.g. galaxy formation require a spatial dynamic range (i.e., ratio of system scale to smallest resolved feature) of 104 or more in three dimensions in arbitrary topologies. We take this as our technical requirement. We have achieved, and in fact, surpassed these goals.

The use of numerical programs in research and academic institutions

NASA Astrophysics Data System (ADS)

Scupi, A. A.

2016-08-01

This paper is conceived on the idea that numerical programs using computer models of physical processes can be used both for scientific research and academic teaching to study different phenomena. Computational Fluid Dynamics (CFD) is used today on a large scale in research and academic institutions. CFD development is not limited to computer simulations of fluid flow phenomena. Analytical solutions for most fluid dynamics problems are already available for ideal or simplified situations for different situations. CFD is based on the Navier- Stokes (N-S) equations characterizing the flow of a single phase of any liquid. For multiphase flows the integrated N-S equations are complemented with equations of the Volume of Fluid Model (VOF) and with energy equations. Different turbulent models were used in the paper, each one of them with practical engineering applications: the flow around aerodynamic surfaces used as unconventional propulsion system, multiphase flows in a settling chamber and pneumatic transport systems, heat transfer in a heat exchanger etc. Some of them numerical results were validated by experimental results. Numerical programs are also used in academic institutions where certain aspects of various phenomena are presented to students (Bachelor, Master and PhD) for a better understanding of the phenomenon itself.

Proper Orthogonal Decomposition in Optimal Control of Fluids

NASA Technical Reports Server (NTRS)

Ravindran, S. S.

1999-01-01

In this article, we present a reduced order modeling approach suitable for active control of fluid dynamical systems based on proper orthogonal decomposition (POD). The rationale behind the reduced order modeling is that numerical simulation of Navier-Stokes equations is still too costly for the purpose of optimization and control of unsteady flows. We examine the possibility of obtaining reduced order models that reduce computational complexity associated with the Navier-Stokes equations while capturing the essential dynamics by using the POD. The POD allows extraction of certain optimal set of basis functions, perhaps few, from a computational or experimental data-base through an eigenvalue analysis. The solution is then obtained as a linear combination of these optimal set of basis functions by means of Galerkin projection. This makes it attractive for optimal control and estimation of systems governed by partial differential equations. We here use it in active control of fluid flows governed by the Navier-Stokes equations. We show that the resulting reduced order model can be very efficient for the computations of optimization and control problems in unsteady flows. Finally, implementational issues and numerical experiments are presented for simulations and optimal control of fluid flow through channels.

Opportunities for Fluid Dynamics Research in the Forensic Discipline of Bloodstain Pattern Analysis

NASA Astrophysics Data System (ADS)

Attinger, Daniel; Moore, Craig; Donaldson, Adam; Jafari, Arian; Stone, Howard

2013-11-01

This review [Forensic Science International, vol. 231, pp. 375-396, 2013] highlights research opportunities for fluid dynamics (FD) studies related to the forensic discipline of bloodstain pattern analysis (BPA). The need for better integrating FD and BPA is mentioned in a 2009 report by the US National Research Council, entitled ``Strengthening Forensic Science in the United States: A Path Forward''. BPA aims for practical answers to specific questions of the kind: ``How did a bloodletting incident happen?'' FD, on the other hand, aims to quantitatively describe the transport of fluids and the related causes, with general equations. BPA typically solves the indirect problem of inspecting stains in a crime scene to infer the most probable bloodletting incident that produced these patterns. FD typically defines the initial and boundary conditions of a fluid system and from there describe how the system evolves in time and space, most often in a deterministic manner. We review four topics in BPA with strong connections to FD: the generation of drops, their flight, their impact and the formation of stains. Future research on these topics would deliver new quantitative tools and methods for BPA, and present new multiphase flow problems for FD.

An ultrasonic flowmeter for measuring dynamic liquid flow

NASA Technical Reports Server (NTRS)

Carpini, T. D.; Monteith, J. H.

1978-01-01

A novel oscillating pipe system was developed to provide dynamic calibration wherein small sinusoidal signals with amplitudes of 0.5 to 10% of the steady-state flow were added to the steady-state flow by oscillating the flowmeter relative to the fixed pipes in the flow system. Excellent agreement was obtained between the dynamic velocities derived from an accelerometer mounted on the oscillating pipe system and those sensed by the flowmeter at frequencies of 7, 19, and 30 Hz. Also described were the signal processing techniques used to retrieve the small sinusoidal signals which were obscured by the fluid turbulence.

Magnetohydrodynamic motion of a two-fluid plasma

DOE PAGES

Burby, Joshua W.

2017-07-21

Here, the two-fluid Maxwell system couples frictionless electron and ion fluids via Maxwell’s equations. When the frequencies of light waves, Langmuir waves, and single-particle cyclotron motion are scaled to be asymptotically large, the two-fluid Maxwell system becomes a fast-slow dynamical system. This fast-slow system admits a formally-exact single-fluid closure that may be computed systematically with any desired order of accuracy through the use of a functional partial differential equation. In the leading order approximation, the closure reproduces magnetohydrodynamics (MHD). Higher order truncations of the closure give an infinite hierarchy of extended MHD models that allow for arbitrary mass ratio, asmore » well as perturbative deviations from charge neutrality. The closure is interpreted geometrically as an invariant slow manifold in the infinite-dimensional two-fluid phase space, on which two-fluid motions are free of high-frequency oscillations. This perspective shows that the full closure inherits a Hamiltonian structure from two-fluid theory. By employing infinite-dimensional Lie transforms, the Poisson bracket for the all-orders closure may be obtained in closed form. Thus, conservative truncations of the single-fluid closure may be obtained by simply truncating the single-fluid Hamiltonian. Moreover, the closed-form expression for the all-orders bracket gives explicit expressions for a number of the full closure’s conservation laws. Notably, the full closure, as well as any of its Hamiltonian truncations, admits a pair of independent circulation invariants.« less

Magnetohydrodynamic motion of a two-fluid plasma

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

Burby, Joshua W.

Here, the two-fluid Maxwell system couples frictionless electron and ion fluids via Maxwell’s equations. When the frequencies of light waves, Langmuir waves, and single-particle cyclotron motion are scaled to be asymptotically large, the two-fluid Maxwell system becomes a fast-slow dynamical system. This fast-slow system admits a formally-exact single-fluid closure that may be computed systematically with any desired order of accuracy through the use of a functional partial differential equation. In the leading order approximation, the closure reproduces magnetohydrodynamics (MHD). Higher order truncations of the closure give an infinite hierarchy of extended MHD models that allow for arbitrary mass ratio, asmore » well as perturbative deviations from charge neutrality. The closure is interpreted geometrically as an invariant slow manifold in the infinite-dimensional two-fluid phase space, on which two-fluid motions are free of high-frequency oscillations. This perspective shows that the full closure inherits a Hamiltonian structure from two-fluid theory. By employing infinite-dimensional Lie transforms, the Poisson bracket for the all-orders closure may be obtained in closed form. Thus, conservative truncations of the single-fluid closure may be obtained by simply truncating the single-fluid Hamiltonian. Moreover, the closed-form expression for the all-orders bracket gives explicit expressions for a number of the full closure’s conservation laws. Notably, the full closure, as well as any of its Hamiltonian truncations, admits a pair of independent circulation invariants.« less

Fracturing And Liquid CONvection

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

2012-02-29

FALCON has been developed to enable simulation of the tightly coupled fluid-rock behavior in hydrothermal and engineered geothermal system (EGS) reservoirs, targeting the dynamics of fracture stimulation, fluid flow, rock deformation, and heat transport in a single integrated code, with the ultimate goal of providing a tool that can be used to test the viability of EGS in the United States and worldwide. Reliable reservoir performance predictions of EGS systems require accurate and robust modeling for the coupled thermal­hydrological­mechanical processes.

Conceptual design for the Space Station Freedom fluid physics/dynamics facility

NASA Technical Reports Server (NTRS)

Thompson, Robert L.; Chucksa, Ronald J.; Omalley, Terence F.; Oeftering, Richard C.

1993-01-01

A study team at NASA's Lewis Research Center has been working on a definition study and conceptual design for a fluid physics and dynamics science facility that will be located in the Space Station Freedom's baseline U.S. Laboratory module. This modular, user-friendly facility, called the Fluid Physics/Dynamics Facility, will be available for use by industry, academic, and government research communities in the late 1990's. The Facility will support research experiments dealing with the study of fluid physics and dynamics phenomena. Because of the lack of gravity-induced convection, research into the mechanisms of fluids in the absence of gravity will help to provide a better understanding of the fundamentals of fluid processes. This document has been prepared as a final version of the handout for reviewers at the Fluid Physics/Dynamics Facility Assessment Workshop held at Lewis on January 24 and 25, 1990. It covers the background, current status, and future activities of the Lewis Project Study Team effort. It is a revised and updated version of a document entitled 'Status Report on the Conceptual Design for the Space Station Fluid Physics/Dynamics Facility', dated January 1990.

Development and Characterization of a Parallelizable Perfusion Bioreactor for 3D Cell Culture.

PubMed

Egger, Dominik; Fischer, Monica; Clementi, Andreas; Ribitsch, Volker; Hansmann, Jan; Kasper, Cornelia

2017-05-25

The three dimensional (3D) cultivation of stem cells in dynamic bioreactor systems is essential in the context of regenerative medicine. Still, there is a lack of bioreactor systems that allow the cultivation of multiple independent samples under different conditions while ensuring comprehensive control over the mechanical environment. Therefore, we developed a miniaturized, parallelizable perfusion bioreactor system with two different bioreactor chambers. Pressure sensors were also implemented to determine the permeability of biomaterials which allows us to approximate the shear stress conditions. To characterize the flow velocity and shear stress profile of a porous scaffold in both bioreactor chambers, a computational fluid dynamics analysis was performed. Furthermore, the mixing behavior was characterized by acquisition of the residence time distributions. Finally, the effects of the different flow and shear stress profiles of the bioreactor chambers on osteogenic differentiation of human mesenchymal stem cells were evaluated in a proof of concept study. In conclusion, the data from computational fluid dynamics and shear stress calculations were found to be predictable for relative comparison of the bioreactor geometries, but not for final determination of the optimal flow rate. However, we suggest that the system is beneficial for parallel dynamic cultivation of multiple samples for 3D cell culture processes.

Development and Characterization of a Parallelizable Perfusion Bioreactor for 3D Cell Culture

PubMed Central

Egger, Dominik; Fischer, Monica; Clementi, Andreas; Ribitsch, Volker; Hansmann, Jan; Kasper, Cornelia

2017-01-01

The three dimensional (3D) cultivation of stem cells in dynamic bioreactor systems is essential in the context of regenerative medicine. Still, there is a lack of bioreactor systems that allow the cultivation of multiple independent samples under different conditions while ensuring comprehensive control over the mechanical environment. Therefore, we developed a miniaturized, parallelizable perfusion bioreactor system with two different bioreactor chambers. Pressure sensors were also implemented to determine the permeability of biomaterials which allows us to approximate the shear stress conditions. To characterize the flow velocity and shear stress profile of a porous scaffold in both bioreactor chambers, a computational fluid dynamics analysis was performed. Furthermore, the mixing behavior was characterized by acquisition of the residence time distributions. Finally, the effects of the different flow and shear stress profiles of the bioreactor chambers on osteogenic differentiation of human mesenchymal stem cells were evaluated in a proof of concept study. In conclusion, the data from computational fluid dynamics and shear stress calculations were found to be predictable for relative comparison of the bioreactor geometries, but not for final determination of the optimal flow rate. However, we suggest that the system is beneficial for parallel dynamic cultivation of multiple samples for 3D cell culture processes. PMID:28952530

Notes on Earth Atmospheric Entry for Mars Sample Return Missions

NASA Technical Reports Server (NTRS)

Rivell, Thomas

2006-01-01

The entry of sample return vehicles (SRVs) into the Earth's atmosphere is the subject of this document. The Earth entry environment for vehicles, or capsules, returning from the planet Mars is discussed along with the subjects of dynamics, aerodynamics, and heat transfer. The material presented is intended for engineers and scientists who do not have strong backgrounds in aerodynamics, aerothermodynamics and flight mechanics. The document is not intended to be comprehensive and some important topics are omitted. The topics considered in this document include basic principles of physics (fluid mechanics, dynamics and heat transfer), chemistry and engineering mechanics. These subjects include: a) fluid mechanics (aerodynamics, aerothermodynamics, compressible fluids, shock waves, boundary layers, and flow regimes from subsonic to hypervelocity; b) the Earth s atmosphere and gravity; c) thermal protection system design considerations; d) heat and mass transfer (convection, radiation, and ablation); e) flight mechanics (basic rigid body dynamics and stability); and f) flight- and ground-test requirements; and g) trajectory and flow simulation methods.

Use of CFD for static sampling hood design: An example for methane flux assessment on landfill surfaces.

PubMed

Lucernoni, Federico; Rizzotto, Matteo; Tapparo, Federica; Capelli, Laura; Sironi, Selena; Busini, Valentina

2016-11-01

The work focuses on the principles for the design of a specific static hood and on the definition of an optimal sampling procedure for the assessment of landfill gas (LFG) surface emissions. This is carried out by means of computational fluid dynamics (CFD) simulations to investigate the fluid dynamics conditions of the hood. The study proves that understanding the fluid dynamic conditions is fundamental in order to understand the sampling results and correctly interpret the measured concentration values by relating them to a suitable LFG emission model, and therefore to estimate emission rates. For this reason, CFD is a useful tool for the design and evaluation of sampling systems, among others, to verify the fundamental hypotheses on which the mass balance for the sampling hood is defined. The procedure here discussed, which is specific for the case of the investigated landfill, can be generalized to be applied also to different scenarios, where hood sampling is involved. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cloud fluid models of gas dynamics and star formation in galaxies

NASA Technical Reports Server (NTRS)

Struck-Marcell, Curtis; Scalo, John M.; Appleton, P. N.

1987-01-01

The large dynamic range of star formation in galaxies, and the apparently complex environmental influences involved in triggering or suppressing star formation, challenges the understanding. The key to this understanding may be the detailed study of simple physical models for the dominant nonlinear interactions in interstellar cloud systems. One such model is described, a generalized Oort model cloud fluid, and two simple applications of it are explored. The first of these is the relaxation of an isolated volume of cloud fluid following a disturbance. Though very idealized, this closed box study suggests a physical mechanism for starbursts, which is based on the approximate commensurability of massive cloud lifetimes and cloud collisional growth times. The second application is to the modeling of colliding ring galaxies. In this case, the driving processes operating on a dynamical timescale interact with the local cloud processes operating on the above timescale. The results is a variety of interesting nonequilibrium behaviors, including spatial variations of star formation that do not depend monotonically on gas density.

On the equivalence among stress tensors in a gauge-fluid system

NASA Astrophysics Data System (ADS)

Mitra, Arpan Krishna; Banerjee, Rabin; Ghosh, Subir

2017-12-01

In this paper, we bring out the subtleties involved in the study of a first-order relativistic field theory with auxiliary field variables playing an essential role. In particular, we discuss the nonisentropic Eulerian (or Hamiltonian) fluid model. Interactions are introduced by coupling the fluid to a dynamical Maxwell (U(1)) gauge field. This dynamical nature of the gauge field is crucial in showing the equivalence, on the physical subspace, of the stress tensor derived from two definitions, i.e. the canonical (Noether) one and the symmetric one. In the conventional equal-time formalism, we have shown that the generators of the space-time transformations obtained from these two definitions agree modulo the Gauss constraint. This equivalence in the physical sector has been achieved only because of the dynamical nature of the gauge fields. Subsequently, we have explicitly demonstrated the validity of the Schwinger condition. A detailed analysis of the model in lightcone formalism has also been done where several interesting features are revealed.

Smoothed dissipative particle dynamics model for mesoscopic multiphase flows in the presence of thermal fluctuations

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

Lei, Huan; Baker, Nathan A.; Wu, Lei

2016-08-05

Thermal fluctuations cause perturbations of fluid-fluid interfaces and highly nonlinear hydrodynamics in multiphase flows. In this work, we develop a novel multiphase smoothed dissipative particle dynamics model. This model accounts for both bulk hydrodynamics and interfacial fluctuations. Interfacial surface tension is modeled by imposing a pairwise force between SDPD particles. We show that the relationship between the model parameters and surface tension, previously derived under the assumption of zero thermal fluctuation, is accurate for fluid systems at low temperature but overestimates the surface tension for intermediate and large thermal fluctuations. To analyze the effect of thermal fluctuations on surface tension,more » we construct a coarse-grained Euler lattice model based on the mean field theory and derive a semi-analytical formula to directly relate the surface tension to model parameters for a wide range of temperatures and model resolutions. We demonstrate that the present method correctly models the dynamic processes, such as bubble coalescence and capillary spectra across the interface.« less

Free Vibration Response Comparison of Composite Beams with Fluid Structure Interaction

DTIC Science & Technology

2012-09-01

fluid damping to vibrating structures when in contact with a fluid medium such as water . The added mass effect changes the dynamic responses of the...200 words) The analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as an added mass effect...INTENTIONALLY LEFT BLANK v ABSTRACT The analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as

Differential invariants in nonclassical models of hydrodynamics

NASA Astrophysics Data System (ADS)

Bublik, Vasily V.

2017-10-01

In this paper, differential invariants are used to construct solutions for equations of the dynamics of a viscous heat-conducting gas and the dynamics of a viscous incompressible fluid modified by nanopowder inoculators. To describe the dynamics of a viscous heat-conducting gas, we use the complete system of Navier—Stokes equations with allowance for heat fluxes. Mathematical description of the dynamics of liquid metals under high-energy external influences (laser radiation or plasma flow) includes, in addition to the Navier—Stokes system of an incompressible viscous fluid, also heat fluxes and processes of nonequilibrium crystallization of a deformable fluid. Differentially invariant solutions are a generalization of partially invariant solutions, and their active study for various models of continuous medium mechanics is just beginning. Differentially invariant solutions can also be considered as solutions with differential constraints; therefore, when developing them, the approaches and methods developed by the science schools of academicians N. N. Yanenko and A. F. Sidorov will be actively used. In the construction of partially invariant and differentially invariant solutions, there are overdetermined systems of differential equations that require a compatibility analysis. The algorithms for reducing such systems to involution in a finite number of steps are described by Cartan, Finikov, Kuranishi, and other authors. However, the difficultly foreseeable volume of intermediate calculations complicates their practical application. Therefore, the methods of computer algebra are actively used here, which largely helps in solving this difficult problem. It is proposed to use the constructed exact solutions as tests for formulas, algorithms and their software implementations when developing and creating numerical methods and computational program complexes. This combination of effective numerical methods, capable of solving a wide class of problems, with analytical methods makes it possible to make the results of mathematical modeling more accurate and reliable.

Solving Component Structural Dynamic Failures Due to Extremely High Frequency Structural Response on the Space Shuttle Program

NASA Technical Reports Server (NTRS)

Frady, Greg; Nesman, Thomas; Zoladz, Thomas; Szabo, Roland

2010-01-01

For many years, the capabilities to determine the root-cause failure of component failures have been limited to the analytical tools and the state of the art data acquisition systems. With this limited capability, many anomalies have been resolved by adding material to the design to increase robustness without the ability to determine if the design solution was satisfactory until after a series of expensive test programs were complete. The risk of failure and multiple design, test, and redesign cycles were high. During the Space Shuttle Program, many crack investigations in high energy density turbomachines, like the SSME turbopumps and high energy flows in the main propulsion system, have led to the discovery of numerous root-cause failures and anomalies due to the coexistences of acoustic forcing functions, structural natural modes, and a high energy excitation, such as an edge tone or shedding flow, leading the technical community to understand many of the primary contributors to extremely high frequency high cycle fatique fluid-structure interaction anomalies. These contributors have been identified using advanced analysis tools and verified using component and system tests during component ground tests, systems tests, and flight. The structural dynamics and fluid dynamics communities have developed a special sensitivity to the fluid-structure interaction problems and have been able to adjust and solve these problems in a time effective manner to meet budget and schedule deadlines of operational vehicle programs, such as the Space Shuttle Program over the years.

The non-equilibrium statistical mechanics of a simple geophysical fluid dynamics model

NASA Astrophysics Data System (ADS)

Verkley, Wim; Severijns, Camiel

2014-05-01

Lorenz [1] has devised a dynamical system that has proved to be very useful as a benchmark system in geophysical fluid dynamics. The system in its simplest form consists of a periodic array of variables that can be associated with an atmospheric field on a latitude circle. The system is driven by a constant forcing, is damped by linear friction and has a simple advection term that causes the model to behave chaotically if the forcing is large enough. Our aim is to predict the statistics of Lorenz' model on the basis of a given average value of its total energy - obtained from a numerical integration - and the assumption of statistical stationarity. Our method is the principle of maximum entropy [2] which in this case reads: the information entropy of the system's probability density function shall be maximal under the constraints of normalization, a given value of the average total energy and statistical stationarity. Statistical stationarity is incorporated approximately by using `stationarity constraints', i.e., by requiring that the average first and possibly higher-order time-derivatives of the energy are zero in the maximization of entropy. The analysis [3] reveals that, if the first stationarity constraint is used, the resulting probability density function rather accurately reproduces the statistics of the individual variables. If the second stationarity constraint is used as well, the correlations between the variables are also reproduced quite adequately. The method can be generalized straightforwardly and holds the promise of a viable non-equilibrium statistical mechanics of the forced-dissipative systems of geophysical fluid dynamics. [1] E.N. Lorenz, 1996: Predictability - A problem partly solved, in Proc. Seminar on Predictability (ECMWF, Reading, Berkshire, UK), Vol. 1, pp. 1-18. [2] E.T. Jaynes, 2003: Probability Theory - The Logic of Science (Cambridge University Press, Cambridge). [3] W.T.M. Verkley and C.A. Severijns, 2014: The maximum entropy principle applied to a dynamical system proposed by Lorenz, Eur. Phys. J. B, 87:7, http://dx.doi.org/10.1140/epjb/e2013-40681-2 (open access).

Influence of fluid dynamics on anaerobic digestion of food waste for biogas production.

PubMed

Wang, Fengping; Zhang, Cunsheng; Huo, Shuhao

2017-05-01

To enhance the stability and efficiency of an anaerobic process, the influences of fluid dynamics on the performance of anaerobic digestion and sludge granulation were investigated using computational fluid dynamics (CFD). Four different propeller speeds (20, 60, 100, 140 r/min) were adopted for anaerobic digestion of food waste in a 30 L continuously stirred tank reactor (CSTR). Experimental results indicated that the methane yield increased with increasing the propeller speed within the experimental range. Results from CFD simulation and sludge granulation showed that the optimum propeller speed for anaerobic digestion was 100 r/min. Lower propeller speed (20 r/min) inhibited mass transfer and resulted in the failure of anaerobic digestion, while higher propeller speed (140 r/min) would lead to higher energy loss and system instability. Under this condition, anaerobic digestion could work effectively with higher efficiency of mass transfer which facilitated sludge granulation and biogas production. The corresponding mean liquid velocity and shear strain rate were 0.082 m/s and 10.48 s -1 , respectively. Moreover, compact granular sludge could be formed, with lower energy consumption. CFD was successfully used to study the influence of fluid dynamics on the anaerobic digestion process. The key parameters of the optimum mixing condition for anaerobic digestion of food waste in a 30 L CSTR including liquid velocity and shear strain rate were obtained using CFD, which were of paramount significance for the scale-up of the bioreactor. This study provided a new way for the optimization and scale-up of the anaerobic digestion process in CSTR based on the fluid dynamics analysis.

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

Grebogi, C.; Yorke, J.A.

This report discusses the following topics: controlling chaotic dynamical systems; embedding of experimental data; effect of noise on critical exponents of crises; transition to chaotic scattering; and distribution of floaters on a fluid surface. (LSP)

Aeronautical Engineering: A Continuing Bibliography. Supplement 384

NASA Technical Reports Server (NTRS)

1998-01-01

This bibliography lists reports, articles and other documents announced in the NASA science and technical information system. Subject coverage includes: Design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical Engineering: A Continuing Bibliography. Supplement 383

NASA Technical Reports Server (NTRS)

1998-01-01

This bibliography lists reports, articles and other documents announced in the NASA science and technical information system. Subject coverage includes: Design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Collaborative Research: Nanopore Confinement of C-H-O Mixed Volatile Fluids Relevant to Subsurface Energy Systems

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

Grady, Brian P.

2015-03-11

The scientific objective of this proposal was to obtain a fundamental atomic- to macro-scale understanding of the sorptivity, structure and dynamics of simple and complex hydrocarbon (HC) fluids at mineral surfaces or within nanoporous matrices over temperatures, pressures and compositions encountered in near-surface and shallow crustal environments. The research supported by this award was complementary to that conducted by the group of Prof. David cole at Ohio State University. The scope of the present award was to utilize molecular-level modeling to provide critically important insights into the interfacial properties of mineral-volatile systems, assist in the interpretation of experimental data andmore » predict fluid behavior beyond the limits of current experimental capability. During the past three years the effort has focused primarily on the behavior of C-H volatiles including methane (CH 4) and propane (C 3H 8), mixed-volatile systems including hydrocarbon - CO 2 with and without H 2O present. The long-range goal is to quantitatively link structure, dynamics and reactivity in complex mineral-/C-H-O systems from the atomic to the molecular to the macroscopic levels. The results are relevant to areas of growing importance such as gas shale, HC-bearing hydrothermal systems, and CO 2 storage.« less

Fluid flow dynamics in MAS systems.

PubMed

Wilhelm, Dirk; Purea, Armin; Engelke, Frank

2015-08-01

The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. Copyright © 2015 Elsevier Inc. All rights reserved.

Evolution of a fracture network in an elastic medium with internal fluid generation and expulsion

NASA Astrophysics Data System (ADS)

Kobchenko, Maya; Hafver, Andreas; Jettestuen, Espen; Renard, François; Galland, Olivier; Jamtveit, Bjørn; Meakin, Paul; Dysthe, Dag Kristian

2014-11-01

A simple and reproducible analog experiment was used to simulate fracture formation in a low-permeability elastic solid during internal fluid/gas production, with the objective of developing a better understanding of the mechanisms that control the dynamics of fracturing, fracture opening and closing, and fluid transport. In the experiment, nucleation, propagation, and coalescence of fractures within an elastic gelatin matrix, confined in a Hele-Shaw cell, occurred due to CO2 production via fermentation of sugar, and it was monitored by optical means. We first quantified how a fracture network develops, and then how intermittent fluid transport is controlled by the dynamics of opening and closing of fractures. The gas escape dynamics exhibited three characteristic behaviors: (1) Quasiperiodic release of gas with a characteristic frequency that depends on the gas production rate but not on the system size. (2) A 1 /f power spectrum for the fluctuations in the total open fracture area over an intermediate range of frequencies (f ), which we attribute to collective effects caused by interaction between fractures in the drainage network. (3) A 1 /f2 power spectrum was observed at high frequencies, which can be explained by the characteristic behavior of single fractures.

Volcano seismology

USGS Publications Warehouse

Chouet, B.

2003-01-01

A fundamental goal of volcano seismology is to understand active magmatic systems, to characterize the configuration of such systems, and to determine the extent and evolution of source regions of magmatic energy. Such understanding is critical to our assessment of eruptive behavior and its hazardous impacts. With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques, rapid progress is being made toward a synthesis of high-quality seismic data to develop a coherent model of eruption mechanics. Examples of recent advances are: (1) high-resolution tomography to image subsurface volcanic structures at scales of a few hundred meters; (2) use of small-aperture seismic antennas to map the spatio-temporal properties of long-period (LP) seismicity; (3) moment tensor inversions of very-long-period (VLP) data to derive the source geometry and mass-transport budget of magmatic fluids; (4) spectral analyses of LP events to determine the acoustic properties of magmatic and associated hydrothermal fluids; and (5) experimental modeling of the source dynamics of volcanic tremor. These promising advances provide new insights into the mechanical properties of volcanic fluids and subvolcanic mass-transport dynamics. As new seismic methods refine our understanding of seismic sources, and geochemical methods better constrain mass balance and magma behavior, we face new challenges in elucidating the physico-chemical processes that cause volcanic unrest and its seismic and gas-discharge manifestations. Much work remains to be done toward a synthesis of seismological, geochemical, and petrological observations into an integrated model of volcanic behavior. Future important goals must include: (1) interpreting the key types of magma movement, degassing and boiling events that produce characteristic seismic phenomena; (2) characterizing multiphase fluids in subvolcanic regimes and determining their physical and chemical properties; and (3) quantitatively understanding multiphase fluid flow behavior under dynamic volcanic conditions. To realize these goals, not only must we learn how to translate seismic observations into quantitative information about fluid dynamics, but we also must determine the underlying physics that governs vesiculation, fragmentation, and the collapse of bubble-rich suspensions to form separate melt and vapor. Refined understanding of such processes-essential for quantitative short-term eruption forecasts-will require multidisciplinary research involving detailed field measurements, laboratory experiments, and numerical modeling.

The NASA Microgravity Fluid Physics Program: Knowledge for Use on Earth and Future Space Missions

NASA Technical Reports Server (NTRS)

Kohl, Fred J.; Singh, Bhim S.; Alexander, J. Iwan; Shaw, Nancy J.; Hill, Myron E.; Gati, Frank G.

2002-01-01

Building on over four decades of research and technology development related to the behavior of fluids in low gravity environments, the current NASA Microgravity Fluid Physics Program continues the quest for knowledge to further understand and design better fluids systems for use on earth and in space. The purpose of the Fluid Physics Program is to support the goals of NASA's Biological and Physical Research Enterprise which seeks to exploit the space environment to conduct research and to develop commercial opportunities, while building the vital knowledge base needed to enable efficient and effective systems for protecting and sustaining humans during extended space flights. There are currently five major research areas in the Microgravity Fluid Physics Program: complex fluids, multiphase flows and phase change, interfacial phenomena, biofluid mechanics, and dynamics and instabilities. Numerous investigations into these areas are being conducted in both ground-based laboratories and facilities and in the flight experiments program. Most of the future NASA-sponsored fluid physics and transport phenomena studies will be carried out on the International Space Station in the Fluids Integrated Rack, in the Microgravity Science Glovebox, in EXPRESS racks, and in other facilities provided by international partners. This paper will present an overview of the near- and long-term visions for NASA's Microgravity Fluid Physics Research Program and brief descriptions of hardware systems planned to achieve this research.

Dynamic Forces Between Two Deformable Oil Droplets in Water

NASA Astrophysics Data System (ADS)

Dagastine, Raymond R.; Manica, Rogério; Carnie, Steven L.; Chan, D. Y. C.; Stevens, Geoffrey W.; Grieser, Franz

2006-07-01

The understanding of static interactions in colloidal suspensions is well established, whereas dynamic interactions more relevant to biological and other suspended soft-matter systems are less well understood. We present the direct force measurement and quantitative theoretical description for dynamic forces for liquid droplets in another immiscible fluid. Analysis of this system demonstrates the strong link between interfacial deformation, static surface forces, and hydrodynamic drainage, which govern dynamic droplet-droplet interactions over the length scale of nanometers and over the time scales of Brownian collisions. The results and analysis have direct bearing on the control and manipulation of suspended droplets in soft-matter systems ranging from the emulsions in shampoo to cellular interactions.

Freezing point and solid-liquid interfacial free energy of Stockmayer dipolar fluids: a molecular dynamics simulation study.

PubMed

Wang, Jun; Apte, Pankaj A; Morris, James R; Zeng, Xiao Cheng

2013-09-21

Stockmayer fluids are a prototype model system for dipolar fluids. We have computed the freezing temperatures of Stockmayer fluids at zero pressure using three different molecular-dynamics simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature two-phase coexistence method, and the constant-pressure and constant-enthalpy two-phase coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with the dimensionless dipole moment μ*=1, √2, √3 is 0.656 ± 0.001, 0.726 ± 0.002, and 0.835 ± 0.005, respectively. The freezing temperature increases with the dipolar strength. Moreover, for the first time, the solid-liquid interfacial free energies γ of the fcc (111), (110), and (100) interfaces are computed using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, i.e., γ100 > γ110 > γ111.

Coiling and Folding of Viscoelastic Jets

NASA Astrophysics Data System (ADS)

Majmudar, Trushant; Varagnat, Matthieu; McKinley, Gareth

2007-11-01

The study of fluid jets impacting on a flat surface has industrial applications in many areas, including processing of foods and consumer goods, bottle filling, and polymer melt processing. Previous studies have focused primarily on purely viscous, Newtonian fluids, which exhibit a number of different dynamical regimes including dripping, steady jetting, folding, and steady coiling. Here we add another dimension to the problem by focusing on mobile (low viscosity) viscoelastic fluids, with the study of two wormlike-micellar fluids, a cetylpyridinum-salicylic acid salt (CPyCl/NaSal) solution, and an industrially relevant shampoo base. We investigate the effects of viscosity and elasticity on the dynamics of axi-symmetric jets. The viscoelasticity of the fluids is systematically controlled by varying the concentration of salt counterions. Experimental methods include shear and extensional rheology measurements to characterize the fluids, and high-speed digital video imaging. In addition to the regimes observed in purely viscous systems, we also find a novel regime in which the elastic jet buckles and folds on itself, and alternates between coiling and folding behavior. We suggest phase diagrams and scaling laws for the coiling and folding frequencies through a systematic exploration of the experimental parameter space (height of fall, imposed flow rate, elasticity of the solution).

A dynamic pressure calibration standard

NASA Technical Reports Server (NTRS)

Schutte, P. C.; Cate, K. H.; Young, S. D.

1985-01-01

A dynamic pressure calibration standard has been developed for calibrating flush diaphragm mounted pressure transducers. Pressures up to 20 kPa (3 psi) have been accurately generated over a frequency range of 50 to 1800 hz. The uncertainty of the standard is +/-5 pct to 5kPa (.75 psi) and +/-10 pct from 5 kPa (.75 psi) to 20 kPa (3 psi). The system consists of two conically shaped, aluminum columns, one 5 cm (2 in.) high for low pressures and another 11 cm (4.3 in.) high for higher pressures, each filled with a viscous fluid. A column is mounted on the armature of a vibration exciter which imparts a sinusoidally varying acceleration to the fluid column. Two pressure transducers mounted at the base of the column sense the sinusoidally varying pressure. This pressure is determined from measurements of the density of the fluid, the height of the fluid, and the acceleration of the column. A section of the taller column is filled with steel balls to control the damping of the fluid to extend its useful frequency range.

Integrated Modeling and Experiments to Characterize Coupled Thermo-hydro-geomechanical-chemical processes in Hydraulic Fracturing

NASA Astrophysics Data System (ADS)

Viswanathan, H. S.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Kang, Q.; Makedonska, N.; Hyman, J.; Jimenez Martinez, J.; Frash, L.; Chen, L.

2015-12-01

Hydraulic fracturing phenomena involve fluid-solid interactions embedded within coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Feedbacks between processes result in complex dynamics that must be unraveled if one is to predict and, in the case of unconventional resources, facilitate fracture propagation, fluid flow, and interfacial transport processes. The proposed work is part of a broader class of complex systems involving coupled fluid flow and fractures that are critical to subsurface energy issues, such as shale oil, geothermal, carbon sequestration, and nuclear waste disposal. We use unique LANL microfluidic and triaxial core flood experiments integrated with state-of-the-art numerical simulation to reveal the fundamental dynamics of fracture-fluid interactions to characterize the key coupled processes that impact hydrocarbon production. We are also comparing CO2-based fracturing and aqueous fluids to enhance production, greatly reduce waste water, while simultaneously sequestering CO2. We will show pore, core and reservoir scale simulations/experiments that investigate the contolling mechanisms that control hydrocarbon production.

DICE/ColDICE: 6D collisionless phase space hydrodynamics using a lagrangian tesselation

NASA Astrophysics Data System (ADS)

Sousbie, Thierry

2018-01-01

DICE is a C++ template library designed to solve collisionless fluid dynamics in 6D phase space using massively parallel supercomputers via an hybrid OpenMP/MPI parallelization. ColDICE, based on DICE, implements a cosmological and physical VLASOV-POISSON solver for cold systems such as dark matter (CDM) dynamics.

X-43A Fluid and Environmental Systems: Ground and Flight Operation and Lessons Learned

NASA Technical Reports Server (NTRS)

Vachon, Michael Jacob; Grindle, Thomas J.; St.John, Clinton W.; Dowdell, David B.

2005-01-01

The X-43A Hyper-X program demonstrated the first successful flights of an airframe integrated scramjet powered hypersonic vehicle. The X-43A vehicles established successive world records for jet-powered vehicles at speeds of Mach 7 and Mach 10. The X-43A vehicle is a subscale version of proposed hypersonic reconnaissance strike aircraft. Scaled down to a length of 12 ft (3.66 m), the lifting body design with high fineness ratio resulted in very small internal space available for fluid systems and their corresponding environmental conditioning systems. Safe testing and operation of the X-43A fluid and environmental systems was critical for mission success, not only for the safety of the flight crew in the NASA B-52B carrier aircraft, but also to maintain the reliability of vehicle systems while exposed to dynamics and hostile conditions encountered during the boost trajectory. The X-43A fluid and environmental systems successfully managed explosive, pyrophoric, inert, and very high pressure gases without incident. This report presents a summary of the checkout and flight validation of the X-43A fluid systems. The testing used for mission assurance is summarized. System performance during captive carry and launch flights is presented. The lessons learned are also discussed.

Aeroelastic Modeling of a Nozzle Startup Transient

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2014-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,

OAST Space Theme Workshop. Volume 3: Working group summary. 9: Aerothermodynamics (M-3). A: Statement. B: Technology needs (form 1). C. Priority assessment (form 2). D. Additional assessments

NASA Technical Reports Server (NTRS)

1976-01-01

Twelve aerothermodynamic space technology needs were identified to reduce the design uncertainties in aerodynamic heating and forces experienced by heavy lift launch vehicles, orbit transfer vehicles, and advanced single stage to orbit vehicles for the space transportation system, and for probes, planetary surface landers, and sample return vehicles for solar system exploration vehicles. Research and technology needs identified include: (1) increasing the fluid dynamics capability by at least two orders of magnitude by developing an advanced computer processor for the solution of fluid dynamic problems with improved software; (2) predicting multi-engine base flow fields for launch vehicles; and (3) developing methods to conserve energy in aerothermodynamic ground test facilities.

Dynamical Systems Theory and Lagrangian Data Assimilation in Geophysical Fluid Dynamics FY 2013 (October 1, 2012 - September 30, 2013)

DTIC Science & Technology

2013-09-30

unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 Co-PI: Christopher K. R. T. Jones ...Co-PI: Stefan Llewellyn Smith Department of Mechanical and Aerospace Engineering University of California, San Diego 9500 Gilman Drive La...systems but looking a weakly 3D systems for long time intervals. ( Llewellyn Smith) Figure 10. We are exploring the effects of submesoscale motions

Dynamics and Emergent Structures in Active Fluids

NASA Astrophysics Data System (ADS)

Baskaran, Aparna

2014-03-01

In this talk, we consider an active fluid of colloidal sized particles, with the primary manifestation of activity being a self-replenishing velocity along one body axis of the particle. This is a minimal model for varied systems such as bacterial colonies, cytoskeletal filament motility assays vibrated granular particles and self propelled diffusophoretic colloids, depending on the nature of interaction among the particles. Using microscopic Brownian dynamics simulations, coarse-graining using the tools of non-equilibrium statistical mechanics and analysis of macroscopic hydrodynamic theories, we characterize emergent structures seen in these systems, which are determined by the symmetry of the interactions among the active units, such as propagating density waves, dense stationary bands, asters and phase separated isotropic clusters. We identify a universal mechanism, termed ``self-regulation,'' as the underlying physics that leads to these structures in diverse systems. Support from NSF through DMR-1149266 and DMR-0820492.

Numerical, analytical, experimental study of fluid dynamic forces in seals

NASA Technical Reports Server (NTRS)

Shapiro, William; Artiles, Antonio; Aggarwal, Bharat; Walowit, Jed; Athavale, Mahesh M.; Preskwas, Andrzej J.

1992-01-01

NASA/Lewis Research Center is sponsoring a program for providing computer codes for analyzing and designing turbomachinery seals for future aerospace and engine systems. The program is made up of three principal components: (1) the development of advanced three dimensional (3-D) computational fluid dynamics codes, (2) the production of simpler two dimensional (2-D) industrial codes, and (3) the development of a knowledge based system (KBS) that contains an expert system to assist in seal selection and design. The first task has been to concentrate on cylindrical geometries with straight, tapered, and stepped bores. Improvements have been made by adoption of a colocated grid formulation, incorporation of higher order, time accurate schemes for transient analysis and high order discretization schemes for spatial derivatives. This report describes the mathematical formulations and presents a variety of 2-D results, including labyrinth and brush seal flows. Extensions of 3-D are presently in progress.

Universal rescaling of flow curves for yield-stress fluids close to jamming

NASA Astrophysics Data System (ADS)

Dinkgreve, M.; Paredes, J.; Michels, M. A. J.; Bonn, D.

2015-07-01

The experimental flow curves of four different yield-stress fluids with different interparticle interactions are studied near the jamming concentration. By appropriate scaling with the distance to jamming all rheology data can be collapsed onto master curves below and above jamming that meet in the shear-thinning regime and satisfy the Herschel-Bulkley and Cross equations, respectively. In spite of differing interactions in the different systems, master curves characterized by universal scaling exponents are found for the four systems. A two-state microscopic theory of heterogeneous dynamics is presented to rationalize the observed transition from Herschel-Bulkley to Cross behavior and to connect the rheological exponents to microscopic exponents for the divergence of the length and time scales of the heterogeneous dynamics. The experimental data and the microscopic theory are compared with much of the available literature data for yield-stress systems.

Long-term exposure to zero-g and the gastro-intestinal tract function

NASA Technical Reports Server (NTRS)

Mccormack, Percial D.

1989-01-01

The gastrointestinal tract (GIT) function is described with emphasis placed on its important role to smooth, delay, and modify sudden fluid load stress applied to the fluid distribution control system in the body. Two basic components of the GIT are considered: stomach dynamics, which involves storage, mixing, and discharge of food into the intestine after addition of gastric juices; and absorption of water and electrolytes from the small intestine. A dynamic model of these components is described, along with performance characteristics computed consecutively for one g and zero g conditions. The main impact of the zero g condition appears to be through a change in osmotic driven transport across the gut wall. A dramatic change in transport characteristics is predicted with implication for many body systems (the immune system in particular) during long-term exposure to zero g. Experimental measurements in zero g are needed to evaluate these predictions.

Mixing Silicate Melts with High Viscosity Contrast by Chaotic Dynamics: Results from a New Experimental Device

NASA Astrophysics Data System (ADS)

de Campos, Cristina; Perugini, Diego; Ertel-Ingrisch, Werner; Dingwell, Donald B.; Poli, Giampiero

2010-05-01

A new experimental device has been developed to perform chaotic mixing between high viscosity melts under controlled fluid-dynamic conditions. The apparatus is based on the Journal Bearing System (JBS). It consists of an outer cylinder hosting the melts of interest and an inner cylinder, which is eccentrically located. Both cylinders can be independently moved to generate chaotic streamlines in the mixing system. Two experiments were performed using as end-members different proportions of a peralkaline haplogranite and a mafic melt, corresponding to the 1 atm eutectic composition in the An-Di binary system. The two melts were stirred together in the JBS for ca. two hours, at 1,400° C and under laminar fluid dynamic condition (Re of the order of 10-7). The viscosity ratio between the two melts, at the beginning of the experiment, was of the order of 103. Optical analyses of experimental samples revealed, at short length scale (of the order of μm), a complex pattern of mixed structures. These consisted of an intimate distribution of filaments; a complex inter-fingering of the two melts. Such features are typically observed in rocks thought to be produced by magma mixing processes. Stretching and folding dynamics between the melts induced chaotic flow fields and generated wide compositional interfaces. In this way, chemical diffusion processes become more efficient, producing melts with highly heterogeneous compositions. A remarkable modulation of compositional fields has been obtained by performing short time-scale experiments and using melts with a high viscosity ratio. This indicates that chaotic mixing of magmas can be a very efficient process in modulating compositional variability in igneous systems, especially under high viscosity ratios and laminar fluid-dynamic regimes. Our experimental device may replicate magma mixing features, observed in natural rocks, and therefore open new frontiers in the study of this important petrologic and volcanological process.

Why have hydrostatic bearings been avoided as a stabilizing element for rotating machines

NASA Technical Reports Server (NTRS)

Bently, D. E.; Muszynska, A.

1985-01-01

The advantages are discussed of hydrostatic, high pressure bearings as providers of higher margin of stability to the rotor/bearing systems. It is apparent that deliberate use of hydrostatic bearing high pressure lubricated (any gas or liquid) can easily be used to build higher stability margin into rotating machinery, in spite of the thirty years bias against high pressure lubrication. Since this supply pressure is controllable (the Direct Dynamic Stiffness at lower eccentricity is also controllable) so that within some rotor system limits, the stability margin and dynamic response of the rotor system is more readily controllable. It may be possible to take advantage of this effect in the various seals, as well as the bearings, to assist with stability margin and dynamic response of rotating machinery. The stability of the bearing can be additionally improved by taking advantage of the anti-swirling concept. The high pressure fluid supply inlets should be located tangentially at the bearing circumference and directed against rotation. The incoming fluid flow creates stability by reducing the swirling rate.

A nonlinear dynamical system approach for the yielding behaviour of a viscoplastic material.

PubMed

Burghelea, Teodor; Moyers-Gonzalez, Miguel; Sainudiin, Raazesh

2017-03-08

A nonlinear dynamical system model that approximates a microscopic Gibbs field model for the yielding of a viscoplastic material subjected to varying external stresses recently reported in R. Sainudiin, M. Moyers-Gonzalez and T. Burghelea, Soft Matter, 2015, 11(27), 5531-5545 is presented. The predictions of the model are in fair agreement with microscopic simulations and are in very good agreement with the micro-structural semi-empirical model reported in A. M. V. Putz and T. I. Burghelea, Rheol. Acta, 2009, 48, 673-689. With only two internal parameters, the nonlinear dynamical system model captures several key features of the solid-fluid transition observed in experiments: the effect of the interactions between microscopic constituents on the yield point, the abruptness of solid-fluid transition and the emergence of a hysteresis of the micro-structural states upon increasing/decreasing external forces. The scaling behaviour of the magnitude of the hysteresis with the degree of the steadiness of the flow is consistent with previous experimental observations. Finally, the practical usefulness of the approach is demonstrated by fitting a rheological data set measured with an elasto-viscoplastic material.

Neural network computer simulation of medical aerosols.

PubMed

Richardson, C J; Barlow, D J

1996-06-01

Preliminary investigations have been conducted to assess the potential for using artificial neural networks to simulate aerosol behaviour, with a view to employing this type of methodology in the evaluation and design of pulmonary drug-delivery systems. Details are presented of the general purpose software developed for these tasks; it implements a feed-forward back-propagation algorithm with weight decay and connection pruning, the user having complete run-time control of the network architecture and mode of training. A series of exploratory investigations is then reported in which different network structures and training strategies are assessed in terms of their ability to simulate known patterns of fluid flow in simple model systems. The first of these involves simulations of cellular automata-generated data for fluid flow through a partially obstructed two-dimensional pipe. The artificial neural networks are shown to be highly successful in simulating the behaviour of this simple linear system, but with important provisos relating to the information content of the training data and the criteria used to judge when the network is properly trained. A second set of investigations is then reported in which similar networks are used to simulate patterns of fluid flow through aerosol generation devices, using training data furnished through rigorous computational fluid dynamics modelling. These more complex three-dimensional systems are modelled with equal success. It is concluded that carefully tailored, well trained networks could provide valuable tools not just for predicting but also for analysing the spatial dynamics of pharmaceutical aerosols.

Coulomb interactions in charged fluids.

PubMed

Vernizzi, Graziano; Guerrero-García, Guillermo Iván; de la Cruz, Monica Olvera

2011-07-01

The use of Ewald summation schemes for calculating long-range Coulomb interactions, originally applied to ionic crystalline solids, is a very common practice in molecular simulations of charged fluids at present. Such a choice imposes an artificial periodicity which is generally absent in the liquid state. In this paper we propose a simple analytical O(N(2)) method which is based on Gauss's law for computing exactly the Coulomb interaction between charged particles in a simulation box, when it is averaged over all possible orientations of a surrounding infinite lattice. This method mitigates the periodicity typical of crystalline systems and it is suitable for numerical studies of ionic liquids, charged molecular fluids, and colloidal systems with Monte Carlo and molecular dynamics simulations.

Imaging and modeling of flow in porous media using clinical nuclear emission tomography systems and computational fluid dynamics

NASA Astrophysics Data System (ADS)

Boutchko, Rostyslav; Rayz, Vitaliy L.; Vandehey, Nicholas T.; O'Neil, James P.; Budinger, Thomas F.; Nico, Peter S.; Druhan, Jennifer L.; Saloner, David A.; Gullberg, Grant T.; Moses, William W.

2012-01-01

This paper presents experimental and modeling aspects of applying nuclear emission tomography to study fluid flow in laboratory packed porous media columns of the type frequently used in geophysics, geochemistry and hydrology research. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are used as non-invasive tools to obtain dynamic 3D images of radioactive tracer concentrations. Dynamic sequences obtained using 18F-FDG PET are used to trace flow through a 5 cm diameter × 20 cm tall sand packed column with and without an impermeable obstacle. In addition, a custom-made rotating column setup placed in a clinical two-headed SPECT camera is used to image 99mTc-DTPA tracer propagation in a through-flowing column (10 cm diameter × 30 cm tall) packed with recovered aquifer sediments. A computational fluid dynamics software package FLUENT is used to model the observed flow dynamics. Tracer distributions obtained in the simulations in the smaller column uniformly packed with sand and in the column with an obstacle are remarkably similar to the reconstructed images in the PET experiments. SPECT results demonstrate strongly non-uniform flow patterns for the larger column slurry-packed with sub-surface sediment and slow upward flow. In the numerical simulation of the SPECT study, two symmetric channels with increased permeability are prescribed along the column walls, which result in the emergence of two well-defined preferential flow paths. Methods and results of this work provide new opportunities in hydrologic and biogeochemical research. The primary target application for developed technologies is non-destructive, non-perturbing, quantitative imaging of flow dynamics within laboratory scale porous media systems.

Imaging and modeling of flow in porous media using clinical nuclear emission tomography systems and computational fluid dynamics.

PubMed

Boutchko, Rostyslav; Rayz, Vitaliy L; Vandehey, Nicholas T; O'Neil, James P; Budinger, Thomas F; Nico, Peter S; Druhan, Jennifer L; Saloner, David A; Gullberg, Grant T; Moses, William W

2012-01-01

This paper presents experimental and modeling aspects of applying nuclear emission tomography to study fluid flow in laboratory packed porous media columns of the type frequently used in geophysics, geochemistry and hydrology research. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are used as non-invasive tools to obtain dynamic 3D images of radioactive tracer concentrations. Dynamic sequences obtained using 18 F-FDG PET are used to trace flow through a 5 cm diameter × 20 cm tall sand packed column with and without an impermeable obstacle. In addition, a custom-made rotating column setup placed in a clinical two-headed SPECT camera is used to image 99m Tc-DTPA tracer propagation in a through-flowing column (10 cm diameter × 30 cm tall) packed with recovered aquifer sediments. A computational fluid dynamics software package FLUENT is used to model the observed flow dynamics. Tracer distributions obtained in the simulations in the smaller column uniformly packed with sand and in the column with an obstacle are remarkably similar to the reconstructed images in the PET experiments. SPECT results demonstrate strongly non-uniform flow patterns for the larger column slurry-packed with sub-surface sediment and slow upward flow. In the numerical simulation of the SPECT study, two symmetric channels with increased permeability are prescribed along the column walls, which result in the emergence of two well-defined preferential flow paths. Methods and results of this work provide new opportunities in hydrologic and biogeochemical research. The primary target application for developed technologies is non-destructive, non-perturbing, quantitative imaging of flow dynamics within laboratory scale porous media systems.

Aeronautical engineering. A continuing bibliography with indexes

NASA Technical Reports Server (NTRS)

1982-01-01

This bibliography lists 326 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1982. Topics on aeronautical engineering and aerodynamics such as flight control systems, avionics, computer programs, computational fluid dynamics and composite structures are covered.

Laboratory investigation of a fluid-dynamic actuator designed for CubeSats

NASA Astrophysics Data System (ADS)

Noack, Daniel; Brieß, Klaus

2014-03-01

In general, the attitude control systems (ACS) for precise spacecraft operations rely on reaction wheel technology for angular momentum exchange. In this paper, an alternative ACS concept using fluid rings for this task is presented. This novel actuator—based on Lorentz body force—uses a direct-current conduction pump to accelerate liquid metal within a circular channel structure. As working fluid for the fluid-dynamic actuator (FDA) serves the eutectic alloy Galinstan. Along with a microcontroller that runs the FDA, a MEMS gyroscope is implemented on the device for closed loop operation. Several models of FDAs for small satellites were tested successfully for various attitude control maneuvers on an air bearing platform. Thus advantageous performance has been achieved in terms of torque and power consumption in comparison to similarly dimensioned reaction wheels. Further considerable advantages are wear-free operations and higher reliability as well as expected passive damping properties. A next generation FDA prototype for nano-satellites is currently in development for in-orbit testing.

Distinct aggregation patterns and fluid porous phase in a 2D model for colloids with competitive interactions

NASA Astrophysics Data System (ADS)

Bordin, José Rafael

2018-04-01

In this paper we explore the self-assembly patterns in a two dimensional colloidal system using extensive Langevin Dynamics simulations. The pair potential proposed to model the competitive interaction have a short range length scale between first neighbors and a second characteristic length scale between third neighbors. We investigate how the temperature and colloidal density will affect the assembled morphologies. The potential shows aggregate patterns similar to observed in previous works, as clusters, stripes and porous phase. Nevertheless, we observe at high densities and temperatures a porous mesophase with a high mobility, which we name fluid porous phase, while at lower temperatures the porous structure is rigid. triangular packing was observed for the colloids and pores in both solid and fluid porous phases. Our results show that the porous structure is well defined for a large range of temperature and density, and that the fluid porous phase is a consequence of the competitive interaction and the random forces from the Langevin Dynamics.

Compressibility of the fluid

NASA Astrophysics Data System (ADS)

Jablonská, Jana

2014-03-01

The presence of air in the liquid causes the dynamic system behaviour. When solve to issue of the dynamics we often meet problems of cavitation. Cavitation is an undesirable phenomenon, since it causes a disruption of the surrounding material and material destruction. Cavitation is accompanied by loud sound effects and reduces the efficiency of such pumps, etc. Therefore, it is desirable to model systems in which the cavitation might occur. A typical example is a solution of water hammer.

Solar dynamic heat receiver thermal characteristics in low earth orbit

NASA Technical Reports Server (NTRS)

Wu, Y. C.; Roschke, E. J.; Birur, G. C.

1988-01-01

A simplified system model is under development for evaluating the thermal characteristics and thermal performance of a solar dynamic spacecraft energy system's heat receiver. Results based on baseline orbit, power system configuration, and operational conditions, are generated for three basic receiver concepts and three concentrator surface slope errors. Receiver thermal characteristics and thermal behavior in LEO conditions are presented. The configuration in which heat is directly transferred to the working fluid is noted to generate the best system and thermal characteristics. as well as the lowest performance degradation with increasing slope error.

Heat Transfer and Fluid Mechanics Institute, Meeting, 25th, University of California, Davis, Calif., June 21-23, 1976, Proceedings

NASA Technical Reports Server (NTRS)

Mckillop, A. A.; Baughn, J. W.; Dwyer, H. A.

1976-01-01

Major research advances in heat transfer and fluid dynamics are outlined, with particular reference to relevant energy problems. Of significant importance are such topics as synthetic fuels in combustion, turbulence models, combustion modeling, numerical methods for interacting boundary layers, and light-scattering diagnostics for gases. The discussion covers thermal convection, two-phase flow and boiling heat transfer, turbulent flows, combustion, and aerospace heat transfer problems. Other areas discussed include compressible flows, fluid mechanics and drag, and heat exchangers. Featured topics comprise heat and salt transfer in double-diffusive systems, limits of boiling heat transfer in a liquid-filled enclosure, investigation of buoyancy-induced flow stratification in a cylindrical plenum, and digital algorithms for dynamic analysis of a heat exchanger. Individual items are announced in this issue.

Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, part 1

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1992-01-01

Experimental and computational fluid dynamic activities in rocket propulsion were discussed. The workshop was an open meeting of government, industry, and academia. A broad number of topics were discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, part 2

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1992-01-01

Presented here are 59 abstracts and presentations and three invited presentations given at the Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at the George C. Marshall Space Flight Center, April 28-30, 1992. The purpose of the workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed, including a computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1993-01-01

Conference publication includes 79 abstracts and presentations and 3 invited presentations given at the Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at George C. Marshall Space Flight Center, April 20-22, 1993. The purpose of the workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 1

NASA Technical Reports Server (NTRS)

Williams, Robert W. (Compiler)

1993-01-01

Conference publication includes 79 abstracts and presentations given at the Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion held at the George C. Marshall Space Flight Center, April 20-22, 1993. The purpose of this workshop is to discuss experimental and computational fluid dynamic activities in rocket propulsion. The workshop is an open meeting for government, industry, and academia. A broad number of topics are discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

A numerical study of the effects of bell pulsation dynamics and oral arms on the exchange currents generated by the upside-down jellyfish Cassiopea xamachana.

PubMed

Hamlet, Christina; Santhanakrishnan, Arvind; Miller, Laura A

2011-06-01

Mathematical and experimental studies of the flows generated by jellyfish have focused primarily on mechanisms of swimming. More recent work has also considered the fluid dynamics of feeding from currents generated during swimming. Here we capitalize on the benthic lifestyle of the upside-down jellyfish (Cassiopea xamachana) to explore the fluid dynamics of feeding uncoupled from swimming. A two-dimensional mathematical model is developed to capture the fundamental characteristics of the motion of the unique concave bell shape. Given the prominence of the oral arms, this structure is included and modeled as a porous layer that perturbs the flow generated by bell contractions. The immersed boundary method is used to solve the fluid-structure interaction problem. Velocity fields obtained from live organisms using digital particle image velocimetry were used to validate the numerical simulations. Parameter sweeps were used to numerically explore the effects of changes in pulse dynamics and the properties of the oral arms independently. Numerical experiments allow the opportunity to examine physical effects and limits within and beyond the biologically relevant range to develop a better understanding of the system. The presence of the prominent oral arm structures in the field of flow increased the flux of new fluid from along the substrate to the bell. The numerical simulations also showed that the presence of pauses between bell expansion and the next contraction alters the flow of the fluid over the bell and through the oral arms.

NAS: The first year

NASA Technical Reports Server (NTRS)

Bailey, F. R.; Kutler, Paul

1988-01-01

Discussed are the capabilities of NASA's Numerical Aerodynamic Simulation (NAS) Program and its application as an advanced supercomputing system for computational fluid dynamics (CFD) research. First, the paper describes the NAS computational system, called the NAS Processing System Network, and the advanced computational capabilities it offers as a consequence of carrying out the NAS pathfinder objective. Second, it presents examples of pioneering CFD research accomplished during NAS's first operational year. Examples are included which illustrate CFD applications for predicting fluid phenomena, complementing and supplementing experimentation, and aiding in design. Finally, pacing elements and future directions for CFD and NAS are discussed.

Self-consistent chaos in a mean-field Hamiltonian model of fluids and plasmas

NASA Astrophysics Data System (ADS)

del-Castillo-Negrete, D.; Firpo, Marie-Christine

2002-11-01

We present a mean-field Hamiltonian model that describes the collective dynamics of marginally stable fluids and plasmas. In plasmas, the model describes the self-consistent evolution of electron holes and clumps in phase space. In fluids, the model describes the dynamics of vortices with negative and positive circulation in shear flows. The mean-field nature of the system makes it a tractable model to study the dynamics of large degrees-of-freedom, coupled Hamiltonian systems. Here we focus in the role of self-consistent chaos in the formation and destruction of phase space coherent structures. Numerical simulations in the finite N and in the Narrow kinetic limit (where N is the number of particles) show the existence of coherent, rotating dipole states. We approximate the dipole as two macroparticles, and show that the N = 2 limit has a family of rotating integrable solutions described by a one degree-of-freedom nontwist Hamiltonian. The coherence of the dipole is explained in terms of a parametric resonance between the rotation frequency of the macroparticles and the oscillation frequency of the self-consistent mean field. For a class of initial conditions, the mean field exhibits a self-consistent, elliptic-hyperbolic bifurcation that leads to the destruction of the dipole and violent mixing of the phase space.

Airborne Shaped Sonic Boom Demonstration Pressure Measurements with Computational Fluid Dynamics Comparisons

NASA Technical Reports Server (NTRS)

Haering, Edward A., Jr.; Murray, James E.; Purifoy, Dana D.; Graham, David H.; Meredith, Keith B.; Ashburn, Christopher E.; Stucky, Mark

2005-01-01

The Shaped Sonic Boom Demonstration project showed for the first time that by careful design of aircraft contour the resultant sonic boom can maintain a tailored shape, propagating through a real atmosphere down to ground level. In order to assess the propagation characteristics of the shaped sonic boom and to validate computational fluid dynamics codes, airborne measurements were taken of the pressure signatures in the near field by probing with an instrumented F-15B aircraft, and in the far field by overflying an instrumented L-23 sailplane. This paper describes each aircraft and their instrumentation systems, the airdata calibration, analysis of the near- and far-field airborne data, and shows the good to excellent agreement between computational fluid dynamics solutions and flight data. The flights of the Shaped Sonic Boom Demonstration aircraft occurred in two phases. Instrumentation problems were encountered during the first phase, and corrections and improvements were made to the instrumentation system for the second phase, which are documented in the paper. Piloting technique and observations are also given. These airborne measurements of the Shaped Sonic Boom Demonstration aircraft are a unique and important database that will be used to validate design tools for a new generation of quiet supersonic aircraft.

Shock Location Dominated Transonic Flight Loads on the Active Aeroelastic Wing

NASA Technical Reports Server (NTRS)

Lokos, William A.; Lizotte, Andrew; Lindsley, Ned J.; Stauf, Rick

2005-01-01

During several Active Aeroelastic Wing research flights, the shadow of the over-wing shock could be observed because of natural lighting conditions. As the plane accelerated, the shock location moved aft, and as the shadow passed the aileron and trailing-edge flap hinge lines, their associated hinge moments were substantially affected. The observation of the dominant effect of shock location on aft control surface hinge moments led to this investigation. This report investigates the effect of over-wing shock location on wing loads through flight-measured data and analytical predictions. Wing-root and wing-fold bending moment and torque and leading- and trailing-edge hinge moments have been measured in flight using calibrated strain gages. These same loads have been predicted using a computational fluid dynamics code called the Euler Navier-Stokes Three Dimensional Aeroelastic Code. The computational fluid dynamics study was based on the elastically deformed shape estimated by a twist model, which in turn was derived from in-flight-measured wing deflections provided by a flight deflection measurement system. During level transonic flight, the shock location dominated the wing trailing-edge control surface hinge moments. The computational fluid dynamics analysis based on the shape provided by the flight deflection measurement system produced very similar results and substantially correlated with the measured loads data.

Rebound and jet formation of a fluid-filled sphere

NASA Astrophysics Data System (ADS)

Killian, Taylor W.; Klaus, Robert A.; Truscott, Tadd T.

2012-12-01

This study investigates the impact dynamics of hollow elastic spheres partially filled with fluid. Unlike an empty sphere, the internal fluid mitigates some of the rebound through an impulse driven exchange of energy wherein the fluid forms a jet inside the sphere. Surprisingly, this occurs on the second rebound or when the free surface is initially perturbed. Images gathered through experimentation show that the fluid reacts more quickly to the impact than the sphere, which decouples the two masses (fluid and sphere), imparts energy to the fluid, and removes rebound energy from the sphere. The experimental results are analyzed in terms of acceleration, momentum and an energy method suggesting an optimal fill volume in the neighborhood of 30%. While the characteristics of the fluid (i.e., density, viscosity, etc.) affect the fluid motion (i.e., type and size of jet formation), the rebound characteristics remain similar for a given fluid volume independent of fluid type. Implications of this work are a potential use of similar passive damping systems in sports technology and marine engineering.

Pore-Scale Investigation on Stress-Dependent Characteristics of Granular Packs and Their Impact on Multiphase Fluid Distribution

NASA Astrophysics Data System (ADS)

Torrealba, V.; Karpyn, Z.; Yoon, H.; Hart, D. B.; Klise, K. A.

2013-12-01

The pore-scale dynamics that govern multiphase flow under variable stress conditions are not well understood. This lack of fundamental understanding limits our ability to quantitatively predict multiphase flow and fluid distributions in natural geologic systems. In this research, we focus on pore-scale, single and multiphase flow properties that impact displacement mechanisms and residual trapping of non-wetting phase under varying stress conditions. X-ray micro-tomography is used to image pore structures and distribution of wetting and non-wetting fluids in water-wet synthetic granular packs, under dynamic load. Micro-tomography images are also used to determine structural features such as medial axis, surface area, and pore body and throat distribution; while the corresponding transport properties are determined from Lattice-Boltzmann simulations performed on lattice replicas of the imaged specimens. Results are used to investigate how inter-granular deformation mechanisms affect fluid displacement and residual trapping at the pore-scale. This will improve our understanding of the dynamic interaction of mechanical deformation and fluid flow during enhanced oil recovery and geologic CO2 sequestration. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Computer code for gas-liquid two-phase vortex motions: GLVM

NASA Technical Reports Server (NTRS)

Yeh, T. T.

1986-01-01

A computer program aimed at the phase separation between gas and liquid at zero gravity, induced by vortex motion, is developed. It utilizes an explicit solution method for a set of equations describing rotating gas-liquid flows. The vortex motion is established by a tangential fluid injection. A Lax-Wendroff two-step (McCormack's) numerical scheme is used. The program can be used to study the fluid dynamical behavior of the rotational two-phase fluids in a cylindrical tank. It provides a quick/easy sensitivity test on various parameters and thus provides the guidance for the design and use of actual physical systems for handling two-phase fluids.

Absorption and folding of melittin onto lipid bilayer membranes via unbiased atomic detail microsecond molecular dynamics simulation.

PubMed

Chen, Charles H; Wiedman, Gregory; Khan, Ayesha; Ulmschneider, Martin B

2014-09-01

Unbiased molecular simulation is a powerful tool to study the atomic details driving functional structural changes or folding pathways of highly fluid systems, which present great challenges experimentally. Here we apply unbiased long-timescale molecular dynamics simulation to study the ab initio folding and partitioning of melittin, a template amphiphilic membrane active peptide. The simulations reveal that the peptide binds strongly to the lipid bilayer in an unstructured configuration. Interfacial folding results in a localized bilayer deformation. Akin to purely hydrophobic transmembrane segments the surface bound native helical conformer is highly resistant against thermal denaturation. Circular dichroism spectroscopy experiments confirm the strong binding and thermostability of the peptide. The study highlights the utility of molecular dynamics simulations for studying transient mechanisms in fluid lipid bilayer systems. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova. Copyright © 2014. Published by Elsevier B.V.

Instability of multi-layer fluid configurations in the presence of time-dependent accelerations in a microgravity environment

NASA Technical Reports Server (NTRS)

Lyell, M. J.; Roh, Michael

1991-01-01

The increasing number of research opportunities in a microgravity environment will benefit not only fundamental studies in fluid dynamics, but also technological applications such as those involving materials processing. In particular, fluid configurations which involve fluid-fluid interfaces would occur in a variety of experimental investigations. This work investigates the stability of a configuration involving fluid-fluid interfaces in the presence of a time-dependent forcing. Both periodic (g-jitter) and nonperiodic accelerations are considered. The fluid configuration is multilayered, and infinite in extent. The analysis is linear and inviscid, and the acceleration vector is oriented perpendicular to each interface. A Floquet analysis is employed in the case of the periodic forcing. In the problem of nonperiodic forcing, the resulting system of equations are integrated in time. Specific nondimensional parameters appear in each problem. The configuration behavior is investigated for a range of parameter values.

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

Zitney, S.E.

This presentation will examine process systems engineering R&D needs for application to advanced fossil energy (FE) systems and highlight ongoing research activities at the National Energy Technology Laboratory (NETL) under the auspices of a recently launched Collaboratory for Process & Dynamic Systems Research. The three current technology focus areas include: 1) High-fidelity systems with NETL's award-winning Advanced Process Engineering Co-Simulator (APECS) technology for integrating process simulation with computational fluid dynamics (CFD) and virtual engineering concepts, 2) Dynamic systems with R&D on plant-wide IGCC dynamic simulation, control, and real-time training applications, and 3) Systems optimization including large-scale process optimization, stochastic simulationmore » for risk/uncertainty analysis, and cost estimation. Continued R&D aimed at these and other key process systems engineering models, methods, and tools will accelerate the development of advanced gasification-based FE systems and produce increasingly valuable outcomes for DOE and the Nation.« less

Dynamic Data-Driven Reduced-Order Models of Macroscale Quantities for the Prediction of Equilibrium System State for Multiphase Porous Medium Systems

NASA Astrophysics Data System (ADS)

Talbot, C.; McClure, J. E.; Armstrong, R. T.; Mostaghimi, P.; Hu, Y.; Miller, C. T.

2017-12-01

Microscale simulation of multiphase flow in realistic, highly-resolved porous medium systems of a sufficient size to support macroscale evaluation is computationally demanding. Such approaches can, however, reveal the dynamic, steady, and equilibrium states of a system. We evaluate methods to utilize dynamic data to reduce the cost associated with modeling a steady or equilibrium state. We construct data-driven models using extensions to dynamic mode decomposition (DMD) and its connections to Koopman Operator Theory. DMD and its variants comprise a class of equation-free methods for dimensionality reduction of time-dependent nonlinear dynamical systems. DMD furnishes an explicit reduced representation of system states in terms of spatiotemporally varying modes with time-dependent oscillation frequencies and amplitudes. We use DMD to predict the steady and equilibrium macroscale state of a realistic two-fluid porous medium system imaged using micro-computed tomography (µCT) and simulated using the lattice Boltzmann method (LBM). We apply Koopman DMD to direct numerical simulation data resulting from simulations of multiphase fluid flow through a 1440x1440x4320 section of a full 1600x1600x5280 realization of imaged sandstone. We determine a representative set of system observables via dimensionality reduction techniques including linear and kernel principal component analysis. We demonstrate how this subset of macroscale quantities furnishes a representation of the time-evolution of the system in terms of dynamic modes, and discuss the selection of a subset of DMD modes yielding the optimal reduced model, as well as the time-dependence of the error in the predicted equilibrium value of each macroscale quantity. Finally, we describe how the above procedure, modified to incorporate methods from compressed sensing and random projection techniques, may be used in an online fashion to facilitate adaptive time-stepping and parsimonious storage of system states over time.

ION ACOUSTIC TURBULENCE, ANOMALOUS TRANSPORT, AND SYSTEM DYNAMICS IN HALL EFFECT THRUSTERS

DTIC Science & Technology

2017-06-30

17394 4 / 13 HALL EFFECT THRUSTERS Hall Effect Thrusters (HET): Traditionally Modeled in R-Z Named for Hall Current in θ Uses Quasi -1D Electron Fluid...HET): Traditionally Modeled in R-Z Named for Hall Current in θ Uses Quasi -1D Electron Fluid Solve Ohm’s Law→ No e−-momentum Zθ Unrolled to YZ...Current in θ Uses Quasi -1D Electron Fluid Solve Ohm’s Law→ No e−-momentum Zθ Unrolled to YZ Electron ExB Drift Unmagnetized Ions Results in Hall Current

Oxazine-based sensor for contaminant detection, fabrication method therefor, and uses thereof

DOEpatents

Nnanna, Agbai Agwu; Jalal, Ahmed Hasnian

2014-05-27

A sensor, a method for its fabrication, and a method for its use to detect contaminants, for example, ammonia, in stagnant and dynamic fluid media, especially liquid media. The sensor is an opto-chemical sensor that includes a polymer optical fiber, a sensing layer comprising oxazine 170 perchlorate on the polymer optical fiber, and a membrane layer on the sensing layer. The membrane layer is gas permeable and not permeable to the fluid in the fluid system, and moisture is entrapped by and between the sensing and membrane layers.

Multitasking the code ARC3D. [for computational fluid dynamics

NASA Technical Reports Server (NTRS)

Barton, John T.; Hsiung, Christopher C.

1986-01-01

The CRAY multitasking system was developed in order to utilize all four processors and sharply reduce the wall clock run time. This paper describes the techniques used to modify the computational fluid dynamics code ARC3D for this run and analyzes the achieved speedup. The ARC3D code solves either the Euler or thin-layer N-S equations using an implicit approximate factorization scheme. Results indicate that multitask processing can be used to achieve wall clock speedup factors of over three times, depending on the nature of the program code being used. Multitasking appears to be particularly advantageous for large-memory problems running on multiple CPU computers.

Computational fluid dynamics simulation of pressure and velocity distribution inside Meniere’s diseased vestibular system

NASA Astrophysics Data System (ADS)

Shamsuddin, N. F. H.; Isa, N. M.; Taib, I.; Mohammed, A. N.

2017-09-01

Meniere’s disease or known as endolymphatic hydrops is an incurable vestibular disorder of the inner ear. This is due to the excessive fluid build-up in the endolymphatic sac which causing the vestibular endolymphatic membrane to start stretching. Although this mechanism has been widely accepted as the likely mechanism of Meniere’s syndrome, the reason for its occurrence remains unclear. Thus, the aims of this study to investigate the critical parameters of fluid flow in membranous labyrinth that is influencing instability of vestibular system. In addition, to visualise the flow behaviour between a normal membranous labyrinth and dilated membranous labyrinth in Meniere’s disease in predicting instability of vestibular system. Three dimensional geometry of endolymphatic sac is obtained from Magnetic Resonance Images (MRI) and reconstructed using commercial software. As basis of comparison the two different model of endolymphatic sac is considered in this study which are normal membranous labyrinth for model I and dilated membranous labyrinth for model II. Computational fluid dynamics (CFD) method is used to analyse the behaviour of pressure and velocity flow in the endolymphatic sac. The comparison was made in terms of pressure distribution and velocity profile. The results show that the pressure for dilated membranous labyrinth is greater than normal membranous labyrinth. Due to abnormally pressure in the vestibular system, it leads to the increasing value of the velocity at dilated membranous labyrinth while at the normal membranous labyrinth the velocity values decreasing. As a conclusion by changing the parameters which is pressure and velocity can significantly affect to the instability of vestibular system for Meniere’s disease.

Dancing disclinations in confined active nematics

NASA Astrophysics Data System (ADS)

Shendruk, Tyler N.; Doostmohammadi, Amin; Thijssen, Kristian; Yeomans, Julia M.

The spontaneous emergence of collective flows is a generic property of active fluids and often leads to chaotic flow patterns characterised by swirls, jets, and topological disclinations in their orientation field. However, the ability to achieve structured flows and ordered disclinations is of particular importance in the design and control of active systems. By confining an active nematic fluid within a channel, we find a regular motion of disclinations, in conjunction with a well defined and dynamic vortex lattice. As pairs of moving disclinations travel through the channel, they continually exchange partners producing a dynamic ordered state, reminiscent of Ceilidh dancing. We anticipate that this biomimetic ability to self-assemble organised topological disclinations and dynamically structured flow fields in engineered geometries will pave the road towards establishing new active topological microfluidic devices.

Fluid Mechanics.

ERIC Educational Resources Information Center

Drazin, Philip

1987-01-01

Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

Internal fluid mechanics research on supercomputers for aerospace propulsion systems

NASA Technical Reports Server (NTRS)

Miller, Brent A.; Anderson, Bernhard H.; Szuch, John R.

1988-01-01

The Internal Fluid Mechanics Division of the NASA Lewis Research Center is combining the key elements of computational fluid dynamics, aerothermodynamic experiments, and advanced computational technology to bring internal computational fluid mechanics (ICFM) to a state of practical application for aerospace propulsion systems. The strategies used to achieve this goal are to: (1) pursue an understanding of flow physics, surface heat transfer, and combustion via analysis and fundamental experiments, (2) incorporate improved understanding of these phenomena into verified 3-D CFD codes, and (3) utilize state-of-the-art computational technology to enhance experimental and CFD research. Presented is an overview of the ICFM program in high-speed propulsion, including work in inlets, turbomachinery, and chemical reacting flows. Ongoing efforts to integrate new computer technologies, such as parallel computing and artificial intelligence, into high-speed aeropropulsion research are described.

Coherent structures and dynamical systems

NASA Technical Reports Server (NTRS)

Jimenez, Javier

1987-01-01

Any flow of a viscous fluid has a finite number of degrees of freedom, and can therefore be seen as a dynamical system. A coherent structure can be thought of as a lower dimensional manifold in whose neighborhood the dynamical system spends a substantial fraction of its time. If such a manifold exists, and if its dimensionality is substantially lower that that of the full flow, it is conceivable that the flow could be described in terms of the reduced set of degrees of freedom, and that such a description would be simpler than one in which the existence of structure was not recognized. Several examples are briefly summarized.

Potential landscape and flux field theory for turbulence and nonequilibrium fluid systems

NASA Astrophysics Data System (ADS)

Wu, Wei; Zhang, Feng; Wang, Jin

2018-02-01

Turbulence is a paradigm for far-from-equilibrium systems without time reversal symmetry. To capture the nonequilibrium irreversible nature of turbulence and investigate its implications, we develop a potential landscape and flux field theory for turbulent flow and more general nonequilibrium fluid systems governed by stochastic Navier-Stokes equations. We find that equilibrium fluid systems with time reversibility are characterized by a detailed balance constraint that quantifies the detailed balance condition. In nonequilibrium fluid systems with nonequilibrium steady states, detailed balance breaking leads directly to a pair of interconnected consequences, namely, the non-Gaussian potential landscape and the irreversible probability flux, forming a 'nonequilibrium trinity'. The nonequilibrium trinity characterizes the nonequilibrium irreversible essence of fluid systems with intrinsic time irreversibility and is manifested in various aspects of these systems. The nonequilibrium stochastic dynamics of fluid systems including turbulence with detailed balance breaking is shown to be driven by both the non-Gaussian potential landscape gradient and the irreversible probability flux, together with the reversible convective force and the stochastic stirring force. We reveal an underlying connection of the energy flux essential for turbulence energy cascade to the irreversible probability flux and the non-Gaussian potential landscape generated by detailed balance breaking. Using the energy flux as a center of connection, we demonstrate that the four-fifths law in fully developed turbulence is a consequence and reflection of the nonequilibrium trinity. We also show how the nonequilibrium trinity can affect the scaling laws in turbulence.

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems.

PubMed

Ferrari, A

2017-03-01

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

Fluid transport properties by equilibrium molecular dynamics. I. Methodology at extreme fluid states

NASA Astrophysics Data System (ADS)

Dysthe, D. K.; Fuchs, A. H.; Rousseau, B.

1999-02-01

The Green-Kubo formalism for evaluating transport coefficients by molecular dynamics has been applied to flexible, multicenter models of linear and branched alkanes in the gas phase and in the liquid phase from ambient conditions to close to the triple point. The effects of integration time step, potential cutoff and system size have been studied and shown to be small compared to the computational precision except for diffusion in gaseous n-butane. The RATTLE algorithm is shown to give accurate transport coefficients for time steps up to a limit of 8 fs. The different relaxation mechanisms in the fluids have been studied and it is shown that the longest relaxation time of the system governs the statistical precision of the results. By measuring the longest relaxation time of a system one can obtain a reliable error estimate from a single trajectory. The accuracy of the Green-Kubo method is shown to be as good as the precision for all states and models used in this study even when the system relaxation time becomes very long. The efficiency of the method is shown to be comparable to nonequilibrium methods. The transport coefficients for two recently proposed potential models are presented, showing deviations from experiment of 0%-66%.

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

NASA Astrophysics Data System (ADS)

Ferrari, A.

2017-03-01

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

PubMed Central

2017-01-01

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh–Plesset equation are examined. PMID:28413332

Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade Cascade

DTIC Science & Technology

2016-11-01

turbine blades to have fluid run through them during use1—a feature which many newer engines include. A cutaway view of a typical rotorcraft engine...ARL-TR-7871 ● NOV 2016 US Army Research Laboratory Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade ...ARL-TR-7871 ● NOV 2016 US Army Research Laboratory Computational Fluid Dynamic (CFD) Study of an Articulating Turbine Blade Cascade by Luis

3-D Model of the Human Respiratory System

EPA Science Inventory

The U.S. EPA’s Office of Research and Development (ORD) has developed a 3-D computational fluid dynamics (CFD) model of the human respiratory system that allows for the simulation of particulate based contaminant deposition and clearance, while being adaptable for age, ethnicity,...

Acquisition system environmental effects study. [for capillary-screen propellant retention devices

NASA Technical Reports Server (NTRS)

1975-01-01

The effects of vibration, warm gas exposure, and feed system startup/shutdown fluid dynamics on capillary-screen propellant retention capabilities are quantified. The existing technology is extended to the point where quantitative conlusions in terms of design criteria may be drawn.

Fluid dynamic analysis of a continuous stirred tank reactor for technical optimization of wastewater digestion.

PubMed

Hurtado, F J; Kaiser, A S; Zamora, B

2015-03-15

Continuous stirred tank reactors (CSTR) are widely used in wastewater treatment plants to reduce the organic matter and microorganism present in sludge by anaerobic digestion. The present study carries out a numerical analysis of the fluid dynamic behaviour of a CSTR in order to optimize the process energetically. The characterization of the sludge flow inside the digester tank, the residence time distribution and the active volume of the reactor under different criteria are determined. The effects of design and power of the mixing system on the active volume of the CSTR are analyzed. The numerical model is solved under non-steady conditions by examining the evolution of the flow during the stop and restart of the mixing system. An intermittent regime of the mixing system, which kept the active volume between 94% and 99%, is achieved. The results obtained can lead to the eventual energy optimization of the mixing system of the CSTR. Copyright © 2014 Elsevier Ltd. All rights reserved.

Real-time contaminant sensing and control in civil infrastructure systems

NASA Astrophysics Data System (ADS)

Rimer, Sara; Katopodes, Nikolaos

2014-11-01

A laboratory-scale prototype has been designed and implemented to test the feasibility of real-time contaminant sensing and control in civil infrastructure systems. A blower wind tunnel is the basis of the prototype design, with propylene glycol smoke as the ``contaminant.'' A camera sensor and compressed-air vacuum nozzle system is set up at the test section portion of the prototype to visually sense and then control the contaminant; a real-time controller is programmed to read in data from the camera sensor and administer pressure to regulators controlling the compressed air operating the vacuum nozzles. A computational fluid dynamics model is being integrated in with this prototype to inform the correct pressure to supply to the regulators in order to optimally control the contaminant's removal from the prototype. The performance of the prototype has been evaluated against the computational fluid dynamics model and is discussed in this presentation. Furthermore, the initial performance of the sensor-control system implemented in the test section of the prototype is discussed. NSF-CMMI 0856438.

Summer Study Program in Geophysical Fluid Dynamics, Woods Hole Oceanographic Institution: Chaos.

DTIC Science & Technology

1985-11-01

Cleopatra, periodic solutions to Galileo and perhaps chaos to Poincar. Today we often think about dynamical systems in terms o- oincae surfaces of section...P. Berge, 1983. Phys. Rev. Lett. L51, 1446 and 2345. Nadal, J.P., B. Derrida and J. Vannimenus, 1982. J. de Phys. 43, , 1561 and V. Hakim and J.P

Investigation of Propellant Sloshing and Zero Gravity Equilibrium for the Orion Service Module Propellant Tanks

NASA Astrophysics Data System (ADS)

Kreppel, Samantha

A scaled model of the downstream Orion service module propellant tank was constructed to asses the propellant dynamics under reduced and zero-gravity conditions. Flight and ground data from the experiment is currently being used to validate computational models of propel-lant dynamics in Orion-class propellant tanks. The high fidelity model includes the internal structures of the propellant management device (PMD) and the mass-gauging probe. Qualita-tive differences between experimental and CFD data are understood in terms of fluid dynamical scaling of inertial effects in the scaled system. Propellant configurations in zero-gravity were studied at a range of fill-fractions and the settling time for various docking maneuvers was determined. A clear understanding of the fluid dynamics within the tank is necessary to en-sure proper control of the spacecraft's flight and to maintain safe operation of this and future service modules. Understanding slosh dynamics in partially-filled propellant tanks is essential to assessing spacecraft stability.

Jochem Weber | NREL

Science.gov Websites

mechanical engineering (design) and physical engineering (fluid and system dynamics), and a Ph.D. in modeling Ph.D. in Engineering, University College Cork (Ireland); M.S. and B.S. in Physical Engineering

Microfluidic Enhancement of Intramedullary Pressure Increases Interstitial Fluid Flow and Inhibits Bone Loss in Hindlimb Suspended Mice

PubMed Central

Kwon, Ronald Y; Meays, Diana R; Tang, W Joyce; Frangos, John A

2010-01-01

Interstitial fluid flow (IFF) has been widely hypothesized to mediate skeletal adaptation to mechanical loading. Although a large body of in vitro evidence has demonstrated that fluid flow stimulates osteogenic and antiresorptive responses in bone cells, there is much less in vivo evidence that IFF mediates loading-induced skeletal adaptation. This is due in large part to the challenges associated with decoupling IFF from matrix strain. In this study we describe a novel microfluidic system for generating dynamic intramedullary pressure (ImP) and IFF within the femurs of alert mice. By quantifying fluorescence recovery after photobleaching (FRAP) within individual lacunae, we show that microfluidic generation of dynamic ImP significantly increases IFF within the lacunocanalicular system. In addition, we demonstrate that dynamic pressure loading of the intramedullary compartment for 3 minutes per day significantly eliminates losses in trabecular and cortical bone mineral density in hindlimb suspended mice, enhances trabecular and cortical structural integrity, and increases endosteal bone formation rate. Unlike previously developed modalities for enhancing IFF in vivo, this is the first model that allows direct and dynamic modulation of ImP and skeletal IFF within mice. Given the large number of genetic tools for manipulating the mouse genome, this model is expected to serve as a powerful investigative tool in elucidating the role of IFF in skeletal adaptation to mechanical loading and molecular mechanisms mediating this process. © 2010 American Society for Bone and Mineral Research. PMID:20200992

Numerical Study of the Cerebro-Spinal Fluid (CSF) Dynamics Under Quasistatic Condition During a Cardiac Cycle

DTIC Science & Technology

2001-10-25

THE CEREBRO -SPINAL FLUID (CSF) DYNAMICS UNDER QUASI- STATIC CONDITION DURING A CARDIAC CYCLE Loïc FIN, Reinhard GREBE, Olivier BALÉDENT, Ilana...from... to) - Title and Subtitle Numerical Study of the Cerebro -Spinal Fluid (CSF) Dynamics Under Quasistatic Condition During a Cardiac Cycle

From viscous to elastic sheets: Dynamics of smectic freely floating films

NASA Astrophysics Data System (ADS)

Stannarius, Ralf; Harth, Kirsten; May, Kathrin; Trittel, Torsten

The dynamics of droplets and bubbles, particularly on microscopic scales, are of considerable importance in biological, environmental, and technical contexts. Soap bubbles, vesicles and components of biological cells are well known examples where the dynamic behavior is significantly influenced by the properties of thin membranes enclosed by fluids. Two-dimensional membrane motions couple to 3D shape transformations. Smectic liquid crystal mesogens form phases with internal molecular layer order. Free-standing films are easily prepared from this class of materials. They represent simple model systems for membrane dynamics and pattern formation in a quasi two-dimensional fluid. These films are usually spanned over a frame, and they can be inflated to bubbles on a support. Recently, closed microscopic shells of liquid-crystalline materials suspended in an outer fluid without contact to a solid support have been introduced and studied. With a special technique, we prepare millimetre to centimetre sized smectic bubbles in air (similar to soap bubbles). Their distinct feature is the fact that any change of surface area is coupled to a restructuring of the layers in the membrane. High-speed cameras are used to observe the shape transformations of freely floating bubbles from a distorted initial shape to a sphere. Bursting dynamics are recorded and compared to models. Most strikingly, an unpreceded cross-over from inviscid to viscous and elastic behaviour with increasing thickness of the membrane is found: Whereas thin bubbles behave almost like inviscid fluids, the relaxation dynamics slows down considerably for larger film thicknesses. Surface wrinkling and formation of extrusions are observed. We will present a characterization and an expalantion for the above phenomena.

Predictive models for moving contact line flows

NASA Technical Reports Server (NTRS)

Rame, Enrique; Garoff, Stephen

2003-01-01

Modeling flows with moving contact lines poses the formidable challenge that the usual assumptions of Newtonian fluid and no-slip condition give rise to a well-known singularity. This singularity prevents one from satisfying the contact angle condition to compute the shape of the fluid-fluid interface, a crucial calculation without which design parameters such as the pressure drop needed to move an immiscible 2-fluid system through a solid matrix cannot be evaluated. Some progress has been made for low Capillary number spreading flows. Combining experimental measurements of fluid-fluid interfaces very near the moving contact line with an analytical expression for the interface shape, we can determine a parameter that forms a boundary condition for the macroscopic interface shape when Ca much les than l. This parameter, which plays the role of an "apparent" or macroscopic dynamic contact angle, is shown by the theory to depend on the system geometry through the macroscopic length scale. This theoretically established dependence on geometry allows this parameter to be "transferable" from the geometry of the measurement to any other geometry involving the same material system. Unfortunately this prediction of the theory cannot be tested on Earth.

On the inclusion of mass source terms in a single-relaxation-time lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Aursjø, Olav; Jettestuen, Espen; Vinningland, Jan Ludvig; Hiorth, Aksel

2018-05-01

We present a lattice Boltzmann algorithm for incorporating a mass source in a fluid flow system. The proposed mass source/sink term, included in the lattice Boltzmann equation, maintains the Galilean invariance and the accuracy of the overall method, while introducing a mass source/sink term in the fluid dynamical equations. The method can, for instance, be used to inject or withdraw fluid from any preferred lattice node in a system. This suggests that injection and withdrawal of fluid does not have to be introduced through cumbersome, and sometimes less accurate, boundary conditions. The method also suggests that, through a chosen equation of state relating mass density to pressure, the proposed mass source term will render it possible to set a preferred pressure at any lattice node in a system. We demonstrate how this model handles injection and withdrawal of a fluid. And we show how it can be used to incorporate pressure boundaries. The accuracy of the algorithm is identified through a Chapman-Enskog expansion of the model and supported by the numerical simulations.

Optimization of a pressure control valve for high power automatic transmission considering stability

NASA Astrophysics Data System (ADS)

Jian, Hongchao; Wei, Wei; Li, Hongcai; Yan, Qingdong

2018-02-01

The pilot-operated electrohydraulic clutch-actuator system is widely utilized by high power automatic transmission because of the demand of large flowrate and the excellent pressure regulating capability. However, a self-excited vibration induced by the inherent non-linear characteristics of valve spool motion coupled with the fluid dynamics can be generated during the working state of hydraulic systems due to inappropriate system parameters, which causes sustaining instability in the system and leads to unexpected performance deterioration and hardware damage. To ensure a stable and fast response performance of the clutch actuator system, an optimal design method for the pressure control valve considering stability is proposed in this paper. A non-linear dynamic model of the clutch actuator system is established based on the motion of the valve spool and coupling fluid dynamics in the system. The stability boundary in the parameter space is obtained by numerical stability analysis. Sensitivity of the stability boundary and output pressure response time corresponding to the valve parameters are identified using design of experiment (DOE) approach. The pressure control valve is optimized using particle swarm optimization (PSO) algorithm with the stability boundary as constraint. The simulation and experimental results reveal that the optimization method proposed in this paper helps in improving the response characteristics while ensuring the stability of the clutch actuator system during the entire gear shift process.

Flutter instability of cantilevered carbon nanotubes caused by magnetic fluid flow subjected to a longitudinal magnetic field

NASA Astrophysics Data System (ADS)

Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

2018-04-01

CNT (Carbon nanotube)-based fluidic systems hold a great potential for emerging medical applications such as drug delivery for cancer therapy. CNTs can be used to deliver anticancer drugs into a target site under a magnetic field guidance. One of the critical issues in designing such systems is how to avoid the vibration induced by the fluid flow, which is undesirable and may even promote the structural instability. The main objective of the present research is to develop a fluid structure interaction (FSI) model to investigate the flutter instability of a cantilevered CNT induced by a magnetic fluid flow under a longitudinal magnetic field. The CNT is assumed to be embedded in a viscoelastic matrix to consider the effect of biological medium around it. To obtain a dynamical model for the system, the Navier-Stokes theory of magnetic-fluid flow is coupled to the Euler-Bernoulli beam model for CNT. The small size effects of the magnetic fluid and CNT are considered through the small scale parameters including Knudsen number (Kn) and the nonlocal parameter. Then, the extended Galerkin's method is applied to solve the FSI governing equations, and to derive the stability diagrams of the system. Results show how the magnetic properties of the fluid flow have an effect on improving the stability of the cantilevered CNT by increasing the flutter velocity.

Aquaporin-4 facilitator TGN-073 promotes interstitial fluid circulation within the blood-brain barrier: [17O]H2O JJVCPE MRI study.

PubMed

Huber, Vincent J; Igarashi, Hironaka; Ueki, Satoshi; Kwee, Ingrid L; Nakada, Tsutomu

2018-06-13

The blood-brain barrier (BBB), which imposes significant water permeability restriction, effectively isolates the brain from the systemic circulation. Seemingly paradoxical, the abundance of aquaporin-4 (AQP-4) on the inside of the BBB strongly indicates the presence of unique water dynamics essential for brain function. On the basis of the highly specific localization of AQP-4, namely, astrocyte end feet at the glia limitans externa and pericapillary Virchow-Robin space, we hypothesized that the AQP-4 system serves as an interstitial fluid circulator, moving interstitial fluid from the glia limitans externa to pericapillary Virchow-Robin space to ensure proper glymphatic flow draining into the cerebrospinal fluid. The hypothesis was tested directly using the AQP-4 facilitator TGN-073 developed in our laboratory, and [O]H2O JJ vicinal coupling proton exchange MRI, a method capable of tracing water molecules delivered into the blood circulation. The results unambiguously showed that facilitation of AQP-4 by TGN-073 increased turnover of interstitial fluid through the system, resulting in a significant reduction in [O]H2O contents of cortex with normal flux into the cerebrospinal fluid. The study further suggested that in addition to providing the necessary water for proper glymphatic flow, the AQP-4 system produces a water gradient within the interstitial space promoting circulation of interstitial fluid within the BBB.

Numerical approach on dynamic self-assembly of colloidal particles

NASA Astrophysics Data System (ADS)

Ibrahimi, Muhamet; Ilday, Serim; Makey, Ghaith; Pavlov, Ihor; Yavuz, Özgàn; Gulseren, Oguz; Ilday, Fatih Omer

Far from equilibrium systems of artificial ensembles are crucial for understanding many intelligent features in self-organized natural systems. However, the lack of established theory underlies a need for numerical implementations. Inspired by a novel work, we simulate a solution-suspended colloidal system that dynamically self assembles due to convective forces generated in the solvent when heated by a laser. In order to incorporate with random fluctuations of particles and continuously changing flow, we exploit a random-walk based Brownian motion model and a fluid dynamics solver prepared for games, respectively. Simulation results manage to fit to experiments and show many quantitative features of a non equilibrium dynamic self assembly, including phase space compression and an ensemble-energy input feedback loop.

Hierarchical organization as a diagnostic approach to volcano mechanics: Validation on Piton de la Fournaise

NASA Astrophysics Data System (ADS)

Grasso, J. R.; Bachèlery, P.

Self-organized systems are often used to describe natural phenomena where power laws and scale invariant geometry are observed. The Piton de la Fournaise volcano shows power-law behavior in many aspects. These include the temporal distribution of eruptions, the frequency-size distributions of induced earthquakes, dikes, fissures, lava flows and interflow periods, all evidence of self-similarity over a finite scale range. We show that the bounds to scale-invariance can be used to derive geomechanical constraints on both the volcano structure and the volcano mechanics. We ascertain that the present magma bodies are multi-lens reservoirs in a quasi-eruptive condition, i.e. a marginally critical state. The scaling organization of dynamic fluid-induced observables on the volcano, such as fluid induced earthquakes, dikes and surface fissures, appears to be controlled by underlying static hierarchical structure (geology) similar to that proposed for fluid circulations in human physiology. The emergence of saturation lengths for the scalable volcanic observable argues for the finite scalability of complex naturally self-organized critical systems, including volcano dynamics.

TESS: A RELATIVISTIC HYDRODYNAMICS CODE ON A MOVING VORONOI MESH

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

Duffell, Paul C.; MacFadyen, Andrew I., E-mail: pcd233@nyu.edu, E-mail: macfadyen@nyu.edu

2011-12-01

We have generalized a method for the numerical solution of hyperbolic systems of equations using a dynamic Voronoi tessellation of the computational domain. The Voronoi tessellation is used to generate moving computational meshes for the solution of multidimensional systems of conservation laws in finite-volume form. The mesh-generating points are free to move with arbitrary velocity, with the choice of zero velocity resulting in an Eulerian formulation. Moving the points at the local fluid velocity makes the formulation effectively Lagrangian. We have written the TESS code to solve the equations of compressible hydrodynamics and magnetohydrodynamics for both relativistic and non-relativistic fluidsmore » on a dynamic Voronoi mesh. When run in Lagrangian mode, TESS is significantly less diffusive than fixed mesh codes and thus preserves contact discontinuities to high precision while also accurately capturing strong shock waves. TESS is written for Cartesian, spherical, and cylindrical coordinates and is modular so that auxiliary physics solvers are readily integrated into the TESS framework and so that this can be readily adapted to solve general systems of equations. We present results from a series of test problems to demonstrate the performance of TESS and to highlight some of the advantages of the dynamic tessellation method for solving challenging problems in astrophysical fluid dynamics.« less

Aeronautical engineering: A continuing bibliography with indexes (supplement 233)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1988. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 283)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 615 reports, articles, and other documents introduced into the NASA scientific and technical information system in Sep. 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 260)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 405 reports, articles, and other documents introduced into the NASA scientific and technical information system in December, 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 247)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 437 reports, articles, and other documents introduced into the NASA scientific and technical information system in December, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 307)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 338 reports, articles, and other documents introduced into the NASA scientific and technical information system in Aug. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical Engineering: a Continuing Bibliography with Indexes (Supplement 243)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 423 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 323)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 518 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 251)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 526 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 292)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 675 reports, articles, and other documents recently introduced into the NASA scientific and technical information system database. Subject coverage includes the following: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 321)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 496 reports, articles, and other documents introduced into the NASA scientific and technical information system in Sep. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 273)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 808 reports, articles, and other documents introduced into the NASA scientific and technical information system in Dec. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 269)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 539 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 281)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 596 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jul. 1992. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 245)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 537 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 314)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 144 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 246)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 690 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 252)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 425 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 308)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 269 reports, articles, and other documents introduced into the NASA scientific and technical information system in Sep. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 264)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 558 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 297)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 825 reports, articles, and other documents introduced into the NASA scientific and technical information system in Nov. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 263)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 517 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 238)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 458 reports, articles, and other documents introduced into the NASA scientific and technical information system in March, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 255)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 529 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 262)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 474 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jan. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 250)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 420 reports, articles, and other documents introduced into the NASA scientific and technical information system in February, 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 270)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 600 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 296)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 592 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 253)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in May, 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 295)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 581 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in Sep. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 239)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 454 reports, articles, and other documents introduced into the NASA scientific and technical information system in April, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 298)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 328 reports, articles, and other documents recently introduced into the NASA scientific and technical information system. Subject coverage includes the following areas: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 242)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 466 reports, articles, and other documents introduced into the NASA scientific and technical information system in July, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 304)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 453 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 272)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 719 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 322)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 719 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 317)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 224 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 257)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 560 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 265)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 554 reports, articles, and other documents introduced into the NASA scientific and technical information system in Apr. 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 249)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1988. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 271)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 666 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1991. Subject coverage includes design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 268)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 406 reports, articles, and other documents introduced into the NASA scientific and technical information system in July, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 240)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 629 reports, articles, and other documents introduced into the NASA scientific and technical information system in May, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 286)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 845 reports, articles, and other documents introduced into the NASA scientific and technical information system in Dec. 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 259)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 774 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical Engineering: a Continuing Bibliography with Indexes (Supplement 244)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 465 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 237)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 572 reports, articles, and other documents introduced into the NASA scientific and technical information system in February, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 236)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 430 reports, articles, and other documents introduced into the NASA scientific and technical information system in January, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 266)

NASA Technical Reports Server (NTRS)

1991-01-01

This bibliography lists 645 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 288)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 661 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jan. 1993. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 318)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 217 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 241)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 526 reports, articles, and other documents introduced into the NASA scientific and technical information system in June, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 279)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 759 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1992. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 276)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 705 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1992. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 299)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 244 reports, articles, and other documents introduced into the NASA scientific and technical information system in Jan. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 315)

NASA Technical Reports Server (NTRS)

1995-01-01

This bibliography lists 217 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 256)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 426 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 290)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 1396 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in Apr. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 309)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 212 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 291)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 757 reports, articles, and other documents introduced into the NASA scientific and technical information system in May. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 258)

NASA Technical Reports Server (NTRS)

1988-01-01

This bibliography lists 536 reports, articles, and other documents introduced into the NASA scientific and technical information system in October 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 254)

NASA Technical Reports Server (NTRS)

1990-01-01

This bibliography lists 538 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 285)

NASA Technical Reports Server (NTRS)

1992-01-01

This bibliography lists 534 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in Nov. 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 234)

NASA Technical Reports Server (NTRS)

1989-01-01

This bibliography lists 539 reports, articles, and other documents introduced into the NASA scientific and technical information system in December, 1988. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 293)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 476 reports, articles, and other documents introduced into the NASA scientific and technical information system in July, 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 305)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 239 reports, articles, and other documents recently introduced into the NASA scientific and technical information system. Subject coverage includes the following: the design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 289)

NASA Technical Reports Server (NTRS)

1993-01-01

This bibliography lists 792 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Aeronautical engineering: A continuing bibliography with indexes (supplement 301)

NASA Technical Reports Server (NTRS)

1994-01-01

This bibliography lists 1291 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1994. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics.

Simulation of a Canard in Fluid Flow Driven by a Piezoelectric Beam with a Software Control Loop

DTIC Science & Technology

2014-04-01

The canard is actuated by a piezoelectric beam that bends as voltage is applied. The voltage is controlled by a software subroutine that measures...Dynamic system Modeling Co-simulation Simulation Abaqus Finite element analysis (FEA) Finite element method (FEM) Computational...is unlimited. i CONTENTS Page Introduction 1 Model Description 1 Fluid Model 2 Structural Model 3 Control Subroutine 4 Results 4

Saliva as a Diagnostic Fluid

PubMed Central

Malamud, Daniel; Rodriguez-Chavez, Isaac R.

2010-01-01

Synopsis Salivary diagnostics is a dynamic and emerging field utilizing nanotechnology and molecular diagnostics to aid in the diagnosis of oral and systemic diseases. Here, we critically review the latest advances using oral biomarkers for disease detection. The use of oral fluids is broadening perspectives in clinical diagnosis, disease monitoring and decision making for patient care. Important elements determining the future possibilities and challenges in this field are also discussed. PMID:21094724

Early dynamics of transversally thermalized matter

NASA Astrophysics Data System (ADS)

Bialas, A.; Chojnacki, M.; Florkowski, W.

2008-10-01

We argue that the idea that the parton system created in relativistic heavy-ion collisions is formed in a state with transverse momenta close to thermodynamic equilibrium and its subsequent dynamics at early times is dominated by pure transverse hydrodynamics of the perfect fluid is compatible with the data collected at RHIC. This scenario of early parton dynamics may help to solve the problem of early equilibration. Quark Matter 2008, Jaipur, India, February 2008.

Phase diagram of a reentrant gel of patchy particles

NASA Astrophysics Data System (ADS)

Roldán-Vargas, Sándalo; Smallenburg, Frank; Kob, Walter; Sciortino, Francesco

2013-12-01

We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities, our simulations show that the system is crystallizing into a BCC structure. Finally, we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.

Thirteenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion and Launch Vehicle Technology. Volume 2

NASA Technical Reports Server (NTRS)

Williams, R. W. (Compiler)

1996-01-01

This conference publication includes various abstracts and presentations given at the 13th Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion and Launch Vehicle Technology held at the George C. Marshall Space Flight Center April 25-27 1995. The purpose of the workshop was to discuss experimental and computational fluid dynamic activities in rocket propulsion and launch vehicles. The workshop was an open meeting for government, industry, and academia. A broad number of topics were discussed including computational fluid dynamic methodology, liquid and solid rocket propulsion, turbomachinery, combustion, heat transfer, and grid generation.

Experimental and theoretical analysis of nanofluids based on high temperature-heat transfer fluid with enhanced thermal properties

NASA Astrophysics Data System (ADS)

Navas, Javier; Sánchez-Coronilla, Antonio; Martín, Elisa I.; Gómez-Villarejo, Roberto; Teruel, Miriam; Gallardo, Juan Jesús; Aguilar, Teresa; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

2017-04-01

In this work, nanofluids were prepared using commercial Cu nanoparticles and a commercial high temperature-heat transfer Fluid (eutectic mixture of diphenyl oxide and biphenyl) as the base fluid, which is used in concentrating solar power (CSP) plants. Different properties such as density, viscosity, heat capacity and thermal conductivity were characterized. Nanofluids showed enhanced heat transfer efficiency. In detail, the incorporation of Cu nanoparticles led to an increase of the heat capacity up to 14%. Also, thermal conductivity was increased up to 13%. Finally, the performance of the nanofluids prepared increased up to 11% according to the Dittus-Boelter correlation. On the other hand, equilibrium molecular dynamics simulation was used to model the experimental nanofluid system studied. Thermodynamic properties such as heat capacity and thermal conductivity were calculated and the results were compared with experimental data. The analysis of the radial function distributions (RDFs) and the inspection of the spatial distribution functions (SDFs) indicate the important role that plays the metal-oxygen interaction in the system. Dynamic properties such as the diffusion coefficients of base fluid and nanofluid were computed according to Einstein relation by computing the mean square displacement (MSD). Supplementary online material is available in electronic form at http://www.epjap.org

Numerical simulation of the non-Newtonian blood flow through a mechanical aortic valve. Non-Newtonian blood flow in the aortic root

NASA Astrophysics Data System (ADS)

De Vita, F.; de Tullio, M. D.; Verzicco, R.

2016-04-01

This work focuses on the comparison between Newtonian and non-Newtonian blood flows through a bileaflet mechanical heart valve in the aortic root. The blood, in fact, is a concentrated suspension of cells, mainly red blood cells, in a Newtonian matrix, the plasma, and consequently its overall behavior is that of a non-Newtonian fluid owing to the action of the cells' membrane on the fluid part. The common practice, however, assumes the blood in large vessels as a Newtonian fluid since the shear rate is generally high and the effective viscosity becomes independent of the former. In this paper, we show that this is not always the case even in the aorta, the largest artery of the systemic circulation, owing to the pulsatile and transitional nature of the flow. Unexpectedly, for most of the pulsating cycle and in a large part of the fluid volume, the shear rate is smaller than the threshold level for the blood to display a constant effective viscosity and its shear thinning character might affect the system dynamics. A direct inspection of the various flow features has shown that the valve dynamics, the transvalvular pressure drop and the large-scale features of the flow are very similar for the Newtonian and non-Newtonian fluid models. On the other hand, the mechanical damage of the red blood cells (hemolysis), induced by the altered stress values in the flow, is larger for the non-Newtonian fluid model than for the Newtonian one.