Parikh, M.
1981-01-01
The construction of an Indian Rs. 186 (US $20.33) flat-plate solar oven is described. Detailed drawings are provided and relevant information on cooking times and temperature for different foods is given.
Corrugated cover plate for flat plate collector
Hollands, K. G. Terry; Sibbitt, Bruce
1978-01-01
A flat plate radiant energy collector is providing having a transparent cover. The cover has a V-corrugated shape which reduces the amount of energy reflected by the cover away from the flat plate absorber of the collector.
NASA Astrophysics Data System (ADS)
Rasekh, A.; Ganji, D. D.
2013-08-01
This work is focused on the study of the mixed convection heat transfer over an inclined flat plate in a porous medium saturated with nanofluids. The governed partial differential equations are transformed into ordinary differential equations, which are obtained by similarity solution. A Padé technique is introduced and combined with differential transform method (DTM) with the aim of extending the convergence area of the series solutions. Comparisons are made between the results of the proposed method and the numerical method (fourth-order Rung-Kutta), as well as available results from the literature in solving this problem, and excellent agreement has been observed. The effects of the pertinent parameters, namely wall suction/injection parameter, mixed convection parameter, prescribed constant, nanoparticles volume fraction factor, and different nanoparticles, on the temperature distribution along with local Nusselt number are presented graphically and the physical aspects of the problem are highlighted and discussed.
Inverted flat plate solar collector. Final report
Brown, M.A.
1981-08-26
Construction and testing of an inverted flat plate solar collector are described. Heat transfer and economic analysis were performed to optimize the collector design. The newly designed collector was tested against two other flat plate collectors and the results and comparison of efficiencies are presented. (BCS)
High performance flat plate solar collector
NASA Technical Reports Server (NTRS)
Lansing, F. L.; Reynolds, R.
1976-01-01
The potential use of porous construction is presented to achieve efficient heat removal from a power producing solid and is applied to solar air heaters. Analytical solutions are given for the temperature distribution within a gas-cooled porous flat plate having its surface exposed to the sun's energy. The extracted thermal energy is calculated for two different types of plate transparency. Results show the great improvement in performance obtained with porous flat plate collectors as compared with analogous nonporous types.
High efficiency flat plate solar energy collector
Butler, R. F.
1985-04-30
A concentrating flat plate collector for the high efficiency collection of solar energy. Through an arrangement of reflector elements, incoming solar radiation, either directly or after reflection from the reflector elements, impinges upon both surfaces of a collector element.
Flat Plate Cascades at Supersonic Speed
NASA Technical Reports Server (NTRS)
El Badrawy, Rashad M
1956-01-01
A brief review of exact two-dimensional supersonic flow theory and Ackeret's linearized theory are first presented. The lift and drag coefficients of a cascade of flat plates are calculated exactly and compared to those obtained using the linearized theory. The forces on the cascade are determined for unsteady inlet flow. The flat plate cascade theory is extended to compute the efficiency of a supersonic propeller with friction and finite blade thickness.
Evacuated flat-plate solar collectors
Whittemore, P.G.
1981-09-15
A structural support system is disclosed for use in an evacuated, flat-plate, solar collector to eliminate the problem of stress fractures in a glass cover plate. Nonlinearly spaced supports are used within the collector to dampen vibrations in the glass cover and to prevent overdeflection before buckling or stress fractures occur.
Analysis of boiling flat-plate collectors
Price, H.W.; Klein, S.A.; Beckman, W.A.
1986-05-01
A detailed model for use with TRNSYS, capable of modelling a wide range of boiling collector types, was used to analyze boiling flat-plate collector systems. This model can account for a subcooled liquid entering the collector, heat losses in the vapor and the liquid return line, pressure drops due to friction in the collector and piping, and pressure drops due to the hydrostatic head of the fluid. The model has been used to determine the yearly performance of boiling flat-plate solar collector systems. A simplified approach was also developed which can be used with the f-Chart method to predict yearly performance of boiling flat-plate collector systems.
Bi-coolant flat plate solar collector
NASA Astrophysics Data System (ADS)
Chon, W. Y.; Green, L. L.
The feasibility study of a flat plate solar collector which heats air and water concurrently or separately was carried out. Air flows above the collector absorber plate, while water flows in tubes soldered or brazed beneath the plate. The collector efficiencies computed for the flow of both air and water are compared with those for the flow of a single coolant. The results show that the bi-coolant collector efficiency computed for the entire year in Buffalo, New York is higher than the single-coolant collector efficiency, although the efficiency of the water collector is higher during the warmer months.
Plume impingement forces on inclined flat plates
NASA Astrophysics Data System (ADS)
Legge, H.
Plume impingement from spacecraft control thrusters on vehicles in space is simulated in wind tunnel scale experiments. Pressure and shear stress are measured on flat plates inclined to the plume axis between 0 and 90 deg. In addition to a nozzle of a 0.5N thruster, a free jet from a thin plate orifice was used, by which the flow regime from nearly free molecular flow to continuum flow was covered. Simple pressure and shear stress laws are given by which the impingement pressure and shear stress can be estimated for engineering applications.
Transverse flat plate heat pipe experiment
NASA Technical Reports Server (NTRS)
Edelstein, F.
1978-01-01
This paper describes a Shuttle-launched flight experiment to evaluate the performance of a transverse flat plate heat pipe that serves as an integral temperature control/mounting panel for electronic equipment. A transverse heat pipe is a gas-controlled variable conductance heat pipe that can handle relatively large thermal loads. An experiment designed to flight test the concept over a 6-9 month period is self-sufficient with respect to electrical power, timing sequences, and data storage.
Engineering surface waves in flat phononic plates
NASA Astrophysics Data System (ADS)
Estrada, Héctor; Candelas, Pilar; Belmar, Francisco; Uris, Antonio; García de Abajo, F. Javier; Meseguer, Francisco
2012-05-01
Surface acoustic-wave phenomena span a wide range of length scales going from the devastation of earthquakes down to image reconstruction of buried nanostructures. In solid-fluid systems, the so-called Scholte-Stoneley waves (SSWs) dominate the scene at the interface with their evanescent fields decaying away into both media. Understanding and manipulating these waves in patterned surfaces would enable new applications of sound to be devised for imaging and acoustic signal processing, although this task has so far remained elusive. Here, we report SSW modes displaying directional gaps and band folding in fluid-loaded solid phononic plates. The plates are inhomogeneously patterned with in-plane periodic modulations of the elastic constants, but present flat surfaces free of corrugations. We experimentally demonstrate control of SSWs, which opens a promising route toward acoustic fluid sensing, microscopy, and signal processing.
Strength of Rectangular Flat Plates Under Edge Compression
NASA Technical Reports Server (NTRS)
Schuman, Louis; Back, Goldie
1931-01-01
Flat rectangular plates of duralumin, stainless iron, monel metal, and nickel were tested under loads applied at two opposite edges and acting in the plane of the plate. The edges parallel to the direction of loading were supported in V grooves. The plates were all 24 inches long and varied in width from 4 to 24 inches by steps of 4 inches, and in thickness from 0.015 to 0.095 inch by steps of approximately 0.015 inch. There were also a few 1, 2, 3, and 6 inch wide specimens. The loads were applied in the testing machine at the center of a bar which rested along the top of the plate. Load was applied until the plate failed to take any more load. The tests show that the loads carried by the plates generally reached a maximum for the 8 or 12 inch width and that there was relatively small drop in load for the greater widths. Deflection and set measurement perpendicular to the plane of the plate were taken and the form of the buckle determined. The number of buckles were found to correspond in general to that predicted by the theory of buckling of a plate uniformly loaded at two opposite edges and simply supported at the edges.
Development of flat - plate solar plate collector - evaporator. Summary report
Abramzon, B.; Yaron, I.
1981-11-01
In the present study the thermal performance of a flat plate solar collector is analyzed theoretically for the case in which the working fluid may undergo a phase change within the tubes of the collector. In addition to the common domestic applications, such a collector - evaporator may be used as a generator of vapors for the production of mechanical or electrical energy, e.g. solar water pumps, solar power stations, etc., as well as for solar - powered absorption refrigeration machines, distillation installations, etc.
Simulation of the Flow Over a Flat Dimpled Plate
NASA Astrophysics Data System (ADS)
Mode, Jeffrey Michael
Passive flow control achieved by surface dimpling can be an effective strategy for reducing drag around bluff bodies - an example of substantial popular interest being the flow around a golf ball. While the general effect of dimples causing a delay of boundary layer separation is well known, the mechanisms contributing to this phenomena are subtle and not thoroughly understood. Numerical models offer a powerful approach for studying drag reduction, however simulation strategies are challenged by complex geometries, and in applications the introduction of ad hoc turbulence models which introduce additional uncertainty. These and other factors provide much of the motivation for the current study, which focused on the numerical simulations of the flow over a simplified configuration consisting of a dimpled flat plate. The principal goals of the work are to understand the performance of the numerical methodology, and gain insight into the underlying physics of the flow. Direct numerical simulation of the incompressible Navier-Stokes equations using a fractional step method was employed, with the dimpled flat plate represented using an immersed boundary method. The dimple geometry utilizes a fixed dimple aspect ratio, with dimples arranged in a single spanwise row. The grid sizes considered ranged from approximately 3 to 99 million grid points. Reynolds numbers of 3000 and 4000 based on the inlet laminar boundary layer thickness were simulated. A turbulent boundary layer was induced downstream of the dimples for Reynolds numbers which did not transition for the flow over an undimpled flat plate. First and second order statistics of the boundary layer that develops agree reasonably well with those for turbulent channel flow and flat plate boundary layers in the sublayer and buffer layers, but differ in the outer layer. Inspection of flow visualizations suggest that early transition is promoted by thinning of the boundary layer, initiation of shear layer instabilities
Asymptotic behavior of a flat plate wake
NASA Technical Reports Server (NTRS)
Weygandt, James H.; Mehta, Rabindra D.
1989-01-01
An experimental study has been conducted to investigate the far-field, self-similar properties of a flat plate wake. A plane turbulent wake was generated at the trailing edge of a smooth splitter plate separating two legs of a Mixing Layer Wind Tunnel, with both initial boundary layers tripped. For the present study, both legs were operated at a free-steam velocity in the test section of 15 m/s, giving a Reynolds number based on wake momentum thickness of about 1750. Single profile measurements were obtained at five streamwise locations using a Pitot probe for the mean velocity measurements and a single cross-wire probe for the turbulence data, which included statistics up to third order. The mean flow data indicated a self-similar behavior beyond a streamwise distance equivalent to about 350 wake momentum thicknesses. However, the turbulence data show better collapse beyond a distance equivalent to about 500 momentum thicknesses, with all the measured peak Reynolds stresses achieving constant, asymptotic levels. The asymptotic mean flow behavior and peak primary stress levels agree well with theoretical predictions based on a constant eddy viscosity model. The present data also agree reasonably well with previous measurements, of which only one set extends into the self-similar region. Detailed comparisons with previous data are presented and discussed in this report.
Handbook of Structural Stability Part I: Buckling of Flat Plates
NASA Technical Reports Server (NTRS)
Gerard, George; Becker, Herbert
1957-01-01
The various factors governing buckling of flat plates are critically reviewed and the results are summarized in a comprehensive series of charts and tables. Numerical values are presented for buckling coefficients of flat plates with various boundary conditions and applied loadings. The effects of plasticity are incorporated in non dimensional buckling charts utilizing the three-parameter description of stress-strain curves.
Collation of quarterly reports on air flat plate collectors
NASA Technical Reports Server (NTRS)
1977-01-01
The solar 2 air flat plate collectors are described. The development and fabrication of a prototype air flat plate collector subsystem containing 320 square feet of collector area are described. Three instrumented panels were completely assembled with glazing and insulation. Manufacture of the last seven prototype collectors was completed in October 1977.
Feasibility of moire contouring for flatness checking of steel plates
NASA Astrophysics Data System (ADS)
Sieczka, Eric J.
1993-05-01
The departure from flatness of a steel plate after rolling, including center buckle and edge wave undulations, is an important parameter indicative of product quality. By monitoring the flatness of steel plates during manufacturing, information can be fed to the rolling press to control the process. A quantitative, three dimensional technique for measuring the surface structure of objects is moire interferometry. This paper presents the results of a project to demonstrate the feasibility of using moire interferometry to monitor the flatness of steel plates. This project involved the design and construction of a demonstration moire optical head, the coding of a fringe interpretation algorithm, and a performance evaluation of each.
Experiments to investigate lift production mechanisms on pitching flat plates
NASA Astrophysics Data System (ADS)
Stevens, P. R. R. J.; Babinsky, H.
2017-01-01
Pitching flat plates are a useful simplification of flapping wings, and their study can provide useful insights into unsteady force generation. Non-circulatory and circulatory lift producing mechanisms for low Reynolds number pitching flat plates are investigated. A series of experiments are designed to measure forces and study the unsteady flowfield development. Two pitch axis positions are investigated, namely a leading edge and a mid-chord pitch axis. A novel PIV approach using twin laser lightsheets is shown to be effective at acquiring full field of view velocity data when an opaque wing model is used. Leading-edge vortex (LEV) circulations are extracted from velocity field data, using a Lamb-Oseen vortex fitting algorithm. LEV and trailing-edge vortex positions are also extracted. It is shown that the circulation of the LEV, as determined from PIV data, approximately matches the general trend of an unmodified Wagner function for a leading edge pitch axis and a modified Wagner function for a mid-chord pitch axis. Comparison of experimentally measured lift correlates well with the prediction of a reduced-order model for a LE pitch axis.
A general small-deflection theory for flat sandwich plates
NASA Technical Reports Server (NTRS)
Libove, Charles; Batdorf, S B
1948-01-01
A small-deflection theory is developed for the elastic behavior of orthotropic flat plates in which deflections due to shear are taken into account. In this theory, which covers all types of flat sandwich construction, a plate is characterized by seven physical constants (five stiffnesses and two Poisson ratios) of which six are independent. Both the energy expression and the differential equations are developed. Boundary conditions corresponding to simply supported, clamped, and elastically restrained edges are considered.
Advanced solar box and flat plate collector cookers
Grupp, M.; Bergler, H.
1992-12-31
Several new solar cooker systems have been developed at Synopsis during the last years: advanced box type cookers, featuring an optimized heat transfer from the absorber into the cooking vessel; flat plate cookers, based on a particular two-way collector with air as transfer fluid; flat plate cookers with heat-pipe transfer; specialized cookers for the baking of bread and flat bread. The working principle of these cookers is described, the structure of a thermal simulation model and results of thermal tests are presented. The results of the first year of local production and use of advanced boxes in India are reported.
Critical range evaluation using a diagonal flat plate
NASA Technical Reports Server (NTRS)
Lee, Teh-Hong; Clark, Tony L.; Burnside, Walter D.; Gupta, Inder J.
1992-01-01
A novel technique is presented to image stray signals in RCS measurement ranges. In this technique, the scattered fields of a flat plate in the diagonal plane are measured in a range for various frequencies and look angles. The scattered field data is then processed to generate an inverse synthetic aperture radar (ISAR) image of the diagonal flat plate. It is shown that scattering mechanisms associated with various stray signals can be identified by using the ISAR image. This leads to better understanding of the range and possible chamber improvements. Scattering mechanisms as small as 90 dB below the plate broadside scattered field level have been observed in the image domain due to the high directivity and low sidelobe characteristics associated with the diagonal flat plate backscattered fields. The results obtained from evaluating the two compact range facilities at The Ohio State University ElectroScience Laboratory are presented to illustrate the virtues of this new range evaluation technique.
Ice Particle Impacts on a Flat Plate
NASA Technical Reports Server (NTRS)
Vargas, Mario; Ruggeri, Charles; Struk, Peter M.; Pereira, Mike; Revilock, Duane; Kreeger, Richard E.
2015-01-01
An experimental study was conducted at the Ballistic Laboratory of NASA Glenn Research Center to study the impact of ice particles on a stationary flat surface target set at 45 degrees with respect to the direction of motion of the impinging particle (Figure 1). The experiment is part of NASA efforts to study the physics involved in engine power-loss events due to ice-crystal ingestion and ice accretion formation inside engines. These events can occur when aircraft encounter high-altitude convective weather.
Flat plate electrohydrodynamic heat pipe experiments
NASA Technical Reports Server (NTRS)
Loehrke, R. I.; Sebits, D. R.
1975-01-01
Performance capabilities of electrohydrodynamic (EHD) flat heat pipes were investigated using Freon 113 and Freon 11 as working fluids. All of the pipes employed straight rod electrodes to form axial liquid flow channels and tranverse grooves for capillary surface wetting. Results show: (1) the EHD pipe will prime under load, (2) voltage controlled conductance can be achieved by varying the active area of the evaporator, and (3) the average evaporator conductances measured in these experiments were consistent with those obtained in other experiments with heat pipes of similar surface geometry using the same or similar working fluids.
Changes in Flat Plate Wake Characteristics Obtained With Decreasing Plate Thickness
NASA Technical Reports Server (NTRS)
Rai, Man Mohan
2016-01-01
The near and very near wake of a flat plate with a circular trailing edge is investigated with data from direct numerical simulations. Computations were performed for four different Reynolds numbers based on plate thickness (D) and at constant plate length. The value of ?/D varies by a factor of approximately 20 in the computations (? being the boundary layer momentum thickness at the trailing edge). The separating boundary layers are turbulent in all the cases. One objective of the study is to understand the changes in wake characteristics as the plate thickness is reduced (increasing ?/D). Vortex shedding is vigorous in the low ?/D cases with a substantial decrease in shedding intensity in the largest ?/D case (for all practical purposes shedding becomes almost intermittent). Other characteristics that are significantly altered with increasing ?/D are the roll-up of the detached shear layers and the magnitude of fluctuations in shedding period. These effects are explored in depth. The effects of changing ?/D on the distributions of the time-averaged, near-wake velocity statistics are discussed.
Three-flat test with plates in horizontal posture
Vannoni, Maurizio; Molesini, Giuseppe
2008-04-20
Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.
Normal pressure tests on unstiffened flat plates
NASA Technical Reports Server (NTRS)
Head, Richard M; Sechler, Ernest J
1944-01-01
Flat sheet panels of aluminum alloy (all 17S-T except for two specimens of 24S-T) were tested under normal pressures with clamped edge supports in the structures laboratory of the Guggenheim Aeronautical Laboratory, California Institute of Technology. The thicknesses used ranged from 0.010 to 0.080 inch; the panel sizes ranged from 10 by 10 inches to 10 by 40 inches; and the pressure range was from 0 to 60-pounds-per-square-inch gage. Deflection patterns were measured and maximum tensile strains in the center of the panel were determined by electric strain gages. The experimental data are presented by pressure-strain, pressure-maximum-deflection, and pressure-deflection curves. The results of these tests have been compared with the corresponding strains and deflections as calculated by the simple membrane theory and by large deflection theories.
Flutter analysis of two parallel elastically coupled flat plates
NASA Technical Reports Server (NTRS)
Shore, C. P.
1975-01-01
Flutter of two parallel elastically coupled flat plates was investigated analytically. A closed-form solution including both aerodynamic and structural damping is presented for flutter of flat orthotropic plates coupled by an elastic medium. Both plates are simply supported along the side edges but are supported by deflectional, rotational, and torsional springs of arbitrary stiffness at the leading and trailing edges. Two-dimensional quasi-steady aerodynamics was utilized in the solution. Since the large number of variables present in the problem precludes extensive parametric studies, results are presented to indicate the basic flutter characteristics of coupled two-plate systems and to assess the validity of previously published modal solutions for similar problems.
Third generation flat plate solar collector. Final report
Not Available
1983-01-01
The design of a flat plate solar collector that meets an allowable cost constraint is studied. The cost constraint is $5 to 6 per square foot. A medium-temperature collector prototype with a non-thin film absorber was constructed and tested. (BCS)
Certification and verification for Calmac flat plate solar collector
NASA Technical Reports Server (NTRS)
1978-01-01
Information used in the certification and verification of the Calmac Flat Plate Collector is presented. Contained are such items as test procedures and results, information on materials used, installation, operation, and maintenance manuals, and other information pertaining to the verification and certification.
Incipient transition phenomena in compressible flows over a flat plate
NASA Technical Reports Server (NTRS)
Erlebacher, G.; Hussaini, M. Y.
1986-01-01
The full three-dimensional time-dependent compressible Navier-Stokes equations are solved by a Fourier-Chebyshev method to study the stability of compressible flows over a flat plate. After the code is validated in the linear regime, it is applied to study the existence of the secondary instability mechanism in the supersonic regime.
Flat plate solar collector with a cantilevered mirror
Cohen, S.; Larson, D.C.
1981-01-01
The use of flat booster mirrors with flat plate collectors provides moderate solar flux concentration and enhanced performance especially when the mirrors are seasonally adjusted. Curved mirrors provide higher flux concentration and a practical system has been developed where the booster mirror is bent elastically. The system employs a single cantilever mirror which is located below a conventional flat plate collector. The mirror is clamped at the base of the collector panel and its free end is deflected upward; a smaller deflection is used in the fall and winter than in the spring and summer. The prototype system consists of a 0.9 by 2.5 m collector panel mounted on its side (horizontal fluid flow) and a 2.7 by 2.5 m elastic mirror. The mirror is made with aluminum sheet with an adherent aluminized acrylic film. The system has been designed for mounting on horizontal surfaces at latitudes of 10 to 50/sup 0/.
Start-up vortex flow past an accelerated flat plate
NASA Astrophysics Data System (ADS)
Xu, Ling; Nitsche, Monika
2015-03-01
Viscous flow past a finite flat plate accelerating in the direction normal to itself is studied numerically. The plate moves with nondimensional speed tp, where p = 0, 1/2, 1, 2. The work focuses on resolving the flow at early to moderately large times and determining the dependence on the acceleration parameter p. Three stages in the vortex evolution are identified and quantified. The first stage, referred to as the Rayleigh stage [Luchini and Tognaccini, "The start-up vortex issuing from a semi-infinite flat plate," J. Fluid Mech. 455, 175-193 (2002)], consists of a vortical boundary layer of roughly uniform thickness surrounding the plate and its tip, without any separating streamlines. This stage is present only for p > 0, for a time-interval that scales like p3, as p → 0. The second stage is one of self-similar growth. The vortex trajectory and circulation satisfy inviscid scaling laws, the boundary layer thickness satisfies viscous laws. The self-similar trajectory starts immediately after the Rayleigh stage ends and lasts until the plate has moved a distance d = 0.5 to 1 times its length. Finally, in the third stage, the image vorticity due to the finite plate length becomes relevant and the flow departs from self-similar growth. The onset of an instability in the outer spiral vortex turns is also observed, however, at least for the zero-thickness plate considered here, it is shown to be easily triggered numerically by underresolution. The present numerical results are compared with experimental results of Pullin and Perry ["Some flow visualization experiments on the starting vortex," J. Fluid Mech. 97, 239-255 (1980)], and numerical results of Koumoutsakos and Shiels ["Simulations of the viscous flow normal to an impulsively started and uniformly accelerated flat plate," J. Fluid Mech. 328, 177-227 (1996)].
NASA Technical Reports Server (NTRS)
Viswanathan, A. V.; Soong, T.; Miller, R. E., Jr.
1971-01-01
A classical buckling analysis is developed for stiffened, flat plates composed of a series of linked plate and beam elements. Plates are idealized as multilayered orthotropic elements. Structural beads and lips are idealized as beams. The loaded edges of the stiffened plate are simply-supported and the conditions at the unloaded edges can be prescribed arbitrarily. The plate and beam elements are matched along their common junctions for displacement continuity and force equilibrium in an exact manner. Offsets between elements are considered in the analysis. Buckling under uniaxial compressive load for plates, sections, and stiffened plates is investigated. Buckling loads are the lowest of all possible general and local failure modes, and the mode shape is used to determine whether buckling is a local or general instability. Numerical correlations with existing analysis and test data for plates, sections, and stiffened plates including boron-reinforced structures are discussed. In general correlations are reasonably good.
Improved mathematical models of flat-plate solar collectors
Siegler, M.
1986-01-01
This thesis examines various mathematical models of flat-plate solar collectors with the intent of analyzing their strengths and weaknesses and investigating various possible improvements. The purpose is to seek the simplest models that can provide sufficient accuracy for efficient control and design of the collector and for reliable estimation of system parameters. The first part of the thesis investigates the effects of the diffusivity of the collector fluid under steady-state operating conditions. It is shown that under zero flow conditions this diffusivity must be included in the model to accurately describe the rapid changes in the temperatures between adjacent components of the system. The second part of the thesis investigates the relationship between two well-known models for the temperature within the flat-plate solar collector. The simpler of the two models determines the temperature of the collector fluid alone and assumes the collector plate is at the same temperature as the fluid. The other model was separate state equations for the fluid and the collector. Finally, through a frequency analysis of these two different models for the flat-plate collector, it is shown how the thermal effects of the two-temperature model can be imitated by the one-temperature model by adding an artificial diffusion term into the one-temperature model.
On the rotation and pitching of flat plates
NASA Astrophysics Data System (ADS)
Jin, Yaqing; Ji, Sheng; Chamorro, Leonardo P.
2016-11-01
Wind tunnel experiments were performed to characterize the flow-induced rotation and pitching of various flat plates as a function of the thickness ratio, the location of the axis of rotation and turbulence levels. High-resolution telemetry, laser tachometer, and hotwire were used to get time series of the plates motions and the signature of the wake flow at a specific location. Results show that a minor axis offset can induce high-order modes in the plate rotation under low turbulence due to torque unbalance. The spectral decomposition of the flow velocity in the plate wake reveals the existence of a dominating high-frequency mode that corresponds to a static-like vortex shedding occurring at the maximum plate pitch, where the characteristic length scale is the projected width at maximum pitch. The plate thickness ratio shows inverse relation with the angular velocity. A simple model is derived to explain the linear relation between pitching frequency and wind speed. The spectra of the plate rotation show nonlinear relation with the incoming turbulence, and the dominating role of the generated vortices in the plate motions.
On the instability of hypersonic flow past a flat plate
NASA Technical Reports Server (NTRS)
Blackaby, Nicholas; Cowley, Stephen; Hall, Philip
1990-01-01
The instability of hypersonic boundary-layer flows over flat plates is considered. The viscosity of the fluid is taken to be governed by Sutherland's law, which gives a much more accurate representation of the temperature dependence of fluid viscosity at hypersonic speeds than Chapman's approximate linear law; although at lower speeds the temperature variation of the mean state is less pronounced so that the Chapman law can be used with some confidence. Attention is focussed on the so-called (vorticity) mode of instability of the viscous hypersonic boundary layer. This is thought to be the fastest growing inviscid disturbance at hypersonic speeds; it is also believed to have an asymptotically larger growth rate than any viscous or centrifugal instability. As a starting point the instability of the hypersonic boundary layer which exists far downstream from the leading edge of the plate is investigated. In this regime the shock that is attached to the leading edge of the plate plays no role, so that the basic boundary layer is non-interactive. It is shown that the vorticity mode of instability of this flow operates on a significantly different lengthscale than that obtained if a Chapman viscosity law is assumed. In particular, it is found that the growth rate predicted by a linear viscosity law overestimates the size of the growth rate by O(M(exp 2). Next, the development of the vorticity mode as the wavenumber decreases is described, and it is shown that acoustic modes emerge when the wavenumber has decreased from it's O(1) initial value to O(M (exp -3/2). Finally, the inviscid instability of the boundary layer near the leading edge in the interaction zone is discussed and particular attention is focussed on the strong interaction region which occurs sufficiently close to the leading edge. It is found that the vorticity mode in this regime is again unstable, and that it is concentrated in the transition layer at the edge of the boundary layer where the temperature
A dynamic simulation of a flat-plate collector system
NASA Astrophysics Data System (ADS)
Annino, A.
1983-04-01
A numerical model for the performance of a flat plate solar collector array is presented, with account taken of thermal transients and calculation on a microcomputer. The system modeled consists of a flat plate array, the heat transfer fluid, an insulated storage tank, an exchange loop for heating a secondary fluid, and a load maintained by a pump. The one-dimensional analysis includes equations for the energy balances, with consideration given to heat losses to the outside. A function is defined for the total incident solar radiation, and behavior is simulated over the entire 24-hr day, weighted by the highest and lowest recorded temperatures. Good agreement has been found with experimental data.
Turbulent thermal boundary layer on a permeable flat plate
Vigdorovich, I. I.
2007-06-15
Scaling laws are established for the profiles of temperature, turbulent heat flux, rms temperature fluctuation, and wall heat transfer in the turbulent boundary layer on a flat plate with transpiration. In the case of blowing, the temperature distribution represented in scaling variables outside the viscous sublayer has a universal form known from experimental data for flows over impermeable flat plates. In the case of suction, the temperature distribution is described by a one-parameter family of curves. A universal law of heat transfer having the form of a generalized Reynolds analogy provides a basis for representation of the heat flux distributions corresponding to different Reynolds numbers and transpiration velocities in terms of a function of one variable. The results are obtained without invoking any special closure hypotheses.
A useful approximation for the flat surface impulse response
NASA Technical Reports Server (NTRS)
Brown, Gary S.
1989-01-01
The flat surface impulse response (FSIR) is a very useful quantity in computing the mean return power for near-nadir-oriented short-pulse radar altimeters. However, for very small antenna beamwidths and relatively large pointing angles, previous analytical descriptions become very difficult to compute accurately. An asymptotic approximation is developed to overcome these computational problems. Since accuracy is of key importance, a condition is developed under which this solution is within 2 percent of the exact answer. The asymptotic solution is shown to be in functional agreement with a conventional clutter power result and gives a 1.25-dB correction to this formula to account properly for the antenna-pattern variation over the illuminated area.
Qualification testing of flat-plate photovoltaic modules
Hoffman, A.R.; Griffith, J.S.; Ross, R.G. Jr.
1982-08-01
The placement of photovoltaic modules in various applications, in climates and locations throughout the world, results in different degrees and combinations of environmental and electrical stress. Early detection of module reliability deficiencies via laboratory testing is necessary for achieving long, satisfactory field service. This overview paper describes qualification testing techniques being used in the US Department of Energy's flat-plate terrestrial photovoltaic development program in terms of their significance, rationale for specified levels and durations, and test results.
Qualification testing of flat-plate photovoltaic modules
NASA Technical Reports Server (NTRS)
Hoffman, A. R.; Griffith, J. S.; Ross, R. G., Jr.
1982-01-01
The placement of photovoltaic modules in various applications, in climates and locations throughout the world, results in different degrees and combinations of environmental and electrical stress. Early detection of module reliability deficiencies via laboratory testing is necessary for achieving long, satisfactory field service. This overview paper describes qualification testing techniques being used in the US Department of Energy's flat-plate terrestrial photovoltaic development program in terms of their significance, rationale for specified levels and durations, and test results.
Testing flat plate photovoltaic modules for terrestrial environment
NASA Technical Reports Server (NTRS)
Hoffman, A. R.; Arnett, J. C.; Ross, R. G., Jr.
1979-01-01
New qualification tests have been developed for flat plate photovoltaic modules. Temperature cycling, cyclic pressure load, and humidity exposure are especially useful for detecting design and fabrication deficiencies. There is positive correlation between many of the observed field effects, such as power loss, and qualification test induced degradation. The status of research efforts for the development of test methodology for field-related problems is reviewed.
Low-cost solar flat-plate-collector development
NASA Astrophysics Data System (ADS)
Wilhelm, W. G.
Cost goals were developed for the collector which led to the rejection of conventional approaches and to the exploration of thin film technology. A thin film solar absorber suited for high speed continous-roll manufacture at low cost was designed. The absorber comprises two sheets of aluminum-foil/polmeric-material laminate bonded together at intervals to form channels with water as the heat transfer fluid. Several flat-plate panels were fabricated and tested.
Flat plate heat exchangers for the new production reactor
Ondrejcin, R.S.
1988-12-07
The New Production Reactor (NPR) will require heat exchangers (HX) as part of the ancillary equipment. The most common type of heat exchanger in the US is the shell and tube, the type presently in SRP reactor service. This type of design is the one that is normally described in detail in heat transfer texts. Other designs are more efficient, and there was a period when these designs were actively modified. The largest driving force for higher efficiency HX was the OPEC produced energy shortage of the early 1970's. Several comments were made by B.S. Spangler about flat plate HX for the NPR after my initial comparison between shell and tube and flat plate HX (DPST-88-729). Since answers were not readily available, Philippe Marchal of Packinox (Louveciennes, France) agreed to visit SRL. This report contains a series of answers to all comments raised in DPST-88-743 and some general statements comparing flat plate HX to shell and tube HX. 1 fig., 2 tabs.
78 FR 31577 - Diffusion-Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan
Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-24
...)] Diffusion-Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan Determination On the basis of the... reason of imports from Japan of diffusion-annealed, nickel-plated flat-rolled steel products, provided... diffusion-annealed, nickel-plated flat-rolled steel products from Japan. Accordingly, effective March 27...
NASA Technical Reports Server (NTRS)
Viswanathan, A. V.; Tamekuni, M.; Baker, L. L.
1974-01-01
A method is presented to predict theoretical buckling loads of long, rectangular flat and curved laminated plates with arbitrary orientation of orthotropic axes each lamina. The plate is subjected to combined inplane normal and shear loads. Arbitrary boundary conditions may be stipulated along the longitudinal sides of the plate. In the absence of inplane shear loads and extensional-shear coupling, the analysis is also applicable to finite length plates. Numerical results are presented for curved laminated composite plates with boundary conditions and subjected to various loadings. These results indicate some of the complexities involved in the numerical solution of the analysis for general laminates. The results also show that the reduced bending stiffness approximation when applied to buckling problems could lead to considerable error in some cases and therefore must be used with caution.
Radar echo from a flat conducting plate, near and far
NASA Astrophysics Data System (ADS)
Williams, C. S.
1982-01-01
Over certain types of terrain, a radar fuze (or altimeter), by virtue of the horizontal component of its velocity, is likely to pass over various flat objects of limited size. The echo from such objects could have a duration less than that of one Doppler cycle, where the Doppler frequency is due to the vertical component of the velocity. If the terrain is principally made up of such objects, their echoes are in most cases entirely uncorrelated with each other. Hence, the total echo after mixing at the radar with the delayed transmitted wave would have a noise-like spectrum not at all confined to the Doppler-frequency band where the desired echo signal is expected. This would seriously degrade the performance of a radar that utilizes correlation. This work shows that the echo from a square flat plate will be of duration greater than the time it takes to pass over the plate if the height h above it satisfies h a squared lambda where a is the plate-edge dimension and lambda is the radar wavelength. The results presented here can be used to determine the spatial region wherein the echo exists, and the magnitude and phase of the echo from such a plate.
Radar echo from a flat conducting plate - near and far
Williams, C.S.
1982-01-01
Over certain types of terrain, a radar fuze (or altimeter), by virtue of the horizontal component of its velocity, is likely to pass over various flat objects of limited size. The echo from such objects could have a duration less than that of one Doppler cycle, where the Doppler frequency is due to the vertical component of the velocity. If the terrain is principally made up of such objects, their echoes are in most cases entirely uncorrelated with each other. Hence, the total echo after mixing at the radar with the delayed transmitted wave would have a noise-like spectrum not at all confined to the Doppler-frequency band where the desired echo signal is expected. This would seriously degrade the performance of a radar that utilizes correlation. This work shows that the echo from a square flat plate will be of duration greater than the time it takes to pass over the plate if the height h above it satisfies h > a/sup 2//lambda where a is the plate-edge dimension and lambda is the radar wavelength. The results presented here can be used to determine the spatial region wherein the echo exists, and the magnitude and phase of the echo from such a plate. I infer from these results that the case where the signal has a noise-like spectrum is not impossible but it is unlikely for the applications with which I am familiar.
Pure and aerated water entry of a flat plate
NASA Astrophysics Data System (ADS)
Ma, Z. H.; Causon, D. M.; Qian, L.; Mingham, C. G.; Mai, T.; Greaves, D.; Raby, A.
2016-01-01
This paper presents an experimental and numerical investigation of the entry of a rigid square flat plate into pure and aerated water. Attention is focused on the measurement and calculation of the slamming loads on the plate. The experimental study was carried out in the ocean basin at Plymouth University's COAST laboratory. The present numerical approach extends a two-dimensional hydro-code to compute three-dimensional hydrodynamic impact problems. The impact loads on the structure computed by the numerical model compare well with laboratory measurements. It is revealed that the impact loading consists of distinctive features including (1) shock loading with a high pressure peak, (2) fluid expansion loading associated with very low sub-atmospheric pressure close to the saturated vapour pressure, and (3) less severe secondary reloading with super-atmospheric pressure. It is also disclosed that aeration introduced into water can effectively reduce local pressures and total forces on the flat plate. The peak impact loading on the plate can be reduced by half or even more with 1.6% aeration in water. At the same time, the lifespan of shock loading is prolonged by aeration, and the variation of impulse is less sensitive to the change of aeration than the peak loading.
NASA Astrophysics Data System (ADS)
Ambarita, Himsar; Kishinami, Koki; Daimaruya, Mashashi; Tokura, Ikuo; Kawai, Hideki; Suzuki, Jun; Kobiyama, Mashayosi; Ginting, Armansyah
The present paper is a study on the optimum plate to plate spacing for maximum heat transfer rate from a flat plate type heat exchanger. The heat exchanger consists of a number of parallel flat plates. The working fluids are flowed at the same operational conditions, either fixed pressure head or fixed fan power input. Parallel and counter flow directions of the working fluids were considered. While the volume of the heat exchanger is kept constant, plate number was varied. Hence, the spacing between plates as well as heat transfer rate will vary and there exists a maximum heat transfer rate. The objective of this paper is to seek the optimum plate to plate spacing for maximum heat transfer rate. In order to solve the problem, analytical and numerical solutions have been carried out. In the analytical solution, the correlations of the optimum plate to plate spacing as a function of the non-dimensional parameters were developed. Furthermore, the numerical simulation is carried out to evaluate the correlations. The results show that the optimum plate to plate spacing for a counter flow heat exchanger is smaller than parallel flow ones. On the other hand, the maximum heat transfer rate for a counter flow heat exchanger is bigger than parallel flow ones.
Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.
Dechant, Lawrence; Smith, Justin
2016-01-01
Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by
Weathering performance of cover materials for flat plate solar collectors
NASA Astrophysics Data System (ADS)
Clark, E. J.; Roberts, W. E.
1982-11-01
Weathering studies were performed to obtain data on the performance and durability of cover plate materials for flat plate solar collectors used in solar heating and cooling systems. Ten materials were evaluated to assess their durability after natural weathering and artificial weathering with a xenon arc light. The materials were weathered for four years on small mini-collectors in Arizona, Florida, and Maryland after which the solar energy transmittance and the effect of dirt on the transmittance were measured. The tensile properties of selected film materials were also assessed after weathering. The effects of the natural weathering are compared for materials exposed as inner and outer cover plates for each weathering site, for the three weathering sites, and with materials artificially weathered with a xenon arc light.
Circulation shedding in viscous starting flow past a flat plate
NASA Astrophysics Data System (ADS)
Nitsche, Monika; Xu, Ling
2013-11-01
Numerical simulations of viscous flow past a flat plate moving in direction normal to itself reveal details of the vortical structure of the flow. At early times, most of the vorticity is attached to the plate. We introduce a definition of the shed circulation at all times and show that it indeed represents vorticity that separates and remains separated from the plate. Scaling laws for the shed circulation, and contributions to the shedding rate across various boundary components are presented, as well as their dependence on Reynolds number. The simulations provide benchmark results to evaluate simpler separation models such as point vortex and vortex sheet models. A comparison with vortex sheet results is included.
Large Angle Unsteady Aerodynamic Theory of a Flat Plate
NASA Astrophysics Data System (ADS)
Manar, Field; Jones, Anya
2016-11-01
A purely analytical approach is taken for the evaluation of the unsteady loads on a flat plate. This allows for an extremely low cost theoretical prediction of the plate loads in the style of Wagner and Theodorsen, without making the assumption of small angle of attack or small disturbance flow. The forces and moments are evaluated using the time rate of change of fluid momentum, expressed as an integral of the vorticity field. The flow is taken as inviscid and incompressible with isolated vorticity bound to the plate and in the shed wake. The bound vorticity distribution on the plate is solved exactly using conformal mapping of the plate to a cylinder. In keeping with the original assumption of Wagner, the wake vorticity is assumed to remain stationary in an inertial reference frame and convection is disregarded. Formulation in this manner allows for a closed form solution of Wagner's problem valid at all angles of attack. Separation from the leading edge of the plate can also be included to further increase the fidelity of the model at high angles.
Accuracy of the Kirchoff formula in determining acoustic shielding with the use of a flat plate
NASA Technical Reports Server (NTRS)
Gabrielsen, R. E.; Davis, J. E.
1977-01-01
It has been suggested that if jet engines of aircraft were placed at above the wing instead of below it, the wing would provide a partial shielding of the noise generated by the engines relative to observers on the ground. The shielding effects of an idealized three-dimensional barrier in the presence of an idealized engine noise source was predicted by the Kirchoff formula. Based on the good agreement between experimental measurements and the numerical results of the current study, it was concluded that the Kirchoff approximation provides a good qualitative estimate of the acoustic shielding of a point source by a rectangular flat plate for measurements taken in the far field of the flat plate at frequencies ranging from 1 kHz to 20 kHz. At frequencies greater than 4 kHz the Kirchoff approximation provides accurate quantitative predictions of acoustic shielding.
Lift generation on a flat plate with unsteady motions
NASA Astrophysics Data System (ADS)
Xia, Xi; Mohseni, Kamran
2013-11-01
The leading edge vortex (LEV) on an airfoil or wing has been considered to be one of the most important sources of lift enhancement according to several previous experimental and theoretical studies. In this work, the unsteady 2D potential flow theory is employed to model the flow field of a flat plate wing undergoing unsteady motions. A multi-vortices model is developed to model both the leading edge and trailing edge vortices (TEVs), which offers improved accuracy compared with using only single vortex at each separation location. The lift prediction is obtained by integrating the unsteady Blasius equation. It is found that the motion of vortices contributes significantly to the overall aerodynamic force on the flat plate. The results of the simulation are then compared with classical numerical, theoretical and experimental data for canonical unsteady flat plat problems. Good agreement with these data is observed. Moreover, these results suggests that the leading edge vortex shedding for small angles of attack should be modeled differently than that for large angles of attack. Finally, the results of vortex motion vs. lift indicate that the lift enhancement during the LEV ``stabilization'' above the wing is a combined effect of both the LEV and TEV motion.
A high performance porous flat-plate solar collector
NASA Technical Reports Server (NTRS)
Lansing, F. L.; Clarke, V.; Reynolds, R.
1979-01-01
A solar collector employing a porous matrix as a solar absorber and heat exchanger is presented and its application in solar air heaters is discussed. The collector is composed of a metallic matrix with a porous surface which acts as a large set of cavity radiators; cold air flows through the matrix plate and exchanges heat with the thermally stratified layers of the matrix. A steady-state thermal analysis of the collector is used to determine collector temperature distributions for the cases of an opaque surface matrix with total absorption of solar energy at the surface, and a diathermanous matrix with successive solar energy absorption at each depth. The theoretical performance of the porous flat plate collector is shown to exceed greatly that of a solid flat plate collector using air as the working medium for any given set of operational conditions. An experimental collector constructed using commercially available, low cost steel wool as the matrix has been found to have thermal efficiencies from 73 to 86%.
Evaluation of flat-Earth approximation results for geopotential missions.
NASA Astrophysics Data System (ADS)
Tapley, M. B.
1997-04-01
Simplified calculations can approximate the formal uncertainties in estimates of the spherical harmonic coefficients representing the Earth's gravitational potential. The calculations model the Earth locally as a plane, producing errors negligible for wavelengths shorter than the radius of the Earth. Information derived from observations of low altitude polar orbiting satellites is considered. With some constraints, the final model uncertainties derive from a priori gravitational field information, specific orbital elements, and parameters describing instrumentation characteristics. The author demonstrates how to refine the technique to accept inputs from the currently operational Navstar Global Positioning System (GPS) constellation and how to use information from partial tensor gravitational gradiometers. This approach is beneficial when evaluating prospective satellite geodesy missions because the covariance analyses for various mission scenarios can be made efficiently and expeditiously. The author demonstrates the utility of the flat Earth approach by comparing results with those of more elaborate and time consuming calculations performed for the European Space Agency ARISTOTELES proposed geopotential mapping mission, the NASA Gravity Probe B Relativity mission, and the NASA/Center National d'Etudes Spatiales Topographic Ocean Experiment Satellite (TOPEX)/Poseidon mission.
Reconfiguration of a flexible flat plate under snow loading
NASA Astrophysics Data System (ADS)
Gosselin, Frédérick; de Langre, Emmanuel
2015-11-01
Snow and wind constitute two of the main sources of mechanical loading on terrestrial plants. Plants bend and twist with large amplitude to bear these loads. For the past ten years, various authors have sought to decompose the problem of plant reconfiguration under fluid flow into its fundamental mechanical ingredients by studying the reconfiguration of simple flexible structures such as beams, plates, rods and strips. Here, we adopt a similar approach to these studies and consider the snow interception of a flexible flat plate. We performed two sets of experiments on thin flexible rectangular plates supported at their center: in the first one, a plate was subjected to real snowing events; in the second one, a plate was loaded with glass beads acting as a granular media similar to snow. Moreover, a theoretical model coupling the Elastica formulation to a loading with a set angle of repose is developed. The model is found to be in good agreement with the experiments on glass beads. Asymptotic scaling laws can be found similarly to the Vogel exponents of reconfiguring structures. For the real snow loading, it is found that the cohesive force in snow which is highly dependent on the snow temperature complicate things greatly.
Lift evaluation of a two-dimensional pitching flat plate
NASA Astrophysics Data System (ADS)
Xia, X.; Mohseni, K.
2013-09-01
Several previous experimental and theoretical studies have shown that a leading edge vortex (LEV) on an airfoil or wing can provide lift enhancement. In this paper, unsteady two-dimensional (2D) potential flow theory is employed to model the flow field of a pitching flat plate wing. A multi-vortices model is developed to model both the leading edge and trailing edge vortices (TEVs), which offers improved accuracy compared with using only single vortex at each separation location. The lift is obtained by integrating the unsteady Blasius equation. It is found that the motion of vortices contributes significantly to the overall aerodynamic force on the flat plate. A Kutta-like condition is used to determine the vortex intensity and location at the leading edge for large angle of attack cases; however, it is proposed to relax this condition for small angle of attack cases and apply a 2D shear layer model to calculate the circulation of the new added vortex. The results of the simulation are then compared with classical numerical, theoretical, and experimental data for canonical unsteady flat plat problems. Good agreement with these data is observed. Moreover, these results suggested that the leading edge vortex shedding for small angles of attack should be modeled differently than that for large angles of attack. Finally, the results of vortex motion vs. lift indicate that the slow convection of the LEV creates less negative lift while the rapid shedding of the TEV creates more positive lift. The difference between these two contributions of lift results in a total positive lift that lasts for about two chord-length travel of the plate. It is therefore concluded that the lift enhancement during the LEV "stabilization" above the wing is a combined effect of both the LEV and TEV motion. This also provides the insights for future active flow control of micro aerial vehicles (MAVs) that the formation and shedding process of LEVs and TEVs can be manipulated to provide lift
Environmental testing of flat plate solar cell modules
NASA Technical Reports Server (NTRS)
Griffith, J.; Dumas, L.; Hoffman, A.
1978-01-01
Commercially available flat-plate solar cell modules have been subjected to a variety of environmental tests designed to simulate service conditions. Among the tests are those simulating heat and rain, wind-driven rains, humidity and freezing, humidity and heat, humidity with a voltage bias, salt fog, hail impact, and fungus infestation. Tests for optical surface soiling and the combined effects of temperature, humidity and UV irradiation are under development. A correlation has been demonstrated between degradation caused by the qualification tests and such observed field effects as power loss.
High Performance Flat Plate Solar Thermal Collector Evaluation
Rockenbaugh, Caleb; Dean, Jesse; Lovullo, David; Lisell, Lars; Barker, Greg; Hanckock, Ed; Norton, Paul
2016-09-01
This report was prepared for the General Services Administration by the National Renewable Energy Laboratory. The Honeycomb Solar Thermal Collector (HSTC) is a flat plate solar thermal collector that shows promising high efficiencies over a wide range of climate zones. The technical objectives of this study are to: 1) verify collector performance, 2) compare that performance to other market-available collectors, 3) verify overheat protection, and 4) analyze the economic performance of the HSTC both at the demonstration sites and across a matrix of climate zones and utility markets.
Parameter Studies on Rotational and Translational Accelerations of Flat Plates
2013-01-01
A., and Schlueter, K. “The Effects of Wall Boundaries on the Flow Field of a Rotating Wing”. AIAA 2012-2776. 7 OL, M. V., Bernal , L., Kang, C.-K...K., OL, M., and Bernal , L. “Experiments on Pitching Plates: Force and Flowfield Measurements at Low Reynolds Numbers”. AIAA – 2011- 0872 9...Granlund, K., OL, M., Bernal , L., and Kast, S. “Experiments on Free-to-Pivot Hover Motions of Flat Plates”. AIAA-2010- 4456. 10 McGowan, G., Granlund, K
Increasing thermal efficiency of solar flat plate collectors
NASA Astrophysics Data System (ADS)
Pona, J.
A study of methods to increase the efficiency of heat transfer in flat plate solar collectors is presented. In order to increase the heat transfer from the absorber plate to the working fluid inside the tubes, turbulent flow was induced by installing baffles within the tubes. The installation of the baffles resulted in a 7 to 12% increase in collector efficiency. Experiments were run on both 1 sq ft and 2 sq ft collectors each fitted with either slotted baffles or tubular baffles. A computer program was run comparing the baffled collector to the standard collector. The results obtained from the computer show that the baffled collectors have a 2.7% increase in life cycle cost (LCC) savings and a 3.6% increase in net cash flow for use in domestic hot water systems, and even greater increases when used in solar heating systems.
Measurement of flat-plate collector heat loss coefficients
NASA Astrophysics Data System (ADS)
Nahar, N. M.
1981-04-01
An indoor method for direct measurement of the overall heat loss coefficient is developed so that solar energy can be more efficiently trapped by optimized flat-plate solar collectors. A schematic diagram of the indoor test set-up is given, with liquid temperature controlled by an electrical contact thermometer, and relay circulated by a pump to maintain a constant flow rate. The overall heat loss coefficient is measured in a bond duct type collector with single and double glazings, and is found to vary from 3.5 to 4.7 per sq Wm-K with zero wind speed. The coefficient is also reported for controlled wind speeds, and heat losses are found to increase by 13.5 and 7.5% for single and double glazed collectors respectively. The coefficient is presented as a function of plate temperature, and results are compared with calculated values, demonstrating good agreement.
On the instability of hypersonic flow past a flat plate
NASA Technical Reports Server (NTRS)
Blackaby, Nicholas D.; Cowley, Stephen J.; Hall, Philip
1993-01-01
Qualitative features of the inviscid instability characteristics of hypersonic boundary-layer flows over a flat plate are considered. The instability of a viscous hypersonic boundary layer which exists far downstream from the leading edge of the plate. It is shown that the vorticity mode of instability operates on a different lengthscale from that obtained using a Chapman viscosity law. The growth rate predicted by a linear viscosity law is found to overestimate the size of the growth rate. The inviscid instability of the boundary layer near the leading edge interaction zone is discussed focusing on the strong-interaction zone which occurs sufficiently close to the leading edge. The vorticity mode in this regime is found to be unstable.
Forced Convection and Sedimentation Past a Flat Plate
NASA Technical Reports Server (NTRS)
Pelekasis, Nikolaos A.; Acrivos, Andreas
1995-01-01
The steady laminar flow of a well-mixed suspension of monodisperse solid spheres, convected steadily past a horizontal flat plate and sedimenting under the action of gravity, is examined. It is shown that, in the limit as Re approaches infinity and epsilon approaches 0, where Re is the bulk Reynolds number and epsilon is the ratio of the particle radius a to the characteristic length scale L, the analysis for determining the particle concentration profile has several aspects in common with that of obtaining the temperature profile in forced-convection heat transfer from a wall to a fluid stream moving at high Reynolds and Prandtl numbers. Specifically, it is found that the particle concentration remains uniform throughout the O(Re(exp -1/2)) thick Blasius boundary layer except for two O(epsilon(exp 2/3)) thin regions on either side of the plate, where the concentration profile becomes non-uniform owing to the presence of shear-induced particle diffusion which balances the particle flux due to convection and sedimentation. The system of equations within this concentration boundary layer admits a similarity solution near the leading edge of the plate, according to which the particle concentration along the top surface of the plate increases from its value in the free stream by an amount proportional to X(exp 5/6), with X measuring the distance along the plate, and decreases in a similar fashion along the underside. But, unlike the case of gravity settling on an inclined plate in the absence of a bulk flow at infinity considered earlier, here the concentration profile remains continuous everywhere. For values of X beyond the region near the leading edge, the particle concentration profile is obtained through the numerical solution of the relevant equations. It is found that, as predicted from the similarity solution, there exists a value of X at which the particle concentration along the top side of the plate attains its maximum value phi(sub m) and that, beyond this
Modal characterization of composite flat plate models using piezoelectric transducers
NASA Astrophysics Data System (ADS)
Oliveira, É. L.; Maia, N. M. M.; Marto, A. G.; da Silva, R. G. A.; Afonso, F. J.; Suleman, A.
2016-10-01
This paper aims to estimate the modal parameters of composite flat plate models through Experimental Modal Analysis (EMA) using piezoelectric transducers. The flat plates are composed of three ply carbon-epoxy fibers oriented in the same direction. Five specimens with different unidirectional fiber nominal orientations θk (0o, 30o, 45o, 60o and 90o) were tested. These models were instrumented with one PZT (Lead Zirconate Titanate) actuator and one PVDF (Polyvinylidene Fluoride) sensor and an EMA was performed. The natural frequencies and damping factors estimated using only a single PVDF response were compared with the estimated results using twelve measurement points acquired by laser doppler vibrometry. For comparison purposes, the percentage error of each natural frequency estimation and the percentage error of the damping factor estimations were computed, as well as their averages. Even though the comparison was made between a SISO (Single-Input, Single-Output) and a SIMO (Single-Input, Multiple-Output) techniques, both results are very close. The vibration modes were estimated by means of laser measurements and were used in the modal validation. In order to verify the accuracy of the modal parameters, the Modal Assurance Criterion (MAC) was employed and a high correlation among mode shapes was observed.
46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 5 2013-10-01 2013-10-01 false Sighting ports, tubular gauge glasses, and flat plate... glasses, and flat plate type gauge glasses. (a) Cargo tanks may have sighting ports as a secondary means... cargo tanks. (c) Plate type gauge glasses must not be liquid level gauges for cargo tanks, except deck...
46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 5 2014-10-01 2014-10-01 false Sighting ports, tubular gauge glasses, and flat plate... glasses, and flat plate type gauge glasses. (a) Cargo tanks may have sighting ports as a secondary means... cargo tanks. (c) Plate type gauge glasses must not be liquid level gauges for cargo tanks, except deck...
46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 5 2011-10-01 2011-10-01 false Sighting ports, tubular gauge glasses, and flat plate... glasses, and flat plate type gauge glasses. (a) Cargo tanks may have sighting ports as a secondary means... cargo tanks. (c) Plate type gauge glasses must not be liquid level gauges for cargo tanks, except deck...
46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 46 Shipping 5 2012-10-01 2012-10-01 false Sighting ports, tubular gauge glasses, and flat plate... glasses, and flat plate type gauge glasses. (a) Cargo tanks may have sighting ports as a secondary means... cargo tanks. (c) Plate type gauge glasses must not be liquid level gauges for cargo tanks, except deck...
Circulation shedding in viscous starting flow past a flat plate
NASA Astrophysics Data System (ADS)
Nitsche, Monika; Xu, Ling
2014-12-01
Numerical simulations of viscous flow past a flat plate moving in the direction normal to itself reveal details of the vortical structure of the flow. At early times, most of the vorticity is attached to the plate. This paper introduces a definition of the shed circulation at all times and shows that it indeed represents vorticity that separates and remains separated from the plate. During a large initial time period, the shed circulation satisfies the scaling laws predicted for self-similar inviscid separation. Various contributions to the circulation shedding rate are presented. The results show that during this initial time period, viscous diffusion of vorticity out of the vortex is significant but appears to be independent of the value of the Reynolds number. At later times, the departure of the shed circulation from its large Reynolds number behaviour is significantly affected by diffusive loss of vorticity through the symmetry axis. A timescale is proposed that describes when the viscous loss through the axis becomes relevant. The simulations provide benchmark results to evaluate simpler separation models such as point vortex and vortex sheet models. A comparison with vortex sheet results is included.
Vortex Formation Behind an Inclined 2-Dimensional Thin Flat Plate
NASA Astrophysics Data System (ADS)
Mohebi, Meraj; Wood, David H.; Martinuzzi, Robert J.
2014-11-01
Stereo Particle Image Velocimetry was used to measure the turbulent wake of a 2D flat plate inclined relative to a uniform stream as a heuristic model for airfoils and wind turbine blades at high incidence. Phase Averaging was performed to study the vortex dynamics and relate these to the force characteristics. Below 90°, immediately behind the plate, rounder and more organized trailing edge vortices form which possess higher circulation and are associated with higher Reynolds stresses than the counter-rotating, weaker and elongated leading edge vortices. The quasi-periodically shed vortices on the sides of the wake decay in strength at different rates to reach a circulation ratio of -1 within a distance less than 5 chords downstream of the plate for all angles. This equalization of vortex strength is related to an increase in turbulence diffusion, due to mostly-incoherent 3-dimensionality which progressively increases as the inclination angle is reduced, and convective transfer of vorticity between counter-rotating vortices. The wake experiences a sudden change in vortex formation mechanism at around 40°. At this angle, the frequency analysis on the signals of a pair of micro-pressure transducers in the wake also shows a discontinuity in the trends. This work was supported by NSERC Discovery grants to R. J. Martinuzzi and D. H. Wood.
Flat-plate solar array project. Volume 7: Module encapsulation
NASA Technical Reports Server (NTRS)
Cuddihy, E.; Coulbert, C.; Gupta, A.; Liang, R.
1986-01-01
The objective of the Encapsulation Task was to develop, demonstrate, and qualify photovoltaic (PV) module encapsulation systems that would provide 20 year (later decreased to 30 year) life expectancies in terrestrial environments, and which would be compatible with the cost and performance goals of the Flat-Plate Solar Array (FSA) Project. The scope of the Encapsulation Task included the identification, development, and evaluation of material systems and configurations required to support and protect the optically and electrically active solar cell circuit components in the PV module operating environment. Encapsulation material technologies summarized include the development of low cost ultraviolet protection techniques, stable low cost pottants, soiling resistant coatings, electrical isolation criteria, processes for optimum interface bonding, and analytical and experimental tools for evaluating the long term durability and structural adequacy of encapsulated modules. Field testing, accelerated stress testing, and design studies have demonstrated that encapsulation materials, processes, and configurations are available that meet the FSA cost and performance goals.
System Advisor Model: Flat Plate Photovoltaic Performance Modeling Validation Report
Freeman, Janine; Whitmore, Jonathan; Kaffine, Leah; Blair, Nate; Dobos, Aron P.
2013-12-01
The System Advisor Model (SAM) is a free software tool that performs detailed analysis of both system performance and system financing for a variety of renewable energy technologies. This report provides detailed validation of the SAM flat plate photovoltaic performance model by comparing SAM-modeled PV system generation data to actual measured production data for nine PV systems ranging from 75 kW to greater than 25 MW in size. The results show strong agreement between SAM predictions and field data, with annualized prediction error below 3% for all fixed tilt cases and below 8% for all one axis tracked cases. The analysis concludes that snow cover and system outages are the primary sources of disagreement, and other deviations resulting from seasonal biases in the irradiation models and one axis tracking issues are discussed in detail.
Flat-plate solar array project. Volume 5: Process development
NASA Technical Reports Server (NTRS)
Gallagher, B.; Alexander, P.; Burger, D.
1986-01-01
The goal of the Process Development Area, as part of the Flat-Plate Solar Array (FSA) Project, was to develop and demonstrate solar cell fabrication and module assembly process technologies required to meet the cost, lifetime, production capacity, and performance goals of the FSA Project. R&D efforts expended by Government, Industry, and Universities in developing processes capable of meeting the projects goals during volume production conditions are summarized. The cost goals allocated for processing were demonstrated by small volume quantities that were extrapolated by cost analysis to large volume production. To provide proper focus and coverage of the process development effort, four separate technology sections are discussed: surface preparation, junction formation, metallization, and module assembly.
Stability of a hypersonic shock layer on a flat plate
NASA Astrophysics Data System (ADS)
Maslov, Anatoly A.; Poplavskaya, Tatiana V.; Smorodsky, Boris V.
2004-11-01
Stability of a hypersonic shock layer on a flat plate is examined with allowance for disturbances conditions on the shock wave within the framework of the linear stability theory. The characteristics of the main flow are calculated on the basis of the Full Viscous Shock Layer model. Conditions for velocity, pressure, and temperature perturbations are derived from steady Rankine-Hugoniot relation on the shock wave. These conditions are used as boundary conditions on the shock wave for linear stability equations. The growth rates of disturbances and density fluctuations are compared with experimental data obtained at ITAM by the method of electron-beam fluorescence and with theoretical data of other authors. To cite this article: A.A. Maslov et al., C. R. Mecanique 332 (2004).
Wind loads on flat plate photovoltaic array fields (nonsteady winds)
NASA Technical Reports Server (NTRS)
Miller, R. D.; Zimmerman, D. K.
1981-01-01
Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.
Flat-plate /vapor-chamber/ heat pipes
NASA Technical Reports Server (NTRS)
Fleischman, G. L.; Marcus, B. D.; Mcintosh, R.; Ollendorf, S.
1975-01-01
This paper discusses the design, fabrication and testing of heat pipes constructed in the form of flat-plate panels. The test panels were constructed of copper with methyl alcohol as the working fluid. Capillary grooves etched on the internal surfaces provided evaporation and condensation heat-transfer coefficients on the order of 1600 Btu/hr-sq ft-deg F. Two panels were launched on board a sounding rocket; the payload reached an altitude of 140 miles, and zero gravity was achieved for almost six minutes. The panel with working fluid inside demonstrated a heat input flux of 2.5 watts/sq cm, with only a 3 to 5 C temperature difference throughout the entire panel.
Evolution Of Traveling Crossflow Modes Over A Swept Flat Plate
NASA Astrophysics Data System (ADS)
Kurian, Thomas; Fransson, Jens H. M.; Alfredsson, P. Henrik
An experimental investigation has been carried out to examine the growth of traveling crossflow instabilities over a swept flat plate mimicking the Falkner Skan-Cooke boundary layer. Different turbulence generating grids were placed upstream of the leading edge to vary incoming parameters. Hot-wire measurements were taken for one component of velocity and compared with linear PSE analysis. These showed a decrease in the growth rate for increasing turbulence intensity, which was most likely cause by nonlinear effects. Streamwise correlation measurements were also taken. All the cases except one triggered the same spanwise integral length scale inside the boundary layer. Receptivity coefficients are needed to do the PSE calculations and to see the need for nonlinear PSE.
Flat-plate solar array project. Volume 1: Executive summary
NASA Technical Reports Server (NTRS)
Callaghan, W.; Mcdonald, R.
1986-01-01
In 1975, the U.S. Government contracted the Jet Propulsion Lab. to develop, by 1985, in conjunction with industry, the photovoltaics (PV) module and array technology required for widespread use of photovoltaics as a significant terrestrial energy source. As a result, a project that eventually became known as the Flat Plate Solar Array (FSA) Project was formed to manage an industry, university, and Government team to perform the necessary research and development. The original goals were to achieve widespread commercial use of PV modules and arrays through the development of technology that would allow them to be profitably sold for $1.07/peak watts (1985 dollars). A 10% module conversion efficiency and a 20 year lifetime were also goals. It is intended that the executive summary provide the means by which one can gain a perspective on 11 years of terrestrial photovoltaic research and development conducted by the FSA Project.
Experimental observation of transition behavior on a flat plate
NASA Technical Reports Server (NTRS)
Nagamatsu, H. T.
1985-01-01
In studying transition behavior a shock tube and tunnel were used to produce high temperatures, and thin-film platinum heat gauges were used to measure local heat flux as well as to detect the transition of the laminar boundary layer over a flat plate and a cone. Initial investigations were conducted in the hypersonic shock tunnel to obtain high-temperature information for the development of an ICBM nose cone. Shock Mach numbers as large as 50 with a temperature of 15,000 K after the incident wave were produced in the driven tube. Shock tubes are used to investigate the heat transfer over various surfaces to 2500 K for the development of future gas turbines.
Comparison of performance of flat plate and parabolic trough solar collectors in several US cities
Stromberg, R.P.; Bush, L.D.
1981-01-01
One very common use of the flat plate collector is residential water heating. Concentrating thermal collectors have been developed for much higher temperature uses, based on the knowledge that the upper limit on output from the flat plate collector is roughly at the boiling point of water. Total annual outputs are extensively compared. There is a significant variation in relative performance of flat plate and concentrating collectors in different climates. There is a noticeable variation in relative output from winter to summer. In some parts of the United States the weather conditions of winter favor the use of concentrating collectors over flat plate collectors for residential water heating.
Rarefied flow past a flat plate at incidence
NASA Technical Reports Server (NTRS)
Dogra, Virendra K.; Moss, James N.; Price, Joseph M.
1989-01-01
Results of a numerical study using the direct simulation Monte Carlo (DSMC) method are presented for the transitional flow about a flat plate at 40 deg incidence. The plate has zero thickness and a length of 1.0 m. The flow conditions simulated are those experienced by the Shuttle Orbiter during reentry at 7.5 km/s. The range of freestream conditions are such that the freestream Knudsen number values are between 0.02 and 8.4, i.e., conditions that encompass most of the transitional flow regime. The DSMC simulations show that transitional effects are evident when compared with free molecule results for all cases considered. The calculated results demonstrate clearly the necessity of having a means of identifying the effects of transitional flow when making aerodynamic flight measurements as are currently being made with the Space Shuttle Orbiter vehicles. Previous flight data analyses have relied exclusively on adjustments in the gas-surface interaction models without accounting for the transitional effect which can be comparable in magnitude. The present calculations show that the transitional effect at 175 km would increase the Space Shuttle Orbiter lift-drag ratio by 90 percent over the free molecule value.
Rarefied flow past a flat plate at incidence
NASA Technical Reports Server (NTRS)
Dogra, Virendra K.; Moss, James N.; Price, Joseph M.
1988-01-01
Results of a numerical study using the direct simulation Monte Carlo (DSMC) method are presented for the transitional flow about a flat plate at 40 deg incidence. The plate has zero thickness and a length of 1.0 m. The flow conditions simulated are those experienced by the Shuttle Orbiter during reentry at 7.5 km/s. The range of freestream conditions are such that the freestream Knudsen number values are between 0.02 and 8.4, i.e., conditions that encompass most of the transitional flow regime. The DSMC simulations show that transitional effects are evident when compared with free molecule results for all cases considered. The calculated results demonstrate clearly the necessity of having a means of identifying the effects of transitional flow when making aerodynamic flight measurements as are currently being made with the Space Shuttle Orbiter vehicles. Previous flight data analyses have relied exclusively on adjustments in the gas-surface interaction models without accounting for the transitional effect which can be comparable in magnitude. The present calculations show that the transitional effect at 175 km would increase the Space Shuttle Orbiter lift-drag ratio by 90 percent over the free molecule value.
Gordon, J.M.
1986-08-01
Low-concentration, stationary, nonimaging concentrators (CPC's) with flat receivers illuminated on both sides are considered as viable alternatives to flat-plate solar collectors. Closed-form, analytic formulae are derived for the geometric characteristics of two concentrator types of greatest interest (i.e., stationary collectors for year-round energy delivery), which enable calculations of collectible energy without computer ray-tracing stimulations. The relative merits of these concentrators in terms of energy collection and production costs are assessed with respect to each other as well as to flat-plate collectors.
LDEF (Flight), S1005 : Transverse Flat-Plate Heat Pipe Experiment, Tray B10
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Flight), S1005 : Transverse Flat-Plate Heat Pipe Experiment, Tray B10 EL-1994-00017 The Transverse Flat-Plate Heat Pipe Experiment flight photograph was taken while the LDEF was attached to the Orbiter's RMS arm prior to berthing in the Orbiter's cargo bay. No change in the color of the white paint dots on experiment tray clamp blocks is apparent. The Transverse Flat-Plate Heat Pipe Experiment consist of three (3) transverse flat heat-pipe modules , a power system for the heaters, a data acquisition and storage system and an aluminum support structure placed in a twelve (12) inch deep LDEF experiment tray. The surface of the experiment exposed to the space environment consist of the three heat pipe modules exterior surfaces, silver TEFLON®, and the thermal blankets covering the aluminum mounting hardware and openings between the hardware and the tray sidewalls. The raised surface at the top of each heat pipe module is the fluid reservoir. Five thermocouples, for monitoring the external surface temperature, are located on each module. The specular surface of the silver TEFLON® has become diffuse and appears white. Numerous impact craters, black specks, can be seen on the white surfaces of the modules. There appears to be a light tan discoloration on the surfaces of all three heat pipe modules. Two different types of discolorations can be seen at the top end of the center heat pipe; a dark brown color to the left of the thermocouple and what appears as two multi-color irregular shaped patterns to the right of the thermocouple. A square shaped light brown discoloration is seen near the left edge of the left thermal blanket, approximately half way between the tray bottom and center clamp blocks and also near the top of the thermal blanket between the left heat pipe module and the center heat pipe module.
Low-cost, high-performance solar flat-plate collectors for applications in northern latitudes
Wilhelm, W.G.
1981-01-01
Solar flat plate collector designs have been developed which incorporate high performance polymer film and laminate technology that have a projected manufacturing cost approaching $15/m/sup 2/ and potential thermal performance consistent with the best commercial solar flat plate collectors available today.
46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Sighting ports, tubular gauge glasses, and flat plate type gauge glasses. 154.1320 Section 154.1320 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... glasses, and flat plate type gauge glasses. (a) Cargo tanks may have sighting ports as a secondary...
Flat-plate boiloff calorimeters for testing of thermal insulation systems
NASA Astrophysics Data System (ADS)
Fesmire, J. E.; Johnson, W. L.; Kelly, A. O.; Meneghelli, B. J.; Swanger, A. M.
2015-12-01
Cryostats have been developed and standardized for laboratory testing of thermal insulation systems in a flat-plate configuration. Boiloff calorimetry is the measurement principle for determining the effective thermal conductivity (ke) and heat flux (q) of test specimens under a wide range of actual conditions. Cryostat-500 is thermally guarded to measure absolute thermal performance when calibrated with a known reference via an adjustable-edge guard ring. With liquid nitrogen as the energy meter, the cold boundary temperature can be adjusted to any temperature between 77 K and approximately 300 K by the interposition of a thermal resistance layer between the cold mass and the specimen. A low thermal conductivity suspension system has compliance rods that adjust for specimen thickness and compression force. Material type, thickness, density, flatness, compliance, outgassing, and temperature sensor placement are important test considerations, and edge effects and calibration techniques for the apparatus are crucial. Over the full vacuum pressure range, the thermal performance capability is nearly four orders of magnitude. The horizontal configuration provides key advantages over the vertical cylindrical cryostats for testing at ambient pressure conditions. Cryostat-500’s design and test methods, other flat-plate boiloff calorimeters, and results for select thermal insulation materials (composites, foams, aerogels) are discussed.
Flat-plate solar array project. Volume 2: Silicon material
NASA Technical Reports Server (NTRS)
Lutwack, R.
1986-01-01
The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.
Flat-plate solar array progress and plans
NASA Technical Reports Server (NTRS)
Callaghan, W. T.; Henry, P. K.
1984-01-01
The Flat-Plate Solar Array Project (FSA), sponsored by the U.S. Department of Energy (DOE) and managed by the Jet Propulsion Laboratory (JPL), has achieved progress in a broad range of technical activities since that reported at the Fourth European Communities Conference. A particularly important analysis has been completed recently which confirms the adoption into practice by the U.S. Photovoltaic (PV Industry, of all the low-cost module technology elements proposed at the 16th Project Integration Meeting for a $2.80/Wp (1980 U.S. Dollars) design approach in the fall of 1980. This work presents along with a projection, using the same techniques, for what is believed to be a very credible ribbon-based module design for less that $0.55/Wp (1980 U.S. Dollars). Other areas to be reported upon include low-cost Si feedstock refinement; ribbon growth; process sequence development for cells; environmental isolation; engineering science investigations; and module testing progress.
Full polarimetric non-specular scattering of flat plate structures
NASA Astrophysics Data System (ADS)
Fath, Jeffrey L.
1986-12-01
This thesis examined the electromagnetic scattering of a dihedral corner reflector for both monostatic and bistatic source-receiver geometries. The full polarization characteristics of the electromagnetic scattering was maintained while the dihedral corner reflector was modeled on and off the principal (horizontal reference) plane. The dihedral corner reflector was composed of two perfectly conducting 9 inch square flat plates joined along a common edge so that they formed an interior angle of 90 degrees. The frequencies of interest included 2, 3, and 10 GHz. THe theoretical modeling utilized the Uniform Theory of Diffraction and the Method of Moments (MOM). The analysis was performed on a Cray X-MP supercomputer and a VAX 11/785 minicomputer. The results from the models were compared with each other, and with measurements for validation. The measurements were taken on the principal plane for same sense and cross polarization components. The MOM model compared well with measurement for the monostatic and bistatic same sense polarization components. However, differences were noted for the cross polarization component comparison. The MOM model was then extended to off principal plane geometries, which was not measured. A substantial amount of cross polarization scattering was predicted for off principal plane geometries.
Wind Loads on Flat Plate Photovoltaic Array Fields
NASA Technical Reports Server (NTRS)
Miller, R.; Zimmerman, D.
1979-01-01
The aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays were investigated. Local pressure distributions and total aerodynamic forces on the arrays are shown. Design loads are presented to cover the conditions of array angles relative to the ground from 20 deg to 60 deg, variable array spacings, a ground clearance gap up to 1.2 m (4 ft) and array slant heights of 2.4 m (8 ft) and 4.8 m (16 ft). Several means of alleviating the wind loads on the arrays are detailed. The expected reduction of the steady state wind velocity with the use of fences as a load alleviation device are indicated to be in excess of a factor of three for some conditions. This yields steady state wind load reductions as much as a factor of ten compared to the load incurred if no fence is used to protect the arrays. This steady state wind load reduction is offset by the increase in turbulence due to the fence but still an overall load reduction of 2.5 can be realized. Other load alleviation devices suggested are the installation of air gaps in the arrays, blocking the flow under the arrays and rounding the edges of the array. A wind tunnel test plan to supplement the theoretical study and to evaluate the load alleviation devices is outlined.
Wind loads on flat plate photovoltaic array fields
NASA Technical Reports Server (NTRS)
Miller, R. D.; Zimmerman, D. K.
1981-01-01
The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.
Second generation large area microchannel plate flat panel phototubes
NASA Astrophysics Data System (ADS)
Ertley, C. D.; Siegmund, O. H. W.; Jelinsky, S. R.; Tedesco, J.; Minot, M. J.; O'Mahony, A.; Craven, C. A.; Popecki, M.; Lyashenko, A. V.; Foley, M. R.
2016-07-01
Very large (20 cm × 20 cm) flat panel phototubes are being developed which employ novel microchannel plates (MCPs). The MCPs are manufactured using borosilicate microcapillary arrays which are functionalized by the application of resistive and secondary emissive layers using atomic layer deposition (ALD). This allows the operational parameters to be set by tailoring sequential ALD deposition processes. The borosilicate substrates are robust, including the ability to be produced in large formats (20 cm square). ALD MCPs have performance characteristics (gain, pulse amplitude distributions, and imaging) that are equivalent or better than conventional MCPs. They have low intrinsic background (0.045 events cm-2 sec-1)., high open area ratios (74% for the latest generation of borosilicate substrates), and stable gain during >7 C cm-2 charge extraction after preconditioning (vacuum bake and burn-in). The tube assemblies use a pair of 20 cm × 20 cm ALD MCPs comprised of a borosilicate entrance window, a proximity focused bialkali photocathode, and a strip-line readout anode. The second generation design employs an all glass body with a hot indium seal and a transfer photocathode. We have achieved >20% quantum efficiency and good gain uniformity over the 400 cm2 field of view, spatial resolution of <1 cm and obtained event timing accuracy of close to 100 ps FWHM.
Flat-plate solar array progress and plans
NASA Technical Reports Server (NTRS)
Callaghan, W. T.; Henry, P. K.
1984-01-01
The Flat-Plate Solar Array Project (FSA), sponsored by the U.S. Department of Energy (DOE) and managed by the Jet Propulsion Laboratory (JPL), has achieved progress in a broad range of technical activities since that reported at the Fourth European Communities Conference. A particularly important analysis has been completed recently which confirms the adoption into practice by the U.S. Photovoltaic (PV Industry, of all the low-cost module technology elements proposed at the 16th Project Integration Meeting for a $2.80/Wp (1980 U.S. Dollars) design approach in the fall of 1980. This work presents along with a projection, using the same techniques, for what is believed to be a very credible ribbon-based module design for less that $0.55/Wp (1980 U.S. Dollars). Other areas to be reported upon include low-cost Si feedstock refinement; ribbon growth; process sequence development for cells; environmental isolation; engineering science investigations; and module testing progress.
On the instability of boundary layers on heated flat plates
NASA Technical Reports Server (NTRS)
Hall, Philip; Morris, Helen
1992-01-01
The stability of a boundary layer on a heated flat plate is investigated in the linear regime. The flow is shown to be unstable to longitudinal vortex structures which in general develop in a nonparallel manner in the streamwise direction. Solutions of the nonparallel equations are obtained numerically at O(1) values of the appropriate stability parameter, i.e., the Grashof number. The particular cases investigated relate to the situations when the instability is induced by localized or distributed wall roughness or nonuniform wall heating. The case when the vortices are induced by freestream disturbances is also considered. The fastest growing mode is found to be governed by a quasi-parallel theory at high wavenumbers. The wavenumber and growth rate of the fastest growing mode are found in closed form. At low wavenumbers the vortex instability is shown to be closely related to Tollmein-Schlichting waves. The effect of wall heating or cooling on the latter type of instability is discussed.
Motion of a Non-Newtonian Fluid in the Wake of a Flat Plate
NASA Astrophysics Data System (ADS)
Zhou, Min; Ladeinde, Foluso; Bluestein, Danny
2004-11-01
A theoretical analysis of two-dimensional steady state laminar flow of a non-Newtonian fluid in the wake of a flat plate is presented. This is a simplified model for blood flow over the bi-leaflet of a mechanical heart valve. The present analysis is also intended to validate large eddy simulations, which are currently being carried out for a more elaborate model of the heart valve. By introducing the power-law model, the Goldstein's near wake solution and Tollmien's first asymptotic approximation in the far wake are extended for applicability to blood flow. On the symmetry line, two velocity distributions are obtained as functions of the distance behind the plate, one from the near wake and the other from the far wake. These are matched to form a continuous distribution. For the other regions, the velocity distribution could be determined by interpolation. The results are contrasted with previous work on Newtonian fluids.
Numerical investigation of laminar-turbulent transition in a flat plate wake
NASA Technical Reports Server (NTRS)
Fasel, Hermann F.; Newell, Alan C.; Dratler, David I.
1990-01-01
Lamina-turbulent transition of high-deficit flat plate wakes is investigated by direct numerical simulations using the complete Navier Stokes equations. The simulations are based on a spatial model so that both the base flow and the disturbance flow can develop in the downstream direction. The Navier Stokes equations are used in a vorticity-velocity form and are solved using a combination of finite difference and spectral approximations. Fourier series are used in the spanwise direction. Second-order finite-differences are used to approximate the spatial derivatives in the streamwise and transverse directions. For the temporal discretion, a combination of ADI, Crank-Nicolson, and Adams-Bashforth methods is employed. The discretized velocity equations are solved using fast Helmholtz solvers. Code validation is accomplished by comparison of the numerical results to both linear stability and to experiments. Calculations of two- and/or three-dimensional sinuous and mode disturbances in the wake of flat plate are undertaken. For calculations of two-dimensional disturbances, the wake is forced at an amplitude level so that nonlinear disturbance development may be observed. In addition, the forcing amplitude is varied in order to determine its effect on the disturbance behavior. To investigate the onset of three-dimensionality, the wake is forced with a small-amplitude three-dimensional disturbance and a larger amplitude two-dimensional disturbance. The two-dimensional forcing amplitude is varied in order to determine its influence on the three-dimensional flow field.
Interacting wakes of a narrow and a wide flat plate in tandem arrangement
NASA Astrophysics Data System (ADS)
Hacışevki, H.; Teimourian, A.
2016-02-01
Flow structures behind two different sized flat plates in tandem arrangement normal to flow at high Reynolds number have been investigated experimentally. A narrow flat plate, as a control plate, has been placed upstream of a wide plate to investigate the interacting wakes behind the wide flat plate. The near wake downstream of the wide plate has been measured by employing constant-temperature hot wire anemometer, quantitatively. The effects of different width ratio (h/D) range from 0.1 to 1.0 together with gap ratio (g/D) ranging from 0.5 to 2.0 have been probed. It was found that Strouhal number variation is directly proportional to gap ratio between the plates. Moreover, it was observed that turbulent kinetic energy production is mostly contributed by transverse normal turbulent stress and therefore follows the transverse stress pattern rather than the stream wise stress.
NASA Technical Reports Server (NTRS)
Moore, Franklin K; Ostrach, Simon
1957-01-01
The time-average characteristics of boundary layers over a flat plate in nearly quasi-steady flow are determined. The plate may be either insulated or isothermal. The time averages are found without specifying the plate velocity explicitly except that it is positive and has an average value.
Drag measurements of an axisymmetric nacelle mounted on a flat plate at supersonic speeds
NASA Technical Reports Server (NTRS)
Flamm, Jeffrey D.; Wilcox, Floyd J., Jr.
1995-01-01
An experimental investigation was conducted to determine the effect of diverter wedge half-angle and nacelle lip height on the drag characteristics of an assembly consisting of a nacelle fore cowl from a typical high-speed civil transport (HSCT) and a diverter mounted on a flat plate. Data were obtained for diverter wedge half-angles of 4.0 deg, 6.0 deg, and 8.0 deg and ratios of the nacelle lip height above a flat plate to the boundary-layer thickness (h(sub n)/delta) of approximately 0.87 to 2.45. Limited drag data were also obtained on a complete nacelle/diverter configuration that included fore and aft cowls. Although the nacelle/diverter drag data were not corrected for base pressures or internal flow drag, the data are useful for comparing the relative drag of the configuration tested. The tests were conducted in the Langley Unitary Plan Wind Tunnel at Mach numbers of 1.50, 1.80, 2.10, and 2.40 and Reynolds numbers ranging from 2.00 x 10(exp 6) to 5.00 x 10(exp 6) per foot. The results of this investigation showed that the nacelle/diverter drag essentially increased linearly with increasing h(sub n)/delta except near 1.0 where the data showed a nonlinear behavior. This nonlinear behavior was probably caused by the interaction of the shock waves from the nacelle/diverter configuration with the flat-plate boundary layer. At the lowest h(sub n)/delta tested, the diverter wedge half-angle had virtually no effect on the nacelle/diverter drag. However, as h(sub n)/delta increased, the nacelle/diverter drag increased as diverter wedge half-angle increased.
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... COMMISSION Diffusion-Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan; Scheduling of the Final... of less-than-fair-value imports from Japan of diffusion-annealed, nickel- plated flat-rolled steel... diffusion-annealed, nickel- plated flat-rolled steel products from Japan are being sold in the United States...
Federal Register 2010, 2011, 2012, 2013, 2014
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NASA Technical Reports Server (NTRS)
Buck, Gregory M.; Powers, Michael A.; Nevins, Stephen C.; Griffith, Mark S.; Wainwright, Gary A.
2006-01-01
Methods, materials and equipment are documented for fabricating flat plate test models at NASA Langley Research Center for Shuttle return-to-flight aeroheating experiments simulating open and closed cavity interactions in Langley s hypersonic 20-Inch Mach 6 air wind tunnel. Approximately 96 silica ceramic flat plate cavity phosphor thermography test models have been fabricated using these methods. On one model, an additional slot is machined through the back of the plate and into the cavity and vented into an evacuated plenum chamber to simulate a further opening in the cavity. After sintering ceramic to 2150 F, and mounting support hardware, a ceramic-based two-color thermographic phosphor coating is applied for global temperature and heat transfer measurements, with fiducial markings for image registration.
CMB spectra and bispectra calculations: making the flat-sky approximation rigorous
Bernardeau, Francis; Pitrou, Cyril; Uzan, Jean-Philippe E-mail: cyril.pitrou@port.ac.uk
2011-02-01
This article constructs flat-sky approximations in a controlled way in the context of the cosmic microwave background observations for the computation of both spectra and bispectra. For angular spectra, it is explicitly shown that there exists a whole family of flat-sky approximations of similar accuracy for which the expression and amplitude of next to leading order terms can be explicitly computed. It is noted that in this context two limiting cases can be encountered for which the expressions can be further simplified. They correspond to cases where either the sources are localized in a narrow region (thin-shell approximation) or are slowly varying over a large distance (which leads to the so-called Limber approximation). Applying this to the calculation of the spectra it is shown that, as long as the late integrated Sachs-Wolfe contribution is neglected, the flat-sky approximation at leading order is accurate at 1% level for any multipole. Generalization of this construction scheme to the bispectra led to the introduction of an alternative description of the bispectra for which the flat-sky approximation is well controlled. This is not the case for the usual description of the bispectrum in terms of reduced bispectrum for which a flat-sky approximation is proposed but the next-to-leading order terms of which remain obscure.
Relaminarization of the boundary layer over a flat plate in shock tube experiments
NASA Technical Reports Server (NTRS)
Hinckel, J. N.; Nagamatsu, H. T.
1986-01-01
The relaminarization of the boundary layer over a flat plate in the shock tube was investigated by using the partially reflected shock wave technique. The flow Mach number was approximately 0.14, which corresponds to the inleft flow Mach number for the first row of vanes in a gas turbine. The thin film platinum heat gauges were used to measure the heat transfer rate and the Stanton number was calculated from the oscilloscope voltage traces. The Reynolds number was varied by changing the operation pressure of the shock tube and the values varied from 2.3 x 10 to the 4th to 5.3 x 10 to the 5th. For a Reynolds number range of 7 x 10 to the 4th to 3.5 x 10 to the 5th, the relaminarization of the boundary layer was observed. This phenomenon is due to the decay of the turbulence level in the flow as the reflected shock wave moves upstream from the flat plate. As the Reynolds number increased, the relaminarization was delayed and the delay was related to the turbulence generated by the reflected shock wave.
Analytical predictions of liquid and air photovoltaic/thermal flat-plate collector performance
Raghuraman, P.; Hendrie, S. D.
1980-01-01
Two separate one-dimensional analyses have been developed for the prediction of the thermal and electrical performance of both liquid and air flat-plate photovoltaic/thermal (PV/T) collectors. The analyses account for the temperature difference between the primary insolation absorber (the photovoltaic cells) and the secondary absorber (a thermal absorber flat plate). The results of the analyses are compared with test measurements, and therefrom, design recommendations are made to maximize the total energy extracted from the collectors.
Flat plate solar collector design and performance. Citations from the Engineering Index data base
NASA Astrophysics Data System (ADS)
Hundemann, A. S.
1980-09-01
Citations on the design, thermal performance, and optimization of air and liquid type flat plate collectors are covered. Topic areas include heat loss and heat transfer, effect of orientation, corrosion protection, optical coatings, enhancement of performance through the use of planar reflectors, and the effect of honeycomb layers on collector performance. A few studies pertain to grooved, corrugated, or V-trough collectors. Methods of measuring the performance of flat plate collectors and computer optimization studies are included.
Effect of a hot spot on the strain response of an acoustically-loaded flat plate
Koval, L.R.; Jong, C.P.
1989-01-01
Previous studies of the acoustic fatigue of heated plates have treated uniformly-heated plates. The current study examines the effect of a 'hot spot' on the acoustic fatigue of a simply-supported flat plate. The hot spot is provided by a concentration of hot gas and is 'applied' to the plate through a convection boundary condition on the upper surface of the plate. For simplicity, the hot spot is assumed to be rectangular with its sides parallel to the sides of the plate. The size of the hot spot, the location of the hot spot, and the temperature of the hot spot were all varied to see their effects. 18 references.
Time domain numerical calculations of unsteady vortical flows about a flat plate airfoil
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Yu, Ping; Scott, J. R.
1989-01-01
A time domain numerical scheme is developed to solve for the unsteady flow about a flat plate airfoil due to imposed upstream, small amplitude, transverse velocity perturbations. The governing equation for the resulting unsteady potential is a homogeneous, constant coefficient, convective wave equation. Accurate solution of the problem requires the development of approximate boundary conditions which correctly model the physics of the unsteady flow in the far field. A uniformly valid far field boundary condition is developed, and numerical results are presented using this condition. The stability of the scheme is discussed, and the stability restriction for the scheme is established as a function of the Mach number. Finally, comparisons are made with the frequency domain calculation by Scott and Atassi, and the relative strengths and weaknesses of each approach are assessed.
Time domain numerical calculations of unsteady vortical flows about a flat plate airfoil
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Ping, YU; Scott, J. R.
1992-01-01
A time domain numerical scheme is developed to solve for the unsteady flow about a flat plate airfoil due to imposed upstream, small amplitude, transverse velocity perturbations. The governing equation for the resulting unsteady potential is a homogeneous, constant coefficient, convective wave equation. Accurate solution of the problem requires the development of approximate boundary conditions which correctly model the physics of the unsteady flow in the far field. A uniformly valid far field boundary condition is developed, and numerical results are presented using this condition. The stability of the scheme is discussed, and the stability restriction for the scheme is established as a function of the Mach number. Finally, comparisons are made with the frequency domain calculation by Scott and Atassi, and the relative strengths and weaknesses of each approach are assessed.
Analysis of the Curved Junction Edge between a Flat Plate and a Prolate Spheroid.
1981-05-01
report. Our approach to this problem is first to find the intersection point between a line (i.e., one edge of the plate) and the prolate spheroid. Then...one can follow the same idea to find the curved junction edge between a flat plate and the prolate spheroid. (Author)
Interference effects on the hypersonic, rarefied flow about a flat plate
NASA Technical Reports Server (NTRS)
Wilmoth, Richard G.
1989-01-01
The Direct Simulatiaon Monte Carlo method is used to study the hypersonic, rarefied flow interference effects on a flat plate caused by nearby surfaces. Calculations focus on shock-boundary-layer and shock-lip interactions in hypersonic inlets. Results are presented for geometries consisting of a flat plate with different leading-edge shapes over a flat lower wall and a blunt-edge flat plate over a 5-degree wedge. The problems simulated correspond to a typical entry flight condition of 7.5 km/s at altitudes of 75 to 90 km. The results show increases in predicted local heating rates for shock-boundary-layer and shock-lip interactions that are quantitatively similar to those observed experimentally at much higher densities.
Interference effects on the hypersonic, rarefied flow about a flat plate
NASA Technical Reports Server (NTRS)
Wilmoth, Richard G.
1988-01-01
The Direct Simulation Monte Carlo method is used to study the hypersonic, rarified flow interference effects on a flat plate caused by nearby surfaces. Calculations focus on shock-boundary-layer and shock-lip interactions in hypersonic inlets. Results are presented for geometries consisting of a flat plate with different leading-edge shapes over a flat lower wall and a blunt-edge flat plate over a 5-degree wedge. The problems simulated correspond to a typical entry flight condition of 7.5 km/s at altitudes of 75 to 90 km. The results show increases in predicted local heating rates for shock-boundary-layer and shock-lip interactions that are quantitatively similar to those observed experimentally at much higher densities.
Flow over a traveling wavy foil with a passively flapping flat plate.
Liu, Nansheng; Peng, Yan; Liang, Youwen; Lu, Xiyun
2012-05-01
Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.
Flow over a traveling wavy foil with a passively flapping flat plate
NASA Astrophysics Data System (ADS)
Liu, Nansheng; Peng, Yan; Liang, Youwen; Lu, Xiyun
2012-05-01
Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.
NASA Astrophysics Data System (ADS)
Vairamani, K.; Venkatesh, K. Arun; Mathivanan, N.
2011-01-01
Computing the efficiency of flat-plate collector is vital in solar thermal system testing. This paper presents the design of ZigBee enabled data acquisition system for instantaneous flat-plate collector efficiency calculation. It involves measurement of parameters like inlet and outlet fluid temperatures, ambient temperature and solar radiation intensity. The designed system has a base station and a sensor node. ZigBee wireless communication protocol is used for communication between the base station and the sensor node for wireless data acquisition. The wireless sensor node which is mounted over the collector plate includes the necessary sensors and associated signal-conditioners. An application program has been developed on LabVIEW platform for data acquisition, processing and analysis and is executed in base station PC. Instantaneous flat-plate collector efficiency is computed and reported.
Turbulent flow over a long flat plate with uniform roughness
NASA Astrophysics Data System (ADS)
Pullin, D. I.; Hutchins, N.; Chung, D.
2017-08-01
For turbulent boundary-layer flow under a uniform freestream speed U∞ over a plate of length L , covered with uniform roughness of nominal sand-grain scale ks, the physical behaviors underlying two distinguished limits at large ReL≡U∞L /ν are explored: the fully rough wall flow where ks/L is fixed and the long-plate limit where Rek≡U∞ks/ν is fixed. For the fully rough limit it is shown that not only is the drag coefficient CD independent of ReL but that a universal skin-friction coefficient Cf and normalized boundary-layer thickness δ /ks can be found that depends only on ks/x , where x is the downstream distance. In the long-plate limit, it is shown that the flow becomes asymptotically smooth at huge ReL at a rate that depends on Rek. Comparisons with wind-tunnel and field data are made.
NASA Technical Reports Server (NTRS)
1983-01-01
The Flat Plate Solar Array Project, focuses on advancing technologies relevant to the design and construction of megawatt level central station systems. Photovoltaic modules and arrays for flat plate central station or other large scale electric power production facilities require the establishment of a technical base that resolves design issues and results in practical and cost effective configurations. Design, qualification and maintenance issues related to central station arrays derived from the engineering and operating experiences of early applications and parallel laboratory reserch activities are investigated. Technical issues are examined from the viewpoint of the utility engineer, architect/engineer and laboratory researcher. Topics on optimum source circuit designs, module insulation design for high system voltages, array safety, structural interface design, measurements, and array operation and maintenance are discussed.
Investigating wake patterns and propulsive frequencies of a flat plate under pitching motion
NASA Astrophysics Data System (ADS)
Moubogha Moubogha, Joseph; Astolfi, Jacques Andre
Fundamental mechanisms of swimming are explored using a simple geometry device - flat plate - in pure-pitching motion in a hydrodynamic tunnel. The experiments are carried out at different Reynolds numbers based on the plate length c. Pitching motion is generated for reduced frequencies k between 0 and 2 and for an angular amplitude of 10 deg. Velocity fields are obtained in the wake of the plate using Particle Image Velocimetry and measurements of drag coefficients are estimated from mean velocity profiles. This study confirms the occurrence of a threshold oscillation frequency beyond which the plate enters a propulsive regime and the wake features organized structures. In this case an inversion of the typical Karman vortex street is observed. The evolution of mean transverse velocity profiles in the wake of the plate shows that the usual wake profile with velocity deficit - plate with drag - can be transformed into a jet - plate with thrust - above a certain reduced frequency. Phd Student Mechanical Engineering Departement.
Friction-factor data for flat-plate tests of smooth and honeycomb surfaces
NASA Technical Reports Server (NTRS)
Ha, T. W.; Childs, Dara W.
1992-01-01
Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.
Friction factor data for flat plate tests of smooth and honeycomb surfaces. M.S. Thesis
NASA Technical Reports Server (NTRS)
Ha, Tae Woong
1989-01-01
Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.
Friction-factor data for flat-plate tests of smooth and honeycomb surfaces
NASA Technical Reports Server (NTRS)
Ha, T. W.; Childs, Dara W.
1992-01-01
Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.
Analysis of the Conformally Flat Approximation for Binary Neutron Star Initial Conditions
NASA Astrophysics Data System (ADS)
Suh, In-Saeng; Mathews, Grant J.; Haywood, J. Reese; Lan, N. Q.
The spatially conformally flat approximation (CFA) is a viable method to deduce initial conditions for the subsequent evolution of binary neutron stars employing the full Einstein equations. Here we review the status of the original formulation of the CFA for the general relativistic hydrodynamic initial conditions of binary neutron stars. We illustrate the stability of the conformally flat condition on the hydrodynamics by numerically evolving ~100 quasi-circular orbits. We illustrate the use of this approximation for orbiting neutron stars in the quasi-circular orbit approximation to demonstrate the equation of state dependence of these initial conditions and how they might affect the emergent gravitational wave frequency as the stars approach the innermost stable circular orbit.
Analysis of the Conformally Flat Approximation for Binary Neutron Star Initial Conditions
Suh, In-Saeng; Mathews, Grant J.; Haywood, J. Reese; ...
2017-01-09
The spatially conformally flat approximation (CFA) is a viable method to deduce initial conditions for the subsequent evolution of binary neutron stars employing the full Einstein equations. Here in this paper, we analyze the viability of the CFA for the general relativistic hydrodynamic initial conditions of binary neutron stars. We illustrate the stability of the conformally flat condition on the hydrodynamics by numerically evolving ~100 quasicircular orbits. We illustrate the use of this approximation for orbiting neutron stars in the quasicircular orbit approximation to demonstrate the equation of state dependence of these initial conditions and how they might affect themore » emergent gravitational wave frequency as the stars approach the innermost stable circular orbit.« less
Design and performance of tubular flat-plate solid oxide fuel cell
Matsushima, T.; Ikeda, D.; Kanagawa, H.
1996-12-31
With the growing interest in conserving the environmental conditions, much attention is being paid to Solid Oxide Fuel Cell (SOFC), which has high energy-conversion efficiency. Many organizations have conducted studies on tubular and flat type SOFCs. Nippon Telegraph and Telephone Corporation (NTT) has studied a combined tubular flat-plate SOFC, and already presented the I-V characteristics of a single cell. Here, we report the construction of a stack of this SOFC cell and successful generation tests results.
Hollow Vortices in Flow Past a Flat Plate
NASA Astrophysics Data System (ADS)
Elcrat, Alan; Zannetti, Luca
2012-11-01
Closed and open hollow wakes are considered as analytic models for the 2D inviscid steady flow past a plate normal to the stream. It is shown that only open configurations which satisfy the Kutta condition exist. The main argument is based on considering a plate located on the edge of a step with varying height. It is shown that solutions for open wakes exist for backward, null and forward-facing steps, while closed wakes only exist for backward-facing steps. The occurrence of secondary separation has been modeled by adding a hollow region attached to the downstream corner. Peculiar accuracy issues of the problem are pointed out which may explain other contradictory results from the literature. It is shown how the Kirchhoff wake is a limiting solution for certain values of the governing parameters.
Performance Study of a Double-Pass Thermoelectric Solar Air Collector with Flat-Plate Reflectors
NASA Astrophysics Data System (ADS)
Lertsatitthanakorn, C.; Rungsiyopas, M.; Therdyothin, A.; Soponronnarit, S.
2012-06-01
In this paper the results of the influence of flat-plate reflectors made of aluminum foil on the performance of a double-pass thermoelectric (TE) solar air collector are presented. The proposed TE solar collector with reflectors was composed of transparent glass, an air gap, an absorber plate, TE modules, a rectangular fin heat sink, and two flat-plate reflectors. The flat-plate reflectors were placed on two sides of the TE solar collector (east and west directions). The TE solar collector was installed on a one-axis sun-tracking system to obtain high solar radiation. Direct and reflected incident solar radiation heats up the absorber plate so that a temperature difference is created across the TE modules to generate a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. Ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel, where it receives additional heating from the absorber plate. Improvements to the thermal energy and electrical power outputs of the system can be achieved by the use of the double-pass collector system with reflectors and TE technology. It was found that the optimum position of the reflectors is 60°, which gave significantly higher thermal energy and electrical power outputs compared with the TE solar collector without reflectors.
NASA Astrophysics Data System (ADS)
Hollands, K. G. T.; Wright, J. L.
1983-01-01
This paper presents an efficient algorithm for solving the set of nonlinear equations governing the total heat transfer across an arbitrary number of parallel flat plate solar collector covers, each of which can be partly transparent to longwave thermal radiation. The governing equations are sufficiently general to permit each cover to have asymmetric radiative properties and to account for absorption of solar energy on the individual covers. This theory is shown to be in good agreement with the approximate equations of Whillier (provided certain interpretations are placed on his quantities) and with experiments using a plastic inner cover and bounding plates of various emissivities. Using this theory, it is demonstrated that if the absorber plate has a selective surface, an inner cover transparent to long wave radiation is to be preferred over one which is opaque.
Analysis of noise produced by jet impingement near the trailing edge of a flat and a curved plate
NASA Technical Reports Server (NTRS)
Mckinzie, D. J., Jr.; Burns, R. J.
1975-01-01
The sound fields produced by the interaction of a subsonic cold gas jet with the trailing edge of a large flat plate and a curved plate were analyzed. The analyses were performed to obtain a better understanding of the dominant noise source and the mechanism governing the peak sound-pressure-level frequencies of the broadband spectra. An analytical expression incorporating an available theory and experimental data predicts sound field data over an arc of approximately 105 deg measured from the upstream jet axis for the two independent sets of data. The dominant noise as detected on the impingement side of either plate results from the jet impact (eighth power of the velocity dependence) rather than a trailing-edge disturbance (fifth or sixth power of the velocity dependence). Also, the frequency of the peak SPL may be governed by a phenomenon which produces periodic formation and shedding of ring vortices from the nozzle lip.
Proposed first edition of the standard for flat-plate photovoltaic modules and panels, UL 1703
Not Available
1984-09-12
The tentative requirements provided cover flat-plate photovoltaic modules and panels intended for installation on or integral with buildings or to be freestanding (that is, not attached to buildings). Modules and panels intended for use in systems with a maximum system voltage of 1000 volts or less are covered. Also covered are components intended to provide electrical connection to and mounting facilities for flat-plate photovoltaic modules and panels. The requirements do not cover equipment intended to accept the electrical output from the array (such as inverters and batteries), tracking mechanisms, cell assemblies intended to operate under concentrated sunlight, optical concentrators, or combination photovoltaic-thermal modules or panels. (LEW)
On the large-scale structure of the turbulent wake of a flat plate
NASA Technical Reports Server (NTRS)
Jovic, S.; Ramaprian, B. R.
1989-01-01
A simple heat-tagging technique was used to isolate and analyze the large-scale coherent structures present in the two-dimensional wake of a flat plate. The results indicate the presence of these coherent structures even at 250 momentum thicknesses downstream of the trailing edge. These structures have a vortexlike topology and carry a significant amount of the total shear stress. The present results for the flat-plate wake seem to be in general agreement with those that have been obtained in cylinder wakes by other comtemporary investigators using more complex techniques of eduction and signal enhancement.
Experimental study on flat plate air solar collector using a thin sand layer
NASA Astrophysics Data System (ADS)
Lati, Moukhtar; Boughali, Slimane; Bouguettaia, Hamza; Mennouche, Djamel; Bechki, Djamel
2016-07-01
A flat plate air solar collector was constructed in the laboratory of New and Renewable Energy in Arid Zones LENREZA, Ouargla University-South East Algeria. The absorber of the flat plate air solar collector was laminated with a thin layer of local sand. This acted as a thermal storage system (packed bed) with a collecting area of 2.15 m2 (0.86 m × 2.5 m). It was noticed that the solar heater integrated with the thermal storage material delivered comparatively higher temperatures; thus, giving a better efficiency than the air heater without the thermal storage system.
Computation of Tone Noise From Supersonic Jet Impinging on Flat Plates
NASA Technical Reports Server (NTRS)
Loh, Ching Y.; Blech, Richard A. (Technical Monitor)
2005-01-01
A supersonic jet impinging normally on a flat plate has both practical importance and theoretical interests. The physical phenomenon is not fully understood yet. Research concentrates either on the hydrodynamics (e.g., lift loss for STOVL) or on the aeroacoustic loading. In this paper, a finite volume scheme - the space-time conservation element and solution element (CE/SE) method - is employed to numerically study the near-field noise of an underexpanded supersonic jet from a converging nozzle impinging normally on a flat plate. The numerical approach is of the MILES type (monotonically integrated large eddy simulation). The computed results compare favorably with the experimental findings.
Analysis of a laminar boundary layer flow over a flat plate with injection or suction
NASA Astrophysics Data System (ADS)
Sadri, S.; Babaelahi, M.
2013-01-01
An analysis is performed to study a laminar boundary layer flow over a porous flat plate with injection or suction imposed at the wall. The basic equations of this problem are reduced to a system of nonlinear ordinary differential equations by means of appropriate transformations. These equations are solved analytically by the optimal homotopy asymptotic method (OHAM), and the solutions are compared with the numerical solution (NS). The effect of uniform suction/injection on the heat transfer and velocity profile is discussed. A constant surface temperature in thermal boundary conditions is used for the horizontal flat plate.
Wrinkling Phenomena of Thin Flat Plates Subjected to Shear Stresses
NASA Technical Reports Server (NTRS)
Bollenrath, F
1931-01-01
This report covers a series of tests on thin flat elastic strips restrained at two parallel edges and subjected to shear by conversely directed stresses. Theoretical treatments, particularly those of Lilly, Southwell and Skan, and Timoshenko are briefly outlined. The problem to be solved by these tests was to find out whether, and to what extent the conditions and assumptions upon which the calculations are based are complied with in the tests. Three materials were used: celluloid, duralumin, brass. Owing to the high elastic deformability of celluloid, it was not only possible to observe the beginning but also to ascertain the type of deflection. The test data on celluloid was affirmed by the experiments with duralumin and brass.
Flat-plate module efficiency versus cost tradeoffs
NASA Technical Reports Server (NTRS)
Aster, R. W.
1984-01-01
The Five Year Research Plan energy cost methodology and in depth analyses based on the extensive data that are relevant to PV systems are used to facilitate the accomplishment of the $0.15/kWh energy cost goal. An equation is given for the five year energy cost methodology. The allocation guidelines are designed to be consistent with flat solar array (FSA) milestones for module cost, module efficiency, and the programmatic goal for energy cost. They are research targets that appear to be achievable, given prior accomplishments and planned activities in the areas of low cost silicon purification, low cost sheet material, high efficiency cell processing, low cost, long life encapsulants, and automated fabrication method. Extensive sensitivity analysis work has been performed that shows that these guidelines represent an efficient way to meet the intent of the DOE program.
NASA Technical Reports Server (NTRS)
Lee, Henry C.; Klopfer, Goetz
2011-01-01
This report documents how OVERFLOW, a computational fluid dynamics code, predicts plume impingement of underexpanded axisymmetric jets onto both perpendicular and inclined flat plates. The effects of the plume impinging on a range of plate inclinations varying from 90deg to 30deg are investigated and compared to the experimental results in Reference 1 and 2. The flow fields are extremely complex due to the interaction between the shock waves from the free jet and those deflected by the plate. Additionally, complex mixing effects create very intricate structures in the flow. The experimental data is very limited, so these validation studies will focus only on cold plume impingement on flat and inclined plates. This validation study will help quantify the error in the OVERFLOW simulation when applied to stage separation scenarios.
Numerical Investigation of a Low Aspect Ratio Flat Plate
2011-05-19
M.R., ―High-Fidelity Simulations of Transitional Flow Over Pitching Airfoils,‖ AIAA Paper 2009- 3693 . Henshaw, W.D., and Petersson, N. A., ―A Split...Amplitude Pitch Problem: Airfoils, Plates and Wings,‖ AIAA Paper 2009-3686, 2009. OL, M.V., Altman, A., Eldredge, J.D., Garmann, D ., and Lian, Y...incompressible flow solver. AIAA J. 39,253 -260, 2001. Thomas, P. D ., and Lombard, C. K., ―Geometric Conservation Law and its Application to Flow
Interaction of part-through cracks in a flat plate
NASA Technical Reports Server (NTRS)
Aksel, B.; Erdogan, F.
1985-01-01
The accuracy of the line spring model is determined. The effect of interaction between two and three cracks is investigated, and extensive numerical results which may be useful in applications are provided. Line spring model with Reissner's plate theory is formulated to be used for any number and configurations of cracks provided that there is symmetry. This model is used to find stress intensity factors for elliptic internal cracks, elliptic edge cracks and two opposite elliptic edge cracks. Despite the simplicity of the line spring model, the results are found to be close.
Scattering of wavepackets by a flat plate in the vicinity of a turbulent jet
NASA Astrophysics Data System (ADS)
Cavalieri, André V. G.; Jordan, Peter; Wolf, William R.; Gervais, Yves
2014-12-01
We present an investigation of the acoustic scattering due to the presence of a flat plate in the vicinity of a turbulent subsonic jet. Experiments have been performed to measure changes in the velocity and sound fields for Mach numbers ranging from 0.4 to 0.6, and for distances between the plate and the jet axis ranging from 1 to 2 jet diameters. Results show only very slight changes in the mean flow induced by the plate, and no differences in the velocity fluctuation amplitudes on the jet centreline, suggesting that wave-packet models derived for jets without installation effects may be representative of the installed case, at least for the jet-plate distances considered here. The acoustic results, on the other hand, include a significant increase in the low-frequency sound radiation, and phase opposition between the shielded and unshielded sides of the plate. There is an exponential decay of the scattered sound with increasing jet-plate distance, suggesting that low-frequency radiation is due to the scattering of evanescent hydrodynamic wavepackets in the jet near field. To model this phenomenon, we calculate sound generation from wave-packet sources in two ways: on one hand we use a tailored Green's function that accounts for the presence of a semi-infinite, rigid flat plate; and, on the other, we solve numerically the Helmholtz equation, with boundary conditions representative of a finite flat plate, using a fast multipole boundary element method. In agreement with the experimental measurements, numerical calculations capture the phase opposition between shielded and unshielded sides, and the scattered sound depends exponentially on the position of the plate. This exponential dependence is related to non-compact effects associated with wavepackets, as compact sources would lead to an algebraic dependence. Acoustic pressure directivities computed for the finite and semi-infinite flat plates agree well where acoustic reflection and diffraction from the trailing
Stable computations with flat radial basis functions using vector-valued rational approximations
NASA Astrophysics Data System (ADS)
Wright, Grady B.; Fornberg, Bengt
2017-02-01
One commonly finds in applications of smooth radial basis functions (RBFs) that scaling the kernels so they are 'flat' leads to smaller discretization errors. However, the direct numerical approach for computing with flat RBFs (RBF-Direct) is severely ill-conditioned. We present an algorithm for bypassing this ill-conditioning that is based on a new method for rational approximation (RA) of vector-valued analytic functions with the property that all components of the vector share the same singularities. This new algorithm (RBF-RA) is more accurate, robust, and easier to implement than the Contour-Padé method, which is similarly based on vector-valued rational approximation. In contrast to the stable RBF-QR and RBF-GA algorithms, which are based on finding a better conditioned base in the same RBF-space, the new algorithm can be used with any type of smooth radial kernel, and it is also applicable to a wider range of tasks (including calculating Hermite type implicit RBF-FD stencils). We present a series of numerical experiments demonstrating the effectiveness of this new method for computing RBF interpolants in the flat regime. We also demonstrate the flexibility of the method by using it to compute implicit RBF-FD formulas in the flat regime and then using these for solving Poisson's equation in a 3-D spherical shell.
1980-09-01
a key ingredient to any industrialized society. Whether it be from petroleum, natural gas, wood , nuclear, or solar, energy com- mands ever increasing...Tubes Insulation Figure 1 Basic Components of a Liquid Flat Plate Collector emittance in the long wavelength range) as well as a cover system which...collector shown in Figure 1 are the absorber plate, covers, insulation , tubes, and frame. Each component has a special purpose. The transparent covers
Flat Plate Wake Velocity Statistics Obtained With Circular And Elliptic Trailing Edges
NASA Technical Reports Server (NTRS)
Rai, Man Mohan
2016-01-01
The near wake of a flat plate with circular and elliptic trailing edges is investigated with data from direct numerical simulations. The plate length and thickness are the same in both cases. The separating boundary layers are turbulent and statistically identical. Therefore the wake is symmetric in the two cases. The emphasis in this study is on a comparison of the wake-distributions of velocity components, normal intensity and fluctuating shear stress obtained in the two cases.
A graphical approach to the efficiency of flat-plate collectors
NASA Technical Reports Server (NTRS)
Selcuk, M. K.
1978-01-01
A nomogram is described which can be used to determine the thermal performance of flat plate solar collectors, resulting in two performance factors: the net absorptance and the net heat loss coefficient. The nomogram takes into account angle of incidence, collector slope, absorber plate design, insulating materials, thicknesses, optical properties of absorbing surfaces and glazing materials, and flow factors. A case example is given to illustrate the use of the nomogram.
NASA Astrophysics Data System (ADS)
Lance, Blake W.
Simulations are becoming increasingly popular in science and engineering. One type of simulation is Computation Fluid Dynamics (CFD) that is used when closed forms solutions are impractical. The field of Verification & Validation emerged from the need to assess simulation accuracy as they often contain approximations and calibrations. Validation involves the comparison of experimental data with simulation outputs and is the focus of this work. Errors in simulation predictions may be assessed in this way. Validation requires highly-detailed data and description to accompany these data, and uncertainties are very important. The purpose of this work is to provide highly complete validation data to assess the accuracy of CFD simulations. This aim is fundamentally different from the typical discovery experiments common in research. The measurement of these physics was not necessarily original but performed with modern, high-fidelity methods. Data were tabulated through an online database for direct use in Reynolds-Averaged Navier-Stokes simulations. Detailed instrumentation and documentation were used to make the data more useful for validation. This work fills the validation data gap for steady and transient mixed convection. The physics in this study included mixed convection on a vertical flat plate. Mixed convection is a condition where both forced and natural convection influence fluid momentum and heat transfer phenomena. Flow was forced over a vertical flat plate in a facility built for validation experiments. Thermal and velocity data were acquired for steady and transient flow conditions. The steady case included both buoyancy-aided and buoyancy-opposed mixed convection while the transient case was for buoyancy-opposed flow. The transient was a ramp-down flow transient, and results were ensemble-averaged for improved statistics. Uncertainty quantification was performed on all results with bias and random sources. An independent method of measuring heat flux was
NASA Technical Reports Server (NTRS)
Deveikis, W. D.; Hunt, L. R.
1973-01-01
Surface pressure and cold-wall heating rate distributions (wall-temperature to total-temperature ratio approximately 0.2) were obtained on a large, flat calibration panel at a nominal Mach number of 7 in an 8-foot high-temperature structures tunnel. Panel dimensions were 42.5 by 60.0 in. Test objectives were: (1) to map available flat-plate loading and heating provided by the facility and (2) to determine effectiveness of leading-edge bluntness, boundary-layer trips, and aerodynamic fences in generating a uniform, streamwise turbulent flow field over the test surface of a flat-sided panel holder.
NASA Technical Reports Server (NTRS)
Dietz, W. E., Jr.
1975-01-01
A model is presented which can be used to study the loss of lift during hovering and horizontal flight of the VTOL aircraft. The model numerically predicts the pressure distribution induced by a round, turbulent, unheated, subsonic jet exhausting normally through a flat plate into a subsonic crossflow. The complete model assumes that the predominant features of the flow are jet entrainment and a pair of contrarotating vortices which form downstream of the jet. Experimentally determined vortex properties and a reasonable assumption concerning jet entrainment were used. Potential flow considerations were used except in the wake region, where a simple method for approximating the pressure distribution was suggested. The calculated pressure distribution, lift, and pitching moments on the flat plate are presented for a jet to crossflow velocity ratio of 8 and were compared with experimental results. A computer program is given which was used to calculate the pressure distribution across the flat plate.
Effects of the foil flatness on irradiation performance of U10Mo monolithic mini-plates
Ozaltun, Hakan; Medvedev, Pavel G.; Rabin, Barry H.
2015-09-03
Monolithic plate-type fuels comprise of a high density, low enrichment, U10Mo fuel foil encapsulated in a cladding material. This concept generates several fabrication challenges such as flatness, centering or thickness variation. There are concerns, if these parameters have implications on overall performance. To investigate these inquiries, the effects of the foil flatness were studied. For this, a representative plate was simulated for an ideal case. The simulations were repeated for additional cases with various foil curvatures to evaluate the effects on the irradiation performance. The results revealed that the stresses and strains induced by fabrication process are not affected by the flatness of the foil. Furthermore, fabrication stresses in the foil are relieved relatively fast in the reactor. The effects of the foil flatness on peak irradiation stressstrains are minimal. There is a slight increase in temperature for the case with maximum curvature. The major impact is on the displacement characteristics. Furthermore, while the case with a flat foil produces a symmetrical swelling, if the foil is curved, more swelling occurs on the thin-cladding side and the plate bows during irradiation.
Effects of the foil flatness on irradiation performance of U10Mo monolithic mini-plates
Ozaltun, Hakan; Medvedev, Pavel G.; Rabin, Barry H.
2015-09-03
Monolithic plate-type fuels comprise of a high density, low enrichment, U10Mo fuel foil encapsulated in a cladding material. This concept generates several fabrication challenges such as flatness, centering or thickness variation. There are concerns, if these parameters have implications on overall performance. To investigate these inquiries, the effects of the foil flatness were studied. For this, a representative plate was simulated for an ideal case. The simulations were repeated for additional cases with various foil curvatures to evaluate the effects on the irradiation performance. The results revealed that the stresses and strains induced by fabrication process are not affected bymore » the flatness of the foil. Furthermore, fabrication stresses in the foil are relieved relatively fast in the reactor. The effects of the foil flatness on peak irradiation stressstrains are minimal. There is a slight increase in temperature for the case with maximum curvature. The major impact is on the displacement characteristics. Furthermore, while the case with a flat foil produces a symmetrical swelling, if the foil is curved, more swelling occurs on the thin-cladding side and the plate bows during irradiation.« less
Vortex induced lift on a flat plate with a curved forward-facing flap
NASA Technical Reports Server (NTRS)
Tanveer, S.
1985-01-01
Free streamline solutions are obtained for two-dimensional inviscid incompressible flow past a flat plate with a forward-facing curved flap. It is shown that it is possible to shape the curved flap to make the adverse pressure gradient on top of the flap less severe than for a straight flap and thus increase the prospects of making the flow experimentally realizable.
Analytical predictions of liquid and air photovoltaic/thermal, flat-plate collector performance
Raghuraman, P.
1981-11-01
Two separate one-dimensional analyses have been developed for the prediction of the thermal and electrical performance of both liquid and air flat-plate, photovoltaic/thermal (PV/T) collectors. The results of the analyses are compared with test measurements, and therefrom design recommendations are made to maximize the total energy extracted from the collectors. 16 refs.
An analysis of a flat-plate solar collector with internal boiling
Abramzon, B.; Borde, I.; Yaron, I.
1983-11-01
The extended mathematical model of a flat-plate solar collector-evaporator permits prediction of the effects of boiling of the working fluid in the collector tubes on the efficiency of the collector. The efficiency increases sharply and approaches the ideal on transition from single phase flow to the subcooled and saturated boiling regimes, regardless of the nature of the working fluid.
A Realistic Theoretical Model for Laminar Flow over a Flat Plate
2010-09-14
laminar flow over a flat plate. For 111= I and a= I, thi s equation reduces to the Hiemenz [6] equation for laminar 2-D stagnation point flow. 6...New York, 1979. [6] K. Hiemenz , "Die Grenzschicht an eimen in den gleichformigen Fllissigkeitsstrom eingetauchten geraden Kreiszylinder," Dingler’s
Preliminary design review package on air flat plate collector for solar heating and cooling system
NASA Technical Reports Server (NTRS)
1977-01-01
Guidelines to be used in the development and fabrication of a prototype air flat plate collector subsystem containing 320 square feet (10-4 ft x 8 ft panels) of collector area are presented. Topics discussed include: (1) verification plan; (2) thermal analysis; (3) safety hazard analysis; (4) drawing list; (5) special handling, installation and maintenance tools; (6) structural analysis; and (7) selected drawings.
Hot-air flat-plate solar collector-design package
NASA Technical Reports Server (NTRS)
1979-01-01
Report contains design data, performance specifications, and drawings for hot-air flat-plate solar-energy collector. Evaluation consists of tests on thermal performance time constance, and incidence angle modifier test. Results are presented in table and graph form and are analyzed in detail.
NASA Technical Reports Server (NTRS)
1983-01-01
A photovoltaic Metallization Research forum, under the sponsorship of the Flat-Plate Solar Array Project consisted of five sessions, covering: (1) the current status of metallization systems, (2) system design, (3) thick-film metallization, (4) advanced techniques, and (5) future metallization challenges.
Flat plate solar collector design and performance. Citations from the NTIS data base
NASA Astrophysics Data System (ADS)
Hundemann, A. S.
1980-09-01
Federally funded research on the design and thermal efficiency of air and liquid type flat plate collectors is discussed. Topic areas cover convection characteristics, methods to reduce heat loss, optical coatings, and corrosion control. Emphasis of the bibliography is on basic research studies. This updated bibliography contains 196 citations, 36 of which are new entries to the previous edition.
A Didactic Experiment and Model of a Flat-Plate Solar Collector
ERIC Educational Resources Information Center
Gallitto, Aurelio Agliolo; Fiordilino, Emilio
2011-01-01
We report on an experiment performed with a home-made flat-plate solar collector, carried out together with high-school students. To explain the experimental results, we propose a model that describes the heating process of the solar collector. The model accounts quantitatively for the experimental data. We suggest that solar-energy topics should…
Flat Plate Solar Array Project: Proceedings of the 20th Project Integration Meeting
NASA Technical Reports Server (NTRS)
Mcdonald, R. R.
1982-01-01
Progress made by the Flat-Plate Solar Array Project during the period November 1981 to April 1982 is reported. Project analysis and integration, technology research in silicon material, large-area silicon sheet and environmental isolation, cell and module formation, engineering sciences, and module performance and failure analysis are covered.
A Didactic Experiment and Model of a Flat-Plate Solar Collector
ERIC Educational Resources Information Center
Gallitto, Aurelio Agliolo; Fiordilino, Emilio
2011-01-01
We report on an experiment performed with a home-made flat-plate solar collector, carried out together with high-school students. To explain the experimental results, we propose a model that describes the heating process of the solar collector. The model accounts quantitatively for the experimental data. We suggest that solar-energy topics should…
Thin flat plate with linear spring as mechanical stop. Final report
Johnson, B.H.
1997-06-01
A mechanical device has been developed which dissipates mechanical energy simply and reliably, without generating debris. The device basically consists of a stack of thin flat metal layers, forming a flexible plate, and a mechanical spring to buffer the impact of the moving object. Equations have been developed which allow the design of such devices for particular applications.
Analysis of turbulent free-convection boundary layer on flat plate
NASA Technical Reports Server (NTRS)
Eckert, E R G; Jackson, Thomas W
1950-01-01
A calculation was made for the flow and heat transfer in the turbulent free-convection boundary layer on a vertical flat plate. Formulas for the heat-transfer coefficient, boundary layer thickness, and the maximum velocity in the boundary layer were obtained.
Separation characteristics of generic stores from lee side of an inclined flat plate at Mach 6
NASA Technical Reports Server (NTRS)
Wilcox, Floyd J., Jr.
1995-01-01
An experimental investigation was conducted to determine the aerodynamic characteristics of a store as it was separated from the lee side of a flat plate inclined at 15 deg to the free-stream flow at Mach 6. Two store models were tested: a cone cylinder and a roof delta. Force and moment data were obtained for both stores as they were moved in 0.5-in. increments away from the flat plate lee-side separated flow region into the free-stream flow while the store angle of attack was held constant at either 0 deg or 15 deg. The results indicate that both stores had adverse separation characteristics (i.e., negative normal force and pitching moment) at an angle of attack of 0 deg, and the cone cylinder had favorable separation characteristics (i.e., positive normal force and pitching moment) at an angle of attack of 15 deg. At an angle of attack of 15 deg, the separation characteristics of the roof delta are indeterminate at small separation distances and favorable at greater separation distances. These characteristics are the result of the local flow inclination relative to the stores as they traversed through the flat plate lee-side flow field. In addition to plotted data, force and moment data are tabulated and schlieren photographs of the stores and flat plate are presented.
Design and installation package for the Sunmat Flat Plate solar collector
NASA Technical Reports Server (NTRS)
1978-01-01
The information used in evaluating the design of a liquid flat plate solar collector is reported. Included in this package are subsystem performance specification, installation, operation and maintenance manuals, collector sizing guides, and detailed drawings of the single-glazed collector.
Hot-air flat-plate solar collector-design package
NASA Technical Reports Server (NTRS)
1979-01-01
Report contains design data, performance specifications, and drawings for hot-air flat-plate solar-energy collector. Evaluation consists of tests on thermal performance time constance, and incidence angle modifier test. Results are presented in table and graph form and are analyzed in detail.
A grooved glass surface-plate for making a flat polished surface
NASA Astrophysics Data System (ADS)
Miyagi, Isoji
2017-01-01
To obtain a flat polished surface for microchemical analyses such as EPMA, SIMS, and ATR micro-FTIR, a glass plate with a grooved surface was developed for hand polishing with an abrasive film. It eases the polishing process by minimizing slipping or sticking, and results in negligible relief in the sample surface.
Safety review package for University of Central Florida flat-plate heat pipe experiment
NASA Technical Reports Server (NTRS)
Chow, Louis C.
1998-01-01
A flat-plate heat pipe (FPHP) experiment has been set up for micro-gravity tests on a NASA supplied aircraft. This report presents an analysis on various components of the experimental setup to certify that it will satisfy the flight safety and operation requirements.
Farallon plate dynamics prior to the Laramide orogeny: Numerical models of flat subduction
NASA Astrophysics Data System (ADS)
Liu, Sibiao; Currie, Claire A.
2016-01-01
The Laramide orogeny (~ 80-50 Ma) was an anomalous period of mountain-building in the western United States that occurred more than 1000 km inboard of the Farallon Plate subduction margin. It is widely believed that this orogeny is coincident with a period of flat (subhorizontal) subduction. However, the factors that caused the Farallon Plate to evolve from a normal (steep) geometry to flat subduction are not well understood. Three proposed factors are: (1) a westward (trenchward) increase in North America motion, (2) an increased slab suction force owing to the presence of thick Colorado Plateau lithosphere, and (3) subduction of a low-density oceanic plateau. This study uses 2D upper mantle scale numerical models to investigate these factors. The models show that trenchward continental motion is the primary control on subduction geometry, with decreasing slab dip as velocity increases. However, this can only create low-angle subduction, as the Farallon Plate was old (> 100 Myr) and denser than the mantle. A transition to flat subduction requires: (1) subduction of a buoyant oceanic plateau that includes an 18-km-thick crust that does not undergo metamorphic densification and an underlying depleted harzburgite layer, and (2) a slab break-off at the landward side of the plateau. The break-off removes the dense frontal slab, and flat subduction develops as the buoyant plateau deflects the slab upward. The slab suction force has only a minor effect on slab flattening, but the thickness of the Colorado Plateau lithosphere controls the depth of the flat slab. With a continental velocity of 4 cm/yr and a 400-km-wide oceanic plateau, flat subduction develops within 15 Ma after plateau subduction. The flat slab underthrusts the continent at ~ 200 km depth, eventually extending > 1500 km inboard of the trench.
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-19
... International Trade Administration Diffusion-Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan... steel products from Japan. See Diffusion- Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan... Japan: Petitioner's Request for Extension of the Antidumping Investigation Preliminary Determination...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-04-02
... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Diffusion-Annealed, Nickel-Plated Steel Flat-Rolled Products From Japan; Institution of... retarded, by reason of imports from Japan of diffusion-annealed, nickel-plated steel flat-rolled products...
Flat plate solar air heater with latent heat storage
NASA Astrophysics Data System (ADS)
Touati, B.; Kerroumi, N.; Virgone, J.
2017-02-01
Our work contains two parts, first is an experimental study of the solar air heater with a simple flow and forced convection, we can use thatlaste oneit in many engineering's sectors as solardrying, space heating in particular. The second part is a numerical study with ansys fluent 15 of the storage of part of this solar thermal energy produced,using latent heat by using phase change materials (PCM). In the experimental parts, we realize and tested our solar air heater in URER.MS ADRAR, locate in southwest Algeria. Where we measured the solarradiation, ambient temperature, air flow, thetemperature of the absorber, glasses and the outlet temperature of the solar air heater from the Sunrise to the sunset. In the second part, we added a PCM at outlet part of the solar air heater. This PCM store a part of the energy produced in the day to be used in peak period at evening by using the latent heat where the PCMs present a grateful storagesystem.A numerical study of the fusion or also named the charging of the PCM using ANSYS Fluent 15, this code use the method of enthalpies to solve the fusion and solidification formulations. Furthermore, to improve the conjugate heat transfer between the heat transfer fluid (Air heated in solar plate air heater) and the PCM, we simulate the effect of adding fins to our geometry. Also, four user define are write in C code to describe the thermophysicalpropriety of the PCM, and the inlet temperature of our geometry which is the temperature at the outflow of the solar heater.
Large amplitude flexural vibration of thin elastic flat plates and shells
NASA Technical Reports Server (NTRS)
Pandalia, K. A. V.
1972-01-01
The general equations governing the large amplitude flexural vibration of any thin elastic shell using curvilinear orthogonal coordinates are derived and consist of two coupled, nonlinear, partial differential equations in the normal displacement w and the stress function F. From these equations, the governing equations for the case of shells of revolution or flat plates can be readily obtained as special cases. The material of the shell or plate is isotropic and homogeneous and Hooke's law for the two-dimensional case is valid. It is suggested that the difference between the hardening type of nonlinearity in the case of flat plates and straight beams and the softening type of nonlinearity in the case of shells and rings can, in general, be traced to the amount of curvature present in the underformed median surface of the structure concerned.
Design of an efficient projector for LED flat lamp without light guide plate
NASA Astrophysics Data System (ADS)
Lai, Li-ping; Zhuang, Qi-ren; Liang, De-juan
2013-11-01
An efficient LED projector is designed for the LED flat lamp without light guide plate (LGP), in order to get high-efficiency lighting capablility and low cost of LED flat lamp. By employing refraction and total reflection, uniform intensity distribution of the emergent light and high-efficiency lighting capablility are achieved. The simulation results show that the output efficiency and intensity distribution on LED flat lamp panel depend on the distance between projector and output panel, the rotation angle of the projector and the gap between projector and LED. It performs well in both lighting efficiency and uniformity, while a distance of 5 mm, a rotation angle of 2° and a gap of 1.2 mm are used with the panel size of 240 mm×360 mm in the LED flat lamp without LGP. And 96.6% of optical uniformity is achieved.
Transient-forced convection film boiling on an isothermal flat plate.
NASA Technical Reports Server (NTRS)
Nagendra, H. R.
1972-01-01
Development of a new approach for the solution of transient-forced convection film boiling on an isothermal flat plate using the boundary layer model. The similarity variables are used to convert the governing partial differential equations to ordinary ones. The results of numerical solutions of these ordinary equations indicate that the transient process can be classified as one-dimensional conduction, intermediate, and the steady-state regions. The time required for the one-dimensional conduction and the time necessary to attain a steady-state condition are obtained. The use of local similarity approximations for the intermediate regime facilitates prediction of complete boundary layer growth. Using the ratio of time at any instant to the steady-state time as abscissa, the curves representing the boundary layer growth can be merged into a single mean curve within 5%. Further, the analysis shows that the average rate of heat transfer during transient is 50 to 100% higher than those at steady state. The average rate of vapor convected away is 10 to 15% lower than at steady state while the average rate of accumulation to form the vapor layer is 1 to 14 times larger.
Transient-forced convection film boiling on an isothermal flat plate
NASA Technical Reports Server (NTRS)
Nagendra, H. R.
1971-01-01
An approach for the solution of transient-forced convection film boiling on an isothermal flat plate using the boundary layer model is developed. The similarity variables are used to convert the governing partial differential equations to ordinary ones. The results of numerical solutions of these ordinary equations indicate that the transient process can be classified as one-dimensional conduction, intermediate, and the steady state regions. The time required for the one-dimensional conduction and the time necessary to attain a steady state condition are obtained. The influence of interfacial shear is seen to be negligible while the Prandtl Number and the ratio (C sub p delta T divided by h sub fg times Pr) have major influence. The use of local similarity approximations for the intermediate regime facilitates prediction of complete boundary layer growth. Using the ratio of time at any instant to the steady state time as abscissa, the curves representing the boundary layer growth can be merged into a single mean curve within 5 percent. Further, the analysis shows that the average rate of heat transfer during transient is 50 to 100 percent higher than those at steady state. The average rate of vapor convected away is 10 to 15 percent lower than at steady state while the average rate of accumulation to form the vapor layer is 1 to 14 times larger. Further, the total heat transferred during transient increases and the evaporation decreases for increasing values of C sub p delta T divided by h sub fg times Pr
Spray Formation during the Impact of a Flat Plate on Water Surface
NASA Astrophysics Data System (ADS)
Wang, An; Duncan, James H.
2015-11-01
Spray formation during the impact of a flat plate on a water surface is studied experimentally. The plate is mounted on a two-axis carriage that can slam the plate vertically into the water surface as the carriage moves horizontally along a towing tank. The plate is 122 cm by 38 cm and oriented with adjustable pitch and roll angle. The port (lower) edge of the plate is positioned with a 3-mm gap from one of the tank walls. A laser sheet is created in a plane oriented perpendicular to the axis of the horizontal motion of the carriage. The temporal evolution of the spray within the light sheet is measured with a cinematic laser induced fluorescence technique at a frame rate of 800 Hz. Experiments are performed with a fixed plate trajectory in a vertical plane, undertaken at various speeds. Two types of spray are found when the plate has nonzero pitch and roll angles. The first type is composed of a cloud of high-speed droplets and ligaments generated as the port edge of the plate hits the water surface during the initial impact. The second type is a thin sheet of water that grows from the starboard edge of the plate as it moves below the local water level. The geometrical features of the spray are found to be dramatically affected by the impact velocity. The support of the Office of Naval Research under grant N000141310587 is gratefully acknowledged.
Heat transfer enhancement downstream of vortex generators on a flat plate
Turk, A.Y.
1984-01-01
This investigation was conducted in order to better understand the augmentation of forced convective heat transfer when a single row of counter-rotating vortex blades is attached to a flat surface. The major emphasis of the work is to study the way in which vortex generators augment the heat transfer coefficient of an initially-laminar boundary layer over a flat, constant heat flux surface exposed to favorable free stream pressure gradients. Particular emphasis is placed on the relationship between the geometry of vortex generators and the augmentation of local and overall heat transfer coefficients. The behavior of the boundary layer downstream of vortex generators is partially explored. This dissertation includes results of an experimental investigation that indicates the amount of heat transfer enhancement depends on the vortex blade height and arrangement on the plate surface. The local enhancement of the heat transfer coefficient was increased up to 300% over that for a plain flat plate mainly because of high turbulence produced over the region adjacent to the plate surface, resulting in increased mixing of the slower fluid near the plate surface with the free stream. A set of guidelines for the design of more efficient surface with vortex generators was proposed.
McGarity, A.E.; Allen, J.W.; Schertz, W.W.
1983-10-01
Three liquid-based solar heating systems employing different types of solar collectors were tested side by side near Chicago, Illinois for one year. The three different types of collectors were: a flat plate collector with a black-chrome coated absorber plate and one low-iron glass cover; an evacuated-tube compound parabolic concentrator (CPC) with a concentration ratio of 1.1, oriented with tubes and troughs along a north-south axis; and an evacuated-tube CPC collector with a concentration ratio of 1.3 and one low-iron glass cover, with tubes and troughs oriented along an east-west axis. Results indicate that the flat plate collector system was the most efficient during warm weather, but the CPC systems were more efficient during cold weather, but the CPC systems were more efficient during cold weather, and the CPC systems operated under conditions too adverse for the flat plate collector. The computer simulation model ANSIM was validated by means of the side-by-side tests. The model uses analytical solutions to the storage energy balance. ANSIM is compared with the general simulation TRNSYS. (LEW)
Experimental study on productivity of modified single-basin solar still with a flat plate absorber
NASA Astrophysics Data System (ADS)
Ramanathan, V.; Kanimozhi, B.; Bhojwani, V. K.
2017-05-01
Solar still is an apparatus which uses solar energyto producedistilled water from saline water. This can be used in remote areas effectively wherein electricity is not available. The output from a conventional single basin solar still is found to be very low. Hence research is required to increase the productivity of the conventional solar still. This work is an attempt to increase the productivity of solar still. A flat mica plate is embedded in the conventional solar still to augment evaporation of the water from the input saline water. The flat plate absorber is placed in such a way that it is parallel to the glass cover of the solar still so as to maximize the absorption of solar radiations. By this modification, the maximum temperature of the absorber plate achieved was 95°C in comparison to 67°C of the conventional solar still. Experimental results of modified solar still were compared with conventional solar still. It was found that distillate output increased by 25% with a flat plate absorber when compared to conventional still.
NASA Technical Reports Server (NTRS)
Kuhlman, J. M.; Ousterhout, D. S.; Warcup, R. W.
1978-01-01
Tabular data are presented for an experimental study of the effects of jet decay rate on the jet-induced pressure distribution on a flat plate for a single jet issuing at right angle to the flat plate into a uniform crossflow. The data are presented in four sections: (1) presents the static nozzle calibration data; (2) lists the plate surface static pressure data and integrated loads; (3) lists the jet centerline trajectory data; and (4) lists the centerline dynamic pressure data.
Approximate Natural Frequencies of Circular Plates with Mixed Boundary Conditions
2004-02-11
natural frequencies have bera investigated. In addition the natural frequencies of plates in asymmetric motion axe presented and exhibit for each modem...points, at which the boundary conditions are satisfied Q transverse shearing force r5 W polar coordinates t time V Kelvin-Kirchhoff edge reaction w(r, ýp
Flat field response of the microchannel plate detectors used on the Extreme Ultraviolet Explorer
NASA Technical Reports Server (NTRS)
Vallerga, J. V.; Gibson, J. L.; Siegmund, O. H. W.; Vedder, P. W.
1989-01-01
The results of the extreme ultraviolet (EUV) flat field calibrations of two of the flight detectors to be flown on the Extreme Ultraviolet Explorer Satellite (EUVE) are presented. Images of about 40 million detected events binned 512 by 512 are sufficient to show microchannel plate fixed pattern noise such as hexagonal microchannel multifiber bundle interfaces, 'dead' spots, edge distortion, and differential nonlinearity. Differences due to photocathode material and dependencies on EUV wavelength are also described. Over large spatial scales, the detector response is flat to better than 10 percent of the mean response, but, at spatial scales less than 1 mm, the variations from the mean can be as large as 20 percent.
Flat field response of the microchannel plate detectors used on the Extreme Ultraviolet Explorer
NASA Technical Reports Server (NTRS)
Vallerga, J. V.; Gibson, J. L.; Siegmund, O. H. W.; Vedder, P. W.
1989-01-01
The results of the extreme ultraviolet (EUV) flat field calibrations of two of the flight detectors to be flown on the Extreme Ultraviolet Explorer Satellite (EUVE) are presented. Images of about 40 million detected events binned 512 by 512 are sufficient to show microchannel plate fixed pattern noise such as hexagonal microchannel multifiber bundle interfaces, 'dead' spots, edge distortion, and differential nonlinearity. Differences due to photocathode material and dependencies on EUV wavelength are also described. Over large spatial scales, the detector response is flat to better than 10 percent of the mean response, but, at spatial scales less than 1 mm, the variations from the mean can be as large as 20 percent.
1983-01-01
The Flat-Plate Solar Array Project, managed by the Jet Propulsion Laboratory for the US Department of Energy, has focused on advancing technologies relevant to the design and construction of megawatt-level central-station systems. Photovoltaic modules and arrays for flat-plate central-station or other large-scale electric power production facilities require the establishment of a technical base that resolves design issues and results in practical and cost-effective configurations. The Central Station Research Forum addressed design, qualification and maintenance issues related to central-station arrays derived from the engineering and operating experiences of early applications and parallel laboratory research activities. Technical issues were examined from the viewpoint of the utility engineer, architect-engineer and laboratory researcher. The forum included presentations on optimum source-circuit designs, module insulation design for high system voltages, array safety, structural interface design, measurements and array operation and maintenance. The Research Forum focused on current capabilities as well as design difficulties requiring additional technological thrusts and/or continued research emphasis. Session topic summaries highlighting major points during group discussions, identifying promising technical approaches or areas of future research, are presented.
NASA Technical Reports Server (NTRS)
Sohn, Ki-Hyeon; Reshotko, Eli
1991-01-01
A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities (TI) from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for R(sub theta) is less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length. The measured laminar value of Reynolds analogy factor was as much as 53 percent higher than the Pr(sup -2/3). A small dependence of turbulent results on TI was observed. Conditional sampling performed in the transitional boundary layer indicated the existence of a near-wall drop in intermittency, pronounced at certain low intermittencies, which is consistent with the cross-sectional shape of turbulent spots observed by others. Non-turbulent intervals were observed to possess large magnitudes of near-wall unsteadiness and turbulent intervals had peak values as much as 50 percent higher than were measured at fully turbulent stations. Non-turbulent and turbulent profiles in transitional boundary layers cannot be simply treated as Blasius and fully turbulent profiles, respectively. The boundary layer spectra indicate predicted selective amplification of T-S waves for TI is approximately 0.4 percent. However, for TI is approximately 0.8 and 1.1 percent, T-S waves are localized very near the wall and do not play a dominant role in transition process.
Acoustic radiation damping of flat rectangular plates subjected to subsonic flows
NASA Technical Reports Server (NTRS)
Lyle, Karen Heitman
1993-01-01
The acoustic radiation damping for various isotropic and laminated composite plates and semi-infinite strips subjected to a uniform, subsonic and steady flow has been predicted. The predictions are based on the linear vibration of a flat plate. The fluid loading is characterized as the perturbation pressure derived from the linearized Bernoulli and continuity equations. Parameters varied in the analysis include Mach number, mode number and plate size, aspect ratio and mass. The predictions are compared with existing theoretical results and experimental data. The analytical results show that the fluid loading can significantly affect realistic plate responses. Generally, graphite/epoxy and carbon/carbon plates have higher acoustic radiation damping values than similar aluminum plates, except near plate divergence conditions resulting from aeroelastic instability. Universal curves are presented where the acoustic radiation damping normalized by the mass ratio is a linear function of the reduced frequency. A separate curve is required for each Mach number and plate aspect ratio. In addition, acoustic radiation damping values can be greater than or equal to the structural component of the modal critical damping ratio (assumed as 0.01) for the higher subsonic Mach numbers. New experimental data were acquired for comparison with the analytical results.
Optimization of a flat plate glass reactor for mass production of Nannochloropsis sp. outdoors.
Richmond, A; Cheng-Wu, Z
2001-02-23
The relationships between areal (g m(-2) per day) and volumetric (g l(-1) per day) productivity of Nannochloropsis sp. as affected by the light-path (ranging from 1.3 to 17.0 cm) of a vertical flat plate glass photobioreactor were elucidated. In general, the shorter the length of the light-path (LP), the smaller the areal volume and the higher the volumetric productivity. The areal productivity in relation to the light-path, in contrast, yielded an optimum curve, the highest areal productivity was obtained in a 10 cm LP reactor, which is regarded, therefore, optimal for mass production of Nannochloropsis. An attempt was made to identify criteria by which to assess the efficiency of a photobioreactor in utilizing strong incident energy. Two basic factors which relate to reactor efficiency and its cost-effectiveness have been defined as (a) the total illuminated surface required to produce a set quantity of product and (b) culture volume required to produce that quantity. As a general guide line, the lower these values are, the more efficient and cost-effective the reactor would be. An interesting feature of this analysis rests with the fact that an open raceways is as effective in productivity per illuminated area as a flat-plate reactor with an optimal light path, both cultivation systems requiring ca. 85 m(2) of illuminated surface to produce 1 kg dry cell mass of Nannochloropsis sp. per day. The difference in light utilization efficiency between the two very different production systems involves three aspects - first, the open raceway requires ca. 6 times greater volume than the 10 cm flat plate reactor to produce the same quantity of cell-mass. Second, the total ground area (i.e. including the ground area between reactors) for the vertical flat plate reactor is less than one half of that occupied by an open raceway, indicating the former is more efficient, photosynthetically, compared with the latter. Finally, the harvested cell density is close to one order of
Resonant Interaction of a Rectangular Jet with a Flat-Plate
NASA Technical Reports Server (NTRS)
Zaman, K. B. M. Q.; Fagan, A. F.; Clem, M. M.; Brown, C. A.
2014-01-01
A resonant interaction between a large aspect ratio rectangular jet and a flat-plate is addressed in this experimental study. The plate is placed parallel to but away from the direct path of the jet. At high subsonic conditions and for certain relative locations of the plate, the resonance accompanied by an audible tone is encountered. The trends of the tone frequency variation exhibit some similarities to, but also marked differences from, corresponding trends of the well-known edge-tone phenomenon. Under the resonant condition flow visualization indicates a periodic flapping motion of the jet column. Phase-averaged Mach number data obtained near the plate's trailing edge illustrate that the jet cross-section goes through large contortions within the period of the tone. Farther downstream a clear 'axis switching' takes place. These results suggest that the assumption of two-dimensionality should be viewed with caution in any analysis of the flow.
Separation over a flat plate-wedge configuration at oceanic Reynolds numbers
NASA Technical Reports Server (NTRS)
Campbell, D. R.
1973-01-01
An experimental study of flow over a two-dimensional flat plate-wedge configuration is presented. The investigation encompasses a range of Reynolds numbers characteristics of conditions encountered by deep submersible oceanic vehicles. Flow separation, similar to that found on high speed aircraft control surfaces, is reported and discussed in light of the laminar or transitional nature of the separated shear layer. As discovered in previous high Mach number studies of plate-wedge or ramp configurations, the dependency of the size of the separated region on free stream Reynolds number is reversed for laminar and transitional types of flow separation.
On the nonlinear stability of viscous modes within the Rayleigh problem on an infinite flat plate
NASA Technical Reports Server (NTRS)
Webb, J. C.; Otto, S. R.; Lilley, G. M.
1994-01-01
The stability has been investigated of the unsteady flow past an infinite flat plate when it is moved impulsively from rest, in its own plane. For small times the instantaneous stability of the flow depends on the linearized equations of motion which reduce in this problem to the Orr-Sommerfeld equation. It is known that the flow for certain values of Reynolds number, frequency and wave number is unstable to Tollmien-Schlichting waves, as in the case of the Blasius boundary layer flow past a flat plate. With increase in time, the unstable waves only undergo growth for a finite time interval, and this growth rate is itself a function of time. The influence of finite amplitude effects is studied by solving the full Navier-Stokes equations. It is found that the stability characteristics are markedly changed both by the consideration of the time evolution of the flow, and by the introduction of finite amplitude effects.
Frozen-plasma boundary-layer flows over adiabatic flat plates
Ben-Dor, G.; Igra, O.
1984-07-01
The boundary-layer equations for a partially ionized frozen flow over a flat plate has been solved using a new approach in which the problem is reduced from a two-point boundary value problem to a Cauchy problem, thus offering a simple, stable, and relatively inexpensive solution technique. The method is applied to a strong shock-induced argon flow over an adiabatic flat plate. The dependence of the flow inside the boundary layer on the Prandtl number Pr, and Lewis number Le, and on the exponential dependence n of the density viscosity product on the temperature are explored, and it is found that while Pr and n strongly affect the obtained flow field, the influence of Le is negligibly small.
Accurate stratospheric particle size distributions from a flat plate collection surface
NASA Technical Reports Server (NTRS)
Zolensky, M. E.; Mackinnon, I. D. R.
1985-01-01
Flat plate particle collections have revealed the presence of a remarkable variety of both terrestrial and extraterrestrial material in the stratosphere. It is found that the ratio of terrestrial to extraterrestrial material and the nature of the material collected may vary significantly over short time scales. These fluctuations may be related to massive injections of volcanic ash, emissions from solid fuel rockets, or variations in the micrometeoroid flux. The variations in particle number density can be of great importance to the earth's atmospheric radiation balance, and, therefore, its climate. With the objective to assess the number density of solid particles in the stratosphere, an examination has been conducted of all particles exceeding 1 micron in average diameter for a representative suite of particles obtained from a single flat plate collection surface. Attention is given to solid particle size distributions in the stratosphere, and the origin of important stratospheric particle types.
Flat plate solar collector for a tropical climate: Determining the solar energy contribution
Kulatunga, A.
1999-10-01
Energy is the lifeblood of most manufacturing processes. Finding an inexpensive and reliable source of energy is a challenge in many developing countries. Due to lack of planning and bureaucratic barriers, state-run energy industries of these countries are unable to meet the demand of booming small industries. Plant managers, struggling to ship their export quotas, seek viable solutions to their energy problems. This report analyzes the hot water needs of a manufacturing plant in Sri Lanka. A solution is proposed to incorporate a flat-plate solar collector to supplement the current water heating system using appropriate technologies. Any proposed solutions to the energy problems in developing countries should consider the socioeconomic status of a given country. Specifically, this article illustrates how one can estimate the thermal energy contribution that can be obtained via a flat-plate solar collector mounted on a plant roof. Once the energy contribution factor is known, one can use it for other economical analysis.
Accurate stratospheric particle size distributions from a flat plate collection surface
NASA Technical Reports Server (NTRS)
Zolensky, M. E.; Mackinnon, I. D. R.
1985-01-01
Flat plate particle collections have revealed the presence of a remarkable variety of both terrestrial and extraterrestrial material in the stratosphere. It is found that the ratio of terrestrial to extraterrestrial material and the nature of the material collected may vary significantly over short time scales. These fluctuations may be related to massive injections of volcanic ash, emissions from solid fuel rockets, or variations in the micrometeoroid flux. The variations in particle number density can be of great importance to the earth's atmospheric radiation balance, and, therefore, its climate. With the objective to assess the number density of solid particles in the stratosphere, an examination has been conducted of all particles exceeding 1 micron in average diameter for a representative suite of particles obtained from a single flat plate collection surface. Attention is given to solid particle size distributions in the stratosphere, and the origin of important stratospheric particle types.
Experimental simulation of the Bubble Membrane Radiator using a rotating flat plate
NASA Astrophysics Data System (ADS)
Al-Baroudi, Homam; Klein, Andrew C.; Pauley, Keith A.
The Bubble Membrane Radiator (BMR), to be used in space reactor systems, uses artificial gravity imposed on the working fluid by means of the centrifugal force to pump the fluid from the radiator. Experimental and analytical studies have been initiated to understand the nature of fluid and heat transport under the conditions of rotation. An experiment is described which measures the condensation of vapor on a rotating flat plate which is oriented normal to the Earth's gravity vector to simulate the BMR physics. The relationship between vapor flow rates and rotation speed of the flat plate and a number of physical parameters including amount of condensate, overall heat transfer coefficient, and condensate film thickness are studied experimentally.
Flat plate vs. concentrator solar photovoltaic cells - A manufacturing cost analysis
NASA Technical Reports Server (NTRS)
Granon, L. A.; Coleman, M. G.
1980-01-01
The choice of which photovoltaic system (flat plate or concentrator) to use for utilizing solar cells to generate electricity depends mainly on the cost. A detailed, comparative manufacturing cost analysis of the two types of systems is presented. Several common assumptions, i.e., cell thickness, interest rate, power rate, factory production life, polysilicon cost, and direct labor rate are utilized in this analysis. Process sequences, cost variables, and sensitivity analyses have been studied, and results of the latter show that the most important parameters which determine manufacturing costs are concentration ratio, manufacturing volume, and cell efficiency. The total cost per watt of the flat plate solar cell is $1.45, and that of the concentrator solar cell is $1.85, the higher cost being due to the increased process complexity and material costs.
NASA Technical Reports Server (NTRS)
Simon, F.
1975-01-01
A Soltex flat plate solar collector was tested with a solar simulator for inlet temperatures of 77 to 201 F, flux levels of 240 and 350 Btu/hr-sq ft, a collant flow rate of 10.5 lb/hr sq ft, and incident angles of 0 deg, 41.5 deg, and 65.2 deg. Collector performance is correlated in terms of inlet temperature, flux level, and incident angle.
On the numerical simulation of spatial disturbances in blunt-nose flat plate flow
NASA Technical Reports Server (NTRS)
Laurien, Eckart
1990-01-01
The feasibility of the simulation of the evolution of spatially amplified disturbances in realistic airfoil flows using a standard Navier-Stokes airfoil code is considered for a blunt-nose flat plate flow. A basic stationary flow and its linear-stability-theory characteristics are analyzed. A computational C-grid is generated using an algebraic grid-generation technique. It is concluded that further improvements to the computational grid and to the code are necessary to make the proposed simulations economical.
The stability of a three dimensional laminar boundary layer over a swept flat plate
NASA Technical Reports Server (NTRS)
Mueller, B.; Bippes, H.; Collier, F. S., Jr.
1990-01-01
The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for a leading-edge sweep angle of 45 degrees and freestream valocity of 19 m/s. Computed disturbance amplification rates and wavelengths for stationary crossflow vortices were compared with available experimental results.
The stability of a three-dimensional laminar boundary layer on a swept flat plate
NASA Technical Reports Server (NTRS)
Collier, F. S., Jr.; Mueller, B.; Bippes, H.
1990-01-01
The linear stability of the laminar boundary layer on a swept flat plate with an imposed favorable pressure gradient was studied utilizing a linear stability model which accounts for streamline curvature for three-dimensional incompressible flows. Calculations were performed for an effective leading-edge sweep angle of 42.5 degrees and freestream velocity of 19 m/s. Computed disturbance amplification rates for the spectrum of amplified frequencies and wavelengths for stationary crossflow vortices were compared with experimental results.
Recommendations for the performance rating of flat plate terrestrial photovoltaic solar panels
NASA Technical Reports Server (NTRS)
Treble, F. C.
1976-01-01
A review of recommendations for standardizing the performance rating of flat plate terrestrial solar panels is given to develop an international standard code of practice for performance rating. Required data to characterize the performance of a solar panel are listed. Other items discussed are: (1) basic measurement procedures; (2) performance measurement in natural sunlight and simulated sunlight; (3) standard solar cells; (4) the normal incidence method; (5) global method and (6) definition of peak power.
Numerical Investigation of Laminar-Turbulent Transition in a Flat Plate Wake
1990-03-02
NUMERICAL INVESTIGATION OF LAMINAR-TURBULENT TRANSITION IN A FLAT PLATE WAKE by David I. Dratler and Hermann F. Fasel D T I C E ECTE MAY 2 5 1990 g...etsear Fows_________________ 12. PERSONAL AUTHOR(S) Hermann F. Fasel and Alan C. Newell 13&. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Yr.. M...discretized velocity equations are solved using fast Helmholtz solvers. Code validation is accomplished by comparison of the numerical results to both
An experimental study on the compatibility of acetone with aluminum flat-plate heat pipes
NASA Astrophysics Data System (ADS)
Hsieh, Jui-Ching; Lin, David T. W.; Huang, Hsin-Jung; Yang, Tzu-Wei
2014-04-01
This study investigates the compatibility of aluminum flat-plate heat pipes (FPHPs) used for filling acetone as a working fluid after long-term operation of and the non-condensable gas (NCG) exhausting process. The rate of NCG generation substantially decreased after conducting the NCG exhausting process, proving the compatibility of acetone with the aluminum FPHPs. However, the thermal resistance was not enhanced because hydroxide bayerite (Al(OH)3) was generated as a product of the reaction.
Performance of a combined photovoltaic/thermal, flat-plate, liquid collector
NASA Astrophysics Data System (ADS)
Aiello, W. A.; Raghuraman, P.
A combined photovoltaic/thermal, flat-plate, liquid collector, where the liquid circulates both below and above the photovoltaic cells (the primary energy-absorbing surface), was designed and tested according to ASHRAE 93-77 specifications to yield collector thermal and electrical efficiencies. A one-dimensional thermal analysis predicts the test results accurately. On the strength of the test and analytical results, design recommendations are made to maximize the total energy extracted from the collectors.
Uncertainty in determining thermal performance of liquid-heating flat-plate solar collectors
NASA Astrophysics Data System (ADS)
Streed, E. R.; Waksman, D.
1981-05-01
Thermal performance measurements of eight types of liquid-heating flat-plate solar collectors were conducted with two to four collectors of each type at four outdoor test sites. Tests were performed in accordance with the procedure prescribed by ASHRAE Standard 93-77. Statistical analysis of data sets for each collector type within test sites and between test sites was done using ASTM recommended methods to evaluate test method measurement uncertainty.
Laminar-Boundary-Layer Oscillations and Transition on a Flat Plate
1943-04-01
attempted to test the stability theory by producing sinusoidal fluetuations in the, bound- ary layer near the leading edge of a flat plate in water...section with the loading edge 6 feet from the upstream end. In order to reduce vibration, the test section of this tun- nel Is supported dirpctly...Boundary Layor Since a theoretical dl the boundary layer has been VI-2D and table IV), the ac est ae a test of agreement Traverses across the bounda
Semicoarsening and Implicit Smoothers for the Simulation of a Flat Plate at Yaw
2001-05-01
Semicoarsening and Implicit Smoothers for the Simulation of a Flat Plate at Yaw Ruben S. Montero and Ignacio M. Llorente Universidad Complutense , Madrid ...yDepartamento de Arquitectura de Computadores y Automatica, Universidad Complutense , 28040 Madrid , Spain zDepartamento de Arquitectura de Computadores...y Automatica, Universidad Complutense , 28040 Madrid , Spain xICASE, Mail Stop 132C, NASA Langley Research Center, Hampton, VA 23681-2199 1
Maximum lift/drag ratio of flat plates with bluntness and skin friction at hypersonic speeds
NASA Technical Reports Server (NTRS)
Tauber, M. E.
1986-01-01
Newtonian theory is used to derive a simple expression for the maximum lift/drag ratio of flat plates with bluntness and skin friction at hypersonic speeds. The bluntness drag is assumed to be independent of angle of attack. Because the effect of skin friction is of second order over the angle of attack range for maximum lift/drag ratio, it was assumed constant. As an example, the expression is applied to the Space Shuttle.
1983-11-15
A Photovoltaic Metallization Research Forum, under the sponsorship of the Jet Propulsion Laboratory's Flat-Plate Solar Array Project and the US Department of Energy, was held March 16-18, 1983 at Pine Mountain, Georgia. The Forum consisted of five sessions, covering (1) the current status of metallization systems, (2) system design, (3) thick-film metallization, (4) advanced techniques and (5) future metallization challenges. Twenty-three papers were presented.
Application of wave mechanics theory to fluid dynamics problems: Flat plate flow
NASA Technical Reports Server (NTRS)
Krzywoblocki, M. Z. V.
1974-01-01
The characteristics of the flow in the laminar boundary layer along an infinitely long flat plate are discussed. The flow may be disturbed or not, depending on the situation. The physical, natural aspects of the flow, either a laminar flow free from disturbances or a flow which originally is a laminar one with disturbances superimposed upon it. Oscillograms of turbulence in wind tunnel tests and in the wake of a cylinder are presented.
NASA Technical Reports Server (NTRS)
1978-01-01
An efficient, low cost, flat-plate solar collector was developed. Computer aided mathematical models of the heat process in the collector were used in defining absorber panel configuration; determining insulation thickness; and in selecting the number, spacing, and material of the covers. Prototypes were built and performance tested. Data from simulated operation of the collector are compared with predicted loads from a number of locations to determine the degree of solar utilization.
Visualization of leading edge vortices on a series of flat plate delta wings
NASA Technical Reports Server (NTRS)
Payne, Francis M.; Ng, T. Terry; Nelson, Robert C.
1991-01-01
A summary of flow visualization data obtained as part of NASA Grant NAG2-258 is presented. During the course of this study, many still and high speed motion pictures were taken of the leading edge vortices on a series of flat plate delta wings at varying angles of attack. The purpose is to present a systematic collection of photographs showing the state of vortices as a function of the angle of attack for the four models tested.
Recommendations for the performance rating of flat plate terrestrial photovoltaic solar panels
NASA Technical Reports Server (NTRS)
Treble, F. C.
1976-01-01
A review of recommendations for standardizing the performance rating of flat plate terrestrial solar panels is given to develop an international standard code of practice for performance rating. Required data to characterize the performance of a solar panel are listed. Other items discussed are: (1) basic measurement procedures; (2) performance measurement in natural sunlight and simulated sunlight; (3) standard solar cells; (4) the normal incidence method; (5) global method and (6) definition of peak power.
Development of electromagnetic welding facility of flat plates for nuclear industry
NASA Astrophysics Data System (ADS)
Kumar, Rajesh; Sahoo, Subhanarayan; Sarkar, Biswanath; Shyam, Anurag
2017-04-01
Electromagnetic pulse welding (EMPW) process, one of high speed welding process uses electromagnetic force from discharged current through working coil, which develops a repulsive force between the induced current flowing parallel and in opposite direction. For achieving the successful weldment using this process the design of working coil is the most important factor due to high magnetic field on surface of work piece. In case of high quality flat plate welding factors such as impact velocity, angle of impact standoff distance, thickness of flyer and overlap length have to be chosen carefully. EMPW has wide applications in nuclear industry, automotive industry, aerospace, electrical industries. However formability and weldability still remain major issues. Due to ease in controlling the magnetic field enveloped inside tubes, the EMPW has been widely used for tube welding. In case of flat components control of magnetic field is difficult. Hence the application of EMPW gets restricted. The present work attempts to make a novel contribution by investigating the effect of process parameters on welding quality of flat plates. The work emphasizes the approaches and engineering calculations required to effectively use of actuator in EMPW of flat components.
Analysis of electromagnetic scattering from irregularly shaped, thin, metallic flat plates
NASA Technical Reports Server (NTRS)
Deshpande, Manohar D.; Cockrell, C. R.; Beck, Fred B.; Vedeler, Erik; Koch, Melissa B.
1993-01-01
This report describes an application of the method of moments to calculate the electromagnetic scattering from irregularly shaped, thin, metallic flat plates in free space. In the present technique, an irregularly shaped plate is enclosed by a rectangle on which the surface-current density is then expressed in terms of subdomain functions by dividing the rectangle into subsections. A shape function is introduced to ensure zero current outside the patch. The surface-current density is determined using the electric field integral equation (EFIE) approach in conjunction with the method of moments, and from a knowledge of the surface-current density, the electromagnetic scattering from a plate is calculated. Using this technique, the electromagnetic scattering from a hexagonal plate; an equilateral triangular plate; an equilateral triangular plate with a concentric, equilateral triangular hole and an inverted, equilateral triangular hole; and a diamond-shaped plate is computed and compared with the numerical results obtained by using the Electromagnetic Surface Patch (ESP) code developed by Ohio State University. The numerical results compare favorably with the measurements performed on these shapes in the Langley Experimental Test Range facility.
In-Flight Boundary-Layer Transition of a Large Flat Plate at Supersonic Speeds
NASA Technical Reports Server (NTRS)
Banks, D. W.; Frederick, M. A.; Tracy, R. R.; Matisheck, J. R.; Vanecek, N. D.
2012-01-01
A flight experiment was conducted to investigate the pressure distribution, local-flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.00. The tests used a NASA testbed aircraft with a bottom centerline mounted test fixture. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating. Boundary-layer transition was captured in both analog and digital formats using an onboard infrared imaging system. Surface pressures were measured on the surface of the flat plate. Flow field measurements near the leading edge of the test fixture revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration.
NASA Astrophysics Data System (ADS)
Tahavvor, Ali Reza
2017-03-01
In the present study artificial neural network and fractal geometry are used to predict frost thickness and density on a cold flat plate having constant surface temperature under forced convection for different ambient conditions. These methods are very applicable in this area because phase changes such as melting and solidification are simulated by conventional methods but frost formation is a most complicated phase change phenomenon consists of coupled heat and mass transfer. Therefore conventional mathematical techniques cannot capture the effects of all parameters on its growth and development because this process influenced by many factors and it is a time dependent process. Therefore, in this work soft computing method such as artificial neural network and fractal geometry are used to do this manner. The databases for modeling are generated from the experimental measurements. First, multilayer perceptron network is used and it is found that the back-propagation algorithm with Levenberg-Marquardt learning rule is the best choice to estimate frost growth properties due to accurate and faster training procedure. Second, fractal geometry based on the Von-Koch curve is used to model frost growth procedure especially in frost thickness and density. Comparison is performed between experimental measurements and soft computing methods. Results show that soft computing methods can be used more efficiently to determine frost properties over a flat plate. Based on the developed models, wide range of frost formation over flat plates can be determined for various conditions.
Xu, Jian-Guang; Wang, Xu-Xia; Ren, Xu-Sheng; Zhang, Jun; Li, Na
2009-06-01
To analyze changes of myoelectrical activity of anterior funicle of temporal muscle (TA) and masseter muscle (MM) after raising vertical distance of occlusion by flat bite plate during treatment of deep overbite in order to approach an optimal raised vertical distance. A total of 70 persons were selected and divided into two groups: Experiment group (36 patients) with deep overbite and control group (34 persons) with individual normal occlusion. The experiment group was subdivided into three groups that were respectively raised D, D+2 mm and D+4 mm (D means free way space, mm). Electromyologram (EMG) was utilized to measure the average peak potential of TA and MM on quiescent condition before treatment and two weeks after wearing flat bite plate. 1) Before treatment, the average peak potential of experiment group was obviously higher than that of the control group (P<0.05). 2) After two weeks the potential of TA and MM of all persons in experiment group was obviously lower than before (P<0.05), the degree between the group D+2 mm and the group D+4 mm was not manifestly different, but both of the two groups were more obvious than the group D. The raised vertical distance of occlusion by flat bite plate, which exceeded free way space, was favourable to the functional recovery of masticatory muscles.
LDEF transverse flat plate heat pipe experiment /S1005/. [Long Duration Exposure Facility
NASA Technical Reports Server (NTRS)
Robinson, G. A., Jr.
1979-01-01
The paper describes the Transverse Flat Plate Heat Pipe Experiment. A transverse flat plate heat pipe is a thermal control device that serves the dual function of temperature control and mounting base for electronic equipment. In its ultimate application, the pipe would be a lightweight structure member that could be configured in a platform or enclosure and provide temperature control for large space structures, flight experiments, equipment, etc. The objective of the LDEF flight experiment is to evaluate the zero-g performance of a number of transverse flat plate heat pipe modules. Performance will include: (1) the pipes transport capability, (2) temperature drop, and (3) ability to maintain temperature over varying duty cycles and environments. Performance degradation, if any, will be monitored over the length of the LDEF mission. This information is necessary if heat pipes are to be considered for system designs where they offer benefits not available with other thermal control techniques, such as minimum weight penalty, long-life heat pipe/structural members.
Numerical modeling of the transitional boundary layer over a flat plate
NASA Astrophysics Data System (ADS)
Ivanov, Dimitry; Chorny, Andrei
2015-11-01
Our example is connected with fundamental research on understanding how an initially laminar boundary layer becomes turbulent. We have chosen the flow over a flat plate as a prototype for boundary-layer flows around bodies. Special attention was paid to the near-wall region in order to capture all levels of the boundary layer. In this study, the numerical software package OpenFOAM has been used in order to solve the flow field. The results were used in a comparative study with data obtained from Large Eddy Simulation (LES). The composite SGS-wall model is presently incorporated into a computer code suitable for the LES of developing flat-plate boundary layers. Presently this model is extended to the LES of the zero-pressure gradient, flat-plate turbulent boundary layer. In current study the time discretization is based on a second order Crank-Nicolson/Adams-Bashforth method. LES solver using Smagorinsky and the one-equation LES turbulence models. The transition models significantly improve the prediction of the onset location compared to the fully turbulent models.LES methods appear to be the most promising new tool for the design and analysis of flow devices including transition regions of the turbulent flow.
NASA Technical Reports Server (NTRS)
Shaw, C. S.; Margason, R. J.
1973-01-01
The induced static pressures due to a highly underexpanded sonic jet ejecting normally from a flat plate into a subsonic crosswind have been investigated. These pressure data have been recorded on the flat plate for a range of nominal jet-to-free-stream dynamic-pressure ratios from 0 to 1000 at free-stream Mach numbers of 0.1, 0.2, 0.4, and 0.6. The static pressure data measured on the flat plate are presented and correlated based upon the Riemann shock geometry in the jet plume. This data correlation improves with increasing free-stream Mach number.
Ground effects on separated laminar flows past an inclined flat plate
NASA Astrophysics Data System (ADS)
Li, Zhen; Lan, Chuanjin; Jia, Laibing; Ma, Yanbao
2016-10-01
The appearance of a ground surface can play an important role in the flow structures for the flows past a flat plate. We conduct two-dimensional numerical simulations on viscous flows past a flat plate inclined at an angle of attack of 20° with ground effects using a finite-volume method. Results show that the effects on the separated flow from the ground are highly dependent on the gap (G) between the plate and the ground. As the gap decreases, the strength of vortices generated from the trailing edge is restrained, which is consistent with experimental observations. Further decrease in the gap even eliminates the vortex shedding and yields a steady flow. It is also found that the flow between the gap can either be accelerated at large gap ratios ({G/L >1} , G is the gap, L is the plate length), or be decelerated at small gap ratios ({G/L <1} ). Furthermore, the numerical results show that the wake flow behind the plate can significantly change the distribution of surface shear stress on the ground. Specifically, the mean shear stress on the ground in the downstream region at a gap ratio G/L = 2.0 is one order of magnitude larger than that at a small gap ratio G/L = 0.3 , and the length of the downstream region where the shear stress can be effectively changed is much larger than the plate length, which provides a guideline to manipulate the ground wall surface shear stress using an inclined plate in the vicinity of the wall.
Ground effects on separated laminar flows past an inclined flat plate
NASA Astrophysics Data System (ADS)
Li, Zhen; Lan, Chuanjin; Jia, Laibing; Ma, Yanbao
2017-04-01
The appearance of a ground surface can play an important role in the flow structures for the flows past a flat plate. We conduct two-dimensional numerical simulations on viscous flows past a flat plate inclined at an angle of attack of 20° with ground effects using a finite-volume method. Results show that the effects on the separated flow from the ground are highly dependent on the gap ( G) between the plate and the ground. As the gap decreases, the strength of vortices generated from the trailing edge is restrained, which is consistent with experimental observations. Further decrease in the gap even eliminates the vortex shedding and yields a steady flow. It is also found that the flow between the gap can either be accelerated at large gap ratios ({G/L >1}, G is the gap, L is the plate length), or be decelerated at small gap ratios ({G/L <1}). Furthermore, the numerical results show that the wake flow behind the plate can significantly change the distribution of surface shear stress on the ground. Specifically, the mean shear stress on the ground in the downstream region at a gap ratio G/L = 2.0 is one order of magnitude larger than that at a small gap ratio G/L = 0.3, and the length of the downstream region where the shear stress can be effectively changed is much larger than the plate length, which provides a guideline to manipulate the ground wall surface shear stress using an inclined plate in the vicinity of the wall.
Vortex-induced noise and vibration in flow past several flat plates
NASA Astrophysics Data System (ADS)
Kim, Chan Mun
A model formulation for the problem of vortex impingement on a pair of elastic tandem cylinders is presented. The parametric relations among a variety of fluid dynamic and structural dynamic properties are illustrated. The noise field essentially responds at the cylinder response frequency and the sound pressure level is generally increased by the vibration of the cylinders. The interaction of an array of vortices is also considered and the results indicate that four vortices are required for the possibility of the chaotic motion and the broadband noise. The vortex shedding off an inclined flat plane is modelled using the discrete vortex method along with the Lamb vortex model. The model tested for the rolling-up of a vortex sheet behind the elliptically loaded wing demonstrates that the smooth rollup is achieved inside the core region of the vortex sheet. The subsequent application of the model to the vortex shedding problem shows that the computed results such as the kinematics of the wake development, the fluid loading and the Strouhal number are in fair agreement with previous experimental measurements. The noise field exhibits a broadband character with the peak occurring at the vortex shedding frequency. A numerical conformal mapping technique is developed to transform multiple flat plates into the same number of circular cylinders. Employing the multiple body mapping method, the flow past a series of flat plates is investigated. The calculated results indicate that the presence of a downstream body in the wake of another body produces a feedback effect upstream which, in turn, has a significant effect on the upstream flow. In the case of vortex shedding, the presence of a downstream splitter plate in the center of the wake of an inclined plate appears to suppress the regular, periodic vortex shedding process. The addition of more inclined plates appears to reduce the Strouhal frequency which is the frequency at which the noise field responds.
The Impact of Reduced Gravity on Free Convective Heat Transfer from a Finite, Flat, Vertical Plate
NASA Astrophysics Data System (ADS)
Lotto, Michael A.; Johnson, Kirstyn M.; Nie, Christopher W.; Klaus, David M.
2017-09-01
Convective heat transfer is governed by a number of factors including various fluid properties, the presence of a thermal gradient, geometric configuration, flow condition, and gravity. Empirically-derived analytical relationships can be used to estimate convection as a function of these governing parameters. Although it is relatively straightforward to experimentally quantify the contributions of the majority of these variables, it is logistically difficult to assess the influence of reduced-gravity due to practical limitations of establishing this environment. Therefore, in order to explore this regime, a series of tests was conducted to evaluate convection under reduced-gravity conditions averaging 0.45 m/sec2 (0.05 g) achieved aboard a parabolic aircraft. The results showed a reduction in net heat transfer of approximately 61% in flight relative to a 1g terrestrial baseline using the same setup. The average experimental Nusselt Number of 19.05 ± 1.41 statistically correlated with the predicted value of 18.90 ± 0.63 (N = 13), estimated using the Churchill-Chu correlation for free convective heat transfer from a finite, flat, vertical plate. Extrapolating this to similar performance in true microgravity (10-6 g) indicates that these conditions should yield a Nusselt Number of 1.27, which is 2.6% the magnitude of free convection at 1g, or a reduction of 97.4%. With advection essentially eliminated, heat transfer becomes limited to diffusion and radiation, which are gravity-independent and nearly equivalent in magnitude in this case. These results offer a general guideline for integrating components that utilize natural (free) convective gas cooling in a spacecraft habitat and properly sizing the thermal control system.
Dynamics of a bubbly turbulent boundary layer along a surface piercing flat plate
NASA Astrophysics Data System (ADS)
Aliseda, Alberto; Lasheras, Juan C.
2003-11-01
The behaviour of a bubble-laden turbulent boundary layer has been studied experimentally in an open channel water flow with Reynolds number up to 10^6. A poly-dispersed bubble cloud with mean diameter around 200 μ m is injected at the leading edge of a vertical, surface piercing flat plate. The high void fraction bubble layer rises along the plate, developing a Kelvin Helmholtz type instability due to the vertical shear. As a result of this instability, streamwise vorticity is generated that combines with the vertical vorticity associated with the boundary layer, tilting the vortex lines. Bubbles are, for the most part, confined to the boundary layer and accumulate as they interact with the turbulent structures present in this type of flows. The flow at the junction between the flat plate and the free surface is also studied in the presence of bubbles. An streamwise submerged vortex is observed, in agreement with previous studies of single phase junction flows. Vorticity originated by the bouyancy-driven instability of the bubbly layer is convected away from the plate when it reaches the surface, and reconects with the streamwise vortex. Thus, the vortex gains strength and starts to accumulate bubbles stripped from the boundary layer, becoming a dominant feature of the flow.
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
NASA Astrophysics Data System (ADS)
Pradhan, Sahadev, , Dr.
2017-01-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
NASA Astrophysics Data System (ADS)
Pradhan, Sahadev
2016-10-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf / {kBTinf /m}) in the range
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
NASA Astrophysics Data System (ADS)
Pradhan, Sahadev, , Dr.
2016-11-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range
Flow past a Flat Plate with a Vortex/sink Combination
NASA Technical Reports Server (NTRS)
Mourtos, N. J.
1984-01-01
An attempt was made to model the so called leading edge vortex which forms over the leading edge of delta wings at high angles of attack. A simplified model was considered, namely that of a two-dimensional, inviscid, incompressible steady flow around a flat plate at an angle of attack with a stationary vortex detached on top, as well as a sink to simulate the strong spanwise flow. The results appear to agree qualitatively with experiments. A comparison was also made between the lift and the drag of this model and the corresponding results for two classical solutions: (1) that of totally attached flow over the plate with the Kutta condition satisfied at the trailing edge only: and (2) the Helmholtz solution of totally separated flow over the plate.
NASA Technical Reports Server (NTRS)
Westphal, R. V.
1986-01-01
Research has been undertaken to experimentally study the alterations in turbulent boundary-layer properties due to turbulence manipulation using thin flat plates. Plate geometry and placement within the boundary layer were selected to coincide with recent studies. Direct, local measurements of skin friction and Reynolds stresses were made within the boundary layer downstream of the manipulator devices for cases with an approach momentum thickness Reynolds number of 3700. A strong tendency for recovery of the Reynolds stresses was observed, accompanied by local skin-friction reductions of up to 15 percent. The mean velocity profile in the manipulated flow displayed the same similarity shape in the logarithmic region as a natural boundary layer, but had an enhanced wake component. The results indicate that the plate wake plays an important role in the boundary layer response to this sort of manipulation.
NASA Technical Reports Server (NTRS)
Westphal, R. V.
1986-01-01
Research has been undertaken to experimentally study the alterations in turbulent boundary-layer properties due to turbulence manipulation using thin flat plates. Plate geometry and placement within the boundary layer were selected to coincide with recent studies. Direct, local measurements of skin friction and Reynolds stresses were made within the boundary layer downstream of the manipulator devices for cases with an approach momentum thickness Reynolds number of 3700. A strong tendency for recovery of the Reynolds stresses was observed, accompanied by local skin-friction reductions of up to 15 percent. The mean velocity profile in the manipulated flow displayed the same similarity shape in the logarithmic region as a natural boundary layer, but had an enhanced wake component. The results indicate that the plate wake plays an important role in the boundary layer response to this sort of manipulation.
Distortion in turbulence upstream of a flat plate and induced pressure fluctuations
NASA Astrophysics Data System (ADS)
Huot, J.-P.; Arbey, H.; Rey, C.
1983-01-01
Wind tunnel trials involving air flow over a flat plate were performed in order to test the feasibility of extending Hunt's (1973) theory of the location of the stagnation point, the pressure distribution, and the turbulence induced upstream from a circular cylinder to other cases. A flow velocity of 10 m/sec was used, with a grid of 0.3 solidity placed 40 mesh sizes upstream. A pressure sensor was placed above the plate, which was progressively drawn downstream during the experiment. The X-wire sensor permitted measurement of longitudinal and transversal velocity disturbances, and a microphone was placed at the stagnation point to measure pressure fluctuations. As Hunt predicted, the low frequency turbulence spectra increased upstream from the plate. A cut-off frequency was found, above which the turbulence decreased.
Min, Booki; Logan, Bruce E
2004-11-01
A microbial fuel cell (MFC) is a device that converts organic matter to electricity using microorganisms as the biocatalyst. Most MFCs contain two electrodes separated into one or two chambers that are operated as a completely mixed reactor. In this study, a flat plate MFC (FPMFC) was designed to operate as a plug flow reactor (no mixing) using a combined electrode/proton exchange membrane (PEM) system. The reactor consisted of a single channel formed between two nonconductive plates that were separated into two halves by the electrode/PEM assembly. Each electrode was placed on an opposite side of the PEM, with the anode facing the chamber containing the liquid phase and the cathode facing a chamber containing only air. Electricity generation using the FPMFC was examined by continuously feeding a solution containing wastewater, or a specific substrate, into the anode chamber. The system was initially acclimated for 1 month using domestic wastewater orwastewater enriched with a specific substrate such as acetate. Average power density using only domestic wastewater was 72+/-1 mW/m2 at a liquid flow rate of 0.39 mL/min [42% COD (chemical oxygen demand) removal, 1.1 h HRT (hydraulic retention time)]. At a longer HRT = 4.0 h, there was 79% COD removal and an average power density of 43+/-1 mW/m2. Power output was found to be a function of wastewater strength according to a Monod-type relationship, with a half-saturation constant of Ks = 461 or 719 mg COD/L. Power generation was sustained at high rates with several organic substrates (all at approximately 1000 mg COD/L), including glucose (212+/-2 mW/ m2), acetate (286+/-3 mW/m2), butyrate (220+/-1 mW/ m2), dextran (150+/-1 mW/m2), and starch (242+/-3 mW/ m2). These results demonstrate the versatility of power generation in a MFC with a variety of organic substrates and show that power can be generated at a high rate in a continuous flow reactor system.
Wakefields of a Beam near a Single Plate in a Flat Dechirper
Bane, Karl; Stupakov, Gennady
2016-11-29
At linac-based, X-ray free electron lasers (FELs), there is interest in streaking the beam by inducing the transverse wakes in a flat dechirper, by passing the beam near to one of its two jaws. For LCLS-II - as has already been done for LCLS-I - this way of using the dechirper will e.g. facilitate two-color and fresh slice schemes of running the FEL. With the beam a distance from the near wall of say b ~ 0.25 mm and from the far wall by ≳ 5 mm, the second wall will no longer affect the results. The physics will be quite different from the two plate case: with two plates the impedance has a resonance spike whose frequency depends on the plate separation 2a; in the single plate case this parameter no longer exists. Formulas for the longitudinal, dipole, and quadrupole wakes for a beam off-axis between two dechirper plates, valid for the range of bunch lengths of interest in an X-ray FEL, are given in reference 3. By taking the proper limit, we can obtain the corresponding wakes for a beam close to one dechirper plate and far from the other. This is the task we perform in this note.
LDEF (Postflight), S1005 : Transverse Flat-Plate Heat Pipe Experiment, Tray B10
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Postflight), S1005 : Transverse Flat-Plate Heat Pipe Experiment, Tray B10 EL-1994-00123 The Transverse Flat-Plate Heat Pipe Experiment postflight photograph was taken in the Orbiter Processing Facility (OPF) at KSC during removal of the LDEF from the Orbiter's cargo bay. The thermal blanket (with the patches) across the lower edge of the photograph is part of the Orbiter thermal protection system and not associated with the heat pipe experiment. The Transverse Flat-Plate Heat Pipe Experiment consist of three (3) transverse flat heat-pipe modules , a power system for the heaters, a data acquisition and storage system and an aluminum support structure placed in a twelve (12) inch deep LDEF experiment tray. The surface of the experiment exposed to the space environment consist of the three heat pipe modules exterior surfaces, silver TEFLON®, and the thermal blankets covering the aluminum mounting hardware and openings between the hardware and the tray sidewalls. The raised surface at the left end of each heat pipe module is the fluid reservoir. The specular surface of the silver TEFLON® has become diffuse and appears white. Numerous impact craters, black specks, can be seen on the white surfaces of the modules and on the thermal blankets. A light tan discoloration is visible on the surfaces of all three heat pipe modules. Two different types of discolorations can be seen at the left end of the center heat pipe; a dark brown color below the thermocouple and what appears as two multi-color irregular shaped patterns above the thermocouple. A square shaped light brown discoloration is seen near the bottom edge of the thermal blanket between the lower heat pipe module and the tray sidewall and also near the left end of the thermal blanket located between the lower and the center heat pipe modules.
1989-01-28
The purpose of this standard is to provide test methods for determining the thermal performance of unglazed flat-plate liquid-type solar energy collector modules which heat a liquid for low temperature applications.
Experimental investigation of jet-induced loads on a flat plate in hover out-of-ground effect
NASA Technical Reports Server (NTRS)
Kuhlman, J. M.; Warcup, R. W.
1979-01-01
Effects of varying jet decay rate on jet-induced loads on a flat plate located in the plane of the jet exit perpendicular to the jet axis were investigated using a small-scale laboratory facility. Jet decay rate has been varied through use of two cylindrical centerbodies having either a flat or hemispherical tip, which were submerged various distances below the flat plate jet exit plane. Increased jet decay rate, caused by the presence of a center-body or plug in the jet nozzle, led to an increased jet-induced lift loss on the flat plate. Jet-induced lift losses reached 1 percent of the jet thrust for the quickest jet decay rates for plate areas equal to 100 times the effective jet exit area. The observed lift loss versus jet decay rate trend agreed well with results of previous investigations.
Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-19
... International Trade Administration Diffusion-Annealed, Nickel-Plated Flat-Rolled Steel Products From Japan... Commerce. SUMMARY: The Department of Commerce (the Department) preliminarily determines that diffusion...-0408, respectively. SUPPLEMENTARY INFORMATION: Scope of the Investigation The diffusion-annealed...
On the Design of an Optimal Waveform to Maximize Scattering from a Flat Plate and a Cone
2007-11-02
direction. This report examines such a possibility. To simplify the problem, the edge effect and creeping waves are neglected. We first review the general scattering problem of a flat plate and a cone.
Large deflection of clamped circular plate and accuracy of its approximate analytical solutions
NASA Astrophysics Data System (ADS)
Zhang, Yin
2016-02-01
A different set of governing equations on the large deflection of plates are derived by the principle of virtual work (PVW), which also leads to a different set of boundary conditions. Boundary conditions play an important role in determining the computation accuracy of the large deflection of plates. Our boundary conditions are shown to be more appropriate by analyzing their difference with the previous ones. The accuracy of approximate analytical solutions is important to the bulge/blister tests and the application of various sensors with the plate structure. Different approximate analytical solutions are presented and their accuracies are evaluated by comparing them with the numerical results. The error sources are also analyzed. A new approximate analytical solution is proposed and shown to have a better approximation. The approximate analytical solution offers a much simpler and more direct framework to study the plate-membrane transition behavior of deflection as compared with the previous approaches of complex numerical integration.
NASA Technical Reports Server (NTRS)
Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.
2015-01-01
This work describes the development of an improved vacuum compatible flat plate radiometric source used for characterizing and calibrating remote optical sensors, in situ, throughout their testing period. The original flat plate radiometric source was developed for use by the VIIRS instrument during the NPOESS Preparatory Project (NPP). Following this effort, the FPI has had significant upgrades in order to improve both the radiometric throughput and uniformity. Results of the VIIRS testing with the reconfigured FPI are reported and discussed.
NASA Astrophysics Data System (ADS)
Ingley, H. A.; Farber, E. A.; Reinhardt, R.
Mildly selective (Chemglaze Z306 and Solarsorb C-1077 paints) surfaces, along with flat black paint and untreated copper, were evaluated as flat-plate solar collector coatings according to the National Bureau of Standards and the American Society of Heating, Refrigeration and Air Conditioning Engineers procedures for determining solar absorptivity. The moderately selective surfaces proved less efficient than flat black paint for operating temperatures less than 180 F. Highly selective (black chrome and copper oxide) surfaces, although tested, were not evaluated.
Sentelhas, Paulo C; Gillespie, Terry J; Santos, Eduardo A
2007-03-01
In general, leaf wetness duration (LWD) is a key parameter influencing plant disease epidemiology, since it provides the free water required by pathogens to infect foliar tissue. LWD is used as an input in many disease warning systems, which help growers to decide the best time to spray their crops against diseases. Since there is no observation standard either for sensor or exposure, LWD measurement is often problematic. To assess the performance of electronic sensors, LWD measurements obtained with painted cylindrical and flat plate sensors were compared under different field conditions in Elora, Ontario, Canada, and in Piracicaba, São Paulo, Brazil. The sensors were tested in four different crop environments--mowed turfgrass, maize, soybean, and tomatoes--during the summer of 2003 and 2004 in Elora and during the winter of 2005 in Piracicaba. Flat plate sensors were deployed facing north and at 45 degrees to horizontal, and cylindrical sensors were deployed horizontally. At the turfgrass site, both sensors were installed 30 cm above the ground, while at the crop fields, the sensors were installed at the top and inside the canopy (except for maize, with a sensor only at the top). Considering the flat plate sensor as a reference (Sentelhas et al. Operational exposure of leaf wetness sensors. Agric For Meteorol 126:59-72, 2004a), the results in the more humid climate at Elora showed that the cylindrical sensor overestimated LWD by 1.1-4.2 h, depending on the crop and canopy position. The main cause of the overestimation was the accumulation of big water drops along the bottom of the cylindrical sensors, which required much more energy and, consequently, time to evaporate. The overall difference between sensors when evaporating wetness formed during the night was around 1.6 h. Cylindrical sensors also detected wetness earlier than did flat plates--around 0.6 h. Agreement between plate and cylinder sensors was much better in the drier climate at Piracicaba. These
NASA Astrophysics Data System (ADS)
Ishiyama, S.; Akiba, M.; Eto, M.
1996-04-01
To design the relevant plasma facing components of fusion experimental reactors such as ITER, irradiation damage analysis, especially on divertor structures exposed to high heat flux and heavy neutron irradiation, is one of the most important problems. This paper presents finite element analytical results of the thermal and irradiation induced stresses which occurred in the divertor structures which are exposed to neutron irradiation at 0-1 dpa with a high heat flux up to 15 MW/m 2. A type of target plate model of the divertor structure studied in present study e.g. flat plate model has bonded structure of one-dimensional high thermal conductivity carbon-carbon composite (C/C) and oxygen-free high conductivity copper (OFHC), as armor and substrate/heat sink materials, respectively. These results show that irradiation induced stresses at edges of bonded interface between an armor and a substrate/heat sink, become higher with increase of dpa and reach up to the critical values of the materials at 0 and 1 dpa. This indicates that drop-off of armor tiles from substrate structure is one of very serious problems for the safety design of target plate; thus the reduction of service conditions and change of divertor materials are important to extend lifetime of the model.
Active Wave Cancellation in a Transitional Flat-Plate Boundary Layer
NASA Astrophysics Data System (ADS)
Izawa, Seiichiro; Sakai, Takeshi; Xiong, Ao-Kui; Fukunishi, Yu
2004-11-01
A semi-automatic feedback control system using an array of piezo-ceramic (PZT) actuators attached on a flat-plate surface is used to suppress the instability waves such as T-S waves and oblique waves in a flat-plate boundary layer. Target waves, T-S waves and oblique waves, are excited upstream by a combination of roughness elements on the plate surface (Scotch tapes) and an acoustic using a loud speaker. Six single hotwire probes are used to monitor the velocity fluctuations downstream. Based on the information, the phase and amplitude of a signal to operate each actuator is updated one by one, every time step. The adjustment continues until the waves are damped to a level below the criterion. The experimental results show that the control system can damp the two-dimensional T-S waves and the oblique waves of a fifteen-degree sweep angle, however the system is not capable of controlling the oblique waves of a thirty-degree sweep angle. The reason why the system has difficulty in controlling the oblique waves of large sweep angle is discussed.
Preliminary Measurements From A New Flat Plate Facility For Aerodynamic Research
D. M. McEligot; D. W. Nigg; E. J. Walsh; D. Hernon; M.R.D. Davies
2005-03-01
This paper details the design and preliminary measurements used in the characterisation of a new flat plate research facility. The facility is designed specifically to aid in the understanding of entropy generation throughout the boundary layer with special attention given to non-equilibrium flows. Hot-wire measurements were obtained downstream of two turbulence generating grids. The turbulence intensity, integral and dissipation length scale ranges measured are 1.6%-7%, 5mm-17mm and 0.7mm-7mm, respectively. These values compared well to existing correlations. The flow downstream of both grids was found to be homogenous and isotropic. Flow visualisation is employed to determine aerodynamic parameters such as flow 2-dimensionality and the effect of the flap angle on preventing separation at the leading edge. The flow was found to be 2-dimensional over all measurement planes. The non-dimensional pressure distribution of a modern turbine blade suction surface is simulated on the flat plate through the use of a variable upper wall. The Reynolds number range based on wetted plate length and inlet velocity is 70,000-4,000,000.
NASA Astrophysics Data System (ADS)
Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki
In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2•s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.
Vortex Formation, Shedding and Energy Harvesting from a Cyber-Physical Pitching Flat Plate
NASA Astrophysics Data System (ADS)
Onoue, Kyohei; Breuer, Kenneth
2014-11-01
We examine the dynamics and energy harvesting capabilities of an elastically mounted flat plate undergoing large amplitude limit cycle oscillations in a uniform flow. All experiments are performed using a cyber-physical system, wherein the structural inertia, stiffness and damping are numerically simulated using a position-following feedback algorithm. The cyber-physical system also allows for implementation of nonlinear spring and damping coefficients, which control the plate dynamics and subsequent energy harvesting characteristics. Analysis of the plate kinematics and the fluid flow over the plate and in the wake (measured using PIV) are used to understand the interplay between structural motion and vortex formation at the sharp leading and trailing edges of the plate. By varying the structural properties of the system we systematically analyze the formation, strength, stability and separation of the leading edge vortex, as well as the dependence on kinematic parameters and Reynolds number. Connections to previous results on vortex formation time and bluff body aerodynamics are discussed. This research is funded by the Air Force Office of Scientific Research (AFOSR).
Exergy efficiency analysis of a flat plate solar collector using graphene based nanofluid
NASA Astrophysics Data System (ADS)
Said, Z.; Alim, M. A.; Janajreh, Isam
2015-10-01
The thermal efficiency of a flat plate solar thermal collector is largely affected by the thermal conductivity of the fluid used. In this paper, we theoretically analyzed the heat transfer performance, the entropy generation rate, and the exergy efficiency of the two different graphene based nanofluids (graphene/Acetone and graphene/water). From the analyses, it is revealed that by inserting a small amount of graphene nanoparticles in water, exergy efficiency could be enhanced by 21%, comparing to conventional fluids and entropy generation is decreased by 4%. However, the graphene/water nanofluid shows a lower entropy generation. This characteristic suggests that graphene/water nanofluid is a better candidate for flat solar thermal application.
Suresh; Walz
1997-12-15
The van der Waals and electrostatic interaction energies between a single particle and a flat plate were measured using the optical technique of total internal reflection microscopy (TIRM). The particles used were 15-µm-diameter polystyrene latex spheres and the flat plate was a polished BK-7 glass slide. The measurements were performed in aqueous solutions of ionic strength ranging from 3 to 7 mM, and the particle-plate separation distances ranged from approximately 25 to 300 nm. During measurement, the particle was trapped in a secondary energy well formed by the repulsive electrostatic and attractive van der Waals forces; however, the particle was free to undergo Brownian motion at all times. These measurements, which capitalize on the extreme sensitivity of the TIRM technique, are believed to be the first direct measurement of the van der Waals interaction energy in aqueous solutions at separation distances where retardation effects are substantial. Comparison of the measured energy wells with predictions made with traditional energy equations produced only fair agreement; specifically, the measured well depths were consistently lower than predicted. However, when the measured results were compared with predictions made using the recent model of L. Suresh and J. Y. Walz ([J. Colloid Interface Sci. 183, 199 (1996)] for rough surfaces, very good agreement was obtained. The asperity heights yielding the best agreement ranged between 14 and 33 nm, with an average height of 26 nm. This value is consistent with previous estimates of the roughness height obtained by measuring the particle sedimentation velocity [J. Y. Walz and L. Suresh, J. Chem. Phys. 103, 10714 (1995)]. Copyright 1997 Academic Press.
NASA Technical Reports Server (NTRS)
Parrott, Tony L.; Jones, Michael G.; Albertson, Cindy W.
1989-01-01
Fluctuating pressures were measured beneath a Mach 5, turbulent boundary layer on a flat plate with an array of piezoresistive sensors. The data were obtained with a digital signal acquisition system during a test run of 4 seconds. Data sampling rate was such that frequency analysis up to 62.5 kHz could be performed. To assess in situ frequency response of the sensors, a specially designed waveguide calibration system was employed to measure transfer functions of all sensors and related instrumentation. Pressure time histories were approximated well by a Gaussian prohibiting distribution. Pressure spectra were very repeatable over the array span of 76 mm. Total rms pressures ranged from 0.0017 to 0.0046 of the freestream dynamic pressure. Streamwise, space-time correlations exhibited expected decaying behavior of a turbulence generated pressure field. Average convection speed was 0.87 of freestream velocity. The trendless behavior with sensor separation indicated possible systematic errors.
Kinetics of inorganic carbon utilization by microalgal biofilm in a flat plate photoreactor.
Lin, Yen H; Leu, Jyh Y; Lan, Chi R; Lin, P-Hsiu P; Chang, Fuh L
2003-11-01
A kinetic model was developed to describe inorganic carbon utilization by microalgae biofilm in a flat plate photoreactor. The model incorporates the fundamental mechanisms of diffusive mass transport and biological reaction of inorganic carbon by microalgal biofilm. An advanced numerical technique, the orthogonal collocation method and Gear's method, was employed to solve this kinetic model. The model solutions included the concentration profiles of inorganic carbon in the microalgal biofilm, the growths of suspended microalgae and microalgal biofilm, the effluent concentrations of inorganic carbon, and the flux of inorganic carbon from bulk liquid into biofilm. The batch kinetic test was independently conducted to determine biokinetic parameters used in the microalgal biofilm model simulation while initial thickness of microalgal biofilm were assumed. A laboratory-scale flat plate photoreactor with a high recycle flow rate was setup and conducted to verify the model. The volume of photoreactor is 60 l which yields a hydraulic retention time of 1.67 days. The model-generated inorganic carbon and the suspended microalgae concentration curves agreed well with those obtained in the laboratory-scale test. The fixation efficiencies of HCO(3)(-) and CO(2) are 98.5% and 90% at a steady-state condition, respectively. The concentration of suspended microalgal cell reached up to 12 mg/l at a maximum growth rate while the thickness of microalgal biofilm was estimated to be 104 microm at a steady-state condition. The approaches of experiments and model simulation presented in this study could be employed for the design of a flat plate photoreactor to treat CO(2) by microalgal biofilm in a fossil-fuel power plant.
In-Flight Boundary-Layer Transition on a Large Flat Plate at Supersonic Speeds
NASA Technical Reports Server (NTRS)
Banks, Daniel W.; Fredericks, Michael Alan; Tracy, Richard R.; Matisheck, Jason R.; Vanecek, Neal D.
2012-01-01
A flight experiment was conducted to investigate the pressure distribution, local flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.0. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. The tests used a F-15B testbed aircraft with a bottom centerline mounted test fixture. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating for future laminar flow flight tests employing infrared thermography. Boundary-layer transition was captured using an onboard infrared imaging system. The infrared imagery was captured in both analog and digital formats. Surface pressures were measured with electronically scanned pressure modules connected to 60 surface-mounted pressure orifices. The local flow field was measured with five 5-hole conical probes mounted near the leading edge of the test fixture. Flow field measurements revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration. The infrared imaging system was able to capture shock wave impingement on the surface of the flat plate in addition to indicating laminar-to-turbulent boundary-layer transition.
Flat plate at incidence as a waverider in rarefied hypersonic flow
NASA Technical Reports Server (NTRS)
Cheng, H. K.; Wong, E. Y.; Hoover, L. N.; Dogra, V. K.
1990-01-01
The physical validity of continuum models and their ability to predict the critical aerothermodynamic properties of a waverider at high altitudes are examined using a flat plate at angle of attack as a generic hypersonic lifting vehicle. For a shock layer far from local translational equilibrium, a theoretical study based on Grad's thirteen-moment equations shows that the Navier-Stokes based solutions can correctly predict the drag, lift, and surface heat transfer rate, with the prediction error comparable to that of the standard shock-layer theory. The conclusion is supported by a comparison with direct simulation Monte Carlo calculations.
Evaluation of all-day-efficiency for selected flat plate and evacuated tube collectors
Not Available
1981-09-01
An evaluation of all day efficiency for selected flat plate and evacuated tube collectors is presented. Computations are based on a modified version of the NBSIR 78-1305A procedure for all day efficiency. The ASHMET and NOAA data bases for solar insolation are discussed. Details of the algorithm used to convert total (global) horizontal radiation to the collector tilt plane of the selected sites are given along with tables and graphs which show the results of the tests performed during this evaluation.
Evaluation of All-Day-Efficiency for selected flat plate and evacuated tube collectors
NASA Technical Reports Server (NTRS)
1981-01-01
An evaluation of all day efficiency for selected flat plate and evacuated tube collectors is presented. Computations are based on a modified version of the NBSIR 78-1305A procedure for all day efficiency. The ASHMET and NOAA data bases for solar insolation are discussed. Details of the algorithm used to convert total (global) horizontal radiation to the collector tilt plane of the selected sites are given along with tables and graphs which show the results of the tests performed during this evaluation.
Flat-plate solar array project: Government and industry responding to national needs
NASA Technical Reports Server (NTRS)
Adcock, J. Patrick; Knecht, Robert D.
1988-01-01
This document recounts the accomplishments of the 11-year Flat-Plate Solar Array Project, which is recognized as one of the most successful and comprehensive technology-transfer efforts ever achieved through government-sponsored research and development. Few Federal research projects can claim the degree of industry involvement that was a fundamental aspect of the FSA Project. This philosophy in turn led to an extraordinary transfer of technology to the private sector, and assured that a maximum amount of the taxpayers' dollars were devoted to research of primary importance to the technology's commercialization.
Velocity and temperature profiles in near-critical nitrogen flowing past a horizontal flat plate
NASA Technical Reports Server (NTRS)
Simoneau, R. J.
1977-01-01
Boundary layer velocity and temperature profiles were measured for nitrogen near its thermodynamic critical point flowing past a horizontal flat plate. The results were compared measurements made for vertically upward flow. The boundary layer temperatures ranged from below to above the thermodynamic critical temperature. For wall temperatures below the thermodynamic critical temperature there was little variation between the velocity and temperature profiles in three orientations. In all three orientations the point of crossing into the critical temperature region is marked by a significant flattening of the velocity and temperature profiles and also a decrease in heat transfer coefficient.
The linear stability of a flat plate boundary-layer approaching a cylindrical obstacle
NASA Technical Reports Server (NTRS)
Spall, R. E.; Malik, M. R.
1992-01-01
The linear stability of the low-speed three-dimensional flow over a flat plate with an attached cylinder is studied. The region of interest is upstream of the initial separation point and includes the effects of both adverse and favorable pressure gradients, as well as crossflow. The resulting boundary-layer is subject to both the Tollmien-Schlichting (TS) and crossflow instabilities. Linear stability calculations, using N-factor correlations, indicate that the transition process would be dominated by TS instabilities, although for low frequencies crossflow-type disturbances are important.
NASA Astrophysics Data System (ADS)
Merges, V.; Klippel, E.
1983-12-01
A solar plant with 21 sq m of highly efficient flat plate collectors and which requires no electricity is described. Heat transport is provided by saturated steam that condenses in a four cubic meter storage tank. The operation temperature is set by the buffer gas pressure between 100 and 140 C, and an absorption chiller is simulated as a heat consumer. The solar collectors were observed to exhibit high performance. Heat transport and temperature control offered high reliability and the thermal stratification in the tank was satisfactory. The positive result permits the design and construction of larger solar plants following the same technical principles.
Design of high-Reynolds-number flat-plate experiments in the NTF
NASA Technical Reports Server (NTRS)
Saric, William S.
1988-01-01
The design of an experiment to measure skin friction and turbulent boundary layer characteristics at Reynolds numbers exceeding 1 x 10 to the 9th is described. The experiment will be conducted in a zero-pressure-gradient flow on a flat plate in the National Transonic Facility (NTF). The development of computational codes to analyze the aerodynamic loads and the blockage is documented. Novel instrumentation techniques and models, designed to operate in cryogenic environments, are presented. Special problems associated with aerodynamic loads, surface finish, and hot-wire anemometers are discussed.
A Module Experimental Process System Development Unit (MEPSDU). [flat plate solar arrays
NASA Technical Reports Server (NTRS)
1981-01-01
The development of a cost effective process sequence that has the potential for the production of flat plate photovoltaic modules which meet the price goal in 1986 of 70 cents or less per Watt peak is described. The major accomplishments include (1) an improved AR coating technique; (2) the use of sand blast back clean-up to reduce clean up costs and to allow much of the Al paste to serve as a back conductor; and (3) the development of wave soldering for use with solar cells. Cells were processed to evaluate different process steps, a cell and minimodule test plan was prepared and data were collected for preliminary Samics cost analysis.
Development of a Flat-plate Cryogenic Oscillating Heat Pipe for Improving HTS Magnet Cooling
NASA Astrophysics Data System (ADS)
Natsume, K.; Mito, T.; Yanagi, N.; Tamura, H.
A new method of including cryogenic oscillating heat pipes (OHPs) in the HTS coil windings as a thermal transport device has been studied. In this work, two type of OHPs are tested in low temperature. Employed working fluids are H2, Ne, N2. We have attained high performance thermal property using a bent-pipe cryogenic OHP as a prototype. Obtained effective conductivities have reached to 46000 W/m K. Then a flat-plate cryogenic OHP has been developed, that is suitable for imbedding in magnet windings. Preliminary experiments have been conducted and the result has been promising.
Analytical prediction of the performance of an air photovoltaic/thermal flat-plate collector
Raghuraman, P.
1980-04-30
A one-dimensional analysis developed by MIT Lincoln Laboratory predicts the electrical and thermal performance of an air photovoltaic/thermal flat-plate collector. The analysis compares well with test measurements, predicting the thermal efficiency to within 2 percent. From the analysis, the poor thermal performance of the collector is attributable, in part, to the large undulations of the cell/silicone pottant surface in contact with the flowing air that results in less effective convective heat-transfer areas between the cell and the air.
Development of an economic solar heating system with cost efficient flat plate collectors
NASA Astrophysics Data System (ADS)
Eder-Milchgeisser, W.; Burkart, R.
1980-10-01
Mass produced flat plate solar collectors were worked into the design of a system for heating a swimming pool and/or providing domestic hot water. The collector characteristics, including physical and mechanical data as well as theoretical energy conversion efficiency, are presented. The collector was tested and service life efficiency was determined. The mounting of the collector, depending on roof type, is explained. Both in service and laboratory test results demonstrate the cost effectiveness of the system. Further improvement of efficiency is envisaged with automatic flow control in the solar collector and hot water circuits.
Koller, Anja Pia; Löwe, Hannes; Schmid, Verena; Mundt, Sabine; Weuster-Botz, Dirk
2017-02-01
Light-dependent growth of microalgae can vary remarkably depending on the cultivation system and microalgal strain. Cell size and the pigmentation of each strain, as well as reactor geometry have a great impact on absorption and scattering behavior within a photobioreactor. In this study, the light-dependent, cell-specific growth kinetics of a novel green algae isolate, Scenedesmus obtusiusculus, was studied in a LED-illuminated flat-plate photobioreactor on a lab-scale (1.8 L, 0.09 m(2) ). First, pH-controlled batch processes were performed with S. obtusiusculus at different constant incident photon flux densities. The best performance was achieved by illuminating S. obtusiusculus with 1400 μmol photons m(-2) s(-1) at the surface of the flat-plate photobioreactor, resulting in the highest biomass concentration (4.95 ± 0.16 gCDW L(-1) within 3.5 d) and the highest specific growth rate (0.22 h(-1) ). The experimental data were used to identify the kinetic parameters of different growth models considering light inhibition for S. obtusiusculus. Light attenuation within the flat-plate photobioreactor was considered by varying light transfer models. Based on the identified kinetic growth model of S. obtusiusculus, an optimum growth rate of 0.22 h(-1) was estimated at a mean integral photon flux density of 1072 μmol photons m(-2) s(-1) with the Beer-Lambert law and 1590 μmol photons m(-2) s(-1) with Schuster's light transfer model in the flat-plate photobioreactor. LED illumination was, thus, increased to keep the identified optimum mean integral photon flux density constant in the batch process assuming Schuster's light transfer model. Compared to the same constant incident photon flux density (1590 μmol photons m(-2) s(-1) ), biomass concentration was up to 24% higher using the lighting profile until a dry cell mass concentration of 14.4 ± 1.4 gCDW L(-1) was reached. Afterward, the biomass concentration remained
A didactic experiment and model of a flat-plate solar collector
NASA Astrophysics Data System (ADS)
Agliolo Gallitto, Aurelio; Fiordilino, Emilio
2011-05-01
We report on an experiment performed with a home-made flat-plate solar collector, carried out together with high-school students. To explain the experimental results, we propose a model that describes the heating process of the solar collector. The model accounts quantitatively for the experimental data. We suggest that solar-energy topics should be included in school programmes to give students the opportunity to gain experience with solar energy and increase their awareness of the benefits that can be obtained from this remarkable and renewable energy source.
PLIF Temperature and Velocity Distributions in Laminar Hypersonic Flat-plate Flow
NASA Technical Reports Server (NTRS)
OByrne, S.; Danehy, P. M.; Houwing, A. F. P.
2003-01-01
Rotational temperature and velocity distributions have been measured across a hypersonic laminar flat-plate boundary layer, using planar laser-induced fluorescence. The measurements are compared to a finite-volume computation and a first-order boundary layer computation, assuming local similarity. Both computations produced similar temperature distributions and nearly identical velocity distributions. The disagreement between calculations is ascribed to the similarity solution not accounting for leading-edge displacement effects. The velocity measurements agreed to within the measurement uncertainty of 2 % with both calculated distributions. The peak measured temperature was 200 K lower than the computed values. This discrepancy is tentatively ascribed to vibrational relaxation in the boundary layer.
NASA Astrophysics Data System (ADS)
Sentelhas, Paulo C.; Gillespie, Terry J.; Santos, Eduardo A.
2007-03-01
In general, leaf wetness duration (LWD) is a key parameter influencing plant disease epidemiology, since it provides the free water required by pathogens to infect foliar tissue. LWD is used as an input in many disease warning systems, which help growers to decide the best time to spray their crops against diseases. Since there is no observation standard either for sensor or exposure, LWD measurement is often problematic. To assess the performance of electronic sensors, LWD measurements obtained with painted cylindrical and flat plate sensors were compared under different field conditions in Elora, Ontario, Canada, and in Piracicaba, São Paulo, Brazil. The sensors were tested in four different crop environments—mowed turfgrass, maize, soybean, and tomatoes—during the summer of 2003 and 2004 in Elora and during the winter of 2005 in Piracicaba. Flat plate sensors were deployed facing north and at 45° to horizontal, and cylindrical sensors were deployed horizontally. At the turfgrass site, both sensors were installed 30 cm above the ground, while at the crop fields, the sensors were installed at the top and inside the canopy (except for maize, with a sensor only at the top). Considering the flat plate sensor as a reference (Sentelhas et al. Operational exposure of leaf wetness sensors. Agric For Meteorol 126:59-72, 2004a), the results in the more humid climate at Elora showed that the cylindrical sensor overestimated LWD by 1.1-4.2 h, depending on the crop and canopy position. The main cause of the overestimation was the accumulation of big water drops along the bottom of the cylindrical sensors, which required much more energy and, consequently, time to evaporate. The overall difference between sensors when evaporating wetness formed during the night was around 1.6 h. Cylindrical sensors also detected wetness earlier than did flat plates—around 0.6 h. Agreement between plate and cylinder sensors was much better in the drier climate at Piracicaba. These
Near Continuum Velocity and Temperature Coupled Compressible Boundary Layer Flow over a Flat Plate
NASA Astrophysics Data System (ADS)
He, Xin; Cai, Chunpei
2017-04-01
The problem of a compressible gas flows over a flat plate with the velocity-slip and temperature-jump boundary conditions are being studied. The standard single- shooting method is applied to obtain the exact solutions for velocity and temperature profiles when the momentum and energy equations are weakly coupled. A double-shooting method is applied if these two equations are closely coupled. If the temperature affects the velocity directly, more significant velocity slip happens at locations closer to the plate's leading edge, and inflections on the velocity profiles appear, indicating flows may become unstable. As a consequence, the temperature-jump and velocity-slip boundary conditions may trigger earlier flow transitions from a laminar to a turbulent flow state.
Linear instability of the supersonic wake behind a flat plate aligned with a uniform stream
NASA Technical Reports Server (NTRS)
Papageorgiou, D. T.
1990-01-01
A theoretical and numerical study is presented of the growth of linear disturbances in the laminar compressible supersonic wake behind a flat plate aligned with a uniform stream. The approach adopted is that of classical linear stability theory and covers both two- and three-dimensional disturbances. The basic flow is described, and the linear stability problem is formulated that leads to the compressible Rayleigh equation. The stability of short-wave disturbances is then analyzed in the very near wake where the compressible analog of the Goldstein double structure provides an asymptotic description for the unperturbed flow. The behavior of long waves is then considered. The waves are not as long as the plate length but are long compared to the boundary-layer thickness. Numerical solutions of the Rayleigh equation are discussed. Numerical results are then presented for a range of streamwise stations, Mach numbers, and wave propagation angles.
Laminar-Boundary-Layer Oscillations and Transition on a Flat Plate
NASA Technical Reports Server (NTRS)
Schubauer, G B; Skramstad, H K
1948-01-01
This is an account of an investigation in which oscillations were discovered in the laminar boundary layer along a flat plate. These oscillations were found during the course of an experiment in which transition from laminar to turbulent flow was being studied on the plate as the turbulence in the wind stream was being reduced to unusually low values by means of damping screens. The first part of the paper deals with experimental methods and apparatus, measurements of turbulence and sound, and studies of transition. A description is then given of the manner in which oscillations were discovered and how they were found to be related to transition, and then how controlled oscillations were produced and studied in detail.
Flat plate heat transfer for laminar transition and turbulent boundary layers using a shock tube
NASA Technical Reports Server (NTRS)
Brostmeyer, J. D.; Nagamatsu, H. T.
1984-01-01
Heat transfer results are presented for laminar, transition, and turbulent boundary layers for a Mach number of 0.12 with gas temperatures of 425 K and 1000 K over a flat plate at room temperature. The measurements were made in air for a Reynolds number range of 600 to 6 million. The heat transfer measurements were conducted in a 70-ft long, 4 in. diameter shock tube. Reflecting wedges were used to reflect the incident shock wave to produce a flow Mach number of 0.12 behind the reflected shock wave. Thin film platinum heat gages were mounted on the plate surface to measure the local heat flux. The laminar results for gas temperatures of 425 K to 1000 K agree well with theory. The turbulent results are also close to incompressible theory, with the 1000 K flow case being slightly higher. The transition results lie between the laminar and turbulent predictions.
Slip effects on MHD flow and heat transfer of ferrofluids over a moving flat plate
NASA Astrophysics Data System (ADS)
Ramli, Norshafira; Ahmad, Syakila; Pop, Ioan
2017-08-01
In this study, the problem of MHD flow and heat transfer of ferrofluids over a moving flat plate with slip effect and uniform heat flux is considered. The governing ordinary differential equations are solved via shooting method. The effect of slip parameter on the dimensionless velocity, temperature, skin friction and Nusselt numbers are numerically studied for the three selected ferroparticles; magnetite (Fe3O4), cobalt ferrite (CoFe2O4) and Mn-Zn ferrite (Mn-ZnFe2O4) with water-based fluid. The results indicate that dual solutions exist for a plate moving towards the origin. It is found that the slip process delays the boundary layer separation. Moreover, the velocity and thermal boundary-layer thicknesses decrease in the first solution while increase with the increase of the value of slip parameters in second solution.
Modeling and analysis of an all-fiberglass flat plate solar collector
NASA Astrophysics Data System (ADS)
Russell, L. D.
1980-11-01
The concept of an all-fiberglass liquid flat plate solar collector was studied. Such a collector eliminates the need for coatings, metals, and all other materials except fiberglass. The concept appears to offer possibilities for the mass production of a low-cost lightweight solar collector which is reasonably efficient. Mathematical models were developed for study of this concept. Convection and nonlinear radiation between the covers was computed in all of the models. In addition, absorptance and conduction in the cover(s) and the fluid cover plate were studied in order to determine their effects on the panel performance. A model panel was fabricated, and computer results were compared with test data for the efficiency of the panel.
Linear instability of the supersonic wake behind a flat plate aligned with a uniform stream
NASA Technical Reports Server (NTRS)
Papageorgiou, D. T.
1990-01-01
A theoretical and numerical study is presented of the growth of linear disturbances in the laminar compressible supersonic wake behind a flat plate aligned with a uniform stream. The approach adopted is that of classical linear stability theory and covers both two- and three-dimensional disturbances. The basic flow is described, and the linear stability problem is formulated that leads to the compressible Rayleigh equation. The stability of short-wave disturbances is then analyzed in the very near wake where the compressible analog of the Goldstein double structure provides an asymptotic description for the unperturbed flow. The behavior of long waves is then considered. The waves are not as long as the plate length but are long compared to the boundary-layer thickness. Numerical solutions of the Rayleigh equation are discussed. Numerical results are then presented for a range of streamwise stations, Mach numbers, and wave propagation angles.
Part A: Nonprincipal-plane scattering from flat plates: Second-order and corner diffractions
NASA Technical Reports Server (NTRS)
Balanis, Constantine A.; Polka, Lesley A.
1989-01-01
Two models of a flat plate for nonprincipal-plane scattering are explored. The first is a revised version of the Physical Optics/Physical Theory of Diffraction (PO/PTD) model with second-order PTD equivalent currents included to account for second-order interactions among the plate edges. The second model uses a heurisitcally derived corner diffraction coefficient to account for the corner scattering mechanism. The patterns obtained using the newer models were compared to the data of previously reported models, the Moment Method (MM), and experimental results. Near normal incidence, all the models agreed; however, near grazing incidence a need for higher-order and corner diffraction mechanisms was noted. In many instances the second-order and corner-scattered fields which were formulated improved the results.
NASA Technical Reports Server (NTRS)
Budweg, H. L.; Shin, Y. S.
1987-01-01
An experimental investigation was conducted to determine the static and dynamic responses of a specific stiffened flat plate design. The air-backed rectangular flat plates of 6061-T6 aluminum with an externally machined longitudinal narrow-flanged T-stiffener and clamped boundary conditions were subjected to static loading by water hydropump pressure and shock loading from an eight pound TNT charge detonated underwater. The dynamic test plate was instrumented to measure transient strains and free field pressure. The static test plate was instrumented to measure transient strains, plate deflection, and pressure. Emphasis was placed upon forcing static and dynamic stiffener tripping, obtaining relevant strain and pressure data, and studying the associated plate-stiffener behavior.
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
NASA Astrophysics Data System (ADS)
Pradhan, Sahadev
2016-09-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range
NASA Astrophysics Data System (ADS)
Xiao, Lan; Wu, Shuang-Ying; Zhang, Qiao-Ling; Li, You-Rong
2012-07-01
Based on the heat transfer characteristics of absorber plate and the heat transfer effectiveness-number of heat transfer unit method of heat exchanger, a new theoretical method of analyzing the thermal performance of heat pipe flat plate solar collector with cross flow heat exchanger has been put forward and validated by comparisons with the experimental and numerical results in pre-existing literature. The proposed theoretical method can be used to analyze and discuss the influence of relevant parameters on the thermal performance of heat pipe flat plate solar collector.
Vortex dynamics and surface pressure fluctuations on a normal flat plate
NASA Astrophysics Data System (ADS)
Hemmati, Arman; Wood, David H.; Martinuzzi, Robert J.; Ferrari, Simon W.; Hu, Yaoping
2016-11-01
The effect of vortex formation and interactions on surface pressure fluctuations is examined in the wake of a normal flat plate by analyzing Direct Numerical Simulations at Re =1200. A novel local maximum score-based 3D method is used to track vortex development in the region close to the plate where the major contributions to the surface pressure are generated. Three distinct vortex shedding regimes are identified by changes in the lift and drag fluctuations. The instances of maximum drag coincide with impingement of newly formed vortices on the plate. This results in large and concentrated areas of rotational and strain contributions to generation of pressure fluctuations. Streamwise vortex straining and chordwise stretching are correlated with the large ratios of streamwise to chordwise normal stresses and regions of significant rotational contribution to the pressure. In contrast at the minimum drag, the vorticity field close to the plate is disorganized, and vortex roll-up occurs farther downstream. This leads to a uniform distribution of pressure. This study was supported by Alberta Innovates Technology Futures (AITF) and Natural Sciences and Engineering Research Council of Canada (NSERC).
Calculating forces on thin flat plates with incomplete vorticity-field data
NASA Astrophysics Data System (ADS)
Limacher, Eric; Morton, Chris; Wood, David
2016-11-01
Optical experimental techniques such as particle image velocimetry (PIV) permit detailed quantification of velocities in the wakes of bluff bodies. Patterns in the wake development are significant to force generation, but it is not trivial to quantitatively relate changes in the wake to changes in measured forces. Key difficulties in this regard include: (i) accurate quantification of velocities close to the body, and (ii) the effect of missing velocity or vorticity data in regions where optical access is obscured. In the present work, we consider force formulations based on the vorticity field, wherein mathematical manipulation eliminates the need for accurate near-body velocity information. Attention is restricted to nominally two dimensional problems, namely (i) a linearly accelerating flat plate, investigated using PIV in a water tunnel, and (ii) a pitching plate in a freestream flow, as investigated numerically by Wang & Eldredge (2013). The effect of missing vorticity data on the pressure side of the plate has a significant impact on the calculation of force for the pitching plate test case. Fortunately, if the vorticity on the pressure side remains confined to a thin boundary layer, simple corrections can be applied to recover a force estimate.
An approximate buckling analysis for rectangular orthotropic plates with centrally located cutouts
NASA Technical Reports Server (NTRS)
Nemeth, M. P.; Stein, M.; Johnson, E. R.
1986-01-01
An approximate analysis for predicting buckling of rectangular orthotropic composite plates with centrally located cutouts is presented. In this analysis, prebuckling and buckling problems are converted from a two-dimensional to a one-dimensional system of linear differential equations with variable coefficients. The conversion is accomplished by expressing the displacements as series with each element containing a trigonometric function of one coordinate and a coefficient that is an arbitrary function of the other coordinate. Ordinary differential equations are then obtained from a variational principle. Analytical results obtained from the approximate analysis are compared with finite element analyses for isotropic plates and for specially orthotropic plates with central circular cutouts of various sizes. Experimental results for the specially orthotropic plates are also presented. In nearly all cases, the approximate analysis predicts the buckling mode shapes correctly and predicts the buckling loads to within a few percent of the finite element and experimental results.
Clinical evaluation of a flat-plate membrane plasma exchange system.
Grossman, L; Benny, W B; Buchanan, J; Erickson, R R; Buffaloe, G W
1983-01-01
A new flat-plate membrane plasma separation system specifically designed for therapeutic plasma exchange (TPE) was clinically evaluated in both research and routine clinical settings. The study included a comparison to a currently available centrifugal cell separation system employed for TPE. A total of 267 membrane procedures were performed on 39 patients over a 14-month period. Both qualitative and quantitative studies showed that membrane plasma exchange procedures were equivalent to centrifugal procedures in the removal of plasma constituents from patients. A notable difference between the two types of procedure was the effect on the peripheral blood platelet count: the plasma filtrate from the membrane system was essentially cell-free and platelet counts fell only 11% during the procedure, compared to a 53% decrease during the centrifugation runs. Patient responses to both types of procedure were similar and the frequency of side-effects was low. A sampling of patient opinion revealed a preference for the membrane system for a variety of reasons. Procedure times were shorter with the membrane system because of higher achievable blood flow rates, and thus higher plasma exchange rates, while the overall nursing time requirement was lower. The results show that this flat-plate membrane TPE system enables rapid and effective plasma exchange therapy, and offered a number of monitoring and control functions that provided a safer, more efficient therapeutic procedure in the majority of patient treatments performed in this study.
Numerical solutions of turbulent models for flow over a flat plate with angle of attack
Truncellito, N.T.; Yeh, H.; Lior, N.
1985-03-01
Numerical solutions of the two-dimensional boundary layer equations were developed as applied to flow over a flat plate at various angles of attack. Three methods of approach were examined. An integral solution was constructed for laminar and turbulent flow, as well as finite difference solutions for zeroth- and first-order turbulence models. The models also account for buoyancy effects. A three part mixing length model was employed in the zeroth-order model, and an additional turbulent kinetic energy equation was utilized for the first-order model. The computational method utilized Patankar-Spalding coordinates and differs from other methods in that no matching procedure is required for the inner and outer flow regions. The Falkner-Skan velocity profile is applied as an edge boundary condition while variable wall temperature conditions can be imposed. The effects of freestream velocity and angle of attack on skin friction and heat transfer were established, and the velocity and temperature fields were determined. Results of the zeroth-order solution are in excellent agreement with the Colburn equation and several other data sources. These solutions provide correlations in terms of Nusselt number and skin friction coefficient versus local Reynolds number which can be used for estimating heat transfer and wind loadings on a flat plate. Results generated are especially useful in predicting the performance of solar system designs.
NASA Astrophysics Data System (ADS)
Haney, Michael W.
2015-12-01
The economies-of-scale and enhanced performance of integrated micro-technologies have repeatedly delivered disruptive market impact. Examples range from microelectronics to displays to lighting. However, integrated micro-scale technologies have yet to be applied in a transformational way to solar photovoltaic panels. The recently announced Micro-scale Optimized Solar-cell Arrays with Integrated Concentration (MOSAIC) program aims to create a new paradigm in solar photovoltaic panel technology based on the incorporation of micro-concentrating photo-voltaic (μ-CPV) cells. As depicted in Figure 1, MOSAIC will integrate arrays of micro-optical concentrating elements and micro-scale PV elements to achieve the same aggregated collection area and high conversion efficiency of a conventional (i.e., macro-scale) CPV approach, but with the low profile and mass, and hopefully cost, of a conventional non-concentrated PV panel. The reduced size and weight, and enhanced wiring complexity, of the MOSAIC approach provide the opportunity to access the high-performance/low-cost region between the conventional CPV and flat-plate (1-sun) PV domains shown in Figure 2. Accessing this portion of the graph in Figure 2 will expand the geographic and market reach of flat-plate PV. This talk reviews the motivation and goals for the MOSAIC program. The diversity of the technical approaches to micro-concentration, embedded solar tracking, and hybrid direct/diffuse solar resource collection found in the MOSAIC portfolio of projects will also be highlighted.
Mean profile of a high-Reynolds-number smooth-flat-plate turbulent boundary layer
NASA Astrophysics Data System (ADS)
Dowling, David R.; Oweis, Ghanem F.; Winkel, Eric S.; Cutbirth, James M.; Ceccio, Steven L.; Perlin, Marc
2010-11-01
Although smooth-flat-plate turbulent boundary layers (TBLs) have been studied for nearly a century, measurements at Reynolds numbers typical of marine & aerospace transportation systems are scarce. Experimental results at momentum-thickness Reynolds numbers (Re) up to 150,000 from the US Navy W.B. Morgan Large Cavitation Channel using a polished 12.9-m-long flat-plate test model at water flow speeds up to 20 m/s are presented. Mean velocity profiles were measured 10.7 m from the leading edge of the model over a wall-normal range from less than one wall unit to more than twice the nominal boundary layer thickness using particle-tracking and laser-Doppler velocimetry. Static pressure and average skin-friction were measured independently. A mild favorable pressure gradient led to a flow speed increase of 2.5% over the test surface. The measurements span a factor of three in Re and were fitted to within experimental uncertainty using one set of constants and modern empirical inner- and outer-profile forms based on traditional TBL asymptotics. The fitted profiles satisfy the von-Karman momentum integral to within 1%, and show distinct differences from equivalent zero pressure gradient results. [Supported by DARPA & ONR
Experimental testing of various heat transfer structures in a flat plate thermal energy storage unit
NASA Astrophysics Data System (ADS)
Johnson, Maike; Fiß, Michael; Klemm, Torsten
2016-05-01
For solar process heat applications with steam as the working fluid and varying application parameters, a novel latent heat storage concept has been developed using an adaptation of a flat plate heat exchanger as the storage concept. Since the pressure level in these applications usually does not exceed 30 bar, an adaptation with storage material chambers arranged between heat transfer medium chambers is possible. Phase change materials are used as the storage medium, so that the isothermal evaporation of steam during discharging of the storage is paired with the isothermal solidification of the storage material. Heat transfer structures can be inserted into the chambers to adjust the power level for a given application. By combining the required number of flat plate heat exchanger compartments and inserting the appropriate heat transfer structure, the design can easily be adjusted for the required power level and capacity for a specific application. Within this work, the technical feasibility of this concept is proven. The dependence of the operating characteristics on the geometry of the heat exchanger is identified. A focus is on varying the power density by integrating conductive heat structures in the PCM.
Mirpuri, R.; Sharp, W.; Villaverde, S.; Jones, W.; Lewandowski, Z.; Cunningham, A.
1997-06-01
A predictive model has been developed to describe degradation of toluene in a flat-plate vapor phase bioreactor (VPBR). The VPBR model incorporates kinetic, stoichiometric, injury, and irreversible loss coefficients from suspended culture studies for toluene degradation by P. putida 54G and measured values of Henry`s law constant and boundary layer thickness at the gas-liquid and liquid-biofilm interface. The model is used to estimate the performance of the reactor with respect to toluene degradation and to predict profiles of toluene concentration and bacterial physiological state within the biofilm. These results have been compared with experimentally determined values from a flat plate VPBR under electron acceptor and electron donor limiting conditions. The model accurately predicts toluene concentrations in the vapor phase and toluene degradation rate by adjusting only three parameters: biomass density and rates of death and endogenous decay. Qualitatively, the model also predicts gradients in the physiological state cells in the biofilm. This model provides a rational design for predicting an upper limit of toluene degradation capability in a VPBR and is currently being tested to assess applications for predicting performance of bench and pilot-scale column reactors.
Flat-plate solar-collector performance data base and user's manual
NASA Astrophysics Data System (ADS)
Kirkpatrick, D. L.; Kolar, W. A.
1983-07-01
The reader is provided with a thorough understanding on the type of collector thermal performance information which is required in active system design and analysis. Thermal performance test data on 109 commercially available solar collectors which were evaluated in a single, uniform test program, the Interim Solar Collector Test (ISCT) Program are given. In addition to recounting the ISCT program and its results, the an introduction is given on the engineering and physics of a flat-plate solar collector operation. A step-by-step analysis of heat gains and losses is provided to help the reader understand both the source and applicability of the parameters used to describe collector thermal performance. A brief description of the engineering basis for the ASHRAE Standard 93-77 test procedure and the method are included. To demonstrate the sensitivity to variations of collector performance parameters of the annual output of representative solar heating systems, three sets of F-Chart (4.0) system performance predictions are given. Finally, a sensitivity analysis study is presented which considers the heat loss and optical gain parameters of flat-plate collectors, in terms of how they affect the overall solar heating system solar fraction.
An experimental study of flow separation over a flat plate with 2D transverse grooves
NASA Astrophysics Data System (ADS)
Jones, Emily Michelle
Nature has long been an inspiration for research in engineering. In particular, the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow, which appear on many aquatic biological surfaces, have been well documented and implemented in practical engineering applications. However the skin of dolphins is embedded with grooves that run perpendicular to the flow of water over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus controlling boundary layer separation over the dolphin's skin. Similarly, sharks are covered with scales that are flexible at the base and capable of bristling, forming grooves running transverse to the flow. It is theorized that the scales bristle when encountering a reversing flow, thereby trapping vortices between the scales and, similarly, delaying boundary layer separation. In an attempt to test this hypothesis and study these affects, a spinning cylinder was used in a water tunnel to induce separation over a flat plate with 2 mm, rectangular transverse grooves and sinusoidal grooves of similar scaling. The results were compared to tripped, turbulent boundary layer separation occurring over a flat plate without grooves using time-resolved particle image velocimetry. The strength of the adverse pressure gradient was varied, and the observed delay in flow separation and other affects upon the boundary layer are discussed.
Gunderson, Aaron M; Marston, Philip L
2016-11-01
The Kirchhoff approximation (KA) is used to model backscatter of sound from a partially exposed, rigid sphere at a flat free interface of two homogenous media. Scattered wavefields are calculated through numerical integration on the sphere of the Kirchhoff integral, requiring detailed knowledge of the illuminated region for each scattering path. This approach avoids amplitude discontinuities resulting from geometric transitions in the number of reflected rays. Reflections from the interface are modeled through use of an image source, positioned symmetrically relative to the real source. Results are compared to experimentally obtained backscattering records from elastic spheres at an air-water interface, as well as to an exact partial wave series for a half exposed sphere. These comparisons highlight the omission of Franz-type reflections from consideration within the KA, and the consequences of this omission are discussed. The results can be extended to boundary conditions beyond the ideal free surface limit, and are applicable to the problem of scattering by underwater objects partially buried in sand.
Flow field and thermal characteristics induced by a rotationally oscillating heated flat plate
NASA Astrophysics Data System (ADS)
Koffi, Moise
The objective of this dissertation is the study the flow and heat transfer in the vicinity of a rectangular flat heated plate of subject to rotational oscillations. Of interest is the effect of the flow field on the thermal characteristics of the plate's surface. A constant heat flux is applied to both sides while the plate is rotated about a fixed edge at a frequency of 2 rad/s in an infinite domain at atmospheric pressure. A computational simulation of the flow with FLUENT reveals a hooked-shape vortex tube around the free edges of the plate, which is confirmed by the flow visualization with smoke particles. During the flapping cycle, vortices form and grow progressively on one face while they shed from the opposite, until they are completely detached from both surfaces at stroke reversal. A data acquisition system uses a numerical computing and programming software (MATLAB) to track the surface temperature recorded by J- type thermocouples at desired locations on the plate. Both experimental and computational results agree with local surface temperature profiles characterized by a transient unsteady periodic variation followed by a steady periodic phase. These characteristics are symmetrical about the median plane of the plate, which is normal to its axis of rotation. The cooling rate of the surface, proportional to the frequency of rotation, depends on the angular position of the plate and the spatial location on the plate's surface. However, the highest heat transfer coefficient is recorded at free edges, especially in the corners swept by strong tip vortices shedding in two orthogonal directions. Conclusions of the present study are used to explain the role of ear flapping in the metabolic heat regulation of large mammals such as elephants. Flow visualization and surface temperature measurements of full size rigid and flexible elephant ear-shape models were carried out. Results indicate improved interaction between the shedding vortex and the model's boundary
Fu, Alexander S; Mehta, Noshir R; Forgione, Albert G; Al-Badawi, Emad A; Zawawi, Khalid H
2003-07-01
This study assessed the maxillomandibular relationship in temporomandibular disorders (TMD) patients, before and after short-term, flat plane bite plate therapy. It was of interest to determine the incidence and degree of mandibular deviation in a group of TMD patients and whether the mandible would shift to the midline and consequently affect reported symptoms. Seventeen female and three male subjects (age range 19-60) were included in the study. Thirteen subjects were diagnosed with myofascial pain while seven were diagnosed as exhibiting disk displacement with reduction (Research Diagnostic Criteria). After taking impressions for these subjects, casts were fabricated and mounted. Maxillomandibular relationship was evaluated by the Denar Centric Check system (Anaheim, CA). The maxillary and mandibular labial frena were used as a reference to evaluate mandibular shift. Symptom questionnaires were used to assess temporomandibular joint pain and clicking. All subjects exhibited deviation (12 subjects to the right and 8 subjects to the left) prior to bite plate therapy. After flat plane bite plate therapy, the mandibular position of all subjects shifted toward the labial frenum midline position. Based on the Binomial test, the shift was significant (p < 0.001). Measurements on the Centric Check system showed a significant movement of both condyles in the anterio-posterior plane as well as the vertical plane. There was also significant reduction in TMJ pain and clicking (p < 0.01). The results support the hypothesis that the balanced position of the mandible is with frena aligned. When occlusal obstructions are eliminated, the mandible will drift to this position.
NASA Technical Reports Server (NTRS)
Jillie, Don W.; Hopkins, Edward J.
1961-01-01
The effects of leading-edge bluntness and sweep on boundary-layer transition on flat plate models were investigated at Mach numbers of 2.00, 2.50, 3.00, and 4.00. The effect of sweep on transition was also determined on a flat plate model equipped with an elliptical nose at a Mach number of 0.27. Models used for the supersonic investigation had leading-edge radii varying from 0.0005 to 0.040 inch. The free-stream unit Reynolds number was held constant at 15 million per foot for the supersonic tests and the angle of attack was 0 deg. Surface flow conditions were determined by visual observation and recorded photographically. The sublimation technique was used to indicate transition, and the fluorescent-oil technique was used to indicate flow separation. Measured Mach number and sweep effects on transition are compared with those predicted from shock-loss considerations as described in NACA Rep. 1312. For the models with the blunter leading edges, the transition Reynolds number (based on free-stream flow conditions) was approximately doubled by an increase in Mach number from 2.50 to 4.00; and nearly the same result was predicted from shock-loss considerations. At all super- sonic Mach numbers, increases in sweep reduced the transition Reynolds number and the amount of reduction increased with increases in bluntness. The shock-loss method considerably underestimated- the sweep effects, possibly because of the existence of crossflow instability associated with swept wings. At a Mach number of 0.27, no reduction in the transition Reynolds number with sweep was measured (as would be expected with no shock loss) until the sweep angle was attained where crossflow instability appeared.
Flow and heat transfer of ferrofluids over a flat plate with uniform heat flux
NASA Astrophysics Data System (ADS)
Khan, W. A.; Khan, Z. H.; Haq, R. U.
2015-04-01
The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three different kinds of magnetic nanoparticles (Fe3O4, CoFe2O4, Mn-ZnFe2O4 are incorporated within the base fluid. We have considered two different kinds of base fluids (kerosene and water) having poor thermal conductivity as compared to solid magnetic nanoparticles. Self-similar solutions are obtained and are compared with the available data for special cases. A simulation is performed for each ferrofluid mixture by considering the dominant effects of slip and uniform heat flux. It is found that the present results are in an excellent agreement with the existing literature. The variation of skin friction and heat transfer is also performed at the surface of the plate and then the better heat transfer and of each mixture is analyzed. Kerosene-based magnetite Fe3O4 provides the higher heat transfer rate at the wall as compared to the kerosene-based cobalt ferrite and Mn-Zn ferrite. It is also concluded that the primary effect of the magnetic field is to accelerate the dimensionless velocity and to reduce the dimensionless surface temperature as compared to the hydrodynamic case, thereby increasing the skin friction and the heat transfer rate of ferrofluids.
Studer, Damien; Vervisch, Pierre
2007-08-01
High temperature air chemistry is a crucial issue concerning next reusable space vehicle thermal protection system. The aim of this paper is to measure N{sub 2} and O{sub 2} densities and characteristic temperatures thanks to spontaneous Raman scattering within the boundary layer of a stainless steel flat plate cooled down at 300 K. This shear-flow test configuration is considered as a nonequilibrium air plasma test case. Vibrational and rotational temperatures are determined by comparing experimental spectra with computed ones. The density calculation is performed using the ratio of first vibrational transition intensities for both cases with and without plasma at 38 hPa. Several sections were investigated between 15 and 40 mm from the leading edge. All these sections exhibit a classical boundary layer pattern. The rotational temperature is completely in equilibrium with the plate and reaches 2500 K at the outer edge of the boundary layer. On the contrary, the vibrational temperature drops to 1500 K near of the plate and is about 5000 K in the freestream. Molecular densities are smaller than expected at equilibrium, about 60% of the equilibrium value in the freestream for N{sub 2}.
A formal derivation for the Blasius similarity solution for flat-plate boundary layer
NASA Astrophysics Data System (ADS)
Lin, Hao
2015-11-01
The Blasius solution is a classical solution for a laminar boundary layer attached to a semi-infinite flat plate. The key of the solution strategy is to reduce the boundary layer equations, which are PDEs, to a set of ODEs, using a similarity variable transform. Conceptually, the similarity suggests that the velocity profile in each transverse cross-section appears ``self-similar''. In many classical text books and typical classroom lectures on fluid mechanics, the existence of the similarity solution is argued heuristically. The similarity variable is defined a priori so as to collapse the PDEs. It appears somewhat mystical that the PDEs can be perfectly reduced via such an approach. Here we present a rigorous derivation for the existence of a similarity solution, which naturally arises from the fact that there is no apparent streamwise length scale for a semi-infinite plate. Conversely, a similarity solution cannot exist if the plate size is finite. This derivation can be useful in fluids education, in topics including similarity, scaling arguments, and boundary layer theory.
Interaction of a Rectangular Jet with a Flat-Plate Placed Parallel to the Flow
NASA Technical Reports Server (NTRS)
Zaman, K. B. M. Q.; Brown, C. A.; Bridges, J. A.
2013-01-01
An experimental study is carried out addressing the flowfield and radiated noise from the interaction of a large aspect ratio rectangular jet with a flat plate placed parallel to but away from the direct path of the jet. Sound pressure level spectra exhibit an increase in the noise levels for both the 'reflected' and 'shielded' sides of the plate relative to the free-jet case. Detailed cross-sectional distributions of flowfield properties obtained by hot-wire anemometry are documented for a low subsonic condition. Corresponding mean Mach number distributions obtained by Pitot-probe surveys are presented for high subsonic conditions. In the latter flow regime and for certain relative locations of the plate, a flow resonance accompanied by audible tones is encountered. Under the resonant condition the jet cross-section experiences an 'axis-switching' and flow visualization indicates the presence of an organized 'vortex street'. The trends of the resonant frequency variation with flow parameters exhibit some similarities to, but also marked differences with, corresponding trends of the well-known edgetone phenomenon.
A method for measuring skin friction drag on a flat plate in contaminated gas flows
NASA Technical Reports Server (NTRS)
Oetting, R. B.; Patterson, G. K.
1984-01-01
A technique for measuring friction drag in turbulent gas and gas/particle flows over flat plates is presented, and preliminary results are reported. A 0.25-in.-thick 72 x 6-in. Al plate is suspended by six horizontal support air bearings and four vertical alignment air bearings between fixed dummy plates and leading-edge and trailing-edge fairings in the 32-in.-high 48-in.-wide 11-ft-long test section of a closed-circuit atmospheric wind tunnel operating at 50-150 ft/sec. Particles of Fe and Al oxides of diameter 20-150 microns and density up to 0.3 lb particles per lb air are injected via a 6 x 0.167-in. nozzle; turbulence is induced by a roughened section of the leading-edge fairing; and friction drag is measured using a load-cell pressure transducer. Sample results are shown in a graph, demonstrating good agreement with theoretical drag calculations.
Nonequilibrium Rotational Temperature Measurements over Flat Plates in Hypersonic Rarefied Gas Flow
NASA Astrophysics Data System (ADS)
Tsuboi, Nobuyuki; Matsumoto, Yoichiro
2008-12-01
An experimental study of the interaction between a shock wave and a boundary layer over a flat plate with a sharp leading edge in hypersonic rarefied gas flow is presented. Experiments in a low-density wind tunnel using an electron beam probe were conducted at the Shock Wave Laboratory, RWTH Aachen, Germany. Rotational temperatures for stagnation temperatures of T0 = 1000 K and Kn = 0.028 based on a reference length of 0.05 m were calculated using Robben and Talbot's method. The rotational temperature profiles at X = 3 mm for LE = 45 and 90 are 100 K larger than those for LE = 30. This means that a bow shock wave in front of the leading edge affects the rotational temperature profiles over the plate. The rotational energy distributions differ from the Maxwell-Boltzmann distributions and they are non-equilibrium distributions. The rotational temperature profiles for α = 12 deg are also 100 K larger than those for α = 0 deg. The feature of the rotational temperature over the plate for α = 12 deg is similar to that for LE = 45 and 90 deg.
NASA Technical Reports Server (NTRS)
Mayers, J; Budiansky, Bernard
1955-01-01
An analysis is presented of the postbuckling behavior of a simply supported square flat plate with straight edges compressed beyond the buckling load into the plastic range. The method of analysis involves the application of a variational principle of the deformation theory of plasticity in conjunction with computations carried out on a high-speed calculating machine. Numerical results are obtained for several plate proportions and for one material. The results indicate plate strengths greater than those that have been found experimentally on plates that do not satisfy straight-edge conditions. (author)
NASA Technical Reports Server (NTRS)
Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.
2016-01-01
In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance.
NASA Astrophysics Data System (ADS)
Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.
2016-09-01
In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance. Keywords: Calibration, radiometry, remote sensing, source.
Potential of size reduction of flat-plate solar collectors when applying MWCNT nanofluid
NASA Astrophysics Data System (ADS)
Faizal, M.; Saidur, R.; Mekhilef, S.
2013-06-01
Flat-plate solar collector is the most popular type of collector for hot water system to replace gas or electric heater. Solar thermal energy source is clean and infinite to replace fossil fuel source that is declining and harmful to the environment. However, current solar technology is still expensive, low in efficiency and takes up a lot of space. One effective way to increase the efficiency is by applying high conductivity fluid as nanofluid. This paper analyzes the potential of size reduction of solar collector when MWCNT nanofluid is used as absorbing medium. The analysis is based on different mass flow rate, nanoparticles mass fraction, and presence of surfactant in the fluid. For the same output temperature, it can be observed that the collector's size can be reduced up to 37% of its original size when applying MWCNT nanofluid as the working fluid and thus can reduce the overall cost of the system.
Flat-plate solar array project. Volume 3: Silicon sheet: Wafers and ribbons
NASA Technical Reports Server (NTRS)
Briglio, A.; Dumas, K.; Leipold, M.; Morrison, A.
1986-01-01
The primary objective of the Silicon Sheet Task of the Flat-Plate Solar Array (FSA) Project was the development of one or more low cost technologies for producing silicon sheet suitable for processing into cost-competitive solar cells. Silicon sheet refers to high purity crystalline silicon of size and thickness for fabrication into solar cells. Areas covered in the project were ingot growth and casting, wafering, ribbon growth, and other sheet technologies. The task made and fostered significant improvements in silicon sheet including processing of both ingot and ribbon technologies. An additional important outcome was the vastly improved understanding of the characteristics associated with high quality sheet, and the control of the parameters required for higher efficiency solar cells. Although significant sheet cost reductions were made, the technology advancements required to meet the task cost goals were not achieved.
Development of flat-plate solar collectors for the heating and cooling of buildings
NASA Technical Reports Server (NTRS)
Ramsey, J. W.; Borzoni, J. T.; Holland, T. H.
1975-01-01
The relevant design parameters in the fabrication of a solar collector for heating liquids were examined. The objective was to design, fabricate, and test a low-cost, flat-plate solar collector with high collection efficiency, high durability, and requiring little maintenance. Computer-aided math models of the heat transfer processes in the collector assisted in the design. The preferred physical design parameters were determined from a heat transfer standpoint and the absorber panel configuration, the surface treatment of the absorber panel, the type and thickness of insulation, and the number, spacing and material of the covers were defined. Variations of this configuration were identified, prototypes built, and performance tests performed using a solar simulator. Simulated operation of the baseline collector configuration was combined with insolation data for a number of locations and compared with a predicted load to determine the degree of solar utilization.
Multi-objective genetic algorithm for the optimization of a flat-plate solar thermal collector.
Mayer, Alexandre; Gaouyat, Lucie; Nicolay, Delphine; Carletti, Timoteo; Deparis, Olivier
2014-10-20
We present a multi-objective genetic algorithm we developed for the optimization of a flat-plate solar thermal collector. This collector consists of a waffle-shaped Al substrate with NiCrOx cermet and SnO(2) anti-reflection conformal coatings. Optimal geometrical parameters are determined in order to (i) maximize the solar absorptance α and (ii) minimize the thermal emittance ε. The multi-objective genetic algorithm eventually provides a whole set of Pareto-optimal solutions for the optimization of α and ε, which turn out to be competitive with record values found in the literature. In particular, a solution that enables α = 97.8% and ε = 4.8% was found.
Relaminarization of turbulent flow on a flat plate by localized surface heating
NASA Technical Reports Server (NTRS)
Maestrello, Lucio; Nagabushana, K. A.
1989-01-01
Relaminarization of a turbulent boundary layer in air on a flat plate is demonstrated experimentally using localized surface heating. Localized heating is achieved by electrically heating a wire embedded in a thermally insulated substrate (Space Shuttle Tile) on the surface. The stability of the flow downstream of the applied control point increases with decreasing stream temperature in the flow direction. The mean and perturbation velocity profiles without control show that the flow is turbulent. With control, these profiles sequentially change from intermittently turbulent to a fully laminar state. In the relaminarization stage, the turbulent energy is dissipated by molecular transport due to viscous and conductivity mechanisms. The new profile adjusts to a lower Reynolds number based on the momentum thickness than that of the previous turbulent state.
Investigation of solar water heater by using flat plate collector and evacuated tubes
NASA Astrophysics Data System (ADS)
Jayakanth, J. J.; Ramasubramanian, S.; Chandrasekaran, M.; Manavalan, S.
2017-03-01
Collection, storage and utilization of solar energy by solar water heating by flat plate collector and evacuated tube is cheapest and effective renewable energy technologies. This solar water heater design uses a nonconventional source of energy which can be used for house hold applications. The cost of production will be comparatively low in cost and high in capacity. The G.I. sheet collector boxes are replaced by copper tube, stainless steel water tank, thick costly PUF insulations and toughened glass etc. Pebbles are used as a medium of heat storage this increases the capacity of solar water heater by using this method natural source of energy can be used instead of depending on electric water heaters.
Flat-plate techniques for measuring reflectance of macro-algae (Ulva curvata)
Ramsey, Elijah W.; Rangoonwala, Amina; Thomsen, Mads Solgaard; Schwarzschild, Arthur
2012-01-01
We tested the consistency and accuracy of flat-plate spectral measurements (400–1000 nm) of the marine macrophyte Ulva curvata. With sequential addition of Ulva thallus layers, the reflectance progressively increased from 6% to 9% with six thalli in the visible (VIS) and from 5% to 19% with ten thalli in the near infrared (NIR). This progressive increase was simulated by a mathematical calculation based on an Ulva thallus diffuse reflectance weighted by a transmittance power series. Experimental and simulated reflectance differences that were particularly high in the NIR most likely resulted from residual water and layering structure unevenness in the experimental progression. High spectral overlap existed between fouled and non-fouled Ulva mats and the coexistent lagoon mud in the VIS, whereas in the NIR, spectral contrast was retained but substantially dampened by fouling.
Wind loads on flat plate photovoltaic array fields. Phase III, final report
Miller, R.D.; Zimmerman, D.K.
1981-04-01
The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads.
Sun, Yahui; Huang, Yun; Liao, Qiang; Fu, Qian; Zhu, Xun
2016-05-01
To offset the adverse effects of light attenuation on microalgae growth, hollow polymethyl methacrylate (PMMA) tubes were embedded into a flat-plate photobioreactor (PBR) as light guides. In this way, a fraction of incident light could be transmitted and emitted to the interior of the PBR, providing a secondary light source for cells in light-deficient regions. The average light intensity of interior regions 3-6cm from surfaces with 70μmolm(-2)s(-1) incident light was enhanced 2-6.5 times after 3.5days cultivation, resulting in a 23.42% increase in biomass production to that cultivated in PBR without PMMA tubes. The photosynthetic efficiency of microalgae in the proposed PBR was increased to 12.52%. Moreover, the installation of hollow PMMA tubes induced turbulent flow in the microalgae suspension, promoting microalgae suspension mixing. However, the enhanced biomass production was mainly attributed to the optimized light distribution in the PBR.
Characterization of the electrical output of flat-plate photovoltaic arrays
Gonzalez, C.C.; Hill, G.M.; Ross, R.G.
1982-09-01
The electric output of flat-plate photovoltaic arrays changes constantly, due primarily to changes in cell temperature and irradiance level. As a result, array loads such as direct-current to alternating-current power conditioners must be able to accommodate widely varying input levels while maintaining operation at or near the array maximum power point. The results of an extensive computer simulation study that was used to define the parameters necessary for the systematic design of array/power-conditioner interfaces are presented as normalized ratios of power-conditioner parameters to array parameters, to make the results universally applicable to a wide variety of system sizes, sites, and operating modes. The advantages of maximum power tracking and a technique for computing average annual power-conditioner efficiency are discussed.
Study of the evolution of temperatures in flat plate solar collectors
NASA Astrophysics Data System (ADS)
Hassoun, Zakaria Sari; Aliane, Khaled; Hıba, Imane Berrezoug
2017-02-01
This work deals with the experimental study of the changing temperatures of the various components of a flat plate solar collector for producing hot air. To do this, it has been the design of this solar collector equipped with thermocouples at the glazing, of the air gap existing within the solar collector and at the absorber. The temperature of the ambient air and that of the output of the solar collector is also measured. Several comparisons between the different temperatures were performed in order to, subsequently, analyzed the changes that can occur in these temperatures. The series of measures were taken during the day of Thursday, April 14, 2016. Starting from a ambient air temperature around 20 °C (temperature of the air inlet), the temperature reached 120 °C at the absorber and 95 °C at the outlet of the solar collector.
Wang, Dawei; Li, Yi; Zhang, Wenlong; Wang, Qing; Wang, Peifang; Wang, Chao
2013-04-01
A flat plate serpentine reactor modified from ultraviolet disinfection pool in municipal wastewater treatment plants was developed for the removal of 17-ethinylestradiol (EE2) for the first time. The photocatalytic degradation performance of EE2 was investigated in this serpentine reactor under different conditions such as inlet concentrations, loaded catalyst concentrations, incident radiations fluxes, and flow velocities. More than 98% of EE2 was removed under certain conditions within 120 min. An integrated model including a six-flux adsorption-scattering model and a modified flow diffusion model was established to investigate the effect of radiation field and flow velocities, respectively. A satisfactory agreement was observed between the model simulation and experimental results, showing a potential for design and scale-up of photocatalytic reactor for wastewater treatment.
Aerodynamic performance of an annular flat plate airfoil cascade with nonuniform inlet velocity
NASA Technical Reports Server (NTRS)
Buffum, D.; Fleeter, S.
1986-01-01
The demand for increased gas turbine engine efficiency with minimum weight is leading to more complex blading designs, in which viscous and three-dimensional effects are significant. As a result, design procedures based on first principle, experimentally verified, three-dimensional aerodynamic analyses are required. This paper describes a series of experiments performed in a large-scale, subsonic, annular cascade facility specifically designed to provide three-dimensional aerodynamic data suitable for code verification. In particular, the effect of inlet velocity profile on the overall three-dimensional performance of a classical flat plate airfoil cascade is investigated over a range of incidence angles including those resulting in airfoil surface flow separation. All of the data are analyzed and correlated with appropriate nonseparated flow predictions.
Flat-plate solar array project. Volume 6: Engineering sciences and reliability
NASA Technical Reports Server (NTRS)
Ross, R. G., Jr.; Smokler, M. I.
1986-01-01
The Flat-Plate Solar Array (FSA) Project activities directed at developing the engineering technology base required to achieve modules that meet the functional, safety, and reliability requirements of large scale terrestrial photovoltaic systems applications are reported. These activities included: (1) development of functional, safety, and reliability requirements for such applications; (2) development of the engineering analytical approaches, test techniques, and design solutions required to meet the requirements; (3) synthesis and procurement of candidate designs for test and evaluation; and (4) performance of extensive testing, evaluation, and failure analysis of define design shortfalls and, thus, areas requiring additional research and development. A summary of the approach and technical outcome of these activities are provided along with a complete bibliography of the published documentation covering the detailed accomplishments and technologies developed.
Turbulent boundary layer over a flat plate with strong stepwise heating
NASA Astrophysics Data System (ADS)
Ng, T. T.; Talbot, L.; Robben, F.
1982-07-01
The turbulent boundary layer over a flat plate with stepwise wall temperature rise from room temperature to 1250 K and free stream velocity of 10.5 m/s was studied. Thermal structures in the heated boundary layer were observed using high speed schlieren cine. Mean and rootmean-square (rms) density distributions were obtained from Rayleigh scattering intensity measurements. Velocity statistics were provided by a single component laser Doppler velocimetry system. Mean and rms velocity profiles, the Reynolds stress, the streamwise and the cross stream turbulent kinetic energy diffusion were determined. Data were collected by a computer based data acquisition and control system. The overall shape of the thermal structures observed in the schlieren pictures of the heated boundary layer is similar to that of the large scale turbulent structures in an isothermal turbulent boundary layer.
NASA Astrophysics Data System (ADS)
Oki, Sae; Suzuki, Ryosuke O.
2017-05-01
The performance of a flat-plate thermoelectric (TE) module consisting of square truncated pyramid elements is simulated using commercial software and original TE programs. Assuming that the temperatures of both the hot and cold surfaces are constant, the performance can be varied by changing the element shape and element alignment pattern. When the angle between the edge and the base is 85° and the small square surfaces of all n-type element faces are connected to the low-temperature surface, the efficiency becomes the largest among all the 17 examined shapes and patterns. By changing the shape to match the temperature distribution, the performance of the TE module is maximized.
NASA Astrophysics Data System (ADS)
Waksman, D.; Thomas, W. C.
1984-12-01
The results of studies, by the National Bureau of Standards, of the reliability and durability of eight different types of flat plate solar collectors representative of equipment available in 1977 are reported. The installations were made in four sites believed to typify various U.S. climates. The stability of the thermal performance and material properties was tracked, and measured again after moving the units inside for exposure to artificial sunlight. The stagnation measurement techniques employed to evaluate the collectors were judged adequate, provided the tests are made on-site and out of doors. It is noted that the instrumentation used to gather sufficient data for valid analyses may experience performance decrements due to the necessarily long monitoring intervals, i.e., several years.
Parallel DSMC Solution of Three-Dimensional Flow Over a Finite Flat Plate
NASA Technical Reports Server (NTRS)
Nance, Robert P.; Wilmoth, Richard G.; Moon, Bongki; Hassan, H. A.; Saltz, Joel
1994-01-01
This paper describes a parallel implementation of the direct simulation Monte Carlo (DSMC) method. Runtime library support is used for scheduling and execution of communication between nodes, and domain decomposition is performed dynamically to maintain a good load balance. Performance tests are conducted using the code to evaluate various remapping and remapping-interval policies, and it is shown that a one-dimensional chain-partitioning method works best for the problems considered. The parallel code is then used to simulate the Mach 20 nitrogen flow over a finite-thickness flat plate. It is shown that the parallel algorithm produces results which compare well with experimental data. Moreover, it yields significantly faster execution times than the scalar code, as well as very good load-balance characteristics.
Characterizing a burst leading-edge vortex on a rotating flat plate wing
NASA Astrophysics Data System (ADS)
Jones, Anya R.; Medina, Albert; Spooner, Hannah; Mulleners, Karen
2016-04-01
Identifying, characterizing, and tracking incoherent vortices in highly separated flows is of interest for the development of new low-order models for unsteady lift prediction. The current work examines several methods to identify vortex burst and characterize a burst leading-edge vortex. Time-resolved stereoscopic PIV was performed on a rotating flat plate wing at Re = 2500. The burst process was found to occur at mid-span and is characterized by axial flow reversal, the entrainment of opposite-sign vorticity, and a rapid expansion of vortex size. A POD analysis revealed that variations in certain mode coefficients are indicative of the flow state changes characteristics of burst. During burst, the leading-edge vortex evolves to a region of inhomogeneous vorticity distributed over a large area. Several methods of defining the vortex size and circulation are evaluated and a combination of these can be used to characterize the leading-edge vortex both pre- and post-burst.
Characterization of the electrical output of flat-plate photovoltaic arrays
NASA Astrophysics Data System (ADS)
Gonzalez, C. C.; Hill, G. M.; Ross, R. G., Jr.
The electric output of flat-plate photovoltaic arrays changes constantly, due primarily to changes in cell temperature and irradiance level. As a result, array loads such as direct-current to alternating-current power conditioners must be able to accommodate widely varying input levels, while maintaining operation at or near the array maximum power point.The results of an extensive computer simulation study that was used to define the parameters necessary for the systematic design of array/power-conditioner interfaces are presented as normalized ratios of power-conditioner parameters to array parameters, to make the results universally applicable to a wide variety of system sizes, sites, and operating modes. The advantages of maximum power tracking and a technique for computing average annual power-conditioner efficiency are discussed.
Experiments on the stability of the flat-plate boundary layer with suction
NASA Technical Reports Server (NTRS)
Reynolds, G. A.; Saric, W. S.
1982-01-01
Experiments have been conducted in the VPI and SU Stability Wind Tunnel on a flat-plate wind-tunnel model equipped with porous suction panels. Detailed hot-wire measurements were conducted in the laminar boundary layer to investigate the stabilizing effects of suction on growing Tollmien-Schlichting waves, which were introduced into the boundary layer using a vibrating ribbon. Special care was taken to minimize external disturbances and to avoid extraneous experimental bias. The measurements, which included mean-flow and disturbance-amplitude profiles across the boundary layer, showed that suction applied through discrete porous strips can be as effective as suction applied continuously over a much longer streamwise length. The measurements also showed that suction is more effective when placed forward, nearer to the region of neutral stability, than when placed in the region of maximum growth rate. These results also provided meaningful comparison with recent theory.
Navier-Stokes simulations of the effects of suction holes on a flat plate boundary layer
NASA Technical Reports Server (NTRS)
Meitz, Hubert L.; Fasel, Hermann F.
1994-01-01
Direct numerical simulations (DNS) of the Navier-Stokes equations are employed to explore the effects of suction holes on transition in a laminar flat plate boundary layer. The Navier-Stokes equations are cast in vorticity-velocity form. Periodicity is imposed in spanwise direction; all other spatial derivatives are discretized with fourth order compact differences. An explicit fourth order Runge-Kutta scheme is employed for the time-integration of the vorticity transport equations. Suction is applied through a row of holes aligned in spanwise direction. For low suction strengths, each hole generates a pair of stable streamwise vortices. When the suction strength exceeds a critical value, the vortices become unstable. For high suction strengths, vortex shedding occurs right at the suction holes. Our numerical findings agree well with experimental observations.
Analysis of turbulent free-convection boundary layer on flat plate
NASA Technical Reports Server (NTRS)
Eckert, E R G; Jackson, Thomas W
1951-01-01
With the use of Karman's integrated momentum equation for the boundary layer and data on the wall-shearing stress and heat transfer in forced-convection flow, a calculation was carried out for the flow and heat transfer in the turbulent free-convection boundary layer on a vertical flat plate. The calculation is for a fluid with a Prandtl number that is close to 1. A formula was derived for the heat-transfer coefficient that was in good agreement with experimental data in the range of Grashof numbers from 10sup10 to 10sup12. Because of the good agreement between the theoretical formula and the experimental data, the formula may be used to obtain data for high Grashof numbers. The calculation also yielded formulas for the maximum velocity in the boundary layer and for boundary-layer thickness.
PV Reliability Development Lessons from JPL's Flat Plate Solar Array Project
NASA Technical Reports Server (NTRS)
Ross, Ronald G., Jr.
2013-01-01
Key reliability and engineering lessons learned from the 20-year history of the Jet Propulsion Laboratory's Flat-Plate Solar Array Project and thin film module reliability research activities are presented and analyzed. Particular emphasis is placed on lessons applicable to evolving new module technologies and the organizations involved with these technologies. The user-specific demand for reliability is a strong function of the application, its location, and its expected duration. Lessons relative to effective means of specifying reliability are described, and commonly used test requirements are assessed from the standpoint of which are the most troublesome to pass, and which correlate best with field experience. Module design lessons are also summarized, including the significance of the most frequently encountered failure mechanisms and the role of encapsulate and cell reliability in determining module reliability. Lessons pertaining to research, design, and test approaches include the historical role and usefulness of qualification tests and field tests.
Correlations for laminar mixed convection flows on vertical, inclined, and horizontal flat plates
NASA Astrophysics Data System (ADS)
Chen, T. S.; Armaly, B. F.; Ramachandran, N.
1986-11-01
Local Nusselt numbers for laminar mixed convection flows along isothermal vertical, inclined, and horizontal flat plates are presented for the entire mixed convection regime for a wide range of Prandtl numbers. Simple correlation equations for the local and average mixed convection Nusselt numbers are developed, which are found to agree well with the numerically predicted values and available experimental data for both buoyancy assisting and opposing flow conditions. The threshold values of significant buoyancy effects on forced convection and forced flow effects on free convection, as well as the maximum increase in the local mixed convection Nusselt number from the respective pure convection limits, are also presented for all flow configurations. It is found that the buoyancy or forced flow effect can increase the surface heat transfer rate from pure forced or pure free convection by about 20 percent.
Comparison of DAC and MONACO DSMC Codes with Flat Plate Simulation
NASA Technical Reports Server (NTRS)
Padilla, Jose F.
2010-01-01
Various implementations of the direct simulation Monte Carlo (DSMC) method exist in academia, government and industry. By comparing implementations, deficiencies and merits of each can be discovered. This document reports comparisons between DSMC Analysis Code (DAC) and MONACO. DAC is NASA's standard DSMC production code and MONACO is a research DSMC code developed in academia. These codes have various differences; in particular, they employ distinct computational grid definitions. In this study, DAC and MONACO are compared by having each simulate a blunted flat plate wind tunnel test, using an identical volume mesh. Simulation expense and DSMC metrics are compared. In addition, flow results are compared with available laboratory data. Overall, this study revealed that both codes, excluding grid adaptation, performed similarly. For parallel processing, DAC was generally more efficient. As expected, code accuracy was mainly dependent on physical models employed.
NASA Astrophysics Data System (ADS)
Liu, J.; Wu, S. P.
2017-04-01
Wall function boundary conditions including the effects of compressibility and heat transfer are improved for compressible turbulent boundary flows. Generalized wall function formulation at zero-pressure gradient is proposed based on coupled velocity and temperature profiles in the entire near-wall region. The parameters in the generalized wall function are well revised. The proposed boundary conditions are integrated into Navier-Stokes computational fluid dynamics code that includes the shear stress transport turbulence model. Numerical results are presented for a compressible boundary layer over a flat plate at zero-pressure gradient. Compared with experimental data, the computational results show that the generalized wall function reduces the first grid spacing in the directed normal to the wall and proves the feasibility and effectivity of the generalized wall function method.
Calculation of oblique-shock-wave laminar-boundary-layer interaction on a flat plate
NASA Technical Reports Server (NTRS)
Goldberg, U.; Reshotko, E.
1980-01-01
A finite difference solution to the problem of the interaction between an impinging oblique shock wave and the laminar boundary layer on a flat plate is presented. The boundary layer equations coupled with the Prandtl-Meyer relation for the external flow are used to calculate the flow field. A method for the calculation of the separated flow region is presented and discussed. Comparisons between this theory and the experimental results of other investigators show fairly good agreement. Results are presented for the case of a cooled wall with an oncoming flow at Mach number 2.0 without and with suction. The results show that a small amount of suction greatly reduces the extent of the separated region in the vicinity of the shock impingement location.
Experimental study of boundary layer transition on a heated flat plate
NASA Technical Reports Server (NTRS)
Sohn, K. H.; Reshotko, E.; Zaman, K. B. M. Q.
1991-01-01
A detailed investigation to the document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were done in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate, and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for momentum thickness Reynolds number, Re(sub theta) less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length and uniform heat flux. A small dependence of turbulence results on the freestream turbulence intensity was observed.
LOVEL: a low-velocity aerodynamic heating code for flat-plates, wedges, and cones
Thornton, A.L.
1981-12-01
The LOVEL computer program calculates the boundary-layer edge conditions for subsonic and supersonic flow over flat-plate, wedge, and cone geometries for freestream Mach conditions (M/sub infinity/ < 3. Cold-wall heat-transfer calculations use reference temperature correlations based on boundary-layer edge Mach number to compute fluid properties. The first part of this report describes the theory used in the computation of the cold-wall heat-transfer rates; the second part describes in detail the input/output format for the LOVEL computer program. Outputs include freestream conditions, boundary-layer edge conditions, cold-wall heat-transfer rates, plots of heating rates, and punched-card output for use in ablation and in-depth transient heat-conduction computer codes.
Fixed flat plate collector with a reversible vee-trough concentrator
NASA Technical Reports Server (NTRS)
Selcuk, M. K.
1976-01-01
An asymmetrical-reversible vee-trough concentrator for use both with nonevacuated and evacuated receivers is proposed in order to improve the performance of a fixed flat plate collector. The device is capable of maintaining a year-round concentration factor of about 2 while eliminating the complications of the tilt adjustments of the collector box assembly. Efficiency improvements and cost reductions for temperatures of about 100 and 200 C are offered for the nonvacuum and vacuum tube versions, respectively. A major advantage of the vee-trough is the enhancement of the incident flux, thus extending the collection period. The vacuum collector is suitable for supplying heat to solar Rankine systems, while the nonvacuum version can be used for air conditioning purposes via an absorption air conditioner.
NASA Technical Reports Server (NTRS)
Sullivan, T. J.; Ibrahim, M.
1989-01-01
A boundary layer computer code, called TEXSTAN, has been used to simulate external, transitional, fluid flow and heat transfer over the flat plate and circular cylinder. Turbulence modeling was accomplished by using a low-Reynolds number K-epsilon turbulence model. The study was made for free-stream turbulence intensities less than 15 percent. The comparison of the flat plate heat transfer predictions to experimental data showed good agreement, for the location of transition as well as in the heat transfer coefficient. The typical discrepancy in predicting the heat transfer coefficient was less than 5 percent of the measured value.
NASA Technical Reports Server (NTRS)
Sullivan, T. J.; Ibrahim, M.
1989-01-01
A boundary layer computer code, called TEXSTAN, has been used to simulate external, transitional, fluid flow and heat transfer over the flat plate and circular cylinder. Turbulence modeling was accomplished by using a low-Reynolds number K-epsilon turbulence model. The study was made for free-stream turbulence intensities less than 15 percent. The comparison of the flat plate heat transfer predictions to experimental data showed good agreement, for the location of transition as well as in the heat transfer coefficient. The typical discrepancy in predicting the heat transfer coefficient was less than 5 percent of the measured value.
Jacobs, C; Sari, R
1986-01-01
The performances and clinical tolerance of a flat plate dialyzer equipped with a polycarbonate polyether copolymer membrane (surface area 1.13 and 0.80 m2, membrane thickness 16 micron) were evaluated in 10 patients, among whom 7 underwent a total of 523 dialysis sessions performed over a 6-month investigation period. Clinical and biological parameters recorded during the study were compared to those observed during an immediately preceding control period during which the same patients were dialyzed with flat plate or hollow fiber Cuprophan dialyzers. The clearances of the 1.13 m2 polycarbonate dialyzer for urea, creatinine, uric acid and inorganic phosphate determined at 36 +/- 14 min after start of the dialysis sessions were found respectively at 132 +/- 23, 103 +/- 22, 120 +/- 23 and 103 +/- 18 ml/min and at significantly higher values (except for uric acid) at the 4th hour of dialysis. The ultrafiltration rate was 490 ml/h for a 100 mm Hg transmembrane pressure and the residual blood volume at the end of dialysis was found at 1.1 +/- 0.3 ml. The main clinical and biological parameters recorded in the 7 patients treated for 6 months with polycarbonate dialyzers were not significantly different from those observed during the preceding control period, although 71% of the polycarbonate dialyzers had a smaller surface area than in those used during the control period. The overall blood leakage rate recorded in 555 polycarbonate dialyzers was 1.08%. No sign or symptom suggestive of clinical intolerance to the polycarbonate membrane was recorded during the entire course of the study.
Transition due to streamwise streaks in a supersonic flat plate boundary layer
NASA Astrophysics Data System (ADS)
Paredes, Pedro; Choudhari, Meelan M.; Li, Fei
2016-12-01
Transition induced by stationary streaks undergoing transient growth in a supersonic flat plate boundary layer flow is studied using numerical computations. While the possibility of strong transient growth of small-amplitude stationary perturbations in supersonic boundary layer flows has been demonstrated in previous works, its relation to laminar-turbulent transition cannot be established within the framework of linear disturbances. Therefore, this paper investigates the nonlinear evolution of initially linear optimal disturbances that evolve into finite amplitude streaks in the downstream region, and then studies the modal instability of those streaks as a likely cause for the onset of bypass transition. The nonmodal evolution of linearly optimal stationary perturbations in a supersonic, Mach 3 flat plate boundary layer is computed via the nonlinear plane-marching parabolized stability equations (PSE) for stationary perturbations, or equivalently, the perturbation form of parabolized Navier-Stokes equations. To assess the effect of the nonlinear finite-amplitude streaks on transition, the linear form of plane-marching PSE is used to investigate the instability of the boundary layer flow modified by the spanwise periodic streaks. The onset of transition is estimated using an N -factor criterion based on modal amplification of the secondary instabilities of the streaks. In the absence of transient growth disturbances, first mode instabilities in a Mach 3, zero pressure gradient boundary layer reach N =10 at Rex≈107 . However, secondary instability modes of the stationary streaks undergoing transient growth are able to achieve the same N -factor at Rex<2 ×106 when the initial streak amplitude is sufficiently large. In contrast to the streak instabilities in incompressible flows, subharmonic instability modes with twice the fundamental spanwise wavelength of the streaks are found to have higher amplification ratios than the streak instabilities at fundamental
NASA Technical Reports Server (NTRS)
Melis, Matthew E.; Brand, Jeremy H.; Pereira, J. Michael; Revilock, Duane M.
2007-01-01
Following the tragedy of the Space Shuttle Columbia on February 1, 2003, a major effort commenced to develop a better understanding of debris impacts and their effect on the Space Shuttle subsystems. An initiative to develop and validate physics-based computer models to predict damage from such impacts was a fundamental component of this effort. To develop the models it was necessary to physically characterize Reinforced Carbon-Carbon (RCC) and various debris materials which could potentially shed on ascent and impact the Orbiter RCC leading edges. The validated models enabled the launch system community to use the impact analysis software LS DYNA to predict damage by potential and actual impact events on the Orbiter leading edge and nose cap thermal protection systems. Validation of the material models was done through a three-level approach: fundamental tests to obtain independent static and dynamic material model properties of materials of interest, sub-component impact tests to provide highly controlled impact test data for the correlation and validation of the models, and full-scale impact tests to establish the final level of confidence for the analysis methodology. This paper discusses the second level subcomponent test program in detail and its application to the LS DYNA model validation process. The level two testing consisted of over one hundred impact tests in the NASA Glenn Research Center Ballistic Impact Lab on 6 by 6 in. and 6 by 12 in. flat plates of RCC and evaluated three types of debris projectiles: BX 265 External Tank foam, ice, and PDL 1034 External Tank foam. These impact tests helped determine the level of damage generated in the RCC flat plates by each projectile. The information obtained from this testing validated the LS DYNA damage prediction models and provided a certain level of confidence to begin performing analysis for full-size RCC test articles for returning NASA to flight with STS 114 and beyond.
Sensitivity analysis of thermal performances of flat plate solar air heaters
NASA Astrophysics Data System (ADS)
Njomo, Donatien; Daguenet, Michel
2006-10-01
Sensitivity analysis is a mathematical tool, first developed for optimization methods, which aim is to characterize a system response through the variations of its output parameters following modifications imposed on the input parameters of the system. Such an analysis may quickly become laborious when the thermal model under consideration is complex or the number of input parameters is high. In this paper, we develop a mathematical model to analyse the heat exchanges in four different types of solar air collectors. When building this thermal model we show that for each collector, at quasi-steady state, the energy balance equations of the components of the collector cascade into a single first-order non-linear differential equation that is able to predict the thermal behaviour of the collector. Our heat transfer model clearly demonstrates the existence of an important dimensionless parameter, referred to as the thermal performance factor of the collector, that compares the useful thermal energy which can be extracted from the heater to the overall thermal losses of that collector for a given set of input parameters. A sensitivity analysis of our thermal model has been performed for the most significant input parameters such as the incident solar irradiation, the inlet fluid temperature, the air mass flow rate, the depth of the fluid channel, the number and nature of the transparent covers in order to measure the impact of each of these parameters on our model. An important result which can be drawn from this study is that the heat transfer model developed is robust enough to be used for thermal design studies of most known flat plate solar air heaters, but also of flat plate solar water collectors and linear solar concentrators.
NASA Astrophysics Data System (ADS)
Batubara, Fatimah; Misran, Erni; Dina, Sari Farah; Heppy
2017-06-01
Research on potato drying using the indirect solar dryer with flat-plate finned collector and forced convection has been done. The research was conducted at the outdoor field of Laboratory of Institute for Research and Standardization of Industry on June 14th-23rd, 2016 from 9:00 am to 4:00 pm. This research aims to obtain the drying kinetics model of potato (Solanumtuberosum L.) using an indirect solar dryer's (ISD) with flat plate-finned collector and forced convection. The result will be compared to the open sun drying (OSD) method. Weather conditions during the drying process took place as follows; surrounding air temperature was in the range 27 to 34.7 °C, relative humidity (RH) 29.5 to 61.0% and the intensity of solar radiation 105.6 to 863.1 Watt/m2. The dried potato thicknesses were 1.0 cm, 1.5 cm and 2.0 cm, with the average initial water content of 76.46%. The average temperature in the collector chamber ranged from 42.2 to 57.4 °C and the drying chamber was at 46.2 °C. The best drying result was obtained from a sample size of 1 cm thickness using the IDS method with an average drying rate of 0.018 kg H2O per kg dry-weight.hour and the water content was constant at 5.02% in 21 hours of drying time. The most suitable kinetics model is Page model, equation MR = exp (-0.049 t1,336) for 1.0 cm thickness, exp (-0.066 t1,222) for 1.5 cm thickness and exp (-0.049 t1,221) for 2.0 cm thickness. The quality of potato drying using ISD method is better than using OSD which can be seen from the color produced.
Confined swirling jet impingement on a flat plate at moderate Reynolds numbers
NASA Astrophysics Data System (ADS)
Herrada, M. A.; Del Pino, C.; Ortega-Casanova, J.
2009-01-01
The behavior of a swirling jet issuing from a pipe and impinging on a flat smooth wall is analyzed numerically by means of axisymmetric simulations. The axial velocity profile at the pipe outlet is assumed flat while the azimuthal velocity profile is a Burger's vortex characterized by two non-dimensional parameters; a swirl number S and a vortex core length δ. We concentrate on the effects of these two parameters on the mechanical characteristics of the flow at moderate Reynolds numbers. Our results for S =0 are in agreement with Phares et al. [J. Fluid Mech. 418, 351 (2000)], who provide a theoretical determination of the wall shear stress under nonswirling impinging jets at high Reynolds numbers. In addition, we show that the swirl number has an important effect on the jet impact process. For a fixed nozzle-to-plate separation, we found that depending on the value of δ and the Reynolds number Re, there is a critical swirl number, S =S∗(δ ,Re), above which recirculating vortex breakdown bubbles are observed in the near axis region. For S >S∗, the presence of these bubbles enhances the transition from a steady to a periodic regime. For S
E.J. Brown; C.T. Ballinger; S.R. Burger; G.W. Charache; L.R. Danielson; D.M. DePoy; T.J. Donovan; M. LoCascio
2000-05-30
The performance of a 1 cm{sup 2} thermophotovoltaic (TPV) module was recently measured in a photonic cavity test system. A conversion efficiency of 11.7% was measured at a radiator temperature of 1076 C and a module temperature of 29.9 C. This experiment achieved the highest direct measurement of efficiency for an integrated TPV system. Efficiency was calculated from the ratio of the peak (load matched) electrical power output and the heat absorption rate. Measurements of these two parameters were made simultaneously to assure the validity of the measured efficiency value. This test was conducted in a photonic cavity which mimicked a typical flat-plate TPV system. The radiator was a large, flat graphite surface. The module was affixed to the top of a copper pedestal for heat absorption measurements. The heat absorption rate was proportional to the axial temperature gradient in the pedestal under steady-state conditions. The test was run in a vacuum to eliminate conductive and convective heat transfer mechanisms. The photonic cavity provides the optimal test environment for TPV efficiency measurements because it incorporates all important physical phenomena found in an integrated TPV system: high radiator emissivity and blackbody spectral shape, photon recycling, Lambertian distribution of incident radiation and complex geometric effects. Furthermore, the large aspect ratio between radiating surface area and radiator/module spacing produces a view factor approaching unity with minimal photon leakage.
Large amplitude nonlinear response of flat aluminum, and carbon fiber plastic beams and plates
NASA Astrophysics Data System (ADS)
Wolfe, Howard F.; Shroyer, Cynthia A.
1994-06-01
This progress report presents the results of a continuing study to improve the understanding of nonlinear dynamic behavior of aerospace structures subjected to high levels of excitation. Tests were continued with a clamped-clamped (C-C) aluminum beam. A summary of the results is presented. Tests were conducted with a C-C carbon fiber reinforced plastic (CFRP) beam and a pinned-pinned (P-P) aluminum beam. A summary of these results is also presented. Flat plate tests began with an aluminum plate. The shapes of the total, axial, and bending strain power spectral densities for the C-C aluminum and the CFRP beams were quite similar. Both showed a small frequency increase and slight peak broadening as the levels of excitation increased. The nonlinear displacement shapes for the two cases were also quite similar. Further analysis is needed for the P-P aluminum beam case. Finally, a method of estimating the RMS stress for the multimodal response of a panel is presented.
Aerothermodynamics of compressible flow past a flat plate in the slip-flow regime
NASA Astrophysics Data System (ADS)
Cheng, Chi-Yang; Dai, Yi; Li, Genong; Hu, Yitao; Lai, Ming-Chia
2015-11-01
Compressible flow past a flat plate in the slip-flow regime features a very simple geometry and flow field, but it retains the most relevant and interesting physics in high-speed rarefied gas dynamics. In the slip-flow regime, the aerothermodynamic issues, especially the recovery factors and the convection heat transfer correlation, are the focus of this presentation. We first present the detailed similarity equations, especially the transformed Maxwell's slip and jump boundary conditions, and the equations for the Chapman-Rubesin parameter as well as how we incorporate the variable gas properties and the constitutive scaling model for the Knudsen layer in the similarity equations. The similarity solutions are compared with results published by E. R. van Driest [NACA Technical Note 2597, 1952]. We point out that van Driest's solutions were computed by using no-slip and no-jump boundary conditions. The recovery factor and Nusselt number of the plate are shown as functions of the Reynolds number and the Mach number. Finally, the similarity solutions are also compared with simulations of a two-dimensional computational fluid dynamics model solving the full Navier-Stokes-Fourier equations with slip and jump boundary conditions.
Geometry Transition in the Cocos Plate, from Flat-Steep to Constant Dip: Smooth or Abrupt?
NASA Astrophysics Data System (ADS)
Perez-Campos, X.; Clayton, R. W.; Brudzinski, M. R.; Valdés-González, C. M.; Cabral-Cano, E.; Arciniega-Ceballos, A.; Córdoba-Montiel, F.
2013-05-01
Subduction of the Cocos Plate beneath North America has a variable and complex behavior along the Middle-American Trench. Initially, its geometry was delineated from regional seismicity. In the last 10 years, seismic experiments have illuminated some details in the geometry. They have reported, from NW to SE an abrupt dip transition, from 50 to 26°, as the result of a tear that splits Cocos North from Cocos South; then there is a smooth transition to a horizontal geometry under central Mexico. Further southeast, under the Isthmus of Tehuantepec, the Cocos plate shows a constant ~26° subduction dip. This last transition has been assumed to be smooth from the sparse seismicity in the region. A first glimpse of the slab geometry under Oaxaca, shows the slab continues to be flat at least until 97.5°W longitude, where the slab suddenly changes to a ~55° dip to the northeast. This occurs at a distance of ~75 km from the Pico de Orizaba volcano, which is a similar distance as the active Popocatepetl volcano from the place where the slab dives into the mantle along the Meso-American Subduction Experiment line, in central Mexico. East of this region, receiver function images show an abrupt change in the geometry and length of the slab.
S receiver function observations of flat subduction and partial delamination of the Farallon plate
NASA Astrophysics Data System (ADS)
Kind, Rainer; Yuan, Xiaohui; Sodoudi, Forough
2015-04-01
We used more than 40,000 S receiver functions recorded by the USArray project to study the transition of the structure of the mantle lithosphere from the Phanerozoic western United States to the cratonic central parts. We observed the lower boundary of the flat subduction of the Farallon plate continuously from near the Pacific coast at about 100 km depth to about the Mid Continental Rift System at about 200 km depth. We also observed a large break in this plate from about 42 to 46°N, striking north-south along about 110°W. Yellowstone is located at the northern end of this break. East of the break the lithosphere-asthenosphere boundary (LAB) is near 200 km depth and to the west of the break it is near 100 km depth. East of the break the LAB is rises to about 100 km depth below the Great Plains. We suggest that this structure is a reversely inclined part of the Farallon slab due to delamination. Our observations agree partly with tomographic models. East of the Mid Continental Rift System we observe the cratonic LAB at its expected depth near 200 km. We observe in addition the bottom of the asthenosphere (Lehmann discontinuity) and a negative discontinuity above the 410 km discontinuity, indicating partial melt.
Earth Reflected Solar Radiation Incident upon an Arbitrarily Oriented Spinning Flat Plate
NASA Technical Reports Server (NTRS)
Cunningham, Fred G.
1963-01-01
A general derivation is given for the earth reflected solar radiation input to a flat plate--a solar cell paddle, for example--which is spinning about an axis coincident with the axis of symmetry of the satellite to which it is affixed. The resulting equations are written for the general case so that arbitrary orientations of the spin axis with respect to the earth-satellite line and arbitrary orientations of the normal to the plate with respect to the spin axis can be treated. No attempt is made to perform the resulting integrations because of the complexity of the equations; nor is there any attempt to delineate the integration limits for the general case. However, the equations governing these limits are given. The appendixes contain: the results, in graphical form, of two representative examples; the general computer program for the calculation is given in Fortran notation; and the results of a calculation of the distribution of albedo energy on the proposed Echo II satellite. The value of the mean solar constant used is 1.395 times 10 (sup 4) ergs per centimeters-squared per second; the mean albedo of the earth is assumed to be 0.34; and the earth is assumed to be a diffuse reflector.
Detached Eddy Simulation of Film Cooling over a GE Flat Plate
NASA Technical Reports Server (NTRS)
Roy, Subrata
2005-01-01
The detached eddy simulation of film cooling has been utilized for a proprietary GE plate-pipe configuration. The blowing ratio was 2.02, the velocity ratio was 1.26, and the temperature ratio was 1.61. Results indicate that the mixing processes downstream of the hole are highly anisotropic. DES solution shows its ability to depict the dynamic nature of the flow and capture the asymmetry present in temperature and velocity distributions. Further, comparison between experimental and DES time-averaged effectiveness is satisfactory. Numerical values of span-averaged effectiveness show better prediction of the experimental values at downstream locations than a steady state Glenn HT solution. While the DES method shows obvious promise, there are several issues that need further investigation. Despite an accurate prediction in the hole vicinity, the simulation still falls short in the region x = 10d to 100d. This should be investigated. Also the model used flat plate. Actual turbine blade should be modeled in the future if additional finding is available.
Experimental Study on Performance of a Box Solar Cooker with Flat Plate Collector to Boil Water
NASA Astrophysics Data System (ADS)
Sitepu, T.; Gunawan, S.; Nasution, D. M.; Ambarita, H.; Siregar, R. E. T.; Ronowikarto, A. D.
2017-03-01
In this study, a flat plate type solar cooker is tested by exposing in solar irradiation. The objective is to examine the performance of solar cooker in boiling water. The solar cooker is a box type with collector area and height are 100 × 100 cm and 40 cm, respectively. Vessel for water is made of aluminum plate with diameter and height of 22 cm and 15 cm. The experiments are performed by varying mass of the water. It is 2 kg and 4 kg, respectively. Every experiment starts from 10:00 AM until the boiling temperature is reached. The parameters measured are radiance intensity, ambient and solar box cooker temperatures, and wind speed. The results show that the duration of water heating up to 100°C with water mass 2 kg within 2 hours 45 minutes and water mass 4 kg within 3 hours 17 minutes. The maximum temperatur of solar box cooker is 117°C at 12:56 PM and maximum efficiency is 46.30%. The main conclusion can be drawn here is that a simple solar box cooker can be used to boil water.
Heat Transfer on a Flat Plate with Uniform and Step Temperature Distributions
NASA Technical Reports Server (NTRS)
Bahrami, Parviz A.
2005-01-01
Heat transfer associated with turbulent flow on a step-heated or cooled section of a flat plate at zero angle of attack with an insulated starting section was computationally modeled using the GASP Navier-Stokes code. The algebraic eddy viscosity model of Baldwin-Lomax and the turbulent two-equation models, the K- model and the Shear Stress Turbulent model (SST), were employed. The variations from uniformity of the imposed experimental temperature profile were incorporated in the computations. The computations yielded satisfactory agreement with the experimental results for all three models. The Baldwin- Lomax model showed the closest agreement in heat transfer, whereas the SST model was higher and the K-omega model was yet higher than the experiments. In addition to the step temperature distribution case, computations were also carried out for a uniformly heated or cooled plate. The SST model showed the closest agreement with the Von Karman analogy, whereas the K-omega model was higher and the Baldwin-Lomax was lower.
Sloane, E D; Muscoplat, C C; Kaneene, J M; Klausner, D J; Thoen, C O; Johnson, D W
1978-02-01
Lymphocytes from Mycobacterium bovis-sensitized and normal cattle were cultured in round- and/or flat-bottom microtiter plates and stimulated with M. bovis purified protein derivative (PPD) tuberculin. Blastogenic responses of lymphocytes from M. bovis-sensitized cattle to PPD cultured in round-bottom plates were significantly greater than those of lymphocytes cultured in flat-bottom microtiter plates. Normal lymphocytes of nonsensitized cattle were not stimulated by PPD in either round- or flat-bottom microtiter plates. Kinetics of lymphocyte responses in round-bottom plates are presented.
Use of a rotating cylinder to induce laminar and turbulent separation over a flat plate
NASA Astrophysics Data System (ADS)
Afroz, F.; Lang, A.; Jones, E.
2017-06-01
An innovative and easy technique using a rotating cylinder system has been implemented in a water tunnel experiment to generate an adverse pressure gradient (APG). The strength of the APG was varied through adjustment in the rotation speed and location of the cylinder. Then the technique was used for inducing a laminar separation bubble (LSB) and turbulent boundary layer (TBL) separation over a flat plate. A theoretical model to predict the pressure variation induced on the plate consists of an inviscid flow over a reverse doublet-like configuration of two counter rotating cylinders. This model quantified the pressure distribution with changes of cylinder speed and location. The dimensionless velocity ratio (VR) of the cylinder rotation rate to the mainstream velocity and gap to diameter ratio \\tfrac{G}{D} were chosen as the two main ways of varying the strength of the APG, which affects the nature and extent of the LSB as well as TBL separation. The experimental parametric study, using time-resolved digital particle image velocimetry, was then conducted in a water tunnel. The variation in height (h), length (l), and the separation point (S) of the LSB was documented due to the variation in the APG. The similar type of experimental parametric study was used to explore the unsteady, turbulent separation bubble in a 2D plane aligned with the flow and perpendicular to the plate. The mean detachment locations of TBL separation are determined by two different definitions: (i) back-flow coefficient (χ) = 50%, and (ii) location of start of negative mean skin friction coefficient (C f). They are in good agreement and separation bubble characteristics agreed well with results obtained using different methods thus proving the validity of the technique.
NASA Technical Reports Server (NTRS)
Borden, C. S.; Schwartz, D. L.
1984-01-01
The purpose of this study is to assess the relative economic potentials of concenrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications in the mid-1990's. Specific objectives of this study are to provide information on concentrator photovoltaic collector probabilistic price and efficiency levels to illustrate critical areas of R&D for concentrator cells and collectors, and to compare concentrator and flat-plate PV price and efficiency alternatives for several locations, based on their implied costs of energy. To deal with the uncertainties surrounding research and development activities in general, a probabilistic assessment of commercially achievable concentrator photovoltaic collector efficiencies and prices (at the factory loading dock) is performed. The results of this projection of concentrator photovoltaic technology are then compared with a previous flat-plate module price analysis (performed early in 1983). To focus this analysis on specific collector alternatives and their implied energy costs for different locations, similar two-axis tracking designs are assumed for both concentrator and flat-plate options.
NASA Astrophysics Data System (ADS)
Kegerise, Michael A.; Rufer, Shann J.
2016-08-01
In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.
NASA Technical Reports Server (NTRS)
Mcgrath, Brian E.; Neuhart, Dan H.; Gatlin, Gregory M.; Oneil, Pat
1994-01-01
A flat-plate wind tunnel model of an advanced fighter configuration was tested in the NASA LaRC Subsonic Basic Research Tunnel and the 16- by 24-inch Water Tunnel. The test objectives were to obtain and evaluate the low-speed longitudinal aerodynamic characteristics of a candidate configuration for the integration of several new innovative wing designs. The flat plate test allowed for the initial evaluation of the candidate planform and was designated as the baseline planform for the innovative wing design study. Low-speed longitudinal aerodynamic data were obtained over a range of freestream dynamic pressures from 7.5 psf to 30 psf (M = 0.07 to M = 0.14) and angles-of-attack from 0 to 40 deg. The aerodynamic data are presented in coefficient form for the lift, induced drag, and pitching moment. Flow-visualization results obtained were photographs of the flow pattern over the flat plate model in the water tunnel for angles-of-attack from 10 to 40 deg. The force and moment coefficients and the flow-visualization photographs showed the linear and nonlinear aerodynamic characteristics due to attached flow and vortical flow over the flat plate model. Comparison between experiment and linear theory showed good agreement for the lift and induced drag; however, the agreement was poor for the pitching moment.
NASA Technical Reports Server (NTRS)
Johnson, S. M.
1976-01-01
Basic test results are reported for a flat plate solar collector whose performance was determined in a solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and one coolant flow rate. Collector efficiency is correlated in terms of inlet temperature and flux level.
NASA Technical Reports Server (NTRS)
Lundquist, Eugene E; Stowell, Elbridge Z
1942-01-01
A chart is presented for the values of the coefficient in the formula for the critical compressive stress at which buckling may be expected to occur in flat rectangular plates supported along all edges and, in addition, elastically restrained against rotation along the unloaded edges. The mathematical derivations of the formulas required in the construction of the chart are given.
Random matrix theory and acoustic resonances in plates with an approximate symmetry.
Andersen, A; Ellegaard, C; Jackson, A D; Schaadt, K
2001-06-01
We discuss a random matrix model of systems with an approximate symmetry and present the spectral fluctuation statistics and eigenvector characteristics for the model. An acoustic resonator like, e.g., an aluminum plate may have an approximate symmetry. We have measured the frequency spectrum and the widths for acoustic resonances in thin aluminum plates, cut in the shape of the so-called three-leaf clover. Due to the mirror symmetry through the middle plane of the plate, each resonance of the plate belongs to one of two mode classes and we show how to separate the modes into these two classes using their measured widths. We compare the spectral statistics of each mode class with results for the Gaussian orthogonal ensemble. By cutting a slit of increasing depth on one face of the plate, we gradually break the mirror symmetry and study the transition that takes place as the two classes are mixed. Presenting the spectral fluctuation statistics and the distribution of widths for the resonances, we find that this transition is well described by the random matrix model.
Random matrix theory and acoustic resonances in plates with an approximate symmetry
Andersen, A.; Ellegaard, C.; Jackson, A. D.; Schaadt, K.
2001-06-01
We discuss a random matrix model of systems with an approximate symmetry and present the spectral fluctuation statistics and eigenvector characteristics for the model. An acoustic resonator like, e.g., an aluminum plate may have an approximate symmetry. We have measured the frequency spectrum and the widths for acoustic resonances in thin aluminum plates, cut in the shape of the so-called three-leaf clover. Due to the mirror symmetry through the middle plane of the plate, each resonance of the plate belongs to one of two mode classes and we show how to separate the modes into these two classes using their measured widths. We compare the spectral statistics of each mode class with results for the Gaussian orthogonal ensemble. By cutting a slit of increasing depth on one face of the plate, we gradually break the mirror symmetry and study the transition that takes place as the two classes are mixed. Presenting the spectral fluctuation statistics and the distribution of widths for the resonances, we find that this transition is well described by the random matrix model.
NASA Astrophysics Data System (ADS)
Kapania, R. K.; Mohan, P.
1996-09-01
Finite element static, free vibration and thermal analysis of thin laminated plates and shells using a three noded triangular flat shell element is presented. The flat shell element is a combination of the Discrete Kirchhoff Theory (DKT) plate bending element and a membrane element derived from the Linear Strain Triangular (LST) element with a total of 18 degrees of freedom (3 translations and 3 rotations per node). Explicit formulations are used for the membrane, bending and membrane-bending coupling stiffness matrices and the thermal load vector. Due to a strong analogy between the induced strain caused by the thermal field and the strain induced in a structure due to an electric field the present formulation is readily applicable for the analysis of structures excited by surface bonded or embedded piezoelectric actuators. The results are presented for (i) static analysis of (a) simply supported square plates under doubly sinusoidal load and uniformly distributed load (b) simply supported spherical shells under a uniformly distributed load, (ii) free vibration analysis of (a) square cantilever plates, (b) skew cantilever plates and (c) simply supported spherical shells; (iii) Thermal deformation analysis of (a) simply supported square plates, (b) simply supported-clamped square plate and (c) simply supported spherical shells. A numerical example is also presented demonstrating the application of the present formulation to analyse a symmetrically laminated graphite/epoxy laminate excited by a layer of piezoelectric polyvinylidene flouride (PVDF). The results presented are in good agreement with those available in the literature.
Herva, E
1977-04-01
To compare microtitre plates with flat-bottomed and round-bottomed wells and to standardize a method for mixed lymphocyte culture (MLC), the effects of cell number, culture time, 3H-thymidine concentration and labelling time were studied. On both plates, allogeneic cells induced increased RNA synthesis beginning at about 30 hours and increased DNA synthesis beginning at about 50 hours, if suitable cell numbers were used. On plates with flat-bottomed wells, 1.5 X 10(5) responding and stimulating cells per well had near-exponential growth on day four and five, often through day six; on plates with round-bottomed wells the corresponding cell number was 0.25-1.0 (optimally 0.5) X 10(5). Near these cell numbers, the response depended closely on the number of responding cells. On plates with flat-bottomed wells, stimulating cells had a dose-dependent effect on the response, whereas on plates with round-bottomed wells, increasing the stimulating cell dose did not consistently strengthen the response. Both plate types proved suitable for MLC experiments; plates with round-bottomed wells have the obvious advantage of requiring smaller cell numbers. 3H-thymidine (spec, act 2000 mCi/mmol) self-suppressed its incorporation, which increased only slightly or even decreased if labelling time exceeded 12-18 hours. Relative responses remained virtually unaltered, however, with 3H-concentrations of 0.5 and 2.0 micronCi/ml and with labelling times of 8 and 24 hours.
NASA Astrophysics Data System (ADS)
Ma, Yanbao; Zhong, Xiaolin
2003-08-01
In this paper, we continue to study the mechanisms of the receptivity of the supersonic boundary layer to free-stream disturbances by using both direct numerical simulation and linear stability theory. Specifically, the receptivity of a Mach 4.5 flow over a flat plate to free-stream fast acoustic waves is studied. The receptivity to free-stream slow acoustic waves, entropy waves and vorticity waves will be studied in the future. The oblique shock wave induced by the boundary-layer displacement plays an important role in the receptivity because the free-stream disturbance waves first pass through the shock before entering the boundary layer. A high-order shock-fitting scheme is used in the numerical simulations in order to account for the effects of interactions between free-stream disturbance waves and the oblique shock wave. The results show that the receptivity of the flat-plate boundary layer to free-stream fast acoustic waves leads to the excitation of both Mack modes and a family of stable modes, i.e. mode I, mode II, etc. It is found that the forcing fast acoustic waves do not interact directly with the unstable Mack modes. Instead, the stable mode I waves play an important role in the receptivity process because they interact with both the forcing acoustic waves and the unstable Mack-mode waves. Through the interactions, the stable mode I waves transfer wave energy from the forcing fast acoustic waves to the second Mack-mode waves. The effects of incident wave angles, forcing wave frequencies, and wall temperature perturbation conditions on the receptivity are studied. The results show that the receptivity mechanisms of the second mode are very different from those of modes I and II, which leads to very different receptivity properties of these discrete wave modes to free-stream fast acoustic waves with different incident wave angles, frequencies, and different wall boundary conditions. The maximum receptivities of the second mode, mode I and mode II to
Leading-edge vortex burst on a low-aspect-ratio rotating flat plate
NASA Astrophysics Data System (ADS)
Medina, Albert; Jones, Anya R.
2016-08-01
This study experimentally investigates the phenomenon of leading-edge-vortex burst on rotating flat plate wings. An aspect-ratio-2 wing was driven in pure rotation at a Reynolds number of Re=2500 . Of primary interest is the evolution of the leading-edge vortex along the wing span over a single-revolution wing stroke. Direct force measurements of the lift produced by the wing revealed a single global lift maximum relatively early in the wing stroke. Stereoscopic particle image velocimetry was applied to several chordwise planes to quantify the structure and strength of the leading-edge vortex and its effect on lift production. This analysis revealed opposite-sign vorticity entrainment into the core of the leading-edge vortex, originating from a layer of secondary vorticity along the wing surface. Coincident with the lift peak, there emerged both a concentration of opposite vorticity in the leading-edge-vortex core, as well as axial flow stagnation within the leading-edge-vortex core. Planar control volume analysis was performed at the midspan to quantify the contributions of vorticity transport mechanisms to the leading-edge-vortex circulation. The rate of circulation annihilation by opposite-signed vorticity entrainment was found to be minimal during peak lift production, where convection balanced the flux of vorticity resulting in stagnation and eventually reversal of axial flow. Finally, vortex burst was found to be correlated with swirl number, where bursting occurs at a swirl threshold of Sw<0.6 .
Flat-plate solar array project. Volume 4: High-efficiency solar cells
NASA Technical Reports Server (NTRS)
Leipold, M.; Cheng, L.; Daud, T.; Mokashi, A.; Burger, D.; Christensen, E. (Editor); Murry, J. (Editor); Bengelsdorf, I. (Editor)
1986-01-01
The High Efficiency Solar Cell Task was assigned the objective of understanding and developing high efficiency solar cell devices that would meet the cost and performance goals of the Flat Plate Solar Array (FSA) Project. The need for research dealing with high efficiency devices was considered important because of the role efficiency plays in reducing price per watt of generated energy. The R&D efforts conducted during the 1982 to 1986 period are summarized to provide understanding and control of energy conversion losses associated with crystalline silicon solar cells. New levels of conversion efficiency were demonstrated. Major contributions were made both to the understanding and reduction of bulk and surface losses in solar cells. For example, oxides, nitrides, and polysilicon were all shown to be potentially useful surface passivants. Improvements in measurement techniques were made and Auger coefficients and spectral absorption data were obtained for unique types of silicon sheets. New modelling software was developed including a program to optimize a device design based on input characteristics of a cell.
Experimental investigation of a large aspect ratio flat plate encountering a steam-wise gust
NASA Astrophysics Data System (ADS)
Mulleners, Karen; Mancini, Peter; Jones, Anya
2015-11-01
While humans are capable of mimicking, and even outperform, the kinematic capabilities of natural flyers, birds and insects are still way ahead of us when it comes to anticipating and dealing with turbulent and gusty flow conditions. To tailor and improve flight control capabilities of low Reynolds number flyers in real weather, we need to bridge this gap of knowledge. As a first step, we experimentally studied the aerodynamic influence of a simplified stream-wise gust on a large aspect ratio flat plate. The experiments were conduction in the 7 × 1 . 5 × 1 m3 towing tank at UMD which was equipped with a 4-axis computer-controlled motion system. The effect of a stream-wise gust was simulated by accelerating or decelerating the wing to a new constant velocity after an initial constant surge. A high-speed camera and light sheet optics were attached to the tow carriage allowing for time-resolved particle image velocimetry along the entire motion in addition to direct force measurements. A proper orthogonal decomposition of the flow field was carried out to study the time scales related to changes induced by the sudden acceleration or deceleration in addition to analyzing the size, position and trajectory of prominent vortices and associated forces during the gust encounter.
Design optimization of sinusoidal glass honeycomb for flat plate solar collectors
NASA Technical Reports Server (NTRS)
Mcmurrin, J. C.; Buchberg, H.
1980-01-01
The design of honeycomb made of sinusoidally corrugated glass strips was optimized for use in water-cooled, single-glazed flat plate solar collectors with non-selective black absorbers. Cell diameter (d), cell height (L), and pitch/diameter ratio (P/d) maximizing solar collector performance and cost effectiveness for given cell wall thickness (t sub w) and optical properties of glass were determined from radiative and convective honeycomb characteristics and collector performance all calculated with experimentally validated algorithms. Relative lifetime values were estimated from present materials costs and postulated production methods for corrugated glass honeycomb cover assemblies. A honeycomb with P/d = 1.05, d = 17.4 mm, L = 146 mm and t sub w = 0.15 mm would provide near-optimal performance over the range delta T sub C greater than or equal to 0 C and less than or equal to 80 C and be superior in performance and cost effectiveness to a non-honeycomb collector with a 0.92/0.12 selective black absorber.
NASA Astrophysics Data System (ADS)
Dhir, Gaurav; Suman, Sawan
2015-11-01
Experimental evidence shows that aircrafts operating under heavy rainfall conditions face deterioration of lift and increase in drag. This scenario can be a critical design challenge especially for slow moving vehicles such as airships. Effective roughening of airfoil surface caused by an uneven water film, loss of flow momentum and the loss of vehicle momentum due to its collision with the raindrops are the primary reasons causing the drag to increase. Our work focuses primarily on the numerical quantification of boundary layer momentum loss caused due to raindrops. The collision of raindrops with a solid surface leads to formation of an ejecta fog of splashed back droplets with their sizes being of the order of micrometers and their acceleration leads to boundary layer momentum loss. We model the airflow within a flat plate boundary layer using a Lagrangian-Eulerian approach with the raindrops being considered as non-deformable, non-spinning and non-interacting droplets. We employ an inter-phase coupling term to account for the interaction between the boundary layer flow and the droplets. Our presentation will focus on several comparisons (velocity field, lift and drag at various angles of attack) with the results of the standard (rain-free) Prandtl boundary layer flow. Indian Institute of Technology, Delhi.
Unsteady forcing on a flat-plate wing in large transverse gusts
NASA Astrophysics Data System (ADS)
Perrotta, Gino; Jones, Anya R.
2017-08-01
The effects of large-amplitude transverse gusts on lift and drag of a flat-plate wing were studied experimentally. Forces were measured and particle imaging velocimetry recorded as the wing was towed through a transverse gust with peak velocity of equal order of magnitude to the steady towing velocity. These results were compared across variations in gust ratio and wing pitch angle. Several cases with similar peak quasi-steady conditions but dissimilar initial conditions were shown to have similar peak measured forces, indicating that those forces are not dominated by the initial conditions. The measured forces were compared to predictions by several existing models, each of which was designed for use in small-amplitude gust encounters. The peak forces during the gust were found to be close to the semi-empirical quasi-steady predictions, but the transient forces after the gust peak were not. A semi-empirical unsteady model is proposed as an adaptation of the existing models. This model incorporates the unsteady characteristics of gust recovery, but it under-predicts the magnitude of the forces caused by the gust encounter.
Development and testing of high concentration flat-plate Fresnel lenses
NASA Astrophysics Data System (ADS)
Shvarts, M. Z.; Soluyanov, A. A.
2009-08-01
In the work, stages of designing, optimizing, manufacturing and testing the circular flat-plate Fresnel lenses (FLs) for photovoltaic modules with multi-junction solar cells (SCs) are presented. A mathematical model based on ray tracing has been developed for optimizing lenses design parameters and calculating their optical-power characteristics (OPCs). In searching the optimum combination of the lens aperture, its focal distance and refracting profile parameters, the optimization criterion was the maximum of the average sunlight concentration at high optical efficiency in the focal spot of minimum size. Analysis of OPCs of circular Fresnel lenses with conical (the generatrix of surface is a straight line) and curvilinear (the generatrix of surface is a curved line) refracting surfaces has been carried out. Fresnel lens specimens were fabricated and a control of their profile parameters has been done. Experimental lens OPCs have been obtained with use of newly developed optical test bench. A degree of the effect of the light flux and Fresnel lens geometrical imperfections on validity of the experimental data interpretation has been determined. To establish the lens optical efficiency values at standard irradiance conditions, the correction of the calculation model was done. Also, the effect of temperature on the lens optical efficiency is studied.
Production of Fatty Acids and Protein by Nannochloropsis in Flat-Plate Photobioreactors
Wijffels, René H.; Bolla, Sylvie; Kiron, Viswanath
2017-01-01
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreactors. Eighteen cultivations were performed at two nutrient concentrations. The fatty acid, protein content and calorific values were analyzed after 8, 12 and 16 days. Neutral lipids were separated and the changes in fatty acids in triglycerides (TAGs) during nutrient depletion were recorded. The maximum cell density reached 4.7 g∙L-1 and the maximum productivity was 0.51 g∙L-1∙d-1. During nutrient-replete conditions, eicosapentaneoic acid (EPA) and total protein concentrations measured 4.2–4.9% and 50–55% of the dry mass, respectively. Nutrient starvation induced the accumulation of fatty acids up to 28.3% of the cell dry weight, largely due to the incorporation of C16:0 and C16:1n-7 fatty acyl chains into neutral lipids. During nutrient starvation the total EPA content did not detectibly change, but up to 37% was transferred from polar membrane lipids to the neutral lipid fraction. PMID:28103296
Patrick, W.P.
1987-03-01
The separation and reattachment of a large-scale, two-dimensional turbulent boundary layer at low subsonic speed on a flat plate has been studied experimentally. The separation bubble was 55 cm long and had a maximum bubble thickness, measured to the height of the mean dividing streamline, of 17 cm, which was twice the thickness of the inlet boundary layer. A combination of laser velocimetry, hot-wire anemometry, pneumatic probing techniques, and flow visualization were used as diagnostics. Principal findings were that an outer inviscid rotational flow was defined which essentially convected over the blockage associated with the inner, viscously dominated bubble recirculation region. A strong backflow region in which the flow moved upstream 100 percent of the time was measured near the test surface over the central 35 percent of the bubble. A laminar backflow boundary layer having pseudo-turbulent characteristics including a log-linear velocity profile was generated under the highly turbulent backflow. Velocity profile shapes in the reversed flow region matched a previously developed universal backflow profile at the upstream edge of the separation region but not in the steady backflow region downstream. A smoke flow visualization movie and hot-film measurements revealed low frequency nonperiodic flapping at reattachment. However, forward flow fraction data at reattachment and mean velocity profiles in the redeveloping boundary layer downstream of reattachment correlated with backward-facing step data when the axial dimension was scaled by the distance from the maximum bubble thickness to reattachment.
Flat-plate solar array project. Volume 8: Project analysis and integration
NASA Technical Reports Server (NTRS)
Mcguire, P.; Henry, P.
1986-01-01
Project Analysis and Integration (PA&I) performed planning and integration activities to support management of the various Flat-Plate Solar Array (FSA) Project R&D activities. Technical and economic goals were established by PA&I for each R&D task within the project to coordinate the thrust toward the National Photovoltaic Program goals. A sophisticated computer modeling capability was developed to assess technical progress toward meeting the economic goals. These models included a manufacturing facility simulation, a photovoltaic power station simulation and a decision aid model incorporating uncertainty. This family of analysis tools was used to track the progress of the technology and to explore the effects of alternative technical paths. Numerous studies conducted by PA&I signaled the achievement of milestones or were the foundation of major FSA project and national program decisions. The most important PA&I activities during the project history are summarized. The PA&I planning function is discussed and how it relates to project direction and important analytical models developed by PA&I for its analytical and assessment activities are reviewed.
Visualization of the contact line during the water exit of flat plates
NASA Astrophysics Data System (ADS)
Tassin, A.; Breton, T.; Forest, B.; Ohana, J.; Chalony, S.; Le Roux, D.; Tancray, A.
2017-08-01
We investigate experimentally the time evolution of the wetted surface during the lifting of a body initially floating at the water surface. This phenomenon is referred to as the water exit problem. The water exit experiments were conducted with transparent (PMMA) mock-ups of two different shapes: a circular disc and a square flat plate. Two different lighting systems were used to diffuse light in the mock-up material: a central high-power LED light normal to the surface and an edge-lighting system featuring an array of LED lights. These setups make it possible to illuminate the contact line, which delimits the surface of contact between the mock-up and the water. The characteristic size of the mock-ups is about 20 cm and the acceleration of the mock-up oscillates between 0 and 25 m/s^2. We show that the central light setup gives satisfactory results for the circular disc and that the edge lighting technique makes it possible to follow a contact line with a time-evolving complex shape (strong changes of convexity) up to 1000 fps. The observations presented in the paper support the possibility of extending this promising technique to more general three-dimensional bodies with arbitrary motion (e.g., including pitch motion).
NASA Astrophysics Data System (ADS)
Ma, Yanbao; Zhong, Xiaolin
2003-08-01
This paper is the first part of a two-part study on the mechanisms of the receptivity to disturbances of a Mach 4.5 flow over a flat plate by using both direct numerical simulations (DNS) and linear stability theory (LST). The main objective of the current paper is to study the linear stability characteristics of the boundary-layer wave modes and their mutual resonant interactions. The numerical solutions of both steady base flow and unsteady flow induced by forcing disturbances are obtained by using a fifth-order shock-fitting method. Meanwhile, the LST results are used to study the supersonic boundary-layer stability characteristics relevant to the receptivity study. It is found that, in addition to the conventional first and second modes, there exist a family of stable wave modes in the supersonic boundary layer. These modes play a very important role in the receptivity process of excitation of the unstable Mack modes, especially the second mode. These stable modes are termed mode I, mode II, etc., in this paper. Though mode I and mode II waves are linearly stable, they can have resonant (synchronization) interactions with both acoustic waves and the Mack-mode waves. Therefore, the stable wave modes such as mode I and mode II are critical in transferring wave energy between the acoustic waves and the unstable second mode. The effects of frequencies and wall boundary conditions for the temperature perturbations on the boundary-layer stability and receptivity are also studied.
Linear stability analysis in compressible, flat-plate boundary-layers
NASA Astrophysics Data System (ADS)
Özgen, Serkan; Kırcalı, Senem Atalayer
2008-01-01
The stability problem of two-dimensional compressible flat-plate boundary layers is handled using the linear stability theory. The stability equations obtained from three-dimensional compressible Navier-Stokes equations are solved simultaneously with two-dimensional mean flow equations, using an efficient shoot-search technique for adiabatic wall condition. In the analysis, a wide range of Mach numbers extending well into the hypersonic range are considered for the mean flow, whereas both two- and three-dimensional disturbances are taken into account for the perturbation flow. All fluid properties, including the Prandtl number, are taken as temperature-dependent. The results of the analysis ascertain the presence of the second mode of instability (Mack mode), in addition to the first mode related to the Tollmien-Schlichting mode present in incompressible flows. The effect of reference temperature on stability characteristics is also studied. The results of the analysis reveal that the stability characteristics remain almost unchanged for the most unstable wave direction for Mach numbers above 4.0. The obtained results are compared with existing numerical and experimental data in the literature, yielding encouraging agreement both qualitatively and quantitatively.
Flow Phenomena in the Very Near Wake of a Flat Plate with a Circular Trailing Edge
NASA Technical Reports Server (NTRS)
Rai, Man Mohan
2014-01-01
The very near wake of a flat plate with a circular trailing edge, exhibiting pronounced shedding of wake vortices, is investigated with data from a direct numerical simulation. The separating boundary layers are turbulent and statistically identical thus resulting in a wake that is symmetric in the mean. The focus here is on the instability of the detached shear layers, the evolution of rib-vortex induced localized regions of reverse flow that detach from the main body of reverse flow in the trailing edge region and convect downstream, and phaseaveraged velocity statistics in the very near wake. The detached shear layers are found to exhibit unstable behavior intermittently, including the development of shear layer vortices as in earlier cylinder flow investigations with laminar separating boundary layers. Only a small fraction of the separated turbulent boundary layers undergo this instability, and form the initial shed vortices. Pressure spectra within the shear layers show a broadband peak at a multiple of shedding frequency. Phase-averaged intensity and shear stress distributions of the randomly fluctuating component of velocity are compared with those obtained in the near wake. The distributions of the production terms in the transport equations for the turbulent stresses are also provided.
Flowfield measurements in a separated and reattached flat plate turbulent boundary layer
NASA Technical Reports Server (NTRS)
Patrick, William P.
1987-01-01
The separation and reattachment of a large-scale, two-dimensional turbulent boundary layer at low subsonic speed on a flat plate has been studied experimentally. The separation bubble was 55 cm long and had a maximum bubble thickness, measured to the height of the mean dividing streamline, of 17 cm, which was twice the thickness of the inlet boundary layer. A combination of laser velocimetry, hot-wire anemometry, pneumatic probing techniques, and flow visualization were used as diagnostics. Principal findings were that an outer inviscid rotational flow was defined which essentially convected over the blockage associated with the inner, viscously dominated bubble recirculation region. A strong backflow region in which the flow moved upstream 100 percent of the time was measured near the test surface over the central 35 percent of the bubble. A laminar backflow boundary layer having pseudo-turbulent characteristics including a log-linear velocity profile was generated under the highly turbulent backflow. Velocity profile shapes in the reversed flow region matched a previously developed universal backflow profile at the upstream edge of the separation region but not in the steady backflow region downstream. A smoke flow visualization movie and hot-film measurements revealed low frequency nonperiodic flapping at reattachment. However, forward flow fraction data at reattachment and mean velocity profiles in the redeveloping boundary layer downstream of reattachment correlated with backward-facing step data when the axial dimension was scaled by the distance from the maximum bubble thickness to reattachment.
Hot press with flat plate heaters and its application to the fabrication of large varistor slugs
Snow, G.S.; Cooper, R.A.
1980-05-01
A hot press was designed and constructed for fabricating large ZnO varistor slugs. The electrical properties of ZnO varistors containing CoO, PbO, and Bi/sub 2/O/sub 3/ are very dependent on processing temperature. To fabricate varistors with the desired field (E = 42.5 +- 1.5 kV/cm at 5 A/cm/sup 2/), it was necessary to maintain temperature uniformity within +- 3.5/sup 0/C throughout the slug and from run to run. The slugs were fabricated in the form of disks approx. = 75 mm in diameter with a final thickness of approx. = 14 mm. Ceramics have been hot pressed previously using apparatus in which the heat source was in the form of a cylinder surrounding, and coaxial to, the slug. Unless the heat source is long compared with its diameter, such a heating method results in poor temperature uniformity, which is aggravated by poor thermal coupling with the heat source and by large heat losses through the pushrods. In the design described herein, these problems are avoided by using flat plate heaters above and below the slug.
Lipid accumulation and growth of Chlorella zofingiensis in flat plate photobioreactors outdoors.
Feng, Pingzhong; Deng, Zhongyang; Hu, Zhengyu; Fan, Lu
2011-11-01
Culturing microalgae using natural sunlight is an effective way to reduce the cost of microalgae-based biodiesel production. In order to evaluate the feasibility of culturing Chlorella zofingiensis outdoors for biodiesel production, effects of nitrogen limitation and initial cell concentration on growth and lipid accumulation of this alga were investigated in 60 L flat plate photobioreactors outdoors. The highest μmax and biomass productivity obtained was 0.994 day(-1) and 58.4 mg L(-1)day(-1), respectively. The lipid content was much higher (54.5% of dry weight) under nitrogen limiting condition than under nitrogen sufficient condition (27.3%). With the increasing initial cell concentrations, the lipid contents declined, while lipid concentrations and productivities increased. The highest lipid content, lipid concentration, and lipid productivity obtained was 54.5%, 536 mg L(-1) and 22.3 mg L(-1)day(-1), respectively. This study demonstrated that it was possible to culture C. zofingiensis under outdoor conditions for producing biodiesel feedstock.
Production of Fatty Acids and Protein by Nannochloropsis in Flat-Plate Photobioreactors.
Hulatt, Chris J; Wijffels, René H; Bolla, Sylvie; Kiron, Viswanath
2017-01-01
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreactors. Eighteen cultivations were performed at two nutrient concentrations. The fatty acid, protein content and calorific values were analyzed after 8, 12 and 16 days. Neutral lipids were separated and the changes in fatty acids in triglycerides (TAGs) during nutrient depletion were recorded. The maximum cell density reached 4.7 g∙L-1 and the maximum productivity was 0.51 g∙L-1∙d-1. During nutrient-replete conditions, eicosapentaneoic acid (EPA) and total protein concentrations measured 4.2-4.9% and 50-55% of the dry mass, respectively. Nutrient starvation induced the accumulation of fatty acids up to 28.3% of the cell dry weight, largely due to the incorporation of C16:0 and C16:1n-7 fatty acyl chains into neutral lipids. During nutrient starvation the total EPA content did not detectibly change, but up to 37% was transferred from polar membrane lipids to the neutral lipid fraction.
Numerical simulation of laminar-turbulent transition in a spatially-developing flat plate wake
NASA Technical Reports Server (NTRS)
Dratler, D. I.; Fasel, H. F.
1993-01-01
Laminar-turbulent transition of an incompressible flat-plate wake is investigated by direct numerical integration of the Navier-Stokes equations. For the numerical integration, a combination of finite-difference and spectral methods along with an ADI/Crank-Nicolson/Adams-Bashforth time integration scheme is employed. Subject to 2D forcing, the wake exhibited a rapidly-growing fundamental disturbance that quickly saturated. This saturation was due partly to the stabilizing effect of the mean flow distortion. Downstream of the saturation point, disturbance energy was concentrated in the fundamental disturbance, the second harmonic, and the mean flow distortion component. At large amplitude levels, a Karman vortex street formed. Variations in the 2D forcing level did not alter the qualitative behavior of the disturbances. Simulations of 3D breakdown indicates that the presence of large-amplitude, 2D disturbances tends to initially suppress small-amplitude 3D disturbance growth. Following this initial suppression, a resumption of 3D growth is observed that may have been due to a secondary instability mechanism. For high levels of 3D disturbance energy, lambda-shaped vortical structures formed between adjacent Karman vortices.
Measuring spectral diffuse solar irradiance with non-cosine flat-plate diffusers
Casiniere, A.A. de; Cabot, T.; Benmansour, S.
1995-03-01
In spectral diffuse solar irradiance measurements, when diffusing devices used are neither perfectly Lambertian nor have an ideal cosine response, significant errors may spoil the collected data. An optical method permits the determination of a spectral correction factor (SCF) which fully compensates for the diffusers` imperfection when the sky radiance is isotropic. A study of the errors introduced when using such a isotropic SCF in anisotropic radiance conditions is presented for two common flat-plate diffusers fitted with a shadow-ring or a tracking disk. The wavelength band explored is 0.29 - 0.90 {mu}m and the clear sky radiance model used is Kittler`s. The relevance of several diffuse irradiance spectra measured on clear sky days with isotropic SCF is analysed by comparison with Brine-Iqbal model spectra and total diffuse measurements. A remarkable coherence is found for small solar zenith angles when using a tracking disk and a diffuser with an isotropic SCF smaller than 1.2. 17 refs., 7 figs., 2 tabs.
Design optimization of sinusoidal glass honeycomb for flat plate solar collectors
NASA Technical Reports Server (NTRS)
Mcmurrin, J. C.; Buchberg, H.
1980-01-01
The design of honeycomb made of sinusoidally corrugated glass strips was optimized for use in water-cooled, single-glazed flat plate solar collectors with non-selective black absorbers. Cell diameter (d), cell height (L), and pitch/diameter ratio (P/d) maximizing solar collector performance and cost effectiveness for given cell wall thickness (t sub w) and optical properties of glass were determined from radiative and convective honeycomb characteristics and collector performance all calculated with experimentally validated algorithms. Relative lifetime values were estimated from present materials costs and postulated production methods for corrugated glass honeycomb cover assemblies. A honeycomb with P/d = 1.05, d = 17.4 mm, L = 146 mm and t sub w = 0.15 mm would provide near-optimal performance over the range delta T sub C greater than or equal to 0 C and less than or equal to 80 C and be superior in performance and cost effectiveness to a non-honeycomb collector with a 0.92/0.12 selective black absorber.
A numerical study of air layer drag reduction phenomenon on a flat plate
NASA Astrophysics Data System (ADS)
Kim, Dokyun; Moin, Parviz
2009-11-01
The objective of the present study is to predict and understand the air layer drag reduction (ALDR) phenomenon. Recent experiments (Elbing et al. JFM 2008) have shown large net drag reductions if air is injected beyond a critical rate at the wall. The stability analysis and numerical simulations are performed to investigate mechanisms of ALDR on a flat plate using the same geometry as in the experiment. The linear stability of air-liquid interface is investigated by solving the Orr-Sommerfeld equations, and numerical simulations of two-phase flow have been performed to describe the evolution of air-water interface. The stability analysis shows that the air flow rates, Reynolds number, Weber number, and Froude number are important parameters determining the stability of the air layer. In laminar boundary layer, it is observed from the numerical simulations that the Froude number is the key to the stability of the air layer. The presentation will include a new and very efficient numerical method for two-phase flow calculations used in this study.
Copper Plating Method on Flat Surface for High Frequency Signal Transfer
NASA Astrophysics Data System (ADS)
Hontake, Koichi; Wakizaka, Yasuhiro; Furuya, Akihiko; Uchida, Daisuke; Kuribayashi, Koichiro; Noda, Tomoko; Sugimura, Masahiko; Chikuma, Mitsuyasu; Toki, Sotaro; Sasaki, Jun; Hagiwara, Muneaki; Nakada, Akira; Kubota, Hiroshi
2005-09-01
A copper plating process for printed wiring boards operating in the GHz frequency range has been developed that improves the adhesion strength between the copper interconnects and the resin substrate by using an imidazole compound to form coordinate bonds. The coordinate bonds are prepared by impregnating the resin substrate with an aqueous solution of amino-group-containing imidazole (AI). The adhesion strength is measured by a tensile test with various concentrations of AI solution and different treatment times of impregnation. As a result, the highest adhesion strength of 4.2-5.1 N\\cdotcm-1 can be obtained on the entire surface of a 340× 340 mm2 substrate, where the flatness is down to 58.7 nm. This result is due to the optimization of the impregnating condition for AI and of the removal condition for weak boundary layers. The signal transmission characteristics of the interconnects on the substrates fabricated by this processes are compared with the conventional process by S21 parameter extraction in the GHz frequency range. The transmission characteristics of this process are markedly improved compared with those of conventional processes.
Investigation of the flow field inside flat-plate collector tube using PIV technique
Sookdeo, Steven; Siddiqui, Kamran
2010-06-15
The thermofluid process inside the tube of flat-plate collectors is complex because the non-uniform heating of the tube results in the formation of stably and unstably stratified layers of fluid that interact with each other. The measurement and investigation of the flow behaviour inside the collector tube is very challenging. We report on a novel application of the particle image velocimetry (PIV) technique to remotely measure the velocity field inside the collector tube. The two-dimensional velocity fields were measured in the midplane of a collector tube for the Reynolds number range of 150-900 at unheated and four different heating conditions. We have presented and discussed in detail the technique implementation and the associated challenges. The results have shown that the collector heating significantly alters the structure and magnitude of the mean velocity field and influences the heat transfer to the fluid. It is observed that the collector heating causes a significant asymmetry in the mean velocity profiles over the given range of Reynolds numbers and heating conditions. (author)
Modeling and experimental verification of a flat-plate solar photoreactor
Rossetti, G.H. |; Albizzati, E.D.; Alfano, O.M.
1998-09-01
The utilization of the ultraviolet (UV) portion of the solar spectrum to drive the chemical destruction of organic pollutants in contaminated air and wastewaters has gained an increasing interest in the last two decades. A nonconcentrating, flat-plate solar photoreactor has been modeled and experimentally verified. The mathematical model considers that the reactor glass window receives direct and diffuse (isotropic) solar radiation. The model was solved numerically and predictions were compared with photodecomposition rate data, employing the uranyl oxalate actinometer. The reaction was conducted in an isothermal, perfectly mixed reactor placed inside a batch recycling system. The experimental values were compared with theoretical predictions and good agreement was obtained, the maximum deviation being 12%. The effect of the actinometer concentration and of the solar zenith angles (for horizontal and tilted reactors) on the actinometer decomposition rate was investigated. Results indicated that the uranyl oxalate reaction rate increases when (1) the initial actinometer concentration increases at almost constant solar zenith angle and (2) the zenith angle decreases at the same initial actinometer concentration.
Jet-induced ground effects on a parametric flat-plate model in hover
NASA Technical Reports Server (NTRS)
Wardwell, Douglas A.; Hange, Craig E.; Kuhn, Richard E.; Stewart, Vearl R.
1993-01-01
The jet-induced forces generated on short takeoff and vertical landing (STOVL) aircraft when in close proximity to the ground can have a significant effect on aircraft performance. Therefore, accurate predictions of these aerodynamic characteristics are highly desirable. Empirical procedures for estimating jet-induced forces during the vertical/short takeoff and landing (V/STOL) portions of the flight envelope are currently limited in accuracy. The jet-induced force data presented significantly add to the current STOVL configurations data base. Further development of empirical prediction methods for jet-induced forces, to provide more configuration diversity and improved overall accuracy, depends on the viability of this STOVL data base. The data base may also be used to validate computational fluid dynamics (CFD) analysis codes. The hover data obtained at the NASA Ames Jet Calibration and Hover Test (JCAHT) facility for a parametric flat-plate model is presented. The model tested was designed to allow variations in the planform aspect ratio, number of jets, nozzle shape, and jet location. There were 31 different planform/nozzle configurations tested. Each configuration had numerous pressure taps installed to measure the pressures on the undersurface of the model. All pressure data along with the balance jet-induced lift and pitching-moment increments are tabulated. For selected runs, pressure data are presented in the form of contour plots that show lines of constant pressure coefficient on the model undersurface. Nozzle-thrust calibrations and jet flow-pressure survey information are also provided.
Nonprincipal plane scattering of flat plates and pattern control of horn antennas
NASA Technical Reports Server (NTRS)
Balanis, Constantine A.; Polka, Lesley A.; Liu, Kefeng
1989-01-01
Using the geometrical theory of diffraction, the traditional method of high frequency scattering analysis, the prediction of the radar cross section of a perfectly conducting, flat, rectangular plate is limited to principal planes. Part A of this report predicts the radar cross section in nonprincipal planes using the method of equivalent currents. This technique is based on an asymptotic end-point reduction of the surface radiation integrals for an infinite wedge and enables nonprincipal plane prediction. The predicted radar cross sections for both horizontal and vertical polarizations are compared to moment method results and experimental data from Arizona State University's anechoic chamber. In part B, a variational calculus approach to the pattern control of the horn antenna is outlined. The approach starts with the optimization of the aperture field distribution so that the control of the radiation pattern in a range of directions can be realized. A control functional is thus formulated. Next, a spectral analysis method is introduced to solve for the eigenfunctions from the extremal condition of the formulated functional. Solutions to the optimized aperture field distribution are then obtained.
Approximate Solution of a Laminar Flow over a Flat Plate with Suction and Pressure Gradient.
1984-01-01
8217nature ywpartment Chair) Date Department of Mechanical Enoineerino Accesslon Por U nIn C, LA ICC -’ .", J, f ! i C I o D irnt rbut ion / A*.-.1 lilt...reduced to a no suction and no pressure gradient condi t ion . Blasius Thesis Linear Prandtl Pohlhausen S(x) 5.8 4.318 3.464 4.64 5.835 S 1 1.729 1.727...2, but he was able to overcome that limitation with another function. 4.2 Suction and Pressure Gradient at Seoaration From Chapter 3 the velocity
Skin friction and heat transfer correlations for high-speed low-density flow past a flat plate
NASA Technical Reports Server (NTRS)
Woronowicz, Michael S.; Baganoff, Donald
1991-01-01
The independent and dependent variables associated with drag and heat transfer to a flat plate at zero incidence in high-speed, rarefied flow are analyzed anew to reflect the importance of kinetic effects occurring near the plate surface on energy and momentum transfer, rather than following arguments normally used to describe continuum, higher density flowfields. A new parameter, the wall Knudsen number Knx,w, based on an estimate of the mean free path length of molecules having just interacted with the surface of the plate, is introduced and used to correlate published drag and heat transfer data. The new parameter is shown to provide better correlation than either the viscous interaction parameter X or the widely-used slip parameter Voo for drag and heat transfer data over a wide range of Mach numbers, Reynolds numbers, and plate-to-freestream stagnation temperature ratios.
NASA Astrophysics Data System (ADS)
Helal, M. M.; Abd-El-Malek, M. B.
2005-01-01
The group theoretic method is applied for solving problem of the flow of an elastico-viscous liquid past an infinite flat plate in the presence of a magnetic field normal to the plate. The application of one-parameter transformation group reduces the number of independent variables, by one, and consequently the system of governing partial differential equations with boundary conditions reduces to a system of ordinary differential equations with appropriate corresponding conditions. Numerical solution of the velocity field and heat transfer have been obtained. The effect of the magnetic parameter M on velocity field, shear stress, temperature fields and heat transfer has been discussed.
NASA Astrophysics Data System (ADS)
Reshetova, A. I.; Poplavskaya, T. V.
2016-10-01
The problem of disturbances evolution in a hypersonic viscous shock layer on a flat plate is considered. Numerical simulation was performed by solving 2D Navier-Stokes equations using the ANSYS Fluent software package within the model of thermally perfect gas. The change of vibrational energy was simulated by the Landau-Teller equation, in which the finite time of vibrational relaxation of CO2 molecules was taken into account. The quantitative data on the effect of vibrational relaxation of CO2 molecules on the evolution of acoustic disturbances in the shock layer on a plate is obtained.
Thermal analysis of a flat-plate boiling collector having sub-cooled inlet and saturated exit states
El-Assy, A.Y.; Clark, J.A. )
1989-01-01
The analysis of the thermal performance of a boiling flat-plate solar collector is presented. A generalized heat removal factor and a new formulation for the overall thermal loss coefficient are developed. It is demonstrated that the conventional heat removal factor for non-boiling collectors is a limiting case of a more generalized result. The new formulation for the overall thermal loss coefficient is shown to be a function of the fractional non-boiling length of the flow channel. The influence of the inlet sub-cooling is evaluated and the operating limits of solar flat-plate collectors are determined. A comparison is made between the thermal model for boiling collectors having sub-cooled inlet states and experimental results. Favorable agreement is obtained.
Experimental investigation of effect of jet decay rate on jet-induced pressures on a flat plate
NASA Technical Reports Server (NTRS)
Kuhlman, J. M.; Ousterhout, D. S.; Warcup, R. W.
1978-01-01
An experimental study of the interaction between a lift jet and an aircraft wing for a jet VTOL aircraft was performed for the simplified model of an unheated, subsonic, circular jet exiting at right angles to a flat plate into a uniform subsonic crosswind. The effects of jet dynamic pressure decay rate upon the jet location and jet induced pressure distribution on the plate were studied over a range of jet to crossflow velocity ratios of 2.2 or = R or = 10. Jet decay rate was varied through use of cylindrical centerbodies with flat or hemispherical tips submerged in the jet nozzle at various depths below the jet exit plane. Quicker jet dynamic pressure decay, caused by the presence of a centerbody, resulted in reductions in the jet induced lift loss by as much as 45 percent relative to values for jets with no centerbody. These reductions in lift loss were observed at the larger values of crossflow velocity.
Optimized Feedback Control of Vortex Shedding on an Inclined Flat Plate
NASA Astrophysics Data System (ADS)
Joe, Won Tae
This thesis examines flow control and the potentially favorable effects of feedback, associated with unsteady actuation in separated flows over airfoils. The objective of the flow control is to enhance lift at post-stall angles of attack by changing the dynamics of the wake vortices. We present results from a numerical study of unsteady actuation on a two-dimensional flat plate at post-stall angles of attack at Reynolds number (Re) of 300 and 3000. At Re=300, the control waveform is optimized and a feedback strategy is developed to optimize the phase of the control relative to the lift with either a sinusoidal or the optimized waveform, resulting in a high-lift limit cycle of vortex shedding. Also at Re=3000, we show that certain frequencies and actuator waveforms lead to stable (high-lift) limit cycles, in which the flow is phase locked to the actuation. First, a two-dimensional flat plate model at a high angle of attack at a Re of 300 is considered. We design the feedback to slightly adjust the frequency and/or phase of actuation to lock it to a particular phase of the lift, thus achieving a phase-locked flow with the maximal period-averaged lift over every cycle of acutation. With the sinusoidal forcing and feedback, we show that it is possible to optimize the phase of the control relative to the lift in order to achieve the highest possible period-averaged lift in a consistent fashion. However, continuous sinusoidal forcing could be adding circulation when it is unnecessary, or undesirable. Thus we employ an adjoint-based optimization in order to find the waveform (time history of the jet velocty) that maximizes the lift for a given actuation amplitude. The adjoint of the linearized perturbed equations is solved backwards in time to obtain the gradient of the lift to changes in actuation (the jet velocity), and this information is used to iteratively improve the controls. Optimal control provides a periodic control waveform, resulting in high lift shedding
Large-Eddy Simulation of the Flat-plate Turbulent Boundary Layer at High Reynolds numbers
NASA Astrophysics Data System (ADS)
Inoue, Michio
The near-wall, subgrid-scale (SGS) model [Chung and Pullin, "Large-eddy simulation and wall-modeling of turbulent channel flow'', J. Fluid Mech. 631, 281--309 (2009)] is used to perform large-eddy simulations (LES) of the incompressible developing, smooth-wall, flat-plate turbulent boundary layer. In this model, the stretched-vortex, SGS closure is utilized in conjunction with a tailored, near-wall model designed to incorporate anisotropic vorticity scales in the presence of the wall. The composite SGS-wall model is presently incorporated into a computer code suitable for the LES of developing flat-plate boundary layers. This is then used to study several aspects of zero- and adverse-pressure gradient turbulent boundary layers. First, LES of the zero-pressure gradient turbulent boundary layer are performed at Reynolds numbers Retheta based on the free-stream velocity and the momentum thickness in the range Retheta = 103-1012. Results include the inverse skin friction coefficient, 2/Cf , velocity profiles, the shape factor H, the Karman "constant", and the Coles wake factor as functions of Re theta. Comparisons with some direct numerical simulation (DNS) and experiment are made, including turbulent intensity data from atmospheric-layer measurements at Retheta = O (106). At extremely large Retheta , the empirical Coles-Fernholz relation for skin-friction coefficient provides a reasonable representation of the LES predictions. While the present LES methodology cannot of itself probe the structure of the near-wall region, the present results show turbulence intensities that scale on the wall-friction velocity and on the Clauser length scale over almost all of the outer boundary layer. It is argued that the LES is suggestive of the asymptotic, infinite Reynolds-number limit for the smooth-wall turbulent boundary layer and different ways in which this limit can be approached are discussed. The maximum Retheta of the present simulations appears to be limited by machine
Numerical Simulations of Vortex Generator Vanes and Jets on a Flat Plate
NASA Technical Reports Server (NTRS)
Allan, Brian G.; Yao, Chung-Sheng; Lin, John C.
2002-01-01
Numerical simulations of a single low-profile vortex generator vane, which is only a small fraction of the boundary-layer thickness, and a vortex generating jet have been performed for flows over a flat plate. The numerical simulations were computed by solving the steady-state solution to the Reynolds-averaged Navier-Stokes equations. The vortex generating vane results were evaluated by comparing the strength and trajectory of the streamwise vortex to experimental particle image velocimetry measurements. From the numerical simulations of the vane case, it was observed that the Shear-Stress Transport (SST) turbulence model resulted in a better prediction of the streamwise peak vorticity and trajectory when compared to the Spalart-Allmaras (SA) turbulence model. It is shown in this investigation that the estimation of the turbulent eddy viscosity near the vortex core, for both the vane and jet simulations, was higher for the SA model when compared to the SST model. Even though the numerical simulations of the vortex generating vane were able to predict the trajectory of the stream-wise vortex, the initial magnitude and decay of the peak streamwise vorticity were significantly under predicted. A comparison of the positive circulation associated with the streamwise vortex showed that while the numerical simulations produced a more diffused vortex, the vortex strength compared very well to the experimental observations. A grid resolution study for the vortex generating vane was also performed showing that the diffusion of the vortex was not a result of insufficient grid resolution. Comparisons were also made between a fully modeled trapezoidal vane with finite thickness to a simply modeled rectangular thin vane. The comparisons showed that the simply modeled rectangular vane produced a streamwise vortex which had a strength and trajectory very similar to the fully modeled trapezoidal vane.
Field-based evaluations of horizontal flat-plate fish screens
Rose, B.P.; Mesa, M.G.; Barbin-Zydlewski, G.
2008-01-01
Diversions from streams are often screened to prevent the loss of or injury to fish. Hydraulic criteria meant to protect fish that encounter screens have been developed, but primarily for screens that are vertical to the water flow rather than horizontal. For this reason, we measured selected hydraulic variables and released wild rainbow trout Oncorhynchus mykiss over two types of horizontal flat-plate fish screens in the field. Our goal was to assess the efficacy of these screens under a variety of conditions in the field and provide information that could be used to develop criteria for safe fish passage. We evaluated three different invertedweir screens over a range of stream (0.24-1.77 m3/s) and diversion flows (0.10-0.31 m3/s). Approach velocities (AVs) ranged from 3 to 8 cm/s and sweeping velocities (SVs) from 69 to 143 cm/s. We also evaluated a simple backwatered screen over stream flows of 0.23-0.79 m3/s and diversion flows of 0.08-0.32 m3/s. The mean SVs for this screen ranged from 15 to 66 cm/s and the mean AVs from 1 to 5 cm/s. The survival rates of fish held for 24 h after passage over these screens exceeded 98%. Overall, the number of fish-screen contacts was low and the injuries related to passage were infrequent and consisted primarily of minor fin injuries. Our results indicate that screens of this type have great potential as safe and effective fish screens for small diversions. Care must be taken, however, to avoid operating conditions that produce shallow or no water over the screen surface, situations of high AVs and low SVs at backwatered screens, and situations producing a localized high AV with spiraling flow. ?? Copyright by the American Fisheries Society 2008.
A bubble column evaporator with basic flat-plate condenser for brackish and seawater desalination.
Schmack, Mario; Ho, Goen; Anda, Martin
2016-01-01
This paper describes the development and experimental evaluation of a novel bubble column-based humidification-dehumidification system, for small-scale desalination of saline groundwater or seawater in remote regions. A bubble evaporator prototype was built and matched with a simple flat-plate type condenser for concept assessment. Consistent bubble evaporation rates of between 80 and 88 ml per hour were demonstrated. Particular focus was on the performance of the simple condenser prototype, manufactured from rectangular polyvinylchlorid plastic pipe and copper sheet, a material with a high thermal conductivity that quickly allows for conduction of the heat energy. Under laboratory conditions, a long narrow condenser model of 1500 mm length and 100 mm width achieved condensate recovery rates of around 73%, without the need for external cooling. The condenser prototype was assessed under a range of different physical conditions, that is, external water cooling, partial insulation and aspects of air circulation, via implementing an internal honeycomb screen structure. Estimated by extrapolation, an up-scaled bubble desalination system with a 1 m2 condenser may produce around 19 l of distilled water per day. Sodium chloride salt removal was found to be highly effective with condensate salt concentrations between 70 and 135 µS. Based on findings and with the intent to reduce material cost of the system, a shorter condenser length of 750 mm for the non-cooled (passive) condenser and of 500 mm for the water-cooled condenser was considered to be equally efficient as the experimentally evaluated prototype of 1500 mm length.
Effect of row-to-row shading on the output of flat-plate south-facing photovoltaic arrays
Goswami, D.Y.; Hassan, A.Y.; Collis, J. ); Stefanakos, E.K. )
1989-08-01
When solar arrays (photovoltaic, thermal, etc.) are arranged in multiple rows of modules, all but the first row suffer reduction in (power) output, even when sufficient spacing between rows is provided. The reduction in output power occurs because the first row prevents some of the diffuse and reflected radiation from reaching the row directly behind it. This work presents estimates of the effect of shading on the amounts of solar radiation received by consecutive rows of flat-plate arrays.
Armstrong, P R; Cox, M; de Winter, F
1980-03-01
A brief summary of the hail risk work previously done under this contract is given, and a summary evaluation of hail impact resistance standards currently being developed is presented. Simulated hail impact test data, field data, and the impact resistance of commercially available glazings are discussed. The use of screens for protection against hail and the threat of vandalism to solar flat plate collectors are discussed. (WHK)
Verification of the proteus two-dimensional Navier-Stokes code for flat plate and pipe flows
NASA Technical Reports Server (NTRS)
Conley, Julianne M.; Zeman, Patrick L.
1991-01-01
The Proteus Navier-Stokes Code is evaluated for 2-D/axisymmetric, viscous, incompressible, internal, and external flows. The particular cases to be discussed are laminar and turbulent flows over a flat plate, laminar and turbulent developing pipe flows, and turbulent pipe flow with swirl. Results are compared with exact solutions, empirical correlations, and experimental data. A detailed description of the code set-up, including boundary conditions, initial conditions, grid size, and grid packing is given for each case.
Verification of the Proteus two-dimensional Navier-Stokes code for flat plate and pipe flows
NASA Technical Reports Server (NTRS)
Conley, Julianne M.; Zeman, Patrick L.
1991-01-01
The Proteus Navier-Stokes Code is evaluated for two-dimensional/axisymmetric, viscous, incompressible, internal and external flows. The particular cases to be discussed are laminar and turbulent flows over a flat plate, laminar and turbulent dveloping pipe flows and turbulent pipe flow with swirl. Results are compared with exact solutions, empirical correlations and experimental data. A detailed description of the code set-up, including boundary conditions, intitial conditions, grid size and grid packing is given for each case.
The effect of aspect ratio on vortex rings within the wake of impulsively-started flat plates
NASA Astrophysics Data System (ADS)
Fernando, John; Rival, David
2014-11-01
Vortex pinch-off has been the focus of many studies since it was first observed for vortices produced via piston-cylinder arrangements. Minimal work has been performed on other vortex generation methods. The current study investigates vortex rings behind impulsively-started circular, square, and elliptical flat plates. Preliminary force and PIV measurements show temporal/spatial similarities between vortex growth in the wake of the circular and square plates. Forces and vortex evolution are also shown to be strongly coupled; the presence of stable wake vortex rings results in a reduction of plate drag. For all three plates, pinch-off is initiated by the formation of a positive pressure gradient on the leeward side of the plate, which terminates mass transport to the vortex. It is hypothesized that an increase in aspect ratio (AR) from unity results in isolated vortex lines with non-uniform vorticity along the leading edges. Strong spanwise velocity gradients and stretching near the plate tips facilities vortex detachment. Results from experiments on rectangular plates with varying ARs are discussed and the effect of stretching and tilting in the tip region is investigated. The United States Air Force Office of Scientific Research.
NASA Astrophysics Data System (ADS)
Lee, Handol; Yook, Se-Jin; Han, Seog Young
2012-10-01
The deposition velocity is used to assess the degree of particulate contamination of wafers or photomasks. A numerical model was developed to predict the deposition velocity under the combined influences of thermophoresis and electrophoresis. The deposition velocity onto a face-up flat plate in parallel airflow was simulated by varying the temperature difference between the plate's surface and ambient air or by changing the strength of the electric field established above the plate. Both attraction and repulsion by thermophoresis or electrophoresis were considered. When the plate's surface was colder than ambient air, the surface of the face-up plate could be at risk of contamination by charged particles even with a repulsive applied electric force. When the temperature of the plate's surface was higher than the ambient temperature, the degree of particulate contamination on the surface of the face-up plate could be remarkably reduced in the presence of an electric field. The effect of repulsive thermophoresis, however, is expected to be reduced for very fine particles of high electric mobility or for micrometer-sized particles with large gravitational settling speed when the charged particles are influenced by an attractive electric force.
NASA Astrophysics Data System (ADS)
Dell'Orso, Haley; Tuna, Burak; Memauro, Edward; Amitay, Michael
2014-11-01
Micro-air vehicles operate in the regime of low Reynolds numbers where the drag associated with skin friction is significant. One proposed method for drag reduction is to control the transition from laminar to turbulent flow by using active surface modification to either excite or suppress instabilities within the flow. To do so, the Piezoelectric-Driven Oscillating Surface (PDOS) actuator was developed and quantified. Two PDOS actuators were placed on a flat plate at two stream wise locations in a low Reynolds number flow. The upstream PDOS was actuated at a characteristic frequency appropriate to phase-lock Tollmien-Schlichting waves within the flow while the downstream PDOS was actuated at the anti-phase to reduce the magnitude of the T-S waves. Particle image velocimetry data were obtained along the centerline of the flat plate at different streamwise locations. Data showed that the upstream PDOS successfully locked-in to the instabilities in the flow and the growth of T-S waves was recorded over the increasing streamwise locations from the leading edge of the flat plate. Finally, the anti-phase (at the proper amplitude) was applied using the downstream PDOS and yielded substantial attenuation of the magnitude of the T-S waves.
NASA Technical Reports Server (NTRS)
Rossow, Vernon J
1958-01-01
The use of a magnetic field to control the motion of electrically conducting fluids is studied. The incompressible boundary-layer solutions are found for flow over a flat plate when the magnetic field is fixed relative to the plate or to the fluid. The equations are integrated numerically for the effect of the transverse magnetic field on the velocity and temperature profiles, and hence, the skin friction and rate of heat transfer. It is concluded that the skin friction and the heat-transfer rate are reduced when the transverse magnetic field is fixed relative to the plate and increased when fixed relative to the fluid. The total drag is increased in all of the areas.
NASA Technical Reports Server (NTRS)
Cook, W. J.
1972-01-01
The unsteady laminar boundary layer induced by the flow-initiating shock wave passing over a flat plate mounted in a shock tube was theoretically and experimentally studied in terms of heat transfer rates to the plate for shock speeds ranging from 1.695 to 7.34 km/sec. The theory presented by Cook and Chapman for the shock-induced unsteady boundary layer on a plate is reviewed with emphasis on unsteady heat transfer. A method of measuring time-dependent heat-transfer rates using thin-film heat-flux gages and an associated data reduction technique are outlined in detail. Particular consideration is given to heat-flux measurement in short-duration ionized shocktube flows. Experimental unsteady plate heat transfer rates obtained in both air and nitrogen using thin-film heat-flux gages generally agree well with theoretical predictions. The experimental results indicate that the theory continues to predict the unsteady boundary layer behavior after the shock wave leaves the trailing edge of the plate even though the theory is strictly applicable only for the time interval in which the shock remains on the plate.
Torii, Kengo; Chiwata, Ichiro
2010-01-01
Splint therapy is a widely used modality for temporomandibular disorders (TMDs). However, questions remain regarding the mechanism of symptom relief. Recently, a relation between TMD and a discrepancy between the habitual occlusal position (HOP) and the anterior flat plane bite plate-induced occlusal position (BPOP) has been reported. Therefore, to understand the mechanism of the symptom relief associated with the use of a bite plate, the changes in both the HOP and BPOP values were observed during anterior bite plate treatment in a patient with TMD. Case presentation Anterior bite plate treatment was started in a patient complaining of arthralgia. A discrepancy between the HOP and BPOP values was recorded three days after the first visit; this discrepancy disappeared on day 6, and the disappearance was maintained between days 6 and 12. The disappearance was associated with a decrease in the severity of the patient’s symptoms; however, the discrepancy reappeared after 15 days, coinciding with the complete disappearance of the patient’s symptoms. Therefore, the effect of the bite plate on the resolution of the discrepancy between the HOP and BPOP values was interpreted as being unsustainable and occlusal equilibration for the BPOP was performed at 17 days. Thereafter, neither a discrepancy in the HOP and BPOP values nor any symptoms of TMD (right temporomandibular joint pain or limited jaw opening) reoccurred during a two-year follow-up period. Conclusion Within the limitations of the present study, the symptom-relieving action of an anterior flat plane bite plate on the resolution of occlusal discrepancy appeared to be temporary. This outcome supports previously reported conclusions that the effectiveness of stabilization splint therapy for reducing symptoms in patients with pain dysfunction syndrome does not differ significantly from that of other conservative therapies or of no treatment at all. PMID:21243070
NASA Technical Reports Server (NTRS)
1976-01-01
Basic test results of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator are given. The collector was tested over ranges of inlet temperature and flux level.
Sun, Yahui; Liao, Qiang; Huang, Yun; Xia, Ao; Fu, Qian; Zhu, Xun; Zheng, Yaping
2016-11-01
Industrially manufactured planar waveguides doped with light scattering nanoparticles, which can dilute and redistribute the intense incident light within microalgae suspension more uniformly, were introduced into a flat-plate photobioreactor (PBR) with a width of 25cm to alleviate the adverse effect of poor light penetrability on microalgae growth. Compared with the flat-plate PBR without waveguides, the illumination surface area per unit volume in the proposed PBR was increased by 10.3 times. During the whole cultivation period, the illuminated volume fractions in the proposed PBR were 21.4-410% higher than those in the flat-plate PBR without waveguides. Consequently, attributed to the optimized light distribution in the proposed PBR, a 220% improvement in biomass production was obtained relative to that in the flat-plate PBR without waveguides. Furthermore, higher light output intensities emitted from the planar waveguide surfaces and increased microalgae growth rates were achieved by decreasing the length of planar waveguides.
An approximate analytic solution for the radiation from a line-driven fluid-loaded plate
NASA Astrophysics Data System (ADS)
Diperna, Daniel T.; Feit, David
2001-12-01
In the analysis of a fluid loaded line-driven plate, the fields in the structure and the fluid are often expressed in terms of a Fourier transform. Once the boundary conditions are matched, the structural displacement can be expressed as an inverse transform, which can be evaluated using contour integration. The result is then a sum of propagating or decaying waves, each arising from poles in the complex plane, plus a branch cut integral. The branch cut is due to a square root in the transform of the acoustic impedance. The complex layer analysis (CLA) used here eliminates the branch cut singularity by approximating the square root with a rational function, causing the characteristic equation to become a polynomial in the transform variable. An approximate analytic solution to the characteristic equation is then found using a perturbation method. The result is four poles corresponding to the roots of the in vacuo plate, modified by the presence of the fluid, plus an infinity of poles located along the branch cut of the acoustic impedance. The solution is then found analytically using contour integration, with the integrand containing only simple poles.
NASA Astrophysics Data System (ADS)
Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis
2014-12-01
This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.
Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis
2014-12-09
This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.
Schepers, Gerben; van Hinsbergen, Douwe J J; Spakman, Wim; Kosters, Martha E; Boschman, Lydian M; McQuarrie, Nadine
2017-05-16
At two trench segments below the Andes, the Nazca Plate is subducting sub-horizontally over ∼200-300 km, thought to result from a combination of buoyant oceanic-plateau subduction and hydrodynamic mantle-wedge suction. Whether the actual conditions for both processes to work in concert existed is uncertain. Here we infer from a tectonic reconstruction of the Andes constructed in a mantle reference frame that the Nazca slab has retreated at ∼2 cm per year since ∼50 Ma. In the flat slab portions, no rollback has occurred since their formation at ∼12 Ma, generating 'horse-shoe' slab geometries. We propose that, in concert with other drivers, an overpressured sub-slab mantle supporting the weight of the slab in an advancing upper plate-motion setting can locally impede rollback and maintain flat slabs until slab tearing releases the overpressure. Tear subduction re-establishes a continuous slab and allows the process to recur, providing a mechanism for the transient character of flat slabs.
NASA Astrophysics Data System (ADS)
Schepers, Gerben; van Hinsbergen, Douwe J. J.; Spakman, Wim; Kosters, Martha E.; Boschman, Lydian M.; McQuarrie, Nadine
2017-05-01
At two trench segments below the Andes, the Nazca Plate is subducting sub-horizontally over ~200-300 km, thought to result from a combination of buoyant oceanic-plateau subduction and hydrodynamic mantle-wedge suction. Whether the actual conditions for both processes to work in concert existed is uncertain. Here we infer from a tectonic reconstruction of the Andes constructed in a mantle reference frame that the Nazca slab has retreated at ~2 cm per year since ~50 Ma. In the flat slab portions, no rollback has occurred since their formation at ~12 Ma, generating `horse-shoe' slab geometries. We propose that, in concert with other drivers, an overpressured sub-slab mantle supporting the weight of the slab in an advancing upper plate-motion setting can locally impede rollback and maintain flat slabs until slab tearing releases the overpressure. Tear subduction re-establishes a continuous slab and allows the process to recur, providing a mechanism for the transient character of flat slabs.
Schepers, Gerben; van Hinsbergen, Douwe J. J.; Spakman, Wim; Kosters, Martha E.; Boschman, Lydian M.; McQuarrie, Nadine
2017-01-01
At two trench segments below the Andes, the Nazca Plate is subducting sub-horizontally over ∼200–300 km, thought to result from a combination of buoyant oceanic-plateau subduction and hydrodynamic mantle-wedge suction. Whether the actual conditions for both processes to work in concert existed is uncertain. Here we infer from a tectonic reconstruction of the Andes constructed in a mantle reference frame that the Nazca slab has retreated at ∼2 cm per year since ∼50 Ma. In the flat slab portions, no rollback has occurred since their formation at ∼12 Ma, generating ‘horse-shoe' slab geometries. We propose that, in concert with other drivers, an overpressured sub-slab mantle supporting the weight of the slab in an advancing upper plate-motion setting can locally impede rollback and maintain flat slabs until slab tearing releases the overpressure. Tear subduction re-establishes a continuous slab and allows the process to recur, providing a mechanism for the transient character of flat slabs. PMID:28508893
NASA Astrophysics Data System (ADS)
Long, J.; New, T. H.
2016-07-01
Vortical structures and dynamics of a Re h = 2100 elliptic jet impinging upon a flat plate were studied at H/ d h = 1, 2 and 4 jet-to-plate separation distances. Flow investigations were conducted along both its major and minor planes using laser-induced fluorescence and digital particle image velocimetry techniques. Results show that the impingement process along the major plane largely consists of primary jet ring-vortex and wall-separated secondary vortex formations, where they subsequently separate from the flat plate at smaller H/ d h = 1 and 2 separation distances. Key vortex formation locations occur closer to the impingement point as the separation distance increases. Interestingly, braid vortices and rib structures begin to take part in the impingement process at H/ d h = 4 and wave instabilities dominate the flow field. In contrast, significantly more coherent primary and secondary vortices with physically larger vortex core sizes and higher vortex strengths are observed along the minor plane, with no signs of braid vortices and rib structures. Lastly, influences of these different flow dynamics on the major and minor plane instantaneous and mean skin friction coefficient levels are investigated to shed light on the effects of separation distance on the wall shear stress distributions.
Kawabata, Hirokazu; Funazaki, Ken-Ichi; Nakata, Ryota; Takahashi, Daichi
2014-06-01
This study deals with the experimental and numerical studies of the effect of flow control devices (FCDs) on the film cooling performance of a circular cooling hole on a flat plate. Two types of FCDs with different heights are examined in this study, where each of them is mounted to the flat plate upstream of the cooling hole by changing its lateral position with respect to the hole centerline. In order to measure the film effectiveness as well as heat transfer downstream of the cooling hole with upstream FCD, a transient method using a high-resolution infrared camera is adopted. The velocity field downstream of the cooling hole is captured by 3D laser Doppler velocimeter (LDV). Furthermore, the aerodynamic loss associated with the cooling hole with/without FCD is measured by a total pressure probe rake. The experiments are carried out at blowing ratios ranging from 0.5 to 1.0. In addition, numerical simulations are also made to have a better understanding of the flow field. LES approach is employed to solve the flow field and visualize the vortex structure around the cooling hole with FCD. When a taller FCD is mounted to the plate, the film effectiveness tends to increase due to the vortex structure generated by the FCD. As FCD is laterally shifted from the centerline, the film effectiveness increases, while the lift-off of cooling air is also promoted when FCD is put on the center line.
NASA Astrophysics Data System (ADS)
Trajkovski, J.; Kunc, R.; Prebil, I.
2017-07-01
Light armored vehicles (LAVs) can be exposed to blast loading by landmines or improvised explosive devices (IEDs) during their lifetime. The bottom hull of these vehicles is usually made of a few millimeters of thin armored plate that is the vehicle's weak point in a blast-loading scenario. Therefore, blast resistance and blast load redirection are very important characteristics in providing adequate vehicle as well as occupant protection. Furthermore, the eccentric nature of loading caused by landmines was found to be omitted in the studies of simplified structures like beams and plates. For this purpose, blast wave dispersion and blast response of centrally and eccentrically loaded flat-, U-, and V-shaped plates are examined using a combined finite-element-smoothed-particle hydrodynamics (FE-SPH) model. The results showed that V-shaped plates better disperse blast waves for any type of loading and, therefore, can be successfully applied in LAVs. Based on the results of the study and the geometry of a typical LAV 6× 6, the minimum angle of V-shaped plates is also determined.
NASA Astrophysics Data System (ADS)
Trajkovski, J.; Kunc, R.; Prebil, I.
2016-12-01
Light armored vehicles (LAVs) can be exposed to blast loading by landmines or improvised explosive devices (IEDs) during their lifetime. The bottom hull of these vehicles is usually made of a few millimeters of thin armored plate that is the vehicle's weak point in a blast-loading scenario. Therefore, blast resistance and blast load redirection are very important characteristics in providing adequate vehicle as well as occupant protection. Furthermore, the eccentric nature of loading caused by landmines was found to be omitted in the studies of simplified structures like beams and plates. For this purpose, blast wave dispersion and blast response of centrally and eccentrically loaded flat-, U-, and V-shaped plates are examined using a combined finite-element-smoothed-particle hydrodynamics (FE-SPH) model. The results showed that V-shaped plates better disperse blast waves for any type of loading and, therefore, can be successfully applied in LAVs. Based on the results of the study and the geometry of a typical LAV 6× 6 , the minimum angle of V-shaped plates is also determined.
Influence of wire-coil inserts on the thermo-hydraulic performance of a flat-plate solar collector
NASA Astrophysics Data System (ADS)
Herrero Martín, R.; García, A.; Pérez-García, J.
2012-11-01
Enhancement techniques can be applied to flat-plate liquid solar collectors towards more compact and efficient designs. For the typical operating mass flow rates in flat-plate solar collectors, the most suitable technique is inserted devices. Based on previous studies from the authors, wire coils were selected for enhancing heat transfer. This type of inserted device provides better results in laminar, transitional and low turbulence fluid flow regimes. To test the enhanced solar collector and compare with a standard one, an experimental side-by-side solar collector test bed was designed and constructed. The testing set up was fully designed following the requirements of EN12975-2 and allow us to accomplish performance tests under the same operating conditions (mass flow rate, inlet fluid temperature and weather conditions). This work presents the thermal efficiency curves of a commercial and an enhanced solar collector, for the standardized mass flow rate per unit of absorber area of 0.02 kg/sm2 (in useful engineering units 144 kg/h for water as working fluid and 2 m2 flat-plate solar collector of absorber area). The enhanced collector was modified inserting spiral wire coils of dimensionless pitch p/D = 1 and wire-diameter e/D = 0.0717. The friction factor per tube has been computed from the overall pressure drop tests across the solar collectors. The thermal efficiency curves of both solar collectors, a standard and an enhanced collector, are presented. The enhanced solar collector increases the thermal efficiency by 15%. To account for the overall enhancement a modified performance evaluation criterion (R3m) is proposed. The maximum value encountered reaches 1.105 which represents an increase in useful power of 10.5% for the same pumping power consumption.
On the tones of round choked jets impinging on normal flat plates
NASA Technical Reports Server (NTRS)
Powell, Alan; Henderson, Brenda
1990-01-01
An experimental investigation of the sound produced by an axisymmetric supersonic jet impinging on plates with variable size and nozzle-to-plate spacings was performed. Spectral analysis and schlieren photography were used to determine the sound characteristics and flow disturbances associated with the production of discrete tones. Two classes of tones, associated with small and large plates, existed for pressure ratios above 2.70. For lower pressure ratios, however, only large plate tones occurred for all plate sizes with choked jet screech appearing at the largest spacings. Reflector tests indicated that both classes of tones were part of a feedback loop to the nozzle. Schlieren photography revealed both symmetric and asymmetric disturbances in the large plate jet flows which corresponded to symmetrical and helical modes of oscillation in the cross-spectrum studies. In addition to this, both symmetric and asymmetric oscillations of the shock waves occurred in the large plate case while symmetric oscillations of the shock wave occurred in the small plate case.
NASA Astrophysics Data System (ADS)
Bhuiyan, A. S.; Biswas, M. R.
2011-11-01
The effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical flat plate have been investigated. The results are obtained numerically by transforming the governing system of boundary layer equations into a system of non-dimensional equations. Numerical results for different values of pressure stress work parameter, viscous dissipation parameter, and Prandtl number have been obtained. The velocity profiles, temperature distributions, skin friction coefficient, and the rate of heat transfer have been presented graphically for the effects of the aforementioned parameters. Results are compared with previous investigation.
NASA Technical Reports Server (NTRS)
Christensen, Elmer
1985-01-01
The Flat-Plate Solar Array (FSA) Project, a Government-sponsored photovoltaics project, was initiated in January 1975 (previously named the Low-Cost Silicon Solar Array Project) to stimulate the development of PV systems for widespread use. Its goal then was to develop PV modules with 10% efficiency, a 20-year lifetime, and a selling price of $0.50 per peak watt of generating capacity (1975 dollars). It was recognized that cost reduction of PV solar-cell and module manufacturing was the key achievement needed if PV power systems were to be economically competitive for large-scale terrestrial use.
NASA Technical Reports Server (NTRS)
Deissler, R. G.; Loeffler, A. L., Jr.
1959-01-01
A previous analysis of turbulent heat transfer and flow with variable fluid properties in smooth passages is extended to flow over a flat plate at high Mach numbers, and the results are compared with experimental data. Velocity and temperature distributions are calculated for a boundary layer with appreciative effects of frictional heating and external heat transfer. Viscosity and thermal conductivity are assumed to vary as a power or the temperature, while Prandtl number and specific heat are taken as constant. Skin-friction and heat-transfer coefficients are calculated and compared with the incompressible values. The rate of boundary-layer growth is obtained for various Mach numbers.
NASA Astrophysics Data System (ADS)
Hossain, Sheikh Imamul; Alam, Md. Mahmud
2016-07-01
An attempt is made to represent the numerical solution of magnetohydrodynamics (MHD) viscoelastic fluid flow through an infinite vertical flat plate with constant suction in the presence of Soret and Dufour effects. The expressions of non-dimensional, coupled partial momentum, energy and concentration differential equations are obtained with the help of the usual non-dimensional variables. Implicit finite difference method is imposed to obtain the non-dimensional equations. Also the stability conditions and convergence criteria are analyzed. The effects of the various parameters entering into the problem on shear stress, Nusselt number, and Sherwood number are demonstrated graphically with physical interpretation.
NASA Astrophysics Data System (ADS)
Yovanovich, M. M.
1993-07-01
It is presently shown that the correlation equations for forced and natural convection-involving bloundary-layer flows, over isothermal flat plates, collapse into a simple expression directly relating the dimensionless wall-temperature excess to a novel Prandtl number function. This function is demonstrated to be applicable for the full, zero-to-infinity Prandtl number range. This formulation allows forced and natural convection heat-transfer results to appear on the same graph, as dimensionless temperature excess vs Prandtl number functions.
Drag and near wake characteristics of flat plates normal to the flow with fractal edge geometries
NASA Astrophysics Data System (ADS)
Nedic, Jovan; Ganapathisubramani, Bharath; Vassilicos, Christos
2012-11-01
Past results have suggested that the coefficient of drag and shedding frequencies of regular polygon plates all fall within a very narrow band of values. In this study, we introduce a variety of length-scales into the perimeter of a square plate and study the effects this has on the wake characteristics and overall drag. The perimeter of the plate can be made as long as allowed by practical constraints with as many length-scales as desired under these constraints without changing the area of the plate. A total of eight fractal-perimeter plates were developed, split into two families of different fractal dimension all of which had the same frontal area. It is found that by increasing the number of fractal iterations, thus the perimeter, the drag coefficient increases by up to 10%. For the family of fractal plates with the higher dimension, it is also found that when the perimeter increases above a certain threshold the drag coefficient drops back again. Furthermore, the shedding frequency remains the same but the intensity of the shedding decreases with increasing fractal dimension. The size of the wake also decreases with increasing fractal dimension and has some dependence on iteration without changing the area of the plate.
Drag and near wake characteristics of flat plates normal to the flow with fractal edge geometries
NASA Astrophysics Data System (ADS)
Nedić, J.; Ganapathisubramani, B.; Vassilicos, J. C.
2013-12-01
Past results have suggested that the drag coefficient and the shedding frequencies of regular polygon plates all fall within a very narrow band of values. In this study, we introduce a variety of length scales into the perimeter of a square plate and study the effects this has on the wake characteristics and overall drag. The perimeter of the plate can be made as long as allowed by practical constraints with as many length scales as desired under these constraints without changing the area of the plate. A total of eight fractal-perimeter plates were developed, split into two families of different fractal dimensions all of which had the same frontal area. It is found that by increasing the number of fractal iterations and thus the perimeter, the drag coefficient increases by up to 7%. For the family of fractal plates with the higher dimension, it is also found that when the perimeter increases above a certain threshold the drag coefficient drops back again. Furthermore, the shedding frequency remains the same but the intensity of the shedding decreases with increasing fractal dimension. The size of the wake also decreases with increasing fractal dimension and has some dependence on iteration without changing the area of the plate.
NASA Astrophysics Data System (ADS)
Jakkareddy, Pradeep S.; Balaji, C.
2016-09-01
This paper employs the Bayesian based Metropolis Hasting - Markov Chain Monte Carlo algorithm to solve inverse heat transfer problem of determining the spatially varying heat transfer coefficient from a flat plate with flush mounted discrete heat sources with measured temperatures at the bottom of the plate. The Nusselt number is assumed to be of the form Nu = aReb(x/l)c . To input reasonable values of ’a’ and ‘b’ into the inverse problem, first limited two dimensional conjugate convection simulations were done with Comsol. Based on the guidance from this different values of ‘a’ and ‘b’ are input to a computationally less complex problem of conjugate conduction in the flat plate (15mm thickness) and temperature distributions at the bottom of the plate which is a more convenient location for measuring the temperatures without disturbing the flow were obtained. Since the goal of this work is to demonstrate the eficiacy of the Bayesian approach to accurately retrieve ‘a’ and ‘b’, numerically generated temperatures with known values of ‘a’ and ‘b’ are treated as ‘surrogate’ experimental data. The inverse problem is then solved by repeatedly using the forward solutions together with the MH-MCMC aprroach. To speed up the estimation, the forward model is replaced by an artificial neural network. The mean, maximum-a-posteriori and standard deviation of the estimated parameters ‘a’ and ‘b’ are reported. The robustness of the proposed method is examined, by synthetically adding noise to the temperatures.
NASA Technical Reports Server (NTRS)
Savin, Raymond C.
1958-01-01
The flow about slender flat-top wing-body configurations traveling at high supersonic speeds and small angles of attack is investigated analytically. In the case of conical configurations, approximate algebraic solutions to the flow field are obtained. In the case of configurations which are conical at the vertex but curved in the stream direction, these solutions are combined with a slender-body approximation to the generalized shock-expansion method to obtain the flow downstream of the vertex. Surface pressures were obtained experimentally at Mach numbers from 3.0 to 6.0 and angles of attack up to 6 deg for several flat-top wing-body configurations. These configurations consisted of half-bodies of revolution mounted beneath thin highly swept wings. Three different bodies were employed. The two conical bodies consisted of one-half of a fineness-ratio-5 cone and one-half of a fineness-ratio-2-1/2 cone. The body of the third configuration consisted of one-half of a fineness-ratio-5 ogive. For the ogive configuration, the leading edges of the wing were curved and designed to just maintain the theoretically determined bow shock along the leading edge at a Mach number of 5.0 and an angle of attack of 3 deg. The predictions of the conical flow theory of this paper for the surface pressures are found to be in good agreement with experiment at Mach numbers of 5.0 and 6.0 up to angles of attack of approximately 3 deg. Estimated lift, drag, and pitching-moment coefficients, as well as maximum lift-drag ratio, are also in good agreement with existing experimental data at a Mach number of 5.0 for a conical configuration having an arrow plan-form wing. It is also found that the generalized shock-expansion method yields reasonable good agreement with experiment for the surface pressures on the half-ogive configuration at a Mach number of 5.0 and an angle of attack of 3 deg.
Testing results of tubeless flat-plate phase-change solar collectors
Tamimi, A. ); Rawajfeh, K. )
1991-01-01
This paper reports on a tubeless solar collector charged with Refrigerant-113 (R-113) that was installed and tested. Steady-state performance of this system showed high efficiency values; this was due to phase-change heat transfer characteristics of a boiling process that is accompanied by low plate temperature as well as low thermal resistance to heat flow from the absorber plate to the working fluid. The only resistance to heat flow toward the working fluid is the conduction resistance through the upper plate, which is negligible.
Gritzo, L.A.; Moya, J.L.; Murray, D.
1997-01-01
A series of three 18.9 m diameter JP-4 pool fire experiments with a large (2.1 m X 4.6 m), flat plate calorimeter adjacent to the fuel pool were recently performed. The objectives of these experiments were to: (1) gain a better understanding of fire phenomenology, (2) provide empirical input parameter estimates for simplified, deterministic Risk Assessment Compatible Fire Models (RACFMs), (3) assist in continuing fire field model code validation and development, and (4) enhance the data base of fire temperature and heat flux to object distributions. Due to different wind conditions during each experiment, data were obtained for conditions where the plate was not engulfed, fully-engulfed and partially engulfed by the continuous flame zone. Results include the heat flux distribution to the plate and flame thermocouple temperatures in the vicinity of the plate and at two cross sections within the lower region of the continuous flame zone. The results emphasize the importance of radiative coupling (i.e. the cooling of the flames by a thermally massive object) and convective coupling (including object-induced turbulence and object/wind/flame interactions) in determining the heat flux from a fire to an object. The formation of a secondary flame zone on an object adjacent to a fire via convective coupling (which increases the heat flux by a factor of two) is shown to be possible when the object is located within a distance equal to the object width from the fire.
NASA Technical Reports Server (NTRS)
Kogan, M. N.; Ustinov, M. V.
1997-01-01
Work is devoted to study of free-stream vorticity normal to leading edge interaction with boundary layer over plate and resulting flow distortion influence on laminar-turbulent transition. In experiments made the wake behind the vertically stretched wire was used as a source of vortical disturbances and its effect on the boundary layer over the horizontally mounted plate with various leading edge shapes was investigated. The purpose of experiments was to check the predictions of theoretical works of M.E. Goldstein, et. al. This theory shows that small free-stream inhomogeneity interacting with leading edge produces considerable distortion of boundary layer flow. In general, results obtained confirms predictions of Goldstein's theory, i.e., the amplification of steady vortical disturbances in boundary layer caused by vortex lines stretching was observed. Experimental results fully coincide with predictions of theory for large Reynolds number, relatively sharp leading edge and small disturbances. For large enough disturbances the flow distortion caused by symmetric wake unexpectedly becomes antisymmetric in spanwise direction. If the leading edge is too blunt the maximal distortion takes place immediately at the nose and no further amplification was observed. All these conditions and results are beyond the scope of Goldstein's theory.
NASA Technical Reports Server (NTRS)
Creager, Marcus O.
1959-01-01
An investigation of the effects of variation of leading-edge sweep and surface inclination on the flow over blunt flat plates was conducted at Mach numbers of 4 and 5.7 at free-stream Reynolds numbers per inch of 6,600 and 20,000, respectively. Surface pressures were measured on a flat plate blunted by a semicylindrical leading edge over a range of sweep angles from 0 deg to 60 deg and a range of surface inclinations from -10 deg to +10 deg. The surface pressures were predicted within an average error of +/- 8 percent by a combination of blast-wave and boundary-layer theory extended herein to include effects of sweep and surface inclination. This combination applied equally well to similar data of other investigations. The local Reynolds number per inch was found to be lower than the free-stream Reynolds number per inch. The reduction in local Reynolds number was mitigated by increasing the sweep of the leading edge. Boundary-layer thickness and shock-wave shape were changed little by the sweep of the leading edge.
NASA Astrophysics Data System (ADS)
Duriez, T.; Thiria, B.; Cambonie, T.; Wesfreid, J. E.; Aider, J. L.
Vortex generators (VG) are among the most popular actuators for flow control. more or less interact with each other depending on many parameters like the size of the VGs or the spacing between each VG (Betterton et al. (2000); Godard ' Stanislas (2006)). From a general point of view, the 3D steady (or unsteady) perturbations induced by the VG are used to modify a boundary layer in order to control some global properties of the flow like heat transfer or aerodynamic forces (Lin (2002); Duriez et al. (2008)). One of the main difficulty in using VG is the large number of parameters the experimentalist has to choose: the type of VG (mechanical or fluidic, stationary or time-dependant), the dimensions, the spacing, the location relative to the flow to be controlled. In this paper we propose a short review describing the structures of the flows produced by two different mechanical VG (trapezoidal blades and cylinders) and continuous jets in a flat-plate boundary layer. The drawback and advantages of each of them will be underlined. The way the longitudinal structures interact with a flat plate boundary layer will also be discussed. In the case of small cylinders it will be shown that one can define new physical properties that can be helpful to choose the proper parameters in the perspective of control of flow separation.
Gertzos, K.P.; Caouris, Y.G.
2008-04-15
Parameters that affect the efficiency of a flat plate integrated collector storage solar water heater (ICSSWH) are examined experimentally and numerically. This specific ICSSWH contains water that is not refreshed. The service water is heated indirectly through an immersed heat exchanger (HE) in contact with the front and back major surfaces. A forced convection mechanism consisting of a pump that brings the storage water into motion by recirculation is used for heat transfer intensification. The two major (front and back) flat plate surfaces need to be well interconnected so that they are not deformed by the weight of the contained water and the exerted high-pressure. Two main factors that influence the performance are optimized: the position and size of the recirculation ports and the arrangement and size of the interconnecting fins. Both factors are explored to maximize the velocity flow field of the recirculated storage water. Consequently, the heat transfer rate between the two water circuits is maintained at high levels. Various 3D computational fluid dynamics (CFD) models are developed using the FLUENT package. An experimental model, made by Plexiglas, is used for the visualization of the flow field. Flow velocities are measured using a laser doppler velocimetry (LDV) system. The optimal arrangement increases the mean storage water velocity by 65% and raises the outlet temperatures up to 8 C. (author)
Pulsed remote field eddy current technique applied to non-magnetic flat conductive plates
NASA Astrophysics Data System (ADS)
Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin
2013-12-01
Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field eddy current (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field eddy current (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.
Borden, C.S.; Schwartz, D.L.
1984-12-31
The purpose of this study is to assess the relative economic potentials of concentrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications in the mid-1990's. Specific objectives of this study are to provide information on concentrator photovoltaic collector probabilistic price and efficiency levels to illustrate critical areas of R and D for concentrator cells and collectors, and to compare concentrator and flat-plate PV price and efficiency alternatives for several locations, based on their implied costs of energy. To deal with the uncertainties surrounding research and development activities in general, a probabilistic assessment of commercially achievable concentrator photovoltaic collector efficiencies and prices (at the factory loading dock) is performed. The results of this projection of concentrator photovoltaic technology are then compared with a previous flat-plate module price analysis (performed early in 1983). To focus this analysis on specific collector alternatives and their implied energy costs for different locations, similar two-axis tracking designs are assumed for both concentrator and flat-plate options. The results of this study provide the first comprehensive assessment of PV concentrator collector manufacturing costs in combination with those of flat-plate modules, both projected to their commercial potentials in the mid-1990's.
NASA Astrophysics Data System (ADS)
Meda, Adimurthy; Katti, Vadiraj V.
2017-02-01
The present work experimentally investigates the local distribution of wall static pressure and the heat transfer coefficient on a rough flat plate impinged by a slot air jet. The experimental parameters include, nozzle-to-plate spacing (Z/D h = 0.5-10.0), axial distance from stagnation point (x/D h ), size of detached rib (b = 4-12 mm) and Reynolds number (Re = 2500-20,000). The wall static pressure on the surface is recorded using a Pitot tube and a differential pressure transmitter. Infrared thermal imaging technique is used to capture the temperature distribution on the target surface. It is observed that, the maximum wall static pressure occurs at the stagnation point (x/D h = 0) for all nozzle-to-plate spacing (Z/D h ) and rib dimensions studied. Coefficient of wall static pressure (C p ) decreases monotonically with x/D h . Sub atmospheric pressure is evident in the detached rib configurations for jet to plate spacing up to 6.0 for all ribs studied. Sub atmospheric region is stronger at Z/D h = 0.5 due to the fluid accelerating under the rib. As nozzle to plate spacing (Z/D h ) increases, the sub-atmospheric region becomes weak and vanishes gradually. Reasonable enhancement in both C p as well as Nu is observed for the detached rib configuration. Enhancement is found to decrease with the increase in the rib width. The results of the study can be used in optimizing the cooling system design.
NASA Astrophysics Data System (ADS)
Meda, Adimurthy; Katti, Vadiraj V.
2017-08-01
The present work experimentally investigates the local distribution of wall static pressure and the heat transfer coefficient on a rough flat plate impinged by a slot air jet. The experimental parameters include, nozzle-to-plate spacing (Z /D h = 0.5-10.0), axial distance from stagnation point ( x/D h ), size of detached rib ( b = 4-12 mm) and Reynolds number ( Re = 2500-20,000). The wall static pressure on the surface is recorded using a Pitot tube and a differential pressure transmitter. Infrared thermal imaging technique is used to capture the temperature distribution on the target surface. It is observed that, the maximum wall static pressure occurs at the stagnation point ( x/D h = 0) for all nozzle-to-plate spacing ( Z/D h ) and rib dimensions studied. Coefficient of wall static pressure ( C p ) decreases monotonically with x/D h . Sub atmospheric pressure is evident in the detached rib configurations for jet to plate spacing up to 6.0 for all ribs studied. Sub atmospheric region is stronger at Z/D h = 0.5 due to the fluid accelerating under the rib. As nozzle to plate spacing ( Z/D h ) increases, the sub-atmospheric region becomes weak and vanishes gradually. Reasonable enhancement in both C p as well as Nu is observed for the detached rib configuration. Enhancement is found to decrease with the increase in the rib width. The results of the study can be used in optimizing the cooling system design.
NASA Technical Reports Server (NTRS)
Kogan, M. N.
1994-01-01
Recent progress in both the linear and nonlinear aspects of stability theory has highlighted the importance of the receptivity problem. One of the most unclear aspects of receptivity study is the receptivity of boundary-layer flow normal to vortical disturbances. Some experimental and theoretical results permit the proposition that quasi-steady outer-flow vortical disturbances may trigger by-pass transition. In present work such interaction is investigated for vorticity normal to a leading edge. The interest in these types of vortical disturbances arise from theoretical work, where it was shown that small sinusoidal variations of upstream velocity along the spanwise direction can produce significant variations in the boundary-layer profile. In the experimental part of this work, such non-uniform flow was created and the laminar-turbulent transition in this flow was investigated. The experiment was carried out in a low-turbulence direct-flow wind tunnel T-361 at the Central Aerohydrodynamic Institute (TsAGI). The non-uniform flow was produced by laminar or turbulent wakes behind a wire placed normal to the plate upstream of the leading edge. The theoretical part of the work is devoted to studying the unstable disturbance evolution in a boundary layer with strongly non-uniform velocity profiles similar to that produced by outer-flow vorticity. Specifically, the Tollmien-Schlichting wave development in the boundary layer flow with spanwise variations of velocity is investigated.
NASA Astrophysics Data System (ADS)
Aljallis, Elias; Sarshar, Mohammad Amin; Datla, Raju; Sikka, Vinod; Jones, Andrew; Choi, Chang-Hwan
2013-02-01
In this paper, we report the measurement of skin friction drag on superhydrophobic-coated flat plates in high Reynolds (Re) number boundary layer flows, using a high-speed towing tank system. Aluminum flat plates with a large area (4 feet × 2 feet, 3/8 in. thick) and sharpened leading/trailing edges (1 in. long) were prepared as a boundary layer flow model. Spray coating of hydrophobic nanoparticles was applied to make two different types of superhydrophobic coatings: one with low contact angle and high contact angle hysteresis, and the other with high contact angle and low contact angle hysteresis. Skin friction drag of the superhydrophobic plates was measured in the flow speed up to 30 ft/s to cover transition and turbulent flow regimes (105 < ReL < 107), and was compared to that of an uncoated bare aluminum plate. A significant drag reduction was observed on the superhydrophobic plate with high contact angle and low contact angle hysteresis up to ˜30% in transition regime (105 < ReL < 106), which is attributed to the shear-reducing air layer entrapped on the superhydrophobic surface. However, in fully turbulence regime (106 < ReL < 107), an increase of drag was observed, which is ascribed to the morphology of the surface air layer and its depletion by high shear flow. The texture of superhydrophobic coatings led to form a rugged morphology of the entrapped air layer, which would behave like microscale roughness to the liquid flow and offset the drag-reducing effects in the turbulent flow. Moreover, when the superhydrophobic coating became wet due to the removal of air by high shear at the boundary, it would amplify the surface roughness of solid wall and increase the drag in the turbulent flow. The results illustrate that drag reduction is not solely dependent on the superhydrophobicity of a surface (e.g., contact angle and air fraction), but the morphology and stability of the surface air layer are also critical for the effective drag reduction using
NASA Astrophysics Data System (ADS)
Chen, Xi
2010-08-01
With the indirect thrust measurement of electric thrusters working at a low vacuum chamber pressure as the research background, this paper analyses the impact force acting on a flat plate exposed normally to a rarefied plasma plume issuing from a thruster with an annular or circular exit section for the free-molecule flow regime (at large Knudsen numbers). The constraint relation proposed by Cai and Boyd (2007 J. Spacecr. Rockets 44 619, 1326) about the velocity components of gas particles leaving a location on the nozzle exit section and arriving at a given spatial point outside the nozzle has been employed here to derive the analytical expressions for calculating the impact force. Sample calculation results show that if the flat plate is sufficiently large, the impact force acting on the flat plate calculated for the case without accounting for gas particle reflection at the plate surface agrees well with the axial momentum flux calculated at the thruster exit or the theoretical thrust force of the studied thruster, while accounting for the contribution of gas particles reflected from the plate surface to the impact force production may significantly increase the calculated impact force acting on the flat plate. For a Hall-effect thruster in which the thrust force is dominantly produced by the ions with high directional kinetic energy and the ions are not directly reflected from the plate surface, the contribution to the impact force production of atom species and of gas particles reflected from the plate surface is negligibly small and thus the measured axial impact force acting on a sufficiently large plate can well represent the thrust force of the thruster. On the other hand, if the contribution of the gas particles reflected from the plate surface to the impact force production cannot be neglected (e.g. for the electric thrusters with comparatively low thruster exit temperatures), appreciable error would appear in the indirect thrust measurement.
NASA Astrophysics Data System (ADS)
Adimurthy, M.; Katti, Vadiraj V.
2016-06-01
Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a normal slot air jet is experimental investigated. Present study focuses on the influence of jet-to-plate spacing (Z/D h ) (0.5-10) and Reynolds number (2500-20,000) on the fluid flow and heat transfer distribution. A single slot jet with an aspect ratio (l/b) of about 22 is chosen for the current study. Infrared Thermal Imaging technique is used to capture the temperature data on the target surface. Local heat transfer coefficients are estimated from the thermal images using `SMART VIEW' software. Wall static pressure measurement is carried out for the specified range of Re and Z/D h . Wall static pressure coefficients are seen to be independent of Re in the range between 5000 and 15,000 for a given Z/D h . Nu values are higher at the stagnation point for all Z/D h and Re investigated. For lower Z/D h and higher Re, secondary peaks are observed in the heat transfer distributions. This may be attributed to fluid translating from laminar to turbulent flow on the target plate. Heat transfer characteristics are explained based on the simplified flow assumptions and the pressure data obtained using Differential pressure transducer and static pressure probe. Semi-empirical correlation for the Nusselt number in the stagnation region is proposed.
NASA Astrophysics Data System (ADS)
Sunderland, Zofia; Patorski, Krzysztof
2016-12-01
A big challenge for standard interferogram analysis methods such as Temporal Phase Shifting or Fourier Transform is a parasitic set of fringes which might occur in the analyzed fringe pattern intensity distribution. It is encountered, for example, when transparent glass plates with quasi-parallel surfaces are tested in Fizeau or Twyman-Green interferometers. Besides the beams reflected from the plate front surface and the interferometer reference the beam reflected from the plate rear surface also plays important role; its amplitude is comparable with the amplitude of other beams. In result we face three families of fringes of high contrast which cannot be easily separated. Earlier we proposed a competitive solution for flatness measurements which relies on eliminating one of those fringe sets from the three-beam interferogram and separating two remaining ones with the use of 2D Continuous Wavelet Transform. In this work we cover the case when the intensity of the reference beam is significantly higher than the intensities of two object beams. The main advantage of differentiating beam intensities is the change in contrast of individual fringe families. Processing of such three-beam interferograms is modified but also takes advantage of 2D CWT. We show how to implement this method in Twyman-Green and Fizeau setups and compare this processing path and measurement procedures with previously proposed solutions.
NASA Astrophysics Data System (ADS)
M, Adimurthy; Katti, Vadiraj V.
2017-02-01
Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a normal slot air jet is experimental investigated. Present study focuses on the influence of jet-to-plate spacing ( Z/D h ) (0.5-10) and Reynolds number (2500-20,000) on the fluid flow and heat transfer distribution. A single slot jet with an aspect ratio ( l/b) of about 22 is chosen for the current study. Infrared Thermal Imaging technique is used to capture the temperature data on the target surface. Local heat transfer coefficients are estimated from the thermal images using `SMART VIEW' software. Wall static pressure measurement is carried out for the specified range of Re and Z/D h . Wall static pressure coefficients are seen to be independent of Re in the range between 5000 and 15,000 for a given Z/D h . Nu values are higher at the stagnation point for all Z/D h and Re investigated. For lower Z/D h and higher Re, secondary peaks are observed in the heat transfer distributions. This may be attributed to fluid translating from laminar to turbulent flow on the target plate. Heat transfer characteristics are explained based on the simplified flow assumptions and the pressure data obtained using Differential pressure transducer and static pressure probe. Semi-empirical correlation for the Nusselt number in the stagnation region is proposed.
Mao, Y.; Besant, R.W.; Chen, H.
1999-07-01
An experimental investigation of frost growth on a flat, cold surface supplied by subfreezing, turbulent, humid, parallel flow of air is presented. The operating conditions are typical of many commercial freezers. A test loop was constructed to perform the tests, and the frost height, frost mass concentration, and cold surface heat flux were measured using specially designed and calibrated instrumentation. Twenty tests were done for steady operating conditions, each starting with no initial frost accumulation, and were run for two to six hours giving 480 data samples. Measured results show that the frost characteristics differ significantly with frost growth data taken previously for room temperature airflow. Depending on the temperature of the cold plate and the relative humidity of the subfreezing supply air, the frost could appear to be either smooth or rough. Smooth frost, which occurred at warmer plate temperatures and lower supply air relative humidities, gave rise to frost growth that was much thinner and denser than that for the rough, thick, low-density frost. Frost growth characteristics are correlated as a function of five independent variables (time, distance from the leading edge, cold plate temperature ratio, humidity ratio, and Reynolds number). These correlations are presented separately for the full data set, the rough frost data, and the smooth frost data.
An analytical investigation of transient effects on rewetting of heated thin flat plates
NASA Technical Reports Server (NTRS)
Platt, J. A.
1993-01-01
The rewetting of a hot surface is a problem of prime importance in the microgravity application of heat pipe technology, where rewetting controls the time before operations can be re-established following depriming of a heat pipe. Rewetting is also important in the nuclear industry (in predicting behavior during loss-of-coolant accidents), as well as in the chemical and petrochemical industries. Recently Chan and Zhang have presented a closed-form solution for the determination of the rewetting speed of a liquid film flowing over a finite (but long) hot plate subject to uniform heating. Unfortunately, their physically unreasonable initial conditions preclude a meaningful analysis of start-up transient behavior. A new nondimensionalization and closed-form solution for an infinitely-long, uniformly-heated plate is presented. Realistic initial conditions (step change in temperature across the wetting front) and boundary conditions (no spatial temperature gradients infinitely far from the wetting front) are employed. The effects of parametric variation on the resulting simpler closed-form solution are presented and compared with the predictions of a 'quasi-steady' model. The time to reach steady-state rewetting is found to be a strong function of the initial dry-region plate temperature. For heated plates it is found that in most cases the effect of the transient response terms cannot be neglected, even for large times.
NASA Technical Reports Server (NTRS)
Rai, Man Mohan
2017-01-01
The near wake of a flat plate is investigated via direct numerical simulations (DNS). Many earlier experimental investigations have used thin plates with sharp trailing edges and turbulent boundary layers to create the wake. This results in large theta divided by D (sub TE) values (theta is the boundary layer momentum thickness towards the end of the plate and D (sub TE) is the trailing edge thickness). In the present study the emphasis is on relatively thick plates with circular trailing edges (CTE) resulting in theta divided by D values less than one (D is the plate thickness and the diameter of the CTE), and vigorous vortex shedding. The Reynolds numbers based on the plate length and D are 1.255 x 10 (sup 6) and 10,000, respectively. Two cases are computed; one with turbulent boundary layers on both the upper and lower surfaces of the plate (statistically the same, symmetric wake, Case TT) and, a second with turbulent and laminar boundary layers on the upper and lower surfaces, respectively (asymmetric case, Case TL). The data and understanding obtained is of considerable engineering interest, particularly in turbomachinery where the pressure side of an airfoil can remain laminar or transitional because of a favorable pressure gradient and the suction side is turbulent. Shed-vortex structure and phase-averaged velocity statistics obtained in the two cases are compared here. The upper negative shed vortices in Case TL (turbulent separating boundary layer) are weaker than the lower positive ones (laminar separating boundary layer) at inception (a factor 1.27 weaker in terms of peak phase-averaged spanwise vorticity at first appearance of a peak). The upper vortices weaken rapidly as they travel downstream. A second feature of interest in Case TL is a considerable increase in the peak phase-averaged, streamwise normal intensity (random component) with increasing streamwise distance (x divided by D) that occurs nears the positive vortex cores. This behavior is
Capacitance Flatness Gauge Prototype
Pitas, A.; Angstadt, R.; /Fermilab
1986-03-20
The DO calorimeter has within it thousands of large plates. Our ability to construct the detector depends on the flatness of these plates. The performance of the detector depends on the flatness of the plates after they are assembled into a module. It has been proposed that the flatness of the plates before and after assembly could be determined by measuring capacitance. This device demonstrates the viability of using capacitance to measure the flatness of individual plates. No attempt has been made to extrapolate the results to measuring the flatness of the plates once they are in a module.
A summary report on the Flat-Plate Solar Array Project Workshop on Transparent Conducting Polymers
NASA Technical Reports Server (NTRS)
Kachare, R.; Moacanin, J.
1985-01-01
The proceedings and technical discussions of a workshop on Transparent Conducting Polymers (TCP) for solar cell applications are reported. This is in support of the Device Research Task of the Flat-Flate Solar Array Project. The workshop took place on January 11 and 12, 1985, in Santa Barbara, California. Participants included university and industry researchers. The discussions focused on the electronic and optical properties of TCP, and on experimental issues and problems that should be addressed for high-efficiency solar cell application.
Design of a photovoltaic central power station: flat-plate array
Not Available
1984-02-01
A design for a photovoltaic central power station using fixed flat-panel arrays has been developed. The 100 MW plant is assumed to be located adjacent to the Saguaro Power Station of Arizona Public Service. The design assumes high-efficiency photovoltaic modules using dendritic web cells. The modules are arranged in 5 MW subfields, each with its own power conditioning unit. The photovoltaic output is connected to the existing 115 kV utility switchyard. The site specific design allows detailed cost estimates for engineering, site preparation, and installation. Collector and power conditioning costs have been treated parametrically.
Postbuckling of flat unstiffened graphite-epoxy plates loaded in shear
NASA Technical Reports Server (NTRS)
Rouse, M.
1985-01-01
An experimental and analytical study was conducted of the postbuckling response and failure characteristics of 8-, 16-, and 24-ply unstiffened graphite/epoxy plates under shear loading, including orthotropic, quasi-orthotropic, entirely +, -45 deg ply, and (0/90)s-class plates. Postbuckling stiffness is noted to be influenced by the stacking sequence and by the inplane boundary condition imposed on the test section by a picture frame test fixture. The ratio of failure load to buckling load was higher for specimens that had higher width-to-thickness ratios. It is noted that high displacement gradients may induce transverse shear stresses, and that delamination was the failure mechanism for many of the 8-ply specimens. An adhesive failure between the composite specimen and metal edge reinforcements initiated failure of the 16- and 24-ply specimens.
Hakan Ozaltun; Pavel Medvedev
2014-11-01
The effects of the foil flatness on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation were studied. Monolithic plate-type fuels are a new fuel form being developed for research and test reactors to achieve higher uranium densities. This concept facilitates the use of low-enriched uranium fuel in the reactor. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. To evaluate the effects of the foil flatness on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate from RERTR-12 experiments (Plate L1P756) was considered. Both fabrication and irradiation processes of the plate were simulated by using actual irradiation parameters. The simulations were repeated for various foil curvatures to observe the effects of the foil flatness on the peak stress and strain magnitudes of the fuel elements. Results of fabrication simulations revealed that the flatness of the foil does not have a considerable impact on the post fabrication stress-strain fields. Furthermore, the irradiation simulations indicated that any post-fabrication stresses in the foil would be relieved relatively fast in the reactor. While, the perfectly flat foil provided the slightly better mechanical performance, overall difference between the flat-foil case and curved-foil case was not significant. Even though the peak stresses are less affected, the foil curvature has several implications on the strain magnitudes in the cladding. It was observed that with an increasing foil curvature, there is a slight increase in the cladding strains.
NASA Technical Reports Server (NTRS)
Joshi, S. M.; Groom, N. J.
1980-01-01
A finite element structural model of a 30.48 m x 30.48 m x 2.54 mm completely free aluminum plate is described and modal frequencies and mode shape data for the first 44 modes are presented. An explanation of the procedure for using the data is also presented. The model should prove useful for the investigation of controller design approaches for large flexible space structures.
NASA Astrophysics Data System (ADS)
Fedoul, Faical; Parras, Luis; Del Pino, Carlos; Fernandez-Feria, Ramon
2012-11-01
Wind tunnel experiments are conducted for the flow around both a single flat plate and a cascade of three parallel flat plates at different angles of incidence to compare their lift and drag coefficients in a range of Reynolds number about 105, and for two values of the aspect ratio of the flat plates. The selected cascade configuration is of interest for a particular type of tidal energy converter. The lift and drag characteristics of the central plate in the cascade are compared to those of the isolated plate, finding that there exist an angle of incidence, which depends on the Reynolds number and the aspect ratio, above which the effective lift of the plate in the cascade becomes larger than that of an isolated plate. These experimental results, which are also analyzed in the light of theoretical predictions, are used as a guide for the design of the optimum configuration of the cascade which extracts the maximum power from a tidal current for a given value of the Reynolds number. Supported by the Ministerio de Ciencia e Innovacion (Spain) Grant no. ENE2010-16851.
NASA Astrophysics Data System (ADS)
Finzel, Emily S.
field that provides evidence that a wide zone of diffuse deformation defines the present-day boundaries between the North America, Pacific, and Bering plates in Alaska and western Canada. In southern Alaska, boundary forces related to flat-slab subduction of the Yakutat microplate are the dominant driver for lithospheric deformation, whereas in central and northern Alaska and inboard parts of western Canada, buoyancy forces and basal tractions may be the dominant contributors.
NASA Astrophysics Data System (ADS)
Kim, Daehwan; Cheong, Cheolung
2012-10-01
of the semi-analytic model deviate more from the other two predictions as the spanwise wavenumber of the acoustic wave increases and the frequency decreases. On a basis of this observation, a formulation is derived for the error in the pressure jump across the flat-plate predicted by using the semi-analytic method. This formulation shows that the error is approximately inversely proportional to the sound speed in the spanwise direction of the concerned acoustic modes. This result quantitatively clarifies the limitations of applying the frequency-domain method of Wei & Cheong (2010) to the three-dimensional turbulence-cascade interaction problems. Secondly, the prediction results using the time-domain CAA method are compared with those from the full three-dimensional rectilinear model that is believed to be exact model for the cascade geometry considered in this paper. This comparison shows the good agreements between two predictions, which support the above arguments for the error and the successful application of the time-domain CAA methods. It is expected that these methods can be extended to the broadband noise problem in an annular cascade, including the nonlinear interaction of the real-airfoil cascade with the incident nonhomogeneous gust.
Rashidi, Mohammad M.; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J.; Freidoonimehr, Navid
2014-01-01
In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, , local Nusselt number, , and local Sherwood number are shown and explained through tables. PMID:25343360
NASA Technical Reports Server (NTRS)
Dumas, K. A. (Editor)
1985-01-01
A Workshop on Crystal Growth for High-Efficiency Silicon Solar Cells was held December 3 and 4, 1984, in San Diego, California. The Workshop offered a day and a half of technical presentations and discussions and an afternoon session that involved a panel discussion and general discussion of areas of research that are necessary to the development of materials for high-efficiency solar cells. Topics included the theoretical and experimental aspects of growing high-quality silicon crystals, the effects of growth-process-related defects on photovoltaic devices, and the suitability of various growth technologies as cost-effective processes. Fifteen invited papers were presented, with a discussion period following each presentation. The meeting was organized by the Flat-Plate Solar Array Project of the Jet Propulsion Laboratory. These Proceedings are a record of the presentations and discussions, edited for clarity and continuity.
Inagaki, T. ); Kitamura, K. )
1990-01-01
The turbulent heat transfer of combined forced and natural convection along a vertical flat plate was investigated experimentally both with aiding and opposing flows of air. Local heat-transfer coefficients were measured in the vertical direction. The results show that the local Nusselt numbers for aiding flow become smaller than those for the forced and the natural convection, while the Nusselt numbers for the opposing flow are increased significantly. These results are compared with the previous results for water. It has been found that the nondimensional parameter Z(= Gr{sub x}*/Nu{sub x}Re{sub x}){sup 2.7}Pr{sup 0.6} can predict the behavior of heat transfer both for air and water. Furthermore, the natural, forced, and combined convection regions can be classified in terms of the above parameter.
de Laat, T W G
2007-03-01
The eigenfrequencies of the potential-flow equilibria of a symmetric vortex pair behind an elliptic cylinder in uniform flow are calculated through the use of conformal mapping. These frequencies are shown to have values in agreement with measured Strouhal numbers reported in various papers. The special cases of the potential-flow equilibrium of a symmetric vortex pair behind a circular cylinder and the equilibrium behind a flat plate perpendicular to the uniform flow, are related to the measured Strouhal numbers of about 0.21 and 0.15, respectively. It is suggested that in the range of subcritical Reynolds numbers, 3x10(2) to 5x10(5) for the circular cylinder, a part of the drag is the result of the presence of a mean recirculation region in the near wake, which sheds vortices in the far wake and which is fed by vorticity from the cylinder wall.
Sforza, Eleonora; Calvaruso, Claudio; Meneghesso, Andrea; Morosinotto, Tomas; Bertucco, Alberto
2015-10-01
In this work, Nannochloropsis salina was cultivated in a continuous-flow flat-plate photobioreactor, working at different residence times and irradiations to study the effect of the specific light supply rate on biomass productivity and photosynthetic efficiency. Changes in residence times lead to different steady-state cell concentrations and specific growth rates. We observed that cultures at steady concentration were exposed to different values of light intensity per cell. This specific light supply rate was shown to affect the photosynthetic status of the cells, monitored by fluorescence measurements. High specific light supply rate can lead to saturation and photoinhibition phenomena if the biomass concentration is not optimized for the selected operating conditions. Energy balances were applied to quantify the biomass growth yield and maintenance requirements in N. salina cells.
NASA Technical Reports Server (NTRS)
Borden, C. S.; Volkmer, K.; Cochrane, E. H.; Lawson, A. C.
1984-01-01
A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems.
Funazaki, K.
1996-04-01
As the second part of the study, detailed hot-wire anemometry measurements of wake-affected boundary layers on the flat plate are made. These measurements are organized in order, first, to check the standpoint of the modeling of the wake-induced transition proposed in Part 1, and second, to observe wake-boundary layer interaction in detail from a viewpoint of direct and indirect effect of the wake passage upon turbulent spot generation within the boundary layer, as described by Walker (1993). The validity of the presumed state of the wake-affected boundary layer in the distance-time domain, which constitutes the basis of the transition model, is confirmed to great extent. However, it is also found that the criterion for the onset of the wake-induced transition adopted in Part 1 should be reconsidered. Some successful attempts are therefore made to specify the transition onset.
Bachok, Norfifah; Ishak, Anuar; Pop, Ioan
2013-01-01
The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity) differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface.
NASA Technical Reports Server (NTRS)
Phillips, M. J.
1986-01-01
Abstracts of final reports, or the latest quarterly or annual, of the Flat-Plate Solar Array (FSA) Project Contractor of Jet Propulsion Laboratory (JPL) in-house activities are presented. Also presented is a list of proceedings and publications, by author, of work connected with the project. The aim of the program has been to stimulate the development of technology that will enable the private sector to manufacture and widely use photovoltaic systems for the generation of electricity in residential, commercial, industrial, and Government applications at a cost per watt that is competitive with utility generated power. FSA Project activities have included the sponsoring of research and development efforts in silicon refinement processes, advanced silicon sheet growth techniques, higher efficiency solar cells, solar cell/module fabrication processes, encapsulation, module/array engineering and reliability, and economic analyses.
Bachok, Norfifah; Ishak, Anuar; Pop, Ioan
2013-01-01
The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity) differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface. PMID:23577156
An experimental study of tip shape effects on the flutter of aft-swept, flat-plate wings
NASA Technical Reports Server (NTRS)
Dansberry, Bryan E.; Rivera, Jose A., Jr.; Farmer, Moses G.
1990-01-01
The effects of tip chord orientation on wing flutter are investigated experimentally using six cantilever-mounted, flat-plate wing models. Experimentally determined flutter characteristics of the six models are presented covering both the subsonic and transonic Mach number ranges. While all models have a 60 degree leading edge sweep, a 40.97 degree trailing edge sweep, and a root chord of 34.75 inches, they are subdivided into two series characterized by a higher aspect ratio and a lower aspect ratio. Each series is made up of three models with tip chord orientations which are parallel to the free-stream flow, perpendicular to the model mid-chord line, and perpendicular to the free-stream flow. Although planform characteristics within each series of models are held constant, structural characteristics such as mode shapes and natural frequencies are allowed to vary.
Huang, Jianke; Feng, Fei; Wan, Minxi; Ying, Jiangguo; Li, Yuanguang; Qu, Xiaoxing; Pan, Ronghua; Shen, Guomin; Li, Wei
2015-04-01
A novel mixer was developed to improve the performance of flat-plate photobioreactors (PBRs). The effects of mixer were theoretically evaluated using computational fluid dynamics (CFD) according to radial velocity of fluid and light/dark cycles within reactors. The structure parameters, including the riser width, top clearance, clearance between the baffles and walls, and number of the chambers were further optimized. The microalgae culture test aiming at validating the simulated results was conducted indoor. The results showed the maximum biomass concentrations in the optimized and archetype reactors were 32.8% (0.89 g L(-1)) and 19.4% (0.80 g L(-1)) higher than that in the control reactor (0.67 g L(-1)). Therefore, the novel mixer can significantly increase the fluid velocity along the light attenuation and light/dark cycles, thus further increased the maximum biomass concentration. The PBRs with novel mixers are greatly applicable for high-efficiency cultivation of microalgae.
NASA Astrophysics Data System (ADS)
Tutkun, M.; Johansson, P. B. V.; George, W. K.; Stanislas, M.; Foucaut, J. M.; Kostas, J.; Coudert, S.; Delville, J.
2006-11-01
Zero pressure gradient flat plate boundary layer experiments have been performed in the 20 meter long test section of the Laboratoire de M'ecanique de Lille, LML, wind tunnel. Measurements were carried out at Reθ=10 000 and Reθ=20 000 using synchronized PIV and a hot wire anemometry rake. The boundary layer thickness at the measurement location was about 30 cm. A hot wire rake of 143 probes was placed in the test section of the wind tunnel to provide the time history of the boundary layer. 2 stereo PIV systems in the wallnormal-spanwise (YZ) plane, and 1 stereo PIV system to record in the streamwise-wallnormal (XY) were used. One high repetition PIV system was used in streamwise-spanwise (XZ) plane. The sampling frequency of the XZ PIV system was 3000 VF/s at Reθ=20 000 and 1500 VF/s at Reθ=10 000.
NASA Technical Reports Server (NTRS)
Madavan, Nateri K.
1995-01-01
This report deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux, were shown to compare well with experiment. The results indicate that the essential features of the transition process have been captured. The numerical method used here can be applied to complex geometries in a straightforward manner.
On a model of oscillations of a thin flat plate with a variety of mounts on opposite sides
NASA Astrophysics Data System (ADS)
Kal'menov, Tynysbek; Iskakova, Ulzada
2016-12-01
In this paper we consider a model case of stationary vibrations of a thin flat plate, one side of which is embedded, the opposite side is free, and the sides are freely leaned. In mathematical modeling there is a local boundary value problem for the biharmonic equation in a rectangular domain. Boundary conditions are given on all boundary of the domain. We show that the considered problem is self-adjoint. Herewith the problem is ill-posed. We show that the stability of solution to the problem is disturbed. Necessary and sufficient conditions of existence of the problem solution are found. Spaces of the ill-posedness of the considered problem are constructed.
On an ill-posed model of oscillations of a flat plate with a variety of mounts on opposite sides
NASA Astrophysics Data System (ADS)
Iskakova, Ulzada A.
2016-08-01
In this paper, we consider a model case of stationary vibrations of a thin flat plate, one side of which is embedded, the opposite side is free, and the sides are freely leaned. In mathematical modeling, there is a local boundary value problem for the biharmonic equation in a rectangular domain. Boundary conditions are given on all boundary of the domain. We show that the considered problem is self-adjoint. Herewith, the problem is ill-posed. We show that the stability of solution to the problem is disturbed. Necessary and sufficient conditions of existence of the problem solution are found. Spaces of the ill-posedness of the considered problem are constructed.
Rashidi, Mohammad M; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J; Freidoonimehr, Navid
2014-01-01
In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, [Formula: see text], local Nusselt number, [Formula: see text], and local Sherwood number [Formula: see text] are shown and explained through tables.
NASA Technical Reports Server (NTRS)
Madavan, Nateri K.
1995-01-01
The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner.
NASA Astrophysics Data System (ADS)
Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio
2002-05-01
The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.
1980-05-30
from two pieces of 4 ft square ’ bakelized paper board’ J in thick. This material was chosen as having a good and robust surface in the ’as-manufactured...AD-A093 459 ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND) F/B 20/4 THE REYNOLDS NUM4BER FOR TRANSITION ON A FLAT PLATE IN TH4E RAE 4-ETC(U) MAY...IAN[DARDk IUA A UNLIMITED v~’ BR75309 TIM. MEMO TEM. X ADO 1854 o 185 0ROYAL AIRCRAFT ESTABLISHMENT THE REYNOLDS NUMBER FOR TRANSITION ON A FLAT PLATE
Stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection
NASA Astrophysics Data System (ADS)
Qin, Shijie; Chu, Ning; Yao, Yan; Liu, Jingting; Huang, Bin; Wu, Dazhuan
2017-03-01
To investigate the stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection, both experiments and simulations of bubble drag reduction (BDR) have been conducted in this paper. Drag reductions at various flow speeds and air injection rates have been tested in cavitation tunnel experiments. Visualization of bubble flow pattern is implemented synchronously. The computational fluid dynamics (CFD) method, in the framework of Eulerian-Eulerian two fluid modeling, coupled with population balance model (PBM) is used to simulate the bubbly flow along the flat plate. A wide range of bubble sizes considering bubble breakup and coalescence is modeled based on experimental bubble distribution images. Drag and lift forces are fully modeled based on applicable closure models. Both predicted drag reductions and bubble distributions are in reasonable concordance with experimental results. Stream-wise distribution of BDR is revealed based on CFD-PBM numerical results. In particular, four distinct regions with different BDR characteristics are first identified and discussed in this study. Thresholds between regions are extracted and discussed. And it is highly necessary to fully understand the stream-wise distribution of BDR in order to establish a universal scaling law. Moreover, mechanism of stream-wise distribution of BDR is analysed based on the near-wall flow parameters. The local drag reduction is a direct result of near-wall max void fraction. And the near-wall velocity gradient modified by the presence of bubbles is considered as another important factor for bubble drag reduction.
The Turbulent Boundary Layer Near the Air-Water Interface on a Surface-Piercing Flat Plate
NASA Astrophysics Data System (ADS)
Washuta, Nathan; Masnadi, Naeem; Duncan, James H.
2015-11-01
Turbulent fluctuations in the vicinity of the water free surface along a flat, vertically oriented surface-piercing plate are studied experimentally using a laboratory-scale experiment. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. This belt device is mounted inside a large water tank with the water level set just below the top edge of the belt. The belt, rollers, and supporting frame are contained within a sheet metal box to keep the device dry except for one 6-meter-long straight test section between rollers. The belt is launched from rest with a 3- g acceleration in order to quickly reach steady state velocity. This creates a temporally evolving boundary layer analogous to the spatially evolving boundary layer created along a flat-sided ship moving at the same velocity, with a length equivalent to the length of belt that has passed the measurement region since the belt motion began. Cinematic Stereo PIV measurements are performed in planes parallel to the free surface by imaging the flow from underneath the tank in order to study the modification of the boundary layer flow field due to the effects of the water free surface. The support of the Office of Naval Research under grant N000141110029 is gratefully acknowledged.
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.
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 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.
The effect of free-stream turbulence on heat transfer from a flat plate
NASA Technical Reports Server (NTRS)
Sugawara, Sugao; Sato, Takashi; Komatsu, Hiroyasu; Osaka, Hiroichi
1958-01-01
Turbulence was generated by using screens, and the turbulence percentage was measured by a hot-wire anemometer both in the boundary layer and the free stream. The local heat-transfer coefficient was measured at 12 locations along the plate for the cases of various turbulence levels. The transition Reynolds number from laminar to turbulent flow decreases as the main-stream turbulence level increases. In the range of laminar heat transfer the effect of turbulence in the main flow was not great, but in the range of turbulent heat transfer the heat-transfer coefficient increases according to the increase of turbulence.
The dynamics of vortex shedding of flow past a vertical flat plate; LES studies
NASA Astrophysics Data System (ADS)
Velez, Carlos; Ilie, Marcel
2010-11-01
Although, apparently flow-induced vibrations represent a canonical problem, a complete understanding of the fluid-structure mechanism of interaction has not yet been achieved. One of the issues associated with flow induced vibrations stems from the vortex shedding phenomenon. It is well known that vortex streets are formed in the wake of bluff bodies over a wide range of Reynolds numbers. The periodic shedding of vortices may result in significant fluctuating loading on the body. When the shedding frequency is close to one of the characteristic frequencies of the body, the resonant oscillations of the body can be excited, causing damaging instabilities. Various studies regarding the vortex shedding resonance or "lock-on" phenomenon have been conducted. However, the effect of Reynolds number on the "lock-on" regime is yet to be fully understood. The "lock-on" phenomenon is of critical importance for the analysis of flow-induced vibration, when the aeroelastic response of the structure is considered. In the present research the influence of sweeping angle on the plate tip vortex formation is studied numerically using large eddy simulation (LES). The results show an increase in magnitude and size of vertical structures developed in the wake of the plate.
NASA Technical Reports Server (NTRS)
Jakubowski, A. L.; Schetz, J. A.; Moore, C. L.; Joag, R.
1985-01-01
An experimental study was conducted to determine surface pressure distributions on a flat plate with dual subsonic, circular jets exhausting from the surface into a crossflow. The jets were arranged in both side-by-side and tandem configurations and were injected at 90 deg and 60 deg angles to the plate, with jet-to-crossflow velocity ratio of 2.2 and 4. The major objective of the study was to determine the effect of a nonuniform (vs uniform) jet velocity profile, simulating the exhaust of a turbo-fan engine. Nonuniform jets with a high-velocity outer annulus and a low-velocity core induced stronger negative pressure fields than uniform jets with the same mass flow rate. However, nondimensional lift losses (lift loss/jet thrust lift) due to such nonuniform jets were lower than lift losses due to uniform jets. Changing the injection angle from 90 deg to 60 deg resulted in moderate (for tandem jets) to significant (for side-by-side jets) increases in the induced negative pressures, even though the surface area influenced by the jets tended to reduce as the angle decreased. Jets arranged in the side-by-side configuration led to significant jet-induced lift losses exceeding, in some cases, lift losses reported for single jets.
Mullick, S.C.; Samdarshi, S.K.
1988-11-01
A different approach to evaluate the top heat loss factor of a flat plate solar collector with a single glass cover is proposed. The equation for the heat loss factor in the analytical form is employed instead of the semi-empirical form hitherto employed for solar collectors. The glass cover temperature is, however, estimated by an empirical relation. (This relation replaces the empirical relation for the factor f of the earlier work). Values of the top heat loss factor calculated by this simple technique are within 3 percent (maximum error) of those obtained by iterative solution of the heat balance equations. There is an improvement in accuracy by a factor greater than five over the current semi-empirical equations. The range of variables covered is 50/sup 0/C to 150/sup 0/C in absorber plate temperature, 0.1 to 0.95 in absorber coating emittance, and 5 W/m/sup 2/C to 45 W/m/sup 2/C in wind heat-transfer coefficient. The effect of variation in air properties with temperature has been taken into account.
NASA Astrophysics Data System (ADS)
Chua, K. J.; Xu, J.; Cui, X.; Ng, K. C.; Islam, M. R.
2016-09-01
In this study the performance of an indirect evaporative cooling system (IECS) of cross-flow configuration is numerically investigated. Considering the variation of water film temperature along the flowing path and the wettability of the wet channel, a two-dimensional theoretical model is developed to comprehensively describe the heat and mass transfer process involved in the system. After comparing the simulation results with available experimental data from literature, the deviation within ±5 % proves the accuracy and reliability of the proposed mathematical model. The simulation results of the plate type IECS indicate that the important parameters, such as dimension of plates, air properties, and surface wettability play a great effect on the cooling performance. The investigation of flow pattern shows that cross-flow configuration of primary air with counter-flow of secondary air and water film has a better cooling performance than that of the parallel-flow pattern. Furthermore, the performance of a novel flat tube working as the separating medium is numerically investigated. Simulation results for this novel geometry indicate that the tube number, tube long axis and short axis length as well as tube length remarkably affect its cooling performance.