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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Cardiovascular system simulation in biomedical engineering education.

Use of complex cardiovascular system models, in conjunction with a large hybrid computer, in biomedical engineering courses. A cardiovascular blood pressure-flow model, driving a compartment model for the study of dye transport, was set up on the computer for use as a laboratory exercise by students who did not have the computer experience or skill to be able to easily set up such a simulation involving some 27 differential equations running at 'real time' rate. The students were given detailed instructions regarding the model, and were then able to study effects such as those due to septal and valve defects upon the pressure, flow, and dye dilution curves. The success of this experiment in the use of involved models in engineering courses was such that it seems that this type of laboratory exercise might be considered for use in physiology courses as an adjunct to animal experiments.

Rideout, V. C.↗
NASA NTRS1982

Determination of boundary shape of cooled porous region

The shape of a cooled porous wall section is found that will provide a uniform surface temperature, as dictated by material limitations, when the surface is subjected to spatially nonuniform heating. In the analysis, local temperatures and pressures in the porous material are expressed in terms of a potential function. From the imposed thermal conditions, this potential function is governed by the dual constraints of both its value and its normal derivative being specified along the heated surface. The unknown shape of this surface is obtained by meeting these dual conditions. The analytical method uses a generalized conformal mapping procedure that includes a curved boundary. The coolant flow can be compressible or incompressible, and its viscosity can depend on temperature.

Snyder, A.↗
NASA NTRS1985

A space-marching method for incompressible Navier-Stokes equations

This paper deals with the development of a space-marching method for incompressible flows. The method solves the continuity and momentum equations as a coupled system at each streamwise station. The character of the system of equations has been changed from elliptic to hyperbolic/parabolic in order to enable the equations to be marched in space. The present method has many advantages compared to the existing parabolic or space-marching methods for incompressible flow: (1) it avoids the solution of Poisson equations, (2) it conserves the mass flow with no additional computation, (3) it does not require the specification of an assumed pressure field when used in the prediction of duct flows. The present method can capture strong secondary velocities and strong transverse pressure gradients. Predictions of the flow through straight and curved ducts are in good agreement with analytical and experimental results.

Pouagare, M.↗
NASA NTRS1987

USC/AIAA student get away special project liquid droplet collector experiment

This experimental payload was developed in order to observe, in a micro-gravity vacuum environment, the characteristics and stability of a thin fluid film flowing across a slightly curved surface. The test apparatus was designed based upon various ground-based thin film investigations, combined with the constraints imposed by the rigors of launch and the space environment. Testing of the fluid test article at atmospheric pressure and in vacuum verified the design provisions employed concerning ultra-low inlet pressure pump construction, as well as confirming expected pressure losses in the system. During the course of hardware development and construction modifications were required; however, the overall payload configuration remained largely unchanged. This will allow for modification and reflight of the apparatus based upon the findings of the initial flight. The specific applications of this experiment include Liquid Droplet Radiator development and various forms of material transport in vacuum.

Levesque, Raymond J., II↗
NASA NTRS1944

Intercooler cooling-air weight flow and pressure drop for minimum drag loss

An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

Reuter, J George↗
NASA NTRS1994

Developments and applications of dynamic models for large eddy simulation of complex flows

The dynamic modeling procedure for large eddy simulation of turbulent flows is reviewed and recent developments in the theoretical aspects and applications are described. Methods for inclusion of backscatter of energy from small to large scale motions are presented. New formulations of the dynamic procedure are proposed which are optimized based on the subgrid scale flux vector or the energy dissipation rate instead of the subgrid scale stress tensor. Recent results from application of the model to forced isotropic turbulence with an inertial subrange, flow over a backward facing step at Reynolds number of 28000, and flow over a concave curved surface are presented.

Moin, P.↗
NASA NTRS2003

Revisiting the Least-squares Procedure for Gradient Reconstruction on Unstructured Meshes

The accuracy of the least-squares technique for gradient reconstruction on unstructured meshes is examined. While least-squares techniques produce accurate results on arbitrary isotropic unstructured meshes, serious difficulties exist for highly stretched meshes in the presence of surface curvature. In these situations, gradients are typically under-estimated by up to an order of magnitude. For vertex-based discretizations on triangular and quadrilateral meshes, and cell-centered discretizations on quadrilateral meshes, accuracy can be recovered using an inverse distance weighting in the least-squares construction. For cell-centered discretizations on triangles, both the unweighted and weighted least-squares constructions fail to provide suitable gradient estimates for highly stretched curved meshes. Good overall flow solution accuracy can be retained in spite of poor gradient estimates, due to the presence of flow alignment in exactly the same regions where the poor gradient accuracy is observed. However, the use of entropy fixes has the potential for generating large but subtle discretization errors.

Mavriplis, Dimitri J.↗
DOE OSTI2024

Ad-Mat: Adaptations of Mature Manufacturing Strategies for Accelerated Redox Flow Battery Deployment

The concept of the Ad-Mat approach is to leverage existing adjacent markets across a broad scope of technologies in order to reduce the manufacturing learning curve and ultimately accelerate redox flow battery (RFB) deployment at scale. Lithium-ion batteries (LIBs) are currently the dominant energy storage technology, and they came to technological maturity under unique market conditions when there was no meaningful competition in the consumer electronic and electric vehicle (EV) space. Today, alternative chemistries that may be technologically better-suited for long-duration storage applications are experiencing a high barrier to entry. This is in large part due to the substantial bias towards the scaled-up production and supply chain that now exists for LIBs. In the case of RFBs in particular, numerous analyses have suggested that RFBs should theoretically have a much lower system cost than LIBs - however, this relies on a mature and competitive manufacturing landscape, which has been extremely challenging to achieve for both flow batteries and other LIB competitors. At the moment, LIB alternatives tend to have isolated small-scale manufacturing pathways, which preclude the economies of scale that would be required to compete with the mature LIB industry. In the present state of the industry, niche manufacturing tools and approaches have evolved to support each alternative technology, such that there is substantial replication and duplication in effort. Continuing to pursue a strategy of isolated manufacturing processes/approaches for each LIB-alternative may never allow for at-scale deployment. In order for RFBs to meaningfully compete with LIBs in the realm of LDES, a new disruptive approach based on cross-industry learning and coordination is needed - and this is exactly what our Ad-Mat concept aims to tackle. In this re-envisioned manufacturing landscape, tools and processes from mature industries can be adapted and deployed across the range of alternative energy storage technologies. Adapting tools, equipment, processes, and industrial learning from mature industries to meet the technological requirements of RFBs would open new markets for existing OEMs in adjacent industries, would prevent unnecessary duplication and re-development, would improve efficiency across the manufacturing chain, and would ultimately support reduced costs and accelerated deployment of RFBs at scale.

adaptive manufacturing↗
NASA NTRS1986

A theory for turbulent curved wall jets

A simple theoretical model is proposed to describe the flow of a turbulent wall jet along a curved surface into a quiescent atmosphere. An integral method is used to solve the momentum equation and identifies three contributions to the spreading rate of the wall jet: (1) turbulent diffusion in the wall jet; (2) wall curvature; and (3) rate of change of wall curvature. Closed from approximate solutions are found for the case of a plane wall, a circular cylinder, and a logarithmic spiral surface. Comparison with experimental data for these three cases is made showing good agreement.

Roberts, Leonard↗
NASA NTRS2008

Calibrating the Helium Pressurization System for the Space Shuttle Liquid-Hydrogen Tank

Analysis of the results from the STS-114 tanking tests and subsequent launch called into question existing thermal and mass models of helium pressurization of the liquid hydrogen tank. This hydrogen tank, which makes up the bottom two-thirds of the External Tank, is pressurized prior to launch to avoid cavitation in the Shuttle Main Engine pumps. At about 2 minutes prior to launch, the main vent valve is closed, and pressurized helium flows into the tank ullage space to achieve set point pressure. As the helium gas cools, its pressure drops, calling for additional helium. Subsequent helium flows are provided in short, timed pulses. The number of pulses is taken as a rough leak indicator. An analysis of thermal models by Marshall Space Flight Center showed considerable uncertainty in the pressure-versus-time behavior of the helium ullage space and the ability to predict the number of pulses normally expected. Kennedy Space Center proposed to calibrate the dime-sized orifice, which together with valves, controls the helium flow quantity (Figure 1). Pressure and temperature sensors were installed to provide upstream and downstream measurements necessary to compute flow rate based on the orifice discharge coefficient. An assessment of flow testing with helium indicated an extremely costly use of this critical resource. In order to reduce costs, we proposed removing the orifices from each Mobile Launcher Platform (MLP) and asking Colorado Engineering Experiment Station Inc. (CEESI) to calibrate the flow. CEESI has a high-pressure air flow system with traceable flow meters capable of handling the large flow rates. However, literature research indicated that square-edged orifices of small diameters often exhibit significant hysteresis and nonrepeatability in the vicinity of choked or sonic flow. Fortunately, the MLP orifices behaved relatively well in testing (Figure 2). Using curve fitting of the air-flow data, in conjunction with ASME orifice modeling equations, a method of relating the helium mass flow to measured air flow data was obtained. This analysis showed that the highest uncertainty in flow occurred in the vicinity of the choking pressure ratio, as would be expected. In addition, analysis of typical flow pulses showed that most of the helium flow occurred either well below or well above this uncertain area. The final result is the ability to provide postlaunch estimates of helium mass flows that are within 1.5 percent of the actual value.

Source record↗
NASA NTRS2019

Effect of Grazing Flow on Grooved Over-the-Rotor Acoustic Casing Treatments

After testing grooved over-the-rotor acoustic casing treatments on a turbofan rotor, a follow-on study was performed to investigate the effect of flow on grooved acoustic liners. The experiment was performed to understand the scaling of acoustic liner absorption with grazing flow and investigate a potential noise source from grooved acoustic liners. Acoustic liner absorption and reflection characteristics were quantified by examining the reduction in amplitude of a plane wave traveling over 2 inch liners with grazing flow. For all liners tested, as the grazing flow Mach number is increased, the absorption curves broadened and the frequency of peak absorption decreased. Grazing flow over a series of grooves was found to generate resonances up to 152 dB sound pressure level. Adding acoustic treatment to the bottom of these grooves was found to reduce the magnitude of this resonance by up to 10 dB sound pressure level and increase its frequency by up to 10%. The quantification of the grazing flow effect and identification of a mechanism behind the noise penalty from the prior turbofan rotor experiment will aid in the design of future over-the-rotor treatments.

acoustic↗
NASA NTRS1985

Computer studies of baroclinic flow

Programs necessary for computing the transition curve on the regime diagram for the atmospheric general circulation experiment (AGOE) were completed and used to determine the regime diagram for the rotating annulus and some axisymmetric flows for one possible AGOE configuration. The effect of geometrical constraints on the size of eddies developing from a basic state is being examined. In AGOE, the geometric constraint should be the width of the shear zone or the baroclinic zone. Linear and nonlinear models are to be used to examine both barotropic and baroclinic flows. The results should help explain the scale selection mechanism of baroclinic eddies in the atmosphere experimental models such as AGOE, and the multiple vortex phenomenon in tornadoes.

Gall, R.↗
NASA NTRS1987

Heat transfer and fluid mechanics measurements in transitional boundary layers on convex-curved surfaces

The test section of the present experiment to ascertain the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii, R. Attention is given to results for the cases of R = infinity, 180 cm, and 90 cm, each with two freestream turbulence intensity levels. While the mild convex curvature of R = 180 cm delays transition, further bending to R = 90 cm leads to no signifucant further delay of transition. Cases with both curvature and higher freestream disturbance effects exhibit the latter's pronounced dominance. These data are pertinent to the development of transition prediction models for gas turbine blade design.

Wang, T.↗
NASA NTRS1951

The method of characteristics for the determination of supersonic flow over bodies of revolution at small angles of attack

The method of characteristics has been applied for the determination of the supersonic-flow properties around bodies of revolution at a small angle of attack. The system developed considers the effect of the variation of entropy due to the curved shock and determines a flow that exactly satisfies the boundary conditions in the limits of the simplifications assumed. Two practical methods for numerical calculations are given. (author)

Ferri, Antonio↗
NASA NTRS1974

Transmission of wave energy in curved ducts

Investigation of the ability of circular bends to transmit acoustic energy flux. A formulation of wave-energy flow is developed for motion in curved ducts. A parametric study over a range of frequencies shows the ability of circular bends to transmit energy in the case of perfectly rigid walls.

Rostafinski, W.↗
NASA NTRS1999

A fluid--structure interaction finite element analysis of pulsatile blood flow through a compliant stenotic artery

A new model is used to analyze the fully coupled problem of pulsatile blood flow through a compliant, axisymmetric stenotic artery using the finite element method. The model uses large displacement and large strain theory for the solid, and the full Navier-Stokes equations for the fluid. The effect of increasing area reduction on fluid dynamic and structural stresses is presented. Results show that pressure drop, peak wall shear stress, and maximum principal stress in the lesion all increase dramatically as the area reduction in the stenosis is increased from 51 to 89 percent. Further reductions in stenosis cross-sectional area, however, produce relatively little additional change in these parameters due to a concomitant reduction in flow rate caused by the losses in the constriction. Inner wall hoop stretch amplitude just distal to the stenosis also increases with increasing stenosis severity, as downstream pressures are reduced to a physiological minimum. The contraction of the artery distal to the stenosis generates a significant compressive stress on the downstream shoulder of the lesion. Dynamic narrowing of the stenosis is also seen, further augmenting area constriction at times of peak flow. Pressure drop results are found to compare well to an experimentally based theoretical curve, despite the assumption of laminar flow.

Non-NASA Center↗
NASA NTRS1983

Aerothermal modeling program, phase 1

The combustor performance submodels for complex flows are evaluated. The benchmark test cases for complex nonswirling flows are identified and analyzed. The introduction of swirl into the flow creates much faster mixing, caused by radial pressure gradients and increase in turbulence generation. These phenomena are more difficult to predict than the effects due to geometrical streamline curvatures, like the curved duct, and sudden expansion. Flow fields with swirl, both confined and unconfined are studied. The role of the dilution zone to achieve the turbine inlet radial profile plays an important part, therefore temperature field measurements were made in several idealized dilution zone configurations.

Srinivasan, R.↗
NASA NTRS1988

Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

Elovic, E.↗