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Results for “COMPRESSIBLE FLUID”

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 NTRS2000

Adiabatic Compression of Oxygen: Real Fluid Temperatures

The adiabatic compression of oxygen has been identified as an ignition source for systems operating in enriched oxygen atmospheres. Current practice is to evaluate the temperature rise on compression by treating oxygen as an ideal gas with constant heat capacity. This paper establishes the appropriate thermodynamic analysis for the common occurrence of adiabatic compression of oxygen and in the process defines a satisfactory equation of state (EOS) for oxygen. It uses that EOS to model adiabatic compression as isentropic compression and calculates final temperatures for this system using current approaches for comparison.

Barragan, Michelle↗
NASA NTRS1991

Theoretical and computational dynamics of a compressible flow

An introduction to the theoretical and computational fluid dynamics of a compressible fluid is presented. The general topics addressed include: thermodynamics and physical properties of compressible fluids; 1D flow of an inviscid compressible fluid; shock waves; fundamental equations of the dynamics of a compressible inviscid non-heat-conducting and radiating fluid, method of small perturbations, linearized theory; 2D subsonic steady potential flow; hodograph and rheograph methods, exact solutions of 2D insentropic steady flow equations, 2D steady transonic and hypersonic flows, method of characteristics, linearized theory of 3D potential flow, nonlinear theory of 3D compressibe flow, anisentropic (rotational) flow of inviscid compressible fluid, electromagnetogasdynamics, multiphase flows, flows of a compressible fluid with transport phenomena.

Pai, Shih-I↗
DOE OSTI2025

Fluid-like shock compression of dilute polymer nanocomposites

The shock Hugoniot of heterogenous mixtures of discrete particles has been experimentally investigated for porous agglomerates and fluids, while the study of full-density solids has been primarily limited to compressed powders and high-dimensional composites. By dispersing ceria nanoparticles in a polyethylene matrix, we are able to examine the hydrodynamic behavior of a nonporous, heterogenous solid in thermal equilibrium during weak shock compression. Phase-driven discontinuities in the Hugoniot particle velocity–shock velocity (u−D) relationship of pure polyethylene are replicated in the nanocomposites but are shifted to lower velocity and to higher pressure with higher particle concentration. The results are explained using an isothermal, two-velocity fluid model under the hydrodynamic approximation. The model, which assumes a theoretical equation-of-state for ceria and either a low-order or high-order fit to the measured polyethylene Hugoniot, reasonably predicts the Hugoniot for two different polyethylene/ceria nanocomposites. Using the model, the mixture Hugoniot is shown to be insensitive to the Hugoniot of the stiffer constituent when the moduli are sufficiently disparate, while dependence on particle density and volume fraction is preserved through fluid-like motion.

Moore, Nathan W. [Sandia National Laboratories (SN↗
NASA NTRS2009

Efficacy of Compression Garments to Simulate Fluid Shifts during Lunar Bedrest

The effectiveness of JOBST(Registered TradeMark) compression stockings for fluid redistribution was examined in the lunar bed rest analog based on Digital Astronaut computer model predictions. NASA's future goals include missions to the moon which will require extended exposure to the lunar gravity environment. To prepare for these missions, physiological adaptations in various systems must be resolved. A bed rest at a 10 degree head-up tilt was used to simulate lunar gravity. Plasma volume (PV) loss may cause some of the cardiovascular adaptations which occur during space flight so PV is measured in the bed rest analog to evaluate fluid loss. PV varies from individual to individual so PV index (PVI) is used to determine the magnitude and time course of fluid shift and cardiovascular adaptation to 1/6 g. The Digital Astronaut, a computer simulation tool, predicts a 6% PV loss during an extended simulated lunar mission for a male with a body surface area of 1.95 m(exp 2). Simple geometry calculations suggest that 10 degree head-up tilt is most useful for simulated measurement of deconditioning in bone and muscle, however, 2 degree head-up tilt may best imitate cardiovascular fluid shifts. In order to reconcile these different models, compression stocking must be used in the 10 degree paradigm to better approximate expected cardiovascular changes.

Brinley, Alaina↗
NASA NTRS1992

Compressible and incompressible fluid seals: Influence on rotordynamic response and stability

The flow field inside a whirling annular seal operating a Reynolds numbers of 12,000 and 24,000 and a Taylor number of 6,600 was measured. The rotor was mounted eccentric (50 percent) upon the facilities shaft which resulted in a circular orbit at a whirl ratio of 1.0. Three papers which summarize the work were written and are presented. Addition measurements were performed for the annular seal operating at an eccentricity ratio of 10 percent for Re = 24,000 and Ta = 6,600. A labyrinth seal was also installed into the facility and operated at an eccentricity ratio of 50 percent at the same Reynolds and Taylor numbers. These data are currently being reduced and analyzed.

Thames, Howard D.↗
DOE OSTI2024

Fuel driven near isothermal compressor

A gas compressor system includes a compression liquid holding tank in fluid communication with a combustion tank. A combustible fluid is directed to the combustion tank. An ignition system is provided for igniting the combustible fluid. A compression liquid flows between the liquid holding tank, the combustion tank, and a compression tank. A compressible gas is provided in the compression tank. The ignition of the combustible fluid drives the compression liquid from the combustion tank to the compression tank, compressing the compressible liquid. An HVAC&R system and a method of compressing gas are also disclosed.

Momen, Ayyoub Mehdizadeh↗
NASA NTRS2003

Enhancement of Mixing and Heat Transfer by Corrugated Permeable Walls

A re-circulation method that is based on the static pressure recovery in the divergent part of a converging-diverging flow channel is discussed. This method can be used to design a static device that can be used to increase the residence time of the fluid and the mixing in the transverse and/or flow directions in compressible and incompressible fluids flowing at subsonic velocities. The device with external reverse flow channels will produce mixing in both transverse and flow directions. If mixing in the flow direction is not desired, the concept can be used to design an insert to provide only transverse mixing. Theoretical relationships for a re-circulating one-dimensional incompressible flow around a converging-diverging channel were obtained. Attempts at numerical simulation of re-circulation in compressible fluids were not successful. Qualitative experimental verification of re-circulating flows for incompressible and compressible fluids were obtained.

Gilinsky, M.↗
DOE OSTI2025

Comparison of Artificial Compressibility Methods for Coupled Laminar Fluid Flow and Heat Transfer

Artificial compressibility (AC) methods for incompressible flows perturb the mass continuity equation by the time derivative of the pressure field to achieve direct coupling between pressure and velocity without the need for a projection method. Several variations of the original AC method have been proposed (e.g., the entropically damped artificial compressibility [EDAC] method) that can, in some scenarios, improve on the original model. In this paper, we methodically compare the results of the original AC model and the EDAC model for both steady-state and transient problems with coupling between the momentum and energy equations. We demonstrate that the EDAC model and the AC model yield similar numerical results, and the EDAC model is 10%-20% faster than the AC model for a given problem.

Oz, Furkan [ORNL] (ORCID:0000000265831724)↗
NASA NTRS1990

Critical speeding up in pure fluids

The extreme compressibility of a pure fluid near its critical point significantly affects its bulk dynamic response to temperature changes through adiabatic processes. Equations that describe the dynamics in the absence of gravity are developed, and the magnitude of the effect is illustrated with numerical solutions in one dimension. The results are remarkable: 5 mm of critical xenon, quenched from 20 to 10 mK above its critical temperature, cools by over 99 percent in less than 5 s. Moreover, adiabatic cooling is faster when the fluid is closer to the critical point.

Boukari, Hacene↗
DOE OSTI2026

Lagrange-Remap strategy for multi-material fluid-solid simulations using compressive limiters

In the present work, the Lagrange-Remap strategy proposed in [1] is extended to multi-material fluid-solid simulations. Both hypo-elastic and hyper-elastic material models are considered to describe the mechanical behavior of the solids. In practice, the deviatoric stress tensor (for hypo-elastic materials) and the left Cauchy-Green tensor (for isotropic hyper-elastic materials) are remapped, while the use of compressive limiters effectively reduces numerical diffusion during the remapping step. The simplicity of this diffuse interface approach is emphasized in the context of multi-material fluid-solid simulations. A series of Lagrange-Remap test cases, involving both solids and fluids, are conducted and compared with reference Lagrangian simulations, demonstrating the robustness and accuracy of the overall numerical strategy.

Compressive limiters↗
DOE OSTI2025

Real-fluid behavior in rapid compression machines: Does it matter?

Rapid compression machines (RCMs) have been extensively used to quantify fuel autoignition chemistry and validate chemical kinetic models at high-pressure conditions. Historically, the analyses of experimental and modeling RCM autoignition data have been conducted based on the adiabatic core hypothesis with ideal gas assumption, where real-fluid behavior has been completely overlooked, though this might be significant at common RCM test conditions. Here, this work presents a first-of-its-kind study that addresses two significant but overlooked questions for autoignition studies within RCMs in the fundamental combustion community: (i) experiment-wise, can unaccounted-for real-fluid behavior in RCMs affect the interpretation and analysis of RCM experimental data? and (ii) simulation-wise, can unaccounted-for real-fluid behavior in RCMs affect RCM autoignition modeling and the validation of chemical kinetic models? To this end, theories for real-fluid isentropic change are newly proposed and derived based on high-order Virial EoS, and are further incorporated into an effective-volume real-fluid autoignition modeling framework newly developed for RCMs. With detailed analyses, the strong real-fluid behavior in representative RCM tests is confirmed, which can greatly influence the interpretation of RCM autoignition experiments, particularly the determination of end-of-compression temperature and evolution of the adiabatic core in the reaction chamber. Furthermore, real-fluid RCM modeling results reveal that considerable error can be introduced into simulating RCM autoignition experiments when following the community-wide accepted effective-volume approach by assuming ideal-gas behavior, which can be as high as 64% in the simulated ignition delay time at compressed pressure of 125 bar and lead to contradictory validation results of chemical kinetic models. Therefore, we recommend the community to adopt frameworks with real-fluid behavior fully accounted for (e.g., the one developed in this study) to analyze and simulate past and future RCM experiments, so as to avoid misinterpretation of RCM autoignition experiments and eliminate the potential errors that can be introduced into the simulation results with the existing RCM modeling frameworks.

High-order Virial equation of state↗
NASA NTRS1955

The Compressible Laminar Boundary Layer with Fluid Injection

A solution of the equations of the compressible laminar boundary layer including the effects of transpiration cooling is presented. The analysis applies to the flow over an isothermal porous plate with a velocity of fluid injection proportional to the reciprocal of the square root of the distance from the leading edge. The effect of several flow parameters on coolant-flow rates is discussed with the aid of representative examples. A stability analysis indicates that, although transpiration cooling requires a lower surface temperature for stable flow than does internal wall cooling, this lower temperature can be obtained with a smaller expenditure of coolant.

Low, George M↗
NASA NTRS1950

Method of designing cascade blades with prescribed velocity distributions in compressible potential flows

By use of the assumption that the pressure-volume relation is linear, a solution to the problem of designing a cascade for a given turning and with a prescribed velocity distribution along the blade in a potential flow of a compressible perfect fluid was obtained by a method of correspondence between potential flows of compressible and incompressible fluids. The designing of an isolated airfoil with a prescribed velocity distribution along the airfoil is considered as a special case of cascade. If the prescribed velocity distribution is not theoretically attainable, the method provides a means of modifying the distribution so as to obtain a physically significant blade shape. Numerical examples are included.

Costello, George R↗
NASA NTRS1953

Application of a Channel Design Method to High-Solidity Cascades and Tests of an Impulse Cascade with 90 Degrees of Turning

A technique is developed for the application of a channel design method to the design of high-solidity cascades with prescribed velocity distributions as a function of arc length along the blade-element profile. The technique is applied to both incompressible and subsonic compressible, nonviscous, irrotational fluid motion. For compressible flow, the ratio of specific heats is assumed equal to -1.0. An impulse cascade with 90 degree turning was designed for incompressible flow and was tested at the design angle of attack over a range of downstream Mach number from 0.2 to coke flow. To achieve good efficiency, the cascade was designed for prescribed velocities and maximum blade loading according to limitations imposed by considerations of boundary-layer separation.

Stanitz, John D↗
NASA NTRS1982

Free vibration analysis of coupled fluid-structure systems

An efficient numerical technique for the eigenvalue solution in the free vibration analysis of compressible fluid-structure coupled systems is presented. The fluid is assumed to be compressible in nature and the incompressible problem is only a special case of the present generalized algorithm. A natural frequency analysis of the structure in the absence of any fluid is achieved by a combined Sturm sequence and inverse iteration technique that computes only the required eigenvalues and vectors. A special inverse iteration scheme is then developed for the coupled system that uses the computed eigenvalues as starting iteration values for convergence. Numerical results obtained by solving a number of standard test cases indicate the pattern of root convergence corresponding to various simplifying assumptions.

Gupta, K. K.↗