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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1952

Detailed computational procedure for design of cascade blades with prescribed velocity distributions in compressible potential flows

A detailed step-by-step computational outline is presented for the design of two-dimensional cascade blades having a prescribed velocity distribution on the blade in a potential flow of the usual compressible fluid. The outline is based on the assumption that the magnitude of the velocity in the flow of the usual compressible nonviscous fluid is proportional to the magnitude of the velocity in the flow of a compressible nonviscous fluid with linear pressure-volume relation.

Costello, George R↗
NASA NTRS1974

Fluid-structure finite-element vibrational analysis

A fluid finite element has been developed for a quasi-compressible fluid. Both kinetic and potential energy are expressed as functions of nodal displacements. Thus, the formulation is similar to that used for structural elements, with the only differences being that the fluid can possess gravitational potential, and the constitutive equations for fluid contain no shear coefficients. Using this approach, structural and fluid elements can be used interchangeably in existing efficient sparse-matrix structural computer programs such as SPAR. The theoretical development of the element formulations and the relationships of the local and global coordinates are shown. Solutions of fluid slosh, liquid compressibility, and coupled fluid-shell oscillation problems which were completed using a temporary digital computer program are shown. The frequency correlation of the solutions with classical theory is excellent.

Feng, G. C.↗
NASA NTRS1984

Fast solutions to the steady state compressible and incompressible fluid dynamic equations

For low speed flows the use of the compressible fluid dynamic equations is inefficient. The use of an explicit scheme requires delta t to be bounded by 1/c. However, the physical parameters change over time scales of order 1/u which is much larger. Hence, it is not appropriate to use explicit schemes for very subsonic flows. Implicit schemes are hard to vectorize and frequently do not converge quickly for very subsonic flows. If one is only interested in the steady state then a minor change to an existing code can greatly increase the efficiency of an explicit method. Even when using an implicit method the proposed changes increase the efficiency of the scheme. The Euler equations for low speed flows will be considered first and then incompressible flows. The method is generalized to include viscous effects. Supersonic flow is accelerated by essentially decoupling the equations.

Turkel, E.↗
NASA NTRS1974

Thermoacoustic convection of fluids in low gravity

The heat flow in a confined perfect gas in low gravity is investigated, including the effects of conduction and thermal convection. Buoyancy-driven flow is neglected, due to the low-gravity environment, but the effect of thermoacoustic motion due to fluid compressibility is included. One-dimensional mathematical models are constructed from the conservation equations for a compressible, viscous, heat-conducting fluid. A conservative, time-dependent finite-difference method is used to generate numerical solutions on a digital computer. Problems for flat plates and cylindrical segments are solved for specified thermal boundary conditions. Numerical results are given which indicate that thermoacoustic convection can significantly increase the transient heat flow over conduction model predictions for cases where a confined gas is rapidly heated.

Spradley, L. W.↗
NASA NTRS2005

Computing Thermal Effects of Cavitation in Cryogenic Liquids

A computer program implements a numerical model of thermal effects of cavitation in cryogenic fluids. The model and program were developed for use in designing and predicting the performances of turbopumps for cryogenic fluids. Prior numerical models used for this purpose do not account for either the variability of properties of cryogenic fluids or the thermal effects (especially, evaporative cooling) involved in cavitation. It is important to account for both because in a cryogenic fluid, the thermal effects of cavitation are substantial, and the cavitation characteristics are altered by coupling between the variable fluid properties and the phase changes involved in cavitation. The present model accounts for both thermal effects and variability of properties by incorporating a generalized representation of the properties of cryogenic fluids into a generalized compressible-fluid formulation for a cavitating pump. The model has been extensively validated for liquid nitrogen and liquid hydrogen. Using the available data on the properties of these fluids, the model has been shown to predict accurate temperature-depression values.

Hosangadi, Ashvin↗
DOE OSTI2025

Undulating transducer for energy harnessing and propulsion apparatuses, methods and systems

Embodiments disclosed may serve the function of a pump, a generator, or a propulsion system. Two flexible fins are coupled via their longitudinal inner edges to fin coupling modules. An external fluid flow causes traveling fin undulations. The angle of the fins relative to each other changes as undulations travel along the fins which can be translated through the fin coupling modules into mechanical work, powered by the external fluid flow. The mechanical work of the fin coupling modules may be the cyclical extension and contraction of pistons or bellows incorporated into the fin coupling modules, which may draw ambient fluid during their extension cycles and compress fluid during their contraction cycles to create a pump. The pistons or bellows may also be sealed from ambient fluid but connected through conduits through which contained fluid is exchanged in a continuous circulation of fluid to power a pump or a turbine.

Filardo, Benjamin Pietro↗
NASA NTRS1965

Coaxial capacitor used to determine fluid density

Sensing device measures directly the density of compressible fluid existing simultaneously in both liquid and gaseous phases. The device is comprised of a capacitor connected as one leg of a bridge circuit, a power source, and an indicator calibrated to indicate density as a direct measurement.

Atkisson, E. A.↗
NASA NTRS1995

Pressure updating methods for the steady-state fluid equations

We consider the steady state equations for a compressible fluid. Since we wish to solve for a range of speeds we must consider the equations in conservation form. For transonic speeds these equations are of mixed type. Hence, the usual approach is to add time derivatives to the steady state equations and then march these equations in time. One then adds a time derivative of the density to the continuity equation, a derivative of the momentum to the momentum equation and a derivative of the total energy to the energy equation. This choice is dictated by the time consistent equations. However, since we are only interested in the steady state this is not necessary. Thus we shall consider the possibility of adding a time derivative of the pressure to the continuity equation and similar modifications for the energy equation. This can then be generalized to adding combinations of time derivatives to each equation since these vanish in the steady state. When using acceleration techniques such as residual smoothing, multigrid, etc. these are applied to the pressure rather than the density. Hence, the code duplicates the behavior of the incompressible equations for low speeds.

Fiterman, A.↗
NASA NTRS1972

Thermodynamic and fluid-dynamic concepts

Some of the fundamental concepts of thermodynamics and compressible fluid mechanics are reviewed. The concepts treated are those that are considered necessary to analyze the flow and energy transfer processes occurring in a turbine.

Glassman, A. J.↗
NASA NTRS2006

Program for Analyzing Flows in a Complex Network

Generalized Fluid System Simulation Program (GFSSP) version 4 is a general-purpose computer program for analyzing steady-state and transient flows in a complex fluid network. The program is capable of modeling compressibility, fluid transients (e.g., water hammers), phase changes, mixtures of chemical species, and such externally applied body forces as gravitational and centrifugal ones. A graphical user interface enables the user to interactively develop a simulation of a fluid network consisting of nodes and branches. The user can also run the simulation and view the results in the interface. The system of equations for conservation of mass, energy, chemical species, and momentum is solved numerically by a combination of the Newton-Raphson and successive-substitution methods.

Majumdar, Alok Kumar↗
NASA NTRS1991

The equations of nearly incompressible fluids. I - Hydrodynamics, turbulence, and waves

An attempt is made to develop a more general theory of nearly incompressible fluids that can then be applied to many different fields. A perturbation expansion is developed for the fully compressible fluid equations which, in the limit of low Mach number (sound or Alfvenic Mach number), reduce to the appropriate incompressible fluid equations. The method developed derives modified systems of fluid equations in which the compressibility effects are admitted only weakly in terms of the incompressible hydrodynamic solutions ('nearly incompressible hydrodynamics'). Molecular viscosity is included self-consistently, and the role of thermal conduction in an ideal fluid is also considered. With heat conduction included, two distinct routes to incompressibility are found to be possible, distinguished according to the relative magnitudes of the temperature, density, and pressure fluctuations.

Zank, G. P.↗
NASA NTRS1982

Magnetohydrodynamic equilibrium. III - Helically symmetric fields. IV - Nonequilibrium of nonsymmetric hydrodynamic topologies

It is pointed out that plasma confinement in stable equilibrium states constitutes a fundamental and still unresolved question in plasma astrophysics and thermonuclear fusion research. The problem has two parts related to the equilibrium states themselves and their mechanical stability. The question of the existence of general solutions of the field and fluid equations for the steady dynamical interaction of inviscid compressible fluids of high electrical conductivity with magnetic and gravity fields is considered. In the absence of fluid motions, the presented equations become the familiar equations of magnetostatics supplemented by an equation of state. Starting from this simplest case of magnetostatic equilibrium, the investigation proceeds to the more complex case of magnetohydrodynamic equilibrium. Examples of helically symmetric fields are presented to illustrate the use of the formulation for treating the dynamics of helically symmetric hydromagnetic flows.

Tsinganos, K. C.↗