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Results for “Steady flows”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Development of a spinning wave heat engine

A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.

Zinn, B. T.↗
NASA NTRS1994

Steady potential solver for unsteady aerodynamic analyses

Development of a steady flow solver for use with LINFLO was the objective of this report. The solver must be compatible with LINFLO, be composed of composite mesh, and have transonic capability. The approaches used were: (1) steady flow potential equations written in nonconservative form; (2) Newton's Method; (3) implicit, least-squares, interpolation method to obtain finite difference equations; and (4) matrix inversion routines from LINFLO. This report was given during the NASA LeRC Workshop on Forced Response in Turbomachinery in August of 1993.

Hoyniak, Dan↗
NASA NTRS1987

Simple numerical method for predicting steady compressible flows

The present numerical method for the solution of the isenthalpic form of the governing equations for compressible viscous and inviscid flows has its basis in the concept of flux vector splitting in its implicit form, and has been tested in the cases of several difficult viscous and inviscid configurations. An acceleration of time-marching to steady state is accomplished by implementing a multigrid procedure which effectively increases the convergence rate. The steady state results obtained are largely of good quality, and required only short computational times.

Von Lavante, E.↗
NASA NTRS1983

Digital analysis of narrow-band imagery of the Cygnus Loop

Calibrated surface brightness and spectral line ratio maps which involve emission from six different ionic species are derived from the digital analysis of narrow passband direct imagery of a field in the southeast part of the Cygnus Loop SNR, and the spatial structure is categorized on the basis of the presence or absence of features in images isolating different emission lines. While features present in all emission lines are found to have spectral behavior consistent with steady flow shock model calculations for a range of v(s), the features present only in such 'hot' lines as the O III forbidden line 5007 A are found to account for relative intensities of that line greater than can be matched by steady flow model calculations.

Parker, R. A. R.↗
NASA NTRS1986

Simple numerical method for predicting steady compressible flows

A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.

Vonlavante, Ernst↗
NASA NTRS1985

A comparison between implicit and hybrid methods for the calculation of steady and unsteady inlet flows

Numerical simulation of steady and unsteady transonic diffuser flows using two different computer codes are discussed and compared with experimental data. The codes solve the Reynolds-averaged, compressible, Navier-Stokes equations using various turbulence models. One of the codes has been applied extensively to diffuser flows and uses the hybrid method of MacCormack. This code is relatively inefficient numerically. The second code, which was developed more recently, is fully implicit and is relatively efficient numerically. Simulations of steady flows using the implicit code are shown to be in good agreement with simulations using the hybrid code. Both simulations are in good agreement with experimental results. Simulations of unsteady flows using the two codes are in good qualitative agreement with each other, although the quantitative agreement is not as good as in the steady flow cases. The implicit code is shown to be eight times faster than the hybrid code for unsteady flow calculations and up to 32 times faster for steady flow calculations. Results of calculations using alternative turbulence models are also discussed.

Coakley, T. J.↗
NASA NTRS1974

Partial equilibrium model for predicting concentration of CO in combustion

A simple kinetic model, based upon the concept of partial equilibrium, is developed for predicting carbon monoxide concentrations in such steady-flow hydrocarbon-air combustion systems as gas-turbine combustors. The only two kinetic constraints used in the model are on the rate of change of the total number of gaseous particles in the system, and on the rate of change of the CO concentration. The accuracy of the model is verified by comparison with experimental results obtained by burning kerosene with air in a 130,000 Btu/hr atmospheric-pressure steady-flow burner. Burnt-gas cooling rates of 1,000,000 K/sec, about the magnitude encountered in the dilution zone of gas-turbine combustors, were obtained with a compact water-cooled heat exchanger. Good agreement between measured CO concentrations and the values predicted by the partial-equilibrium model was obtained.

Morr, A. R.↗
NASA NTRS1987

Unsteady aerodynamics of blade rows

The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The main emphasis is placed on the description of a linearized inviscid theory which fully accounts for the effects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this theory has been developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to blade motions. The resulting equations consist of a system of three field equations along with conditions imposed at blade, wake and shock surfaces and in the far field. These equations can be solved to determine the fluctuations in all fluid dynamic properties throughout the required solution domain. Example solutions are presented to demonstrate several effects associated with nonuniform steady flows on the linearized unsteady aerodynamic response to prescribed blade motions.

Verdon, J. M.↗
NASA NTRS1974

Analysis of sound propagation in ducts using the wave envelope concept

A finite difference formulation is presented for sound propagation in a rectangular two-dimensional duct without steady flow for plane wave input. Before the difference equations are formulated, the governing Helmholtz equation is first transformed to a form whose solution does not oscillate along the length of the duct. This transformation reduces the required number of grid points by an order of magnitude, and the number of grid points becomes independent of the sound frequency. Physically, the transformed pressure represents the amplitude of the conventional sound wave. Example solutions are presented for sound propagation in a one-dimensional straight hard-wall duct and in a two-dimensional straight soft-wall duct without steady flow. The numerical solutions show evidence of the existence along the duct wall of a developing acoustic pressure diffusion boundary layer which is similar in nature to the conventional viscous flow boundary layer. In order to better illustrate this concept, the wave equation and boundary conditions are written such that the frequency no longer appears explicitly in them. The frequency effects in duct propagation can be visualized solely as an expansion and stretching of the suppressor duct.

Baumeister, K. J.↗
DOE OSTI2024

Ferrocene Bis(Sulfonate) Salt as Redoxmer for Fast and Steady Redox Flow Desalination

Desalination is considered a promising solution to alleviate water shortages, yet current methods are often restricted, due to challenges like high energy consumption, significant cost, or limited desalination capacity. In this study, we present a novel approach of redox flow desalination (RFD) utilizing the highly aqueous-soluble and reversible redox-active compound, potassium 1,1'-bis(sulfonate) ferrocene (1,1'-FcDS). This water-soluble organic compound yielded stable and rapid desalination, sustaining extended operation without notable decay and achieving an impressive desalination rate of up to 457.5 mmol·h -1 ·m -2 and energy consumption as low as 40.2 kJ·mol NaCl -1 . Specifically, the RFD device effectively desalinated a 50 mM NaCl solution to potable standards within 6000 s using 1,1'-FcDS. It maintained an average energy consumption of 178.16 kJ·mol NaCl -1 and exhibited negligible deterioration in desalination rate, energy efficiency, and charge efficiency throughout a rigorous 12,000 s cycling test. Furthermore, the versatility of this method was demonstrated by effectively treating saline water with varying initial concentrations from 10 mM to 50 mM, showcasing its potential across a broad spectrum of applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

The steady-state flow quality in a model of a non-return wind tunnel

The structural cost of non-return wind tunnels is significantly less than that of the more conventional closed-circuit wind tunnels. However, because of the effects of external winds, the flow quality of non-return wind tunnels is an area of concern at the low test speeds required for V/STOL testing. The flow quality required at these low speeds is discussed and alternatives to the traditional manner of specifying the flow quality requirements in terms of dynamic pressure and angularity are suggested. The development of a non-return wind tunnel configuration which has good flow quality at low as well as at high test speeds is described.

Mort, K. W.↗
NASA NTRS1972

The steady-state flow quality of an open return wind tunnel model.

The structural cost of open return wind tunnels is significantly less than that of the more conventional closed return wind tunnels. However, because of the effects of external winds, the flow quality of open return wind tunnels is an area of concern at the low speeds required for V/STOL testing. The development of a configuration which has good flow quality at low as well as at high test speeds is described. The flow quality required at the low test speeds of interest for V/STOL aircraft is discussed and alternatives to the traditional manner of specifying the flow quality requirements in terms of dynamic pressure and angle of attack are suggested.

Mort, K. W.↗
NASA NTRS1980

Numerical simulation of steady supersonic flow over an ogive-cylinder-boattail body

A recently reported parabolized Navier-Stokes code has been employed to compute the supersonic flow field surrounding an ogive-cylinder-boattail body at incidence. The computations were performed for flow conditions where an extensive series of experimental surface pressure and turbulent boundary-layer profile measurements had been obtained. Comparison between the computational results and experimental measurements for angles of attack up to 6 deg show excellent agreement. At angles greater than 6 deg discrepancies are observed which are tentatively attributed to three-dimensional turbulence modeling errors.

Schiff, L. B.↗
NASA NTRS1981

Numerical simulation of steady transonic flow about airfoils

A computer code has been developed that couples a fast transonic full-potential AF2 solver with both an efficient integral boundary-layer method and a viscous wedge approximation of the shock/boundary-layer interaction. The efficiency of the coupled analysis methods and the method of coupling has resulted in a uniquely efficient analysis tool. The airfoil geometry is modified by the displacement thickness before the shock and the displacement thickness plus the viscous wedge thickness after the shock by considering the viscous effects as an equivalent transpiration boundary condition. The flow about conventional and supercritical airfoils under moderately strong shock situations has been calculated. Comparisons with experimental data indicate that this viscous correction method has improved the accuracy of the full-potential analysis. Furthermore, the computer time required to obtain a converged solution has been reduced.

Lee, S. C.↗