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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Thermal network correction techniques

Correction techniques for thermal network lumped parameter inaccuracies with conduction and radiation coupling, considering temperature control system

Ishimoto, T.↗
NASA NTRS1972

SINDA, Systems Improved Numerical Differencing Analyzer

Computer program has been written to analyze group of 100-node areas and then provide for summation of any number of 100-node areas to obtain temperature profile. SINDA program options offer user variety of methods for solution of thermal analog modes presented in network format.

Fink, L. C.↗
NASA NTRS1972

Analysis of oil lubricated, fluid film, thrust bearings with allowance for temperature dependent viscosity

A preliminary design study was performed to seek a fluid-film thrust bearing design intended to be part of a high-speed, hybrid (rolling element/fluid film) bearing configuration. The base line used is a design previously tested. To improve the accuracy of theoretical predictions of load capacity, flow rate, and friction power loss, an analytical procedure was developed to include curvature effects inherent in thrust bearings and to allow for the temperature rise in the fluid due to viscous heating. Also, a narrow-groove approximation in the treatment of the temperature field was formulated to apply the procedure to the Whipple thrust bearing. A comparative trade-off study was carried out assuming isothermal films; its results showed the shrouded-step design to be superior to the Whipple design for the intended application. An extensive parametric study was performed, employing isoviscous calculations, to determine the optimized design, which was subsequently recalculated allowing for temperature effects.

Pan, C. H. T.↗
NASA NTRS1972

High pressure pulsed capillary viscometry

An analytical and test program was conducted in order to establish the feasibility of a multichamber pulsed-capillary viscometer. The initial design incorporated a piston, ram, and seals which produced measured pulses up to 30,000 psi in the closed chamber system. Pressure pulses from one to ten milliseconds were investigated in a system volume of 1 cuin. Four test fluids: a MIL-L-7808, a 5P4E polyphenyl ether, a MIL-L-23699A, and a synthetic hydrocarbon were examined in the test pressure assembly. The pressure-viscosity coefficient and viscosity delay time were determined for the MIL-L-7808 lubricant tested.

Smith, R. L.↗
NASA NTRS1974

A method for studying near- and far-field noise characteristics of impinging jets

A new method based on cross-correlation techniques is presented for studying the near- and far-field noise characteristics of a jet impinging on a surface. Analyses show that, in near and far fields, the noise characteristics due to the contribution of fluctuating pressure on the surface and due to the combined contribution of turbulence in the impinging jet and fluctuating pressure on the surface can be determined. Both far-field noise intensities and near-field acoustic energy fluxes can be expressed in terms of appropriate cross correlations. These correlations are obtained by making microphone measurements in three different regions: on the surface, in the near field, and in the far field. The method is currently being applied to study a cold, circular, subsonic jet impinging on a large rigid surface. Some preliminary experimental data are presented on fluctuating surface pressures and narrow-band far-field noise characteristics.

Pan, Y. S.↗
NASA NTRS1974

Cross-correlation methods for studying near- and far-field noise characteristics of several flow-surface interaction problems

Systematic methods based on cross-correlation techniques are presented for experimental studies of near- and far-field noise characteristics of airflow-surface interaction problems. By cross-correlating any two of three-kinds of microphone measurements: one flush-mounted on the surface, one located in the near field, and one placed in the far field, far-field noise intensities and near-field acoustic energy fluxes can be determined. In both near and far fields, the noise characteristics due to the flow turbulence and surface fluctuating pressure contributions can be evaluated separately. Specific applications to the noise field generated by impinging jets, by surface blowing jets, and by turbulent flow over trailing edges are discussed.

Pan, Y. S.↗
NASA NTRS1975

Noise radiation from turbulent flows over compliant surfaces

The present study is based on Lighthill-Curle's theory of aerodynamic noise. Using a correlation approach and the image concept of Powell, the volume contribution of turbulent flow over a large surface is approximated by a surface contribution of pressure fluctuations. Far-field noise intensities are expressed in terms of the surface pressure fluctuations and surface impedance. Based on available experimental measurements, numerical examples are performed for noise radiated from a turbulent boundary layer and from a normal jet impingement over rigid surfaces. Comparisons with available noise measurements are made. For general turbulent flows over compliant surfaces, measurements are suggested to obtain useful data for noise predictions.

Pan, Y. S.↗
NASA NTRS1975

Remarks on the theory of aerodynamic noise

The accuracy of approximations employed in the Lighthill theory in current aerodynamic noise research is critically evaluated. Based on the method of matched asymptotic expansions, the full Navier-Stokes equations are expanded for small Mach numbers. To the first order, the near-field is generally nonisentropic. The pressure field (pseudo-sound) is generated by the incompressible Reynolds stresses in the turbulent flow and the velocity, pressure perturbation, and their derivatives on the boundaries. In the far-field, the first-order pressure (acoustic) field satisfying a linear wave equation is obtained by matching with the pseudo-sound field. A uniformly valid solution for the pressure field in a stationary or uniformly moving medium is obtained. The solution shows that the generation of the first-order aerodynamic noise does not depend on the viscous, thermal, or entropy effects in the adiabatic flow nor on the shear stress on a smooth rigid boundary.

Pan, Y. S.↗
NASA NTRS1975

Cross-correlation methods for studying near- and farfield noise characteristics of flow-surface interactions

Systematic methods based on cross-correlation techniques are presented for experimental studies of near- and farfield noise characteristics in airflow-surface interaction problems. Analyses show that, in near- and farfields, the noise characteristics due to the surface contribution of fluctuating pressures and velocities and due to the volume contribution of the turbulence in the flow can be determined separately. Both farfield noise intensities and nearfield acoustic energy fluxes can be expressed in terms of appropriate cross correlations. These correlations can be obtained by making microphone measurements in the farfield, in the nearfield, and on the surface. Examples of the applications to the noise field generated by impinging jets, by surface blowing jets, and by turbulent flow over trailing edges are presented. Advantages of the present method over conventional methods are also discussed.

Pan, Y. S.↗
NASA NTRS1976

Experiment to Evaluate the Feasibility of Utilizing Skylab-EREP Remote Sensing Data for Tectonic Analysis Through a Study of the Big Horn Mountain Region, Wyoming, South Dakota and Wyoming

The author has identified the following significant results. S190B imagery was the best single product from which fairly detailed structural and some lithologic mapping could be accomplished in the Big Horn basin, the Owl Creek Mountains, and the northern Big Horn Mountains. The Nye-Bowler lineament could not be extended east of its presently mapped location although a linear (fault or monocline) was noted that may be part of the lineament, but north of postulated extensions. Much more structure was discernible in the Big Horn basin than could be seen on LANDSAT-1 imagery; RB-57 color IR photography, in turn, revealed additional folds and faults. A number of linears, several of which could be identified as faults and one a monocline, cut obliquely the east-west trending Owl Creek uplift. The heavy forest cover of the Black Hills makes direct lithologic delineation impossible. However, drainage and linear overlays revealed differences in pattern between the areas of exposed Precambrian crystalline core and the flanking Paleozoic rocks. S192 data, even precision corrected segments, were not of much use.

Hoppin, R. A.↗
NASA NTRS1975

Perturbation solution of the Navier-Stokes equations and its relation to the Lighthill-Curle solution of aerodynamic sound

The aerodynamic sound described by the Lighthill-Curle solution is reexamined using a method of matched asymptotic expansions. The governing Navier-Stokes equations written in nondimensional form are expanded for a small Mach number. First- and second-order solutions for the pressure field are obtained, and the singular nature of the expansion at large distances is indicated. The nearfield pressure is governed by the Poisson equation, whereas the farfield equations describe a linear wave system in a dissipative medium. The pseudosound is related to the incompressible Reynolds stresses associated with a solenoidal velocity field, the velocity, the pressure perturbation, and their derivatives on the boundaries. A uniformly valid first-order solution for the pressure is obtained. It is shown that viscosity, thermal conductivity, and entropy in the flow do not contribute to the first-order noise generation, while the viscous stress contributes to noise only from some boundaries. The application of the proposed perturbation method to a subsonically moving surface and a hot jet is discussed.

Pan, Y. S.↗