Search NASA⌕ Search

SEARCH · Search NASA

Results for “PRESSURE FIELD”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Random response of rectangular panels to the pressure field beneath a turbulent boundary layer in subsonic flows

The response of a rectangular panel under the excitation of a turbulent boundary layer with a zero longitudinal mean pressure gradient in a subsonic flow was studied in detail. The method of normal mode was used together with the technique of spectral analysis. Both simply supported and clamped edge conditions of a panel were considered, and the displacement power spectral density of the panel response was computed. The results for the clamped edge panel compare favorably with existing data. Charts of structural acceptance, which provide a framework for estimating the response of other rectangular panels, are presented, and the physical significances of structural acceptances discussed.

Chyu, W. J.↗
NASA NTRS1975

Simulation by vortex rings of the unsteady pressure field near a jet

A coordinated theoretical and experimental program has been undertaken to construct a model for the shedding of vortex rings in order to simulate the real-time pressure variation in the acoustic region near the jet. The basic parameters in the analytic solutions are the eddy viscosity coefficient and the time intervals between successive shedding of vortex rings from the nozzle lip. The experimental and theoretical results show good qualitative agreement.

Liu, C. H.↗
NASA NTRS1965

Prediction of Airplane Sonic-Boom Pressure Fields

This paper presents a discussion of the sensitivity of supersonic-transport design and operation to sonic-boom considerations and shows the necessity for a study of these problems early in the development program. Methods of predicting pressure signatures are outlined and examples of the correlation of these estimates with wind-tunnel and flight measurements are shown. Estimates of sonic-boom characteristics for a representative supersonic transport show that in the critical transonic acceleration portion of the flight, overpressures somewhat lower than estimated by the use of far-field assumptions may be expected. Promising design possibilities for the achievement of further overpressure reductions are explored.

Carlson, Harry W.↗
NASA NTRS2017

Independent Assessment of the Backshell Pressure Field for Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2)

The Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) project requested that the NASA Engineering and Safety Center (NESC) support a ballistic range test to measure backshell pressures on scale models of the Mars 2020 entry capsule. The MEDLI2 project needed the test to provide important dynamic pressure data to help select a backshell pressure port, quantify drag coefficient reconstruction uncertainties, and design the data acquisition hardware. This document contains the outcome of the NESC assessment.

Prince, Jill L.↗
NASA NTRS1951

Error in Airspeed Measurement Due to Static-Pressure Field Ahead of the Wing Tip of a Swept-Wing Airplane Model at Transonic Speeds

As part of a study of means of airspeed measurement at transonic speeds the use of static orifices located ahead of the wing tip has been investigated for possible application to service or research airspeed installations. The local static pressure and local Mach number have been measured at a distance of 1 tip chord ahead of the wing tip of a model of a swept-wing fighter airplane at true Mach numbers between 0.7 and 1.08 by the NACA wing-flow method. All measurements were made at or near zero lift. The local Mach number was found to be essentially equal to the true Mach numbers less than about 0.90. The local Mach number was found to be about 0.97 at a true Mach number of 0.95, and to be about 1.04 at a true Mach number of 1.08. The local Mach number provided a reasonable sensitive measure of true Mach number except for a restricted region near a true Mach number of 1.0 where the local Mach number did not change appreciably with true Mach number. The linear theory was found to predict qualitatively the effect of the fuselage on the static pressure ahead of the wing time but gave a reasonable prediction of the effect of the wing on the static pressure only at Mach numbers below 0.95.

Danforth, Edward C.B.↗
NASA NTRS1993

Active control of acoustic pressure fields using smart material technologies

An overview describing the use of piezoceramic patches in reducing noise in a structural acoustics setting is presented. The passive and active contributions due to patches which are bonded to an Euler-Bernoulli beam or thin shell are briefly discussed and the results are incorporated into a 2-D structural acoustics model. In this model, an exterior noise source causes structural vibrations which in turn lead to interior noise as a result of nonlinear fluid/structure coupling mechanism. Interior sound pressure levels are reduced via patches bonded to the flexible boundary (a beam in this case) which generate pure bending moments when an out-of-phase voltage is applied. Well-posedness results for the infinite dimensional system are discussed and a Galerkin scheme for approximating the system dynamics is outlined. Control is implemented by using linear quadratic regulator (LQR) optimal control theory to calculate gains for the linearized system and then feeding these gains back into the nonlinear system of interest. The effectiveness of this strategy for this problem is illustrated in an example.

Banks, H. T.↗
NASA NTRS1975

Effects of spanwise blowing on the pressure field and vortex-lift characteristics of a 44 deg swept trapezoidal wing

Wind-tunnel data were obtained at a free-stream Mach number of 0.26 for a range of model angle of attack, jet thrust coefficient, and jet location. Results of this study show that the sectional effects to spanwise blowing are strongly dependent on angle of attack, jet thrust coefficient, and span location; the largest effects occur at the highest angles of attack and thrust coefficients and on the inboard portion of the wing. Full vortex lift was achieved at the inboard span station with a small blowing rate, but successively higher blowing rates were necessary to achieve full vortex lift at increased span distances. It is shown that spanwise blowing increases lift throughout the angle-of-attack range, delays wing stall to higher angles of attack, and improves the induced-drag polars. The leading-edge suction analogy can be used to estimate the section and total lifts resulting from spanwise blowing.

Campbell, J. F.↗
NASA NTRS1986

An approach to the calculation of the pressure field produced by rigid wide chord dual rotation propellers of high solidity in compressible flow

An unsteady lifting service theory for the counter-rotating propeller is presented using the linearized governing equations for the acceleration potential and representing the blades by a surface distribution of pulsating acoustic dipoles distributed according to a modified Birnbaum series. The Birnbaum series coefficients are determined by satisfying the surface tangency boundary conditions on the front and rear propeller blades. Expressions for the combined acoustic resonance modes of the front prop, the rear prop and the combination are also given.

Ramachandra, S. M.↗