Author: M. E. FrankePublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Suppression of Flow-induced Pressure Oscillations in Cavities
Author: M. E. FrankeAn Experimental Investigation Into the Suppression of Flow-induced Pressure Oscillations in Two-dimensional Open Cavities
Author: Randall S. Mainquist (1LT, USAF.)Publisher:
ISBN:
Category : Holes
Languages : en
Pages : 170
Book Description
Suppression of Aerodynamically Induced Cavity Pressure Oscillations
Author: Leonard L. ShawPublisher:
ISBN:
Category : Oscillations
Languages : en
Pages : 68
Book Description
A flight test program was performed to gain further insight into the phenomenon of flow-induced cavity pressure oscillations and to evaluate the effectiveness of suppression concepts in eliminating or reducing the pressure oscillations. The cavities tested were rectangular with approximate dimensions of 17 inches long, 8.5 inches deep, and 8.75 inches wide and were instrumented with microphones, static pressure ports, and a thermocouple. The flight speeds ranged from Mach number 0.6 to 1.3 at pressure altitudes of 3,000, 20,000, and 30,000 feet. The suppression devices included leading edge spoilers and deflectors and trailing edge ramps and deflectors. Several combinations of these were tested. The results indicate that the flow-induced pressure oscillations in a cavity of the dimensions tested and for the speed range tested can be significantly reduced with leading edge spoilers in conjunction with a trailing edge ramp. Reductions as large as 30 dB were achieved for the predominant model frequency for a one-third octave band. Other combinations of the suppression devices afforded some reduction, but the spoiler ramp combination proved most effective. (Author).
Experimental Investigation to Suppress Flow-Induced Pressure Oscillations in Open Cavities
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 119
Book Description
High speed tangential flow over open cavities (e.g. aircraft weapon bays) can invoke large pressure oscillations within the cavity. These large oscillations can damage the cavity structure as well as items placed within the cavity. The purpose of this experimental study was to determine the effectiveness of suppressing pressure oscillations by manipulating the shear layer over a two-dimensional cavity with a length-to-depth ratio of two. Two methods, a frequency controllable control surface (fence) and pulsating secondary airflow at the cavity leading edge, were used to manipulate the shear layer. The suppression effectiveness of the fence utilized in both passive and active modes (zero to 120 Hz) was evaluated at six airflow Mach numbers (0.62, 0.76, 0.90, 1.07, 1.28, 1.53). The effectiveness of pulsating secondary airflow was evaluated at one airflow Mach number (1.28) and two flow injection angles (parallel and 45 degrees to the flow) at frequencies ranging from zero to 80 Hz. The effect of steady flow injection was also evaluated at mass flow rates per unit width ranging from 0.323 to 1.27 (lbm/sec/ft). Pressure recordings from within the cavity were made for each test. The effectiveness of a pulsating fence in suppressing the peak mode pressure oscillations proved to be less than that achievable with the fence static. The pulsed secondary flow injection technique was most effective when pulsed at a 45 degree angle to the external flow. Theses.
Investigation for Suppressing Flow-induced Pressure Oscillations in an Open Cavity
Author: Fa-li Yang (CAPT, CAF.)Publisher:
ISBN:
Category : Holes
Languages : en
Pages :
Book Description
Aerodynamically Induced Pressure Oscillations in Cavities - Physical Mechanisms and Suppression Concepts
Author: Hanno H. HellerPublisher:
ISBN:
Category :
Languages : en
Pages : 225
Book Description
This report presents the results of an analytical and experimental research program to (1)improve the understanding of the physical mechanisms that control the occurrence of pressure fluctuations in long and shallow rectangular cavities, exposed to high-speed external flow, and (2)devise and evaluate devices that would either substantially reduce the amplitude of such pressure fluctuations, or totally suppress the occurrence of pressure fluctuations. During this investigation, the understanding of the complex interaction of the external shear layer and the cavity internal fluid medium, which constitutes the generating mechanism of high-intensity periodic pressure fluctuations was substantially furthered. Both the analysis and investigation of the physical mechanisms were aided through extensive shallow-water flow-simulation experiments. Large-scale experiments, using the NASA-Lewis Research Center 8 X 6 ft Supersonic Wind Tunnel were conducted to substantiate some of the analytical predictions and to study in detail the aeroacoustic behavior of cavities in the length-to-depth ratio range, L/D, of 2.3 to 5.5, and the Mach number range of 0. 8 to 2.0. Detailed information was obtained on the normalized levels of the first three resonant modes in the cavity for a range of cavity length-to-depth ratios and freestream Mach numbers. Several concepts for pressure oscillation suppression were developed and evaluated in wind tunnel experiments. The most promising concept utilizes a slanted trailing edge, which stabilizes the free shear flow above the cavity, thus effectively suppressing discrete-tone generation. (Author).
Suppression of Pressure Oscillations in Flow Past Resonant Cavities
Author: Stephen F. McGrathExperimental Investigation of Flow-induced Cavity Resonance
Author: Paul Zoccola (Jr., J.)Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 200
Book Description
Suppression of Pressure Oscillations in an Open Cavity by Passive Pneumatic Control
Author: N. ChokaniFlow-Induced Vibrations
Author: Eduard NaudascherPublisher: Courier Corporation
ISBN: 0486136132
Category : Science
Languages : en
Pages : 434
Book Description
Despite their variety, the vibration phenomena from many different engineering fields can be classified into a relatively few basic excitation mechanisms. The classification enables engineers to identify all possible sources of excitation in a given system and to assess potential dangers. This graduate-level text presents a synthesis of research results and practical experience from disparate fields in the form of engineering guidelines. It is particularly geared toward assessing the possible sources of excitation in a flow system, in identifying the actual danger spots, and in finding appropriate remedial measures or cures. Flow-induced vibrations are presented in terms of their basic elements: body oscillators, fluid oscillators, and sources of excitation. By stressing these basic elements, the authors provide a basis for the transfer of knowledge from one system to another, as well as from one engineering field to another. In this manner, well-known theories on cylinders in cross-flow or well-executed solutions from the field of wind engineering--to name just two examples--may be useful in other systems or fields on which information is scarce. The unified approach is broad enough to permit treatment of the major excitation mechanism, yet simple enough to be of practical use.