Author: V. Sarohia
Publisher:
ISBN:
Category : Oscillations
Languages : en
Pages : 42
Book Description
An experimental investigation was conducted of subsonic turbulent flows over shallow, axi-symmetric cavities located downstream of the leading edge of a flat-nosed fuse contour and on an ellipsoidal nose contour. The objective was to evaluate cavity performance in terms of pressure oscillations inside the cavity for various cavity configurations and other pertinent parameters for various modes of cavity operation. Free-stream velocities over the contours ranged up to 650 ft/sec, and Reynolds numbers based on maximum diameter of the contour ranged between 10000 and about 1000000. It was found that pressure signals at the base of the cavity for an oscillating cavity flow as high as 150 dB, could be obtained and that a total acoustic power as high as 20 W was estimated. Furthermore, pressure oscillations existed for cavity depths as small as 0.050 in. It may be that this is not the minimum depth for which oscillations are generated, since the next smaller depth tested was 0.020 in. For the smallest depth, of 0.020 in., pressure oscillations in the cavity did not occur. Cavity oscillations were more pronounced when the cavity was located in the favorable (negative) pressure gradient region of the axi-symmetric body. Instant spark shadowgraphs taken for both laminar and for turbulent boundary layer flow separation at the upstream cavity corner showed the presence of large, organized vortex structures in the oscillating shear layer. Mean velocity measurements of an oscillating cavity shear layer indicated an entrainment rate as large as 0.046 as compared to a non-oscillating cavity shear layer entrainment of approximately 0.021.
Investigation of Pressure Oscillations in Axi-Symmetric Cavity Flows
Author: V. Sarohia
Publisher:
ISBN:
Category : Oscillations
Languages : en
Pages : 42
Book Description
An experimental investigation was conducted of subsonic turbulent flows over shallow, axi-symmetric cavities located downstream of the leading edge of a flat-nosed fuse contour and on an ellipsoidal nose contour. The objective was to evaluate cavity performance in terms of pressure oscillations inside the cavity for various cavity configurations and other pertinent parameters for various modes of cavity operation. Free-stream velocities over the contours ranged up to 650 ft/sec, and Reynolds numbers based on maximum diameter of the contour ranged between 10000 and about 1000000. It was found that pressure signals at the base of the cavity for an oscillating cavity flow as high as 150 dB, could be obtained and that a total acoustic power as high as 20 W was estimated. Furthermore, pressure oscillations existed for cavity depths as small as 0.050 in. It may be that this is not the minimum depth for which oscillations are generated, since the next smaller depth tested was 0.020 in. For the smallest depth, of 0.020 in., pressure oscillations in the cavity did not occur. Cavity oscillations were more pronounced when the cavity was located in the favorable (negative) pressure gradient region of the axi-symmetric body. Instant spark shadowgraphs taken for both laminar and for turbulent boundary layer flow separation at the upstream cavity corner showed the presence of large, organized vortex structures in the oscillating shear layer. Mean velocity measurements of an oscillating cavity shear layer indicated an entrainment rate as large as 0.046 as compared to a non-oscillating cavity shear layer entrainment of approximately 0.021.
Publisher:
ISBN:
Category : Oscillations
Languages : en
Pages : 42
Book Description
An experimental investigation was conducted of subsonic turbulent flows over shallow, axi-symmetric cavities located downstream of the leading edge of a flat-nosed fuse contour and on an ellipsoidal nose contour. The objective was to evaluate cavity performance in terms of pressure oscillations inside the cavity for various cavity configurations and other pertinent parameters for various modes of cavity operation. Free-stream velocities over the contours ranged up to 650 ft/sec, and Reynolds numbers based on maximum diameter of the contour ranged between 10000 and about 1000000. It was found that pressure signals at the base of the cavity for an oscillating cavity flow as high as 150 dB, could be obtained and that a total acoustic power as high as 20 W was estimated. Furthermore, pressure oscillations existed for cavity depths as small as 0.050 in. It may be that this is not the minimum depth for which oscillations are generated, since the next smaller depth tested was 0.020 in. For the smallest depth, of 0.020 in., pressure oscillations in the cavity did not occur. Cavity oscillations were more pronounced when the cavity was located in the favorable (negative) pressure gradient region of the axi-symmetric body. Instant spark shadowgraphs taken for both laminar and for turbulent boundary layer flow separation at the upstream cavity corner showed the presence of large, organized vortex structures in the oscillating shear layer. Mean velocity measurements of an oscillating cavity shear layer indicated an entrainment rate as large as 0.046 as compared to a non-oscillating cavity shear layer entrainment of approximately 0.021.
Effect of Angle of Attack on Cavity Flow Oscillations
Author: V. Sarohia
Publisher:
ISBN:
Category : Fluctuations (Physics)
Languages : en
Pages : 54
Book Description
Publisher:
ISBN:
Category : Fluctuations (Physics)
Languages : en
Pages : 54
Book Description
An Experimental Study of Axisymmetric Cavity Oscillations in Low Speed Incompressible Flow
Author: Jeremy David Brice Smith
Publisher:
ISBN:
Category :
Languages : en
Pages : 79
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 79
Book Description
Scientific and Technical Aerospace Reports
Research in Progress
Bibliography
Author: Jet Propulsion Laboratory (U.S.)
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 192
Book Description
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 192
Book Description
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
Publisher:
ISBN:
Category : Holes
Languages : en
Pages :
Book Description
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.
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.
Effect of Finite Cavity Width on the Self-sustained Oscillation in a Low-mach-number Cavity Flow
An Experimental Investigation of Pressure Oscillations in Two- Dimensional Open Cavities
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
Book Description
An experimental study was conducted to determine the characteristics of the pressure oscillations in a small two-dimensional cavity exposed to tangential air flow. Various cavity configuration changes, involving the shape of the leading and trailing edge, were investigated to determine the relative capability to suppress the resonance in the cavity response. Five airflow Mach numbers (0.5, 0.6, 1.0, 1.3, 1.5) were used to investigate the Mach-response relationship. Two cavity lengths were considered (2 and 4 1/4 inches). The depth of the cavities was kept constant at one inch. Fluctuating pressure recordings and schlieren photographs were made of each test.
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
Book Description
An experimental study was conducted to determine the characteristics of the pressure oscillations in a small two-dimensional cavity exposed to tangential air flow. Various cavity configuration changes, involving the shape of the leading and trailing edge, were investigated to determine the relative capability to suppress the resonance in the cavity response. Five airflow Mach numbers (0.5, 0.6, 1.0, 1.3, 1.5) were used to investigate the Mach-response relationship. Two cavity lengths were considered (2 and 4 1/4 inches). The depth of the cavities was kept constant at one inch. Fluctuating pressure recordings and schlieren photographs were made of each test.