Author: Jesse Clayton Little
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 252
Book Description
Abstract: Grazing flow over a shallow cavity is characterized by a shear layer instability feedback loop that induces strong pressure fluctuations at discrete frequencies. Examples include flow over aircraft weapons bays, aircraft landing gear openings and transmission or reception optical ports on aircraft. In the first application, this behavior can result in decreased accuracy of weapons delivery, fatigue failures and lowered efficiencies. Because of the variety of unwanted effects inherent to cavity flows, their control is of interest to both military and commercial aircraft applications. The complex nature of cavity flow has been explored since the mid-20th century with accelerated study over the past 25 years in hopes of understanding and controlling major pressure fluctuations within the cavity. A key to developing a successful control scheme for this fluidic system is a detailed understanding of the physics that govern the flow-acoustic coupling mechanisms. This work provides both qualitative and quantitative measurements for use in characterizing the fluid and acoustic physics that govern the resonance phenomenon. Focus is placed on the subsonic regime with an emphasis on Mach 0.30 flow and its control. Results include the analysis of surface pressure spectra and spatial correlations, flow visualization and velocity measurement using particle image velocimetry (PIV) in various controlled and baseline (unforced) cases. These results show that a well chosen actuation scheme at or near the receptivity region of the cavity shear layer can interrupt or weaken the acoustic feedback loop and significantly reduce the sound pressure level in the cavity. Physically, this amounts to modifying the development and evolution of the coherent structures spanning the cavity and thereby changing the frequency at which these vortices impact the trailing edge of the geometry. In addition, simultaneous dynamic surface pressure and planar velocity measurements are used in low dimensional modeling for closed-loop controller design purposes. Modeling using this method allows design of accurate models from experimental results rather than relying on numerical data, which is incapable of resolving the complex nonlinear production of acoustics in the low subsonic cavity flows at this time.
An Experimental Investigation of Subsonic Cavity Flows Without and with Forcing
An Experimental Investigation of High Subsonic Flow Over an Off Axis Longitudinal Cavity with Antiresonance Devices
Author: Kenneth Vaccaro (2LT, USAF.)
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 172
Book Description
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 172
Book Description
A Theoretical and Experimental Investigation of the Acoustic Response of Cavities in an Aerodynamic Flow
Author: H. E. Plumblee
Publisher:
ISBN:
Category : Sound
Languages : en
Pages : 166
Book Description
Publisher:
ISBN:
Category : Sound
Languages : en
Pages : 166
Book Description
A Theoretical and Experimental Investigation of the Acoustic Response of Cavities in an Aerodynamic Flow
Author: H. E. Plumblee
Publisher:
ISBN:
Category :
Languages : en
Pages : 167
Book Description
Theory is developed for the resonant frequencies and pressure amplifications of a rectangular cavity of arbitrary dimensions in a flow field. An intermediate step involves the derivation of radiation impedance for a cavity at all Mach numbers, using the concepts of retarded pot ntial t eory. Experim ntal results are given for small cavities tested in the subsonic regime and for cavities up to 8 in. in length at supersonic Mach numbers from 1.75 to 5 0. Comparisons are drawn between theoretical and experimental frequency and amplitude response, indicating that the theory developed gives very good definition of the problem.
Publisher:
ISBN:
Category :
Languages : en
Pages : 167
Book Description
Theory is developed for the resonant frequencies and pressure amplifications of a rectangular cavity of arbitrary dimensions in a flow field. An intermediate step involves the derivation of radiation impedance for a cavity at all Mach numbers, using the concepts of retarded pot ntial t eory. Experim ntal results are given for small cavities tested in the subsonic regime and for cavities up to 8 in. in length at supersonic Mach numbers from 1.75 to 5 0. Comparisons are drawn between theoretical and experimental frequency and amplitude response, indicating that the theory developed gives very good definition of the problem.
Experimental Cavity Pressure Measurements at Subsonic and Transonic Speeds. Static-Pressure Results
Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781730884757
Category :
Languages : en
Pages : 80
Book Description
An experimental investigation was conducted to determine cavity flow-characteristics at subsonic and transonic speeds. A rectangular box cavity was tested in the Langley 8-Foot Transonic Pressure Tunnel at Mach numbers from 0.20 to 0.95 at a unit Reynolds number of approximately 3 x 10(exp 6) per foot. The boundary layer approaching the cavity was turbulent. Cavities were tested over a range of length-to-depth ratios (l/h) of 1 to 17.5 for cavity width-to-depth ratios of 1, 4, 8, and 16. Fluctuating- and static-pressure data in the cavity were obtained; however, only static-pressure data is analyzed. The boundaries between the flow regimes based on cavity length-to-depth ratio were determined. The change to transitional flow from open flow occurs at l/h at approximately 6-8 however, the change from transitional- to closed-cavity flow occurred over a wide range of l/h and was dependent on Mach number and cavity configuration. The change from closed to open flow as found to occur gradually. The effect of changing cavity dimensions showed that if the vlaue of l/h was kept fixed but the cavity width was decreased or cavity height was increased, the cavity pressure distribution tended more toward a more closed flow distribution. Plentovich, E. B. and Stallings, Robert L., Jr. and Tracy, M. B. Langley Research Center...
Publisher:
ISBN: 9781730884757
Category :
Languages : en
Pages : 80
Book Description
An experimental investigation was conducted to determine cavity flow-characteristics at subsonic and transonic speeds. A rectangular box cavity was tested in the Langley 8-Foot Transonic Pressure Tunnel at Mach numbers from 0.20 to 0.95 at a unit Reynolds number of approximately 3 x 10(exp 6) per foot. The boundary layer approaching the cavity was turbulent. Cavities were tested over a range of length-to-depth ratios (l/h) of 1 to 17.5 for cavity width-to-depth ratios of 1, 4, 8, and 16. Fluctuating- and static-pressure data in the cavity were obtained; however, only static-pressure data is analyzed. The boundaries between the flow regimes based on cavity length-to-depth ratio were determined. The change to transitional flow from open flow occurs at l/h at approximately 6-8 however, the change from transitional- to closed-cavity flow occurred over a wide range of l/h and was dependent on Mach number and cavity configuration. The change from closed to open flow as found to occur gradually. The effect of changing cavity dimensions showed that if the vlaue of l/h was kept fixed but the cavity width was decreased or cavity height was increased, the cavity pressure distribution tended more toward a more closed flow distribution. Plentovich, E. B. and Stallings, Robert L., Jr. and Tracy, M. B. Langley Research Center...
An Experimental Investigation of the Effects of a Base Cavity on the Near-wake Flowfield of a Body at Subsonic and Transonic Speeds
Author: Richard William Kruiswyk
Publisher:
ISBN:
Category :
Languages : en
Pages : 166
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 166
Book Description
Experimental Investigation of Supersonic Internal Cavity Flows
Author: Kazuyuki Sakamoto
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
An Experimental Investigation of the Airflow Over a Cavity with Antiresonance Devices
Author: Donald A. Buell
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 84
Book Description
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 84
Book Description
Experimental Investigation of Flow-induced Cavity Resonance
Author: Paul Zoccola (Jr., J.)
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 200
Book Description
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 200
Book Description
An experimental investigation of cavity flow
Author: Richard M. Cannon
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 269
Book Description
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 269
Book Description