Control of turbulent boundary layer flows by sound

Ahuja, K. K.; Whipkey, R. R.; Jones, Gordon

doi:10.2514/6.1983-726

Cited by 51 publications

(21 citation statements)

References 14 publications

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“…2 " 8 Collins 2 ' 3 first observed that the application of the external acoustic excitation could change the lift on an airfoil. Ahuja and his coworkers 4 ' 5 then conducted a series of studies of the excitation effects using the same technique. Further study of the interaction between the external acoustics and the separated flow was carried out by Zaman et al 6 A beneficial effect of the external acoustic excitation on the separated boundary layer over the airfoil was presented in those papers.…”

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confidence: 99%

Control of wall-separated flow by internal acoustic excitation

1990

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This paper explores the control of wall-separated flow on a NACA 63 3 -018 airfoil and a circular cylinder by using the internal acoustic excitation technique. Experimental study of the characteristics of the flow under internally emanating acoustic waves is performed in an open-type, suction wind tunnel. Tests are carried out at the Reynolds number ranging from 6.3 x 10 3 to 5.0 x 10 5 based on the relevant characteristic lengths, the airfoil chord, and the cylinder diameter. The control effectiveness is verified by the measurements of parameters such as the excitation frequency, the excitation level, and the forcing location. Data indicate that the excitation frequency and the forcing location are the key parameters for controlling the separated flow, and the forcing level is the least-effective parameter for the study. As long as the emanating acoustics is "locked in" to the separated shear-layer instability frequency and forcing is applied at the separation point, the separated flow is controlled most effectively. Moreover, the b'ft is increased and the drag reduced dramatically. Nomenclaturecircular cylinder f e = excitation frequency f s = vortex shedding frequency f t = shear layer instability frequency P = static pressure P t -total pressure p tao = total pressure in freestream P^ = static pressure in freestream Re c = Reynolds number based on chord, Re c = U^ C/v Re D = Reynolds number based on diameter, Re D -U^D/v St = Strouhal number, (/,<:/#«,) or (f.D/U^) U^ = freestream velocity X = coordinate along the freestream direction Y = coordinate normal to the freestream direction p = fluid density v = kinematic viscosity a = sound emission angle of the circular cylinder 0 = polar coordinate in the azimuthal direction

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confidence: 99%

Control of wall-separated flow by internal acoustic excitation

1990

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“…This type of flow condition occurs in shear layers near flow separation regions such as in the upper surfaces of airfoils at high angle of attack. The experiments of Ahuja et al (1983 are excellent examples.…”

Section: Receptivitymentioning

confidence: 99%

Engine Test Cell Aeroacoustics and Recommendations

Tam¹

2007

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)AEDC/XRS SPONSOR/MONITOR'S REPORT NUMBER(S)Arnold Engineering Development Center/XRS Arnold AFB, TN 37389 DISTRIBUTION/AVAILABILITY STATEMENTStatement A: Approved for public release; distribution is unlimited. SUPPLEMENTARY NOTESAvailable in the Defense Technical Information Center (DTIC). ABSTRACTGround testing of turbojet engines in test cells necessarily involves very high acoustic amplitudes, often enough and severe enough that testing is interrupted and facility hardware and test articles are damaged. The acoustic response of test cells containing energetic jets is poorly understood and generally unpredictable. Nevertheless, there is a clear need to be able to predict deleterious acoustic events in advance of facility entry. A predictive capability would permit evaluating possible fixes in advance of the entry to preclude interruption of testing and damage to hardware, both of which are costly and disruptive of weapons systems program schedules. To establish the needed predictive capability, the Arnold Engineering Development Center (AEDC) is implementing a computational aeroacoustics (CAA) capability. This report by C. K. Tam is one of several steps toward that goal. Here, Tam consolidates what is presently known about the aeroacoustics of jets and flowing ducts. The material presented includes analytical and semi-empirical models of various acoustic situations as well as test data. Also included is a proposal to ameliorate a particularly damaging acoustic event referred to as "super resonance." A future report will present CAA technology appropriate for numerical solution of the flow equations as applied to jet cells. The reproducibles used in the reproduction of this report were supplied by the author. IntroductionOne of the primary objectives of this report is to provide an overview of the sources of noise in engine test cells. An engine test cell is either a closed or a partially closed system. The solid surfaces that form the cell reflect back any incident acoustic waves. Thus a test cell creates a special acoustic environment depending on its...

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“…It has been well-know that flow control is most effective when applied near the transition or separation points Ahuja et al (1983), Hsiao and Shyu (1991). The flow instabilities can be amplified quickly near these critical regions.…”

Section: Mlsmentioning

confidence: 99%

Vortex-induced vibration control by micro actuator

Liu

Chu

2007

J Mech Sci Technol

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The control of vortex-induced vibration of two side-by-side circular cylinders in a cross flow is carried out experimentally. One cylinder is elastically supported and the other is fix-supported at both ends. The two cylinders vibrate under the action of the unsteady flow-induced forces. A micro actuator is embedded on the surface of each cylinder to perturb the boundary layer. The spacing ratio is set at 1.2. The measurement shows that the structural vibration can be suppressed significantly when the reduced excitation frequency is around 2.655.

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Control of turbulent boundary layer flows by sound

Cited by 51 publications

References 14 publications

Control of wall-separated flow by internal acoustic excitation

Control of wall-separated flow by internal acoustic excitation

Engine Test Cell Aeroacoustics and Recommendations

Vortex-induced vibration control by micro actuator

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