Control of flow separation and mixing by aerodynamic excitation

The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

[1]  K. K. Ahuja,et al.  Prediction and measurement of flows over cavities - A survey , 1987 .

[2]  D. Rockwell,et al.  Self-sustaining oscillations of flow past cavities. , 1978 .

[3]  J. Rossiter.  Wind tunnel experiments on the flow over rectangular cavities at subsonic and transonic speeds , 1964 .

[4]  Christopher L. Rumsey,et al.  A natural low-frequency oscillation of the flow over an airfoil near stalling conditions , 1989, Journal of Fluid Mechanics.

[5]  Saeed Farokhi,et al.  Modern developments in shear flow control with swirl , 1992 .

[6]  M. D. Dahl,et al.  Some Observations on Transitory Stall in Conical Diffusers , 1990 .

[7]  D. J. Mckinzie,et al.  Control of laminar separation over airfoils by acoustic excitation , 1989 .

[8]  Ganesh Raman,et al.  Initial turbulence effect on jet evolution with and without tonal excitation , 1987 .

[9]  Saeed Farokhi,et al.  Large amplitude acoustic excitation of swirling turbulent jets , 1989 .

[10]  Reda R. Mankbadi,et al.  Saturation and the limit of jet mixing enhancement by single frequency plane wave excitation - Experiment and theory , 1988 .

[11]  Ganesh Raman,et al.  Subharmonic and fundamental high amplitude excitation of an axisymmetric jet , 1989 .

[12]  K. Ahuja,et al.  Control of turbulent boundary layer flows by sound , 1983 .

[13]  A. Hussain,et al.  Coherent structures and turbulence , 1986, Journal of Fluid Mechanics.

[14]  Reda R. Mankbadi,et al.  On the interaction between fundamental and subharmonic instability waves in a turbulent round jet , 1985, Journal of Fluid Mechanics.

[15]  A. Roshko,et al.  On density effects and large structure in turbulent mixing layers , 1974, Journal of Fluid Mechanics.

[16]  Ganesh Raman,et al.  Effects of core turbulence on jet excitability , 1989 .

[17]  E. J. Rice,et al.  Control of shear flows by artificial excitation , 1987 .

[18]  A. Michalke,et al.  INSTABILITY OF A COMPRESSIBLE CIRCULAR FREE JET WITH CONSIDERATION OF THE INFLUENCE OF THE JET BOUNDARY LAYER THICKNESS , 1977 .

[19]  Saeed Farokhi,et al.  Controlled excitation of a cold turbulent swirling free jet , 1988 .

[20]  Israel J Wygnanski,et al.  Coherent Motion in Excited Free Shear Flows , 1987 .

[21]  R. Mankbadi,et al.  A study of the interactions between large-scale coherent structures and fine-grained turbulence in a round jet , 1981, Philosophical transactions of the Royal Society of London. Series A: Mathematical and physical sciences.