Accession Number : ADA264797


Title :   A Numerical Study of Wave Propagation in a Confined Mixing Layer by Eigenfunction Expansions


Descriptive Note : Contractor rept.,


Corporate Author : INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA


Personal Author(s) : Hu, Fang Q


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a264797.pdf


Report Date : Mar 1993


Pagination or Media Count : 21


Abstract : It is well known that the growth rate of instability waves to a two- dimensional free shear layer is reduced greatly at supersonic convective Mach numbers. In previous works, it has been shown that new wave modes exist when the shear layers are bounded by a channel due to the coupling effect between the acoustic wave modes and the motion of the mixing layer. The present work studies the simultaneous propagation of multiple stability waves using numerical simulation. It is shown here that the co-existence of two wave modes in the flow field can lead to an oscillatory growth of disturbance energy with each individual wave mode propagating linearly. This is particularly important when the growth rates of the unstable waves are small. It is also shown here that the propagation of two neutrally stable wave models can lead to a stationary periodic structure of r.m.s. fluctuations. In the numerical simulations presented here the forced wave modes are propagating at same frequency but with different phase velocities. In order to track the growth of each wave mode as it propagates downstream, a numerical method which can effectively detect and separate the contribution of individual wave is given. It is demonstrated that by a least square fitting of the disturbance field with eigenfunctions the amplitude of each wave mode can be found. Satisfactory results as compared to linear theory are obtained. (Author)


Descriptors :   *AERODYNAMIC STABILITY , *SUPERSONIC FLOW , *JET MIXING FLOW , SHEAR PROPERTIES , ACOUSTIC WAVES , EIGENVECTORS , DIGITAL SIMULATION , CONVECTION , MACH NUMBER , TWO DIMENSIONAL FLOW


Subject Categories : Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE