Nonmodal growth of three-dimensional disturbances on plane Couette-Poiseuille flows -: art. no. 014105

The time development of three-dimensional disturbances superimposed on a variety of mean flow profiles representing plane Couette - Poiseuille flow is investigated numerically. Specifically, with y representing the wall normal coordinate, the mean flow profiles U(y) are represented by U(y) = A(1- y(2))+ By, where B= 1 when 0 less than or equal to A less than or equal to 1/2 and B = 2rootA(1-A) when 1/2 less than or equal to A less than or equal to 1. For streamwise independent disturbances, which are the most amplified ones, there is an increase of the disturbance peak amplification when the parameter A increases in the interval 1/10 less than or equal to A less than or equal to 1/2. In the interval 1/2 less than or equal to A less than or equal to 9/10, and especially for 9/10 less than or equal to A less than or equal to 1, the disturbance peak amplification decreases rapidly when A is increased. For A close to 1, a slight reduction of A will therefore cause a strong increase of the disturbance amplification. (C) 2005 American Institute of Physics.