The secondary instability in Goertler flow

The ‘‘high-frequency’’ secondary instability of nonlinearity developed and strongly modified Goertler vortices is numerically studied by considering two kinds of secondary instability modes, i.e., sinuous modes and varicose modes. A spectral collocation method with Chebyshev polynomials is used for calculations. It is found that secondary instabilities are more correlated with the vertical vorticity and the sinuous type disturbance would prevail over the varicose one for the same frequency and streamwise wave number found in experiments.