A 3-DIMENSIONAL INSTABILITY IN MIXED CONVECTION WITH STREAMWISE PERIODIC HEATING

Three-dimensional numerical simulations of flow through a channel with spatially periodic temperature boundary conditions in the streamwise direction have been carried out. A spectral method employing Fourier series expansion in the streamwise and spanwise directions and Chebyshev expansion in the vertical direction is used. A supercritical bifurcation to three-dimensional flow is found to occur before the onset of unsteadiness. The bifurcation to unsteady three-dimensional flow is also found to be supercritical. The unsteady three-dimensional flow oscillates at a slightly lower frequency than the two-dimensional flow, and introduces a slightly higher incommensurate frequency causing quasiperiodic flow and a slow spanwise wave motion. (C) 1995 American Institute of Physics.