Calculated and measured results are presented to quantify the effects of surface waves in laminar flow through high-aspect ratio channels typical of many in microturbine recuperators. Flow structures were calculated with spectral methods that solve incompressible Navier-Stokes equations and use Fourier expansions to represent the corrugated-wall boundary condition. Stability analysis with a generalized Floquet formulation that accounts for spatial modulation of the flow was used with the spectral flow field to predict the shape of streamlines that lead to streamwise vortices. Results indicate that vortices are produced in a very narrow range of streamline wavelengths and amplitudes. Streamlines were also calculated using a RANS method for the purpose of finding a surface that would produce the necessary streamline patterns. Hot-wire measurements show the frequency and amplitude of streamwise vortex structures increases in the flow over a sinusoidal wall with the predicted surface waves.

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