Abstract

Numerical investigations of transition scenarios due to flow bifurcations from laminar to time-dependent transitional flows in asymmetric wavy channels with different spatial periodicity on the sinusoidal wall are performed by direct numerical simulations of the mass and momentum conservation equations using a spectral element method computational program. Three aspect ratios r=a/(2L) are considered in this study: 0.125, 0.25, y 0.375. Computational meshes for both extended and periodic computational domains are used to determine first, the existence of spatial periodicity and second, the transitional flow behavior for increasing Reynolds numbers Numerical results shows that the transition scenarios are highly dependent on the aspect ratio, r. The following scenarios develop: a) a first transition scenario with one flow bifurcation to a relatively low Reynolds numbers, Re c; b) a second scenario, with also one flow bifurcation, to a relatively high Reynolds numbers, Re c*; and, c) a third flow transition scenario with two Hopf bifurcations B 1 and B 2, occurring at critical Reynolds numbers Re c1 y Re c2, respectively. In this third scenario, fundamental frequencies ? 1 and ? 2, and sub and super harmonic combinations of the fundamental frequencies develop as the Reynolds number increases from a laminar to higher transitional flow regime. This transition scenario from a laminar flow to high transitional flow regimes is very similar to the Ruelle-Takens-Newhouse (RTN) found in another confined flow channels such as symmetric wavy, grooved and communicating channels. Copyright © 2008 by ASME.