The purpose of this study is to investigate the mixing phenomena in a sinusoidal microchannel and call into question the effect of unequal wave length magnitude in the upper and lower walls on mixing efficiency. Nondimensional parameters in this study were Schmidt number set to remain at 100, Reynolds number ranging from 0.5 to 1.5 and different wave length ratio values for lower wall, while the upper wall wave length was invariant. To answer this question, all governing equations are solved numerically using the lattice Boltzmann method, while channel walls are modelled by the aid of a general curved boundary treatment. This analysis revealed that corrugated patterns led to higher pressure drop and preferable mixing efficiency at lower distance from the beginning of the channel. Interestingly, results showed that the mixing efficiency decreases as the Reynolds number increases. The evidence from this research intimates that almost complete mixing (up to 98 %) was achieved at Peclet=50 at the outlet of the channel in which the dimensionless wave length magnitude for the upper and lower walls are equal to 3 and 4 respectively. A pressure drop of 277 Pa is obtained for this case.

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