Experimental and theoretical study of the interfacial instability between two shear fluids in a channel Couette flow

The instabilities of a channel Couette flow composed of two layers of immiscible fluids were investigated experimentally and compared with the theoretical predictions of a linear instability analysis. The results show that in the shortwave instability regime, the experimental results agree well with the theoretical predictions of the linear instability analysis. However, we can find shortwaves even in the range of the depth ratios when the linear instability predicts only longwaves are unstable. The reasons are believed to be the dimensional limitation of the experimental apparatus and the existence of the outside and inside wall. In addition, we studied the dependence of the onset of the shortwaves on the viscosity and density of the fluids.