Experimental investigation of the fundamental-subharmonic coupling -Effect of the initial phase difference

Abstract

The effect of forcing the fundamental and subharmonic modes at different initial phases on the subharmonic growth in a transitioning free shear layer is investigated. The variations in the development of the subharmonic and fundamental modes under natural and phase controlled excitation are pointed out. Statistical measurements and analysis are used to look at the effect of the initial phase difference on the nonlinear couplings associated with the growth of the subharmonic mode. The results show that the growth and saturation level of the subharmonic mode are affected by its phase relation with the fundamental. The level of nonlinear coupling between the fundamental and the subharmonic is also dependent on the phase difference between the two modes.