Systems in which flow of two jets collide from a close distance and create a thin layer with high turbulences at the incidence area are called Collisional flows. They provide suitable conditions for transfer processes. Although many studies have been carried out on the modeling of two stable impulse jets but there are little studies of such subjects about unstable opposite jets. In this study heat and flow field of two slow fluctuating impulse jets have been considered in order to understand the various effects of instabilities on mixing processes. The parameters studied in this study are frequency, amplitude, phase difference, Reynolds number and temperature difference of two impulse jets.