Influence of pulses frequency on forced convection in nonstationary jets inpingement

The authors have modeled axisymmetric nonstationary pulsed and synthetic impinging jets and compared the transport processes in such flows with varying pulses frequency. In unsteady impinging jets, the friction on the wall is higher than the corresponding value for a stationary impact jet (up to 25%). It is found that, at the Strouhal number St = 0.08, the time averaged heat transfer at the stagnation point of unsteady impinging jets is the most important. The ranges of values of the Strouhal numbers are shown, where the use of non-stationary impinging jets gives an advantage in heat transfer intensification, and where its deterioration is observed.