The heat transfer and flow characteristics of square wave impinging jets under different duty cycles are studied by numerical simulation method.This paper presents the heat transfer characteristics of target varied with traditional variables such as Reynolds number

pulse frequency and jet to plate spacing.The heat transfer and flow characteristics in the stagnation area with different duty cycles are analyzed emphatically.The numerical result is verified with the experimental result of impinging jet and pulsating jet.The results show that in the stagnation area

with the duty cycles of 0.5 and 0.7

the Nusselt numbers are very closed to each other.In the wall jet region

the Nusselt number with duty cycle of 0.5 is improved by 10% than that with duty cycle of 0.7.The Nusselt number with duty cycle of 0.9 is improved by 3% than that of steady jet in the whole jet region.Under duty cycle of 0.7

the vortex structure movement is much stronger in the stagnation area

compared to that under duty cycles of 0.5 and 0.9

and steady jet.