A numerical simulation was carried out to study the effects of the flow field of periodically impinging jets on heat transfer characteristics. The numerical model was validated by experimental results. Numerical simulations were performed for typical periodical jets such as sinusoidal, triangular and rectangular jets. The history profiles of temperature, coefficient of heat transfer and turbulence intensity at stagnation point were numerically obtained and the different heat transfer chracteristics for the three periodical jets were analyzed. The investigation shows that turbulence intensities for the sinusoidal, triangular jets will have a suddenly augumentation, which is beneficial to heat transfer enhancement, when the velocities of these two periodical jets increase. However, the turbulence intensities change slowly in the rest time of a period. The turbulence intensity for a rectangular jet will have a sudden enhancement when the jet have a step change, no matter an increasing step or a decreasing step change. But the turbulence intensity enhancement happened in the velocity decreasing step change is much larger than another one. Such a turbulence intensity abrupt enhancement is obviously good for the rectangular impinging jet heat transfer. The influence of a periodical jet can be observed all over the flow field, although the oscillation of the velocity far from the stagnation point is very small. However, the average velocity of a rectangular jet is still significantly larger than those for sinusoidal, triangular jets.

采用经过实验验证的数值模型研究了周期性射流冲击下的流场对传热强化的影响。根据不同波形(正弦波、三角形波和矩形波)规律变化的射流对平板的冲击会产生不同的传热特性，研究得到了滞止点处的温度、传热系数和湍流强度随时间变化的规律。研究结果表明：当正弦波射流、三角形波射流的信号处于上升阶段时，湍流强度在稍有延迟后会产生一个瞬时的增强，可对强化传热起到促进作用，但在它们随后的波形变化中湍流强度仅有缓慢的升降,矩形波射流在信号发生阶跃变化时,会产生湍流强度的脉冲增强，尤其是在信号跃降时产生的瞬时脉冲增强比信号跃升时产生的脉冲增强更大，可有效强化传热;远离滞止点的流场的周期性波动仍然存在，但幅值大大减小，矩形波射流的平均速度大于其他波形射流的速度。

周期性冲击射流, 传热, 流场, 数值模拟