周期性冲击射流, 传热, 流场, 数值模拟

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.