粗糙壁热交换实验研究

 本文介绍了来流马赫数5的条件下,典型球锥模型的粗糙壁热交换实验结果。模型头部半径R为27.4毫米,底部直径D为60毫米,对五个不同粗糙度的模型进行了实验。模型表面粗糙颗粒直径d分别为0、0.3、0.5、0.7、0.9毫米。风洞前室总压P_t为10～45公斤/厘米。,相应的来流雷诺数R_eD为（O.8～3.6）×10⁶。 实验结果表明:光滑壁模型表面是层流加热,驻点热流与层流理论计算值较一致。粗糙度的影响,在低总压条件下（10公斤/厘米）主要在于促使边界层的转捩和发展。随着风洞总压的提高,物面静压和局部雷诺数的相应增大,粗糙度对热流的影响才明显增强,而严重的区域在端头。在实验最大粗糙度和最大总压条件下（d=O.9毫米、p_t=45公斤/厘米。）,除驻点值外,热流与光滑壁层流驻点值相比(q_i/q_so)的峰值在音点区域且接近4,而在驻点,此模型有别于其它模型,较为特殊,比热流最大值接近6,看来这可能与驻点局部外形变化有关。

EXPERIMENTAL STUDY ON HEAT TRANSFER TO ROUGH WALLS

Experimental results of heat transfer to rough walls are given here for sphere cone models at Mach number 5. The nose radius of the models is 27.4mm and base diameter 60mm. Five models have been tested with different roughness in its bead diameter range from 0 to 0.9mm. The tests were conducted in a conventional hypersonic wind tunnel at total pressures from 10kg/cm2 and Reynolds numbers ReD from 0.8×106 to 3.6×106.The test results indicate that the smooth wall model heating is the laminar flow heating, its heat flux at the stagnation point is quite close to the theoretical data, and the influence of roughness at low total pressure （10kg/ cm2） occurs mainly to promote the transition and development of a boundary layer. With the increasing total pressure in the wind tunnel the static pressure on model and local Reynolds numbers increase correspondently. In this case the effect of roughness on heat transfer becomes remarkable, and the most remarkable region appears at sonic point region on the nose. At the highest total pressure （pt =45kg/cm2） and with the largest roughness （d = 0.9mm） the ratio of rough wall heat flux to laminar flow smooth one could be up to 4 except at stagnation point, where it could approach 6. Its raise seems to be related to the local shape change in the vicinity of the stagnation point.