变热线过热比可压缩流湍流度测量方法优化

Measurement technique optimization of turbulence level in compressible fluid by changing overheat ratio of hot wire anemometer

开展了可压缩流中湍流度测量技术的优化研究,以满足对试验数据高精度评估的需求。在变热线过热比湍流度测量方法推导过程中,忽略了压力脉动项以简化湍流度求解过程。为更加准确评估高速风洞流场湍流度,引入了压力脉动项,以恒温热线风速仪响应关系式为基础,从理论上对可压缩流中湍流度的求解方法进行了优化。在马赫数0.3~0.7进行了湍流度测量试验,并分别利用优化前后的湍流度求解方法对试验数据进行了处理。结果表明两种求解方法所得的湍流度结果量值相近,但优化后的湍流度求解方法所得的湍流度结果随马赫数的变化趋势更加符合客观物理规律。利用蒙特卡洛模拟方法对湍流度的不确定度进行了求解,不确定度量值远小于湍流度量值,表明优化后的湍流度求解方法所得的湍流度结果基本能够代表真实值。试验结果证明了优化后湍流度测量方法的正确性及应用恒温热线风速仪对高速风洞流场湍流度进行测量的可行性。

In order to increase the measurement precision of a compressible flow,an optimization of turbulence level measurement technique is studied.By changing the overheat ratio of hot-wire anemometer and neglecting the pressure fluctuation terms in the governing equations,the turbulence level is solved.In order to evaluate the turbulence level in high speed flow more precisely,the algorithm for turbulence level based on response function of constant temperature hot-wire anemometer in compressible fluid is theoretically optimized by introducing pressure fluctuation.Turbulence level measurement experiments are carried out with the Mach number varied from 0.3 to 0.7 and the experimental data is processed by using algorithm of turbulence level before and after optimization.The results indicate that the magnitudes of turbulence level from the two methods are similar,but the variation tendency of turbulence level with Mach number obtained by using the optimized method is in accordance with the objective physical law.The uncertainty of turbulence level is obtained using Monte Carlo simulation,and the magnitude of the uncertainty is much smaller than that of the turbulence level.The results suggest that the turbulence level obtained using the optimized method could be regarded as the true values.The results proved the correctness of the turbulence level measurement technique after optimization and the feasibility of application of constant temperature hot-wire anemometer into turbulence level measurement in high speed wind tunnels.