Most effective method to find the roughness parameters in rarefied gas flow is to calculate them from aerodynamic measurements, solving the inverse problem. The value of the main roughness parameter obtained from the solution of inverse problem is substantially higher (at least 1,25–1,5 times) than similar value of the same parameter measured from the profile diagrams. Thus, the effect of surface roughness in aerodynamic values of rough surface in rarefied gas flow is always significantly underestimated. First main reason of it is the low precision of roughness parameter measurements from the profile diagrams, and the second is based on usual lack of taking into account aerodynamic shadowing effect.

中文翻译：

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应用反问题求解的稀薄气流中粗糙表面气动计算

寻找稀薄气流中的粗糙度参数的最有效方法是通过空气动力学测量来计算它们，解决逆问题。从反问题的解中获得的主要粗糙度参数的值比从轮廓图中测量的相同参数的类似值要高得多（至少1.25-1.5倍）。因此，表面粗糙度对稀薄气流中粗糙表面空气动力学值的影响总是被大大低估。其主要原因一是轮廓图粗糙度参数测量精度较低，二是通常缺乏考虑气动阴影效应。