近真空条件下火箭排气吹蚀土壤的速度快于连续介质尺度定律的预测
Rocket Exhaust Blowing Soil in Near Vacuum Conditions is Faster than Predicted by Continuum Scaling Laws
AI总结：
通过101 kPa至0.3 kPa条件下的气体射流冲蚀实验，研究发现近真空中沙粒绕流脱离连续介质区时，土壤侵蚀速率快于密度弗劳德数平方定律预测。
摘要：
为研究火箭排气在月球和火星条件下如何吹蚀土壤，开展了实验。气体射流向下喷射到各种颗粒材料上，同时用相机记录材料被移除时冲刷坑的形成过程。实验在从环境压力101 kPa到低至0.3 kPa的一系列条件下进行。这涵盖了与月球条件相关的范围，因为在土壤遭受侵蚀的火箭排气内部并非硬真空。此前在环境条件下开展的研究表明，侵蚀速率与密度弗劳德数的平方成正比。然而，此前的研究并未在低压条件下进行。在这项新研究中，初步结果表明，当气体密度低到沙粒周围的气体流动不再处于连续介质区时，侵蚀速率会快于早期结果的预测。研究确定了侵蚀速率对各种参数的依赖关系，但结果表明这种依赖比预期更为复杂，因此需要开展更多实验工作来建立完整的尺度关系。
英文摘要：
Experiments were performed to study how rocket exhaust blows soil in lunar and Martian conditions. Jets of gas were blown downwardly at various granular materials while a camera recorded the formation of scour holes as the material was removed. The experiments were performed in a series of conditions ranging from ambient 101 kPa pressure down to 0.3 kPa. This includes the range that is relevant for lunar conditions, because it is not hard vacuum inside the rocket exhaust where soil is being eroded. Prior work in ambient conditions showed that erosion rate is proportional to the square of the densimetric Froude number. However, the prior work was not performed at low pressures. In the new work, preliminary results show that as the gas density is so low that gas flow around the sand grains is no longer in the continuum regime, then erosion rate is faster than predicted by the earlier results. The dependency of erosion rate on various parameters is determined, but it turns out to be more complex than expected so additional experimental work will be required to develop complete scaling relationships.
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