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Predicting Regolith Erosion during a Lunar Landing: Role of Continuous Size Distribution

机译：预测月球着陆期间的雷格石侵蚀：连续尺寸分布的作用

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When a rocket lands on the Moon, the exhaust plume causes the lunar regolith (soil) to be ejected in all directions. Such highspeed ejection poses a threat to nearby equipment and structures. As a step toward better understanding the ejection process and mitigating the corresponding destruction, the discrete element method (DEM) is used to investigate the erosion flux of soil with a (continuous) lognormal distribution of particle size. The results show that the erosion flux increases relative to a monodisperse (single particle size) case with the same Sauter mean diameter due to an increase in the erosion flux of large particles and a reduction in that of small particles. The physical underpinnings of this counterintuitive behavior involve the interaction between small and large particles, particularly through collisions and static packing. Namely, the faster-moving smaller particles preferentially transfer momentum via collision to larger particles from a lower vertical position, causing an increase in large-particle flux and vice versa for small particles. Polydisperse mixtures also pack tighter than monodisperse mixtures, thereby increasing the erosion flux of both species by increasing the bulk density of the soil and the eroding material. Finally, to facilitate the use of kinetic-theory-based continuum models for this application, the discretization of continuous distributions is explored (e.g., representing a Gaussian distribution with a discrete approximation, e.g., particles of five different sizes). Two techniques are considered: the method of matching moments and a new method known as volumetric discretization. For the parameter space studied here, the volumetric discretization performs better when comparing the erosion flux of the continuous and discretized distributions. (C) 2017 American Society of Civil Engineers.
机译：当火箭降落在月球上时，排气羽流导致月球重石（土壤）向各个方向弹出。这样的高速弹出会对附近的设备和结构造成威胁。为了更好地了解喷射过程并减轻相应破坏，迈出了一步，使用离散元方法（DEM）来研究土壤粒径（连续（对数）对数正态分布）的侵蚀通量。结果表明，相对于具有相同Sauter平均直径的单分散（单个粒径）情况，腐蚀通量增加，这是由于大颗粒的腐蚀通量增加而小颗粒的腐蚀通量减小了。这种违反直觉的行为的物理基础涉及大小颗粒之间的相互作用，尤其是通过碰撞和静态堆积。即，运动较快的小颗粒优先通过冲撞将动量从较低的垂直位置传递到大颗粒，从而导致大颗粒通量增加，反之亦然。多分散混合物的堆积也比单分散混合物更紧密，从而通过增加土壤和侵蚀物质的堆积密度来增加两种物质的侵蚀通量。最后，为了便于在此应用中使用基于动力学理论的连续体模型，研究了连续分布的离散化（例如，代表具有离散近似的高斯分布，例如，五种不同大小的粒子）。考虑了两种技术：匹配力矩的方法和称为体积离散的新方法。对于此处研究的参数空间，当比较连续分布和离散分布的腐蚀通量时，体积离散化效果更好。 （C）2017年美国土木工程师学会。

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  • 来源
    《Journal of aerospace engineering》 |2017年第5期|04017027.1-04017027.10|共10页
  • 作者

    Berger K. J.; Hrenya C. M.;

  • 作者单位

    Univ Colorado, Dept Chem & Biol Engn, Boulder, CO 80309 USA;

    Univ Colorado, Dept Chem & Biol Engn, Boulder, CO 80309 USA;

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