软着陆过程中，登月舱发动机产生高速高温羽流冲蚀月表月壤层形成弹孔状的月坑，会对着陆后的稳定性造成影响， 同时也会卷起松散的月壤颗粒。 大量的月壤颗粒以及月尘卷起后高速运动形成的喷砂效应， 极有可能阻塞发动机并对精密仪器造成损耗。 同时， 被羽流场卷起的大量月尘与月壤颗粒很难在短时间内重新落回月面，它们悬浮在近月表运动，会对出舱人员与相关机械带来危险恶劣的工作环境。 因此，降落区域内铺设着陆垫提高承载稳定性， 尽量避免或减弱软着陆过程中羽流对月壤的冲蚀效应、 产生的喷砂效应和对月壤地基承载稳定性的削弱很有必要。

本文首先收集研究月壤相关物理力学特性与参数， 随后通过建立 ABAQUS 有限元模型研究不同密实度月壤地基的承载性能， 并结合实际荷载情况给出月壤承载能力满足荷载要求的结论。 然后， 将 Mohr-Coulomb 本构模型写入 ICEM-CFD 中划分的多孔结构中改变其液态特性， 再赋予该区域月壤物理参数引入流化床模型达到建立月壤模型的目的， 并导入 FLUENT 中建立欧拉-欧拉法多相模型。 FLUENT 中导入DSMC 计算源程序处理羽流场计算域， 将 Apollo 11 号登月舱铅垂下降过程中的 4 秒时间步均分 4 组， 每 1 秒时间步内取平均下降速度进行计算， 以插值计算的思想来达到数值模拟登月舱软着陆过程中发动机羽流冲蚀月壤的目的，在此之前设计并开展了模拟发动机冲蚀月壤试验工作，根据试验参数建立数值仿真模型计算，将试验结果与仿真结果对比验证数值计算的可信度与精确度。
仿真结果与试验结果误差为 6.1%-6.3%，满足精度要求，数值计算方法可靠度得到验证。 仿真结果与 Apollo 11 号登月拍摄的影像资料与实测数据进行对比后， 得出该方法精确度很高， 月坑深度误差为 5.7%，月壤颗粒运动轨迹与水平面夹角误差为11%。 本文最后提出着陆垫铺设方案， 增设月面着陆垫重复上述仿真方法进行计算，分析增添着陆垫对阻挡羽流冲刷月壤效果以及羽流扩散影响范围的变化，旨在对未来月球着陆舱登陆月面时需铺设的着陆垫范围以及功能区布置有实际指导意义。

关键词：月壤、羽流场、冲蚀效应、着陆垫、 CFD 仿真计算

During the soft landing process, the lunar module engine generates high-speed and high-temperature exhaust flow that erodes the lunar surface, creating pit-like craters that can affect the stability after landing and kick up loose lunar soil particles. The large amount of lunar soil and dust particles kicked up by the high-speed sandblasting effect can potentially block the engine and cause damage to delicate instruments. Additionally, a significant amount of lunar dust and soil particles lifted by the exhaust flow will remain suspended near the surface for a considerable time, creating a hazardous working environment for astronauts and machinery. Therefore, it is necessary to lay a landing pad in the landing area to increase stability and minimize the erosive effect of the exhaust flow on the lunar surface, sandblasting, and weakening of the lunar soil foundation's bearing capacity during the soft landing process.
This thesis first collected physical and mechanical properties of lunar soil and related parameters. Then, using an ABAQUS finite element model, the bearing capacity of different dense lunar soil foundations was studied. Combined with actual load conditions, the conclusion was drawn that the lunar soil bearing capacity meets the load requirements. Next, the Mohr-Coulomb constitutive model was written into the porous structure partitioned by ICEM-CFD to change its liquid characteristics. The physical parameters of the lunar soil were introduced to establish a lunar soil model, and an Euler-Euler multiphase model was established in FLUENT. The DSMC calculation program was imported into FLUENT to calculate the exhaust flow field during the descent of the Apollo 11 lunar module. The 4- second time step of the vertical descent was divided into four groups, and the average descent speed was calculated for each one-second time step using the interpolation calculation method to simulate the exhaust flow erosion of the lunar soil during the soft landing process. Prior to this, simulation experiments on engine erosion of lunar soil were designed and carried out, and a numerical simulation model was established based on experimental parameters. The reliability and accuracy of the numerical calculations were verified by comparing the simulation results with the experimental results.
The error between the simulation results and experimental results was 6.1%-6.3%, which meets the precision requirement, and the reliability of the numerical calculation method has been verified. After comparing the simulation results with the image data and actual measurements taken by Apollo 11's lunar landing, it was concluded that this method has a high accuracy, with an error of 5.7% in the depth of lunar craters and an error of 11% in the angle between the trajectory of lunar soil particles and the horizontal plane. Finally, this thesis added the calculation of the lunar landing pad using the same simulation method, analyzed the impact of adding a landing pad on blocking the erosion of the lunar soil by exhaust flow and the range of its diffusion, aiming to provide practical guidance for the future layout of landing pads and functional areas for lunar landers.