The regolith particle flow induced by propulsive spacecraft landing on the unprepared surfaces of Moon and Mars occurs in a combination of complex environments that combine low gravity, little or no atmosphere, with rocket exhaust gas flow that is supersonic and partially rarefied, and unusual mechanical properties of the regolith. Of these environmental factors, characterizing the regolith granular material fluidic behavior and gas-granular interactions is the most complex and least developed. In modeling these flows, constitutive relationships are incorporated as collisional, kinetic and frictional stresses as well as drag terms due to momentum exchange with the carrier phase, which become increasingly complex with increasing particle cloud density, compressibility effects in supersonic gas flow, and complexity of multi-size irregularly shaped particle mixtures. Formulation and validation of these closure models is very difficult, mainly due to lack of experimental data covering the broad range of operating conditions and variables. This project aims to generate first of their kind experimental data for gas-granular interaction physics in relevant conditions and implement a constitutive model formulation, maturation and implementation process to arrive at accurate predictive modeling tools for NASA lander project support. In the Phase I, an integrated approach for developing a combined measurement and modeling methodology to further improve accuracy of the gas granular flow solvers used for analysis and design was developed and demonstrated. Targeted experiments analyzing gas-particle flows in high-speed dilute conditions were conducted. Model improvements were made and further modeling requirements were identified. In Phase II the parametric space for gas-particle flows, and conditions will be expanded. Model improvements to gas-granular flow solver will be based on information obtained from high-resolution simulations and experimental data.
NASA commercial applications include NASA and commercial partner lunar lander development projects and future Mars landers. Small commercial lander activities under the CLEPS program and NASA sponsored instrument payloads will require accurate definition of the plume-particle distribution environment near the surface encountered by the landers and payload instruments. Accurate modeling that defines the gas and particle distribution is essential to properly design the instruments to measure spatial features of interest.
Non-NASA applications include wide range of sand and dust related military and civilian applications such as rotorcraft sand/dust brownout and engine dust ingestion. In addition, multiphase flows occur in many applications in chemical, petro-chemical and fossil-energy conversion industries where accurate modeling of particle shape play a huge role in the flow behavior of real particulate systems.