Experimental investigations of crater formation on granular bed subjected to an air-jet impingement

Abstract

The crater formation on granular particle beds is important for engineering applications, chemical and process industries as well as for an explanation of related natural phenomena. In this article, experimental studies on the formation of a crater and the subsequent movement of granular particles are carried out. Granular beds consisting of mono-dispersed or poly-dispersed spherical glass-beads are subjected to an air-jet impingement. The impinging air-jet causes creation of craters of various sizes and shapes (such as saucer shape, parabolic shape, parabolic shape with an intermediate region, U shape, and craters with conical slants with a curved bottom surface). The experimental observations reveal two predominant regimes, categorized based on the crater stability, namely, a stable regime or an unstable regime. The mechanisms for the crater formation such as viscous erosion, diffused gas eruption, bearing capacity failure, and diffusion driven flow or combination of them are identified. It is observed that the steady-state depth of a crater increases linearly with an increase in the air-jet flow-rate. The temporal growth of crater depth shows logarithmic variation for a given flow rate. A regime map of the observed crater shapes is presented.

Lunar plume-surface interactions using rarefiedMultiphaseFoam

“…He presented a figure of the crater formed under the conditions of the lunar and Martian rocket plume impingement. The size of the crater formed in rarefied conditions was larger than that under ambient Earth atmospheric conditions, and neither an intermediate region nor a rim Guleria and Patil (2020) was found in this crater. Metzger (2016) recognised that the surface erosion rate according to experiments in the continuum flow regime resulted in an under-estimation in the transition flow regime and implied that the Knudsen number exacerbated the complexity of the plume erosion physics.…”

“…Data, including videos recorded during actual missions and lab experiments (Immer et al, 2011;Roberts, 1963;Land and Clark, 1965;Guleria and Patil, 2020;Kuhns et al, 2021), has been extensively used to understand PSI behaviour, but it is easily influenced by the thrust level, nozzle height, angle of the nozzle, the period of firing, and soil physical properties (Scott andKo, 1968. Metzger et al, 2009) have concluded that the plume impingement will move regolith particles owing to a combination of any four mechanisms: viscous erosion, diffused gas eruption, bearing capacity failure, and diffusion-driven shearing.…”

“…It has been found that viscous erosion is the most important mechanism during the period of landing Metzger et al (2011). Guleria and Patil (2020) found craters in five different forms, including saucer, parabolic, parabolic with an intermediate region, U, and conical slants with a curved bottom. Their experiments proved that the particle size and distribution have a significant impact on the crater shape, dimensions, and the formation mechanism, but this experiment is done intrusively with the nozzle close to a transparent splitter plate to allow observation of the crater formation.…”

Scaling laws of plume-induced granular cratering

“…1 a. The influence of the nozzle exit diameter ( ) ( 19 ), nozzle height ( h ) ( 6 ), mass flow rate ( ) ( 12 ), particle parameters (shape, size, density) ( 20 ), and gravity ( 21 ) have all been studied for subsonic impinging jets. Given the experimental challenges, very few studies have been able to focus on the supersonic jet impingement, even though the jet Mach number could drastically change the jet structures, shock dynamics, and the interaction between gas and granular beds.…”

Erosion of cohesive grains by an impinging turbulent jet

“…Numerical studies for laminar jets have also shown the relevance of the Shields number to describe the erosion threshold of the granular bed [35,36]. Beyond the erosion threshold, i.e., for larger Shields numbers, different morphologies of craters were highlighted, from shallow parabolic craters (type I) to deep conical craters (type II) [31,37,38]. These different morphologies depend on the distance of the jet from the granular bed, the velocity of the jet, and the size of the particles.…”