Search for: All records

Plume-surface interactions (PSI) occur during the take-off and landing of interplanetary vehicles, leading to particle ejection and the formation of craters. This can be detrimental to the vehicle and any structures or infrastructure near the landing site. A major challenge in developing a comprehensive understanding of this three-dimensional phenomenon is the need to characterize the ejecta and cratering dynamics simultaneously. Here, experiments are conducted in a vacuum chamber at different nozzle heights and ambient pressure conditions using high-speed stereo-photogrammetry and planar particle tracking velocimetry to quantify the cratering and ejecta dynamics. Predictably, it was observed that the trajectory of ejecta with a large Stokes number was mostly unaffected by the nozzle flow after leaving the crater. Under rarefied conditions, the ejecta kinematics (velocity, ejection angle, range, and height) were significantly different compared to continuum conditions. Finally, the findings demonstrate a dependency between ejecta kinematics and crater topology for the current test cases, providing critical insights into particle ejection’s initial characteristics. 

Novel cloth face masks to mitigate the spread of COVID-19 have been developed and tested for particle (0.1 μm in size) filtration efficiency, bacterial filtration efficiency, breathability, leakage, heart rate, and blood oxygen level, and then compared with the available N95 masks and surgical masks. It was found that this novel mask had better filtration efficiency than that of surgical masks and was very close to that of N95 masks. The breathability was also improved and was in the range of the designated levels for barrier face coverings. The flow visualization technique was utilized to study the leakage of the mask and it was found to have significantly lower leakage as compared to surgical masks. Heart rate and blood oxygen level tests were performed by wearing the mask during 10-minute walking sessions and it was found that wearing the mask did not adversely affect heart rate or blood oxygen levels or add any other strain on the wearer. It is believed that this novel face mask would reduce the spread of COVID-19 as well as provide an environmentally and economically conscious alternative to the N95 respirators for the public. The mask developed in this study can be washed, reused, and therefore worn for longer periods of time.