Experimental Studies on Flow Past Mound-Bearing Craters and Flexible Vegetation Elements

The work presented herein covers two separate research projects. The first is a study of the flow dynamics over impact craters that host a central mound by utilizing a model with an idealized geometry and another model with a geometry sourced from that of a Martian impact crater. The second project consists of the fabrication of flexible idealized vegetation elements seeded with fluorescent particles to facilitate the quantification of both the flow and solid deformation field.

Both projects leveraged the experimental methods of high-resolution planar particle image velocimetry (PIV) and refractive-index matching (RIM). The RIM approach acts to render the models optically invisible and thus facilitate measurements throughout the full domain.

The first research project investigated the intracrater and extracrater flow structures over mounded craters induced by unidirectional flow. Results showed that the mean flow within the idealized crater exhibits more complexity compared to an empty crater. Second-order statistics highlighted regions of elevated turbulent stresses, which revealed a complex interaction between shear layers at the upstream and downstream parts of the rim and the central mound. These results have implications mass and momentum exchange, and for sediment transport processes. Lastly, results from the realistic crater model showed both similarities and differences with the primary flow features over the idealized model.

Quantification of the hydroelastic phenomena linking plant deformation and fluid flow is critical in investigating key fluvial processes. In the second project, measurements of unidirectional flow surrounding idealized, submerged flexible canopy elements, together with the corresponding solid displacement field, were simultaneously obtained by combining fluorescent imaging and RIM. The operating principle of the approach involves seeding the two phases with different tracers, facilitating independent interrogation of the dynamics of each. Furthermore, time-resolved data allowed for observation of the dynamic link between a deformable object and the surrounding flow field.