ABSTRACT

Dusty flows are common in nature and engineering applications. Sand storms and volcanic ash are among examples widely occurring in nature. In engineering applications, dusty flows may represent significant operating and safety challenges. Dust clouds kicked up by rotary aircrafts in ground proximity may reduce visibility, damage blades, and lead to engine degradation. Dust clouds kicked up by thrusters on planetary landing modules are known to interfere with on-board telemetry, create electrostatic hazard, and lead to uneven landing surfaces. Due to limited understanding of how the feedback force from micron-sized particles alters the carrier flow, predicting the evolution of semi-dilute dust clouds, such as those encountered in engineering, remains a challenge. The proposed research will enable predictive models of semi-dilute dust cloud, support the development of planetary landing modules, science missions relying on robotic helicopters to explore and collect soil samples, and the development of mitigation strategies for rotary aircrafts operating in desert conditions. This award also aims at inspiring high-school students from underserved communities to pursue STEM education. These students will get hands-on experience as part of a learning module that will be delivered to them during a field trip to Arizona State University.

The proposed research in this award addresses poorly understood vortex dynamics in semi-dilute dusty flows where the feedback force by suspended dust particles on the fluid leads to growth and pairing processes remarkably different from those of conventional particle-free vortices. This award will answer the following questions: 1) What are the mechanisms by which dispersed inertial particles modulate an isolated vortex tube under two-way coupling? 2) How does particle inertia affect particle-vortex instabilities? 3) How does the conventional vortex-pair merger change in semi-dilute dusty flows? These questions will be addressed using a combination of theoretical and numerical analyses, namely, Linear Stability Analysis, and high-fidelity Euler-Lagrange simulations. The fate of particle-laden vortical structures will be characterized using scaling laws that take into account the characteristics of the particle phase, including Stokes number, volume fraction, mass loading, and density ratio.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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