Development and characterization of a microfluidic nozzle for water sheet jet cooling

Future hypersonic transport concepts demand high aerodynamic performance, requiring sharp and slender geometries. However, these designs lead to extreme heat fluxes and temperatures, while the limited space available for active cooling systems adds significant thermal management challenges. This thesis proposes the development of a microfluidic nozzle for cooling ultra-sharp leading edges. A planar microfluidic nozzle is designed and fabricated using lithographic techniques to produce liquid sheet jets with thicknesses in the micrometer range. This study investigates the effects of nozzle design and fabrication on the dimensions and stability of the liquid sheets, which are influenced by the interplay between flow dynamics and geometric factors. Internal nozzle flow characterization is performed using PIV measurements and CFD simulations, while shadowgraph-imaging experiments over a range of Weber numbers provide insights into the sheets’ length, width, and dynamic behavior. The results show that flow rate and nozzle outlet aspect ratio primarily determine the liquid sheet size, with increased Weber numbers leading to longer, wider sheets, though with greater flow instability. However, sheet stability is more strongly influenced by the nozzle’s converging angle and fabrication-induced perturbations. The findings suggest that nozzle design must be tailored to specific applications, rather than optimized singularly.

The work is towards M.Sc. degree under the supervision of Assistant Professor Alexandros Terzis, Department of Aerospace Engineering, Technion – Israel Institute of Technology