ISS: Solving a Fluids Mystery: Hydraulic Jumps in Corner Flows

When water from a kitchen faucet splashes at the bottom of a sink, it's sometimes possible to observe a circular ridge where the splashing water abruptly changes thickness. This ridge is called a hydraulic jump. This seemingly mundane and innocuous behavior may, in fact, be key to understanding why it is often difficult for modern, high power electronic devices to keep their cool. To unravel this enigma, spaceflight experiments, which are free of the confounding effects of gravity, will be performed on a simple model of an important class of cooling devices known as heat pipes. Should, as expected, the mechanism of hydraulic jumps be observed and characterized in this setting, this will set the stage for new approaches for developing novel methods of cooling high power applications such as CPUs/GPUs, electric vehicles, and large-scale energy storage facilities for solar and wind farms. Additionally, project researchers will deliver non-technical lectures on the proposed work to students and to the general public, with the goal of exposing a broader audience to the excitement of cutting-edge research in science and engineering. The proposed research aims to resolve a decade-old fluid dynamics puzzle involving driven free-surface flows in confined geometries. Prior experiments observed unexpected liquid flooding at the hot end of containers under high heat, contradicting models predicting drying due to evaporation and thermos-capillarity. This unresolved mystery impedes effective thermal and fluid management device design. Inertial effects, previously neglected, are hypothesized to be critical. Specifically, high-speed liquid jets and hydraulic jumps in driven corner flows with free surfaces may be the underlying mechanism causing hot-end flooding. The research will conduct flight experiments, measuring fluid velocities under conditions where, in past studies, flooding was observed. Both flight and ground-based measurements of velocimetry, temperature, pressure, and meniscus shape will guide and validate the development of theoretical and numerical models of two-phase (liquid and vapor) flow. The broader impacts include advancements in thermal and fluid management in diverse applications. Moreover, the project will promote education and diversity by training new scientists, encouraging underrepresented groups' participation, and engaging the public through outreach efforts. 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.