An internal hydraulic jump is a hydraulic jump that forms on the interface between two fluids with similar densities, such as fresh and salt water, cold and hot air. An important consequence of internal hydraulic jumps is turbulent mixing, which dissipates energy and redistributes fluid properties. Hence they are crucial to the understanding of small-scale mixing processes. While current knowledge of such jumps in marine environment are mostly relevant to nonlinear topographic effects on stratified flows, recent observations from SAR images have suggested another mechanism, i.e. the nonlinear interaction between a buoyant plume and a constricted lateral boundary. Such an oblique internal hydraulic jump was observed near an engineering-constrained jetty at the Mouth of Columbia River, which also recurred with tidal cycles. This presentation will report the ongoing study on the physics of such a phenomenon. The first part will present theoretical modeling efforts on the basic characteristics of an idealized oblique internal hydraulic jump. The second part will focus on an idealized numerical investigation of jump evolution process. Results indicate that a hysteresis mechanism might explain why jumps were mostly detected during a period after ebb maximum.
Yang Lu is a PhD candidate, majoring in coastal engineering at Hohai University. Yang have a broad range of research interests in coastal engineering, physical oceanography and fluid dynamics, with an emphasis on the underlying physics of natural flow phenomena. Yang does research with both analytical and numerical modeling methods. During 2015-2017, Yang was co-sponsored by China Scholarship Council and the Delaware Sea Grant to work with Prof. Fengyan Shi and Prof. James T. Kirby from University of Delaware. This presentation will report their recent progress on the study of an estuarine, oblique internal hydraulic jump, and will also introduce a high-resolution, non-hydrostatic coastal ocean model —— NHWAVE.