Research Fellow, Mechanical Engineering
Shallow-water jets refer to the jetting flows with a more extended horizontal length scale compared to the vertical length scale. Unique features of such flows include their meandering motion characterised by counter-rotating vortices on both sides of the jet. Examples of shallow-water jet flows abound in nature and industry, such as the river flows near a river mouth and flows at an outfall, being discharged into shallow coasts. It is essential to understand the flow dynamics in such flow motions for environmental and geophysical purposes, for example, to facilitate the water quality control near the shallow coastal areas.
The underlying mechanism of the aforementioned meandering motion is believed to be a result of the linear instability of the shallow jet, which, as an extensive flow phenomenon in horizontal directions, naturally entails a global perspective. However, most of the previous studies focused on a local stability analysis at a certain position, revealing only part of the story of how the shallow jet meanders. Thus, the current postdoctoral position invites you to close the gap by performing a global linear stability analysis of numerically simulated shallow jet flows with physically relevant parameters to further our understanding of the linear mechanism in these flows.
The candidate should hold a PhD degree in mechanical engineering or civil engineering or computational science. S/he should have experience in solving large-scale eigenvalue problems and direct numerical simulations (DNS). The candidate will first use a high-order open-source numerical code utilising the spectral element method to simulate the depth-averaged Navier-Stokes (NS) equations to generate the time-averaged shallow jet flows, which will be used as the base flow in the linear stability analysis. Then, s/he will couple the DNS with the Arnoldi method using ARPACK/LAPACK software to calculate the global eigenmodes in the linearised equations for the shallow jet. In the end, the adjoint depth-averaged NS equations will be derived to probe the sensitivity of the flow. With these numerical tools and results, we are going to understand and find out when and how the meandering flow pattern begins and evolves in shallow jets. The starting time of the position is Feb. 2020.
Location: Kent Ridge Campus
Department : Mechanical Engineering