A 6:1 prolate spheroid at an angle of attack is often used as a representative model for studying the wake dynamics of slender bodies, particularly in geophysical flows where stratification plays a crucial role. In this study, we conducted high-resolution large-eddy simulations (LES) to examine the flow past a 6:1 spheroid positioned at a 10-degree angle of attack under varying levels of stratification. 

Our analysis focuses on the near-body flow characteristics, the evolution of the mean wake, and the formation and progression of streamwise vortex pairs resulting from flow separation. This work aims to provide a deeper understanding of how stratification influences the complex wake dynamics associated with slender bodies in stratified environments.

Preliminary results were published in the 2022 TSFP12 conference proceeding held at Osaka, Japan (Online). 

Despite the widespread use of slender bodies in engineering applications, most research has focused on the wakes of bluff bodies. Simulating turbulent boundary layers over elongated bodies while accurately resolving their far wake is computationally expensive, which has led to a scarcity of studies on this topic.

In this project, we employ a hybrid approach to simulate the far wake of a 6:1 spheroid under both stratified and unstratified conditions, addressing these computational challenges and providing new insights into the turbulent wake dynamics of slender bodies.

Results from unstratified wake analysis are reported in Ortiz-Tarin, Nidhan, and Sarkar 2021. A detailed investigation of stratified slender-body wakes was published in JFM where we focus on the peculiarities of slender-body wake topology with respect to the bluff-body wakes at comparable Reynolds numbers and Froude numbers: Ortiz-Tarin*, Nidhan* (*co-first authors), and Sarkar 2023.

Turbulent shear flows are dominated by coherent structures, which play a crucial role in influencing turbulent kinetic energy (TKE), shear stresses, and phenomena like wave generation in stratified flows. Despite their significance, these structures have not been systematically explored and analyzed in high-Reynolds-number turbulent wakes, particularly under stratified conditions.

In this study, we employ spectral proper orthogonal decomposition (SPOD) to extract and analyze these coherent structures in both unstratified and stratified environments. Results from the project on unstratified and stratified wakes are published in Nidhan et al. 2020 and Nidhan at al. 2022, respectively.

A follow-up study reporting the existence of streaks for the first time in an unstratified turbulent wake was published in JFM.