Performance of Overset Mesh in Modeling the Wake of Sharp-Edge Bodies

Abstract

The wake dynamics of sharp-edge rigid panels is examined using Overset Grid Assembly (OGA) utilized in OpenFOAM, an open-source platform. The OGA method is an efficient solution technique based on overlap of a single or multiple moving grids on a stationary background grid. Five test cases for a stationary panel at different angle of attack are compared with available computational data, which show a good agreement in predicting global flow variables, such as mean drag. The models also provided accurate results in predicting the main flow features and structures. The flow past a pitching square panel is also investigated at two Reynolds numbers. The study of surface pressure distribution and shear forces acting on the panel suggests that a higher streamwise pressure gradient exists for the high Reynolds number case, which leads to an increase in lift, whereas the highly viscous effects at low Reynolds number lead to an increased drag production. The wake visualizations for the stationary and pitching motion cases show that the vortex shedding and wake characteristics are captured accurately using the OGA method.

Evolution of wake structures behind oscillating hydrofoils with combined heaving and pitching motion

“…Apart from these, we have performed a thorough evaluation of the solver on predicting the wake of a stationary inclined square panel (at several angles of attack) and a pitching square panel, which all agreed well with the results in literature. Details on this validation effort can be found in Verma & Hemmati (2020). Furthermore, we replicated the wake of a pitching NACA0012 airfoil that was reported by Koochesfahani (1989), which is not shown here for brevity.…”

“…OpenFOAM is an open-source finite volume solver that is widely used in the literature for numerical simulation of wakes in underwater swimming (Senturk & Smits 2018;Verma & Hemmati 2020;Bose, Gupta & Sarkar 2021).…”

“…Figure 4(b) shows the hole and calculated cells on the background grid, along with the interpolated cell fringe located on and around the foil. The 'inverse distance' technique was implemented for the interpolation of velocity and pressure data, which had previously been validated for highly refined grids (Chandar 2019;Verma & Hemmati 2020). The interpolation function for the inverse distance scheme is…”

“…Further details regarding this formulation can be found in Chandar (2019) and Petra (2019). A detailed validation study of the solver was also recently completed in Verma & Hemmati (2020).…”

“…Mainly, the outlet boundary is located sufficiently far (15c) from the foil, so that there are no adverse effects on the flow in the critical region behind the foil. The sensitivity analysis with respect to the domain size was carried out following previous work of Hemmati et al (2018), Gungor & Hemmati (2020) and Verma & Hemmati (2020), which determined that the domain used in SIM0, SIM1 and SIM2 are sufficiently large.…”