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

Suyash Verma,Arman Hemmati

doi:10.3390/computation8030066

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.

Highlights

The study of flow over stationary and moving bodies has been an important area of investigation in fluid mechanics which dates back to the pioneering work of Karman [1]
In order to have an optimum size for the grid and to sufficiently resolve the flow characteristics, grid independence analysis was completed for the angle of attack (α) of 30◦
Aarnes et al [22] further showed that for the study of two dimensional flow over a circular cylinder using Immersed Boundary method (IBM) implementation, the domain requires an approximately 18.1 times more grid points than that used in the Overset method to achieve a similar accuracy [22]

Summary

Introduction

The study of flow over stationary and moving bodies has been an important area of investigation in fluid mechanics which dates back to the pioneering work of Karman [1]. Oscillating hydrofoils are commonly investigated for various industrial applications including underwater propulsors, marine propellers and bio-inspired ocean profilers [4,5]. These applications commonly experience vibratory or steady uniform loading, which is most often a direct consequence of flow separation and vortex detachment [3,6]. The Strouhal number (St = f Aw /U∞ ), where f and Aw are the oscillation frequency and the wake width, respectively was kept constant at 0.2 This generally promotes production of drag force instead of thrust [7,11].

Methods

Results

Conclusion