Numerical Study on the Drag Reduction for a D-Shaped Bluff Body with Wavy Trailing Edge Structures

Abstract

The intricate and complex flow structures of three-dimensional unsteady incompressible turbulence surrounding bluff bodies have garnered considerable attention from numerous researchers. Using computational fluid dynamics (CFD) methodologies, the underlying mechanism by which a wavy trailing edge (TE) design for a D-shaped bluff body achieves drag reduction was explored. The wavy TE was in the form of a cosine wave with two design parameters: amplitude and wavelength. To ascertain optimal control parameters, we employed an improved delayed detached eddy simulation (IDDES) technique for a comprehensive parametric analysis, focusing on the amplitudes and wavelengths of the cosine wave. Furthermore, to gain a more holistic understanding of the factors influencing the design of wavy TE structures, we conducted parametric studies on three distinct groups of wavy structures. After identifying the optimal amplitude, wavelength, and wave type, we further investigated the control mechanism of the wavy structures in reducing the drag and mitigating lift fluctuations for Reynolds numbers in the range 3.6×10⁵–3.6×10⁶. Present investigation revealed that compared with the original D-shaped bluff body, the wavy TE structures significantly reduced the average drag coefficient, with a maximum drag reduction of 60.2%. Moreover, it effectively curtailed the fluctuations in the lift coefficient. With careful parameter adjustments, the wavy TE significantly enhanced the characteristics of the flow field. This improvement was evident in the reduction in vortex scales, enhancement of instability characteristics in separated shear layers, and effective suppression of periodic vortex shedding.