Channels, Fall 2020

Channels • 20 20 • Volume 5 • Number 1 Page 1 The authors thank the Cedarville University School of Engineering and Computer Science for their support in funding the research presented in this paper. The authors are with the Mechanical Engineering Department, Cedarville University, Cedarville, OH 45314 USA, as undergraduate senior students. M. T. Brocker (email: mbrocker@cedarville.edu) D. J. McDonell (email: davidmcdonell@cedarville.edu ) D. L. Pensworth (email: dpensworth@cedarville.edu) J. J. Swimm (email: jswimm@cedarville.edu) Experimental and Numerical Study of Drag Reduction on Elliptical Cylinders Using Surface Grooves Michael T. Brocker, David J. McDonell, Drake L. Pensworth, Joshua J. Swimm Engineering and Computer Science Abstract — Drag reduction on an object subject to external flow remains a topic of interest due to a wide range of applications. Previous studies showed that grooves on the surface of a circular cylinder lead to drag reduction, which had thus been applied to save energy in various implementations. In the present study, the effects of longitudinal surface grooves with respect to drag reduction on circular and elliptical cylinders were experimentally explored through resin additive manufacturing and a wind tunnel. Significant drag reduction originated by surface grooves was observed. In conjunction with experimental investigations, numerical analyses were performed with computational fluid dynamics (CFD) to examine the physical causes of the drag reduction. The numerical studies included two- and three-dimensional simulations of flow over circular and elliptical cylinders. The turbulent energy and wake regions of flow were discussed. Key factors in drag reduction were the location of the beginning of turbulence or vortices in the grooves, the boundary layer separation angle, and the size of the turbulent wake region. Through the numerical CFD simulations and experimental results, spanwise surface grooves on elliptical cylinders are verified to reduce drag. Keywords — CFD (Computational Fluid Dynamics), Drag Reduction, Elliptical Cylinders, Wind Tunnel Introduction n a world of transportation and constant motion, drag induced by air flowing over a body is an adversary of energy efficiency and aeronautical performance. Reducing the drag on an object moving through a fluid is a goal for which many fluid dynamics researchers strive. The most common method of drag reduction is to alter the profile of an object and make it more streamlined. Bluff bodies transformed into more aerodynamic profiles are highlighted in the transportation industry. However, for some applications, the geometry of the body cannot be modified and an alternative method of drag reduction is required. Such reduction of drag in bluff bodies is the focus of this paper. The study presented is an experimental and I