The Study about Drag Reduction of a Circular Cylinder with Grooves

Abstract

In this study, two kinds of circular cylinders which cut grooves to the cylinder surface for the purpose of cylinder drag reduction were produced. One of which is the circular cylinder which set 2 grooves in the cylinder upstream side, and other is the circular cylinder which provided 6 grooves every 60 degrees. Experiments were performed using a wind tunnel varying an attack angel α = 0 to 60 degrees in the range of Reynolds number Re= 1×10 4 to 1.2×10 5 . The relationship between a Strouhal number and Reynolds number, the pressure distribution on the surface of cylinder, the flow feature around the cylinder, and drag reduction effect were investigated. As the results of experiments, in the case of 2 groove cylinder, the Strouhal number of the cylinder with grooves increases from 0.20 to 0.28-0.30, the base pressure coefficient rises from -1.4 to -0.8, then the drag coefficient decreases from 1.3 to 0.55 at α + θ f < 80 degrees, in the range of Re > 4×10 4 . However, it became clear that the drag reduction effect was lost as an attack angle α is attached.In order to compensate this weak point, the 6 groove cylinder was proposed, and the characteristic test was performed. It was obtained that the cylinder with the deep depth of groove is not influenced by the direction of wind. The value of drag coefficient was about 56% of value of the drag coefficient of smooth cylinder. It was shown that the wake width of the proposed cylinders narrows from the wake width of the smooth cylinder.

Application and optimization of drag reduction characteristics on the flow around a partial grooved cylinder by using the response surface method

“…However, the non-smooth cover on the surface of the cylinder will reduce the coefficient of drag in great efficiency as it causes the critical regime at a lower Reynolds number (Rodriguez et al, 2017). This phenomenon has been verified by different experiments, which tested different non-smooth structures on the cylindrical surface of certain applications such as dimples (Bearman & Harvey, 1993;Tan, Koh, & Ng, 2016), grooves (Yamagishi, Kimura, & Oki, 2013;Yokoi, Igarashi, & Hirao, 2011). Numerous researches have drawn the conclusion, that non-smooth structure can delay the full separation of the boundary layer and optimize the flow condition behind the cylinder as the drag force is directly related to the Karman vortex street and the full separation point of the airflow (Yamagishi & Oki, 2007).…”

Surface pressure distribution on patterned cylinders under simulated atmospheric boundary layer winds

“…The following ideas have been previously tested: grooves, [3][4][5] bumps and dimples, [6][7][8] and screens, [9,10] among others. These studies showed that surface manipulation can effectively delay the separation point.…”

“…[2] The current paper will deal strictly with passive mechanisms.The majority of techniques researched with cylindrical structures involves surface manipulation, such as added roughness or patterns. The following ideas have been previously tested: grooves, [3][4][5] bumps and dimples, [6][7][8] and screens, [9,10] among others. These studies showed that surface manipulation can effectively delay the separation point.…”

Investigation of Drag Coefficient at Subcritical and Critical Reynolds Number Region for Circular Cylinder with Helical Grooves

“…The idea to make grooves on the cylinder is also from a study made by Talley and Mungal [12] they noticed that the plants of cactus have a strong resistance against the wind forces and that returns to their longitudinal grooves. Yokoi et al [13] carried out experiments on grooved cylinders and they found that the drag effect with lower number of grooves on circular cylinder is negligible when the angle of attack varies. However, as long as the number of grooves increases over the cylinder surface, the drag coefficient is independent on the angle of attack.…”