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- MakaleYalnız künye2025Scopus SJRQ1Reduction of fluid forces on a circular cylinder in the laminar flow regime using a pair of airfoils
Fırat, Erhan; Oruç, Vedat; You, Rui; Biçer, Uğur; Devecioğlu, Atilla G.
Flow around the cylinder, with/without a pair of airfoils symmetrical to the cylinder's horizontal axis, was simulated for a diameter-based Reynolds number (Re) of 100. The objective of this numerical study is to simultaneously reduce the values of the time-averaged and fluctuating forces acting on a system consisting of a pair of airfoils and a cylinder below those of a single cylinder by using different combinations of the parameters chord (c), angle of rotation (β), angle of attack (α), and the shortest distance between the aerodynamic center of the airfoil and the surface of the cylinder (g). The values of these key parameters are determined primarily through two approaches. The first approach involves emulating the flow pattern surrounding the system to match the potential flow pattern. The second approach involves disrupting the interaction between the shear layers from the cylinder by stretching them in the mean flow direction. The second approach has been demonstrated to exhibit superior performance in terms of reducing both time-averaged and fluctuating forces concurrently. The second approach has been demonstrated to exhibit superior performance in terms of reducing both time-averaged and fluctuating forces concurrently. The optimal geometrical parameters that yield the desired end results are determined to be c = 0.5D, α = 0°, β = 60°, and g = 0.2D. Utilizing these parameters has been demonstrated to result in a substantial reduction in the time-averaged drag, fluctuating drag, and fluctuating lift coefficients of the system, with the respective percentage reductions reaching 14.4 %, 92.1 %, and 73 %, respectively, when compared to the values obtained for a single cylinder.
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İncele - MakaleAçık Erişim2023Scopus SJRQ3Aerodynamic Drag Improvements on a Simplified Heavy Vehicle using Three-sided Plain and Notched Base Flaps
Fırat, E.
An experimental investigation has been undertaken to determine the effects of plain and notched base flaps on the drag performance of simplified tractor-trailer combination without any intermediate gap, Generalized European Transport System (GETS). Both plain and notched base flaps are rigid, made up of three identical flaps whose length is equal to the width of the GETS model, and not angled inward or outward. The experiments examined three-sided flap configurations corresponding to various combinations of seven heights of the plain part (from 10 to 40 mm in steps of 5 mm), four notch amplitudes (from 2.5 to 10 mm in steps of 2.5 mm), and five notch wavelengths (from 10 to 50 mm in steps of 10 mm). It is shown that the drag performance of the plain flap at zero yaw highly depends on the height of the plain flap. The maximum drag reduction occurs for e/w=0.1 yielding a drag reduction of 1.9% when compared to the GETS model without flap (baseline GETS). It was shown that the time-averaged drag coefficient increased slightly until a maximum was reached at e/w=0.3 but then decreased slightly with increasing e/w. Under zero yaw angle conditions, GETS model with a notched base flap, e10-a05.0-λ20, gives the lowest drag. The addition of this base flap to the GETS model resulted in a 2.8% drag reduction. This notched base flap was shown to be more effective not only at reducing <CD> under yawed flow conditions tested but also at reducing time-averaged side coefficient under yawed flow conditions tested, compared to the e10-a00.0-λ00 flap
AtıfScopus8WoS6OpenAlex4İncele - MakaleYalnız künye2011Scopus SJRQ2THE EFFECT OF ATTACK ANGLE TO VORTEX SHEDDING PHENOMENON OF FLOW AROUND A SQUARE PRISM WITH A FLOW CONTROL ROD
Akansu, Yahya Erkan; Özmert, Mehmet; Firat, Erhan
In this study, the effect of attack angle on vortex shedding phenomena in the case of flow around the square prism as a bluff body and the circular rod which used as flow control component was experimentally investigated. While the value of attack angle equal to 0 degrees, the upstream control rod and square prism are in tandem arrangement to free stream. Experiments were conducted at Reynolds number of 1.0 x 10(4), for the diameter ratio of d/D=0.25, the attack angle between 0 degrees <= alpha <= 90 degrees, and the value of normalized distance between two prism LID is 1, 2, 3, and 4. The velocity measurements were conducted by means of constant temperature anemometer (CTA) as well as vortex shedding frequencies obtained by the spectral analysis of velocity-time history. Characteristics of the vortex formation region and location of flow attachments, reattachments, and separations were observed by means of the smoke-wire flow visualizations. At the angle of attack 0 degrees of the location L/D=2 and 3, the flow structure that possess high vorex shedding frequency which causes remarkable reductions on the drag force and significant increase in the heat transfer was obtained. This flow structure continous to decrease with increasing attack angle up to around 10 degrees. By further increasing of attack angle, the effect of flow control rod on vortex shedding frequency disappears completely.
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