Aerospace Science and Technology
غلامحسین پوریوسفی; Mostafa Amiri tayyebi; Masoud Mirzaei
Abstract
This paper has investigated the flow interference between four circular cylinders of equal diameters in a square arrangement in a cross-flow. Wind tunnel experiments were conducted to measure the mean force coefficients and Strouhal numbers (St) for six spacing ratios (l/d) varying from 1.5 to 4 at five ...
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This paper has investigated the flow interference between four circular cylinders of equal diameters in a square arrangement in a cross-flow. Wind tunnel experiments were conducted to measure the mean force coefficients and Strouhal numbers (St) for six spacing ratios (l/d) varying from 1.5 to 4 at five subcritical Reynolds numbers (Re) ranging from 1.26×〖10〗^4 to 6.08×〖10〗^4. The pressure distributions on the surface of the cylinders were measured using pressure transducers. Furthermore, the hot-wire anemometer was employed to measure the vortex shedding frequencies behind each cylinder. It is revealed that for l/d=1.5, due to severe flow interference between cylinders, there is a difference between lift coefficients for the upstream cylinders. Also, for l/d≤2, the mean drag coefficients for downstream cylinders are negative. In addition, for l/d=2 and l/d=2.5, there is no vortex shedding from the upstream cylinders. Moreover, it is found that the effects of variations in this range of the Reynolds numbers, on the quality of the vortex shedding and Strouhal numbers are negligible; whereas the variations in l/d, strongly affect the flow pattern around the cylinders and aerodynamic coefficients. Also, by decreasing the amount of l/d, the effects of the flow interference between the cylinders increase.
Mohammad Reza Dr. Soltani; M. Masdari; M. Seidjafari; Kaveh Ghorbanian
Volume 7, Issue 2 , September 2010, , Pages 132-137
Abstract
Extensive wind tunnel tests are conducted to evaluate surface pressure distribution of a semi span swept wing. The wing section has a laminar flow airfoil similar to NACA 6-series airfoils. The investigations are conducted at various speeds and angles of attack. Surface pressure distribution over the ...
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Extensive wind tunnel tests are conducted to evaluate surface pressure distribution of a semi span swept wing. The wing section has a laminar flow airfoil similar to NACA 6-series airfoils. The investigations are conducted at various speeds and angles of attack. Surface pressure distribution over the wing upper surface is measured for both chordwise and spanwise sections. Statistical analyses are performed on the data to realize the transition point at each chordwise section. The 3D pressure profiles are compared to the corresponding 2D results at the same conditions. Calculation of the standard deviation, SD, of time variable pressure data shows that SD increases in the transition area and then decreases again when the flow becomes fully turbulent downstream. The measured transition points are further compared with 2D computational results.
