Steady Separated Flow Past Elliptic Cylinders Using a Stabilized Finite-Element Method
Subhankar Sen;  Sanjay Mittal;  Gautam Biswas

doi:10.3970/cmes.2012.086.001
Source CMES: Computer Modeling in Engineering & Sciences, Vol. 86, No. 1, pp. 1-28, 2012
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Keywords Elliptic cylinder, Stabilized finite-element, GMRES, Laminar separation, Wake topology.
Abstract The steady flow around elliptic cylinders is investigated using a stabilized finite-element method. The Reynolds number, Re, is based on cylinder major axis and free-stream speed. Results are presented for Re 40 and 0 a 90 , where a is angle of attack. Cylinder aspect ratios, AR considered are 0.2 (thin), 0.5, 0.8 (thick) and 1.0. Results for the laminar separation Reynolds number, Res available in the literature are only for thin cylinder and exhibit large scatter. Also, very limited information is available for separation angle. The present study attempts to provide this data. In addition, issues concerning initial separation, such as location of separation and its evolution with a and Re, are studied. Symmetric cylinders are associated with a closed wake and consists of two attached eddies which appear at Res. Wake topology for asymmetric separation is proposed and compared with those of ` 12 `
12 `$12 `&12 `#12 `^12 `_12 `%12 `~12 *smith83 and ` 12 `
12 `$12 `&12 `#12 `^12 `_12 `%12 `~12 *dennis03. The proposed topology differs significantly from the existing ones. For asymmetric cylinders, the wake is open and consists of an attached upper bubble and an unattached recirculation zone. The attached bubble appears at Res while the unattached zone appears at a larger Re. While symmetric separation initiates from base point, bubbles for asymmetric separation form near the trailing tip of thin and center of thick cylinders. For symmetric cylinders, the bubble elongates, approximately, linearly with Re. Irrespective of AR, Res exhibits non-monotonic variation with a.
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