Vortex shedding in flows of dilute polymer solutions

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• 作者：C.J. Pipe and P.A. Monkewtiz
• 关键词：Flow round a cylinder ; Dilute polymer solutions ; Vortex shedding ; Flow instability
• 刊名：Journal of Non-Newtonian Fluid Mechanics
• 出版年：2006
• 出版时间：15 November 2006
• 年：2006
• 卷：139
• 期：1-2
• 页码：54-67
• 全文大小：853 K

文摘

Experiments on vortex shedding from a cylinder placed in uniform flows of low concentration polymer solutions are reported for Reynolds numbers from 50 to 150. The fluids used were aqueous solutions of polyethylene oxide (PEO) and Weissenberg numbers were O (decoration:none; color:black"" href=""/science?_ob=MathURL&_method=retrieve&_udi=B6TGV-4KRY8VH-1&_mathId=mml99&_user=10&_cdi=5264&_rdoc=5&_handle=V-WA-A-W-AA-MsSAYWW-UUA-U-AAZCWABWUW-AAZWDEVUUW-VWUUYYVW-AA-U&_acct=C000050221&_version=1&_userid=10&md5=acb2af1bee5df3f075c26c8844979098"" title=""Click to view the MathML source"">10⁻¹). It is shown that even small amounts of PEO have a significant stabilizing effect on the von Kármán instability which is in turn destabilized by shear-thinning at higher concentrations. The presence of PEO is also observed to reduce the saturated vortex shedding frequency and cause a redistribution of velocity fluctuations in the attached shear layers. At higher concentrations further changes in the velocity fluctuations are noted in the wake. Downstream of the cylinder an overshoot in the time-average streamwise velocity is measured for the polymer solutions and an analogy is drawn to the negative wake behind a sphere falling in a viscoelastic fluid.