Low-Reynolds-number flow past a cylinder with uniform blowing or sucking

We analyse the low-Reynolds-number flow generated by a cylinder (of radius a) in a stream (of velocity U-infinity) which has a uniform through-surface blowing component (of velocity U-b). The flow is characterized in terms of the Reynolds number Re (= 2aU(infinity)/nu, where nu is the kinematic viscosity of the fluid) and the dimensionless blow velocity Lambda (= U-b/U-infinity). We seek the leading-order symmetric solution of the vorticity field which satisfies the near-and far-field boundary conditions. The drag coefficient is then determined from the vorticity field. For the no-blow case Lamb's (Phil. Mag., vol. 21, 1911, pp. 112-121) expression is retrieved for Re -> 0. For the strong-sucking case, the asymptotic limit, C-D approximate to -2 pi Lambda, is confirmed. The blowing solution is valid for Lambda < 4/Re, after which the flow is unsymmetrical about theta = pi/2. The analytical results are compared with full numerical solutions for the drag coefficient CD and the fraction of drag due to viscous stresses. The predictions show good agreement for Re = 0.1 and Lambda = -5, 0, 5.