Flow and air-entrainment around partially submerged vertical cylinders*

This work presents experimental and numerical results of the flow around cylinders. Experimentally, the cylinders are partially immersed with a height h. The motion induces turbulent wake and free-surface deformation. Eleven cylinder diameters from D=1.4 to 16 cm were translated at varying speed for runs at constant h and h/D. The Reynolds and Froude numbers, based on the cylinder diameter, govern the flow. The explored range of parameters are in the regime of air-entrainment behind the cylinder with experiments carried out for 4 500 < Re < 240 000 and 0.2 < Fr < 2.4. The focus here is on drag force measurements and strong free-surface deformation up to rupture and air-entrainment. New data on air-entrainment mechanisms are provided. In addition, numerical simulations, based on finite volume method of high order, and level-set method are used to reproduce the flow behind the cylinder and free-surface deformation. Numerical and experimental results are compared with each other and with previous works without air-entrainment. The present work highlights free-surface effects on drag forces.