LES investigation on cavity shedding of a Clark-Y hydrofoil under different attack angle with an integration method

Numerical simulations of unsteady cavitating turbulent flow around a Clark-Y hydrofoil were performed using the Large Eddy Simulation method under different attack angles. The shedding of the cavity cloud was captured and the numerical results of the total vapour volume accords well with the experimental results. In this paper the concept of entrainment ability (generally adopted in water jet) was firstly introduced to describe the process of the cavity shedding. Based on the integral time averaged Navier-Stokes equations, the integration of p+ρ1v2 was adopted to describe the entrainment ability. A horizontal line from upstream to the leading edge was defined to monitor the flow rate and entrainment ability being transferred to the suction side. It is found that the entrainment ability directly determines the level of the re-entrant jet, which sees a sudden rise at the breakdown of the cavity cloud with the re-entrant jet reaching to the leading edge. Moreover, compared with no-cavitating flow, the entrainment ability was greatly hindered by the intensive cavity cloud over the foil. The pressure fluctuation at the trailing edge can be transferred upstream through the pressure side and influences the entrainment ability and flow rate across Line B(QB, Line B is defined as a horizontal line from upstream to the leading edge). In addition, as the attack angle increases, the time averaged QB greatly increases, while the time averaged entrainment ability experiences a marginal rise. Thus, the variation of attack angle only impacts the entrainment ability from Line A (mA), since mA varies linearly with QB.