Global cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness
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RESEARCH PAPER
Global cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness Qian Chen1 · Yunqing Liu1 · Qin Wu1 · Yong Wang2 · Taotao Liu1 · Guoyu Wang1 Received: 20 November 2019 / Revised: 18 May 2020 / Accepted: 23 June 2020 © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The objective of this paper is to experimentally investigate the cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness. The aims are to (1) understand the effect of the leading edge roughness on the hydrodynamic performance, and (2) have a good knowledge of the interaction between the leading edge roughness and the cavitation patterns. Experimental results are indicated for the NACA 66 hydrofoils with and without leading edge roughness at different incidence angles for sub and cavitation conditions. The experiments are conducted in the EPFL highspeed cavitation tunnel (Avellan 2015). The results showed that the leading edge roughness has a significant effect on the hydrodynamic performance at the sub cavitation, suppressing the formation of the incipient cavitation. The lift coefficient of the hydrofoil without leading edge roughness is larger than that of the hydrofoil with leading edge roughness, while for the drag coefficients, the results are contrary for the lift coefficient, and the maximum lift-to-drag ratio angle is delayed for the hydrofoil with leading edge roughness. The leading edge roughness modified the local pressure distribution at the leading edge region, which in turn significantly increased the minimum pressure coefficient, hence the incipient cavitation number of the hydrofoil with leading edge roughness. The formation and evolution of the transient cavity for the cloud cavitation is little affected by the leading edge roughness. Keywords Cavitation · Hydrofoil · Hydrodynamics · Leading edge roughness
Abbreviations u b
B B
Inflow velocity [m/s] Span lengths [m] Qin Wu [email protected] Taotao Liu [email protected] Qian Chen [email protected] Yunqing Liu [email protected] Yong Wang [email protected] Guoyu Wang [email protected]
1
School of Mechanical Engineering, Beijing Institute of Technology, 100081 Beijing, China
2
Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, 212013 Jiangsu, China
c h h s v Re ρ α αe α cr α0 σ σi P∞ Pv Cl Cd Cm L D
Mean chord [m] Roughness [m] Cavity height [m] Distance between roughness and re-entrant jet [m] Fluid kinematic viscosity [m2 /s] Reynolds number, Re uc/v Fluid density [kg/m3] Hydrofoil geometry incidence relative to freestream flow (incidence angle) Maximum lift-to-drag ratio angle Stall angle Zero-lift angle Cavitation number Incipient cavitation number Fluid static pressure [Pa] Saturated vapor pressure [Pa] Lift coefficient Drag coefficient Moment coefficient Hydrodynamic lift [N] Hydrodynamic drag [N]
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Q. Chen, et al.
M K C p,min Pi
Hydrodynamic mom
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