The objective of this paper is to investigate the hysteresis effect of cavitating flow over a Clark-Y hydrofoil undergoing a transient pitching motion at Reynolds number Re=4.55×105,cavitation numberσ=1.33,pitch...The objective of this paper is to investigate the hysteresis effect of cavitating flow over a Clark-Y hydrofoil undergoing a transient pitching motion at Reynolds number Re=4.55×105,cavitation numberσ=1.33,pitching frequency f*=2 Hz via combined experimental and numerical studies.A hysteresis phenomenon is observed in the hydrodynamic curve and cavity area in increasing and decreasing of the angle of attackα.The hydrodynamic curves are divided into three regions:Regions A,B and C.For Region A,the lift coefficient of downstroke is lower than that of the upstroke,and the lift coefficient curve of the downstroke is more unstable.The formation and development of counterclockwise trailing edge vortex(TEV)are responsible for the decline and fluctuation of lift during the downstroke,thus leading to the increase of the hysteresis loop.Compared with the upstroke,the hydrodynamic curve in downstroke is shifted laterally to some extent in Region B.The delay effect is the main factor leading to the shift of the hydrodynamic curve,which corresponds to the minimum hysteresis loop.In Region C,the hysteresis loop is maximum and the evolution trend of the hydrodynamic curve is peak-valley opposites.When the direction of oscillation changes,the detachment and dwell time of the cavity are advanced,thus leading to the difference of hydrodynamic curve and the increase of hysteresis loop.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.52109111,52079004,and U20B2004)the Natural Science Foundation of Beijing(Grant No.3212023)the State Key Program for Basic Research of China(Grant No.MKS20210003).
文摘The objective of this paper is to investigate the hysteresis effect of cavitating flow over a Clark-Y hydrofoil undergoing a transient pitching motion at Reynolds number Re=4.55×105,cavitation numberσ=1.33,pitching frequency f*=2 Hz via combined experimental and numerical studies.A hysteresis phenomenon is observed in the hydrodynamic curve and cavity area in increasing and decreasing of the angle of attackα.The hydrodynamic curves are divided into three regions:Regions A,B and C.For Region A,the lift coefficient of downstroke is lower than that of the upstroke,and the lift coefficient curve of the downstroke is more unstable.The formation and development of counterclockwise trailing edge vortex(TEV)are responsible for the decline and fluctuation of lift during the downstroke,thus leading to the increase of the hysteresis loop.Compared with the upstroke,the hydrodynamic curve in downstroke is shifted laterally to some extent in Region B.The delay effect is the main factor leading to the shift of the hydrodynamic curve,which corresponds to the minimum hysteresis loop.In Region C,the hysteresis loop is maximum and the evolution trend of the hydrodynamic curve is peak-valley opposites.When the direction of oscillation changes,the detachment and dwell time of the cavity are advanced,thus leading to the difference of hydrodynamic curve and the increase of hysteresis loop.
