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 ...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 high-speed 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.展开更多
The background of the application of leading edge roughness is given and results of comparative tests with one propeller,carried out by the Cavitation Committee of the ITTC,are shown.Leading edge roughness reduces the...The background of the application of leading edge roughness is given and results of comparative tests with one propeller,carried out by the Cavitation Committee of the ITTC,are shown.Leading edge roughness reduces the differences between the results of four facilities.Possible new scale effect,notabiy on propeller performance,are mentioned.展开更多
Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and ste...Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.展开更多
基金The authors gratefully acknowledge the great help of Dr.Mohamed Farhat(EPFL-LMH)and the support by the National Natural Science Foundation of China(Grant Nos:51909002,51839001.and 91752105)the Fundamental Research Funds for the Central Universities,and the Open Fund for Key Laboratory of Fluid and Power Machinery,Ministry of Education(Grant Nos:szjj2018-124 and szjj2019-024).
文摘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 high-speed 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.
文摘The background of the application of leading edge roughness is given and results of comparative tests with one propeller,carried out by the Cavitation Committee of the ITTC,are shown.Leading edge roughness reduces the differences between the results of four facilities.Possible new scale effect,notabiy on propeller performance,are mentioned.
文摘Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.
