In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the bala...In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the balance equations for mass,momentum,and energy.An area ratio of four is considered and numerical simulations are carried out at Mach M=1.2,1.4,1.6,and 1.8 assuming no cavity or cavity locations 0.5D,1D,1.5D,and 2D.The inlet pressure of the nozzle is considered as a flow variable.The Taguchi method is also used,and the considered cases are then analyzed using a full factorial experimental design.The results show that the cavity is effective in increasing the base pressure for the conditions examined.For other nozzle pressure ratios,cavities do not lead to passive control due the change in the reattachment length.The distribution of wall pressure reveals that,in general,a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.展开更多
Water quality determines the success of inland aquaculture.The factor determining water quality is the concentration of dissolved oxygen(DO).To find effective paddlewheel aerators to enhance DO concentration,nine mode...Water quality determines the success of inland aquaculture.The factor determining water quality is the concentration of dissolved oxygen(DO).To find effective paddlewheel aerators to enhance DO concentration,nine model aerators were examined:aerator 4 blades,6 blades and 8 blades with variations of 12 holes per blade,16 holes per blade and 20 holes per blade.They were rotated at 80 RPM,100 RPM,120 RPM and 140 RPM.The results show the higher the rotation speed is,the bigger the increment of DO concentration is,but their relationship is not linier.There is a condition when increasing rotation does not affect the DO concentration meaningly.The results also indicate the greater number of blades increase more DO concentration.The results also suggest the greater number of holes per blade initially increase DO concentration increment,but after 16 holes the increment tends to reduce.It is predicted owing to that widening surface interaction due to the holes in the blade is taken over by reducing the volume of splashed water.In this research,likely the aerator with 8 blades,16 holes per blade and rotated at 120 RPM is the optimum one to increase DO concentration.However,if the energy consumption is also the concern,the aerator with 6 blades and 16 holes per blade likely is the better choice.展开更多
文摘In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the balance equations for mass,momentum,and energy.An area ratio of four is considered and numerical simulations are carried out at Mach M=1.2,1.4,1.6,and 1.8 assuming no cavity or cavity locations 0.5D,1D,1.5D,and 2D.The inlet pressure of the nozzle is considered as a flow variable.The Taguchi method is also used,and the considered cases are then analyzed using a full factorial experimental design.The results show that the cavity is effective in increasing the base pressure for the conditions examined.For other nozzle pressure ratios,cavities do not lead to passive control due the change in the reattachment length.The distribution of wall pressure reveals that,in general,a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.
基金the Ministry of Education and Culture,Research and Technology,Higher Education of the Republic of Indonesia(grant number 069/E5/PG.02.00.PT/2022).
文摘Water quality determines the success of inland aquaculture.The factor determining water quality is the concentration of dissolved oxygen(DO).To find effective paddlewheel aerators to enhance DO concentration,nine model aerators were examined:aerator 4 blades,6 blades and 8 blades with variations of 12 holes per blade,16 holes per blade and 20 holes per blade.They were rotated at 80 RPM,100 RPM,120 RPM and 140 RPM.The results show the higher the rotation speed is,the bigger the increment of DO concentration is,but their relationship is not linier.There is a condition when increasing rotation does not affect the DO concentration meaningly.The results also indicate the greater number of blades increase more DO concentration.The results also suggest the greater number of holes per blade initially increase DO concentration increment,but after 16 holes the increment tends to reduce.It is predicted owing to that widening surface interaction due to the holes in the blade is taken over by reducing the volume of splashed water.In this research,likely the aerator with 8 blades,16 holes per blade and rotated at 120 RPM is the optimum one to increase DO concentration.However,if the energy consumption is also the concern,the aerator with 6 blades and 16 holes per blade likely is the better choice.
