In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,locati...In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,location of free-surface aeration inception,Froude number at the spillway’s toe,and pressure,flow velocity,air concentration and cavitation index were evaluated.The realizable k–εwas applied as the turbulence model,and Volume of Fluid(VOF)model was used to determine the free surface flow profiles of the spillway.The model was verified using experimental data.In order to investigate the different characteristics of Nappe flow regime,17 numerical runs was designed,in which,four step angles,four flow discharge were considered to investigate the flow characteristics over the stepped spillway.The results indicated that the numerical model is well suited with the experimental data over the stepped spillway(RMSE=0.147 and ARE=6.9%).In addition,with increasing the step angles,the aeration inception point is generally moved downstream.By increasing the step angles from zero to 10 degrees,the Froude number does not change significantly,however,at the angle of 15 degrees,the Froude number decreases by about 42 percent.展开更多
Mosquitoes possess the striking ability to walk on water because each of their legs has a huge water supporting force（WSF） that is 23 times their body weight.Aiming at a full understanding of the origins of this ext...Mosquitoes possess the striking ability to walk on water because each of their legs has a huge water supporting force（WSF） that is 23 times their body weight.Aiming at a full understanding of the origins of this extremely large force,in this study,we concentrate on two aspects of it：the intrinsic properties of the leg surface and the active control of the initial stepping angle of the whole leg.Using a measurement system that we developed ourselves,the WSFs for the original leg samples are compared with those whose surface wax and microstructures have been removed and with those of a different stiffness.The results show that leg f exibility plays a dominant role over surface wax and microstructures on the leg surface in creating the supporting force.Moreover,we discuss the dependence relationship between the maximum WSF and the initial stepping angle,which indicates that the mosquito can regulate this angle to increase or decrease the WSF during landing or takeoff.These finding are helpful for uncovering the locomotion mechanism of aquatic insects and for providing inspiration for the design of microfluids miniature boats,biomimetic robots,and microsensors.展开更多
文摘In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,location of free-surface aeration inception,Froude number at the spillway’s toe,and pressure,flow velocity,air concentration and cavitation index were evaluated.The realizable k–εwas applied as the turbulence model,and Volume of Fluid(VOF)model was used to determine the free surface flow profiles of the spillway.The model was verified using experimental data.In order to investigate the different characteristics of Nappe flow regime,17 numerical runs was designed,in which,four step angles,four flow discharge were considered to investigate the flow characteristics over the stepped spillway.The results indicated that the numerical model is well suited with the experimental data over the stepped spillway(RMSE=0.147 and ARE=6.9%).In addition,with increasing the step angles,the aeration inception point is generally moved downstream.By increasing the step angles from zero to 10 degrees,the Froude number does not change significantly,however,at the angle of 15 degrees,the Froude number decreases by about 42 percent.
基金supported by the National Natural Science Foundation of China (Grants 11302093,11302094 and 11272357)the Natural Science Fund for Distinguished Young Scholars of Shandong Province (JQ201302)
文摘Mosquitoes possess the striking ability to walk on water because each of their legs has a huge water supporting force（WSF） that is 23 times their body weight.Aiming at a full understanding of the origins of this extremely large force,in this study,we concentrate on two aspects of it：the intrinsic properties of the leg surface and the active control of the initial stepping angle of the whole leg.Using a measurement system that we developed ourselves,the WSFs for the original leg samples are compared with those whose surface wax and microstructures have been removed and with those of a different stiffness.The results show that leg f exibility plays a dominant role over surface wax and microstructures on the leg surface in creating the supporting force.Moreover,we discuss the dependence relationship between the maximum WSF and the initial stepping angle,which indicates that the mosquito can regulate this angle to increase or decrease the WSF during landing or takeoff.These finding are helpful for uncovering the locomotion mechanism of aquatic insects and for providing inspiration for the design of microfluids miniature boats,biomimetic robots,and microsensors.
