Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, ...Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.展开更多
Riblets are a series of small protrusions formed along the flow direction,which have been extensively studied as a passive turbulent drag reduction technique.Experiments and numerical simulations have shown that well-...Riblets are a series of small protrusions formed along the flow direction,which have been extensively studied as a passive turbulent drag reduction technique.Experiments and numerical simulations have shown that well-designed riblets can significantly reduce drag in turbulent flows,making them highly promising and valuable for various applications.In this study,we focus on a scalloped riblet,which is designed by smoothly connecting two third-order polynomials,and thus the sharpness of the tip and the curvature of the valley can be well defined.We conduct direct numerical simulations of turbulent channel with smooth plate,scalloped riblet-mounted and triangular riblet-mounted walls.Width in wall units of W^(+)=20 and height-width ratio ofγ=0.5 are selected for both riblet cases.Compared with the smooth plate case,the scalloped riblet case achieves an 8.68%drag reduction,while the triangular riblet case achieves a 4.79%drag reduction.The obtained drag reduction rate of the triangular riblet is consistent with previous experiments and simulations,and the results indicate that the scalloped riblet is more effective in reducing drag and deserves further investigation.We compare turbulent statistics of the scalloped riblet case with those of the triangular riblet case.The mean velocity profiles of riblets are similar,but both the Reynolds shear stress and second-order statistics of velocity fluctuations and Liutex are significantly reduced in the scalloped riblets controlled turbulent channel,indicating that the scalloped riblet can more effectively suppress the spanwise and wall-normal turbulent intensity near the wall.We also compare the pre-multiplied spectra of streamwise velocity and streamwise Liutex component for the three cases to investigate the energy distribution and characteristics of Liutex distribution.The Liutex vortex identification method is also utilized to analyze the instantaneous flow field,which provides insights into the flow field and could be beneficial for the further optimization of riblet.展开更多
基金supported by the Base Platform Construction Project of Jilin University Basic Scientific Research (Grant No 421060202466)the Technology Development Plan Project of Jilin Province (Grant No 20096032)+2 种基金the Youth Research Foundation of the Jilin University Agron-omy Faculty (Grant No 4305050102k7)the Key Program of National Natural Science Foundation of China (Grant No 50635030)the Ma-jor Program of the Science and Technology Development of Jilin Province (Grant No 09ZDGG001)
文摘Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.
基金supported by the Jiangsu Shuangchuang Project(Grant No.JSSCTD202209)the National Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.22KJB130011).
文摘Riblets are a series of small protrusions formed along the flow direction,which have been extensively studied as a passive turbulent drag reduction technique.Experiments and numerical simulations have shown that well-designed riblets can significantly reduce drag in turbulent flows,making them highly promising and valuable for various applications.In this study,we focus on a scalloped riblet,which is designed by smoothly connecting two third-order polynomials,and thus the sharpness of the tip and the curvature of the valley can be well defined.We conduct direct numerical simulations of turbulent channel with smooth plate,scalloped riblet-mounted and triangular riblet-mounted walls.Width in wall units of W^(+)=20 and height-width ratio ofγ=0.5 are selected for both riblet cases.Compared with the smooth plate case,the scalloped riblet case achieves an 8.68%drag reduction,while the triangular riblet case achieves a 4.79%drag reduction.The obtained drag reduction rate of the triangular riblet is consistent with previous experiments and simulations,and the results indicate that the scalloped riblet is more effective in reducing drag and deserves further investigation.We compare turbulent statistics of the scalloped riblet case with those of the triangular riblet case.The mean velocity profiles of riblets are similar,but both the Reynolds shear stress and second-order statistics of velocity fluctuations and Liutex are significantly reduced in the scalloped riblets controlled turbulent channel,indicating that the scalloped riblet can more effectively suppress the spanwise and wall-normal turbulent intensity near the wall.We also compare the pre-multiplied spectra of streamwise velocity and streamwise Liutex component for the three cases to investigate the energy distribution and characteristics of Liutex distribution.The Liutex vortex identification method is also utilized to analyze the instantaneous flow field,which provides insights into the flow field and could be beneficial for the further optimization of riblet.
