基于混合网格和CGNS(CFD General Notation System)数据结构,建立了一种各向同性加密/稀疏的网格自适应方法。在悬空点的后处理中,让含有悬空点的单元转化为任意多面体,从而简化了自适应单元剖分模版,同时自适应网格单元之间可完全相容...基于混合网格和CGNS(CFD General Notation System)数据结构,建立了一种各向同性加密/稀疏的网格自适应方法。在悬空点的后处理中,让含有悬空点的单元转化为任意多面体,从而简化了自适应单元剖分模版,同时自适应网格单元之间可完全相容,自适应生成的网格能够直接用于可处理任意多面体的流场求解器。将该自适应方法与脱体涡模拟(DES)算法相结合,开展了65°后掠三角翼大迎角流动的数值模拟应用,并与初始网格的模拟结果进行了详细比较。对比表明:采用网格自适应方法适当增加局部网格量,能够以较小的成本迅速提高三角翼背风区的空间分辨率,增强数值模拟对小尺度涡系结构的解析能力,从而弥补了基于混合网格的脱体涡模拟中常用二阶格式计算的空间分辨率相对偏低、不利于湍流多尺度结构精细模拟的不足。展开更多
Ship bow wave breaking contains complex flow mechanism,which is very important for ship performance.In this study,a practical numerical simulation scheme for bow wave breaking is proposed and the scheme is applied to ...Ship bow wave breaking contains complex flow mechanism,which is very important for ship performance.In this study,a practical numerical simulation scheme for bow wave breaking is proposed and the scheme is applied to the simulation of bow wave breaking of KCS ship model with Fr=0.26,0.30,0.35,0.40,analyzing the impact of speed on the bow wave breaking.The results indicate that an increase in speed leads to a significant rise in viscous pressure resistance and more pronounced bow wave breaking.Moreover,it is found that the traditional wave height function in OpenFOAM is not suitable for detailed studies of bow wave breaking.This study extracts different free surfaces through top and bottom views to further analyze the free surface overturning,droplet splashing,and cavity entrainment in bow wave breaking.Additionally,the spatial and temporal distribution of cavities at Fr=0.40 is analyzed,revealing that cavity distribution is closely related to vortex structures and exhibits a periodic pulsation characteristic of approximately 12 s.展开更多
Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-S...Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-SJTU,coupled with delayed detached-eddy simulation(DDES)is adopted to analyze the vortex structures around the benchmark model Yupeng Ship in dynamic pure yaw tests,which are captured by third generation of vortex identification method.The good agreement of the predicted force/moment by DDES method with the experimental data indicates that the present numerical schemes are reliable and robust.Three vortex identification methods,Q-criteria,Ω_(R) and Liutex,are used to capture the vortex structures around the hull.The large separated flow is able to be investigated by these three methods,in which more vortex structures are captured byΩ_(R) approach and Liutex method with scalar,vector and tensor form seems to be more suitable for analyzing the flow mechanism around the hull in dynamic pure yaw test.In general,each vortex structure corresponds to a dominant positive/negative axial Liutex and a bound vortex pair.The streamlines are spiral in the large separated flow,indicating that the flow in corresponding region is rotational.But the rotation of the flow is not directly related to the intensity of Liutex.展开更多
Detached eddy simulation(DES)model was used to better capture large vortex structure and unsteady flow feature near cone base.Good base heating results were achieved using proper grid and numerical method.The influenc...Detached eddy simulation(DES)model was used to better capture large vortex structure and unsteady flow feature near cone base.Good base heating results were achieved using proper grid and numerical method.The influence of inflow conditions(like Mach number,Reynolds number)and configuration(bluntness ratio of the cone)on base heating was discussed based on numerical computational results.Compared with base heat flux,base pressure can be predicted more accurately by numerical simulation and the time consuming was shorter.A hybrid method combining numerical simulation with experimental correlation was proposed to predict supersonic turbulent base heating.A review of base heating experiment and correlations for slender cone was presented,and a revised correlation was proposed based on the above simulation results.Compared with the experiment data,the maximum error was 24%,agood result for base heating prediction.This proves that the hybrid method using the revised correlation performs well in predicting supersonic turbulent base heating of slender sphere cone and can meet needs of engineering design.展开更多
In order to correct the unphysical log-layer mismatch commonly encountered in detached eddy simulation(DES) of flows with attached boundary layers,a function M,ML,which has a multi-layer structure with scaling laws in...In order to correct the unphysical log-layer mismatch commonly encountered in detached eddy simulation(DES) of flows with attached boundary layers,a function M,ML,which has a multi-layer structure with scaling laws in each layer and a plateau related to the Kármán constant,is defined.The height of this plateau is found to be crucial for obtaining the correct log-layer.A target scaling function is designed which equals M,ML in the near-wall region,but with the height of plateau determined analytically from the classical log-law.This scaling function is used as a target function according to which the resolved turbulent fluctuations are renormalized,in order to recover the height of plateau prescribed by the log-law.The renormalization procedure guarantees the height of M,ML required by log-law,resulting in correct log layer slope.The method is also shown to maintain similar turbulent properties in the large eddy simulation(LES) region of DES method.Hence it predicts the turbulent intensity correctly.The results demonstrate the relationship between constant M,ML and log-law profile of mean velocity,and relate the Kármán constant to turbulent fluctuations,implying a complete description of turbulent structural ensemble dynamics.The proposed method can be extended to more general flows with log layers since it uses only the log-law with Kármán constant as the input,while the intercept of log layer depends on the solution of Spalart-Allmaras(SA) model in the near-wall field,where Reynolds-averaged Navier-Stokes(RANS) solutions are accurate.展开更多
The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by...The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by the Detached Eddy Simulation（DES） method,and a new method to control the horseshoe vortex by vortex control baffler is proposed.The numerical simulation shows that a kind of attached vortex,with the rotation direction opposite to that of horseshoe vortex,is generated by the vortex control baffler.With the attached vortex,the strength of the horseshoe vortex is significantly reduced.The wind tunnel experiment on a submarine model is carried out,and the axial velocities at the propeller disc of the submarine with and without vortex control baffler are measured by a hot wire anemometer system.It is shown from the experimental results that the vortex control baffler can enhance the uniformity of the wake at the propeller disc,which helps to improve the propeller performance.The engineering applicability of the vortex control baffler is discussed.展开更多
In order to study the cavitation damage in a side-wall when a sudden lateral enlargement and a vertical drop are imposed at the radial gate, a new arrangement-scheme is proposed, where the sudden lateral enlargement a...In order to study the cavitation damage in a side-wall when a sudden lateral enlargement and a vertical drop are imposed at the radial gate, a new arrangement-scheme is proposed, where the sudden lateral enlargement and the vertical drop can be imposed at the outlet of the gate chamber. The hydraulic characteristics along the side-wall are simulated by the detached eddy simulation and the Volume Of Fluid （VOF） method. The numerical results agree well with those of experiment. The experimental and numerical results show that the flow condition is smooth with only a weak water-wing appearing behind the lateral cavity, and the length of the lateral cavity becomes longer and is mainly affected by the size of the lateral enlargement and the zone of negative pressure after the water impacts the side-wall would disappear. The hydraulic characteristics of the new arrangement-scheme are beneficial to the prevention of the cavitation damage in the side-wall and the Detached Eddy Simulation （DES） with the VOF method can well predict the hydraulic characteristics after the new arrangement-scheme of the sudden lateral enlargement and the vertical drop.展开更多
文摘基于混合网格和CGNS(CFD General Notation System)数据结构,建立了一种各向同性加密/稀疏的网格自适应方法。在悬空点的后处理中,让含有悬空点的单元转化为任意多面体,从而简化了自适应单元剖分模版,同时自适应网格单元之间可完全相容,自适应生成的网格能够直接用于可处理任意多面体的流场求解器。将该自适应方法与脱体涡模拟(DES)算法相结合,开展了65°后掠三角翼大迎角流动的数值模拟应用,并与初始网格的模拟结果进行了详细比较。对比表明:采用网格自适应方法适当增加局部网格量,能够以较小的成本迅速提高三角翼背风区的空间分辨率,增强数值模拟对小尺度涡系结构的解析能力,从而弥补了基于混合网格的脱体涡模拟中常用二阶格式计算的空间分辨率相对偏低、不利于湍流多尺度结构精细模拟的不足。
基金Project supported by the National Natural Science Foundation of China(Grant No.52131102).
文摘Ship bow wave breaking contains complex flow mechanism,which is very important for ship performance.In this study,a practical numerical simulation scheme for bow wave breaking is proposed and the scheme is applied to the simulation of bow wave breaking of KCS ship model with Fr=0.26,0.30,0.35,0.40,analyzing the impact of speed on the bow wave breaking.The results indicate that an increase in speed leads to a significant rise in viscous pressure resistance and more pronounced bow wave breaking.Moreover,it is found that the traditional wave height function in OpenFOAM is not suitable for detailed studies of bow wave breaking.This study extracts different free surfaces through top and bottom views to further analyze the free surface overturning,droplet splashing,and cavity entrainment in bow wave breaking.Additionally,the spatial and temporal distribution of cavities at Fr=0.40 is analyzed,revealing that cavity distribution is closely related to vortex structures and exhibits a periodic pulsation characteristic of approximately 12 s.
基金supported by the National Natural Science Foundation of China(Grant Nos.51909160,51879159,52131102)the National Key Research and Development Program of China(Grant No.2019YFB1704200).
文摘Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-SJTU,coupled with delayed detached-eddy simulation(DDES)is adopted to analyze the vortex structures around the benchmark model Yupeng Ship in dynamic pure yaw tests,which are captured by third generation of vortex identification method.The good agreement of the predicted force/moment by DDES method with the experimental data indicates that the present numerical schemes are reliable and robust.Three vortex identification methods,Q-criteria,Ω_(R) and Liutex,are used to capture the vortex structures around the hull.The large separated flow is able to be investigated by these three methods,in which more vortex structures are captured byΩ_(R) approach and Liutex method with scalar,vector and tensor form seems to be more suitable for analyzing the flow mechanism around the hull in dynamic pure yaw test.In general,each vortex structure corresponds to a dominant positive/negative axial Liutex and a bound vortex pair.The streamlines are spiral in the large separated flow,indicating that the flow in corresponding region is rotational.But the rotation of the flow is not directly related to the intensity of Liutex.
基金National Natural Science Foundation of China(11302016)
文摘Detached eddy simulation(DES)model was used to better capture large vortex structure and unsteady flow feature near cone base.Good base heating results were achieved using proper grid and numerical method.The influence of inflow conditions(like Mach number,Reynolds number)and configuration(bluntness ratio of the cone)on base heating was discussed based on numerical computational results.Compared with base heat flux,base pressure can be predicted more accurately by numerical simulation and the time consuming was shorter.A hybrid method combining numerical simulation with experimental correlation was proposed to predict supersonic turbulent base heating.A review of base heating experiment and correlations for slender cone was presented,and a revised correlation was proposed based on the above simulation results.Compared with the experiment data,the maximum error was 24%,agood result for base heating prediction.This proves that the hybrid method using the revised correlation performs well in predicting supersonic turbulent base heating of slender sphere cone and can meet needs of engineering design.
基金supported by the National Natural Science Fund of China(Grant No. 90716008)the National Basic Research Program of China(Grant No. 2009CB72410)
文摘In order to correct the unphysical log-layer mismatch commonly encountered in detached eddy simulation(DES) of flows with attached boundary layers,a function M,ML,which has a multi-layer structure with scaling laws in each layer and a plateau related to the Kármán constant,is defined.The height of this plateau is found to be crucial for obtaining the correct log-layer.A target scaling function is designed which equals M,ML in the near-wall region,but with the height of plateau determined analytically from the classical log-law.This scaling function is used as a target function according to which the resolved turbulent fluctuations are renormalized,in order to recover the height of plateau prescribed by the log-law.The renormalization procedure guarantees the height of M,ML required by log-law,resulting in correct log layer slope.The method is also shown to maintain similar turbulent properties in the large eddy simulation(LES) region of DES method.Hence it predicts the turbulent intensity correctly.The results demonstrate the relationship between constant M,ML and log-law profile of mean velocity,and relate the Kármán constant to turbulent fluctuations,implying a complete description of turbulent structural ensemble dynamics.The proposed method can be extended to more general flows with log layers since it uses only the log-law with Kármán constant as the input,while the intercept of log layer depends on the solution of Spalart-Allmaras(SA) model in the near-wall field,where Reynolds-averaged Navier-Stokes(RANS) solutions are accurate.
文摘The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by the Detached Eddy Simulation（DES） method,and a new method to control the horseshoe vortex by vortex control baffler is proposed.The numerical simulation shows that a kind of attached vortex,with the rotation direction opposite to that of horseshoe vortex,is generated by the vortex control baffler.With the attached vortex,the strength of the horseshoe vortex is significantly reduced.The wind tunnel experiment on a submarine model is carried out,and the axial velocities at the propeller disc of the submarine with and without vortex control baffler are measured by a hot wire anemometer system.It is shown from the experimental results that the vortex control baffler can enhance the uniformity of the wake at the propeller disc,which helps to improve the propeller performance.The engineering applicability of the vortex control baffler is discussed.
基金supported by the Natural National Science Foundation of China (Grant No. 50779041)the Ph. D. Program Foundation of Ministry of Education of China (Grant No.20060610039)
文摘In order to study the cavitation damage in a side-wall when a sudden lateral enlargement and a vertical drop are imposed at the radial gate, a new arrangement-scheme is proposed, where the sudden lateral enlargement and the vertical drop can be imposed at the outlet of the gate chamber. The hydraulic characteristics along the side-wall are simulated by the detached eddy simulation and the Volume Of Fluid （VOF） method. The numerical results agree well with those of experiment. The experimental and numerical results show that the flow condition is smooth with only a weak water-wing appearing behind the lateral cavity, and the length of the lateral cavity becomes longer and is mainly affected by the size of the lateral enlargement and the zone of negative pressure after the water impacts the side-wall would disappear. The hydraulic characteristics of the new arrangement-scheme are beneficial to the prevention of the cavitation damage in the side-wall and the Detached Eddy Simulation （DES） with the VOF method can well predict the hydraulic characteristics after the new arrangement-scheme of the sudden lateral enlargement and the vertical drop.
