Numerical Simulation Of Three-dimensional Cylindrical Flow In Subcritical Area

The flow around the cylinder has always been a research hotspot in the field of fluid mechanics.There are mainly two types of research method,wind tunnel experiments and numerical simulation methods.The cost of wind tunnel tests is very high and then numerical simulation has become one of the most important research methods at present.Although there have been a lot of research results,they are mostly concentrated in the low Reynolds number region.There are few simulations of the flow around the cylinder with high Reynolds number.The crux of the problem is that the structure of the flow field in the high Reynolds number is extremely complex.When the numerical treatment is different,the results vary greatly depending on the method,which sometimes leads to serious distortion of the simulation results.What kind of numerical model is adopted can achieve both the accuracy of calculation and the adaptability of existing computing equipment.It is a problem that the relevant academic circles are concerned about and continue to explore.ANSYS Fluent software was used to model and calculate the three-dimensional flow around a subcritical region.Firstly,the Large-Eddy Simulation method,Reynolds average method and Detached Eddy Simulation method were used to simulate and calculate the uniform wind field around single cylinder with 3:1 slenderness ratio.The comparative analysis shows that the separation vortex simulation method has higher accuracy than the Reynolds average method,and has little difference with the large eddy simulation method,but the calculation efficiency is higher.Secondly,the Detached Eddy Simulation method was used to simulate the flow around a single cylinder under the four Reynolds numbers in the subcritical Reynolds number range.The results were analyzed from lift coefficient,drag coefficient and vorticity contour.The results show that the numerical results can describe the three-dimensional characteristics of the flow around the cylinder accurately,and further verify the applicability of the Detached Eddy Simulation method for solving the flow around the cylinder in the subcritical Reynolds number region.Finally,simulations were carried out for a tandem double cylinder with Reynolds number of 10~5 and four different pitch ratios.The drag coefficient,lift coefficient,vortex figure and streamline diagram were analyzed.Summarized the law of change.The amplitude of the lift coefficient and the drag coefficient will decrease as the pitch ratio increases.When the distance is relatively small,the two cylinders can be regarded as a whole,and the subsequent wake situation is similar to that of a single cylinder.As the spacing ratio increases slowly,the wake of the upstream cylinder will gradually adhere to the downstream cylinder and has an impact on its tail flow.