The Effection Of Flow Instability In Wind Tunnel Contrction On Flow Field Quality

When fluid flows through the concave wall,due to the instability of centrifugal force,streamwise vortex may appear near the concave boundary layer.The vortex which axis is parallel to the concave wall will develop in the normal and spanwise along the concave wall.The vortex is named as G(o|¨)rtler Vortices in memory of the German G(o|¨)rtler who is the first person to find and study the instability problem.G(o|¨)rtler instability is an important boundary layer instability,and in some cases it may cause the boundary layer transiention.In some special practice,it’s necessary to control the boundary layer transition.In recent research,it has been proved that G(o|¨)rtler Vortices can enhance the heat tansfer near the concave wall.In view of the practical application,it’s necessary to study the G(o|¨)rtler Vortices which produce along the concavewall.The study is based on the the classical theory of flow instability,and then use FLUENT to simulate the G(o|¨)rtler Vortices.The whole study is as follows:(1)Establish the differential equation with disturbing form,introduce the theory of stability analysis on flow instability and then deduce the characteristic number G which is related with G(o|¨)rtler Vortices.(2)Summarize the numerical simulation method about flow problem by the FLUENT software.But focus on the principle and method for large eddy simulation,then analyze the grid,boundary conditons,and turbulence model problems.At last,give successful solution for G(o|¨)rtler vortex.(3)Establish the calculation model based on the experiment model,and compare the calculation results with the experiment results from qualitative angle.By which to verify the feasibility of numerical simulation for this type of problem.In additon,explore the variatation of G(o|¨)rtler Vortices by changing the calculation conditions.(4)In consideration of G(o|¨)rtler Vortices in practice,we choose the contraction of wind tunnel as the research object,judge whether the G(o|¨)rtler Vortices will appear in the contraction,and if so,whether it will influence the flow quality.As the research result,we hope it will provide guidance on wind tunnel design and production.