Flow Pattern Construction-based Shape Design Of Flow Channels

Internal structure optimization of chemical production equipments is an important approach for process intensification.Different transport phenomena happen in different internal structure,which leads to different performace of chemical process.Therefore,constructing transport phenomena by shape desgin can be an effective way to intensify chemical processes.In the present study,fluid flow process(moment transfer phenomena),widely existed in chemical processes,is aimed at.Based on flow pattern construction,practical and effective methods to design flow channels are investigated.Firstly,this study develops an evolutionary optimization method to design flow channel shapes and reduce the pressure drop.The optimization method includes three steps.Firstly,an initial channel shape is given,and the original velocity field can be simulated numerically.Then by adding a virtual body force to the original flow field,the optimal flow pattern can be constructed with minimum viscous dissipation.Finally,the fluid cells having lower dynamic pressure are automatically substituted with the solid zones in the constructed flow pattern.This process is repeated until the channel volume constraint is satisfied,and the optimal channel shape can be obtained.To demonstrate the validity of the multistep evolution optimization method,three numerical examples are presented,including a T-shape channel,a bend and a diffuser.Secondly,this study presents a hybrid optimization method aiming to reduce the flow resistance of three-dimensional flow channel.This method combines a flow pattern construction-based optimization with a natural heuristic optimization.Firstly,an optimal flow field with minimum viscous dissipation is constructed using calculus of variations.Then the channel shape is optimized by substituting the fluid cells that have lower dynamic pressure in the constructed flow field with solid.This process is repeated until the channel volume constraint is satisfied,and a primary channel shape is obtained as an intermediate result.After that,the primary shape is further optimized using the natural heuristic optimization.That is,the positions of the solid and fluid cells are exchanged stepwise according to a certain criterion.Ultimately,the streamlined channel shape is garnered with reduced pressure drop.To demonstrate the validity of the method,the structures of an elbow with different Re and geometrical size,a tee channel and a multi-inlet channel are optimized through the hybrid optimization method.In terms of fluid flow processes,the moment transfer phenomena construction builds the bridge between the optimal flow pattern and flow channel optimization.As prelimnary exploration,this research provides effective strategies for shape design of flow channels.