Research Of Adjoint-Based Grid Adaptation And Error Correction

With the developing of computer science and programming language,computational fluid dynamics(CFD)has become a major method in aircraft design processes,and it plays a more and more important role in fluid mechanics and aircraft design or optimization processes.Aircraft design has a strict and urgent demand to high-precision numerical simulation,which depends on high-order numerical schemes and high-resolution computational grid.It is very convenient to distribute grids using unstructured grid that has good flexibility but no limit of nodes as structured grids,the unstructured grid can be easily refined in sensitive areas so that the high-resolution computational grid will produce high-precision result.Nowadays CFD researchers pay more attention to error correction technology,which can correct the numerical result and provide a possibility to improve the accuracy of numerical simulation.Combined with unstructured grid,adjoint theory and a mature flowfield solver named MFlow,a modified grid adaptation and error correction method which suits for cell-centred scheme finite volume method is built.The sensitive grid areas of the objective functions could be refined and optimized,the accuracy of numerical simulation could be improved with error correction technology by less grids.The contents of this article are divided into following 5 chapters:The first chapter is a brief introduction to the background and research status of adjoint-based grid adaptation and error correction,and the main contents of this article are given.The second chapter is for numerical simulation method.The numerical simulation of this article is computed by a mature flowfield solver named Mflow.A method to bulid and solve adjoint equation is presented,an error correction method based on adjoint equation and unstructured grid is given,a comprehensive adaptation parameter is given to reduce the error of the objective functions.The third chapter is for adaptation strategies.A method to divide coarse grid is presented,a polynomial interpolation technology which suits for cell-centred scheme finite volume method and unstructured grid is given,and it behaves better compared with other interpolation method in references.An adjoint-based grid adaptation standard is given to reduce the error of objective functions.Finally,the flowsheet of adjoint-based grid adaptation and error correction is presented.The fourth chapter is accompanied by validation and analysis.The grid adaptation and error correction method is applied to the simulation of inviscid flows around NACA0012 and ONERA-M6 airfoils.A compare between adjoint-based grid adaptation and feature-based grid adaptation is presented,each method has its advantages.The characteristic of adjoint-based grid adaptation and is given,and the effect to grid adaptation process caused by surface grid projection method is analyzed.Finally,some suggestions to grid generation in common CFD numerical simulation is given.The fifth chapter is closing remarks,the review is given about this article,whit pointing out the deficiencies and future research directions.