The mesh divergence problem occurring at subsonic and transonic speeds with the adjoint Euler equations is reviewed. By examining a recently derived analytic adjoint solution, it is shown that the explanation is that the adjoint solution is singular at the wall. The wall singularity is caused by the adjoint singularity at the trailing edge, but not in the way it was previously conjectured.

翻译：回顾了伴随欧拉方程在亚声速和跨声速条件下出现的网格发散问题。通过分析最近推导的解析伴随解，表明该现象的解释是伴随解在壁面处存在奇点。壁面奇点由尾缘处的伴随奇点引起，但并非如先前猜想的那样。