“…We refer to [7,8,14,19] for further details. In the context of the present vorticity-streamfunction formulation, the problem of "vorticity boundary conditions" has been studied by Anderson [1], Quartapelle et al [10,29,30] and E and Liu [11][12][13]. Roughly speaking, the basic idea is to derive linear ("orthogonality") conditions that must be satisfied by the vorticity, as is seen from (2.9).…”