“…One brief remark here is that the Prandtl equations are well posed only under strong conditions on the flow, such as when boundary and the data have some degree of analyticity [5,128,95,23,84] or the data is monotonic in the normal direction to the boundary [122,124,83]. The most classical result verifying (3.9) is [128] in the analytic functional framework, after the pioneering work of [5,6].…”