The sonic line as a free boundary
Barbara Lee Keyfitz, Allen M. Tesdall, Kevin R.VE Payne, Nedyu I. Popivanov · Quarterly of Applied Mathematics · 2012
We consider the steady transonic small disturbance equations on a domain and with data that lead to a solution that depends on a single variable. After writing down the solution, we show that it can also be found by using a hodograph transformation followed by a partial Fourier transform. This motivates considering perturbed problems that can be solved with the same technique. We identify a class of such problems.