Generalizations of Kadanoff's solution of the Saffman-Taylor problem in   a wedge
  We consider a zero-surface-tension two-dimensional Hele-Shaw flow in an infinite wedge. There exists a self-similar interface evolution in this wedge, an analogue of the famous Saffman-Taylor finger in a channel, exact shape of which has been given by Kadanoff. One of the main features of this evolution is its infinite time of existence and stability for the Hadamard ill-posed problem. We derive several exact solutions existing infinitely by generalizing and perturbing the one by Kadanoff. 
Irina Markina, Rodrigo Meneses, Alexander Vasil'ev