The Chan-Robbins-Yuen polytope can be thought of as the flow polytope of the complete graph with netflow vector (1,0, . . . ,0,−1). The normalized volume of the Chan-Robbins-Yuen polytope equals the product of consecutive Catalan numbers, yet there is no combinatorial proof of this fact. We give same type of results for generalizations of the complete graph and also for the flow vector  (1,1, . . . ,0,−2). We also compute volume of flow polytopes on complete signed graphs.  This is joint work with Jang Soo Kim and Karola Meszaros.