“…These difficulties occur in any fluid-structure problem. In the last decade, several papers have been devoted to the existence of solutions for such systems when the fluid motion is governed by Navier-Stokes equations; to quote a few, Desjardins and Esteban [5,6], Conca, San Martín and Tucsnak [2], Gunzburger, Lee and Seregin [16], Hoffmann and Starovoitov [18,19], Grandmont and Maday [15], San Martín, Starovoitov and Tucsnak [26], Feireisl [7][8][9], Takahashi [30] (in the case of a bounded domain) and Serre [27], Judakov [20], Silvestre [28], Takahashi-Tucsnak [31], Galdi and Silvestre [11] (in the case where the fluid-rigid body system fills the whole space). The stationary problem was studied in Serre [27] and in Galdi [10].…”