“…To get the simplest system possible, we set v (t, x) =γc 0ṽ (γc 0 t, x) and c (t, x) = c 0 + γc 0c (γc 0 t, x). This problem, of course, has already been studied in numerous articles; our reference list, although far from exhaustive, contains more items than we will refer to in the text [1,6,7,8,19,20,21,22,24,26]. Fluids evolving in different domains have been considered (R N , torus, bounded domain), essentially under two kinds of hypotheses: in the well-prepared case [19,20], one assumes that divṽ 0, → 0 andc 0, → 0 as → 0; in the ill-prepared case, one only assumes thatṽ 0, andc 0, are bounded in certain Sobolev spaces (for example) and that the incompressible part ofṽ 0, tends to some field v 0 .…”