Ondes variqueuses absolument instables dans un canal élastique

Conditions for absolute instability of the elastic walls of a plane channel with potential flow are investigated. The absolute instability threshold is given in closed form in the thin film approximation for walls made of plates or membranes. The more general case is solved numerically and is compared with more classical results for a single wall in the presence of a semi-infinite fluid domain. It is found that absolute instability is strongly influenced by the membrane or plate nature of the wall stiffness.