Enrico Valdinoci The Bernoulli jets and the zero mean curvature equation (50K, LaTeX) ABSTRACT. We consider an elliptic PDE problem related with fluid mechanics. We show that level sets of rescaled solutions satisfy the zero mean curvature equation in a suitable weak viscosity sense. In particular, such level sets cannot be touched by below (above) by a convex (concave) paraboloid in a suitably small neighborhood.