We develop a new numerical framework, employing physics-informed neural networks, to find a smooth self-similar solution for the Boussinesq equations. The solution in addition corresponds to an asymptotic self-similar profile for the 3-dimensional Euler equations in the presence of a cylindrical boundary. In particular, the solution represents a precise description of the Luo-Hou blow-up scenario [G. Luo, T. Hou, Proc. Natl. Acad. Sci. 111(36): 12968-12973, 2014] for 3-dimensional Euler. To the best of the authors' knowledge, the solution is the first truly multi-dimensional smooth backwards selfsimilar profile found for an equation from fluid mechanics. The new numerical framework is shown to be both robust and readily adaptable to other equations.
SignificanceThis paper sheds light on the question of finite time blow-up for the 2-dimensional Boussinesq and the 3-dimensional Euler equations with boundary, questions of fundamental importance to the field of mathematical fluid mechanics. Using a novel numerical method employing physics-informed neural networks, we construct smooth backwards self-similar solutions for the Boussinesq equations. The solutions themselves could potentially form the basis of a future computer-assisted proof of blow-up for the 2-dimensional Boussinesq and the 3-dimensional Euler equations with boundary.