A semi-implicit meshless method for incompressible flows in complex geometries

We present an exponentially convergent semi-implicit meshless algorithm for the solution of Navier-Stokes equations in complex domains. The algorithm discretizes partial deriva-tives at scattered points using radial basis functions (RBF) as interpolants. Higher-order polynomials are appended to the polyharmonic splines (PHS-RBF) and a collocation method is used to derive the interpolation coefficients. The interpolating kernels are then differen-tiated and the partial-differential equations are satisfied by collocation at the scattered points. The PHS-RBF interpolation is shown to be exponentially convergent with discretiza-tion errors decreasing as a high power of a representative distance between points. We present here a semi-implicit algorithm for time-dependent and steady state fluid flows in complex domains. At each time step, several iterations are performed to converge the momentum and continuity equations. A Poisson equation for pressure corrections is formu-lated by imposing divergence free condition on the iterated velocity field. At each time step, the momentum and pressure correction equations are repeatedly solved until the velocities and pressure converge to a pre-specified tolerance. We have demonstrated the convergence and discretization accuracy of the algorithm for two model problems and simulated four other complex problems. In all cases, the algorithm is stable for Courant numbers in excess of ten. The algorithm has the potential to accurately and efficiently solve many fluid flow and heat transfer problems in complex domains. An open source code Meshless Multi -Physics Software (MeMPhyS) [1] is available for interested users of the algorithm.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

We introduce an exponentially convergent semi-implicit meshless algorithm for solving Navier-Stokes equations in complex domains. The algorithm discretizes partial derivatives using radial basis functions (RBF) as interpolants. A collocation method is employed to derive interpolation coefficients. The algorithm shows exponential convergence with decreasing discretization errors. It has the potential to accurately and efficiently solve time-dependent and steady state fluid flows in complex domains.