TRANSIENT SOLUTIONS BY A LEAST-SQUARES FINITE-ELEMENT METHOD AND JACOBI CONJUGATE-GRADIENT TECHNIQUE

We present a least-squares finite-element method that can provide implicit, fully coupled transient solutions for time-dependent incompressible fluid flows and thermal convection. The algorithm consists of the Crank-Nicolson scheme for time discretization, Newton's method for linearization, and a matrix-free Jacobi conjugate gradient method as an iterative solver for the symmetric, positive-definite linear system of equations. The combined algorithm is first validated by two-dimensional flows: flows in a square cavity with a periodically oscillating lid and mixed convection in a driven cavity. Then the algorithm is used to obtain transient solutions of a three-dimensional lid-driven cavity flow for Re = 400.