Convergence Acceleration for the Three Dimensional Compressible Navier-Stokes Equations

We consider a multistage algorithm to advance in pseudo-time to find a steady state solution for the compressible Navier-Stokes equations. The rate of convergence to the steady state is improved by using an implicit preconditioner to approximate the numerical scheme. This properly addresses the stiffness in the discrete equations associated with highly stretched meshes. Hence, the implicit operator allows large time steps i.e. CFL numbers of the order of 1000. The proposed method is applied to three dimensional cases of viscous, turbulent flow around a wing, achieving dramatically improved convergence rates

A Boundary Condition for Simulation of Flow Over Porous Surfaces

A new boundary condition is presented for simulating the flow over passively porous surfaces. The model builds on the prior work of R.H. Bush to eliminate the need for constructing grid within an underlying plenum, thereby simplifying the numerical modeling of passively porous flow control systems and reducing computation cost. Code experts for two structured-grid flow solvers, TLNS3D and CFL3D, and one unstructured solver, USM3Dns, collaborated with an experimental porosity expert to develop the model and implement it into their respective codes. Results presented for the three codes on a slender forebody with circumferential porosity and a wing with leading-edge porosity demonstrate a good agreement with experimental data and a remarkable ability to predict the aggregate aerodynamic effects of surface porosity with a simple boundary condition