The WENO Limiter
When computing discontinuous solutions to conservation laws, spurious oscillations and instabilities might arise. For controlling oscillations around discontinuities and stabilizing the computations of typically nonlinear conservation laws, a WENO (weighted essentially nonoscillatory) limiter (Ref. 37) is implemented for use in the discontinuous Galerkin method. WENO is available for the Wave Form PDE and Compressible Euler Equations interfaces.
In order to save computational cost, the WENO limiter is applied where deemed needed. To this end a TVB (total variation bounded) troubled cell indicator is used. You can specify the TVB constant. A larger value means that a smaller number of cells will use WENO.
To avoid generating significant oscillations in the numerical solution, the WENO limiter is applied in each inner stage of a Runge-Kutta scheme. The third-order SSP (strong stability preserving) Runge-Kutta is recommended and is the default for the Compressible Euler Equations interface.
Numerical simulation of the compressible Euler equations might for stability require both a limiter for shocks and a positivity limiter of density and pressure. Together with the WENO limiter it is possible to enforce pressure and density positivity for the Compressible Euler Equations interface. The positivity limiter based on Ref. 38 is active by default and can be controlled by the Positivity-preserving limiter for density and pressure check box.