  In this work, we propose a novel selective discontinuity sensor approach for
numerical simulations of the compressible Navier-Stokes equations. Since
transformation to characteristic space is already a common approach to reduce
high-frequency oscillations during interpolation to cell interfaces, we exploit
the characteristic wave structure of the Euler equations to selectively treat
the various waves that the equations comprise. The approach uses the Ducros
shock sensing criterion to detect and limit oscillations due to shocks while
applying a different criterion to detect and limit oscillations due to contact
discontinuities. Furthermore, the method is general in the sense that it can be
applied to any method that employs characteristic transformation and shock
sensors. However, in the present work, we focus on the Gradient-Based
Reconstruction family of schemes. A series of inviscid and viscous test cases
containing various types of discontinuities are carried out. The proposed
method is shown to markedly reduce high-frequency oscillations that arise due
to improper treatment of the various discontinuities; i.e., applying the Ducros
shock sensor in a flow where a strong contact discontinuity is present.
Moreover, the proposed method is shown to predict similar volume-averaged
kinetic energy and enstrophy profiles for the Taylor-Green vortex simulation
compared to the base Ducros sensor, indicating that it does not introduce
unnecessary numerical dissipation when there are no contact discontinuities in
the flow.
