Quasi-reversibility equation

In case contaminants are found in an aircraft cabin, it is useful to identify the contaminant source location and strength. This can be done through inverse Computational Fluid Dynamics (CFD) modeling. Since inverse CFD equations are ill-posed, this study proposes to solve a quasi-reversibility (QR) equation and a pseudo-reversibility (PR) equation. The QR equation improves the numerical stability by replacing the second-order diffusion term with a  fourth-order stabilization term in the governing equation of contaminant transport.