  The accurate and robust simulation of transcritical real-fluid flows is
crucial for many engineering applications. Diffused interface methods are
frequently employed and several numerical schemes have been developed for
simulating transcritical flows. These schemes can be categorized into two
types, namely fully conservative and quasi-conservative schemes. An adaptive
scheme which is a hybrid of the two is developed in this study. By considering
several numerical test cases, it is shown that different schemes predict
distinctly different mixing behaviors. It is shown that the mixing processes
follow the isobaric-adiabatic and isobaric-isochoric mixing models for fully
and quasi-conservative schemes, respectively, and the adaptive scheme yields a
mixing behavior that spans both models. The distinct mixing behaviors are a
consequence of numerical diffusion instead of physical diffusion and can be
attributed to insufficient numerical spatial resolution. This work provides a
better understanding on the interpretation of numerical simulation results and
the mixing models that are commonly used to study transcritical flows.
