semi-Lagrangian

In some emergencies, such as fire or accidental release of chemical/biological agents in buildings, it is very useful to simulate the flow on real time or even faster than real time so that proper measures can be taken to minimize casualties. The traditional computational fluid dynamics (CFD) simulation of fire or transient contaminant transport in buildings is accurate but too time consuming, such as by using unsteady Reynolds averaged Navier-Stokes equations (URANS) and large eddy simulation (LES).