Although most Ansys Chemkin Reactor Models are concerned with sub-sonic flows, the Shock Reactor Model is used to simulate chemical kinetics behind a normal incident or reflected shock. A common use of the Shock Reactor Model is to simulate the behavior of a shock tube experiment for studying reaction kinetics. This model may also be used to look at reactions that occur behind a bow shock for a supersonic vehicle. In order to follow the evolution of chemical species after a shock has passed over, it is first important to determine the post-shock conditions. The initial conditions behind a shock wave are related to conditions in front of the shock by gas-dynamic relations that depend on the thermodynamic properties of the gas mixture.

In this chapter we introduce the gas-dynamic equations that are solved within the Shock Reactor Model. There are several options for specifying the shock conditions, which are described in Shock Tube Experiments . Rankine-Hugoniot Relations for Normal Shocks describes the gas-dynamic equations used to determine the conditions immediately behind a shock, while Downstream Model Equations discusses the equations that are then solved to track the thermochemical state of the system as a function of time or distance after the shock has passed.