PRES

In the PRES monitored volume, the relative pressure is defined as P_rel = pressure inside of monitored volume - atmospheric pressure.

The relative pressure is defined using a function in one of two ways. By default, the relative pressure is defined as a function of the relative volume $P_{rel}\left(\frac{V_0}{V}\right)$ , or the pressure can be a function of time $P_{rel}\left(t\right)$ .