For small gaps, flow is modelled as or viscous slit flow . The mass flow rate ( \dotm leak ) for a given clearance area ( A leak ) and upstream/downstream pressures ( p_u, p_d ):
Use when detailed geometry or computational resources are limited. Assumptions: uniform polytropic exponent n, volumetric efficiency correlation, constant leakage fraction. For small gaps, flow is modelled as or viscous slit flow
A differential equation describes the change in volume over time ( For small gaps