Screw Compressors- Mathematical Modelling And Performance Calculation

For a symmetric profile: $$ V(\theta) = V_max \cdot \left[ 1 - \frac\theta\theta_w \cdot (1 - \frac1V_i) \right] $$

If the pressure ratio exceeds the critical pressure ratio, choked flow conditions apply: For a symmetric profile: $$ V(\theta) = V_max