Calculate the Specific Speed (Ns) to determine the best fan geometry for the required operating point.
Note on Specific Speed (Ns): The Ns value links the target performance (Q, P) to the optimal geometry and RPM for highest efficiency. The formula used is Ns = [RPM * sqrt(Q_SI)] / [(P_SI / rho_SI)^0.75]. Selecting a fan type that falls outside its optimal Ns range will result in significantly reduced efficiency and increased noise. The Ns value calculated here is unitless, based on SI base inputs (m³/s, Pa, kg/m³, RPM).