Slip coefficient by GÜLICH/ WIESNER
Outflow (slip) coefficient γ is defined for the decreased energy transmission:
The cu-difference is called slip velocity.
The smaller the outflow coefficient, the higher the deviation of flow compared to the direction given by blade.
Wiesner developed an empirical equation for the estimation of outflow coefficient:
Gülich modified this formula by two additional correction factors:
with the correction factors:
Circumferential component of blade congruent flow can be calculated as follows:
Contrary to Wiesner's original suggestion an average inlet diameter d1m is not used for the calculation of kw in CFturbo but the diameter at hub and shroud respectively. Doing so a slip coefficient for hub and shroud can be calculated. An average slip coefficient is determined by:
The switch between radial and mixed-flow calculation of the correction factor f1 is done by: