Your turbulent power number looks good.  The attached formula is a viscosity correction factor, which is reasonably accurate for all hydrofoil impellers.  To use the formula, calculate the Reynolds number with impeller diameter, rotational speed, fluid density and viscosity.  Then select the expression matching the range for the Reynolds number.  The calculated value from the exponential expression should be multiplied times the turbulent power number to get a corrected power number.  Then calculate impeller power using the corrected power number.
 
The expressions are nothing more than curve fits for a typical log-log curve for power number as a function of Reynolds number.