Calculating Power number of stirred vessel
 

I am simulating a 2D planar baffled mixing tank with a rushton turbine as the agitator, and I'm having difficulties getting Power number values from from torque. Using the equation
Np= 2*pi*N*m*torque/(Diameter^5)*density*N^3
m=number-of-blades, N=rotational-speed ,
I am using the calculating torque from a moment plot on the impeller blades, which I assume means that is the total torque thus m=1 instead of 6.
This still results in my solution converging around Np=16.6. Eventhough standard Np for the test case is ~5.
My question is, is this difference explainable from simplifying 3D to 2D, or have I made an error somewhere.

Any help is greatly appreciated