[siw]

Hi,

Can anyone suggest a suitable set-up for modelling this scenario?

I have an internal system upstream of a centrifugal fan and when the fan is operating it pulls a volumetric flow rate of 346 litres/second through the system. My CFD model is of the system upstream of the fan only and I would use an outlet mass flow rate and a total pressure inlet (the air is drawn in from the atmosphere) to model this condition - so far so good. However, I need to include a restrictor, e.g. orifice plate, into the system so that the volumetric flow rate is reduced to 250 litres/second. There would be a corresponding pressure loss across the restrictor.

I could simply alter the outlet flow rate boundary condition to the new value of 250 L/s then let CFX calculate the restrictor pressure loss. But this would not produce the reduction in flow rate as part of the calculation because it is the restrictor which reduces the flow rate and not the boundary conditions. Since CFD works on mass conservation then specifying 346 L/s at the outlet and having CFX alter the flow rate through the model does not seem possible to me.

Thanks.