[chenxi05]

I am simulating the pressure drop coefficient of different subchannels, such as typical
cell, side cell, corner cell, at spacers grids. Generally, there are two methods to get the drag coefficient of blockage in a subchannel composed by rod bundles. Because of the mass, momentum, and energy exchangement between the subchannels, it’s extremely inaccurate to get drag coefficient of subchannels over the second method.

Cd=Fd/0.5*rho*v*v*ref_area, Fd = force_z()@BLOKAGE(1)

Cd=dp/0.5*rho*v*v, (2)

In order to get Fd, you need to get force integral on surfaces of blockage, so we consider it as hydrodynamic drag coefficient;

In equation (2), we consider it as pressure drop coefficient.

Above all, I wanna ask the following questions:

1, are the two coefficients the same?

2, how to define the ref_area? According to the flow in channels, should we define the ref_area with the cross section area？