How to open/block CFD cells in FLUENT?
 

I saw a paper of "A simplified approach to describe complex diffusers in displacement"

In it, the author mentioned in FLUENT it is easy to open/block CFD cells as below:"his paper proposed to specify flow conditions on CFD cells of simplified diffuser geometry. The new method assigns the actual velocities on a certain ratio of CFD cells while the other cells are randomly blocked. According to the mass conservation principle, the ratio to be treated as openings should be equal to the effective area ratio of the diffuser. Figure 2 shows the randomly open and blocked cells for the four diffusers in displacement ventilation. This method uses the following random mathematical function to determine if a CFD cell is open..."

"Since commercial CFD software such as FLUENT (http://www.fluent.com) provides very friendly user interface for programming, the specification of discharge velocity and open/blocked CFD cells are relatively easy"

Does anyone know how to open/block CFD cells in FLUENT??