# How do I simplify populated areas in Cabinet into Flow resistances

 Icepak has a flow resistance object that can be used to simulate a populated electronics region. Here is the method that can be used to do that. The aim of this process is to create pressure loss curves in all the three directions for the definition of the 3D resistance.1. Identify the populated areas1.1 Identify an area where you have the objects to be converted into a flow resistance.1.2 Create an equivalent sized 3-D rectangular block of the right size. This 3-D should completely conceal all the electronics it`s meant to replace. However it should not be larger than the bounding box created by the electronics. Inactivate this block at this time.2 Run a wind tunnel based calibration for the flow resistance2.1 Create a long wind tunnel model in Icepak with openings on both sides. The wind tunnel should be at least ten times longer than the largest distance of the populated region identified to be converted into resistance objects. Place the populated electronics region in the center of this wind tunnel. Make one side of the tunnel a velocity opening and other side a normal opening.2.2 The wind tunnel cross section should be such that there is no bypass around electronics objects.2.3 Place an inlet velocity at one end of this tunnel and the other end should be an outlet,2.4 Create trials of inlet velocity at the inlet of the wind tunnel. Calibrate over a pre-defined range of flow velocities. You need to decide on minimum speed, maximum speed and number of trials to be run. Keep trials at least 3.2.5 Calculate the pressure drop across the heat sink and it is associated with the inlet velocity.2.6 After all trials are done you will get your pressure loss curve in that direction2.7 Perform the same wind tunnel calibration in all the three directions to get the pressure loss curves in all 3 directions.3 Replace the detailed electronics with simplified flow resistance block3.1 Inactivate all the electronics we are going to replace.3.2 Activate the equivalent resistance block created in step 1.2.3.3 Apply the pressure loss curves in all the three directions as calculated in step 2.5.3.4 Run the simulation