Dear all,

I am trying to run a flow simulation to determine the flow rate of air I need to have to deliver enough filtered air to the user of a mask. Unfortunately I have now idea how to realistically set the computational domain as small changes already result in completely different values.

To explain the system: An airflow (inlet volume flow) streams into the mask and protects the user from inhaling outside air. The outside air has a wind speed of 12 m/sec. I set surface goals to get the volume fraction of outside air at mouth and nose. After determining the flow rate I want to make another time dependent study including the human breath.

Do you have any idea how to size the computational domain for this scenario?