fan ascending curve problem

[Marc Abadie]

 Dear CONTAM users,

We are trying to model a fan for air extraction that has an ascending curve (meaning increasing pressure with increasing airflow rate)... but the airflow rate becomes negative through the fan converting it as a supply fan?

We do understand that with ascending curve, 2 solutions may arise, one positive (the one we want) and one negative (the one CONTAM founds) so is there a way to "help" CONTAM to find the right solution?

Thank you all,

-- Zohreh and Marc