I have problem with implementation of an equation in the code. I have a relation as follow:
βπ₯=β(ππ’/ππ)+πΌπΉ on inlet

where u is obtained in the former step and is known and F is known also. to reach the descent direction I need to calculate βπ₯ on inlet. I donβt know how to implement it in the code. I will be grateful if help me.

Thanks very much. I already wrote the equation but my problem is that how I can say that it is for inlet boundary not the other domain. is any definition for that in the code?