How to achieve constant static pressure in inlet?

Zou Jianfeng

I simulate a sonic hydrogen injection and use pressure inlet or mass flow inlet. For all these two condition,total pressure and total temperature are set, which are calculated according to the static pressure and the inlet velocity.

But when the unsteady flow simulation continues, the static pressure and the inlet velocity values are changed, yet the total pressure didn't change.

pls tell me how to achieve constant static pressure in inlet. Thanks in advance.