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Hallo,I hope somebody can help me to solve this problem I am trying to simulate a Open channel flow in 3-D. As far as I am concered, you choose the open channel flow in Fluent, which means that the downstream flow will not effect on the upstream flow. But why can I find the reverse flow at the outlet boundary? and the vector direction of gas phase is opposite to that of liquid phase. Is it conflict with open channel flow? A friend of mine has simulated a similar case like me, but he did it in 2-D. He said the vector direction of gas phase is the same as that of liquid phase. How to interpret it?