To apply an "open boundary" condition in ANSYS Fluent without using a User-Defined Function (UDF), you can use:

1.Use the "Pressure Outlet" or "Pressure Inlet" Boundary Conditions

2.Use the "Far-Field" Boundary Condition (for Compressible Flows)

3.Symmetry or Outflow Boundary Conditions (Less Preferred for Open Ends)

we can use the Pressure Outlet boundary condition with 0 Pa gauge pressure and appropriate backflow settings without using a UDF.

Hi,

What do you mean by open boundary?

regarda

Hossain Nemati

Boundaries where fluid can easily enter and exit

Dear,

If a fluid enters, its direction and magnitude must be known and the "velocity inlet" boundary condition shall be used. If a flow is to leave the domain, its magnitude and direction are calculated. So, the "pressure outlet" boundary condition shall be used. Otherwise, no boundary condition allows both the inlet and outlet.

Hossain Nemati

It is not true. We can use this boundary condition in COMSOL.

Suppose we have an outlet where the backflow happening in it.

Of course, backflow may occur at the outlet. But since its direction, velocity, and temperature (if available) are based on estimation and not on calculation or a known value, this reduces the accuracy. If the volume of backflow is large, it may result in a serious error.