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7.9 Pressure Far-Field Boundary Conditions

Pressure far-field conditions are used in FLUENT to model a free-stream condition at infinity, with free-stream Mach number and static conditions being specified. The pressure far-field boundary condition is often called a characteristic boundary condition, since it uses characteristic information (Riemann invariants) to determine the flow variables at the boundaries.

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This boundary condition is applicable only when the density is calculated using the ideal-gas law (see Section  8.3). Using it for other flows is not permitted. To effectively approximate true infinite-extent conditions, you must place the far-field boundary far enough from the object of interest. For example, in lifting airfoil calculations, it is not uncommon for the far-field boundary to be a circle with a radius of 20 chord lengths.

For an overview of flow boundaries, see Section  7.2.




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