Follow these steps:
1)Use for mesh regions or boundaries normal to one of the X, Y or Z axes.
2)Define expressions and one additional variable to get information on the percentage of area of that region or boundary with backflow. Expressions: (example here: BOUNDARY normal to global Z axis) Backflow = areaInt(AV Backflow Step)@BOUNDARY / area()@BOUNDARY Backflow Step = 1 – step(Velocity w / 1[m/s])
3) Additional Variable: LIBRARY: ADDITIONAL VARIABLE: AV Backflow Step Option = Definition Tensor Type = SCALAR Units = [] Variable Type = Unspecified END END
4)Setting for “AV Backflow Step” in all Domains, under “FLUID MODELS”: ADDITIONAL VARIABLE: AV Backflow Step Additional Variable Value = Backflow Step Option = Algebraic Equation END
5)Monitor the expression “Backflow” in Solver Manager to get percentage of area of BOUNDARY, where backflow into the negative Z direction occurs. Value will be between 0 and 1.