 ## Fluids

• Khaled_Mohamad
Subscriber

Hi Every one

I am doing multiphase flow for air and wastewater such that waste water is dragging air inside a pipe

For model simplicity, I am trying to do a 2D analysis using Ansys fluent such that I am doing a 2D analysis for a half pipe as shown in the figure such that the flow is perpendicular to the surface

And since it is assumed steady and fully-developed flow I want to assign a normal velocity component to the horizontal line representing some water drag and the curved surface will represent pipe wall

But how to assign a velocity component different to the analysis dimensions itself?

Because i found that X and Y velocity are open for edit in the boundary conditions however i want to assign a Z direction Velocity

For more follow up there is a paper had done something similar but using a built up code instead of Ansys Fluent

• Nikhil Narale
Ansys Employee
Hello,

For your requirement, I believe, you might need to create an UDF, which will be quite a complex approach. For 2D, boundary conditions can be assigned to the edges (which acts as a boundary zones in 2d) and not to the surfaces/faces (which acts as a cell zones in 2d).
However, I would recommend considering end-to-end rectangular geometry to plot the pipe, which will be pretty straightforward.

Nikhil
• Khaled_Mohamad
Subscriber
I cannot simplify it into a rectangle because the curvature has an effect on the obtained results also i will be able to observe the effect of secondary currents
Ok i will simulate it 3D better
I also Want to input the velocity of the water interface as U (at any point in X direction) = UCL (((W-2*Absolute(X))/W)^(0.25) (Not just a fixed velocity)
Where UCL is the velocity at the centerline of the pipe, W is the width of water interface X is the distance from the center line
Such that velocity will have power 1/4 distribution and at the walls U will be equal 0 