Large error in Pressure Drop in pipe
I have a single pipe with a triangular input and output:
Picture of the geometry (basically a pipe filled with water shaped like a triangle)
When i do a hand calculation based on the width and height of the flow path and the velocity at the inlet, I get about 10 psi pressure drop that I should be getting from inlet to outlet. When I run Ansys, I get approximately 20 psi.
I have made sure that I have an inflation for the boundary layer, I have made the mesh ridiculously fine, and that I run it to 1e-5 convergence criteria. I have also confirmed with my professor that I should be getting around 10 psi (meaning that I did not make a math error when doing the hand calculation).
Any ideas why this is occurring?
What is the hand calculation based on? Is the hand calculation based on fully developed flow? Did you model fully developed flow in CFX? If you just modelled a constant velocity across the entire inlet the flow would develop in the simulation and have a much higher pressure drop - his could explain your error.
The mesh you show is horribly coarse. I trust that is not the mesh you used.
Is the triangle cut out of the cylinder (ie the flow is a cylinder pipe with a triangle in the middle ) or does the flow go through the triangle bit?
Also, have you looked at the FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
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