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Pressure Drop vs Velocity in a Rectangular Pipe
Posted Sep 27, 2009, 8:30 a.m. EDT 1 Reply
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Hi
I'm currently modeling a single rectangular channel found in a fuel cell (with symmetry boundary). Dimension of the inlet and outlet area is of the order 10e-3 and the length of the pipe is 0.1 m.
I am having difficulty getting the expected result. The pressure drop vs velocity of fluid flow should be a curve that can be mapped by a second order quadratic equation (as the velocity increases, the pressure increases with increasing rate) But no matter how I try I keep getting a relationship that is close to linear, and only very slightly curved.
Here's what I've done, tried different solvers, played around with the meshing, changed the viscosity, but the result is the same, an almost linear graph, which does not fit the expectation.
Can anyone offer any advice regards to this problem? Thanks in advance.
I'm currently modeling a single rectangular channel found in a fuel cell (with symmetry boundary). Dimension of the inlet and outlet area is of the order 10e-3 and the length of the pipe is 0.1 m.
I am having difficulty getting the expected result. The pressure drop vs velocity of fluid flow should be a curve that can be mapped by a second order quadratic equation (as the velocity increases, the pressure increases with increasing rate) But no matter how I try I keep getting a relationship that is close to linear, and only very slightly curved.
Here's what I've done, tried different solvers, played around with the meshing, changed the viscosity, but the result is the same, an almost linear graph, which does not fit the expectation.
Can anyone offer any advice regards to this problem? Thanks in advance.
1 Reply Last Post Sep 28, 2009, 1:03 p.m. EDT
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Posted:
2 decades ago
This might just be an issue of not covering enough pressure (or flow rate) range to notice the nonlinearity. All smooth functions are linear to a first order meaning they will all look approximately linear over small enough ranges of the independent parameters (recall Taylor series).
I think an analytical solution exists for laminar flow in rectangular ducts (I am guessing it would be in the form of Fourier series). I would look up that solution, plug in the numbers and see how that compares to your numerical solution.
Good luck,
Ozgur
I think an analytical solution exists for laminar flow in rectangular ducts (I am guessing it would be in the form of Fourier series). I would look up that solution, plug in the numbers and see how that compares to your numerical solution.
Good luck,
Ozgur