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Erroneous pressure profile at the boundary cells (1D case) |
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February 25, 2020, 10:47 |
Erroneous pressure profile at the boundary cells (1D case)
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Senior Member
Saideep
Join Date: Apr 2015
Location: INDIA
Posts: 203
Rep Power: 12 |
Hi,
I am trying to solve the following Laplacian equation in a 1D channel: Code:
fvm::laplacian(var, p) I use a fixedValue boundary condition (inlet/ outlet) for pressure and zeroGradient boundary condition for velocity. When I run the case, I notice that pressure at the boundary cells (inlet, outlet) are not accurate which show a larger slope (which shall not happen). See, Fig. 1 (near the inlet), Fig 2 (near the inlet), Fig. 3 (near the inlet and outlet). As, a consequence the flux computed is not accurate. At the end of the run (Fig. 3), I loose a subtantial amount of pressure gradient due to this artefact and my flow velocity is much slower that what shall actually be. In reality, the pressure profile in Fig. 3 must be a straight line (with constant slope) connecting 70 Pa near inlet and 0 Pa near outlet. I tried refining the mesh, time step and different numerical solvers, schemes but could not solve the issue. In short, the pressure is happy to convergence to a wrong value at the boundaries and this happens in only 1 iteration (I reach a residual of e-20 in 1 iteration). Any hints on how to solve this? |
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Tags |
laplace equation, pressure and velocity |
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