Pressure Singularities and Ripples at Corners in 3D Laminar Flow

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Hello everyone,

I am developing a 3D Laminar Flow model for a variable-thickness domain, but I am encountering severe numerical stability issues, specifically pressure ripples and massive non-physical pressure spikes at the domain corners.

I would appreciate any insights on how to properly treat the boundary conditions or mesh to resolve these singularities.

Model Setup & Geometry:

  • Domain: A 3D rectangular footprint (L1xL2). The bottom surface is flat, but the top surface has a spatially varying height profile z(x,y) that tapers down toward the edges

  • Physics: 3D Single-Phase Laminar Flow (Stationary).

Boundary Conditions:

  • Bottom (z=0): Slip wall.
  • Side 1 (x=0): Symetry.
  • Side 2 (y=0): Slip wall.
  • Top Surface: Inlet with a spatially varying, pointwise prescribed mass flux
  • Outlet 1 (x=L1): Static Pressure = 0 Pa.
  • Outlet 2 (y=L2): Constant mass flow rate.

Mesh: Physics-controlled and User-controlled mesh.

The Problem: As you can see in the attached pressure field plot, the solver converges, but the resulting pressure field at z=0 is mathematically highly unstable. Resulting pressure significantly changes when mesh is changed

  1. There is a massive negative pressure singularity at the corners of (L1,0) and (L1,L2) where.
  2. There are significant numerical ripples propagating along the boundaries, especially near the P=0 outlet.

What should I do to overcome this problem and obtain smooth pressure field?

I have attached screenshots of my geometry, top surface profile, applied mass flux and resulting pressure field for different meshes.

Thank you in advance for your time and expertise.




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