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moving walls + static walls in adjointShapeOptimizationFoam

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Old   July 21, 2020, 03:43
Default moving walls + static walls in adjointShapeOptimizationFoam
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Christophe
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Hello,

I am doing my first adjointShapeOptimizationFoam case (and second real study with openFOAM), it does run but starts to slowly diverge after 15 to 30 iterations and completely crashes after 250 to 550 iterations (depending on the underrelaxation applied to "alpha": I tried setting it anywhere from 0.01 to 0.2).

The part that shows signs of divergence is the "Adjoint continuity errors."

My domain is a volute-like channel scooping fluid from a spinning pool of water (see attached pictures, that should seriously help), and the bounding box of the whole thing is roughly 1ft x 1ft x 6in.
The boundaries are:
  • a cylindricalInletVelocity (in red, 2000 rpm, axial velocity 5.4 m/s, located at the bottom and near the outer diameter of the water pool),
  • a totalPressure outlet (in green, p=0, static, connected to the volute-like channel that I am trying to optimize),
  • rotating walls (in teal, 2850 rpm, top, bottom, and outer diameter of the water pool),
  • static walls (in beige, both the surroundings of the volute-like channel, but also the inner radius wall of the water pool),
  • symmetry zones (in pink, to prevent direct contact of the static and rotating walls, and where the water should come into contact with air),
  • and a pair of cyclicAMI surfaces coupled with one another (in yellow and blue, cutting through the water pool, because the whole domain is supposed to be repeated 4 times in a circular pattern).

The mesh was generated with snappyHexMesh keeping all cells at level0: no refinement, no boundary layers, just some snapping to the surfaces.

I am using the realizableKE turbulence model, the medium is warm water (nu=4.7e-7), the "lambda" and "alphaMax" (in transportProperties) are respectively at 1e-5 and 200. A quick look at the files saved show that porosity is added virtually everywhere (alpha varying between 15 and 180 throughout the domain at iteration#500).

I built my case by modifying the adjointShapOptimizationFoam\pitzDaily tutorial, so all the schemes and most other parameters are kept as they were in the tutorial.

So I have a few questions:
  • is adjointShapeOptimizationFoam known to be able to manage this kind of settings?
  • how can I help it find its way to a solution (should I run it first with at very low alphaMax to get a stable flow pattern before allowing it to optimize the shapes, should I use simpleFoam instead for that flow initialization purpose)?
  • any idea on other parameters I should adjust?

NB: for what it's worth, the case is run in MPI/parallel mode (24 cores) with BlueCFD Core 2017 (openFOAM v5 ported to Windows).
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