Thermalized LB: test 4 rel time model velocity and pressure fluctuations

This changes the fluctuating LB test to match as closely as possible what we are going to use. Model with 4 relaxation times for shear/bulk/odd/even modes. Tests:

• mass conservation
• momentum conservation
• <m v^2> = k_B T
• Maxwell velocity distribution
• average stress tensor
• stress tensor fluctuations accodring to Duenweg, Schiller, Ladd

It turns out that the test only passes by chance, which is surprising given that the relaxation rates were chosen randomly.

marked as a Work In Progress

This merge request needs to be updated with the conclusions from https://github.com/espressomd/espresso/pull/3847/files#diff-68221c97b867ed41f0dc69ef4a7e6ad8, which I believe added an extra kB*T to the equilibrium stress.

assigned to @RudolfWeeber

added 13 commits

• 788ad27c...2198c894 - 12 commits from branch pycodegen:master
• 9c03af2b - Thermalized LB: test 4 rel time model velocity and pressure

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unmarked as a Work In Progress

approved this merge request

assigned to @holzer and unassigned @RudolfWeeber

added 2 commits

• 5c4c739a - Test: Separate out lb instance generation for fluctuating lb test
• c18e7077 - WIP: Test momentum conservation for fluctuating LB with force

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marked as a Work In Progress from RudolfWeeber/lbmpy@c18e7077

added 1 commit

• 76cce232 - Test momentum conservation for fluctuating LB with point forces

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assigned to @RudolfWeeber and unassigned @holzer

mentioned in issue walberla/walberla#125 (closed)

added 1 commit

• 20bf501c - Test momentum conservation for fluctuating LB with point forces

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unmarked as a Work In Progress

assigned to @holzer and unassigned @RudolfWeeber

merged

mentioned in commit 13f670d1