Add P-U with M&M Switch

This is the version of Pressure-Energy SPH that includes the Morris & Monaghan (1997) variable artificial viscosity with a Balsara switch.

This should not contain too many changes in the central code. The hydro test suite is currently running but we see marginally improved convergence, see below for the 3D Gresho Vortex.

With variable AV: Without:

Morris, J. P., & Monaghan, J. J. (1997). A Switch to Reduce SPH Viscosity. Journal of Computational Physics, 136(1), 41–50. http://doi.org/10.1006/jcph.1997.5690

Here is the SodShock 1D for direct comparison with Fig. 3 of that paper. Note we see differences because we underestimate the velocities at the minima and they overestimate them at the maxima of the rarefaction wave.

Why do we get that difference? Also we have a spike in alpha at x=-0.3 whilst theirs is at the contact discontinuity.

It's unclear why we get that difference. It's the same difference we see with all schemes, though - it's related to the thing we were talking to Phil about with the over-shooting. It could be something to do with time-stepping but I don't have a clue really so won't speculate.

As for the spike at the contact discontinuity, that's just because I chose l=0.1 instead of l=0.2 (as in Price 2012). See below for the fixed plot.

Can you try a c4 kernel with eta=1.6 ?

The Sedov shows significantly improved convergence.

With variable AV:

Without:

For a specific test or for all?

Sod at least. Where is the improved convergence on the images? What bit are you focusing on?

In particular the scatter in the velocities and densities.

ok

Sod 2D, C4 Sod 2D, Cublic Spline

So a reduction in the noise level.

Here's the Gresho 3D with the new kernel.

Ah, now we are talking!

added 3 commits

• c19894c9 - Updated value of viscosity constant
• acf6c008 - Added divv for AV to the cosmology theory
• e2651425 - Updated the Pressure Energy schemes to include new divv for cosmoology

Compare with previous version

added 105 commits

• e2651425...cee4c633 - 80 commits from branch master
• 0e7da9bc - Copied over PressureEnergy stuff to start M&M AV.
• dbc3f8fe - Added include flags, minor function changes, for new scheme.
• fa83d6cc - Added M&M viscosity scheme. Tested and working with SodShock_1D.
• ffb8ac2c - Added comments to show explicitly that the gradient loop is not used.
• 60b449fc - Updated constants to use values from M&M1997
• f5949417 - Minor documentation changes, ensured correct global constants are used throughout.
• 1ee32914 - Changed the Sod_1D script to plot the artificial viscosity if available
• 4e7e08e5 - Added discussion about variable artificial viscosity
• 9400bbdc - Added paper reference to all of the briefs for the hydro_*.h
• 502e9cb0 - Reverted the hydro_end_gradient signature to not require the engine.
• 1119f02e - Removed border for KHmovie
• 1126d71d - Added the timestep for kick_hydro as a pass-by-value parameter to…
• 1c0eb754 - Added the kicking of the AV to hydro_prepare_force.
• ed045e7f - Added include flags, minor function changes, for new scheme.
• 7102aa96 - Added M&M viscosity scheme. Tested and working with SodShock_1D.
• a1d1913d - Added comments to show explicitly that the gradient loop is not used.
• 491202bd - Minor documentation changes, ensured correct global constants are used throughout.
• aeb4abcd - Reverted the hydro_end_gradient signature to not require the engine.
• 4e481781 - Added the kicking of the AV to hydro_prepare_force.
• 46236d1b - Rebased to include the new changes from Pressure-Energy
• 04e89445 - Fixed a botched merge
• 87e7b9d1 - Changed limits in SodShock 1D to match those in the Morris & Monaghan paper.
• 3f9249c1 - Updated value of viscosity constant
• 93c906e0 - Added divv for AV to the cosmology theory
• cfdbac9b - Updated the Pressure Energy schemes to include new divv for cosmoology

Compare with previous version

marked as a Work In Progress

changed the description

This will need rebasing given the new functions that have been added to the particles' API.

added 72 commits

• cfdbac9b...1f656ea1 - 47 commits from branch master
• 3e3e73c2 - Copied over PressureEnergy stuff to start M&M AV.
• 85637a95 - Added include flags, minor function changes, for new scheme.
• d6fd2809 - Added M&M viscosity scheme. Tested and working with SodShock_1D.
• 4b5c223d - Added comments to show explicitly that the gradient loop is not used.
• 4f18f6d4 - Updated constants to use values from M&M1997
• b5ce7658 - Minor documentation changes, ensured correct global constants are used throughout.
• 0553879b - Changed the Sod_1D script to plot the artificial viscosity if available
• c6009768 - Added discussion about variable artificial viscosity
• 33ba5f14 - Added paper reference to all of the briefs for the hydro_*.h
• 11d8eebd - Reverted the hydro_end_gradient signature to not require the engine.
• 3705000c - Removed border for KHmovie
• 6152bcb9 - Added the timestep for kick_hydro as a pass-by-value parameter to…
• 988383d0 - Added the kicking of the AV to hydro_prepare_force.
• b827190f - Added include flags, minor function changes, for new scheme.
• 89fada96 - Added M&M viscosity scheme. Tested and working with SodShock_1D.
• 0bde8b19 - Added comments to show explicitly that the gradient loop is not used.
• 83e95658 - Minor documentation changes, ensured correct global constants are used throughout.
• c86e412a - Reverted the hydro_end_gradient signature to not require the engine.
• 8423e54c - Added the kicking of the AV to hydro_prepare_force.
• 27639e5e - Rebased to include the new changes from Pressure-Energy
• 667182e5 - Fixed a botched merge
• b0c9547c - Changed limits in SodShock 1D to match those in the Morris & Monaghan paper.
• 7b0dc396 - Updated value of viscosity constant
• 05a49f7d - Added divv for AV to the cosmology theory
• 0b3865f1 - Updated the Pressure Energy schemes to include new divv for cosmoology

Compare with previous version

Does that require any re-writing of the interaction functions, etc. or just a basic rebase?