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Background

This does two things.

  1. Refactors our stopping times to be specialized classes following the diffusion coefficients.
  2. Adds a more sophisticated model from https://iopscience.iop.org/article/10.1088/0004-637X/806/2/203

This relies on #44 .

Closes #41 .

Description of Changes

Checklist

  • New features are documented
  • Tests added for bug fixes and new features
  • (@lanl.gov employees) Update copyright on changed files

@adamdempsey90
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TODO:

  • Add new test for new model

@pdmullen pdmullen mentioned this pull request Jan 14, 2025
3 tasks
Comment on lines +206 to +209
const Real cv = eos.SpecificHeatFromDensityTemperature(dg, Tg);
const Real gm1 = eos.GruneisenParamFromDensityTemperature(dg, Tg);
// kb T/ mu = cv * gm1 * T
const Real vth = std::sqrt(8.0 / M_PI * gm1 * cv * Tg);
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Now that we have constants, we can just directly use kb/mu*T

@pdmullen
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pdmullen commented Jul 3, 2025

Why did this never get merged?

@adamdempsey90
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Why did this never get merged?

The plan was to do some testing

@111-1000
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111-1000 commented Nov 6, 2025

In src/drag/drag.hpp, in

const Real CEu = 1. / (sgam * Mu) * (4.6 / (1. + M) + 1.7 /* srt(Td/Tg) */);

we may want to apply the following correction:

4.6 -> (8/3)*sqrt(8/pi)~~4.25538612146777
1.7 -> (pi/3)*sqrt(8/pi)~~1.67108481066774

which would provide the original Epstein drag limit. I was aware of the 4.6-4.26 discrepancy in Melosh & Goldin paper, but at the time, I decided to leave it and defer for later (I was working on planetesimals, so Epstein regime was irrelevant). I still don't know if it was a typo or something else. But I think we are OK reverting to the original Epstein formulation.

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Expand stopping time

4 participants