Hacktoberfest 2026: le issue che i maintainer hanno segnato per ottobre, aperte e adatte ai principianti. Sfoglia le issue Hacktoberfest

Behavior at low temperatures

Aperta
  • Qualcosa non va?
#117 2 commenti 0 reazioni 0 assegnatari Vedi su GitHub

Nessuno ha ancora preso questa issue.

Valutazione

Difficoltà
5/5
Tempo stimato
Più di una settimana
Idoneità per principianti
20/100
Tipo di issue
Funzionalità
Chiarezza
Abbastanza chiara
Stato di attività
Ferma
Stack tecnologico
cpp
Ambito
backend

Direzione di ricerca

The issue concerns low-temperature viscosity behavior and NASA-9 polynomial validity in Mutation++; it does not name source files, tests, or entry points. Start by reading the collision model and NASA-9 thermodynamic data handling, then trace how temperature limits are applied. Done means agreeing on the desired behavior for both cases and validating it against the reported low-temperature nitrogen example.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Hello,
I remember we talked about this topic a long time ago, but I am not sure what was the conclusion.

I am trying to use Mutation++ to determine thermal and transport properties in our free-stream rebuilding code (based on CABARET) for the Longshot facility. We assume nitrogen in thermal equilibrium everywhere. The static temperature can be as low as 70K.

  • The first issue is regarding viscosity, which is now overestimated at such low temperatures, see the attached plot. With the help of George, I have found a workaround for me resulting in a “corrected” curve shown in the plot (basically switching back to "exp-poly" for the pairs of interest in the collisions file). I was wondering if a more systematic solution could be found. See, that in the past, the behavior for low temperatures was just okay.

  • The second “issue” is concerning the NASA-9 polynomials. I prefer them over RRHO. However, they are usually limited to about 200K. When extrapolated below this limit, they result in unrealistic data. My workaround was to add a temperature range from 50K to 200K, where data smoothly go from the polynomials to the result of RRHO. Would it be possible just to clamp the values at the lower bound instead of using the polynomials beyond their validity? I believe this would result in more reasonable behavior.

I know that your concern is not at such low temperatures. However, it could help Mutation++ to spread for use in ground test facilities.

As a (dummy) user, I apologize in advance if I missed some options already implemented.

Thanks!

viscosity_Mutation++_NEW.pdf

Lingua principale
C++
Stelle
145
Fork
79
Merge medio
1g 15h
PR unite (30g)
2

Preparare l'ambiente

Come iniziare

  1. Leggi tutta la issue e poi la guida ai contributi del progetto.
  2. Commenta sulla issue per dire che te ne occupi tu — evita che due persone facciano lo stesso lavoro.
  3. Fai un fork del repository e lavora su un branch.
  4. Apri una pull request che faccia riferimento al numero della issue.

Altre issue di mutationpp/Mutationpp

Tutte le issue di mutationpp/Mutationpp

Issue simili

Altre issue su C++

Ricevi le nuove issue nella tua casella

Un breve riepilogo di issue GitHub adatte ai principianti.