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IDProjectCategoryView StatusLast Update
0003293OpenFOAMBugpublic2019-06-24 14:37
ReporterShortyAssigned Tohenry 
PrioritylowSeverityminorReproducibilityalways
Status closedResolutionno change required 
PlatformGNU/LinuxOSUbuntuOS Version16.04
Product Versiondev 
Fixed in Version 
Summary0003293: Density field is not updated in chtMultiRegionFoam while using "frozenFlow = true"
DescriptionHi all,

this is not a critical bug but the density field in the conjugated heat tansfer solver is not been updated while using the frozenFlow option. Internally (in the thermodynamic) the density field is updated but the saved field is not. The reason is based on the fact, that we do not copy the thermo:rho field into the stored rho field.

Thus,
- while doing a normal calculation, the rho field is updated in the pEqn.H
- while doing a frozenFlow calculation, the rho field is not updated

In order to update. We simply should add the following into the solveFluid.H file:


if (pimple.frozenFlow())
{
    #include "EEqn.H"

    rho = thermo.rho();
}
TagsNo tags attached.

Activities

henry

2019-06-19 11:05

manager   ~0010518

Should rho be updated with frozen-flow? Surely density changes would cause changes in the flow. If the frozen flow is initially conservative but the density changes without the corresponding changes to the flow it would no longer be conservative.

Shorty

2019-06-19 15:24

reporter   ~0010519

Correct, the density field should be always constant. Maybe we should clarify the need of frozenFlow option first. Maybe I misunderstood it. If we have a steadyState flow field, I thought, we use the frozenFlow calc to speed up the energy calculation, right or not? Assume the following situation: we solve in rhoSimpleFoam (or chtMultiRegionFoam in steadyState mode) a fluid flow inside a pipe. Now one wants to do a cht while resetting the temperature field to e.g. 300K. Doing so will reset the density field too (based on thermo.correct()).

I guess I misunderstand the frozenFlow keyword or it is assumed that the temperature distribution inside the fluid flow is not changing as well. So I agree Henry, changing the density as I mentioned is not the correct thing. Nevertheless, if one changes the temperature field (as mentioned above), the density field will be updated in the thermo.correct() function but the saved density field will not.

henry

2019-06-19 15:40

manager   ~0010520

Different people may want to use the frozen flow option for different purposes, with or without density change. Certainly the frozen flow option is only consistent with temperature change if the density is not a function of temperature, so you could choose the constant density equation of state.

Shorty

2019-06-24 08:45

reporter   ~0010525

I agree Henry. Therefore, you can close the report.

Issue History

Date Modified Username Field Change
2019-06-19 10:48 Shorty New Issue
2019-06-19 11:05 henry Note Added: 0010518
2019-06-19 15:24 Shorty Note Added: 0010519
2019-06-19 15:40 henry Note Added: 0010520
2019-06-24 08:45 Shorty Note Added: 0010525
2019-06-24 14:37 henry Assigned To => henry
2019-06-24 14:37 henry Status new => closed
2019-06-24 14:37 henry Resolution open => no change required