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IDProjectCategoryView StatusLast Update
0003339OpenFOAMPatchpublic2019-08-26 17:41
Reporterdavvalok Assigned Tohenry  
PrioritylowSeveritytrivialReproducibilityhave not tried
Status resolvedResolutionfixed 
Product Versiondev 
Fixed in Versiondev 
Summary0003339: Bug in Ergun drag model - Multiphase
DescriptionIn Ergun.C, following path:
Line 69-72:
Max(scalar(1) - pair_.continuous(), pair_.continuous().residualAlpha())
pair_.continuous().residualAlpha() should be pair_.dispersed().residualAlpha() since (scalar(1) - pair_.continuous()) refers
to the dispersed pair in reality.
Additional InformationThis bug will also affect the GidaspowErgunWenYu drag model, if not being fixed.
TagsNo tags attached.



2019-08-25 15:47

manager   ~0010697

scalar(1) - pair_.continuous() relates to the dispersed phase fraction in a two-phase system but not in a multiphase system. Given that pair_.continuous() is used in the expression it makes sense that pair_.continuous().residualAlpha() is used. Can you provide a case which demonstrates the need to change the expression to use pair_.dispersed().residualAlpha() instead?


2019-08-26 08:17

reporter   ~0010699

Hi Henry,
Thank you for your reply. I am afraid I do not have a case for it, from the mathematical point of view it seems not very accurate. If you look at the WenYu.C you can see:
volScalarField alpha2
        max(scalar(1) - pair_.dispersed(), pair_.continuous().residualAlpha())
Which in the content of two phase system make sense. It might be better to use max(pair_.continuous(), pair_.continuous().residualAlpha()) for the content of multiphase?

For Ergun I would suggest to use:
scalar(1) - max(pair_.continuous(), pair_.continuous().residualAlpha()) instead of max(scalar(1) - pair_.continuous(), pair_.continuous().residualAlpha()) in Ergun.C.

In either cases I guess the effect should be negligible if residualAlpha for phases are set correctly by user.


2019-08-26 17:36

manager   ~0010700

It is not clear how this change would affect accuracy. If you really think this change is necessary I can make it as I do not see how it will either improve or reduce accuracy or stability.


2019-08-26 17:41

manager   ~0010701

commit 7d6b7a78d758540fec56cd960a5a9f6aa11e7a91

Issue History

Date Modified Username Field Change
2019-08-24 19:25 davvalok New Issue
2019-08-25 15:47 henry Note Added: 0010697
2019-08-26 08:17 davvalok Note Added: 0010699
2019-08-26 17:36 henry Note Added: 0010700
2019-08-26 17:41 henry Priority normal => low
2019-08-26 17:41 henry Severity minor => trivial
2019-08-26 17:41 henry Category Bug => Patch
2019-08-26 17:41 henry Assigned To => henry
2019-08-26 17:41 henry Status new => resolved
2019-08-26 17:41 henry Resolution open => fixed
2019-08-26 17:41 henry Fixed in Version => dev
2019-08-26 17:41 henry Note Added: 0010701