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IDProjectCategoryView StatusDate SubmittedLast Update
0003809OpenFOAMBugpublic2022-02-24 08:232022-02-24 16:06
Reportergeth03 Assigned Tohenry  
PrioritynoneSeverityminorReproducibilityalways
Status closedResolutionno change required 
PlatformUnixOSOtherOS Version(please specify)
Summary0003809: multiphaseEulerFoam does not reproduce single-phase behaviour when other phases are absent
Descriptiongoal:
laminar pipe flow can be solved analytically. my aim was to check if multiphaseEulerFoam would reproduce single-phase behaviour when other phases are non-existend (alpha_otherPhases = 0 in the whole domain and patches).

comparisons:
1. analytical solution for entry length (=0.6*Re*d), pressure drop per length for laminar flow (=64/Re*rho/2*u_avrg^2/d), maximal velocity (u_max = 2*u_avrg)
2. first i tried 3 solvers: icoFoam, pisoFoam and simpleFoam
All 3 solvers matched the expectations really good.
3. now i tried the multiphaseEulerFoam solver, with 2 phases in total, but the 2nd phase has volume fraction of 0, meanwhile the 1st phase has volume fraction of 1 (initially and at inlet). my expectation was, that the equation system would reduce to single-phase NSE and reproduce the result of the other solvers.
unfortunately, the pressure output looks really odd.
Steps To Reproduce1. mesh: pipe (half geometry), diameter d = 50 mm = 0.050 m, length = 5 m

2. u_inlet = 10 mm/sek = 0.01 m/sek ; rho = 1000 kg/m³ ; mu = 0.001 kg/(m*sek) -> Re = 500 (laminar flow)

3. analytical: entry length = 1.44 m ; pressure drop per length = 0.128 Pa ; u_max = 0.020 m/sek

All files are attached, just run "multiphaseEulerFoam" and look at pressure.
Additional Informationbecause other solvers do not have gravity, for multiphaseEulerFoam g was set to (0 0 0).
TagsNo tags attached.

Activities

geth03

2022-02-24 09:30

reporter   ~0012498

part 1 of 2
multiphaseEulerFoam_OF9.7z.001 (1,500,000 bytes)

geth03

2022-02-24 09:30

reporter   ~0012499

part 2 of 2
multiphaseEulerFoam_OF9.7z.002 (1,062,851 bytes)

henry

2022-02-24 10:29

manager   ~0012500

Try running with only one phase defined in phaseProperties phases list.

geth03

2022-02-24 11:26

reporter   ~0012501

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location "constant";
    object phaseProperties;
}

type basicMultiphaseSystem;

phases (hp);

hp
{
    type pureIsothermalPhaseModel;
    diameterModel constant;
    constantCoeffs
    {
        d 1e-6;
    }
    residualAlpha 1e-6;
}

blending
{
    default
    {
        type none;
        continuousPhase hp;
    }

    drag
    {
        $default
    }
}

surfaceTension
();

interfaceCompression
();
aspectRatio
();

drag
();

virtualMass
();

heatTransfer
();

phaseTransfer
();

lift
();

wallLubrication
();

turbulentDispersion
();

//Minimum allowable pressure
pMin 0;

-------------------------------------------------------------------------

i) the old setting with 2 phases (void fraction 0 for 2nd phase) gives a velocity profile with u_max=1.5*u_avrg
ii) the new setting with only one phase has a better velocity profile with u_max = approx. 2*u_avrg

but in the end it did not fix the odd pressure output.

henry

2022-02-24 11:44

manager   ~0012502

You will need to study the way in which the drag term is stabilised in the case of 0 phase-fraction to resolve this.
We could work on this for you but would need to secure funding.

geth03

2022-02-24 12:29

reporter   ~0012503

please find attached screenshot.

this is the simulation with the phaseProperties you suggested.
it doesn't matter which setting i use, the pressure looks really really odd.
i don't think the drag term is the reason for that.

please have a look at that and if you think it is user error, thank i apologize for wasting your time.
screenshot.png (31,243 bytes)   
screenshot.png (31,243 bytes)   

henry

2022-02-24 12:54

manager   ~0012504

This looks like a case setup problem and everything to do with multiphaseEulerFoam is time consuming and we cannot provide free support for it.
If you would like us to help you use multiphaseEulerFoam please contact us directly to arrange a support contract.

henry

2022-02-24 16:06

manager   ~0012505

User support request

Issue History

Date Modified Username Field Change
2022-02-24 08:23 geth03 New Issue
2022-02-24 09:30 geth03 File Added: multiphaseEulerFoam_OF9.7z.001
2022-02-24 09:30 geth03 Note Added: 0012498
2022-02-24 09:30 geth03 File Added: multiphaseEulerFoam_OF9.7z.002
2022-02-24 09:30 geth03 Note Added: 0012499
2022-02-24 10:29 henry Note Added: 0012500
2022-02-24 11:26 geth03 Note Added: 0012501
2022-02-24 11:44 henry Note Added: 0012502
2022-02-24 12:17 henry Priority high => none
2022-02-24 12:17 henry Severity major => minor
2022-02-24 12:29 geth03 File Added: screenshot.png
2022-02-24 12:29 geth03 Note Added: 0012503
2022-02-24 12:54 henry Note Added: 0012504
2022-02-24 16:06 henry Assigned To => henry
2022-02-24 16:06 henry Status new => closed
2022-02-24 16:06 henry Resolution open => no change required
2022-02-24 16:06 henry Note Added: 0012505