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IDProjectCategoryView StatusDate SubmittedLast Update
0002680OpenFOAMPatchpublic2017-08-29 10:372017-09-01 13:45
Reporterpsippola Assigned Towill  
PrioritylowSeveritytweakReproducibilityN/A
Status resolvedResolutionfixed 
Product Versiondev 
Summary0002680: Calculating tangential contact force and slip velocity in SpringSliderDashpot- contact model
DescriptionIn PairSpringSliderDashpot.C, calculating the tangential contact force between non-slipping surfaces is currently done as

                fT_AB =
                    -kT*tangentialOverlapMag
                   *tangentialOverlap_AB/tangentialOverlapMag
                  - etaT*USlip_AB;

and in WallSpringSliderDashpot.C as

            fT_PW =
                -kT*tangentialOverlapMag
               *tangentialOverlap_PW/tangentialOverlapMag
              - etaT*USlip_PW;

These lines contain an ineffective multiplication and a division with 'tangentialOverlapMag'. Should this simply be

                fT_AB =
                  - kT*tangentialOverlap_AB
                  - etaT*USlip_AB;

and respectively for a particle-wall contact?

Also as a possible trivial tweak, the slip velocity of particle surfaces is currently calculated as

        vector USlip_AB =
            U_AB - (U_AB & rHat_AB)*rHat_AB
          + (pA.omega() ^ (dAEff/2*-rHat_AB))
          - (pB.omega() ^ (dBEff/2*rHat_AB));

. Could it be rather be

        vector USlip_AB =
            U_AB - (U_AB & rHat_AB)*rHat_AB
          - (dAEff/2*pA.omega()+dBEff/2*pB.omega()) ^ rHat_AB;

to avoid computing a cross product twice?
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Activities

will

2017-09-01 13:45

manager   ~0008654

Thanks for the report. Resolved by commit 937dba8c.

Issue History

Date Modified Username Field Change
2017-08-29 10:37 psippola New Issue
2017-09-01 13:45 will Assigned To => will
2017-09-01 13:45 will Status new => resolved
2017-09-01 13:45 will Resolution open => fixed
2017-09-01 13:45 will Note Added: 0008654