[ansubru]

Hey fellow foamers!!

I have been using the DPMFoam solver quite a lot these days. My application deals with objects contacting a vibrating boundary layer. I would ideally want the objects to propagate in the net direction of vibration. For now I use the oscillatingFixedValue b.c (which specifes a moving wall velocity) and the simulation does look very promising.

However, when I increase the particle density (number of particles), the same cases which run without issues, begin to crash. I use OF 2.3.0 debug build, and I do my debugging with gdb.. This is the crash report I obtain after about 0.2 secs of my simulations

Courant Number mean: 3.1823238 max: 7818.7169
Time = 0.2065

Evolving kinematicCloud

Solving 3-D cloud kinematicCloud
    101 move-collide subCycles

Program received signal SIGFPE, Arithmetic exception.
0x00007ffff5914802 in Foam::WallCollisionRecord<Foam::Vector<double> >::match (
    this=0x4ca4d58, pRel=..., radius=0.00052589805000000003)
    at lnInclude/WallCollisionRecordI.H:67
67	    bool matched = (pRel & pRel_)/(magpRel_*magpRel) > cosAcceptanceAngle;
(gdb) bt
#0  0x00007ffff5914802 in Foam::WallCollisionRecord<Foam::Vector<double> >::match (this=0x4ca4d58, pRel=..., radius=0.00052589805000000003)
    at lnInclude/WallCollisionRecordI.H:67
#1  0x00007ffff5910e4a in Foam::CollisionRecordList<Foam::Vector<double>, Foam::Vector<double> >::matchWallRecord (this=0x16f3e80, pRel=..., 
    radius=0.00052589805000000003) at lnInclude/CollisionRecordList.C:339
#2  0x00007ffff590a00e in Foam::WallSpringSliderDashpot<Foam::CollidingCloud<Foam::KinematicCloud<Foam::Cloud<Foam::CollidingParcel<Foam::KinematicParcel<Foam::particle> > > > > >::evaluateWall (this=0x3d7da40, p=..., site=..., data=..., 
    pREff=0.00052589805000000003, kN=2446.1298302965579, cohesion=false)
    at lnInclude/WallSpringSliderDashpot.C:119........(and some more lines.. but these are the primary errors..

The colored line is the cause of this crash (floating point exception i.e division by zero). I am not very adept at programming as such, but I do know my way around it. However, this error has really baffled me . I do not understand why it would arise after 0.2 secs into my case (almost 500 time steps in..). I believe that the error is due to 'unphysical' relative positions between wall contact and particle centres. Also note the high 'Courant number' this is also indicating that something is not right. What is the physical significance of such an error?? Moreover, is there a work around for this error without violating the physics of the system.

Any insights will greatly be appreciated .

Thanks

ansubru