2020-6-4 Meeting notes Dariel

Owned by Thomas Weinhart
Last updated: Jun 04, 2020 by Dariel Hernández Delfin
2 min read

Attendees

Discussion items

TopicComments
SuperQuadrics: BoundingSphereRadius

Prolate ellipsoids don't work; Mercury does not detect overlaps;

this is because teh BoundingSphereRadius is miscomputed;

Dariel is looking at correcting that function, using the Alexander Podzhuk paper.

He needs to add special cases in if-statements.

Problems
  • outputting axis in setBoundingRadius results in wrong values
SuperQuadrics: Contact detection
  • Blockiness of 0.1 causes contact point detection to fail
  • The paper by Alexander P. on which the Mercury algorithm is based says convergence is guaranteed for blockiness >0.25
  • Dariel will take a look whether this can be fixed; but not priority
MercuryCG

Dariel reported a problem running MercuryCG on SuperQuadric particles (loadRestart does nto seem to work)

Thomas will take a look once he has Dariels restart files

Angle distributionDariel corrected the distribution of angles (relative to the velocity vector) by sin(theta)/2, but the data for spheres (AR=1) is not perfectly uniform (it should be); also, the data has a large standard deviation
  • I told him to use the data files instead of the restart files because they contain more timesteps; and look for errors
Surface velocity profilesDariel sees a  difference with aspect ratio in surface velocity profiles of mixed flows: The peak velocity is reached earlier for high aspect ratios. Unknown origin
Working Document

To write a paper, we need to understand what are teh two segregation drivers that cause  a flip in segregation direction at AR~3

Dariel should start a working document, where we keep results as they come in

kinetic stress

The kinetic stress trace is higher at the flowing layer in each aspect ratio, The kinetic pressure is lower in the range of aspect ratios which are close to AR = 1.

fstat files for nonspherical particlesThere are NaN numbers. It is important to know how they come.
coarse graining (fstatics and MercuryCG)

Dariel obtained the error: This function should not be used

Actions

  • Find difference between the velocity of elongated particles and the total velocity field |Vne - V|/V.
  • Find kinetic stress gradients.

 

For elongated particles, we always see an s-shaped curve, even at Fr=0.01; could it be a "rotation inertia" effect: flows are more frictional when particles still have to orient itself, are less frictional when elongated.

  • Check whether angle of orientation w.r.t. streamlines of elongated particle vs r/R_0 shows a re-orientation of particles
  • Find transition points rolling-cataracting as function of Froude and AR



Actions

  • Dariel Hern├índez Delfin: correct the definition of BoundingSphereRadius in Mercury
  • Dariel Hern├índez Delfin: make a shared Google Drive; put your existing results in (angle distribution, surface velocity profiles, cg data, snapshots); also include the restart files of simulations with different aspect ratio.