Particles are not closely arranged during initialization

Hi everyone
In my cases, the thickness of computational domain is 3 times larger (180μm) than the particle diamater (60μm). However, those particles were loosely arranged when the lattice is hexa or hexagonal even with zero particle spaceing. I am practising a case published on a reference and do not want to increase the domain size. Could you help me how to solve this problem? Thank you.

Cohesive_originalVDH.mfx (11.1 KB)

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See this post:

(Particles in the computational domain: two abnormal phenomena - #5 by Fei)