Changing Inputs During a Calculation

You can edit DEM inputs while a calculation is running, which is useful for calibrating a model without restarting each time. What happens next depends on which input you changed: some apply to the whole simulation on the very next step, while others are fixed into each particle at the moment it is created and so only affect particles fed from then on.

Applied immediately to every particle

These are re-read on every calculation step, so a change takes effect at once – including for particles already falling through the chute.

• Particle – Particle Friction
• Rolling Friction
• Cohesion Energy Density k (on the Cohesion tabsheet – see Simulating Wet/Sticky Material)
• Particle – Particle Co-eff of Restitution, and the Apply to particle contacts switch that turns it on – both are re-read every step, so you can tick the box or change the value mid-run and see the effect straight away (see Particle – Particle Damping)
• Critical Time Step dt
• Global Space Limits (the X, Y, Z min/max particle existence box)
• Calculation Recording frames per second – this affects how often frames are recorded, not the physics

Chute face properties behave the same way: editing a layer's Friction or e in the Layers table on the Chute Faces tabsheet applies to that layer's faces straight away – see Add/Edit Layers, Faces, Vertices.

Applied only to newly created particles

Each particle is given its own stiffness values when it is created at a feed box, scaled to that particle's size. Those values stay with the particle for its whole life, so changing these inputs mid-calculation affects only particles fed after the change:

• Particle Stiffness co-eff Kn
• Face Stiffness co-eff Kn
• Shear Stiffness co-eff Ks
• Particle Penetration % – this sets a minimum face stiffness worked out per particle from its own size and mass, so it is applied at creation along with the stiffness values above

Inputs that do nothing

There are none left on the tabsheets. Several fields that had no effect on a calculation – "Particle – Particle Cohesion" (Cohesion Distance) and "Use QuickSort DEM calculation" on the DEM Inputs tab, and Fc / Sc on the Cohesion tab – were removed rather than left in place labelled as inactive, so every input you can now see and change is one the calculation actually reads. Their values are still stored in your project file, so older projects open and re-save unchanged.