jostle · a hard-disk gas

Space pauses, S steps, R restarts with the same seed, N draws a new one.

Speeds

disks now Maxwell–Boltzmann at this temperature

KS distance: –
Mean speed: –
Theory: –

Boltzmann's H

H now: –
Maxwell floor: –

Brownian motion

Heavy tracer in the middle

Mass Radius

tracer free flight (2kT/M)τ² fit 4Dτ

D fitted: –
Diffusive from: –
Record: –

Effusion

Partition with a hole, gas starts on the left Hole Heavy share Mass ratio

light heavy, share on the right

Light / theory: –
Heavy / theory: –
Light : heavy: –
Graham: –
Free path: –
Crossings: –

Rates are crossings per unit time, per unit gap, per unit density on the near side, as a multiple of √(kT/2πm). Effusion needs the free path well above the hole; a wider hole lets the gas flow through faster.

Pressure

Z on the walls: –
Z, Henderson: –
Pressure: –
Packing: –
Collisions: –
Energy drift: –

Z = PA / NkT, the pressure as a multiple of an ideal gas with the same disks and temperature. Disks take up room, so Z rises above 1 as the box fills.

Gas

Start Disks Radius Temperature Speed Colour Trace one disk