This is the 2D sibling of the 3D ventricular-anatomy CSF simulator, and it computes the aqueduct flow differently on purpose. The 3D version moves particles along a fixed 3D curve at a single scalar speed. This 2D version instead treats the aqueduct as a real planar (two-plate) Poiseuille channel: its gap height h is derived geometrically from the outflow resistance via R = C/h³ (planar-channel Poiseuille resistance), so raising resistance visibly narrows the channel, and every particle's horizontal speed is read off an actual parabolic velocity profile v(y) = v_max·(1 − (2y/h)²) computed fresh each frame from the instantaneous outflow Q — not a single uniform speed.
mass balance: dV/dt = Q_in − Q_out
Davson's eq.: Q_out = (ICP − P_venous) / R_out
channel geom.: h(resist) = h0 · resist^(−1/3) [R = C/h³]
velocity field: v(y) = 1.5·Q_out·(1 − (2y/h)²) / h for y ∈ [−h/2, h/2]
Intracranial pressure follows the same Monro-Kellie pressure-volume relation as the 3D model, ICP = ICP0 + k·(V−V0)² for V>V0, and the right-hand phase-plane plot draws that analytic curve alongside the live (V, ICP) trajectory, so you can watch the state point ride up the compliance curve in real time — a view the 3D scene can't show directly. The scrolling strip chart underneath gives the same information as a bedside ICP monitor trace.
Fixed discrepancy vs. the 3D source: the 3D sim hardcodes outflow resistance R_out = 8.0 mmHg/(mL/min), which is inconsistent with its own baseline — at ICP0=10 mmHg, P_venous=5 mmHg and default production 0.35 mL/min, Davson's equation gives Q_out = (10−5)/8 = 0.625 mL/min, which doesn't match Q_in = 0.35 mL/min, so the 3D model's "normal physiology" default is never actually at equilibrium. This 2D model uses the physiologically-consistent value R_out = (ICP0−P_venous)/Q_in ≈ 14.29, verified numerically to hold the default sliders exactly at V=25 mL, ICP=10 mmHg.
- Choroid plexus production — sets Q_in; raising it (e.g. choroid plexus papilloma) pushes the phase-plane point up and to the right along the compliance curve.
- Aqueduct / outflow resistance — narrows the drawn channel and raises R_out; the classic driver of obstructive hydrocephalus.
- Heart rate — sets the frequency of the pulsatile component superimposed on Q_out, visible as the channel's velocity-field arrows and particle speed oscillating.
- Simulate Aqueductal Stenosis — snaps resistance to a pathological value; watch the channel narrow, the phase point climb the compliance curve, and ICP rise in real time.