BGMod Two hydraulic ports: 1 is the inlet, 2 is the outlet. The square symbol shows a spring-loaded ball and seat. Flow is allowed from 1 to 2, regardless of the reference arrows on the external bonds.
Q₁ = max(Δp − p_crack, 0)/R_open; Q₂ = −Q₁
P_loss = Δp Q₁ ≥ 0
R_open > 0 [Pa·s/m³], default 10⁹. Cracking pressure p_crack ≥ 0 [Pa], default 10⁴. The valve opens above the cracking pressure; at or below it, flow is exactly zero. There is no external control input.
Classic bond graph
The component packages a common-flow 1-junction and a one-port nonlinear R. The junction imposes Q₁ = Q_R = −Q₂ and p₁ − p₂ − e_R = 0. R supplies Q_R = max(e_R − p_crack, 0)/R_open. The solver uses the internal resistance and threshold in these equations. After analysis, select the valve and click Internal bond graph.
Half-arrows define positive power. Causal strokes are omitted here; the analysis shows the initial operating mode. Closing the valve retains both bonds and imposes zero flow, while the two pressures can differ.
Outputs and example
Plots and CSV include pressure difference, forward flow, dissipation, and Open (0 or 1). Choose Hydraulics: check valve closes against reverse pressure. Initially p₁ = 200000 Pa and p₂ = 100000 Pa, so Q = 0.00009 m³/s. At 2 s the inlet falls to 0 Pa, the outlet stays at 100000 Pa, and the valve closes.
Model limits
Instantaneous, memoryless closure; finite linear open resistance; no leakage, poppet motion, spring energy storage or fluid inertia. The spring in the symbol represents the cracking threshold. Closed isolated branches still need pressure-determining storage or boundary conditions. A forced reverse flow is inconsistent and is reported as an error. This model does not predict water hammer.