อัปเดต 2026-09-07

Transient panel & scenarios

setup / run

The Transient panel defines scenarios (valve closures, pump trips, startups) on top of a converged steady state and runs the MOC in the time domain.

Open the builder

เมื่อไรจึงใช้

Surge analysis, valve-closure studies, pump-trip protection design.

ค่าที่ต้องกรอก

ค่า	คำอธิบาย
Scenario	Event type + timing (e.g. valve closure over 5 s, linear/exponential/two-stage).
Duration & wave speed	Simulation time and pipe wave speed (or elastic properties).

คำนวณอย่างไร

The water-hammer PDEs are solved by the Method of Characteristics on a grid where the Courant number equals 1, so wave transport is exact. At each interior point two characteristic equations (C+ and C−) combine to give the new head and flow; boundaries and junctions close the system. A converged steady solve provides the initial condition.

สมการ

Characteristic compatibility equations

C^{+} : H_{P} = C_{P} - B Q_{P}, C^{-} : H_{P} = C_{M} + B Q_{P}

Solved together at each node: adding gives H_P, subtracting gives Q_P.

Constants

B = \frac{a}{g A}, R = \frac{f Δ x}{2 g D A ^{2}}

B = characteristic impedance (a = wave speed, A = area), R = friction resistance per reach. C_P, C_M carry the upstream/downstream H, Q and the R Q|Q| friction term.

ข้อควรระวัง

noteScenarios and config persist across reloads; a valve closure pattern is honored exactly (a past bug slammed every API closure at t=0 — fixed).

ที่เกี่ยวข้อง

Wave speed & Joukowsky Column separation (DGCM)Surge protection devices

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