Dynamic Transient Mode (MOC)

While Extended Period Simulation (EPS) provides the macro-level view of your system's operational and energy performance, Dynamic Transient Mode (MOC) allows you to analyze the rapid, split-second pressure events known as water hammer.

When a pump suddenly trips or a valve slams shut, the kinetic energy of moving water is converted into high-pressure shockwaves that travel through your pipes at the speed of sound. EPS is not designed to capture these events, as it treats water as an incompressible fluid. MOC, however, treats water as a compressible fluid and accounts for the elasticity of your pipe walls, allowing you to see exactly how these shockwaves propagate, reflect, and interact within your network.

When to Use MOC

You should engage MOC when you need to verify system safety during emergency scenarios or rapid operational changes. Common applications include:

• Analyzing Pump Trips: Observing the pressure drop and subsequent rebound when a pump loses power instantaneously.
• Rapid Valve Closures: Testing how different valve closure speeds or patterns affect the resulting pressure spikes in your pipes.
• Surge Protection Design: Evaluating the effectiveness of your surge tanks, air chambers, or pressure relief valves in mitigating wave amplitudes.
• Grid Failure Simulations: Studying the impact of a total site power loss on system-wide pressures.

Integrating EPS and MOC

The true strength of R-THYM is the ability to bridge these two modes. You do not need to build two separate models.

1. Optimize in EPS: Start by running an EPS simulation to establish the steady-state operating conditions of your system. You can adjust your pump schedules, optimize reservoir levels, and ensure your system is running efficiently.
2. Trigger the Event: Once your system is at a critical flow state or a specific operating point you wish to test, you can trigger the MOC mode.
3. Dynamic Hand-off: R-THYM automatically carries forward the steady-state velocities and pressures from your EPS run into the MOC engine. This "hot swap" ensures that your transient analysis begins from a physically realistic starting point rather than an idealized, empty state.

Operational Interaction in MOC

Like EPS, the MOC environment is fully interactive. Once MOC is engaged, you can trigger transient events manually. You might initiate a pump trip by switching off a power source, or simulate a sudden pipe burst or valve closure.

Because the MOC engine solves physics at a frame-by-frame resolution (calculating pressures every 10 milliseconds), you will see the pressure waves traveling through your system in real-time. The interface remains responsive even during these intense calculations, allowing you to watch the waves bounce through the network and see exactly where they might exceed your pipe pressure ratings.

Performance and Accuracy

The R-THYM MOC solver is custom-built to be browser-native, meaning it leverages your local hardware to provide immediate feedback. By modeling frequency-dependent boundary layer shear stress (Unsteady Friction), the engine ensures that pressure wave decay matches the physical damping you would expect in real-world infrastructure.

While the MOC mode is computationally intensive, it provides the high-fidelity physics required for infrastructure protection that static, steady-state modeling simply cannot provide.

[!NOTE] Detailed derivation of the characteristic equations, wave speed calculations, and the numerical stability criteria (Courant condition) used in this engine can be found in the Appendix: Hydraulic Reference.