MSX multi-species simulation

EPANET-MSX models the transport and reaction of multiple chemical species through a water network. With epanet-js 0.9.0 you can run MSX simulations directly in the browser by loading the default workspace, or by loading any of the *-msx engine variants through the slim Workspace.

This example walks through:

1. Loading an MSX-enabled engine.
2. Writing the INP file and the MSX configuration file into the workspace virtual filesystem.
3. Running a full hydraulic + multi-species water-quality simulation.
4. Reading the species concentrations back out.

Setup

import { Workspace } from "epanet-js/slim";
import { Project } from "epanet-js";
import { MsxConstant } from "epanet-js/engines/v2.3.5-msx";

const ws = new Workspace();
await ws.loadModuleVersion(() => import("epanet-js/engines/v2.3.5-msx"));
const project = new Project(ws);

The chosen engine variant has the -msx suffix, which exposes MSX functions in the Project. Loading a non-MSX engine and calling msxOpen would throw an exception.

Writing the INP and MSX files

You need both:

• The EPANET INP file that defines the network (nodes, links, demands…).
• The MSX configuration file that defines species, reaction equations, sources, and patterns.

ws.writeFile("network.inp", inpText);
ws.writeFile("network.msx", msxText);

Running the simulation

// 1. Open the EPANET project.
project.open("network.inp", "network.rpt", "network.bin");

// 2. Bind the MSX configuration to the project.
project.msxOpen("network.msx");

// 3. Run hydraulics + multi-species quality in one shot.
project.msxSolveH();
project.msxSolveQ();

// 4. Read species concentrations.
const speciesCount = project.msxGetCount(MsxConstant.MSX_SPECIES);
const nodeCount = project.getCount(CountType.Node);

for (let s = 1; s <= speciesCount; s++) {
  const { type, units } = project.msxGetSpecies(s);
  for (let n = 1; n <= nodeCount; n++) {
    const value = project.msxGetQual(MsxConstant.MSX_NODE, n, s);
    console.log(`species ${s} at node ${n}: ${value} ${units}`);
  }
}

// 5. Write a formatted report and read it back.
project.msxReport();
const report = ws.readFile("network.rpt");

// 6. Tear down.
project.msxClose();
project.close();

Stepping through the simulation

If you need intermediate results (e.g. to drive an animation), use the step-based form:

project.msxSolveH();
project.msxInit(/* saveFlag */ 0);

let { t, tleft } = project.msxStep();
while (tleft > 0) {
  // …inspect species concentrations at simulation time `t`…
  ({ t, tleft } = project.msxStep());
}

project.msxClose();
project.close();

See the MSX functions reference for the full list of MSX methods.