From 6c79d0ef9bf00ee8273ce3d5b1afcdce357fb752 Mon Sep 17 00:00:00 2001
From: "p.vanderwilt" <p.van.der.wilt@brabantsedelta.nl>
Date: Mon, 29 Sep 2025 15:34:54 +0200
Subject: [PATCH] Use improved boundary conditions for upstream and downstream
 reactors

---
 src/specificClass.js | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/specificClass.js b/src/specificClass.js
index 636f678..fe580bf 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -27,6 +27,7 @@ class Reactor {
     this.measurements = new MeasurementContainer();
     this.upstreamReactor = null;
     this.childRegistrationUtils = new childRegistrationUtils(this); // Child registration utility
+    this.parent = null; // Gets assigned via child registration
 
     this.asm = new ASM3();
 
@@ -126,7 +127,6 @@ class Reactor {
       position = measurement.config.functionality.positionVsParent;
     }
     const measurementType = measurement.config.asset.type;
-    const key = `${measurementType}_${position}`;
     const eventName = `${measurementType}.measured.${position}`;
 
     // Register event listener for measurement updates
@@ -145,13 +145,13 @@ class Reactor {
   }
 
 
-  _connectReactor(reactor) {
-    if (!reactor) {
+  _connectReactor(reactorChild) {
+    if (!reactorChild) {
       this.logger.warn("Invalid reactor provided.");
       return;
     }
 
-    this.upstreamReactor = reactor;
+    this.upstreamReactor = reactorChild;
 
     reactor.emitter.on("stateChange", (data) => {
       this.logger.debug(`State change of upstream reactor detected.`);
@@ -338,15 +338,25 @@ class Reactor_PFR extends Reactor {
    * @param {Array} state - Current reactor state without enforced BCs.
    */
   _applyBoundaryConditions(state) {
-    if (math.sum(this.Fs) > 0) { // Danckwerts BC
-      const BC_C_in = math.multiply(1 / math.sum(this.Fs), [this.Fs], this.Cs_in)[0];
-      const BC_dispersion_term = (1-this.alpha)*this.D*this.A/(math.sum(this.Fs)*this.d_x);
-      state[0] = math.multiply(1/(1+BC_dispersion_term), math.add(BC_C_in, math.multiply(BC_dispersion_term, state[1])));
+    if (this.upstreamReactor) {
+      state[0] = this.upstreamReactor.state[this.n_x-1];
     } else {
-      state[0] = state[1];
+      if (math.sum(this.Fs) > 0) { // Danckwerts BC
+        const BC_C_in = math.multiply(1 / math.sum(this.Fs), [this.Fs], this.Cs_in)[0];
+        const BC_dispersion_term = (1-this.alpha)*this.D*this.A/(math.sum(this.Fs)*this.d_x);
+        state[0] = math.multiply(1/(1+BC_dispersion_term), math.add(BC_C_in, math.multiply(BC_dispersion_term, state[1])));
+      } else {
+        state[0] = state[1];
+      }
+    }
+
+    const downstreamReactor = this.parent;
+    if (downstreamReactor) {
+      state[this.n_x-1] = downstreamReactor.state[0];
+    } else {
+      // Neumann BC (no flux)
+      state[this.n_x-1] = state[this.n_x-2];
     }
-    // Neumann BC (no flux)
-    state[this.n_x-1] = state[this.n_x-2];
   }
 
   /**