void setNewNodeState(int j, float dt)
//
// Input: j = node index
// dt = time step (sec)
// Output: none
// Purpose: updates state of node after current time step
// for Steady Flow or Kinematic Wave flow routing.
//
{
int canPond; // TRUE if ponding can occur at node
float newNetInflow; // inflow - outflow at node (cfs)
// --- update stored volume using mid-point integration
newNetInflow = Node[j].inflow - Node[j].outflow;
Node[j].newVolume = Node[j].oldVolume +
0.5 * (Node[j].oldNetInflow + newNetInflow) * dt;
if ( Node[j].newVolume < 0.0 ) Node[j].newVolume = 0.0;
// --- determine any overflow lost from system
Node[j].overflow = 0.0;
canPond = (AllowPonding && Node[j].pondedArea > 0.0);
if ( Node[j].newVolume > Node[j].fullVolume )
{
if ( !canPond )
{
Node[j].overflow = (Node[j].newVolume - Node[j].fullVolume) / dt;
Node[j].newVolume = Node[j].fullVolume;
// --- ignore any negligible overflow
if ( Node[j].overflow <= FUDGE ) Node[j].overflow = 0.0;
}
}
// --- compute a depth from volume
// (depths at upstream nodes are subsequently adjusted in
// setNewLinkState to reflect depths in connected conduit)
if ( canPond )
{
Node[j].newDepth = node_getPondedDepth(j, Node[j].newVolume);
}
else
{
Node[j].newDepth = node_getDepth(j, Node[j].newVolume);
}
}
void updateStorageState(int i, int j, int links[], double dt)
//
// Input: i = index of storage node
// j = current position in links array
// links = array of topo-sorted link indexes
// dt = routing time step (sec)
// Output: none
// Purpose: updates depth and volume of a storage node using successive
// approximation with under-relaxation for Steady or Kin. Wave
// routing.
//
{
int iter; // iteration counter
int stopped; // TRUE when iterations stop
double vFixed; // fixed terms of flow balance eqn.
double v2; // new volume estimate (ft3)
double d1; // initial value of storage depth (ft)
double d2; // updated value of storage depth (ft)
double outflow; // outflow rate from storage (cfs)
// --- see if storage node needs updating
if ( Node[i].type != STORAGE ) return;
if ( Node[i].updated ) return;
// --- compute terms of flow balance eqn.
// v2 = v1 + (inflow - outflow)*dt
// that do not depend on storage depth at end of time step
vFixed = Node[i].oldVolume +
0.5 * (Node[i].oldNetInflow + Node[i].inflow) * dt;
d1 = Node[i].newDepth;
// --- iterate finding outflow (which depends on depth) and subsequent
// new volume and depth until negligible depth change occurs
iter = 1;
stopped = FALSE;
while ( iter < MAXITER && !stopped )
{
// --- find total flow in all outflow links
outflow = getStorageOutflow(i, j, links, dt);
// --- find new volume from flow balance eqn.
v2 = vFixed - 0.5 * outflow * dt - node_getLosses(i, dt);
// --- limit volume to full volume if no ponding
// and compute overflow rate
v2 = MAX(0.0, v2);
Node[i].overflow = 0.0;
if ( v2 > Node[i].fullVolume )
{
Node[i].overflow = (v2 - MAX(Node[i].oldVolume,
Node[i].fullVolume)) / dt;
if ( !AllowPonding || Node[i].pondedArea == 0.0 )
v2 = Node[i].fullVolume;
}
// --- update node's volume & depth
Node[i].newVolume = v2;
if ( v2 > Node[i].fullVolume ) d2 = node_getPondedDepth(i, v2);
else d2 = node_getDepth(i, v2);
Node[i].newDepth = d2;
// --- use under-relaxation to estimate new depth value
// and stop if close enough to previous value
d2 = (1.0 - OMEGA)*d1 + OMEGA*d2;
if ( fabs(d2 - d1) <= STOPTOL ) stopped = TRUE;
// --- update old depth with new value and continue to iterate
Node[i].newDepth = d2;
d1 = d2;
iter++;
}
// --- mark node as being updated
Node[i].updated = TRUE;
}
