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fixed under damping inertance

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max
2026-05-09 02:29:09 +02:00
parent cf1bf30c81
commit 1489f278dc
2 changed files with 21 additions and 14 deletions
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32
Core/BoundarySystem.cs
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@@ -184,45 +184,51 @@ namespace FluidSim.Core
if (d.UseInertance) if (d.UseInertance)
{ {
// ---- Inertance ODE with loss ----
float rhoUp = d.CurrentMdot >= 0 ? volRho : pipeRho; float rhoUp = d.CurrentMdot >= 0 ? volRho : pipeRho;
float inertance = rhoUp * d.EffectiveLength / MathF.Max(area, 1e-12f); float inertance = rhoUp * d.EffectiveLength / MathF.Max(area, 1e-12f);
float dp = volP - pipeP; float dp = volP - pipeP;
float Rlin = d.LossCoefficient; // linear resistance float Rlin = d.LossCoefficient;
// Forward Euler // Forward Euler
float dmdot_dt = (dp - Rlin * d.CurrentMdot) / MathF.Max(inertance, 1e-12f); float dmdot_dt = (dp - Rlin * d.CurrentMdot) / MathF.Max(inertance, 1e-12f);
float mdotNew = d.CurrentMdot + dmdot_dt * dt; float mdotNew = d.CurrentMdot + dmdot_dt * dt;
// ---------- Symmetric flow limiter ---------- // ---------- Symmetric flow limiters (existing) ----------
// 1) limit by cavity mass
if (d.VolumePort.Owner is Volume0D vol0) if (d.VolumePort.Owner is Volume0D vol0)
{ {
float maxOut = vol0.Mass / dt; float maxOut = vol0.Mass / dt;
if (mdotNew > maxOut) mdotNew = maxOut; // cavity → pipe if (mdotNew > maxOut) mdotNew = maxOut;
if (mdotNew < -maxOut) mdotNew = -maxOut; // pipe → cavity if (mdotNew < -maxOut) mdotNew = -maxOut;
} }
// 2) limit by mass in the adjacent pipe cell
int adjCell = d.IsLeftEnd ? _pipeSystem.GetPipeStart(d.PipeIndex) int adjCell = d.IsLeftEnd ? _pipeSystem.GetPipeStart(d.PipeIndex)
: _pipeSystem.GetPipeEnd(d.PipeIndex) - 1; : _pipeSystem.GetPipeEnd(d.PipeIndex) - 1;
float pipeRhoAdj = _pipeSystem.GetCellDensity(adjCell); float pipeRhoAdj = _pipeSystem.GetCellDensity(adjCell);
float pipeDxAdj = _pipeSystem.GetCellDx(adjCell); // uses the new public method float pipeDxAdj = _pipeSystem.GetCellDx(adjCell);
float pipeCellMass = pipeRhoAdj * area * pipeDxAdj; float pipeCellMass = pipeRhoAdj * area * pipeDxAdj;
float maxFromPipe = pipeCellMass / dt; float maxFromPipe = pipeCellMass / dt;
if (mdotNew < -maxFromPipe) mdotNew = -maxFromPipe; // prevent emptying the pipe cell if (mdotNew < -maxFromPipe) mdotNew = -maxFromPipe;
// ---------- Velocity clamp to Mach 0.9 ----------
float rhoFacePrelim = mdotNew >= 0 ? volRho : pipeRho;
float uFacePrelim = MathF.Abs(mdotNew) / MathF.Max(rhoFacePrelim * area, 1e-12f);
float cUp = mdotNew >= 0 ? MathF.Sqrt(Gamma * Rgas * volT) : MathF.Sqrt(Gamma * Rgas * pipeT);
float maxU = 0.9f * cUp;
if (uFacePrelim > maxU)
{
uFacePrelim = maxU;
mdotNew = rhoFacePrelim * uFacePrelim * area * (mdotNew >= 0 ? 1f : -1f);
}
// NaN safety // NaN safety
if (float.IsNaN(mdotNew)) mdotNew = 0f; if (float.IsNaN(mdotNew)) mdotNew = 0f;
// Store for next step
d.CurrentMdot = mdotNew; d.CurrentMdot = mdotNew;
mdotFinal = mdotNew; mdotFinal = mdotNew;
// Ghost state: use the isentropic face pressure (pFaceEst) as reference, // Ghost state
// but compute velocity from mdotFinal.
rhoFace = mdotFinal >= 0 ? volRho : pipeRho; rhoFace = mdotFinal >= 0 ? volRho : pipeRho;
pFace = pFaceEst; // approximate face pressure pFace = pFaceEst;
uFace = MathF.Abs(mdotFinal) / MathF.Max(rhoFace * area, 1e-12f); uFace = MathF.Abs(mdotFinal) / MathF.Max(rhoFace * area, 1e-12f);
} }
else else

3
Scenarios/HelmholtzScenario.cs
View File

@@ -56,6 +56,7 @@ namespace FluidSim.Tests
float rho0 = 101325f / (287f * 300f); float rho0 = 101325f / (287f * 300f);
pipeSystem = new PipeSystem(neckCells, pipeStart, pipeEnd, areas, dxs, rho0, 0f, 101325f); pipeSystem = new PipeSystem(neckCells, pipeStart, pipeEnd, areas, dxs, rho0, 0f, 101325f);
pipeSystem.DampingMultiplier = 500f;
// --- Boundary system --- // --- Boundary system ---
boundaries = new BoundarySystem(pipeSystem, maxOrifices: 1, maxOpenEnds: 1); boundaries = new BoundarySystem(pipeSystem, maxOrifices: 1, maxOpenEnds: 1);
@@ -72,7 +73,7 @@ namespace FluidSim.Tests
areaIndex: cavityOrificeIdx, areaIndex: cavityOrificeIdx,
dischargeCoeff: 0.9f, dischargeCoeff: 0.9f,
effectiveLength: neckLength, // physical length (or L_eff) effectiveLength: neckLength, // physical length (or L_eff)
lossCoefficient: 9000 // start with this, adjust for decay time lossCoefficient: 7000 // start with this, adjust for decay time
); );
// Open end at right side of pipe // Open end at right side of pipe