all of the changes

include/FluidSim/Silencer.hpp

@@ -0,0 +1,54 @@
+#pragma once
+#include "FluidSim/PipeProfile.hpp"
+
+namespace fluidsim::port {
+enum class SilencerType { StraightThrough, ExpansionResonator, Chambered };
+struct SilencerConfig {
+    SilencerType type{SilencerType::Chambered};
+    float volume{.018f}, length{.65f}, core_diameter{.055f};
+    int chambers{2};
+    float passage_diameter{.058f};
+    float resistance{2.f}; // linear momentum decay, 1/s (packing surrogate)
+    float loss_coefficient{.35f}; // total dimensionless quadratic flow resistance
+    float diameter() const { return std::sqrt(4*volume/(pi*length)); }
+};
+struct ExhaustConfig {
+    bool enabled{true};
+    float inlet_length{1.4f}, outlet_length{.35f}, connecting_length{.8f}, diameter{.060f}, cell_length{.035f};
+    SilencerConfig resonator{SilencerType::StraightThrough,.006f,.40f,.060f,1,.060f,2, .1f};
+    SilencerConfig muffler{SilencerType::StraightThrough,.018f,.65f,.060f,1,.060f,4, .35f};
+};
+inline Pipe1D make_silenced_exhaust(const ExhaustConfig& c) {
+    std::vector<PipeSection> sections;
+    std::vector<float> linear, quadratic;
+    auto add=[&](float length,float a,float b,float r=0,float k=0) {
+        if(!std::isfinite(length)||length<=0||!std::isfinite(r)||r<0||!std::isfinite(k)||k<0)
+            throw std::invalid_argument("invalid silencer resistance or length");
+        sections.push_back({length,a,b}); linear.push_back(r); quadratic.push_back(k/length);
+    };
+    add(c.inlet_length,c.diameter,c.diameter);
+    if(c.enabled) for(int index=0;index<2;++index) {
+        if(index) add(c.connecting_length,c.diameter,c.diameter);
+        const auto& s=index?c.muffler:c.resonator;
+        if(!std::isfinite(s.volume)||s.volume<=0||!std::isfinite(s.length)||s.length<=0||s.chambers<1||s.chambers>16 || s.core_diameter<=0 || s.passage_diameter<=0)
+            throw std::invalid_argument("invalid silencer geometry");
+        const float d=s.type==SilencerType::StraightThrough?s.core_diameter:s.diameter();
+        const int n=s.type==SilencerType::Chambered?s.chambers:1;
+        float previous=c.diameter;
+        for(int i=0;i<n;++i) {
+            add(s.length*.1f/n,previous,d,s.resistance,s.loss_coefficient*.5f/n);
+            add(s.length*.8f/n,d,d,s.resistance,0);
+            const float end=i+1==n?c.diameter:s.passage_diameter;
+            add(s.length*.1f/n,d,end,s.resistance,s.loss_coefficient*.5f/n);
+            previous=end;
+        }
+    }
+    add(c.outlet_length,c.diameter,c.diameter);
+    auto pipe=make_profiled_pipe(sections,c.cell_length);
+    for(std::size_t i=0;i<sections.size();++i) {
+        const int n=int(std::ceil(sections[i].length/c.cell_length));
+        for(int j=0;j<n;++j) { pipe.linear_resistance.push_back(linear[i]);pipe.quadratic_resistance.push_back(quadratic[i]); }
+    }
+    return pipe;
+}
+}