Extend eta file time range for IRF convolution

When reading wave elevation from an eta file, the IRF convolution needs to access free surface elevation at negative times (time - tau) at the start of the simulation. Previously, only spectrum-generated waves extended the time range backwards; eta file imports did not.

This caused a crash at t=0 when the convolution tried to access elevation at negative times that weren't in the data.

Fix: Extend eta file data backwards to -t_irf_max with zero-padded elevation, matching the behavior of CreateFreeSurfaceElevation().

Also removes unused FSE mesh visualization code from the irregular waves eta demo and test.

Author: dav-og

demos/sphere/demo_sphere_irreg_waves_eta_import.cpp

@@ -130,39 +130,6 @@ int main(int argc, char* argv[]) {
     std::cout << "Adding waves to TestHydro object..." << std::endl;
     hydro_forces.AddWaves(my_hydro_inputs);
 
-    std::cout << "Creating fse mesh..." << std::endl;
-    // set up free surface from a mesh
-    auto fse_plane = chrono_types::make_shared<ChBody>();
-    fse_plane->SetPos(ChVector3d(0, 0, 0));
-    fse_plane->SetFixed(true);
-    fse_plane->EnableCollision(false);
-    system.AddBody(fse_plane);
-
-    // std::cout << "SetUpWaveMesh..." << std::endl;
-    // my_hydro_inputs->SetUpWaveMesh();
-    // std::shared_ptr<ChBody> fse_mesh = chrono_types::make_shared<ChBodyEasyMesh>(  //
-    //     my_hydro_inputs->GetMeshFile(),                                            // file name
-    //     1000,                                                                      // density
-    //     false,                                                                     // do not evaluate mass
-    //     automatically true,                                                                      // create
-    //     visualization asset false                                                                      // do not
-    //     collide
-    //);
-    // fse_mesh->SetMass(1.0);
-    // fse_mesh->SetPos_dt(my_hydro_inputs->GetWaveMeshVelocity());
-    // std::cout << "system.Add(fse_mesh)..." << std::endl;
-    // system.Add(fse_mesh);
-    // auto fse_prismatic = chrono_types::make_shared<ChLinkLockPrismatic>();
-    // fse_prismatic->Initialize(fse_plane, fse_mesh, ChFramed(ChVector3d(1.0, 0.0, 0.0), QuatFromAnglY(CH_PI_2)));
-    // system.AddLink(fse_prismatic);
-
-    //// Create a visualization material
-    // std::cout << "Create a visualization material..." << std::endl;
-    // auto fse_texture = chrono_types::make_shared<ChVisualMaterial>();
-    // fse_texture->SetDiffuseColor(ChColor(0.026f, 0.084f, 0.168f));
-    // fse_texture->SetOpacity(0.1);
-    // fse_mesh->GetVisualShape(0)->SetMaterial(0, fse_texture);
-
     // for profiling
     auto start = std::chrono::high_resolution_clock::now();
     // main simulation loop

src/hydro/waves/irregular_wave.cpp

@@ -40,6 +40,43 @@ void IrregularWaves::InitializeIRFVectors() {
 
     if (!params_.eta_file_path_.empty()) {
         ReadEtaFromFile();
+        
+        // Populate free_surface_time_sampled_ from time_data_, extending backwards
+        // to cover negative times needed for IRF convolution (same as CreateFreeSurfaceElevation does)
+        double t_irf_max = 0.0;
+        for (size_t b = 0; b < ex_irf_time_sampled_.size(); b++) {
+            if (ex_irf_time_sampled_[b].size() > 0) {
+                double t_end = ex_irf_time_sampled_[b][ex_irf_time_sampled_[b].size() - 1];
+                if (t_end > t_irf_max) t_irf_max = t_end;
+            }
+        }
+        
+        double eta_tmin = time_data_.front();
+        double required_tmin = -t_irf_max;
+        
+        if (required_tmin < eta_tmin && time_data_.size() > 1) {
+            // Extend backwards with zero elevation padding
+            double dt = time_data_[1] - time_data_[0];
+            int num_pad = static_cast<int>(std::ceil((eta_tmin - required_tmin) / dt));
+            
+            std::vector<double> extended_time(num_pad + time_data_.size());
+            std::vector<double> extended_eta(num_pad + free_surface_elevation_sampled_.size());
+            
+            for (int i = 0; i < num_pad; ++i) {
+                extended_time[i] = eta_tmin - (num_pad - i) * dt;
+                extended_eta[i] = 0.0;
+            }
+            for (size_t i = 0; i < time_data_.size(); ++i) {
+                extended_time[num_pad + i] = time_data_[i];
+                extended_eta[num_pad + i] = free_surface_elevation_sampled_[i];
+            }
+            
+            free_surface_time_sampled_ = std::move(extended_time);
+            free_surface_elevation_sampled_ = std::move(extended_eta);
+        } else {
+            free_surface_time_sampled_ = time_data_;
+        }
+        
         spectrumCreated_ = false;
     } else if (params_.wave_height_ != 0.0 && params_.wave_period_ != 0.0) {
         CreateSpectrum();

tests/regression/sphere/test_sphere_irreg_waves_eta.cpp

@@ -189,34 +189,6 @@ int main(int argc, char* argv[]) {
         HydroForces hydro_forces(bodies, h5fname);
         hydro_forces.AddWaves(my_hydro_inputs);
 
-        // set up free surface from a mesh
-        auto fse_plane = chrono_types::make_shared<ChBody>();
-        fse_plane->SetPos(ChVector3d(0, 0, 0));
-        fse_plane->SetFixed(true);
-        fse_plane->EnableCollision(false);
-        system.AddBody(fse_plane);
-
-        my_hydro_inputs->SetUpWaveMesh();
-        std::shared_ptr<ChBody> fse_mesh = chrono_types::make_shared<ChBodyEasyMesh>(  //
-            my_hydro_inputs->GetMeshFile(),                                            // file name
-            1000,                                                                      // density
-            false,                                                                     // do not evaluate mass automatically
-            true,                                                                      // create visualization asset
-            false                                                                      // do not collide
-        );
-        fse_mesh->SetMass(1.0);
-        fse_mesh->SetPosDt(my_hydro_inputs->GetWaveMeshVelocity());
-        system.Add(fse_mesh);
-        auto fse_prismatic = chrono_types::make_shared<ChLinkLockPrismatic>();
-        fse_prismatic->Initialize(fse_plane, fse_mesh, ChFramed(ChVector3d(1.0, 0.0, 0.0), QuatFromAngleY(CH_PI_2)));
-        system.AddLink(fse_prismatic);
-
-        // Create a visualization material
-        auto fse_texture = chrono_types::make_shared<ChVisualMaterial>();
-        fse_texture->SetDiffuseColor(ChColor(0.026f, 0.084f, 0.168f));
-        fse_texture->SetOpacity(0.1);
-        fse_mesh->GetVisualShape(0)->SetMaterial(0, fse_texture);
-
         // for profiling
         auto start = std::chrono::high_resolution_clock::now();
         // main simulation loop