From 79196db2ac3d31543056b3b7abe90ad609c51b4f Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Tue, 22 Sep 2026 09:27:15 +0200
Subject: Fixing two way coupling

---
 examples/one_particle_sedimentation_2d/sim.cpp  | 21 ++++++++++++++++-----
 examples/one_particle_sedimentation_2d/step.hpp | 11 ++++++-----
 2 files changed, 22 insertions(+), 10 deletions(-)

(limited to 'examples')

diff --git a/examples/one_particle_sedimentation_2d/sim.cpp b/examples/one_particle_sedimentation_2d/sim.cpp
index 0cb3ce0..86a7b1c 100644
--- a/examples/one_particle_sedimentation_2d/sim.cpp
+++ b/examples/one_particle_sedimentation_2d/sim.cpp
@@ -48,10 +48,13 @@ saw::error_or<void> lbm_main(const saw::data<args::LbmArgs>& args){
 		// delta_x
 		{{0.02 / dim_x}},
 		// delta_t
-		{{1.5e-6}}
+		{{3e-7}}
 	};
+	saw::data<sch::SiKinematicViscosity<T>> kin_vis_si{1e-3};
+	auto kin_vis_lbm = conv.kinematic_viscosity_si_to_lbm(kin_vis_si);
+	auto tau = conv.template kinematic_viscosity_lbm_to_tau<Desc>(kin_vis_lbm);
 	
-	print_lbm_meta<T,Desc>(conv,{1e-3},{1e-4},{2});
+	print_lbm_meta<T,Desc>(conv,kin_vis_si,{1e-4},{2});
 	std::cout<<"Position: "<<conv.meter_si_to_lbm({{0.01}}).handle().get()<<", "<<conv.meter_si_to_lbm({{0.04}}).handle().get()<<std::endl;
 
 	// saw::data<sch::FixedArray<sch::UInt64,Desc::D>> meta{{dim_x,dim_y}};
@@ -123,21 +126,29 @@ saw::error_or<void> lbm_main(const saw::data<args::LbmArgs>& args){
 	auto lsdm_view = make_view(lbm_sycl_macro_data);
 	auto lsdp_view = make_view(lbm_sycl_particle_data);
 	
-	saw::data<sch::UInt64> time_steps{64u*1024ul};
+	saw::data<sch::UInt64> time_steps{1024ul * 1024ul};
 
 	auto& info_f = lsd_view.template get<"info">();
 
 	for(saw::data<sch::UInt64> i{0u}; i < time_steps and krun; ++i){
 		// BC + Collision
 		{
-			auto eov = step<T,Desc,Coll>(conv,lsd_view,lsdm_view,lsdp_view,i,dev);
+			auto eov = step<T,Desc,Coll>(
+				conv, 
+				tau, 
+				lsd_view, 
+				lsdm_view, 
+				lsdp_view, 
+				i, 
+				dev
+			);
 			if(eov.is_error()){
 				return eov;
 			}
 		}
 
 		sycl_q.wait();
-		if(i.get() % 64u == 0u){
+		if(i.get() % 1024u == 0u){
 			{
 				auto eov = dev.copy_to_host(lbm_sycl_macro_data,*lbm_macro_data_ptr);
 				if(eov.is_error()){
diff --git a/examples/one_particle_sedimentation_2d/step.hpp b/examples/one_particle_sedimentation_2d/step.hpp
index c3a3b8a..4bc9dde 100644
--- a/examples/one_particle_sedimentation_2d/step.hpp
+++ b/examples/one_particle_sedimentation_2d/step.hpp
@@ -8,6 +8,7 @@ namespace lbm {
 template<typename T, typename Desc, typename Coll>
 saw::error_or<void> step(
 		const converter<T>& conv,
+		const saw::data<sch::Pure<T>>& tau,
 		saw::data<sch::Ptr<sch::ChunkStruct<T,Desc>>,encode::Sycl<saw::encode::Native>>& fields,
 		saw::data<sch::Ptr<sch::MacroStruct<T,Desc>>,encode::Sycl<saw::encode::Native>>& macros,
 		saw::data<sch::Ptr<sch::ParticleSpheroidGroup<T,Desc>>,encode::Sycl<saw::encode::Native>>& particles,
@@ -47,7 +48,7 @@ saw::error_or<void> step(
 		}).wait();
 
 		q.submit([&](acpp::sycl::handler& h){
-			component<T,Desc,cmpt::Hlbm,encode::Sycl<saw::encode::Native>> collision{1.0};
+			component<T,Desc,cmpt::Hlbm,encode::Sycl<saw::encode::Native>> collision{tau};
 			component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 
 			h.parallel_for(acpp::sycl::range<Desc::D>{dim_x,dim_y}, [=](acpp::sycl::id<Desc::D> idx){
@@ -99,14 +100,14 @@ saw::error_or<void> step(
 					index.at({{i}}).set(idx[i]);
 				}
 
-				fplbm_one_part.apply(fields,macros,particles,index,t_i,{16u});
+				fplbm_one_part.apply(fields,macros,particles,index,t_i,{32u});
 			});
 		}).wait();
 
 		// auto coll_ev = 
 		q.submit([&](acpp::sycl::handler& h){
-			component<T,Desc,cmpt::BGK,encode::Sycl<saw::encode::Native>> bgk{1.0};
-			component<T,Desc,cmpt::FpLbm,encode::Sycl<saw::encode::Native>> collision{1.0};
+			component<T,Desc,cmpt::BGK,encode::Sycl<saw::encode::Native>> bgk{tau};
+			component<T,Desc,cmpt::FpLbm,encode::Sycl<saw::encode::Native>> collision{tau};
 			component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 			component<T,Desc,cmpt::ZouHeHorizontal<false>,encode::Sycl<saw::encode::Native>> flow_out{1.0};
 
@@ -182,7 +183,7 @@ saw::error_or<void> step(
 		// auto coll_ev = 
 		q.submit([&](acpp::sycl::handler& h){
 			component<T,Desc,cmpt::BGK,encode::Sycl<saw::encode::Native>> bgk{1.0};
-			component<T,Desc,cmpt::Psm,encode::Sycl<saw::encode::Native>> collision{1.0};
+			component<T,Desc,cmpt::Psm,encode::Sycl<saw::encode::Native>> collision{tau};
 			component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 			component<T,Desc,cmpt::ZouHeHorizontal<false>,encode::Sycl<saw::encode::Native>> flow_out{1.0};
 
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