From aa4e8707758a235fa0c4b2b101b0a3b30a2e64a7 Mon Sep 17 00:00:00 2001
From: Alex Selimov <alex@alexselimov.com>
Date: Sun, 29 Mar 2026 19:17:33 -0400
Subject: [PATCH] Add transport property calculations

---
 src/properties/transport_fit.rs | 165 ++++++++++++++++++++++++++++++++
 1 file changed, 165 insertions(+)

diff --git a/src/properties/transport_fit.rs b/src/properties/transport_fit.rs
index 8489d3c..0f5ea20 100644
--- a/src/properties/transport_fit.rs
+++ b/src/properties/transport_fit.rs
@@ -4,6 +4,26 @@ pub struct SpeciesTransportData {
     pub conductivities: Vec<TransportFit>,
 }
 
+impl SpeciesTransportData {
+    pub fn viscosity_at(&self, temp: f64) -> f64 {
+        let i_viscosity = self
+            .viscosities
+            .iter()
+            .rposition(|viscosity| temp > viscosity.temp_range.0)
+            .unwrap_or(0);
+        self.viscosities[i_viscosity].compute(temp)
+    }
+
+    pub fn conductivity_at(&self, temp: f64) -> f64 {
+        let i_conductivity = self
+            .conductivities
+            .iter()
+            .rposition(|conductivity| temp > conductivity.temp_range.0)
+            .unwrap_or(0);
+        self.conductivities[i_conductivity].compute(temp)
+    }
+}
+
 pub struct TransportFit {
     pub temp_range: (f64, f64),
     pub a: f64,
@@ -11,3 +31,148 @@ pub struct TransportFit {
     pub c: f64,
     pub d: f64,
 }
+
+impl TransportFit {
+    pub fn compute(&self, temp: f64) -> f64 {
+        let inv_temp = 1.0 / temp;
+        self.a * temp.ln() + self.b * inv_temp + self.c * inv_temp * inv_temp + self.d
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{
+        assert_delta,
+        properties::transport_fit::{SpeciesTransportData, TransportFit},
+    };
+
+    #[test]
+    fn test_transport_fit_compute() {
+        let fit = TransportFit {
+            temp_range: (1.0, 2.0),
+            a: 10.0,
+            b: 20.0,
+            c: 30.0,
+            d: 40.0,
+        };
+
+        assert_delta!(fit.compute(1.0), 90.0, 1e-12);
+    }
+
+    #[test]
+    fn test_calc_transport_properties() {
+        let viscosities = vec![
+            TransportFit {
+                temp_range: (1.0, 100.0),
+                a: 10.0,
+                b: 20.0,
+                c: 30.0,
+                d: 40.0,
+            },
+            TransportFit {
+                temp_range: (100.0, 200.0),
+                a: 1.0,
+                b: 2.0,
+                c: 3.0,
+                d: 4.0,
+            },
+        ];
+
+        let conductivities = vec![
+            TransportFit {
+                temp_range: (1.0, 100.0),
+                a: 10.0,
+                b: 20.0,
+                c: 30.0,
+                d: 40.0,
+            },
+            TransportFit {
+                temp_range: (100.0, 200.0),
+                a: 1.0,
+                b: 2.0,
+                c: 3.0,
+                d: 4.0,
+            },
+        ];
+
+        let data = SpeciesTransportData {
+            viscosities,
+            conductivities,
+            name: "".to_string(),
+        };
+
+        assert_delta!(
+            data.conductivity_at(0.5),
+            data.conductivities[0].compute(0.5),
+            1e-12
+        );
+        assert_delta!(
+            data.conductivity_at(1.0),
+            data.conductivities[0].compute(1.0),
+            1e-12
+        );
+        assert_delta!(
+            data.conductivity_at(50.0),
+            data.conductivities[0].compute(50.0),
+            1e-12
+        );
+        assert_delta!(
+            data.conductivity_at(100.0),
+            data.conductivities[0].compute(100.0),
+            1e-12
+        );
+        assert_delta!(
+            data.conductivity_at(100.0 + 1e-12),
+            data.conductivities[1].compute(100.0 + 1e-12),
+            1e-12
+        );
+
+        assert_delta!(
+            data.conductivity_at(200.0),
+            data.conductivities[1].compute(200.0),
+            1e-12
+        );
+        assert_delta!(
+            data.conductivity_at(500.0),
+            data.conductivities[1].compute(500.0),
+            1e-12
+        );
+
+        assert_delta!(
+            data.viscosity_at(0.5),
+            data.viscosities[0].compute(0.5),
+            1e-12
+        );
+        assert_delta!(
+            data.viscosity_at(1.0),
+            data.viscosities[0].compute(1.0),
+            1e-12
+        );
+        assert_delta!(
+            data.viscosity_at(50.0),
+            data.viscosities[0].compute(50.0),
+            1e-12
+        );
+        assert_delta!(
+            data.viscosity_at(100.0),
+            data.viscosities[0].compute(100.0),
+            1e-12
+        );
+        assert_delta!(
+            data.viscosity_at(100.0 + 1e-12),
+            data.viscosities[1].compute(100.0 + 1e-12),
+            1e-12
+        );
+
+        assert_delta!(
+            data.viscosity_at(200.0),
+            data.viscosities[1].compute(200.0),
+            1e-12
+        );
+        assert_delta!(
+            data.viscosity_at(500.0),
+            data.viscosities[1].compute(500.0),
+            1e-12
+        );
+    }
+}