Merge pull request #73 from andrsd/tr-model-pow-of-tr

Transport model: Powers of T reduced

include/fprops/transport_models.h

@@ -159,4 +159,49 @@ class ModifiedBatshinskiHildebrand {
     std::vector<double> l;
 };
 
+/// Powers of T reduced
+///
+/// @tparam T The basic data type
+///
+/// \f$ v = \displaystyle\sum_{i=0}^{n} a_i T_{r}^{t_i}\f$
+template <typename TYPE>
+class PowersOfTreduced {
+public:
+    ///
+    ///
+    /// @param T_critical Critical temperature [K]
+    /// @param a Array of \f$a_i\f$ coefficients
+    /// @param t Array of \f$t_i\f$ exponents
+    PowersOfTreduced(double T_critical,
+                     const std::vector<double> & a,
+                     const std::vector<double> & t) :
+        T_crit(T_critical),
+        a(a),
+        t(t)
+    {
+    }
+
+    /// Evaluate the model
+    ///
+    /// @param T Temperature
+    /// @return Computed value
+    TYPE
+    value(TYPE T) const
+    {
+        TYPE Tr = T / this->T_crit;
+        TYPE sum = 0;
+        for (std::size_t i = 0; i < a.size(); ++i)
+            sum += this->a[i] * math::pow(Tr, this->t[i]);
+        return sum;
+    }
+
+private:
+    /// Critical temperature [K]
+    double T_crit;
+    /// a_i coefficients
+    std::vector<double> a;
+    /// t_i exponents
+    std::vector<double> t;
+};
+
 } // namespace fprops

test/src/transport_models_test.cpp

@@ -20,3 +20,9 @@ TEST(TransportTest, modified_batshinski_hildebrand)
     ModifiedBatshinskiHildebrand<double> mbh({ 2, 3 }, { 3, 4 }, { 4, 5 }, { 4, 3 }, { 2, 3 });
     EXPECT_DOUBLE_EQ(mbh.value(2., 3.), 0.000097523945419603);
 }
+
+TEST(TransportTest, powers_of_T_reduced)
+{
+    PowersOfTreduced<double> potr(300, { 3. }, { 5. });
+    EXPECT_DOUBLE_EQ(potr.value(600), 96.);
+}