From c408d38815e9274fd0d1ab6801ce51f72d674b27 Mon Sep 17 00:00:00 2001
From: Ian Bell <ian.bell@nist.gov>
Date: Sun, 31 Jul 2022 15:42:37 -0400
Subject: [PATCH] And this time with a test
---
src/tests/catch_test_cubics.cxx | 56 +++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/src/tests/catch_test_cubics.cxx b/src/tests/catch_test_cubics.cxx
index ef98d14..838d253 100644
--- a/src/tests/catch_test_cubics.cxx
+++ b/src/tests/catch_test_cubics.cxx
@@ -185,4 +185,60 @@ TEST_CASE("Check manual integration of subcritical VLE isotherm for binary mixtu
double pfinal = J.back().at("pL / Pa").back();
CHECK(std::abs(pfinal / pfinal_goal-1) < 1e-5);
}
+}
+
+TEST_CASE("Check infinite dilution of subcritical VLE derivatives", "[cubic][isochoric][infdil]")
+{
+ // Values taken from http://dx.doi.org/10.6028/jres.121.011
+ std::valarray<double> Tc_K = { 190.564, 154.581 },
+ pc_Pa = { 4599200, 5042800 },
+ acentric = { 0.011, 0.022 };
+ auto model = canonical_PR(Tc_K, pc_Pa, acentric);
+ const auto N = Tc_K.size();
+ using state_type = std::valarray<double>;
+ REQUIRE(N == 2);
+ auto get_start = [&](double T, auto i) {
+ std::valarray<double> Tc_(Tc_K[i], 1), pc_(pc_Pa[i], 1), acentric_(acentric[i], 1);
+ auto PR = canonical_PR(Tc_, pc_, acentric_);
+ auto [rhoL, rhoV] = PR.superanc_rhoLV(T);
+ state_type o(N * 2);
+ o[i] = rhoL;
+ o[i + N] = rhoV;
+ return o;
+ };
+ int i = 1;
+ double T = 120;
+ auto rhostart_dil = get_start(T, i);
+ auto rhostart_notdil = rhostart_dil;
+ rhostart_notdil[1-i] += 1e-6;
+ rhostart_notdil[1-i+N] += 1e-6;
+
+ SECTION("Along isotherm") {
+ // Derivative function with respect to p
+ auto xprime = [&](const state_type& X) {
+ REQUIRE(X.size() % 2 == 0);
+ auto N = X.size() / 2;
+ // Memory maps into the state vector for inputs and their derivatives
+ auto rhovecL = Eigen::Map<const Eigen::ArrayXd>(&(X[0]), N);
+ auto rhovecV = Eigen::Map<const Eigen::ArrayXd>(&(X[0]) + N, N);
+ return get_drhovecdp_Tsat(model, T, rhovecL, rhovecV);
+ };
+ auto dernotdil = xprime(rhostart_notdil);
+ auto derdil = xprime(rhostart_dil);
+ CHECK(true);
+ }
+ SECTION("Along isobar") {
+ // Derivative function with respect to T
+ auto xprime = [&](const state_type& X) {
+ REQUIRE(X.size() % 2 == 0);
+ auto N = X.size() / 2;
+ // Memory maps into the state vector for inputs and their derivatives
+ auto rhovecL = Eigen::Map<const Eigen::ArrayXd>(&(X[0]), N);
+ auto rhovecV = Eigen::Map<const Eigen::ArrayXd>(&(X[0]) + N, N);
+ return get_drhovecdT_psat(model, T, rhovecL.eval(), rhovecV.eval());
+ };
+ auto dernotdil = xprime(rhostart_notdil);
+ auto derdil = xprime(rhostart_dil);
+ CHECK(true);
+ }
}
\ No newline at end of file
--
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