Added a Python mirror of the polyester line test (a friend complained about moordyn.GetPointForce())

Author: sanguinariojoe

tests/polyester.cpp

@@ -73,7 +73,7 @@ double get_average_tension(MoorDynLine line,
 	REQUIRE(MoorDyn_GetPointForce(fairlead, force) == MOORDYN_SUCCESS);
 	tension += vec_norm(force);
 	for (unsigned int i = 0; i < n; i++) {
-		REQUIRE(MoorDyn_GetLineNodeTen(line, i, force) == MOORDYN_SUCCESS);
+		REQUIRE(MoorDyn_GetLineNodeTen(line, i + 1, force) == MOORDYN_SUCCESS);
 		tension += vec_norm(force);
 	}
 	return tension / (n + 1);

tests/test_minimal.py

@@ -1,4 +1,3 @@
-import sys
 from unittest import TestCase, main as unittest_main
 import os
 import tempfile

tests/test_poliester.py

@@ -0,0 +1,112 @@
+from unittest import TestCase, main as unittest_main
+import os
+import csv
+import math
+import moordyn
+from test_minimal import setup_case
+
+
+MBL = 25.3e6
+KRS = 13.4
+KRD1 = 16.0
+KRD2 = 0.35
+TC = 200.0
+TTIMES = [320.0, 640.0, 960.0, 1280.0, 1599.0]
+TMEANS = [0.1, 0.2, 0.3, 0.4, 0.5]
+
+
+def vec_norm(v):
+    return math.sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2])
+
+
+def get_average_tension(line, anchor, fairlead):
+    n = moordyn.GetLineN(line)
+    # To average the tensions along the line, we are considering the
+    # connections instead of the line end up nodes, as long as the latter are
+    # not that accurate
+    tension = 0.0
+    force = moordyn.GetPointForce(anchor)
+    tension += vec_norm(force)
+    force = moordyn.GetPointForce(fairlead)
+    tension += vec_norm(force)
+    for i in range(n):
+        force = moordyn.GetLineNodeTen(line, i + 1)
+        tension += vec_norm(force)
+    return tension / (n + 1)
+
+
+class PoliesterTests(TestCase):
+    def setUp(self):
+        pass
+
+    def test_rampup_stabilization_cycles(self):
+        global TTIMES, TMEANS
+
+        tmp_folder = setup_case("polyester/simple.txt")
+        cwd = os.getcwd()
+        os.chdir(tmp_folder)
+        system = moordyn.Create()
+        os.chdir(cwd)
+
+        n_dof = moordyn.NCoupledDOF(system)
+        self.assertEqual(moordyn.NCoupledDOF(system), 3,
+                         "Incorrect number of DOFs")
+
+        anchor = moordyn.GetPoint(system, 1)
+        fairlead = moordyn.GetPoint(system, 2)
+        line = moordyn.GetLine(system, 1)
+
+        l0 = moordyn.GetLineUnstretchedLength(line)
+        r = moordyn.GetPointPos(fairlead)
+        dr = [0, 0, 0]
+        moordyn.Init(system, r, dr)
+
+        tdata, xdata = [], []
+        with open('Mooring/polyester/motion.csv') as csvfile:
+            reader = csv.reader(csvfile, delimiter=',', quotechar='"')
+            skip = 2
+            for row in reader:
+                if skip > 0:
+                    skip -= 1
+                    continue
+                tdata.append(float(row[0]))
+                xdata.append(float(row[1]))
+
+        t = 0
+        times, tensions = [], []
+        for i in range(len(tdata)):
+            t_dst = tdata[i]
+            x_dst = xdata[i]
+            dt = t_dst - t
+            dr[0] = (x_dst - r[0]) / dt
+            f = moordyn.Step(system, r, dr, t, dt)
+            t += dt
+            times.append(t)
+            tensions.append(get_average_tension(line, anchor, fairlead))
+
+            if (times[-1] - times[0] < TC):
+                continue
+
+            tension = 0.0;
+            for f in tensions:
+                tension += f
+            tension /= len(tensions)
+            times = times[1:]
+            tensions = tensions[1:]
+
+            ks = KRS * MBL
+            kd = (KRD1 + KRD2 * tension / MBL * 100) * MBL
+            l = l0 * (1.0 + tension / ks) / (1.0 + tension / kd)
+            moordyn.SetLineConstantEA(line, kd)
+            moordyn.SetLineUnstretchedLength(line, l)
+
+            if (t >= TTIMES[0]):
+                tmean = TMEANS[0]
+                TTIMES = TTIMES[1:]
+                TMEANS = TMEANS[1:]
+                assert(abs(tension / MBL - tmean) < 0.025)
+
+        moordyn.Close(system)
+
+if __name__ == '__main__':
+    unittest_main()