Modified system.unload for visco-elastic stiffness

-uses optional mean load input to the unload function

moorpy/system.py

@@ -971,7 +971,7 @@ def readBathymetryFile(self, filename):
 
 
 
-    def unload(self, fileName, MDversion=2, line_dL=0, rod_dL=0, flag='p', outputList=[]):
+    def unload(self, fileName, MDversion=2, line_dL=0, rod_dL=0, flag='p', outputList=[], Lm = 0):
         '''Unloads a MoorPy system into a MoorDyn-style input file
 
         Parameters
@@ -984,6 +984,8 @@ def unload(self, fileName, MDversion=2, line_dL=0, rod_dL=0, flag='p', outputLis
             Optional specified for target segment length when discretizing Rods
         outputList : list of strings, optional
             Optional list of additional requested output channels
+        Lm : float
+            Mean load on mooring line as percentage of MBL, used for dynamic stiffness calculation. Only used if line type has a nonzero EAd
 
         Returns
         -------
@@ -1201,8 +1203,18 @@ def unload(self, fileName, MDversion=2, line_dL=0, rod_dL=0, flag='p', outputLis
             for key, lineType in self.lineTypes.items(): 
                 di = lineTypeDefaults.copy()  # start with a new dictionary of just the defaults
                 di.update(lineType)           # then copy in the lineType's existing values
-                L.append("{:<12} {:7.4f} {:8.2f}  {:7.3e} {:7.3e} {:7.3e}   {:<7.3f} {:<7.3f} {:<7.2f} {:<7.2f}".format(
-                         key, di['d_vol'], di['m'], di['EA'], di['BA'], di['EI'], di['Cd'], di['Ca'], di['CdAx'], di['CaAx']))
+                if di['EAd'] > 0:
+                    if Lm > 0:
+                        print('Calculating dynamic stiffness with Lm = ' + str(Lm)+'% of MBL')
+                        L.append("{:<12} {:7.4f} {:8.2f}  {:7.3e}|{:7.3e} 4E9|11e6 {:7.3e}   {:<7.3f} {:<7.3f} {:<7.2f} {:<7.2f}".format(
+                             key, di['d_vol'], di['m'], di['EA'], di['EAd'] + di['EAd_Lm']*Lm*di['MBL'], di['EI'], di['Cd'], di['Ca'], di['CdAx'], di['CaAx']))
+                    else:
+                        print('No mean load provided!!! using the static EA value ONLY')
+                        L.append("{:<12} {:7.4f} {:8.2f}  {:7.3e} {:7.3e} {:7.3e}   {:<7.3f} {:<7.3f} {:<7.2f} {:<7.2f}".format(
+                                 key, di['d_vol'], di['m'], di['EA'], di['BA'], di['EI'], di['Cd'], di['Ca'], di['CdAx'], di['CaAx']))
+                else:
+                    L.append("{:<12} {:7.4f} {:8.2f}  {:7.3e} {:7.3e} {:7.3e}   {:<7.3f} {:<7.3f} {:<7.2f} {:<7.2f}".format(
+                             key, di['d_vol'], di['m'], di['EA'], di['BA'], di['EI'], di['Cd'], di['Ca'], di['CdAx'], di['CaAx']))
 
 
             L.append("--------------------- ROD TYPES -----------------------------------------------------")