Static-dynamic EA improvement and LineProps CdAx bugfixes:

- Added a System flag dynamic_stiffness_activated to track the state of
  the stiffness assumptions.
- Changed activateDynamicStiffness methods to only run if the system
  is currently in a static stiffness state. Otherwise calling these
  methods twice in a row would result in exagerated stiffnesses.
- Fixed a bug found by kasia129 with misnaming of CdAx and CaAx when
  loading line properties. The keys should now be consistent.

moorpy/helpers.py

@@ -714,7 +714,8 @@ def getLineProps(dnommm, material, lineProps=None, source=None, name="", rho=102
 
     lineType = dict(name=typestring, d_vol=d_vol, m=mass, EA=EA, w=w,
                     MBL=MBL, EAd=EAd, EAd_Lm=EAd_Lm, input_d=d,
-                    cost=cost, notes=notes, material=material, Cdn=Cd, Cdt=CdAx,Can=Ca,Cat=CaAx)
+                    cost=cost, notes=notes, material=material, 
+                    Cd=Cd, CdAx=CdAx, Ca=Ca, CaAx=CaAx)
 
     lineType.update(kwargs)   # add any custom arguments provided in the call to the lineType's dictionary
 
@@ -776,9 +777,9 @@ def loadLineProps(source):
         output[mat]['EAd_MBL'  ] = getFromDict(props, 'EAd_MBL'  , default=0.0)
         output[mat]['EAd_MBL_Lm']= getFromDict(props, 'EAd_MBL_Lm',default=0.0)
         output[mat]['Cd'       ] = getFromDict(props, 'Cd'       , default=0.0)
-        output[mat]['CdAx'     ] = getFromDict(props, 'Cd_ax'    , default=0.0)
+        output[mat]['Cd_ax'    ] = getFromDict(props, 'Cd_ax'    , default=0.0)
         output[mat]['Ca'       ] = getFromDict(props, 'Ca'       , default=0.0)
-        output[mat]['CaAx'     ] = getFromDict(props, 'Ca_ax'    , default=0.0)
+        output[mat]['Ca_ax'    ] = getFromDict(props, 'Ca_ax'    , default=0.0)
 
         output[mat]['MBL_0'    ] = getFromDict(props, 'MBL_0'    , default=0.0)
         output[mat]['MBL_d'    ] = getFromDict(props, 'MBL_d'    , default=0.0)

moorpy/line.py

@@ -977,10 +977,10 @@ def attachLine(self, lineID, endB):
 
 
     def activateDynamicStiffness(self, display=0):
-        '''Switch mooring line model to dynamic line stiffness
-        value, including potential unstretched line length
-        adjustment. This only works when dynamic line properties
-        are used.'''
+        '''Switch mooring line model to dynamic line stiffness value, 
+        including potential unstretched line length adjustment, taking the 
+        current state as the mean/static offset position to work from. 
+        This only works when dynamic line properties are used.'''
 
         if self.type['EAd'] > 0:
             # switch to dynamic stiffness value

moorpy/subsystem.py

@@ -472,7 +472,8 @@ def setDynamicOffset(self, offset, z=0):
         Optional argument z can be added for a z offset.
         '''
 
-        self.activateDynamicStiffness()  # use dynamic EA values
+        if not self.dynamic_stiffness_activated: # if not already using them,
+            System.activateDynamicStiffness(self)  # switch to dynamic EA values
 
         # adjust end B to the absolute offsets specified
         self.rB = np.array([-self.rad_fair + offset, 0, self.z_fair+z]) 
@@ -486,16 +487,12 @@ def setDynamicOffset(self, offset, z=0):
 
 
     def activateDynamicStiffness(self, display=0):
-        '''Switch mooring system model to dynamic line stiffness
-        values and adjust the unstretched line lengths to maintain the
-        same tensions. This only has an effect when dynamic line properties
-        are used.'''
+        '''Calls the dynamic stiffness method from System rather than from Line.'''
         System.activateDynamicStiffness(self, display=display)
 
 
     def revertToStaticStiffness(self):
-        '''Revert mooring system model back to the static stiffness
-        values and the original unstretched lenths.'''
+        '''Calls the static stiffness method from System rather than from Line.'''
         System.revertToStaticStiffness(self)
 
 

moorpy/system.py

@@ -107,6 +107,7 @@ def __init__(self, file="", dirname="", rootname="", depth=0, rho=1025, g=9.81,
 
         self.MDoptions = {} # dictionary that can hold any MoorDyn options read in from an input file, so they can be saved in a new MD file if need be
 
+        self.dynamic_stiffness_activated = False  # flag turned on when dynamic EA values are activate
 
         # read in data from an input file if a filename was provided
         if len(file) > 0:
@@ -1046,7 +1047,7 @@ def unload(self, fileName, MDversion=2, line_dL=0, rod_dL=0, flag='p',
 
             # Some default settings to fill in if coefficients aren't set
             #lineTypeDefaults = dict(BA=-1.0, EI=0.0, Cd=1.2, Ca=1.0, CdAx=0.2, CaAx=0.0)
-            lineTypeDefaults = dict(BA=-1.0, cIntDamp=-0.8, EI=0.0, Can=1.0, Cat=1.0, Cdn=1.0, Cdt=0.5)
+            lineTypeDefaults = dict(BA=-1.0, EI=0.0, Ca=1.0, CaAx=1.0, Cd=1.0, CdAx=0.5)
             rodTypeDefaults  = dict(Cd=1.2, Ca=1.0, CdEnd=1.0, CaEnd=1.0)
 
             # bodyDefaults = dict(IX=0, IY=0, IZ=0, CdA_xyz=[0,0,0], Ca_xyz=[0,0,0])
@@ -3045,13 +3046,16 @@ def checkTensions(self, N = None):
 
 
     def activateDynamicStiffness(self, display=0):
-        '''Switch mooring system model to dynamic line stiffness
-        values and adjust the unstretched line lengths to maintain the
-        same tensions. This only has an effect when dynamic line properties
-        are used.'''
+        '''Switch mooring system model to dynamic line stiffness values and 
+        adjust the unstretched line lengths to maintain the same tensions. 
+        If dynamic stiffnesses are already activated, it does nothing.
+        This only has an effect when dynamic line properties are used. '''
 
-        for line in self.lineList:
-            line.activateDynamicStiffness(display=display)
+        if not self.dynamic_stiffness_activated:
+            for line in self.lineList:
+                line.activateDynamicStiffness(display=display)
+
+            self.dynamic_stiffness_activated = True
 
 
     def revertToStaticStiffness(self):
@@ -3060,6 +3064,8 @@ def revertToStaticStiffness(self):
 
         for line in self.lineList:
             line.revertToStaticStiffness()
+
+        self.dynamic_stiffness_activated = False
 
 
     def setBathymetry(self, x, y, depth):