Subsystem update to support shared/symmetrical lines

moorpy/Catenary.py

@@ -1466,7 +1466,8 @@ def step_func_cat(X, args, Y, info, Ytarget, err, tols, iter, maxIter):
 
     #(fAH1, fAV1, fBH1, fBV1, info1) =  catenary(0.16525209064463553, 1000.1008645356192, 976.86359774357, 861890783.955385, -5.663702119364548, 0.0, -0.0, 0.0, 17325264.3383085, 5.000000000000001e-05, 101, 1, 1000)
     #(fAH1, fAV1, fBH1, fBV1, info1) =  catenary(0.0, 997.8909672113768, 1006.0699998926483, 361256000.00000006, 2.4952615384615333, 0, 0.0, 0, 0, 0.0001, 101, 100, 1, 1000)
-    (fAH1, fAV1, fBH1, fBV1, info1) =  catenary(148.60942473375343, 1315.624259105325, 1279.7911844766932, 17497567581.802254, -81.8284437736437, CB=0.0, alpha=-0.0, HF0=795840.9590915733, VF0=6399974.444658389, Tol=0.0005, MaxIter=100, depth=1300.0, plots=1)
+    #(fAH1, fAV1, fBH1, fBV1, info1) =  catenary(148.60942473375343, 1315.624259105325, 1279.7911844766932, 17497567581.802254, -81.8284437736437, CB=0.0, alpha=-0.0, HF0=795840.9590915733, VF0=6399974.444658389, Tol=0.0005, MaxIter=100, depth=1300.0, plots=1)
+    (fAH1, fAV1, fBH1, fBV1, info1) =  catenary(2887.113193120885, -838.1577017360617, 2979.7592390255295, 41074520109.87981, 1104.878355564403, CB=0.0, alpha=81.41243787249468, HF0=0.0, VF0=3564574.0622291695, Tol=0.0005, MaxIter=100, depth=3000.0, plots=1)
 
     #(fAH1, fAV1, fBH1, fBV1, info1) = catenary(274.9, 15.6, 328.5, 528887323., -121., 
     #         CB=-48., alpha=0, HF0=17939., VF0=20596., Tol=2e-05, MaxIter=100, plots=1)

moorpy/line.py

@@ -753,6 +753,8 @@ def staticSolve(self, reset=False, tol=0.0001, profiles=0):
             w = np.linalg.norm(w_vec)
             w_hat = w_vec/w
 
+            # >>> may need to adjust to handle case of buoyant vertical lines <<<
+
             # get rotation matrix from gravity down to w_vec being down
             if w_hat[0] == 0 and w_hat[1] == 0: 
                 if w_hat[2] < 0:

moorpy/subsystem.py

@@ -89,7 +89,9 @@ def __init__(self, mooringSys=None, num=0, depth=0, rho=1025, g=9.81,
             self.currentMod = 1
             self.current = getFromDict(kwargs, 'current', shape=3)
 
-        self.shared     = getFromDict(kwargs, 'shared', dtype=bool, default=False)  # flag to indicate shared line
+        # flag to indicate shared line or suspended cable being modeled as symmetric
+        self.shared = getFromDict(kwargs, 'shared', dtype=bool, default=False)
+
         self.span   = getFromDict(kwargs, 'span', default=0)  # horizontal end-end distance [m]
         self.rad_fair = getFromDict(kwargs, 'rad_fair', default=0)  # [m] fairlead radius [m]
         self.z_fair   = getFromDict(kwargs, 'z_fair'  , default=0)  # [m] fairlead z coord [m]
@@ -192,6 +194,7 @@ def makeGeneric(self, lengths, types, connectors=[], suspended=0):
         # set end A location depending on whether configuration is suspended/symmetrical
         if suspended==2:  # symmetrical suspended case
             rA = np.array([-0.5*self.span-self.rad_fair, 0, -1])  # shared line midpoint coordinates
+            self.shared = True  # flag that it's being modeled as symmetric
         elif suspended==1:  # general suspended case
             rA = np.array([-self.span-self.rad_fair, 0, self.z_fair])  # other suspended end
         else:  # normal anchored line case
@@ -323,11 +326,28 @@ def staticSolve(self, reset=False, tol=0, profiles=0):
             Kt = -self.fB_L[0]/LH  
 
         # expand to get 3D stiffness matrices
+        '''
         R = np.eye(3)
         self.KA_L  = from2Dto3Drotated(K[:2,:2],  Kt, R.T)  # reaction at A due to motion of A
         self.KB_L  = from2Dto3Drotated(K[2:,2:],  Kt, R.T)  # reaction at B due to motion of B
         self.KBA_L = from2Dto3Drotated(K[2:,:2], -Kt, R.T)  # reaction at B due to motion of A
+        '''
+        self.KA_L = np.array([[K[0,0], 0 , K[0,1]],
+                              [  0   , Kt,   0   ],
+                              [K[1,0], 0 , K[1,1]]])
+
+        # If symmetrical model, ignore midpoint stiffness and force
+        if self.shared:  
+            self.KB_L = np.array(self.KA_L)  # same stiffness as A
+            self.fB_L = np.array([-self.fA_L[0], 0, self.fA_L[1]]) # mirror of fA
+        else:
+            self.KB_L = np.array([[K[2,2], 0 , K[2,3]],
+                                  [  0   , Kt,   0   ],
+                                  [K[3,2], 0 , K[3,3]]])
+
+        self.KBA_L = -self.KB_L
 
+        # Save tension magnitudes
         self.TA = np.linalg.norm(self.fA_L)  # tensions [N]
         self.TB = np.linalg.norm(self.fB_L)