Catenary now supports more buoyant cases and stops at surface

- Added depth input to catenary, and buoyant sections now stop
  at the surface rather than crossing it.
- A few related changes eliminate some errors that can occur
  with non-ideal dynamic cables.

moorpy/Catenary.py

@@ -8,7 +8,8 @@
 
 
 
-def catenary(XF, ZF, L, EA, W, CB=0, alpha=0, HF0=0, VF0=0, Tol=0.000001, nNodes=20, MaxIter=100, plots=0):
+def catenary(XF, ZF, L, EA, W, CB=0, alpha=0, HF0=0, VF0=0, Tol=0.000001, 
+             nNodes=20, MaxIter=100, plots=0, depth=0):
     '''
     The quasi-static mooring line solver. Adapted from catenary subroutine in FAST v7 by J. Jonkman.
     Note: this version is updated Oct 7 2020 to use the dsolve solver.
@@ -69,7 +70,7 @@ def catenary(XF, ZF, L, EA, W, CB=0, alpha=0, HF0=0, VF0=0, Tol=0.000001, nNodes
     # make info dict to contain any additional outputs
     info = dict(error=False)
 
-    info['call'] = f"catenary({XF}, {ZF}, {L}, {EA}, {W}, CB={CB}, alpha={alpha}, HF0={HF0}, VF0={VF0}, Tol={Tol}, MaxIter={MaxIter}, plots=1)"
+    info['call'] = f"catenary({XF}, {ZF}, {L}, {EA}, {W}, CB={CB}, alpha={alpha}, HF0={HF0}, VF0={VF0}, Tol={Tol}, MaxIter={MaxIter}, depth={depth}, plots=1)"
 
 
     # make some arrays if needed for plotting each node
@@ -96,7 +97,11 @@ def catenary(XF, ZF, L, EA, W, CB=0, alpha=0, HF0=0, VF0=0, Tol=0.000001, nNodes
     if W < 0:
         W = -W
         ZF = -ZF
-        CB = 0 #-10000.   # <<< TODO: could set hA, hB to distances to sea surface <<<
+        CB = 0
+        # Set hA, hB to distances to sea surface
+        if depth > 0:
+            hB = depth - hB
+            hA = depth - hA
         flipFlag = True
     else:
         flipFlag = False
@@ -648,8 +653,8 @@ def dV_dZ_s(z0, H):   # height off seabed to evaluate at (infinite if 0), horizo
             info["Sextreme"] = 0.0
             info["Zextreme"] = 0.0
             info["Xextreme"] = 0.0    
-           
-            
+
+
         # handle special case of a U-shaped line that has seabed contact (using 2 new catenary solves)
         if info['ProfileType']==1 and info["Zextreme"] < -hA:
 
@@ -725,8 +730,8 @@ def step_func_U(X, args, Y, info, Ytarget, err, tols, iter, maxIter):
                     info['Te'] =      info['Te'][::-1]
                 '''
 
-            if flipFlag:
-                raise Exception("flipFlag connot be True for the case of a U shaped line with seabed contact. Something must be wrong.")
+            #if flipFlag:
+            #    raise Exception("flipFlag connot be True for the case of a U shaped line with seabed contact. Something must be wrong.")
 
 
 
@@ -1429,7 +1434,32 @@ def step_func_cat(X, args, Y, info, Ytarget, err, tols, iter, maxIter):
 
     # Tricky case for sloped seabed (prone to overestimating LBot unless trapped corrected in the solve)      
     #(fAH1, fAV1, fBH1, fBV1, info1) = catenary(121.5, 17.5, 138.5, 1232572089, 2456.8, CB=0.0, alpha=-2.6, HF0=428113, VF0=396408, Tol=0.0005, nNodes=41, plots=1)
-    (fAH1, fAV1, fBH1, fBV1, info1) = catenary(121.09772794232714, -1.8384100597014594, 101.50770310432262, 1232572089.6, 2456.820077481978, CB=0.0, alpha=-0.8659609923714943, HF0=20534.12538249187, VF0=53055.020668169294, Tol=0.0005, nNodes=41, plots=1)
+
+    # case from Emma
+    #(fAH1, fAV1, fBH1, fBV1, info1) = catenary(0.006002402242302196, 52.088735921752004, 105, 440229677.8451713, 362.2187847407355, CB=0, HF0=0.0, VF0=30883.56235473299, Tol=5.000000000000001e-05, MaxIter=100, plots=1)
+
+    # cable case
+    #(fAH1, fAV1, fBH1, fBV1, info1) = catenary(39., 3.675, 37., 528., -5152., 
+    #         CB=0.0, alpha=-0.0, HF0=0.0, VF0=0.0, Tol=2e-05, MaxIter=100, plots=1, depth=200)
+
+
+    #(fAH1, fAV1, fBH1, fBV1, info1) = catenary(274.9, 15.6, 328.5, 528887323., -121., 
+    #         CB=-48., alpha=0, Tol=2e-05, MaxIter=100, plots=1, depth=200)
+
+    (fAH1, fAV1, fBH1, fBV1, info1) =  catenary(267.60271224572784, 11.629753388110558, 383.52733838297667, 528887323.6999998, -121.77472470613236, 
+        CB=-81.79782970374734, alpha=0, HF0=13369.512495199759, VF0=24221.869928543758, Tol=2e-05, 
+        MaxIter=100, depth=180, plots=1, nNodes=100)
+
+    #(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)
+
+
+    # First attempt's iterations are as follows:
+    # Iteration 0: HF= 5.0000e-05, VF= 2.8450e+04, EX= 0.00e+00, EZ= 0.00e+00
+    # Second attempt's iterations are as follows:
+    # Iteration 0: HF= 5.0000e-05, VF= 2.8450e+04, EX= 0.00e+00, EZ= 0.00e+00
+    # Last attempt's iterations are as follows:
+    # Iteration 0: HF= 5.0000e-05, VF= 2.8450e+04, EX= 0.00e+00, EZ= 0.00e+00
 
     """
     Tol =2e-05
@@ -1480,5 +1510,5 @@ def step_func_cat(X, args, Y, info, Ytarget, err, tols, iter, maxIter):
     plt.plot(info1['X'], info1['Z'] )
     #plt.axis('equal')
 
-    plt.close('all')
-    #plt.show()
+    #plt.close('all')
+    plt.show()

moorpy/line.py

@@ -803,9 +803,10 @@ def staticSolve(self, reset=False, tol=0.0001, profiles=0):
         #If EA is found in the line properties we will run the original catenary function 
         if 'EA' in self.type:
             try:
-                (fAH, fAV, fBH, fBV, info) = catenary(LH, LV, self.L, self.EA, w,
-                                                      CB=cb, alpha=alpha, HF0=self.HF, VF0=self.VF, 
-                                                      Tol=tol, nNodes=self.nNodes, plots=profiles)                                                    
+                (fAH, fAV, fBH, fBV, info) = catenary(LH, LV, self.L, self.EA, 
+                     w, CB=cb, alpha=alpha, HF0=self.HF, VF0=self.VF, Tol=tol, 
+                     nNodes=self.nNodes, plots=profiles, depth=self.sys.depth)
+
             except CatenaryError as error:
                 raise LineError(self.number, error.message)       
         #If EA isnt found then we will use the ten-str relationship defined in the input file