Added option to set nCrit (#29)

* added option to change ncrit

* use the actual Reynolds number instead of Reynolds per length

* revert Reynolds change, update comments

* added nCrit test

* bumped minor version

cmplxfoil/CMPLXFOIL.py

@@ -263,13 +263,18 @@ def __call__(self, aeroProblem, useComplex=False, deriv=False):
         self.setAeroProblem(aeroProblem)
 
         # Set flight condition and options
-        xfoil.cr15.reinf1 = aeroProblem.re  # Reynolds number
-        xfoil.cr09.minf1 = aeroProblem.mach  # Mach Number set
-        xfoil.cr09.adeg = aeroProblem.alpha
-        xfoil.ci04.itmax = self.getOption("maxIters")  # Iterations Limit Set
+        xfoil.cr15.reinf1 = aeroProblem.re  # Reynolds number per unit length
+        xfoil.cr09.minf1 = aeroProblem.mach  # Mach number
+        xfoil.cr09.adeg = aeroProblem.alpha  # Angle of attack
+        xfoil.ci04.itmax = self.getOption("maxIters")  # Iterations limit
         if not np.any(np.isnan(self.getOption("xTrip"))):  # NaN is default to not set, otherwise set it
             xfoil.cr15.xstrip = self.getOption("xTrip")
 
+        # Set nCrit (The Fortran variable is acrit)
+        # lvconv needs to be set to False to update internal variables
+        xfoil.cr15.acrit = self.getOption("nCrit")
+        xfoil.cl01.lvconv = False
+
         # Call XFOIL
         xfoil.oper()
 
@@ -1073,6 +1078,7 @@ def _getDefaultOptions():
                 np.ndarray,
                 np.full(2, np.NaN),
             ],  # boundary layer trip x coordinate of upper and lower surface, respectively (two-element array)
+            "nCrit": [float, 9.0],
         }
 
     @staticmethod

cmplxfoil/__init__.py

@@ -1,4 +1,4 @@
-__version__ = "2.0.4"
+__version__ = "2.1.0"
 
 from .CMPLXFOIL import CMPLXFOIL
 

doc/options.yaml

@@ -30,3 +30,8 @@ xTrip:
   desc: >
     The boundary layer trip location specified as a two-element numpy array where the first element is the chordwise location at which to trip the upper surface and the second is the chordwise location at which to trip the lower surface.
     By default will not trip the boundary layer and instead use XFOIL's transition model.
+nCrit:
+  desc: >
+    The critical amplification exponent for boundary layer transition.
+    This parameter represents the background turbulence level.
+    Lower values will result in earlier turbulent transition.

tests/test_solver_class.py

@@ -89,7 +89,7 @@ def test_function_values(self):
             self.assertAlmostEqual(true_val, funcs[key])
 
 
-class TestTrip(unittest.TestCase):
+class TestTransition(unittest.TestCase):
     def test_trip(self):
         """
         Test that setting the trip changes the result.
@@ -116,6 +116,28 @@ def test_trip(self):
         for func in evalFuncs:
             self.assertNotEqual(funcs["fc_" + func], funcsTripped["fc_" + func])
 
+    def test_nCrit(self):
+        """
+        Test that setting nCrit changes the result.
+        """
+        evalFuncs = ["cl", "cd", "cm"]
+        self.ap = AeroProblem(
+            name="fc", alpha=3, mach=0.2, altitude=1e3, areaRef=1.0, chordRef=1.0, evalFuncs=evalFuncs
+        )
+        self.CFDSolver = CMPLXFOIL(os.path.join(baseDir, "naca0012.dat"))
+        self.CFDSolverNCrit = CMPLXFOIL(os.path.join(baseDir, "naca0012.dat"), options={"nCrit": 5.0})
+
+        funcs = {}
+        self.CFDSolver(self.ap)
+        self.CFDSolver.evalFunctions(self.ap, funcs)
+
+        funcsNCrit = {}
+        self.CFDSolverNCrit(self.ap)
+        self.CFDSolverNCrit.evalFunctions(self.ap, funcsNCrit)
+
+        for func in evalFuncs:
+            self.assertNotEqual(funcs["fc_" + func], funcsNCrit["fc_" + func])
+
 
 class TestDerivativesFFD(unittest.TestCase):
     def setUp(self):