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Fix rotor cg calc without double counting Rhub #694

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Merged
ptrbortolotti merged 3 commits into from
Jan 22, 2026
+8 −10
Merged

Fix rotor cg calc without double counting Rhub #694

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1ca2945
remove double counting of rhub in cg calculation
gbarter Jan 21, 2026
7cbdc8c
update unit tests for better representation of r that has r[0]=rhub
gbarter Jan 21, 2026
bee51a1
correct truth values with RNA cg now slightly shifted impacting tower…
gbarter Jan 22, 2026
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7 changes: 3 additions & 4 deletions wisdem/rotorse/rotor_structure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,6 @@ def setup(self):
self.add_input("precurve", val=np.zeros(n_span), units="m", desc="location in blade x-coordinate")
self.add_input("presweep", val=np.zeros(n_span), units="m", desc="location in blade y-coordinate")
self.add_input("precone", val=0.0, units="deg", desc="precone angle")
self.add_input("Rhub", val=0.0, units="m", desc="hub radius")
self.add_input("blade_span_cg", val=0.0, units="m", desc="Distance along the blade span for its center of gravity")

# Outputs
Expand All @@ -49,12 +48,12 @@ def setup(self):
self.add_output("blades_cg_hubcc", val=0.0, units="m", desc="cg of all blades relative to hub along shaft axis. Distance is should be interpreted as negative for upwind and positive for downwind turbines")

def compute(self, inputs, outputs):
# Note that r[0]=Rhub here
r = inputs["r"]
precurve = inputs["precurve"]
presweep = inputs["presweep"]
precone = inputs["precone"]
r_cg = inputs["blade_span_cg"]
Rhub = inputs["Rhub"]

n = len(r)
dx_dx = np.eye(3 * n)
Expand All @@ -74,7 +73,7 @@ def compute(self, inputs, outputs):

# Compute cg location of all blades in hub coordinates
cone_cg = np.interp(r_cg, r, totalCone)
cg = (r_cg + Rhub) * np.sin(np.deg2rad(cone_cg))
cg = r_cg * np.sin(np.deg2rad(cone_cg))
outputs["blades_cg_hubcc"] = cg


Expand Down Expand Up @@ -1125,7 +1124,7 @@ def setup(self):
self.add_subsystem(
"curvature",
BladeCurvature(modeling_options=modeling_options),
promotes=["r", "precone", "precurve", "presweep", "Rhub", "blade_span_cg", "3d_curv", "x_az", "y_az", "z_az"],
promotes=["r", "precone", "precurve", "presweep", "blade_span_cg", "3d_curv", "x_az", "y_az", "z_az"],
)
promoteListTotalBladeLoads = ["r", "theta", "tilt", "rhoA", "3d_curv", "z_az"]
self.add_subsystem(
Expand Down
2 changes: 1 addition & 1 deletion wisdem/test/test_postprocessing/test_getters.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ def testAll(self):
npt.assert_almost_equal(getter.get_monopile_cost(prob), 3108099.1, 1)
npt.assert_almost_equal(getter.get_structural_mass(prob), getter.get_tower_mass(prob)+getter.get_monopile_mass(prob))
npt.assert_almost_equal(getter.get_structural_cost(prob), getter.get_tower_cost(prob)+getter.get_monopile_cost(prob))
npt.assert_almost_equal(getter.get_tower_freqs(prob), np.array([0.1744686, 0.175398 , 0.7489153, 0.8640253, 0.9475382, 1.8933329]))
npt.assert_almost_equal(getter.get_tower_freqs(prob), np.array([0.1744692, 0.1754122, 0.7511913, 0.8640732, 0.9489718, 1.8933818]), decimal=3)
npt.assert_almost_equal(getter.get_tower_cm(prob), 52.18670343496422, 2)
npt.assert_almost_equal(getter.get_tower_cg(prob), 52.18670343496422, 2)

Expand Down
9 changes: 4 additions & 5 deletions wisdem/test/test_rotorse/test_rotor_structure.py
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Expand Up @@ -26,12 +26,11 @@ def testBladeCurvature(self):
myobj = rs.BladeCurvature(modeling_options=options)

# Straight blade: Z is 'r'
inputs["r"] = np.linspace(0, 100, npts)
inputs["r"] = np.linspace(1, 101, npts) # assumes rhub=1
inputs["precurve"] = myzero
inputs["presweep"] = myzero
inputs["precone"] = 0.0
inputs["Rhub"] = 1.0
inputs["blade_span_cg"] = 0.5 * inputs["r"].max()
inputs["blade_span_cg"] = inputs["r"].mean()
myobj.compute(inputs, outputs)
npt.assert_equal(outputs["3d_curv"], myzero)
npt.assert_equal(outputs["x_az"], myzero)
Expand All @@ -52,7 +51,7 @@ def testBladeCurvature(self):
inputs["precurve"] = np.linspace(0, 1, npts)
inputs["precone"] = 0.0
myobj.compute(inputs, outputs)
cone = -np.rad2deg(np.arctan(inputs["precurve"] / (inputs["r"] + 1e-20)))
cone = -np.rad2deg(np.arctan(inputs["precurve"] / (inputs["r"] - 1.0 + 1e-20)))
cone[0] = cone[1]
npt.assert_almost_equal(outputs["3d_curv"], cone)
npt.assert_equal(outputs["x_az"], inputs["precurve"])
Expand All @@ -75,7 +74,7 @@ def testBladeCurvature(self):
inputs["presweep"] = np.linspace(0, 1, npts)
inputs["precone"] = 0.0
myobj.compute(inputs, outputs)
cone = -np.rad2deg(np.arctan(inputs["precurve"] / (inputs["r"] + 1e-20)))
cone = -np.rad2deg(np.arctan(inputs["precurve"] / (inputs["r"] - 1.0 + 1e-20)))
cone[0] = cone[1]
npt.assert_almost_equal(outputs["3d_curv"], cone)
npt.assert_equal(outputs["x_az"], inputs["precurve"])
Expand Down
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