CurledWake: use non-dimensional Ct in Gamma_0

mitwindfarm/CurledWake.py

@@ -252,7 +252,7 @@ def stamp_ic(
         # rotate points into yaw-and-tilt frame
         _, y_i, z_i = eff_yaw_inv_rotation(np.zeros_like(r_i), np.zeros_like(r_i), r_i, eff_yaw, rotor.yaw, rotor.tilt)
         # NOTE: rotor.Ct differs from Shapiro et al. (2018) definition - includes cos^2(eff_yaw)
-        Gamma_0 = 0.5 * D * rotor.REWS * rotor.Ct * np.sin(eff_yaw)
+        Gamma_0 = 0.5 * D * rotor.REWS * rotor.extra.Ct * np.sin(eff_yaw)
         Gamma_i = (
             Gamma_0 * 4 * r_i / (self.N_vortex * D * np.sqrt(1 - (2 * r_i / D) ** 2))
         )

tests/test_uref_invariance.py

@@ -0,0 +1,52 @@
+"""
+Test that the CurledWake solver produces non-dimensionally invariant results
+when the freestream velocity U0 is rescaled (and k-l is used).
+"""
+
+import numpy as np
+from pytest import approx
+from mitwindfarm import Uniform, Layout
+from mitwindfarm.windfarm import CurledWindfarm
+from mitwindfarm.Rotor import UnifiedAD_TI
+
+
+def _run_curled_farm(U0, k_model="const"):
+    """Run a 2-turbine yawed farm at given U0."""
+    wf = CurledWindfarm(
+        rotor_model=UnifiedAD_TI(),
+        base_windfield=Uniform(U0=U0, TIamb=0.05),
+        solver_kwargs=dict(
+            dy=0.1, dz=0.1,
+            integrator="scipy_rk23",
+            k_model=k_model,
+            verbose=False,
+        ),
+    )
+    layout = Layout([0, 5], [0, 0], [0, 0])
+    yaw = np.radians(20)
+    setpoints = [(2, yaw, 0)] * 2
+    return wf(layout, setpoints)
+
+
+def test_uref_invariance_kl():
+    """REWS/U0 must be identical at U0=1 and U0=2 (k-l turbulence model)."""
+    sol1 = _run_curled_farm(U0=1.0, k_model="k-l")
+    sol2 = _run_curled_farm(U0=2.0, k_model="k-l")
+
+    for i in range(2):
+        rews_ratio_1 = sol1.rotors[i].REWS / 1.0
+        rews_ratio_2 = sol2.rotors[i].REWS / 2.0
+        assert rews_ratio_2 == approx(rews_ratio_1, rel=1e-2), (
+            f"Turbine {i}: REWS/U0 differs between U0=1 ({rews_ratio_1:.4f}) "
+            f"and U0=2 ({rews_ratio_2:.4f})"
+        )
+
+
+def test_downstream_rews_below_freestream():
+    """Downstream turbine in a wake cannot see REWS > U0 with uniform inflow."""
+    sol = _run_curled_farm(U0=8.0, k_model="const")
+    for i in range(1, 2):  # skip turbine 0 (upstream)
+        assert sol.rotors[i].REWS <= 8.0 * 1.01, (
+            f"Turbine {i}: REWS={sol.rotors[i].REWS:.2f} exceeds U0=8.0 "
+            f"— physically impossible with uniform inflow"
+        )