Merge pull request #374 from OpenSourceAWE/agent/347-k2-and-k4-in-the-artificial-damping-sett

Remove artificial damping, as the Python package did

Author: 1-Bart-1

CHANGELOG.md

@@ -29,6 +29,12 @@
 
 ### Changed
 
+- BREAKING: artificial damping is removed: the `is_with_artificial_damping` and
+  `artificial_damping` keyword arguments of `Solver`, and the `artificial_damping`, `k2`
+  and `k4` solver settings. `k2` and `k4` had no effect; `artificial_damping: true`
+  smoothed the circulation with fixed factors, so a solve that had it on now gives
+  different results. A settings file that still sets these keys loads with a warning. The post-stall stabiliser is
+  `is_with_artificial_viscosity`.
 - BREAKING: `ObjAdapter.center_to_com!`, `calculate_inertia_tensor` and
   `calc_inertia_y_rotation` are removed. Mesh mass properties are computed by
   SymbolicAWEModels, which reads the mesh with `read_faces`.
@@ -85,8 +91,6 @@
 - Inside its vortex core, `velocity_3D_trailing_vortex!` induces an azimuthal velocity
   instead of a radial one. Only points within the millimetre-scale Oseen core of a
   panel's chordwise trailing segment were affected.
-- With `artificial_damping` on, an iteration whose circulation is already smooth no longer
-  re-applies the previous iteration's damping correction.
 
 ## VortexStepMethod v5.1.1 2026-09-12
 

data/TUDELFT_V3_KITE/vsm_settings.yaml

@@ -66,9 +66,6 @@ solver_settings:
     relaxation_factor: 0.01          # [0.001-0.1] Under-relaxation for stability
 
     # --- Numerical Stability ---
-    artificial_damping: false        # Enable artificial damping for unstable cases
-    k2: 0.1                          # 2nd-order damping coefficient
-    k4: 0.0                          # 4th-order damping coefficient
     core_radius_fraction: 0.05      # Vortex core radius (fraction of filament length)
 
     # --- Initial Conditions ---

data/TUDELFT_V3_KITE/vsm_settings_coarse.yaml

@@ -70,9 +70,6 @@ solver_settings:
   relaxation_factor: 0.01 # [0.001-0.1] Under-relaxation for stability
 
   # --- Numerical Stability ---
-  artificial_damping: false # Enable artificial damping for unstable cases
-  k2: 0.1 # 2nd-order damping coefficient
-  k4: 0.0 # 4th-order damping coefficient
   core_radius_fraction: 1e-20 # Vortex core radius (fraction of filament length)
 
   # --- Initial Conditions ---

data/pyramid_model/vsm_settings.yaml

@@ -65,9 +65,6 @@ solver_settings:
     relaxation_factor: 0.01          # [0.001-0.1] Under-relaxation for stability
 
     # --- Numerical Stability ---
-    artificial_damping: false        # Enable artificial damping for unstable cases
-    k2: 0.0                          # 2nd-order damping coefficient
-    k4: 0.0                          # 4th-order damping coefficient
     core_radius_fraction: 0.05      # Vortex core radius (fraction of filament length)
 
     # --- Initial Conditions ---

data/ram_air_kite/vsm_settings.yaml

@@ -23,9 +23,6 @@ solver_settings:
     rtol: 1e-5                       # relative error   [-]
     tol_reference_error: 0.001
     relaxation_factor: 0.03          # relaxation factor for convergence
-    artificial_damping: false        # whether to apply artificial damping
-    k2: 0.1                          # artificial damping parameter
-    k4: 0.0                          # artificial damping parameter
     type_initial_gamma_distribution: ELLIPTIC
     use_gamme_prev: false
     core_radius_fraction: 0.05

data/ram_air_kite/vsm_settings_dual.yaml

@@ -28,9 +28,6 @@ solver_settings:
     rtol: 1e-5                       # relative error   [-]
     tol_reference_error: 0.001
     relaxation_factor: 0.03          # relaxation factor for convergence
-    artificial_damping: false        # whether to apply artificial damping
-    k2: 0.1                          # artificial damping parameter
-    k4: 0.0                          # artificial damping parameter
     type_initial_gamma_distribution: ELLIPTIC
     use_gamme_prev: false
     core_radius_fraction: 1e-20

docs/src/private_functions.md

@@ -38,7 +38,6 @@ calculate_stall_angle_list
 wing_span_flip
 calculate_circulation_distribution_elliptical_wing
 _compute_reference_velocity_from_distribution
-smooth_circulation!
 smooth_distribution!
 make_dual_shadow
 ```

examples/V3_neuralfoil.jl

@@ -37,8 +37,8 @@ XF_SOLVER = XFoilSolver(npan=XF_NPAN, max_iter=XF_MAX_ITER, ncrit=N_CRIT,
                         xtrip=(XTR_UPPER, XTR_LOWER), mach=XF_MACH)
 
 # VSM solver stability settings.
-RELAXATION         = 0.03   # iteration relaxation factor
-ARTIFICIAL_DAMPING = false   # smooth-circulation stabiliser for difficult cases
+RELAXATION           = 0.03   # iteration relaxation factor
+ARTIFICIAL_VISCOSITY = false  # post-stall stabiliser for difficult cases
 
 # V3_25.obj is already in slicer convention (x=chord, y=span, z=up).
 ROTATION = I
@@ -76,7 +76,7 @@ angle_range = range(-5, 25, length=31)
 println("\nCreating wing with CFD polars...")
 settings_cfd = VSMSettings("TUDELFT_V3_KITE/vsm_settings.yaml")
 settings_cfd.solver_settings.relaxation_factor = RELAXATION
-settings_cfd.solver_settings.artificial_damping = ARTIFICIAL_DAMPING
+settings_cfd.solver_settings.is_with_artificial_viscosity = ARTIFICIAL_VISCOSITY
 wing_cfd = Wing(settings_cfd)
 refine!(wing_cfd)
 body_cfd = BodyAerodynamics([wing_cfd])
@@ -91,7 +91,7 @@ VortexStepMethod.reinit!(body_nf)
 settings_nf = VSMSettings("TUDELFT_V3_KITE/vsm_settings.yaml")
 settings_nf.wings[1].geometry_file = nf_yaml
 settings_nf.solver_settings.relaxation_factor = RELAXATION
-settings_nf.solver_settings.artificial_damping = ARTIFICIAL_DAMPING
+settings_nf.solver_settings.is_with_artificial_viscosity = ARTIFICIAL_VISCOSITY
 solver_nf = Solver(settings_nf)
 
 # Compare CFD-polar and NeuralFoil-polar wings against published references

examples/bench.jl

@@ -68,7 +68,6 @@ body_aero = BodyAerodynamics([wing])
 vsm_solver = Solver(
     wing.n_panels, wing.n_unrefined_sections;
     aerodynamic_model_type=VSM,
-    is_with_artificial_damping=false,
     solver_type=LOOP,
 )
 

examples/linearize_check.jl

@@ -25,7 +25,6 @@ body_aero = BodyAerodynamics([wing])
 
 solver = Solver(wing.n_panels, wing.n_unrefined_sections;
     aerodynamic_model_type=VSM,
-    is_with_artificial_damping=false,
     rtol=1e-7,
     solver_type=LOOP,
     use_gamma_prev=false,