Take a live polar onto a wing whose table carries a delta axis

CHANGELOG.md

@@ -22,13 +22,16 @@
 
 ### Added
 
-- A `POLAR_VECTORS` panel's table can be rewritten at run time by `set_polar!`,
-  which is what a live polar source does every solve. The knots and values reuse
-  the panel's own storage, and the panel records the range the table covers, so
-  a table generated over a window around one angle of attack is held at its end
+- A panel's polar table can be rewritten at run time by `set_polar!`, which is
+  what a live polar source does every solve. The knots and values reuse the
+  panel's own storage, and the panel records the range the table covers, so a
+  table generated over a window around one angle of attack is held at its end
   values rather than extrapolated past them, and the stall-angle scan skips a
-  table that stops short of it. A rewritten table is an ordinary polar in every
-  other way: same evaluation, same `delta` handling, no separate aero model.
+  table that stops short of it. The table keeps the shape the panel was built
+  with, so a `POLAR_MATRICES` wing takes one too, at every `delta` it spans: a
+  regenerated polar carries its deflection as shape and says the same at each. A
+  rewritten table is an ordinary polar in every other way, with no separate aero
+  model.
 - Live in-memory polars in `AirfoilAero`: `KulfanBasis` and `deform_kulfan`
   deform a fixed Kulfan fit analytically (a matvec against a constant CST basis,
   never a refit, which is non-unique); `control_point_deflection` resamples a
@@ -81,6 +84,14 @@
   `KulfanParameters` moved from `AirfoilAero` into the core module for it; it is
   still exported from both.
 
+### Changed
+
+- A `POLAR_VECTORS` table of at most 24 angles now scans for its knot rather
+  than bisecting, which is faster at that length and is what a live polar's grid
+  is; longer tables keep the binary search. The knot container is part of a
+  panel's interpolation types, so which one a wing uses is fixed when it is
+  built.
+
 ## VortexStepMethod v4.2.0 2026-08-25
 
 ### Added

src/panel.jl

@@ -293,8 +293,11 @@ set_polar!(panel::Panel{<:Any, Nothing}, alphas, cl, cd, cm; shape=nothing) =
 """
     set_polar!(panel, alphas, cl, cd, cm; shape=nothing)
 
-Rewrite a panel's `POLAR_VECTORS` table with values at `alphas` [rad], ascending, and
-rebuild its interpolations. The panel's `alpha_ref` and `alpha_window` are taken from the
+Rewrite a panel's polar table with values at `alphas` [rad], ascending, and rebuild its
+interpolations. The table keeps the shape the panel was built with: a `POLAR_VECTORS`
+panel takes the angles as they are, and a `POLAR_MATRICES` panel takes them at every
+`delta` it already spans, since a regenerated polar carries its deflection as shape
+rather than as a flap angle and so says the same thing at each. The panel's `alpha_ref` and `alpha_window` are taken from the
 angles, so a table covering only a window around one angle is held at its ends rather than
 extrapolated past them (see [`window_alpha`](@ref)).
 
@@ -317,7 +320,7 @@ function set_polar!(panel::Panel, alphas, cl, cd, cm; shape=nothing)
         throw(ArgumentError("A polar table needs at least two angles."))
     issorted(alphas) ||
         throw(ArgumentError("A polar table needs ascending angles."))
-    panel.aero_model = POLAR_VECTORS
+    panel.aero_model = polar_model(panel.cl_interp)
     panel.alpha_ref = (alphas[1] + alphas[end]) / 2
     panel.alpha_window = (alphas[end] - alphas[1]) / 2
     panel.live_shape = shape
@@ -344,14 +347,30 @@ container, so the rebuilt object has the type the panel's field was parameterise
 Only the values need rebuilding — `Interpolations` holds the knots by reference — but
 they are what it copies, so the object is rebuilt until it can take them in place.
 """
-rebuild_polar(old, knots, values) =
+rebuild_polar(old::Interpolations.Extrapolation{<:Any, 1}, knots, values) =
     linear_interpolation(same_knots(old.itp.knots[1], knots), values;
                          extrapolation_bc=old.et)
 
+function rebuild_polar(old::Interpolations.Extrapolation{<:Any, 2}, knots, values)
+    deltas = old.itp.knots[2]
+    return linear_interpolation((same_knots(old.itp.knots[1], knots), deltas),
+                                repeat(values, 1, length(deltas));
+                                extrapolation_bc=old.et)
+end
+
 "The angles in the container the panel's interpolations were parameterised with."
 same_knots(::ScanKnots, knots) = ScanKnots(knots)
 same_knots(::AbstractVector, knots) = knots
 
+"""
+    polar_model(interp) -> AeroModel
+
+The model a rewritten table leaves the panel on: the one its interpolations were built
+with, since their shape is fixed by the panel's type.
+"""
+polar_model(::Interpolations.Extrapolation{<:Any, 1}) = POLAR_VECTORS
+polar_model(::Interpolations.Extrapolation{<:Any, 2}) = POLAR_MATRICES
+
 """
     reinit!(panel, section_1, section_2, aero_center, control_point, bound_point_1,
             bound_point_2, x_airf, y_airf, z_airf, delta, vec; kwargs...)

test/airfoil_aero/test_live_polar.jl

@@ -131,6 +131,33 @@ end
                                           zeros(5))
 end
 
+@testset "a rewritten polar lands on a matrix panel too" begin
+    # A wing whose offline polars carry a delta axis still has to take a live polar:
+    # the deflection is in the shape it was generated from, so the table says the same
+    # at every delta rather than having no answer for one.
+    alpha = collect(deg2rad.(-15.0:1.0:15.0))
+    delta = collect(deg2rad.(-40.0:10.0:40.0))
+    na, nd = length(alpha), length(delta)
+    grid = [0.1 * i for i in 1:na, _ in 1:nd]
+    data = (alpha, delta, grid, fill(0.02, na, nd), fill(-0.05, na, nd))
+    section = Section([0.0, 0.0, 0.0], [1.0, 0.0, 0.0], POLAR_MATRICES, data)
+    CL, CD, CM, CP = panel_interp_types(section, true)
+    panel = Panel{Float64, CL, CD, CM, CP}()
+    init_aero!(panel, section, section)
+
+    knots = collect(deg2rad.(-12.0:3.0:12.0))
+    cl = collect(range(0.0, 1.2, length(knots)))
+    set_polar!(panel, knots, cl, fill(0.03, 9), fill(-0.1, 9))
+
+    @test panel.aero_model == POLAR_MATRICES
+    @test calculate_cl(panel, knots[3]) ≈ cl[3]
+    # The flap axis is gone from the answer: every delta reads the same polar.
+    @test calculate_cl(panel, knots[3], deg2rad(-40.0)) ≈
+          calculate_cl(panel, knots[3], deg2rad(40.0)) ≈ cl[3]
+    # And it is held past the window it was sampled over, as on a vector panel.
+    @test calculate_cl(panel, deg2rad(40.0)) ≈ cl[end]
+end
+
 @testset "live polars" begin
     base = KulfanParameters(fill(0.15, 8), fill(-0.05, 8), 0.0, 0.0)
     n_panels = 3