drag-polarlisted

Use when you must compute the parabolic drag-polar of a wing from the zero-lift-drag coefficient cd0, the Oswald span-efficiency, and the aspect-ratio: calculate the induced-drag factor k with k = 1 / (pi * e * AR), the drag coefficient at a given lift coefficient, the lift-to-drag ratio at a point, and the maximum lift-to-drag ratio with its optimal lift coefficient. Also fit a parabolic drag-polar to two measured lift and drag points to recover cd0 and k. Produces the fitted polar coefficients and the peak performance values that gate the wing aerodynamic efficiency assessment. Trigger: drag-polar, parabolic, Oswald span-efficiency, induced-drag factor, aspect-ratio, cd0, lift-to-drag, max L/D, polar fit.
ashfordeOU/aero-agent-skills · ★ 0 · AI & Automation · score 78

Install: claude install-skill ashfordeOU/aero-agent-skills

# Parabolic Drag Polar Analysis (aerodynamics/drag-polars/drag-polar) Use when the task is wing-level drag modeling with the parabolic drag-polar: CD = CD0 + k * CL^2, where k = 1 / (pi * e * AR). ## Domain quick reference - Parabolic drag polar: CD = CD0 + k * CL^2, k = 1 / (pi * e * AR). - Oswald span-efficiency e is the ratio of ideal (elliptic loading) induced drag to the actual induced drag at the same lift and aspect ratio. e = 1 for elliptic loading; typical wings run 0.7 to 0.85. - AR = span^2 / area, dimensionless. CD0, CD, CL, and k are dimensionless coefficients. - Peak efficiency: cl_opt = sqrt(cd0 / k), L/D max = 1 / (2 * sqrt(cd0 * k)). - The quadratic fit from two points recovers k = (cd2 - cd1) / (cl2^2 - cl1^2) and cd0 = cd1 - k * cl1^2. - Validation anchor: NACA Report 824 (public domain) supplies measured section polars that a parabolic fit should reproduce within fit tolerance. ## Workflow 1. Gather CD0, Oswald span-efficiency e, and aspect-ratio AR for the wing. 2. Compute k with induced_drag_factor(e, ar). 3. Evaluate the polar at the design CL with drag_coefficient(cd0, cl, e, ar). 4. Score the point with lift_to_drag(cl, cd). 5. Find the peak with max_lift_to_drag(cd0, e, ar): cl_opt, ld_max. 6. Fit measured points with fit_parabolic_polar(cl1, cd1, cl2, cd2) to recover cd0 and k. ## Pitfalls - Accepting e <= 0 or e > 1 instead of rejecting it. - Fitting with coincident or antisymmetric cl points, which vanishes the denom