Aerodynamic Tool — 01

AIRFOIL DESIGN

Define your operating conditions to find a matching airfoil from the database, design a custom shape, or apply to a wing.

How the Search Algorithm Works

NoteThis is NOT a shape optimization. It is a drag minimization search across a database of pre-analyzed airfoils, enforced by your geometric constraints.

• 1. Hard Constraints

The database is first filtered by your geometric requirements. Airfoils falling outside your Thickness or Camber ranges are immediately discarded. Max Cm acts as a stability filter.

• 2. Aerodynamic Operating Points

For each speed entry, the system calculates the required lift coefficient and Reynolds number based on your wing geometry.

• 3. Performance Interpolation

The remaining airfoils are searched for polars matching your target \(Re\). Drag is linearly interpolated at the exact required \(C_L\). If stall occurs, a heavy penalty is applied.

• 4. Weighted Suitability Calculation

A global cost function sums the drag scores from all operating points. This cost is mapped to a percentage score, where 100% represents minimal drag across the envelope.

Vehicle Definition

m²

Mass is the load this one surface carries under L = m·g — for a main wing that is the whole craft. A stabiliser or tailplane usually sees a different, sometimes downward, trim load: mark that operating point Constraint below and enter the load directly in newtons instead of back-solving a mass. A constraint point is checked, not scored — the search keeps only sections that reach that load with margin (at most 90% of Clmax at that Reynolds number, or of the negative stall for a downward load, Gudmundsson's stall check) and excludes the rest, saying why.

If you do not know that load, connect an assistant — it can solve the moment balance from your fuselage length, CG and main-foil lift, and hand you a load in newtons to type here directly. A downward load is entered as a negative number; note that a cambered section is not symmetric in ±C_L, so its drag at a negative constraint is not simply its drag at the mirrored positive one.

Environment

Flight Envelope

Unit
Speed
Kind
Wt. / Load

Optional Filters

Selection Criteria

Drag only (default)

By default the search ranks candidates on drag alone, exactly as it always has. Raise the other sliders to score a decision matrix instead (after Gudmundsson §8.3.9): each criterion is scaled across the candidates that match your operating points, multiplied by its weight and summed — lowest total ranks first. Every result on the next page shows where it stood on each one.

Preset
×1

CD at each operating CL, weighted by the operating points — the only criterion the default ranking uses

×0

pre-stall lift peak at the main operating Re

×0

share of lift lost 3° past the peak; a gentle stall scores better than a higher, abrupt one

×0

mean |Cm| at the operating points; a large moment becomes trim drag

×0

Clmax divided by minimum CD at the main operating Re

×0

degrees between the best-L/D angle and the main operating angle

Airfoil Design | Foil.tools