Aerodynamic analysis

Raven

Flight model · 10 October 2026

24 CFD solutions: α 0° to 14°, sideslip, 12 control deflections

Wing area: 0.494 m²
Span: 2.49 m
Aspect ratio: 12.6
Mean chord: 0.214 m
Mass: 9.5 kg
CG from the nose · 25% MAC: 0.420 m
Cruise speed: 20 m/s
Reynolds number: 2.9 × 10⁵

Pressure on Raven. Surface pressure from the solver’s wall values at α 2°, 20 m/s. Suction (blue) on the upper wing pulls it up; red marks the stagnation lines on the leading edges and nose. — **Pressure on Raven**Surface pressure from the solver’s wall values at α 2°, 20 m/s. Suction (blue) on the upper wing pulls it up; red marks the stagnation lines on the leading edges and nose.
Pressure coefficient Cp
−1.520.00+1.31

1Summary

Best glide

13.5L/D

at α 4°, CL 0.99

Stall speed

15.2m/s

CLmax 1.33 at α 8°, 9.5 kg

Power at 20 m/s

140W

airframe drag × speed · L/D 13.3

Static margin

37%MAC

stable in pitch

Best glide 13.5 at α 4°. At 9.5 kg that is 17.7 m/s for the longest range; minimum power, 113 W, comes at 15.4 m/s for the longest endurance.
Cruise at 20 m/s: L/D 13.3. Needs CL 0.77 at about α 2.0°. Airframe drag costs 140 W before propeller and motor losses.
Stall at α 8°, CLmax 1.33. At 9.5 kg the stall speed is 15.2 m/s in sea-level air.
Stable in pitch · margin 37%. Neutral point 0.50 m behind the nose (62% MAC); with neutral controls it trims at α -1.2° (CL 0.40, extrapolated).
Weathercock stable. Cnβ 0.055 and Clβ 0.024 per radian from the 5° sideslip run.

2The aircraft and the method

Raven was analysed from Raven.step (5 parts, 100,006 surface triangles; 1.31 × 0.43 × 2.49 m). Coefficients use the wing area, mean chord and span above; moments are taken about the centre of gravity, 0.420 m behind the nose (25% of the mean chord).

Steady, incompressible RANS (OpenFOAM) with the k-ω SST turbulence model and the γ–Reθ transition model (SST-LM), on body-fitted meshes of 5.6–6.3 million cells with 20 prism layers resolving the boundary layer (first-cell y+ 0.5 at the 95th percentile). The aircraft is pitched by α and yawed by β in a box several body lengths across, at 20 m/s in sea-level air (ρ 1.225 kg/m³) with 0.25% freestream turbulence. Loads are averaged over each solution’s final iterations.

Control and sideslip derivatives come from steady, incompressible RANS (OpenFOAM) with the k-ω SST turbulence model, on body-fitted meshes of 2.0–2.1 million cells with wall functions, as increments from the neutral case at α 2° on the same mesh.

3The flow around Raven

From the solution at α 2° and 20 m/s, as is the pressure picture on the first page: the solver’s wall pressures, cuts through its mesh and streamlines through its flow.

Upper surface. Seen from above, nose up, in 12 bands of Cp. — **Upper surface**Seen from above, nose up, in 12 bands of Cp.
Pressure coefficient Cp
−1.520.00+1.31

Lower surface. Seen from below, nose up; the same scale. — **Lower surface**Seen from below, nose up; the same scale.
Pressure coefficient Cp
−1.520.00+1.31

Flow around the wing section. A cut through the wing 40% of the way to the tip, in the air’s frame (the wing at 2°). Colour is the local speed; the white lines follow the flow in the cut. — **Flow around the wing section**A cut through the wing 40% of the way to the tip, in the air’s frame (the wing at 2°). Colour is the local speed; the white lines follow the flow in the cut.
Speed |U| / U∞
0.551.001.45

The wake, seen from behind. A cross-flow cut just behind the tail, with Raven’s outline faintly behind it. Colour is the speed the air has lost; the lines show the air’s sideways motion, turning round the two tip vortices and down between them. — **The wake, seen from behind**A cross-flow cut just behind the tail, with Raven’s outline faintly behind it. Colour is the speed the air has lost; the lines show the air’s sideways motion, turning round the two tip vortices and down between them.
Speed lost 1 − Ux / U∞
0.000.200.40

Streamlines. Air released ahead of Raven just above the wing, traced by the solver through its solution and coloured by speed. It speeds up as it passes over the wing (orange), the low pressure that carries the aircraft, then slows again and leaves the trailing edge turned down. — **Streamlines**Air released ahead of Raven just above the wing, traced by the solver through its solution and coloured by speed. It speeds up as it passes over the wing (orange), the low pressure that carries the aircraft, then slows again and leaves the trailing edge turned down.
Speed |U| / U∞
0.551.001.45

4Aerodynamics

Lift curveCLα 6.54 per radian; zero lift at α -4.7°; CLmax 1.33 at α 8°

Drag polarLowest drag 0.0481 at CL 0.53 (α 0°)

Lift to dragBest 13.5 at α 4°

Pitching moment about the CGZero at α -1.2° (extrapolated) with neutral controls

α	CL	CD	L/D	Cm
0°	0.533	0.0481	11.1	-0.051
2°	0.767	0.0578	13.3	-0.135
4°	0.989	0.0731	13.5	-0.218
6°	1.199	0.0920	13.0	-0.293
7°	1.298	0.1023	12.7	-0.323
8°	1.327	0.1205	11.0	-0.355
9°	1.290	0.1449	8.9	-0.379
10°	1.173	0.1814	6.5	-0.495
12°	1.116	0.2361	4.7	-0.539
14°	1.081	0.2924	3.7	-0.603

Neutral controls, β 0°. Lift and drag in wind axes; Cm about the CG on the mean chord, nose-up positive.

5Stability and control

Static margin

37%MAC

typically 5–20% for a stable aircraft

Neutral point

0.50m

62% MAC, behind the nose

Elevator to trim at 20 m/s

−3.8°

at α 2.0°, CL 0.77; trailing edge up

dCm/dCL

-0.366

the static margin with its sign flipped

Sideslip derivative (β 5° at α 2°)	Per radian	Reading
Side force CYβ	-0.413	Restoring
Roll Clβ (dihedral effect)	0.024	Rolls into the slip
Yaw Cnβ (weathercock)	0.055	Stable

Control effectiveness

Per degree of deflection	∂CL/∂δ	∂Cm/∂δ	∂CY/∂δ	∂Cl/∂δ	∂Cn/∂δ	ΔCD at ±10°
Aileron	−0.0001	+0.0001	−0.0002	+0.0053	−0.0002	+0.0070 / +0.0068
Elevator	+0.0101	−0.0360	−0.0000	+0.0000	−0.0000	+0.0016 / +0.0067
Rudder	−0.0000	+0.0001	+0.0043	−0.0005	−0.0014	+0.0047 / +0.0049

From ±5° and ±10° deflections at α 2°, 20 m/s. Body axes: Cl rolls right, Cm pitches nose-up and Cn yaws nose-right when positive.

6Performance

Stall speed

15.2m/s

CLmax 1.33 at α 8°, 9.5 kg

Best range speed

17.7m/s

L/D 13.5

Best endurance

15.4m/s

113 W airframe power

At 20 m/s

140W

L/D 13.3 · α 2.0°

Power to fly level · 9.5 kgDrag × speed, airframe only

Efficiency against speedLift to drag along the level-flight line

Speeds are true airspeed at sea level. Electrical power is higher: divide by the propeller’s efficiency (typically 0.6–0.75) and the motor’s and ESC’s (0.8–0.9).

AComputations

Case	Model	Cells	Iterations	Wall time	Loads
α 0°	SST-LM, wall-resolved	5.60 M	607	1 h 20 min	Steady loads
α 2°	SST-LM, wall-resolved	5.65 M	575	1 h 18 min	Steady loads
α 4°	SST-LM, wall-resolved	5.76 M	730	1 h 36 min	Steady loads
α 6°	SST-LM, wall-resolved	5.79 M	803	1 h 42 min	Steady loads
α 7°	SST-LM, wall-resolved	5.90 M	939	1 h 58 min	Steady loads
α 8°	SST-LM, wall-resolved	5.90 M	1063	2 h 14 min	Steady loads
α 9°	SST-LM, wall-resolved	5.94 M	1157	2 h 28 min	Steady loads
α 10°	SST-LM, wall-resolved	6.05 M	1004	2 h 15 min	Steady loads
α 12°	SST-LM, wall-resolved	6.14 M	864	1 h 58 min	Steady loads
α 14°	SST-LM, wall-resolved	6.29 M	681	1 h 37 min	Steady loads
α 2° · control baseline	SST, wall functions	2.04 M	404	52 min	Converged
α 2° · β 5°	SST, wall functions	2.05 M	404	42 min	Converged
α 2° · aileron −10°	SST, wall functions	2.04 M	404	42 min	Converged
α 2° · aileron −5°	SST, wall functions	2.04 M	404	46 min	Converged
α 2° · aileron +5°	SST, wall functions	2.04 M	404	54 min	Converged
α 2° · aileron +10°	SST, wall functions	2.04 M	404	54 min	Converged
α 2° · elevator −10°	SST, wall functions	2.04 M	404	53 min	Converged
α 2° · elevator −5°	SST, wall functions	2.04 M	404	53 min	Converged
α 2° · elevator +5°	SST, wall functions	2.04 M	404	53 min	Converged
α 2° · elevator +10°	SST, wall functions	2.04 M	404	54 min	Converged
α 2° · rudder −10°	SST, wall functions	2.04 M	404	54 min	Converged
α 2° · rudder −5°	SST, wall functions	2.04 M	404	53 min	Converged
α 2° · rudder +5°	SST, wall functions	2.04 M	404	53 min	Converged
α 2° · rudder +10°	SST, wall functions	2.04 M	404	53 min	Converged

Generated by Deneb Aero from the solutions above.