DFDC — Ducted Fan Design Calculator

Blade Element Momentum Theory · Axisymmetric Duct Analysis · Based on DFDC v0.70

Not run yet Press ▶ Calculate to run the DFDC panel solver.

Flow Conditions

Freestream Vinf 0 m/s

Rotor RPM 1,875

Atmosphere

Density ρ (kg/m³)

Altitude (m)

Speed of sound (m/s)

V_ref for Cp (m/s)

Viscosity μ (Pa·s)

Wake length X_D/L

Disk Geometry

Tip Radius (m)

Hub/Tip Ratio

Tip Gap (m) DFDC default 0 · not stored in .case

Disk position X/L fraction of duct chord

Blade Design

Blades B

Radial Stations N = # blade sections

Root Chord (m) 0.059

Tip Chord (m) 0.038

Root Pitch (deg) 73.0

Tip Pitch (deg) 30.0

Disk Definition (per-station)

Disk type choose Bladed rotor to define blade sections below

Blade sections define r, chord, β° at each radial station (overrides root/tip sliders)

# blade sections

raw / paste (r chord β per line)

Disk X (absolute, m) same position as “Disk position X/L” — kept in sync

Stator / 2nd Disk OFF

Drag Objects (optional)

Drag objects one row: x r CDA

# points

raw / paste (x r CDA per line)

Airfoil Lookup

Aero Sections (airfoil polar per span)

Section interpolation how properties blend between xi sections

DFDC: computes CL/CD at each bounding section, then linearly blends the results by FRAC=(xi−xi₁)/(xi₂−xi₁) — matches DFDC.exe. Parameters: linearly blends a0/dCLdα/CLmax… first, then computes CL/CD. (Same in the linear range; differs only at stall/clamp.)

Aero sections define airfoil properties at each span fraction xi = r/R_tip

# aero sections

raw / paste (xi a0 dCLdα CLmax CLmin CDmin CL@CDmin dCD/dCL² per line)

Each row = an airfoil polar at span fraction xi = r/R_tip (1 row = uniform blade). Auto-filled from the loaded case.

Duct Wall Geometry

Duct Chord (m)

Wall Thickness (m)

Inlet Expansion R_in/R_tip 1.060

Diffuser Angle (deg) 3.0

Lip Radius / Chord 0.040

Airfoil Shape Modifiers

Thickness / Chord (t/c) 0.12

Δ Chord (%) 0

Δ Thickness (%) 0

Independent Shape Controls

Δ Camber (%c) 0.0

Camber Position (%c) 40

Max-Thickness Position (%c) 30

LE Radius 1.00

TE Thickness (%c) 0.0

Incidence (deg) 0.0

Throat r Offset (%) 0

Duct Wall Coordinates

Paste the duct wall X R profile, or use the Centerbody tab to upload a full .case file (auto-extracts duct + centrebody).

Duct Wall X R

Duct Thrust Solver

● Duct thrust is computed directly by the DFDC axisymmetric panel method from the duct + centrebody geometry — no manual efficiency needed. Run Calculate to solve.

Advanced — hover fallback efficiency (only used if no geometry loaded)

Fallback η_d 0.42

Auto: 0.42 = [0.20 + 7·r_lip/c]·[1−0.028·α_diff]·[0.80 + 2·(R_in/R−1)]. This empirical estimate is used only when the panel solver can't run (no duct/CB coordinates). With geometry loaded it is ignored.

Centerbody

The inner body is a solid centrebody on the axis (DFDC standard). Set it parametrically or load a .case / coordinates below, then press Calculate.

CB Chord (m)

CB Max Radius (m)

Δ CB Length (%) 0

Δ CB Radius (%) 0

Upload Geometry Coordinates

Upload a DFDC .case file to auto-extract both profiles, or paste X R coordinates manually.

Centerbody X R

The duct wall is on the Duct tab. Apply uses both the centrebody and duct coordinate boxes.

Spinner-Ducted Mode

Models the inner body as a spinner: a closed aerofoil ring at the hub radius with an open centre hole (air flows through). In meridional section it shows an upper and lower aerofoil; the blades span from the spinner's outer surface to the duct's inner surface. Same DFDC panel solve, but the centrebody is replaced by this hollow spinner. Needs a duct loaded for the full solve.

Parametric Aerofoil Ring

Outer radius / blade root (m) 0.085

Hole radius (m) 0.030

Chord / axial length (m) 0.090

Section

Outer surface peaks at the blade root, inner surface at the hole edge; centre below the hole is open. The ring is centred near the rotor disk; generating sets the rotor hub radius to the spinner outer radius.

Or load spinner coordinates

Paste the spinner meridional profile as X R (nose→tail, r ≥ 0), or upload a file.

Spinner X R

Forces (N)

—

N

Total Thrust

—

N

Rotor Thrust

—

N

Duct Thrust

—

N

Rotor Blade Drag

already in Rotor & Total Thrust — don't add

Duct & Centerbody Viscous Drag

Note: Total Thrust and Power above are inviscid — they do NOT include this duct/centerbody viscous drag. Subtract it from Total Thrust for the viscous net; Power/Torque are the inviscid shaft values.
Limitation: this is skin-friction (viscous) drag only. The duct pressure (form) drag — the thrust lost when the inner-wall boundary layer separates and the suction recovery collapses — is not modelled (DFDC/ESOTEC compute only attached-wall friction). On a separated duct the true loss is larger than the friction shown here; capturing it needs viscous-inviscid coupling beyond this tool.

—

N

Duct Viscous Drag

—

N

Centerbody Viscous Drag

—

N

Net Duct (incl. visc.)

Power & Torque

—

N·m

Rotor Torque

—

W

Shaft Power

—

rpm

Rotor Speed

Performance

—

—

Figure of Merit

—

%

Prop. Efficiency

—

N/m²

Disk Loading

Flow

—

m/s

Axial Velocity at Disk

—

m/s

Tip Speed

—

—

Tip Mach

Configuration

Disks: — Drag objects: — 2nd rotor/stator: —

Per-Disk Forces & Viscous Breakdown

Disk	# blades	RPM	Thrust (N)	Torque (N·m)	Power (W)	Tvisc (N)	Pvisc (W)	radius (m)
—

Drag Objects

—

Pressure Distribution — Cp vs X

Radial Blade Loading vs r/R

Duct Cross-Section (x – r plane) 🔍 Click to enlarge

Per-Station Blade Distribution

i	r/R	c/R	β (deg)	CL	Cd	Mach	B·Gam
— (actuator-disk cases have no blade table)

DFDC.exe — Raw Output & Case

Raw DFDC.exe console output

Press ▶ Calculate to run DFDC.exe.

Case file fed to DFDC.exe

(the .case assembled from your inputs appears here)