Lab 04: Forces and Moments on a Canard Delta Wing

Lab Overview

Course: AE 315 – Experimental Aerodynamics, Section 04 (Robert Bryan) | April 4, 2025
Objective: Use the ERAU Micaplex closed-circuit wind tunnel and an external six-component force balance to measure lift, drag, side force, and pitching, rolling, and yawing moments on a canard-delta wing model across a wide angle-of-attack range and two yaw conditions.
Tunnel: Embry-Riddle Micaplex Wind Tunnel (closed-circuit)
Model geometry: Main wing S_w = 242.01 in², c_w = 9.88 in, b_w = 24.5 in; Canard S_c = 71.97 in², c_c = 5.68 in, b_c = 12.67 in
Test matrix: 75 fps and 100 fps × 0° and 10° yaw; AoA swept −4° to 34° in 2° increments
Ambient conditions: P = 102,438 Pa, T = 295.15 K, ρ = 1.205 kg/m³

Micaplex wind tunnel test section

Canard-delta wing model on force balance

Six-component force balance sting mount

Procedure & Methodology

Before extracting aerodynamic forces, tare corrections were applied using the image–invert method: the model was run in its normal orientation (image) and then inverted, and the average of those readings subtracted from the test data to eliminate structural and gravitational interference loads. Data was collected at four conditions: 0° yaw at 75 fps and 100 fps, and 10° yaw at 75 fps and 100 fps.

Lift, drag, side force, pitch, roll, and yaw were read directly from the WAFBC force balance output. Each force was normalized by dynamic pressure and reference area to produce non-dimensional coefficients: C_L = Lift/(qS_w), C_D = Drag/(qS_w), C_m = Pitch/(qS_w c_w), C_l = Roll/(qS_w b_w), C_n = Yaw/(qS_w b_w). A quadratic drag polar (C_D = C_D0 + K C_L²) was fit to extract parasitic drag and induced drag factor.

Reynolds numbers based on mean wing chord were computed from the "Reynolds Number per ft" column in the raw data files and scaled to the wing geometry. A 1% systematic uncertainty was assumed for all force balance outputs per the Micaplex calibration specification.

Lift vs AoA — 4 conditions (Fig. 1)

Drag vs AoA (Fig. 2)

Side Force vs AoA (Fig. 3)

Results & Analysis

C_L increased nearly linearly with AoA up to ≈25°, after which flow separation caused a gradual roll-off rather than a sharp stall, characteristic of delta wing vortex lift.
Higher Reynolds numbers (100 fps) produced marginally higher C_L at a given AoA and lower C_D due to improved flow attachment.
10° yaw had negligible influence on lift but introduced measurable side force and increased yawing moment across the AoA range.
C_D rose steeply above 15° AoA as separated flow and vortex breakdown increased pressure drag.
C_m increased with pitch angle, reflecting a growing nose-up pitching moment; higher Re amplified this trend.
C_l and C_n remained near zero at 0° yaw; at 10° yaw, both showed small but consistent offsets consistent with lateral asymmetry.

Re	Speed	Yaw	Best C_L/C_D	Best AoA
4.61 × 10⁵	75 fps	0°	4.21	12°
6.10 × 10⁵	100 fps	0°	3.77	12°
4.60 × 10⁵	75 fps	10°	3.19	12°
6.09 × 10⁵	100 fps	10°	2.67	12°

Lift Coefficient vs AoA (Fig. 7)

Drag Polar — CL vs CD (Fig. 9)

Lift-to-Drag Ratio vs AoA (Fig. 10)

MATLAB Code

Raw force balance data was loaded from CSV files for each test condition. Aerodynamic tares were applied before computing non-dimensional coefficients. Below is a representative excerpt; the full script is AE315_LAB4.m.

% Apply aerodynamic tares: image-invert method
lift0_75 = yaw0_75data.("WAFBC Lift") ...
         - image0_75data.("WAFBC Lift")(2:2:end) ...
         + invert0_75data.("WAFBC Lift")(2:2:end);

% Non-dimensional coefficients
q  = mean(yaw0_75data.("Dynamic Pressure"));  % psf
sw = 242.01;  % in² reference area
CL = lift0_75 ./ (q * sw);
CD = drag0_75 ./ (q * sw);

% Drag polar curve fit: CD = CD0 + K*CL^2
[p, ~] = polyfit(CL, CD, 2);
CD0 = p(3);   % parasitic drag
K   = p(1);   % induced drag factor

% Reynolds number from tunnel data
RE0_75 = mean(yaw0_75data.("Reynolds Number per ft"));

Full MATLAB script — AE315_LAB4.m

Tare data files (image/invert CSVs)

Force balance output column layout