Chapter_12: Human-Powered Aircraft Wing Design: A Case Study in Aerodynamic Shape Optimization

musculair2

Human powered aircraft design is a caricature of the classic structural efficiency (thick, short wing) versus aerodynamic efficiency (thin, long wing) tradeoff. The `sport’ is going through a renaissance in the UK, with the advent of the Royal Aeronautical Society’s Icarus Cup, and the authors have been involved with the design of SUHPA (Southampton University Human Powered Aircraft). Here we will follow a basic planform optimization (see Chapter 8) and demonstrate the use of two aerofoil parameterization strategies from chapters 3 and 7 to optimize a wing for SUHPA for a steady, level flight speed of 12.5 m/s (world record speed) and a wing loading of 75 N/m^2 (based on previous aircraft data). The fluid dynamics analysis is be based on XFOIL, with which we have already showed how analyse parametric aerofoils in Chapter 11.

Our Aircraft Geometry Toolbox contains the functions used for this design example. To estimate the drag of a wing for SUHPA with a NACA44xx aerofoil (t/c is allowed to vary in the analysis) try the following script:

% set global parameters
global wingParameters constants
% constants
constants.g=9.81; % acceleration due to gravity [ms^-2]
constants.rho=1.2; % density of air [kgm^-3]
constants.nu=1.461e-5; % kinematic viscosity of air [m^2s^-1]
constants.V=12.5; % flight speed [ms^-1]
constants.xfoil_path=‘…’; % YOUR local file path
constants.file_path=‘…’; % YOUR Xfoil executable path
% wing parameters
wingParameters.loading=75; % wing loading [Nm^-2]
wingParameters.e=0.85; % Oswald efficiency (estimate!)
wingParameters.wSpar=50; % width of spar [mm]
wingParameters.tCap=2.0; % thickness of carbon pulstrusion [mm]
wingParameters.weight=850; % weight of aircraft minus wing [N]
wingParameters.deflection=600; % maximum deflection at tip [mm]
wingParameters.foil=‘naca44xx’; % aerofoil defintion type
b=20;  % wing span [m]
rootThick=100; % spar thickness at root [mm]
tipThick=50; % spar thickness at tip [mm] 
D=suhpadrag([b rootThick tipThick], 1); % calculate drag and plot results

This should yield a drag of 20.4 N and plot the airfoils and pressure profiles, as shown below. Of course the wing parameters and constants may be changed to your own design scenario. The book chapter details the use of various aerofoil parameterization methods and using the Matlab optimizers to design improved wings.

suhpadrag

 

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