Determination of drag force on a bicycle using MATLAB

OBJECTIVES

• To calculate the value of drag force using MATLAB
• Plot velocity vs drag force
• Plot drag coefficient vs drag force

THEORY

A person riding a bicycle would experience a drag force and it can be found out using the following formula;

df=(1/2)*d*v^2*A*cd

where df= drag force experienced by the rider and bicycle, d=density of the medium around the bicycle which is air in this case (the density of air is kept at 1.225 according to International Standard Atmosphere), A=frontal area, cd=drag coefficient which would change according to the shape of frontal area.

In this project, the relationship between drag force and velocity is found out by keeping drag force constant and similarly, the relationship between drag coefficient and drag force is found out by keeping velocity constant.

PROGRAM

clear all
close all
clc
%program plotting Velocity vs Drag force and Drag-coefficent vs Drag force

%density of air in kg/m^3
rho=1.225

%frontal area in m^2
A=0.5

%dragcoefficient
cd=1.1

%velocity
v=[1:10];

%dragforce
df=rho*A*v.^2*cd*0.5;
plot(v,df)
xlabel('Velocity')
ylabel('Drag force')
grid on

%when drag coefficient is varying
cdv=[0,3];

%velocity is assumed to be a constant
v2=5
df2=rho*A*v2.*cdv*0.5;
figure(2)
plot(cdv,df2)
xlabel('Drag coefficient')
ylabel('Drag force')
grid on

RESULTS AND CONLUSION

Figure 1

Figure 2

From Figure 1, we can observe that the graph follows a parabolic path and the relationship between drag force and velocity is found out to be linear, similarly, from Figure 2 we can observe that the graph follows a linear path and hence it can be concluded that the drag force and drag coefficent has a linear relationship.