Flow Over Bicycle

Aim: write program to calculate Drag force and plote graph of properties like

1] velocity vs Drag Force and

2] Drag coefficient vs Drag Force.

Discription: Drag force is an impotant factor considresion while design. There are many factor that effect the drag force like velocity ,frontal area, density of the Air and drag coieficient. Here we will calculate the drag force value and plote the graph.

Drag force equation:

Dag force = `0.5 ⋅ A ⋅ ẟ ⋅ C d ⋅ V ^2`

A= Frontal area m²

ẟ= density of air kg/m³

Cd= drag coieficent

V= velocity m/s²

Case-1: Intially we take input from user of Drag coificient, Area and velocity. We consider air density is 1.2 as costant. We take multipule value of velocity in array form. Next we calculate drag coeficent with Dag force = 0.5*A*ẟ*Cd*V² equation.

Then we get out put of diffent drag force. With the help of plot command we plote the graph of velocity vs drag force. And lebel it by xlabel to velocity Ylabel to drag force.

% Program to claculate the  drag force.
% Plot graph of  drag force vs velocity.
clear all
close all 
clc
% Inputs
% Drag coeficent
c_d=input('please enter drag coificent accoding to shape:\n');
% Frontal Area m^2
A=input('please enter Frontal area:\n');
% Density kg/m^3
rho=1.2;
% Velocity  
[v]=input('please enter  diffrent velocities values:\n');
% Formulae for drag force claculation
[drag_force] = rho*A*v.^2*c_d*0.5
% Plot velocity vs drag force
plot(v,drag_force,'color','r')
xlabel('velocity')
ylabel('drag_force')
grid on

Output:

please enter drag coificent accoding to shape:

0.8

please enter Frontal area:

00.5

please enter diffrent velocities values:

[1:10]

drag_force =

Columns 1 through 9

0.2400 0.9600 2.1600 3.8400 6.0000 8.6400 11.7600 15.3600 19.4400

Column 10

24.0000

Case-2: Intially we take input from user of Area. We consider velocity constant 40, air density is 1.2 as costant. We take multipule value of drag coeficient in array form. Next we calculate drag coeficent with Dag force = 0.5*A*ẟ*Cd*V² equation.

Then we get out put of diffent drag force. With the help of plot command we plote the graph of velocity vs drag force. And lebel it by xlabel to drag force Ylabel to drag coeficent.

% program to claculate the  drag force.
% Plot graph of  drag force vs drag coeficient.
clear all
close all 
clc
% Inputs
% Drag coeficent
c_d=[0.47 0.42 0.50 1.05 0.80 0.82 1.15 0.04 0.09];
% Frontal Area m^2
A=input('please enter Frontal area:\n');
% Density kg/m^3
rho=1.2;
% Velocity  
v=40;
% Formulae for drag force claculation
[drag_force] = rho*A*v^2*c_d*0.5

%Plot drag coeficient vs drag force
 plot(drag_force,c_d)
 xlabel('drag_force')
 ylabel('drag_coeficent')
 grid on

please enter Frontal area:
0.5

drag_force =

225.6000 201.6000 240.0000 504.0000 384.0000 393.6000 552.0000 19.2000 43.2000

Conclusion: from the plot of velocity vs drag force , it is clear that drag force increase rapidly when velocity increase.

Note:

• The frontal area is assumed that 0.5 m^2
• Velocity variation taken from 1 to 10.
• The drag force values is used for flate face, plate , prism .bullet,sphere ect.