Flow over Bicycle- Python

Drag Force Calculations for Flow Over Bicycle

1.AIM:

• To calculate drag force acting on a cyclist driving the cycle using Python.

2.GOVERNING EQUATIONS IF ANY:

`(F)= 1/2 ρAV^2 C_d`

Where, `ρ`= density of the fluid in which cycle and cyclists exist ()

A= Frontal area / front area of exposure of cyclist ()

v= velocity of the cyclist respective to the fluid ()

C_d= Drag coefficient (unitless)

Pressure = and thus, Drag Force = Pressure x Area x (some constant)

So, we get Drag Force (F) = A

3.OBJECTIVES OF THE PROJECT:

• To find the total drag force acting on cyclist and cycle travelling with some velocity through a fluid medium.
• Write a python program to calculate drag force against a cyclist.
• Write a program to plot Velocity vs Drag force.
• Write a program to plot Drag Co-efficient vs Drag force.

4.FLOW OF THE PROJECT

1. Assign values to the input variables.
2. Get the value of drag force using the formula.
3. Plot the graphs mentioned in the objectives.

5.PYTHON CODE

• plot for velocity vs drag force

import matplotlib.pyplot as plt 

#plot for velocity vs drag force
#inputs

#Coefficent of Drag as an array
cd=0.8

#Density (kg/m^3)
rho=1.2   

#frontal Area(m^2)
A=0.1

#velocity as an array (m/s)
v=[4 ,4 ,6 ,8 ,10 ,12]

c=0.5                                  #for putting in formula

drag_force=[]
for velocity in v:                     #for loop to repeat process for all values of velocity
	a= c*cd*rho*A*velocity*velocity    #Drag force value stored in a
	drag_force.append(a)               #append all the values in drag force list.
plt.figure(1)
plt.plot(v,drag_force)                 #plot the data
plt.xlabel('velocity')                 #label x axis as velocity
plt.ylabel('Drag Force')               #label y axis as Drag Force
plt.savefig("plot1.png")               #save
plt.show()                             # show

• Plot for cd and Drag Force

import matplotlib.pyplot as plt 
#plot for cd and Drag Force
#inputs

#Coefficent of Drag as an array
cd=[0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.15]

#Density (kg/m^3)
rho=1.2   

#frontal Area(m^2)
A=0.1

#velocity as an array (m/s)
v=8

c=0.5                                  #for putting in formula

drag_force=[]
for Coefficent in cd:                     #for loop to repeat process for all values of velocity
	a= c*Coefficent*rho*A*v*v             #Drag force value stored in a
	drag_force.append(a)                  #append all the values in drag force list.
plt.figure(2)
plt.plot(cd,drag_force)                 #plot the data
plt.xlabel('cd')                 #label x axis as velocity
plt.ylabel('Drag Force')               #label y axis as Drag Force
plt.savefig("plot2.png")               #save
plt.show()                             # show

6.OBSERVATION:

Figure 1: Velocity vs. Drag Force

Figure 2: Drag Coefficient vs Drag Force

7.CONCLUSION:

• From figure 1, we can say that as velocity increases, drag force also increases. The plot verifies the quadratic nature of the direct proportion of drag force with velocity.
• From figure 2, we can say that as drag coefficient increases, drag force also increases. The plot verifies the linear nature of direct proportion of drag coefficient with drag force.