FLOW OVER A BICYCLE

FLOW OVER A BICYCLE

AIM:- find the drag force occuring on a bicycle at various velocity & how the drag force increase with our bicycle velocity and at different drag co-efficient what is the value of drag force

objects:-

plot the graph by using MATLAB

1.velocity vs drag force

2.co-efficient of drag vs drag force

THEORY

If the bike and rider are considered to be a single system, the forces that act on that system and its components can be roughly divided into two groups: internal and external. The external forces are due to gravity, inertia, contact with the ground, and contact with the atmosphere. The internal forces are caused by the rider and by interaction between components.

External forces

As with all masses, gravity pulls the rider and all the bike components toward the earth. At each tire contact patch there are ground reaction forces with both horizontal and vertical components. The vertical components mostly counteract the force of gravity, but also vary with braking and accelerating. For details, see the section on longitudinal stability below. The horizontal components, due to friction between the wheels and the ground, including rolling resistance, are in response to propulsive forces, braking forces, and turning forces.

Aerodynamic forces due to the atmosphere are mostly in the form of drag, but can also be from crosswinds. At normal bicycling speeds on level ground, aerodynamic drag is the largest force resisting forward motion. At faster speed, aerodynamic drag becomes overwhelmingly the largest force resisting forward motion.

Internal forces

Internal forces, those between components of the bike and rider system, are mostly caused by the rider or by friction. In addition to pedaling, the rider can apply torques between the steering mechanism (front fork, handlebars, front wheel, etc.) and rear frame, and between the rider and the rear frame. Friction exists between any parts that move against each other: in the drive train, between the steering mechanism and the rear frame, etc

subject

Aerodynamic forces due to the atmosphere are mostly in the form of drag,but can also be from crosswinds.

At normal bicycling speeds on level ground, aerodynamic drag is the largest force resisting forward motion.

At faster speed, aerodynamic drag becomes overwhelmingly the largest force resisting forward motion.

so we are going to derive the drag force affecting

formula to derive drag force:-

is the drag force, which is by definition the force component in the direction of the flow velocity,(newtons)

is the mass density of the fluid(kg/m^3)

is the flow velocity relative to the object(m/s)

is the reference area(m^2)

is the drag coefficient – a dimensionless coefficient

note;-

C D {\displaystyle C_{D}} depends on the Reynolds number

program to calculate drag force to plot the graph b/w( velocity vs drag force) at varible velocitys

%calculating drag force for bicycle

% inputs
% drag coefficient

c_drag=[0.9]

% density kg/m^3

den=1.5 

% velocity

v=linspace(1,10,10)

% area m^2

a=0.3


drag_force=den*a*v.^2*c_drag*0.5

plot(v,drag_force)
xlabel('velocity');
ylabel('drag_force');
grid on 

result :-

program to calculate the drag force at different co-efficient of drag value

%calculating drag force for bycycle at different co-efficient drag


% inputs
% drag coefficient

c_drag=0.1:0.1:0.9

% density kg/m^3

den=1.5 

% velocity

v=2

% area m^2

a=0.3


drag_force=den*a*v.^2*c_drag*0.5

plot(c_drag,drag_force)
xlabel('c_drag');
ylabel('drag_force');
grid on 

result:-