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Flight

Storyboard

To fly at a constant height the object (airplane / bird) must adjust the angle of attack of the wing to the propulsion so as to counteract the weight and maintain the desired speed.

>Model

ID:(1463, 0)



Mechanisms

Iframe

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Code
Concept
Flight, balance of forces
Force on the wing
Wing in the flow

Mechanisms

Flight, balance of forcesForce on the wingWing in the flow

ID:(15169, 0)



Wing in the flow

Concept

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If we assume that the flow around a wing is laminar, we can observe multiple layers surrounding the wing. Those on the upper side tend to be slightly longer due to the upward curvature, while the lower layers tend to be shorter and, therefore, closer to the wing.

Supposing that the flow is such that these layers converge in a way that points close together on either side of the wing return to the same relative position once the flow separates, the speed of the upper layers will necessarily be higher than that of the lower layers. It's important to keep in mind that this is just an assumption, and there is no real necessity for them to converge; in fact, they could end up being out of phase without any issues.

ID:(7016, 0)



Force on the wing

Concept

>Top


Since the velocity in the upper layers of the wing is greater than in the lower layers, this implies that the pressure on the upper surface of the wing is lower than on the lower surface.

This effectively means that there is a greater force from below the wing compared to above the wing, which leads to the generation of lift force.

ID:(7018, 0)



Flight, balance of forces

Concept

>Top


The forces that influence an aircraft or bird can be categorized into two fundamental groups:

Forces that impact the control of the center of mass's movement:

• the lift force (F_L), which counteracts the gravitational force (F_g).
• the propulsion force (F_p), which opposes the resistance force (F_W).

Forces aimed at achieving the rotation of the aircraft or bird around the center of mass, achieved through the ailerons on the wings and the rudder:

• Ailerons allow the generation of a turning moment by asymmetrically altering lift on each wing.
• The rudder controls the direction of the aircraft or bird by redirecting the airflow.

Boeing Images - 777-300ER Illustration in Boeing Livery



Key parameters for controlling the center of mass's movement are:

• the surface that generates lift (S_w) and the total object profile (S_p).
• the coefficient of lift (C_L) and the coefficient of resistance (C_W), the latter being dependent on the angle of attack of a wing (\alpha).

ID:(11080, 0)



Model

Top

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Parameters

Symbol
Text
Variable
Value
Units
Calculate
MKS Value
MKS Units
m
m
Body mass
kg
C_W
C_W
Coefficient of resistance
-
\rho
rho
Density
kg/m^3
g
g
Gravitational Acceleration
m/s^2
c
c
Proportionality constant coefficient sustainability
1/rad
S_w
S_w
Surface that generates lift
m^2
S_p
S_p
Total object profile
m^2

Variables

Symbol
Text
Variable
Value
Units
Calculate
MKS Value
MKS Units
\alpha_s
alpha_s
Angle required for lift
rad
F_g
F_g
Gravitational Force
N
F_L
F_L
Lift force
N
P
P
Power of flight
W
F_W
F_W
Resistance force
N
C_L
C_L
Simple Model for Sustainability Coefficient
-
v
v
Speed with respect to the medium
m/s
F_R
F_R
Total resistance force
N

Calculations


First, select the equation: to , then, select the variable: to
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_R = F_W *cos( alpha )+ F_L *sin( alpha ) F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) F_W = rho * S_p * C_W * v ^2/2 P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

Calculations

Symbol
Equation
Solved
Translated

Calculations

Symbol
Equation
Solved
Translated

Variable Given Calculate Target : Equation To be used
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_R = F_W *cos( alpha )+ F_L *sin( alpha ) F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) F_W = rho * S_p * C_W * v ^2/2 P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R




Equations

#
Equation

F_g = m g

F_g = m_g * g


F_L =\displaystyle\frac{1}{2} \rho S_w C_L v ^2

F_L = rho * S_w * C_L * v ^2/2


F_R = F_W \cos \alpha + F_L \sin \alpha

F_R = F_W *cos( alpha )+ F_L *sin( alpha )


F_R = \displaystyle\frac{1}{2} \rho S_p C_w v ^2 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v ^2}

F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2)


F_W =\displaystyle\frac{1}{2} \rho S_p C_W v ^2

F_W = rho * S_p * C_W * v ^2/2


P = F_R v

P = F_R * v


P =\displaystyle\frac{1}{2} \rho S_p C_W v ^3 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v }

P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v )

ID:(15170, 0)



Gravitational Force

Equation

>Top, >Model


The gravitational Force (F_g) is based on the gravitational mass (m_g) of the object and on a constant reflecting the intensity of gravity at the planet's surface. The latter is identified by the gravitational Acceleration (g), which is equal to 9.8 m/s^2.

Consequently, it is concluded that:

F_g = m g

F_g = m_g g

g
Gravitational Acceleration
9.8
m/s^2
5310
F_g
Gravitational Force
N
4977
m_g
m
Body mass
kg
6150
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

ID:(3241, 0)



Lift force

Equation

>Top, >Model


To generate higher pressure below than above the wing and generate lift, Bernoulli's principle is employed, correcting for the lack of energy density conservation using ($$). The pressure over the wing, the lift force (F_L), can be estimated using the density (\rho), the surface that generates lift (S_w), the coefficient of lift (C_L), and the speed with respect to the medium (v) through the following formula:

F_L =\displaystyle\frac{1}{2} \rho S_w C_L v ^2

\rho
Density
kg/m^3
5342
F_L
Lift force
N
6120
C_L
Simple Model for Sustainability Coefficient
-
6164
v
Speed with respect to the medium
m/s
6110
S_w
Surface that generates lift
m^2
6117
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

The lift force (F_L), along with the wing span (L), the density (\rho), the wing top speed factor (c_t), the wing bottom speed factor (c_b), the upper wing length (l_t), the bottom wing length (l_b), and the speed with respect to the medium (v), is found in

F_L = \rho L ( c_b l_b - c_t l_t ) v ^2



If we consider the surface that generates lift (S_w), given by the wing span (L), the upper wing length (l_t), and the bottom wing length (l_b),

S_w = \displaystyle\frac{1}{2} L ( l_t + l_b )



and for the coefficient of lift (C_L), defined as

C_L = 4\displaystyle\frac{ c_t l_t - c_b l_b }{ l_t + l_b }



we obtain

F_L =\displaystyle\frac{1}{2} \rho S_w C_L v ^2

ID:(4417, 0)



Total force of resistance

Equation

>Top, >Model


To calculate the total resistance force (F_R), we assume small angles and consider a situation where the angle is such that it maintains the body mass (m). Using this approximation and the variables the coefficient of lift (C_L), the coefficient of resistance (C_W), the surface that generates lift (S_w), the total object profile (S_p), the gravitational Acceleration (g), the proportionality constant coefficient sustainability (c), the density (\rho), and the speed with respect to the medium (v), we obtain the following expression:

F_R = \displaystyle\frac{1}{2} \rho S_p C_w v ^2 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v ^2}

m
Body mass
kg
6150
C_w
Coefficient of resistance
-
6122
\rho
Density
kg/m^3
5342
g
Gravitational Acceleration
9.8
m/s^2
5310
c
Proportionality constant coefficient sustainability
1/rad
6165
v
Speed with respect to the medium
m/s
6110
S_w
Surface that generates lift
m^2
6117
S_p
Total object profile
m^2
6123
F_R
Total resistance force
N
8480
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

Using the relationships of the total resistance force (F_R) with the lift force (F_L), the resistance force (F_W), and the angle of attack of a wing (\alpha):

F_R = F_W \cos \alpha + F_L \sin \alpha



we can calculate using the resistance force with the density (\rho), the coefficient of resistance (C_W), the total object profile (S_p), and the speed with respect to the medium (v):

F_W =\displaystyle\frac{1}{2} \rho S_p C_W v ^2



and the lift force with the surface that generates lift (S_w) and the coefficient of lift (C_L):

F_L =\displaystyle\frac{1}{2} \rho S_w C_L v ^2



using the relationship for the coefficient of lift (C_L) with the proportionality constant coefficient sustainability (c):

C_L = c \alpha



using the relationship for the sine of the small angle of attack \alpha:

\sin\alpha\sim\alpha



and the cosine:

\cos\alpha\sim 1



with the condition to balance the weight of the bird or aircraft for the body mass (m) and the gravitational Acceleration (g):

\alpha =\displaystyle\frac{2 m g }{ c \rho S_w }\displaystyle\frac{1}{ v ^2}



we obtain:

F_R = \displaystyle\frac{1}{2} \rho S_p C_w v ^2 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v ^2}

ID:(4546, 0)



Total resistance force calculation

Equation

>Top, >Model


The total force of resistance is composed of the horizontal components of the wing profile's resistance force F_W and the lift force F_L, which can be calculated from the angle of attack \alpha:

F_R = F_W \cos \alpha + F_L \sin \alpha

\alpha
Angle required for lift
rad
6167
F_L
Lift force
N
6120
F_w
Resistance force
N
6124
F_R
Total resistance force
N
8480
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

The horizontal component of the lift force corresponds to the force F_L multiplied by the sine of the angle of attack \alpha:

F_L \sin\alpha



And the horizontal component of the drag force corresponds to the force F_W multiplied by the cosine of the angle of attack \alpha:

F_W \cos\alpha



Therefore, the total resistance force can be calculated as:

F_R = F_W \cos \alpha + F_L \sin \alpha

ID:(9579, 0)



Resistance force

Equation

>Top, >Model


The resistance force (F_W) kann mit the density (\rho), the coefficient of resistance (C_W), the total object profile (S_p) und the speed with respect to the medium (v) entsprechend berechnet werden folgende Formel:

F_W =\displaystyle\frac{1}{2} \rho S_p C_W v ^2

C_W
Coefficient of resistance
-
6122
\rho
Density
kg/m^3
5342
F_W
Resistance force
N
6124
v
Speed with respect to the medium
m/s
6110
S_p
Total object profile
m^2
6123
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

Similarly to how the equation for the lift force (F_L) was derived using the density (\rho), the coefficient of lift (C_L), the surface that generates lift (S_w), and the speed with respect to the medium (v)

F_L =\displaystyle\frac{1}{2} \rho S_w C_L v ^2



in this analogy, what corresponds to the surface that generates lift (S_w) will be equivalent to the total object profile (S_p) and the coefficient of lift (C_L) to the coefficient of resistance (C_W), thus the resistance force (F_W) is calculated:

F_W =\displaystyle\frac{1}{2} \rho S_p C_W v ^2

The drag coefficient is measured and, in turbulent flows over aerodynamic bodies, values are generally found around 0.4.

ID:(4418, 0)



Flight power

Equation

>Top, >Model


Power P is the energy per unit of time that needs to be supplied to sustain a given force F_R. Therefore, it can be calculated based on the force by multiplying it by the velocity v:

P = F_R v

P
Power of flight
W
6331
v
Speed with respect to the medium
m/s
6110
F_R
Total resistance force
N
8480
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

The power is defined as the energy \Delta W per time \Delta t according to the equation:

P =\displaystyle\frac{ \Delta W }{ \Delta t }



Since energy is equal to force F multiplied by the distance traveled \Delta s, we have:

\Delta W = F \Delta s



Thus, we obtain:

P=\displaystyle\frac{\Delta W}{\Delta t}= F_R \displaystyle\frac{\Delta s}{\Delta t}



However, since the distance traveled in a time interval is the velocity v:

\bar{v} \equiv\displaystyle\frac{ \Delta s }{ \Delta t }



Finally, we can write the expression for power as:

P = F_R v

ID:(4547, 0)



General flight power

Equation

>Top, >Model


To obtain the power of flight (P), you need to multiply the total resistance force (F_R) by the speed with respect to the medium (v). Since the total resistance force (F_R) is a function of the density (\rho), the surface that generates lift (S_w), the total object profile (S_p), the coefficient of resistance (C_W), the proportionality constant coefficient sustainability (c), the body mass (m), and the gravitational Acceleration (g), which is equal to

F_R = \displaystyle\frac{1}{2} \rho S_p C_w v ^2 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v ^2}

,

the potential is

P =\displaystyle\frac{1}{2} \rho S_p C_W v ^3 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v }

m
Body mass
kg
6150
C_w
Coefficient of resistance
-
6122
\rho
Density
kg/m^3
5342
g
Gravitational Acceleration
9.8
m/s^2
5310
P
Power of flight
W
6331
c
Proportionality constant coefficient sustainability
1/rad
6165
v
Speed with respect to the medium
m/s
6110
S_w
Surface that generates lift
m^2
6117
S_p
Total object profile
m^2
6123
F_g = m * g F_L = rho * S_w * C_L * v ^2/2 F_W = rho * S_p * C_W * v ^2/2 F_R = rho * S_p * C_w * v ^2/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ^2) P = F_R * v P = rho * S_p * C_W * v ^3/2+2* m ^2* g ^2/( c ^2* S_w * rho * v ) F_R = F_W *cos( alpha )+ F_L *sin( alpha )alpha_smC_WrhogF_gF_LPcF_WC_LvS_wS_pF_R

The total resistance force (F_R) is a function of the density (\rho), the surface that generates lift (S_w), the total object profile (S_p), the coefficient of resistance (C_W), the proportionality constant coefficient sustainability (c), the body mass (m), and the gravitational Acceleration (g), which is equal to

F_R = \displaystyle\frac{1}{2} \rho S_p C_w v ^2 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v ^2}

,

therefore, using the equation for the power of flight (P)

P = F_R v

,

we obtain:

P =\displaystyle\frac{1}{2} \rho S_p C_W v ^3 + \displaystyle\frac{2 m ^2 g ^2}{ c ^2 S_w \rho }\displaystyle\frac{1}{ v }

.

ID:(4548, 0)