Flow of an incompressible liquid

Storyboard

When a liquid is in motion, we refer to it as flow, and its measurement is based on the volume that passes through a section in a given period of time. Assuming that the volume moves without deformation, the velocity at which the liquid passes through the section remains constant. In this case, flow can also be defined as the product of velocity and the cross-sectional area.

>Model

ID:(875, 0)



Flow of an incompressible liquid

Storyboard

When a liquid is in motion, we refer to it as flow, and its measurement is based on the volume that passes through a section in a given period of time. Assuming that the volume moves without deformation, the velocity at which the liquid passes through the section remains constant. In this case, flow can also be defined as the product of velocity and the cross-sectional area.

Variables

Symbol
Text
Variable
Value
Units
Calculate
MKS Value
MKS Units
$j_{s1}$
j_s1
Flux density 1
m/s
$j_{s2}$
j_s2
Flux density 2
m/s
$\Delta s_1$
Ds_1
Length of element 1
m
$\Delta s_2$
Ds_2
Length of element 2
m
$r_1$
r_1
Radius of Section 1
m
$r_2$
r_2
Radius of Section 2
m
$S_1$
S_1
Section in point 1
m^2
$S_2$
S_2
Section in point 2
m^2
$\Delta t$
Dt
Time elapsed
s
$J_{V1}$
J_V1
Volume flow 1
m^3/s
$J_{V2}$
J_V2
Volume flow 2
m^3/s
$\Delta V_1$
DV_1
Volume of the element 1
m^3
$\Delta V_2$
DV_2
Volume of the element 2
m^3

Calculations


First, select the equation:   to ,  then, select the variable:   to 

Symbol
Equation
Solved
Translated

Calculations

Symbol
Equation
Solved
Translated

 Variable   Given   Calculate   Target :   Equation   To be used



Equations

Flow is defined as the volume the volume element ($\Delta V$) divided by time the time elapsed ($\Delta t$), which is expressed in the following equation:

equation=4347

and the volume equals the cross-sectional area the section Tube ($S$) multiplied by the distance traveled the tube element ($\Delta s$):

equation=4346

Since the distance traveled the tube element ($\Delta s$) per unit time the time elapsed ($\Delta t$) corresponds to the velocity, it is represented by:

equation=4348

Thus, the flow is a flux density ($j_s$), which is calculated using:

equation

Flow is defined as the volume the volume element ($\Delta V$) divided by time the time elapsed ($\Delta t$), which is expressed in the following equation:

equation=4347

and the volume equals the cross-sectional area the section Tube ($S$) multiplied by the distance traveled the tube element ($\Delta s$):

equation=4346

Since the distance traveled the tube element ($\Delta s$) per unit time the time elapsed ($\Delta t$) corresponds to the velocity, it is represented by:

equation=4348

Thus, the flow is a flux density ($j_s$), which is calculated using:

equation


Examples


mechanisms

During a time elapsed ($\Delta t$), the fluid with a mean Speed of Fluid ($v$) moves a tube element ($\Delta s$). If the section ($S$) represents the amount of fluid crossing that section in the time elapsed ($\Delta t$), it is calculated as:

$\Delta V = S \Delta s = Sv \Delta t$



This equation states that the volume of fluid flowing through section the section ($S$) during a time elapsed ($\Delta t$) is equal to the product of the cross-sectional area and the distance the fluid travels during that time.

image

This facilitates the calculation of the volume element ($\Delta V$), which is the volume of fluid flowing through the channel in a specific period of the time elapsed ($\Delta t$), corresponding to the volume flow ($J_V$).

equation=4347

Flow is defined as the volume the volume element ($\Delta V$) divided by time the time elapsed ($\Delta t$), which is expressed in the following equation:

equation=4347

and the volume equals the cross-sectional area the section Tube ($S$) multiplied by the distance traveled the tube element ($\Delta s$):

equation=4346

Since the distance traveled the tube element ($\Delta s$) per unit time the time elapsed ($\Delta t$) corresponds to the velocity, it is represented by:

equation=4348

Thus, the flow is a flux density ($j_s$), which is calculated using:

equation=4349

It is important to note that in this model:

The flow density acts as an average velocity across the entire flow section.

Considering a tube that neither leaks nor receives additional liquid, the flow entering at point 1 The volume flow 1 ($J_{V1}$) will be equal to the flow exiting at point 2 The volume flow 2 ($J_{V2}$):

equation=939

Within a channel or tube, there may be a change in cross-sectional area, either widening or narrowing.

image

This variation will directly affect the flow through the flux density ($j_s$), which represents the velocity, increasing (if the section narrows) or decreasing (if it widens) according to the section Tube ($S$) to keep the volume flow ($J_V$) constant, as indicated by:

equation=4349

The conservation of flow, along with the definition of flow density, leads to the conservation law such that the section in point 1 ($S_1$), the section in point 2 ($S_2$), the flux density 1 ($j_{s1}$), and the flux density 2 ($j_{s2}$) satisfy:

equation=4350

The continuity equation assumes that the flow is uniform, with no reverse flows or turbulence present. Therefore, it is necessary to verify that the flow is indeed laminar and free of turbulence, especially when applying the equation to analyze fluid flows in pipes and channels.

There are various methods for detecting turbulence in the flow, such as using flow meters or visually observing the flow. It is essential to ensure that the flow is stable before applying the continuity equation, as any disturbance in the flow can affect the accuracy of the calculations and the overall efficiency of the system.


model

If we have a tube with a the section Tube ($S$) moving a distance the tube element ($\Delta s$) along its axis, having displaced the volume element ($\Delta V$), then it is equal to:

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If we have a tube with a the section Tube ($S$) moving a distance the tube element ($\Delta s$) along its axis, having displaced the volume element ($\Delta V$), then it is equal to:

kyon

The volume flow ($J_V$) corresponds to the volume flowing ($\Delta V$) flowing through the channel at the time elapsed ($\Delta t$). Therefore, we have:

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The volume flow ($J_V$) corresponds to the volume flowing ($\Delta V$) flowing through the channel at the time elapsed ($\Delta t$). Therefore, we have:

kyon

The flux density ($j_s$) is related to the distance traveled in a time ($\Delta s$), which is the distance that the fluid travels in the time elapsed ($\Delta t$), as follows:

kyon

The flux density ($j_s$) is related to the distance traveled in a time ($\Delta s$), which is the distance that the fluid travels in the time elapsed ($\Delta t$), as follows:

kyon

A flux density ($j_s$) can be expressed in terms of the volume flow ($J_V$) using the section or Area ($S$) through the following formula:

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A flux density ($j_s$) can be expressed in terms of the volume flow ($J_V$) using the section or Area ($S$) through the following formula:

kyon

One of the most basic laws in physics is the conservation of mass, which holds true throughout our macroscopic world. Only in the microscopic world does a conversion between mass and energy exist, which we will not consider in this case. In the case of a fluid, this means that the mass entering through a pipe must be equal to the mass exiting it.

If density is constant, the same applies to volume. In such cases, when we treat the flow as an incompressible fluid, it means that a given volume entering one end of the pipe must exit the other end. This can be expressed as the equality between the flow in Position 1 ($J_1$) and the flow in Position 2 ($J_2$), with the equation:

kyon

The surface of a disk ($S$) of ERROR:5275.1 is calculated as follows:

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The surface of a disk ($S$) of ERROR:5275.1 is calculated as follows:

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The principle of continuity dictates that the flow at the first point, which is equal to the flux density 1 ($j_{s1}$) times the section in point 1 ($S_1$), must be equal to the flow at the second point, given by the flux density 2 ($j_{s2}$) times the section in point 2 ($S_2$). From this, it follows that:

kyon


>Model

ID:(875, 0)



Mechanisms

Definition


ID:(15485, 0)



Volume flow

Image

During a time elapsed ($\Delta t$), the fluid with a mean Speed of Fluid ($v$) moves a tube element ($\Delta s$). If the section ($S$) represents the amount of fluid crossing that section in the time elapsed ($\Delta t$), it is calculated as:

$\Delta V = S \Delta s = Sv \Delta t$



This equation states that the volume of fluid flowing through section the section ($S$) during a time elapsed ($\Delta t$) is equal to the product of the cross-sectional area and the distance the fluid travels during that time.



This facilitates the calculation of the volume element ($\Delta V$), which is the volume of fluid flowing through the channel in a specific period of the time elapsed ($\Delta t$), corresponding to the volume flow ($J_V$).

ID:(2212, 0)



Volume Flow and its Speed

Note

Flow is defined as the volume the volume element ($\Delta V$) divided by time the time elapsed ($\Delta t$), which is expressed in the following equation:



and the volume equals the cross-sectional area the section Tube ($S$) multiplied by the distance traveled the tube element ($\Delta s$):



Since the distance traveled the tube element ($\Delta s$) per unit time the time elapsed ($\Delta t$) corresponds to the velocity, it is represented by:



Thus, the flow is a flux density ($j_s$), which is calculated using:



It is important to note that in this model:

The flow density acts as an average velocity across the entire flow section.

ID:(15715, 0)



Variable section channel

Quote

Considering a tube that neither leaks nor receives additional liquid, the flow entering at point 1 The volume flow 1 ($J_{V1}$) will be equal to the flow exiting at point 2 The volume flow 2 ($J_{V2}$):



Within a channel or tube, there may be a change in cross-sectional area, either widening or narrowing.



This variation will directly affect the flow through the flux density ($j_s$), which represents the velocity, increasing (if the section narrows) or decreasing (if it widens) according to the section Tube ($S$) to keep the volume flow ($J_V$) constant, as indicated by:



The conservation of flow, along with the definition of flow density, leads to the conservation law such that the section in point 1 ($S_1$), the section in point 2 ($S_2$), the flux density 1 ($j_{s1}$), and the flux density 2 ($j_{s2}$) satisfy:

ID:(2213, 0)



Validity of Continuity Equation

Exercise

The continuity equation assumes that the flow is uniform, with no reverse flows or turbulence present. Therefore, it is necessary to verify that the flow is indeed laminar and free of turbulence, especially when applying the equation to analyze fluid flows in pipes and channels.

There are various methods for detecting turbulence in the flow, such as using flow meters or visually observing the flow. It is essential to ensure that the flow is stable before applying the continuity equation, as any disturbance in the flow can affect the accuracy of the calculations and the overall efficiency of the system.

ID:(978, 0)



Model

Equation


ID:(15488, 0)