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In fluid dynamics, a flow in which liquid undergoes chaos and fluctuations or mixing is called turbulent flow. It lies parallel with the laminar flow, in which layers of fluid move without any disruption and smoothly. In the turbulent flow, the fluid receives disruptions due to changes in pressure and velocity. In turbulent flow, fluid does not flow in streamlines. Instead, it is a random disruptive flow. The calculations involving turbulent flow are very complex.
Streamline flow, also known as laminar flow, occurs in fluid substances. It is described as a flow where there is no mixing of layers, no turbulence, and no fluctuations in the velocity of the fluid particles, all of them remain constant. In contrast, to streamline flow, another flow is known as turbulent flow. Turbulent flow is when the fluid layers tend to cross each other and never move parallel to each other, and may meet at some point.
In the turbulent flow, the fluid receives disruptions due to changes in pressure and velocity.
WHAT ARE STREAMLINES?
Streamlines are defined as directly elected by the particles of the fluids below constant flow circumstances. If we constitute the flow lines with curves, Then the tangent drawn from any point on the curve tells us about the direction of the fluid velocity at the point given to us.
EXAMPLES OF STREAMLINED FLOW
- Blood flow in veins
- Water coming out from a tap
- Smoke coming out from a cigarette till few centimeters
- Water fountains placed in gardens
- Flow in rivers and canals
- Flow in water balloons
- Aircraft flying at a constant speed
- Viscous fluid like honey
Examples Of Turbulences
The following depicts the turbulences in real-life events:
- Smoke rising from a cigarette. For the initial few centimetres, the smoke shows features of laminar flow, but after rising, it changes to turbulent flow.
- Flow over the golf ball.
- Clear air turbulence is usually experienced during flight take-offs.
- Oceanic and mixed atmospheric layers, along with strong oceanic currents.
- Flow of blood through arteries during heart conditions
- Piers in water as water moves softly around the legs while the river’s flow is soft.
STREAMLINE AND TURBULENT FLOW
The difference between streamline and turbulent flow could be understood with the following:
The difference between streamline and turbulent flow could be understood with the following:
S.no | STREAMLINE FLOW | TURBULENT FLOW |
1. | In this fluid flow, the fluid layers move parallel and never tend to meet and cross each other | In this fluid flow, the fluid layers tend to cross each other and never move parallel to each other, and may meet at some point. |
2. | This flow is evident in the fluids that flow with low velocity. | This flow is evident in the fluids that flow with high velocity. |
3. | Laminar flow is experienced in the small diameter pipes where fluid flows with low velocity. | Turbulent flow is experienced in large diameter pipes where fluid flows with high velocity. |
4. | The fluid flow is laminar when calculated Reynolds number (Re) is less than or equal to 2000. | The fluid flow is turbulent when the calculated Reynolds number is greater than or equal to 4000. |
5. | The amount of stress in laminar flow lies in the viscosity of the fluid. | The amount of stress in the turbulent flow lies upon the density of the fluid. |
6. | The fluid flow runs in an orderly manner, i.e., there is no mixing or meeting of side layers of the fluid, and they keep moving parallel to each other. | The fluid flow doesn’t run in an orderly manner, i.e. there is mixing and meeting of side layers at some point with each other, and they do not move parallel to each other. |
LAMINAR AND TURBULENT BOUNDARY LAYERS
A boundary layer is defined as both laminar and turbulent. A laminar boundary layer is referred to when the flow is in different layers, i.e. when layers move smooth and glide over side layers. On the other hand, a turbulent boundary layer is inferred as one where the flow of layers keeps on mixing.
REYNOLDS NUMBER FORMULA
The formula for the Reynolds number could be written as:
Re= VL
Where,
ρ = density of fluid
V = velocity of fluid
μ = viscosity of fluid
L = length or diameter of the fluid.
Based on the different values of Re, we can infer that:
- If Re < 2000, the flow is called Laminar
- If Re > 4000, the flow is called turbulent
- If 2000 < Re < 4000, the flow is called transition.
REYNOLDS NUMBER UNITS
The variables in Reynolds number possess different units. These are as follows:
- R in the Reynolds number is unitless
- ρ in the fluid density is taken in kilograms-per-cubic-meter (kg/m3)
- v in the velocity is taken in meters-per-second (m/s)
- D in the diameter of the pipe is always in meters (m)
- μ in the viscosity of the fluid is taken in pascal-seconds (Pa⋅s)
Conclusion:
This article explains about streamline and turbulent flow. In the streamline flow the fluid layers move parallel and never tend to meet and cross each other. This flow is evident in the fluids that flow with low velocity. Example of streamline flow are, blood flow in veins, water coming out from a tap, smoke coming out from a cigarette till few centimeters and many more. In the turbulent flow, the fluid layers tend to cross each other and never move parallel to each other, and may meet at some point. This flow is evident in the fluids that flow with high velocity. Some example of turbulent flow are, flow over the golf ball, clear air turbulence is usually experienced during flight take-offs, oceanic and mixed atmospheric layers, along with strong oceanic currents.
