Determining Flow Type: Turbulent or Laminar?

In summary, turbulent flow is characterized by an unstable pressure differential across the sail, while laminar flow is required for generating lift on sailboats and aircraft wings. Reynold's number and appropriate characteristic data can be used to determine the type of flow. The links provided in the conversation offer further information on the topic.
  • #1
semc
368
5
Hey guys how do you know when will a flow be turbulent or laminar?i came across a question asking what's the flow of the wind on the sail of a sailboat.i thought that since there is the sail to block the wind when the boat is surfing against the wind, the flow will be turbulent but the ans is laminar flow :confused: any help on how to determine the flow?
 
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  • #2
Usually one uses Reynold's number with appropriate characteristic data to determine if the flow is laminar or turbulent.

If the flow was turbulent, the flow would not form a pressure differential across the sail. Aircraft wings/foils require laminar flow to generate lift. If the flow was turbulent, the low pressure area would not be stable.

This might be of interest - http://www.grc.nasa.gov/WWW/K-12/airplane/shortc.html

Also -
http://www.grc.nasa.gov/WWW/K-12/airplane/

http://history.nasa.gov/SP-367/contents.htm
 
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  • #3
wow thanks man the links are great!really wonder where i got the stupid idea that the flow above the aerofoil is turbulent...haha
 

1. What is the difference between streamline and turbulent flow?

Streamline flow refers to a smooth and orderly flow of a fluid, where the fluid particles move in a parallel direction and do not mix with each other. Turbulent flow, on the other hand, is a chaotic and irregular flow where the fluid particles mix and flow in different directions.

2. How is streamline flow beneficial?

Streamline flow is beneficial as it reduces friction between the fluid and the surface it is flowing over, resulting in lower energy consumption and less wear and tear on surfaces. It also allows for more precise and accurate flow measurements.

3. What causes turbulent flow?

Turbulent flow is caused by various factors such as high flow velocity, surface roughness, and sudden changes in the flow direction. These factors disrupt the smooth flow of the fluid and create chaotic movements.

4. Is it possible for a fluid to transition from streamline to turbulent flow?

Yes, it is possible for a fluid to transition from streamline to turbulent flow. This transition usually occurs when the flow velocity exceeds a critical value, and the flow becomes unstable, resulting in turbulence.

5. How is turbulent flow measured?

Turbulent flow is measured using various instruments such as anemometers, hot-wire probes, and laser Doppler velocimeters. These instruments measure the velocity and direction of the fluid particles, which can then be used to determine the level of turbulence in the flow.

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