Reynolds number through a pipe

In summary, the Reynolds number for flow through a pipe changes along its length due to the increase in freestream velocity as the boundary layer thickens. This is because the Reynolds number is defined as the ratio of inertial to viscous forces, and with higher velocities in thicker boundary layers, the inertial forces increase. Additionally, the Reynolds number is proportional to velocity, assuming density, cross-sectional area, and viscosity are constant. As velocity increases, the boundary layer thickness decreases, resulting in a turbulent flow and a higher Reynolds number.
  • #1
Jonny6001
20
0
Hello, can someone tell me how the reynolds number for flow through a pipe change along it's length? Is the only method that the boundary layer gets thicker along the pipe so the freestream velocity increases? Assuming no gas temperature change along the pipe's length.
From thinking of the actual definition of the reynolds number, the ratio of inertial to viscous forces, I can see that the higher free stream flow in the thicker boundary layer regions would increase the local inertia force of the gas.

I would like someone just to clarify.

Thanks a lot.
 
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  • #2
My basic understanding as per the formula is Re no proportional to velocity.If considering density,c/s and viscocity factors constant,Re no depends upon velocity.Thus as the velocity increases,boundary layer thickness vanishes to zero,flow becomes turbulent and Re no is higher.

Only first part of your Q was understandable.
 

What is Reynolds number through a pipe?

The Reynolds number is a dimensionless quantity used in fluid mechanics to predict the type of flow that will occur in a given fluid or fluid mixture in a pipe. It is a ratio of inertial forces to viscous forces and is defined as the product of fluid velocity, pipe diameter, and fluid density divided by fluid viscosity.

Why is Reynolds number important in fluid mechanics?

Reynolds number is important because it helps determine the type of flow that will occur in a fluid or fluid mixture in a pipe. This is crucial in understanding the behavior of fluids in various applications such as in pipelines, pumps, and turbines. It also helps in predicting the occurrence of turbulence and can aid in optimizing the design and efficiency of fluid systems.

What is the significance of Reynolds number in pipe flow?

In pipe flow, Reynolds number is significant because it determines the type of flow that will occur, which can greatly affect the pressure drop, flow rate, and energy losses in the system. It is also used to determine the critical velocity, at which the flow transitions from laminar to turbulent, and to predict the occurrence of flow separation and cavitation.

What is the range of Reynolds number for laminar and turbulent flow?

The range of Reynolds number for laminar flow is typically less than 2300, while turbulent flow occurs at numbers greater than 4000. In the transitional range between 2300 and 4000, the type of flow depends on the specific fluid and pipe characteristics. For example, a smaller pipe diameter or higher fluid viscosity can result in a lower critical Reynolds number for turbulent flow.

How can Reynolds number be calculated?

Reynolds number can be calculated using the formula Re = (ρVD)/μ, where ρ is the fluid density, V is the fluid velocity, D is the pipe diameter, and μ is the fluid viscosity. The values for these parameters can be obtained experimentally or through known values for the fluid and pipe being used.

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