Flow through a pipe along a reduced diameter

[TSN79]

Imagine a pipe of d=50mm with water flowing through. The pipe's diameter is reduced along a small section to 40, and then returned to 50. If I have a flow of x l/s along the first 50mm piece, will I also get x l/s along and after the reduction? Will the only change be more speed through the reduced section and then back to normal, accompanied by a big pressure loss?

 

[Mech. Engineer]

actually the flow rate will be constant if it is one stream...

the velocity will increase in the 40...pressure will reduced...

then velocity will come back to its normal...

but with very long pipes the pressure will drop due to friction...

so it is not a must that the velocity and the pressure will be same at the

second 50 mm pipe...

 

[ravenprp]

The flow rate through a pipe is determined by various factors such as the pipe diameter, fluid velocity, and viscosity. In this scenario, the flow rate through the reduced section of the pipe may not necessarily be the same as the flow rate through the initial 50mm section.

When the pipe diameter is reduced, the fluid velocity increases due to the restriction of flow area. This increase in velocity can result in a decrease in pressure along the reduced section, known as pressure loss. This pressure loss can also be affected by the length and smoothness of the reduced section.

As the fluid exits the reduced section and returns to the original diameter, the velocity decreases back to its initial value and the pressure returns to normal. Therefore, the flow rate may not be the same along the entire pipe, but it will eventually return to its initial value after the reduction.

In summary, the flow rate through the reduced section may be different from the initial 50mm section due to changes in velocity and pressure. However, the overall flow rate will eventually return to its initial value after the reduction.