Boggling result of venturi experiment

[charitym]

Hi! I'm boggled by the results of my experiment...maybe you can help me... I made an improvised venturi meter which I used to determine for the velocity of water flowing in a pipe. Then just to confirm my velocity value I allowed the water to just gush out of the venturi meter (disconnected on the outflowing part) then I measured the height and maximum distance of its trajectory (by the way the pipe & venturi meter set-up were horizontal) and solve for the water velocity using equations of projectile motion. The velocity computation I got using the second method was much less than the one I got using the venturi meter. I wanted to account for the head loss when I stumbled into the Darcy-Weisbach equation... can I use it to solve for the head loss in the conical portions of the venturi meter? If yes, can you help me how? If no...any idea what alternative method I can use? Thanks in advance!

 

[FredGarvin]

First thing I would do is to repeat your test but instead of calculating the distance/trajectory stuff, simply allow the flow to be collected in a bucket or graduate cylinder to measure the volume. That is going to be much easier and more reliable than the previous method you chose. By your descriptions, I am doubtful about your method using projectile motion equations.

 

[sir-pinski]

Hi there! It sounds like you have conducted a very interesting experiment. I can understand your confusion with the results, as they seem to contradict each other. However, there are a few things to consider when analyzing the data.

Firstly, it is important to remember that the venturi meter measures the average velocity of the water flow, while the projectile motion method measures the maximum velocity at one specific point in the flow. It is possible that there is a difference in these values due to variations in the flow throughout the pipe.

Additionally, the Darcy-Weisbach equation is typically used for calculating head loss in a straight pipe, not in a venturi meter with conical portions. It is possible to use it, but it may not give an accurate result due to the unique shape of the venturi meter.

One alternative method you could try is using the Bernoulli's equation, which relates the velocity of a fluid to the pressure and height of the fluid. By measuring the pressure at different points in the venturi meter, you may be able to calculate the head loss.

I hope this helps! Good luck with your experiment.