Is There an Error in My Bernoulli's Equation Application for Fluid Dynamics?

[rambo5330]

attached is the problem. I use bernoulli's equation along a "streamline" from the inlet at point 1 to outlet at point 2. I do this to obtain the velocity V2. After working through it (simple algebra) I end up with 10.20 m/s ...seems right to me... however upon doing a conservation of mass analyses afterwards to get V3... I am getting 8.71 m/s this is nowhere on the multiple choice solution. This prof has been really really good at making sure the numbers are correct with very little round off error in the multiple choice options. It is possible that there is an error in the solutions but I think its more likely that I am doing something wrong.. Is it not correct to apply Bernoulli's equation to this example?

Thanks for any help! this is driving me crazy!

 

[LawrenceC]

The question asks for the velocity at the upper section which you calculate as 10.2 m/sec.
It is listed in the answers.

 

[rambo5330]

ya sorry ..I phrased it poorly.

I This question is part A. I can calculate a velocity 10.2 m/s which does appear on the list yes.

However when I move to part B it wans to know what the velocity V3 of the lower section is.
I use conservation of mass to determine this and i get an answer of 8.71. Which does not appear on the sheet. The closest is 8.60.

So my question is, is it correct to apply Bernoulli's law to this problem, and can anyone else confirm an answer of 10.2? for V2?

Thank you!

 

[rude man]

No contradiction. If they had given you the length of the bottom pipe you could have written a bernoulli streamline equation for water running from A1 to A3. Combined with mass flow conservation (since you now know the mass flow at A1 and at A2) you could have solved for v3 and p3 also.

 

[paranormal]

I would suggest double-checking your calculations and assumptions before assuming there is an error in the solutions. It is important to carefully follow the steps and equations in fluid dynamics problems, as even small errors can lead to significantly different results. It is also possible that there may be other factors or variables at play that could affect the outcome, so it is important to thoroughly analyze the problem and consider all possible factors. Additionally, it may be helpful to consult with a colleague or mentor for a second opinion or to discuss any potential errors or discrepancies. Remember to always approach scientific problems with a critical and analytical mindset, and don't hesitate to seek clarification or further guidance if needed. Good luck!