Fundamentals of Fluid Mechanics Questions and Answers

Question by AME536A Student For the midterm exam, you excluded certain derivations as a possibility of being on the exam. Are these same exclusions applied to the Final Exam?	12.14.19

The problems A1Q1, A1Q3, A4Q1, A6Q1, A6Q2, A7Q3 are excluded from the final. All other problems given in the assignments are included.

Question by AME536A Student Is the final at 10AM on Tuesday 12/17 in the normal room?	12.16.19

As noted in the Syllabus, the final exam is given at the time specified by UA: ​ https://www.registrar.arizona.edu/cours ... -fall-2019

Question by AME536A Student I put some more thought on your question about ‘Industry/academia’ and here are some thoughts. I think Eng. undergraduate programs do not prepare students to do industry work and I think the reasons are the following: (1) Too much material per class. (2) Lack of soft skills. (3) Professors lack industry experience. (1) Imagine that there is water (knowledge) pouring out from a fire hydrant (engineering classes) at very high pressure. Your job as a student is to use a bucket and collect all this water (knowledge) pouring out from the fire hydrant (engineering classes). Every bit of water that you are not able to collect is the knowledge that you are not learning. That's how all my undergrad Eng. classes were, and I have talked to undergrad students in other engineering programs and they feel the same way. However, I don’t think this is entirely bad. In the case of a graduate program, you take fewer classes. Ergo, you are given more time to learn the material. (2) Because (1) companies do hire undergrads knowing that they have to spend a lot of time training them. However, they don’t want to spend much time teaching them soft skills. Companies know that a 4.0GPA doesn’t mean that the student will be successful in the industry. However, they do know that someone with soft skills (public speaking, teamwork, communication, leadership, flexibility, etc) is more willing to succeed in the industry than someone with only a 4.0GPA and no soft skills. Engineering classes do not incentivize students to develop their leadership skills, public speaking skills, collaboration skills. Some do but not many and this is why many 4.0GPA students can not find jobs while 2.5GPA students can find jobs. The biggest misconception is that a good GPA will get you a job, and many students focus all their energy in finding the right answer to get the perfect score instead of joining an organization such as Engineering Without Borders (EWB) that will help them develop the skills needed to be successful in the industry. (3) Professors who have never worked in the industry don’t understand the differences between work in industry and research. Ergo, their teaching techniques/style are focus to develop researchers over engineers fit to do industry work. For example, professors without industry experience tend to focus more on theoretical understanding and memorization. From my experience in the industry, the classes that I took were more oriented to build a strong connection between the theory and the application by understanding how and why the theory is making your application better and/or the limits that the theory has in the applications on the real world.

08.27.20

But this doesn't answer why someone with a M.A.Sc. or a Ph.D. is very well prepared for industry work (according to the Raytheon and Honeywell managers we spoke to) while those who only took courses and didn't do a thesis are not.. ​ If some of your friends have problems finding a job, tell them to come and join my lab or one of my colleagues' laboratories: Raytheon indicated to me recently they would hire anyone graduating with a PhD from my lab.

Question by AME536A Student I think that writing a thesis/dissertation will force you to develop some skills that someone who has not done that doesn’t have. I think that to write a thesis/dissertation you first have to define a problem, and understanding the import of it. Then you have to think and figure out how to solve the problem (critical thinking); after that you need to defend/present (public speaking) your solution and finally you have to write it down (technical writing). You will also learn networking skills in conferences. I do agree that having a thesis helps you to be more prepare for industry work. However, this does not guarantee that you will be sucessfull in the industry. During my time at Raytheon I mainly worked with PhD's and MS's (thesis option), and the most sucessful engineers there were the ones with higher soft skills and EQ. Even the fellow engineers that I had the chance to work with, had a lot of soft skills, tech skills and were very passionate about mentoring and sharing their experiences and mistakes with new engineers. Just because you can be hire at a company doesnt mean that you will be sucessful on it. And Raytheon will def hired people from your lab because of the tech skills that they learn on it, but I am not sure that just having the techincal skills is all you need to be succesful on industry.

I can see how personality (soft skills) matters especially for the management positions. It's not so different in academia: personality plays a significant role in being famous/successful. But, technical/scientific skills (hard skills) also matter and are in demand. Whether in industry or academia, someone has to invent new stuff at one point and get things to work! Hard skills are needed for that. I see a thesis in academia as being not so different as a project in industry. You need to take your responsibilities and get the job done right and not halfway, or you'll be in hot waters.

Question by AME536A Student For problem $\#3$. Are we missing the lengths from $h_a, L_w$, I was trying to calculate them using trig functions but I am missing dimensions. Fluids Hmwk.pdf	09.11.20

No, this would over specify the problem. Also, when showing drawings/figures on this thread, use a png or jpg format and include them within your text so that they are easier to read.

Question by AME536A Student For homework 2 question 3, does the mass sit at the end of the plate? If not, what is the length of the plate?	09.13.20

The mass sits at a distance $L$ from the hinge as indicated on the figure. The plate end is located a bit farther away. You can indicate it with another symbol, $L_2$, if you wish.

Question by AME536A Student Continuation from the previous question ("For homework 2 question 3, does the mass sit at the end of the plate? If not, what is the length of the plate?"): Is the difference between the length of the plate (L), and the distance of the mass from the hinge ($L_{2}$) negligible?

In solving problems in this course, you'll need to make assumptions here and there. List the assumptions made along with your answer and if one is wrong or superfluous I will let you know.

Question by AME536A Student Hello Dr. Parent. For Homework #3, Problem #1, is y=0 defined as the centerline of the duct (blue line in attachment) or is y=0 defined as the bottom edge of the duct (red line in attachment)? The location of the axes in the problem located on the bottom edge combined with the shape of the $\overrightarrow{v_1}$ equation strongly implies y=0 is defined as the bottom edge, but I want to confirm before finishing working through the problem. Thank you!

09.22.20

I can't see any attachment. Also, you should include your figures inline within the text using the inline button, and preview.

Question by AME536A Student Pardon the submission issue, this is my first time asking a question here. I realized my question also incorrectly referenced Homework #3, Question #1. I meant Homework #3, Question #2 (the first question we are asked to solve). Here is the figure I mistakenly didn't include the first time:

Yes, $y=0$ refers to the bottom of the duct, not the centerline.

Question by AME536A Student Are the answers given for prob #2 right? There are 4 answers and problem 2a is asking for 2 forces, one on $\hat{x}$ and one on $\hat{y}$. Would you mind checking this please?	09.29.20

Yes the answers for A4Q2 are correct. I see no issues.

Question by AME536A Student I have a question about Prob.#3 in the assignment 3. Can $\mathbf{\dot m_{12}}$ be obtained using the given conditions in the problem? Are there some missed conditions in order to get $\mathbf{\dot m_{12}}$?	10.01.20

Yes, you can obtain $\dot{m}_{12}$ from the given properties.

Question by AME536A Student I am still struggling to solve the #Prob 3 in the assignment. Is the mass flow rate of air added in each tank equal to the mass flow rate of water displaced out of each tank? In other words, is $\mathbf{\dot m_{12}}$ displaced out of tank 1 equal to $\mathbf{\dot m_{air1}}$ flowing into tank 1 ?	10.02.20

No, $\dot{m}_{12}$ is not equal to $\dot{m}_{\rm air1}$. This is not a steady-state problem.

Question by AME536A Student Hello Dr. Parent, I am resolving homework #3 problem 3 and am having issues when trying to solve for $\dot{m}_{wout}$. After integrating the mass conservation equation with respect to dS (setting the control volume to contain both chambers) I end with $\rho_{air}\dot{V}_{Air}+\rho_{w}\dot{V}_{win}=\rho_w\dot{V}_{wout}$ We know $\dot{V}=\frac{\dot{m}}{\rho}$, but if I plug it into the previous equation all the densities will cancel and I will be left with $\dot{m}_{win}+\dot{m}_{Air}=\dot{m}_{wout}$. Do you have any recommendations on where I am making my mistake?

10.07.20

I don't understand your approach. What does $\dot{V}$ stand for? Don't use this notation, this is confusing and will lead to errors. Use $dV/dt$ for the rate of change of the volume in time.

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