Fundamentals of Fluid Mechanics Questions and Answers  
Question by AME536A Student
I got all the respective forces for all 3 dimensions using the momentum conservation equation from table, and then I have tried to get the resultant force for all 3 dimensions. The result have exceeded the correct answer. What have I made a mistake and missed?
Did you find the power needed to push the plow? The force that is asked for is the force you would use when calculating the power. If you don't get the answer listed within 1% accuracy, there is a (serious) flaw with your logic or a calculation mistake.
Question by AME536A Student
I'm having a hard time finding the logical flaw in my solution, I'm hoping you can point me in the right direction. I drew a control volume around the plow and used Bernoulli's equation ...(and more explanations..). This yields me with equations for each of the force components as follows:
$F_x=Bd\rho q^2(1+\sin({\theta})\cos({\theta}))$
$F_y=Bd\rho q^2\cos({\theta})$
$F_z=Bd\rho q^2\sin({-\theta})$
When I plug in the given values for the problem this yields a cumulative force $F=4045 N$
$F=\sqrt{(F_x)^2+(F_y)^2+(F_z)^2}$. I believe that the issue lies in $F_x$ as its value in this solution is $F_x=3317 N$, where the cumulative force of the correct solution is roughly 100N greater. Can you point me in the direction of where my mistake is?
I mentioned in class the difficulty to this problem is to get the correct direction of the reflected snow velocity vector. Your equations for the force show that you're not doing it correctly. Focus on finding correctly the reflected snow velocity direction.
Question by AME536A Student
Which part(s) of Problem 2 do the answers given correspond to?
Problem 2 of which assignment?
Question by AME536A Student
Problem 2 of the 2019 midterm (Pop Quiz 2). Also is the mass of the rotating upper wall negligible in your solution?
You should work out the problem on your own first without looking at the answers, and then check if some of your answers match those listed.
Question by AME536A Student
If we submit our answer early will you provide feedback on it (I understand the grade received would be that of the first submission)? I was able to solve the problem and get the same answer as the solution listed, but I have a sine in the numerator for the "e" term instead of cosine. I have looked through my work and cannot find the math error.
Better to work more on it and treat it as an assignment problem. A sin instead of a cos sounds like a big difference to me. Find ways to check your solution and come on this thread and discuss about why you think your answer is correct or incorrect.
Question by AME536A Student
How do we apply the mass conservation equation to a control volume with a working fluid that undergoes a phase change? For example, let us draw a control volume around a boiler (see image attached). Liquid water flows into the boiler at station 4, where it is then boiled and exits as gaseous steam at station 1. Please show how we would use the mass conservation equation
( $\frac{d}{dt}\int{\rho dV} +\int {\rho (\vec{v} \cdot \vec{n})dS}=0$) for this system?
We don't deal with phase change in this course. You can see this in the thermodynamics courses.
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