Fundamentals of Fluid Mechanics Questions and Answers  
Question by AME536A Student
I am sorry about that. I will upload a question per post. Yes. $\alpha$ is 35 degree indicated in the assignment file. For the second question, I miss S, representing the distant from the hinge, on the right hand side, so my equation will be as follows. $$ \int_{S=0}^\frac{h}{sin\alpha} \rho g \left(h-Ssin\alpha \right)SD dS=\int_{S=0}^L \left(mgcos\alpha\right) SDdS $$ I replace 35 degree with $\alpha$ to make you understand better and define D as a variable of the depth. Thus, my equation means that the moment of plate developed by hydrostatic pressure is equal to that developed by the normal force of a mass. I was wondering if my equation is correct.
10.09.20
Yes this seems fine, but you're missing on the contribution from atmospheric pressure. If it cancels out, this should be shown.
Question by AME536A Student
For the prob #3 in the assignment 5, is that answer correct?
10.10.20
Yes the answers are correct. You should be able to get the same answer within 1% or less error.
Question by AME536A Student
Do we have enough conditions given in HW5 problem #2 to solve it? There have 1 continuity eq, 1 momentum eq (in one direction), 2 Bernoulli eqs. But the unknowns are the area at station 1, area/pressure/velocity at station 2 and 3. With 4 equations and 7 unknowns, am I missing any assumptions or relations here?
If you don't have enough equations for the number of unknowns, first try to solve the problem and it sometimes occurs that one unknown will cancel out and not affect the solution of the other unknowns. If this strategy doesn't work, you need to make assumptions so that the problem becomes solvable.
Question by AME536A Student
I have a question about the problem #3 in the assignment 5. Is the pipe suspended in the air by the holder? or are all components consisting of the system, including wedge, pipe and water, falling down by the gravitational acceleration?
10.11.20
Sure, the pipe and wedge are held at the same location with respect to the ground using a holder.
Question by AME536A Student
In problem 2 of homework 5 I am finding some difficulties with velocities at the outlets (sections 2 and 3). Using the mass conservation equation and the momemtum equation in the tangent direction of the plate I am able to find two equations to calculate the mass flow rates that the problem asks for as a function of the angle $\theta, q_{01}, q_{02}, q_{03}$.

In order to calculate $q_{02}$ and $q_{03}$ I intended to use Bernoulli's equation. However, if I neglect the gravity terms I end up getting, $$ q_{02}=q_{01} $$ $$ q_{03}=q_{01} $$ and then the equations I previously got make no longer sense. Where is the mistake in my reasoning?
I don't understand your question. First, you mention you can find the answer asked for if given $q_{01}$, $q_{02}$, etc. Then you find a way to determine these velocities. So what is your question?
Question by AME536A Student
My question is where am I wrong because if $q_{02}=q_{01}$ and $q_{03}=q_{01}$ then the result I get is an indetermination since my equation is, $$ \frac{m_{2}}{m_{1}} = \frac{q_{01}cos\theta - q_{03}}{q_{02}-q_{03}} $$
Ah, now I understand your question. Well, this means you made a mistake somewhere which you need to find... You can not have a division by zero here. Look into your solution carefully and find the bug.
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