Questions tagged [flow]
The flow tag has no usage guidance.
20
questions
-2
votes
0answers
47 views
Factors affecting flow separation on wing
Got this question in my quiz and don´t know the correct answer, or if it´s even possible to determine a single one and why.
Which of the following parameters has the least effect on the flow ...
1
vote
0answers
23 views
What is the definition of flow angle of a blade?
I am confusing what is the flow angle of a blade with the angle of attack of a blade, so I was wondering if it was the same?
1
vote
3answers
162 views
How the pitch of a blade must change along the length so that the blade does not stall?
I have to finish an assignment in the next couple of days. One of the questions asks to show how the pitch of the blade must change along the length so that the blade does not stall. I have no idea ...
2
votes
1answer
63 views
What exactly happens to kinetic energy in the turbulent layer on an aerofoil?
Sources I've read contains contradicting information.
As far as I know, when the laminar airflow breaks up, it becomes a thicker and draggy layer, causing a layer of what essentially is slowed air; ...
6
votes
2answers
2k views
Why do planes employ vortex generators if the laminar flows exhibit a far lower skin friction drag than turbulent flows?
I am a student and still relatively new regarding fluid flows. Our professor asked this and I can't find a source to answer this question.
2
votes
1answer
149 views
Does an airfoil in supersonic flow have zero circulation?
In incompressible flow, the Kutta-Joukowski theorem can be used to relate the lift (per unit span) to the circulation around an airfoil. However, if we look at an airfoil or the flat plate (see below) ...
1
vote
2answers
143 views
Is it possible to have the laminar flow above $Re=10^7$?
For pipe flow I came across the information that the onset of turbulent flow occurs at approximately $Re=10^3$ to $Re=10^4$, while for boundary layers on the airfoil the onset occurs in between $Re=10^...
4
votes
2answers
365 views
Why can't commercial aircraft have a wing boundary layer suction system?
I've read that NASA's boundary layer suction system on the wings can reduce drag by removing the boundary layer through the suction holes. If this can reduce a lot of drag (hence improving fuel ...
25
votes
5answers
4k views
Why does airflow separate from the wing during stall?
What causes the airflow separation from the airplane wing, that triggers a stall?
To be more precise, what is the detailed explanation of the physics for why flow separation occurs at certain speeds ...
1
vote
1answer
707 views
Boundary layer momentum thickness
Could someone please explain the concept of the boundary layer momentum thickness and its difference to boundary layer thickness calculation? Some explanation about the application of the boundary ...
1
vote
0answers
88 views
What is subcritical and supercritical boundary layer?
What is subcritical and supercritical boundary layer?
What is the difference between them?
2
votes
1answer
4k views
What causes the adverse pressure gradient that leads to flow separation?
When reading about flow separation I generally see a diagram like this:
imp source: Wikimedia commons
This shows that the boundary layer slows as it passes over the wing, eventually creating an ...
2
votes
1answer
418 views
What is the fuel mass flow rate at stationary full power for the CFM56 5C2/3C1 engines?
Does anyone know what is the value of fuel mass flow rate when stationary at full power for CFM56-5C2 or CFM65-3C1 turbofan engines? I am doing a work on engine performance and it seems that only ...
1
vote
1answer
2k views
How to calculate the static pressure in a pitot tube?
In a pitot-static tube, we have two different pressure, the static pressure $p_s$ and the total pressure $p_0 = p_s + \frac{1}{2}\rho v^2$, which comes from the Beroulli equation for incompressible ...
9
votes
2answers
1k views
Is there a physical argument for the Kutta-Joukowski theorem?
I am doing the following exercise:
Consider inviscid, incompressible, steady flow. The Kutta-Joukowski theorem $$L' = \rho_\infty V_\infty\Gamma$$ where
$L'$ is the lift per unit span
$\rho_\infty$ ...
4
votes
1answer
176 views
Does this formula hold true for a source sheet covering a closed body of arbitrary shape?
Let me explain the picture above: We have a uniform flow and a source sheet cover the the surface of an arbitrary closed body. Let s be the distance measured along the source sheet, λ=λ(s) is the ...
3
votes
1answer
339 views
How do I calculate the normal component of the velocity at the midpoint of a source straight panel?
I am reading "Fundamental of Aerodynamics " by J.D.Anderson Fifth edition. Now I am at the chapter 3. If you got the book, please go to the page 286, the part that says: "when j = i, the contribution ...
1
vote
0answers
318 views
What causes these losses in this propeller simulation?
While running a CFD simulation comparison of 2 vs 3 blade propeller versions (48" diameter, 23" pitch, 3570RPM), I've come up with:
2-blade: 347N of static thrust @ 110Nm Torque
3-blade: 220N of ...
7
votes
1answer
245 views
Why is the flow ahead of a shock wave chaotic?
Here is the image of a shock wave on a cone in a small supersonic wind tunnel, the white lines are the condensations formed in the test chamber due to flow expansion.
Why are the condensations so ...
23
votes
6answers
7k views
What is the difference between a flow and a checklist?
Use of checklists is a 'special emphasis area' during FAA private and commercial checkrides but there are a lot of comments in pilot forums about using flows instead, often - but not always - in the ...
