Questions tagged [reynolds-number]
It refers to a dimensionless quantity used in fluid mechanichs. It measures the relevance of inertial terms compared to viscous terms.
22
questions
0
votes
1
answer
142
views
Wind turbine airfoil on low Reynolds number aircraft
I read that the criteria considered when designing a wind turbine airfoil are slightly different to the ones when designing an airfoil for an aircraft. I was wondering, for a low Reynolds number ...
4
votes
1
answer
440
views
Why XFOIL predicts a lower drag coefficient at higher Re?
A well known idea is that for aerodynamic/streamlined bodies the friction drag is larger than pressure drag. Hence, a laminar boundary layer is preferable (only looking at minimal drag, no other ...
- 181
1
vote
2
answers
421
views
What chord should I use to calculate Reynolds number?
Mean geometric chord of exposed wing, or mean aerodynamic chord of gross wing? It's not particularly clear in the literature.
- 692
1
vote
0
answers
39
views
Distance where transition from laminar to turbulent boundary takes place
How do we work out where the distance from the leading edge the laminar boundary layer would turn into a turbulent boundary layer? Assuming we have been given the length of the plate, speed, dynamic ...
- 41
1
vote
1
answer
119
views
How do i find a supercritical airfoil for my preliminary design?
The following information is available but i don't exactly know where to get the information about SC Airfoils from. Do Airbus , Boeing use secret airfoil that they don't disclose?
Cruise Speed = 240 ...
- 158
1
vote
2
answers
294
views
Why don't we simulate similarity parameters simultaneously in the same wind tunnel?
As 'Fundamentals of Aerodynamics' by JD Anderson suggest
Today, for the most part, we do not attempt to simulate all the
parameters simultaneously; rather, Mach number simulation is achieved
in one ...
- 1,567
0
votes
1
answer
1k
views
Leading edge or trailing edge stall?
As I wrote last week, I'm doing a Benedek 10355 airfoil performance report.
At this point of the work I am analyzing the stall of the profile at a fixed Reynolds number.
The Benedek 10355 airfoil has ...
- 35
3
votes
1
answer
146
views
Is it possible that as the Reynolds number increases, a laminar bubble increases in extension?
I'm studying the Benedek 10355 airfoil (Plot), which should be a profile used in air-controlled models.
While I was carrying out a boundary layer analysis, I realized the particularity that I have ...
- 35
1
vote
1
answer
206
views
At which point in scale reduction do slats and flaps become unnecessary?
Imagine some Fi-156 Storch, and reduce its scale down gradually to 10cm span. Let's assume full scale Fiesler Storch is 100% efficient at, for example, minimizing stall speed.
During this reduction ...
- 4,454
1
vote
1
answer
124
views
Turbulent flows over 6 series airfoils
6 Series Airfoils were developed to enhance the laminar flow region over the airfoil. But, the Reynolds number at which planes fly are high for the flow to be Laminar. Then what's point of introducing ...
- 461
2
votes
1
answer
345
views
Is the Reynolds number the same for both the airfoil and wing? If not, why/how does it change?
This question might be stupid, but I don't understand this one thing: does the Reynolds number change when you go from the airfoil to the wing? Or is it the same for both?
- 21
0
votes
0
answers
214
views
How does the critical Angle of attack changes with Increasing Reynolds Number?
I am simulating NACA 2415 Airfoil for different Reynolds Number i.e. 2 million,3 million and 4 million on ANSYS Fluent. The difference between the critical Angle of attack is quite vast. For the 4 ...
8
votes
3
answers
4k
views
Why does a turbulent boundary layer cause more friction drag than a laminar boundary layer?
From what I understand, friction is caused by viscosity and a bigger Reynolds number signifies lower viscosity.
Thus, a higher Reynolds number(i.e. turbulent flow) results in lower friction.
But, ...
- 359
1
vote
1
answer
1k
views
How does drag change with Reynolds number?
If you want to scale down an airframe, i.e., for wind tunnel testing, you have to adjust for the Reynolds number. I want to ask if in case I forgot to adjust the Reynolds number, would the drag on the ...
- 2,484
1
vote
1
answer
2k
views
How to calculate Reynolds number?
How do I calculate the Reynolds number of a wing with wing chord,1.2m and speed of 60km/h
- 2,905
1
vote
2
answers
195
views
would a dimpled heat shield reduce heat transfer during reentry? [closed]
Would a large ceramic golfball absorb less heat on reentry than a standard sphere?
"The difference in the flowfields around a smooth sphere and a rough, or dimpled, sphere can be seen above. Since ...
- 131
4
votes
1
answer
1k
views
Does zero-lift angle of attack depend on Reynolds number?
In this post I read that, due to viscous effects, the $C_{l}$ at a given angle of attack increases slightly with the Reynolds number but it seems that it just happens near the stall angle of attack.
...
- 257
4
votes
2
answers
4k
views
Does Lift/Drag generally improve at higher Reynolds numbers?
I have been looking at the lift/drag polars for various airfoil profiles. The L/D ratio seems to improve at higher Reynolds numbers. Obviously different wings are optimized for different speeds, and ...
- 41
16
votes
2
answers
9k
views
Is airflow ever laminar in the boundary layer, near the wing leading edge?
I often see images of the boundary layer over a wing indicating the airflow is laminar over the first portion of the wing:
Transition from laminar to turbulent flow over the wing. Left: source, right:...
- 70.9k
1
vote
0
answers
242
views
What is the order of Reynolds number inside the Compressor at cruise conditions?
I am doing a CFD study on a probe that will be installed inside a compressor of a civil aircraft for my final year project. I need to know the Reynolds number inside a compressor at cruise conditions. ...
- 386
13
votes
1
answer
18k
views
What is the relation between an airplane's altitude and the drag it is experiencing?
The Reynolds-Number $Re$ is defined as $Re = \frac{c \cdot L \cdot \rho}{\mu} = \frac{c \cdot L}{\nu}$, with
the velocity $c~\left[ \frac{m}{s} \right]$,
the reference length $L~\left[ m \right]$,
...
user12485
8
votes
1
answer
2k
views
When should I use the global Reynolds number and when the local Reynolds number?
I know that for the wing, the Reynolds number is based on the MAC. This makes sense to me, as the boundary layer develops along the length of the wing.
However, what kind of Reynolds number needs to ...
- 6,607