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.

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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 ...
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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 ...
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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?
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Do the drag force (D) and the drag coefficient (Cd) vary with altitude? [duplicate]

And also how is it related to Reynolds number? Image source Edit: Consider two airplanes, one flying at sea level and the other at altitude and both are at the same angle of attack and true airspeed....
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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 ...
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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, ...
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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 ...
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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
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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 ...
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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. ...
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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 ...
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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:...
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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. ...
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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 $L~\left[ m \right]$, ...
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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 ...