Reynolds number for case flow over airfoil

In summary, the transition point for laminar flow on an airfoil is not determined by a specific Reynolds number, but rather depends on various factors such as airfoil shape, surface roughness, and flow quality. However, it is typically well into the millions even in noisy wind tunnels. Internal flow is also different and determining the transition Reynolds number is not possible in general, even on a simple flat plate.
  • #1
maomao39
12
0
In which range of Reynolds numeber is laminar flow for airfoil?
Is it Re < 5 x 10^5?
How about turbulence case?
 
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  • #2
There is no general transition point Retnolds number. It depends on the shape of te airfoil and the surface roughness of the airfoil and the freestream flow quality and a host of other things besides Reynolds number. Typically though, even in a noisy wind tunnel the transition Retnolds number will be well into the millions. Still, that is very much an overgeneralization.
 
  • #3
The reynolds number for internal flow are much more easier.
My airfoil is NACA 0012 symmetrical airofoil.
Currently running on CFD simulation
 
  • #4
Yes but internal flow is fundamentally different. Even on a simple flat plate there is no way to determine the transition Reynolds number in general.
 
  • #5


The Reynolds number for case flow over an airfoil is a dimensionless parameter that represents the ratio of inertial forces to viscous forces in the flow. It is defined as the product of the fluid density, velocity, and characteristic length of the airfoil, divided by the fluid viscosity.

In general, laminar flow for an airfoil occurs at lower Reynolds numbers, typically below 5 x 10^5. At this range, the flow is smooth and orderly, with the fluid particles moving in parallel layers. However, as the Reynolds number increases, the flow becomes more turbulent, with chaotic and unpredictable motion of fluid particles.

The transition from laminar to turbulent flow for an airfoil depends on various factors such as airfoil shape, angle of attack, and surface roughness. Therefore, the exact range of Reynolds number for the occurrence of turbulence can vary. However, it is generally accepted that turbulence occurs at Reynolds numbers above 5 x 10^5 for airfoils.

In summary, the range of Reynolds number for laminar flow over an airfoil is typically below 5 x 10^5, while turbulence can occur at higher Reynolds numbers. The exact value of Reynolds number at which turbulence occurs may vary depending on various factors.
 

Related to Reynolds number for case flow over airfoil

1. What is the Reynolds number for flow over an airfoil?

The Reynolds number for flow over an airfoil is a dimensionless quantity that represents the ratio of inertial forces to viscous forces in the flow. It is given by the formula Re = (ρVc)/μ, where ρ is the density of the fluid, V is the velocity of the flow, c is the characteristic length (such as the chord length of the airfoil), and μ is the dynamic viscosity of the fluid.

2. Why is the Reynolds number important in studying flow over airfoils?

The Reynolds number is important because it helps determine the type of flow that will occur over an airfoil. At low Reynolds numbers, the flow is laminar and smooth, while at high Reynolds numbers, the flow becomes turbulent. This has a significant impact on the aerodynamic characteristics of the airfoil, such as lift and drag.

3. How does the Reynolds number affect the lift and drag of an airfoil?

The Reynolds number has a significant impact on the lift and drag of an airfoil. At low Reynolds numbers, the flow is laminar and the lift and drag coefficients are relatively low. As the Reynolds number increases, the flow becomes turbulent and the lift and drag coefficients increase. This is because turbulent flow creates more drag and reduces the lift generated by the airfoil.

4. What is the ideal Reynolds number for optimal aerodynamic performance of an airfoil?

The ideal Reynolds number for optimal aerodynamic performance of an airfoil varies depending on the specific design and application. In general, for subsonic flow over airfoils, the ideal Reynolds number is typically between 100,000 and 500,000. However, this can vary significantly for different airfoil shapes and operating conditions.

5. How is the Reynolds number related to the boundary layer on an airfoil?

The Reynolds number is directly related to the thickness and behavior of the boundary layer on an airfoil. At low Reynolds numbers, the boundary layer is thin and laminar, while at high Reynolds numbers, the boundary layer becomes thicker and more turbulent. This can have a significant impact on the aerodynamic performance of the airfoil, as well as its stability and control characteristics.

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