Does drag increase with Reynolds number?

(1)Reynolds number plays a very major role in the airfoil aerodynamics for the NACA0012 airfoil without and with Gurney flap. Lift decreases and drag increases when Reynolds number is decreased.

How is drag coefficient related to Reynolds number?

Note that the drag coefficient decreases with the Reynolds number, and it becomes almost a constant (CD = 0.4) for a Reynolds number between 103 and 2×105. As the Reynolds number increases (Re > 2×105), the boundary layer becomes thinner in the front of the sphere and begins its transition to turbulent.

Why does drag decrease with Reynolds number?

The drag coefficient decreases at low Reynolds numbers because the flow is in a regime called creeping flow. That is, the inertial forces are negligible.

What is drag on a cylinder?

Drag is the heart of aerodynamic design. The drag coefficient of a cylinder was calculated from data obtained by performing tests in an air flow bench (AF12) with varying flow velocities and diameters as 12.5mm, 15 mm, 20 mm, and 25 mm.

What is the Reynolds number of a cylinder?

(1) Re is the Reynolds number of the shape; u is the wind velocity in unobstructed flow, d is the diameter of the cylinder and is the kinematic viscosity of air. Many researches had been carried out to predict the variation of Co-efficient of drag vs. Reynolds number for circular cylinder.

How does the Reynolds number affect the drag coefficient?

The variation of the drag coefficient with Reynolds number is shown in figure 2, and the corresponding flow patterns are shown in figure 3. We see that as the Reynolds number increases the variation in the drag coefficient (based on cross-sectional area) decreases, and over a large range in Reynolds number it is nearly constant.

When does the drag coefficient of a cylinder decrease?

Drag Coefficient. As the Reynolds number is increased this drag decreases. At Reynolds numbers around 2 – 30, there is a separation of boundary layer, but the wake is of a limited length. The eddies formed seem fixed behind the cylinder. For Reynolds numbers close to 40 -70, there is a periodic oscillation of the wake.

How are the eddies formed in a Reynolds cylinder?

The eddies formed seem fixed behind the cylinder. For Reynolds numbers close to 40 -70, there is a periodic oscillation of the wake. For higher Reynolds numbers the eddies break off from the cylinder.