Table of Contents

## What is pressure side and suction side of an airfoil?

The airfoils are curved, convex on one side and concave on the other, with the rotor rotating toward the concave side. The concave side is called the pressure side of the blade, and the convex side is called the suction side of the blade.

## What is the suction side of an airfoil?

Airfoil terminology The suction surface (a.k.a. upper surface) is generally associated with higher velocity and lower static pressure. The pressure surface (a.k.a. lower surface) has a comparatively higher static pressure than the suction surface.

## What is aerodynamic suction?

Boundary layer suction is a boundary layer control technique in which an air pump is used to extract the boundary layer at the wing or the inlet of an aircraft. Improving the air flow can reduce drag. Improvements in fuel efficiency have been estimated as high as 30%.

## What is the airfoil theory?

Thin airfoil theory is a straightforward hypothesis of airfoils that relates angle of attack to lift for an incompressible and inviscid flow past an airfoil. Thin airfoil theory is a straightforward hypothesis of airfoils that relates angle of attack to lift for an incompressible and inviscid flow past an airfoil.

## What is the most efficient airfoil?

If the airplane is designed for low-speed flight, a thick airfoil is most efficient, whereas a thin airfoil is more efficient for high-speed flight. There are generally two kinds of airfoils: laminar flow and conventional.

## What is a symmetrical airfoil?

The symmetrical airfoil is distinguished by having identical upper and lower surfaces. The mean camber line and chord line are the same on a symmetrical airfoil, and it produces no lift at zero AOA. With symmetric airfoils, the stall angle is the same for positive and negative stalls.

## How does boundary layer suction work?

Boundary layer suction reduces drag by stabilizing the laminar boundary preventing transition and conceding higher regions of laminar ow. It has been brought out that there is a convincing decrease in drag and pressure loss and an increase in max lift which in turn improves the overall performance of the aircraft.

## How does airfoil affect drag?

For airfoils, the drag is nearly constant at small angles (+/- 5 degrees). As the angle increases above 5 degrees, the drag quickly rises because of increased frontal area and increased boundary layer thickness. As an object moves through the air, air molecules stick to the surface.

## Why Bernoulli’s Principle is wrong?

False explanation based on equal transit-time Bernoulli’s principle states that under certain conditions increased flow speed is associated with reduced pressure. It is concluded that the reduced pressure over the upper surface results in upward lift. The longer-path-length explanation is simply wrong.

## What are 3 techniques to increase the lift of an airfoil shape?

Let’s summarize what we’ve learned: Increasing the altitude will decrease the lift. Increasing the airspeed will increase the lift. Increasing the camber will increase the lift. A symmetric airfoil, or even a flat plate at angle of attack, will generate lift.

## How do I know if my airfoil is symmetrical?

Those airfoils are asymmetrical, because their two sides are differently shaped. Other airfoils are shaped the same on both sides, so they’re symmetrical. The symmetrical airfoil is distinguished by having identical upper and lower surfaces.

## Why does the upper side of an airfoil have to be higher?

This means the pressure at the upper side of the airfoil has to be lower. The opposite is true for the pressure (lower) side of the air foil. Here, the streamlines converge which means a higher pressure is present.

## Which is higher the suction side or the pressure side?

In most cases the pressure distribution on the pressure-side is higher than on the suction-side (with respect to the chord-wise location). There is not general answer to this question since the pressure distribution on the pressure-side is (although mostly close to static ambient pressure) connected to the profile shape.

## How are the flow around air foil governed?

The flow around and air foil is governed by a set of equations (i.e. momentum and energy conservations). These are the Navier Stokes Equations. Without going into detail the equations are not linear. This means we end up with a chicken-and-egg problem.

## Where is the pressure on the pressure side?

Then the pressure-distribution on the pressure side needs to fulfil two boundary conditions. 1) high pressure ($C_p$) at the leading edge which is a result of the free stream velocity and 2) the pressure ($C_p$) at the trailing edge which is given by the pressure-distribution on the suction-side.