Aerodynamic Principles Of Flapping Wing

Aerodynamic Principles of Flapping Wings

The aerodynamic principles of the aircraft with flapping wings or the ornithopters are different from the principles of the normal aircraft (in which the wings are fixed). For the normal aircraft, there is only one component or one source of the airflow passing through the aerofoil which is the airflow that caused by the forward motion of the aircraft. It acts in the direction that is parallel to the flight path but in the opposite direction. In this case, the force that acts perpendicular to the airflow will be equal to the lift force.

However, for the ornithopters, there are two airflows passing through its aerofoil. The first component is the same as the normal aircraft. However, the second component

During the downstroke motion, there will be air flowing upwards towards the wing from the bottom in the direction against the wing motion. This causes the resultant airflow to point in the more upward direction. Due to this, the direction of the perpendicular force will also tilt forward as well, assume that the angle of attack is zero. Therefore, when this force is separated into two components which are perpendicular and parallel to the flight path, it will provide both lift force and the forward thrust. Figure 1,1 shows the force acting on the cross-sectional area of the wing during this motion. The concept for this motion is similar to the propeller blade on an aircraft when the downward motion of the wing is considered to be similar to the rotating motion of the blade and the propeller torque force that must be overcome by the motion is the lift force produced on the

First of all, noticed that when the wings flapped, the vertical distance at each point along the wingspan is different. At the root of the wing, the vertical motion of the wing is very little while the outer part of the wing moves down much further. Therefore the magnitude of the vertical airflow that caused by the wings moving up and down will be different along the wingspan as well. This leads to different direction of the relative airflow at each cross-sectional area of the aerofoil and as a result, the angle of attack will not be constant along the wingspan. At the tip, the angle of attack will be higher than at the root. This is not good because the angle of attack at the root may be too great and it may be too little at the root cause the wing to be able to produce less