Lecture _

 Lecture _

Date: 

Magnus Effect: The Magnus effect is an observable phenomenon that is commonly associated with a spinning object moving through the air or another fluid. The path of the spinning object is deflected in a manner that is not present when the object is not spinning. The deflection can be explained by the difference in pressure of the fluid on opposite sides of the spinning object. The Magnus Effect depends on the speed of rotation. [Source]

    Case 1: [Ball not rotating]

In this case, the velocity at the upper surface (Vu) and at the lower surface (Vl) is the same. thus pressure at the upper (Pu) and lower (Pl) will be the same. As there is no pressure difference there will be no lift.

    Case 2: [Ball rotating clockwise]

When Ball is rotating clockwise direction, the movement of the upper surface of the ball is along with the airflow. The movement of the lower surface is against the airflow. So the velocity of the air at the upper surface will be higher than the velocity at the lower surface. Therefore, the pressure at the upper surface will be greater than the pressure at the lower surface (Pu>Pl). As result, positive lift will be generated.

    Case 3: [Ball rotating Anti-clockwise]

The ball rotating anti-clockwise, the movement of the lower surface of the ball is along with the airflow. The movement of the upper surface is against the airflow. So the velocity of the upper surface is less than the velocity of the lower surface (Vu<Vl). Therefore, the pressure of the upper surface will be higher than the pressure of the lower surface (Pu>Pl). As result, negative lift will be generated.

    Nomenclature of Aerofoil:

The full form of NACA is National Advisory Committee for Aeronautics.

1. 4 Digit (NACA-2412)
2. 5 Digit (NACA-23018)
3. 6 Digit (NACA-623158) 

    NACA 4 Digit Aeorfoil Numbering:

1. First digit represents the maximum camber in percent of chord length.
2. Second digit represents the location of maximum camber in percentage of chord length.
3. Last two digits represent its thickness in percentage of chord length.

    Example: NACA-2412

The first Digit 2 indicates maximum camber is 2% of the chord length.

The Second digit 4 indicates maximum camber is located at 40% of chord length from leading edge.

The Last Two Digits 12 represents maximum thickness of aerofoil is 12% of chord length.

    Practice Question: Draw a NACA-2412 Aerofoil within 10cm of chord line. 

    Answer: 

            Maximum camber = 2%   of 10cm = .2cm

            Location                = 40% of 10cm = 4cm

            Thickness              = 12% of 10cm=1.2cm

                                          

    NACA 5 Digit Aerofoil Numbering:

1. First Digit when multiplied by (3/2) gives design CL in tenths.
2. The next two digits when divided by 2, gives the location of maximum camber from the leading edge in hundredths.
3. Last two digits gives maximum thickness in percentage of chord length.