Force Generation
Unlike conventional trawls, the ATS does not make use of fixed aerofoil-shaped doors, towed at an angle of attack to
generate the spreading force. Instead it makes use of a number of spinning rotors or “Magnus Effect” devices.
When a spinning rotor is placed in a moving stream, a force is generated at right angles to the direction of flow and
at right angles to the axis of the rotor. This is known as the "Magnus Effect".
The direction of the force is determined by the
direction of rotation of the rotor. The size of the
force is dependant on the ratio between the speed
of flow of the stream and the tangential speed of
the rotor.
Coefficients of lift greater than 11 are obtainable. A
lift/drag ratio of 5/1 is typical for a coefficient of lift
of 8.
When compared to a conventional "aerofoil" device,
for the same lift force, the projected area of the
rotor is smaller and the drag force is less.
Besides the above, one of the main reasons for
selecting this particular technology for the ATS is
that the lift force is easily and fully controllable
with a fast response time. However this feature
does come at a cost - power is required to drive the
rotor.
Force generation is but one aspect of the system, the others being able to direct this force in a specific direction and
being able to change this direction as required. For this a minimum of two rotors is required and, in the case of this
version of the ATS, one rotor is placed on top of the other to form a Variable Thrust Vector Device (VTVD).
For a more mathematical description of Vectors and Thrust Vectoring click here
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