Controllability of
Cavitating Bodies

In the upper half of the figure the body moves in direction of his rotational axis. On the head of the body acts the drag force W. On the center of gravity acts the gravitational force. The body is in an instable state of equilibrium.

Any disturbance causes a rotation of the body because of the lifting force A acting on the head if an angle exists between body axis and direction of motion . The resulting momentum rotates the body until the heck touches the wall of the bubble. Then a reverse momentum is initiated caused by the drag and lift of the heck sliding on the wall of the bubble.

The motion of the body is calculable by the equations of forces and turning moments. The forces on the head are determinated by its drag and lift coefficients. For a cone shaped head the coefficients can be extracted from the last figure in the Reichardt side. The forces on the heck can be estimated by different sources in technical reports (to find for example in Hoerner, Fluid Dynamic Drag).

If head and heck are adequately constructed it can be achieved that the body oscillates in the bubble and thereby runs quasi straight line.

This method of stabilisation is appropriate for small bodies.

For larger bodies steering can be managed by a head with movable cone and or steering mechanisms at the heck. By electronic controlling any trajectory can be provided.