 Kirchhoff equations

In fluid dynamics, the Kirchhoff equations, named after Gustav Kirchhoff, describe the motion of a rigid body in an ideal fluid.where formula_2 and formula_3 are the angular and linear velocity vectors at the point formula_4, respectively; formula_5 is the moment of inertia tensor, formula_6 is the body's mass; formula_7 is
a unit normal to the surface of the body at the point formula_4;
formula_9 is a pressure at this point; formula_10 and formula_11 are the hydrodynamic
torque and force acting on the body, respectively;
formula_12 and formula_13 likewise denote all other torques and forces acting on the
body.