  The overcoming of a mechanics problem on origin of secondary jet flows, on
dynamics of its development and interaction with the main stream of the viscous
fluid is reached by means of elucidation of the energy distribution in the
stream at its interaction with the flow system walls and a body surface. In
contrast to a traditional conception on a total head of a fluid stream in a
pipe as a sum of a velocity head and a static pressure, it is ascertained that
this sum is only longitudinal component of the stream total head vector. It is
stated a new conception and it is produced the expressions for quantitative
evaluation of radial and tangential components of the stream total head vector
and for angle of its deflection from the stream axis. The new approach has
allowed rationally to explain the causes of origin of the secondary jet flows
and dynamics of its interaction with the main stream in various cases. Thereby
with the taking into account of previous articles of the author the necessary
theoretical preconditions has been created for a working out of the modern
physically valuable apparatus for mathematical modeling of the real - viscous -
fluid motion in any problems of hydromechanics and gas dynamics.
