The difference-quotient turbulence model, describing the Reynold's she
ar stress of an axi-symmetric jet, has now been modified to relate to
the normal stress in the main flow direction. The simple analytical re
sults shaw, that in an experiment self-preservation has not been achie
ved completely. A proposition of the theory states, that a relative tu
rbulence intensity is just equal to the square root of the spreading p
arameter of the jet. This result is confirmed by experimental data.