By introducing the empirically constructed difference-quotient turbule
nce model (DQM), in the last decade for some problems of simple turbul
ent flows analytical solutions have been worked out. Now, for an axi-s
ymmetric case a proof of the DQM is outlined, based on physical laws (
continuity equation and Navier-Stokes equation) and physical principle
s (Galilean invariance, self-similarity, isotropy of the turbulence fi
eld). A weakness remains, namely the usage of the closure hypotheses.