  We study the self-similarity and dissipation scalings of a turbulent planar
jet and the theoretically implied mean flow scalings. Unlike turbulent wakes
where such studies have already been carried out (Dairay et al. 2015; Obligado
et al. 2016), this is a boundary- free turbulent shear flow where the local
Reynolds number increases with distance from inlet. The Townsend-George theory
revised by Dairay et al. (2015) is applied to turbulent planar jets. Only a few
profiles need to be self-similar in this theory. The self- similarity of mean
flow, turbulence dissipation, turbulent kinetic energy and Reynolds stress
profiles is supported by our experimental results from 18 to at least 54 nozzle
sizes, the furthermost location investigated in this work. Furthermore, the
non-equilibrium dissipation scaling found in turbulent wakes, decaying
grid-generated turbulence, various instances of periodic turbulence and
turbulent boundary layers (Vassilicos 2015, Dairay et al. 2015, Goto &
Vassilicos 2015, Nedic et al. 2017) is also observed in the present turbulent
planar jet and in the turbulent planar jet of Antonia et al. (1980). Given
these observations, the theory implies new mean flow and jet width scalings
which are found to be consistent with our data and the data of Antonia et al.
(1980). In particular, it implies a hitherto unknown entrainment behaviour: the
ratio of characteristic cross-stream to centreline streamwise mean flow
velocities decays as the -1/3 power of streamwise distance in the region where
the non-equilibrium dissipation scaling holds.
