HOMOGENEOUS TURBULENCE EVOLUTION IN STABLY STRATIFIED FLOW .1. INTERNAL GRAVITY-WAVES AT LOW INVERSE FROUDE NUMBERS

The evolution of homogeneous grid-generated turbulence in stratified f luid is investigated analytically. A small parameter decomposition on inverse Froude number is applied to the theory of nearly homogeneous t urbulence developed earlier in refs. [1] and [2]. Applying the multipl e scale method we calculate the frequency and amplitude of internal gr avity waves and formulate differential system describing the wave-aver aged behaviour of turbulence characteristics. The comparison with the numerical results published in (?1 and with known experimental data sh ows a very good agreement as to internal waves as to small scale turbu lence in collapsed state. The long-term turbulence evolution in weakly stratified media can be regarded as a singular perturbation problem p ermitting us to gain an insight into the interaction between gravity w aves and active turbulence. (C) 1997 Elsevier Science Ltd.