Reports in Meteorology and Oceanography Number 9. Momentum and Mass Transfer in a Neutral and Stratified Turbulent Shear Flow.

摘要

A fully developed, two dimensional turbulent flow is established in a water channel with a free surface. The unstratified case is first examined in regards to requirements for two dimensionality, steady state, and properties near the free surface with hot film anemometry. The flow is then stratified by injecting saturated salt water at mid depth. Downstream from the salt injector in the test section the properties of the flow are then examined. Cross sections in the center of the channel one foot apart are taken of the mean and streamwise fluctuating velocities as well as the mean density profiles. This information along with the boundary conditions of the stress at the wall and the pressure gradient at the wall are then fed into the numerical program of the first integral of the equations of motion. This yields the momentum and salinity fluxes, as well as the inertial terms and pressure gradient as a function of depth and the local Richardson Number. The salinity flux and Austausch coefficient behave with the expected reciprocal relationship to the Richardson Number. The momentum results do not. The flow exhibits internal regimes in which the dynamics are different. In the lower region of the flow the turbulent momentum flux is negative, u' and w' are either both positive or negative, and the mean gradient steepens in the streamwise direction. Also the turbulent momentum flux is balanced by the mean advective fluxes.