Mean Speed Of Flow Research Articles

Times of rise for turbulent forced plumes

The motion of turbulent forced plumes, issuing vertically from isolated sources into an otherwise stable environment, is examined using a Lagrangian approach. Previous Eulerian approaches have yielded only numerical solutions whereas the present approach yields partial analytic solutions from which times of rise, from the source to levels of zero buoyancy and zero momentum, are evaluated for fluid elements travelling with the mean speed of flow. Consideration of previous work describing the asymptotic behaviour of starting plumes shows that times of rise may also be found for the leading front of a starting plume rising in a neutral environment. DOI: 10.1111/j.2153-3490.1979.tb00885.x

Times of rise for turbulent forced plumes

The motion of turbulent forced plumes, issuing vertically from isolated sources into an otherwise stable environment, is examined using a Lagrangian approach. Previous Eulerian approaches have yielded only numerical solutions whereas the present approach yields partial analytic solutions from which times of rise, from the source to levels of zero buoyancy and zero momentum, are evaluated for fluid elements travelling with the mean speed of flow. Consideration of previous work describing the asymptotic behaviour of starting plumes shows that times of rise may also be found for the leading front of a starting plume rising in a neutral environment.

Dispersion of soluble matter in solvent flowing slowly through a tube

When a soluble substance is introduced into a fluid flowing slowly through a small-bore tube it spreads out under the combined action of molecular diffusion and the variation of velocity over the cross-section. It is shown analytically that the distribution of concentration produced in this way is centred on a point which moves with the mean speed of flow and is symmetrical about it in spite of the asymmetry of the flow. The dispersion along the tube is governed by a virtual coefficient of diffusivity which can be calculated from observed distributions of concentration. Since the analysis relates the longitudinal diffusivity to the coefficient of molecular diffusion, observations of concentration along a tube provide a new method for measuring diffusion coefficients. The coefficient so obtained was found, with potassium permanganate, to agree with that measured in other ways. The results may be useful to physiologists who may wish to know how a soluble salt is dispersed in blood streams.

Societies and Academies

Societies and Academies