English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We study experimentally temperature fluctuations in stably stratified forcedturbulence in air flow. In the experiments with an imposed vertical temperaturegradient, the turbulence is produced by two oscillating grids located nearbythe side walls of the chamber. Particle Image Velocimetry is used to determinethe turbulent and mean velocity fields, and a specially designed temperatureprobe with sensitive thermocouples is employed to measure the temperaturefield. We found that the ratio $\big[(\ell_x \nabla_x \bar{T})^2 + (\ell_y\nabla_y \bar{T})^2 + (\ell_z \nabla_z \bar{T})^2\big] / <\theta^2 >$ is nearlyconstant, is independent of the frequency of the grid oscillations and has thesame magnitude for both, stably and unstably stratified turbulent flows, where$\ell_i$ are the integral scales of turbulence along $x, y, z$ directions,$\bar{T}$ and $\theta$ are the mean and turbulent fluctuations components ofthe fluid temperature. We demonstrated that for large frequencies of the gridoscillations, the temperature field can be considered as a passive scalar,while for smaller frequencies the temperature field behaves as an active field.The theoretical predictions based on the budget equations for turbulent kineticenergy, turbulent potential energy ($\propto <\theta^2 >)$ and turbulent heatflux, are in a good agreement with the experimental results. Detailedcomparison with experimental results obtained previously in unstably stratifiedforced turbulence is performed.

Experimental study of temperature fluctuations in forced stably stratified turbulent flows