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On the inference of the state of turbulence and mixing efficiency in stably stratified flows
| Content Provider | Scilit |
|---|---|
| Author | Garanaik, Amrapalli Venayagamoorthy, Subhas K. |
| Copyright Year | 2019 |
| Description | Scaling arguments are presented to quantify the widely used diapycnal (irreversible) mixing coefficient $\unicode[STIX]{x1D6E4}=\unicode[STIX]{x1D716}_{PE}/\unicode[STIX]{x1D716}$ in stratified flows as a function of the turbulent Froude number $Fr=\unicode[STIX]{x1D716}/Nk$ . Here, $N$ is the buoyancy frequency, $k$ is the turbulent kinetic energy, $\unicode[STIX]{x1D716}$ is the rate of dissipation of turbulent kinetic energy and $\unicode[STIX]{x1D716}_{PE}$ is the rate of dissipation of turbulent potential energy. We show that for $Fr\gg 1$ , $\unicode[STIX]{x1D6E4}\propto Fr^{-2}$ , for $Fr\sim \mathit{O}(1)$ , $\unicode[STIX]{x1D6E4}\propto Fr^{-1}$ and for $Fr\ll 1$ , $\unicode[STIX]{x1D6E4}\propto Fr^{0}$ . These scaling results are tested using high-resolution direct numerical simulation (DNS) data from three different studies and are found to hold reasonably well across a wide range of $Fr$ that encompasses weakly stratified to strongly stratified flow conditions. Given that the $Fr$ cannot be readily computed from direct field measurements, we propose a practical approach that can be used to infer the $Fr$ from readily measurable quantities in the field. Scaling analyses show that $Fr\propto (L_{T}/L_{O})^{-2}$ for $L_{T}/L_{O}>O(1)$ , $Fr\propto (L_{T}/L_{O})^{-1}$ for $L_{T}/L_{O}\sim O(1)$ , and $Fr\propto (L_{T}/L_{O})^{-2/3}$ for $L_{T}/L_{O} |
| Related Links | https://www.cambridge.org/core/services/aop-cambridge-core/content/view/502A0E47AFED8A206A7DE1E0AE9CDDD3/S0022112019001423a.pdf/div-class-title-on-the-inference-of-the-state-of-turbulence-and-mixing-efficiency-in-stably-stratified-flows-div.pdf |
| Ending Page | 333 |
| Page Count | 11 |
| Starting Page | 323 |
| ISSN | 00221120 |
| e-ISSN | 14697645 |
| DOI | 10.1017/jfm.2019.142 |
| Journal | Journal of Fluid Mechanics |
| Volume Number | 867 |
| Language | English |
| Publisher | Cambridge University Press (CUP) |
| Publisher Date | 2019-05-25 |
| Access Restriction | Open |
| Subject Keyword | Journal of Fluid Mechanics Fluids and Plasmas Physics Stratified Flows Stratified Turbulence Turbulent Mixing |
| Content Type | Text |
| Resource Type | Article |
| Subject | Applied Mathematics Mechanics of Materials Condensed Matter Physics Mechanical Engineering |
