Impact of turbulence on the stratified flow around small particles
Abstract
We study the turbulent flow of the densitystratified fluid around a small translating (either passively or selfpropelled) particle. It was found recently [A. M. Ardekani and R. Stocker, Phys. Rev. Lett. vol. 105, 084502 (2010)] that without turbulence, the familiar Stokes flow is dramatically altered by the stratification. Stratificationinduced inhomogeneity "turns on" the buoyancy introducing a new "cutoff" or "screening" length scale for the flow, yielding closed streamlines and a faster (exponentiallike) decay of velocity. This result, however, did not account for the potential role of the background turbulence, intrinsically present in many aquatic environments. Turbulence mixes the density opposing the effect. Here we derive and solve the advectiondiffusion equation that describes the interplay of turbulent mixing, diffusion of the stratifying agent and buoyancy. We derive an exact expression for fluctuations due to weak background turbulence and show that stronger turbulence can completely change the flow around the particle, canceling the effect of stratification and restoring the unstratified Stokes flow.
 Publication:

arXiv eprints
 Pub Date:
 January 2013
 DOI:
 10.48550/arXiv.1301.6358
 arXiv:
 arXiv:1301.6358
 Bibcode:
 2013arXiv1301.6358F
 Keywords:

 Physics  Fluid Dynamics;
 Physics  Atmospheric and Oceanic Physics
 EPrint:
 the problem was revisited following the critique of the anonymous Referee to take into account the effect of turbulence on background density stratification