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Tangling clustering instability for small particles in temperature stratified turbulence
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Ben Gurion Univ Negev, Dept Mech Engn, Pearlstone Ctr Aeronaut Engn Studies, IL-84105 Beer Sheva, Israel.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Ben Gurion Univ Negev, Dept Mech Engn, Pearlstone Ctr Aeronaut Engn Studies, IL-84105 Beer Sheva, Israel.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Ben Gurion Univ Negev, Dept Mech Engn, Pearlstone Ctr Aeronaut Engn Studies, IL-84105 Beer Sheva, Israel.
2013 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 25, no 8, 085104- p.Article in journal (Refereed) Published
Abstract [en]

We study tangling clustering instability of inertial particles in a temperature stratified turbulence with small finite correlation time. It is shown that the tangling mechanism in the temperature stratified turbulence strongly increases the degree of compressibility of particle velocity field. This results in the strong decrease of the threshold for the excitation of the tangling clustering instability even for small particles. The tangling clustering instability in the temperature stratified turbulence is essentially different from the inertial clustering instability that occurs in non-stratified isotropic and homogeneous turbulence. While the inertial clustering instability is caused by the centrifugal effect of the turbulent eddies, the mechanism of the tangling clustering instability is related to the temperature fluctuations generated by the tangling of the mean temperature gradient by the velocity fluctuations. Temperature fluctuations produce pressure fluctuations and cause particle accumulations in regions with increased instantaneous pressure. It is shown that the growth rate of the tangling clustering instability is root Re (l(0)/L-T)(2)/(3Ma)(4) times larger than that of the inertial clustering instability, where Re is the Reynolds number, Ma is the Mach number, l(0) is the integral turbulence scale, and L-T is the characteristic scale of the mean temperature variations. It is found that depending on the parameters of the turbulence and the mean temperature gradient there is a preferential particle size at which the particle clustering due to the tangling clustering instability is more effective. The particle number density inside the cluster after the saturation of this instability can be by several orders of magnitude larger than the mean particle number density. It is also demonstrated that the evaporation of droplets drastically changes the tangling clustering instability, e. g., it increases the instability threshold in the droplet radius. The tangling clustering instability is of a great importance, e. g., in atmospheric turbulence with temperature inversions.

Place, publisher, year, edition, pages
2013. Vol. 25, no 8, 085104- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-94191DOI: 10.1063/1.4816643ISI: 000323946200047OAI: oai:DiVA.org:su-94191DiVA: diva2:652477
Note

AuthorCount:4;

Funding Agencies:

Israel Science Foundation  259/07;  EU COST Actions  MP0806,  ES1004;  EC FP7 project ERC PBL-PMES  227915;  Russian Government Mega Grant  11.G34.31.0048;  Russian Ministry of Science and Education  8648 

Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06Bibliographically approved

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