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Akademický článek

Robustness of highly complex radial carpet beams in turbulent atmospheres

Autor: Saifollah Rasouli, Mohammad Bagheri, J. J. Niemela

Publikováno v: Scientific Reports, Vol 14, Iss 1, Pp 1-13 (2024)

Abstract In this study, we report observations of propagating radial carpet beams (RCBs) through a turbulent atmosphere at ground level with a 120 m path length. RCBs are a class of nondiffracting, accelerating, self-healing, and self-amplifying beam

Externí odkaz: https://doaj.org/article/96b38ee225384df6a483f6961d4f078c

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Investigation of the anisotropy and scaling of the phase structure function of a spatially coherent light beam propagating through convective air turbulence

Autor: Saifollah Rasouli, Ebrahim Mohammadi Razi, J. J. Niemela

Publikováno v: Journal of the Optical Society of America. A, Optics, image science, and vision. 39(9)

We report on applications of moiré deflectometry in measurements of the anisotropy and scaling of the phase structure function (PSF), obtained after passing a laser beam through an indoor enclosure containing convective air turbulence. We combine th

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::6abcaa2b919270b344283fbaf444aa58
https://pubmed.ncbi.nlm.nih.gov/36215632

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Validating the California Puff (CALPUFF) Modelling System Using an Industrial Area in Accra, Ghana as a Case Study

Autor: E. H. K. Akaho, H. A. Affum, V. Armenio, J. J. Niemela, K. A. Danso

Publikováno v: Open Journal of Air Pollution. :27-36

The performance of the California Puff (CALPUFF) modelling system has been evaluated using a case study in Ghana. The performance evaluation consisted of a quantitative comparison of dispersion simulation results of SO2 and NO2 with measurements at t

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::738046685bc9239449129b3e5d30a6b2
https://doi.org/10.4236/ojap.2016.51003

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High Rayleigh Number Thermal Convection

Autor: J. J. Niemela

Publikováno v: Journal of Low Temperature Physics. 134:447-456

This paper considers the manner in which low temperature helium gas is used to generate turbulent convection, reviews the lessons learned so far, and finally suggests a possible experiment that draws upon these lessons and should yield unambiguous re

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::98351a896550bfd5bc51f93eb5472b10
https://doi.org/10.1023/b:jolt.0000012594.47945.f6

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Turbulent flows at cryogenic temperatures: a new frontier

Autor: J J Niemela, Ladislav Skrbek, R J Donnelly

Publikováno v: Journal of Physics: Condensed Matter. 11:7761-7781

Cryogenic helium is of significant value in generating, and studying, the highest possible Reynolds and Rayleigh number flows under controlled laboratory conditions, primarily due to its extremely low value of kinematic viscosity. We consider here cr

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::ca3ff1747c92bf51f36e64e17f98c361
https://doi.org/10.1088/0953-8984/11/40/308

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Aspects of Hydrodynamic Turbulence in Classical and Quantum Systems

Autor: J. J. Niemela

Publikováno v: Astrophysics and Space Science Proceedings ISBN: 9781402088674

Turbulence is a complex phenomenon, characterized by many interacting degrees of spatial and temporal freedom. It is widespread, and indeed nearly the rule, in the flow of classical fluids. The complexity of the underlying equations has impeded analy

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::ee492705648b6873d4df8e92edf2087a
https://doi.org/10.1007/978-1-4020-8868-1_1

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Static and dynamic measurements of the Nusselt number in turbulent convection

Autor: J J Niemela

Publikováno v: Physica Scripta. :014059

Measurements of the dimensionless heat transfer rate, or Nusselt number Nu, are typically made by static measurements of the heat flux and the average resulting temperature difference across a horizontal layer of fluid under steady state conditions.

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::6edc2020d1639a21fb9f44fcd36ce088
https://doi.org/10.1088/0031-8949/2013/t155/014059

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High Rayleigh number flows with unsteady applied heat flux

Autor: J J Niemela

Publikováno v: Physica Scripta. :014003

This talk describes experimental observations of Rayleigh–Benard convection at very high Rayleigh numbers using cryogenic helium gas as the working fluid. Here, a cylindrical container with diameter-to-height aspect ratio unity was subject to unste

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::c7ea4de2fce8bb021d3e6827e60cbb00
https://doi.org/10.1088/0031-8949/2008/t132/014003

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