We report on comprehensive experimental studies of turbulence spreading in edge plasmas. These studies demonstrate the relation of turbulence spreading and entrainment to intermittent convective density fluctuation events or bursts (i.e. blobs and holes). The non-diffusive character of turbulence spreading is thus elucidated. The turbulence spreading velocity (or mean jet velocity) manifests a linear correlation with the skewness of density fluctuations, and increases with the auto-correlation time of density fluctuations. Turbulence spreading by positive density fluctuations is outward, while spreading by negative density fluctuations is inward. The degree of symmetry breaking between outward propagating blobs and inward propagating holes increases with the amplitude of density fluctuations. Thus, blob-hole asymmetry emerges as crucial to turbulence spreading. These results highlight the important role of intermittent convective events in conveying the spreading of turbulence, and constitute a fundamental challenge to existing diffusive models of spreading.
@article{osti_2345815,
author = {Long, Ting and Diamond, P. H. and Ke, Rui and Chen, Zhipeng and Cao, Mingyun and Xu, Xin and Xu, Min and Hong, Rongjie and Tian, Wenjing and Yuan, Jinbang and others},
title = {On how structures convey non-diffusive turbulence spreading},
annote = {Abstract We report on comprehensive experimental studies of turbulence spreading in edge plasmas. These studies demonstrate the relation of turbulence spreading and entrainment to intermittent convective density fluctuation events or bursts (i.e. blobs and holes). The non-diffusive character of turbulence spreading is thus elucidated. The turbulence spreading velocity (or mean jet velocity) manifests a linear correlation with the skewness of density fluctuations, and increases with the auto-correlation time of density fluctuations. Turbulence spreading by positive density fluctuations is outward, while spreading by negative density fluctuations is inward. The degree of symmetry breaking between outward propagating blobs and inward propagating holes increases with the amplitude of density fluctuations. Thus, blob-hole asymmetry emerges as crucial to turbulence spreading. These results highlight the important role of intermittent convective events in conveying the spreading of turbulence, and constitute a fundamental challenge to existing diffusive models of spreading.},
doi = {10.1088/1741-4326/ad40c0},
url = {https://www.osti.gov/biblio/2345815},
journal = {Nuclear Fusion},
issn = {ISSN 0029-5515},
number = {6},
volume = {64},
place = {IAEA},
publisher = {IOP Publishing},
year = {2024},
month = {05}}
Univ. of California, San Diego, CA (United States)
Sponsoring Organization:
Engineering and Physical Sciences Research Council (EPSRC); Ministry of Science and Technology, China; National Natural Science Foundation of China (NSFC); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, Vol. 197, Issue 1048, p. 124-140https://doi.org/10.1098/rspa.1949.0054
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 381, Issue 2242https://doi.org/10.1098/rsta.2021.0227