A three-point velocity estimation method for two-dimensional coarse-grained imaging data

被引:1
作者
Losada, J. M. [1 ]
Helgeland, A. D. [1 ]
Terry, J. L. [2 ]
Garcia, O. E. [1 ]
机构
[1] UiT Arctic Univ Norway, Dept Phys & Technol, N-9037 Tromso, Norway
[2] MIT Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA
关键词
SCRAPE-OFF LAYER; ALCATOR C-MOD; TIME-DELAY ESTIMATION; EDGE TURBULENCE; INTERMITTENT FLUCTUATIONS; PLASMA FLUCTUATIONS; VELOCIMETRY; DRIFT; FLOW;
D O I
10.1063/5.0197251
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Time delay and velocity estimation methods have been widely studied subjects in the context of signal processing, with applications in many different fields of physics. The velocity of waves or coherent fluctuation structures is commonly estimated as the distance between two measurement points divided by the time lag that maximizes the cross correlation function between the measured signals, but this is demonstrated to result in erroneous estimates for two spatial dimensions. We present an improved method to accurately estimate both components of the velocity vector, relying on three non-aligned measurement points. We introduce a stochastic process describing the fluctuations as a superposition of uncorrelated pulses moving in two dimensions. Using this model, we show that the three-point velocity estimation method, using time delays calculated through cross correlations, yields the exact velocity components when all pulses have the same velocity. The two- and three-point methods are tested on synthetic data generated from realizations of such processes for which the underlying velocity components are known. The results reveal the superiority of the three-point technique. Finally, we demonstrate the applicability of the velocity estimation on gas puff imaging data of strongly intermittent plasma fluctuations due to the radial motion of coherent, blob-like structures at the boundary of the Alcator C-Mod tokamak.
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页数:9
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