Investigations of Helicopter Wake Flow Including Rotor-Head Motion

2018 ◽  
Vol 55 (5) ◽  
pp. 2114-2126 ◽  
Author(s):  
M. Stuhlpfarrer ◽  
A. Kümmel ◽  
C. Breitsamter
Keyword(s):  
Wake Flow ◽  
Head Motion ◽  
Rotor Head

COMPARISON BETWEEN CLASSICAL AND THREE-COLOR PIV IN A WAKE FLOW

1993 ◽  
Vol 1 (4) ◽  
pp. 371-384 ◽  
Author(s):  
Antonio Cenedese ◽  
Giovanni P. Romano
Keyword(s):  
Wake Flow

fMRI Simulator Training to Suppress Head Motion

2016 ◽  
Vol 4 (2) ◽  
pp. 96-103 ◽  
Author(s):  
S. J. Graham ◽  
S. Ranieri ◽  
S. Boe ◽  
J. E. Ween ◽  
F. Tam ◽  
...  
Keyword(s):  
Simulator Training ◽  
Head Motion

Wake Flow of Single and Multiple Yawed Cylinders

2004 ◽  
Vol 126 (5) ◽  
pp. 861-870 ◽  
Author(s):  
A. Thakur ◽  
X. Liu ◽  
J. S. Marshall
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wake Flow ◽  
Upstream Region ◽  
Two Dimensional ◽  
Cylinder Wake ◽  
Dimensional Approximation ◽  
The Face ◽  
Drag And Lift

An experimental and computational study is performed of the wake flow behind a single yawed cylinder and a pair of parallel yawed cylinders placed in tandem. The experiments are performed for a yawed cylinder and a pair of yawed cylinders towed in a tank. Laser-induced fluorescence is used for flow visualization and particle-image velocimetry is used for quantitative velocity and vorticity measurement. Computations are performed using a second-order accurate block-structured finite-volume method with periodic boundary conditions along the cylinder axis. Results are applied to assess the applicability of a quasi-two-dimensional approximation, which assumes that the flow field is the same for any slice of the flow over the cylinder cross section. For a single cylinder, it is found that the cylinder wake vortices approach a quasi-two-dimensional state away from the cylinder upstream end for all cases examined (in which the cylinder yaw angle covers the range 0⩽ϕ⩽60°). Within the upstream region, the vortex orientation is found to be influenced by the tank side-wall boundary condition relative to the cylinder. For the case of two parallel yawed cylinders, vortices shed from the upstream cylinder are found to remain nearly quasi-two-dimensional as they are advected back and reach within about a cylinder diameter from the face of the downstream cylinder. As the vortices advect closer to the cylinder, the vortex cores become highly deformed and wrap around the downstream cylinder face. Three-dimensional perturbations of the upstream vortices are amplified as the vortices impact upon the downstream cylinder, such that during the final stages of vortex impact the quasi-two-dimensional nature of the flow breaks down and the vorticity field for the impacting vortices acquire significant three-dimensional perturbations. Quasi-two-dimensional and fully three-dimensional computational results are compared to assess the accuracy of the quasi-two-dimensional approximation in prediction of drag and lift coefficients of the cylinders.

A Critical, Event-Related Appraisal of Denoising in Resting-State fMRI Studies

2020 ◽  
Vol 30 (10) ◽  
pp. 5544-5559 ◽  
Author(s):  
Jonathan D Power ◽  
Charles J Lynch ◽  
Babatunde Adeyemo ◽  
Steven E Petersen
Keyword(s):  
Resting State ◽  
Resting State Fmri ◽  
Critical Event ◽  
Head Motion ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Decay Properties ◽  
Signal Decay ◽  
Biological Variables ◽  
Related Approach

Abstract This article advances two parallel lines of argument about resting-state functional magnetic resonance imaging (fMRI) signals, one empirical and one conceptual. The empirical line creates a four-part organization of the text: (1) head motion and respiration commonly cause distinct, major, unwanted influences (artifacts) in fMRI signals; (2) head motion and respiratory changes are, confoundingly, both related to psychological and clinical and biological variables of interest; (3) many fMRI denoising strategies fail to identify and remove one or the other kind of artifact; and (4) unremoved artifact, due to correlations of artifacts with variables of interest, renders studies susceptible to identifying variance of noninterest as variance of interest. Arising from these empirical observations is a conceptual argument: that an event-related approach to task-free scans, targeting common behaviors during scanning, enables fundamental distinctions among the kinds of signals present in the data, information which is vital to understanding the effects of denoising procedures. This event-related perspective permits statements like “Event X is associated with signals A, B, and C, each with particular spatial, temporal, and signal decay properties”. Denoising approaches can then be tailored, via performance in known events, to permit or suppress certain kinds of signals based on their desirability.

Flame stabilization in the wake flow behind a slit V-gutter

1994 ◽  
Vol 99 (2) ◽  
pp. 288-294 ◽  
Author(s):  
Jing-Tang Yang ◽  
Chang-Wu Yen ◽  
Go-Long Tsai
Keyword(s):  
Flame Stabilization ◽  
Wake Flow

scholarly journals Individual Differences in Impulsivity Predict Head Motion during Magnetic Resonance Imaging

PLoS ONE ◽  
2014 ◽  
Vol 9 (8) ◽  
pp. e104989 ◽  
Author(s):  
Xiang-zhen Kong ◽  
Zonglei Zhen ◽  
Xueting Li ◽  
Huan-hua Lu ◽  
Ruosi Wang ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Individual Differences ◽  
Magnetic Resonance ◽  
Head Motion ◽  
Resonance Imaging
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