Coherent instability in wall-bounded shear

2018 ◽  
Vol 844 ◽  
pp. 917-955 ◽  
Author(s):  
M. J. Philipp Hack ◽  
Parviz Moin
Keyword(s):  
Multiple Scales ◽  
Streamwise Velocity ◽  
Similar Process ◽  
Morphological Operations ◽  
Data Set ◽  
Time Resolved ◽  
Statistical Characterization ◽  
Moderate Reynolds Number ◽  
Streamwise Velocity Component

The mechanism underlying the coherent hairpin process in wall-bounded shear flows is studied. An algorithm for the identification and analysis of flow structures based on morphological operations is presented. The method distils the topology of the flow field into a discrete data set and enables the time-resolved sampling of coherent flow processes across multiple scales. Application to direct simulation data of transitional and turbulent boundary layers at moderate Reynolds number sheds light on the flow physics of the hairpin process. The analysis links the hairpin to an exponential instability which is amplified in the flow distorted by a negative perturbation in the streamwise velocity component. Linear analyses substantiate the connection to an inviscid instability mechanism of varicose type. The formation of packets of hairpins is related to a self-similar process which originates from a single patch of low-speed fluid and describes a recurrence of the dynamics that leads to the formation of an individual hairpin. Analysis of the evolution of several thousand turbulent hairpins provides a statistical characterization of the principal dynamics and yields a time-resolved average of the hairpin process. Comparisons with the transitional hairpin show qualitatively consistent trends and thus support earlier hypotheses of their equivalence. In terms of the causality of events, the results suggest that the hairpin is a manifestation of the varicose instability and as such is a consequence rather than a cause of the primary perturbations of the flow.

scholarly journals Experimental Characterization of the Jet Wiping Process

2018 ◽  
Vol 180 ◽  
pp. 02064
Author(s):  
Miguel Alfonso Mendez ◽  
Adriana Enache ◽  
Anne Gosset ◽  
Jean-Marie Buchlin
Keyword(s):  
Gas Flow ◽  
Detection Algorithm ◽  
Gas Flows ◽  
Experimental Characterization ◽  
Data Set ◽  
Time Resolved ◽  
Numerical Studies ◽  
Image Velocimetry ◽  
The Impact

This paper presents an experimental characterization of the jet wiping process, used in continuous coating applications to control the thickness of a liquid coat using an impinging gas jet. Time Resolved Particle Image Velocimetry (TR-PIV) is used to characterize the impinging gas flow, while an automatic interface detection algorithm is developed to track the liquid interface at the impact. The study of the flow interaction is combined with time resolved 3D thickness measurements of the liquid film remaining after the wiping, via Time Resolved Light Absorption (TR-LAbs). The simultaneous frequency analysis of liquid and gas flows allows to correlate their respective instability, provide an experimental data set for the validation of numerical studies and allows for formulating a working hypothesis on the origin of the coat non-uniformity encountered in many jet wiping processes.

scholarly journals Characterization of a Novel FRET Probe in a Crowded Environment using Time-Resolved Anisotropy

2017 ◽  
Vol 112 (3) ◽  
pp. 346a
Author(s):  
Hannah Leopold ◽  
Megan Currie ◽  
Jacob Schwarz ◽  
Arnold J. Boersma ◽  
Erin D. Sheets ◽  
...  
Keyword(s):  
Time Resolved ◽  
Crowded Environment

scholarly journals Critical Review of EMC Standards for the Measurement of Radiated Electromagnetic Emissions from Transit Line and Rolling Stock

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 759
Author(s):  
Andrea Mariscotti
Keyword(s):  
Time Distribution ◽  
Communication Systems ◽  
Electromagnetic Compatibility ◽  
Transportation Systems ◽  
Operating Conditions ◽  
Rolling Stock ◽  
Intrinsic Variability ◽  
Statistical Characterization ◽  
Electromagnetic Emissions

Accurate and comprehensive methods for the assessment of radiated electromagnetic emissions in modern electric transportation systems are a necessity. The characteristics and susceptibility of modern victim signaling and communication radio services, operating within and outside the right-of-way, require an update of the measurement methods integrating or replacing the swept frequency technique with time domain approaches. Applicable standards are the EN 50121 (equivalent to the IEC 62236) and Urban Mass Transport Association (UMTA) with additional specifications from project contracts. This work discusses the standardized methods and settings, and the representative operating conditions, highlighting areas where improvements are possible and opportune (statistical characterization of measurement results, identification and distinction of emissions and line resonances, and narrowband and broadband phenomena). In particular for the Electromagnetic Compatibility (EMC) assessment with new Digital Communication Systems, the characterization of time distribution of spectral properties is discussed, e.g., by means of Amplitude Probability Distribution and including time distribution information. The problem of determination of site and setup uncertainty and repeatability is also discussed, observing on one hand the lack of clear indications in standards and, on the other hand, the non-ideality and intrinsic variability of measurement conditions (e.g., rolling stock operating conditions, synchronization issues, and electric arc intermittence).

Statistical characterization of the signal-in-space errors of the BDS: a comparison between BDS-2 and BDS-3

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Guo Chen ◽  
Renyu Zhou ◽  
Zhigang Hu ◽  
Yifei Lv ◽  
Na Wei ◽  
...  
Keyword(s):  
Statistical Characterization

scholarly journals KD determination from time-resolved experiments on live cells with LigandTracer and reconciliation with end-point flow cytometry measurements

2021 ◽  
Author(s):  
Diana Spiegelberg ◽  
Jonas Stenberg ◽  
Pascale Richalet ◽  
Marc Vanhove
Keyword(s):  
Flow Cytometry ◽  
Live Cells ◽  
Time Resolved ◽  
Surface Receptors ◽  
Full Characterization ◽  
End Point ◽  
Titration Curves ◽  
Kinetics Of

AbstractDesign of next-generation therapeutics comes with new challenges and emulates technology and methods to meet them. Characterizing the binding of either natural ligands or therapeutic proteins to cell-surface receptors, for which relevant recombinant versions may not exist, represents one of these challenges. Here we report the characterization of the interaction of five different antibody therapeutics (Trastuzumab, Rituximab, Panitumumab, Pertuzumab, and Cetuximab) with their cognate target receptors using LigandTracer. The method offers the advantage of being performed on live cells, alleviating the need for a recombinant source of the receptor. Furthermore, time-resolved measurements, in addition to allowing the determination of the affinity of the studied drug to its target, give access to the binding kinetics thereby providing a full characterization of the system. In this study, we also compared time-resolved LigandTracer data with end-point KD determination from flow cytometry experiments and hypothesize that discrepancies between these two approaches, when they exist, generally come from flow cytometry titration curves being acquired prior to full equilibration of the system. Our data, however, show that knowledge of the kinetics of the interaction allows to reconcile the data obtained by flow cytometry and LigandTracer and demonstrate the complementarity of these two methods.

scholarly journals Time-Resolved Spectroscopic Study of N,N-Di(4-bromo)nitrenium Ions in Selected Solutions

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3182 ◽  
Author(s):  
Lili Du ◽  
Xin Lan ◽  
Zhiping Yan ◽  
Ruixue Zhu ◽  
David Phillips
Keyword(s):  
Transient Absorption ◽  
Direct Detection ◽  
Reaction Pathway ◽  
Addition Reactions ◽  
Time Resolved ◽  
Nitrenium Ions ◽  
Future Studies ◽  
Nitrenium Ion ◽  
Design Time

Nitrenium ions are important reactive intermediates in chemistry and biology. In this work, femtosecond and nanosecond transient absorption (fs-TA and ns-TA) along with nanosecond time-resolved resonance Raman (ns-TR3) experiments were employed to examine the photochemical pathways of N-(4,4′-dibromodiphenylamino)-2,4,6-trimethylpyridinium BF4− (salt (DN) from just absorption of a photon of light to the production of the important N,N-di(4-bromophenyl)nitrenium ion 2. In acetonitrile (MeCN), the formation of halogenated diarylnitrenium ion 2 was observed within 4 ps, showing the vibrational spectra with strong intensity. The nucleophilic adduct reaction of ion 2 with H2O was also examined in aqueous solutions. The direct detection of the unique ortho adduct intermediate 3 shows that there is an efficient and exclusive reaction pathway for 2 with H2O. The results shown in this paper give new characterization of 2, which can be used to design time-resolved spectroscopy investigations of covalent addition reactions of nitrenium ions with other molecules in future studies.

Uncertainty analysis of time resolved transmittance characterization of solid tissue phantoms

2010 ◽  
Author(s):  
Jean-Pierre Bouchard ◽  
Israël Veilleux ◽  
Isabelle Noiseux ◽  
Sébastien Leclair ◽  
Rym Jedidi ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Time Resolved ◽  
Solid Tissue ◽  
Tissue Phantoms
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