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Concept

Four-velocity

Related publications (27)

Gyrokinetic moment-based simulations of the Dimits shift

Paolo Ricci, Baptiste Jimmy Frei, Antoine Cyril David Hoffmann

We present a convergence study of the gyromoment (GM) approach, which is based on projecting the gyrokinetic distribution function onto a Hermite–Laguerre polynomial basis, focused on the cyclone base case (CBC) (Lin et al., Phys. Rev. Lett., vol. 83, no. ...

Cambridge University Press2023

Impact of the turbulence wavenumber spectrum and probing beam geometry on Doppler reflectometry perpendicular velocity measurements

Frank Nüesch

The perpendicular propagation velocity of turbulent density fluctuations is an important parameter in fusion plasmas, since sheared plasma flows are crucial for reducing turbulence, and thus an essential input parameter for turbulent transport simulations. ...

IOP Publishing Ltd2023

Device for measuring instantaneous sprint velocity

Kamiar Aminian, Farzin Dadashi, Benoît Mariani, Salil Apte

The invention concerns a device for measuring instantaneous sprint velocity, said device consisting of at least one position and/or one velocity sensor and one IMU sensor that respectively provide position and/or velocity and acceleration signals and where ...

2021

One-minute average cruise track and ship velocity of the Antarctic Circumnavigation Expedition (ACE) undertaken during the austral summer of 2016/2017

Julia Schmale, Sebastian Johannes Heinz-Josef Landwehr

Dataset abstract The ship's cruise track, velocity, course over ground and heading at one-minute resolution for all five legs of the Antarctic Circumnavigation Expedition (ACE) are derived from a combination of: - the latitude/longitud ...

2020

Continuously-fed density currents over impermeable and porous substrates

Sara Venuleo

Gravity currents are buoyancy-driven flows having a significant impact on the environment and human life. They can be observed in a vast range of natural and anthropogenic scenarios, such as seawater and freshwater, the atmosphere, or industrial processes. ...

EPFL2020

Synthesis of grid compliant substitute natural gas from a representative biogas mixture in a hybrid Ni/Ru catalysed reactor

Andreas Züttel, Robin Tobias Andreas Mutschler, Emanuele Moioli, Marco Calizzi, Alexandre Borsay

We demonstrate biogas upgrading towards full CO2 conversion in mild conditions in a three-step reactor system using Ru- and Ni-based catalysts. In each of the three reactor stages, the temperature is carefully controlled, thus optimizing the reaction therm ...

2020

Self-Propulsion of Active Colloids via Ion Release: Theory and Experiments

Ignacio Pagonabarraga Mora

We study the self-propulsion of a charged colloidal particle that releases ionic species using theory and experiments. We relax the assumptions of thin Debye length and weak nonequilibrium effects assumed in classical phoretic models. This leads to a numbe ...

2020

Multirotor UAV-based platform for the measurement of atmospheric turbulence: validation and signature detection of tip vortices of wind turbine blades

Fernando Porté Agel, Fernando Carbajo Fuertes, Lionel Wilhelm

The present study describes the development of a technique for the measurement of atmospheric turbulence and temperature at a point in space based on the integration of a fast-response multi-hole pressure probe and a thermocouple with an inertial measureme ...

2019

Particle transport at arbitrary timescales with Poisson-distributed collisions

Ambrogio Fasoli, Ivo Furno, Paolo Ricci, Marcelo Baquero Ruiz, Fabian Manke

We develop a model to investigate the time evolution of the mean location and variance of a random walker subject to Poisson-distributed collisions at constant rate. The collisions are instantaneous velocity changes where a new value of velocity is generat ...

2019

Pulses in Upward Negative Lightning at the Säntis Tower in Northeastern Switzerland

Farhad Rachidi-Haeri, Marcos Rubinstein, Davide Pavanello, Mohammad Azadifar, Lixia He

Upward lightning happens predominantly from tall objects. The channel-base currents associated with upward negative lightning initiated from towers exhibit pulses that can be classified, based on their waveform features and on the concurrence with other pr ...

2019

Diagnostic of fast-ion energy spectra and densities in magnetized plasmas

Olivier Sauter, Richard Pitts, Ambrogio Fasoli, Stefano Coda, Basil Duval, Henri Weisen, Yves Martin, Yann Camenen, Javier García Hernández, Duccio Testa, Marco Wischmeier, Nicola Vianello, Mikhail Maslov, Patrick Blanchard, Alessandro Pau, Davide Galassi, Antonio José Pereira de Figueiredo, Liang Yao, Dalziel Joseph Wilson, Cristian Sommariva, Jan Horacek, Jonathan Graves, Federico Nespoli, Hamish William Patten, Samuel Lanthaler, David Pfefferlé, Jonathan Marc Philippe Faustin

The measurement of the energy spectra and densities of alpha-particles and other fast ions are part of the ITER measurement requirements, highlighting the importance of energy-resolved energetic-particle measurements for the mission of ITER. However, it ha ...

IOP PUBLISHING LTD2019

An algebraic least squares reduced basis method for the solution of nonaffinely parametrized Stokes equations

Alfio Quarteroni, Simone Deparis, Andrea Manzoni, Niccolò Dal Santo

In this paper we propose a new, purely algebraic, Petrov-Galerkin reduced basis (RB) method to solve the parametrized Stokes equations, where parameters serve to identify the (variable) domain geometry. Our method is obtained as an algebraic least squares ...

ELSEVIER SCIENCE SA2019

LES investigation of the influence of cavitation on flow patterns in a confined tip-leakage flow

Mohamed Farhat

In the present paper, Large Eddy Simulations combined with the Zwart-Gerber-Belamri cavitation model are conducted to study the flow characteristics in a tip-leakage flow. A reasonable agreement is obtained between the numerical and experimental data. With ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Effect of spilling from adjacent orifices on the velocity field and pressures in front of needle stop-logs

Giovanni De Cesare, Azin Amini, Ivan Stojnic, Cédric Bron

In this study, the effect of spilling from neighboring sluice gates on stop-logs was experimentally investigated on a 1:65 physical scale model comprised of a double arch dam, a reservoir area, six spillway orifices and two stop-logs. Two types of measurem ...

2018

Innovative measurement techniques for atmospheric turbulence and wind energy

Fernando Carbajo Fuertes

The measurement of different atmospheric flow quantities is of utmost importance for a correct understanding of most atmospheric phenomena. Researchers and industry in the fields of meteorology and wind engineering demand extensive and accurate measurement ...

EPFL2018

Absolute/convective secondary instabilities and the role of confinement in free shear layers

François Gallaire

We study the linear spatiotemporal stability of an infinite row of equal point vortices under symmetric confinement between parallel walls. These rows of vortices serve to model the secondary instability leading to the merging of consecutive (Kelvin-Helmho ...

2018

Influence of heterogeneities on crack propagation

Jean-François Molinari, Okan Yilmaz, Jérémy Bleyer

The influence of material heterogeneities is studied in the context of dynamic failure. We consider a pre-strained plate problem, the homogeneous case of which has been widely studied both experimentally and numerically. This setup is used to isolate the e ...

2018

Doppler-Based Acoustic Gyrator

Romain Christophe Rémy Fleury, Farzad Zangeneh Nejad

Non-reciprocal phase shifters have been attracting a great deal of attention due to their important applications in filtering, isolation, modulation, and mode locking. Here, we demonstrate a non-reciprocal acoustic phase shifter using a simple acoustic wav ...

2018

Higher order Larmor radius corrections to guiding-centre equations and application to fast ion equilibrium distributions

Jonathan Graves, Wilfred Anthony Cooper, David Pfefferlé, Samuel Lanthaler

An improved set of guiding-centre equations, expanded to one order higher in Larmor radius than usually written for guiding-centre codes, are derived for curvilinear flux coordinates and implemented into the orbit following code VENUS-LEVIS. Aside from gre ...

Iop Publishing Ltd2017

Scale anomalies, states, and rates in conformal field theory

Marc Gillioz

This paper presents two methods to compute scale anomaly coefficients in conformal field theories (CFTs), such as the c anomaly in four dimensions, in terms of the CFT data. We first use Euclidean position space to show that the anomaly coefficient of a fo ...

Springer Nature2017