Torque-coupling and particle–turbulence interactions

2012 ◽  
Vol 696 ◽  
pp. 319-329 ◽  
Author(s):  
Helge I. Andersson ◽  
Lihao Zhao ◽  
Mustafa Barri
Keyword(s):  
Stress Tensor ◽  
Fluid Phase ◽  
Turbulent Channel Flow ◽  
Coupled Simulation ◽  
Prolate Spheroidal ◽  
Strongly Coupled ◽  
Mechanical Coupling ◽  
Point Particles ◽  
Torque Vector ◽  
Force Coupling

AbstractA novel scheme for strong coupling between inertial Lagrangian point particles and a continuous Eulerian fluid phase has been developed. A full mechanical coupling can only be achieved if torque-coupling is applied along with the more conventional force-coupling. The torque vector acting from the particles on the fluid is expressed in terms of a new antisymmetric particle stress tensor which adds to the Stokes stress tensor. A strongly-coupled simulation of a turbulent channel flow laden with prolate spheroidal particles with aspect ratio 5:1 demonstrated that the inclusion of torque-coupling reduced the modulation of the turbulent flow field observed in a two-way force-coupled simulation. The spin and orientation of the spheroids were significantly affected.

Acceleration statistics of prolate spheroidal particles in turbulent channel flow

2018 ◽  
Vol 19 (10) ◽  
pp. 827-848 ◽  
Author(s):  
Rafik Ouchene ◽  
Juan Ignacio Polanco ◽  
Ivana Vinkovic ◽  
Serge Simoëns
Keyword(s):  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Prolate Spheroidal

Stochastic Resonance in Strongly Coupled Duffing and Van der pol Oscillators Under Trichotomous Noise and Bearing Fault Diagnosis

2019 ◽  
Vol 19 (03) ◽  
pp. 2050023
Author(s):  
Gang Zhang ◽  
Xia Wu ◽  
Tianqi Zhang
Keyword(s):  
Stochastic Resonance ◽  
Coupling Coefficient ◽  
Damping Coefficient ◽  
System Response ◽  
Damping Force ◽  
Van Der Pol ◽  
Restoring Force ◽  
Strongly Coupled ◽  
Force Coupling ◽  
Trichotomous Noise

Weak signal detection is an important topic, which has been widely studied in various fields. Different from other signal processing methods, stochastic resonance (SR) can utilize noise to enhance the characteristic frequency. Inspired by the unique advantage of SR, the strongly coupled Duffing and Van der pol SR system (SCD-VSR) is investigated. The simulation results show that the relationship between the output average signal–noise ratio increase (MSNRI) and different jump values of trichotomous noise presents different odd symmetrical distribution. It is also found that a double SR phenomenon could be observed when the damping coefficient of Van der pol system is small. Moreover, as the damping coefficient of the Duffing system increases, the output response would become gradually smooth. In addition,a smaller damping force coupling coefficient combined with a large restoring force coupling coefficient would achieve better system response. In the case of detecting an analog signal, MSNRI of SCD-VSR is larger than that of both classical bistable SR system (CBSR) and coupled Duffing SR system (CDSR). In addition, the experiments suggest that SCD-VSR could obtain a higher MSNRI and better detection effect, which implies the performance is superior to CBSR and CDSR.

On the gravitational dual to strongly coupled fluids

2021 ◽  
Author(s):  
◽  
Mark Musonda Webster Shawa
Keyword(s):  
Scattering Amplitudes ◽  
Stress Tensor ◽  
Quark Gluon Plasma ◽  
Gluon Plasma ◽  
High Energy ◽  
Gravitational Theory ◽  
Strongly Coupled ◽  
Tensor Correlation ◽  
High Energy Scattering ◽  
Gauge Gravity

This thesis discusses the prospect of finding the gravitational dual to the strongly coupled conformal fluids, with a special interest in the quark-gluon plasma. Such a task can be achieved by matching certain physical observables of two apparently different theories that are dually related owing to the fact that the same string theory can be viewed in two different ways. This is particularly useful when one of the theories is intractable while its dual is manageable. We begin by postulating a particular type of gravitational theory from which we determine graviton scattering amplitudes in a special regime of high momentum. Using the gauge–gravity duality dictionary, the graviton scattering amplitudes can be mapped to stress-tensor correlation functions in the gauge theory. One of the outcomes of high-energy scattering experiments involving the quark-gluon plasma is stress-tensor correlator data. This thesis provides an algorithm for matching graviton scattering amplitudes with stress-tensor correlator data which, in principle, can be used to identify the gravitational dual to the quark-gluon plasma.

scholarly journals On the fields and equations of motion of point particles

1946 ◽  
Vol 185 (1002) ◽  
pp. 250-268 ◽  
Keyword(s):  
Stress Tensor ◽  
World Line ◽  
Equations Of Motion ◽  
Mean Field ◽  
Point Particle ◽  
Point Particles ◽  
Symmetric Field ◽  
The World ◽  
Actual Field ◽  
A Charge

The investigation covers point particles possessing a charge, dipole and higher multipole moments interacting with fields of any spin satisfying the generalized wave equation (8). It is shown that the radiation field defined as the retarded minus the advanced field and all its derivatives is always finite at all points including those on the world line of the point particles. The symmetric field, defined as half the sum of the retarded and advanced fields, is shown to contain apart expressible as an integral along the world line from minus to plus infinity, which is continuous and finite everywhere. This integral vanishes if X = 0. The modified symmetric field is defined as the symmetric field minus this integral. The actual field is expressed as a sum of the modified symmetric field plus the modified mean field defined as half the sum of the Ingoing and outgoing fields plus the integral just mentioned. It is proved that the part of the stress tensor of the field quadratic in the modified symmetric field plays no part in determining the equations of motion of the point particle. Being conserved by itself, it can always be subtracted away, thus defining a new stress tensor which is free from all the highest singularities in the usual stress tensor. The equations of motion of the particle are shown to depend only on the usual ‘mixed terms’ in the inflow with the modified mean field substituted for the ingoing field. The formulation for several particles is given.

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