Hydrodynamic effect of elastic and inelastic collisions in fluidized bubbling bed reactor

Abstract We study the effects of inelastic dark matter self-interactions on the internal structure of a simulated Milky Way (MW)-size halo. Self-interacting dark matter (SIDM) is an alternative to collisionless cold dark matter (CDM) which offers a unique solution to the problems encountered with CDM on sub-galactic scales. Although previous SIDM simulations have mainly considered elastic collisions, theoretical considerations motivate the existence of multi-state dark matter where transitions from the excited to the ground state are exothermic. In this work, we consider a self-interacting, two-state dark matter model with inelastic collisions, implemented in the Arepo code. We find that energy injection from inelastic self-interactions reduces the central density of the MW halo in a shorter timescale relative to the elastic scale, resulting in a larger core size. Inelastic collisions also isotropize the orbits, resulting in an overall lower velocity anisotropy for the inelastic MW halo. In the inner halo, the inelastic SIDM case (minor-to-major axis ratio s ≡ c/a ≈ 0.65) is more spherical than the CDM (s ≈ 0.4), but less spherical than the elastic SIDM case (s ≈ 0.75). The speed distribution f(v) of dark matter particles at the location of the Sun in the inelastic SIDM model shows a significant departure from the CDM model, with f(v) falling more steeply at high speeds. In addition, the velocity kicks imparted during inelastic collisions produce unbound high-speed particles with velocities up to 500 km s−1 throughout the halo. This implies that inelastic SIDM can potentially leave distinct signatures in direct detection experiments, relative to elastic SIDM and CDM.

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Numerical Analysis of Thermophoresis of a Charged Spheroidal Colloid in Aqueous Media

Micromachines ◽

10.3390/mi12020224 ◽

2021 ◽

Vol 12 (2) ◽

pp. 224

Author(s):

Yi Zhou ◽

Yang Yang ◽

Changxing Zhu ◽

Mingyuan Yang ◽

Yi Hu

Keyword(s):

Numerical Analysis ◽

Aqueous Media ◽

Concentration Field ◽

Ion Concentration ◽

Spherical Particles ◽

Hydrodynamic Effect ◽

Oblate Spheroids ◽

Thermodiffusion Coefficient ◽

Arbitrary Electric Double Layer ◽

Dimension Ratio

Thermophoresis of charged colloids in aqueous media has wide applications in biology. Most existing studies of thermophoresis focused on spherical particles, but biological compounds are usually non-spherical. The present paper reports a numerical analysis of the thermophoresis of a charged spheroidal colloid in aqueous media. The model accounts for the strongly coupled temperature field, the flow field, the electric potential field, and the ion concentration field. Numerical simulations revealed that prolate spheroids move faster than spherical particles, and oblate spheroids move slower than spherical particles. For the arbitrary electric double layer (EDL) thickness, the thermodiffusion coefficient of prolate (oblate) spheroids increases (decreases) with the increasing particle’s dimension ratio between the major and minor semiaxes. For the extremely thin EDL case, the hydrodynamic effect is significant, and the thermodiffusion coefficient for prolate (oblate) spheroids converges to a fixed value with the increasing particle’s dimension ratio. For the extremely thick EDL case, the particle curvature’s effect also becomes important, and the increasing (decreasing) rate of thermodiffusion coefficient for prolate (oblate) spheroids is reduced slightly.

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Probabilistic seismic response analysis of coastal highway bridges under scour and liquefaction conditions: does the hydrodynamic effect matter?

Advances in Bridge Engineering ◽

10.1186/s43251-020-00021-8 ◽

2020 ◽

Vol 1 (1) ◽

Author(s):

Xiaowei Wang ◽

Yutao Pang ◽

Aijun Ye

Keyword(s):

Seismic Response ◽

Seismic Design ◽

Highway Bridges ◽

Element Model ◽

Response Analysis ◽

Hydrodynamic Effect ◽

Strong Earthquakes ◽

Influence Of Water ◽

Scour Hazard ◽

Ground Motion Records

AbstractCoastal highway bridges are usually supported by pile foundations that are submerged in water and embedded into saturated soils. Such sites have been reported susceptible to scour hazard and probably liquefied under strong earthquakes. Existing studies on seismic response analyses of such bridges often ignore the influence of water-induced hydrodynamic effect. This study assesses quantitative impacts of the hydrodynamic effect on seismic responses of coastal highway bridges under scour and liquefaction potential in a probabilistic manner. A coupled soil-bridge finite element model that represents typical coastal highway bridges is excited by two sets of ground motion records that represent two seismic design levels (i.e., low versus high in terms of 10%-50 years versus 2%-50 years). Modeled by the added mass method, the hydrodynamic effect on responses of bridge key components including the bearing deformation, column curvature, and pile curvature is systematically quantified for scenarios with and without liquefaction across different scour depths. It is found that the influence of hydrodynamic effect becomes more noticeable with the increase of scour depths. Nevertheless, it has minor influence on the bearing deformation and column curvature (i.e., percentage changes of the responses are within 5%), regardless of the liquefiable or nonliquefiable scenario under the low or high seismic design level. As for the pile curvature, the hydrodynamic effect under the low seismic design level may remarkably increase the response by as large as 15%–20%, whereas under the high seismic design level, it has ignorable influence on the pile curvature.

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Comparative CFD modeling of a bubbling bed using a Eulerian–Eulerian two-fluid model (TFM) and a Eulerian-Lagrangian dense discrete phase model (DDPM)

Powder Technology ◽

10.1016/j.powtec.2021.01.063 ◽

2021 ◽

Vol 383 ◽

pp. 418-442

Author(s):

Muhammad Adnan ◽

Jie Sun ◽

Nouman Ahmad ◽

Jin Jia Wei

Keyword(s):

Fluid Model ◽

Phase Model ◽

Cfd Modeling ◽

Discrete Phase Model ◽

Bubbling Bed ◽

Discrete Phase ◽

Two Fluid Model ◽

Two Fluid

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Inelastic collisions in radiofrequency-dressed mixtures of ultracold atoms

Physical Review Research ◽

10.1103/physrevresearch.2.033163 ◽

2020 ◽

Vol 2 (3) ◽

Author(s):

Elliot Bentine ◽

Adam J. Barker ◽

Kathrin Luksch ◽

Shinichi Sunami ◽

Tiffany L. Harte ◽

...

Keyword(s):

Ultracold Atoms ◽

Inelastic Collisions

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Motion periodicity and bifurcation of a wave excited hopping ball

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2019.0137 ◽

2019 ◽

Vol 475 (2228) ◽

pp. 20190137

Author(s):

Gaurang Ruhela ◽

Anirvan DasGupta

Keyword(s):

Wave Amplitude ◽

Harmonic Wave ◽

Inelastic Collisions ◽

Loss Of Stability ◽

Elastic Surface ◽

Minimum Frequency ◽

Surface Motion ◽

Return Map ◽

Ball Problem ◽

Subsequent Loss

We consider the problem of a hopping ball excited by a travelling harmonic wave on an elastic surface. The ball, considered as a particle, is assumed to interact with the surface through inelastic collisions. The surface motion due to the wave induces a horizontal drift in the ball. The problem is treated analytically under certain approximations. The phase space of the hopping motion is captured by constructing a phase-velocity return map. The fixed points of the return map and its compositions represent periodic hopping solutions. The linear stability of the obtained periodic solution is studied in detail. The minimum frequency for the onset of periodic hops, and the subsequent loss of stability at the bifurcation frequency, have been determined analytically. Interestingly, for small values of wave amplitude, the analytical solutions reveal striking similarities with the results of the classical bouncing ball problem.

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