Dynamics of internal jets in the merging of two droplets of unequal sizes

2016 ◽  
Vol 795 ◽  
pp. 671-689 ◽  
Author(s):  
Chenglong Tang ◽  
Jiaquan Zhao ◽  
Peng Zhang ◽  
Chung K. Law ◽  
Zuohua Huang
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Volume Of Fluid Method ◽  
Internal Mixing ◽  
Mixing Dynamics ◽  
Mixing Patterns ◽  
The Impact ◽  
Refinement Algorithm

The head-on collision, merging and internal mixing dynamics of two unequal-sized droplets were experimentally studied and interpreted, using water, $n$-decane and $n$-tetradecane to identify the distinguishing effects of surface tension and liquid viscosity on the merging and mixing patterns. It is shown that, upon merging of water and $n$-decane droplets, mushroom-like jets of dissimilar characteristics develop within the merged mass for small and large values of the impact Weber number (We), and that such jets are not developed for intermediate values of We. Furthermore, such jet-like mixing patterns were not observed for droplets of $n$-tetradecane, which has smaller surface tension and larger viscosity as compared to water. A regime nomogram relating the Ohnesorge and symmetric Weber numbers is constructed, providing a unified interpretation of the internal mixing patterns. Numerical simulations based on an improved volume-of-fluid method and an adaptive mesh refinement algorithm provide auxiliary diagnoses of the flow fields and the observed phenomena.

scholarly journals The impact of AGN feedback on the 1D power spectra from the Ly α forest using the Horizon-AGN suite of simulations

2020 ◽  
Vol 495 (2) ◽  
pp. 1825-1840 ◽  
Author(s):  
Solène Chabanier ◽  
Frédéric Bournaud ◽  
Yohan Dubois ◽  
Nathalie Palanque-Delabrouille ◽  
Christophe Yèche ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Adaptive Mesh Refinement ◽  
Power Spectra ◽  
Adaptive Mesh ◽  
Processing Stage ◽  
Galactic Winds ◽  
Upper Limits ◽  
Feeding Parameters ◽  
Future Work ◽  
The Impact

ABSTRACT The Lyman-α forest is a powerful probe for cosmology, but it is also strongly impacted by galaxy evolution and baryonic processes such as active galactic nucleus (AGN) feedback, which can redistribute mass and energy on large scales. We constrain the signatures of AGN feedback on the 1D power spectrum of the Lyman-α forest using a series of eight hydro-cosmological simulations performed with the adaptive mesh refinement code ramses. This series starts from the Horizon-AGN simulation and varies the subgrid parameters for AGN feeding, feedback, and stochasticity. These simulations cover the whole plausible range of feedback and feeding parameters according to the resulting galaxy properties. AGNs globally suppress the Lyman-α power at all scales. On large scales, the energy injection and ionization dominate over the supply of gas mass from AGN-driven galactic winds, thus suppressing power. On small scales, faster cooling of denser gas mitigates the suppression. This effect increases with decreasing redshift. We provide lower and upper limits of this signature at nine redshifts between z = 4.25 and 2.0, making it possible to account for it at post-processing stage in future work given that running simulations without AGN feedback can save considerable amounts of computing resources. Ignoring AGN feedback in cosmological inference analyses leads to strong biases with 2 per cent shift on σ8 and 1 per cent shift on ns, which represents twice the standards deviation of the current constraints on ns.

Pattern Formation in Directional Solidification

2003 ◽  
Vol 782 ◽  
Author(s):  
Mike Greenwood ◽  
Mikko Haataja ◽  
Nikolas Provatas
Keyword(s):  
Surface Tension ◽  
Directional Solidification ◽  
Thermal Gradient ◽  
Adaptive Mesh Refinement ◽  
Interface Velocity ◽  
Adaptive Mesh ◽  
Field Method ◽  
Phase Field Method ◽  
Dendrite Morphology ◽  
Small Surface

We simulate directional solidification using the phase field method solved with adaptive mesh refinement. We examine length scale selection for two cases. For small surface tension anisotropy directed at forty five degrees relative to the pulling direction, we observe a transition from a seaweed to dendrite morphology as the thermal gradient is lowered, consistent with recent experimental findings. We show that the morphology of crystal structures can be unambiguously characterized through the local interface velocity distribution. We derive semi-empirically a phase diagram for the transition from seaweed to dendrites as a function of thermal gradient and pulling speed. As surface tension anisotropy is increased and aligned with the pulling direction we observe cellular and dendritic arrays directed in the pulling direction. We characterize wavelength selection and obtain a new universal scaling of the wavelength that differs from previous theories.

An adaptive mesh refinement algorithm for compressible two-phase flow in porous media

2011 ◽  
Vol 16 (3) ◽  
pp. 577-592 ◽  
Author(s):  
George Shu Heng Pau ◽  
John B. Bell ◽  
Ann S. Almgren ◽  
Kirsten M. Fagnan ◽  
Michael J. Lijewski
Keyword(s):  
Porous Media ◽  
Adaptive Mesh Refinement ◽  
Two Phase Flow ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Flow In Porous Media ◽  
Phase Flow ◽  
Two Phase ◽  
Refinement Algorithm

scholarly journals Adaptive mesh refinement algorithm development and dissemination

1997 ◽  
Author(s):  
J.S. Saltzman ◽  
D.L. Brown ◽  
K.D. Brislawn ◽  
G.S. Chesshire ◽  
D.J. Quinlan ◽  
...  
Keyword(s):  
Adaptive Mesh Refinement ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Algorithm Development ◽  
Refinement Algorithm

scholarly journals What determines the formation and characteristics of protoplanetary discs?

2020 ◽  
Vol 635 ◽  
pp. A67 ◽  
Author(s):  
Patrick Hennebelle ◽  
Benoit Commerçon ◽  
Yueh-Ning Lee ◽  
Sébastien Charnoz
Keyword(s):  
Adaptive Mesh Refinement ◽  
Initial Conditions ◽  
Adaptive Mesh ◽  
Small Scale ◽  
Initial Structure ◽  
Solar Mass ◽  
Central Object ◽  
The Impact ◽  
Protoplanetary Discs

Context. Planets form in protoplanetary discs. Their masses, distribution, and orbits sensitively depend on the structure of the protoplanetary discs. However, what sets the initial structure of the discs in terms of mass, radius and accretion rate is still unknown. Aims. It is therefore of great importance to understand exactly how protoplanetary discs form and what determines their physical properties. We aim to quantify the role of the initial dense core magnetisation, rotation, turbulence, and misalignment between rotation and magnetic field axis as well as the role of the accretion scheme onto the central object. Methods. We performed non-ideal magnetohydrodynamics numerical simulations using the adaptive mesh refinement code Ramses of a collapsing, one solar mass molecular core to study the disc formation and early, up to 100 kyr, evolution. We paid particular attention to the impact of numerical resolution and accretion scheme. Results. We found that the mass of the central object is almost independent of the numerical parameters such as the resolution and the accretion scheme onto the sink particle. The disc mass and to a lower extent its size, however heavily depend on the accretion scheme, which we found is itself resolution dependent. This implies that the accretion onto the star and through the disc are largely decoupled. For a relatively large domain of initial conditions (except at low magnetisation), we found that the properties of the disc do not change too significantly. In particular both the level of initial rotation and turbulence do not influence the disc properties provide the core is sufficiently magnetised. After a short relaxation phase, the disc settles in a stationary state. It then slowly grows in size but not in mass. The disc itself is weakly magnetised but its immediate surrounding on the contrary is highly magnetised. Conclusions. Our results show that the disc properties directly depend on the inner boundary condition, i.e. the accretion scheme onto the central object. This suggests that the disc mass is eventually controlled by a small-scale accretion process, possibly the star-disc interaction. Because of ambipolar diffusion and its significant resistivity, the disc diversity remains limited and except for low magnetisation, their properties are weakly sensitive to initial conditions such as rotation and turbulence.

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