Rossby-wave instability in viscous discs

The Rossby wave instability (RWI), which depends on the density bumps and extremum in the vortensities in the differentially rotating discs, plays an important role in the evolution of the protoplanetary discs. In this article, we investigate the effect of viscosity on the non-axisymmetric RWI in the self-graviting accretion discs. For this purpose, we add the viscosity to the work of Lovelace and Hohlfeld (2013). Consideration of viscosity complicates the problem so that we use the numerical method to investigate the stable and unstable modes. We consider three ranges of viscosities: high viscosity in the ranges $0.1\leq \alpha\leq 0.4$, moderate viscosity in the ranges $0.01\leq \alpha < 0.1$, and low viscosity in the ranges $\alpha < 0.01$. The results show that the occurrence of the RWI is related to the value of viscosity so that the effect of high viscosity is important, while the low viscosity is negligible. These results may be applied for the study of the RWI role in planet formation and angular momentum transport for different kinds of the protoplanetary discs with different viscosities.Comment: Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1212.0443 by other author

TechnoFile: Viscosity

The article focuses on the effect the viscosity of a glaze or slip has on a piece of pottery. The article explains the term and provides tests that can be performed to determine the viscosity of a substance. It goes on to describe how one can manipulate the viscosity of a glaze or slip through the addition of water or other aids and includes step-by-step instructions for making a slip

The effects of viscosity on the circumplanetary disks

The effects of viscosity on the circumplanetary disks residing in the vicinity of protoplanets are investigated through two-dimensional hydrodynamical simulations with the shearing sheet model. We find that viscosity can affect properties of the circumplanetary disk considerably when the mass of the protoplanet is $M_p \lesssim 33M_\oplus$, where $M_\oplus$ is the Earth mass. However, effects of viscosity on the circumplanetary disk are negligibly small when the mass of the protoplanet $M_p \gtrsim 33M_\oplus$. We find that when $M_p \lesssim 33M_\oplus$, viscosity can disrupt the spiral structure of the gas around the planet considerably and make the gas smoothly distributed, which makes the torques exerted on the protoplanet weaker. Thus, viscosity can make the migration speed of a protoplanet lower. After including viscosity, size of the circumplanetary disk can be decreased by a factor of $\gtrsim 20$. Viscosity helps to transport gas into the circumplanetary disk from the differentially rotating circumstellar disk. The mass of the circumplanetary disk can be increased by a factor of 50% after viscosity is taken into account when $M_p \lesssim 33M_\oplus$. Effects of viscosity on the formation of planets and satellites are briefly discussed.Comment: 17 pages, 8 figures; accepted by RA

Viscosity and viscosity anomalies of model silicates and magmas: a numerical investigation

We present results for transport properties (diffusion and viscosity) using computer simulations. Focus is made on a densified binary sodium disilicate 2SiO$_2$-Na$_2$O (NS2) liquid and on multicomponent magmatic liquids (MORB, basalt). In the NS2 liquid, results show that a certain number of anomalies appear when the system is densified: the usual diffusivity maxima/minima is found for the network-forming ions (Si,O) whereas the sodium atom displays three distinct r\'egimes for diffusion. Some of these features can be correlated with the obtained viscosity anomaly under pressure, the latter being be fairly well reproduced from the simulated diffusion constant. In model magmas (MORB liquid), we find a plateau followed by a continuous increase of the viscosity with pressure. Finally, having computed both diffusion and viscosity independently, we can discuss the validity of the Eyring equation for viscosity which relates diffusion and viscosity. It is shown that it can be considered as valid in melts with a high viscosity. On the overall, these results highlight the difficulty of establishing a firm relationship between dynamics, structure and thermodynamics in complex liquids.Comment: 13 pages, 8 figure

Simulations of splashing high and low viscosity droplets

In this work simulations are presented of low viscosity ethanol and high viscosity silicone oil droplets impacting on a dry solid surface at atmospheric and reduced ambient pressure. The simulations are able to capture both the effect of the ambient gas pressure and liquid viscosity on droplet impact and breakup. The results suggests that the early time droplet impact and gas film behavior for both low and high viscosity liquids share the same physics. However, for later time liquid sheet formation and breakup high and low viscosity liquids behave differently. These results explain why for both kinds of liquids the pressure effect can be observed, while at the same time different high and low viscosity splashing regimes have been identified experimentally

Inferences of mantle viscosity based on ice age data sets: Radial structure

We perform joint nonlinear inversions of glacial isostatic adjustment (GIA) data, including the following: postglacial decay times in Canada and Scandinavia, the Fennoscandian relaxation spectrum (FRS), late-Holocene differential sea level (DSL) highstands (based on recent compilations of Australian sea level histories), and the rate of change of the degree 2 zonal harmonic of the geopotential, $J_2$. Resolving power analyses demonstrate the following: (1) the FRS constrains mean upper mantle viscosity to be ∼3 × 10$^{20}$ Pa s, (2) postglacial decay time data require the average viscosity in the top ∼1500 km of the mantle to be 10$^{21}$ Pa s, and (3) the $J_2$ datum constrains mean lower mantle viscosity to be ∼5 × 10$^{21}$ Pa s. To reconcile (2) and (3), viscosity must increase to 10$^{22}$-10$^{23}$ Pa s in the deep mantle. Our analysis highlights the importance of accurately correcting the $J_2$ observation for modern glacier melting in order to robustly infer deep mantle viscosity. We also perform a large series of forward calculations to investigate the compatibility of the GIA data sets with a viscosity jump within the lower mantle, as suggested by geodynamic and seismic studies, and conclude that the GIA data may accommodate a sharp jump of 1-2 orders of magnitude in viscosity across a boundary placed in a depth range of 1000-1700 km but does not require such a feature. Finally, we find that no 1-D viscosity profile appears capable of simultaneously reconciling the DSL highstand data and suggest that this discord is likely due to laterally heterogeneous mantle viscosity, an issue we explore in a companion study