scholarly journals Effects of Dust Evolution on the Vertical Shear Instability in the Outer Regions of Protoplanetary Disks

2021 ◽  
Vol 914 (2) ◽  
pp. 132
Author(s):  
Yuya Fukuhara ◽  
Satoshi Okuzumi ◽  
Tomohiro Ono
Keyword(s):  
Protoplanetary Disks ◽  
Shear Instability ◽  
Vertical Shear ◽  
Dust Evolution

scholarly journals The coexistence of the streaming instability and the vertical shear instability in protoplanetary disks

2020 ◽  
Vol 635 ◽  
pp. A190 ◽  
Author(s):  
Urs Schäfer ◽  
Anders Johansen ◽  
Robi Banerjee
Keyword(s):  
Mach Number ◽  
Protoplanetary Disks ◽  
Scale Height ◽  
Shear Instability ◽  
Vertical Shear ◽  
Two Dimensional ◽  
Dust Layer ◽  
Fundamental Nature ◽  
Streaming Instability

The streaming instability is a leading candidate mechanism to explain the formation of planetesimals. However, the role of this instability in the driving of turbulence in protoplanetary disks, given its fundamental nature as a linear hydrodynamical instability, has so far not been investigated in detail. We study the turbulence that is induced by the streaming instability as well as its interaction with the vertical shear instability. For this purpose, we employ the FLASH Code to conduct two-dimensional axisymmetric global disk simulations spanning radii from 1  to 100 au, including the mutual drag between gas and dust as well as the radial and vertical stellar gravity. If the streaming instability and the vertical shear instability start their growth at the same time, we find the turbulence in the dust midplane layer to be primarily driven by the streaming instability. The streaming instability gives rise to vertical gas motions with a Mach number of up to ~10−2. The dust scale height is set in a self-regulatory manner to about 1% of the gas scale height. In contrast, if the vertical shear instability is allowed to saturate before the dust is introduced into our simulations, then it continues to be the main source of the turbulence in the dust layer. The vertical shear instability induces turbulence with a Mach number of ~10−1 and thus impedes dust sedimentation. Nonetheless, we find the vertical shear instability and the streaming instability in combination to lead to radial dust concentration in long-lived accumulations that are significantly denser than those formed by the streaming instability alone. Therefore, the vertical shear instability may promote planetesimal formation by creating weak overdensities that act as seeds for the streaming instability.

scholarly journals Hydrodynamical simulations of protoplanetary disks including irradiation of stellar photons

2020 ◽  
Vol 644 ◽  
pp. A50
Author(s):  
Lizxandra Flores-Rivera ◽  
Mario Flock ◽  
Riouhei Nakatani
Keyword(s):  
Large Scale ◽  
Protoplanetary Disks ◽  
Scale Height ◽  
The Body ◽  
Shear Instability ◽  
Vertical Shear ◽  
Small Scale ◽  
X Ray ◽  
Hydrodynamical Simulations ◽  
Energy Saturation

Context. In recent years hydrodynamical (HD) models have become important to describe the gas kinematics in protoplanetary disks, especially in combination with models of photoevaporation and/or magnetically driven winds. Our aim is to investigate how vertical shear instability (VSI) could influence the thermally driven winds on the surface of protoplanetary disks. Aims. In this first part of the project, we focus on diagnosing the conditions of the VSI at the highest numerical resolution ever recorded, and suggest at what resolution per scale height we obtain convergence. At the same time, we want to investigate the vertical extent of VSI activity. Finally, we determine the regions where extreme UV (EUV), far-UV (FUV), and X-ray photons are dominant in the disk. Methods. We perform global HD simulations using the PLUTO code. We adopt a global isothermal accretion disk setup, 2.5D (2 dimensions, 3 components) which covers a radial domain from 0.5 to 5.0 and an approximately full meridional extension. Our simulation runs cover a resolution from 12 to 203 cells per scale height. Results. We determine 50 cells per scale height to be the lower limit to resolve the VSI. For higher resolutions, ≥50 cells per scale height, we observe the convergence for the saturation level of the kinetic energy. We are also able to identify the growth of the “body” modes, with higher growth rate for higher resolution. Full energy saturation and a turbulent steady state is reached after 70 local orbits. We determine the location of the EUV heated region defined by Σr = 1019 cm−2 to be at HR ~ 9.7 and the FUV–X-ray heated boundary layer defined by Σr = 1022 cm−2 to be at HR ~ 6.2, making it necessary to introduce a hot atmosphere. For the first time we report the presence of small-scale vortices in the r − Z plane between the characteristic layers of large-scale vertical velocity motions. Such vortices could lead to dust concentration, promoting grain growth. Our results highlight the importance of combining photoevaporation processes in the future high-resolution studies of turbulence and accretion processes in disks.

scholarly journals Vertical Shear Instability in the Solar Nebula

2015 ◽  
Vol 10 (S314) ◽  
pp. 195-196
Author(s):  
Min-Kai Lin ◽  
Andrew N. Youdin
Keyword(s):  
Solar Nebula ◽  
Protoplanetary Disks ◽  
Shear Instability ◽  
Vertical Shear ◽  
Hydrodynamic Turbulence

AbstractWe quantify the thermodynamic requirement for the Vertical Shear Instability and evaluate its relevance to realistic protoplanetary disks as a potential route to hydrodynamic turbulence.

scholarly journals Including Dust Coagulation in Hydrodynamic Models of Protoplanetary Disks: Dust Evolution in the Vicinity of a Jupiter-mass Planet

2019 ◽  
Vol 885 (1) ◽  
pp. 91 ◽  
Author(s):  
Joanna Dra̧żkowska ◽  
Shengtai Li ◽  
Til Birnstiel ◽  
Sebastian M. Stammler ◽  
Hui Li
Keyword(s):  
Protoplanetary Disks ◽  
Hydrodynamic Models ◽  
Dust Evolution

scholarly journals High resolution parameter study of the vertical shear instability

2020 ◽  
Vol 499 (2) ◽  
pp. 1841-1853
Author(s):  
Natascha Manger ◽  
Hubert Klahr ◽  
Wilhelm Kley ◽  
Mario Flock
Keyword(s):  
Aspect Ratio ◽  
Large Scale ◽  
Dead Zone ◽  
Pressure Ratio ◽  
Theoretical Models ◽  
Shear Instability ◽  
Vertical Shear ◽  
Parameter Study ◽  
Aspect Ratios ◽  
Strong Scaling

ABSTRACT Theoretical models of protoplanetary discs have shown the vertical shear instability (VSI) to be a prime candidate to explain turbulence in the dead zone of the disc. However, simulations of the VSI have yet to show consistent levels of key disc turbulence parameters like the stress-to-pressure ratio α. We aim to reconcile these different values by performing a parameter study on the VSI with focus on the disc density gradient p and aspect ratio h = H/R. We use full 2π 3D simulations of the disc for chosen set of both parameters. All simulations are evolved for 1000 reference orbits, at a resolution of 18 cells per h. We find that the saturated stress-to-pressure ratio in our simulations is dependent on the disc aspect ratio with a strong scaling of α∝h2.6, in contrast to the traditional α model, where viscosity scales as ν∝αh2 with a constant α. We also observe consistent formation of large scale vortices across all investigated parameters. The vortices show uniformly aspect ratios of χ ≈ 10 and radial widths of approximately 1.5H. With our findings we can reconcile the different values reported for the stress-to-pressure ratio from both isothermal and full radiation hydrodynamics models, and show long-term evolution effects of the VSI that could aide in the formation of planetesimals.

scholarly journals Gravity Wave Emission by Shear Instability

2019 ◽  
Vol 49 (9) ◽  
pp. 2393-2406 ◽  
Author(s):  
Carsten Eden ◽  
Manita Chouksey ◽  
Dirk Olbers
Keyword(s):  
Gravity Wave ◽  
Single Layer ◽  
Internal Gravity Waves ◽  
Shear Instability ◽  
Vertical Shear ◽  
Wave Signal ◽  
Wave Emission ◽  
Balanced Flow ◽  
Single Layer Model

AbstractGravity wave emission by geostrophically balanced flow is diagnosed in numerical simulations of lateral and vertical shear instabilities. The diagnostic method in use allows for a separation of balanced flow and residual wave signal up to fourth order in the Rossby number (Ro). While evidence is found for a small but finite gravity wave emission from balanced flow in a single-layer model with large lateral shear and large Ro, a vertically resolved model with moderate velocity amplitudes appropriate to the interior ocean hardly shows any wave emission. Only when static instabilities generated by the shear instability of the balanced flow are allowed can a gravity wave signal similar to the ones reported in earlier studies be detected in the vertically resolved case. This result suggests a relatively small role of spontaneous wave emission in the classical sense of Lighthill radiation, and emphasizes the role of convective or symmetric instabilities during frontogenesis for the generation of internal gravity waves in the ocean and atmosphere.

scholarly journals Kelvin–Helmholtz Billows in the Eyewall of Hurricane Erin

2006 ◽  
Vol 134 (3) ◽  
pp. 1036-1038 ◽  
Author(s):  
Sim D. Aberson ◽  
Jeffrey B. Halverson
Keyword(s):  
Tropical Cyclone ◽  
High Altitude ◽  
Shear Instability ◽  
Vertical Shear ◽  
Vertically Aligned ◽  
Aircraft Pilots

Abstract A photograph of vertically aligned Kelvin–Helmholtz billows in the eastern eyewall of Hurricane Erin on 10 September 2001 is presented. The vertical shear instability in the horizontal winds necessary to produce the billows is confirmed with a high-altitude dropwindsonde observation. This shear instability is not known to be common in tropical cyclone eyewalls and is likely only in cases with a very large eyewall tilt. However, research and reconnaissance aircraft pilots need to be aware of the possibility of their existence, along with other types of hazardous conditions, in such rare circumstances.

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