Growth Rate Of Rayleigh-Taylor Instability Research Articles

Rayleigh-Taylor Kararsızlığının Büyüme Hızına Manyetik Alanın Etkisi Nano Yapılı Gözenekli Kaplamaların Kullanılması Eylemsiz Hapsedilme Füzyon Yakıt Hedeflerinde

Hydrodynamic instabilities, the most significant of which is Rayleigh-Taylor instability (RTI), play a significant role in many physical phenomena. So how to decrease the growth rate of these instabilities is an important purpose in ICF fuel targets. In this research, reducing the growth rate of RTI for various fusion fuel targets has been investigated in two stages: First, it is indicated that applying different nanostructured porous linings at the ablation front of them in the absence of a strong magnetic field causes to decrease RTI growth rate and second, it is shown that using various nanostructured porous linings at the ablation front of these targets accompanying magnetic field exerting to the ablative surface of them, leads to more reduction of RTI growth rate. In both of these two phases, RTI growth rate is acquired analytically using conservation equations, boundary conditions and approximate methods and it is indicated that applying nanostructured porous linings and exerting a powerful magnetic field, will decrease RTI growth rate.

Rayleigh-Taylor instability in an adiabatic-radiative rare plasma

Considering the particle nature of photons, the impact of electromagnetic radiation pressure is examined on the Rayleigh-Taylor instability (RTI) in a non-uniform rare magnetoplasma. For low-density and high-temperature rare plasma, the RTI with radiation pressure is revisited in the adiabatic limit. The growth rate conditions and propagating modes are derived using the framework of a developed fluid model. For specific values of ion temperature, the cut-off values of propagation of the fringing instability is found to be temperature dependent. A numerical comparison of the present results with previous work Maryam N, Rozina C and Ali S (2021, IEEE Transactions on Plasma Science 49 1072–1078) is displayed in table 1. It is found that the radiative acoustic speed is increased due to electromagnetic radiation pressure in rare plasmas as compared to radiative acoustic speed in dense plasmas. However, the growth rate of RTI increases comparatively as function of radiation pressure in rare plasmas. The present findings reveals that the consequences of RTI are remarkably concerned with the choice of electromagnetic radiation pressure either in dense (astrophysical) or rare (laboratory) plasmas. These findings are relevant to the observations of long-lived irregularities for explaining the gravitational instability in laboratory plasmas, e.g. in fusion devices like tokamaks.

Multi-instrumental analysis of the day-to-day variability of equatorial plasma bubbles

This paper presents a multi-instrument observational analysis of the equatorial plasma bubbles (EPBs) variation over the American sector during a geomagnetically quiet time period of 07–10 December 2019. The day-to-day variability of EPBs and their underlying drivers are investigated through coordinately utilizing the Global-scale Observations of Limb and Disk (GOLD) ultraviolet images, the Ionospheric Connection Explorer (ICON) in-situ and remote sensing data, the global navigation satellite system (GNSS) total electron content (TEC) observations, as well as ionosonde measurements. The main results are as follows: 1) The postsunset EPBs’ intensity exhibited a large day-to-day variation in the same UT intervals, which was fairly noticeable in the evening of December 07, yet considerably suppressed on December 08 and 09, and then dramatically revived and enhanced on December 10. 2) The postsunset linear Rayleigh-Taylor instability growth rate exhibited a different variation pattern. It had a relatively modest peak value on December 07 and 08, yet a larger peak value on December 09 and 10. There was a 2-h time lag of the growth rate peak time in the evening of December 09 from other nights. This analysis did not show an exact one-to-one relationship between the peak growth rate and the observed EPBs intensity. 3) The EPBs’ day-to-day variation has a better agreement with that of traveling ionospheric disturbances and atmospheric gravity waves signatures, which exhibited relatively strong wavelike perturbations preceding/accompanying the observed EPBs on December 07 and 10 yet relatively weak fluctuations on December 08 and 09. These coordinate observations indicate that the initial wavelike seeding perturbations associated with AGWs, together with the catalyzing factor of the instability growth rate, collectively played important roles to modulate the day-to-day variation of EPBs. A strong seeding perturbation could effectively compensate for a moderate strength of Rayleigh-Taylor instability growth rate and therefore their combined effect could facilitate EPB development. Lacking proper seeding perturbations would make it a more inefficient process for the development of EPBs, especially with a delayed peak value of Rayleigh-Taylor instability growth rate.

Relationships between ionospheric parameters derived from ionosonde observations and characteristics of post-sunset GHz scintillation during high solar activities (2012−2013) at Sanya (18.3°N, 109.6°E), China

In this study, we presented the characteristics of post-sunset GHz scintillation occurrence and ionospheric parameters derived from ionosonde observations, including the critical frequency of F2-layer (foF2), peak height of F2-layer (hmF2), minimum virtual height of F-layer (h’F), scale height around the F2-layer peak (Hm), virtual height (h’F5) and true height (hF5) measured at 5 MHz, in high solar activity years (2012-2013) of solar cycle 24 at Sanya (18.3°N, 109.6°E; dip lat.: 12.8°N), China. Furthermore, we investigated the relationships between the equinoctial asymmetry of scintillation and these ionospheric parameters. In addition, the growth rates of Rayleigh-Taylor instability were calculated on the basis of the ionosonde measurements and models, respectively. The results showed that the equinoctial asymmetry of scintillation onset time would be associated with the scale length of vertical electron density gradient (L), which affects the growth of Rayleigh-Taylor instability at the bottom of F-layer. The seasonal variations of foF2, Hm and scale length of vertical electron density gradient would be the reason to cause the seasonal variations of scintillation occurrence, and the equinoctial asymmetry of scintillation occurrence rate over low latitude can be related to the background electron density and the vertical drifts around sunset in F-layer. The correlations between the scintillation strength represented by the daily maximum S4 and the daily maximum values of foF2, hmF2, h’F, Hm, and also the drifts over low latitudes were weak, which need to be further studied.

Bell–Plesset effects on Rayleigh–Taylor instability at cylindrically divergent interfaces between viscous fluids

We report the first experiments on divergent Rayleigh–Taylor instability (RTI) at well-controlled single-mode cylindrical interfaces between air and viscous liquid. At early stages, only the amplitude of the dominant single mode grows with time while the higher harmonics starts to grow in the late stage. The transition point from the linear stage to the nonlinear stage is defined as the moment when the higher harmonics starts to grow and the linear stage before the Poiseuille flow fully developed is concerned in this paper. We find that the growth rate is lower than that in convergent or planar geometry due to geometric divergence. Both divergent Bell–Plesset (BP) effects and viscosity effect inhibit the growth rate of RTI. The attenuation strength of viscosity effect is reduced by divergent BP effects compared with the planar case. It is observed that the value ka ∼ (0.188–0.314), at the transition point, is much lower than that in planar geometry (ka ∼ 1), where a is the amplitude of the dominant single mode and k is the initial wavenumber. To take viscosity into account, a new approximate model based on the Bell theory is proposed, which well predicts the perturbation growth in a divergent geometry in the linear stage before the Poiseuille flow fully developed.

Rayleigh–Taylor Instability in Electron–Ion Radiative Dense Plasmas

A new feature of electromagnetic radiation is studied by investigating the Rayleigh–Taylor (RT) instability in a radiative electron–ion magnetoplasma. Within the adiabatic limit, the linear RT instability supports against the gravity and is primarily provided by the radiation pressure, which is a complicated function of both temperature and density concentration of electrons. It is examined that, for superdense plasma environments, the radiation pressure becomes comparable or even more than the usual gas pressure, which may lead to enhance the growth rate of RT instability via varying the electron temperature and density concentration. Diamagnetic drifts are also taken into account due to the presence of thermal and radiation pressures apart from the gravitational drift. The results of RT instability are significantly affected by the variation of radiation pressure in dense magnetized nonuniform plasmas and have relevance for understanding dense astrophysical environments, such as massive star clusters and white dwarfs.

On the Rayleigh-Taylor unstable dynamics of three-dimensional interfacial coherent structures with time-dependent acceleration

Rayleigh-Taylor instability (RTI) occurs in a range of natural and industrial processes. Whereas the majority of existing studies have considered constant acceleration, RTI is in many instances driven by variable acceleration. Here we focus on RTI driven by acceleration with a power-law time-dependence, and, by applying a group theoretic method, find solutions to this classical nonlinear boundary value problem. We deduce that the dynamics is dominated by the acceleration and that the solutions depend critically on the acceleration parameters for values of the acceleration exponent greater than (-2). We find that in the early-time dynamics, the RTI growth-rate is defined by modified Bessel functions. For the late-time dynamics, we link the interface dynamics with an interfacial shear function, find a continuous family of regular asymptotic solutions and identify invariant properties of nonlinear RTI. The essentially interfacial and multi-scale character of the dynamics is also demonstrated. The velocity field is potential in the bulk, and vortical structures may appear at the interface due to interfacial shear. The multi-scale character becomes clear from the invariance properties of the dynamics. We achieve good agreement with existing observations and elaborate new benchmarks for future research.

The rotating Rayleigh-Taylor instability in a strongly coupled dusty plasma

The linear Rayleigh-Taylor instability (RTI) in a uniformly rotating strongly coupled dusty plasma (SCDP) is investigated both analytically and numerically. The influence of the Coriolis force on the dust particles is considered mainly owing to the drag force of the magnetized ions. The dispersion relation is analytically derived using appropriate boundary conditions and velocity profile. The dispersion characteristics are analyzed in the strongly coupled (kinetic) limit, and it is observed that the criterion of linear RTI is modified due to the presence of rotation and shear velocity comprising strong correlation effects. It is found that in the presence of intermediate magnetic field in SCDP, dust cloud rotation and strong correlation effects altogether stabilize the growth rate of linear RTI. The analytical growth rate of RTI shows a good agreement with the growth rate calculated numerically.

Quantum and FLR effects on the Rayleigh Taylor instability of stratified plasmas

The combined effects of quantum corrections and finite Larmor radius (FLR) have been investigated on the linear hydrodynamic Rayleigh-Taylor (RT) instability of an incompressible stratified plasma. The basic quantum magnetohydrodynamic equations incorporating quantum and FLR effects are constructed and linearized under the small amplitude approximation. The general dispersion relation is derived considering appropriate magnetic field and density profiles using the normal mode analysis. It is analyzed numerically to study the effects of quantum and FLR corrections on the growth rate of RT instability in the stratified hydrodynamic fluids. It is found that the cut-off wavenumber (kmax) and critical wavenumber (kc) determining the growth rate of RT instability are modified due to the presence of FLR corrections and quantum effects. The FLR and quantum corrections have a stabilizing effect on the growth rate of RT instability of a stratified plasma.

Solar effect on the Rayleigh-Taylor instability growth rate as simulated by the NCAR TIEGCM

The TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) is used to investigate the solar effect on the equatorial ionospheric Rayleigh-Taylor (R-T) instability growth rate, which is responsible for the occurrence of the plasma bubbles. The R-T growth rate is calculated for the solar maximum year 2003 and minimum 2009. The growth rate is strongly dependent on the solar activity. During solar maximum, the pre-reversal enhancement is much stronger leading to higher R-T growth rate. The R-T growth rates from the TIEGCM follow the same solar dependence as the observed occurrence of equatorial plasma bubbles by DMSP satellites. The R-T growth rate also enhances when the day/night terminator is parallel to the magnetic field line near the equator. The R-T growth rate does not correlate well with the solar F10.7 index on a short time scale (~10 days) because the field-line integrated electron content gradient cancels out the positive correlation between the vertical ion drift with the F10.7 index. The TIEGCM result shows the importance of the electron content gradient to the R-T growth rate and the plasma bubble occurrence. The bubble occurrence rates were estimated based on the vertical ion drift simulation results.

Quantum effects on the Rayleigh–Taylor instability of stratified plasma in the presence of suspended particles

The effects of quantum correction on the Rayleigh–Taylor instability (RTI) in stratified plasma layer have been investigated in the presence of suspended particles. A general dispersion relation is obtained from the linearized set of quantum hydrodynamic (QHD) equations. Two particular cases of suspended particle parameters (f ∗ and α 0) with and without quantum corrections are analysed. The condition of RTI is derived while the stability of the system is discussed by applying Routh–Hurwitz (RH) criterion in the polynomial equation. The results show that, in the absence of quantum term, the relaxation frequency of the suspended particles has a destabilizing effect, while the mass concentration of the suspended particles has a stabilizing effect on the growth rates of RTI. In the presence of the quantum term, the relaxation frequency of the suspended particle yields to the stability behaviour on the growth rates of RTI.

Effect of different dust flow velocities on combined Kelvin-Helmholtz and Rayleigh-Taylor instabilities in magnetized incompressible dusty fluids

We investigate the effect of different dust flow velocities and two dimensional magnetic fields on the combined Kelvin-Helmholtz instability (KHI) and Rayleigh-Taylor instability (RTI) of two superimposed incompressible dusty fluids. A single fluid reduced dusty magnetohydrodynamic model is obtained for the three component magnetized incompressible dusty plasma, and it is assumed that a plane interface of infinite boundaries separates heavy and light dusty fluids at z = 0. The general dispersion relations for RT and KH configurations are obtained using appropriate boundary conditions and discussed in the case of equal and different dust fluid flow velocities. In the case of the stable RT configuration, we find that the condition of RTI depends upon both longitudinal and transverse magnetic field components and relative dust flow velocity. In the case of the KH configuration, the effect of magnetic field and relative dust flow velocity is observed and it is shown that dust flow velocity must be larger than a particular value of Alfven speed in order to excite KHI. Numerical calculations have been performed to illustrate the linear growth rates of RTI and KHI in both magnetized and unmagnetized dusty plasmas. We observe that the magnetic field has stabilizing whereas the dust Atwood number has destabilizing influence on the growth rate of RTI. The different dust flow velocities have destabilizing whereas magnetic field has stabilizing influence on the growth rate of KHI in dusty plasmas. The dust Mach number yields a stabilizing influence on the linear growth rate of KHI.

Level-by-level artificial viscosity and visualization for MHD simulation with adaptive mesh refinement

We propose a numerical method to determine the artificial viscosity in magnetohydrodynamics (MHD) simulations with adaptive mesh refinement (AMR) method, where the artificial viscosity is adaptively changed due to the resolution level of the AMR hierarchy. Although the suitable value of the artificial viscosity depends on the governing equations and the model of target problem, it can be determined by von Neumann stability analysis. By means of the new method, “level-by-level artificial viscosity method,” MHD simulations of Rayleigh–Taylor instability (RTI) are carried out with the AMR method. The validity of the level-by-level artificial viscosity method is confirmed by the comparison of the linear growth rates of RTI between the AMR simulations and the simple simulations with uniform grid and uniform artificial viscosity whose resolution is the same as that in the highest level of the AMR simulation. Moreover, in the nonlinear phase of RTI, the secondary instability is clearly observed where the hierarchical data structure of AMR calculation is visualized as high resolution region floats up like terraced fields. In the applications of the method to general fluid simulations, the growth of small structures can be sufficiently reproduced, while the divergence of numerical solutions can be suppressed.

Rayleigh-Taylor instability in non-uniform magnetized rotating strongly coupled viscoelastic fluid

The Rayleigh-Taylor instability (RTI) in an incompressible strongly coupled viscoelastic fluid is investigated considering the effects of inhomogeneous magnetic field, density gradient, and uniform rotation. The generalized hydrodynamic equations have been formulated, and linear dispersion relation is derived taking appropriate density and magnetic field profiles for the considered system. The gravity induced stable and unstable configurations of RTI are analyzed in hydrodynamic and kinetic limits. In the kinetic limit, shear wave modified dispersion relation and the condition of RTI are derived in terms of magnetic-viscoelastic Mach number and viscoelastic Froude number. The criteria of RTI and critical wavenumber for the growth of RTI to be unstable are estimated numerically for white dwarf and inertial confinement fusion target. It is observed that magnetic field, rotation, and viscoelastic effects play a significant role in the suppression of RTI in these systems. The stabilizing influence of magnetic field, rotation, and magnetic-viscoelastic Mach number while the destabilizing influence of viscoelastic Froude on the growth rate of RTI number is observed graphically. The growth rate of RTI decreases faster in kinetic limit as compared to the hydrodynamic limit.

Stabilization of Rayleigh–Taylor instability in the presence of viscosity and compressibility: A critical analysis

The stabilization of the Rayleigh–Taylor instability growth rate due to the combined effect of viscosity and compressibility has been studied. A detailed explanation of the observed results has been made from theoretical point of view. The numerical results have been compared qualitatively with those of Plesset and Whipple [Phys. Fluids 17, 1 (1974)] and Bernstein and Book [Phys. Fluids 26, 453 (1983)].

Observation of Rayleigh-Taylor-instability evolution in a plasma with magnetic and viscous effects.

We present time-resolved observations of Rayleigh-Taylor-instability (RTI) evolution at the interface between an unmagnetized plasma jet colliding with a stagnated, magnetized plasma. The observed instability growth time (∼10 μs) is consistent with the estimated linear RTI growth rate calculated using experimentally inferred values of density (∼10(14) cm(-3)) and deceleration (∼10(9) m/s(2)). The observed mode wavelength (≳1 cm) nearly doubles within a linear growth time. Theoretical estimates of magnetic and viscous stabilization and idealized magnetohydrodynamic simulations including a physical viscosity model both suggest that the observed instability evolution is subject to magnetic and/or viscous effects.

运动流体界面Rayleigh-Taylor不稳定性研究

Starting from the nonrelativistic fluid and relativistic fluid models, we study the linear growth of the Rayleigh-Taylor instability (RTI) at the interface of two ideal fluids moving with certain speed under a gravitational field, where the fluid velocity is along the gravitational field and is perpendicular to interface. Calculation shows that, the RTI growth rate for nonrelativistic fluids is independent of its reference frame or the fluid velocity. A general formula of the RTI growth rate is obtained for relativistic fluids. It shows that both the relativistic thermal pressure and macroscopic fluid velocity tend to suppress the RTI growth. Physically, when the thermal velocities of microparticles of the relativistic fluids are considerable as compared to the light speed in vacuum, the contribution of the thermal pressure to the fluid inertia cannot be ignored. Also when the fluid velocities are not negligible as compared to the light speed, the effect of relativistic-mass-increase leads to the decreased RTI growth rate. The latter is basically consistent with the time transformation effect in different reference frames.

Rayleigh-Taylor Instability of Magnetized Plasma through Darcy Porous Medium

Effects of horizontal and vertical magnetic field components on the Rayleigh-Taylor instability of stratified incompressible plasmas layer of variable density through Darcy porous medium are studied. The basic magnetohydrodynamic (MHD) set of equations has been constructed and linearized. Then the linear normalized growth rate is obtained analytically as a function of the physical parameters of the system considered. Numerical calculations have been performed to see the effects of various parameters on the normalized growth rate of Rayleigh-Taylor instability.(For more information,please refer to the PDF.)

Reduction of growth rate of Rayleigh-Taylor instability using nano-structured porous lining at ICF target shell

In the present paper, the role of the nano-structured porous lining is being considered on the control and the decrease of the growth rate of the Rayleigh-Taylor instability (RTI) at the ablative surface of a target shell in inertial confinement fusion. For this reason, the dispersion relation for the growth rate of the Rayleigh-Taylor instability is extracted. Although the Rayleigh-Taylor instability takes place in two phases (acceleration and deceleration phases), in this study this instability is considered only in the acceleration phase using the linear stability analysis. Knowing that the porous layer absorbs the energy of the fluid and dampens the system, the growth rate of RTI for different porous linings is explored and the porous parameter for these nano-structured porous linings are calculated. It has been shown that with a decrease in the value of the Bond number, the growth rate versus wave number decreases, and an increase in the value of the permeability increases the growth rate of RTI. Finally, it is shown that an increase in the amount of the porous parameter causes the decrease of the growth rate of RTI.

Rayleigh–Taylor instability at ionization fronts: perturbation analysis

The linear growth rate of the Rayleigh-Taylor instability (RTI) at ionization fronts is investigated via perturbation analysis in the limit of incompressible fluids. In agreement with previous numerical studies is found that absorption of ionizing radiation inside the HII region due to hydrogen recombinations suppresses the growth of instabilities. In the limit of a large density contrast at the ionization front the RTI growth rate has the simple analytical solution n=-nur+(nur^2+gk)^(1/2), where nur is the hydrogen recombination rate inside the HII region, k is the perturbation's wavenumber and g is the effective acceleration in the frame of reference of the front. Therefore, the growth of surface perturbations with wavelengths lambda >> lambda_{cr} = 2\pi g/nur^2 is suppressed by a factor (lambda_{cr}/4lambda)^(1/2) with respect to the non-radiative incompressible RTI. Implications on stellar and black hole feedback are briefly discussed.