Labakanta Mandal

Effect of magnetic field on temporal development of Rayleigh–Taylor instability induced interfacial nonlinear structure

The effect of magnetic field on the nonlinear growth rate of Rayleigh–Taylor instability induced two fluid interfacial structures has been investigated. The magnetic field is assumed to be parallel to the plane of the two fluid interface and acts in a direction perpendicular to the wave vector. If the magnetic field is restricted only to either side of the interface, the growth rate may be depressed (may almost disappear) or be enhanced depending on whether the magnetic pressure on the interface opposes the instability driving pressure difference g(ρh−ρl)y or acts in the same direction. If magnetic field is present on both sides of the two fluid interface, stabilization may also take place in the sense that the surface of separation undulates periodically when the force due to magnetic pressure on two sides is such as to act in opposite direction. This result differs from the classical linear theory result which predicts that the magnetic field parallel to the surface has no influence on the growth rate w...

Effect of viscosity and surface tension on the growth of Rayleigh–Taylor instability and Richtmyer–Meshkov instability induced two fluid interfacial nonlinear structure

The effect of viscous drag and surface tension on the nonlinear two fluid interfacial structures induced by Rayleigh–Taylor instability and Richtmyer–Meshkov instability have been investigated. Viscosity and surface tension play important roles on the fluid instabilities. It is seen that the magnitude of the suppression of the terminal growth rate of the tip of the bubble height depends only on the viscous coefficient of the upper (denser) fluid through which the bubble rises. However, in regard to spike it is shown that in an inviscid fluid spike does not remain terminal but approaches a free fall

Effect of viscosity and shear flow on the nonlinear two fluid interfacial structures

\sim \frac{1}{2} \gamma g t^{2}

Bubble and spike growth rate of Rayleigh Taylor and Richtmeyer Meshkov instability in finite layers

(γ is of order unity) as the Atwood number A increases. In this respect there exits qualitative agreement with simulation result and also with some earlier theoretical results. Viscosity reduces the free fall velocity appreciably and with increasing viscosity tends to make it terminal. Results obtained from numerical integration of the relevant nonlinear equations describing the temporal development of the spike support the foregoing observations.

Combined Effect of Viscosity, Surface Tension and Compressibility on Rayleigh-Taylor Bubble Growth Between Two Fluids

The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh–Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

Evolution of nonlinear interfacial structure induced by combined effect of Rayleigh–Taylor and Kelvin–Helmholtz instability

A nonlinear formulation is presented to deal with the combined action of Rayleigh-Taylor and Kelvin-Helmholtz instabilities as well as combined Ricthmyer-Meshkov and Kelvin-Helmholtz instabilities at the two fluid interface under the influence of viscosity and consequent shear flow. Using Layzers model, the development of the interfacial structures like bubbles is investigated analytically and numerically. It is found that the growth and normal velocity of the structures are dependent on the relative velocity shear and the kinematic coefficient of viscosity of both the fluids. Both the bubble growth and growth rate are reduced significantly for fluids of higher viscosity coefficient with small velocity shear difference. It is also observed that, for viscous fluids, the transverse velocity of the perturbed interface becomes slower under certain conditions.

Spiky Development at the Interface in Rayleigh-Taylor Instability: Layzer Approximation with Second Harmonic

Fluid instabilities like Rayleigh–Taylor (R–T), Richtmyer–Meshkov (R–M) and Kelvin–Helmholtz (K–H) instability can occur in a wide range of physical phenomenon from astrophysical context to Inertial Confinement Fusion (ICF). Using Layzers potential flow model, we derive the analytical expressions of growth rate of bubble and spike for ideal magnetized fluid in R–T and R–M cases. In the presence of transverse magnetic field, the R–M and R–T instabilities are suppressed or enhanced depending on the direction of magnetic pressure and hydrodynamic pressure. Again the interface of two fluid may oscillate if both the fluids are conducting. However, it is observed that the magnetic field has no effect in linear case.