Week 5 - Rayleigh Taylor Instability

Objective: -

Study of Rayleigh Taylor Instability phenomenon and state some practical CFD model based on mathematical analysis fo Rayleigh Taylor Waves.

Perform Rayleigh Taylor Instability simulation with 2 different mesh size, with base simulation with 0.5mm size. Comparing the results with the help of animation. Explain why Steady - state approach is not suitable for this simulation.

Run the RTI simulation with water and user defined material having density = 400kg / mm^3 and viscocity = 0.001 kg/m-s for refined mesh.

Learn about the Atwood number and find the Atwood number for above simulations. An explain how variation in Atwood number affects the behaviou r of the instability.

Introduction: -

The theory of Rayleigh Taylor Instability is attributed to many natural phenomena observed in nature. Its basic form is developed for accelerated fluid layer from basic fluid equations. It starts from classical potential flow theory for moving contact surfaces and extends to the various fluid system describing the inhomogeneous, viscous, compressible and isobaric flows. Thereby an overview on major instability issues under a broad variety of physical conditions can be given. In particular, the stability analysis is addressed to layered materials in plane or spherical geometries under various dynamic conditions, to inhomogeneous media with variable gradients and different boundary conditions, to different boundary conditions, to viscous boundary layers, compressible atmospheres, and to stationary ablation fronts in laser-driven plasma experiments. The instability theory is further extended to the non-linear stage of Rayleigh-Taylor instability and to a discussion of bubble dynamics in two- and three-dimensions for closed and open bubble domain. For this purpose, simple flow models are studied that can describe essential features of bubble rise and bubble growth in buoyancy-driven mixing layer.