Week 5 - Rayleigh Taylor Instability
RT instability is the instability of an interface between two fluids of different densities which occurs when the lighter fluid is pushing the heavier fluid .water suspended atop oil is an everyday example of Rayleigh Taylor and it may be modeled by two completely plane-parallel layers of immiscible fluid the denser on top of the less dense one and both subjected to earth gravity. the equilibrium here is unstable to any perturbations or disturbance of interface; if a parcel of heavier fluid is displaced downward with an equal volume of lighter fluid displace upward .potentila energy of configuration is lower than the initial state .thus the disturbance will grow and lead to further release of potential energy, as the more dense material moves down under the gravitational field and the less dense material is further displaced upwards.
Practical CFD models have been based on mathematical analysis of RT waves
1)Kelvin -Helmholtz instability
2)Richmyer -Meskov instability
3)plateau-rayleigh instability
#geometry
# meshing
elements size 0.5mm
nodes-3321
elements-3200
elements size 03.mm
nodes-9180
elements-8978
elements size 0.2mm
nodes-20301
elements-20000
we can't run this simulation in the steady buzz of multiphase volume ,the different change the interface with respect to time
https://drive.google.com/drive/folders/1MAHDcEWYfq9MZqneiCxEQrBQbZn6GM8F?usp=sharing
results drive link
Atwood Number
The Atwood number is a dimensionless number in fluid dynamics used in the study of hydrodynamic instabilities in density stratified flow .it is dimensionless density ratio defined as
A=(rho1-rho2)/(rho1+rho2)
where rho1=density of heavier fluid
rho2=density of lighter fluid
Application -it is an important parameter in the study of Rayleigh -tayor instability and richer -mechkow instability .in RTI the penetration distance of heavy fluid bubbles into the lighter fluid is a function of acceleration rime scale, where g is the gravitational acceleration &t is the time
conclusion
*A mesh become smaller the mixing becomes more clear and visible
*the computation also increases with an increase in a finer mesh
*as material changes we observed the take taking change mix the fluid also increase