Theoretical Study Of Rayleigh - Taylor Instability

Firstly, by applying a local assumption to the perturbation amplitudes in this article, one analyzes an ideal unmagnetized plasma and obtains the analytical growth rate of the ablative Rayleigh-Taylor (RT) instability. It can be concluded that: 1) The RT instability can only occur when - (gL/2)^1/2 < u₀ < (gL)^1/2 due to the effect of ablation flow. 2) When ablation flow is in the same direction as the gravity g, results show that ablation produces stable effect on the RT instability and the instability can be completely suppressed when the ablation is strong enough. 3) If ablation direction is opposite to the gravity g, although ablation exhibits two competitive effects simultaneously ( stabilizing effect and destabilizing effect ) via the analytical growth rate expression, ablation flow destabilizes the RT instability and the destabilizing intensity increases firstly to the maximum and then decreases as the ablation enhances. 4) As the inhomogeneous scale length rises, the growth rate goes up rapidly, and after reaches its maximum the growth rate slowly slides to zero.Next, the role of compressibility on RT instability is focused on. Compressible RT instability in inviscid fluid has been studied by several authors. Some attributed a stabilizing effect to compressibility, some noted only a destabilizing effect, while others concluded either is possible. The reason of the controversy is that some authors coupled the effects of compressibility and density distribution, obscuring the real role played by compressibility. One can definitely obtain the destabilizing effect of compressibility by eliminating the stabilizing effect of density distribution.When compressibility effect on the RT instability is discussed in magnetized plasma, one can find the magnetic field only effect the compressible RT instability though magnetic pressure if it is normal to wave vector. If it is along the wave vector, one finds the coupling of compressibility and magnetic field can destabilize the RT instability. Furthermore, one can also obtain: 1 ) The destabilizing effect decreases when the pressure enhances; 2 ) The destabilizing effect increases as the magnetic field enhances; 3 )The destabilizing effect has inverse ratio to adiabatic index γ₁ ( or γ₂ ); 4 )The destabilizing effects of coupling of compressibility and magnetic field are larger at small Atwood numbers; 5 ) The instability will be suppressed by magnetic: field at larger cut-off wave number due to the destabilizing effect; 6 ) The destabilizing effect increases nearly linearly as the gravity increases. At last, by analyzing the equilibrium flow along the wave vector one find there is only Doppler shift if the equilibrium flow is constant.