Physics of a Re-shocked Three-Dimensional Multimode Richtmyer-Meshkov Turbulent Layer

摘要: This paper presents a numerical study of a re-shocked turbulent mixing layer using high-order accurate Implicit Large-Eddy-Simulations (ILES). Two specific initial perturbation power spectra are examined:(i) a narrowband high wavenumber perturbation (a constant power spectrum); and (ii) a broadband perturbation having a power spectrum P= Ck-2 (typical of an ICF capsule). The first shock is modelled as a velocity impulse, and the initial mixing layer is allowed to develop to a self-similar state with reference to prior results [1]. Once a self-similar state is achieved (Fig. 1), the layer is re-shocked and evolves to a new self-similar state which is significantly different from the original mixing layer (Fig. 1).. The results are compared to existing theoretical approaches, and the broadband theory of Youngs [2] is extended to predict the behaviour of a re-shocked broadband mixing layer formed initially from a shock interacting with a broadband instability integrated with the ideas of Brouillette and Sturtevant [3]. If P~ km before the first shock then for the linear long wavelength modes before the re-shock P~ km+ 2. Then according to the broadband theory the growth rate exponent (width= W~ t θ) should change from