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Paul L. Miller

Bio: Paul L. Miller is an academic researcher from Lawrence Livermore National Laboratory. The author has contributed to research in topics: Deflection (engineering) & Impact crater. The author has an hindex of 10, co-authored 37 publications receiving 472 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a large-eddy simulation technique is described for computing Rayleigh-Taylor instability, based on high-wavenumber-preserving subgrid-scale models, combined with high-resolution numerical methods.
Abstract: A large-eddy simulation technique is described for computing Rayleigh-Taylor instability. The method is based on high-wavenumber-preserving subgrid-scale models, combined with high-resolution numerical methods. The technique is verified to match linear stability theory and validated against direct numerical simulation data. The method is used to simulate Rayleigh-Taylor instability at a grid resolution of 1152 3 . The growth rate is found to depend on the mixing rate. A mixing transition is observed in the flow, during which an inertial range begins to form in the velocity spectrum and the rate of growth of the mixing zone is temporarily reduced. By measuring growth of the layer in units of dominant initial wavelength, criteria are established for reaching the hypothetical self-similar state of the mixing layer. A relation is obtained between the rate of growth of the mixing layer and the net mass flux through the plane associated with the initial location of the interface. A mix-dependent Atwood number is defined, which correlates well with the entrainment rate, suggesting that internal mixing reduces the layer's growth rate

263 citations

Journal ArticleDOI
01 May 2016-Icarus
TL;DR: In this paper, the authors numerically model asteroid response to kinetic impactors under a wide range of initial conditions, using an Adaptive Smoothed Particle Hydrodynamics code.

76 citations

Journal ArticleDOI
01 Sep 2006
TL;DR: In this article, a hierarchical segmentation of the mixing envelope surface is proposed to identify bubbles and analyze analogous segmentations of fields on the original interface plane, which reveals the evolution of topological features and corroborates the observations made by scientists.
Abstract: When a heavy fluid is placed above a light fluid, tiny vertical perturbations in the interface create a characteristic structure of rising bubbles and falling spikes known as Rayleigh-Taylor instability. Rayleigh-Taylor instabilities have received much attention over the past half-century because of their importance in understanding many natural and man-made phenomena, ranging from the rate of formation of heavy elements in supernovae to the design of capsules for Inertial Confinement Fusion. We present a new approach to analyze Rayleigh-Taylor instabilities in which we extract a hierarchical segmentation of the mixing envelope surface to identify bubbles and analyze analogous segmentations of fields on the original interface plane. We compute meaningful statistical information that reveals the evolution of topological features and corroborates the observations made by scientists.

46 citations

Journal ArticleDOI
01 Mar 2020-Icarus
TL;DR: A benchmarking and validation program using different numerical codes to solve a set of standard problems to test the effects of material strength, porosity, damage models, and target geometry on the ejecta following an impact and thus the momentum transfer efficiency was designed and implemented.

40 citations

Journal ArticleDOI
TL;DR: In this article, the authors present results from simulations using the shock physics codes CTH and Spheral of a DART-like impact into an asteroid target, which can be used to estimate the momentum enhancement of the moon from the impact.

37 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, Zhou et al. presented the initial condition dependence of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) mixing layers, and introduced parameters that are used to evaluate the level of mixedness and mixed mass within the layers.

606 citations

Journal ArticleDOI
TL;DR: In this paper, a large-scale simulation of the Rayleigh-Taylor instability is presented, which reaches a Reynolds number of 32,000, far exceeding that of all previous Rayleigh−Taylor simulations, and the scaling constant cannot be found by fitting a curve to the width of the mixing layer, but can be obtained by recourse to the similarity equation for the expansion rate of the turbulent region.
Abstract: Spontaneous mixing of fluids at unstably stratified interfaces occurs in a wide variety of atmospheric, oceanic, geophysical and astrophysical flows. The Rayleigh–Taylor instability, a process by which fluids seek to reduce their combined potential energy, plays a key role in all types of fusion. Despite decades of investigation, fundamental questions regarding turbulent Rayleigh–Taylor flow persist, namely: does the flow forget its initial conditions, is the flow self-similar, what is the scaling constant, and how does mixing influence the growth rate? Here, we show results from a large direct numerical simulation addressing such questions. The simulated flow reaches a Reynolds number of 32,000, far exceeding that of all previous Rayleigh–Taylor simulations. We find that the scaling constant cannot be found by fitting a curve to the width of the mixing layer (as is common practice) but can be obtained by recourse to the similarity equation for the expansion rate of the turbulent region. Moreover, the ratio of kinetic energy to released potential energy is not constant, but exhibits a weak Reynolds number dependence, which might have profound consequences for flame propagation models in type Ia supernova simulations.

407 citations

Journal ArticleDOI
TL;DR: In this article, an alternative methodology is described for large-scale simulation of flows involving shocks, turbulence and mixing, in which the modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes.
Abstract: An alternative methodology is described for Large-Eddy Simulation of flows involving shocks, turbulence and mixing. In lieu of filtering the governing equations, it is postulated that the large-scale behavior of an ''LES'' fluid, i.e., a fluid with artificial properties, will be similar to that of a real fluid, provided the artificial properties obey certain constraints. The artificial properties consist of modifications to the shear viscosity, bulk viscosity, thermal conductivity and species diffusivity of a fluid. The modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes. Requisite behavior of the artificial properties is discussed and results are shown for a variety of test problems, each designed to exercise different aspects of the models. When combined with a 10th-order compact scheme, the overall method exhibits excellent resolution characteristics for turbulent mixing, while capturing shocks and material interfaces in crisp fashion.

207 citations

Journal ArticleDOI
TL;DR: A new algorithm and easily extensible framework for computing MS complexes for large scale data of any dimension where scalar values are given at the vertices of a closure-finite and weak topology (CW) complex, therefore enabling computation on a wide variety of meshes such as regular grids, simplicial meshes, and adaptive multiresolution (AMR) meshes is described.
Abstract: The Morse-Smale (MS) complex has proven to be a useful tool in extracting and visualizing features from scalar-valued data. However, efficient computation of the MS complex for large scale data remains a challenging problem. We describe a new algorithm and easily extensible framework for computing MS complexes for large scale data of any dimension where scalar values are given at the vertices of a closure-finite and weak topology (CW) complex, therefore enabling computation on a wide variety of meshes such as regular grids, simplicial meshes, and adaptive multiresolution (AMR) meshes. A new divide-and-conquer strategy allows for memory-efficient computation of the MS complex and simplification on-the-fly to control the size of the output. In addition to being able to handle various data formats, the framework supports implementation-specific optimizations, for example, for regular data. We present the complete characterization of critical point cancellations in all dimensions. This technique enables the topology based analysis of large data on off-the-shelf computers. In particular we demonstrate the first full computation of the MS complex for a 1 billion/10243 node grid on a laptop computer with 2 Gb memory.

201 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of different three-dimensional multi-mode initial conditions on the rate of growth of a mixing layer initiated via a Richtmyer-Meshkov instability through a series of well-controlled numerical experiments is investigated.
Abstract: This paper investigates the influence of different three-dimensional multi-mode initial conditions on the rate of growth of a mixing layer initiated via a Richtmyer–Meshkov instability through a series of well-controlled numerical experiments. Results are presented for large-eddy simulation of narrowband and broadband perturbations at grid resolutions up to 3 × 109 points using two completely different numerical methods, and comparisons are made with theory and experiment. It is shown that the mixing-layer growth is strongly dependent on initial conditions, the narrowband case giving a power-law exponent θ ≈ 0.26 at low Atwood and θ ≈ 0.3 at high Atwood numbers. The broadband case uses a perturbation power spectrum of the form P(k) ∝ k−2 with a proposed theoretical growth rate of θ = 2/3. The numerical results confirm this; however, they highlight the necessity of a very fine grid to capture an appropriately broad range of initial scales. In addition, an analysis of the kinetic energy decay rates, fluctuating kinetic energy spectra, plane-averaged volume fraction profiles and mixing parameters is presented for each case.

171 citations