The book aims to provide the reader with an updated general presentation of multiscale/multiresolution approaches in turbulent flow simulations. All modern approaches (LES, hybrid RANS/LES, DES, SAS) are discussed and recast in a global comprehensive framework. Both theoretical features and practical implementation details are addressed. Some full scale applications are described, to provide the reader with relevant guidelines to facilitate a future use of these methods.

The book aims to provide the reader with an updated general presentation of multiscale/multiresolution approaches in turbulent flow simulations. All modern approaches (LES, hybrid RANS/LES, DES, SAS) are discussed and recast in a global comprehensive framework. Both theoretical features and practical implementation details are addressed. Some full scale applications are described, to provide the reader with relevant guidelines to facilitate a future use of these methods./a

The properties of turbulent jet scalar interfaces are investigated using a high-resolution experimental database of fully-developed turbulent scalar fields and interfaces in jets. The database was recorded at the UC Irvine turbulence atmospheric pressure flow facility using laser-induced fluorescence of disodium fluorescein in water, with the Reynolds number of the jet Re ∼ 2 x 104, and the Schmidt number Sc ∼ 2 x 103. The probability density function (pdf) of turbulent jet scalar fields is examined with emphasis on the extent to which the pdf depends on resolution scale effects. Coarse graining is conducted by a two-step method consisting of applying an averaging filter and performing quadratic B-spline interpolation. The scalar pdf is examined as the product of the interfacial area-volume ratio, or perimeter-area ratio for two-dimensional data, and the interfacial thickness quantified as the averaged inverse magnitude of the scalar gradient across each interface. It is demonstrated that because the area-volume ratio decreases with reduced resolution, whereas the interfacial thickness increases with reduced resolution, the scalar pdf exhibits significant, robustness to resolution scale effects over a wide range of resolution scales as well as scalar thresholds. It is demonstrated that the observed robustness arises from the dual self-similarity of the interfacial perimeter and thickness which are found to exhibit two self-similarity exponents of opposite signs and approximately equal magnitudes for the present jet conditions. In other flows, the degree of the multiresolution robustness can be expected to depend on the extent of the dual self-similarity and the relative magnitudes of the corresponding exponents. Significant robustness to reduction in resolution scale is found for the enclosed volume as well and is attributed to the dual self-similarities exhibited by the interfacial protrusions and indentations with similar scaling exponents. The interfacial protrusions and indentations provide nearly-opposite positive and negative contributions respectively to the volume enclosed by the turbulent scalar interface, in contrast to the interfacial surface area for which the protrusions and indentations both generate additive contributions. In order to improve the understanding of the turbulent interfaces, the multifractal aspects of scalar dissipation field conditional on the outer fluid interface are examined using multifractal analysis. The singularity exponents are calculated for every point on the outer fluid interface. The singularity exponent field is then analyzed by computing the generalized dimensions of iso sets using standard box-counting method as well as recently developed meshless M3 method. Examination of the generalized dimensions of the iso sets indicates strong dependence on scale. The average generalized dimension of iso set is found to depend strongly on the value of the singularity exponent of the iso set, with the highest average generalized dimension achieved for singularity exponent corresponding to the average generalized dimension of the interface. The present study is expected to be useful for comparison to higher Reynolds numbers and different Schmidt numbers, as a high-resolution reference case.

Accurate and efficient turbulence simulation in complex geometries is a formidable chal-lenge. Traditional methods are often limited by low accuracy and/or restrictions to simplegeometries. We explore the merger of Discontinuous Galerkin (DG) spatial discretizationswith Variational Multi-Scale (VMS) modeling, termed Local VMS (LVMS), to overcomethese limitations. DG spatial discretizations support arbitrarily high-order accuracy on un-structured grids amenable for complex geometries. Furthermore, high-order, hierarchicalrepresentation within DG provides a natural framework fora prioriscale separation crucialfor VMS implementation. We show that the combined benefits of DG and VMS within theLVMS method leads to promising new approach to LES for use in complex geometries. The efficacy of LVMS for turbulence simulation is assessed by application to fully-developed turbulent channelflow. First, a detailed spatial resolution study is undertakento record the effects of the DG discretization on turbulence statistics. Here, the localhp refinement capabilites of DG are exploited to obtain reliable low-order statistics effi-ciently. Likewise, resolution guidelines for simulating wall-bounded turbulence using DGare established. We also explore the influence of enforcing Dirichlet boundary conditionsindirectly through numericalfluxes in DG which allows the solution to jump (slip) at thechannel walls. These jumps are effective in simulating the influence of the wall commen-surate with the local resolution and this feature of DG is effective in mitigating near-wallresolution requirements. In particular, we show that by locally modifying the numericalviscousflux used at the wall, we are able to regulate the near-wall slip through a penaltythat leads to improved shear-stress predictions. This work, demonstrates the potential ofthe numerical viscousflux to act as a numerically consistent wall-model and this successwarrents future research. As in any high-order numerical method some mechanism is required to control aliasingeffects due to nonlinear interactions and to ensure nonlinear stability of the method. Inthis context, we evaluate the merits of two approaches to de-aliasing -- spectralfilteringand polynomial dealiasing. While both approaches are successful, polynomial-dealiasingis found to be better suited for use in large-eddy simulation. Finally, results using LVMSare reported and show good agreement with reference direct numerical simulation therebydemonstrating the effectiveness of LVMS for wall-bounded turbulence. This success pavesthe way for future applications of LVMS to more complex turbulentflows. 3.

Advanced Approaches in Turbulence: Theory, Modeling, Simulation and Data Analysis for Turbulent Flows focuses on the updated theory, simulation and data analysis of turbulence dealing mainly with turbulence modeling instead of the physics of turbulence. Beginning with the basics of turbulence, the book discusses closure modeling, direct simulation, large eddy simulation and hybrid simulation. The book also covers the entire spectrum of turbulence models for both single-phase and multi-phase flows, as well as turbulence in compressible flow. Turbulence modeling is very extensive and continuously updated with new achievements and improvements of the models. Modern advances in computer speed offer the potential for elaborate numerical analysis of turbulent fluid flow while advances in instrumentation are creating large amounts of data. This book covers these topics in great detail. Covers the fundamentals of turbulence updated with recent developments Focuses on hybrid methods such as DES and wall-modeled LES Gives an updated treatment of numerical simulation and data analysis

The book provides basic and recent research insights concerning the small scale modeling and simulation of turbulent multi-phase flows. By small scale, it has to be understood that the grid size for the simulation is smaller than most of the physical time and space scales of the problem. Small scale modeling of multi-phase flows is a very popular topic since the capabilities of massively parallel computers allows to go deeper into the comprehension and characterization of realistic flow configurations and at the same time, many environmental and industrial applications are concerned such as nuclear industry, material processing, chemical reactors, engine design, ocean dynamics, pollution and erosion in rivers or on beaches. The work proposes a complete and exhaustive presentation of models and numerical methods devoted to small scale simulation of incompressible turbulent multi-phase flows from specialists of the research community. Attention has also been paid to promote illustrations and applications, multi-phase flows and collaborations with industry. The idea is also to bring together developers and users of different numerical approaches and codes to share their experience in the development and validation of the algorithms and discuss the difficulties and limitations of the different methods and their pros and cons. The focus will be mainly on fixed-grid methods, however adaptive grids will be also partly broached, with the aim to compare and validate the different approaches and models.