scholarly journals Wavelet-Based Adaptive Eddy-Resolving Methods for Modeling and Simulation of Complex Wall-Bounded Compressible Turbulent Flows

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 331
Author(s):  
Xuan Ge ◽  
Giuliano De De Stefano ◽  
M. Yousuff Hussaini ◽  
Oleg V. Vasilyev
Keyword(s):  
Modeling And Simulation ◽  
Turbulent Flows ◽  
Compressible Flows ◽  
High Efficiency ◽  
Incompressible Flows ◽  
Adaptive Methods ◽  
Companion Paper ◽  
High Fidelity ◽  
Detached Eddy Simulation ◽  
Predictive Tool

This article represents the second part of a review by De Stefano and Vasilyev (2021) on wavelet-based adaptive methods for modeling and simulation of turbulent flows. Unlike the hierarchical adaptive eddy-capturing approach, described in the first part and devoted to high-fidelity modeling of incompressible flows , this companion paper focuses on the adaptive eddy-resolving framework for compressible flows in complex geometries, which also includes model-form adaptation from low to high fidelity models. A hierarchy of wavelet-based eddy-resolving methods of different fidelity has been developed for different speed regimes, various boundary conditions, and Reynolds numbers. Solutions of various fidelity are achieved using a range of modeling approaches from unsteady Reynolds-averaged Navier–Stokes simulation to delayed detached eddy simulation, wall-modeled and wall-resolved large eddy simulations. These novel methodologies open the door to construct a hierarchical approach for simulation of compressible flows covering the whole range of possibilities, from only resolving the average or dominant frequency, to capturing the intermittency of turbulence eddies, and to directly simulating the full turbulence spectrum. The generalized hierarchical wavelet-based adaptive eddy-resolving approach, once fully integrated into a single inherently interconnected simulation, results in being a very competitive and predictive tool for complicated flows in industrial design and analysis with high efficiency and accuracy.

scholarly journals High-fidelity simulations of unsteady civil aircraft aerodynamics: stakes and perspectives. Application of zonal detached eddy simulation

2014 ◽  
Vol 372 (2022) ◽  
pp. 20130325 ◽  
Author(s):  
Sébastien Deck ◽  
Fabien Gand ◽  
Vincent Brunet ◽  
Saloua Ben Khelil
Keyword(s):  
Turbulent Flows ◽  
Hybrid Methods ◽  
Landing Gear ◽  
High Fidelity ◽  
Detached Eddy Simulation ◽  
High Lift ◽  
Eddy Simulation ◽  
Civil Aircraft ◽  
Aircraft Aerodynamics ◽  
Transonic Buffet

This paper provides an up-to-date survey of the use of zonal detached eddy simulations (ZDES) for unsteady civil aircraft applications as a reflection on the stakes and perspectives of the use of hybrid methods in the framework of industrial aerodynamics. The issue of zonal or non-zonal treatment of turbulent flows for engineering applications is discussed. The ZDES method used in this article and based on a fluid problem-dependent zonalization is briefly presented. Some recent landmark achievements for conditions all over the flight envelope are presented, including low-speed (aeroacoustics of high-lift devices and landing gear), cruising (engine–airframe interactions), propulsive jets and off-design (transonic buffet and dive manoeuvres) applications. The implications of such results and remaining challenges in a more global framework are further discussed.

scholarly journals Hierarchical Adaptive Eddy-Capturing Approach for Modeling and Simulation of Turbulent Flows

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 83
Author(s):  
Giuliano De Stefano ◽  
Oleg V. Vasilyev
Keyword(s):  
Modeling And Simulation ◽  
Collocation Method ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Adaptive Methods ◽  
Short Review ◽  
Wavelet Thresholding ◽  
Modeling Framework ◽  
Adaptive Wavelet ◽  
Wavelet Collocation Method

A short review of wavelet-based adaptive methods for modeling and simulation of incompressible turbulent flows is presented. Wavelet-based computational modeling approaches of different fidelities are recast into an integrated hierarchical adaptive eddy-capturing turbulence modeling framework. The wavelet threshold filtering procedure and the associated wavelet-filtered Navier–Stokes equations are briefly discussed, along with the adaptive wavelet collocation method that is used for numerical computations. Depending on the level of wavelet thresholding, the simulation is possibly supplemented with a localized closure model. The latest advancements in spatiotemporally varying wavelet thresholding procedures along with the adaptive-anisotropic wavelet-collocation method make the development of a fully adaptive approach feasible with potential applications for complex turbulent flows.

Direct Numerical Simulation Of Turbulent Flows

1996 ◽  
Author(s):  
Anthony Leonard
Keyword(s):  
Numerical Simulation ◽  
Turbulent Flows ◽  
Compressible Flows ◽  
Incompressible Flows ◽  
Isotropic Turbulence ◽  
Turbulent Channel Flow ◽  
Spectral Element ◽  
Von Neumann ◽  
Eddy Simulation ◽  
Parallel Supercomputers

The numerical simulation of turbulent flows has a short history. About 45 years ago von Neumann (1949) and Emmons (1949) proposed an attack on the turbulence problem by numerical simulation. But one could point to a beginning 20 years later when Deardorff (1970) reported on a large-eddy simulation of turbulent channel flow on a 24x20x14 mesh and a direct simulation of homogeneous, isotropic turbulence was accomplished on a 323 mesh by Orszag and Patterson (1972). Perhaps the arrival of the CDC 6600 triggered these initial efforts. Since that time, a number of developments have occurred along several fronts. Of course, faster computers with more memory continue to become available and now, in 1994, 2563 simulations of homogeneous turbulence are relatively common with occasional 5123 simulations being achieved on parallel supercomputers (Chen et al., 1993) (Jimenez et al., 1993). In addition, new algorithms have been developed which extend or improve capabilities in turbulence simulation. For example, spectral methods for the simulation of arbitrary homogeneous flows and the efficient simulation of wall-bounded flows have been available for some time for incompressible flows and have recently been extended to compressible flows. In addition fast, viscous vortex methods and spectral element methods are now becoming available, suitable for incompressible flow with complex geometries. As a result of all these developments, the number of turbulence simulations has been increasing rapidly in the past few years and will continue to do so. While limitations exist (Reynolds, 1990; Hussaini et al., 1990), the potential of the method will lead to the simulation of a wide variety of turbulent flows. In this chapter, we present examples of these new developments and discuss prospects for future developments.

Review on Space-Time Correlations in Turbulent Fluids

1965 ◽  
Vol 32 (2) ◽  
pp. 241-257 ◽  
Author(s):  
A. J. Favre
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Incompressible Flows ◽  
Space Time ◽  
Main Flow ◽  
Wall Pressure ◽  
Time Correlations ◽  
The Mean ◽  
Supersonic Wake ◽  
Turbulent Fluids

Turbulent flows, even when stationary on the average, are time-dependent. The study of such flows must take into account their statistical properties, not only spatial but temporal as well. A review is given of the main results of space-time measurements pertaining to: (a) In incompressible flows, double and triple velocity correlations, double correlations of wall pressure and of wall pressure and velocity of the main flow; (b) in compressible flows, double correlations of pressure at the wall and outside supersonic boundary layers, and autocorrelations of velocity in a supersonic wake. The space-time correlations give evidence to the heredity and (a) the convection velocities of the vorticity and entropy modes, as compared to the mean material convection velocity, and (b) the propagation of the acoustical mode.

scholarly journals ILES and LES of Complex Engineering Turbulent Flows

2007 ◽  
Vol 129 (12) ◽  
pp. 1514-1523 ◽  
Author(s):  
C. Fureby
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Incompressible Flows ◽  
Phase Changes ◽  
Aerodynamic Noise ◽  
Complex Geometries ◽  
Flow Problems ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Complex Engineering

The present study concerns the application of large eddy simulation (LES) and implicit LES (ILES) to engineering flow problems. Such applications are often very complicated, involving both complex geometries and complex physics, such as turbulence, chemical reactions, phase changes, and compressibility. The aim of the study is to illustrate what problems occur when attempting to perform such engineering flow calculations using LES and ILES, and put these in relation to the issues originally motivating the calculations. The issues of subgrid modeling are discussed with particular emphasis on the complex physics that needs to be incorporated into the LES models. Results from representative calculations, involving incompressible flows around complex geometries, aerodynamic noise, compressible flows, combustion, and cavitation, are presented, discussed, and compared with experimental data whenever possible.

DDES Analysis of Wake Vortex Related Unsteadiness and Losses in the Environment of High-Pressure Turbine Stage

2017 ◽  
Author(s):  
Dun Lin ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
High Pressure ◽  
Boundary Layer Transition ◽  
Wake Vortex ◽  
High Fidelity ◽  
Strong Impact ◽  
Detached Eddy Simulation ◽  
High Pressure Turbine ◽  
Layer Transition ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

In this work, the flows inside the high pressure turbine (HPT) vane and stage are studied with the help of a high-fidelity delayed detached eddy simulation (DDES) code. This work intends to study the fundamental nozzle/blade interaction with special attention paid to the development and transportation of the vane wake vortex. There are two motivations for this work. On the one hand, the high pressure turbine operates at both transonic Mach numbers and high Reynolds numbers, which imposes a great challenge to modern computational fluid dynamics (CFD), especially for scale-resolved simulation methods. An accurate and efficient high-fidelity CFD solver is very important for a thorough understanding of the flow physics and the design of more efficient HPT. On the other hand, the periodic wake vortex shedding is an important origin of turbine losses and unsteadiness. The wake and vortex not only cause losses themselves, but also interact with the shock wave (under transonic working condition), pressure waves, and have a strong impact on the downstream blade surface (affecting boundary layer transition and heat transfer). Built on one of our previous DDES simulations of a HPT vane VKI LS89, this work further investigates the development and length characteristics of the wake vortex, provides explanations of the length characteristics and reveals the transportation of the wake vortex into the downstream rotor passage along with its impact on the downstream aero-thermal performance.

A Viscous-Inviscid Interaction Procedure—Part 1: Method for Computing Two-Dimensional Incompressible Separated Channel Flows

1986 ◽  
Vol 108 (1) ◽  
pp. 64-70 ◽  
Author(s):  
O. K. Kwon ◽  
R. H. Pletcher
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Turbulent Flows ◽  
Inviscid Flow ◽  
Companion Paper ◽  
Separated Flows ◽  
Two Dimensional ◽  
Boundary Layer Equations ◽  
Interaction Scheme ◽  
Laminar And Turbulent Flows

A viscous-inviscid interaction scheme has been developed for computing steady incompressible laminar and turbulent flows in two-dimensional duct expansions. The viscous flow solutions are obtained by solving the boundary-layer equations inversely in a coupled manner by a finite-difference scheme; the inviscid flow is computed by numerically solving the Laplace equation for streamfunction using an ADI finite-difference procedure. The viscous and inviscid solutions are matched iteratively along displacement surfaces. Details of the procedure are presented in the present paper (Part 1), along with example applications to separated flows. The results compare favorably with experimental data. Applications to turbulent flows over a rearward-facing step are described in a companion paper (Part 2).

LPC Blade and Non-Axisymmetric Hub Profiling Optimization Using Multi-Fidelity Non-Intrusive POD Surrogates

2017 ◽  
Author(s):  
Tariq Benamara ◽  
Piotr Breitkopf ◽  
Ingrid Lepot ◽  
Caroline Sainvitu
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
High Fidelity ◽  
Present Contribution ◽  
Compressor Blades ◽  
High Fidelity Simulations ◽  
Optimization Methodology ◽  
Set Up ◽  
Automated Optimization ◽  
Proper Orthogonal

The present contribution proposes a Reduced Order Model based multi-fidelity optimization methodology for the design of highly loaded blades in low pressure compressors. Environmental, as well as, economical limitations applied to engine manufacturers make the design of modern turbofans an extremely complex task. A smart compromise has to be found to guarantee both a high efficiency and a high average stage loading imposed for mass reduction constraints, while satisfying stability requirements. The design of compressor blades, usually involves at the same time a dedicated parametrization set-up in highdimensional space and high-fidelity simulations capturing, at least, efficiency and stability as most impacting phenomena. Despite recent advances in the high-performance computing area, introducing high-fidelity simulations into automated optimization, or even surrogate assisted optimization, loops still stands as a endeavor for engineers. In this framework, the proposed methodology is based on multi-fidelity surrogate models capable of representing the physics at hand in reduced spaces inferred from both precise, albeit costly, high-fidelity simulations and abundant, yet less accurate lower-fidelity data. Finally, we investigate the coupling of the proposed hierarchised multi-fidelity non-intrusive Proper Orthogonal Decomposition based surrogates with an evolutionary algorithm to reduce the number of high-fidelity simulation calls towards the targeted optimum.

New space-averaging procedure for inhomogeneous flow fields using balance equation formulations

2006 ◽  
Vol 220 (9) ◽  
pp. 1363-1374
Author(s):  
S Wattananusorn
Keyword(s):  
Compressible Flows ◽  
Incompressible Flows ◽  
Flow Fields ◽  
Coupling Factor ◽  
Balance Equations ◽  
Mean Velocity ◽  
New Space ◽  
Inhomogeneous Flow ◽  
The Mean ◽  
Dependent Flow

This paper features the possibility of averaging space-dependent flow fields using a coupling factor that links the equations of momentum and energy. The scheme is applied to the mean velocity, which is derived straightforwardly through the continuity equation. It creates a small imbalance, which can be eliminated later completely. Smaller discrepancies in the integration of systems of balance equations for inhomogeneous flow are the consequence. The procedure is verified on various flow patterns, and comparisons are made with other conventional methods and with some available experimental data. Despite investigating only numerical examples of incompressible flows here, the technique, in principle, is capable of dealing with compressible flows as well. Furthermore, the proposed method discards some variables required in other techniques while still providing useful and acceptable results for practical problems.

scholarly journals Adaptive method of detecting traffic anomalies in high-speed multi-service communication networks

2020 ◽  
Vol 157 ◽  
pp. 04027 ◽  
Author(s):  
Sergey Ageev ◽  
Vladimir Karetnikov ◽  
Evgeny Ol’khovik ◽  
Andrey Privalov
Keyword(s):  
Network Security ◽  
Real Time ◽  
Communication Networks ◽  
High Speed ◽  
High Efficiency ◽  
Adaptive Methods ◽  
Adaptive Method ◽  
Anomalous Behavior ◽  
Preliminary Training ◽  
Network Attacks

In the paper, an adaptive hybrid heuristic (behavioral) method for detecting small traffic anomalies in high-speed multiservice communication networks, which operates in real time, is proposed and investigated. The relevance of this study is determined by the fact that network security management processes in high-speed multiservice communication networks need to be implemented in a mode close to real-time mode, as well as identifying possible network security threats in the early stages of the implementation of possible network attacks. The proposed method and algorithm belong to the class of adaptive methods and algorithms with preliminary training. The average relative error in estimating the evaluated traffic parameters does not exceed 10%, which is sufficient for the implementation of operational network management tasks. Anomalies of the expectation of traffic intensity and its dispersion are identified if their valuesexceed the normal values by 15% or more, which makes it possible to detect possible network attacks in the early phases of their implementation, for example, at the stage of scanning ports and interfaces of the attacked system. The procedure for detecting anomalous traffic behavior is implemented based on the Mamdani’s method of hierarchical fuzzy logical inference. A study of the proposed method for detecting anomalous behavior of network traffic showed its high efficiency.

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