CERFACS CERFACS Scientific Activity Report Jan. 2010 â Dec. 2011

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3 Turbomachinery The turbomachine group is the most recent component of the CFD team and gathers around 12 people. The main effort of the group has been put on the development and the application of methods to simulate unsteady flows in compressor and turbine components. Recent breakthroughs include the successful implementation of the harmonic balance method in elsA and the application of LES (both with elsA and AVBP) to address complex flow phenomena (such as shock/boundary layer interaction and laminarturbulent transition) in turbomachine configurations. Another promising work is the code coupling activity : coupling methods are developed in cooperation within the CFD team (COMB and AAM groups) and with the GLOBC team (which develops the code coupling tool Open-PALM). The target is to prepare techniques for the 2020 challenge ”COUGAR” (for which the objective is to perform an unsteady flow simulation in a whole gas turbine). The work of the turbomachinery group also led to industrial applications, supported by SAFRAN, Airbus and EDF. The group is involved in European Projects (e.g. COPA-GT, a Marie-Curie program, and FACTOR). The cooperation with research partners (VKI, LMFA, ONERA) has also been strengthened through the co-direction of Phd students and the definition of common test cases (CREATE, LS89, etc.). 3.1 Numerical methods and software The development of numerical methods for turbomachinery focuses on three main topics : the reduction of the computational cost for unsteady flows, the quantification of the solution to unknown/uncertain parameters and the code coupling activity. 3.1.1 Spectral methods : development of the Harmonic Balance Technique (T. Guedeney) Some flows are controlled by a strong periodic forced activity : for turbomachinery flows for example, developing a method which includes this information allows computations that are more efficient than classical unsteady CFD approaches (Dual Time Stepping, etc.). The Time Spectral Method (TSM) has been implemented in the code elsA following this philosophy. Thanks to Fourier spectral analysis, the unsteady Navier-Stokes equations can be read as 2N + 1 steady problems coupled by a source term (with N the number of harmonic of a frequency given by the user). The phase-lagged functionality [7] has been also implemented in the spectral method to reduce the computational domain to only one single blade passage per blade row. The TSM is able to deal with only one frequency and its harmonics (for example the blade passing frequency) and is therefore limited to a single stage computation. To extend the method to multistage turbomachines, it is mandatory to take into account several frequencies which are not necessarily multiples of a base frequency. This new method is called the Harmonic Balance Technique (HBT). To implement the HBT, all features developped for TSM were adapted to a multifrequential formulation. However, while the position of the time instants with TSM was simply equally distributed along the flow period, the same approach with HBT led to serious conditioning problems, especially for multifrequential test cases. To circumvent this issue, different methods such as the APFT algorithm (which stands for Almost Periodic Fourier Transform) or genetic algorithms have been implemented. The development of the HBT is now completed and the validation step has already started [CFD42]. 146 Jan. 2010 – Dec. 2011
COMPUTATIONAL FLUID DYNAMICS (a) (b) FIG. 3.1: Application of a UQ method to turbomachine configurations : influence of inlet turbulent Reynolds number Re t and turbulent intensity Tu on (a) the transition abscissa in a turbine guide vane (the leading edge, resp. the trailing edge, is located at S = 0mm, resp. S = 85mm) and (b) the wall heat flux. 3.1.2 Uncertainty quantification : development of a stochastic collocation method (K. Dewandel, N. Gourdain) The simulations of flows in real gas turbine configurations usually consider geometries and flows that are different from the reality (ill-defined boundary conditions, inaccuracy of the geometry, etc.). These differences can significantly affect the accuracy of the numerical solution. The aim of this work was thus to apply a method to turbomachinery test cases, in order to estimate the influence of unknown/uncertain parameters on the numerical solution. The approach is based on a Stochastic-Collocation (SC) method, based on Clenshaw-Curtis sampling points. This method is validated against the classical Monte-Carlo (MC) method (that uses random sample points to describe the space of parameters) [CFD38]. The computational cost required to evaluate the sensitivity to two parameters is reduced by a factor 30 with the SC method compared to MC. The SC method is then applied to an inlet guide vane of a high-pressure turbine (shown in Fig. 3.7) and a three and a half stage compressor (shown in Fig. 3.4). For the turbine case, the results quantify the sensitivity of the wall heat transfer to inlet turbulent intensity, inlet turbulent Reynolds number and outlet Mach number. For the compressor case, the study shows the dependence of the overall performance (pressure ratio, efficiency and stability) to the size of the rotor tip clearances. An example of how such methods can provide useful information is reported for the turbine test case in Fig. 3.1(a) (dependency of the transition abscissae to inlet turbulence) and Fig. 3.1(b) (dependency of wall heat fluxes prediction to inlet turbulence). 3.1.3 Code coupling methods : application to elsA / AVBP (E. Collado Morata, F. Duchaine, M. Montagnac) CFD for turbomachinery usually focuses only on isolated components while real systems involve interactions between different components and physics (aerodynamics, heat transfer, combustion, etc.). The goal of this research topic is to enable large-scale integrated simulations of unsteady turbulent flows in gas turbines. The study is a preliminary mandatory work to achieve the objective of other ambitious projects, such as FACTOR (flow simulation in a combustion chamber simulator coupled with the high-pressure turbine) and COPA-GT (flow simulation in the compressor/combustor module). Due to the specificity CERFACS ACTIVITY REPORT 147
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CERFACS Scientific Activity Report
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Table des matières 1 Foreword xiii
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9 Publications 40 9.1 Books . . . .
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3 The OpenPALM coupler 104 3.1 Intr
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Table des figures CERFACS chart as
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TABLE DES FIGURES 6 Computational F
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Foreword Welcome to the 2010-2011 S
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CERFACS STRUCTURE CERFACS organizat
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CERFACS STAFF NAME POSITION PERIOD
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CERFACS STAFF SILVA GARZON Ph.D stu
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CERFACS STAFF NAME POSITION PERIOD
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CERFACS Wide-Interest Seminars Pete
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1 Introduction 1.1 Introduction The
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PARALLEL ALGORITHMS PROJECT success
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PARALLEL ALGORITHMS PROJECT Visitor
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3 List of Members of HiePACS HiePAC
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4 Dense and Sparse Matrix Computati
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PARALLEL ALGORITHMS PROJECT Working
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5 Iterative Methods and Preconditio
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PARALLEL ALGORITHMS PROJECT 5.5 Pre
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PARALLEL ALGORITHMS PROJECT We are
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PARALLEL ALGORITHMS PROJECT is to e
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PARALLEL ALGORITHMS PROJECT automor
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PARALLEL ALGORITHMS PROJECT 7.4 Sol
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PARALLEL ALGORITHMS PROJECT precond
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PARALLEL ALGORITHMS PROJECT 7.16 An
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PARALLEL ALGORITHMS PROJECT solutio
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8 Conferences and Seminars 8.1 Conf
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PARALLEL ALGORITHMS PROJECT Decembe
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PARALLEL ALGORITHMS PROJECT July WC
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PARALLEL ALGORITHMS PROJECT Septemb
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PARALLEL ALGORITHMS PROJECT [ALG15]
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PARALLEL ALGORITHMS PROJECT [ALG54]
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1 Overview presentation The main ex
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ELECTROMAGNETISM AND ACOUSTICS TEAM
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1 Introduction Data assimilation is
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DATA ASSIMILATION 2.3 Calibrating o
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3 Data assimilation for atmospheric
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DATA ASSIMILATION BECM using or not
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DATA ASSIMILATION the potential vor
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DATA ASSIMILATION A two years simul
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DATA ASSIMILATION FIG. 4.1: Reducti
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DATA ASSIMILATION FIG. 4.3: April 2
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DATA ASSIMILATION by a surface mode
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6 Data assimilation with EDF neutro
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DATA ASSIMILATION demonstrate that
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Page 124 and 125: 2 The OASIS coupler The OASIS coupl
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Page 132 and 133: 4 HPC Climate modelling 4.1 General
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Page 153 and 154: 1 Introduction The CFD (Computation
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Page 191 and 192: 5 Publications 5.1 Conferences Proc
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Page 201: 7 Aviation and Environment
Page 204 and 205: INTRODUCTION instead of regular ker
Page 206 and 207: SIMULATIONS OF AIRCRAFT WAKES AND R
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CERFACS CERFACS Scientific Activity Report Jan. 2010 â Dec. 2011

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CERFACS CERFACS Scientific Activity Report Jan. 2010 â Dec. 2011