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

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TURBOMACHINERY 3.2.1 Application of spectral methods to aero-elasticity (F. Sicot, G. Dufour) Aeroelasticity studies the impact of a flow on a flexible structure. Fluid/structure interactions can potentially be destructive (e.g. the flutter phenomena) and therefore must be thoroughly investigated. One way to assess the sensitivity of a turbomachinery to flutter is the so-called weak-coupling approach where the response of the fluid to a forced harmonic motion of the structure is simulated. Correlated to the lag (i.e. advance or delay) of the fluid with respect to the excitation, a stability analysis can tell if the fluid is damping or exciting the structure vibrations. CERFACS is developing a harmonic balance method in the elsA solver. This method is well suited for weak-coupling simulations [CFD68] and the CFD team was involved in many projects concerning the aeroelasticity of turbomachinery with harmonic balance methods : – the MACAO project [CFD149] studied an isolated axial compressor. This first successful application was made possible thanks to a collaboration with the aeroelasticity department of ONERA [CFD63], – the Aerovista project (with ONERA and Safran [CFD166]) encompasses several configurations : – an isolated centrifugal compressor [CFD167], – an isolated axial compressor with technological effects [CFD165]. This requires the use of overset grids (i.e. Chimera technique) to represent complex geometry, – a counter-rotating fan [CFD164] : the blade passing frequency and vibration frequency can be different and this configuration requires a non-uniform harmonic balance using an arbitrary set of frequencies and a non-uniform time sampling to capture all phenomena, – open rotors (CROR) will also be investigated in this project. – the validation against experimental data has been assessed for the 11 th standard configuration for aeroelasticity (namely the STCF11) which is a turbine blade oscillating in its first bending mode. The results have been submitted to the AIAA journal in January 2012, – Finally Cerfacs is involved in the FUTURE (Flutter-Free Turbomachinery Blades) FP7 European project. 3.2.2 Application of spectral methods to multistage turbomachines (T. Guedeney, Y. Sadoudi) The Harmonic Balance Technique (HBT), presented in section 3.1.1, is used to predict the unsteady flow induced by the relative motion between rotating and non-rotating blades. The main interest is to reduce the cost of unsteady RANS simulations. For example, in the case of a 3.5 stage compressor (CREATE, Fig. 3.4), HBT presents a gain of 4 for the same level of accuracy compared to the classical approach based on a Dual Time Stepping algorithm. Since the periodicity of this test case is 2π/16, the gain expected for other configurations should be of one order of magnitude higher (the usual periodicity for a turbomachinery is 2π, which corresponds to primary blade numbers). Other complex 3D test cases have also been successfully performed, such as a transonic 1.5 stage compressor (ECL4) and a multistage turbine (HTLC). These results show that HBT is a efficient method to reduce the cost of unsteady flow simulations in turbomachinery. The evaluation of the influence of the frequency set on the HBT results is now under progress as well as the quantification of the computational speedup compared to classical unsteady RANS simulations. 3.2.3 Compressor flows : control with casing treatment (G. Legras, N. Gourdain) Passive control devices based on casing treatments have already shown their capability to improve the flow stability in axial compressors. Among many geometries that have been investigated, axisymmetric (axial grooves) and non-axisymmetric (slots, etc.) geometries have shown a good ability to enhance stall margin. However their optimization remains complex due to a partial understanding of related flow mechanisms. The objective of this work was to numerically investigate different compressor configurations equipped with casing treatments, such as a transonic axial compressor rotor with slot-type casing treatment or a multistage compressor with axial grooves or honey-comb (Fig. 3.5). 150 Jan. 2010 – Dec. 2011
COMPUTATIONAL FLUID DYNAMICS FIG. 3.4: Application of HBT to compressor CREATE. Entropy field at 50% of the compressor span. FIG. 3.5: Influence of the casing treatment on the tip leakage vortex (TLV) in a transonic compressor. Left : smooth wall and right : casing treatment case. Unsteady flow simulations of casing treatments are performed using elsA. Control devices are connected to the main compressor grid using either a Chimera technique or a sliding mesh method. Numerical results obtained with and without casing treatment are compared and validated with experimental data [CFD78]. In order to understand the influence of casing treatment on the flow, a budget analysis of the unsteady axial momentum equation is performed on a control volume located in the rotor tip region (the so-called MARS tool [CFD50]), following the idea proposed by Shabbir and Adamczyk [24]. CERFACS ACTIVITY REPORT 151
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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 We are
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PARALLEL ALGORITHMS PROJECT automor
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8 Conferences and Seminars 8.1 Conf
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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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DATA ASSIMILATION [DA13] S. Massart
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4 Coupling tools and HPC Climate Mo
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Page 153 and 154: 1 Introduction The CFD (Computation
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Page 216: PUBLICATIONS 4.2 Technical Reports
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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