. Au-sens-de-la-moyenne-de-phase, la moyenne et l'écart-type sont calculés d'après (3.2). sur la figure 3.3, les quantités moyennes (?W ? ou ?U ?) sont tracées la première colonne lorsque les écarts-types associés

. Intéressons, une baisse de ?W ? est constatée de 120 dv à 180 dv le long de la droite A (Fig. 3.3c), elle est maximale dans la région centrale pour x ? [?B/4 La descente du jet des soupapes est importante au début de l'admission et elle diminue jusqu'au PMB. La figure 3.3c indique une réduction de la fluctuation. Le long de la droite B, la vitesse verticale est très importante à 120 dv lorsque elle est presque nulle au PMB (Fig. 3.3d) De plus, l'écoulement est plus fluctuante au voisinage du piston (Fig. 3.3e). A 270 dv, nous observons que les vitesses sont ascendantes le long des droites A et B (Fig. 3.3b et d). Il est intéressant de remarquer que le long

L. Profils-de-vitesse and ?. ?. , ) démontre que l'écoulement tourne dans le sens horaire dans le repère xOz (Fig. 3.3f) De plus, le module de la vitesse moyenne ?U ? se réduit pendant l'admission puis s'amplifie, ceci entraîne une variation de l

R. Arcoumanis, C. Hu, Z. Whitelaw, and J. , Tumbling Motion: A Mechanism for Turbulence Enhancement in Spark-Ignition Engines, SAE Technical Paper Series, 1990.
DOI : 10.4271/900060

C. G. Bishop, E. Mancaruso, S. Merola, and B. Vaglieco, Pattern recognition and machine learning (information science and statistics) POD-based analysis of combustion images in optically accessible engines, Comb Flame, vol.157, pp.632-640, 2006.

J. Borée, P. Miles, D. Crolla, D. Foster, T. Kobayashi et al., In-cylinder flow Encyclopedia of automotive engineering Modern multidimensional scaling: theory and applications) On the use and interpretation of proper orthogonal decomposition of in-cylinder flows, Meas Sci Technol, vol.23, issue.8, pp.1-14, 2005.

H. Chen, D. Hung, M. Xu, H. Zhuang, and Y. J. , Proper orthogonal decomposition analysis of fuel spray structure variation in a spark-ignition direct-injection optical engine, Experiments in Fluids, vol.25, issue.5, pp.1703-1715, 2014.
DOI : 10.1007/s00348-014-1703-y

I. Cosadia, J. Borée, G. Charnay, and P. Dumont, Cyclic variations of the swirling flow in a Diesel transparent engine, Experiments in Fluids, vol.15, issue.3, pp.115-134, 2006.
DOI : 10.1007/s00348-006-0163-4
URL : https://hal.archives-ouvertes.fr/hal-00123450

Q. Du and M. Gunzburger, Centroidal Voronoi tessellation based proper orthogonal decomposition analysis Control and estimation of distributed parameter systems, Birkhäuser, pp.137-150, 2003.

M. Fogleman, J. Lumley, D. Rempfer, and D. Haworth, Low dimensionnal models of internal combustion engine flows using the proper orthogonal decomposition Application of the proper orthogonal decomposition to datasets of internal combustion engine flows, J Turbul, vol.5, pp.1-18, 2004.

A. Gosman, Flow processes in cylinders Thermodynamics and gas dynamics of internal combustion engines, pp.616-772, 1986.

C. Hasse, V. Sohm, and B. Durst, Numerical investigation of cyclic variations in gasoline engines using a hybrid URANS/LES modeling approach, Computers & Fluids, vol.39, issue.1, pp.25-48, 2010.
DOI : 10.1016/j.compfluid.2009.07.001

J. Heywood, Internal combustion engines fundamentals The effects of swirl and tumble on combustion in spark-ignition engines, Prog Energy Combust Sci, vol.20, pp.373-429, 1988.

P. Holmes, J. Lumley, G. Berkooz, C. Rowley, E. Kaiser et al., Turbulence, coherent structures, dynamical systems and symmetry, 2nd edn Cluster-based reduced-order modelling of a mixing layer, J Fluid Mech, vol.754, pp.365-414, 2012.

L. Kapitsa, O. Imberdis, H. Bensler, J. Willand, and D. Thévenin, An experimental analysis of the turbulent structures generated by the intake port of a DISI-engine, Experiments in Fluids, vol.45, issue.3, pp.265-280, 2010.
DOI : 10.1007/s00348-009-0736-0

A. Keromnes, C. Dujol, and P. Guibert, Aerodynamic control inside an internal combustion engine, Measurement Science and Technology, vol.21, issue.12, pp.125-404, 2010.
DOI : 10.1088/0957-0233/21/12/125404

K. Liu and D. Haworth, Development and assessment of POD for analysis of turbulent flow in piston engines. SAE Technical paper, pp.2011-2012, 2011.

S. Lloyd and S. P. Lloyd, Least squares quantization in PCM, IEEE Transactions on Information Theory, vol.28, issue.2, pp.129-1371056489, 1957.
DOI : 10.1109/TIT.1982.1056489
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.131.1338

J. Lumley, The structure of inhomogeneous turbulence Atmospheric turbulence and wave propagation, pp.166-178, 1967.

J. Lumley, Engines. An introduction Transition to turbulence in an elliptic vortex, J Fluid Mech, vol.307, pp.43-62, 1996.

J. Macqueen, Some methods for classification and analysis of multivariate observations, Proceedings of the fifth Berkeley symposium on mathematical statistics and probability, pp.281-297, 1967.

T. Schneider, B. Eckhardt, and J. Vollmer, Statistical analysis of coherent structures in transitional pipe flow, Physical Review E, vol.75, issue.6, p.66313, 2007.
DOI : 10.1103/PhysRevE.75.066313

M. Voisine, L. Thomas, J. Borée, and P. Rey, Spatio-temporal structure and cycle to cycle variations of an in-cylinder tumbling flow, Experiments in Fluids, vol.156, issue.6, pp.1393-1407, 2011.
DOI : 10.1007/s00348-010-0997-7

R. J. Adrian, Scattering particle characteristics and their effect on pulsed laser measurements of fluid flow: speckle velocimetry vs particle image velocimetry, Applied Optics, vol.23, issue.11, pp.1690-1691, 1984.
DOI : 10.1364/AO.23.001690

R. J. Adrian, Particle-Imaging Techniques for Experimental Fluid Mechanics, Annual Review of Fluid Mechanics, vol.23, issue.1, pp.261-304, 1991.
DOI : 10.1146/annurev.fl.23.010191.001401

R. J. Adrian, Twenty years of particle image velocimetry, Experiments in Fluids, vol.10, issue.2, pp.159-169, 2005.
DOI : 10.1007/s00348-005-0991-7

A. Alkidas, R. Drews, and W. Miller, Effects of piston crevice geometry on the steadystate engine-out hydrocarbons emissions of a si engine. Rap. tech., SAE Technical Paper, 1995.

C. Arcoumanis, S. N. Godwin, and J. Kim, Effect of tumble strength on combustion and exhaust emissions in a single-cylinder, four-valve, spark-ignition engine. Rap. tech., SAE Technical Paper, 1998.

X. Baby, Optimisation de l'aérodynamique interne dans un moteur à injection directe essence Analyse de l'écoulement de tumble par vélocimètre par images de particules, 2000.

G. Batchelor, An Introduction to Fluid Mechanics, Journal of Applied Mechanics, vol.35, issue.3, 1967.
DOI : 10.1115/1.3601282

E. Baum, B. Peterson, B. Böhm, and A. Dreizler, On The Validation of LES Applied to Internal Combustion Engine Flows : Part 1 : Comprehensive Experimental Database. Flow, Turbulence and Combustion, pp.269-297

L. H. Benedict and R. D. Gould, Towards better uncertainty estimates for turbulence statistics, Experiments in Fluids, vol.22, issue.2, pp.129-136, 1996.
DOI : 10.1007/s003480050030

C. Blunsdon and J. Dent, The simulation of Autoignition and knock in a spark ignition engine with disk geometry. Rap. tech, SAE Technical Paper, 1994.

J. Bonnet and J. Delville, Review of coherent structures in turbulent free shear flows and their possible influence on computational methods. Flow, Turbulence and combustion, pp.333-353, 2001.

J. Bonnet, J. Delville, M. Glauser, R. Antonia, D. Bisset et al., Collaborative testing of eddy structure identification methods in free turbulent shear flows, Experiments in Fluids, vol.25, issue.3, pp.197-225, 1998.
DOI : 10.1007/s003480050224

J. Borée and P. C. , Miles : In-cylinder flow, Encyclopedia of Automotive Engineering, pp.1-31, 2014.

M. Brunt, The effect of combustion chamber design on the combustion rate in an SI engine URL https, Thèse de doctorat, © MFJ Brunt, 1980.

F. Brusiani, S. Falfari, and G. Cazzoli, Tumble Motion Generation in Small Gasoline Engines: A New Methodological Approach for the Analysis of the Influence of the Intake Duct Geometrical Parameters, Energy Procedia, vol.45, pp.997-1006, 2014.
DOI : 10.1016/j.egypro.2014.01.105

I. Bücker, D. Karhoff, J. Dannemann, K. Pielhop, M. Klaas et al., Comparison of PIV Measured Flow Structures in Two Four-Valve Piston Engines, pp.633-640
DOI : 10.1007/978-3-642-35680-3_75

I. Bücker, D. Karhoff, M. Klaas, and W. Schröder, Engine in-cylinder flow control via variable intake valve timing. Rap. tech

H. Chen, D. L. Reuss, and V. , Analysis of misfires in a direct injection engine using proper orthogonal decomposition, Experiments in Fluids, vol.25, issue.4, pp.1139-1151, 2011.
DOI : 10.1007/s00348-011-1133-z

H. Chen, D. L. Reuss, and V. , Sick : On the use and interpretation of proper orthogonal decomposition of in-cylinder engine flows, Measurement Science and Technology, vol.23238, issue.8, pp.1-140957, 2012.

M. Christensen, B. Johansson, and A. Hultqvist, The effect of piston topland geometry on emissions of unburned hydrocarbons from a homogeneous charge compression ignition (HCCI) engine. Rap. tech., SAE Technical Paper, 2001.

M. Christensen, B. Johansson, and A. Hultqvist, The effect of combustion chamber geometry on HCCI operation. Rap. tech, SAE Technical Paper, 2002.

A. Clenci, A. Bîzîiac, P. Podevin, G. Descombes, M. Deligant et al., Idle Operation with Low Intake Valve Lift in a, Port Fuel Injected Engine. Energies, vol.6, issue.666, pp.2874-2891, 2013.
URL : https://hal.archives-ouvertes.fr/hal-01502041

A. C. Clenci, V. Iorga-sim?n, M. Deligant, P. Podevin, G. Descombes et al., A CFD (computational fluid dynamics) study on the effects of operating an engine with low intake valve lift at idle corresponding speed. Energy, pp.202-217, 2014.
URL : https://hal.archives-ouvertes.fr/hal-01502039

I. Cosadia, Variabilité cyclique de l'aérodynamique interne d'un moteur diesel. Mise en oeuvre de diagnostics optiques pour l'analyse spatiale et temporelle, 2006.

W. Deslandes, Structure et dispersion de l'aérodynamique interne des moteurs Diesel Caractérisation par diagnostic optique, 2004.

Q. Du and M. D. Gunzburger, Centroidal voronoi tessellation based proper orthogonal decomposition analysis In Control and estimation of distributed parameter systems, pp.137-150, 1007.

V. Dugué, Etude du potentiel des simulations aux grandes échelles pour la prédiction des variations cycliques dans les moteurs automobiles, Thèse de doctorat, Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (E.M.2.C.) du CNRS et de l'ECP, 2007.

B. Enaux, V. Granet, O. Vermorel, C. Lacour, C. Pera et al., Poinsot : LES study of cycle-to-cycle variations in a spark ignition engine, the 33rd international symposium on combustion, 2010.

A. Enotiadis, C. Vafidis, and J. Whitelaw, Interpretation of cyclic flow variations in motored internal combustion engines, Experiments in Fluids, vol.10, issue.2-3, pp.77-86, 1990.
DOI : 10.1007/BF00215014

S. Falfari, F. Brusiani, and G. M. Bianchi, Assessment of the influence of intake duct geometrical parameters on the tumble motion generation in a small gasoline engine. Rap. tech., SAE Technical Paper, 2012.

T. D. Fansler and D. T. French, Cycle-resolved laser-velocimetry measurements in a reentrant-bowl-in-piston engine. Rap. tech., SAE Technical Paper, 1988.

A. Floch, J. Van-frank, and A. Ahmed, Comparison of the effects of intake-generated swirl and tumble on turbulence characteristics in a 4-valve engine. Rap. tech., SAE Technical Paper, 1995.

M. Fogleman, J. Lumley, and D. Rempfer, Haworth : Application of the proper orthogonal decomposition to datasets of internal combustion engine flows, Journal of Turbulence, vol.5, issue.23, pp.1-18, 2004.

E. Foucault, M. P. Laurent, P. Szeger, and J. Laumonier, Débitmètre instationnaire temps réel, 2010.

T. B. Gatski, C. L. Rumsey, and R. Manceau, Current trends in modelling research for turbulent aerodynamic flows, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol.1, issue.1, pp.2389-2418, 1859.
DOI : 10.1098/rsta.2007.2015

C. L. Genzale, R. D. Reitz, and M. P. , Musculus : Effects of piston bowl geometry on mixture development and late-injection low-temperature combustion in a heavy-duty diesel engine. Rap. tech., SAE Technical Paper, 2008.

O. Hadded and I. Denbratt, Turbulence characteristics of tumbling air motion in four-valve si engines and their correlation with combustion parameters. Rap. tech., SAE Technical Paper, 1991.

B. Harshavardhan and J. Mallikarjuna, CFD Analysis of in-Cylinder Flow and Air-Fuel Interaction on Different Combustion Chamber Geometry in DISI Engine, IJACECT, pp.1-5, 2013.

D. Haworth, Large-eddy simulation of in-cylinder flows. Oil & Gas Science and Technology, pp.175-185, 1999.

J. B. Heywood, Combustion chamber design for optimum spark-ignition engine performance, International Journal of Vehicle Design, vol.5, pp.336-357, 1984.

P. Hill and D. Zhang, The effects of swirl and tumble on combustion in spark-ignition engines. Progress in energy and combustion science, pp.373-429, 1994.

H. Hong, G. Parvate-patil, and B. Gordon, Review and analysis of variable valve timing strategies--eight ways to approach, Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol.218, issue.10, pp.1179-1200, 2004.
DOI : 10.1177/095440700421801013

Z. Hu, J. Whitelaw, and C. , Vafidis : Flame propagation studies in a four-valve pentroofchamber spark ignition engine, 1992.

R. F. Huang, K. H. Lin, C. Yeh, and J. Lan, In-cylinder tumble flows and performance of a motorcycle engine with circular and elliptic intake ports, Experiments in Fluids, vol.43, issue.1, pp.165-179, 2009.
DOI : 10.1007/s00348-008-0551-z

M. Jia, Y. Li, M. Xie, and T. Wang, Numerical evaluation of the potential of late intake valve closing strategy for diesel pcci (premixed charge compression ignition) engine in a wide speed and load range. Energy, pp.203-215, 2013.

T. Justham, S. Jarvis, A. Clarke, C. Garner, G. Hargrave et al., Halliwell : Simultaneous study of intake and in-cylinder ic engine flow fields to provide an insight into intake induced cyclic variations, Journal of Physics : Conference Series, pp.1461742-6596019, 2006.

L. Kapitza, O. Imberdis, H. Bensler, and J. Willand, An experimental analysis of the turbulent structures generated by the intake port of a DISI-engine, Experiments in Fluids, vol.45, issue.3, pp.265-280, 2010.
DOI : 10.1007/s00348-009-0736-0

P. Kreuter, P. Heuser, and M. Schebitz, Strategies to improve si-engine performance by means of variable intake lift, timing and duration. Rap. tech., SAE Technical Paper, 1992.

C. Lacour, C. Pera, B. Enaux, O. Vermorel, C. Angelberger et al., Exploring cyclic variability in a spark-ignition engine using experimental techniques, system simulation and large-eddy simulation, European Combustion Meeting, 2009.

Y. Laurent, Variabilité aérodynamique d'un moteur à combustion interne pendant la phase d'admission Vers l'origine des fluctuations cycliques, Thèse de doctorat, 2008.

B. Lecointe and G. Monnier, Downsizing a gasoline engine using turbocharging with direct injection. Rap. tech., SAE Technical Paper, pp.2003-2004, 2003.

B. Lecordier, Etude de l'interaction de la propagation d'une flamme prémélange avec le champ aérodynamique par association de la tomographie laser et de la vélocimétre par image de particules, Thèse de doctorat, 1997.

P. Leduc, B. Dubar, and A. Ranini, Monnier : Downsizing of gasoline engine : an efficient way to reduce CO 2 emissions. Oil & gas science and technology, pp.115-127, 2003.

J. Lewalle, Wavelet analysis of experimental data - Some methods and the underlying physics, Fluid Dynamics Conference, p.2281, 1994.
DOI : 10.2514/6.1994-2281

L. Lin, D. Shulin, X. Jin, and W. Jinxiang, Xiaohong : Effects of combustion chamber geometry on in-cylinder air motion and performance in DI diesel engine. Rap. tech, 2000.

D. Liu, T. Wang, M. Jia, and G. Wang, Cycle-to-cycle variation analysis of in-cylinder flow in a gasoline engine with variable valve lift, Experiments in Fluids, vol.29, issue.3, pp.585-602, 2012.
DOI : 10.1007/s00348-012-1314-4

K. Liu and D. C. , Haworth : Development and assessment of POD for analysis of turbulent flow in piston engines, pp.2011-2012

J. L. Lumley, Engines : an introduction, 1999.
DOI : 10.1017/CBO9781139175135

D. Marc, J. Boree, R. Bazile, and G. Charnay, Tumbling vortex flow in a model square piston compression machine : PIV and LDV measurements. Rap. tech., SAE Technical Paper, 1997.

K. Michel, Explosion or internal combustion engine, déc. 14 1937, US Patent, vol.2102, p.559

S. Müller, B. Böhm, M. Gleißner, R. Grzeszik, and S. Arndt, Flow field measurements in an optically accessible, direct-injection spray-guided internal combustion engine using high-speed PIV, Experiments in Fluids, vol.32, issue.2, pp.281-290, 2010.
DOI : 10.1007/s00348-009-0742-2

M. Namazian and J. B. Heywood, Flow in the piston-cylinder-ring crevices of a sparkignition engine : effect on hydrocarbon emissions, efficiency and power. Rap. tech., SAE Technical Paper, 1982.

N. Ozdor, M. Dulger, and E. Sher, Cyclic variability in spark ignition engines -a litterature survey, Rap. tech. 940987, SAE Technical Paper, 1994.

B. Petersen and P. Miles, PIV Measurements in the Swirl-Plane of a Motored Light-Duty Diesel Engine, SAE International Journal of Engines, vol.4, issue.1, pp.2011-2012
DOI : 10.4271/2011-01-1285

C. J. Pickering and N. A. , Laser speckle photography and particle image velocimetry: photographic film noise, Applied Optics, vol.23, issue.17, pp.2961-2969, 1984.
DOI : 10.1364/AO.23.002961

S. G. Poulos and J. B. Heywood, The effect of chamber geometry on spark-ignition engine combustion. Rap. tech., SAE Technical Paper, 1983.

W. Qin, M. Xie, M. Jia, T. Wang, and D. Liu, Large eddy simulation and proper orthogonal decomposition analysis of turbulent flows in a direct injection spark ignition engine: Cyclic variation and effect of valve lift, Science China Technological Sciences, vol.5, issue.3, pp.489-504, 2014.
DOI : 10.1007/s11431-014-5472-x

D. L. Reuss, Cyclic variability of large-scale turbulent structures in directed and undirected IC engine flows. Rap. tech, SAE Technical Paper, 2000.

D. L. Reuss, T. Kuo, B. Khalighi, D. Haworth, and M. Rosalik, Particle image velocimetry measurements in a high-swirl engine used for evaluation of computational fluid dynamics calculations. Rap. tech, SAE Technical Paper, 1995.

S. Richard, O. Colin, O. Vermorel, A. Benkenida, and C. Angelberger, Veynante : Towards large eddy simulation of combustion in spark ignition engines, Proceedings of the Combustion Institute, pp.3059-3066, 2007.

F. Söderberg, B. Johansson, and B. Lindoff, Wavelet analysis of in-cylinder ldv measurements and correlation against heat-release. Rap. tech., SAE Technical Paper, 1998.

S. M. Soloff, R. J. Adrian, and Z. Liu, Distortion compensation for generalized stereoscopic particle image velocimetry, Measurement Science and Technology, vol.8, issue.12, pp.1441-1454, 1997.
DOI : 10.1088/0957-0233/8/12/008

P. Stansfield, G. Wigley, T. Justham, J. Catto, and G. Pitcher, PIV analysis of in-cylinder flow structures over a range of realistic engine speeds, Experiments in Fluids, vol.15, issue.D03398, pp.135-146, 2007.
DOI : 10.1007/s00348-007-0335-x

P. Sullivan, R. Ancimer, and J. Wallace, Turbulence averaging within spark ignition engines, Experiments in Fluids, vol.27, issue.1, pp.92-101, 1999.
DOI : 10.1007/s003480050333

P. Szeger, Débimètre Instationnaire temps réel modèle LEA-0901, 2010.

H. Tenekees and J. L. Lumley, A First Course in Turbulence M.I.T. Press,. Cambridge, 1972.

G. Tippelmann, A new method of investigation of swirl ports. Rap. tech., SAE Technical Paper, 1977.

T. Uzkan, C. Borgnakke, and T. Morel, Characterization of flow produced by a highswirl inlet port. Rap. tech., SAE Technical Paper, 1983.

O. Vermorel, S. Richard, O. Colin, C. Angelberger, and A. Benkenida, Towards the understanding of cyclic variability in a spark ignited engine using multi-cycle LES, Combustion and Flame, vol.156, issue.8, pp.1525-1541, 2009.
DOI : 10.1016/j.combustflame.2009.04.007
URL : https://hal.archives-ouvertes.fr/hal-00430394

M. Voisine, Etude expérimentale de l'aérodynamique interne des moteurs Mise en oeuvre de diagnostics d'analyses spatio-temporels pour un écoulement de rouleau compressé, 2010.

T. Vu and P. Guibert, Proper orthogonal decomposition analysis for cycle-to-cycle variations of engine flow. Effect of a control device in an inlet pipe, Experiments in Fluids, vol.8, issue.12, pp.1519-1532, 2012.
DOI : 10.1007/s00348-012-1268-6

T. Wang, D. Liu, B. Tan, G. Wang, and Z. Peng, An investigation into in-cylinder tumble flow characteristics with variable valve lift in a gasoline engine. Flow, Turbulence and Combustion, pp.1-20

H. Xu, Some critical technical issues on the steady flow testing of cylinder heads. Rap. tech, SAE Technical Paper, 2001.

K. Xu, H. Xie, M. Wan, T. Chen, and H. Zhao, Effect of valve timing and residual gas dilution on flame development characteristics in a spark ignition engine. Rap. tech

F. Zhao, T. N. Asmus, D. N. Assanis, J. E. Dec, J. A. Eng et al., Homogeneous charge compression ignition (HCCI) engines. Rap. tech., SAE Technical Paper, 2003.

F. Zhao, M. Lai, and D. L. Harrington, Automotive spark-ignited direct-injection gasoline engines. Progress in energy and combustion science, pp.437-562, 1999.

H. Zhao, J. Li, T. Ma, and N. Ladommatos, Performance and analysis of a 4-stroke multicylinder gasoline engine with CAI combustion. Rap. tech., SAE Technical paper, 2002.