https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Fri, 05 Jun 2026 22:46:59 GMT 2026-06-05T22:46:59Z http://hdl.handle.net/10985/15156 High-speed stereoscopic PIV study of rotating instabilities in a radial vaneless diffuser CAVAZZINI, Giovanna; PAVESI, Giorgio; DUPONT, Patrick; COUDERT, Sebastien; ARDIZZON, Giorgio; CAIGNAERT, Guy; BOIS, Gérard; DAZIN, Antoine This paper presents an experimental analysis of the unsteady phenomena developing in a vaneless diffuser of a radial flow pump. Partial flow operating conditions were investigated using 2D/3C high repetition rate PIV, coupled with unsteady pressure transducers. Pressure measurements were acquired on the shroud wall of the vaneless diffuser and on the suction pipe of the pump, whereas PIV flow fields were determined on three different heights in the hub to shroud direction, inside the diffuser. The classical Fourier analysis was applied to both pressure signals to identify the spectral characteristics of the developing instabilities, and the high-order spectral analysis was exploited to investigate possible non-linear interaction mechanisms between different unsteady structures. A dedicated PIV averaging procedure was developed and applied to the PIV flow fields so as to capture and visualize the topology of the spectrally identified phenomena. The influence of these phenomena on the diffuser efficiency was also investigated. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/15156 2011-01-01T00:00:00Z CAVAZZINI, Giovanna PAVESI, Giorgio DUPONT, Patrick COUDERT, Sebastien ARDIZZON, Giorgio CAIGNAERT, Guy BOIS, Gérard DAZIN, Antoine This paper presents an experimental analysis of the unsteady phenomena developing in a vaneless diffuser of a radial flow pump. Partial flow operating conditions were investigated using 2D/3C high repetition rate PIV, coupled with unsteady pressure transducers. Pressure measurements were acquired on the shroud wall of the vaneless diffuser and on the suction pipe of the pump, whereas PIV flow fields were determined on three different heights in the hub to shroud direction, inside the diffuser. The classical Fourier analysis was applied to both pressure signals to identify the spectral characteristics of the developing instabilities, and the high-order spectral analysis was exploited to investigate possible non-linear interaction mechanisms between different unsteady structures. A dedicated PIV averaging procedure was developed and applied to the PIV flow fields so as to capture and visualize the topology of the spectrally identified phenomena. The influence of these phenomena on the diffuser efficiency was also investigated. http://hdl.handle.net/10985/7623 UNSTEADY VELOCITY PIV MEASUREMENTS AND 3D NUMERICAL CALCULATION COMPATISONS INSIDE THE IMPELLER OF A RADIAL PUMP MODEL CAVAZZINI, Giovanna; DUPONT, Patrick; PAVESI, Giorgio; BOIS, Gérard; DAZIN, Antoine; BAYEUL-LAINÉ, Annie-Claude PIV measurements were performed at mid hub section inside the impeller of a vaned diffuser pump model working with air. Several previous papers have already presented part of impeller flow characteristics mainly for vaneless diffuser and near nominal mass flow rate. This paper concerns the pump configuration where the diffuser blades interacted with the impeller flow. Each PIV measuring plane was related to one particular impeller blade to blade channel and analyzed according to different relative positions of the vaned diffuser. A fully unsteady calculation of the whole pump has been performed and comparisons between numerical and experimental results are presented and discussed for four different mass flow rates. The present analysis is restricted to the outlet section of the impeller blade to blade passage for one particular impeller blade position relative to the diffuser. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7623 2013-01-01T00:00:00Z CAVAZZINI, Giovanna DUPONT, Patrick PAVESI, Giorgio BOIS, Gérard DAZIN, Antoine BAYEUL-LAINÉ, Annie-Claude PIV measurements were performed at mid hub section inside the impeller of a vaned diffuser pump model working with air. Several previous papers have already presented part of impeller flow characteristics mainly for vaneless diffuser and near nominal mass flow rate. This paper concerns the pump configuration where the diffuser blades interacted with the impeller flow. Each PIV measuring plane was related to one particular impeller blade to blade channel and analyzed according to different relative positions of the vaned diffuser. A fully unsteady calculation of the whole pump has been performed and comparisons between numerical and experimental results are presented and discussed for four different mass flow rates. The present analysis is restricted to the outlet section of the impeller blade to blade passage for one particular impeller blade position relative to the diffuser. http://hdl.handle.net/10985/9699 Comparisons rans and urans numerical results with experiments in a vaned diffuser of a centrifugal pump; Comparaisons de différents modèles numériques à des résultats expérimentaux dans un diffuseur aubé de pompe centrifuge DUPONT, Patrick; CAVAZZINI, Giovanna; PAVESI, Giorgio; CHERDIEU, Patrick; BOIS, Gérard; ROUSSETTE, Olivier; DAZIN, Antoine; BAYEUL-LAINÉ, Annie-Claude The paper presents the analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV (particles image velocimetry) technique, pressure probe traverses and numerical simulations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given rotational speed and various flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. Probe traverses have also been performed using a 3 holes pressure probe from hub to shroud diffuser width at different radial locations in between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 8.02.011 (RANS (Reynolds Averaged Navier Stokes) turbulence model, frozen rotor and unsteady calculations), ii-CFX 10.0 (turbulence modelled with DES model (Detached Eddy Simulation) combining RANS with LES (Large Eddy Simulation), unsteady calculations). Comparisons between numerical (fully unsteady calculations) and experimental results are presented and discussed for two flow rates. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed.; L’analyse des performances et de l’écoulement interne dans un diffuseur aubé de la pompe centrifuge SHF (testée en air) fait l’objet de ce papier. La particularité de cette pompe est qu’il n’y a pas de volute à l’aval de telle sorte que l’écoulement refoule à l’air libre. Une caractéristique de ce diffuseur est que son débit nominal correspond à 80% du débit nominal de la roue. L’analyse des performances est réalisée grâce à la technique PIV (Vélocimétrie par images de particules), aux sondes de pression trois trous et aux simulations numériques. Les mesures PIV ont été réalisées pour différents plans entre le carter et le moyeu dans un canal du diffuseur, pour une vitesse de rotation de roue fixée, et différents débits. Dans chaque cas, les mesures PIV ont été effectuées pour sept différentes positions angulaires de la roue, deux positions seulement sont ici présentées. Des sondes de pression trois trous ont également été utilisées dans le diffuseur à différentes positions radiales et axiales, en entrée et sortie du diffuseur et dans le canal inter-aubes. Les simulations numériques ont été réalisées à l’aide de deux codes de calcul: i-Star CCM+ 8.02.011 (modélisations RANS en « frozen rotor » et en calculs instationnaires), ii-CFX 10.0 (calculs instationnaires, modélisation de la turbulence par DES combinant un modèle RANS avec la LES ). Les mesures réalisées avec les sondes trois trous et les résultats des simulations numériques donnent des informations sur les évolutions des coefficients de pressions statiques et dynamiques. On a pu constater que les performances globales de la machine dépendaient peu des débits de fuite. D’un point de vue local, seules les vitesses radiales et tangentielles sont ici comparées. Les courbes vr en fonction du rayon, dans le canal inter-aubes du diffuseur, pour deux débits encadrant le débit nominal de la roue, montrent que les résultats expérimentaux sont en bonne correspondance avec la courbe de simulation numérique tenant compte de fuites entre le diffuseur et la roue. L’analyse quantitative des iso valeurs vr et vu donne une idée des structures présentes dans le diffuseur. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9699 2015-01-01T00:00:00Z DUPONT, Patrick CAVAZZINI, Giovanna PAVESI, Giorgio CHERDIEU, Patrick BOIS, Gérard ROUSSETTE, Olivier DAZIN, Antoine BAYEUL-LAINÉ, Annie-Claude The paper presents the analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV (particles image velocimetry) technique, pressure probe traverses and numerical simulations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given rotational speed and various flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. Probe traverses have also been performed using a 3 holes pressure probe from hub to shroud diffuser width at different radial locations in between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 8.02.011 (RANS (Reynolds Averaged Navier Stokes) turbulence model, frozen rotor and unsteady calculations), ii-CFX 10.0 (turbulence modelled with DES model (Detached Eddy Simulation) combining RANS with LES (Large Eddy Simulation), unsteady calculations). Comparisons between numerical (fully unsteady calculations) and experimental results are presented and discussed for two flow rates. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed. L’analyse des performances et de l’écoulement interne dans un diffuseur aubé de la pompe centrifuge SHF (testée en air) fait l’objet de ce papier. La particularité de cette pompe est qu’il n’y a pas de volute à l’aval de telle sorte que l’écoulement refoule à l’air libre. Une caractéristique de ce diffuseur est que son débit nominal correspond à 80% du débit nominal de la roue. L’analyse des performances est réalisée grâce à la technique PIV (Vélocimétrie par images de particules), aux sondes de pression trois trous et aux simulations numériques. Les mesures PIV ont été réalisées pour différents plans entre le carter et le moyeu dans un canal du diffuseur, pour une vitesse de rotation de roue fixée, et différents débits. Dans chaque cas, les mesures PIV ont été effectuées pour sept différentes positions angulaires de la roue, deux positions seulement sont ici présentées. Des sondes de pression trois trous ont également été utilisées dans le diffuseur à différentes positions radiales et axiales, en entrée et sortie du diffuseur et dans le canal inter-aubes. Les simulations numériques ont été réalisées à l’aide de deux codes de calcul: i-Star CCM+ 8.02.011 (modélisations RANS en « frozen rotor » et en calculs instationnaires), ii-CFX 10.0 (calculs instationnaires, modélisation de la turbulence par DES combinant un modèle RANS avec la LES ). Les mesures réalisées avec les sondes trois trous et les résultats des simulations numériques donnent des informations sur les évolutions des coefficients de pressions statiques et dynamiques. On a pu constater que les performances globales de la machine dépendaient peu des débits de fuite. D’un point de vue local, seules les vitesses radiales et tangentielles sont ici comparées. Les courbes vr en fonction du rayon, dans le canal inter-aubes du diffuseur, pour deux débits encadrant le débit nominal de la roue, montrent que les résultats expérimentaux sont en bonne correspondance avec la courbe de simulation numérique tenant compte de fuites entre le diffuseur et la roue. L’analyse quantitative des iso valeurs vr et vu donne une idée des structures présentes dans le diffuseur. http://hdl.handle.net/10985/6823 Post-processing methods of PIV instantaneous flow fields for unsteady flows in turbomachines CAVAZZINI, Giovanna; PAVESI, Giorgio; DUPONT, Patrick; BOIS, Gérard; DAZIN, Antoine The Particle Image Velocimetry is undoubtedly one of the most important technique in Fluid-dynamics since it allows to obtain a direct and instantaneous visualization of the flow field in a non-intrusive way. This innovative technique spreads in a wide number of research fields, from aerodynamics to medicine, from biology to turbulence researches, from aerodynamics to combustion processes. The book is aimed at presenting the PIV technique and its wide range of possible applications so as to provide a reference for researchers who intended to exploit this innovative technique in their research fields. Several aspects and possible problems in the analysis of large- and micro-scale turbulent phenomena, two-phase flows and polymer melts, combustion processes and turbo-machinery flow fields, internal waves and river/ocean flows were considered. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/6823 2012-01-01T00:00:00Z CAVAZZINI, Giovanna PAVESI, Giorgio DUPONT, Patrick BOIS, Gérard DAZIN, Antoine The Particle Image Velocimetry is undoubtedly one of the most important technique in Fluid-dynamics since it allows to obtain a direct and instantaneous visualization of the flow field in a non-intrusive way. This innovative technique spreads in a wide number of research fields, from aerodynamics to medicine, from biology to turbulence researches, from aerodynamics to combustion processes. The book is aimed at presenting the PIV technique and its wide range of possible applications so as to provide a reference for researchers who intended to exploit this innovative technique in their research fields. Several aspects and possible problems in the analysis of large- and micro-scale turbulent phenomena, two-phase flows and polymer melts, combustion processes and turbo-machinery flow fields, internal waves and river/ocean flows were considered. http://hdl.handle.net/10985/6818 Experimental and Numerical Investigation of Unforced unsteadiness in a Vaneless Radial Diffuser PAVESI, Giorgio; CAVAZZINI, Giovanna; CAIGNAERT, Guy; BOIS, Gérard; ARDIZZON, Guido; DAZIN, Antoine The paper reports combined experimental and numerical investigations of unforced un- steadiness in a vaneless radial diffuser. Experimental data were obtained within the diffuser using stereoscopic time resolved Particle Image Velocimetry (PIV) recording three velocity components in a plane (2D/3C), coupled with unsteady pressure transducers. To characterize the inception and the evolution of the unsteady phenomena, spectral analyses of the pressure signals were carried out both in frequency and time-frequency domains and the PIV results were post processed by an original averaging method. Two partial flow rates were investigated in detail in this paper. A single unforced unsteadiness was identified for the lowest flow rate, whereas, two competitive intermittent modes were recognized for the higher mass flow. Numerical analyses were carried out on the same pump by the commercial code CFX. All the computations were performed using the unsteady transient model and the turbulence was modelled by the Scale-Adaptive Simulation (SAS) model. Numerical pressure signals were compared with the experimental data to verify the development of the same pressure fluctua- tions. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10985/6818 2011-01-01T00:00:00Z PAVESI, Giorgio CAVAZZINI, Giovanna CAIGNAERT, Guy BOIS, Gérard ARDIZZON, Guido DAZIN, Antoine The paper reports combined experimental and numerical investigations of unforced un- steadiness in a vaneless radial diffuser. Experimental data were obtained within the diffuser using stereoscopic time resolved Particle Image Velocimetry (PIV) recording three velocity components in a plane (2D/3C), coupled with unsteady pressure transducers. To characterize the inception and the evolution of the unsteady phenomena, spectral analyses of the pressure signals were carried out both in frequency and time-frequency domains and the PIV results were post processed by an original averaging method. Two partial flow rates were investigated in detail in this paper. A single unforced unsteadiness was identified for the lowest flow rate, whereas, two competitive intermittent modes were recognized for the higher mass flow. Numerical analyses were carried out on the same pump by the commercial code CFX. All the computations were performed using the unsteady transient model and the turbulence was modelled by the Scale-Adaptive Simulation (SAS) model. Numerical pressure signals were compared with the experimental data to verify the development of the same pressure fluctua- tions.