The analysis of the error propagation from the velocity field to the pressure field using the pre... more The analysis of the error propagation from the velocity field to the pressure field using the pressure estimation method proposed by Jeon et al (2015 11th Int. In Symp. Part. Image Velocim. PIV15) is achieved. The accuracy of the method is assessed based on numerical data. The flow around a rigid profile (NACA0015) with a free tip is considered. From the numerical simulation data, tomographic-PIV (TPIV)-like data are generated. Two types of error are used to distort the data: a Gaussian noise and a pixel-locking effect are modelled. Propagation of both types of error during the pressure estimation process and the effect of the TPIV resolution are evaluated. Results highlight the importance of the resolution to accurately estimate the pressure in presence of small structures but also to limit the propagation of error from the velocity to the pressure. The study of the sensitivity of the method for the two models of errors, Gaussian or pixel-locking, shows different trends. This reveals also the importance of the model of errors for the analysis of the uncertainties for PIV-based pressure.
Sustainable Energy Technologies and Assessments, 2021
Abstract Unlike the previous scientific works on the vertical axis turbines which were mostly lim... more Abstract Unlike the previous scientific works on the vertical axis turbines which were mostly limited to design improvements, performance metrics and flow dynamics but significantly ignored the effect of operational uncertainties on the power output, this paper presents how the performance of a low-speed vertical axis hydrokinetic turbine can be attributed to the inherent uncertainties in the operating conditions. While a complete set of uncertainty sources in the design, development and operation of a water turbine is pictured with real and hypothetical relationships, this study focuses mainly on two uncertainties. Starting from the methodological illustration of a towing tank experiment, the sources of uncertainty are defined as ±0.7% in free-stream velocity V 0 and ±1.06% in the turbine’s rotational velocity Ω . The stochastic space is constructed on a two-dimensional Clenshaw-Curtis grid and finite-volume-based deterministic computations are performed at each grid node. The sensitivity of the turbine’s performance to these input uncertainties is quantified using probability methods, including response surface, PDF and CDF. Flow-related non-linearities such as vortex release and blade-vortex interaction are directly reported in stochastic space and corresponding variations in the force coefficients of the turbine’s blade are identified. It is observed that the uncertainty in the turbine’s rotation is more influential on the power output compared to free-stream velocity.
Analytical and computational studies of flow across a low-speed marine turbine of Darrieus type w... more Analytical and computational studies of flow across a low-speed marine turbine of Darrieus type with pitching blades have been carried out for flowfield and performance evaluation. The objective of this study is to develop efficient blade pitching laws to arrest or control the vortex shedding from the blades during turbine’s operation. This is achieved by imparting an arbitrary constant amount of circulation to the blades, where Kelvin’s theorem is respected. This paper presents the extension of the application of conformal mapping to produce the time-dependent flow over a rotating turbine blade in order to develop a quantified relationship between the blade’s orientation with respect to the rotor’s tangent and its rotational motion. The flow development is based on the analytical treatment given to potential flow formulation through Laurent series decomposition, where the Kutta condition is satisfied. The pitch control law and the analytical modeling of the hydrodynamic forces acti...
14th International Symposium on Particle Image Velocimetry, 2021
An experimental study of vortex shedding on a hydrofoil Eppler 817 was conducted using two-dimens... more An experimental study of vortex shedding on a hydrofoil Eppler 817 was conducted using two-dimensional two components Particle Image Velocimetry. This foil section’s characteristics are adapted for naval applications but sparsely documented. The characterization of the flow modes was realized based on statistical data such as the mean velocity field and the standard deviation of the vertical velocities. The data were acquired at very low Reynolds number which are not often covered for such hydrofoil and at four angles of attack ranging from 2◦ to 30◦. A map of different characteristic flow modes was made for this space of parameters and was used to identify flow configurations exhibiting particular dynamics.
Suite a l'observation de vibrations d'un profil NACA0015 soumis a un ecoulement turbulent... more Suite a l'observation de vibrations d'un profil NACA0015 soumis a un ecoulement turbulent, une technique de mesure de surface d'un solide a ete developpee pour caracteriser les modes vibratoires. Cet article presente en detail le fonctionnement de la technique HNC (Hauteur, Normale, Courbure) utilisee pour caracteriser les deplacements du profil. La precision de la mesure de surface est evaluee et les deplacements sont mesures pour des vitesses d'ecoulement allant de 0. 3/ a 2 /. Enfin les deplacements du profil sont correles avec des mesures d'efforts realisees simultanement aux mesures de surface.
The present study focuses on the analysis of the flow-induced vibration phenomenon typically enco... more The present study focuses on the analysis of the flow-induced vibration phenomenon typically encountered on piping systems containing an elbow. The correlation between the turbulent flow through the elbow and the dynamic forcing it yields on the piping walls was assessed experimentally. A closed water loop containing a transparent elbow was designed in order to develop fully turbulent duct flow condition. Particle Image Velocimetry (PIV) was applied in the transparent zone in order to provide unsteady data on the flow dynamics through the elbow; simultaneously, wall pressure fluctuations were measured on and around the elbow. Several flow configurations were tested in order to obtain a large coupled database linking the flow features to the resulting dynamic excitation on the walls. Finally, Partial Least Square Regression (PLSR) was applied in order to harvest the correlated information contained in multiple pressure signals at multiple time-delays and build a relationship capable ...
In the field of the fluid mechanics, the team HYDEE (Hydrodynamics and Environmental flow section... more In the field of the fluid mechanics, the team HYDEE (Hydrodynamics and Environmental flow section) of the institute Pprime is involved in the understanding of flows around moving profiles for environmental applications, the maritime transport, the renewable energy production, The research interests cover fundamental aspects of unsteady flows with moving structures, turbulent free-surface flows, environmental flows and mixing through different national and European programs. Fundamental contributions to optical flow measurements include PIV stereoscopy PIV measurement techniques and recently free surface measurement and volumetric measurement techniques have been obtained.
The analysis of the error propagation from the velocity field to the pressure field using the pre... more The analysis of the error propagation from the velocity field to the pressure field using the pressure estimation method proposed by Jeon et al (2015 11th Int. In Symp. Part. Image Velocim. PIV15) is achieved. The accuracy of the method is assessed based on numerical data. The flow around a rigid profile (NACA0015) with a free tip is considered. From the numerical simulation data, tomographic-PIV (TPIV)-like data are generated. Two types of error are used to distort the data: a Gaussian noise and a pixel-locking effect are modelled. Propagation of both types of error during the pressure estimation process and the effect of the TPIV resolution are evaluated. Results highlight the importance of the resolution to accurately estimate the pressure in presence of small structures but also to limit the propagation of error from the velocity to the pressure. The study of the sensitivity of the method for the two models of errors, Gaussian or pixel-locking, shows different trends. This reveals also the importance of the model of errors for the analysis of the uncertainties for PIV-based pressure.
Sustainable Energy Technologies and Assessments, 2021
Abstract Unlike the previous scientific works on the vertical axis turbines which were mostly lim... more Abstract Unlike the previous scientific works on the vertical axis turbines which were mostly limited to design improvements, performance metrics and flow dynamics but significantly ignored the effect of operational uncertainties on the power output, this paper presents how the performance of a low-speed vertical axis hydrokinetic turbine can be attributed to the inherent uncertainties in the operating conditions. While a complete set of uncertainty sources in the design, development and operation of a water turbine is pictured with real and hypothetical relationships, this study focuses mainly on two uncertainties. Starting from the methodological illustration of a towing tank experiment, the sources of uncertainty are defined as ±0.7% in free-stream velocity V 0 and ±1.06% in the turbine’s rotational velocity Ω . The stochastic space is constructed on a two-dimensional Clenshaw-Curtis grid and finite-volume-based deterministic computations are performed at each grid node. The sensitivity of the turbine’s performance to these input uncertainties is quantified using probability methods, including response surface, PDF and CDF. Flow-related non-linearities such as vortex release and blade-vortex interaction are directly reported in stochastic space and corresponding variations in the force coefficients of the turbine’s blade are identified. It is observed that the uncertainty in the turbine’s rotation is more influential on the power output compared to free-stream velocity.
Analytical and computational studies of flow across a low-speed marine turbine of Darrieus type w... more Analytical and computational studies of flow across a low-speed marine turbine of Darrieus type with pitching blades have been carried out for flowfield and performance evaluation. The objective of this study is to develop efficient blade pitching laws to arrest or control the vortex shedding from the blades during turbine’s operation. This is achieved by imparting an arbitrary constant amount of circulation to the blades, where Kelvin’s theorem is respected. This paper presents the extension of the application of conformal mapping to produce the time-dependent flow over a rotating turbine blade in order to develop a quantified relationship between the blade’s orientation with respect to the rotor’s tangent and its rotational motion. The flow development is based on the analytical treatment given to potential flow formulation through Laurent series decomposition, where the Kutta condition is satisfied. The pitch control law and the analytical modeling of the hydrodynamic forces acti...
14th International Symposium on Particle Image Velocimetry, 2021
An experimental study of vortex shedding on a hydrofoil Eppler 817 was conducted using two-dimens... more An experimental study of vortex shedding on a hydrofoil Eppler 817 was conducted using two-dimensional two components Particle Image Velocimetry. This foil section’s characteristics are adapted for naval applications but sparsely documented. The characterization of the flow modes was realized based on statistical data such as the mean velocity field and the standard deviation of the vertical velocities. The data were acquired at very low Reynolds number which are not often covered for such hydrofoil and at four angles of attack ranging from 2◦ to 30◦. A map of different characteristic flow modes was made for this space of parameters and was used to identify flow configurations exhibiting particular dynamics.
Suite a l'observation de vibrations d'un profil NACA0015 soumis a un ecoulement turbulent... more Suite a l'observation de vibrations d'un profil NACA0015 soumis a un ecoulement turbulent, une technique de mesure de surface d'un solide a ete developpee pour caracteriser les modes vibratoires. Cet article presente en detail le fonctionnement de la technique HNC (Hauteur, Normale, Courbure) utilisee pour caracteriser les deplacements du profil. La precision de la mesure de surface est evaluee et les deplacements sont mesures pour des vitesses d'ecoulement allant de 0. 3/ a 2 /. Enfin les deplacements du profil sont correles avec des mesures d'efforts realisees simultanement aux mesures de surface.
The present study focuses on the analysis of the flow-induced vibration phenomenon typically enco... more The present study focuses on the analysis of the flow-induced vibration phenomenon typically encountered on piping systems containing an elbow. The correlation between the turbulent flow through the elbow and the dynamic forcing it yields on the piping walls was assessed experimentally. A closed water loop containing a transparent elbow was designed in order to develop fully turbulent duct flow condition. Particle Image Velocimetry (PIV) was applied in the transparent zone in order to provide unsteady data on the flow dynamics through the elbow; simultaneously, wall pressure fluctuations were measured on and around the elbow. Several flow configurations were tested in order to obtain a large coupled database linking the flow features to the resulting dynamic excitation on the walls. Finally, Partial Least Square Regression (PLSR) was applied in order to harvest the correlated information contained in multiple pressure signals at multiple time-delays and build a relationship capable ...
In the field of the fluid mechanics, the team HYDEE (Hydrodynamics and Environmental flow section... more In the field of the fluid mechanics, the team HYDEE (Hydrodynamics and Environmental flow section) of the institute Pprime is involved in the understanding of flows around moving profiles for environmental applications, the maritime transport, the renewable energy production, The research interests cover fundamental aspects of unsteady flows with moving structures, turbulent free-surface flows, environmental flows and mixing through different national and European programs. Fundamental contributions to optical flow measurements include PIV stereoscopy PIV measurement techniques and recently free surface measurement and volumetric measurement techniques have been obtained.
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