Article
Thermodynamics
Y. T. Cheng, J. Sun, P. Chen, W. Y. Chen
Summary: Particle imaging velocimetry (PIV) was used to study the near-field variation of a pyramid rough element in clear water and a liquid-solid boundary layer. The experiments collected instantaneous velocity field information to compare the average velocity field and turbulence intensity of the rough element wake under single-phase and two-phase conditions. The results showed that particles had different effects on the recirculation area in different planes and influenced the velocity gradient and turbulence intensity.
JOURNAL OF APPLIED FLUID MECHANICS
(2023)
Article
Construction & Building Technology
Emmanuel Belut, Sullivan Lechene, Benoit Trouette, Stephane Vincent, Georges Halim Atallah
Summary: This contribution presents an experimental and numerical study on the breach of a containment barrier caused by the transient wake of a moving obstacle. The study shows that pollutant leakage is inherently variable, even under stable ventilation conditions, and up to 100% variation in contaminant concentration peaks can be observed depending on the initial turbulent state of the room. The numerical model used in this study is found to be able to accurately reproduce the experimental results within the experimental inaccuracies.
BUILDING AND ENVIRONMENT
(2023)
Article
Engineering, Multidisciplinary
Yanhua Liu, Xiaojing He, Yuncheng He, Dacan Zhang, Hongyao Chen, Jiyang Fu
Summary: This study investigates the surface wind pressure distribution and wake flow of finite blunt plates with different leading edge geometries. The results show that the wind pressure distribution is greatly influenced by the leading edge geometry. A larger leading edge angle leads to a decrease in the peak values of the mean pressure coefficient and peak suction pressure coefficient, while increasing the peak value of the r.m.s pressure coefficient. The wake flow analysis reveals that an increase in leading edge angle results in a longer low-velocity recirculation zone in the wake, accompanied by a more unstable and complex flow field.
Article
Engineering, Civil
L. H. O. Hellstrom, T. C. Hohman, A. J. Smits
Summary: Proper orthogonal decomposition (POD) is used to analyze the structure and evolution of the wake behind a model vertical axis wind turbine. The study reveals the presence of high energy coherent structures associated with vortex shedding from dynamic stall and downstream of the tower, as well as the dynamics of the wake interactions. Vortex pairing is identified as an important characteristic of wake evolution. Changing the inflow conditions and the blade sweep angle can reduce the energy associated with dynamic stall, which is beneficial for mitigating fatigue caused by torque and force variations on the blades.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Engineering, Mechanical
William D. P. Fonseca, Rafael F. L. Cerqueira, Rodolfo M. Perissinotto, William Monte Verde, Marcelo S. Castro, Erick M. Franklin
Summary: This study investigates the flow field of a centrifugal pump using time-resolved particle image velocimetry and proper orthogonal decomposition. The results show that the flow at the pump's best efficiency point is well-organized, while flow separation and vortex structures occur at lower flow rates. Additionally, intense jets appear near the suction blades at higher flow rates. The study sheds light on the turbulence characteristics inside the impeller, providing valuable information for cost-effective reduced-order models in turbomachinery.
FLOW MEASUREMENT AND INSTRUMENTATION
(2023)
Article
Thermodynamics
Wenhua Chen, Junjie Liu, Jiayu Li, Xilei Dai, Pan Wang, Congcong Wang
Summary: A study was conducted on the flow characteristics of thermal plumes during cooking, focusing on the influence of cooker hoods. Results showed that the behavior of thermal plumes was altered under confinement, with velocity and temperature distributions affected by mounting height and heating temperature.
APPLIED THERMAL ENGINEERING
(2021)
Article
Energy & Fuels
Marcellin Perceau, Philippe Guibert, Stephane Guilain
Summary: This study presents a method to reconstruct the mean velocity field of a cyclic flow for an input parameter value that has not been measured, reducing the number of tests needed. The method was applied to a gasoline engine following a Miller cycle, using experimental data collected with PIV and interpolation of POD coefficients. The accuracy of the method was evaluated by comparing interpolated and measured flow fields, allowing for close tracking of the tumble's center of rotation and the creation of a rotation rate map for future developments.
Article
Energy & Fuels
Lun'ang Li, Xun Li, Ze Wang, Bo Wang, Hongjun Lin, Wencheng Hu, Feng Chang, Bo Zhou
Summary: This study investigated the flow and spray fields in a realistic concentric staged high-temperature-rise combustor using high-speed particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF). The results showed strong coupling between the pilot and main swirling flows, leading to the formation of recirculation zones. The presence of a precessing vortex core was observed when the two stages were flowing jointly. Comparing the flow field with the spray field revealed the importance of the unsteady flow motion in understanding the spray distribution. The findings provide valuable insights into the complex flow-spray coupling in the combustor.
Article
Engineering, Chemical
Yan Zheng, Dan Zhang, Hiroka Rinoshika, Akira Rinoshika
Summary: This study investigates the particle velocities of a horizontal self-exited gas-solid two-phase pipe flow with soft fins using high-speed particle image velocimetry. The results show that the fins delay the particle acceleration process and decrease the vertical particle velocity near the top part of the fully-developed regime. The analysis of axial particle fluctuation velocity reveals that the fins lower the particle motion frequency in the acceleration regime. In the fully-developed regime, the fins decrease the dominating frequencies of large-scale particle flows and weaken the streaks appearing in the high frequency range. The energy distributions of proper orthogonal decomposition modes indicate that the relative energy of POD mode1 is increased by using fins in both acceleration and fully-developed regimes, with a significant enhancement in the fully-developed regime. The auto-correlation coefficients and central frequencies of POD modes demonstrate that the fins enhance the dominating large-scale particle motion and suppress the small-scale particle motion.
Article
Engineering, Chemical
Fei Yan, PanPan Tu, Xin Li, Yun Chen, Yan Zheng, Rui Zhu
Summary: The experimental study focuses on the particle motion characteristic of bends in a horizontal-vertical pneumatic conveying system, highlighting the importance of particle rope as a large-scale motion affecting particle movement and the suppression of small-scale motion to reduce pressure drop.
ADVANCED POWDER TECHNOLOGY
(2021)
Article
Biophysics
Francesco Fiusco, Julien Lemetayer, Lars Mikael Broman, Lisa Prahl Wittberg
Summary: In this study, a validated numerical simulation of a conventional lighthouse tip cannula was conducted to characterize the flow structures and their influence on hemolysis. The results showed the presence of strong shear layers and backflow regions, which may pose a potential risk of blood damage. However, the global hemolysis index did not show significant deviations.
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2023)
Article
Energy & Fuels
Pavithra Premaratne, Wei Tian, Hui Hu
Summary: This study conducted a comprehensive analysis on the turbine wake characteristics using a Proper-Orthogonal-Decomposition (POD) method. The experiments revealed the presence of characteristic helical-tip vortex filaments and secondary vortex filaments behind the turbine model, which breakup near the hub to form shear layers. The study also used a high-resolution Particle Image Velocimetry (PIV) system to capture detailed flow field measurements and extract coherent flow structures using POD analysis.
Article
Engineering, Mechanical
Yann Watine, Celine Gabillet, Boris Lossouarn, Jean-Francois Deue, Jacques-Andre Astolfi
Summary: The present study experimentally characterized the vortex shedding and induced vibrations of a rectangular aluminium plate immersed in water flow. The hydrodynamic properties of the wake were evaluated and the structural response of the plate was examined. Three different vibration regimes were analyzed, and the features of the first nine Proper Orthogonal Decomposition (POD) modes were studied. The study identified the control factors of the primary Karman vortices and the coexistence of different vortex shedding modes in different vibration regimes.
JOURNAL OF FLUIDS AND STRUCTURES
(2023)
Article
Energy & Fuels
Bo Chen, Xiaojun Li, Zuchao Zhu
Summary: Time-resolved particle image velocimetry (TR-PIV) was used to analyze the unsteady flow field in a centrifugal pump at different flow rates. The study of proper orthogonal decomposition (POD) modes revealed coherent flow structures under varying flow rates, showing changes in flow structures and flow direction under extreme part-load conditions. This study highlights the variations in turbulent kinetic energy generation mechanisms in the flow passage at extreme part-load conditions.
FRONTIERS IN ENERGY RESEARCH
(2022)
Article
Thermodynamics
E. Yu Gorelikov, I. Litvinov, S. Shtork
Summary: This paper presents an experimental study on the characteristics of swirling flow with the formation of vortex structures in a radial burner under different flow swirling parameters. The distributions of average and fluctuating velocity fields are analyzed for isothermal conditions, and the contribution of the precessing vortex structure to the overall level of turbulence is determined. The experiments also investigate the flame visualization and frequency characteristics of the vortex core precession (VCP) for reacting conditions. The results reveal the nonmonotonic relationship between the dimensionless frequency of VCP and the flow swirl parameter.
COMBUSTION EXPLOSION AND SHOCK WAVES
(2022)
