Article
Mechanics
Zongming Xie, Hongping Wang, Duo Xu
Summary: This study introduces an optimization method for the cross-correlation operation in particle image velocimetry by locating the correlation peaks assisted with constraint conditions. By constructing an objective function that includes the residual of the normalized cross-correlation term, a component for spatial smoothness, and a component for temporal smoothness, optimized velocity fields for a series of tracer images can be obtained for spatiotemporal smoothness.
Article
Engineering, Civil
Jin-Hua Si, Siow-Yong Lim, Xikun Wang
Summary: This laboratory study utilized PIV to measure transitional flow regimes during the jet-flipping process downstream of a sluice gate, capturing and discussing the transitional vortical structures. The study found that various vortices are formed in the scour hole by component jets, with opposite developments of the major vortex and bed vortex. Additionally, the kinetic energy of the issuing jet is dynamically distributed across the vortices, which transform interactively in terms of their location, size, and magnitude during jet-flipping.
JOURNAL OF HYDRAULIC RESEARCH
(2021)
Article
Engineering, Mechanical
Douglas W. Carter, Bharathram Ganapathisubramani
Summary: This study presents an aeroacoustic investigation of planar time-resolved Particle Image Velocimetry (PIV) measurements on a NACA 0012 airfoil in static stall at a chord-based Reynolds number of 7.1 x 10(4). Instantaneous planar pressure reconstructions are obtained using a Poisson solver, and the dipole noise emanating from the airfoil surface is estimated using Curle's acoustic analogy. By applying a data-driven framework based on Proper Orthogonal Decomposition (POD) and Spectral Linear Stochastic Estimation (sLSE), the flow structures responsible for noise generation are identified, primarily concentrated near the trailing edge. Furthermore, a conditional analysis of extreme noise events reveals correlations between downwash and upwash events near the trailing edge, and local maxima and minima in acoustic fluctuations associated with slow and fast-moving fluid in the incipient shear layer.
EXPERIMENTS IN FLUIDS
(2023)
Article
Thermodynamics
A. Mitra, S. Murugan, R. van Hout, A. Kleiman, M. Raizner, B. Cukurel
Summary: This study presents detailed planar PIV measurements of the flow field in the near-field of a free coaxial air jet. The measurements were conducted at different outer to inner jet velocity ratios while keeping the inner jet velocity constant. The results show that the nozzle geometry and flow exit conditions have a significant impact on the vortex generation frequency, and the outer and inner jet are strongly coupled for the present nozzle geometry and jet exit flow conditions.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
Article
Engineering, Civil
Jin-Hua Si, Siow-Yong Lim, Jianmin Zhang, Xikun Wang
Summary: Previous studies mainly focused on the flow in a local scour hole from the perspectives of mean velocity and turbulence, while this study explored it from the perspective of pressure for the first time. A comparison between two cases revealed that turbulence can reinforce the pressure in the local scour hole.
JOURNAL OF HYDRAULIC RESEARCH
(2022)
Article
Energy & Fuels
Wanruo Lou, Nicolas Baudin, Yilin Fan, Lingai Luo
Summary: This paper focuses on the characterization and management of dynamic thermocline behaviors in a single-medium thermocline thermal energy storage tank. The study reveals that the thermal jet entering the tank causes thermal overturning and degradation of temperature stratification, but this impact can be mitigated by an optimized distributor structure. Experimental results demonstrate that the optimized distributor consistently outperforms the initial uniform distributor, providing more flexible operating conditions for SMT storage systems in various industrial sectors.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Energy & Fuels
Ming Li, Jianchun Guo, Tao Zhang, Xianjin Zeng, Ruoyu Yang, Haoran Gou
Summary: This study establishes a quantitative experimental device to simulate the injection of fluid into a fracture. By using particle image velocimetry (PIV) technology, the device acquires the flow field information in the fracture for the first time. The study finds that the fluid forms vortices in the perforation tunnel, but as it flows towards the end of the fracture, the vortices disappear and the flow field becomes stable. The flow field is divided into different characteristic areas based on the distribution of vorticity. This study provides theoretical guidance for the design and optimization of fracturing schemes and has significance for microscopic studies of flow in fractures.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2022)
Article
Engineering, Mechanical
Yulu Liu, Yuze Wang, Jiahua Li, Yizhou Tao, Xiang Qiu
Summary: The study investigates the dynamics of the vortex structure in a three-dimensional, round counterflow wall jet and explores its generation mechanism. It is found that the vortex ring is formed while the jet is fluttering upwards and the turbulent kinetic energy contribution of the wall-normal component in the recirculation region is particularly significant.
EXPERIMENTS IN FLUIDS
(2022)
Article
Engineering, Mechanical
Ujjawal Arya, Wyatt Peterson, Farshid Sadeghi, Andreas Meinel, Hannes Grillenberger
Summary: This investigation experimentally and analytically studied the oil flow inside an angular contact ball bearing using Bubble Image Velocimetry (BIV). The study developed a counter-rotating angular contact ball bearing test rig (CRACTR) and observed the oil flow using a high-speed camera. The results from the analytical model matched well with the experimental observations and provided valuable information for cage design.
TRIBOLOGY INTERNATIONAL
(2023)
Article
Mechanics
Ling-xin Zhang, Xin-sheng Cheng, Ze-cai Zhou, Qi Gao, Xue-ming Shao
Summary: In this study, we conducted a series of experiments to investigate the velocity fluctuations caused by the flow past fixed spheres. The results show that the fluctuations can be classified into temporal fluctuations and spatial fluctuations, representing the contributions of flow instability and spatial inhomogeneity, respectively. At low Reynolds numbers, the total fluctuation is mainly caused by the spatial fluctuation, while at higher Reynolds numbers, both flow instability and spatial inhomogeneity contribute to the total velocity fluctuation. Moreover, the energy distribution and wavenumber spectra of the fluctuations also change significantly with the increase of Reynolds number.
JOURNAL OF HYDRODYNAMICS
(2022)
Article
Engineering, Chemical
A-E Sommer, H. Rox, P. Shi, K. Eckert, R. Rzehak
Summary: This study conducted solid-liquid two-phase flow experiments in stirred tanks and accumulated a CFD-grade database, including experimental data for single-phase flows. The experimental data covers a range of density ratios, particle diameters, solid volume fractions and impeller rotation speeds.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Green & Sustainable Science & Technology
A. H. Samitha Weerakoon, Byung-Ha Kim, Young-Jin Cho, Deepak Divashkar Prasad, M. Rafiuddin Ahmed, Young-Ho Lee
Summary: A novel vertical augmentation channel housing a direct-drive cross-flow turbine with optimized geometry of nozzles on both sides was designed and evaluated for wave energy conversion. The optimized design achieved a maximum output power of 13.2 W and an efficiency of 48.31% under specific wave conditions, with a small space footprint compared to other wave energy converters.
Article
Engineering, Aerospace
Zhi Deng, Donglai Gao, Guanbin Chen, Wen-Li Chen
Summary: Experimental investigation on an active-flow control scheme involving leeward slot jet over a circular cylinder showed that the symmetrical jet vortices generated by the slot interact effectively with the sheared layer from the cylinder wall, modifying the flow features in the cylinder wake and transitioning the wake from asymmetric to symmetric. This control technique also significantly reduces Reynolds shear stress and turbulent kinetic energy, demonstrating the potential to manipulate stability characteristics in the flow field behind the cylindrical model.
JOURNAL OF AEROSPACE ENGINEERING
(2021)
Article
Multidisciplinary Sciences
Zhuo Fu, Kun Li, Yongjun Pang, Liyong Ma, Zhanying Wang, Bin Jiang
Summary: This article studies the influence of the internal flow channel structure of the nozzle on water jet, and finds that a smaller length-to-diameter ratio and contraction angle can improve the cohesion of the water jet and reduce dynamic pressure, making it more suitable for long-distance, low-pressure water jet operations.
Article
Thermodynamics
Zhu Yang, Victor Castaneda, Guven Ogus, Thomas Holemans, Maarten Vanierschot, Agustin Valera-Medina
Summary: Swirl stabilised flows are commonly used for gas turbine combustion stabilisation. This research focuses on the identification and visualisation of coherent structures in two types of jet flows, namely Open Jet Flow (OJF) and Coanda Jet Flow (CoJF). High speed stereo particle image velocimetry (S-PIV) was used to obtain time-resolved flow fields, and spectral proper orthogonal decomposition was used to identify the coherent structures. The results show that similar precessing coherent flow structures exist in wall attached Coanda swirling flows and swirling jet flows undergoing vortex breakdown.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2023)
Article
Multidisciplinary Sciences
Matthew Pinchak, Timothy Ombrello, Campbell Carter, Ephraim Gutmark, Viswanath Katta
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2015)
Article
Thermodynamics
Matthew D. Pinchak, Vincent G. Shaw, Ephraim J. Gutmark
COMBUSTION AND FLAME
(2018)
Article
Thermodynamics
Matthew D. Pinchak, Vincent G. Shaw, Ephraim J. Gutmark
COMBUSTION AND FLAME
(2019)