Article
Mechanics
Haotian Hang, Sina Heydari, John H. Costello, Eva Kanso
Summary: The study found that passive bending is more efficient but may reduce swimming speed, while adding active bending can enhance both speed and efficiency. Importantly, the phase difference between the posterior and anterior sections of the body is a key factor that influences performance, and active antiphase flexion can simultaneously improve speed and efficiency.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Xiao Hu, Aimee S. Morgans
Summary: This study numerically investigated the three-dimensional flow structures around a high-rise building in different wind conditions using wall-resolved large eddy simulations. The study found that synthetic jet actuation can reduce side-force fluctuations, enhance the downwash flow, and successfully attenuate vortex shedding. These findings could motivate future exploration of experimental active control strategies to mitigate unsteady wind loading.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Xiao Hu, Aimee S. Morgans
Summary: This paper investigates the impact of unsteady wind loading on high-rise buildings and proposes two feedback control strategies to mitigate aerodynamic side-force fluctuations. The study shows that a linear controller exhibits better performance by delaying the formation of dominant vortices. Additionally, comparable control effect can be achieved by using a smaller sensing area.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Sarah Christin, Patrice Meunier, Stephane Le Dizes
Summary: The study characterizes the influence of continuous stratification on wake-induced vibrations of a circular cylinder, revealing two vibration modes: vortex-induced vibration and galloping mode. Aerodynamic parameters show minimal impact on stability characteristics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Yiqing Li, Wenshi Cui, Qing Jia, Qiliang Li, Zhigang Yang, Marek Morzynski, Bernd R. Noack
Summary: The explorative gradient method (EGM) addresses the challenge of optimizing multiple actuation parameters by alternately performing exploitative and explorative steps, ensuring convergence rate of a gradient based method and exploration of better minima. EGM outperforms other optimization methods in analytical tests and applications to flow control problems.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Suyash Verma, Arman Hemmati
Summary: The study found that an oscillating teardrop hydrofoil with combined heaving and pitching motion generates larger thrust with higher Strouhal numbers, but at the expense of lower propulsive efficiency. The evolution of vortex and the formation and interaction of primary structures are influenced by elliptic instability characteristics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Jiaojiao Chen, Feng Qu, Xuanting Wu, Zirui Wang, Junqiang Bai
Summary: This paper investigates the interaction between shock waves and bubbles with different shapes, revealing that vorticity generation and distribution play a crucial role in bubble deformation, and the aspect ratio affects the degree of deformation and collapse speed of bubbles.
Article
Mechanics
E. Duran Venegas, P. Rieu, S. Le Dizes
Summary: In this work, Joukowski's rotor wake model is applied to a two-blade rotor, providing solutions using a free-vortex method. The analysis includes stability and performance evaluation of the solutions obtained.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Andrey I. Aleksyuk, Matthias Heil
Summary: We investigate the initial development of three-dimensional mode A instability in the wake behind a circular cylinder. We observe that long-wavelength perturbations organize in a time-shifting pattern, where the in-plane velocity of each streamwise slice corresponds to the base flow solution at shifted times. We analyze the mechanisms governing the growth or decay of these perturbations, emphasizing the crucial role of the tilting mechanism and its non-local interactions similar to Biot-Savart induction. We also discuss the generalization of our findings to other flow types.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Siddharth Gupta, Jisheng Zhao, Atul Sharma, Amit Agrawal, Kerry Hourigan, Mark C. C. Thompson
Summary: The study investigates the 2-D and 3-D wake transitions of a NACA0012 airfoil at different angles of attack and Reynolds numbers. The results show that the transition from 2-D to 3-D flow occurs through a mode C transition. Further instabilities of the 2-D periodic base flow are also observed. The study provides valuable insights into the flow transitions of aerodynamic bodies.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Manuel Lorite-Diez, Patricia Ern, Sebastien Cazin, Jerome Mougel, Remi Bourguet
Summary: This study experimentally investigates the fluid-structure interaction problem of an elongated, finite-length, flexible cylinder falling in a fluid at rest. The combination of tomographic reconstruction of the cylinder and three-dimensional particle tracking velocimetry of the surrounding fluid allows for the capture of both solid and fluid motions. The study reveals specific organizations of vortical structures in different motion regimes and highlights the spatio-temporal synchronization of the unsteady flow and moving body.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Weilin Chen, Chunning Ji, Md Mahbub Alam, Dong Xu, Hongwei An, Feifei Tong, Yawei Zhao
Summary: This paper presents a numerical investigation of the response and wake modes of a freely vibrating D-section prism with varying angles of attack. The study reveals six types of response with increasing angle of attack and elucidates the flow physics through analyzing various parameters. This research is important in understanding the characteristics of prism vibration behavior.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Banafsheh Seyed-Aghazadeh, Bridget Benner, Xhino Gjokollari, Yahya Modarres-Sadeghi
Summary: The experimental study of vortex-induced vibration on a curved flexible cylinder in a water tunnel revealed that the system response is sensitive to the curvature direction, with mode transition occurring at higher reduced velocities. Both odd and even modes were excited in the cross-flow directions.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
A. Nitti, G. De Cillis, M. D. de Tullio
Summary: Flow-induced vibrations of a circular cylinder with coupled rotation are investigated through two-dimensional simulations. The results show that the kinematic coupling introduces a novel scenario where the oscillation amplitude is magnified in locked configurations. It is also found that there is a significant widening of the reduced velocity domain where the lock-in condition takes place. By ensuring phase alignment between lift and displacement, the coupled rotation allows the oscillation amplitude to grow indefinitely with the reduced velocity.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Jisheng Zhao, Mark C. Thompson, Kerry Hourigan
Summary: In this study, a decomposition of the streamwise fluid force for in-line vortex-induced vibration (VIV) was presented, providing insights into how wake drag acts as a driving force in fluid-structure interaction. The validity of this force decomposition was verified through experiments on a freely vibrating circular cylinder in line with the free stream. It was found that the vibration process exhibits both phase-synchronized and desynchronized regimes, with competition between non-stationary frequency responses of the cylinder vibration and the vortex shedding. Interestingly, such a desynchronization regime near resonance was not observed in the transverse vibration case.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Construction & Building Technology
Muhammad Zeeshan, Zaib Ali, Emad Ud Din
Summary: Climate change and urban heat island effects have negative impacts on thermal comfort in cities. This study demonstrates that integrating street trees can improve thermal comfort and reduce energy consumption.
JOURNAL OF BUILDING PERFORMANCE SIMULATION
(2023)
Article
Thermodynamics
Usman Latif, Earl H. Dowell, Emad Uddin, M. Yamin Younis
Summary: Extensive wind tunnel experiments were conducted to determine the optimal parameters for energy harvesting from piezoelectric membranes. The stiffness and length of the membranes, as well as the shape of the bluff body, were found to significantly impact power generation. By altering the stiffness of the membrane, a substantial increase in power generation was achieved. The results also highlighted the importance of using a bluff body to enhance energy generation, allowing for lower wind speeds and practical applications in remote areas.
ENERGY CONVERSION AND MANAGEMENT
(2023)
Article
Mechanics
Dong Zhang, Wei-Xi Huang
Summary: The flow around a tethered model of a swimming batoid fish is studied using wall-modelled large-eddy simulation and the immersed boundary method. High Reynolds numbers up to 148,000 are chosen and hairpin vortical (HV) structures near the body surface are observed for the first time. The HVs are mainly formed through two mechanisms and create strong fluctuations in the pressure distribution and frequency spectrum.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Qian Mao, Yingzheng Liu, Hyung Jin Sung
Summary: The hydrodynamic mechanism of drag reduction by flapping flexible filaments behind a cylinder was investigated using the penalty immersed boundary method. The effects of phase difference, attachment height, and flapping amplitude on drag reduction were studied. Flapping filaments weaken vortex shedding through destructive interaction, with out-of-phase filaments showing better drag reduction than in-phase filaments. Minimum drag is achieved at appropriate attachment height and flapping amplitude to avoid filament collision and weaken shear-layer-filament interaction. The clapping filaments are more effective than snaking filaments. The total drag decreases with increasing Reynolds number, transitioning from 2S mode to P + S mode wake pattern.
Article
Green & Sustainable Science & Technology
Usman Latif, M. Yamin Younis, Saad Idrees, Emad Uddin, Abdessattar Abdelkefi, Adnan Munir, Ming Zhao
Summary: In this study, the effect of asymmetric wake flow of two side-by-side cylindrical bluff bodies on power output is experimentally examined. Different synchronization modes of the flag with wake flow are observed. The streamwise gap between the flag and cylinders (Gx) and the center-to-center gap between cylinders have a significant impact on the flag's dynamical behavior, resulting in a fluctuation in power output. The levels of output power are analyzed by varying the Gx and the cross-stream or lateral gap (N/d) between the two cylinders.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2023)
Article
Thermodynamics
Guo-Zhen Ma, Chun-Xiao Xu, Hyung Jin Sung, Wei-Xi Huang
Summary: Large-eddy simulations (LESs) were conducted to study the effects of roughness on the secondary motions (SMs) and wall-attached structures in a turbulent open-channel flow. It was found that different roughness arrangements had minor differences in the mean streamwise velocity. The clustered arrangement generated large-scale SMs, while the homogeneous random arrangement maintained outer-layer similarity. Wall-attached structures were also identified and shown to play a significant role in rough-wall turbulence.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
Article
Engineering, Chemical
Hassan Ejaz, A. Mubashar, Ahsan Tanveer, Emad Uddin, Zaib Ali, Nabeel Arif
Summary: In this research, the effects of adding different types of nanomaterials on the mechanical behavior of structural adhesive were comprehensively compared. It was found that the introduction of carbonaceous nanomaterials, including graphene nanoplatelets (GNPs), Multi-Walled Carbon Nanotubes (MWCNTs), and reduced graphene oxide (RGO), significantly influenced the mechanical properties of the epoxy adhesive. Specifically, GNPs increased the brittleness of the adhesive, while MWCNTs reduced brittleness.
JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Guo-Zhen Ma, Chun-Xiao Xu, Hyung Jin Sung, Wei-Xi Huang
Summary: Direct numerical simulations (DNSs) were conducted to investigate the effects of roughness on statistical properties and large-scale coherent structures in turbulent channel flow over three-dimensional sinusoidal rough walls. The study examined the similarities in mean streamwise velocity and Reynolds stresses in the outer layer by varying the roughness Reynolds number and the ratio of roughness height to the half-channel height. Spectral analysis and scale-energy path display were used to explore the energy transfer mechanism of turbulent motions with different sized roughness elements. The results showed that increasing roughness Reynolds number led to a downward shift of the mean velocity profile and decreased intensity of turbulent Reynolds stresses.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Qian Mao, Yingzheng Liu, Hyung Jin Sung
Summary: The flow-induced snap-through dynamics of a buckled flexible filament were studied by using the penalty immersed boundary method. The effects of filament length, bending rigidity, and Reynolds number on the mode transition were systematically investigated. Three different modes were observed when these parameters were varied: equilibrium mode, streamwise oscillation mode, and snap-through oscillation mode. The increase in transverse fluid force induced the snap-through oscillation mode, while a vortex-induced vibration and a self-excited vibration occurred in the streamwise oscillation mode and snap-through oscillation mode respectively.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Chensheng Luo, Ruiyong Mou, Xingrong Huang, Wei-Xi Huang, Le Fang
Summary: This study investigates the small-amplitude oscillation regime of a square cylinder under vortex-induced rotation through numerical simulations and an analytical model, and explains the mechanism of this regime. Additionally, an alternative method for determining local flow parameters through global dynamic quantities is proposed.
Article
Chemistry, Multidisciplinary
Naveed Raza, Rifat Mehdi, Muhammad Ahsan, Muhammad Taqi Mehran, Salman Raza Naqvi, Emad Uddin
Summary: An experimental investigation is conducted to study the hydrodynamics of gas-solid flow using different designs of air distributor plates. The analysis reveals the differences in pressure drop and minimum fluidization velocities (Umf) for three different plates. CFD analysis is also carried out, showing promising results that agree with the experimental findings. The study concludes that the novel hybrid plate is the optimum distributor plate due to its low pressure drop, adequate Umf, intermediary bed height rise ratio, and moderate bubble rise velocity ratio across the bed.
APPLIED SCIENCES-BASEL
(2023)
Article
Radiology, Nuclear Medicine & Medical Imaging
Muhammad Abdullah, Aamir Mubashar, Emad Uddin
Summary: This research explores the weight reduction of hip implants through both parametric and non-parametric optimization techniques. Different materials can be used for orthopaedic hip implants and they are typically solid structures. However, the stiffness of the implants can cause stress shielding and weaken the adjacent bones, leading to osteoporosis. The reduction in mass of the femur stem can help to alleviate these issues. Non-parametric topology optimization achieves a 34.9% mass reduction, while parametric optimization based on Central Composite Design technique achieves a 22% mass reduction by utilizing hole diameters as parameters.
BIOMEDICAL PHYSICS & ENGINEERING EXPRESS
(2023)
Article
Biochemical Research Methods
Hyeono Nam, Jong-Eun Park, Waqas Waheed, Anas Alazzam, Hyung Jin Sung, Jessie S. Jeon
Summary: Traveling surface acoustic waves (SAWs) were used for the lysis of cancer cells without any chemical reagents, followed by Raman spectrum profiling to explore detailed cell-derived data. Mechanical cell lysis was achieved using polystyrene microparticles (PSMPs) and the Raman signals from the lysed cells were enhanced by gold nanoparticles (AuNPs) through nanogaps formed by the AuNPs. The lysis efficiency was evaluated by varying the size and concentration of the PSMPs.
Article
Energy & Fuels
Ali Ammar Naqvi, Emad Uddin, Muhammad Zia Ullah Khan
Summary: In this study, an improved method for heat transfer in microchannels is proposed, which achieved better heat transfer performance by introducing vortex generators and base corrugation. Through numerical simulations, the optimal design for microchannels and corrugation patterns was determined, and the enhanced heat transfer effect of the proposed design was validated.
