Article
Mechanics
Azadeh Jafari, Beverley J. McKeon, Maziar Arjomandi
Summary: The potential of frequency-tuned surfaces as a passive control strategy for reducing drag in wall-bounded turbulent flows is investigated using resolvent analysis. It is shown that wall impedance can suppress the modes resembling the near-wall cycle and the very-large-scale motions and the Reynolds stress contribution of these modes. Furthermore, a wall with only shear-driven impedance is found to suppress turbulent structures over a wider range in spectral space, leading to an overall turbulent drag reduction.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Azadeh Jafari, Benjamin Cazzolato, Maziar Arjomandi
Summary: This study investigates the potential of finite-length porous surfaces with a subsurface chamber for controlling the turbulent boundary layer. Different chamber configurations were tested, and it was found that a short porous surface with individual cavities underneath each perforation was the most effective in reducing turbulence.
Article
Thermodynamics
Marian Albers, Wolfgang Schroeder
Summary: Large-eddy simulations were conducted on the flow over an actuated NACA4412 airfoil at a chord-based Reynolds number of Re-c = 400,000, using spanwise traveling transversal surface waves to improve aerodynamic efficiency. The results showed significant reductions in wall-shear stress and boundary layer thickness, leading to drag reduction and lift increase. Comparisons with an actuated DRA2303 flow revealed similar flow field modifications and positive drag reduction for both airfoils, demonstrating the robustness of the transversal-traveling-wave drag reduction technique.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2021)
Article
Mechanics
Marwa Fakhfekh, Wael Ben Amira, Malek Abid, Aref Maalej
Summary: In this study, the mean deflection evolution of a flexible rotor blade is examined using a coupled model based on Navier-Stokes equations for fluid flow and linear elasticity equations for blade deformation. The elastic behavior of the flexible rotor blade is characterized under different parameter ranges, and the vorticity field is compared with that of a rigid rotor. The effect of pitch, tip speed ratio (or frequency), and its sign on blade deformation is investigated, revealing the non-monotonic relationship between deformation and rotation frequency and pitch angle. Additionally, the flexible rotor demonstrates the ability to develop a vortex ring state under specific conditions, which is not observed in the rigid rotor.
Article
Mechanics
Johan Sundin, Umberto Ciri, Stefano Leonardi, Marcus Hultmark, Shervin Bagheri
Summary: Liquid-infused surfaces can reduce friction drag and enhance heat transfer, but research in this area is limited. Numerical simulations show that recirculation in the surface texture can lead to increased heat transfer in both laminar and turbulent flows. The contribution of recirculation to heat transfer can be significant in microchannels but is limited in turbulent flows. Nonetheless, a heat transfer enhancement of around 10% is observed in turbulent channel flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Energy & Fuels
Hoai Thanh Nguyen, Kyoungsik Chang, Sang-Wook Lee, Jaiyoung Ryu, Minjae Kim
Summary: In this study, the effect of parameters on drag-reducing performance of superhydrophobic surfaces was investigated using direct numerical simulation (DNS). The results reveal the drag reduction mechanism through turbulent kinetic energy budget and observation of coherent structures. The study demonstrates that significant drag reduction can be achieved under specific solid fraction and distribution conditions.
Article
Mechanics
Yuehao Sun, Ze-Rui Peng, Dan Yang, Yongliang Xiong, Lei Wang, Lin Wang
Summary: This article investigates the dynamics of a two-dimensional flow over a rigid flat plate with a trailing closed flexible filament acting as a deformable afterbody. Numerical methods are used to study the flow patterns and dynamics of the rigid-flexible coupling system and to explore the effects of Reynolds number and length ratio. The study identifies five typical state modes based on the filament shape and dynamics and demonstrates the significant drag reduction achieved by utilizing the flexible filament.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Sheng-Hong Peng, Yi-Bao Zhang, Heng-Dong Xi
Summary: We conducted an experimental study on the impact of polymer additives on the entrainment of a circular water jet. The results showed that the entrainment rate depends on the concentration of the polymer and the Weissenberg number. The polymer-laden jet exhibited two different regimes compared to the pure water case: in the first regime, the jet spreading rate was smaller and the centerline mean velocity decayed more slowly, while in the second regime, the entrainment rate was enhanced by up to 33% compared to the water jet.
Article
Thermodynamics
Samuel D. Tomlinson, Francois J. Peaudecerf, Fernando Temprano-Coleto, Frederic Gibou, Paolo Luzzatto-Fegiz, Oliver E. Jensen, Julien R. Landel
Summary: Superhydrophobic surfaces (SHSs) have the ability to reduce friction drag in turbulent flows. However, the impact of surfactants on the drag-reducing properties of SHSs under turbulent flow conditions has not been thoroughly studied, as it is currently expensive to predict in direct numerical simulations.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
Article
Multidisciplinary Sciences
Giulio Foggi Rota, Alessandro Monti, Marco E. Rosti, Maurizio Quadrio
Summary: Viscous dissipation in fluid flows causes significant energy losses. Laminar flows in ducts have minimum resistance, while turbulence increases friction and energy requirements for pumping. A novel technique of intermittently pumping the flow accelerates it to a quasi-laminar state, saving energy compared to constant pumping and reducing harmful emissions.
SCIENTIFIC REPORTS
(2023)
Article
Engineering, Marine
Daiwen Jiang, Hui Zhang, Weiguang Yao, Zijie Zhao, Mingyue Gui, Zhihua Chen
Summary: This paper numerically studies the fully developed turbulent channel flow with sinusoidal deformation controlled by space-dependent electromagnetic forces at Re = 4000. The relationships among characteristic structures in the flow field, mean Reynolds shear stress, and drag reduction are discussed. The results show that quasi-streamwise vortexes generated near the wall can modify the flow structures, suppress mean Reynolds shear stress, and achieve drag reduction. Additionally, the contributions to drag reduction vary at different locations.
Article
Thermodynamics
D. Hirata, J. Morita, H. Mamori, T. Miyazaki
Summary: Direct numerical simulations were conducted to study turbulent channel flow with superhydrophobic surfaces (SHS). A robust staggered SHS pattern was designed, and the Reynolds number was set to Re ⠜ = 180 and 395 with a constant-pressure gradient condition. The bulk mean velocity increased in the SHS case compared with the no-slip case, mainly due to the increase in slip velocity. The drag-reduction rate was found to be proportional to the slip velocity when the size of the free-shear region was small, but the turbulent contribution to the bulk mean velocity remained almost unchanged in the no-slip case due to the negative coherent component of the Reynolds shear stress.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
Article
Mechanics
A. Chavarin, G. Gomez-de-Segura, R. Garcia-Mayoral, M. Luhar
Summary: Utilizing the resolvent framework, this study explores the impact of anisotropic permeable substrates on turbulent channel flow, revealing the potential of porous materials to reduce drag in wall-bounded turbulent flows. The findings suggest that substrates with high streamwise permeability and low spanwise permeability can suppress the gain of the corresponding resolvent mode, leading to drag reduction.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Qian Mao, Jiazhen Zhao, Yingzheng Liu, Hyung Jin Sung
Summary: This study investigates the hydrodynamic mechanism of drag reduction by a flexible hairy coating through simulations and experimental data comparison, revealing the importance of flexible hairy coatings in drag reduction and the effects of different parts of the coating on drag reduction.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Thermodynamics
Shumpei Hara, Kana Watanabe, Yuichi Kaiho, Takahiro Tsukahara, Yasuo Kawaguchi
Summary: This experimental study investigates the momentum and heat transfer in drag-reducing turbulent channel flow of surfactant solution. The study discovers a novel type of ordered turbulent motion called Viscoelastic Vibration (VEV) near the wall, where elastic energy is converted into turbulent kinetic energy. VEV is characterized by wave-like motion in the streamwise direction with low-frequency modes, resulting in zero average Reynolds shear stress. However, thermal diffusion still occurs continuously due to the movement of a fluid lump caused by VEV.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Review
Mechanics
Steffen Hardt, Glen McHale
Summary: This review article focuses on the fluid mechanics properties of liquid-infused surfaces (LISs) and the behavior of drops on such surfaces. By designing the wettability and topography of LIS, low-friction drop motion can be achieved.
ANNUAL REVIEW OF FLUID MECHANICS
(2022)
Article
Nanoscience & Nanotechnology
Yufeng Zhu, Glen McHale, Jack Dawson, Steven Armstrong, Gary Wells, Rui Han, Hongzhong Liu, Waldemar Vollmer, Paul Stoodley, Nicholas Jakubovics, Jinju Chen
Summary: Biofilms are a major concern in various fields and the development of effective anti-biofilm strategies is crucial. This study presents the use of slippery omniphobic covalently attached liquid (SOCAL) surfaces as a stable antibiofilm strategy under shear stress. The SOCAL surface significantly reduces biofilm formation of key pathogens, offering a promising solution to biofilm-related issues in medical devices and other applications.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Fluids & Plasmas
Azmaine Iqtidar, Joseph J. Kilbride, Fouzia F. Ouali, David J. Fairhurst, Howard A. Stone, Hassan Masoud
Summary: In this study, we analyze the diffusion-controlled evaporation of multiple droplets placed near each other on a planar substrate. We calculate the change in volume of sessile droplets with different initial contact angles and arrangements. Experimental measurements using a pattern placed beneath the droplet array validate the theoretical predictions and offer additional insights into the droplet volume evolution.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Nanoscience & Nanotechnology
Anam Abbas, Gary G. Wells, Glen McHale, Khellil Sefiane, Daniel Orejon
Summary: Wetting is crucial in the interactions between liquids and solid surfaces, and can be controlled by modifying the chemistry and structures of the surface. This study investigates the grafting of silicone oil with different viscosities and layers on smooth silicon substrates, and demonstrates the fabrication of low-contact line-pinning hydrophobic surfaces with high contact angles and low contact angle hysteresis. The findings provide a basis for selecting appropriate silicone oil grafting methods and parameters for specific applications.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Physical
Alex Jenkins, Gary G. G. Wells, Rodrigo Ledesma-Aguilar, Daniel Orejon, Steven Armstrong, Glen McHale
Summary: The evaporation of sessile droplets on a surface is affected by factors such as surface wettability, environment, contact angle hysteresis, and surface roughness. The presence of constituents and impurities in non-pure liquids complicates the evaporation characteristics of droplets. This study demonstrates that by using smooth surfaces with low contact angle hysteresis, the crystallization of saline droplets can be suppressed, leading to stable droplets above the saturation concentration. These findings have implications for heat and mass transfer in low humidity environments.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Mehdi H. Biroun, Luke Haworth, Hossein Abdolnezhad, Arash Khosravi, Prashant Agrawal, Glen McHale, Hamdi Torun, Ciro Semprebon, Masoud Jabbari, Yong-Qing Fu
Summary: Droplet impact behavior on solid surfaces is crucial for industrial applications such as spray coating, food production, printing, and agriculture. The challenge lies in modifying and controlling the impact regime and contact time of the droplets, which becomes more critical for non-Newtonian liquids. This study explores the impact dynamics of non-Newtonian liquids on superhydrophobic surfaces and shows that the addition of Xanthan alters the shape and reduces the contact time of the droplets.
Article
Chemistry, Analytical
Martin Bencsik, Adam McVeigh, Costas Tsakonas, Tarun Kumar, Luke Chamberlain, Michael I. Newton
Summary: NDIR detectors are widely used to measure atmospheric CO2, but their application in honeybee colony health assessment is limited. This study presents a microcontroller-based system that collects data from NDIR sensors in honeybee colonies. The data suggests that colony size can be estimated from changes in CO2 levels, but no correlation with humidity was observed. The study also reveals a decreasing trend of CO2 levels over weeks as colonies die.
Review
Physics, Applied
Jian Zhou, Yihao Guo, Yong Wang, Zhangbin Ji, Qian Zhang, Fenglin Zhuo, Jingting Luo, Ran Tao, Jin Xie, Julien Reboud, Glen McHale, Shurong Dong, Jikui Luo, Huigao Duan, Yongqing Fu
Summary: Flexible and wearable acoustic wave technology has gained tremendous attention due to its wide applications in wearable electronics, sensing, acoustofluidics, and lab-on-a-chip. This review provides an overview of the advances in fundamental principles, design, fabrication, and applications of flexible and wearable acoustic wave devices. The challenges in material selections and structural designs for high-performance devices are discussed, along with recent advances in fabrication strategies and performance evaluation. Key applications in wearable sensors, acoustofluidics, and lab-on-a-chip systems are highlighted, and future perspectives in this field are discussed.
APPLIED PHYSICS REVIEWS
(2023)
Article
Physics, Applied
J. J. Kilbride, K. E. Fagg, F. F. Ouali, D. J. Fairhurst
Summary: We propose an experimental technique called pattern-distortion (PD) technique that links the shape of a liquid lens to its magnification. We optimize this technique for various droplet sizes and optical configurations and demonstrate its applicability in three different situations. Firstly, we use the PD technique to overcome experimental limitations in determining individual droplet volumes in multiple sessile droplets configurations. Secondly, we show how our technique can inform the design of liquid lenses. Thirdly, we extend the method to composite droplet systems, using it to extract the size of trapped air bubbles inside liquid droplets.
PHYSICAL REVIEW APPLIED
(2023)
Review
Materials Science, Composites
Marina Gorbunova, Leonid Grunin, Robert H. Morris, Arina Imamutdinova
Summary: This review summarizes the study of semi-crystalline thermoplastic polyurethane elastomers and composites based on the shape memory effect. The shape recovery ability of these polymers depends on their sensitivity to temperature, moisture, and magnetic or electric fields, which in turn are influenced by the chemical properties and composition of the matrix and nanofillers. Nanocellulose, a nanomaterial with unique properties, can enhance the mechanical properties of polymer matrices and act as a switching element in shape memory applications. The review also discusses the production methods, properties, and potential applications of nanocellulose-based polyurethane composites.
JOURNAL OF COMPOSITES SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Luke Haworth, Deyu Yang, Prashant Agrawal, Hamdi Torun, Xianghui Hou, Glen McHale, Yongqing Fu
Summary: Ice nucleation and accretion on structural surfaces are major safety and operational concerns. Various methods are used to tackle this issue, and in this study, the ice adhesion properties of different coated substrates were explored. Among the studied surfaces, the SOCAL coating with flexible polymer brushes and liquid-like structure significantly reduced ice adhesion. This reduction is attributed to the flexible nature of the brush-like structures, allowing ice to detach easily.
NANOTECHNOLOGY AND PRECISION ENGINEERING
(2023)
Article
Physics, Applied
H. Y. Erbil, G. McHale
Summary: In recent years, there has been extensive research on synthetic superhydrophobic surfaces, which possess unique anti-wetting properties. Apart from their stay-dry and self-cleaning properties, the evaporation process of water droplets has also attracted significant interest. Studies on surface contamination and droplet evaporation during the Covid-19 pandemic have gained attention. Superhydrophobic surfaces alter the contact between droplets and the substrate/environment, and affect the diffusion of vapor.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Glen McHale, Rodrigo Ledesma-Aguilar, Chiara Neto
Summary: In 1948, Cassie proposed an equation for the wetting of a smooth, heterogeneous surface. This equation uses weighted averages based on the fractional surface areas and cosines of contact angles to predict the contact angle of a droplet on a composite surface. The equation has proven fundamental in understanding the wetting of superhydrophobic and superoleophobic surfaces. However, little attention has been given to the complete wetting of one surface component.
Article
Chemistry, Multidisciplinary
Michele Pelizzari, Glen McHale, Steven Armstrong, Hongyu Zhao, Rodrigo Ledesma-Aguilar, Gary G. Wells, Halim Kusumaatmaja
Summary: This study presents a new method to create patterned liquid lubricant surfaces, demonstrates low-friction droplet self-propulsion on such surfaces, and sheds light on the interactions between liquid droplets and liquid surfaces.
Article
Materials Science, Multidisciplinary
Haidong Wang, Daniel Orejon, Dongxing Song, Xing Zhang, Glen McHale, Hiroshi Takamatsu, Yasuyuki Takata, Khellil Sefiane
Summary: By combining chemical hydrophobicity and surface topography, we have achieved high non-wetting behavior on a suspended monolayer of graphene. This unique non-wetting behavior could be induced by the interaction between liquid molecules across the suspended monolayer, surpassing the non-wetting possible on smooth hydrophobic surfaces.
COMMUNICATIONS MATERIALS
(2022)