Article
Mechanics
Vinh-Tan Nguyen, Pierre Ricco, Gianluca Pironti
Summary: By imposing an oscillating spanwise pressure gradient, flow separation can be controlled and drag can be reduced, with a maximum reduction of 25%. This reduction is mainly due to lower pressure and skin-friction drag forces. The control method decreases pressure and wall-shear stress, leading to a reduction in total drag.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Physical
Xiaodie Guo, Xuejiao Chen, Wenjing Zhou, Jinjia Wei
Summary: This study investigates the rheological properties of rocket kerosene solutions containing drag reduction agent (DRA) using coarse-grained molecular dynamics simulations. The results show that the viscosity of DRA-kerosene solutions decreases with increasing shear rate and becomes similar to that of pure kerosene. The shear viscosity of DRA-kerosene solutions increases with longer chain lengths and higher polymer concentrations. The study provides microscopic insights into the relation between the morphologic change of polymer molecules and the rheological properties of DRA-kerosene solutions.
Article
Physics, Fluids & Plasmas
J. J. J. Gillissen
Summary: In contrast to Newtonian turbulence, elastoinertial turbulence dissipates energy mainly through polymer chain relaxation, which is effective on all scales and does not require interscale energy transport.
Article
Mechanics
Rodrigo S. Mitishita, Gwynn J. Elfring, Ian. A. Frigaard
Summary: In this study, the effects of flexible and rigid polymer solutions on turbulent drag reduction in a 2:1 aspect ratio rectangular duct were investigated experimentally. The results showed that both xanthan gum (XG) and partially hydrolysed polyacrylamide (HPAM) had similar effects on turbulence at similar Reynolds numbers and drag reduction percentages. At high drag reduction levels, the power spectral densities of streamwise velocity fluctuations exhibited a power-law decay near -3, indicating the presence of elasto-inertial turbulence (EIT). Additionally, the flexible polymer solutions were found to be more effective at reducing drag at relatively low concentrations compared to XG.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2023)
Article
Mechanics
Daniel J. Coxe, Yulia T. Peet, Ronald J. Adrian
Summary: Research on how drag created by turbulent flow over a surface can be reduced by oscillating the surface transversely has shown that under specific conditions, it is possible to reduce the drag caused by turbulence, improving fluid flow.
Article
Engineering, Chemical
Hayder A. Abdulbari, Rasidah Amir
Summary: Long-chained polymeric drag-reducing agents are prone to mechanical degradation in high-shear environments. Physically formed complexes show improved drag reduction performance.
CHEMICAL ENGINEERING & TECHNOLOGY
(2021)
Article
Mechanics
H. W. Mueller, L. Brandfellner, A. Bismarck
Summary: The long-term drag reduction capability of poly(ethylene oxide) with a nominal molar weight of M-w = 4 x 10(6 )g/mol dissolved in water was investigated. It was found that the drag reduction capability decreased to 75% of the initial value when the molar weight of the polymer was approximately 5 x 10(5) g/mol. This decrease was attributed to mechanical degradation in the turbulent flow and aging of the polymer dissolved in water. A statistical model was used to describe the degradation process.
Article
Engineering, Marine
Wagih Abu Rowin, Anika Benozir Asha, Ravin Narain, Sina Ghaemi
Summary: A novel coating that bonds drag-reducing polymers to metallic surfaces has been developed, achieving drag reduction by slowly dissolving in water. Maximum drag reduction was achieved with an optimum deposition of APAM at high Reynolds numbers, although the reduction gradually diminished over time.
Article
Mechanics
Tongtong Tao, Zhaochang Wang, Jiawei Ji, Yuhang Guo, Yongqing Zhu, Xidong Hu, Kun Liu, Yunlong Jiao
Summary: In this study, a deflecting air cavity generation strategy utilizing superhydrophobic area occupancy and impact angle control is reported. The influence of these factors on water entry dynamics and drag reduction characteristics of spheres is investigated through experimental and theoretical analysis. The results show that the deflection displacement of a hemispherically coated sphere reaches its maximum when the impact angle is 90 degrees. The SHB region-modulated sphere exhibits different air cavity morphologies and achieves faster movement with reduced drag.
Article
Mechanics
J. M. Floryan, N. N. Haq
Summary: The study focused on the effects of surface vibrations on propulsion augmentation and resistance in the relative movement of parallel plates. It was found that wave velocity plays a crucial role in flow resistance, with slower waves tending to increase flow resistance, while supercritical waves generally decrease resistance and can lead to a complete elimination of resistance.
JOURNAL OF FLUID MECHANICS
(2022)
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
Mechanics
Longyin Jiao, J. M. Floryan
Summary: Analysis of pressure losses in laminar, pressure-gradient-driven channel flows with wall transpiration shows that reduction in effective channel opening, nonlinear streaming, and elimination of direct contact between fluid and walls influence these losses. Proper selection of transpiration pattern can reduce pressure losses, with nonlinear streaming being the dominant effect. Increasing transpiration at both walls can further decrease losses when in proper relative position, but concentrating transpiration at a single wave number achieves the largest reduction. The use of transpiration increases energy cost of flow, with optimization of conditions leading to minimization of this cost for most effective propulsion augmentation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
M. Z. Hossain, J. M. Floryan
Summary: It is found that applying thermal waves on a horizontal slot surface can generate a pumping effect. The change in flow field due to thermal inertia drives the net fluid movement in the horizontal direction. The induced flow rate increases with wave speed but decreases when the convection becomes limited. Excessive wavelength and excessive decrease in wavelength reduce the flow rate. The pumping effect can be optimized by selecting the appropriate wave speed and wavelength of the thermal wave. The magnitude of pumping increases with a reduction of Prandtl number.
JOURNAL OF FLUID MECHANICS
(2023)
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)
Review
Engineering, Mechanical
Min Liu, Liran Ma
Summary: Friction drag is a significant issue when there is relative motion between solid and liquid phases, causing inconveniences in various applications. Numerous methods have been developed to reduce friction drag, and this article reviews several widely studied methods, discussing their advantages and limitations in practical applications. A comparison of different methods is made, and the development prospect of drag reduction is concluded.
Article
Engineering, Chemical
Xin Pu, Guangxiao Li, Yang Song, Minjing Shang, Yuanhai Su
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2017)
Article
Engineering, Chemical
Guangxiao Li, Xin Pu, Minjing Shang, Li Zha, Yuanhai Su
Article
Engineering, Chemical
Hong Zhang, Minjing Shang, Chong Shen, Guangxiao Li, Yuanhai Su
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2019)
Article
Engineering, Chemical
Detao Pan, Guangxiao Li, Yuanhai Su, Huilong Wei, Zhenghong Luo
Summary: A comprehensive model for the adipic acid production reaction based on kinetic study was developed, showing a significant impact of temperature and nitric acid concentration on the formation rate of adipic acid. The model accurately predicted the yield of adipic acid at different temperatures, providing valuable insights for industrial tubular reactor design.
CHINESE JOURNAL OF CHEMICAL ENGINEERING
(2021)
Article
Engineering, Chemical
Guangxiao Li, Saier Liu, Xiaoyong Dou, Huilong Wei, Minjing Shang, Zheng-Hong Luo, Yuanhai Su
Article
Engineering, Chemical
Hui-Long Wei, Sai-Er Liu, Guang-Xiao Li, Yuan-Hai Su, Wei-Cheng Yan, Zheng-Hong Luo
Summary: This study investigated the performance of a microreactor system in conducting the oxidation of KA oil with nitric acid through mathematical models. Different models were compared based on their accuracy in predicting conversion rates and product yields, with the 2D reactor model proving to be the most accurate. Further research will help guide the design and operation of industrial-scale microreactors.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
Xinxiang Jiang, Guangxiao Li, Saier Liu, Yang Song, Yuanhai Su
Summary: The process characteristics of preparing 4-nitrobiphenyl from 4-nitroaniline were revealed using two continuous-flow microreactors. The two main steps involved were the synthesis of 4-nitrobenzene diazonium tetrafluoroborate through diazotization reaction, and the Suzuki-Miyaura cross-coupling reaction. By optimizing reaction conditions and reactant ratios, high yields of 4-NBDT and 4-NBP were achieved efficiently.
JOURNAL OF FLOW CHEMISTRY
(2021)
Article
Engineering, Chemical
Guangxiao Li, Minjing Shang, Yang Song, Yuanhai Su
Article
Engineering, Chemical
Yang Song, Minjing Shang, Guangxiao Li, Zheng-Hong Luo, Yuanhai Su
