Article
Mechanics
Sourabh S. Diwan, Jonathan F. Morrison
Summary: The study proposed a three-layer asymptotic structure for turbulent pipe flow, revealing the existence of a Reynolds-number-invariant logarithmic region for the streamwise mean velocity and variance in terms of intermediate variables. The analysis determined the classical von Karman and Townsend-Perry constants from the intermediate-scaled log-law constants.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Alexander J. Smits, Marcus Hultmark, Myoungkyu Lee, Sergio Pirozzoli, Xiaohua Wu
Summary: The new scaling shows a Reynolds-number-independent profile for all components of the Reynolds stress in the near-wall region of wall-bounded flows, highlighting the significance of wall shear stress fluctuations and the role of large eddies in determining the Reynolds number dependence of near-wall turbulence behavior.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Eugen Magyari
Summary: The paper revisits three outstanding rotating disk flows described by an exact solution of the Navier-Stokes equations, aiming to investigate the mapping relationships between them. It is found that flow (A) is similar to flow (C), and can generate flow (B) through suitable scaling transformations, while flow (B) can generate a continuous set of solutions of flow (A).
ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK
(2021)
Article
Mechanics
Xi Chen, Katepalli R. Sreenivasan
Summary: This passage discusses the potential exceptions to wall-scaling in turbulent flows, with a focus on the streamwise velocity fluctuation. It introduces a new formula for peak magnitude which approaches a finite limit due to the natural constraint of boundedness on the dissipation rate at the wall, in contrast to the existing logarithmic growth explanation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Tie Wei, Daniel Livescu
Summary: This study investigates proper scaling in turbulent planar plumes using a scaling patch approach, determining appropriate scales for mean velocity, temperature, Reynolds shear stress, and turbulent heat flux. It highlights the critical role of mean transverse flow in the scaling of turbulent planar plumes.
Article
Mechanics
Xin Li, Yue Zhang, Huijun Tan, Shu Sun, Hang Yu, Yi Jin, Jie Zhou
Summary: This study experimentally and analytically investigates the length scaling for the boundary layer separation induced by two incident shock waves in a Mach 2.73 flow. The experimental results show that the separation point moves downstream with increasing shock wave distance. For the dual-incident shock wave-turbulent boundary layer interactions exhibiting a coupling separation state, the upstream interaction length approximately linearly decreases with increasing distance, and the decrease rate increases with the second deflection angle. A prediction method for the upstream interaction length is proposed, with a relative error of about 10% compared to the experimental result.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Pierre Ricco
Summary: This study presents theoretical results related to the experimental findings of the energy spectra of streamwise-elongated vortical disturbances generated by free-stream turbulence in a flat-plate transitional boundary layer. The scaling of the energy spectra is explained using a model that describes the streamwise evolution of the streamwise and spanwise energy spectra.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Erik Lindborg
Summary: In this study, we investigate the Nusselt-Rayleigh number problem of Rayleigh-Benard convection and propose that the velocity and thermal boundary layer widths, delta(u) and delta(T), are controlled by the dissipation scales of turbulence outside the boundary layers. We derive the scaling relations for Nu, delta(T)/L, and delta(u)/L in the high Ra limit and find that they are independent of the Prandtl number. For Pr close to 1, we make a more general assumption and show that Nu scales with Ra-alpha/(3-alpha), where alpha is the intermediate scaling coefficient. We argue that the boundary layers will retain the intermediate scaling alpha = 3/4 in the limit of high Ra.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Civil
T. O'Donoghue, A. G. Davies, M. Bhawanin, D. A. A. van der A
Summary: The experimental results show that modulation has little effect on hydrodynamics, especially on turbulence propagation from the bed and time-averaged turbulent characteristics.
COASTAL ENGINEERING
(2021)
Article
Mechanics
S. Bhardwaj, K. Hemanth Chandra Vamsi, R. Sriram
Summary: Supersonic flow over three-dimensional bodies protruding out of the turbulent boundary layer was investigated through experiments and numerical computations. The study varied the shape and dimensions of the protuberance, as well as the freestream Mach numbers, to examine the complex flow features such as separation lines, shock patterns, and the horseshoe vortex. The findings suggest that the mid-span separation can be predicted by modifying scaling laws and considering the effects of the spanwise relieving effect.
Article
Multidisciplinary Sciences
Chuanhui Huang, Xinglong Shang, Xinyuan Zhou, Zhe Zhang, Xing Huang, Yang Lu, Mingchao Wang, Markus Loeffler, Zhongquan Liao, Haoyuan Qi, Ute Kaiser, Dana Schwarz, Andreas Fery, Tie Wang, Stefan C. B. Mannsfeld, Guoqing Hu, Xinliang Feng, Renhao Dong
Summary: A hierarchical-structure-accelerated interfacial dynamic strategy is reported to improve interfacial gas transfer on conductive metal-organic framework films. Hierarchical c-MOF films with hollow structures are synthesized, which increase gas permeability and enhance the motion velocity of gas molecules towards the film surface.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Mohsan Hassan, Muhammad Ahsan, Usman, Metib Alghamdi, Taseer Muhammad
Summary: Shear thinning fluids with unique flow characteristics are widely used in the food and polymer industries. This study investigates the transport characteristics of a Powell Eyring fluid under different shear rates and calculates the rate of entropy generation. The results show that velocity and temperature profiles change with the time scale parameter.
SCIENTIFIC REPORTS
(2023)
Article
Engineering, Multidisciplinary
Keshav Rajasekaran, Hyung Dae Bae, Sarah Bergbreiter, Miao Yu
Summary: This paper presents the development of a micro-scale artificial hair sensor for small-scale unmanned air vehicles. The sensor utilizes a high-aspect ratio hair structure and a thin flexible membrane to transduce directional airflow. Capacitive sensing and orthogonal electrodes are employed for airflow direction detection. Experimental results show good agreement with simulations and the sensor is capable of detecting flow separation.
BIOINSPIRATION & BIOMIMETICS
(2022)
Article
Mechanics
Nils T. Basse
Summary: The study extends a procedure outlined in Basse's work to investigate the global scaling of streamwise velocity fluctuations and identifies a transition at a friction Reynolds number of order 10000. The position and amplitude of the global peak are characterized and the impact of including an additional wake term is analyzed.
Article
Engineering, Electrical & Electronic
Jiali Wu, Yong Yan, Yonghui Hu, Shan Li, Weicheng Xu
Summary: This article presents a study on measuring the flame boundary using an electrostatic sensor array, which shows reliable results for predicting flame properties. The methodology provides important information for the design and operation of combustion systems. The system is capable of providing accurate measurements and determining the overall polarity of charges in a flame.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2021)
Article
Engineering, Aerospace
Jared R. Hammerton, Weihua Su, Guoming Zhu, Sean Shan-Min Swei
AEROSPACE SCIENCE AND TECHNOLOGY
(2018)
Article
Engineering, Aerospace
Natsuki Tsushima, Weihua Su
AEROSPACE SCIENCE AND TECHNOLOGY
(2018)
Article
Engineering, Aerospace
Tianyi He, Ali K. Al-Jiboory, Guoming G. Zhu, Sean S. -M. Swei, Weihua Su
AEROSPACE SCIENCE AND TECHNOLOGY
(2018)
Article
Engineering, Aerospace
Tianyi He, Guoming G. Zhu, Sean S. -M. Swei, Weihua Su
AEROSPACE SCIENCE AND TECHNOLOGY
(2019)
Article
Engineering, Aerospace
Natsuki Tsushima, Tomohiro Yokozeki, Weihua Su, Hitoshi Arizono
AEROSPACE SCIENCE AND TECHNOLOGY
(2019)
Article
Engineering, Aerospace
Xiaochen Hang, Qingguo Fei, Weihua Su
Article
Engineering, Aerospace
Weihua Su, Wei Song
AEROSPACE SCIENCE AND TECHNOLOGY
(2019)
Article
Engineering, Aerospace
Xiaochen Hang, Weihua Su, Qingguo Fei, Dong Jiang
AEROSPACE SCIENCE AND TECHNOLOGY
(2020)
Article
Engineering, Aerospace
Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei, Mariko Hashimoto, Tao Zeng
Summary: This article investigates motor failure control of a six-rotor electric vertical take-off and landing (eVTOL) urban air mobility aircraft using adaptive model predictive control (MPC) based on the linear parameter-varying (LPV) model. Simulation results demonstrate that the designed adaptive MPC controller is able to recover and maintain the aircraft at desired stable condition after motor failure, showing the effectiveness of the proposed control method.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING
(2022)
Article
Engineering, Aerospace
Weihua Su, Shen Qu, Guoming Zhu, Sean Shan-Min Swei, Mariko Hashimoto, Tao Zeng
Summary: This paper aims to develop a control-centric analytical formulation for the aeromechanics and flight dynamics of urban air mobility (UAM) vehicles. A comprehensive nonlinear rigid-body dynamic model is developed, and a linear parameter-varying model is utilized to design flight controllers for stable transition flight.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Aerospace
Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei
Summary: This paper presents the development of novel transition flight controllers for urban air mobility aircrafts. The controllers utilize fixed-wing and six electric rotor assemblies to achieve stable altitude control by adjusting rotor angles and aerodynamic lift. A series of linear models are obtained by linearizing the nonlinear aircraft model, and a novel transition flight control architecture is developed using these models. The simulation results demonstrate the effectiveness and robustness of the controllers.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING
(2022)
Article
Engineering, Aerospace
Yanxin Huang, Weihua Su
Summary: This paper investigates the issue of model updating in multidisciplinary design optimization of aerospace structures, and proposes a method using neural networks to determine the structural dynamic characteristics of a higher fidelity model. The feasibility of this approach is demonstrated through case studies.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING
(2023)
Article
Automation & Control Systems
Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei
Summary: This paper applies novel LPV (linear parameter-varying) model and MPC (model predictive control) methods to a tilt-transition process with rotor failure for electric vertical take-off and landing aircraft. An LPV model is constructed based on a predefined tilting trajectory and a significantly reduced number of linear time invariant models obtained by linearizing the nonlinear eVTOL aircraft model. An adaptive model predictive controller is designed based on the LPV model for successful tilt-transition control with rotor failure.
INTERNATIONAL JOURNAL OF CONTROL AUTOMATION AND SYSTEMS
(2023)
Article
Engineering, Aerospace
Tianyi He, Weihua Su
Summary: This paper applies reinforcement learning to optimize the placement of sensors/actuators and control strategies for a flexible wing. The co-design objective is to achieve optimal closed-loop performance by finding the optimal sensor/actuator placement (OSAP) and associated controller. The problem is formulated as mixed-integer semi-definite programming (MISDP) and solved using a modified reinforcement learning algorithm, which outperforms the greedy algorithm and genetic algorithm in solving high-dimensional MISDP.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING
(2023)
Article
Engineering, Aerospace
Tianyi He, Weihua Su
Summary: This paper addresses the gust suppression and alleviation of highly flexible aircraft using a model predictive controller (MPC) based on linear parameter-varying (LPV) models. The study models the dynamic behavior of the aircraft and uses conventional flaps to control wing vibration and flight attitude. LPV models are derived through linearization and model reduction, and MPC is designed to minimize wing vibration and rigid-body motions induced by gust perturbation.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)