Article
Engineering, Mechanical
S. Bull, N. Chiereghin, I Gursul, D. J. Cleaver
Summary: Understanding the aerodynamic response to transient disturbances during gusts, turbulence, or extreme maneuvers, particularly in the presence of Leading-Edge Vortices (LEVs), is crucial for aircraft of all scales. The study found a strong dependence of peak loads on motion amplitude, but relative insensitivity to motion duration. Peak lift did not exceed the prediction of quasi-static thin airfoil theory within the tested parameter range, providing a safe limit for structural design.
JOURNAL OF FLUIDS AND STRUCTURES
(2021)
Article
Energy & Fuels
Jinjing Sun, Shuhan Zhang, Peiyu Cao, Linze Qi
Summary: This study explores the effect of different blade shapes on the aerodynamic performance of NACA series airfoils at Reynolds number Re = 700,000. The CFD method using the SST k-omega turbulence model was used to investigate the effect of leading edge erosion on the aerodynamic performance. The results show that there exists an optimal thickness range for the blade considering the leading edge erosion.
FRONTIERS IN ENERGY RESEARCH
(2023)
Article
Mechanics
Lei Wang, Li-Hao Feng, Yan Liang, Yi-Long Chen, Zhen-Yao Li
Summary: Increasing the momentum coefficient within a certain range can enhance the leading-edge vortex (LEV) and increase the maximum unsteady lift, but may also lead to a reduced duration of high lift compared to the baseline case.
Article
Engineering, Aerospace
Emanuel A. R. Camacho, Flavio D. Marques, Andre R. R. Silva
Summary: The present study focuses on the importance of leading-edge dynamic incidence in the propulsive performance of flapping airfoils. By adding a pitching leading-edge to a conventional NACA0012 airfoil, the propulsive characteristics can be improved. Numerical results show that the leading-edge pitching amplitude greatly affects the propulsive power and efficiency, providing significant improvements.
Article
Engineering, Mechanical
Tong Wang, Li-Hao Feng, Zhen-Yao Li
Summary: This study investigates the impact of leading-edge protuberances on the aerodynamic characteristics of dynamic NACA 0012 wings. It is found that the motion styles significantly affect the lift coefficient of the modified airfoil. Leading-edge protuberances inhibit the formation of secondary vortex and weaken the coherency of the leading-edge vortex, affecting the aerodynamic characteristics of the modified airfoil.
EXPERIMENTS IN FLUIDS
(2021)
Article
Engineering, Aerospace
Yudi Xing, Weijie Chen, Xingyu Wang, Fan Tong, Weiyang Qiao
Summary: This paper presents a numerical study on controlling trailing-edge bluntness noise using bio-inspired wavy leading edges. The results show that the wavy leading edges can significantly reduce the noise level, with a maximum reduction of 35 dB.
Article
Engineering, Aerospace
Sushil Kumar Singh, Mohit Garg, S. Narayanan, Lorna Ayton, Paruchuri Chaitanya
Summary: The present study investigates the efficacy of sinusoidal trailing-edge serrations as a passive means for the reductions of airfoil broadband noise. Comprehensive parametric studies were conducted to determine the effect of serration amplitudes and wavelengths on the noise reduction performance. The study reveals that the relationship between serration wavelength and the transverse turbulence integral scale has a significant impact on the noise reduction. Additionally, TE serrations are found to reduce both trailing-edge noise and leading-edge noise along with the total far-field noise.
JOURNAL OF AEROSPACE ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Yong Wang, Fan Tong, Zhengwu Chen, Chao Wang, Shujie Jiang
Summary: This study aims to reduce rod-airfoil interaction noise by constructing bio-inspired gradient distributed porous leading edges. Experimental comparison of noise radiations from airfoils with nonporous aluminum and porous leading edges was conducted. The results showed that the proposed porous leading edges can significantly reduce noise radiation.
APPLIED SCIENCES-BASEL
(2022)
Article
Thermodynamics
Ming Zhao, Tong Wei, Yijia Zhao, Zhengxian Liu
Summary: In this study, the effects of leading-edge tubercle amplitude on airfoil flow field at high angle of attack were analyzed. The accuracy of large eddy simulation (LES) research was validated through comparisons with experimental results. Proper orthogonal decomposition (POD) analysis was then conducted to identify the fluid mechanisms of corresponding POD modes and uncover the influences of leading-edge tubercle amplitude. It was found that the momentum transfer process and the generation of laminar separation bubble (LSB) were affected by both amplitude and wavelength, and the destruction of Karman vortex shedding process was strengthened with the increase of amplitude.
JOURNAL OF THERMAL SCIENCE
(2023)
Article
Acoustics
Xin Yong, Kun Zhao, Xunnian Wang, Yong Li
Summary: This study investigates the use of detached micro-perforated fairings for reducing turbulence interaction noise. The efficiency of noise control is evaluated by varying the porosity, windward width, and gap distance between the fairing and airfoil LE. The results show that micro-perforated fairings can significantly reduce airfoil LE turbulence interaction noise.
Article
Engineering, Multidisciplinary
Weijie Chen, Liangji Zhang, Liangfeng Wang, Zuojun Wei, Weiyang Qiao
Summary: Numerical studies have shown that leading-edge tubercles inspired by humpback whale flippers can effectively reduce noise. The simulations demonstrate that bionic airfoils with tubercled leading-edges can achieve a considerable noise reduction, and the tubercles with larger amplitudes exhibit better noise reduction performance.
JOURNAL OF BIONIC ENGINEERING
(2022)
Article
Engineering, Mechanical
Mohammad-Reza Pendar, Jose Carlos Pascoa
Summary: The present study investigates the use of wavy leading-edge (WLE) airfoils in combination with curved multidielectric barrier discharge (DBD) plasma actuators as hybrid passive and active flow control mechanisms. The impact of these mechanisms on the flow field is analyzed, including the frequency and noise signals, acoustic effect, vortical structure, aerodynamic forces, velocity variation, and spanwise flow. Two specific DBD plasma actuators are designed and a large eddy simulation (LES) turbulence model is used. The study also employs continuous wavelet transform (CWT) and fast Fourier transform (FFT) methods to analyze the plasma flow spectral content. The results demonstrate that using DBD plasma actuators with WLE airfoils leads to reduced flow separation, faster turbulent transition, and improved efficiency and noise reduction under low Reynolds number conditions.
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2022)
Article
Thermodynamics
Sujit Roy, Agnimitra Biswas, Biplab Das, Bale Reddy
Summary: This study investigates the aerodynamic performance of a modified airfoil with a spherical dimple on the leading edge. The results show that the modification helps in delaying stall by sacrificing a small amount of maximum lift coefficient. The modified airfoil forms two circulation zones, while the plain airfoil only has one.
INTERNATIONAL JOURNAL OF GREEN ENERGY
(2023)
Article
Engineering, Multidisciplinary
Yu Lu, Ziying Li, Xin Chang, Zhenju Chuang, Junhua Xing
Summary: This paper proposes a groundbreaking method for the aerodynamic optimization design of bio-inspired wing with leading-edge tubercles, focusing on the optimization design of spanwise waviness in the leading edge to delay stall and increase lift. Numerical investigations using CFD computations validate the numerical scheme, while the combination of Non-dominated Sorting Genetic Algorithm II and Response Surface Method based Kriging Model is adopted as the aerodynamic optimization strategy.
ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS
(2021)
Article
Thermodynamics
Chengyong Zhu, Yingning Qiu, Yanhui Feng, Tongguang Wang, Hui Li
Summary: Dynamic stall on wind turbines causes highly unsteady and nonlinear aerodynamic loads. This study investigates the combined effect of passive vortex generators (VGs) and leading-edge roughness (LER) on dynamic stall of the NREL S809 airfoil. Results show that LER accelerates separated flow and dynamic stall onset, while VGs delay dynamic stall and reduce aerodynamic hysteresis. Additionally, double-row VGs outperform single-row VGs in improving aerodynamic performance of roughened airfoils.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Engineering, Mechanical
Anoop Sasidharan, Ratna Kishore Velamati, Venkata Ramana Murthy Oruganti, Akram Mohammad
Summary: This study presents an unsteady analysis of the aerodynamic characteristics and stability derivatives of an aerostat. The analysis considers the effect of wind gusts and oscillations on the aerostat's motion. The study validates the aerostat model using experimental data and examines parameters such as phase shift, wind gust amplitude, angle of attack, and gust duration. The stability derivatives are extracted using CFD simulations and validated with experimental data. The results show that drag response is highest at a 180-degree phase shift, while lift and moment responses lag at 0-degree phase shift. The aerostat's response to gust amplitude variation is linear, and drag response is less influenced by changes in angle of attack.
JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
(2022)
Article
Thermodynamics
Satender Singh, Jithin Edacheri Veetil, Neeraj Kumbhakarna, Ratna Kishore Velamati, Sudarshan Kumar
Summary: The effect of hydrogen addition on the flame dynamics of premixed methane/air mixtures in a microchannel was investigated using numerical computations. It was found that hydrogen addition induces flame repetitive extinction and ignition, and affects the frequency and duration of the repetitive cycles. Furthermore, hydrogen addition decreases the maximum temperature and heat of the reaction, and shifts the ignition and extinction locations.
COMBUSTION THEORY AND MODELLING
(2022)
Article
Chemistry, Physical
Jithin Edacheri Veetil, Neeraj Kumbhakarna, Satender Singh, Ratna Kishore Velamati, Sudarshan Kumar
Summary: The effect of hydrogen addition on the flame dynamics of premixed C1-C4 alkane/air mixtures in a microchannel was investigated using numerical computations. The addition of hydrogen enhanced the flame stability of hydrocarbon/air mixtures in the microchannel, but had little effect on high carbon alkanes.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Chemistry, Physical
Ratna Kishore Velamati, Sathyajith Raj, P. Parthasarathy, Jithin Edacheri Veetil
Summary: Hot surface ignition of combustible gas mixtures is a safety concern in many engineering applications. This study investigates the impact of heating rates, wire diameters, mixture inlet velocities, and mixture equivalence ratios on the ignition threshold using numerical simulations. The results show that ignition occurs mainly at the rear stagnation point, and the wire heating rate has minimal influence on the ignition phenomenon. However, the ignition threshold increases with higher mixture inlet velocities and equivalence ratios, while it decreases with larger wire diameters. The study also examines the role of local equivalence ratios and reaction rates in understanding the ignition process under different conditions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Multidisciplinary Sciences
Sakthi Prakash Murugu, A. R. Srikrishnan, Bharath Kumar Krishnaraj, Anguraj Jayaraj, Akram Mohammad, Ratna Kishore Velamati
Summary: This study focuses on the numerical modeling of the acoustic field in a compressible jet issuing from a chevron nozzle. The effectiveness of different turbulence modeling approaches was evaluated, and the results showed that the Large Eddy Simulation method had a good agreement with experimental data, while the Unsteady Reynolds Averaged Navier-Stokes model significantly underestimated the sound pressure levels.
Review
Energy & Fuels
Vinay Sankar, Sreejith Sudarsanan, Sudipto Mukhopadhyay, Prabhu Selvaraj, Aravind Balakrishnan, Ratna Kishore Velamati
Summary: As the demand for powerful, light energy sources grows, traditional electrochemical batteries cannot meet the requirements, and combustion-based power generation devices with high energy density, compact size, fast recharging time, and long service life have become an attractive alternative. In the research on miniature-scale combustors, the use of liquid fuels has the potential to be highly portable and economical. However, the complex processes of droplet atomization, evaporation, mixing, and burning in a limited volume and short residence time present significant challenges. This review focuses on various methodologies proposed by researchers to overcome these challenges and explores the combustion behavior and different instabilities associated with liquid fuels at small scales.
Article
Energy & Fuels
Priyadharshini Murugesan, A. R. Srikrishnan, Akram Mohammad, Ratna Kishore Velamati
Summary: Numerical simulations were conducted to investigate the influence of convective heat transfer on flow separation in a DLP-PAR nozzle. Different heat transfer coefficients (0, 200, and 1000 w/m(2)K) were applied on the nozzle wall for various gas inlet temperatures (1000 to 1500 K). The cooling effect was analyzed by examining the nozzle wall temperature and wall static pressure, which also characterized the movement of the separation point. The study found that convective cooling can delay flow separation for inlet gas temperatures below 1500 K, contributing to the optimal performance of the nozzle.
Article
Energy & Fuels
Lakshmi Srinivasan, Nishanth Ram, Sudharshan Bharatwaj Rengarajan, Unnikrishnan Divakaran, Akram Mohammad, Ratna Kishore Velamati
Summary: In this paper, a 2D URANS numerical analysis is used to study the performance of an H-Darrieus VAWT. The study finds that random velocity inlet can improve the turbine's performance compared to uniform velocity inlet, with the optimal tip speed ratio being around 4.1. Additionally, the effect of wind speed fluctuations on turbine performance in a turbulent environment is analyzed using the IEC Extreme Operating Gust model. It is found that the mean coefficient of power decreases as gust amplitude increases, due to large fluctuations in incoming velocity.
Article
Physics, Multidisciplinary
Nithin Somasekharan, A. R. Srikrishnan, Harihara Sudhan Kumar, Krishna Prasad Ganesh, Akram Mohammad, Ratna Kishore Velamati
Summary: Film cooling of rocket nozzles is numerically analyzed in this study, with focus on assessing the mixing effect of coolant and hot stream. The cooling effectiveness is studied for three different coolants in a three-dimensional, turbulent flow field of a supersonic convergent-divergent nozzle operating at a hot stream temperature of 2500 K. Factors such as coolant injector configuration and mixing layer are analyzed to understand their influence on the cooling performance. The results provide insights into the film cooling performance and heat transfer characteristics of the three gases studied, and indicate that the cooling effectiveness can be significantly improved through optimization of blowing ratio and coolant injector configuration.
Article
Remote Sensing
Anoop Sasidharan, Ratna Kishore Velamati, Sheeja Janardhanan, Venkata Ramana Murthy Oruganti, Akram Mohammad
Summary: This study proposes the use of an aerostat with a single tether for low-altitude wind measurements. The aerodynamic model parameters of the aerostat are investigated using a CFD-based approach, and both static and dynamic stability derivatives are presented. The results suggest that the Zhiyuan aerostat has better performance in terms of lift-drag ratio and dynamic stability derivatives, making it a suitable choice for the proposed low-altitude wind measurement system.
Article
Engineering, Aerospace
Andre F. P. Ribeiro, Carlos Ferreira, Damiano Casalino
Summary: This study compares a filament-based free wake panel method to experimental and validated numerical data in order to simulate propeller slipstreams and their interaction with aircraft components. The results show that the free wake panel method is able to successfully capture the slipstream deformation and shearing, making it a useful tool for propeller-wing interaction in preliminary aircraft design.
AEROSPACE SCIENCE AND TECHNOLOGY
(2024)