Article
Mechanics
S. Probsting, Y. Yang, H. Zhang, P. Li, Y. Liu, Y. Li
Summary: This study experimentally explores the effect of Mach number on airfoil tonal noise generation, finding that it has a significant impact on the frequencies and frequency intervals of the separation bubble and vortex shedding process under different angles of attack, while the dependence of tonal noise level on details of the laminar separation bubble and vortex shedding process is more complex.
Article
Mechanics
Lei Shi, Ruiqing Mao, Hongwei Ma, Tianyou Wang
Summary: This study investigates the mean flow topology and vortex dynamics of the transitional flow on the near-tip region of a C4 compressor blade. The experiment reveals the presence of a laminar separation bubble at the aft portion of the blade and strong secondary flow effects near the blade tip. However, there is a transition region between the tip flow and the bottom flow where the velocity fluctuations are significantly reduced.
Article
Mechanics
Gaurav Chopra, Sanjay Mittal
Summary: The impact of the height and location of a trip on the transition of boundary layer on a cylinder is investigated using large eddy simulations. Two modes of transition are observed, with natural transition resulting in lower drag and a larger delay.
Article
Mechanics
Weilin Chen, Yuzhu Li
Summary: It was previously believed that the afterbody is essential for the vortex-induced vibration (VIV) of a bluff body. However, a recent study disproved this belief by successfully demonstrating VIV without an afterbody. This study further confirmed the possibility of VIV in a triangular prism without an afterbody and investigated the physical mechanisms behind it.
Article
Engineering, Aerospace
Yi-Hui Lai, Jiun-Jih Miau, Guang-Ting Zhung, Ming-Che Tsai, Ji-Ci Wu
Summary: This study conducted experiments on three finite circular cylinder models with different aspect ratios in the critical transition range. Oil-film flow visualization revealed the three-dimensionality and nonstationarity of multiple separation lines on each model surface due to intermittent formation of a separation bubble. The symmetry of flow was found to vary with Reynolds number based on the time-averaged pressure coefficients obtained at different heights on each model. A modified peak-valley method was proposed to identify the intermittent events of separation bubble formation.
Article
Engineering, Multidisciplinary
Sujit Kumar, S. Narayanan
Summary: This study numerically investigates the aerodynamic characteristics of symmetric NACA airfoils at various thickness ratios, revealing lift/drag fluctuations at lower thickness ratios and proposing an empirical expression to predict lift and drag coefficients. The far-field acoustic measurements show that thicker airfoils emit lower acoustic emissions compared to thinner ones.
ALEXANDRIA ENGINEERING JOURNAL
(2022)
Article
Engineering, Aerospace
Hua-feng Xu, Sheng-feng Zhao, Ming-yang Wang, Xiao-Ying Sheng, Ge Han, Xin-gen Lu
Summary: This study utilizes experimentally validated Large Eddy Simulation method and Dynamic Mode Decomposition analysis technique to investigate the unsteady flow characteristics on a compressor cascade under different Reynolds number conditions. The results show that at low Reynolds number, large-scale vortices dominate the flow, while at high Reynolds number, vortices become dispersed and smaller. The study also reveals the significant roles of Kelvin-Helmholtz instability and harmonic instability in the flow.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Charles T. Haddad, Joseph Majdalani
Summary: This work investigates traveling and standing vorticoacoustic waves in circular tubes induced by axisymmetric headwall injection using perturbation tools, field decomposition, and boundary-layer theory. An explicit formulation for arbitrary headwall injection is obtained and validated numerically. The characteristics of the evolving vorticoacoustic wave and the velocity features of the vortical field are systematically explored using four canonical cases, revealing the significant amplitudes of the standing modes compared to traveling waves. A uniformly valid wave approximation is achieved by extending the boundary-layer analysis from the headwall to the sidewall.
Article
Mechanics
J. D. Tank, B. F. Klose, G. B. Jacobs, G. R. Spedding
Summary: By combining experimental and numerical studies, the importance of viscous dynamics in understanding the flow field and aerodynamic forces on a cambered airfoil is highlighted. The impact of angle of attack on flow states, including separation, instabilities, and transition to turbulence, is crucial for predicting lift and drag coefficients. Understanding the viscous dynamics of the boundary layer is essential for comprehending the aerodynamics at this scale, as elegantly described by Frank White.
Article
Engineering, Aerospace
Damiano Casalino, Gianluca Romani, Raoyang Zhang, Hudong Chen
Summary: The goal of this paper is to demonstrate the predictive capabilities of the Lattice-Boltzmann/Very-Large-Eddy-Simulation CFD solver SIMULIA PowerFLOW (R) in simulating transitional flow past a small drone rotor blade. The results validate the new PowerFLOW VLES model in predicting boundary layer flow transitional phenomena and corresponding broadband trailing-edge noise radiation.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Marine
Kemal Koca, Mustafa Serdar Genc, Ramazan Ozkan
Summary: The detailed experimental investigation in this study demonstrated that different airfoils on turbine blades can cause the formation of LSB, leading to stochastic vibrations that limit the lifespan of turbine blades.
Article
Geochemistry & Geophysics
Masatoshi Ohashi, Mie Ichihara, Ben Kennedy, Darren Gravley
Summary: The study found that bubble deformation during the Taupo volcanic eruption is mainly controlled by the velocity profile across the conduit, and a piston-like velocity profile reduces the amount of bubble elongation compared to a parabolic velocity profile. This conduit flow condition can explain the frequent occurrence of tube pumice in ignimbrite deposits.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Thermodynamics
Wang Kai, Hong Zhenhan, Liang Hui, Inoue Junya, Cheng Songbai, Koji Okamoto
Summary: Previous studies have focused more on the upward-facing or vertical surface bubble behavior, and the studies on downward-facing bubble behavior are relatively scarce. In this experiment, the bubble moving speed and expanding speed were investigated under different heat flux and mass flux conditions. The results showed that the bubble moving speed followed a normal distribution and was close to the liquid velocity. The bubble expanding speed increased with the heat flux and remained constant for each bubble. A parameter called the heater factor was proposed and found to be relatively constant under different conditions, potentially following a lognormal distribution. These findings provide valuable insights for future development of boiling models.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Thermodynamics
Qiao Lan, Dingding Ye, Xun Zhu, Rong Chen, Qiang Liao
Summary: By embedding a paper separator in microfluidic fuel cells, the rapid gas removal and low ohmic resistance lead to improved fuel transfer and reduced ohmic loss, enhancing cell performance. Although there is frequent fluctuation in current density due to periodic bubble growth and removal, the fluctuation amplitude decreases with the paper separator present, resulting in better cell performance.
Article
Chemistry, Multidisciplinary
Xiaotian Niu, Jie Li
Summary: Reducing drag is crucial in aircraft design and laminar technology plays an important role in drag reduction. This study conducted parameter sensitivity analysis and improved design to optimize the laminar characteristics of the central experimental wing.
APPLIED SCIENCES-BASEL
(2022)
Article
Thermodynamics
Sungmin Ryu, Olaf Marxen, Gianluca Iaccarino
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2015)
Article
Mechanics
Olaf Marxen, Rupesh B. Kotapati, Rajat Mittal, Tamer Zaki
Article
Engineering, Mechanical
Diogo B. Pitz, John W. Chew, Olaf Marxen, Nicholas J. Hills
JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME
(2017)
Article
Computer Science, Interdisciplinary Applications
Olaf Marxen, Thierry E. Magin, Eric S. G. Shaqfeh, Gianluca Iaccarino
JOURNAL OF COMPUTATIONAL PHYSICS
(2013)
Article
Engineering, Mechanical
Diogo B. Pitz, John W. Chew, Olaf Marxen
JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME
(2019)
Article
Mechanics
Rupesh B. Kotapati, Rajat Mittal, Olaf Marxen, Frank Ham, Donghyun You, Louis N. Cattafesta
JOURNAL OF FLUID MECHANICS
(2010)
Article
Mechanics
Olaf Marxen, Dan S. Henningson
JOURNAL OF FLUID MECHANICS
(2011)
Article
Mechanics
Olaf Marxen, Matthias Lang, Ulrich Rist
JOURNAL OF FLUID MECHANICS
(2012)
Article
Mechanics
Olaf Marxen, Matthias Lang, Ulrich Rist
JOURNAL OF FLUID MECHANICS
(2013)
Article
Mechanics
Olaf Marxen, Gianluca Iaccarino, Eric S. G. Shaqfeh
JOURNAL OF FLUID MECHANICS
(2014)
Article
Mechanics
Olaf Marxen, Gianluca Iaccarino, Thierry E. Magin
JOURNAL OF FLUID MECHANICS
(2014)
Article
Mechanics
Olaf Marxen, Thierry Magin, Gianluca Iaccarino, Eric S. G. Shaqfeh
Proceedings Paper
Thermodynamics
Diogo B. Pitz, John W. Chew, Olaf Marxen
PROCEEDINGS OF THE ASME TURBO EXPO: TURBOMACHINERY TECHNICAL CONFERENCE AND EXPOSITION, 2018, VOL 5B
(2018)
Article
Mechanics
Diogo B. Pitz, Olaf Marxen, John W. Chew
JOURNAL OF FLUID MECHANICS
(2017)