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Journal articles on the topic 'Vortex-motion. Boundary layer. Aerodynamics'

Author: Grafiati

Published: 4 June 2021

Last updated: 19 February 2022

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1

Volchkov, �. P., S. V. Semenov, and V. I. Terekhov. "Aerodynamics of end-wall boundary layer in a vortex chamber." Journal of Applied Mechanics and Technical Physics 27, no. 5 (1987): 740–48. http://dx.doi.org/10.1007/bf00916149.

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2

Štorch, Vít, and Jiří Nožička. "CONTRA-ROTATING PROPELLER AERODYNAMICS SOLVED BY A 3D PANEL METHOD WITH COUPLED BOUNDARY LAYER." Acta Polytechnica 57, no. 5 (2017): 355. http://dx.doi.org/10.14311/ap.2017.57.0355.

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The aerodynamics of contra-rotating propellers is a complex three-dimensional problem of an unsteady flow, which is often approached by assuming numerous simplifications. Presented computational model combines a 3D panel method with a force-free vortex wake and a two-dimensional two-equation boundary layer model in an attempt to capture all the main contributing elements of the flow physics. An emphasis is placed on the interaction of the viscous boundary layer region with the inviscid region and the development of a portable method of their coupling. The kinematics of a force-free vortex wake

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3

Ayudia, Siti Aisyah, Artoto Arkundato, and Lutfi Rohman. "Study of Vortex Generator Effect on Airfoil Aerodynamics Using the Computational Fluids Dynamics Method." Computational And Experimental Research In Materials And Renewable Energy 3, no. 2 (2020): 23. http://dx.doi.org/10.19184/cerimre.v3i2.23547.

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The lift force is one of the important factors in supporting the aircraft flying capabilities. The airplane has a section called the aircraft wing. In particular, the wing section of aircraft is called the airfoil. One of the efforts to increase the lift force is to make the flow of air fluid at the top of the airfoil more turbulent. Turbulent flow can attract momentum from the boundary layer, the result of this momentum transfer has energy that is more resistant to the adverse pressure gradient which can trigger the flow separation. Efforts that can be made to reduce separation flow and incre

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4

Ibaraki, Seiichi, Tetsuya Matsuo, Hiroshi Kuma, Kunio Sumida, and Toru Suita. "Aerodynamics of a Transonic Centrifugal Compressor Impeller." Journal of Turbomachinery 125, no. 2 (2003): 346–51. http://dx.doi.org/10.1115/1.1540117.

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High-pressure ratio centrifugal compressors are applied to turbochargers and turboshaft engines because of their small dimensions, high efficiency, and wide operating range. Such a high-pressure ratio centrifugal compressor has a transonic inlet condition accompanied with a shock wave in the inducer portion. It is generally said that extra losses are generated by interaction of the shock wave and the boundary layers on the blade surface. To improve the performance of high-pressure ratio centrifugal compressor, it is necessary to understand the flow phenomena. Although some research works on tr

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5

Ladopoulos, E. G. "Nonlinear unsteady flow problems by multidimensional singular integral representation analysis." International Journal of Mathematics and Mathematical Sciences 2003, no. 50 (2003): 3203–16. http://dx.doi.org/10.1155/s0161171203112318.

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A two-dimensional nonlinear aerodynamics representation analysis is proposed for the investigation of inviscid flowfields of unsteady airfoils. Such problems are reduced to the solution of a nonlinear multidimensional singular integral equation as the source and vortex strength distributions are dependent on the history of these distributions on the NACA airfoil surface. A turbulent boundary layer model is further investigated, based on the formulation of the unsteady behaviour of the momentum integral equation. An application is finally given to the determination of the velocity and pressure

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6

JEONG, MIN-SOO, SEUNG-JAE YOO, and IN LEE. "WIND TURBINE AERODYNAMICS PREDICTION USING FREE-WAKE METHOD IN AXIAL FLOW." International Journal of Modern Physics: Conference Series 19 (January 2012): 166–72. http://dx.doi.org/10.1142/s2010194512008707.

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Wind turbine aerodynamics remains a particularly challenging and crucial research for wind energy industry. The blade element momentum theory is the most widely used in predicting the performance of wind turbine, since the method is simple and fast numerical algorithm. The flow field generated by rotary wing is considerably important and complicated, however, the BEM method has some limitations to model the unsteady effects. To overcome these limitations, the aerodynamic analysis using a time-marching free-vortex wake method was performed in this paper. Moreover, the inboard region of the blad

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7

Furukawa, M., M. Inoue, K. Saiki, and K. Yamada. "The Role of Tip Leakage Vortex Breakdown in Compressor Rotor Aerodynamics." Journal of Turbomachinery 121, no. 3 (1999): 469–80. http://dx.doi.org/10.1115/1.2841339.

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The breakdown of tip leakage vortex has been investigated on a low-speed axial compressor rotor with moderate blade loading. Effects of the breakdown on the rotor aerodynamics are elucidated by Navier–Stokes flow simulations and visualization techniques for identifying the breakdown. The simulations show that the leakage vortex breakdown occurs inside the rotor at a lower flow rate than the peak pressure rise operating condition. The breakdown is characterized by the existence of the stagnation point followed by a bubblelike recirculation region. The onset of breakdown causes significant chang

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8

Wellenberg, Sören, Markus Marnett, Benedikt Roidl, Davis Kirkendall, Frederik Thönnißen, and Wolfgang Schröder. "Assessment of a numerical design tool for pitching airfoils." Wind Engineering 43, no. 6 (2019): 639–56. http://dx.doi.org/10.1177/0309524x18821883.

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The aim of this study was to assess the applicability of a numerical design tool for pitching airfoils; by evaluating their aerodynamic performance comparing experimental and numerical data at different levels of complexity. Experimental findings of non-harmonically pitching airfoil configurations in a water tunnel at medium Reynolds numbers are compared to solutions of a modified double-wake vortex-panel method with boundary-layer formulation and unsteady Reynolds-averaged Navier–Stokes simulations. For steady-state airfoil configurations at high angle of attack, large eddy simulation data ar

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9

Gennaretti, M., and C. Ponzi. "Finite-state aerodynamic modelling for gust load alleviation of wing–tail configurations." Aeronautical Journal 103, no. 1021 (1999): 147–58. http://dx.doi.org/10.1017/s0001924000064964.

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Abstract A finite-state aerodynamics methodology is proposed for the analysis of the forces generated by a gust. To illustrate and assess the methodology, gust-response and gust-alleviation applications are included. Finite-state aerodynamics denotes a technique to approximate aerodynamic loads so as to yield an aircraft model of the type ẋ = Ax + Bu (state-space formulation). In this paper, a finite-state formulation is proposed to include the presence of a gust. The aerodynamic loads to be approximated are evaluated here by using a frequency-domain boundary-element formulation; the flow is a

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10

Anwar Bég, O., H. S. Takhar, G. Nath, and A. J. Chamkha. "Mathematical Modelling of Hydromagnetic Convection from a Rotating Sphere with Impulsive Motion and Buoyancy Effects." Nonlinear Analysis: Modelling and Control 11, no. 3 (2006): 227–45. http://dx.doi.org/10.15388/na.2006.11.3.14744.

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The convective heat transfer on a rotating sphere in the presence of magnetic field, buoyancy forces and impulsive motion is examined theoretically and numerically in this paper. We apply a boundary layer model comprising the balance equations for x and y direction translational momentum and heat transfer, and solve these coupled non-linear partial differential equations using Blottner’s finite-difference method [1]. The numerical solutions are benchmarked with the earlier study by Lee [2] on laminar boundary layer flow over rotating bodies in forced flow and found to be in excellent agreement

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11

Tamada, Chandan Varma, and Sai Ganesh Sabbavarapu. "Flow Visualization of Footballs to Analyze the Factors Affecting their Aerodynamic Performance Using CFD." Volume 5 - 2020, Issue 9 - September 5, no. 9 (2020): 460–75. http://dx.doi.org/10.38124/ijisrt20sep296.

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The motion of a football in air is influenced by the combination of various aerodynamic effects caused by the parameters such as velocity, surface roughness, panel orientation and shape. This paper analyzes the individual and combined effects of these parameters on the flight characteristics of various footballs using CFD Analysis. Four balls, a smooth sphere, a 32-panel conventional football, 14-panel Teamgeist and 6-panel Brazuca ball are subjected to different velocities of air flow over them, both in the laminar and turbulent regime, different surface roughness values and the influence of

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12

MARZOUK, YOUSSEF M., and AHMED F. GHONIEM. "Vorticity structure and evolution in a transverse jet." Journal of Fluid Mechanics 575 (March 2007): 267–305. http://dx.doi.org/10.1017/s0022112006004411.

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Transverse jets arise in many applications, including propulsion, effluent dispersion, oil field flows, and V/STOL aerodynamics. This study seeks a fundamental, mechanistic understanding of the structure and evolution of vorticity in the transverse jet. We develop a high-resolution three-dimensional vortex simulation of the transverse jet at large Reynolds number and consider jet-to-crossflow velocity ratiosrranging from 5 to 10. A new formulation of vorticity-flux boundary conditions accounts for the interaction of channel wall vorticity with the jet flow immediately around the orifice. We de

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13

Pribytkov, I. A., and S. I. Kondrashenko. "AERODYNAMICS OF JETS INTERACTING WITH A FLAT SURFACE." Izvestiya. Ferrous Metallurgy 62, no. 4 (2019): 263–69. http://dx.doi.org/10.17073/0368-0797-2019-4-263-269.

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In this paper, the development features of a single free jet of hightemperature nitrogen interacting with a ﬂat surface were studied. Calculation of the heat exchange process during heating by the attacking jets is very difficult to implement analytically due to complexity of the gas-dynamic processes occurring both in a single jet and in a system of jets interacting with the metal. The computational difficulties are aggravated by the fact that when interacting with the surface the jet as such disappears. The ﬂat (fan) ﬂow interacts with the surface: form, aerodynamic properties and thermal st

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14

Dearing, S., S. Lambert, and J. Morrison. "Flow control with active dimples." Aeronautical Journal 111, no. 1125 (2007): 705–14. http://dx.doi.org/10.1017/s0001924000004887.

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Abstract The long-term goal is to design and manufacture optimal ‘on-demand’ vortex generators, ‘dimples’ that can produce vortices of prescribed strength and duration for the real-time control of aerodynamic flows that are either undergoing transition or are fully turbulent, attached or separating. Electro-active polymers (EAP) are ideal for a dimple control surface, offering high strain rate, fast response, and high electromechanical efficiency. EAP can also be used as the basis of a resistanc – or capacitance – change pressure sensor, development of which has just begun. In terms of manufac

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15

Löffler, Stephan, Carola Ebert, and Julien Weiss. "Fluidic-Oscillator-Based Pulsed Jet Actuators for Flow Separation Control." Fluids 6, no. 4 (2021): 166. http://dx.doi.org/10.3390/fluids6040166.

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The control of flow separation on aerodynamic surfaces remains a fundamental goal for future air transportation. On airplane wings and control surfaces, the effects of flow separation include decreased lift, increased drag, and enhanced flow unsteadiness and noise, all of which are detrimental to flight performance, fuel consumption, and environmental emissions. Many types of actuators have been designed in the past to counter the negative effects of flow separation, from passive vortex generators to active methods like synthetic jets, plasma actuators, or sweeping jets. At the Chair of Aerody

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16

Zaman, K. B. M. Q., D. J. Mckinzie, and C. L. Rumsey. "A natural low-frequency oscillation of the flow over an airfoil near stalling conditions." Journal of Fluid Mechanics 202 (May 1989): 403–42. http://dx.doi.org/10.1017/s0022112089001230.

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An unusually low-frequency oscillation in the flow over an airfoil is studied experimentally as well as computationally. Wind-tunnel measurements are carried out with two-dimensional airfoil models in the chord Reynolds number (Rc) range of 0.15 × 105−3.0 × 105. During deep stall, at α [gsim ] 18°, the usual ‘bluff-body shedding’ occurs at a Strouhal number, Sts ≈ 0.2. But at the onset of static stall around α = 15°, a low-frequency periodic oscillation is observed, the corresponding Sts being an order of magnitude lower. The phenomenon apparently takes place only with a transitional state of

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17

Chughtai, F. A., J. Masud, and S. Akhtar. "Unsteady aerodynamics computation and investigation of magnus effect on computed trajectory of spinning projectile from subsonic to supersonic speeds." Aeronautical Journal 123, no. 1264 (2019): 863–89. http://dx.doi.org/10.1017/aer.2019.32.

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AbstractThis paper describes the extensive numerical investigation carried out on a 203-mm spin-stabilised projectile to study the effects of Magnus force at high angles of attack on the stability and flight-trajectory parameters, for further validation and incorporation in a 6-DOF trajectory solver for flight-stability analysis. Magnus force typically influences the course of flight by causing the projectile to drift from its intended path in addition to generation of inbuilt dynamic instabilities in pitch and yaw orientation and is a function of AoA and spin rate. This study is a consolidati

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18

Conway, Ciaran, and Jeff Punch. "The Influence of Surface Roughness on the Flow Fields Generated by an Oscillating Cantilever." EPJ Web of Conferences 180 (2018): 02017. http://dx.doi.org/10.1051/epjconf/201818002017.

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With the current trend of miniaturisation of electronic devices, piezoelectric fans have attracted increasing interest as a means of inducing forced convection cooling, instead of traditional rotary solutions. Although there exists an abundance of research on various piezo-actuated flapping fans in the literature, the geometries of these fans all consist of a smooth rectangular cross section with thicknesses typically of the order of 100 μm. The focus of these studies has primarily been on variables such as frequency, amplitude and, in some cases, resonance mode. It is generally noted that the

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19

Régis, Koch, Sanjosé Marlène, and Moreau Stéphane. "Aerodynamic investigation of a linear cascade with tip gap using large-eddy simulation." Journal of the Global Power and Propulsion Society 5 (April 7, 2021): 39–49. http://dx.doi.org/10.33737/jgpps/133601.

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The flow in a linear compressor cascade with tip gap is simulated using a wall-resolved compressible Large-Eddy Simulation. The cascade is based on the Virginia Tech Low Speed Cascade Wind Tunnel. The Reynolds number based on the chord is 3.88 x 10⁵ and the Mach number is 0.07. The gap considered in this study is 4.0 mm (2.9% of axial chord). An aerodynamic analysis of the tip-leakage flow allow us identifying the main mechanisms responsible for the development and the convection of the tip-leakage vortex downstream of the cascade. A region of high turbulence and vorticity levels is located al

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20

Sutardi, S., and Agung E. Nurcahya. "Experimental Study on the Effect of Vortex Generator on the Aerodynamic Characteristics of NASA LS-0417 Airfoil." Applied Mechanics and Materials 758 (April 2015): 63–69. http://dx.doi.org/10.4028/www.scientific.net/amm.758.63.

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Boundary layer flow structure developing on an airfoil surfaces strongly affects drag and lift forces acting on the body. Many studies have been done to reduce drag, such as introducing surface roughness on the airfoil surface, gas injection, attachment of vortex generators, or moving surface on the airfoil. Previous results showed that the attachment of vortex generators has potentially been able to control boundary layer separation compared to other controlling devices. This study is focused on the evaluation of the effect of vortex generator attachment on the NASA LS-0417 airfoil profile as

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21

Li, Xinkai, Ke Yang, and Xiaodong Wang. "Experimental and Numerical Analysis of the Effect of Vortex Generator Height on Vortex Characteristics and Airfoil Aerodynamic Performance." Energies 12, no. 5 (2019): 959. http://dx.doi.org/10.3390/en12050959.

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To explore the effect of the height of vortex generators (VGs) on the control effect of boundary-layer flow, the vortex characteristics of a plate and the aerodynamic characteristics of an airfoil for VGs were studied by both wind tunnel experiments and numerical methods. Firstly, the ratio of VG height (H) to boundary layer thickness (δ) was studied on a flat plate boundary layer; the values of H are 0.1δ, 0.2δ, 0.5δ, 1.0δ, 1.5δ, and 2.0δ. Results show that the concentrated vortex intensity and VG height present a logarithmic relationship, and vortex intensity is proportional to the average k

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22

Showkat Ali, Syamir Alihan, Mahdi Azarpeyvand, and Carlos Roberto Ilário da Silva. "Trailing-edge flow and noise control using porous treatments." Journal of Fluid Mechanics 850 (July 2, 2018): 83–119. http://dx.doi.org/10.1017/jfm.2018.430.

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This paper is concerned with the application of porous treatments as a means of flow and aerodynamic noise reduction. An extensive experimental investigation is undertaken to study the effects of flow interaction with porous media, in particular in the context of the manipulation of flow over blunt trailing edges and attenuation of vortex shedding. Comprehensive boundary layer and wake measurements have been carried out for a long flat plate with solid and porous blunt trailing edges. Unsteady velocity and surface pressure measurements have also been performed to gain an in-depth understanding

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23

Zhang, Chen Kai, Jun Hu, Zhi Qiang Wang, and Shi Qi Yu. "Experimental Studies of the Endwall Flow in a Multistage Low-Speed Axial Compressor." Advanced Materials Research 718-720 (July 2013): 1504–9. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.1504.

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Detailed flowfield measurements are made in the end-wall region of a four-stage low-speed large-scare axial compressor test rig. Two ten-hole survey boundary layer probes, one four-hole pneumatic probe, and six dynamic pressure probes each bedded with a high-frequence response Kulite sensor, are designed and manufactured to aid the test. Boundary layer region and mainflow region can be clearly distinguished from the boundary layer measurement results. A few parameters, including boundary layer thickness, displace thickness, momentum loss thickness, energy loss thickness and blockage coefficien

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24

Fernandez-Gamiz, Unai, Jon Ruiz de Loizaga, Iñigo Errasti, Ana Boyano, Ekaitz Zulueta, and Jose Manuel Lopez-Guede. "Computational modelling of TRIANGULAR sub-boundary-layer vortex generators." MATEC Web of Conferences 307 (2020): 01054. http://dx.doi.org/10.1051/matecconf/202030701054.

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Vortex generators (VGs) are used increasingly more by the wind turbine manufacture industry as flow control devices to improve rotor blade aerodynamic performance. The VG height is usually designed with equal thickness of the local boundary layer at the VG position. Nevertheless, these conventional VGs may produce excess residual drag in some applications. The so-called sub boundary layer VGs can provide enough momentum transfer over a region several times their own height for effective flow-separation control with much lower drag. The main objective is to investigate how well the simulations

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25

Šoltýs, Robert, and Michal Tomko. "Numerical Estimation of Aerodynamic Characteristics of Footbridge Deck." Applied Mechanics and Materials 617 (August 2014): 291–95. http://dx.doi.org/10.4028/www.scientific.net/amm.617.291.

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For estimation of aerodynamic characteristics of cable-stayed footbridge deck a computational fluid dynamics (CFD) has been used. An incompressible fluid flow with Navier-Stokes equations has been applied. An adequate numerical model has been created to obtain accurate values of aerodynamic characteristics. Preliminary determination of simulation parameters have been estimated using laminar fluid flow model. Subsequently, Smagorinsky large-eddy simulation (LES) turbulent model has been applied with different simulation parameters to obtain converged values. The boundary layer separation region

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26

Dhanak, M. R. "Equation of motion of a diffusing vortex sheet." Journal of Fluid Mechanics 269 (June 25, 1994): 265–81. http://dx.doi.org/10.1017/s0022112094001552.

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Moore's (1978) equation for following the evolution of a thin layer of uniform vorticity in two dimensions is extended to the case of a non-uniform, instantaneously known, vorticity distribution, using the method of matched asymptotic expansions. In general, the vorticity distribution satisfies a boundary-layer equation. This has a similarity solution in the case of a vortex layer of small thickness in a viscous fluid. Using this solution, an equation of motion of a diffusing vortex sheet is obtained. The equation retains the simplicity of Birkhoff's integro-differential equation for a vortex

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27

Tejero Embuena, Fernando, Piotr Doerffer, Pawel Flaszynski, and Oskar Szulc. "Passive flow control application for rotorcraft in transonic conditions." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 5 (2018): 1080–95. http://dx.doi.org/10.1108/hff-06-2017-0231.

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Purpose Helicopter rotor blades are usually aerodynamically limited by the severe conditions present in every revolution: strong shock wave boundary layer interaction on the advancing side and dynamic stall on the retreating side. Therefore, different flow control strategies might be applied to improve the aerodynamic performance. Design/methodology/approach The present research is focussed on the application of passive rod vortex generators (RVGs) to control the flow separation induced by strong shock waves on helicopter rotor blades. The formation and development in time of the streamwise vo

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28

Li, Xin-kai, Wei Liu, Ting-jun Zhang, Pei-ming Wang, and Xiao-dong Wang. "Analysis of the Effect of Vortex Generator Spacing on Boundary Layer Flow Separation Control." Applied Sciences 9, no. 24 (2019): 5495. http://dx.doi.org/10.3390/app9245495.

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During the operation of wind turbines, flow separation appears at the blade roots, which reduces the aerodynamic efficiency of the wind turbine. In order to effectively apply vortex generators (VGs) to blade flow control, the effect of the VG spacing (λ) on flow control is studied via numerical calculations and wind tunnel experiments. First, the large eddy simulation (LES) method was used to calculate the flow separation in the boundary layer of a flat plate under an adverse pressure gradient. The large-scale coherent structure of the boundary layer separation and its evolution process in the

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29

Lu, Hua-wei, Yi Yang, Shang Guo, Yu-xuan Huang, Hong Wang, and Jing-jun Zhong. "Flow control in linear compressor cascades by inclusion of suction side dimples at varying locations." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (2018): 706–21. http://dx.doi.org/10.1177/0957650917752276.

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The flow characteristics and loss behavior over an array of parallel recessed dimples on a high turning linear compressor cascade have been investigated using the Reynolds-averaged Navier–Stokes approach. Steady simulations have been carried out at three dimple locations of 10–32%, 38–60%, 60–82% chord length of suction surface with the inlet Mach number of 0.7. Flow conditions were compared in exit loss coefficient, static pressure rise, streamline patterns, vortex structures, boundary layer parameters, and blade surface pressure between the smooth and the modified cascades. The results indic

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30

Kubo, Yoshinobu. "Prospects for the Suppression of Aeroedynamic Vibrations of a Long-Span Bridge Using Boundary-Layer Control." Journal of Vibration and Control 10, no. 9 (2004): 1359–73. http://dx.doi.org/10.1177/1077546304042050.

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Aerodynamic vibrations inherently occur on a long-span-length bridge. The vibrations are roughly classified into vortex-excited vibration and self-excited vibration both are induced by separation flow from the leading edge of the structure. As aerodynamic vibrations frequently cause fatal damage to the structure, the suppression method of vibration has been studied for a long time. Two methods have been proposed for suppression of the vibrations: a structural method and an aerodynamic method. The former is a tuned mass damper or a tuned liquid damper, and the latter is a separation flow contro

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31

Ersoy, S., and J. D. A. Walker. "The boundary layer due to a three-dimensional vortex loop." Journal of Fluid Mechanics 185 (December 1987): 569–98. http://dx.doi.org/10.1017/s002211208700332x.

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The nature of the boundary layer induced by the motion of a three-dimensional vortex loop towards a plane wall is considered. Initially the vortex is taken to be a ring approaching a plane wall at an angle of attack in an otherwise stagnant fluid; the ring rapidly distorts into a loop shape due to the influence of the wall and the trajectory is computed from a numerical solution of the Biot-Savart integral. As the vortex loop moves, an unsteady boundary-layer flow develops on the wall. A method is described which allows the computation of the flow velocities on and near the symmetry plane of t

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32

Wilfert, G., and L. Fottner. "The Aerodynamic Mixing Effect of Discrete Cooling Jets With Mainstream Flow on a Highly Loaded Turbine Blade." Journal of Turbomachinery 118, no. 3 (1996): 468–78. http://dx.doi.org/10.1115/1.2836692.

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For the application of film cooling to turbine blades, experimental investigations were performed on the mixing processes in the near-hole region with a row of holes on the suction suction side of a turbine cascade. Data were obtained using pneumatic probes, pressure tappings, and a three-dimensional subminiature hot-wire probe, as well as surface flow visualization techniques. It was found that at low blowing rates, a cooling jet behaves very much like a normal obstacle and the mixing mainly takes place in the boundary layer. With increasing blowing rates, the jet penetrates deeper into the m

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33

Martinez Suarez, Javier, Pawel Flaszynski, and Piotr Doerffer. "Streamwise vortex generator for separation reduction on wind turbine rotors." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 5 (2018): 1047–60. http://dx.doi.org/10.1108/hff-05-2017-0203.

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Purpose The purpose of this paper is to describe numerical investigations focused on the reduction of separation and the aerodynamic enhancement of wind turbine blades by a rod vortex generator (RVG). Design/methodology/approach A flow modelling approach through the use of a Reynolds-averaged Navier–Stokes solver is used. The numerical tools are validated with experimental data for the NREL Phase VI rotor and the S809 aerofoil. The effect of rod vortex generator’s (RVG) configuration on aerofoil aerodynamic performance, flow structure and separation is analysed. RVGs’ chordwise locations and s

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34

Widmann, A., and C. Tropea. "Parameters influencing vortex growth and detachment on unsteady aerodynamic profiles." Journal of Fluid Mechanics 773 (May 26, 2015): 432–59. http://dx.doi.org/10.1017/jfm.2015.259.

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Experiments with a pitching and plunging airfoil are conducted in order to investigate the mechanisms responsible for the formation and detachment of leading edge vortices (LEVs). The chord length is varied from 90 to 180 mm, keeping all other non-dimensional parameters constant, specifically the Reynolds number (17 000), the Strouhal number (0.25), the reduced frequency (0.5) and the effective angle of attack history. It is shown that the mechanism of vortex detachment changes with chord length, evident in a corresponding change in flow topology. One mechanism scales with chord length, the ot

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35

Sonoda, T., T. Arima, and M. Oana. "The Effect of Inlet Boundary Layer Thickness on the Flow Within an Annular S-Shaped Duct." Journal of Turbomachinery 121, no. 3 (1999): 626–34. http://dx.doi.org/10.1115/1.2841361.

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Experimental and numerical investigations were carried out to gain a better understanding of the flow characteristics within an annular S-shaped duct, including the effect of the inlet boundary layer (IBL) on the flow. A duct with six struts and the same geometry as that used to connect compressor spools on our experimental small two-spool turbofan engine was investigated. A curved downstream annular passage with a similar meridional flow path geometry to that of the centrifugal compressor has been fitted at the exit of S-shaped duct. Two types of the IBL (i.e., thin and thick IBL) were used.

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36

LÖGDBERG, OLA, JENS H. M. FRANSSON, and P. HENRIK ALFREDSSON. "Streamwise evolution of longitudinal vortices in a turbulent boundary layer." Journal of Fluid Mechanics 623 (March 6, 2009): 27–58. http://dx.doi.org/10.1017/s0022112008004825.

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In this experimental study both smoke visualization and three-component hot-wire measurements have been performed in order to characterize the streamwise evolution of longitudinal counter-rotating vortices in a turbulent boundary layer. The vortices were generated by means of vortex generators (VGs) in different configurations. Both single pairs and arrays in a natural setting as well as in yaw have been considered. Moreover three different vortex blade heights h, with the spacing d and the distance to the neighbouring vortex pair D for the array configuration, were studied keeping the same d/

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Jiang, Yubiao, Wanbo Wang, Chen Qin, Patrick N. Okolo, and Kun Tang. "Investigation of the Normal Blowing Approach to Controlling Wingtip Vortex Using LES." International Journal of Aerospace Engineering 2021 (May 25, 2021): 1–15. http://dx.doi.org/10.1155/2021/6688569.

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The characteristics and control of a wingtip vortex are of great significance when considering drag reduction and flight safety of transportation aircrafts. The associated aerodynamic phenomenon resulting from rolling up of a wingtip vortex includes boundary layer flow, shear layer separation, and vortex breakdown, while the interaction of a wingtip vortex with the airframe causes induced drag, wingtip noise, etc. This paper studies a normal blowing method utilized to control the wingtip vortex. Large eddy simulation (LES) technique applied to a straight NACA0012 wing having a chord length ( c

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Ye, Qingqing, Ferry F. J. Schrijer, and Fulvio Scarano. "Boundary layer transition mechanisms behind a micro-ramp." Journal of Fluid Mechanics 793 (March 14, 2016): 132–61. http://dx.doi.org/10.1017/jfm.2016.120.

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The early stage of three-dimensional laminar-to-turbulent transition behind a micro-ramp is studied in the incompressible regime using tomographic particle image velocimetry. Experiments are conducted at supercritical micro-ramp height $h$ based Reynolds number $Re_{h}=1170$. The measurement domain encompasses 6 ramp widths spanwise and 73 ramp heights streamwise. The mean flow topology reveals the underlying vortex structure of the wake flow with multiple pairs of streamwise counter-rotating vortices visualized by streamwise vorticity. The primary pair generates a vigorous upwash motion in th

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Russell, Craig L., P. J. Blennerhassett, and P. J. Stiles. "Strongly nonlinear vortices in magnetized ferrofluids." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 40, no. 2 (1998): 146–70. http://dx.doi.org/10.1017/s0334270000012443.

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AbstractNonlinear convective roll cells that develop in thin layers of magnetized ferrofluids heated from above are examined in the limit as the wavenumber of the cells becomes large. Weakly nonlinear solutions of the governing equations are extended to solutions that are valid at larger distances above the curves of marginal stability. In this region, a vortex flow develops where the fundamental vortex terms and the correction to the mean are determined simultaneously rather than sequentially. The solution is further extended into the nonlinear region of parameter space where the flow has a c

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Affes, H., Z. Xiao, and A. T. Conlisk. "The boundary-layer flow due to a vortex approaching a cylinder." Journal of Fluid Mechanics 275 (September 25, 1994): 33–57. http://dx.doi.org/10.1017/s0022112094002272.

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The three-dimensional unsteady boundary layer induced by a vortex filament moving outside a circular cylinder is considered. In the present paper, we focus attention on the situation where the inviscid flow is fully three-dimensional but is symmetric with respect to the top centreline of the cylinder. The motion of the vortex toward the cylinder leads to separation of the boundary layer; in the present work a large unsteady adverse pressure gradient develops as well. Results for the three-dimensional streamlines, the vorticity distribution, and the velocity component normal to the cylinder ind

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Liu, Chaoqun, Lin Chen, and Ping Lu. "New Findings by High-Order DNS for Late Flow Transition in a Boundary Layer." Modelling and Simulation in Engineering 2011 (2011): 1–16. http://dx.doi.org/10.1155/2011/721487.

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This paper serves as a summary of new discoveries by DNS for late stages of flow transition in a boundary layer. The widely spread concept “vortex breakdown” is found theoretically impossible and never happened in practice. The ring-like vortex is found the only form existing inside the flow field. The ring-like vortex formation is the result of the interaction between two pairs of counter-rotating primary and secondary streamwise vortices. Following the first Helmholtz vortex conservation law, the primary vortex tube rolls up and is stretched due to the velocity gradient. In order to maintain

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Mimic, Dajan, Christoph Jätz, and Florian Herbst. "Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters." Journal of the Global Power and Propulsion Society 2 (August 27, 2018): I9AB30. http://dx.doi.org/10.22261/jgpps.i9ab30.

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Diffusers convert kinetic flow energy into a rise in static pressure. This pressure recovery is the primary aerodynamic design objective for exhaust gas diffusers in power-generating steam and gas turbines. The total pressure loss is an equally important diffuser design parameter. It is strongly linked to the pressure recovery and the residual kinetic energy of the diffuser outlet flow. A reduction benefits the overall thermodynamic cycle, which requires the adjacent components of a diffuser to be included in the design process. This paper focuses on the total pressure losses in the boundary l

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Nourbakhsh, Amireh, Souzan Piri, Mohsen Goudarzi, and Morteza Bayareh. "Viscosity Ratio Effect on Drop Deformation in the Boundary Layer." International Journal of Heat and Technology 38, no. 4 (2020): 847–53. http://dx.doi.org/10.18280/ijht.380410.

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In the present study, the motion of a droplet in the boundary layer is investigated numerically. Volume of Fluid method is employed to solve the governing equations. It is found that the presence of the droplet leads to an increase in the pressure inside the boundary layer and on the wall. The results show that the droplets create a vortex on the bottom surface. The friction coefficient increases due to the presence of the droplets and is reduced before and after the droplet due to the formation of a vortex. It is concluded that increasing the viscosity and reducing the density at the same tim

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Chuang, Fu-Sheng, and A. T. Conlisk. "The effect of interaction on the boundary layer induced by a convected rectilinear vortex." Journal of Fluid Mechanics 200 (March 1989): 337–65. http://dx.doi.org/10.1017/s0022112089000686.

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The effect of interaction on the boundary layer induced by a convected rectilinear vortex is considered. Two schemes are employed in the numerical discretization of the edge interaction condition; the first, developed by Veldman (1981) is useful at larger Reynolds numbers but fails to capture the interactive phase of the motion for Reynolds numbers less than 8 × 104. A scheme devised by Napolitano, Werlé & Davis (1978) is employed at smaller Reynolds numbers and yields similar results to Veldman's scheme at higher Reynolds numbers, while exhibiting greater numerical stability during the in

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Launay, Gaby, E. Mignot, N. Riviere, and R. Perkins. "An experimental investigation of the laminar horseshoe vortex around an emerging obstacle." Journal of Fluid Mechanics 830 (September 29, 2017): 257–99. http://dx.doi.org/10.1017/jfm.2017.582.

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An emerging long obstacle placed in a boundary layer developing under a free surface generates a complex horseshoe vortex (HSV) system, which is composed of a set of vortices exhibiting a rich variety of dynamics. The present experimental study examines such flow structure and characterizes precisely, using particle image velocimetry (PIV) measurements, the evolution of the HSV geometrical and dynamical properties over a wide range of dimensionless parameters (Reynolds number$Re_{h}\in [750,8300]$, boundary layer development ratio$h/\unicode[STIX]{x1D6FF}\in [1.25,4.25]$and obstacle aspect rat

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Chima, R. V. "Calculation of Tip Clearance Effects in a Transonic Compressor Rotor." Journal of Turbomachinery 120, no. 1 (1998): 131–40. http://dx.doi.org/10.1115/1.2841374.

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The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearanc

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Magnico, Pierre. "Electro-Kinetic Instability in a Laminar Boundary Layer Next to an Ion Exchange Membrane." International Journal of Molecular Sciences 20, no. 10 (2019): 2393. http://dx.doi.org/10.3390/ijms20102393.

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The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation contained two aspects: analysis of the instability modes and description of the Lagrangian transport of fluid and ions. Regarding the first aspect, the modes were analyzed as a function of the potential drop. The analysis revealed how the spatial distribution of forces controls the dynamics of vortex asso

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Liu, Yu, and Yi Lin Wu. "Model-Based Verifying and Design of Autonomous Airship." Applied Mechanics and Materials 66-68 (July 2011): 1748–54. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.1748.

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Based on the Kirchhoff equations, Newton-Euler laws, boundary layer theory and mass definition, the six degrees of freedom dynamic model of airship complete with aerodynamic forces, wind effect is presented. Then, the nonlinear dynamic model is divided into three group equations by restricting airship motion in different planes respectively. The motion characteristics of airship, including stability, the effect of ballast position and rotational damping, are studied using linearized model. The results of simulation verify the correctness of the theoretical analysis and airship design.

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Riemer, M., M. T. Montgomery, and M. E. Nicholls. "A new paradigm for intensity modification of tropical cyclones: thermodynamic impact of vertical wind shear on the inflow layer." Atmospheric Chemistry and Physics 10, no. 7 (2010): 3163–88. http://dx.doi.org/10.5194/acp-10-3163-2010.

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Abstract. An important roadblock to improved intensity forecasts for tropical cyclones (TCs) is our incomplete understanding of the interaction of a TC with the environmental flow. In this paper we re-visit the canonical problem of a TC in vertical wind shear on an f-plane. A suite of numerical experiments is performed with intense TCs in moderate to strong vertical shear. We employ a set of simplified model physics – a simple bulk aerodynamic boundary layer scheme and "warm rain" microphysics – to foster better understanding of the dynamics and thermodynamics that govern the modification of T

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CARSTENSEN, STEFAN, B. MUTLU SUMER, and JØRGEN FREDSØE. "Coherent structures in wave boundary layers. Part 1. Oscillatory motion." Journal of Fluid Mechanics 646 (March 8, 2010): 169–206. http://dx.doi.org/10.1017/s0022112009992825.

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This work concerns oscillatory boundary layers over smooth beds. It comprises combined visual and quantitative techniques including bed shear stress measurements. The experiments were carried out in an oscillating water tunnel. The experiments reveal two significant coherent flow structures: (i) Vortex tubes, essentially two-dimensional vortices close to the bed extending across the width of the boundary-layer flow, caused by an inflectional-point shear layer instability. The imprint of these vortices in the bed shear stress is a series of small, insignificant kinks and dips. (ii) Turbulent sp

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