scholarly journals Studying the unsteady characteristics of a laminar transonic buffet depending on the angle of attack

2021 ◽  
Vol 2057 (1) ◽  
pp. 012009
Author(s):  
P A Polivanov ◽  
A A Sidorenko
Keyword(s):  
Shock Wave ◽  
Unsteady Flow ◽  
High Speed ◽  
Angle Of Attack ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Unsteady Characteristics ◽  
Basic Experiments ◽  
Transonic Buffet ◽  
Amplitude Characteristics

Abstract Laminar transonic buffet on the airfoil for low Reynolds numbers of 0.5-0.7⋅106 was experimentally studied. Basic experiments were performed using high-speed schlieren imaging. The unsteady flow structure was investigated using various methods. It was found that shock wave oscillations can be significantly different from the turbulent case. The frequency and amplitude characteristics of oscillations from the angle of attack were found.

scholarly journals Plunging Airfoil: Reynolds Number and Angle of Attack Effects

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 216
Author(s):  
Emanuel A. R. Camacho ◽  
Fernando M. S. P. Neves ◽  
André R. R. Silva ◽  
Jorge M. M. Barata
Keyword(s):  
Reynolds Number ◽  
High Performance ◽  
Angle Of Attack ◽  
Systems Design ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Low Reynolds Numbers ◽  
Operational Conditions ◽  
Naca0012 Airfoil ◽  
The Mean

Natural flight has consistently been the wellspring of many creative minds, yet recreating the propulsive systems of natural flyers is quite hard and challenging. Regarding propulsive systems design, biomimetics offers a wide variety of solutions that can be applied at low Reynolds numbers, achieving high performance and maneuverability systems. The main goal of the current work is to computationally investigate the thrust-power intricacies while operating at different Reynolds numbers, reduced frequencies, nondimensional amplitudes, and mean angles of attack of the oscillatory motion of a NACA0012 airfoil. Simulations are performed utilizing a RANS (Reynolds Averaged Navier-Stokes) approach for a Reynolds number between 8.5×103 and 3.4×104, reduced frequencies within 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the mean angle-of-attack is also studied in the range of 0∘ to 10∘. The outcomes show ideal operational conditions for the diverse Reynolds numbers, and results regarding thrust-power correlations and the influence of the mean angle-of-attack on the aerodynamic coefficients and the propulsive efficiency are widely explored.

Separation and Transition Control on an Aft-Loaded Ultra-High-Lift LP Turbine Blade at Low Reynolds Numbers: High-Speed Validation

2006 ◽  
Vol 129 (2) ◽  
pp. 340-347 ◽  
Author(s):  
Maria Vera ◽  
Xue Feng Zhang ◽  
Howard Hodson ◽  
Neil Harvey
Keyword(s):  
Surface Roughness ◽  
Mach Number ◽  
Surface Finish ◽  
High Speed ◽  
Reynolds Numbers ◽  
High Lift ◽  
Low Reynolds Numbers ◽  
Low Speed ◽  
Transition Mechanism ◽  
Low Reynolds

This paper presents the second part of an investigation of the combined effects of unsteadiness and surface roughness on an aft-loaded ultra-high-lift low-pressure turbine (LPT) profile at low Reynolds numbers. The investigation has been performed using low- and high-speed cascade facilities. The low- and high-speed profiles have been designed to have the same normalized isentropic Mach number distribution. The low-speed results have been presented in the first part (Zhang, Vera, Hodson, and Harvey, 2006, ASME J. Turbomach., 128, pp. 517–527). The current paper examines the effect of different surface finishes on an aft-loaded ultra-high-lift LPT profile at Mach and Reynolds numbers representative of LPT engine conditions. The surface roughness values are presented along with the profile losses under steady and unsteady inflow conditions. The results show that the use of a rough surface finish can be used to reduce the profile loss. In addition, the results show that the same quantitative values of losses are obtained at high- and low-speed flow conditions. The latter proves the validity of the low-speed approach for ultra-high-lift profiles for the case of an exit Mach number of the order of 0.64. Hot-wire measurements were carried out to explain the effect of the surface finish on the wake-induced transition mechanism.

scholarly journals Unsteadiness in Flow over a Flat Plate at Angle-of-Attack at Low Reynolds Numbers

2007 ◽  
Author(s):  
Kunihiko Taira ◽  
William Dickson ◽  
Tim Colonius ◽  
Michael Dickinson ◽  
Clarence Rowley
Keyword(s):  
Flat Plate ◽  
Angle Of Attack ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds

The LBE Simulation and PIV Experimental Study on a Novel Viscous Pump

2005 ◽  
Author(s):  
Fan Yang ◽  
Shuhong Liu ◽  
Jinwei Li ◽  
Yulin Wu
Keyword(s):  
Boundary Condition ◽  
Unsteady Flow ◽  
Cross Sections ◽  
Lattice Boltzmann ◽  
Moving Boundary ◽  
Flow Problem ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Moving Boundary Condition

A numerical study and PIV investigation of flow in a novel viscous-based pumping device appropriate for microscale applications is described. The device, essentially consisting of a rotating cylinder eccentrically placed in a channel, is shown to be capable of generating a net flow. The two shape cross-sections of cylinders, the circular and four semi-elliptic lobed contour are studied, which is the steady and unsteady flow problem, respectively. The lattice Boltzmann equation (LBE) simulations at low Reynolds numbers are carried out to study the influence of various geometric parameters, which the results are compared with the PIV experiment ones. The unified solid curved wall boundary condition based on interpolation and the balance of momentum on the wall of the LBE simulation is used in steady and unsteady flow, and the moving boundary condition is also used in the latter. The numerical results indicated that the more effective pumping and better performance is obtained with the decrease of Reynolds number, as well as the increase regular degree of cylinder cross-section.

Drone Scale Coaxial Rotor Aerodynamic Interactions Investigation

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Dhwanil Shukla ◽  
Narayan Komerath
Keyword(s):  
High Speed ◽  
Vortex Sheet ◽  
Reynolds Numbers ◽  
Thrust Coefficient ◽  
Low Reynolds Numbers ◽  
Rotor Aerodynamics ◽  
Induced Drag ◽  
Coaxial Rotor ◽  
Simplifying Assumptions ◽  
Uninhabited Aerial Vehicles

Coaxial rotor uninhabited aerial vehicles (UAVs) are compact compared to single rotor UAVs of comparable capacity. At the low Reynolds numbers (Re) where they operate, the simplifying assumptions from high Re rotor aerodynamics are not valid. The low Re coaxial rotor flowfield is studied including aerodynamic interactions and their effect on performance. The evolution of the wake is captured using high-speed stereo particle image velocimetry (SPIV). Improvement of upper rotor performance due to viscous swirl recovery from the lower rotor is discovered and then verified by analyzing PIV data. Interesting vortex–vortex sheet interactions are observed under the coaxial rotor affecting wake structure spatially and temporally. A qualitative model explaining the observed wake interaction phenomena is presented. Comparison with the performance of high Re rotors shows higher profile and induced drag at low Re for the same thrust coefficient.

scholarly journals Unsteady flow over flexible wings at different low Reynolds numbers

2016 ◽  
Vol 114 ◽  
pp. 02030 ◽  
Author(s):  
Mustafa Serdar Genç ◽  
Mustafa Özden ◽  
Halil Hakan Açikel ◽  
Hacımurat Demir ◽  
Iliasbek Isabekov
Keyword(s):  
Unsteady Flow ◽  
Reynolds Numbers ◽  
Flexible Wings ◽  
Low Reynolds Numbers ◽  
Low Reynolds
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