Vortex Trapping by Different Cavities on an Airfoil
TL;DR: In this paper, the authors presented the flow over an airfoil with different cavity shapes placed on the suction surface of a symmetric airframe, and the cavity with both sharp edges showed better results in terms of lift and drag as compared to other shapes of the cavity.
Abstract: The paper presents the flow over an airfoil with different cavity shapes placed on the suction surface of a symmetric airfoil. Unsteady simulations of flow over the airfoil with and without cavities were performed by Reynolds averaged Navier-Stokes (RANS) solver. Lift and drag were checked and the separation point identified at different Reynolds numbers and different angles of attack. The airfoil with cavity produced more drag and less lift as compared to the airfoil without cavity. The cavity with both sharp edges showed better results in terms of lift and drag as compared to other shapes of the cavity.
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22 Jun 2020
TL;DR: In this article, the authors study periodic, infinitely long spanwise grooves on a laminar boundary layer over a plate for 1000 $R\phantom{\rule{0}{0ex}}{e}_{L}$ 25000 below a certain width-to-depth aspect ratio (AR), a primary vortex inside each groove causes the freestream to slip over, reducing skin friction.
Abstract: Engineered surface textures can manipulate boundary layers affecting fluid drag We study periodic, infinitely long spanwise grooves on a laminar boundary layer over a plate for 1000 $R\phantom{\rule{0}{0ex}}{e}_{L}$ 25000 Below a certain width-to-depth aspect ratio (AR), a primary vortex inside each groove causes the freestream to ``slip over'', reducing skin friction Increasing AR poses a tradeoff in drag reduction due to pressure drag from groove vertical walls Overall, transverse grooves for laminar flow can reduce total drag up to 10% compared to a flat plate, despite increasing the wetted surface area
7 citations
TL;DR: In this paper , the flow characteristics and velocity fields over the vertical axis wind turbines DU 06 W 200 airfoil developed by Delft University of Technology and some other innovative designs are examined by computational fluid dynamics (CFD) simulation and particle image velocimetry (PIV) measurements.
Abstract: In this paper the flow characteristics and velocity fields over the vertical axis wind turbines DU 06 W 200 airfoil developed by Delft University of Technology and some other innovative designs are examined by computational fluid dynamics (CFD) simulation and particle image velocimetry (PIV) measurements. In these case studies a modification of the plain airfoil upper and/or lower surfaces was applied with the assistance of different techniques. CFD was conducted using the turbulent model of RANS k- ω SST. The PIV experiments were performed using a wind tunnel test and smoke flow visualization. Different practical cases, namely riblet under surface, riblet above surface, cavity front, cavity back, double cavity, single riblet, and spoiler, were designed and examined. Moreover, two hybrid blade airfoils designed and inspired by combining the DU 06 W 200 and NACA 63215 developed by National Advisory Committee for Aeronautics (NACA) were also tested. The results show that the new design hybrid blade airfoil can significantly modify the flow pattern over the airfoil and improve aerodynamic performance. The new design hybrid blade airfoil could deliver improved efficiency for industrial applications, specifically for the design and development of vertical axis wind turbines.
6 citations
5 citations
01 Jun 2021
3 citations
TL;DR: In this article, a Computational Fluid Dynamics (CFD) investigation is carried out for analyzing the simultaneous effect of suction and cavity for controlling flow separation on NACA 0012 airfoil.
Abstract: In the present research, a Computational Fluid Dynamics (CFD) investigation is carried out for analyzing the simultaneous effect of suction and cavity for controlling flow separation on NACA 0012 airfoil. Hence, a perpendicular suction jet (jet = -90°) is employed with Rjet equal to 0.15 at Ljet = 0.1c. Simultaneously, a cavity is used at 90% of chord length (0.9c) with 20 mm width and 10 mm depth. The fluid flow is assumed to be 2D turbulent, and incompressible. The results demonstrate that lift coefficient has raised by 30% and drag coefficient has decreased by 40% at α = 14° by using simultaneous suction and cavity. The flow control method improves lift to drag ratio and stall angle has increased from 14° to 22°. Consequently, the flow separation has been delayed, the recirculation zone has gone downstream and completely eliminated by utilizing simultaneous suction and cavity as an effective flow control method.
2 citations
Cites background from "Vortex Trapping by Different Caviti..."
...Besides, several efforts have been done on the aerodynamic characteristic of the airfoil with cavity [25-28]....
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5 citations
"Vortex Trapping by Different Caviti..." refers methods in this paper
...With appropriate optimization of the various parameters with the new airfoil-design concept such as steps, cavities along the chord length of the airfoil, it may be possible to achieve improvements in aerodynamic characteristics at much higher Reynolds numbers [21]....
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26 Oct 2012
TL;DR: In this article, a step was introduced at mid-chord, with a depth of 50% of the airfoil thickness at midchord position extending till the trailing edge of a NACA 4415.
Abstract: The objective of this research was to investigate the lift and drag characteristics of a stepped airfoil with backward facing steps; apply active flow control technique to enhance the aerodynamic performance of stepped airfoils and examine the possibility of using such airfoils on UAVs. A step was introduced at mid-chord, with a depth of 50% of the airfoil thickness at mid-chord position extending till the trailing edge of a NACA 4415 airfoil. Computational studies were conducted with the use of passive flow control constituting the activation of step and active flow control with the use of air injecting jets placed in the step cavity of the NACA 4415 airfoil with a goal of enhancing the aerodynamic performance. The jet angle and jet momentum coefficient were varied independently to identify the best setting for optimizing the aerodynamic performance of the stepped airfoil. Experimental studies of a scaled wing model with the same airfoil were conducted in a wind tunnel for a range of Reynolds numbers to validate some of the numerical results obtained for the cases of base and stepped airfoils. The results produced show that as much as 12 % increase in L/D ratio could be obtained.
5 citations
01 Jan 2004
TL;DR: 2D steady k-s Navier-Stoke s results are presented for 2 angles of attack and compared to averaged PIV data to improve the understanding of the complex flow phenomena in high lift conditions and to develop numerical methods capable to predict this flow with high accuracy.
Abstract: Airplane high lift systems allow to obtain aerodynamic characteristics required for take-off and landing stages. In order to optimize such systems, it is necessary to improve the understanding of the complex flow phenomena in high lift conditions and to develop numerical methods capable to predict this flow with high accuracy. In the framework of the Europiv2 project, velocity fields provided by PIV for the ONERA RAI6SCI three component airfoil in high lift configuration offer an opportunity to acquire flow characteristics, to assess and validate numerical tools. In this paper, 2D steady k-s Navier-Stoke s results are presented for 2 angles of attack and compared to averaged PIV data.
4 citations
TL;DR: In this article, a 2D LES is used to simulate flow past a wind turbine airfoil in deep stall, which is a classical separated flow proved by experiments and compared with that of a 3D model using RNS/LES hybrid methods.
Abstract: In order to assess the performance of the two-dimensional (2D) large eddy simulation (LES) as a computational tool for analyzing separated flows. LES in various models has been developed to simulate turbulent flows, especially to separated flows. In this investigation, 2D LES is used to simulate flow past a wind turbine airfoil in deep stall which is a classical separated flow proved by experiments. The results of 2D LES are compared with that of a 3D model using RNS/LES hybrid methods and with experimental data. This shows that the 2D LES method can not only be used to simulate separated flows, but also the calculation time of 2D LES is significantly decreased to compare with the 3D model using RNS/LES hybrid methods.
1 citations
"Vortex Trapping by Different Caviti..." refers methods in this paper
...Two dimensional simulation of airfoil using large eddy simulation (LES) is presented by Fu et al [13]....
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...It was also observed that calculation time taken for 2D LES was less when compared to 3D model using RANS method [13]....
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