Effects of Tunable Angle for Vortex Generators on Aerodynamic Performances of Airfoils

2017 ◽  
Vol 872 ◽  
pp. 192-197
Author(s):  
Hu Yu ◽  
Bin Tang Yang ◽  
Xiao Qing Sun ◽  
Xi Wang ◽  
Hang Jie Mo
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Vortex Generators ◽  
Installation Angle ◽  
Fluctuation Phenomenon ◽  
Aerodynamic Performances ◽  
Finite Wing ◽  
Three Dimensional Models ◽  
Drag Ratio

Vortex generators (VGs) are commonly adopted to control the flow separation, and many researches have investigated their effects on the aerodynamic performance of wind turbines. However, nearly no attentions are paid to the VGs’ installation angle. Thus, in this paper, to investigate the effects of the VGs’ installation angle on airfoils, numerical simulations are conducted by CFD on the finite wing of NACA0012. According to the finite airfoil with or without VGs, three-dimensional models are established and numerical simulations are carried out in detail. It could be seen clearly that the VGs’ installation angle produces a significant impact on the aerodynamic performances. For some installation angles, special ranging from 45° to 90°, VGs can improve the lift-drag ratio apparently, even by 34.5%. While angle ranges from 15° to 30°, VGs negatively influence the lift-drag ratio. Furthermore, the fluctuation phenomenon is discussed through analysis of the streamlines and vortices. Based on those results, optimal aerodynamic performances could be achieved by the active control of the VGs’ installation angle.

Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

2020 ◽  
pp. 146808742095133 ◽  
Author(s):  
Konstantinos Bardis ◽  
Panagiotis Kyrtatos ◽  
Guoqing Xu ◽  
Christophe Barro ◽  
Yuri Martin Wright ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Design Parameters ◽  
Combustion Model ◽  
Experimental Investigations ◽  
Computationally Efficient ◽  
Lean Burn ◽  
Dimensional Models ◽  
Three Dimensional Models

Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters.

Winglet Dihedral Effect on Flow Behavior and Aerodynamic Performance of NACA0012 Wings

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Shun C. Yen ◽  
Yu F. Fei
Keyword(s):  
Flow Behavior ◽  
Three Dimensional ◽  
Major Axis ◽  
Aerodynamic Performance ◽  
Oil Flow ◽  
Force Moment ◽  
Flow Configurations ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Surface Vortex

This study investigates the effects of Reynolds number, angle of attack, and winglet dihedral (δ) on the smoke-streak flow patterns, surface oil-flow configurations, and aerodynamic performance of the wingleted wings. The airfoil is NACA 0012 and the winglet dihedral varies from −30° to 135°. The smoke-wire technique was utilized to visualize the three-dimensional flow structures. Furthermore, the effect of δ on the wingtip surface vortex was examined using the surface oil-flow scheme. The wingtip surface vortex was observed on a baseline wing using the smoke-streak flow and surface-oil flow visualization schemes. Moreover, the length of wingtip surface vortex (Lb) decreases with increasing δ for δ > 15° where Lb denotes the major axis of wingtip surface vortex. The maximum Lb/C of 1.2 occurs at δ = 15° which is about 42% higher than that of a baseline wing, where C represents the wing chord length. The high flow momentum expands the wingtip surface vortex toward the winglet when δ < 15°. However, the minimum Lb/C of 0.55 occurs at δ = 90° which is about 34% lower than that of a baseline wing because the wingtip surface vortex is squeezed intensely at high δ. The aerodynamic performance was measured using a force-moment balance. The experimental data indicates that the lift-drag ratio at stalling (CL/CD)stall and maximum lift-drag ratio (CL/CD)max occurs at δ = 90°.

Effects of Probe Stem Surface Suction on the Aerodynamic Performance of a Compressor

2021 ◽  
Author(s):  
Yafei Zhong ◽  
Hongwei Ma ◽  
Yi Yang
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Stability Margin ◽  
Aerodynamic Performance ◽  
Vortex Identification ◽  
Flow Angle ◽  
Surface Suction ◽  
Three Dimensional Models ◽  
Downstream Flow

Abstract Pneumatic probes can be used to obtain the flow field parameters such as pressure, temperature and air flow angle, and has been widely used to measure the flow field in compressors. When probes are inserted into the compressor to measure the flow field, the probe stems will cause blockage in the flow field and interfere with it, reducing the pressure ratio and efficiency of the compressor. This paper proposes a method to reduce the interference of the stems by their surface suction. Three-dimensional models of a compressor with different types of probe stems were established. Computational Fluid Dynamics (CFD) simulations of the flow within a low-speed compressor without/with the probe stems and the stems having surface suction holes were conducted. The involved numerical methods were validated by the experimental data. The effects of the surface suction holes on the performance of this compressor were compared and analyzed in terms of blockage coefficient in the passage by the vortex identification method. The results show that probe stem surface suction can reduce the blockage of the stems on the downstream flow field. Compared with the situation of no suction, there is an optimal suction mass flow rate that can minimize the adverse effect of probe stems on the compressor aerodynamic performance. For the same type of the probe stems, the compressor performances, i.e., pressure ratio, efficiency and stability margin, are recovered with the increase of the number of suction holes along the span-wise direction.

STUDY ON AERODYNAMIC PERFORMANCE OF THE BIONIC AIRFOIL BASED ON THE SWALLOW'S WING

2013 ◽  
Vol 13 (06) ◽  
pp. 1340022 ◽  
Author(s):  
WEIJUN TIAN ◽  
FANGYUAN LIU ◽  
QIAN CONG ◽  
YURONG LIU ◽  
LUQUAN REN
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Wind Tunnel Tests ◽  
Small Wind Turbines ◽  
Aerodynamic Performances ◽  
Drag Ratio ◽  
Bionic Airfoil

This paper demonstrates the design of the airfoil of small wind turbines, the bionic airfoil was inspired by the morphology of the swallow's extended wing. The wind tunnel tests on the bionic and standard airfoils NACA4412 were conducted, and the aerodynamic performances of the airfoils were numerically investigated. The results show that the bionic airfoil has better aerodynamic performance, the lift coefficient and lift-drag ratio are larger than those of the NACA4412; with the angle of attack increases, both the bionic and standard airfoils stall, but the stall characteristics of the bionic airfoil are better.

Numerical investigation of aerodynamic effects of opposite wrap-around fins at supersonic speeds

2018 ◽  
Vol 233 (7) ◽  
pp. 2410-2425 ◽  
Author(s):  
Amir Bagheri ◽  
Mahmoud Pasandidehfard ◽  
Seyed Ali Tavakoli Sabour
Keyword(s):  
Numerical Simulations ◽  
Research Work ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Opening Angle ◽  
Three Dimensional Flow ◽  
Rolling Moment ◽  
Drag Coefficients ◽  
Mach Numbers ◽  
Volume Method

In this research work, using numerical simulations, the three-dimensional flow around a standard projectile is investigated with two fin arrangement models, namely opposite and conventional wrap-around fins. Eliminating the rolling moment and investigation of aerodynamic performance of the new geometries are the purpose of this paper. Finite volume method is used to undertake the numerical simulations where flow is considered to be compressible, steady, nonviscous, and three-dimensional. For this purpose, the research begins with simulating the flow around a projectile with conventional fin arrangement and then the obtained values of drag coefficients and rolling moment are compared against experimental data, indicating the validity of the simulation results. After then, the effect of wrap-around fins in an opposite arrangement is investigated, with the results compared against those of the conventional configuration. The opposite fins are investigated at different opening angles and joint position, while the area of fins shading is assumed constant in all cases. Simulations were conducted at three Mach numbers of 1.5, 2.5, and 3.5, different angles of attack ranging within 0–14°, and lateral wind angles up to 8°. According to the results, the rolling moment in conventional wrap-around fins is a result of the pressure difference between sides of the fins, so that it can be avoided by configuring the fins in an opposite arrangement, which contributes to slightly higher drag coefficients too. Fin dimensions and their opening angle influence the regime of the flow passing through the fins, making their aerodynamic performance variable at different Mach numbers.

Effects of Curvature Radius of Volute Profile on Aerodynamic Performance of Squirrel Cage Fan

2019 ◽  
Author(s):  
Ke Wang ◽  
Yaping Ju ◽  
Chuhua Zhang
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Curvature Radius ◽  
Dynamic Simulations ◽  
Continuous Increase ◽  
Squirrel Cage ◽  
Aerodynamic Performances ◽  
Computation Fluid Dynamic ◽  
Continuous Curvature

Abstract Volute profile exerts great influences on flow losses and aerodynamic performance of squirrel cage fan. In practical, equilateral- or inequilateral-element method is usually applied to design the volute profile for convenient manufacture. This kind of volute profile consists of several arc segments, however, is discontinuous for curvature radius at the junctions of adjacent arc segments. To overcome this issue, we propose a new volute profiling method to guarantee the continuity of curvature radius along the whole volute profile. By means of three-dimensional computation fluid dynamic simulations, the proposed method is validated through comprehensive comparisons of aerodynamic performances and flow fields of squirrel cage fans with and without continuous curvature radius of volute profile. The results show that the continuous curvature radius of volute profile is of benefit to the aerodynamic performance increase of squirrel cage fan. The velocity downstream the volute tongue is improved. The local sudden diffusion-expansion around the junctions of volute arc segments nearly disappears with continuous increase of static pressure along the volute wall.

Computation of Turbulent Flow Around Blade With Local Surface Roughness

2003 ◽  
Author(s):  
Yin-han Chang ◽  
Kazuyuki Toda ◽  
Makoto Yamamoto
Keyword(s):  
Surface Roughness ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Local Surface ◽  
Three Dimensional Flow ◽  
Virtual Force ◽  
Roughness Elements ◽  
Aerodynamic Performances

To improve aerodynamic performance of a blade and to maintain its designed performance, many study have been focused on this point. The factors for aerodynamic performances of a blade are its geometry and operating conditions, which are almost fixed during its lifetime. On the other hand, the factor such as surface roughness generated by impure sand grain or oil droplet is variable one. The surface roughness on the blade affects the flow past it by its aerodynamic nature. The blade design can be improved by revealing this change in aerodynamic performance due to surface roughness. In this study, three-dimensional computations are carried out on the blade root with local surface roughness to investigate how the roughness will change the aerodynamic performance. The locality of the surface roughness distribution is simulated with particle tracks in three-dimensional flow. The model replacing the effect of roughness elements with virtual force is used to simulate turbulent flow around blade with local surface roughness.

scholarly journals Frequency Behavior of Conformal Wire Structures

2016 ◽  
Vol 5 (3) ◽  
pp. 14
Author(s):  
G. Leone ◽  
F. Mattiello ◽  
G. Ruvio ◽  
R. Pierri
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Conical Surface ◽  
Antenna Impedance ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Frequency Behavior

Three-dimensional models are built to examine the frequency behavior of wire structures conforming onto nonplanar surfaces. The effects of altered periodicity on frequency selectiveness of the structures are considered. An analogy is drawn with the antenna impedance behavior of a single active wire surrounded by a number of passive similar ones. Numerical simulations are performed for different wire geometries over a conical surface.

Aerodynamic performance enhancement of an Airfoil using trapezoidal vortex generators

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rawad Himo ◽  
Charbel Bou-Mosleh ◽  
Charbel Habchi
Keyword(s):  
Performance Enhancement ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Dynamic Simulations ◽  
Content Type ◽  
Inclination Angles ◽  
Drag Ratio

Purpose Flow separation on wings, blades and vehicles can be delayed or even suppressed by the use of vortex generators (VG). Numerous studies, documented in the literature, extensively describe the performance of triangular and rectangular VG winglets. This paper aims to focus on the use of non-conventional VG shapes, more specifically an array of trapezoildal-perforated VG tabs. Design/methodology/approach In this study, computational fluid dynamic simulations are performed on an inline array of trapezoidal VG with various dimensions and inclination angles, in addition to considering perforations in the VG centers. The methodology of the present numerical study is validated with experimental data from the literature. Findings The performance and the associated flow structures of these tested non-conventional VG are compared to classical triangular winglets. For the proposed non-conventional trapezoidal VG, at the onset of stall, a 21% increase of lift over drag on the airfoil is observed. The trapezoidal VG enhancement is also witnessed during stall where the lift over drag ratio is increased by 120% for the airfoil and by 10% with respect to the triangular winglets documented in the literature. Originality/value The originality of this paper is the use of non-conventional vortex generator shape to enhance lift over drag coefficient using three-dimensional numerical simulations.

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