scholarly journals Lift and drag force measurements on basic models of low-speed axial fan blade sections

2018 ◽  
Vol 233 (2) ◽  
pp. 165-175 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Drag Force ◽  
Aerodynamic Force ◽  
Measurement Data ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Force Measurements ◽  
Axial Fan ◽  
Low Speed ◽  
Fan Blade ◽  
Lift And Drag

This paper presents comparative data on the aerodynamic lift and drag of basic model representations of low-speed axial fan blade sections. Three main types of blades are investigated: flat plate, cambered plate and RAF6-E profiled airfoil. Lift and drag force are measured at three different Reynolds numbers (0.6 × 105, 105 and 1.4 × 105) around the threshold value of 105. The measurement data are compared to literature data. The aerodynamic force measurements reveal that, for Reynolds numbers below 105, cambered plate blade sections can be superior to airfoil profiles in terms of aerodynamic efficiency, especially in the high-load range. The effect of leading edge bluntness is also investigated. Leaving the leading edge of cambered plates blunt, tends to be uncritical for low Reynolds numbers at angles of attack between 4° and 10° but is critical at angles between 0° and 4°.

scholarly journals Establishment of a Beamforming Dataset on Basic Models of Low-Speed Axial Fan Blade Sections

2017 ◽  
Vol 61 (2) ◽  
pp. 122 ◽  
Author(s):  
Esztella Balla ◽  
János Vad
Keyword(s):  
Phased Array ◽  
Reynolds Numbers ◽  
Strength Level ◽  
Source Strength ◽  
Axial Fan ◽  
Frequency Bands ◽  
Low Speed ◽  
Noise Characteristics ◽  
Wide Range ◽  
Fan Blade

The paper presents wind tunnel experiments, supplemented with phased array microphone measurements, on 2D basic models of low-speed axial fan blade sections: a flat plate, a cambered plate, and a RAF6-E airfoil. It aims at documenting the establishment of an acoustic beamforming dataset for the three profiles. The phased array microphone measurements offer spatially resolved information on the generated noise. The measurement setup enables the correlation of the streamwise evolution of the blade boundary layer with the associated noise characteristics. The dataset incorporates a wide range of incidence and Reynolds-numbers investigated. The present paper is confined to reporting on experimental results for arbitrarily selected representative incidences, Reynolds numbers, frequency bands, and profiles. The paper outlines a methodology for the evaluation and representation of the beamforming data in the following forms: source strength level based third-octave spectra obtained using background noise subtraction; maps presenting the loci of source strength level maxima; noise source maps for frequency bands of anticipated vortex shedding noise.

A Numerical Study Into the Influence of Leading Edge Tubercles on the Aerodynamic Performance of a Highly Cambered High Lift Airfoil Wing at Different Reynolds Numbers

2020 ◽  
Author(s):  
Amr Abdelrahman ◽  
Amr Emam ◽  
Ihab Adam ◽  
Hamdy Hassan ◽  
Shinichi Ookawara ◽  
...  
Keyword(s):  
Control Method ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Stall Angle ◽  
Lifting Surfaces ◽  
Lift And Drag

Abstract Through the last two decades, many studies have demonstrated the ability of leading-edge protrusions (tubercles), inspired from the pectoral flippers of the humpback whale, to be an effective passive flow control method for the stall phase of an airfoil in some cases depending on the geometrical features and the flow regime. Nevertheless, there is a little work associated with revealing tubercles performance for the lifting surfaces with a highly cambered cross-section, used in numerous applications. The present work aims to investigate the effect of implementing leading edge tubercles on the performance of an infinite span rectangular wing with the highly cambered S1223 foil at different flow regimes. Two sets; baseline one and a modified with tubercles have been studied at Re = 0.1 × 106, 0.3 × 106 and 1.5 × 106 using computational fluid dynamics with a validated model. The numerical results demonstrated that Tubercles have the ability to entirely alter the flow structure over the airfoil, confining the separation to troughs, hence, softening the stall characteristics. However, the tubercle modification expedites the presence of the stalled flow over the suction side, lowering the stall angle for the three mentioned Reynolds numbers. While, no considerable difference occurs in lift and drag before the stall.

scholarly journals Experiments on the Effects of Reynolds Number and Advance Ratio on the Unfolding of Disorganization in Low-Speed Underwater Propulsors With Vibrating Blades

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Promode R. Bandyopadhyay
Keyword(s):  
Acoustic Radiation ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Limit Cycle Oscillation ◽  
Blade Vibration ◽  
Low Reynolds Numbers ◽  
Low Speed ◽  
Aircraft Wings ◽  
Wall Boundary Layer ◽  
Cycle Oscillation

Ships and submarines are acoustic hazards to marine life. The rational control of acoustic radiation would be possible at least at low Reynolds numbers if the underlying organization buried in seeming randomness is revealed. We build a novel low-speed propulsor where all blades undergo small-amplitude pitch oscillation while spinning at large pitch angles at transitional chord Reynolds numbers (3.75 × 103 ≤ Rec ≤ 3.75 × 104) and advance ratios (0.51 ≤ J ≤ 4.89). We measure and model time-averaged and temporal thrust. The relationship between the time-averaged and the temporal thrust is observed when the latter is mapped as limit cycle oscillation (LCO), or departure from it. High-thrust coefficients occurring at large (30 deg and 45 deg) angles of amplitude of blade vibration are modeled assuming poststall lift enhancement due to flapping blades when a leading edge vortex (LEV) forms, while the lower thrust coefficients occurring at 20 deg are modeled by its absence. The disorganization in temporal thrust increases with J and Rec. An external orthogonal oscillator, perhaps a vibration, is modeled to couple with the thrust oscillator for temporal control of disorganization. The unfolding disorganization is seen as a departure from LCO, and it is attenuated by smooth-wall boundary-layer fencing, compared to unfenced smooth and rough surfaces. When the fencing properties of the leading edge tubercles of whale fins are recognized, the ratio of the spacing of the fences and chord is found to be similar (0.5–1.0) in both whale flippers and aircraft wings.

Fan Blade Design Methods: Cascade Versus Isolated Airfoil Approach — Experimental and Numerical Comparison

2016 ◽  
Author(s):  
Stefano Castegnaro
Keyword(s):  
Reynolds Numbers ◽  
Medium Size ◽  
Numerical Comparison ◽  
Blade Design ◽  
Axial Fan ◽  
Local Flow ◽  
Flow Features ◽  
Fan Blade ◽  
Mixed Approach ◽  
Cfd Analyses

Both cascade and isolated airfoil methods are considered valid in axial fan blade design, for high (σ≳1) and low (σ≲0.7) solidities respectively. For bladings that feature intermediate solidities the modified isolated approach is commonly employed. This method uses isolated airfoil data, with proper adjustments to take into account multiplane interference effects. Contrarily, the literature does not refer about modifications of the cascade approach to design medium solidity fans. Such method would use cascade data, properly adjusted for the blade sections at lower solidities. Thus, with the aim of comparing these two opposite design approaches (modified cascade versus modified isolated) for medium solidity blades, two free-vortex blading were designed for a 315 mm rotor-only axial fan and experimentally tested. CFD analyses were performed as well to obtain the local flow features. NACA-65 series airfoils were employed, as both cascade and isolated data are available for chord Reynolds numbers typical of axial fans applications. Results highlight the differences between the two approaches. Finally, a mixed approach that employs both isolated and cascade data is suggested as the most accurate one. Moreover, results also show the detrimental effects of the low chord Reynolds numbers on the performance of the blades. This effect should be taken into account in blade design for small-to-medium size machines.

Morphology Effects of Leading-edge Serrations on Aerodynamic Force Production: An Integrated Study Using PIV and Force Measurements

2018 ◽  
Vol 15 (4) ◽  
pp. 661-672 ◽  
Author(s):  
Teruaki Ikeda ◽  
Tetsuya Ueda ◽  
Toshiyuki Nakata ◽  
Ryusuke Noda ◽  
Hiroto Tanaka ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Force Production ◽  
Leading Edge ◽  
Force Measurements ◽  
Integrated Study

Vortex Generators Contribution to the Enhancement of the Aerodynamic Performances

2014 ◽  
Vol 950 ◽  
pp. 268-274
Author(s):  
Hocine Tebbiche ◽  
Mohamed S. Boutoudj
Keyword(s):  
Wind Tunnel ◽  
Flow Control ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Drag Coefficients ◽  
Passive Devices ◽  
Aerodynamic Performances ◽  
Lift And Drag ◽  
Naca 0015

This study interest flow control using a new vortex generators (VGs) shape with counter-rotating vortices, obtained by adding a new element to a configuration mostly investigated. The experiments were performed in the aim to determine the VGs answer when placed on the suction face at 10% from the leading edge of an airfoil Naca 0015 in order to improve the lift and drag coefficients. The investigations were accomplished in wind tunnel for two Reynolds numbers and geometrical vortex generators configurations. The obtained results are analyzed according to several parameters such as the VG height, the space between the same VG pair and the additional factor. The results show a profit brought by the passive devices estimated at about 28% of the CL/Cd ratio.

Aerodynamic Characteristics and Noise Analysis of a Low-Speed Axial Fan

2018 ◽  
Author(s):  
Bo Luo ◽  
Wuli Chu ◽  
Wei Dong ◽  
Xiangyi Chen
Keyword(s):  
Noise Analysis ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Low Noise ◽  
Axial Fan ◽  
Tonal Noise ◽  
Low Speed ◽  
Optimum Choice ◽  
Aerodynamic Performances ◽  
Axial Fans

Axial fans are widely used in modern industry and new regulations and stringent environmental concerns are prompting manufacturer to design efficient low-noise axial fans. This paper is focused on improving the aerodynamic performances and reducing the tonal noise at BPF and its harmonics by the optimum choice of lean-swept blade and the stacking line for the low-speed axial fan. The aerodynamic characteristics of the axial fan with a shroud are explored by CFD with ANASYS CFX. A hybrid method, SST turbulence model for flow and FW-H equation for acoustics, is chosen to predict the radiated noise. The accuracy and reliability of predicted aerodynamic and aeroacoustics results are verified by comparing both computation and experimental data. A number of modified blades with different leaned angle, swept angle and the stacking lines are modeled and analyzed, and the investigation into the optimum choice of lean-swept blade and the stacking line is conducted according to aerodynamic performances and tonal noise. Q-criterion which can visualize the major flow disturbances is applied for the purpose of identification of acoustic sources. The turbulent flow structures on the leading edge, tip and suction side of the blade are main noise sources. An optimal modification is determined through the analysis of the aerodynamic performances and noise, which is to achieve the desired performances by blade sweep and lean and adjusting the stacking line. The results show that aerodynamic and acoustic performances of the optimized fan are better than that of the original fan and the improvement is more obvious to change the stacking line with centre of gravity compare to blade sweep and lean for the low-speed axial fan.

scholarly journals Evolution of the leading-edge vortex over a flapping wing mechanism

2020 ◽  
Vol 14 (2) ◽  
pp. 6888-6894
Author(s):  
Muhamad Ridzuan Arifin ◽  
A.F.M. Yamin ◽  
A.S. Abdullah ◽  
M.F. Zakaryia ◽  
S. Shuib ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Flapping Wing ◽  
Unsteady State ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Advance Ratio ◽  
Lift Enhancement ◽  
Lift And Drag

Leading-edge vortex governs the aerodynamic force production of flapping wing flyers. The primary factor for lift enhancement is the leading-edge vortex (LEV) that allows for stall delay that is associated with unsteady fluid flow and thus generating extra lift during flapping flight. To access the effects of LEV to the aerodynamic performance of flapping wing, the three-dimensional numerical analysis of flow solver (FLUENT) are fully applied to simulate the flow pattern. The time-averaged aerodynamic performance (i.e., lift and drag) based on the effect of the advance ratio to the unsteadiness of the flapping wing will result in the flow regime of the flapping wing to be divided into two-state, unsteady state (J<1) and quasi-steady-state(J>1). To access the benefits of aerodynamic to the flapping wing, both set of parameters of velocities 2m/s to 8m/s at a high flapping frequency of 3 to 9 Hz corresponding to three angles of attacks of α = 0o to α = 30o. The result shows that as the advance ratio increases the generated lift and generated decreases until advance ratio, J =3 then the generated lift and drag does not change with increasing advance ratio. It is also found that the change of lift and drag with changing angle of attack changes with increasing advance ratio. At low advance ratio, the lift increase by 61% and the drag increase by 98% between α =100 and α =200. The lift increase by 28% and drag increase by 68% between α = 200 and α = 300. However, at high advance ratio, the lift increase by 59% and the drag increase by 80% between α =100 and α = 200, while between α =200 and α =300 the lift increase by 20% and drag increase by 64%. This suggest that the lift and drag slope decreases with increasing advance ratio. In this research, the results had shown that in the unsteady state flow, the LEV formation can be indicated during both strokes. The LEV is the main factor to the lift enhancement where it generated the lower suction of negative pressure. For unsteady state, the LEV was formed on the upper surface that increases the lift enhancement during downstroke while LEV was formed on the lower surface of the wing that generated the negative lift enhancement. The LEV seem to breakdown at the as the wing flap toward the ends on both strokes.      

Sign in / Sign up

Export Citation Format

Share Document