Aerodynamics of hovering flight in the long-eared bat Plecotus auritus

1976 ◽  
Vol 65 (2) ◽  
pp. 459-470 ◽  
Author(s):  
U. M. Norberg
Keyword(s):  
Steady State ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Quasi Steady State ◽  
Hovering Flight ◽  
Drag Coefficients ◽  
Lift And Drag

Steady-state aerodynamic and momentum theories were used for calculations of the lift and drag coefficients of Plecotus auritus in hovering flight. The lift coefficient obtained varies between 3-1 and 6-4, and the drag coefficient between --5-0 and 10-5, for the possible assumptions regarding the effective angles of attack during the upstroke. This demonstrates that hovering flight in Plecotus auritus can not be explained by quasi-steady-state aerodynamics. Thus, non-steady-state aerodynamics must prevail.

Gliding Flight of the Fulmar Petrel

1960 ◽  
Vol 37 (2) ◽  
pp. 330-338 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Drag Coefficient ◽  
Power Output ◽  
Lift Coefficient ◽  
Wing Area ◽  
Drag Coefficients ◽  
Minimum Drag ◽  
Gliding Flight ◽  
Lift And Drag

1. The basis used for estimating lift and drag coefficients is explained. A method of obtaining a photograph of a bird flying at known airspeed and rate of sink is described. 2. 96% of the speed measurements fall between 22 and 65 ft./sec., the average being 40 ft./sec. 3. A maximum lift coefficient of 1.8 can be achieved. Wing area is reduced with increasing speed. 4. The feet are used as airbrakes. 5. A comparison of the minimum drag coefficient (0.06) with the maximum estimated power output of the pectoral muscles leaves only a narrow margin of power available for climbing. 6. The performance diagram gives a minimum gliding angle of 1 in 8½, and a minimum sinking speed of just under 4 ft./sec. 7. The fulmar has apparently sacrificed the ability to soar dynamically over the sea in order to be able to fly slowly and thus utilize light upcurrents at cliff faces.

Effect of Gurney flap on the aerodynamic behavior of an airfoil in mutational ground effect

2020 ◽  
pp. 095441002094375
Author(s):  
Elham Roozitalab ◽  
Masoud Kharati-Koopaee
Keyword(s):  
Numerical Model ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Drag Coefficients ◽  
Airfoil Section ◽  
Gurney Flap ◽  
Presence And Absence ◽  
Lift And Drag

In this research, the effect of Gurney flap on the aerodynamic behavior of an airfoil in mutational ground effect is investigated. To perform this, lift and drag coefficients of NACA 4412 airfoil section in the presence and absence of Gurney flap in mutational ground effect are evaluated and compared. To provide a better illustration of the effect of Gurney flap on the aerodynamic behavior of the airfoil section in the mutational ground effect, results are obtained during the takeoff and landing processes. Validation of the used numerical model is also performed by comparison of the obtained results with those of other works and reasonable agreements were seen. Results show that inclusion of Gurney flap to the airfoil leads to higher variations of lift and drag coefficients during takeoff and landing process. During the takeoff process, the flapped airfoil results in a higher lift decrement and drag increment although an increase in distance of airfoil from the ground or angle of attack causes the lift decrement of the flapped airfoil to get close to that of clean airfoil. It is shown that during takeoff process, downwash is generated around the airfoil as the airfoil leaves the step and as the airfoil gets away from the step, the generated downwash decreases. During the landing process, at each distance of airfoil form the ground and angle of attack, the lift decrement and drag increment of the flapped airfoil are significant compared to that of the clean airfoil. Results exhibit that during landing process, upwash is generated around the airfoil as the airfoil reaches the step and further airfoil move on the step leads to the decrease in the upwash. The decrement in lift coefficient and also the increment in drag coefficient during landing process are more remarkable than those in takeoff process.

Analysis of Vortex-Induced Vibration of Riser using Spalart-Almaras Model

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Jaswar Koto ◽  
Abdul Khair Junaidi
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Offshore Structures ◽  
The Other ◽  
Main Concern ◽  
Vortex Induced Vibration ◽  
Simulation Results ◽  
Lift And Drag

Vortex-induced vibration is natural phenomena where an object is exposed to moving fluid caused vibration of the object. Vortex-induced vibration occurred due to vortex shedding behind the object. One of the offshore structures that experience this vortex-induced vibration is riser. The riser experience vortex-induced vibration due to vortex shedding caused by external load which is sea current. The effect of this vortex shedding to the riser is fatigue damage. Vortex-induced vibration of riser becomes the main concern in oil and gas industry since there will be a lots of money to be invested for the installation and maintenance of the riser. The previous studies of this vortex-induced vibration have been conducted by experimental method and Computational Fluid Dynamics (CFD) method in order to predict the vortex shedding behaviour behind the riser body for the determination of way to improve the riser design. This thesis represented the analysis of vortex induced vibration of rigid riser in two-dimensional. The analysis is conducted using Computational Fluid Dynamic (CFD) simulations at Reynolds number at 40, 200, 1000, and 1500. The simulations were performed using Spalart-Allmaras turbulent model to solve the transport equation of turbulent viscosity. The simulations results at Reynolds number 40 and 200 is compared with the other studies for the validation of the simulation, then further simulations were conducted at Reynolds number of 1000 and 1500. The coefficient of lift and drag were obtained from the simulations. The comparison of lift and drag coefficient between the simulation results in this study and experiment results from the other studies showed good agreement. Besides that, the in-line vibration and cross-flow vibration at different Reynolds number were also investigated. The drag coefficient obtained from the simulation results remain unchanged as the Reynolds number increased from 200 to 1500. The lift coefficient obtained from the simulations increased as the Reynolds number increased from 40 to 1500.

Drag and lift measurements of solid sports balls in still air

2017 ◽  
Vol 232 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Jeff R Kensrud ◽  
Lloyd V Smith
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Rough Surface ◽  
Lift Coefficient ◽  
Laboratory Setting ◽  
Air Drag ◽  
High Speeds ◽  
Drag And Lift ◽  
Lift And Drag

The following article considers lift and drag measurements of solid sports balls propelled through still air in a laboratory setting. The balls traveled at speeds ranging from 26 to 134 m/s with spin rates up to 3900 r/min. Light gates measured the speed and location of the balls at two locations from which lift and drag values were determined. Ball roughness varied from polished to rough surface protrusions, that is, seams as high as 1.5 mm. Lift and drag were observed to depend on speed, spin rate, surface roughness, and seam orientation. A drag crisis was observed on smooth balls as well as non-rotating seamed balls with seam heights less than 0.9 mm. The drag coefficient of approximately 0.42 was nearly constant with speed for spinning seamed balls with seam height greater than 0.9 mm. The still air drag coefficient of smooth balls was comparable to wind tunnel drag at low speeds ( Re < 2 × 105) and higher than wind tunnel results at high speeds ( Re > 2 × 105). The lift and drag coefficients of spinning balls increased with increasing spin rate. The lift coefficient of baseballs was not sensitive to ball orientation or seam height.

Effects of surface flow visualisation on aerodynamic loads at low Reynolds number

2015 ◽  
Vol 119 (1215) ◽  
pp. 663-672
Author(s):  
L. W. Traub ◽  
R. Waghela ◽  
E. M. Botero
Keyword(s):  
Drag Coefficient ◽  
Lift Coefficient ◽  
Time History ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Distribution Method ◽  
History Of ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

AbstractIn this article, the effect of on-surface flow visualisation (SVF) techniques on measured loads over an airfoil are explored. Titanium dioxide based mixture effects on the lift and drag coefficient are experimentally quantified at low Reynolds numbers by recording the time history as the patterns evolve and freeze. With statistical comparison based on Student’s t-distribution method, it was determined that the effect on the drag coefficient was minimal but the lift coefficient was slightly attenuated. Additionally, it was observed that at high angles-of-attack the temporal history of the flow as the wind tunnel ramps up may alter the steady-state flow field in the presence of a SFV mixture.

scholarly journals Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

2020 ◽  
Vol 01 (02) ◽  
pp. 29-36
Author(s):  
Md Rhyhanul Islam Pranto ◽  
Mohammad Ilias Inam
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Numerical Results ◽  
Ansys Fluent ◽  
Coefficient Increase ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.

scholarly journals Analysis on Flow Field Characteristics of Airfoil in Pitching Motion

2021 ◽  
Vol 2076 (1) ◽  
pp. 012069
Author(s):  
Rui Yin ◽  
Jing Huang ◽  
Zhi-Yuan He
Keyword(s):  
Flow Field ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Decisive Role ◽  
Aerodynamic Characteristics ◽  
Pitching Motion ◽  
Maximum Value ◽  
Flow Field Characteristics ◽  
Lift And Drag

Abstract Based on CFD, the flow field characteristics of NACA4412 airfoil are analyzed under pitching motion, and its aerodynamic characteristics are interpreted. The results show that streamline changes on the upper surface of the airfoil play a decisive role in the aerodynamic characteristics. The interaction between the vortex leads to fluctuations in the lift and drag coefficients. Under a big angle of attack, the secondary trailing vortex on the upper surface of the airfoil adheres to the trailing edge of the airfoil, resulting in an increased drag coefficient. Under a small angle of attack, the secondary trailing vortex can break away from the airfoil. The lift coefficient reaches the maximum value of 2.961 before the airfoil is turned upside down, and the drag coefficient reaches the maximum value of 1.515 after the airfoil is turned upside down, but the corresponding angles of attack of the two are equal.

Dragonfly flight. I. Gliding flight and steady-state aerodynamic forces.

1997 ◽  
Vol 200 (3) ◽  
pp. 543-556 ◽  
Author(s):  
JM Wakeling ◽  
CP Ellington
Keyword(s):  
Steady State ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
The Body ◽  
Flat Plates ◽  
Viscous Forces ◽  
Drag Forces ◽  
Aerodynamic Properties ◽  
Gliding Flight ◽  
Lift And Drag

The free gliding flight of the dragonfly Sympetrum sanguineum was filmed in a large flight enclosure. Reconstruction of the glide paths showed the flights to involve accelerations. Where the acceleration could be considered constant, the lift and drag forces acting on the dragonfly were calculated. The maximum lift coefficient (CL) recorded from these glides was 0.93; however, this is not necessarily the maximum possible from the wings. Lift and drag forces were additionally measured from isolated wings and bodies of S. sanguineum and the damselfly Calopteryx splendens in a steady air flow at Reynolds numbers of 700-2400 for the wings and 2500-15 000 for the bodies. The maximum lift coefficients (CL,max) were 1.07 for S. sanguineum and 1.15 for C. splendens, which are greater than those recorded for all other insects except the locust. The drag coefficient at zero angle of attack ranged between 0.07 and 0.14, being little more than the Blassius value predicted for flat plates. Dragonfly wings thus show exceptional steady-state aerodynamic properties in comparison with the wings of other insects. A resolved-flow model was tested on the body drag data. The parasite drag is significantly affected by viscous forces normal to the longitudinal body axis. The linear dependence of drag on velocity must thus be included in models to predict the parasite drag on dragonflies at non-zero body angles.

scholarly journals Effect of the Backward-Facing Step Location on the Aerodynamics of a Morphing Wing

2021 ◽  
Author(s):  
Fadi Magdy R Mishriky ◽  
Paul Walsh
Keyword(s):  
Drag Coefficient ◽  
Transition Point ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Suction Side ◽  
Backward Facing Step ◽  
Viscous Boundary Layer ◽  
Airfoil Surface ◽  
Aerodynamic Properties ◽  
Lift And Drag

Over the last decade, aircraft morphing technology has drawn a lot of attention in the aerospace community, because it is likely to improve the aerodynamic performance and the versatility of aircraft at different flight regimes. With the fast paced advancements in this field, a parallel stream of research is studying different materials and designs to develop reliable morphing skins. A promising candidate for a viable morphing skin is the sliding skin, where two or more rigid surfaces remain in contact and slide against each other during morphing. The overlapping between each two panels create a backward-facing step on the airfoil surface which has a critical effect on the aerodynamics of the wing. This paper presents a numerical study of the effect of employing a backward-facing step on the suction side of a National Advisory Committee for Aeronautics (NACA) 2412 airfoil at a high Reynolds number of 5.9 × 106. The effects of the step location on the lift coefficient, drag coefficient and critical angle of attack are studied to find a favorable location for the step along the chord-wise direction. Results showed that employing a step on the suction side of the NACA 2412 airfoil can adversely affect the aforementioned aerodynamic properties. A drop of 21.1% in value of the lift coefficient and an increase of 120.8% in the drag coefficient were observed in case of a step located at 25% of the chord length. However, these effects are mitigated by shifting the step location towards the trailing edge. Introducing a step on the airfoil caused the airfoil’s thickness to change, which in turn has affected the transition point of the viscous boundary layer from laminar to turbulent. The location of the step, prior or post the transition point, has a noteworthy effect on the pressure and shear stress distribution, and consequently on the values of the lift and drag coefficients.

scholarly journals Effect of the Backward-Facing Step Location on the Aerodynamics of a Morphing Wing

2021 ◽  
Author(s):  
Rshare Library ◽  
Fadi Magdy R Mishriky ◽  
Paul Walsh
Keyword(s):  
Drag Coefficient ◽  
Transition Point ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Suction Side ◽  
Backward Facing Step ◽  
Viscous Boundary Layer ◽  
Airfoil Surface ◽  
Aerodynamic Properties ◽  
Lift And Drag

Over the last decade, aircraft morphing technology has drawn a lot of attention in the aerospace community, because it is likely to improve the aerodynamic performance and the versatility of aircraft at different flight regimes. With the fast paced advancements in this field, a parallel stream of research is studying different materials and designs to develop reliable morphing skins. A promising candidate for a viable morphing skin is the sliding skin, where two or more rigid surfaces remain in contact and slide against each other during morphing. The overlapping between each two panels create a backward-facing step on the airfoil surface which has a critical effect on the aerodynamics of the wing. This paper presents a numerical study of the effect of employing a backward-facing step on the suction side of a National Advisory Committee for Aeronautics (NACA) 2412 airfoil at a high Reynolds number of 5.9 × 106. The effects of the step location on the lift coefficient, drag coefficient and critical angle of attack are studied to find a favorable location for the step along the chord-wise direction. Results showed that employing a step on the suction side of the NACA 2412 airfoil can adversely affect the aforementioned aerodynamic properties. A drop of 21.1% in value of the lift coefficient and an increase of 120.8% in the drag coefficient were observed in case of a step located at 25% of the chord length. However, these effects are mitigated by shifting the step location towards the trailing edge. Introducing a step on the airfoil caused the airfoil’s thickness to change, which in turn has affected the transition point of the viscous boundary layer from laminar to turbulent. The location of the step, prior or post the transition point, has a noteworthy effect on the pressure and shear stress distribution, and consequently on the values of the lift and drag coefficients.

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