scholarly journals Fin sweep angle does not determine flapping propulsive performance

2020 ◽  
Author(s):  
Andhini N. Zurman-Nasution ◽  
Bharathram Ganapathisubramani ◽  
Gabriel D. Weymouth
Keyword(s):  
Correlation Coefficient ◽  
Large Range ◽  
Three Dimensional ◽  
Leading Edge ◽  
Potential Sweep ◽  
Sweep Angle ◽  
Propulsive Performance ◽  
Maximum Angle ◽  
And Robotics ◽  
Three Dimensional Simulations

The importance of the leading-edge sweep angle of propulsive surfaces used by unsteady swimming and flying animals has been an issue of debate for many years, spurring studies in biology, engineering, and robotics with mixed conclusions. In this work we provide results from an extensive set of three-dimensional simulations of finite foils undergoing tail-like (pitch-heave) and flipper-like (twist-roll) kinematics for a range of sweep angles while carefully controlling all other parameters. No significant change in force and power is observed for tail-like motions as the sweep angle increases, with a corresponding efficiency drop of only ≈ 2%. Similar findings are seen in flipper-like motion and the overall correlation coefficient between sweep angle and propulsive performance is 0.1-6.7%. This leads to a conclusion that fish tails or mammal flukes can have a large range of potential sweep angles without significant negative propulsive impact. A similar conclusion applies to flippers; although there is a slight benefit to avoid large sweep angles for flippers, this could be easily compensated by adjusting other hydrodynamics parameters such as flapping frequency, amplitude and maximum angle of attack to gain higher thrust and efficiency.

scholarly journals Fin sweep angle does not determine flapping propulsive performance

2021 ◽  
Vol 18 (178) ◽  
pp. 20210174
Author(s):  
Andhini N. Zurman-Nasution ◽  
Bharathram Ganapathisubramani ◽  
Gabriel D. Weymouth
Keyword(s):  
Large Range ◽  
Three Dimensional ◽  
Leading Edge ◽  
Potential Sweep ◽  
Sweep Angle ◽  
Maximum Angle ◽  
Primary Finding ◽  
Similar Range ◽  
And Robotics ◽  
Three Dimensional Simulations

The importance of the leading-edge sweep angle of propulsive surfaces used by unsteady swimming and flying animals has been an issue of debate for many years, spurring studies in biology, engineering, and robotics with mixed conclusions. In this work, we provide results from three-dimensional simulations on single-planform finite foils undergoing tail-like (pitch-heave) and flipper-like (twist-roll) kinematics for a range of sweep angles covering a substantial portion of animals while carefully controlling all other parameters. Our primary finding is the negligible 0.043 maximum correlation between the sweep angle and the propulsive force and power for both tail-like and flipper-like motions. This indicates that fish tails and mammal flukes with similar range and size can have a large range of potential sweep angles without significant negative propulsive impact. Although there is a slight benefit to avoiding large sweep angles, this is easily compensated by adjusting the fin’s motion parameters such as flapping frequency, amplitude and maximum angle of attack to gain higher thrust and efficiency.

Kinematic Analysis of 3-D Swept Shock Surfaces in Axial Flow Compressors

2000 ◽  
Vol 123 (3) ◽  
pp. 490-500 ◽  
Author(s):  
Peng Shan
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
Research Field ◽  
High Loading ◽  
Kinematic Characteristic ◽  
Sweep Angle ◽  
Quantitative Classification ◽  
Axial Flow Compressors ◽  
Blade Leading Edge

This paper is part II of a comprehensive study on the blade leading edge sweep/bend of supersonic and transonic axial compressors. The paper explores and analyzes the kinematic characteristic variables of three-dimensional (3-D) swept shock surfaces. In the research field studying the sweep aerodynamics of axial flow compressors and fans, many types of high loading swept blades are under intensive study. So, in both direct and inverse design methods and experimental validations, an accurate grasp of the sweep characteristic of the blade’s 3-D swept shock surface becomes of more concern than before. Associated with relevant blading variables, this paper studies the forward and zero and backward sweeps of shock surfaces, defines and resolves every kind of useful sweep angle, obtains dimensionless sweep similarity factors, suggests a kind of method for the quantitative classification of 3-D shock structures, and proposes the principle of 3-D shock structure measurements. Two rotor blade leading edge shock surfaces from two high loading single stage fans are analyzed and contrasted. This study is the foundation of the kinematic design of swept shock surfaces.

A scaling for vortex formation on swept and unswept pitching wings

2017 ◽  
Vol 832 ◽  
pp. 697-720 ◽  
Author(s):  
Kyohei Onoue ◽  
Kenneth S. Breuer
Keyword(s):  
Control Volume ◽  
Vortex Formation ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Leading Edge ◽  
Sweep Angle ◽  
Reduced Frequency ◽  
Vortex Formation Time ◽  
The Stability ◽  
Vorticity Transport

We examine the dynamics of the leading-edge vortex (LEV) on a rapidly pitching plate with the aim of elucidating the underlying flow physics that dictates the stability and circulation of the LEV. A wide variety of flow conditions is considered in the present study by systematically varying the leading-edge sweep angle ($\unicode[STIX]{x1D6EC}=0^{\circ }$, $11.3^{\circ }$, $16.7^{\circ }$) and the reduced frequency ($f^{\ast }=0.064{-}0.151$), while keeping the pitching amplitude and the Reynolds number fixed. Tomographic particle image velocimetry is used to characterise the three-dimensional fluid motion inside the vortex core and its relation to the LEV stability and growth. A series of control volume analyses are performed to quantify the relative importance of the vorticity transport phenomena taking place inside the LEV to the overall vortex development. We show that, near the wing apex where tip effects can be neglected, the vortex develops in a nominally two-dimensional manner, despite the presence of inherently three-dimensional vortex dynamics such as vortex stretching and compression. Furthermore, we demonstrate that the vortex formation time and circulation growth are well-described by the principles of optimal vortex formation number, and that the occurrence of vortex shedding is dictated by the relative energetics of the feeding shear layer and the resulting vortex.

Numerical Study of the Propulsive Performance of the Hollow Rotating Detonation Engine with a Laval Nozzle

2017 ◽  
Vol 34 (1) ◽  
Author(s):  
Songbai Yao ◽  
Xinmeng Tang ◽  
Jianping Wang
Keyword(s):  
Laval Nozzle ◽  
Numerical Study ◽  
Specific Impulse ◽  
Three Dimensional ◽  
Propulsive Performance ◽  
Rotating Detonation Engine ◽  
Detonation Engine ◽  
One Step ◽  
Rotating Detonation ◽  
Three Dimensional Simulations

AbstractThe aim of the present paper is to investigate the propulsive performance of the hollow rotating detonation engine (RDE) with a Laval nozzle. Three-dimensional simulations are carried out with a one-step Arrhenius chemistry model. The Laval nozzle is found to improve the propulsive performance of hollow RDE in all respects. The thrust and fuel-based specific impulse are increased up to 12.60 kN and 7484.40 s, respectively, from 6.46 kN and 6720.48 s. Meanwhile, the total mass flow rate increases from 3.63 kg/s to 6.68 kg/s. Overall, the Laval nozzle significantly improves the propulsive performance of the hollow RDE and makes it a promising model among detonation engines.

scholarly journals Comparison and analyses of a variable span-morphing of the tapered wing with a varying sweep angle

2020 ◽  
Vol 124 (1278) ◽  
pp. 1146-1169
Author(s):  
M. Elelwi ◽  
M.A. Kuitche ◽  
R.M. Botez ◽  
T.M. Dao
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Original Position ◽  
Concept Design ◽  
Wing Design ◽  
Sweep Angle ◽  
Ansys Fluent ◽  
Fixed Part ◽  
Variable Span

ABSTRACTThis work presents a comparative study of design and development, in addition, of analyses of variable span morphing of the tapered wing (VSMTW) for the unmanned aerial vehicle (UAV). The proposed concept consists in the sliding of the inner section into the fixed part along the wing with varying the angle of the inner section inside the fixed part (parallel with the leading edge and the moving-wing axis is coincident to the fixed-wing axis) within two configurations. The wing design is based on a NACA 4412 aerofoil with the root chord of 0.675m and the tip chord of 0.367m for the fixed segment and 0.320m for the moving segment. Morphing wing analysis occurs at three selected locations that have been specified for extending and modifying span length by (25%, 50%, and 75%) of its original length to fulfill various flight mission requirements. The main objective of this paper is to compare the aerodynamic characteristics for several span lengths and sweep angles and to find their most efficient combinations. The wing is optimised for different velocities during all phases of flight (min speed, loiter, cruise, and max speed) which are 17, 34, 51, and 68m/s, respectively. The analyses are performed by computing forces (drag and lift) and moments at various altitudes, such as at the sea level, at 5,000 and 10,000ft. Two-dimensional aerodynamic analyses are carried out using XFLR5 code, and the ANSYS Fluent solver is used for investigating the flow field on the three-dimensional wing structure. It has been observed that a variable span morphing of tapered wing technology with a variable sweep angle can deliver up to 32.93% improved aerodynamic efficiency. This concept design can also be used for the aircraft roll motion technique instead of conventional control devices. Furthermore, the range flight mission increases up to 46.89% when the wing is placed at its full length compared to an original position. Finally, it has been concluded from this study that the wing design is more sensitive to the changing angle of the inner section and more efficient in terms of aerodynamic characteristics.

Swimming performance, resonance and shape evolution in heaving flexible panels

2018 ◽  
Vol 847 ◽  
pp. 386-416 ◽  
Author(s):  
Alexander P. Hoover ◽  
Ricardo Cortez ◽  
Eric D. Tytell ◽  
Lisa J. Fauci
Keyword(s):  
Computational Model ◽  
Swimming Speed ◽  
Material Properties ◽  
Computational Study ◽  
Swimming Performance ◽  
Three Dimensional ◽  
Leading Edge ◽  
Trailing Edge ◽  
Propulsive Performance ◽  
Flexible Panels

Many animals that swim or fly use their body to accelerate the fluid around them, transferring momentum from their flexible bodies and appendages to the surrounding fluid. The kinematics that emerge from this transfer result from the coupling between the fluid and the active and passive material properties of the flexible body or appendages. To elucidate the fundamental features of the elastohydrodynamics of flexible appendages, recent physical experiments have quantified the propulsive performance of flexible panels that are actuated on their leading edge. Here we present a complementary computational study of a three-dimensional flexible panel that is heaved sinusoidally at its leading edge in an incompressible, viscous fluid. These high-fidelity numerical simulations enable us to examine how propulsive performance depends on mechanical resonance, fluid forces, and the emergent panel deformations. Moreover, the computational model does not require the tethering of the panel. We therefore compare the thrust production of tethered panels to the forward swimming speed of the same panels that can move forward freely. Varying both the passive material properties and the heaving frequency of the panel, we find that local peaks in trailing edge amplitude and forward swimming speed coincide and that they are determined by a non-dimensional quantity, the effective flexibility, that arises naturally in the Euler–Bernoulli beam equation. Modal decompositions of panel deflections reveal that the amplitude of each mode is related to the effective flexibility. Panels of different material properties that are actuated so that their effective flexibilities are closely matched have modal contributions that evolve similarly over the phase of the heaving cycle, leading to similar vortex structures in their wakes and comparable thrust forces and swimming speeds. Moreover, local peaks in the swimming speed and trailing edge amplitude correspond to peaks in the contributions of the different modes. This computational study of freely swimming flexible panels gives further insight into the role of resonance in swimming performance that is important in the engineering and design of robotic propulsors. Moreover, we view this reduced model and its comparison to laboratory experiments as a building block and validation for a more comprehensive three-dimensional computational model of an undulatory swimmer that will couple neural activation, muscle mechanics and body elasticity with the surrounding viscous, incompressible fluid.

Investigation on the effect of leading edge tubercles of sweptback wing at low reynolds number

2020 ◽  
Vol 21 (6) ◽  
pp. 621
Author(s):  
Veerapathiran Thangaraj Gopinathan ◽  
John Bruce Ralphin Rose ◽  
Mohanram Surya
Keyword(s):  
Leading Edge ◽  
Reynolds Numbers ◽  
Sweep Angle ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Flow Energy ◽  
Airplane Wing ◽  
Low Reynolds ◽  
Naca 0015 ◽  
Wing Performance

Aerodynamic efficiency of an airplane wing can be improved either by increasing its lift generation tendency or by reducing the drag. Recently, Bio-inspired designs have been received greater attention for the geometric modifications of airplane wings. One of the bio-inspired designs contains sinusoidal Humpback Whale (HW) tubercles, i.e., protuberances exist at the wing leading edge (LE). The tubercles have excellent flow control characteristics at low Reynolds numbers. The present work describes about the effect of tubercles on swept back wing performance at various Angle of Attack (AoA). NACA 0015 and NACA 4415 airfoils are used for swept back wing design with sweep angle about 30°. The modified wings (HUMP 0015 A, HUMP 0015 B, HUMP 4415 A, HUMP 4415 B) are designed with two amplitude to wavelength ratios (η) of 0.1 & 0.24 for the performance analysis. It is a novel effort to analyze the tubercle vortices along the span that induce additional flow energy especially, behind the tubercles peak and trough region. Subsequently, Co-efficient of Lift (CL), Co-efficient of Drag (CD) and boundary layer pressure gradients also predicted for modified and baseline (smooth LE) models in the pre & post-stall regimes. It was observed that the tubercles increase the performance of swept back wings by the enhanced CL/CD ratio in the pre-stall AoA region. Interestingly, the flow separation region behind the centerline of tubercles and formation of Laminar Separation Bubbles (LSB) were asymmetric because of the sweep.

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