Scaling laws for the propulsive performance of three-dimensional pitching propulsors – ADDENDUM

2019 ◽  
Vol 873 ◽  
pp. 1206-1206
Author(s):  
Fatma Ayancik ◽  
Qiang Zhong ◽  
Daniel B. Quinn ◽  
Aaron Brandes ◽  
Hilary Bart-Smith ◽  
...  
Keyword(s):  
Scaling Laws ◽  
Three Dimensional ◽  
Propulsive Performance

scholarly journals Scaling laws for the propulsive performance of three-dimensional pitching propulsors

2019 ◽  
Vol 871 ◽  
pp. 1117-1138 ◽  
Author(s):  
Fatma Ayancik ◽  
Qiang Zhong ◽  
Daniel B. Quinn ◽  
Aaron Brandes ◽  
Hilary Bart-Smith ◽  
...  
Keyword(s):  
Scaling Laws ◽  
Three Dimensional ◽  
Added Mass ◽  
Scaling Relations ◽  
The Novel ◽  
Vortex System ◽  
Propulsive Performance ◽  
Dimensional Scaling ◽  
Aspect Ratios ◽  
Thrust Production

Scaling laws for the thrust production and energetics of self-propelled or fixed-velocity three-dimensional rigid propulsors undergoing pitching motions are presented. The scaling relations extend the two-dimensional scaling laws presented in Moored & Quinn (AIAA J., 2018, pp. 1–15) by accounting for the added mass of a finite-span propulsor, the downwash/upwash effects from the trailing vortex system of a propulsor and the elliptical topology of shedding trailing-edge vortices. The novel three-dimensional scaling laws are validated with self-propelled inviscid simulations and fixed-velocity experiments over a range of reduced frequencies, Strouhal numbers and aspect ratios relevant to bio-inspired propulsion. The scaling laws elucidate the dominant flow physics behind the thrust production and energetics of pitching bio-propulsors, and they provide guidance for the design of bio-inspired propulsive systems.

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 Dimension reduction for thin films prestrained by shallow curvature

2021 ◽  
Vol 477 (2247) ◽  
Author(s):  
Silvia Jiménez Bolaños ◽  
Marta Lewicka
Keyword(s):  
Dimension Reduction ◽  
Scaling Laws ◽  
Three Dimensional ◽  
Riemannian Metrics ◽  
Regular Solutions ◽  
Shell Models ◽  
Energy Scaling ◽  
New Energy ◽  
Monge Ampere ◽  
Equivalent Conditions

We are concerned with the dimension reduction analysis for thin three-dimensional elastic films, prestrained via Riemannian metrics with weak curvatures. For the prestrain inducing the incompatible version of the Föppl–von Kármán equations, we find the Γ -limits of the rescaled energies, identify the optimal energy scaling laws, and display the equivalent conditions for optimality in terms of both the prestrain components and the curvatures of the related Riemannian metrics. When the stretching-inducing prestrain carries no in-plane modes, we discover similarities with the previously described shallow shell models. In higher prestrain regimes, we prove new energy upper bounds by constructing deformations as the Kirchhoff–Love extensions of the highly perturbative, Hölder-regular solutions to the Monge–Ampere equation obtained by means of convex integration.

scholarly journals Extraction of mechanical properties of materials through deep learning from instrumented indentation

2020 ◽  
Vol 117 (13) ◽  
pp. 7052-7062 ◽  
Author(s):  
Lu Lu ◽  
Ming Dao ◽  
Punit Kumar ◽  
Upadrasta Ramamurty ◽  
George Em Karniadakis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Deep Learning ◽  
Scaling Laws ◽  
Three Dimensional ◽  
Instrumented Indentation ◽  
Multilayered Structures ◽  
Mechanical Properties Of Materials ◽  
Properties Of Materials ◽  
Indentation Problem ◽  
And Function

Instrumented indentation has been developed and widely utilized as one of the most versatile and practical means of extracting mechanical properties of materials. This method is particularly desirable for those applications where it is difficult to experimentally determine the mechanical properties using stress–strain data obtained from coupon specimens. Such applications include material processing and manufacturing of small and large engineering components and structures involving the following: three-dimensional (3D) printing, thin-film and multilayered structures, and integrated manufacturing of materials for coupled mechanical and functional properties. Here, we utilize the latest developments in neural networks, including a multifidelity approach whereby deep-learning algorithms are trained to extract elastoplastic properties of metals and alloys from instrumented indentation results using multiple datasets for desired levels of improved accuracy. We have established algorithms for solving inverse problems by recourse to single, dual, and multiple indentation and demonstrate that these algorithms significantly outperform traditional brute force computations and function-fitting methods. Moreover, we present several multifidelity approaches specifically for solving the inverse indentation problem which 1) significantly reduce the number of high-fidelity datasets required to achieve a given level of accuracy, 2) utilize known physical and scaling laws to improve training efficiency and accuracy, and 3) integrate simulation and experimental data for training disparate datasets to learn and minimize systematic errors. The predictive capabilities and advantages of these multifidelity methods have been assessed by direct comparisons with experimental results for indentation for different commercial alloys, including two wrought aluminum alloys and several 3D printed titanium alloys.

scholarly journals On inertial-range scaling laws

1996 ◽  
Vol 306 ◽  
pp. 167-181 ◽  
Author(s):  
John C. Bowman
Keyword(s):  
Steady State ◽  
High Resolution ◽  
Scaling Laws ◽  
State Energy ◽  
Three Dimensional ◽  
Inertial Range ◽  
Energy Spectra ◽  
Two Dimensional ◽  
Unified Framework ◽  
Asymptotic Nature

Inertial-range scaling laws for two- and three-dimensional turbulence are re-examined within a unified framework. A new correction to Kolmogorov's k−5/3 scaling is derived for the energy inertial range. A related modification is found to Kraichnan's logarithmically corrected two-dimensional enstrophy-range law that removes its unexpected divergence at the injection wavenumber. The significance of these corrections is illustrated with steady-state energy spectra from recent high-resolution closure computations. Implications for conventional numerical simulations are discussed. These results underscore the asymptotic nature of inertial-range scaling laws.

scholarly journals Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes' shape and kinematics

2020 ◽  
Vol 17 (163) ◽  
pp. 20190655 ◽  
Author(s):  
Fatma Ayancik ◽  
Frank E. Fish ◽  
Keith W. Moored
Keyword(s):  
Aspect Ratio ◽  
Scaling Laws ◽  
Three Dimensional ◽  
Force Production ◽  
Numerical Data ◽  
Added Mass ◽  
Cetacean Species ◽  
Propulsive Efficiency ◽  
Fluid Environment ◽  
Pitch Ratio

Cetaceans convert dorsoventral body oscillations into forward velocity with a complex interplay between their morphological and kinematic features and the fluid environment. However, it is unknown to what extent morpho-kinematic features of cetaceans are intertwined to maximize their efficiency. By interchanging the shape and kinematic variables of five cetacean species, the interplay of their flukes morpho-kinematic features is examined by characterizing their thrust, power and propulsive efficiency. It is determined that the shape and kinematics of the flukes have considerable influence on force production and power consumption. Three-dimensional heaving and pitching scaling laws are developed by considering both added mass and circulatory-based forces, which are shown to closely model the numerical data. Using the scaling relations as a guide, it is determined that the added mass forces are important in predicting the trend between the efficiency and aspect ratio, however, the thrust and power are driven predominately by the circulatory forces. The scaling laws also reveal that there is an optimal dimensionless heave-to-pitch ratio h * that maximizes the efficiency. Moreover, the optimal h * varies with the aspect ratio, the amplitude-to-chord ratio and the Lighthill number. This indicates that the shape and kinematics of propulsors are intertwined, that is, there are specific kinematics that are tailored to the shape of a propulsor in order to maximize its propulsive efficiency.

scholarly journals Scaling the propulsive performance of heaving and pitching foils

2017 ◽  
Vol 822 ◽  
pp. 386-397 ◽  
Author(s):  
Daniel Floryan ◽  
Tyler Van Buren ◽  
Clarence W. Rowley ◽  
Alexander J. Smits
Keyword(s):  
Strouhal Number ◽  
Linear Dependence ◽  
Scaling Laws ◽  
Biological Data ◽  
Viscous Drag ◽  
Water Tunnel ◽  
Two Dimensional ◽  
Propulsive Performance ◽  
Reduced Frequency ◽  
Two Dimensional Flow

Scaling laws for the propulsive performance of rigid foils undergoing oscillatory heaving and pitching motions are presented. Water tunnel experiments on a nominally two-dimensional flow validate the scaling laws, with the scaled data for thrust, power and efficiency all showing excellent collapse. The analysis indicates that the behaviour of the foils depends on both Strouhal number and reduced frequency, but for motions where the viscous drag is small the thrust closely follows a linear dependence on reduced frequency. The scaling laws are also shown to be consistent with biological data on swimming aquatic animals.

Self-similar behaviour of a rotor wake vortex core

2014 ◽  
Vol 740 ◽  
Author(s):  
Mohamed Ali ◽  
Malek Abid
Keyword(s):  
Vortex Core ◽  
Scaling Laws ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Azimuthal Velocity ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Rotating Blade ◽  
Self Similar

AbstractWe report a self-similar behaviour of solutions (obtained numerically) of the Navier–Stokes equations behind a single-blade rotor. That is, the helical vortex core in the wake of a rotating blade is self-similar as a function of its age. Profiles of vorticity and azimuthal velocity in the vortex core are characterized, their similarity variables are identified and scaling laws of these variables are given. Solutions of incompressible three-dimensional Navier–Stokes equations for Reynolds numbers up to $Re= 2000$ are considered.

scholarly journals NOTE ON THE CALCULATION OF PROPELLER EFFICIENCY USING ELONGATED BODY THEORY

1994 ◽  
Vol 192 (1) ◽  
pp. 169-177 ◽  
Author(s):  
JY Cheng ◽  
R Blickhan
Keyword(s):  
Wave Speed ◽  
Plate Theory ◽  
Three Dimensional ◽  
Optimum Ratio ◽  
Fish Swimming ◽  
Amplitude Function ◽  
Propulsive Performance ◽  
Zero Values ◽  
Body Theory ◽  
Biological Literature

The elongated body theory has been widely used for calculations of the hydrodynamic propulsive performance of swimming fish. In the biological literature, terms containing the slope of the amplitude function at the tail end have been neglected in the calculations of thrust and efficiency, and a slope of zero has been assumed. However, some fishes, such as saithe and trout, have non-zero values of the slope near the tail end and, when this term is taken into account, the efficiency may be reduced by as much as 20 % and approaches the result given by the three-dimensional waving plate theory. The inclusion of the slope in the efficiency considerations results in an optimum ratio of the swimming speed to the wave speed that is clearly less than 1. It is suggested that the slope terms should be included in the estimation of propulsive performance for fish swimming with variable amplitude.

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