Energy harvesting characteristics of flapping wings with the free-surface effect

2021 ◽  
Author(s):  
Bing Zhu ◽  
Wenhao Cheng ◽  
Jingyan Geng ◽  
Junwei Zhang
Keyword(s):  
Free Surface ◽  
Energy Harvesting ◽  
Surface Effect ◽  
Flapping Wings

Irreversible Adsorption Erases the Free Surface Effect on the Tg of Supported Films of Poly(4-tert-butylstyrene)

2017 ◽  
Vol 6 (4) ◽  
pp. 354-358 ◽  
Author(s):  
Natalia G. Perez-de-Eulate ◽  
Michele Sferrazza ◽  
Daniele Cangialosi ◽  
Simone Napolitano
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
Irreversible Adsorption

Practical Evaluation of Steady Flow Resulting from a Free-Surface Pressure Patch

2009 ◽  
Vol 53 (03) ◽  
pp. 137-150
Author(s):  
Francis Noblesse ◽  
Gérard Delhommeau ◽  
Chi Yang
Keyword(s):  
Free Surface ◽  
Surface Pressure ◽  
High Speed ◽  
Surface Effect ◽  
Practical Method ◽  
Analytical Approximation ◽  
Surface Boundary ◽  
Steady Flows ◽  
Local Flow ◽  
The Green Function

The linearized potential flow resulting from a distribution of pressure that advances at constant speed along a straight path at the free surface of calm water, of effectively infinite depth and lateral extent, is considered. A practical method for evaluating the free-surface elevation caused by the moving free-surface pressure patch—which can be used to model steady flows of air-cushion vehicles, high-speed planing boats, surface-effect ships, and some types of hybrid ships—is given. The key ingredient of this method is a highly simplified analytical approximation to the local-flow component in the expression for the Green function associated with the classic Michell-Kelvin linearized free-surface boundary condition.

An Analysis of Heave Added Mass and Damping of a Surface-Effect Ship

1981 ◽  
Vol 25 (01) ◽  
pp. 44-61
Author(s):  
C. H. Kim ◽  
S. Tsakonas
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Surface Effect ◽  
Practical Method ◽  
Added Mass ◽  
Damping Coefficients ◽  
Calm Water ◽  
Surface Effect Ship ◽  
Long Time ◽  
Computational Procedures

The analysis presents a practical method for evaluating the added-mass and damping coefficients of a heaving surface-effect ship in uniform translation. The theoretical added-mass and damping coefficients and the heave response show fair agreement with the corresponding experimental values. Comparisons of the coupled aero-hydrodynamic and uncoupled analytical results with the experimental data prove that the uncoupled theory, dominant for a long time, that neglects the free-surface effects is an oversimplified procedure. The analysis also provides means of estimating the wave elevation of the free surface, the escape area at the stern and the volume which are induced by a heaving surface-effect ship in uniform translation in otherwise calm water. Computational procedures have been programmed in the FORTRAN IV language and adapted to the PDP-10 high-speed digital computer.

Radiation Hydrodynamics of a Surface Effect Ship

2013 ◽  
Author(s):  
Palaniswamy Ananthakrishnan
Keyword(s):  
Free Surface ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Stokes Equations ◽  
Surface Effect ◽  
Wave Radiation ◽  
Absolute Pressure ◽  
Radiation Hydrodynamics ◽  
Surface Effect Ship ◽  
Air Cushion

The radiation hydrodynamics of a heaving surface effect ship (SES) is examined including the effect of air compressibility on the hydrodynamic forces and surface waves. Of particular focus of the study has been on determining the nonlinear viscous and air compressibility effects at natural frequencies corresponding to the piston and sloshing wave modes between the hulls and at the natural frequency corresponding to the heave motion of a surface effect ship with the restoring force dominated by the compressibility of the air cushion. In the present paper, the air cushion pressure is assumed to be uniform with its variation due to change of volume modeled using the adiabatic gas law pVγ = constant, where p denotes the absolute pressure of the air, V the air volume bounded by the side hulls, the free surface and the wet deck, and γ the ratio of specific heats Cp/Cv which is about 1.4 for air. The incompressible Navier-Stokes equations governing the nonlinear viscous wave-air-body interaction problem is solved in the time domain using a finite-difference method based on boundary fitted coordinates. New results presented in this paper show that air cushion compressibility affects the generation of waves and wave radiation forces significantly even at small amplitude of hull motion. As already well known, the free surface nonlinearity due to hull motion is significant for large amplitude of oscillation. At small amplitude of body oscillation, significant nonlinearity can be caused by air compressibility resulting in the generation of higher harmonic waves and forces. The results also highlight the significance of viscosity and flow separation, in conjunction with air compressibility, in the case of large amplitude hull motion with a small draft.

Comparison of Single and Overset Grid Techniques for CFD Simulations of a Surface Effect Ship

2014 ◽  
Author(s):  
Colton G. Clark ◽  
David G. Lyons ◽  
Wayne L. Neu
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
The Body ◽  
Computational Domain ◽  
Overset Grid ◽  
Hexahedral Mesh ◽  
Surface Effect Ship ◽  
Mesh Resolution ◽  
Refined Meshes ◽  
Air Cushion

Overset, or Chimera meshes are used to discretize the governing equations within a computational domain using multiple meshes that overlap in an arbitrary manner. The overset mesh technique is most applicable to problems dealing with multiple or moving bodies. In order to extend existing full craft CFD (RANS) simulations of a surface effect ship (SES) into shallow water and maneuvering cases, an overset mesh is needed. Deep water simulations were carried out using both single and overset grid techniques for evaluation of the overset grid application. The single grid technique applies a hexahedral mesh to the fluid domain and SES geometry. An adequate mesh resolution was determined by performing a grid convergence study on a series of systematically refined meshes. An overset mesh of the same resolution was then constructed and was fixed to the body. Drag and pitch results are compared among the two simulations. Free surface elevations around the craft and under the air cushion for simulations with the single and overset meshes are compared. Steady-state simulations using the overset mesh and the single mesh show general similarities in drag, pitch, and free surface elevations.

Multiscale modeling of free-surface effect on crack formation in unidirectional off-axis laminates

2017 ◽  
Vol 98 ◽  
pp. 136-146 ◽  
Author(s):  
Yuta Kumagai ◽  
Sota Onodera ◽  
Yoshiko Nagumo ◽  
Tomonaga Okabe ◽  
Kenichi Yoshioka
Keyword(s):  
Free Surface ◽  
Multiscale Modeling ◽  
Crack Formation ◽  
Surface Effect

scholarly journals Numerical investigations of the free surface effect in three-dimensional polycrystalline aggregates

2013 ◽  
Vol 70 ◽  
pp. 150-162 ◽  
Author(s):  
Yoann Guilhem ◽  
Stéphanie Basseville ◽  
François Curtit ◽  
Jean-Michel Stéphan ◽  
Georges Cailletaud
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
Three Dimensional ◽  
Numerical Investigations ◽  
Polycrystalline Aggregates

Resonance wave pumping with surface waves

2016 ◽  
Vol 811 ◽  
pp. 1-36 ◽  
Author(s):  
Remi A. Carmigniani ◽  
Michel Benoit ◽  
Damien Violeau ◽  
Morteza Gharib
Keyword(s):  
Free Surface ◽  
Energy Harvesting ◽  
Mass Transport ◽  
Surface Condition ◽  
Simplified Model ◽  
Mean Flow ◽  
Resonance Wave ◽  
Unidirectional Flow ◽  
Wave Resonance ◽  
Resonance Frequencies

In this paper, we present a novel extension of impedance (Liebau) wave pumping to a free-surface condition where resonance pumping could be used for hydraulic energy harvesting. Similar pumping behaviours are reported. Surface envelopes of the free surface are shown and outline two different dynamics: U-tube oscillator and wave/resonance pumping. The latter is particularly interesting, since, from an oscillatory motion, a unidirectional flow with small to moderate oscillations is generated. A linear theory is developed to evaluate pseudo-analytically the resonance frequencies of the pump using eigenfunction expansions, and a simplified model is proposed to understand the main pumping mechanism in this type of pump. It is found that the Stokes mass transport is driving the pump. The conversion of energy from paddle oscillation to mean flow is evaluated. Efficiency up to 22 % is reported.

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