Nonlinear oscillations of shape-morphing submerged structures: Control of hydrodynamic forces and power dissipation via active flexibility

2017 ◽  
Vol 74 ◽  
pp. 35-52 ◽  
Author(s):  
Syed N. Ahsan ◽  
Matteo Aureli
Keyword(s):  
Power Dissipation ◽  
Nonlinear Oscillations ◽  
Hydrodynamic Forces ◽  
Shape Morphing

Three-Dimensional Analysis of Shape-Morphing Cantilever Oscillations in Viscous Fluids

2017 ◽  
Author(s):  
Syed N. Ahsan ◽  
Matteo Aureli
Keyword(s):  
Power Dissipation ◽  
Stokes Problem ◽  
Three Dimensional ◽  
Optimum Level ◽  
Power Losses ◽  
Linear Vibration ◽  
Shape Morphing ◽  
Propulsion Performance ◽  
Newtonian Viscous Fluid ◽  
Actuation Systems

In this paper, we study the linear flexural oscillations of a cantilever beam undergoing chord-wise shape-morphing deformation in a quiescent, Newtonian, viscous fluid. The shape-morphing deformation is prescribed for the beam cross section to an arc of a circle by specifying a periodic maximum curvature continuously along the axis of the structure. This particular strategy is investigated as a possible way to manipulate fluid-structure interaction mechanisms by modifying the hydrodynamic interactions in the vicinity of the submerged structure. Since we focus on the linear vibration of the beam, the fluid flow is described using three-dimensional unsteady Stokes hydrodynamics. By solving the linear unsteady Stokes problem in the frequency domain with a Stokeslet method, we identify the effect of the proposed shape-morphing strategy on the propulsion performance by estimating thrust, lift, and hydrodynamic power dissipation for a range of prescribed deformations. We verify the results obtained from our boundary element method against results from the existing literature. Our findings show a possible improvement in propulsion characteristics and minimization of hydrodynamic power dissipation, for an optimum level of shape-morphing deformation which is aspect ratio-dependent. Results from this study can aid in designing and operating cantilever-based underwater actuation systems for which the multi-objective goal of power losses reduction and propulsion performance improvement is sought.

Torsional Oscillations of a Shape-Morphing Plate in Viscous Fluids

2019 ◽  
Author(s):  
Syed N. Ahsan ◽  
Matteo Aureli
Keyword(s):  
Power Dissipation ◽  
Stokes Equations ◽  
Oscillation Amplitude ◽  
Finite Amplitude ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Torsional Oscillations ◽  
Shape Morphing ◽  
Moment Control ◽  
Interaction Problem

Abstract In this paper, we investigate finite amplitude torsional oscillations of a shape-morphing plate submerged in a quiescent, Newtonian, incompressible fluid. To address this problem, we focus on a two-dimensional cross section of the plate and para-metrically study hydrodynamic moments and power dissipation during the plate oscillation as a function of the shape-morphing deformation intensity and the oscillation amplitude. This fluid-structure interaction problem is tackled within the framework of a computational fluid dynamics model where the fluid flow is described via the Navier-Stokes equations and the deformations of the structure are prescribed. The results demonstrate a gradual reduction of hydrodynamic moment and nonmonotonic power dissipation behavior as the imposed shape-morphing becomes more aggressive. In addition, power dissipation can be minimized for an optimum value of the shape-morphing intensity. Results from this study are relevant in underwater systems subjected to torsional oscillations and demonstrate an avenue for hydrodynamic moment control and reduction of energy losses.

Minimization of Hydrodynamic Power Losses in Oscillating Submerged Structures by a Novel Shape-Morphing Strategy

2016 ◽  
Author(s):  
Syed N. Ahsan ◽  
Matteo Aureli
Keyword(s):  
Power Dissipation ◽  
Flexible Structures ◽  
Energy Losses ◽  
Moving Wall ◽  
Shape Morphing ◽  
Computational Fluid Dynamics Simulations ◽  
Expenditure Reduction ◽  
Newtonian Viscous Fluid ◽  
Dynamics Simulations ◽  
Interaction Problem

In this paper, we investigate the two dimensional fluid-structure interaction problem of the oscillation of a shape-morphing plate in a quiescent, Newtonian, viscous fluid. The plate is considered as a moving wall for the fluid undergoing two concurrent periodic motions: a rigid oscillation along its transverse direction coupled to a shape-morphing deformation to an arc of a circle with prescribed maximum curvature. Differently from studies concerned with passive flexible structures, here, we introduce the prescribed deformation to specifically manipulate vortex-shedding and modulate hydrodynamic forces and energy losses during underwater oscillations. Computational fluid dynamics simulations are performed to evaluate the effect of the prescribed deformation strategy on the added mass and damping effect along with the hydrodynamic power dissipation. We observe that a minimum in the hydrodynamic power dissipation exists for an optimum curvature of the plate. This finding may allow significant power expenditure reduction in underwater vibrating systems where minimization of energy losses or maximization of quality factor are desirable.

Analyzing the On-State Power Dissipation in Stepped-Output Diode-Clamped Multi-Level Inverter

2010 ◽  
Vol E93-C (12) ◽  
pp. 1670-1678 ◽  
Author(s):  
Ehsan ESFANDIARI ◽  
Norman Bin MARIUN ◽  
Mohammad Hamiruce MARHABAN ◽  
Azmi ZAKARIA
Keyword(s):  
Power Dissipation ◽  
State Power ◽  
Multi Level

MULTIPLE-SCALE AND NUMERICAL ANALYSES FOR THE NONLINEAR OSCILLATIONS OF A GAS BUBBLE SURROUNDED BY A MAXWELL'S FLUID

2019 ◽  
Vol 46 (3) ◽  
pp. 261-275
Author(s):  
César Yepes ◽  
Jorge Naude ◽  
Federico Mendez ◽  
Margarita Navarrete ◽  
Fátima Moumtadi
Keyword(s):  
Nonlinear Oscillations ◽  
Multiple Scale ◽  
Numerical Analyses ◽  
Gas Bubble
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