Qualitative and Quantitative Study of the Flow Physics in the Vicinity of an Oscillating Plate in Viscous Fluids

2017 ◽  
Author(s):  
Bishwash Shrestha ◽  
Syed N. Ahsan ◽  
Matteo Aureli
Keyword(s):  
Vortex Shedding ◽  
Force Measurement ◽  
Hydrodynamic Forces ◽  
Primary Objective ◽  
Analytical Models ◽  
Sensors And Actuators ◽  
Fluid Structure ◽  
Qualitative And Quantitative ◽  
Newtonian Viscous Fluid ◽  
Mechanical Sensors

In this paper, we report on a comprehensive experimental study on the fluid-structure interactions of a submerged rigid plate undergoing harmonic oscillations in a quiescent, Newtonian, viscous fluid. We conduct a detailed qualitative and quantitative analysis of the problem for broad ranges of oscillation parameters, including frequency and amplitude, to highlight the fluid-structure interaction mechanisms responsible for the hydrodynamic forces acting on the plate. The primary objective of this study is to understand the effect of the oscillation parameters on the resulting qualitative flow patterns and analyze their relation with vortex shedding and hydrodynamic forces. We classify different flow regimes depending on the behavior of the flow in the vicinity of the structure, with particular focus on vortex shedding and symmetry breaking phenomena, and analyze the forces in each regime by using particle image velocimetry and direct force measurement via a load cell. Comparison of the obtained experimental results against values predicted from numerical and semi-analytical models shows good agreement between our approach and the literature. Fundamental findings from this work have direct relevance to various engineering applications, including energy harvesting devices, biomimetic robotic system, and micro-mechanical sensors and actuators.

Behavior of a smart one-way micro-valve considering fluid–structure interaction

2018 ◽  
Vol 29 (20) ◽  
pp. 3960-3971 ◽  
Author(s):  
H Mazaheri ◽  
AH Namdar ◽  
A Amiri
Keyword(s):  
Interaction Effect ◽  
Fluid Structure Interaction ◽  
Pressure Head ◽  
Soft Materials ◽  
Crosslinking Density ◽  
Operational Parameters ◽  
Sensors And Actuators ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Different Temperatures

Smart hydrogels are soft materials which can be applied in sensors and actuators especially in microfluidics in which the fluid–structure interaction is important. In this work, first, the behavior of a one-way hydrogel micro-valve is investigated by considering the fluid–structure interaction effect for a specified geometry of the micro-valve. Second, both the fluid–structure interaction and non-fluid–structure interaction simulations are conducted to study the fluid flow effect on the operational parameters of the micro-valve. The obtained results show that the fluid–structure interaction effects are important and have a considerable influence on the micro-valve parameters especially on its closing temperature. Thereafter, a precise study on the micro-valve is executed by considering the micro-valve operational parameters such as inlet pressure, head size, crosslinking density, and breaking pressure at different temperatures. The results show the importance of considering the fluid–structure interaction effect in the design of these devices.

scholarly journals Design of a 3-RPR Flexure System for Optical Switch Assembly

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Guiyue Kou ◽  
Mouyou Lin ◽  
Changbao Chu
Keyword(s):  
Permanent Magnets ◽  
Optical Switch ◽  
Low Cost ◽  
Mechanical Vibration ◽  
Analytical Models ◽  
Assembly System ◽  
Sensors And Actuators ◽  
Damping Force ◽  
Element Analysis ◽  
Compact Size

In the MEMS optical switch assembly, the collision is likely to happen between the optical fiber and the U-groove of the chip due to the uncontrollable assembly errors. However, these errors can hardly be completely eliminated by the active control using high precision sensors and actuators. It will cause the large acting force and part damage, which further leads to the assembly failure. To solve this question, this paper presents a novel low-cost three-degree-of-freedom (three-DOF) passive flexure system to adaptively eliminate the planar assembly errors. The flexure system adopts three parallel kinematic chains with a novel 3-RPR structure and has a compact size with a diameter of 125 mm and thickness of 12 mm. A novel eddy current damper with the structure of Halbach array permanent magnets (PMs) is utilized to suppress the adverse mechanical vibration of the assembly system from the background disturbances. Analytical models are established to analyze the kinematic, static, and dynamic performances of the system in detail. Finally, finite element analysis is adopted to verify the established models for optimum design. The flexure system can generate a large deformation of 1.02 mm along the two translational directions and 0.02° along the rotational direction below the yield state of the material, and it has much higher natural frequencies than 200 Hz. Moreover, the large damping force means that the designed ECD can suppress the system vibration quickly. The above results indicate the excellent characteristics of the assembly system that will be applied into the optical switch assembly.

An Improved Analytical Model for Deflections of a Circular Multi-Layer Piezoelectric Actuator

2005 ◽  
Author(s):  
Mandar Deshpande ◽  
Laxman Saggere
Keyword(s):  
Analytical Solution ◽  
Closed Form ◽  
Piezoelectric Actuator ◽  
Plate Theory ◽  
Analytical Models ◽  
Sensors And Actuators ◽  
Closed Form Solutions ◽  
Design And Optimization ◽  
Closed Form Analytical Solution ◽  
Model Correlation

Models for simple closed-form analytical solutions for accurately predicting static deflections of circular thin-film piezoelectric microactuators are very useful in design and optimization of a variety of MEMS sensors and actuators utilizing piezoelectric actuators. While closed-form solutions treating actuators with simple geometries such as cantilevers and beams are available, simple analytical models treating circular bending-type actuators commonly used in MEMS applications are generally lacking. This paper presents a closed-form analytical solution for accurately estimating the deflections and the volume displacements of a circular multi-layer piezoelectric actuator under combined voltage and pressure loading. The model for the analytical solution presented in this paper, which is based on classical laminated plate theory, allows for inclusion of multiple layers and non-uniform diameters of various layers in the actuator including bonding and electrode layers, unlike other models previously reported in the literature. The analytical solution presented is validated experimentally as well as through a finite element solution and excellent experiment-model correlation within 1% variation is demonstrated. General guidelines for optimization of circular piezoelectric actuator are also discussed. The utility of the model for design optimization of a multi-layered piezoelectric actuator is demonstrated through a numerical example wherein the dimensions of a test actuator are optimized to improve the displaced volume by three-fold under combined voltage and resisting pressure loads.

Material perspective on the evolution of micro- and nano-scale cutting of metal alloys

2018 ◽  
Vol 1 (2) ◽  
pp. 97-114 ◽  
Author(s):  
M. Azizur Rahman ◽  
Mustafizur Rahman ◽  
A. Senthil Kumar
Keyword(s):  
Active Role ◽  
Machining Process ◽  
Metal Alloys ◽  
Sensors And Actuators ◽  
Nano Scale ◽  
Subtractive Manufacturing ◽  
Manufacturing Technologies ◽  
Mechanical Sensors ◽  
Metallic Parts ◽  
Mechanical Machining

Microfabrication plays an active role in miniaturization of products and components in various emerging fields ranging from pharmaceuticals and bio-medical applications to electro-mechanical sensors and actuators to chemical microreactors and mechanical microturbines. Tool-based machining is one of the key technologies of microfabrication. The machining of materials on the micrometre and nanometre scales is fundamental for the fabrication of 3D micro components. However, there are limitations of scaling down the mechanical machining process from the macro- to micro- to nanoscales. Several factors that are not significant in conventional machining become significant in micro/nano-scale machining. This article identifies the important material-related issues on the evolution of micro cutting from conventional cutting process. The main focus is given to the state-of-the art micro/nano-cutting technologies of metal alloys with material perspective. Furthermore, a promising research of coupling the additive and subtractive manufacturing technologies has been highlighted to improve the surface quality of 3D-printed metallic parts.

The hydroelastic response of a surface-piercing hydrofoil in multi-phase flows. Part 1. Passive hydroelasticity

2019 ◽  
Vol 881 ◽  
pp. 313-364 ◽  
Author(s):  
Casey M. Harwood ◽  
Mario Felli ◽  
Massimo Falchi ◽  
Steven L. Ceccio ◽  
Yin L. Young
Keyword(s):  
Vortex Shedding ◽  
Angle Of Attack ◽  
Flow Regimes ◽  
Vertical Surface ◽  
Beam Model ◽  
Fluid Structure Interactions ◽  
Trailing Edge ◽  
Fluid Structure ◽  
Effective Angle ◽  
Multi Phase

Compliant lift-generating surfaces have widespread applications as marine propellers, hydrofoils and control surfaces, and the fluid–structure interactions (FSI) of such systems have important effects upon their performance and stability. Multi-phase flows like cavitation and ventilation alter the hydrodynamic and hydroelastic behaviours of lifting surfaces in ways that are not yet completely understood. This paper describes experiments on one rigid and two flexible variants of a vertical surface-piercing hydrofoil in wetted, ventilating and cavitating conditions. Tests were conducted in a towing tank and a free-surface cavitation channel. This work, which is Part 1 of a two-part series, examines the passive, or flow-induced, fluid–structure interactions of the hydrofoils. Four characteristic flow regimes are described: fully wetted, partially ventilated, partially cavitating and fully ventilated. Hydroelastic coupling is shown to increase the hydrodynamic lift and yawing moments across all four flow regimes by augmenting the effective angle of attack. The effective angle of attack, which was derived using a beam model to account for the effect of spanwise twisting deflections, effectively collapses the hydrodynamic load coefficients for the three hydrofoils. A generalized cavitation parameter, using the effective angle of attack, is used to collapse the lift and moment coefficients for all trials at a single immersed aspect ratio, smoothly bridging the four distinct flow regimes. None of the hydrofoils approached the static divergence condition, which occurs when the hydrodynamic stiffness negates the structural stiffness, but theory and experiments both show that ventilation increases the divergence speed by reducing the hydrodynamic twisting moment about the elastic axis. Coherent vortex shedding from the blunt trailing edge of the hydrofoil causes vortex-induced vibration at an approximately constant Strouhal number of 0.275 (based on the trailing edge thickness), and leads to amplified response at lock-in, when the vortex-shedding frequency approaches one of the resonant modal frequencies of the coupled fluid–structure system.

Transient Hydrodynamic Forces on a Disconnectable Turret Buoy

2014 ◽  
Author(s):  
Z. J. Huang ◽  
K. M. Walker ◽  
S. Lee ◽  
W. Thanyamanta ◽  
D. Spencer
Keyword(s):  
Hydrodynamic Forces ◽  
Analytical Models ◽  
Hydrodynamic Analysis ◽  
Simplified Approach ◽  
Large Size ◽  
High Production Rate ◽  
Calm Water ◽  
Computational Fluid Dynamics Cfd ◽  
High Production ◽  
True Time

For disconnectable turret-moored FPSOs, accurate prediction of turret buoy and FPSO motions during the buoy disconnection process is essential for safe operations. For deepwater high production rate systems, large size buoys are required to accommodate the large number of risers and heavy mooring legs. Analytical models of hydrodynamic forces on large size buoys must be verified before they are applied to motion predictions. To gain a better understanding of the transient hydrodynamic loads on the buoy and hydrodynamic interactions between the buoy and the hull during disconnection, we conducted a specially designed model test in a tow tank. In the model tests, both the buoy and the FPSO models were forced to oscillate by two independent actuators in calm water and in waves. Summary of test results, computed transient hydrodynamic forces from a simplified approach, a true time-domain transient hydrodynamic analysis based on instantaneous buoy positions, and computational fluid dynamics (CFD) results are presented in this paper.

Vortex-Induced Vibration of a Spherical Body With Free Surface Effects: Application to Tugboats With Low Length-to-Beam Ratio

2020 ◽  
Author(s):  
A. Chizfahm ◽  
V. Joshi ◽  
R. K. Jaiman
Keyword(s):  
Free Surface ◽  
Vortex Shedding ◽  
Degrees Of Freedom ◽  
Nonlinear Dynamical System ◽  
Open Water ◽  
Surface Effects ◽  
Spherical Body ◽  
Wake Flow ◽  
Coupled Dynamics ◽  
Fluid Structure

Abstract Flow-structure interactions of submerged or floating bodies can lead to undesired behavior in many marine and offshore engineering applications. In this paper, we consider a complex nonlinear dynamical system of unsteady wake flow interacting with a freely moving tugboat in open water. To meet the operational demands of compact, agile, and high power ship-handling, new hull forms of tugboats are designed with low length-to-beam ratios and rounded sterns. While the hydrodynamic design with low length-to-beam ratios provides improved directional controllability, it can be challenging for tractor tugboats due to the massively separated wake flow with the vortex shedding. These wake vortices can cause large fluctuating yaw moments and possibly a strong fluid-structure coupling via synchronization or lock-in. Of particular interest, the proposed study will focus on the physical mechanism and control of flow-induced oscillations with free-surface effects via our in-house fully-coupled three-dimensional fluid-structure-free-surface interaction solver. Stabilized finite element based methods will be employed to discretize the partial differential equations that arise from the mathematical modeling of the physical phenomena considered. We will begin with a fundamental understanding of coupled dynamics of a canonical geometry of a freely vibrating sphere at free-surface. The physical insight gained will then be applied to a realistic tugboat configuration. We aim to understand the fundamentals of vortex-shedding modes and the coupled dynamics pertaining to the flow-induced vibration (FIV) response of a freely vibrating sphere (a prototypical problem for a rounded tugboat) in all three spatial directions. To predict and analyze the vortex synchronization regimes and the wake patterns, the FIV response of the sphere at a low mass ratio is investigated over a broad range of reduced velocities and Reynolds numbers. We find that the sphere begins to move along a linear trajectory with hairpin vortex-shedding mode, eventually transforming into a circular trajectory with spiral mode in its stationary state for Re ∈ [2000–6000]. We systematically examine these mode transitions and the motion trajectories in the three degrees-of-freedom for higher Reynolds number up to 15,000 which has not been studied in detail in the literature. Finally, we will look into the effect of free surface on the FIV response of the sphere piercing the free surface and will link our fundamental results with a realistic configuration of tugboat undergoing vortex-induced oscillation with free surface effects.

Sign in / Sign up

Export Citation Format

Share Document