scholarly journals Vibrations due to Flow-Driven Repeated Impacts

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Sumin Jeong ◽  
Natalie Baddour
Keyword(s):  
Failure Mechanism ◽  
Resonance Condition ◽  
Coefficient Of Restitution ◽  
Flowing Fluid ◽  
Drag Forces ◽  
Fluid Drag ◽  
Repetitive Impact ◽  
Ice Failure ◽  
Two Degree Of Freedom ◽  
Good Agreement

We consider a two-degree-of-freedom model where the focus is on analyzing the vibrations of a fixed but flexible structure that is struck repeatedly by a second object. The repetitive impacts due to the second mass are driven by a flowing fluid. Morison’s equation is used to model the effect of the fluid on the properties of the structure. The model is developed based on both linearized and quadratic fluid drag forces, both of which are analyzed analytically and simulated numerically. Conservation of linear momentum and the coefficient of restitution are used to characterize the nature of the impacts between the two masses. A resonance condition of the model is analyzed with a Fourier transform. This model is proposed to explain the nature of ice-induced vibrations, without the need for a model of the ice-failure mechanism. The predictions of the model are compared to ice-induced vibrations data that are available in the open literature and found to be in good agreement. Therefore, the use of a repetitive impact model that does not require modeling the ice-failure mechanism can be used to explain some of the observed behavior of ice-induced vibrations.

scholarly journals Wide CPW-Fed Multiband Wearable Monopole Antenna with Extended Grounds for GSM/WLAN/WiMAX Applications

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Danvir Mandal ◽  
S. S. Pattnaik
Keyword(s):  
Resonance Condition ◽  
Coplanar Waveguide ◽  
Impedance Matching ◽  
Monopole Antenna ◽  
Antenna Performance ◽  
Quarter Wavelength ◽  
Triangular Patch ◽  
Matching Structure ◽  
Standard Limit ◽  
Good Agreement

A novel wide coplanar waveguide- (CPW-) fed multiband wearable monopole antenna is presented. The multiband operation is achieved by generating slanted monopoles of different lengths from an isosceles triangular patch. The different operating frequencies of the proposed antenna are associated with the lengths of the slanted monopoles, which are determined under quarter wavelength resonance condition. The CPW line is used as a multiband impedance-matching structure. The two grounds are slightly extended for better impedance matching. The proposed antenna is designed to cover the 1800 MHz GSM, 2.4 GHz/5.2 GHz WLAN, and 3.5 GHz WiMAX bands. The measured peak gains and impedance bandwidths are about 4.18/3.83/2.6/2.94 dBi and 410/260/170/520 MHz for the 1550-1960 MHz/2.3-2.56 GHz/3.4-3.57 GHz/5.0-5.52 GHz bands, respectively. The calculated averaged specific absorption rate (SAR) values at all the resonant frequencies are well below the standard limit of 2 W/kg, which ensures its feasibility for wearable applications. The antenna performance under different bending configurations is investigated and the results are presented. The reflection coefficient characteristics of the proposed antenna is also measured for different on-arm conditions and the results are compared. A good agreement between experimental and simulation results validates the proposed design approach.

Computer Simulation of a Test Rig to Model Sloshing in Spin-Stabilized Satellites

1992 ◽  
Vol 114 (4) ◽  
pp. 689-698 ◽  
Author(s):  
D. R. Flugrad ◽  
L. A. Obermaier
Keyword(s):  
Model Simulation ◽  
Test Rig ◽  
Dynamic Motion ◽  
Experimental Project ◽  
Rotating Structure ◽  
Simulation Results ◽  
Parameter Values ◽  
The Mathematical Model ◽  
Two Degree Of Freedom ◽  
Good Agreement

Certain communications satellites carry liquid stores on board for station tending and attitude adjustment. However, sloshing of the liquid can cause an undesirable nutational motion of the spin-stabilized vehicle. In previous work a test rig was designed, built and instrumented to study the interaction between the rotating structure and liquid. To augment that experimental project, a computer model of the test rig has been developed to simulate the dynamic motion of the system for various parameter values. The sloshing liquid was replaced by a two degree-of-freedom pendulum in the mathematical model. Simulation results were compared with those from a general multibody dynamics program and with experimental measurements of the test rig motion to demonstrate the mathematical model’s validity. Good agreement was achieved in both instances.

Enhanced Nanoparticle Removal Using Surfactants

MRS Advances ◽  
2016 ◽  
Vol 1 (31) ◽  
pp. 2213-2224
Author(s):  
Michael L. Free
Keyword(s):  
Critical Micelle Concentration ◽  
Semiconductor Manufacturing ◽  
Chemical Mechanical Planarization ◽  
Ionic Surfactant ◽  
Electrostatic Repulsion ◽  
Particle Removal ◽  
Precision Manufacturing ◽  
Manufacturing Operations ◽  
Drag Forces ◽  
Fluid Drag

ABSTRACTNanoparticles are used in chemical mechanical planarization for semiconductor manufacturing as well as in other precision manufacturing operations. Particles used in processing need to be removed from surfaces in order to enhance yields. Nanoparticles are difficult to remove from surfaces during cleaning due to the high van der Waals attractive forces between particles and surfaces relative to the low fluid drag forces that are used for typical removal methods. Ionic surfactant molecules can adsorb on particles and surfaces to create an electrostatic repulsion between particles and surfaces as well as provide a steric barrier to mitigate adsorption and adhesion. The effectiveness of the surfactant in enhancing particle removal is related to surfactant properties, and it can be correlated with and modeled relative to the critical micelle concentration of the surfactant. The general approach for modeling will be discussed, and the model will be compared with particle removal data.

Analysis of Attitude and Dynamics Characteristic of a Kind of Submerged Buoy

2012 ◽  
Vol 226-228 ◽  
pp. 516-520 ◽  
Author(s):  
Jian Xun Wang ◽  
Hong Bin Gui ◽  
Xi Chen ◽  
Qiang Fu
Keyword(s):  
Low Frequency ◽  
Small Scale ◽  
Normal Fluid ◽  
Fluid Forces ◽  
Dynamical Characteristics ◽  
Drag Forces ◽  
Low Frequency Vibration ◽  
Fluid Drag ◽  
Mooring Cable ◽  
Dynamics Characteristic

In this paper, the attitude and dynamical characteristics of a kind of submerged buoy are studied. The attitude of the buoy system is calculated relatively accurately by mathematical derivations and programming, in which all the tangent and normal fluid drag forces and elastic deformation of the mooring cable are considered. Based on the ANSYS FEA software, the model of system in fluid is established, which takes the effects of fluid drag forces, pretension and additional mass into account. Then the analysis of the effect on dynamics characteristic of the system by considering the attitude or not is carried out. The results indicate that, for small-scale submerged buoy system, the completed fluid forces should not be ignored, and the vibration of mooring system of submerged buoy is most likely to be low-frequency vibration, which should be avoided in some ways.

Autoparametric Vibration of Coupled Beams Under Random Support Motion

1986 ◽  
Vol 108 (4) ◽  
pp. 421-426 ◽  
Author(s):  
R. A. Ibrahim ◽  
H. Heo
Keyword(s):  
Resonance Condition ◽  
Wide Band ◽  
Random Excitation ◽  
State Response ◽  
Coupled Beams ◽  
The Moment ◽  
Non Gaussian ◽  
Two Degree Of Freedom ◽  
Support Motion ◽  
Gaussian Closure

The dynamic response of a two degree-of-freedom system with autoparametric coupling to a wide band random excitation is investigated. The analytical modeling includes quadratic nonlinearity, and a general first-order differential equation of the moments of any order is derived. It is found that the moment equations form an infinite hierarchy set which is closed via two different closure methods. These are the Gaussian closure and the non-Gaussian closure schemes. The Gaussian closure solution shows that the system does not reach a stationary response while the non-Gaussian closure solution gives a complete stationary steady-state response. In both cases, the response is obtained in the neighborhood of the autoparametric internal resonance condition for various system parameters.

Nonlinear Vibration Absorber Design: An Asymptotic Approach

2015 ◽  
Author(s):  
Arnaldo Casalotti ◽  
Walter Lacarbonara
Keyword(s):  
Nonlinear Vibration ◽  
Multiple Scales ◽  
Equations Of Motion ◽  
Sensitivity Analyses ◽  
Vibration Absorber ◽  
Asymptotic Approach ◽  
Nonlinear Vibration Absorber ◽  
The One ◽  
Two Degree Of Freedom ◽  
Good Agreement

The one-to-one internal resonance occurring in a two-degree-of-freedom (2DOF) system composed by a damped non-linear primary structure coupled with a nonlinear vibration absorber is studied via the method of multiple scales up to higher order (i.e., the first nonlinear order beyond the internal/external resonances). The periodic response predicted by the asymptotic approach is in good agreement with the numerical results obtained via continuation of the periodic solution of the equations of motion. The asymptotic procedure lends itself to manageable sensitivity analyses and thus to versatile optimization by which different optimal tuning criteria for the vibration absorber can possibly be found in semi-closed form.

Forced Oscillations of Non-Linear Two-Degree-of-Freedom Systems

1966 ◽  
Vol 8 (3) ◽  
pp. 252-258 ◽  
Author(s):  
G. N. Bycroft
Keyword(s):  
Numerical Integration ◽  
Transient Response ◽  
Internal Resonance ◽  
Perturbation Technique ◽  
Degree Of Freedom ◽  
Forced Oscillations ◽  
Oscillatory Systems ◽  
Non Linear ◽  
Two Degree Of Freedom ◽  
Good Agreement

This paper shows how the Lighthill-Poincaré perturbation technique may be used to determine the transient response of ‘lightly coupled’ non-linear multi-degree-of-freedom oscillatory systems subject to arbitrary forcing functions. The results in general are complex but simplify in many important cases. A comparison is made between the analytical results and results obtained by a numerical integration of the equations on a computer. Good agreement is noted. The method fails under conditions of ‘internal resonance’ of the system.

scholarly journals Follower Forces in Pre-Stressed Fixed-Fixed Rods to Mimic Oscillatory Beating of Active Filaments

2018 ◽  
Author(s):  
Soheil Fatehiboroujeni ◽  
Arvind Gopinath ◽  
Sachin Goyal
Keyword(s):  
Geometric Constraints ◽  
Elastic Rod ◽  
Mucus Clearance ◽  
Drag Forces ◽  
Fluid Drag ◽  
Non Linear ◽  
Follower Forces ◽  
Elastic Rod Model ◽  
Spatiotemporal Response ◽  
The Continuum

Flagella and cilia are examples of actively oscillating, whiplike biological filaments that are crucial to processes as diverse as locomotion, mucus clearance, embryogenesis and cell motility. Elastic driven rod-like filaments subjected to compressive follower forces provide a way to mimic oscillatory beating in synthetic settings. In the continuum limit, this spatiotemporal response is an emergent phenomenon resulting from the interplay between the structural elastic instability of the slender rods subjected to the non-conservative follower forces, geometric constraints that control the onset of this instability, and viscous dissipation due to fluid drag by ambient media. In this paper, we use an elastic rod model to characterize beating frequencies, the critical follower forces and the non-linear rod shapes, for pre-stressed, clamped rods subject to two types of fluid drag forces, namely, linear Stokes drag and non-linear Morrison drag. We find that the critical follower force depends strongly on the initial slack and weakly on the nature of the drag force. The emergent frequencies however, depend strongly on both the extent of pre-stress as well as the nature of the fluid drag.

scholarly journals Preliminary study of software tracker usage to analyze inhibitory style on free fall movie events

2018 ◽  
Vol 197 ◽  
pp. 02012
Author(s):  
Seni Susanti ◽  
Ea Cahya Septia Mahen ◽  
Ade Yeti Nuryantini
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Free Fall ◽  
Force Analysis ◽  
Drag Coefficients ◽  
Drag Forces ◽  
Preliminary Study ◽  
Free Falling ◽  
Good Agreement

This paper presents drag force analysis of free falling object using software tracker. We use video cupclips that have been embedded in this software. The video featured cupcakes to which hung a number of different paper clips were dropped simultaneously. We track the trajectory of free falling cupclips using the software to get the information of position, speed, and acceleration of each cupcake against time. From the data we get the value of drag forces and drag coefficients for each time. The result shows that the drag force value increased to almost constant value, otherwise the drag coefficient is reduced to almost constant values well. According to the results, the analyzed data has good agreement with the theory. Thus, software tracker can be used as media to learn drag force easily and inexpensively.

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