A Model for Vortex Induced Oscillation of Structures

A semi-empirical, dynamic model for investigating the fluid forces induced on a bluff cylinder by vortex shedding is developed using random vibration theory. The model includes both spanwise correlation effects and the amplitude dependence of the correlated vortex forces. Model parameters are determined by experimental data. The results are then applied to determine the forces exerted on elastic cylinders at resonance with vortex shedding. The predictions are in good agreement with experimental data.

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Simulating tubulin-associated unit transport in an axon: using bootstrapping for estimating confidence intervals of best-fit parameter values obtained from indirect experimental data

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2017.0045 ◽

2017 ◽

Vol 473 (2201) ◽

pp. 20170045 ◽

Cited By ~ 7

Author(s):

I. A. Kuznetsov ◽

A. V. Kuznetsov

Keyword(s):

Experimental Data ◽

Confidence Intervals ◽

Surrogate Data ◽

Model Parameters ◽

Model Predictions ◽

Estimate Parameter ◽

Minimum Number ◽

Percentile Bootstrap ◽

Parameter Values ◽

Best Fit

In this paper, we first develop a model of axonal transport of tubulin-associated unit (tau) protein. We determine the minimum number of parameters necessary to reproduce published experimental results, reducing the number of parameters from 18 in the full model to eight in the simplified model. We then address the following questions: Is it possible to estimate parameter values for this model using the very limited amount of published experimental data? Furthermore, is it possible to estimate confidence intervals for the determined parameters? The idea that is explored in this paper is based on using bootstrapping. Model parameters were estimated by minimizing the objective function that simulates the discrepancy between the model predictions and experimental data. Residuals were then identified by calculating the differences between the experimental data and model predictions. New, surrogate ‘experimental’ data were generated by randomly resampling residuals. By finding sets of best-fit parameters for a large number of surrogate data the histograms for the model parameters were produced. These histograms were then used to estimate confidence intervals for the model parameters, by using the percentile bootstrap. Once the model was calibrated, we applied it to analysing some features of tau transport that are not accessible to current experimental techniques.

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Model-Based Design and Optimization of Blood Oxygenators

Journal of Medical Devices ◽

10.1115/1.4047872 ◽

2020 ◽

Vol 14 (4) ◽

Author(s):

Ge He ◽

Tao Zhang ◽

Jiafeng Zhang ◽

Bartley P. Griffith ◽

Zhongjun J. Wu

Keyword(s):

Experimental Data ◽

Carbon Dioxide ◽

Fiber Bundle ◽

Cfd Modeling ◽

Design Parameters ◽

Model Parameters ◽

Transfer Rates ◽

Design And Optimization ◽

Model Based ◽

Model Predictions

Abstract Blood oxygenators, also known as artificial lungs, are widely used in cardiopulmonary bypass surgery to maintain physiologic oxygen (O2) and carbon dioxide (CO2) levels in blood, and also serve as respiratory assist devices to support patients with lung failure. The time- and cost-consuming method of trial and error is initially used to optimize the oxygenator design, and this method is followed by the introduction of the computational fluid dynamics (CFD) that is employed to reduce the number of prototypes that must be built as the design is optimized. The CFD modeling method, while having progress in recent years, still requires complex three-dimensional (3D) modeling and experimental data to identify the model parameters and validate the model. In this study, we sought to develop an easily implemented mathematical models to predict and optimize the performance (oxygen partial pressure/saturation, oxygen/carbon dioxide transfer rates, and pressure loss) of hollow fiber membrane-based oxygenators and this model can be then used in conjunction with CFD to reduce the number of 3D CFD iteration for further oxygenator design and optimization. The model parameters are first identified by fitting the model predictions to the experimental data obtained from a mock flow loop experimental test on a mini fiber bundle. The models are then validated through comparing the theoretical results with the experimental data of seven full-size oxygenators. The comparative analysis show that the model predictions and experimental results are in good agreement. Based on the verified models, the design curves showing the effects of parameters on the performance of oxygenators and the guidelines detailing the optimization process are established to determine the optimal design parameters (fiber bundle dimensions and its porosity) under specific system design requirements (blood pressure drop, oxygen pressure/saturation, oxygen/carbon dioxide transfer rates, and priming volume). The results show that the model-based optimization method is promising to derive the optimal parameters in an efficient way and to serve as an intermediate modeling approach prior to complex CFD modeling.

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Hydrodynamics of the Flow Around a Circular Cylinder Sheathed by a Porous Layer

Volume 2, Parts A and B ◽

10.1115/ht-fed2004-56548 ◽

2004 ◽

Cited By ~ 1

Author(s):

M. P. Sobera ◽

C. R. Kleijn ◽

P. Brasser ◽

H. E. A. van den Akker

Keyword(s):

Experimental Data ◽

Circular Cylinder ◽

Porous Layer ◽

Vortex Shedding ◽

Small Distance ◽

Grid Refinement ◽

Solid Cylinder ◽

Local Grid Refinement ◽

Local Grid ◽

Good Agreement

A detailed study of the turbulent flow at Re = 3900 around a circular cylinder, sheathed at some small distance by a porous layer, has been performed by means of Direct Numerical Simulation with a commercial unstructured finite volume based Computational Fluid Dynamics solver. First, to benchmark the performance of this code and the validity of the applied local grid refinement, simulations of the flow around a bare circular cylinder at the same Re were performed. Results were compared to that of an academic CFD solver and to numerical and experimental data from literature and good agreement was found. Subsequently, a detailed study of the flow around a porous layer sheathed cylinder at the same Re, was performed. The flow in the space between the outer porous and the inner solid cylinder was found to be laminar and periodic, with a frequency locked to that of the vortex shedding in the wake behind the cylinder. A good agreement was found to experimental data from literature.

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Performance Analysis and Optimization of a Dual Warhead System

International Journal of Nonlinear Sciences and Numerical Simulation ◽

10.1515/ijnsns-2011-100 ◽

2012 ◽

Vol 13 (1) ◽

Cited By ~ 1

Author(s):

Xiao-Jun Guo ◽

He-Ming Wen

Keyword(s):

Experimental Data ◽

Performance Analysis ◽

Analytical Model ◽

Present Model ◽

Shaped Charge ◽

Weapon Systems ◽

Model Predictions ◽

Modern Warfare ◽

Good Agreement ◽

Concrete Target

AbstractIn modern warfare earth penetrating weapons are often used to defeat enemy’s hardened and deeply buried targets such as aircraft shelters and bunkers. A dual warhead system (DWS) is one of such weapons composed of a forward shaped charge (FSC) and a following through warhead (FTW). In this paper, an analytical model is first proposed to analyze the penetration of an FTW into concrete targets with pre-drilled holes and a DWS is then optimized in order to achieve its best penetration performance. The effects of various parameters on the performance of a dual warhead system penetrating a concrete target are delineated. It transpires that the present model predictions are in good agreement with available experimental data and that the results obtained may be useful for designing such weapon systems.

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Numerical Investigation of Vortex-Induced Vibration of a Circular Cylinder Close to a Plane Boundary

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 6 ◽

10.1115/omae2010-21147 ◽

2010 ◽

Author(s):

Ming Zhao ◽

Liang Cheng

Keyword(s):

Experimental Data ◽

Circular Cylinder ◽

Vortex Shedding ◽

Stokes Equations ◽

Degree Of Freedom ◽

Plane Boundary ◽

Structural Dynamic ◽

Vortex Induced Vibration ◽

Two Degree Of Freedom ◽

Bounce Back

Two-degree of freedom vortex-induced vibration (VIV) of a circular cylinder close to a plane boundary is investigated numerically. Two-dimensional (2D) Reynolds-Averaged Navier-Stokes Equations (RANS) and structural dynamic equation are solved using a finite element method (FEM). If the cylinder is initially very close to the plane boundary, it will be bounced back after it collides with boundary. It is assumed that the bouncing back only alters the cylinder’s velocity component perpendicular to the boundary. After it is bounced back, the cylinder’s velocity are determined by Uc = Uc′, Vc = −bVc′, where Uc and Vc are the cylinder’s velocity parallel to the boundary and that perpendicular to the boundary respectively, Uc′ and Vc′ are the velocities before cylinder is bounced back, b is the bounce back coefficient which is between 0 and 1. Numerical results of the vibration amplitude and frequency of a one-degree-of-freedom vibration (transverse to flow direction) of a circular cylinder close to a plane boundary are compared with the experimental data by Yang et al. [1]. The overall trends of the variation of the VIV amplitude with the reduced velocity were found to be in agreement with the experimental results. The calculated amplitude is smaller than the measured data. The frequency of the vibration increases with the increase of reduced velocity. The calculated vibrating frequency agrees well with the experimental data. It was found in this study that vortex-induced vibration (VIV) occurs even when the gap between the cylinder and the plane boundary is zero. This contradicts a perception that VIV would not occur for a pipeline close to the seabed with a gap ratio smaller than 0.3, this is because it was understood that vortex shedding would have been suppressed if the gap between the cylinder and the plane boundary is less than about 0.3 times of cylinder diameter for a fixed cylinder. Two-degree-of-freedom VIV of a circular cylinder close to a plane boundary is studied. The XY-trajectories, the frequency and the amplitude of the vibration are studied. The effects of the cylinder-to-boundary gap and the bounce back coefficient on VIV and the link between the vortex shedding mode and the VIV are discussed.

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Modeling of Contact and Stiction in Electrostatic Microcantilever Actuators

Journal of Nanotechnology in Engineering and Medicine ◽

10.1115/1.4006618 ◽

2012 ◽

Vol 3 (1) ◽

Cited By ~ 5

Author(s):

C. P. Vyasarayani ◽

Eihab M. Abdel-Rahman ◽

John McPhee

Keyword(s):

Experimental Data ◽

Dynamic Model ◽

Analytical Model ◽

Equilibrium Configurations ◽

Mems Actuators ◽

Model Predictions ◽

Contact Impact

A dynamic model of a microcantilever actuator is developed to simulate the events of contact, impact, stiction, and pull-off from the substrate. The model accounts for geometric, electrostatic, adhesive, and contact nonlinearities. The model is validated by comparison to experimental data and other analytical model predictions. We find that microcantilever electrostatic microelectromechanical (MEMS) actuators can exhibit bistable and tristable equilibrium configurations. We also find that the transients subsequent to pull-in play an important role in determining whether or not stiction will occur.

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Performance Analysis and Optimization of a Dual Warhead System

International Journal of Nonlinear Sciences and Numerical Simulation ◽

10.1515/ijnsns-2011-0100 ◽

2012 ◽

Vol 13 (1) ◽

Cited By ~ 3

Author(s):

Xiao-Jun Guo ◽

He-Ming Wen

Keyword(s):

Experimental Data ◽

Performance Analysis ◽

Analytical Model ◽

Present Model ◽

Shaped Charge ◽

Weapon Systems ◽

Model Predictions ◽

Modern Warfare ◽

Good Agreement ◽

Concrete Target

AbstractIn modern warfare earth penetrating weapons are often used to defeat enemy’s hardened and deeply buried targets such as aircraft shelters and bunkers. A dual warhead system (DWS) is one of such weapons composed of a forward shaped charge (FSC) and a following through warhead (FTW). In this paper, an analytical model is first proposed to analyze the penetration of an FTW into concrete targets with pre-drilled holes and a DWS is then optimized in order to achieve its best penetration performance. The effects of various parameters on the performance of a dual warhead system penetrating a concrete target are delineated. It transpires that the present model predictions are in good agreement with available experimental data and that the results obtained may be useful for designing such weapon systems.

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Simulating intervertebral disc cell behaviour within 3D multifactorial environments

Bioinformatics ◽

10.1093/bioinformatics/btaa939 ◽

2020 ◽

Author(s):

L Baumgartner ◽

J J Reagh ◽

M A González Ballester ◽

J Noailly

Keyword(s):

Experimental Data ◽

Intervertebral Disc ◽

Cell Viability ◽

Mrna Expression ◽

Collagen Type ◽

Supplementary Information ◽

Model Parameters ◽

Type I ◽

Cell Behaviour ◽

Model Predictions

Abstract Motivation Low back pain is responsible for more global disability than any other condition. Its incidence is closely related to intervertebral disc (IVD) failure, which is likely caused by an accumulation of microtrauma within the IVD. Crucial factors in microtrauma development are not entirely known yet, probably because their exploration in vivo or in vitro remains tremendously challenging. In silico modelling is, therefore, definitively appealing, and shall include approaches to integrate influences of multiple cell stimuli at the microscale. Accordingly, this study introduces a hybrid Agent-based (AB) model in IVD research and exploits network modelling solutions in systems biology to mimic the cellular behaviour of Nucleus Pulposus cells exposed to a 3D multifactorial biochemical environment, based on mathematical integrations of existing experimental knowledge. Cellular activity reflected by mRNA expression of Aggrecan, Collagen type I, Collagen type II, MMP-3 and ADAMTS were calculated for inflamed and non-inflamed cells. mRNA expression over long periods of time is additionally determined including cell viability estimations. Model predictions were eventually validated with independent experimental data. Results As it combines experimental data to simulate cell behaviour exposed to a multifactorial environment, the present methodology was able to reproduce cell death within 3 days under glucose deprivation and a 50% decrease in cell viability after 7 days in an acidic environment. Cellular mRNA expression under non-inflamed conditions simulated a quantifiable catabolic shift under an adverse cell environment, and model predictions of mRNA expression of inflamed cells provide new explanation possibilities for unexpected results achieved in experimental research. Availabilityand implementation The AB model as well as used mathematical functions were built with open source software. Final functions implemented in the AB model and complete AB model parameters are provided as Supplementary Material. Experimental input and validation data were provided through referenced, published papers. The code corresponding to the model can be shared upon request and shall be reused after proper training. Contact [email protected] Supplementary information Supplementary data are available at Bioinformatics online.

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