bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the Central Airways for Identifying Airway Partial Obstruction
Authors: Al-Jumaily A. M. , Du Y.
Published: November 2021

The frequency spectrum of the input impedance determined at the throat is analysed to identify partial occlusion in the branched central bronchi. The airways are modelled starting from the trachea to the second generation and the result demonstrates that the input impedance resonant frequencies can map the location, severity and degree of an obstruction in any of the considered branches.
Numerical Analysis of Blood Flow in a Left Ventricle
Authors: Iwase Hidehito , Liu Hao , Fujimoto Shinichi , Himeno Ryutaro
Published: November 2021

We present a numerical study of dynamical blood flow in a left ventricle of human heart using Computational Fluid Dynamics (CFD). Three-dimensional shape of the left ventricle model was reconstructed using spline interpolation, based on a set of two-dimensional ultrasound echocardiogram images. Blood flow in the left ventricle was computed by solving the incompressible, unsteady Navier-Stokes equations in a manner of Finite Volume Method (FVM). In the present preliminary results the asymmetric intracardiac flow pattern is detected very similar to observed in vivo (Kilner, 2000) which shows a large vortex and a small vortex at diastole.
Modelling and Simulation Methodology for the Human Cardio Vascular System
Authors: Krus Petter , Teien Dag
Published: November 2021

In this paper a methodology for closed loop simulation of the human cardiovascular system is described. It includes a functional heart model and a closed loop circulatory system. Using this model a range of physiological and patophysical phenomena can be studied, such as valvar regurgitation (valve leakage), valvar stenosis, congenital cardiac malformations i.e. coarctation of the aorta and the circulation in univentricular hearts. The model can be extended to accommodate detail descriptions of the subsystems. In this paper, however, a very basic model is shown to highlight the basic principles of cardio vascular system simulation.
The Convexity Properties of the Fung Model for Soft Tissues
Authors: Wilber J. Patrick , Walton Jay R.
Published: November 2021

During the last three decades, the theory of nonlinear elasticity has been used extensively to model biological soft tissues. The now widely accepted belief that an understanding of the mechanical properties of these tissues is critical in order to understand the advent, progression, and treatment of disease has driven this research. More recently, those interested in how soft tissues grow and remodel themselves in response to both normal and pathological conditions have used nonlinear continuum mechanics as a basic tool.
ABAQUS Finite Element Models of Convective Transport in the Walls of Arteries Subjected to Steady and Pulsatile Pressure
Authors: Simon B. R. , Rigby P. H. , Williams S. K.
Published: November 2021

Porohyperelastic (PHE) finite element models (FEMs) have been useful in vascular biomechanics to study the coupled structural response and mobile fluid flux in arterial wall tissues for steady state and cyclic pressures. Previous papers [1,2,3] described PHE FEMs, which determined fluid transport response to representative pulsatile pressures. Those FE analyses have been extended and additional results are given here for cyclic (pulsatile) pressurization of rabbit aortas. The ABAQUS program and a PHE material model were used to simulate fluid transport for “intact” and “de-endothelialized” aortas subjected to “normal” and “hypertensive” pulsatile pressures at heart rates (HRs) of 60 and 120 BPM.
Effect of Position and Flow Waveform on the Fluid Mechanics of a Stenosed Human Right Coronary Artery
Authors: Chandran K. B. , Ramaswamy S. D. , Lai Y.-G. , Wahle A. , Sonka M.
Published: November 2021

Complete occlusion in any of the coronary vessels leads to a myocardial infarction. The role of fluid mechanical forces in atheroma development has been widely accepted because of preferential plaque growth at certain locations of the vessel geometry, such as a bifurcation or regions of high degrees of curvature. Areas of low and/or oscillatory shear stress have been correlated with atheroma development [1]. In order to determine the relationship between fluid mechanical stresses and development of lesions in the coronary vessels, it is important to analyze the fluid mechanics in actual three-dimensional geometries, incorporating the time-dependent translation and geometric alterations of these vessels [2,3].
Hemodynamic Simulations of Flow in Normal and Stenotic Carotid Arteries
Authors: Berger Stanley A. , Stroud Jennifer S. , Rayz Vitaliy
Published: November 2021

Much of the recent work attempting to simulate arterial flows has been motivated by attempts to elucidate the relationship between flow in the arteries and atherogenesis, and the focalization of plaque development. The aspect of the flow of most interest in this context was wall shear stresses, there being substantial evidence that the most susceptible sites are where shear stresses are low, or change rapidly in time or space [1]. These conditions are most likely to occur where there are sudden changes in flow geometry, and/or when the flow is unsteady. (For a recent review see [2].) We have studied flow in the carotid arterial bifurcation. Carrying out extensive simulations of the fully three-dimensional unsteady flow in realistic normal carotid bifurcation geometries allows us to identify the more dangerous sites for plaque development according to the above criteria. In the later stages of progression of atherosclerotic disease the relevant issues become vessel occlusion, embolic events, or plaque rupture, especially since recent clinical investigations have suggested that the danger posed by a particular plaque depends not only on the degree of occlusion but also on the so-called “vulnerability” of the plaque, the tendency of the plaque, depending on its composition, to fracture and rupture. To address these issues we have simulated flow in realistic severely stenotic carotid bifurcations toward the end of identifying critical features of plaque geometry and “risk factors” for plaque fracture and rupture.
Micromechanics of Fibroblast Contraction of a Collagen-Gag Matrix
Authors: Freyman Toby M. , Yannas Ioannis V. , Pek Yuri-Shona , Yokoo Rayka , Gibson Lorna J.
Published: November 2021

Contractile fibroblasts play a major role in the synthesis and remodeling of scar tissue following dermal injury. Inhibition of dermal wound contraction by contractile fibroblasts, using a collagen-GAG matrix, has been linked to the blocking of scar formation[1]. Scar tissue is mechanically and functionally inferior to the dermal tissue which it replaces. Specifically, scar tissue is weaker, physically disfiguring, and can lead to restricted joint mobility.
Injection Molding of Tissue Engineered Tympanic Membrane Patches Utilizing Computer-Aided Design
Authors: Hott Morgan E. , Beane Richard M. , Megerian Cliff , Bonassar Lawrence J.
Published: November 2021

Over two million tympanostomy tubes are inserted annually in the United States, making this the most commonly performed of all surgical procedures (Isaacson 1996). In approximately 10% of cases the patient treated with tympanostomy tubes is left with a permanent perforation of the tympanic membrane that requires surgical repair. Current surgical technique involves grafting of an autologous tissue such as temporalis fascia or tragal cartilage to the perforated membrane (Paterson 1999). This is an involved surgical procedure requiring general anesthesia. We propose tissue engineering an autologous cartilage tympanic membrane patch. If successful this approach has the potential to transform an operating room procedure to an office procedure. This would provide tremendous healthcare savings, and potentially obviate the need for tens of thousands of children to undergo general anesthesia.
Effect of Cryoprocessing on Umbilical Cord Blood for Hematological Disorders
Authors: Pal Subrata , David R. Sheba N.
Published: November 2021

Cellular therapies promise to become major therapeutic modalities of this new century. The hematopoietic restoration with umbilical cord blood transplant can be a useful source of hematopoietic stem cells for routine bone marrow reconstitution. Thus it can be used as an effective source of stem cells for the treatment of various hematological disorders like leukemia, thalessaemia, aplastic anemia and it also can be used to replace the damaged tissue in various pathological conditions like Parkinson’s disease, Alzheimer’s, osteoarthritis etc. The advantage of the umbilical cord blood transplant being, use of unrelated umbilical cord blood transplantation with upto 2 to 3 HLA mismatch (Wagner et al, 1996).
An Axisymmetric Elastic Layered Half-Space Model for Micropipette Aspiration of the Chondrocyte Pericellular Matrix
Authors: Alexopoulos Leonidas G. , Haider Mansoor A. , Guilak Farshid
Published: November 2021

Articular cartilage is an aneural, avascular connective tissue that serves as the resilient load-bearing surface at the articulating ends of diarthrodial joints. A sparse single population of cells known as chondrocytes maintains the extracellular matrix (ECM) of this tissue through a balance of anabolic and catabolic activities. The mechanical environment of chondrocytes, in conjunction with other genetic and environmental factors (e.g., growth factors, cytokines), plays an important role in regulating cartilage homeostasis and, as a consequence, the health of the joint.
An Exploration of Cell Stress and Deformation Under Shear Flow
Authors: Guo X. Edward , Takai Erica , Liu Kai , Wang Xiaodong
Published: November 2021

The biological response of bone cells (osteoblasts and/or osteocytes) to mechanical loading is an important basic science topic in the mechanism of mechano-signal transduction in bone adaptation to mechanical loading. The characterization of this mechanism of signal transduction is crucial in the understanding of the etiology of age-related bone loss, bone loss during space flight and the optimal design of implants for total joint replacements. It has been hypothesized that deformation-generated fluid shear stress is one of the major mechanical stimuli that bone cells respond to. Many in vitro experiments utilize a parallel-plate flow chamber by imposing fluid shear stress on cultured osteoblasts. For example, changes in intracellular Ca++ levels and mitogen-activated protein kinase (MAPK) phosphorylation has been quantified in response to applied shear flow [1,2]. In these studies, the flow shear stress at the wall of the flow chamber τ wall = 6 μ Q w h 2 , where Q is the volumetric flow rate, w and h are the width and height of the flow chamber, respectively, and μ is the media viscosity. However, this wall shear stress may not indicate the actual stress state which bone cells experience, which depends on the details of the flow-cell interaction, including the mechanical properties of the cell, the attachment condition of the cell to the wall as well as the cell density. In order to obtain a quantitative relationship between the biological response of bone cells to applied shear flow, it is necessary to quantify in detail the flow-cell interaction in a typical shear flow experiment. The objective of this study was to quantify the shear stress within the cell under applied shear flow, incorporating fully coupled flow and solid deformation analyses using the finite element technique. Specifically, we examined the influence of the elastic modulus of the cell and the spacing distance between cells on the shear stress within the cell.
Hybridization Dynamics and Kinetics of Fret-Enhanced Molecular Beacons
Authors: Tsourkas Andrew , Xu Jason , Bao Gang
Published: November 2021

Many human diseases start with a defect in the genome. Cancer, for example, is a genetic disease that arises from a single cell that behaves abnormally, dividing uncontrollably and leading, eventually, to the development of a tumor. A critical step in diagnosing and treating cancer is to detect cancer cells that result from the mutated genes. In spite of the extensive biomedical research efforts during the last few decades, it is still difficult to detect cancer at its early stages — when a cancer is diagnosed it is often too late to cure. A novel way of achieving early detection of cancer is to detect mRNA transcripts that arise from mutated genes in living cells [1]. We have developed a FRET-enhanced molecular beacons methodology which, combined with the state-of-the-art fluorescence imaging techniques, has the potential to detect cancer cells. FRET (Fluorescence resonance energy transfer) refers to the non-radiative transfer of energy from a donor molecule to an acceptor molecule through dipole-dipole coupling. As shown schematically in Figure 1, molecular beacons are dual labeled antisense oligonucleotides (ODNs) with a fluorophore (A or D) at one end and a quencher (Q) at the other; they are designed to form a hairpin structure in the absence of a complimentary target such that fluorescence of the fluorophore is quenched. Upon hybridization with the target mRNA, the molecular beacon opens up, leading to fluorescence [2,3].
The Modeling of Mechatronic Servo Systems and Vibration Control
Authors: Zou Junzhong , Jing Zhongliang , Nakamura Masatoshi , Luo Albert C. J.
Published: November 2021

A mathematical model of industrial mechatronic servo systems is developed and a method for determining the servo parameters without vibration in the servo controller is proposed. The effectiveness of the method is verified through the experimental results.
Multi-Body Contact Dynamics Modeling of Roll Mechanisms in Paper Manufacturing Systems
Authors: Keskinen Erno , Launis Sirpa , Kivinen Juha-Matti
Published: November 2021

A multi-body contact dynamics formulation is introduced to model the dynamic motion of roll mechanisms typical for paper manufacturing systems. Physical contact forces acting on the bodies in the joints are connecting the links of roll mechanisms together instead of purely kinematic constraints used in existing classical algorithms. In a similar way, external contacts between rolls manipulating the paper web are modeled as contact line loads in normal pressing and tangential traction directions. In the case study the loading dynamics of a paper finishing unit used in paper industry has been simulated in order to find out dynamically stable dimensioning for the critical parts in a new four-bar-linkage roll loading mechanism.
Induced Vibration of Suspension Bridges Traversed by Moving Vehicles
Authors: Esmailzadeh Ebrahim , Jalili Nader
Published: November 2021

An investigation into the dynamics of vehicle-structure interaction of a suspension bridge traversed by a moving vehicle is presented. The vehicle including the occupants is modeled as a half-car model with six degrees-of-freedom, and the bridge is assumed to obey the Euler-Bernoulli beam theory. Due to the continuously moving location of the loads on the bridge, the governing differential equations will have time-varying coefficients and hence, become rather complicated. The relationship between the bridge vibration characteristics and the vehicle speed is rendered, which yields into a search for a particular speed that determines the maximum values of dynamic deflection and the bending moment of the bridge. Results at different vehicle speeds demonstrate that the maximum dynamic deflection occurs at the vicinity of the bridge mid-span (±3%), while the maximum bending moment is found at ±20% of the mid-span. It is shown that one can find a critical speed at which the maximum values of bridge dynamic deflection and bending moment attain their global maxima.
Dynamic Interaction of a Moving Oscillator With an Elastically Supported Continuum
Authors: Chen Yonghong , Tan Chin An , Bergman Lawrence A.
Published: November 2021

In this paper, the problem of a simple oscillator traversing an elastically supported continuum is investigated. Numerical results for the shear force distribution of the continuum are obtained. To circumvent convergence difficulties associated with the evaluation of the shear force, an improved series expansion is derived. Effects of boundary flexibility on the shear force spatial and temporal distributions, as well as the series convergence properties, are examined. Results reveal the presence of a high amplitude, high frequency component in the shear force due to significant contributions of the higher order modal terms in the series expansion. This is important from the viewpoint of understanding the cumulative fatigue failure of the continuum. A useful and compact formula estimating the value of the support stiffness above which the boundary can be idealized as simply supported is also derived.
In-Plane Free Vibrations of the Double-Segment Compound Rotating Disks
Authors: Hamidzadeh Hamid R. , Karim Reza U.
Published: November 2021

An analytical method is presented for determination of vibration characteristics of high speed Double-Segment Compound Rotating disks. More specifically, a systematic approach based on established solution for linear in-plane vibration of each segment satisfying the displacement and stresses compatibility is developed. Fixed and free boundary conditions for the compound spinning annular disks are considered and natural frequencies and mode shapes of rotating disks are computed. The medium for each segment is considered to be a homogenous, isotropic, and elastic. The developed analytical solution was achieved by implementing two-dimensional plane stress theory. The modal displacements and stresses at both inner and outer boundaries are determined. The dimensionless natural frequencies for different modes, rotating speeds, and thickness ratios are computed. The effect of stiffness changes for each segment on the natural frequencies are also studied.
Crack Influences on the Vibration, Buckling and Parametric Instability of Plates
Authors: Vafai Abolhassan , Javidruzi Mahyar , Estekanchi Homayoon E.
Published: November 2021

The vibration, buckling and parametric instability behavior of a simply supported rectangular plate with a crack emanating from one edge, subjected to in-plane compressive periodic edge loading is studied in this paper. Several plates, each with a different dimension and crack length size are analyzed using an analytical approach. The results of this study show that the vibration, buckling and parametric instability behavior of plates with length to width ratio greater than unity are considerably affected by the crack length size.
Nonlinear Supersonic Flutter of Imperfect Circular Cylindrical Shells
Authors: Amabili M. , Pellicano F.
Published: November 2021

The aeroelastic stability of simply supported, circular cylindrical shells in supersonic flow is investigated by using both linear aerodynamics (first-order piston theory) and nonlinear aerodynamics (third-order piston theory). Geometric nonlinearities, due to finite amplitude shell deformations, are considered by using the Donnell’s nonlinear shallow-shell theory, and the effect of viscous structural damping is taken into account. The system is discretized by Galerkin method and is investigated by using a model involving up to 22 degrees of freedom, allowing for travelling-wave flutter around the shell and axisymmetric contraction of the shell. Asymmetric and axisymmetric geometric imperfections of circular cylindrical shells are taken into account. Results show that the system loses stability by travelling-wave flutter around the shell through supercritical bifurcation. Non-simple harmonic motion is observed for sufficiently high post-critical dynamic pressure. A good agreement between theoretical and existing experimental data has been found for the onset of flutter, flutter amplitude and frequency. Results show that onset of flutter is very sensible to small initial imperfections of the shells. The influence of pressure differential across the shell skin has also been deeply investigated. The present study gives, for the first time, results in good agreement with experimental data obtained at the NASA Ames Research Center more than three decades ago.
Elasto-Multi-Body Dynamics of Multi-Cylinder Internal Combustion Engine
Authors: Gupta S. , Kelly P. , Rahnejat H.
Published: November 2021

The paper presents a multi-body model of a 4-cylinder, 4-stroke diesel engine, incorporating component flexibility. The model also comprises engine firing order and experimentally measured combustion time history. The paper presents numerical predictions for conical motion of the flywheel due to combined torsion-deflection modes of the flexible crankshaft system. The half-engine order responses induce the complex 3-dimensional whirling motion of the flywheel, which is responsible for repetitive shock loading of the drivetrain system through impact with the clutch system. This leads to an assortment of noise and vibration concerns, one of which is the in-cycle vibration of the clutch system. Numerical prediction of this vibration response conforms well with the experimental findings, both of which are reported in this paper.
Development of an Innovative Space Boom
Authors: Lou Michael C. , Fang Houfei , Yang Ben , Palmer Nathaniel Lee
Published: November 2021

This paper presents the development of a new type of ultra-lightweight space boom, called the Self-deployable Spring Strip Boom or simply the S3 Boom. It describes the fundamental design concept and several variations of design configurations. Test results of proof-of-concept models are discussed and compared with results obtained by analytical simulations.
A Study on the Effect of Preview Uncertainties in Preview Control of Vehicle Suspensions
Authors: Vahidi Ardalan , Eskandarian Azim
Published: November 2021

The benefit of previewing the “future” road inputs in improving the performance of active suspensions of a vehicle has been demonstrated in many publications. It is shown that smoother and more effective control is possible when the preview length is increased up to a certain limit. Most of these studies assume perfect preview measurements in their numerical simulations. In a real scenario however, the presence of uncertainties can not be neglected. The uncertainties can be due to sensor measurement noise or false objects on the surface of the road. In order to gain an insight to the problem this paper addresses the influence of preview uncertainty on the performance of a preview controller. The stochastic optimal control scheme for preview control of a quarter-car suspension model is briefly presented. Then results of numerical simulations, which are carried out for various levels of uncertainty in the preview and for different preview lengths, are compared. These comparisons show that noise/uncertainty can be an issue with an adverse effect that sometimes increases with preview length. In other words, it is shown that controllers with longer preview can be more susceptible to noise. However the limits of tolerable noise are not very restrictive and the well-known benefits of preview can still be achieved if the measurement errors are maintained below a limited level.
Simplified FEM Model of Paper Machine Roll for Multibody Rolling Contact Analyses
Authors: Järvenpää Veli-Matti , Keskinen Erno K.
Published: November 2021

In this paper a finite element model of a rotating paper machine roll for nip unit rolling contact analyses is discussed. This work presented here is based on the earlier work of the authors presented in [1] and [2]. The major motivations for developing a tailored FE-model including the large spin rotation are firstly to include the complex vibration phenomena as the shell vibrations of the roll structure in the analyses and secondly to reduce the computational costs of the numerical simulations due to the large number of degrees of freedom. The approach used is the use of the modal analysis i.e. to express the dynamics of the roll in terms of the lowest eigenmodes. The equations of motion are at first written in the rotating coordinates and then in addition to this the equations are expressed by using the modal coordinates. Numerical tests executed show that this modeling technique reduces computational costs significantly. Furthermore, use of the (semidefinite) eigenmode basis maintains the vibration characteristics of the roll structure. For verification purposes a test model was constructed and these simulation results were compared to the standard geometrically non-linear finite element analysis.
Genetic Algorithm-Based Maximum Likelihood Parameter Estimation for Transit Buses
Authors: Xiao Jie , Kulakowski Bohdan T.
Published: November 2021

Vehicle dynamic models include parameters that qualify the dependence of input forces and moments on state and control variables. The accuracy of the model parameter estimates is important for modeling, simulation, and control. In general, the most accurate method for determining values of model parameters is by direct measurement. However, some parameters of vehicle dynamics, such as suspension damping or moments of inertia, are difficult to measure accurately. This study aims at establishing an efficient and accurate parameter estimation method for developing dynamic models for transit buses, such that this method can be easily implemented for simulation and control design purposes. Based on the analysis of robustness, as well as accuracy and efficiency of optimization techniques, a parameter estimation method that integrates Genetic Algorithms and the Maximum Likelihood Estimation is proposed. Choices of output signals and estimation criterion are discussed involving an extensive sensitivity analysis of the predicted output with respect to model parameters. Other experiment-related aspects, such as imperfection of data acquisition, are also considered. Finally, asymptotic Cramer-Rao lower bounds for the covariance of estimated parameters are obtained. Computer simulation results show that the proposed method is superior to gradient-based methods in accuracy, as well as robustness to the initial guesses and measurement uncertainty.
Performance of Developed Driving Simulator With Full Vehicle Model of Multibody Dynamics
Authors: Shiiba Taichi , Suda Yoshihiro
Published: November 2021

In this paper, the authors propose to apply the full vehicle model of multibody dynamics to driving simulator with 6 degrees of freedom motion system. By this proposal, the characteristics of driving simulator become very similar to the actual automobiles. It becomes possible to predict the performance of vehicle dynamics and the riding comfort by feeling test without prototyping automobile. To realize real-time calculation that is necessary for driving simulator, the authors proposed approximated real-time analysis method. By this method, real-time vehicle analysis of 2 ms step time of numerical integration is achieved with 91 degrees of freedom vehicle model.
Computer Simulation of the Dynamic Properties of a Complex Man-Railway Vehicle-Environment System
Authors: Grabarek Iwona , Choromański Włodzimierz
Published: November 2021

This paper presents a model of the driver-locomotive-environment system achieved through the integration of separate models simulating the locomotive’s mechanical properties and the driver’s behaviour. The paper is focused on the modelling and simulation of the “driver” subsystem — for this purpose, the theory of fuzzy sets is used to present the simulation results of the system’s behaviour during a specific manoeuvre.
Confirmation of the Natural Yawing Frequency of Large Sized Vehicle: Distinguishing the Vehicle System From the Driver-Vehicle System
Authors: Momiyama Fujio , Sasaki Takashi , Nagae Hiroyasu
Published: November 2021

The low yawing natural frequency of vehicle system and/or the coupled natural frequency of driver-vehicle system is considered as a reason for vehicle fluctuation. In the case of passenger cars, it is well known that the yaw-gain-peak of vehicle system exists at 1–2 Hz and that of driver-vehicle system exists at 0.3–0.4Hz. In the case of large sized vehicle systems, I, Momiyama, reported in SAE No.892519 that the yaw-gain exists at 0.3–0.4 Hz. As this value is so close to the value of driver-vehicle system, sometimes the discussion regarding the vehicle dynamics of large sized vehicles seems to be confused. The purpose of this paper is to confirm the yawing behavior and to clarify the reason for the low yawing frequency of vehicle system. Firstly verification procedure and a 7DOF vehicle model considering the lateral and rotational motion of sprung mass, front/rear un-sprung mass and rotational motion of steering system are introduced. Secondly the lateral fluctuation running under fixed steering wheel is shown. We named this behavior “tottering”. Thirdly the yaw response test results by random steering input based upon ISO/TR8726 are shown. From the above testing and calculating analysis the existence of a low yaw-eigen value is confirmed. From the vector analysis of the low yaw-eigen value it is known the main factor of the low frequency is the low rigidity of steering with power steering system. The low rigidity is caused by the low spring constant of power steering servo-valve that has the dead zone at on-center.
A Comparison of the Relative Benefits of Active Front Steering and Active Rear Steering When Coordinated With Direct Yaw Moment Control
Authors: Selby M. A. , Manning W. J. , Brown M. D. , Crolla D. A.
Published: November 2021

This paper studies the benefits of coordinating stability and steerability controllers to reduce vehicle deceleration during limit handling situations. The stability controller, DYC, uses the vehicle brakes to apply a restoring moment when the vehicle sideslip angle and sideslip velocity exceed fixed bounds. This use of the brakes interferes with the longitudinal dynamics of the vehicle in a way that drivers find undesirable. Active front steering (AFS) and active rear steering(ARS) can be used to tune the vehicle handling balance in the low to mid-range lateral-acceleration regime. Earlier work has shown that the use of AFS can reduce the interference observed using DYC alone. The levels of improvement achievable by coordinating AFS and ARS with DYC are quantified using open loop handling simulations tests by predicting the deceleration of the vehicle in an extreme manoeuvre. The results from these simulations are compared to assess the relative benefits of AFS and ARS when coordinated with DYC. The computer simulations are based on a four-degree of freedom vehicle model incorporating longitudinal, lateral, yaw, roll, and load transfer effects.
Finite Element Modeling of Non-Orthogonal Loosely Woven Fabrics in Advanced Occupant Restraint Systems
Authors: Tanov Romil R. , Brueggert Marlin
Published: November 2021

The behavior of loosely woven fabrics differs significantly from other types of woven fabrics. Its unique characteristics have been successfully utilized for the correct operation of some recently developed occupant protection devices for the automotive and heavy machine and truck industry. However, this behavior cannot be efficiently modeled using the currently available material models within a finite element analysis scheme. Therefore, the aim of this work is to present the basics of a formulation of a material model for the analysis of loosely woven fabrics and its implementation in a general-purpose explicit finite element code. To assess the performance of the model, results from the simulation are presented and compared to real test data.
Racing Car Simulation and the Virtual Race Track
Authors: Siegler Blake , Crolla David
Published: November 2021

A number of handling models of a small high performance formula type racing car have been produced. These have been used to optimise the performance of the vehicle whilst under going simple manoeuvres and around a complete race track. Recently the vehicle was fitted with a data acquisition system and objective data was taken of the vehicle’s handling performance.

The paper details an investigation into the accuracy of two (a simple and more sophisticated) vehicle handling models in predicting the actual vehicle’s performance from the data collected by comparing measured and simulated results. The investigation studies the steady state and transient response of the vehicle up to the limit of the vehicle’s handling performance.

A description is also given of the use of the more sophisticated model in a virtual race track simulation where it is used as a development tool to tune the performance of future vehicles.
Optimal Engine Operations in Series Hybrid Electric Vehicles
Authors: Wang Wenping
Published: November 2021

Numerical optimal control techniques are employed to define the best engine operating strategies for series hybrid electric vehicles in this paper. On the basis of formulating the energy management as a linear minimum-fuel problem with linear input and state constraints, both linear programming (LP) and mixed integer linear programming (MILP) are applied to find the numerical solutions. In particular, the on-line computations of the resultant LP-based and MILP-based optimal controllers are reduced to simple linear function evaluations via using recursive linear program equivalents. Therefore, the resulting optimal engine control strategies are attractive for real-time control and optimization of fuel economy in hybrid vehicles. Simulation results of the proposed approach show improvement in fuel economy over the “Load Leveling” and “Load Following” engine operating modes.
Modeling of Continuous and Intermittent Gas Jet Impingement and Heat Transfer on a Solid Surface
Authors: Chaniotis A. K. , Poulikakos D.
Published: November 2021

The present work focuses on the effect of flow pulsation on the characteristics of the planar jet impingement normally on a heated surface. Specifically, the influence of frequency, amplitude and Reynolds number of the jet is examined, concerning the instantaneous and time average convective heat transfer. The simulations are conducted using a novel, improved Smooth Particle Hydrodynamics (SPH) methodology that is based on particle discretization of the governing compressible Navier-Stokes equations. The simulation of jet impingement focuses on the quantitative description of the flow field and the energy exchange between jet and surface. The strong aerodynamic and thermal interaction that exists between the gaseous jet and the impingement surface greatly enhances the local heat transfer in the stagnation and wall jet regions as well as the average heat transfer over the surface. This study is the first step toward modeling the same process but in the presence of chemical reactions and ablation between the gaseous jet and the plate.
Higher-Order Boundary Element Methods for Unsteady Convective Transport
Authors: Dargush G. F. , Grigoriev M. M.
Published: November 2021

Higher-order boundary element methods (BEM) are presented for time-dependent convective diffusion problems. The time-dependent convective diffusion free-space fundamental solutions originally proposed by Carslaw and Jaeger are used to obtain the boundary integral formulation. For the linear, quadratic and quartic time interpolation functions considered in this paper, a complete set of closed form time integrals for the one-dimensional formulation are developed. Boundary element method solutions are obtained for four problems of unsteady convection-diffusion, including shock wave propagation. It is shown that the BEM solutions are extremely accurate in contrast to finite-difference and finite-element methods. Moreover, no upwinding is needed for the boundary element methods, even for high Peclet number flows. Finally, the conventional BEM formulation is extended to a problem involving singular flux arising due to a sudden rise of temperature on the boundary. This infinite flux BEM formulation provides significantly more accurate numerical results than the conventional approach.
Slip-Flow Constant-Wall-Temperature Nusselt Number in Circular Tubes in the Presence of Axial Heat Conduction
Authors: Simek Olga , Hadjiconstantinou Nicolas G.
Published: November 2021

We present an investigation of slip-flow constant-wall-temperature convective heat transfer in circular tubes under hydrodynamically and thermally fully developed conditions. Our analysis includes the contribution of axial heat conduction (finite Peclet number) which is important in small scale flows, and has not been included in previous investigations of slip-flow heat transfer. The Nusselt number is found to decrease with increasing Knudsen number for all Peclet numbers in the fully accommodating case, as expected. The effect of axial heat conduction is found to be most important at Kn = 0, and results in an increase in the Nusselt number of the order of 15%; as Kn increases, the effect of axial heat conduction decreases.
Transition to Weak Turbulence, Chaos and Hysteresis in Natural Convection
Authors: Vadasz Peter
Published: November 2021

The fundamental understanding of the transition from laminar to turbulent convection is far from being conclusive. While major efforts are under way, there is still a significant challenge in front of the scientist and engineer to uncover the complex behavior linked to this transition. In isothermal shear flows the time dependent and three dimensional form of turbulence is well established experimentally and numerically. It is caused by the non-linear terms in the isothermal Navier-Stokes equations. Weak turbulence is linked to the problem of natural convection where an additional non-linear interaction appears as a result of the coupling between the equations governing the fluid flow and the energy equation. The latter can typically cause a transition to a non-steady and non-periodic regime (referred to as weak turbulent) at much lower values of the parameter controlling the flow, when compared to the corresponding isothermal system.
Controlled Contact Angle and Droplet Evaporation Using Photo-Induced Hydrophilic Surface
Authors: Takata Y. , Hidaka S. , Nakamura T. , Yamamoto H. , Masuda M. , Ito T.
Published: November 2021

Titanium Dioxide, TiO2, is one of the photocatalysts that has a very unique characteristic. The surface coated with TiO2 exhibits extremely high affinity for water by exposing the surface to ultraviolet ray and the contact angle decreases nearly to zero. On the contrary, the contact angle increases when the surface is shielded from ultraviolet ray. We have developed two types of TiO2 surface by sputtering process. One is the copper surface with TiO2 layer and the other is with TiO2 and SiO2 layer. The contact angle of the former varies between 30–82° and the latter varies between 4–13°. We applied these surfaces to control the contact angles with the other thermal properties of the surface being constant. Experiment of droplet evaporation has been performed to manifest the effect of contact angle on the evaporation curves. It is found that the wetting limit temperature increases as the contact angle decreases to 13°, but it decreases again as the contact angle decreases to 4°.
Design and Fabrication of an Optomechanical Uncooled Infrared Imaging System
Authors: Zhao Y. , Yamaguchi J. , Choi J. , Morales S. , Horowitz R. , Majumdar A. , Norton P. , Kitching J. , Li H. , Athavale M.
Published: November 2021

This paper discusses the design of an uncooled optomechanical infrared imaging system. A micromachined micro-cantilever array serves as an uncooled infrared imaging sensor known as focal-plane array (FPA). When exposed to an infrared source, the absorption of the incoming radiation energy by the cantilever will raise its temperature. Due to the thermal expansion mismatch of the two materials, the temperature rise will induce bending of the cantilever. The pixel design based on considerations of thermal, mechanical, and optical properties, and also compatibility with micro-fabrication process has been described in detail. By detecting the deformation of the cantilever optically using a laser interfometry system, the thermal information of the infrared source can be extracted. The paper describes the microfabrication process of the FPA, and a primary test on the temperature response of the pixel shows reasonable agreement with the theoretical analysis.
Photonic and Radiative Properties of Bubble Arrays
Authors: Miyazaki Koji , Yang Bao , Narayanaswamy Arvind , Chen Gang
Published: November 2021

In this paper we explore the photonic and radiative properties of regular bubble arrays. The photonic band structure and transmissivity, reflectivity and absorptivity of the arrays are calculated numerically. In particular we investigate the effects of packing density and lattice constant on the absorptivity by the numerical simulation.
A Pore Network Model for Drying Processes in Porous Media
Authors: Yiotis A. G. , Stubos A. K. , Boudouvis A. G. , Yortsos Y. C.
Published: November 2021

A pore network model for the drying of capillary porous media is presented in this work. The model accounts for various processes at the pore scale including evaporation of a volatile liquid, mass transfer of the vapors by advection and diffusion in the gas phase and viscous flow in the liquid and gas phases. Both viscous and capillary forces at the liquid menisci in pore throats are also modeled. We consider isothermal drying in a rectilinear horizontal geometry, with no flow conditions in all but one boundary, at which a purge gas is injected at a constant rate. Drying rates, phase distribution and concentration patterns are reported as a function of time and the gas flow rate. We also refer to the evolution of trapped liquid clusters.
An Experimental Investigation of Reflux Condensation Phenomena in Multiple U-Tubes With and Without Noncondensible Gas
Authors: Chun Moon-Hyun , Lee Kyung-Won , Chu In-Cheol
Published: November 2021

A series of experiments were performed to investigate the thermal-hydraulic phenomena inside U-tubes in a reflux condensation mode. A total of 512 data for local condensation heat transfer coefficients (108 for pure steam flow and 404 for steam-air flow conditions, respectively) have been obtained for various inlet flow rates of steam and air under atmospheric condition. A new correlation, which includes the effects of flow rates of steam and noncondensible gases (air) on the heat transfer coefficient and is applicable to the reflux condensation mode, has been developed using the concept of degradation factor based on the steam-air experimental results. In addition, the effects of multiple U-tubes with different lengths (i.e., two-long and two-short U-tubes) and noncondensible gases on the onset of flooding during a reflux condensation have been examined.
Cooling Characteristics of Two-Phase Impinging Jets
Authors: Kakumoto Taiki , Tomemori Hideki , Horiki Sachiyo , Osakabe Masahiro
Published: November 2021

Cooling of surfaces is often carried out in devices consisting of arrays of round nozzles, through which coolant impinges vertically upon the surfaces. To enhance the heat transfer coefficient and save the amount of coolant, two-phase jets were applied to the cooling of copper surface of 30mm in diameter. Experiments were conducted with using water and air at atmospheric pressure.

The heat transfer coefficient by single-phase water jets was well described with an empirical correlation. The experimental heat transfer coefficient increased with addition of air. When the volumetric air flow ratio β is less than 0.2, the heat transfer coefficient by air/water two-phase jets was larger than the prediction where the volumetric two-phase velocity and the physical properties of water were used in the empirical correlation for single phase heat transfer. However, the experimental data gradually decreased with increase of gas phase at β > 0.2.

To study the enhancement and degradation mechanism of impinging two-phase heat transfer, the flow pattern in a capillary tube such as the nozzle tube and the impinging behavior on a transparent glass plate were observed with a high-speed video camera. When β was small, numerous air micro bubbles of very small diameter were impinging on the heat transfer surface. When β was large, impinging micro bubbles could not be observed. Gas and water phases intermittently impinged on the glass plate as the heat transfer surface. In the observed photograph, a hexagonal pattern resulting from interference among the adjusting two-phase jets could be recognized.

The enhancement of heat transfer at β < 0.2 is considered to be due to the micro bubbles sweeping on the surface. The degradation at β > 0.2 is mainly due to the lower thermal capability of gas-phase than that of liquid-phase. The gas-phase intermittently impinged on the surface and its heat transfer was relatively low.
Numerical Modeling of Aerosol Transport and Removal in Channels Using the Particle Tracking Method
Authors: Wu X. M. , Ghiaasiaan S. M. , Abdel-Khalik S. I.
Published: November 2021

Turbulent transport and deposition of microscopic particles in commonly-used large, and micro-channels were investigated. The objective was to examine the suitability of the Reynolds-averaged Navier-Stokes (RANS)-type turbulence models, along with a Monte-Carlo Lagrangian particle tracking method that accounts for the stochastic particle-turbulent eddy interactions, for the modeling of aerosol transport when a multitude of forces act on the particles.

The computer program KIVA-3 (Amsden et al., 1993) was modified and enhanced by adding several turbulence models, and including appropriate models for the effect of the following mechanisms on particle motion: drag, gravity, thermophoresis, Brownian dispersion, and shear-induced (Saffman) lift force. The effect of Brownian motion was modeled by including a random, white noise force term in the particle equation of motion. Parametric simulations were performed, leading to the following main observations. For the transport and deposition of microscopic particles, in addition to the turbulent dispersion, several other dispersion mechanisms were important. The k-ε and Reynolds-stress transport models provided similar predictions for sub-micron particles, but differed significantly for larger particles.

The model provided physically consistent results with correct trends in all the simulations. The methodology, however, appears to be expensive in terms of computations, and further work is needed for streamlining the numerical solution methods and physical models.
Transport Characteristics of a Multi-Species Slurry in a Horizontal Pipeline
Authors: Skudarnov P. V. , Kang H. J. , Lin C. X. , Ebadian M. A. , Gibbons P. W. , Erian F. F. , Rinker M.
Published: November 2021

In the course of the U.S. Department of Energy’s (DOE) tank waste retrieval, immobilization, and disposal activities, high-level waste transfer lines have the potential to become plugged. In response to DOE’s needs, Florida International University’s Hemispheric Center for Environmental Technology (FIU-HCET) is studying the mechanism and behavior of pipeline plugging to determine the pipeline operating conditions for safe slurry transport.

Transport behavior of multi-species slurry has been studied in a 1-in O.D. pipeline flow loop. The slurry was a five-species mixture of Fe2O3, Al2O3, MnO2, Ni2O3, and SiO2, which simulated actual waste at the Savannah River DOE site. The relationship between the pressure drop in the straight horizontal sections of the flow loop and the mean slurry flow velocity was determined for two solids volume concentrations of 5.2 and 7.8%. Critical deposition velocity was measured from visual observations. An existing empirical model that predicts the pressure gradient for a single-species slurry flow in a horizontal pipeline was used to describe the pressure drop data.