bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Elaboration of Numerical Method to Simulate Gas-Liquid-Solid Three-Phase Flows Based on MPS Method
Authors: Takahashi Ryohei , Yamamoto Makoto
Published: July 2018

In recent years, the utilization of computational fluid dynamics (CFD) in various industrial fields has broadened following developments in computer technology. Although mainstream CFD is currently based on a grid method in an Eulerian framework, it is difficult to apply this to the simulation of problems in which large deformations of interfaces between phases occur or where microscopic scale phenomena have a great influence on the entire flow field. For this reason, particle methods, which can offer advantages for dealing with interface deformations and microscopic scale phenomena, are now receiving attention. Among the various particle methods, the moving-particle semi-implicit (MPS) method [1] is the most well-established and various physical models and extended numerical methods have been developed using it. In this study, we developed a numerical method to simulate a gas-liquid-solid three-phase flow based on the MPS approach. This method makes possible the coupling of independent computations of different phases. We conducted numerical tests on gas-liquid two-phase, liquid-solid two-phase and gas-liquid-solid three-phase simulations. Computational targets are modelling the dam break and solid-particle impingement phenomena. The computational results indicate reasonable agreement with the experimental results. We confirmed that the present method can reproduce the interactions between gas, liquid and solid phases that are difficult to reproduce with conventional grid methods.
Study of Partial Cavitation on a Plane-Convex Hydrofoil With Mesh Development by Using GMSH Free Software
Authors: Hidalgo Victor , Luo XianWu , Escaler Xavier , Yu An , Valencia Esteban
Published: July 2018

Commercial programs are widely used to do unstructured and structured meshes for CFD simulations. However, grids and meshes based on free-open source software (FOSS) give to researchers and engineers the possibility to adapt and improve the meshing process for special study cases with a high Reynolds numbers, such as unsteady partial cavitating flows. In order to improve the grid qualities, the FOSS GMSH has been used to do three types of grid, unstructured hexahedral mesh, hybrid mesh and structured hexahedral mesh for the simulation of partial cavitation around a plane-convex hydrofoil. Numerical simulations have been carried out by using the FOSS OpenFOAM based on the Zwart cavitation model and the implicit large eddy simulation (ILES). The results show that the structured mesh provides the best simulating to experimental data. On the other hand, the hybrid mesh induces unreliable results at leading edge without shedding.
Research on Structural Optimization for Regenerative-Cooling Thrust Chamber
Authors: Ji Jialong , Sun Bing
Published: July 2018

A regenerative-cooling liquid rocket engine chamber is applied as the study object, and the heat transfer models are established to get the distributions of chamber parameters. A thermal-fatigue simulation is carried out go get the strain of the throat section with the thermal field and pressure field applied as the boundary conditions of a two-dimensional finite-element model. A usage factor is used for the life estimation of chamber, and the structural parameters of cooling channels are optimized aiming for a smallest usage factor which means a longest life. The influence of parameter changes is researched in this paper respectively. Three methods, linear search method, conjugate gradient method and gradient free method are respectively applied for the structural parametric optimization of cooling channels. The result of the research shows that the optimized structures have a longer life than the initial one has.
Effect of Port Configurations on the Performance of Hydraulic Actuator
Authors: Kim Jin-Hyoung , Han Su-Min , Kim Youn-Jea
Published: July 2018

Hydraulic actuator is a primary component of the hydraulic valve systems. In this paper, the actuation speed of hydraulic actuator was studied with different port configurations. Numerical analysis was performed using the commercial CFD code, ANSYS with k-ε turbulent model. The results of pressure and velocity distributions of working fluid in the hydraulic actuator were graphically depicted.
Large-Scale Numerical Simulation of Unsteady Flow Field in a Half-Ducted Propeller Fan Using Lattice Boltzmann Method
Authors: Yamada Kazutoyo , Kusano Kazuya , Furukawa Masato
Published: July 2018

Recently, the lattice Boltzmann method (LBM) is being applied in turbomachinery field, regarded as a good candidate for tool of flow simulation as well as aerodynamic sound analysis.

For better prediction of broadband noise with high frequecy, which is generally generated in high Reynolds number flows, not only high grid resolution is required to capture very small eddies of the sound source inside the turbulent boundary layer, but also the computation of acoustic field is often needed. In such case, the direct simulation of flow field and acoustic field is straight-forward and effective. However, the computational cost becomes extremely expensive. Moreover, for low Mach number flows the compressible Navier-Stokes simulation not only requires high-order scheme which is unsuitable for parallel computation, but also suffers from stiff problem. LBM is suitable for such simulation thanks to its advantages.

In the present study, a large-scale numerical simulation of flow field around a half-ducted propeller fan is conducted with LBM, and its result is validated by comparing with the experimental result.
Vortex Shedding From Trailing Edge of Rotor Blade of Axial Flow Fan at Design Operating Condition
Authors: Hamakawa Hiromitsu , Oda Kaisei , Asai Yuta , Hosokai Kazuki , Kurihara Eru , Hayashi Hidechito
Published: July 2018

In the present paper the attention is focused on the vortex shedding from the trailing edge of the rotor blade at the design operating condition. We measured the relative velocity, the turbulence intensity, the spectrum of velocity fluctuation and the in-phase velocity fluctuation near the trailing edge along the blade span. The time variations of amplitude of velocity fluctuations from 1500 Hz to 1900 Hz in the wake of the suction and pressure side of the trailing edge are out of phase with each other simultaneously at the mid span region. Karman vortices were formed in the near wake of the trailing edge of rotor blade intermittently. As the distance between two measured locations along the blade span increased, the in-phase rate of two velocity fluctuations decreased. This rate became maximum value at the time lag of 0 s. As the measured radius of the moved sensor increased, the time lag decreased. The rotational axis of Karman vortex inclined for the trailing edge of rotor blade.
Study on Manufacturing Tolerances for the Laminar Airfoil
Authors: Lee Jaehun , Jung Kyoung Jin
Published: July 2018

The procedure to determine manufacturing tolerances for the laminar airfoil is explained using the CFD (computational fluid dynamics) analysis. This procedure is applied to a laminar airfoil for the tolerance of the forward-facing step and rearward-facing step. In the CFD analysis the Langtry-Menter SST Transition model is used to simulate a natural transition over the laminar airfoil. The computed tolerances showed good agreement with experimental data.
A Dynamically Adaptive Lattice Boltzmann Method for Flapping Wing Aerodynamics
Authors: Wood Stephen L. , Deiterding Ralf
Published: July 2018

The essential components of a parallel dynamically adaptive lattice Boltzmann method coupled to a 6-degree-of-freedom rigid body motion solver are presented. This Cartesian approach with automatic fluid meshing is particularly well suited for simulating the interaction of low Reynolds number flows and moving structures with good accuracy and high computational performance. The fully coupled fluid-structure simulation method is demonstrated for the experiment of a two-segment hinged wing with torsion damper by Toomey & Eldredge, a simplistic model of a flapping wing in air. A grid convergence study assesses the prediction accuracy of the overall method and required CPU times. Our computations show very good agreement with measurements of the evolving hinge angle by Toomey & Eldredge; forces and moments are predicted with an error margin of generally <5% with respect to their computational results.
Development of Efficient Water Purifier by Cavitation Nozzle With Electrode
Authors: Shin Dong Ho , Yoon Joon Shik , Ko Han Seo
Published: July 2018

Water is a limited and vital resource, so it should not be wasted by pollution. A development of new water purification technology is urgent nowadays since the original and biological treatments are not sufficient. And, they have some disadvantages such as sludge. Thus, the detailed experimental data about the development of the water purifier with a cavitation nozzle (venturi-type tube) and electrodes using an electrochemical technology, so called electrolysis were analyzed in this study. Two platinum-coated titanium meshes were used as electrodes, and DC voltage was supplied on the electrodes. Optimum electrode interval and applied power were determined for the electrolysis of indigo carmine solutions. And then, the optimized electrodes were installed in the venturi-type tube for generating cavitation. The cavitation effect of water could be enhanced by the bubbly flow induced by the electrolysis of the electrodes without any byproduct. Finally, the prototype of the water purifier with the electrodes and the cavitation nozzle was developed, and its advantages for the purification and removal of algal bloom were confirmed. As a result, the energy saving and high efficient water purifier was fabricated in this study.
Towed Underwater SPIV Measurement of Flow Fields Around a Surface-Piercing Cylinder With Free Surface Effects
Authors: Seo Jeonghwa , Han Bumwoo , Rhee Shin Hyung
Published: July 2018

Effects of free surface on development of turbulent boundary layer and wake fields were investigated. By measuring flow field around a surface piercing cylinder in various advance speed conditions in a towing tank, free surface effects were identified. A towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was used to measure the flow field under free surface. The cross section of the test model was water plane shape of the Wigley hull, of which longitudinal length and width were 1.0 m and 100 mm, respectively. With sharp bow shape and slender cross section, flow separation was not expected in two-dimensional flow. Flow fields near the free-surface and in deep location that two-dimensional flow field was expected were measured and compared to identify free-surface effects. Some planes perpendicular to longitudinal direction near the model surface and behind the model were selected to track development of turbulent boundary layer. Froude numbers of the test conditions were from 0.126 to 0.40 and corresponding Reynolds numbers were from 395,000 to 1,250,000. In the lowest Froude number condition, free-surface wave was hardly observed and only free surface effects without surface wave could be identified while violent free-surface behavior due to wave-induced separation dominated the flow fields in the highest Froude number condition. From the instantaneous velocity fields, Time-mean velocity, turbulence kinetic energy, and flow structure derived by proper orthogonal decomposition (POD) were analyzed. As the free-surface effect, development of retarded wake, free-surface waves, and wave-induced separation were mainly observed.
Color Particle Image Velocimetry Improved by Decomposition of RGB Distribution Integrated in Depth Direction
Authors: Murai Yuichi , Yonezawa Norio , Oishi Yoshihiko , Tasaka Yuji , Yumoto Takeaki
Published: July 2018

A single-camera color PIV system based on the combination of a color-coded illumination and a color high-speed video camera has been developed. The system realizes flow velocity vector fields in multiple layers in the depth direction for a relatively wide volume. The working principle belongs to smoke-imaging PIV since particle per pixel is larger than unity in the digital image plane, which is different from the case of color 3-D PTV. The accuracy of the present color PIV depends on how the integral equation of color-signal overlapping among three wavelengths (R,G,B) is solved as inverse analysis. We propose in this paper a method to reasonably solve the equation, which removes color contamination in RGB sensors, and decomposes the color-illuminated smoke images into the smoke distributions inside individual layers. The first half of the paper deals with linear backward analysis for the color de-contamination to establish triple-layer velocimetry by a single-view imaging of smoke. Based on the success, we present in the second half an extended system that realizes simultaneous six-layer color PIV to which three intermediate colors are additionally illuminated into the measurement volume.
Influence of Spoke Geometry on Performance and Internal Flow of Contra-Rotating Small-Sized Hydroturbine
Authors: Shigemitsu Toru , Takeshima Yasutoshi , Tanaka Chihiro , Fukutomi Junichiro
Published: July 2018

Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydroturbines is lower than that of large one, and these small hydroturbine’s common problems are out of operation by foreign materials. Then, there are demands for small hydroturbines to keep high performance and wide flow passage. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance and enable to use low-solidity rotors with wide flow passage, in order to accomplish high performance and stable operation. Final goal of this study is development of a small hydroturbine like electrical goods, which has high portability and makes an effective use of unused small hydro power energy source. Efficiency of the contra-rotating small hydroturbine was high in pico-hydroturbine and high efficiency could be kept in wide flow rate range. On the other hand, the relatively large loss occurred at the spokes which should be installed for this small hydroturbine to support the rotors. Then, the new spoke to increase its performance is proposed in this research. Internal flow condition, which was difficult to measure experimentally, was shown by the numerical flow analysis. Further, the influence of spoke geometry was clarified. Then, a relation between the performance and internal flow condition was considered by the numerical analysis results.

In the present paper, the performance of the contra-rotating small hydroturbine using different spoke geometry is shown by the numerical results. Further, internal flow condition between the front and rear rotors are investigated.
Simulation of Jet Issued Into Two-Layer Density-Stratified Fluid by Vortex in Cell Method Combined With Immersed Boundary Method
Authors: Aozasa Isao , Uchiyama Tomomi
Published: July 2018

Jet flow issued into two-layer density-stratified fluid in a cylindrical tank is numerically simulated. Vortex in cell (VIC) method combined with an Immersed Boundary (IB) method, which is presented by the current authors, is applied to the simulation. The upper and lower fluids are water and a NaCl-water solution, respectively, and the lower fluid is issued vertically upward from a nozzle on the bottom of the tank. The Reynolds number Re defined by the jet velocity and the nozzle diameter ranges from 95 to 1188, and the mass concentration of the NaCl-water solution C0 is set at 0 and 0.02. The simulation highlights that the jet behavior relative to the density interface and the resultant mixing phenomena depend on Re. Such simulated results are confirmed to agree well with the experimentally visualized ones, demonstrating the validity of the present simulation method.
DNS of Turbulent Channel Flow With a Flexible Square Cylinder
Authors: Takeuchi Makoto , Tsujimoto Koichi , Shakouchi Toshihiko , Ando Toshitake
Published: July 2018

In the present paper in order to investigate possibility of flow control using elastic body, we conduct a simulation of a finite-length flexible cylinder installed in turbulent channel flow. For the flexible cylinder, the rigorous equation of motion for elastic continuum is solved with a finite volume method; the effect of existence of cylinder in the flow computation is taken into account using the immersed boundary method. From instantaneous and time averaged flow quantities, we demonstrate that the flexible cylinder markedly modulates the wake structure depending on the elasticity of cylinder. Further in order to extract coherent structures, the DMD (dynamic mode decomposition) method are applied. The primary flow structures in the wake of cylinder are demonstrated.
Efficient Generation of High-Reynolds-Number Homogeneous Turbulence by Disturbances Composed of Two Frequency Components
Authors: Takamure Kotaro , Ozono Shigehira
Published: July 2018

We attempted to determine the number of frequency components required for efficient turbulence generation using a multi-fan type wind tunnel where 99 fans were driven to generate turbulence. In a previous study, a random-phase mode was applied, where an input signal composed of forty frequency components was fed to each fan with quasi-random phases. Using this driving mode, we achieved high-Reynolds-number homogeneous turbulence of Reλ ∼ 750 in a relatively short distance. In the present study, in order to understand the elementary process of the evolution, one single frequency or two frequencies were used, instead of forty. When using the single frequency, initial dominant spectral peaks remain at lower frequencies over the tunnel length. In the case of two frequencies, f1 and f2 (f1 = n1f0 and f2 = n2f0; n1 < n2), where n1 and n2 are integers, and f0 is defined as the reciprocal of a basic input data period, the turbulence characteristics depend on the relation between n1 and n2. When n1 and n2 are not coprime (i.e., n2 can be divided by n1), dominant spectral peaks remain over the tunnel length as in the case of using a single frequency, but when coprime (i.e., n2 cannot be divided by n1), the spectral shape becomes relatively smooth with the initial dominant peaks disappearing. However, it was found that the development of turbulence is much slower for the two-frequency case than for the forty-frequency case.
Experimental Characterization of Particle-Laden Air Flow in a Horizontal Pipe
Authors: Dai Y. , Khan T. S. , Alshehhi M. S. , Khezzar L.
Published: July 2018

In many engineering applications, movement of micron and submicron size solid particles with compressed air or gas causes major engineering problems as in the case of black powder in oil and gas industry. Therefore, understanding its physical and flow dynamics characteristics inside a pipeline can be very useful to efficiently manage pipelines contamination issues.

This paper presents an experimental study carried out to simulate characteristics of air-sand particles flow through a transparent horizontal pipe with various flow conditions. Experimental analysis focuses on determination of critical pickup velocity of the solid particles and measurement of pressure drop across the sand bed of various blockage ratios. Results have been compared with previous studies in literature. Limited experiments are conducted using black powder samples as well. Comparison of results shows vast deviation between sand and black powder behavior.
Measurements of Axial and Radial Thrust Forces Working on a Three-Stages Centrifugal Pump Rotor
Authors: Yamashita Tetsuya , Watanabe Satoshi , Hara Yoshinori , Watanabe Hiroyoshi , Miyagawa Kazuyoshi
Published: July 2018

In this study, radial and axial thrust forces working on the whole rotor in a three-stages centrifugal pump are measured in a wide range of flow rate. The forces are measured at two floating journal bearings and one floating ball bearing, which are supported by the individual load cells. The effects of the offset of rotor position in the axial direction on the thrust forces are investigated. It is found that the effect of the axial offset is significant for the axial thrust force in the low flow rate range, whereas it has little influence on the head and efficiency performances in the whole flow rate range.
Vibration Dynamics of a Wind Turbine Drive Train High Speed Subsystem: Modelling and Validation
Authors: Asadi Saeed , Berbyuk Viktor , Johansson Håkan
Published: July 2018

Modern wind turbines are enormous large-scale electromechanical systems. They operate in complex conditions, determined by a turbulent wind field, by possible disturbances in the electricity grid and by the behavior of sea waves for offshore turbines. Guaranteeing the structural integrity of these machines during a lifetime of 20 years is an enormous challenge. In this paper the dynamics of a wind turbine drive train high speed subsystem is studied both by modeling and experiments with focus on system torsional and flexural vibrations and transient events which can reduce fatigue life of functional components (gearbox, bearings, shafts, couplings, others). A scaled down drive train high speed shaft test rig has been developed. Main components of the test rig are six-pole motor with variable frequency drive controller (up to 1000 rpm), shafts’ disk coupling and flexible mounting structure representing gearbox housing with output high speed bearing. The test rig is equipped with measurement system comprising a set of accelerometers and displacement sensors, data acquisition hardware and software (SKF WindCon3.0). Mathematical and computational models of the test rig have been developed and went through validation tests. The system kinematic and dynamic responses are studied for different operational scenarios and structural parameters (ratio of shaft bending stiffness and stiffness of mounting structures, unevenly inertia load distribution, others). The ultimate goal of the test rig is to get insight into interaction between internal dynamics of drive train functional components to be used the results obtained in developing novel methods to detect, predict and prevent faults and failures in wind turbine drive trains arising due to misalignments and transient external loads.
Detection of Rotating Blade Faults From Lateral Vibrations of a Rotor-Disk-Blade System
Authors: Adewusi Surajudeen
Published: July 2018

Competition and high quality requirements in the industries have necessitated the need for reliable rotating machines. This can be partly achieved by continuous monitoring of operation conditions to detect any fault before it causes serious problem or breakdown of rotating machines. The detection of faults in rotating blades via direct blade vibration measurements and analysis is somewhat difficult because blades often operate in a very harsh environment (gas turbine blades are rotating in high temperature and pressure environment). This paper presents indirect detection of blade faults from lateral vibrations of a rotor-disk-blade system, which can easily be measured, using laboratory test-rig. A rotor, disk, 6 normal blades and 3 blades with different defects were designed. The modal parameters of the normal and defective blades were determined experimentally and by modal analysis using ANSYS. The lateral vibrations, in the x- and y-axis, of the rotor-disk system with normal 6 blades and with 5 normal blades and 1 defective blade at a time were measured and analyzed. The results revealed that defective blades showed some distinct characteristics in the frequency domain, which can be used to identify blade faults in a bladed rotor-disk system.
Estimating Constitutive Law of a Filament From its Deformed Shapes Using Input Reconstruction
Authors: Chavan Roshan , Palanthandalam-Madapusi Harish , Goyal Sachin
Published: July 2018

Twisting and bending dynamics of biological filaments such as DNA play a central role in their biological activity including gene expression. The elastic rod model is an efficient tool to simulate such deformations. However, the accuracy of elastic rod predictions depend strongly on the constitutive law, which follows from the atomistic structure of the DNA molecule and is known to be nonlinear and to vary along the length according to the base pair sequence of the DNA. Unfortunately, it is impractical to derive the constitutive law analytically from the atomistic structure. Identification of the nonlinear sequence-dependent constitutive law from experimental data and feasible molecular dynamics simulations remains a significant challenge. In this paper, we extend earlier work by employing techniques based on input reconstruction and state estimation filters to estimate the constitutive law using molecular dynamics data of deformations in bio-filaments.
Piecewise Nonlinear Energy Sink
Authors: Al-Shudeifat Mohammad A.
Published: July 2018

Symmetric piecewise nonlinearities are employed here to design highly efficient nonlinear energy sink (NES). These symmetric piecewise nonlinearities are usually called in the literature as dead-zone nonlinearities. The proposed dead-zone NES includes symmetric clearance about its equilibrium position in which zero stiffness and linear viscous damping are incorporated. At the boundaries of the symmetric clearance, the NES is coupled to the linear structure by either linear or nonlinear stiffness components in addition to similar viscous damping to that in the clearance zone. By this flexible design of the dead-zone NES, we obtain a considerable enhancement in the NES efficiency at moderate and severe energy inputs. Moreover, the dead-zone NES is also found here through numerical simulations to be more robust for damping and stiffness variations than the linear absorber and some other types of NESs.
An Emergency Tracking Controller Design for a Manipulator After its Actuator Failure
Authors: Jarzębowska Elżbieta , Szewczyk Adam
Published: July 2018

This paper presents a development of two model-based emergency tracking controllers which can be turned on when one of actuators of a system fails during motion. The system is represented by a manipulator possessing 3 degrees of freedom, which may work in horizontal or vertical planes. The control goal is to enable an end effector of a broken manipulator completing tracking a predefined task as good as possible and then get back to its rest position. Simulation results confirm good performance of the designed emergency tracking controllers.
A Novel Multi-Directional Nonlinear Piezoelectric Energy Harvester Coupled With Nonlinear Conditioning Circuits
Authors: Yang Zhengbao , Zu Jean
Published: July 2018

Energy harvesting from vibrations has become, in recent years, a recurring target of a quantity of research to achieve self-powered operation of low-power electronic devices. However, most of energy harvesters developed to date, regardless of different transduction mechanisms and various structures, are designed to capture vibration energy from single predetermined direction. To overcome the problem of the unidirectional sensitivity, we proposed a novel multi-directional nonlinear energy harvester using piezoelectric materials. The harvester consists of a flexural center (one PZT plate sandwiched by two bow-shaped aluminum plates) and a pair of elastic rods. Base vibration is amplified and transferred to the flexural center by the elastic rods and then converted to electrical energy via the piezoelectric effect. A prototype was fabricated and experimentally compared with traditional cantilevered piezoelectric energy harvester. Following that, a nonlinear conditioning circuit (self-powered SSHI) was analyzed and adopted to improve the performance. Experimental results shows that the proposed energy harvester has the capability of generating power constantly when the excitation direction is changed in 360. It also exhibits a wide frequency bandwidth and a high power output which is further improved by the nonlinear circuit.
Piezoelectric Energy Harvesting From Torsional Vibration
Authors: Musgrave Patrick , Zhou Wanlu , Zuo Lei
Published: July 2018

Torsional vibration is present in various applications, such as in oil drilling pipes, engine crankshafts, and wind turbine gearboxes. In the case of oil drilling, ever deeper wells are being drilled and sensors used to gather data from the bottom of the well. Providing an energy source for these sensors is a big challenge. Harvesting energy from torsional vibrations presents a promising solution for powering the sensors on rotational systems. We investigated the concept of torsional vibration energy harvesting using a piezoelectric transducer attached to a shaft at an arbitrary angle with respect to the axis of the shaft. A comprehensive theoretical model considering all the working modes, including d15, d31, and d33 mode, has been developed to express the voltage outputs as functions of the mounting angle. The frequency responses of the voltage outputs over the input torque have also been studied and compared. A finite element model was also implemented to verify the theoretical results and illustrate the voltage distribution within the piezoelectric material under an external torque input.
Efficient and Accurate Calculation of Discrete Frequency Response Functions and Impulse Response Functions
Authors: Xu Y. F. , Zhu W. D.
Published: July 2018

Modal properties of a structure can be identified by experimental modal analysis (EMA). Discrete frequency response functions (FRFs) and impulse response functions (IRFs) between responses and excitation are bases for EMA. In calculation of a discrete FRF, discrete Fourier transform (DFT) is applied to both response and excitation data series, and a transformed data series in DFT is virtually extended to have an infinite length and be periodic with a period equal to the length of the series; the resulting periodicity can be physically incorrect in some cases, which depends on an excitation technique used. There are various excitation techniques in EMA, and periodic extension in DFT for EMA using periodic random and burst random excitation is physically correct. However, EMA using periodic random excitation needs a relatively long excitation time to have responses to be steady-state and periodic, and EMA using burst random excitation needs a long sampling period for responses to decay to zero, which can result in relatively long response and excitation data series and necessitate a large number of spectral lines for associated DFTs, especially for a high sampling frequency. An efficient and accurate methodology for calculating discrete FRFs and IRFs is proposed here, by which fewer spectral lines are needed and accuracies of resulting FRFs and IRFs can be maintained. The relationship between an IRF from the proposed methodology and that from the least-squares method is shown. A new coherence function that can evaluate qualities of FRFs and IRFs from the proposed methodology in the frequency domain is used, from which meaningful coherence function values can be obtained even with response and excitation series of one sampling period. Based on the new coherence function, a fitting index is used to evaluate overall qualities of the FRFs and IRFs. The proposed methodology was numerically and experimentally applied to a two-degree-of-freedom mass-spring-damper system and an aluminum plate to estimate their FRFs, respectively. In the numerical example, FRFs from the proposed methodology agree well with the theoretical one; in the experimental example, a FRF from the proposed methodology with a random impact series agreed well with the benchmark one from a single impact test.
Nonlinear Dynamics of Flexible Rotating Shafts With Centrifugal Pendulum Vibration Absorbers
Authors: Acar Mustafa A. , Shaw Steven W. , Feeny Brian F.
Published: July 2018

We consider the nonlinear vibration response of rotating flexible shafts fitted with centrifugally driven pendulum vibration absorbers (CPVAs) that are used to address engine-order torsional vibrations. The model used to represent the behavior of the flexible shaft consists of two lumped inertial elements with an interconnecting stiffness element, which captures the rigid body and fundamental torsional vibration modes of the rotor. The absorbers are centrifugally driven pendulums fitted to a rotor element, such that their natural frequencies scale with the rotor speed, and can thus tuned to a given order of rotation. Previous analysis of a linearized version of this coupled rotor-absorber system revealed frequency veering behavior as the rotation speed varies, and showed that one can detune the absorber to eliminate key system resonances. In this paper the behavior of the system is analyzed for large absorber amplitudes using perturbation methods and numerical simulations. It is shown that the absorbers remain effective in reducing torsional vibration when moving through large amplitudes, and that the resonance avoidance is similarly robust. This has practical implications for the tuning of absorbers in certain applications.
Topology Optimization for the Natural Frequency of Multibody Dynamics Systems With Multi-Functional Components
Authors: Dong Guang
Published: July 2018

The multi-functional components layout design problem, which may have various options associated with it, including passive, active, and reactive components in given multibody dynamics systems, is defined in this study. The defined layout design problem is able to address the objective functions that are related to the dynamic responses of multibody dynamics systems, rather than static responses. The target of the multi-functional components layout design problem in given multibody dynamics systems is to seek the optimal interactive system layout between given multiple multibody dynamics system in order to maximize or minimize the dynamic objective function. The governing equations for the interactive system and the given multibody dynamics systems are derived first. The optimization objective is the first order natural frequency of the multibody dynamics system with multi-functional components in this study. The sensitivity analysis was then implemented based on the system eigen equation. Two numerical examples are presented in this study, it shows that the topology optimization method can be applied to the multibody dynamics system natural frequency optimization successfully.
Linearized Electromagnetic and Vibration Modeling of Switched Reluctance Motors
Authors: Mathis Allen , Quinn D. Dane
Published: July 2018

Switched reluctance (SR) motors are becoming more and more prominent in both industry and academia due to their simple design characteristics and flexibility [3]. However, the pulsating nature of the torque in this kind of motor tends to generate unwanted accoustical noise and large, undesirable vibrations [2]. Many researchers have conducted complex experimental and finite-element studies to determine the sources of these vibrations, but comparatively little work has been done to analytically model these phenomena using first principles [2] [8] [3]. The goal of this paper then is to derive an anlytical model for the vibrations of an SR motor, and to predict the frequency response of a particular motor configuration. These results will help guide future work to reduce vibrations in these motors, therby making them more industrially viable.
Calibration of Measured FRFs Based on Mass Identification Method
Authors: Ren Jun , Wang Jun , Ting Kwun-Lon , Wang Quan , Wei Qiong , Sun Jinfeng
Published: July 2018

It is necessary to calibrate the equipment during each test in modal testing. This paper presented a practical method for the calibration of the measured FRFs based on mass identification method. One advantage of this proposed method is that the calibration is performed directly on the test structure. Thus, it is more reliable and convenient. It is shown that if the mass identification method is applied to the uncalibrated system, a different level between the identified mass and the given exact mass reveals that the set up is not calibrated. And the measured FRFs can be calibrated using the ratio factor of the identified mass and exact mass. The simulation testing demonstrates good performance. In practical testing, however, the accuracy of mass identification results may be vulnerable to the noise and further work is necessary in order to solve this difficulty.
Real-Time, Non-Contact Position Tracking of Medical Devices and Surgical Tools Through the Analysis of Magnetic Field Vectors
Authors: Odeh Mohammad , Nichols Edward Daniel , Lobo Fenoglietto Fluvio L. , Stubbs Jack
Published: July 2018

The adoption of robotically assisted surgeries is increasing at a dramatic rate. The Da Vinci “was used in 80% of radical prostatectomies performed in the U.S. for 2008, just nine years after the system went on the market” [8]. The Da Vinci is but one of the systems driving the development of more versatile, more cost-effective and more autonomous systems. Robotic systems require real-time, accurate position information of the anatomy and surgical instruments to allow the surgical team to perform critical tasks. For example, Renishaw’s neuromate and Accuray’s CyberKnife both require the precise location of fiducial markers [9]. Others, like Cambridge Medical Robotics’ Versius and Medrobotics’ Flex operators rely upon active imaging or access to direct line of sight [10].
Examination of Fluid-Structure Interaction in Stent Grafts and its Hemodynamic Implications
Authors: Looyenga Eric M. , Gent Stephen P.
Published: July 2018

Every year in the United States, 4,500 deaths occur from abdominal aortic aneurysm (AAA) rupture. Aneurysms develop when the arterial wall weakens. Many risk factors can contribute to aneurysm formation, including age, sex, ethnicity, smoking and hypertension [1]. AAAs are the most common form of aneurysm because the aorta experiences the highest wall shear stress (WSS) of any vessels in the human body. These aneurysms are 5–6% prevalent in men and 1–2% in women, both over 65 years of age [2]. In the aorta, high WSS causes plaque formation, but in peripheral arteries where the flow rate is lower, atherosclerosis can also trigger aneurysm formation.
Wearable and Stretchable Piezoelectric Nanogenerator for Skin Applications
Authors: Voiculescu Ioana , Li Fang , Kowach Glen , Su Hao , Lee Kun Lin
Published: July 2018

The paper describes a stretchable piezoelectric nanogenerator that is intended to harvest energy. The nanogenerator was fabricated from zinc oxide (ZnO) piezoelectric thin film embedded in polymer materials. The microfabricated nanogenerator has the thickness in the micrometer scale to be attached on the skin and stretched by the natural movements of arms, legs or neck. We expect that energy harvested by this device will be able to power wearable skin sensors.
Revised Design of a Passive Hydraulic Training Simulator of Biceps Spasticity
Authors: Pei Yinan , Ewoldt Randy H. , Zallek Christopher M. , Hsiao-Wecksler Elizabeth T.
Published: July 2018

Spasticity is a common abnormal muscle behavior associated with neurological disorders and is characterized by speed-dependent increased tone in the affected muscle when induced by passive movement [1]. During the passive stretch of the muscle, additional unique clinical signs that accompany spasticity are (a) sudden increase in muscle tone at a certain joint position (catch angle), called the “catch”, (b) after the “catch”, a quick drop of muscle resistance, called the “release”, where (a) and (b) together are usually referred to as the “catch-release” behavior, and (c) limited range of motion (ROM) [1,2]. With the evolution of spasticity, these symptoms will worsen.
Design and Evaluation of the PosturSense Cushion
Authors: Garag Prateek , Chen Austin , McDonagh Deana , Hsiao-Wecksler Elizabeth T.
Published: July 2018

In recent history, the convention that adopting an ‘upright’ seated posture would decrease lumbar strain has shifted. The idea of dynamically varying seated posture is being considered as optimal for reducing lumbar strain and possibly lower back pain [1–2]. Thus, it would seem vital to design a device that helps alert users of the need to change their seated postures in workplace or study environments.
Validation of a Wearable Position, Velocity, and Resistance Meter for Assessing Spasticity and Rigidity
Authors: Song Seung Yun , Pei Yinan , Tippett Steven R. , Lamichhane Dronacharya , Zallek Christopher M. , Hsiao-Wecksler Elizabeth T.
Published: July 2018

Patients with neuromuscular disorders such as Parkinson’s disease (PD), traumatic brain or spinal cord injury, or multiple sclerosis (MS) can develop different levels of abnormal muscle behavior (hypertonia) such as rigidity and spasticity [1], [2]. Hypertonia can affect different parts of the body such as upper or lower extremities. Symptoms include pain, increased muscle tone, spasms, and decreased functional abilities. Hypertonia can interfere with many activities of daily living, greatly affecting the quality of life in patients and causing anxiety, depression, and social isolation [2].
An In Silico Investigation of a Lobe-Specific Targeted Pulmonary Drug Delivery Method
Authors: Feng Yu , Chen Xiaole , Yang Mingshi
Published: July 2018

Nowadays, “personalized medicine” is starting to replace the current “one size fits all” approach. The goal is to have the right drug with the right dose for the right patient at the right time and location. Indeed, conventional pulmonary drug delivery devices still have poor efficiencies (<25%) for delivering drugs to the lung tumor sites. Major portions of the aggressive medicine deposit on healthy tissue, which causes severe side effects and induces extra health care expenses. Therefore, a new targeted pulmonary drug delivery method is proposed and evaluated using the Computational Fluid-Particle Dynamics (CFPD) method to achieve the lobe-specific delivery. By controlling the release position and velocity of the drug particles at the mouth inlet, drug deposition efficiency (DE) in a designated lobe can be increased up to 90%. Intersubject variability has also been investigated using the noninvasive in silico tool. Results indicate that the glottis constriction ratio is a key factor to influence the effectiveness of the purposed targeted drug delivery method. Although lobe-specific pulmonary drug delivery can be realized, the actuation flow rate must be lower than 2 L/min, and the glottis constriction ratio has a significant impact on the effectiveness of the targeting method. Also, a design idea using e-cigarette as the prototype is proposed as the next-generation inhaler to accommodate the operational flexibility restrictions.
PANTOE II: Improved Version of a Powered Transtibial Prosthesis With Ankle and Toe Joints
Authors: Zhu Jinying , She Haotian , Huang Qiang
Published: July 2018

Most existing transtibial prostheses are energetically passive. Amputees using passive prostheses exhibit asymmetrical gait patterns [1], consume more metabolic energy [2–3], and walk at lower speed compared with able-bodied individuals [2–3]. As a result, powered transtibial prostheses are gaining increasing popularity. Several studies have shown that powered prostheses can improve the walking performance of the amputees [4–5]. However, most studies only focus on the importance of the ankle joint and few pay attention to the effects of toe joint during walking.
Multiscale Entropy Technique Discriminates Single Lead ECG’s With Normal Sinus Rhythm and Sleep Apnea
Authors: Shivaram Suganti , Muthyala Anjani , Meghji Zahara Z. , Karki Susan , Poigai Arunachalam Shivaram
Published: July 2018

Sleep apnea is characterized by abnormal interruptions in breathing during sleep due to partial or complete airway obstructions affecting middle-aged men and women on an estimated ∼4% of the population [1]. While the disorder is clinically manageable to relieve patients, the challenge occurs with diagnosis, with many patients going undiagnosed leading to further complications such as ischemic heart diseases, stroke etc. Sleep apnea also significantly affects the quality of day to day life causing sleepiness and fatigue. Polysomnography (PSG) technique is currently a used for detecting sleep apnea which is a comprehensive sleep test to diagnose sleep disorders by recording brain waves, the oxygen level in the blood, heart rate, breathing, eye and leg movements during the study. However, PSG test is very expensive, requires patients to stay overnight and is known to cause inconvenience to the patients.
An MRI Compatible Brain Probe for Signal Recording and Deep Brain Stimulation
Authors: Cruttenden Corey , Ahmadi Mahdi , Zhu Xiao-Hong , Chen Wei , Rajamani Rajesh
Published: July 2018

Electrical stimulation of neural tissue is a promising therapy for a variety of neurological diseases. For example, electrical stimulation of deep thalamic nuclei has been used extensively to treat symptoms of Parkinson’s disease, and there is growing interest in treating other conditions including epilepsy and depression with similar techniques. However, the mechanisms of electrical brain stimulation for disease therapy are not fully understood [1].
Wearable Olfactory Augmentation Device for Hazardous Gas Detection
Authors: Choi Mi Hyun , Lee Joshua , Hammond Frank L.
Published: July 2018

The goal of this study was to develop a wearable olfactory augmentation device (Fig. 1) that provides an intuitive and objective delivery of complex olfactory information via haptic feedback, in the form of cutaneous vibrotactile stimuli, in order to enhance environmental awareness of odor signals. The hypothesis is that displaying olfactory information through the skin enables intuitive and prompt identification of potentially hazardous chemicals and odors before they pose actual threats to the human body. In this work, an olfactory augmentation prototype is designed and manufactured, and experiments are conducted to assess the performance of device components and to improve the functionality of the device.
Prediction of Ground Profile for Lower-Leg Prosthesis Control Using a Visual-Inertial System
Authors: A. Ribeiro G. , Rastgaar M.
Published: July 2018

The field of control of powered lower-leg prostheses has advanced due to the improvements in sensors and computational power. Much effort has been done to improve the capabilities of prostheses, such as mimicking the stiffness, weight, and mobility of a human ankle-foot [1] and autonomously commanding the robotic prosthesis for gait [2].