bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison in High-Speed Droplet Impact Between Single and Multiple Collisions Against a Wall Covered With a Liquid Film
Authors: Fukuchi Yoichiro , Kondo Tomoki , Ando Keita
Published: November 2019

In semiconductor industry, liquid jet cleaning plays an important role because of its high cleaning efficiency and low environmental load. However, its cleaning mechanism is not revealed in detail because the experimental observation of high-speed and sub-micron droplets is challenging. Furthermore, higher impact velocity may give rise to surface erosion due to water-hammer shock loading from the impingement. To study cleaning mechanisms and surface erosion, numerical simulation of droplet impingement accounting for both viscosity and compressibility is an effective approach. In the previous study, wall-shear-flow generation has evaluated from the simulation of high-speed single droplet impingement. To evaluate more practical model of jet cleaning application, simulation of two droplets simplifying mono-dispersed splay of droplet train is favorable. Here, we numerically simulated impingement of two droplets, which allows for evaluating water-hammer pressure and wall shear stress. We consider the case of two water droplets (200 μm in diameter) that collides continuously, at speed 50 m/s, at the inter-droplet distance from 250 to 400 μm, with a no-slip rigid wall covered with a water layer (100 μm in thickness). The simulation is based on compressible Navier-Stokes equations for axisymmetric flow and the mixture of two components appears in numerically diffusion interface expressed by the volume average and advection equation. The simulation is solved by finite-volume WENO scheme that can capture both shock waves and material interface. In our simulation, the impingement of second droplet impingement gain higher shear stress than the single droplet impingement. At the case that the inter-droplet distance is 300 μm, maximum shear stress is 30.22 kPa (at the second droplet impingement), which is much larger than at the first droplet impingement (8.42 kPa). This result indicates how the second droplet impingement make wall shear flow induced by first droplet impingement stronger. From the parameter study of the inter-droplet distance, we can say that wall shear stress gets stronger as water layer thickness decreases. Furthermore, the maximum wall pressure is 1.96 MPa at the second droplet impingement, which is larger than at the first droplet impingement (1.46 MPa). From this study, the evaluation of surface erosion caused by jet cleaning is expected. The simulation suggests that multiple droplets impingement continuously may gain higher cleaning efficiency, which will give us a fundamental insight into liquid jet cleaning technologies. For further study, simulation of water column impingement and comparing the result of impingement of two droplets are expected.
An Explicit Modeling Approach for Simulating Fluid-Structure Interaction Problems With Immersed-Boundary Finite-Volume Method
Authors: Huang Yanbo , Li Shanshan , Pan Zhenhai
Published: November 2019

Fluid-structure interaction (FSI) is an important fundamental problem with wide scientific and engineering applications. The immersed boundary method has proved to be an effective way to model the interaction between a moving solid and its surrounding fluid. In this study, a novel modeling approach based on the coupled immersed-boundary and finite-volume method is proposed to simulate fluid-structure interaction problems. With this approach, the whole computational domain is treated as fluid and discretized by only one set of Eulerian grids. The computational domain is divided into solid parts and fluid parts. A goal velocity is locally determined in each cell inside the solid part. At the same time, the hydrodynamic force exerted on the solid structure is calculated by integrating along the faces between the solid cells and fluid cells. In this way, the interaction between the solid and fluid is solved explicitly and the costly information transfer between Lagranian grids and Eulerian grids is avoided. The interface is sharply restricted into one single grid width throughout the iterations. The proposed modeling approach is validated by conducting several classic numerical experiments, including flow past static and freely rotatable square cylinders, and sedimentation of an ellipsoid in finite space. Throughout the three numerical experiments, satisfying agreements with literatures have been obtained, which demonstrate that the proposed modeling approach is accurate and robust for simulating FSI problems.
Control of Particle Distribution at the Outlet of a Double Y-Microchannel Using Pulsatile Flow
Authors: Nguyen Minh Chau , Peerhossaini Hassan , Salek Mohammad Mehdi , Jarrahi Mojtaba
Published: November 2019

While a variety of active and passive techniques have been proposed for steady flows, pulsatile flow has received much less attention. Pulsation makes more control parameters available for passive methods and enables them to separate particles. The purpose of this work is to determine the effects of phase shift between two entering flows (only one includes the particles) on particle separation inside a double Y-microchannel. Numerical simulations were carried out for both steady and pulsating flow conditions. The results showed that when the velocity amplitude ratio (β) is less than 2, the separation index increases with the phase shift (φ) and the highest efficiency occurs at φ = 180°. A similar trend can be observed for higher values of β only if the pulsation period is short enough. A series of experiments qualitatively validated the numerical results.
Bubble Generation Behavior Around a Rotating Body in Highly Viscous Fluid
Authors: Akatsuka Shigeto , Saito Shimpei , Yuasa Tomohisa , Kaneko Akiko , Abe Yutaka
Published: November 2019

Inside an automobile engine, there are a camshaft, a crankshaft, a chain sprocket, etc. that transmit driving force. There are many rotating parts installed there. For example, there are gears soaking in engine oil, and bubbles are generated by rotating gears which drag air into engine oil. That raises void fraction of the engine oil. The void fraction is the gas phase fraction per unit volume. In general, high void fraction causes decreasing performance of the engine oil, such as lubrication, cooling and pressure transmission. Although it is required to reduce void fraction and establish a defoaming technique, the processes of bubble generation have not been clarified. One of the reasons is difficulty to measure void fraction and other physical parameters in oil flow using a real engine. Therefore, the influence of rotating speed, number of teeth, and kinematic viscosity of test fluid on bubble generation behavior is not grasped in detail.

In this study, the motivation is to understand the mechanism of bubble generation behavior around a rotating body. Detailed visualization was conducted around a rotating body soaking in fluid. The actual phenomena were reproduced by using silicone oil having the same kinematic viscosity of real engine oil. From the visualization using a high speed video camera, there are some characteristic phenomena such as dragging air, subdividing bubbles, and bubbles coalescence. By using observed images, we measured bubble diameter and bubble number density with image processing. Rotating speed, shapes of the rotating bodies, and kinematic viscosity of the test fluids affected on bubble generation behavior. In particular, as the rotating speed increased, the bubble diameter decreased and the bubble number density increased.
A Comprehensive Study of Asymmetric Micro-Droplet Splitting in T-Junction
Authors: Cheng Way Lee , Sadr Reza , Han Arum
Published: November 2019

Splitting a single droplet into two unequal portions using a microfluidic T-junction has been an important functional feature of many modern lab-on-a-chip devices. A recent study introduced a general criterion for asymmetric droplet break-up in the range of intermediate Capillary numbers. The current work attempts to analyze, in more details, the different underlying mechanisms governing the asymmetric break-up process. In particular, this work focuses on the relationship between the break-up mechanism versus the splitting ratio of the daughter droplets. CFD simulation is used to closely monitor the effect of different fluid properties on the evolution of droplet break-up process. The splitting ratio under different flow conditions is characterized. Four mechanisms for primary droplet break-up are defined as follows: break-up with permanent obstruction, unstable break-up, breakup with tunnels and non-breakup. In particular, the main focus of this study is on the unstable break-up mechanisms where is very likely results to a much-deviated splitting ratio. Typically, yet unexpectedly, the resulting splitting ratio is often larger than the pressure gradient ratio in the T-junction. However, the two ratios are approximately equals to each other under a limited set of flow conditions. It has been observed that the splitting ratio could be more than double the pressure gradient ratio of the T-junction. The break-up is observed to be in the permanent obstruction mode if the splitting ratio is about the same magnitude as the pressure gradient ratio. The effects of the T-junction geometry on the break-up will also be examined.
Computational Study of Mach Number Effects on Dynamic Stall
Authors: Kim Taesoon , Kim Seungtae , Lim Jiseop , Kim Junkyu , Jee Solkeun
Published: November 2019

A rotorcraft main-rotor blade experiences a broad range of the Mach number in high-speed forward flights or rapid maneuvering conditions. Near the boundary of the flight envelope, the rotor blade often encounters severe dynamic stall which limits the overall aerodynamic performance. Of interest here is effects of the Mach number on the dynamic stall. A rotor airfoil, VR-12, is computationally investigated for both static and dynamic stall conditions with varying the Mach number from 0.2 to 0.4. For the small enough Mach number 0.2, both static and dynamic stall are significantly influenced by flow separation due to adverse pressure gradient. For the highest Mach number 0.4, compressibility near the leading edge is no longer negligible, forming a shock there. The shock-induced separation occurs near the leading edge, which dominates both the static and dynamic stall at the high Mach number. At the intermediate Mach number 0.3, it is observed that both adverse pressure gradient and the shock affect the stall. Current computations are conducted with the unsteady Reynolds-averaged Navier Stokes approach with the Spalart-Allmaras model. Numerical results are compared to relevant wind-tunnel test data.
3D Numerical Study of the Transport Characteristics of an Evaporating Water Droplet Sessile on Heated Superhydrophobic Substrates
Authors: Peng Yikun , Li Shanshan , Pan Zhenhai
Published: November 2019

Evaporation of sessile droplets on superhydrophobic substrates is an important fundamental problem. Classic diffusion-based model only considers vapor diffusion and assumes an isothermal profile along the droplet interface. The diffusion based model extremely overestimates the evaporation rate for droplets evaporating on heated superhydrophobic substrates, and results in a deviation of evaporation lifetime up to 52.5%. The present 3D numerical model considers various effects including vapor diffusion, buoyancy-driven flow and evaporative cooling, etc., with conjugate heat and mass transfer solved throughout the computational domain. Evaporation of a sessile water droplet with an initial volume of 3 μL is investigated on superhydrophobic substrates (contact angle: 160 deg) with heating temperature ranging from 40 °C to 60 °C. The deviation of evaporation lifetime is less than 2% for 40 °C and 50 °C substrates. A single-roll asymmetric vortex is produced inside the droplet rather than the symmetric recirculation flow predicted by 2D axisymmetric simulation. The evaporative cooling along the droplet interface is observed, but the coolest point appears on the one side of the droplet instead of the droplet top owing to the asymmetrical rolling flow inside the droplet. It is seen that the buoyancy-driven convection significantly speeds up the evaporation as the substrate temperature increases. Influence of relative humidity is also discussed and indicates a stronger impact for low substrate temperature. The present model not only precisely predicts the instantaneous evaporation rate and the total evaporation time, but also reveals the important underlying transport characteristics, which provides new insights into evaporation of water droplets resting on heated superhydrophobic substrates.
Influence of Plasma-Induced Flow Direction on the Instability of the Jet Boundary Layer
Authors: Miyagi Norimasa , Kimura Motoaki
Published: November 2019

In this study, the influence of the direction of the plasma-induced flow generated by a plasma actuator (PA) on the jet flow was investigated. Nozzles equipped with two types of PAs to generate forward (Type A) and backward (Type B) flows were used in this investigation. At a duty ratio was 50%, for both Types A and B, the fluctuation due to the plasma-induced flow yielded the most stable fluctuation near the nozzle exit. In the case of the Type B PA, the centerline velocity was increased by the contraction of the main flow near the nozzle exit due to the influence of the backflow. Additionally, the fluctuation of the jet boundary layer became stronger as the duty ratio was increased. From these factors, it is considered that the backflow by the plasma induced flow effectively works on the diffusion of the jet structure.
Experimental Study of Bubble-Droplet Interactions in Improved Primary Oil Separation
Authors: Karp Joel R. , Mancilla Ernesto , Santos Paulo H. D. , Neto Moisés A. Marcelino , Morales Rigoberto E. M.
Published: November 2019

The interactions between dispersed oil droplets and gas bubbles was experimentally studied in this work. An experimental set-up was built in the Multiphase Flow Research Center (NUEM) in the Federal University of Technology – Paraná (UTFPR) to conduct a fundamental evaluation of the interactions between sessile gas bubbles and oil droplets employing side-view flow visualization. Tap water was used as the continuous phase, whereas pure nitrogen and colored vegetable oil were employed as the dispersed phases. The bubble-droplet attachment consisted in the encapsulation of the bubble by the droplet, presenting phenomenological similarities to droplet-droplet coalescence. The contact between the dispersed phases induces the formation of a connecting bridge, which grows rapidly with time, with the height of the bridge being comparable to the size of the droplet after 57.0 ms. The inherent asymmetry of the phenomenon induced a significant horizontal displacement of the bubble towards the droplet, whose position remained unaltered. The evaluation of the bridge meniscus corroborated to this observation, since the contact angle on the droplet side decayed faster with time in comparison to the contact angle on the bubble side. The hydrodynamics of the rising aggregate is also evaluated, by the obtainment of its size, three-dimensional trajectory and terminal velocity. The stable aggregates formed presented an increase factor of 150 to 180%, based on the terminal velocity of the individual droplet. The radius of the bubble was found to be the major influence on the hydrodynamics of the aggregate, allowing the definition of a critical bubble radius based on trajectory instabilities.
Immobilization of Magnetic Beads for Microfluidic Immunoassays
Authors: Nguyen Thanh-Qua , Kim Jeongyun , Lee Daewoong , Choi Ji-Seob , Park Jaeho , Jeon Hojeong , Park Woo-Tae , Lee Sangyoup
Published: November 2019

Employing magnetic beads (MBs) to microfluidic chips has enabled diverse microscale biomedical applications involving isolation of target molecules, such as, separation, and biosensing. In this report a microfluidic immunoassay chip that can temporarily immobilize MBs for the detection of target biomarkers within a sample solution flown through its channels is introduced. A through-hole structure of the MB capture zone and valves that can control the direction of the flow enabled immobilization of MBs with high reproducibility. Controlling immobilization of MBs shows promise for reproducible immunoassay signal detections for the same concentration of biomarker which is crucial for quantification of the assay. In addition, the structure and position of the captured MBs can potentially be optimal for immunoassay performances where immunoassay reagents including the antigen and the detection antibody are flown through the MB captured through hole maximizing contact for high binding efficiencies.
Experimental Analysis of a Liquid-Gas Two-Phase Flow in a Flow Distributor
Authors: Lino Luiz H. M. , Eidt Henrique K. , Rodrigues Carolina C. , Ofuchi Cesar Y. , Santos Paulo H. D. , Neves Flavio , Silva Marco J. , Morales Rigoberto E. M.
Published: November 2019

The main goal of this work is to analyze the efficiency of a two-phase flow distribution system for different operational conditions, which was designed and built by the Multiphase Flow Research Center (NUEM). The distribution system is composed of a two tangential inlets, a cyclonic chamber, and four outlets. The working principle of this apparatus is based on the combined action of centrifugal and gravitational forces, which causes the development of a liquid film, facilitating the flow distribution. Four outlets are located perpendicularly to the cyclonic chamber in order to distribute the flow equally to some extent. Experimental tests were performed using water and air in a vertical 52-mm ID acrylic pipe. Two flow patterns (bubble and slug) at the input of the inlets were visually identified through the use of a high-speed camera. To verify the flow distribution, wire-mesh sensors were installed at each outlet and graduated beakers and a timer was used in order to estimate the liquid volume flowing at the outlets. The results showed that the flow distribution system has a satisfactory efficiency of distribution.
Design and Modelling of a Cartridge Pressure Amplifier
Authors: Zardin Barbara , Cillo Giovanni , Zavadinka Peter , Hanusovsky Juraj , Borghi Massimo
Published: November 2019

This works describes the modelling and simulation of a compact cartridge pressure amplifier for linear actuators, especially designed to fit within the rod of the piston. Hydraulic pressure amplifiers of the cylinder type are appreciated in hydraulic systems where high pressure work is needed, especially for a small part of the overall duty cycle. The use of these boosters allows the designer not to oversize the system, which will perform confining the high pressure operation only on the side of the hydraulic actuator.

Starting from a previous research work on the same topic, this work proposes new designs for the cartridge amplifier to explore the influence of the control valve, which is the responsible for the delivering of the fluid to the amplifier. The new designs are discussed and then the results coming from the simulation performed with a lumped parameter model in a virtual test rig are shown. The operation of the amplifier is then applied to a more realistic duty cycle to illustrate and validate its operation.
Effects of Cyclist Size and Position Within Formations on Drag and Side Force in the Presence of Cross Winds
Authors: Nedyalkov Ivaylo , Cunningham Alec , Lovell Adam
Published: November 2019

In the absence of cross-winds, a cyclist can expend up to 90% of their energy to overcome drag and can save up to 30% of that energy if riding behind another cyclist. The aerodynamic forces acting on cyclists in the presence of cross wind have not been studied in much detail. The effect of the offset distances between cyclists on the aerodynamic forces has been investigated in the literature for configurations of two cyclists. In the present study, 1:11 scale models of two different cyclists were rapid-prototyped and tested in a wind tunnel. The effect of the size of the cyclist was studied by placing the larger cyclist model behind the smaller one; the smaller behind the larger one; and the larger model behind an identical (larger model) copy. The effect of position within the group was studied by measuring the forces on each of the four cyclists placed in a favorable formation. The results suggest that the size of the cyclist matters, particularly when the leading cyclist is smaller than the drafting cyclist, and the effect is more prominent for the side forces. The results also show that in a formation of four cyclists, the leading cyclist experiences minor drag reduction compared to riding alone. The second and third cyclists experience the largest force reductions within the group, and the fourth cyclist experiences force reduction, which is not as significant. The results appear to be dependent on the Reynolds number, but may still be valuable for racing strategies and recreational cycling.
Study of Enhanced Self Mixing in Ferrofluid Flow in an Elbow Channel Under the Influence of Non-Uniform Magnetic Field
Authors: Anand Nadish , Gould Richard
Published: November 2019

This paper investigates numerically the various parameters dictating the vortical (self)-mixing induced by a non-uniform magnetic field in a ferrofluid flow in an elbow channel. The elbow bend region of the channel has two current carrying conductors placed symmetrically and parametrically from the channel and are used to generate a non-uniform magnetic field. The ferrofluid is assumed to be pre-magnetized, isothermal and electrically non-conductive as it enters the channel and has a prescribed inlet magnetization and temperature. The mixing efficiency is characterized by introducing different mixing scalars based on velocity of the fluid and are compared in order to determine the overall suitability of each scalar to quantify the flow vortical (self)-mixing. Parametric studies were performed by varying parameters influencing the magnetic field and the initial flow field. This resulted in variations in non-dimensional groups which control different aspects of the flow and helped establish their relationship with mixing efficiency. It was found that at higher Reynolds numbers the flow mixing induced by the lateral gradient in the Kelvin Body Force (KBF) dissipates and higher electrical inputs are required to sustain mixing in the flow. The effects of mixing enhancement on the pressure gradient across the channel was also established, along with the introduction of an enhanced viscosity term which is due to the non-collinearity of the magnetization vector and the magnetic field vector.
On the Effect of Trailing Edge Under-Filing on the Apparent Slip Factor of Centrifugal Impellers
Authors: Litfin Oliver , Delgado Antonio
Published: November 2019

The trailing edge flow in a centrifugal impeller is of great importance as it determines the exit flow velocity triangle and therefore the work transferred to the fluid. The present study deals with the impact of trailing edge under-filing on the impeller exit flow and the resulting slip factor. Different under-filed trailing edge shapes are investigated by means of numerical simulations. 2D-RANS simulations are performed for a wide range of blade angles. For the default cut-off trailing edge configuration an attached and a separated flow regime around the blade trailing edge can be distinguished, mainly depending on the blade exit angle. The occurrence of the separated flow regime is associated with a significant change in performance, mainly due to the reduced flow deflection at the impeller exit. Under-filing of the trailing edge leads to less apparent slip for blade angles up to 40 degrees. This can be attributed to the fact that under-filing prevents the attached flow regime occurring in case of the default trailing edge. Additional DES simulations provide deeper insight into the detailed flow structures involved in this phenomena and reveal the turbulent flow structures in the trailing edge and wake flow. The obtained results provide a deep insight into trailing edge flows in centrifugal pump impellers and help to get a better understanding of the phenomena involved. Moreover, the results can provide an explanation to the often observed deviation of the apparent impeller slip from the theoretical slip predicted by slip factor models.
The Minimum Flow Rate of Liquid-Oxygen When Considering a Throttling of a Gas Generator Cycle Engine
Authors: Nakata Daisuke , Minato Ryojiro , Yoshikawa Inaho , Yagihashi Hiromitsu , Arimatsu Koki , Uchiumi Masaharu
Published: November 2019

Currently in development at Muroran Institute of Technology, a small gas-generator-cycle air turbo ramjet engine (GG-ATR) for a supersonic unmanned aerial vehicle requiring deep throttling uses liquid oxygen/ethanol as a propellant. However, it is difficult to maintain a liquid-phase flow at a low mass flow rate or at a low pressure due to flashing in the feedline. In response, we investigated the ability of our ground test facility to feed liquid oxygen at a low mass flow rate. The experimental results of the flow tests validated the proposed one-dimensional model, including heat input and the density change in the feed line. The minimum possible flow rate as a subcooled liquid flow was examined with the model and the throttling level of 75 % was possible when assuming 110 K in tank temperature.
CFD-Based Hydraulic Design and Manufacturing of a Multistage Low Specific-Speed Diffuser Pump
Authors: van der Schoot Martijn , Bruurs Kevin , van der Zijden Eric
Published: November 2019

A multistage low specific-speed diffuser pump was designed to achieve very good hydraulic performance with a newly designed integrated diffuser, crossover and return guide vane. The diffuser was designed using a continuous crossover design. The design space of this diffuser was limited because of the usage of a mechanical pump design from a similar existing pump. This paper presents the simulation-based design of this new pump and the role that simulation can play in the manufacturing process.

A new diffuser has been designed to obtain optimum efficiency and to ensure that the pump will operate most of its time very close its best efficiency point. The new diffuser was designed using an approach where the diffuser vane was stretched to completely cover the area starting just behind the impeller trailing edge towards the eye of the next stage impeller. This means that the diffuser vanes should now convert velocity into pressure, guide the fluid to the next stage impeller eye while reducing the swirl and uniformizing the flow. The shape of the diffuser has been optimized using response surfaces that were created using Computation Fluid Dynamics (CFD). This way, a diffuser with a minimum amount of losses was obtained, due to smooth and gradual area changes of the waterway.

The final design incorporating this diffuser was analyzed using steady-state CFD to create the full performance curve. The design was transferred into a real physical product by manufacturing it. The resulting casting of the diffuser component was scanned using a 3D scanner. The 3D model of the scan was used to make a comparison using CFD between the performance of the designed and the manufactured diffuser. This provided understanding in how deviations due to the manufacturing process influence the performance. Finally, the complete pump underwent a performance test and its results closely matched the performance as calculated using CFD.
Numerical Simulation for Optimizing Tooth Profile Using Bezier Curve
Authors: Qiu Kevin , Samadi Reza
Published: November 2019

The research hereby introduces a novel approach to reduce tooth bending stress using a parametric numeric simulation. This Finite Element Method (FEM) is used to determine optimal design variables for an asymmetric root profile of a helical gear defined by a rational cubic Bezier curve. The gear is first modelled using a machine design software and later implemented into a 3D computer aided design (CAD) package to modify the root spline geometry using a script. A nonlinear relationship exists between the design variables and tooth bending stress. Additionally, certain trends exist between the design variables to exhibit a more optimal root profile. The simulation results show that the proposed method is feasible as the general optimization process results in significant bending stress reduction. The numerical simulation demonstrates that bending stress can be reduced by as much as 10.75% by the proposed approach.
To Identify Key Geometric Errors of 3-Axis NC Machine Tool by Machining Accuracy Failure Mode Analysis
Authors: Qi Baobao , Cheng Qiang , Liu Zhifeng , Sun Dongyang
Published: November 2019

Machine tools usually cut two or more surfaces after the work piece clamped on work table. In order to improve the machining accuracy and optimize accuracy design, it is hoped that the geometric errors that influence the accuracy of machined surface prominently can be known beforehand, so the adjustment will be carried out with a definite objective rather than without any clue. Because the machining accuracy of each direction in 3-D space is different value, in this paper, machining accuracy failure mode was defined as the various combination of the machining accuracy of each direction according to whether it is up to the reserved objective value or not. A three-axis machine tool was selected as an example and there were 7 machining accuracy failure modes for it. Based on the generalized correlation analysis, the correlation relationships between 7 machining accuracy failure modes were analyzed, and the main failure modes that affect the machining accuracy of work piece to be machined were identified. For each machining accuracy failure mode, key geometric error that had major influence on it was identified based on sensitivity analysis. Finally, four stepped work pieces were milled by a 3-axis machine tool to illustrate the analytical method proposed in this study.
The Effect of Gravity and Rotor Configuration on Dry Friction Whip and Safe Rotor/Stator Clearance
Authors: Vashisht Rajiv Kumar
Published: November 2019

A mathematical model is developed for a real rotor/stator system with high degrees-of-freedoms, multiple disks, flexible bearing supports and couplings. The safe clearance level for coasting up of the rotor is calculated for a general high degree-of-freedom rotor/stator system. The harmful phenomena of dry friction whip, which is generally observable for simple 2 degree-of-freedom Jeffcott rotors in the absence of gravity only, can be proved to exist (in real rotor/stator systems) even in the presence of gravity for a wide range of clearance levels. In case of Jeffcott rotors, by fixing the clearance and increasing the rotor spin frequency, the response of the system follows the pattern: No rub - Forward Annular Rub (FAR) - Partial Forward Whirl (PFW) - Partial Backward Whirl (PBW) - dry whip (WHIP). In case of a real rotor/stator system, at certain frequencies, the system directly jumps to dry whip. The simulated results show a rich variety of system dynamics including FAR, PFW and WHIP in case of vertical rotors where the effect of gravity is neglected. For horizontal rotors, under the effect of gravity, the system response contains multi-harmonics, chaotic responses and multi-period vibrations. Based on these responses, a robust fault diagnosis strategy can be designed to identify the rubbing action in rotating machinery.
Influence of Different Design Parameters on the Theoretical Flow Ripple in Balanced Vane Pumps
Authors: Battarra Mattia , Mucchi Emiliano
Published: November 2019

The present study focuses the attention on the correlation between the cam ring design and the kinematic flow ripple in balanced vane pumps. In particular, the work addresses the influence of the main pump design parameters on the oscillations of the flow rate produced by the volume variation of both undervane pockets and displaced chambers, which is considered as one of the main sources of excessive noise and vibration. The pump operating principle is firstly defined and the design philosophy is presented, together with the theoretical approach used to determine both then vane motion and resulting flow ripple. The proposed methodology is evaluated by means of a parametric study involving design parameters such as vane thickness and tip radius. The analysis suggests that these geometrical parameters, together with the cam ring shape, affect the pump dynamic behavior due to their correlation with the fluid-dynamics of the machine.
Deflection Maps of Elastic Catenary Cable-Driven Robots
Authors: Notash Leila
Published: November 2019

In this paper, the cable tension and platform deflection of cable-robots are investigated. The significance of cable density, elasticity and cross-sectional area; platform mass, radius and center of mass; external wrench and platform orientation on the cable tension, platform deflection and workspace of the planar cable robots is investigated. It is shown that, in addition to cable mass, the effect of external wrench on the workspace of catenary cable model could be more prominent. Moreover, design issues and parameters affecting the manipulator deflection are examined, and those that would result in disjointed workspace regions and deflection maps are identified. It is presented that the change in deflection is gradual throughout the workspace for constant external wrench. For the catenary model, depending on the cable properties, platform orientation, manipulator design, and external wrench, the workspace with deflection limit may consist of disconnected regions.
Internal Resonance and Nonlinear Vibrations of Eccentric Rotating Composite Laminated Circular Cylindrical Shell
Authors: Liu Tao , Zhang Wei , Zheng Yan , Zhang Yufei
Published: November 2019

This paper is focused on the internal resonances and nonlinear vibrations of an eccentric rotating composite laminated circular cylindrical shell subjected to the lateral excitation and the parametric excitation. Based on Love thin shear deformation theory, the nonlinear partial differential equations of motion for the eccentric rotating composite laminated circular cylindrical shell are established by Hamilton’s principle, which are derived into a set of coupled nonlinear ordinary differential equations by the Galerkin discretization. The excitation conditions of the internal resonance is found through the Campbell diagram, and the effects of eccentricity ratio and geometric papameters on the internal resonance of the eccentric rotating system are studied. Then, the method of multiple scales is employed to obtain the four-dimensional nonlinear averaged equations in the case of 1:2 internal resonance and principal parametric resonance-1/2 subharmonic resonance. Finally, we study the nonlinear vibrations of the eccentric rotating composite laminated circular cylindrical shell systems.
On Practice and Theory of Constructive Composite Geometry and Topology
Authors: Hedberg Thomas D. , Feeney Allison Barnard , Srinivasan Vijay
Published: November 2019

This paper synthesizes a theory from industrial best practices codified in recent standards. Recent editions of ASME and ISO standards codify the evolving industrial best practices in defining and modeling the information about products made from fibrous composite materials. A theory of constructive composite geometry and topology is synthesized from these practices. Major features of this theory include (1) a constructive composite geometry tree that is equivalent to the ply/laminate tables of the standards, (2) an adjacency graph that captures a crucial aspect of the topology of the geometric cell complex structure of composite products, and (3) conformal mapping of ply surfaces using rosettes in the lay-up process. It also addresses the geometrical and topological structure of fiber arrangements inside the plies. The goal of the theory is to provide a scientific basis for standards that enable the digital transformation of composite product manufacturing.
Calibration Experiments on a Visual Measurement System for Pinion Gears
Authors: Tang Jie , Liu Xiaobing , Chai Lingyu , Shi Zhaoyao , Li Rui
Published: November 2019

Visual measurement is one of the important measurement methods for pinion gears. The measurement principle and the systematic structure of a pinion gear visual measuring system were given. Pixel equivalent is the key parameter in the visual measurement system, which needs to be calibrated before dimensions evaluation. A glass dot calibration plate was applied in the system calibration. Pixel equivalent calibration experiment, LED brightness experiment, edge compensation experiment and multiposition edge compensation experiment was carried out. The parameter pixel equivalent is determined by the comparison between the physical size of center distance of adjacent mark circle in the glass dot calibration plate and its pixels number obtained by the visual system. The center distance of adjacent mark circle was chosen to avoid the affection of the brightness of light source and the sub-pixel technology was used. The proper brightness condition of LED light was selected in the LED brightness experiment. Under this condition, the compensation of edge deviation was obtained by analyzing the edge position deviation in the diameter measurement of the mark circle of the calibration plate. The experimental results show that the pixel equivalent is 5.59522μm/Pixel, and the compensation of edge deviation is 0.54μm. 49 diameters of the circular marker were measured in edge compensation experiment, the largest difference between the measured diameter in central vision after compensation and its physical dimensions is 0.3μm, which is 0.2μm in muti-position edge compensation experiment. The calibration methods and the experimental research are important for the designed visual measurement system for pinion gears.
Effect of Intermediate Support on Instabilities of a Cantilever With Terminal Dynamic Moment
Authors: Abdullatif Mahmoud , Mukherjee Ranjan
Published: November 2019

The stability characteristics of a cantilever beam, with and without an intermediate support, subjected to a dynamic terminal moment, is investigated. The moment is assumed to be proportional to the slope of a point along the length of the beam. The proportionally constant, which can be positive or negative, is varied to find the critical stability point. In the absence of intermediate support, stability is lost through divergence when the dynamic moment is proportional to the positive slope, and through flutter when the dynamic moment is proportional to the negative slope. In contrast, the nature of instability switches between divergence and flutter, and between different flutter instability modes while undergoing flutter, in the presence of an intermediate support.
Review of Models and Robotic Devices for Stroke Survivors’ Upper Extremity Rehabilitation
Authors: Tahmid Shadman , Yang James , Font-Llagunes Josep M.
Published: November 2019

Stroke is one of the leading causes of upper extremity disability around the world. Whenever a stroke happens stroke survivor’s brain commands cannot reach some muscles of upper extremities although those muscles could contract. Therefore, shoulder, elbow or wrist joint cannot perform expected motion, and this will hamper their activities of daily living (ADLs). The objective of rehabilitation is to externally drive the upper extremity move to improve muscle movements. The current state of upper extremity rehabilitation may improve by using a model-based computer simulation of arm movement for personalizing robotic devices and interventions. This study attempts to review technologies used in upper extremity rehabilitation on two aspects: computer models and robotic devices. A summary of existing virtual upper extremity models is provided. As well, different robotic devices that are developed for upper limb rehabilitation is also discussed here.
Research on Transmission Error Test and Analysis of RV Reducer
Authors: Zhu Zhonggang , Zhang Jing
Published: November 2019

Aiming at exactly measuring the transmission error of RV reducer, a set of test device is developed and the data acquisition and processing program is designed using LabVIEW. RV reducers from imported and domestic brands are tested and the test results are compared. The test data is also processed by the filtering method, and the result can show the main source of the transmission error, which providing a reliable reference in the process of optimization design and improving of manufacture technics.
Vibration Characteristics Analysis of Multibody Systems With Random Parameters Based on MSTMM
Authors: Wang Guoping , Miao Yunfei , Rui Xue , Tu Tianxiong , Rui Xiaoting
Published: November 2019

Dynamics characteristics of linear multibidy systems are governed by the eigenfrequencies and the eigenvectors. The study of probabilistic characterization of the eigensolutions is now an important research topic in the field of multibody systems with random parameters. In this paper, by combining transfer matrix method for multibody system (MSTMM) and perturbation approach, a new method named as perturbation MSTMM is presented for random eigenvalue problems of multibody systems. This method has the advantages of, such as low memory storage requirement, high computational efficiency and high computational stability, etc., for dynamic design of multibody systems with random parameters. By using the proposed method, the rapid computation of random eigenvalue problems of general systems with random parameters can be realized, and the problem of repeated eigenvalues can be solved simply and conveniently. Formulations of the proposed method as well as some numerical examples are given to validate the proposed method. The simulation results of the eigenfrequencies are validated by experiment results. All the numerical applications show the merits and efficacy of the proposed method.
Neighborhood Optimization Method for Shaping Bode Plot With Larger Phase Margin
Authors: Shang Bo , Wu Chengdong , Chen YangQuan
Published: November 2019

When controlling complex non-linear systems, classic flat-phase specification (FPS) method for tuning fractional order controllers employs graphic method. However, following this step of graphic method, the tuning method cannot work automatically. In this study, a novel optimization method is employed to enable it to work automatically. An approximation is used to avoid solving derivatives, thereby simplify computation of the method. Frequency-domain analysis reveals that, compared with the classic FPS method, this method is capable of covering more conditions, especially those with larger phase margin. A linear model and a non-linear model (Simscape) are used to demonstrate that the proposed method can ensure both transient performance and robustness. For the relevant working folder, please refer to: http://bit.ly/npm-simscape-code. For video demonstrations, please click: http://bit.ly/npm_simscape_video.
Tracking Performance Improvement of Repetitive Controller for Nano-Manipulating Systems With Time Delays
Authors: Liu Pengbo , Yan Peng
Published: November 2019

This paper investigates the robust repetitive controller design with improved tracking performance for nano-manipulating systems with time delay. In order to handle the time delay caused by the analog-to-digital (A/D) conversion of the capacitive sensors with ultra high precision, we modify the conventional repetitive control structure where the design of low pass filter is formulated as an H∞ optimization problem. For the purpose of tracking performance improvement, we further modify the structure of the low pass filter by shaping the sensitivity functions of the closed-loop system. With consideration of the existing of model uncertainties, the design of the modified low pass filter is also formulated as an H∞ optimization of infinite dimensional systems. The effectiveness of the proposed repetitive control architecture is further verified by real time experiments on a piezo driven nano-stage, where significant tracking performance improvements are demonstrated comparing with the traditional repetitive controller.
Optimization Design and Analysis for Pre-Shift Control Parameters of Wet Dual Clutch Transmissions Based on Dynamic Modeling of Synchronizer
Authors: Zheng Ke , Hu Jianjun , Wu Bangzhi , Wang Yin
Published: November 2019

The DCTs have increased in prevalence for achieving power uninterrupted shifting and pre-shift process significantly influences the DCTs shift quality. Research on the multistage and nonlinear characteristics of the gear preselect process is not comprehensive so that there are shortcomings such as high impact, long synchronization time and poor economy. In view of above detrimental phenomenon, control parameters optimization is conducted in order to realize fast, smooth and economic pre-shifting on the basis of analyzing the sensitivity of the factors affecting pre-shift process. Considering the engagement of sleeve, synchro ring and dog gear, the multi-body dynamics theory is applied to establish an accurate synchronizer dynamics model. Based on the model, simulations are conducted to confirm factors like sleeve mass, cone angle fluctuating the pre-shift quickness and smoothness, sorting structure parameters according to factors sensitivity. Furthermore, the formula of energy loss characteristics relating to two control parameters which are pre-shift force and pre-shift trigger time is obtained, deriving from exploring the hydraulic loss caused by pre-shift force and the drag torque energy loss created by pre-shift trigger time. The optimal synchronizer structure parameters are obtained by adopting multi-objective optimization method. Simulation results indicate the optimal control parameters improve pre-shift comprehensive performance including quickness, smoothness and economy compared with conventional scheme.