bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bubble Formation at Impingement of a Liquid Droplet on a Solid Surface
Authors: Fujimoto Hitoshi , Ogino Tomoyuki , Takahashi Osamu , Takuda Hirohiko , Hatta Natsuo 
Published: November 2021

Abstract
The collision of liquid droplets with a solid has been studied experimentally. The time evolution of the liquid/solid contact area as well as the shape of droplets has been observed by means of a flash-photographic method using two video cameras. It has been found that some air between the solid surface and the incoming droplet is entrapped at the moment of impact. In the case where the solid temperature is high (= 450 °C), numerous vapor bubbles appear at the liquid/solid interface after the collision. The bubble formation due to the entrapment of air has been examined for various experimental conditions. Water, and ethanol are used as test liquid. The droplet diameter is 2.4 mm for water and 1.9 mm for ethanol. The impact velocity varies from 0.8 to 3.1 m/s. The entrapment of air has been observed for both liquids under all conditions in the present study.
Spark Discharge Induced Flame Kernel Growth
Authors: Arpaci Vedat , Agarwal Apoorva , Ko Yongseo 
Published: November 2021

Abstract
An intuitive study of the growth of a flame kernel immediately following a spark discharge is presented. It is shown that the radius of the flame kernel, R grows with time, t as R ∼ ( Δ E ρ o ) 1 / 5 t 1 / 5 where ΔE is the integrated energy (∫ Edt) deposited by the spark discharge and ρo is the initial ambient density. The 1/5 scaling law is confirmed by comparing with measurements in a quiescent combustion bomb.
If the energy is deposited or released instantly (e.g. in an atomic explosion), the growth of a blast wave can be shown to scale with time as R ∼ ( E ρ o ) 1 / 5 t 2 / 5 . This is the same result obtained by Sir Geoffrey Taylor for a blast wave formed by a very intense explosion.
A similarity analysis of the governing equations of mass, momentum and energy is performed to reveal the internal structure of the spark-induced flame kernel as a function of its radius.
Direct Numerical Simulation of Turbulent Spray Combustion
Authors: Réveillon J. 
Published: November 2021

Abstract
Turbulent combustion of two-phase flows is studied by 2D direct numerical simulation. A spray of droplets is injected inside a jet with a preheated coflow. Triple flames appear to represent the global structure of the flame around the spray. Attention is focused upon global and local flame structures and droplet histories. A whole range of combustion phenomena are observed and described. The observed prevailing occurrence, for example, of the rich premixed flame compared to the diffusion flame is of great importance for any turbulent combustion model which must accurately estimate the heat release rate. This prevailing structure depends strongly on the droplet size and combustion. A competition between premixed and diffusion regimes may also occur. It has been shown that in some cases, local clusters of droplets are able either to cross the main flame front and burn in pure oxidizer or to break through the diffusion flame. It is observed that very complex interactions can emerge locally between premixed flames, diffusion flames and droplets.
Three-Dimensional Stereo Measurements in Bubbly Pipe Flows With Particle Tracking Velocimetry
Authors: Ortiz-Villafuerte Javier , Hassan Yassin A. , Schmidl William D. 
Published: November 2021

Abstract
In a two-phase bubbly flow, the continuous phase velocity field can be captured using standard PIV techniques, and the gas phase configuration can be determined using, for example, a shadow technique. If the PIV system includes a three-dimensional shadow PIV measurement set up, the bubble locations in the standard PIV measurements can be determined. Then, the bubble images are removed, and a typical anlysis of the liquid phase can be performed. An experimental set up that combines the traditional PIV technique with a shadow technique will be described and sample PIV images will be analyzed to demonstrate an advanced velocity vector analysis method in a two-phase bubbly flow system.
Evolution of Vortices Behind Single Diamond-Shaped Cylinders in Free Stream
Authors: Torii Shuichi , Yang Wen-Jei , Umeda Shinzaburo 
Published: November 2021

Abstract
Two-dimensional flow over a single diamond-shaped cylinder in the free stream are experimentally and theoretically investigated. The experimental program includes visualization of the flow field using the tracer method. In the theoretical program, the Navier-Stoeks equations are discretized using finite difference methods to determine the time history of velocity vector distribution in the flow field. Efforts directed to examine the effects of the Reynolds number, Re, and the upstream angle of the diamond shape, θ, on flow phenomena. The study discloses that (i) the generation of von Karman vortex streets behind the diamond-shaped cylinder are intensified with an increase in the Reynolds number, (ii) the flow pattern in the wake region of the diamond-shaped island is affected by θ, and (iii) the relationship among the Strouhal number, St, Re and θ is determined and compared with the existing St-Re relationship for flow over a circular cylinder.
Effects of Riblets on Goertler Vortex Flow
Authors: Winoto S. H. , Chen X. , Shah D. A. 
Published: November 2021

Abstract
To investigate the effects of riblets on the onset of Goertler vortex flow transition, an experiment was carried out on a ribletted concave surface of 2.0 m radius of curvature in a perspex curved rectangular duct connected to a low speed wind tunnel. Semi circular section riblets with height (h) of 1.0 mm and spacing (s) of 2.2 mm (that is, with h/s = 0.48) were used. The investigation was carried out by means of measurements using a single sensor hot wire anemometer. The boundary layer transitions were detected by turbulent intermittency measurements using the modified turbulent energy recognition algorithm (M-TERA) method. The experimental results obtained show that for free-stream velocities of 3m/s and 6m/s, boundary layer transition on the ribletted concave surface starts and ends slightly earlier than on the corresponding smooth concave surface. However, for free-stream velocities of 9m/s and 12m/s, the boundary layer transitions (both the starts and the ends) on the ribletted concave surface were delayed compared to the Goertler vortex flows on the corresponding smooth concave surface.
Numerical Simulation of Taylor Vortex Flow by GDQ Method
Authors: Wang L. , Shu C. , Chew Y. T. 
Published: November 2021

Abstract
In this study, the GDQ method was used to simulate a specific flow regime, Taylor vortex flow, of the motion of fluids between two concentric cylinders with rotating inner cylinder and stationary outer cylinder. An approach combining the SIMPLE strategy and GDQ discretization based on non-staggered mesh was proposed to solve the time-dependent, three-dimensional incompressible Navier-Stokes equations in primitive variable form. The numerical solution obtained has the accuracy of second-order in temporal discretization and high-order in spatial discretization. Also, this numerical code may allow the direct numerical simulations for the various regimes of Couette-Taylor flow problem. The performance of this approach was studied through a test case of Taylor vortex flow. The reported numerical results were compared with those from others. For this approach, accurate numerical results can be obtained by using fewer grid points compared with low-order methods. As a consequence, the computational effort can be greatly reduced.
Two-Dimensional Study of the Turbulent Wake Behind a Square Cylinder Subject to Uniform Shear
Authors: Saha A. K. , Biswas G. , Muralidhar K. 
Published: November 2021

Abstract
The flow past a square cylinder at a high Reynolds number has been simulated through direct calculations and through the calculations using turbulence models. The present investigation highlights significant differences between the two approaches in terms of instantaneous flow, Strouhal number and the aerodynamic forces. The time-averaged drag coefficient and the rms fluctuations due to the direct calculation are higher than those due to the turbulence model. However, Strouhal number is underpredicted in direct calculations. The effect of shear on the flow has also been determined using the turbulence model. The time-averaged drag coefficient is found to decrease with the increase in shear parameter up to a certain value. Then it increases with the further increase in the shear parameter. On the other hand, the lift coefficient increases with the increase in shear parameter. Strouhal number shows a decreasing trend with the increase in shear parameter whereas the rms values of the drag and lift coefficients increase with the shear parameter. Kármán Vortex Street, mainly comprising of clockwise vortices due to shear, decays slowly compared to uniform flow condition.
Characterization of Wide Area Network Computing
Authors: Freitas Christopher J. , Coffin Derrick B. , Murphy Richard L. 
Published: November 2021

Abstract
Distributed parallel computing using message-passing techniques on Networks of Workstations (NOW) has achieved widespread use in the context of Local Area Networks (LAN). Recently, the concept of Grid-based computing using Wide Area Networks (WAN) has been proposed as a general solution to distributed high performance computing. The use of computers and resources at different geographic locations connected by a Wide Area Network and executing a real application introduces additional variables that potentially complicate the efficient use of these resources. Presented here are the results of a study that begins to characterize the performance issues of a WAN-based NOW, connecting resources that span an international border.
Simulation of Solid-Fluid Interactions on Cartesian Grids
Authors: Udaykumar H. S. , Mittal R. , Rampunggoon P. 
Published: November 2021

Abstract
We present a numerical technique for computing flowfields around moving solid boundaries immersed in flows on fixed meshes. The mixed Eulerian-Lagrangian framework treats the immersed boundaries as sharp interfaces and a finite volume formulation for the flow solver allows boundary conditions at the moving surfaces to be exactly applied. A second-order accurate spatial and temporal discretization is employed with a fractional-step scheme for solving the flow equations. A multigrid accelerator for the pressure Poisson equations has been developed to apply in the presence of multiple embedded solid regions on the mesh. We validate the numerics by comparing against experimental and numerical results on two problems: 1) The flow in a channel with a moving indentation in one wall and 2) The dynamics of vortex shedding from a cylinder oscillating in the free-stream.
The Effect of Discontinuity Size on the Initiation of Shattered Rim Defects
Authors: Stone Daniel H. , Dahlman Geoffrey E. 
Published: November 2021

Abstract
Shattered rim defects are the result of large fatigue cracks that propagate roughly parallel to the wheel tread surface. They form and grow 12 to 20 millimeters (1/2 to 3/4 in.) below the tread surface. A typical shattered rim is shown in Figure 1. The clamshell pattern of the fracture surface is also typical of shattered rims. The clamshell pattern is formed because fatigue cracks at this depth in wheels have a shear component and, when the rolling direction is opposite, the cracks grow in a different direction forming a series of ridges and valleys. Miezoso, et alia have presented a mixed mode fracture mechanics analysis of the process of forming a clam-shell fatigue crack surface in wheels.
Rail Passenger Equipment Crashworthiness Testing Requirements and Implementation
Authors: Tyrell David , Severson Kristine , Perlman A. Benjamin , Brickle Barrie , VanIngen-Dunn Caroline 
Published: November 2021

Abstract
This paper describes the requirements and the implementation of a series of impact tests of rail passenger equipment. The test requirements — the desired measurements — are dictated by the characteristics of the vehicle, as well as uncertainties in the analysis techniques used to evaluate the collision behavior of the equipment. The required measurements are implemented with available measurement transducers, including accelerometers, strain gages, and string potentiometers. The measurement data are gathered using an on-board data acquisition system.
Manufacture of Multi-Direction Composites (MDC) Flywheels
Authors: Abdel-Hady Faissal , Gowayed Yasser , Flowers George T. 
Published: November 2021

Abstract
The design and manufacture of a universal winding and tape laying machine has been developed is presented in this paper. This machine is used to manufacture a multi-direction composite (MDC) flywheel. The machine is capable, due to its modular design, to be used in wet filament and tape laying either with thermoset or thermoplastic prepregs. The MDC flywheel rims are realized by assembling the radial plies with hoop rings in a special assembly mold.
Fatigue of Notched CMC Plates Under Variable Thermomechanical Loads
Authors: Nagar Arvind , Xie Ming 
Published: November 2021

Abstract
The work is a part of a major study to develop design analysis methods for strength and life of CMC structural joints. This paper describes results of thermomechanical fatigue tests conducted on open hole ceramic matrix composite laminated plates. The open hole represent the zero load transfer in a joint. The thermomechanical spectrum loads included mechanical load cycle blocks of various stress levels and stress ratios. The thermal loads were varied simultaneously with mechanical loads for the duration of a representative generic flight. The spectrum peak stress versus life data was developed for the case when the peak temperature is 1500 F. An empirical relation to describe the fatigue life is presented. The results show that a CMC laminate with an open hole spend most of the life during initiation.
An Alternative Design Approach for Vehicle Crash Safety Using Crash Pulse Optimization
Authors: Yang R. J. , Tho C. H. , Gearhart C. C. , Fu Y. 
Published: November 2021

Abstract
This paper presents an approach, based on numerical optimization techniques, to identify an ideal (5 star) crash pulse and generate a band of acceptable crash pulses surrounding that ideal pulse. This band can be used by engineers to quickly determine whether a design will satisfy government and corporate safety requirements, and whether the design will satisfy the requirements for a 5 star crash rating. A piecewise linear representation of the crash pulse with two plateaus is employed for its conceptual simplicity and because such a pulse has been shown to be sufficient for reproducing occupant injury behavior when used as input into MADYMO models. The piecewise linear crash pulse is parameterized with 7 design variables (5 for time domain and 2 for acceleration domain) in the optimization process. A series of sample runs are conducted to validate that pulses falling within the acceptable crash pulse band do in fact satisfy 5 star requirements.
Free Vibration of In-Planar Rotating Ring: An Analytical Solution
Authors: Hamidzadeh Hamid R. 
Published: November 2021

Abstract
An analytical method is presented to consider the vibration characteristics of high speed rotating rings. More specifically, a systematic approach based on an established solution for linear in-plane vibration of spinning annular disks is used to compute natural frequencies and mode shapes of rotating rings. The medium is considered to be homogenous, and elastic isotropic. The developed analytical solution is achieved by implementing the two-dimensional plane stress theory. The modal displacements and stresses at both inner and outer boundaries are determined, and the required boundary conditions are satisfied to obtain the frequency equation. The dimensionless natural frequencies for different modes, rotating speeds, and thickness ratios are computed. In addition, variations of dimensionless critical speeds for several circumferential wave numbers versus radius ratio of the ring are presented. The provided results are for the two different cases of clamped-free and free-free rings.
Blind Identification of Impact Forces From Multiple Remote Vibratory Measurements
Authors: Antunes J. , Izquierdo P. , Paulino M. 
Published: November 2021

Abstract
Structures and mechanical components are often subjected to impulsive forces. There is a need for identification techniques which enable monitoring of such loads under operating conditions. For safety reasons and convenience, force identification must often be based on response motions sensed at accessible locations, remote from the impact points.
In our previous work we presented techniques for the experimental identification of both isolated impacts and complex rattling forces on a beam, generated at a single and also at several impacting supports. The system dynamical behavior was modeled using traveling flexural beam waves. Although successful, these techniques obviously assume a good understanding of the system dynamic parameters.
This is not always the case, a fact that highlights the practical interest of blind identification techniques. This relatively recent field, connected with higher-order statistics, avoids any explicit knowledge of the system transfer functions or impulse responses. Our previous work, based on a single response measurement, is extended in this paper to include several simultaneous responses.
We develop a multi-trace version of Wiggins minimum-entropy blind deconvolution algorithm. From numerical simulations and experiments, it is shown that the robustness to noise contamination is increased by using multiple response data. These results suggest that blind identification techniques will prove very useful in practical situations.
Simulation of Vibration and Acoustic Radiation of Finite Underwater Cylindrical Shells
Authors: Zhang X. M. , Liu G. R. , Lam K. Y. 
Published: November 2021

Abstract
A coupled structural-acoustic analysis of vibration and sound radiation of underwater finite cylindrical shells is investigated in this paper. The coupled vibration and radiation problem is formulated using Finite Element Method (FEM) for the structure and Boundary Element Method (BEM) for the acoustic domain. Vibration and sound radiation under symmetrical and unsymmetrical point force excitations are examined. It is shown that the coupled modals are the causes of large vibration of the shell and high sound pressure radiation of the acoustic fields. The shapes of frequency response curves of pressure are quite similar in the far fields but change greatly in the near fields.
A Macromodel for Dynamic Simulation of Microelectromechanical Systems
Authors: Lin W. Z. , Lee K. H. , Lim S. P. , Lu P. 
Published: November 2021

Abstract
This paper describes a method of model reduction by using Karhunen-Loève decomposition and Galerkin procedure to effectively perform the dynamic simulation and analysis of nonlinear microelectromechanical systems and devices. The Karhunen-Loève decomposition is a procedure for extracting a basis for a modal decomposition from an ensemble of signals, e.g. numerical or experimental data, thus converts the original systems into a lumped low-order macromodel with minimum number of degree of freedom. The macromodel can be used to carry out the dynamic simulation of the original systems resulting in dramatic reduction of computation time while not losing flexibility and accuracy. The method is evaluated to simulate the pull-in dynamics of a microrelay MEMS device, e.g. doubly clamped microbeam, subjected to different input voltage spectrum of electrostatic actuation. The results are compared with those of the fully meshed finite difference method (FDM) and found to be very accurate, efficient and flexible.
Nonlinear Dynamic Analysis of Rotor Supported by Finite Journals With a New Unsteady Nonlinear Oil-Film Force Model
Authors: Zhang Wen , Guo Jianping , Qiu Pengqing 
Published: November 2021

Abstract
A new approximate method for evaluating oil-film force acting on a finite journal bearing with unsteady and larger perturbed motion is presented. The nonlinear dynamic analysis of rotor supported by finite oil-film bearings is carried out by the new oil-film force model. Unsteady and large perturbed motion of journal is considered. From the numerical results the following conclusions are obtained: 1. At very low speed, oil-film force can be ignored, the motion is synchronous whirl. It is unbalance response motion. 2. At very high speed or lager eccentricity, unbalance force prevails over the influence of oil-film force. The motion is also synchronous and stable. 3. In the middle interval of speed, oil-film force and unbalance force have the same order of magnitude, or oil-film force play the main role, the motion is much complex. The nonlinear properties are appeared obviously. The running danger of the rotor would be happened in this running interval.
Time-Varying Modal Analysis by SDOF Wavelets
Authors: Masuda Arata , Sone Akira 
Published: November 2021

Abstract
The purpose of this paper is to provide a modal expression of a time-varying MDOF system and to develop an identification method for it. The single-input-multi-output relation of a time-varying N-DOF system is expressed as a superposition of N time-varying SDOF subsystems in the time domain, where the expansion coefficients represent the time-varying mode-shapes, and the natural frequency and the damping ratio of each subsystem represent the time-varying modal parameters of each mode. Then we define the SDOF wavelets, which correspond to the time-varying impulse responses of SDOF subsystems and show that the output of the entire system can be expressed by a superposition of SDOF wavelets. Then, the identification problem is reduced to an atomic decomposition problem of choosing the nearly best set of SDOF wavelets and determining the expansion coefficients. We develop a modified matching pursuit algorithm, called modal pursuit, to solve the problem. Basic examples are numerically examined to show that the proposed modal representation and the identification method are applicable to track the modal characteristics of time-varying systems.
Using Analytical/Numerical Matching With Finite Element Analysis to Solve a Fluid-Loaded Structural Dynamics Problem
Authors: Park Christopher D. , Franzoni Linda P. 
Published: November 2021

Abstract
Two model problems are solved using a combination of Analytical/Numerical Matching (ANM) and Finite Element Analysis (FEA). The first problem is that of a thick, finite length beam driven by the motion of a small rigid support attached to its lower boundary. The second problem is a thick, infinitely long fluid-loaded beam driven by the motion of periodically spaced rigid supports (identical to the support of the first problem). The ANM process divides an original problem into local, matching, and global sub-problems through the use of a smooth force and the principle of superposition. In the two model problems presented, the same high-resolution local (in vacuo) problem is solved using FEA. The fluid loading effects can be accounted for entirely by the global problem. The problems presented show that ANM is a computationally efficient method that retains the high accuracy needed near structural discontinuities.