bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Model for Fluid Flow in Artificially Roughened Microchannels
Authors: Wagner Rebecca N. , Kandlikar Satish G.
Published: July 2010

Two dimensional lubrication approximation is applied to the analysis of fluid flow in a rectangular microchannel with structured roughness. Each of two major walls is composed of designed microscale transverse ribs, modeled by two-dimensional functions. A pressure drop correlation is formed as a direct function of these surface equations and the resultant velocity profile is incorporated into boundary layer analysis. Friction factors are calculated based on the obtained pressure drop values for comparison with conventional theory. The method presented here is consistent with conventional correlations in the case of hydraulically smooth channels, and is a stronger function of structured roughness geometry than the existing methods.
Non-Uniform Control Moments Induced by a Skew-Quad Actuator Design Applied to Plate Controls
Authors: Jiang Jing , Yue Hong-Hao , Deng Zong-Quan , Tzou Horn-Sen
Published: July 2010

Distributed vibration control of flexible structures using piezoelectric materials has been extensively studied for decades. A number of design configurations of distributed actuators with uniform control forces and moments have been investigated to improve modal control effectiveness of distributed structures, e.g., shells and plates. In this study, a new skew-quad actuator design which consists of four pieces of mono-axial piezoelectric actuator is proposed and evaluated. Due to the uneven boundary conditions of each region, this new actuator can induce non-uniform control forces and moments. Based on the variation method, the non-uniform distribution of the actuator induced forces and moments are defined. The coupling equation of a simply supported plate laminated with this new design is derived; distributed control action resulting from the non-uniform control moments is also defined in the modal domain. The actuator induced control actions are calculated respectively on a square plate and a rectangle plate, and the effects of varying actuator size are also evaluated. These control effects of the skew-quad actuator are compared with those of a multi-DOF actuator. Parametric analyses suggest that due to the non-uniform control moments, the new skew-quad actuator induces better modal control actions in certain plate modes as compared with the multi-DOF actuator. This new skew-quad actuator has great potential to improve control effects to other shell structures.
Computational Fluid Dynamics for Hydrokinetic Turbines
Authors: Miller Veronica B. , Schaefer Laura A.
Published: July 2010

Hydrokinetic energy extraction (HEE) has received increasing attention recently as a sustainable means to alleviate the strain on current energy technologies. HEE extracts kinetic energy, rather than potential (as in traditional hydropower dams), and can be applied to tidal, some ocean, and river energy applications. In this paper, we will focus primarily on river hydrokinetic energy extraction. Although many new types of hydrokinetic devices have been proposed, there has been a dearth of research applying computational fluid dynamics (CFD) to further our fundamental understanding of these systems. Furthermore, the bulk of work in this field continues to draw conclusions for hydrokinetic turbine performance purely based on wind turbine theory. In our previous publications, we have shown that this is, at best, a broad estimate. The comparisons of wind turbine theory to hydrokinetic governing principles and CFD are discussed in this paper. This work presents a CFD analysis for a submerged water wheel turbine for both 2D and 3D cases. Insights into the resulting flow, behavior, and the implications for power extraction and the environmental impact are discussed.
Computational Investigation of Backward-Facing Step Flow Preceding a Porous Medium
Authors: Krishnamoorthy C. , Ravi K. C. , Yao S. , Chambers F. W.
Published: July 2010

Optimal performance of air filters and heat exchangers requires uniform inlet flow, but flow separation produces nonuniformity. The backward-facing step flow has a separation resembling those found in industrial flows. Flow resistance of the devices is a parameter which alters upstream pressure gradients, thereby affecting separation and device performance. Air filters often are modeled as porous media using an extended Darcy Law. The present work applied Computational Fluid Dynamics (CFD) to examine the changes in the step flow resulting from the resistance of a downstream air filter. Computations were performed for a backward-facing step with a 2:1 expansion ratio for a case without a filter (reattachment at ∼6 step heights) and for filters located 4.25 and 6.75 step heights downstream. FLUENT commercial CFD software was used and results were compared to many no-filter case results in the literature and our own experimental studies for the step with downstream filters. The simulations were performed for Reynolds numbers based on approach channel mean velocity and hydraulic diameter of 2000, 3750, 6550 and 10000. The different turbulence models available in FLUENT were evaluated and the Realizable k-ε model was used for the final computations. Grid independence studies were conducted. The effects of different values of the filter modeling permeability, inertial constant and thickness also were investigated for Re = 10000 with the filter at 4.25 step heights. It was found that the computational results did not compare well to no-filter cases or the experiments with filters at the lower Reynolds numbers. It is believed that the turbulence models were unsuitable for these flows at transitional Reynolds numbers. Good agreement for no-filter results and for the experiments with filters was observed for Re = 10,000. The CFD model seems to capture the physics of the separation better at the higher Reynolds numbers. The CFD velocity profiles at Re = 10,000 with the filters agree with those of the experiments. When the filter is placed at 4.25 step heights, the flow reattaches upstream of the filter with a reduction in recirculation area. When the filter is at 6.75 step heights, the separated flow tends to reattach and the opposite side tends to separate. At Re = 10,000 and the filter at 4.25 step heights, the variations of porous medium permeability, inertial constant and the filter thickness have negligible effects on the recirculation region over the parameter ranges considered.
Experiments and Modeling of a Liquid Droplet Transported by a Gas Stream Impinging on a Heated Surface: Evaporative Regime
Authors: Anderson Ryan P. , Ortega Alfonso
Published: July 2010

Understanding the transport mechanisms involved in a single droplet impinging on a heated surface is imperative to the complete understanding of droplet and spray cooling. Evidence in the literature suggests that gas assisted sprays and mist flows are more efficient than sprays consisting only of liquid droplets. There has been few if any fundamental studies on gas-assisted droplets or spray cooling, in which a carrier gas or vapor stream propels the droplet to the target surface. The current work extends previous studies of a droplet impinging on a heated surface conducted by the same group from the single phase regime into the evaporative regime. For both regimes, understanding the transport physics due to the heat transfer from the heated surface to the droplet and then by convection and evaporation to the airflow is of fundamental importance. High-speed photography was used to capture the spreading process and yielded results that correlated well with previously published isothermal and single-phase results. The heat transfer was measured with a fitting approach by which the instantaneous temperature profile was matched to an analytic solution to determine the instantaneous value of the centerline heat transfer coefficient. A very large increase in the heat dissipation was observed when compared to previously published single-phase results. Heat transfer was optimized at Reynolds numbers that produced an optimally thin liquid film and high heat and mass transfer coefficients on the surface of the film.
Controlled Geometry Nanopore Fabrication in Silicon Nitride Membranes With a Transmission Electron Microscope
Authors: Sosnov Eugene , Karavadi Subba Rao , Prakash Shaurya
Published: July 2010

Fabrication of controlled geometry solid-state nanopores (SSNs) using a transmission electron microscope (TEM) is described. Controlling nanopore geometry allows for optimization of the shape and structure of the pore based on the need for specific applications. By manipulating TEM parameters such as current, relative stage settings, and dwell time it is possible to manufacture controlled geometry SSNs in silicon nitride (Si3N4) membranes. Nanopores with circular, elliptical, and triangle-like cross-sectional areas were fabricated.
Alternate Approach of Using Spectral Decomposition for the Identification of Structural Resonant Regions
Authors: Mankevich Steven M. , Hambric Stephen
Published: July 2010

This paper investigates a method called spectral decomposition and is presented as an alternate approach to determine the system frequency response functions of turbomachinery. Spectral decomposition is a method that is based on the principals established by the acoustic similarity laws to determine the spectral characteristics of a source function. The decomposition process was originally implemented to investigate the isolated acoustic source spectra of fans specifically excluding structureborne sources; however, this paper focuses on using the method for the purpose of characterizing the system response functions associated with rotating machinery. During this investigation, static impact test data was acquired on a large industrial motor to characterize the frequency response functions of the motor/compressor system. Spectral decomposition results are then calculated using the motor operational structureborne data and compared to the results of the static impact test. This paper shows that the spectral decomposition is a viable option to use in place of the static impact test results where qualitative frequency response functions are desired.
Stepladder Spreader Bar Structural Integrity and the Impact on Accidents
Authors: Van Bree Michael P. , Knox Erick H. , Smith Kenneth M. , Eganhouse Joseph T.
Published: July 2010

Ladder accidents involving stepladders usually reveal damage to the spreader bars. This paper addresses the sufficiency of the present stepladder safety standards, design and testing requirements related to spreader bars. Spreader bars are the hinge members affixed to the sides of the stepladder that facilitate folding. Post-accident observation of buckled spreader bars or detachment from the side rails is frequently suggested as the cause of a user’s fall and injury. In addition to complete detachment at an end of one or both spreaders, several different bending configurations to varying degrees have been observed during accident investigations. These include bars bent into an “S” shape, bars bowed out/in, and bars with compound bending. In order to study these various post accident spreader conditions, stepladders of different size, weight ratings (i.e. types III (200 lb.), II (225 lb.), I (250 lb.), etc.) and material (wood, aluminum and fiberglass) were instrumented with strain gages in relevant locations to monitor stresses during normal use and misuse, as well as during various load tests and during live user falls from ladders. This extensive measurement experience of multiple loading configurations empirically demonstrated that spreader bar forces were minimal both in normal use, and even some circumstances of misuse. The resulting stress does not result in disconnection or deformation. Conversely, the loading of the stepladder structure that occurs in a tip over accident was observed to be more than sufficient to cause the frequently-identified post accident spreader bar damage patterns. On ladders that meet the applicable safety standards, all post accident spreader bar damage was found to be the result of the accident and not the cause.
The Steady-State Modeling and Analysis of a Two-Loop Cooling System for High Heat Flux Removal
Authors: Zhou Rongliang , Catano Juan , Zhang Tiejun , Wen John T. , Michna Greg J. , Peles Yoav , Jensen Michael K.
Published: July 2010

Steady-state modeling and analysis of a two-loop cooling system for high heat flux removal applications are studied. The system structure proposed consists of a primary pumped loop and a vapor compression cycle (VCC) as the secondary loop to which the pumped loop rejects heat. The pumped loop consists of evaporator, condenser, pump, and bladder liquid accumulator. The pumped loop evaporator has direct contact with the heat generating device and CHF must be higher than the imposed heat fluxes to prevent device burnout. The bladder liquid accumulator adjusts the pumped loop pressure level and, hence, the subcooling of the refrigerant to avoid pump cavitation and to achieve high critical heat flux (CHF) in the pumped loop evaporator. The vapor compression cycle of the two-loop cooling system consists of evaporator, liquid accumulator, compressor, condenser and electronic expansion valve. It is coupled with the pumped loop through a fluid-to-fluid heat exchanger that serves as both the vapor compression cycle evaporator and the pumped loop condenser. The liquid accumulator of the vapor compression cycle regulates the cycle active refrigerant charge and provides saturated vapor to the compressor at steady state. The heat exchangers are modeled with the mass, momentum, and energy balance equations. Due to the projected incorporation of microchannels in the pumped loop to enhance the heat transfer in heat sinks, the momentum equation, rarely seen in previous refrigeration system modeling efforts, is included to capture the expected significant microchannel pressure drop witnessed in previous experimental investigations. Electronic expansion valve, compressor, pump, and liquid accumulators are modeled as static components due to their much faster dynamics compared with heat exchangers. The steady-state model can be used for static system design that includes determining the total refrigerant charge in the vapor compression cycle and the pumped loop to accommodate the varying heat load, sizing of various components, and parametric studies to optimize the operating conditions for a given heat load. The effect of pumped loop pressure level, heat exchangers geometries, pumped loop refrigerant selection, and placement of the pump (upstream or downstream of the evaporator) are studied. The two-loop cooling system structure shows both improved coefficient of performance (COP) and CHF overthe single loop vapor compression cycle investigated earlier by authors for high heat flux removal.
Nonlinear Control of an Air Handling Unit Using Feedback Linearization
Authors: Moradi Hamed , Saffar-Avval Majid
Published: July 2010

Heating, ventilation and air conditioning (HVAC) systems are equipments used to maintain satisfactory comfort conditions in buildings. Also, energy consumption of ventilated buildings highly depend on the design, performance and control of HVAC systems. In this paper, nonlinear model of a multi-variable HVAC system is considered in which the control inputs are the air and cool water flow rates. Using thermodynamics and heat transfer rules, differential and consequently state space equations of the system are represented. To achieve a good performance, dynamic variables such as output temperature and relative humidity must be controlled. Using input-output feedback linearization, a PI controller is designed. It is shown that by applying the controller, system tracks from one operating point to another with an appropriate specification of time response. In addition, using feedback linearization guarantees robustness of the system against the parametric uncertainties associated with dynamic model.
Structural Stepladder Failure: Analysis of Root Cause
Authors: Knox Erick H. , Van Bree Michael P. , Kenner Matthew T. , Wilkinson John A.
Published: July 2010

It is estimated that over 100,000 people each year are injured as a result of falls from ladders. Stepladders are one of the many different types of portable ladders, and are used frequently both on the job and around the home. Many times a fall from a stepladder is accompanied by a damaged ladder. In particular, one or both front side rails are often bent inward below the lowest step, and the lowest step buckled upward. This paper investigates the root cause of these types of structural failures through multiple analytical methods, including calculations, strain gage analysis, computer modeling, specialized strength and stability testing, and analysis of the user dynamics on the ladder. Results include data collected from various ladder makes (wood, aluminum, or fiberglass), sizes, and duty ratings (200 pounds, 225 pounds, 250 pounds, and 300 pounds). Additionally, the results were compared to the requirements of the existing ladder safety standards. The results demonstrate that the above described damage patterns do not occur when the ladder is upright on all four legs under normal use circumstances. Instead, the analyses conducted herein show that the damage results from the dynamic forces of the user impacting the ladder after the ladder has already substantially tipped over.
Finite Element Modeling of Intraneural Ganglion Cysts of the Common Peroneal Nerve
Authors: Elangovan Shreehari , Odegard Gregory M.
Published: July 2010

Intraneural Ganglion Cysts [IGC] are a set of medical conditions that result in denervation of the muscles innervated by the cystic nerve leading to pain and loss of function. Current treatment approaches only temporarily alleviate pain and denervation which, however, does not prevent cyst recurrence. Hence, a mechanistic understanding of the pathogenesis of IGC can help clinicians understand them better and therefore device more effective treatment options. In this study, a preliminary analysis methodology is established to investigate the pathogenesis of IGC.
A Multibody System Approach to the Wedge Damper Friction Formulation
Authors: Baruffaldi Leonardo B. , de Arau´jo Henrique B. , dos Santos Auteliano A.
Published: July 2010

Secondary suspension of railway three-piece-trucks hasn’t changed much in the past century. Despite this, its most common damping element, the friction wedge, is not yet fully understood. The frictional damping is a known source of non-linearity and non-smoothness that imposes chaotic behaviors to the system, making the mathematical modeling of such devices a difficult task. The present paper presents a multi-body model of a three-piece-truck’s secondary suspension and the results of its simulations with three types of commonly used friction models.
Non Linear Eddy Viscosity Model Applied to U-Bend Industrial Geometry
Authors: Mereu Riccardo , Colombo Emanuela , Inzoli Fabio
Published: July 2010

The use of numerical approach to support design and product development on industrial applications is nowadays quite widespread. Many industrial applications involve turbulent fluid flows, whose modeling still represents the bottleneck for a wider usage of numerical methods. Indeed, the application of the CFD approach to industrial problem has a number of high demanding requirements since it must deal with relatively short computational time, high geometrical complexity and high Reynolds numbers. These industrial constrains nowadays may be partially faced through RANS approach even if poor capability in predicting accurately the fluid dynamics of complex flows still represents their well known weakness. The aim of this work is to provide a model able to improve the prediction of the flow field in complex flows of industrial interest, with special attention to the presence of strong curvature. Therefore, in order to obtain an increase in the accuracy of the results compared with traditional k-ε models, the implementation of a two-equation Non Linear Eddy Viscosity Model (NLEVM) is proposed. The quadratic formulation of this model has already been validated by experimental and DNS data from literature. In the present work the cubic formulation of this model is applied to a strong-curve-geometry of industrial interest. The data are obtained through an experimental facility developed by the CFDLab of the Department of Energy at Politecnico di Milano. The measures are taken in cooperation with the Combustion and Optical Diagnostic Laboratory research group. The comparison between experimental and numerical data is carried out downstream a strong curvature by looking at mean axial velocity profiles and reattachment point prediction.
Axial Heat Conduction in Parallel Flow Microchannel Heat Exchangers
Authors: Mathew B. , Hegab H.
Published: July 2010

This paper deals with the effect of axial heat conduction on the hot and cold fluid effectiveness of a balanced parallel flow microchannel heat exchanger. The ends of wall separating the fluids are subjected to Dirichlet boundary condition. This leads to heat transfer between the microscale heat exchanger and its surroundings and thereby leading to axial heat conduction through the wall separating the fluids. Three one dimensional energy equations were formulated, one for each of the fluids and one for the wall. These equations were solved using finite difference method. The effectiveness of the fluids depends on the NTU, axial heat conduction parameter, and the temperature of the ends of the wall separating the fluids. With decrease in temperature of the end wall at the inlet section of the fluids, while keeping the temperature of the other end wall constant, the effectiveness of the hot and cold fluid increased and decreased, respectively. When the temperature at the ends of the wall separating the heat exchanger is average of the inlet temperature of the fluids then there is no axial heat conduction through the heat exchanger. The effectiveness of a counter flow microchannel heat exchanger is better than that of a parallel flow microchannel heat exchanger subjected to similar operating conditions, i.e. axial heat conduction parameter and end wall temperatures.
Microvia Non-Destructive Inspection Method
Authors: Choi Cholmin , Dasgupta Abhijit
Published: July 2010

In this paper, the effectiveness of two non-destructive inspection techniques were investigated for quality assessment of microvias in high-density PWBs. Manufactured PWBs can fail during the reflow process due to microvia quality issues such as thin metallization in the barrel or shoulder of microvia or poor adhesion between the microvias and the metal layer underneath. The two investigated non-destructive inspection techniques are Transient Infra-red Thermography (IRT) and Time Domain Reflectometry (TDR). This study develops experimental methods to obtain thermal signatures of microvias using IRT technique and RF impedance signatures of microvias using TDR technique. Numerical analysis methods are also developed in this study to quantify and interpret the obtained microvia signatures to validate the functionality of selected non-destructive microvia inspection techniques.
Characteristic Study on the Optimization of Pin-Fin Micro Heat Sink
Authors: John T. J. , Mathew B. , Hegab H.
Published: July 2010

The need for dissipating heat from microsystems has increased drastically in the last decade. Several methods of heat dissipation using air and liquids have been proposed by many studies, and pin-fin micro heat sinks are one among them. Researchers have developed several effective pin-fin structures for use in heat sinks, but not much effort has been taken towards the optimization of profile and dimensions of the pin-fin. In this paper the authors studied the effect of different pin-fin shapes on the thermal resistance and pressure drop in a specific micro heat-sink. Optimization subjected to two different constraints is studied in this paper. The first optimization is subjected to constant flow rate and the second one is subjected to constant pressure drop. Both optimization processes are carried out using computer simulations generated using COVENTORWARE™. Two of the best structures from each of these optimization studies are selected and further analysis is performed for optimizing their structure dimensions such as width, height and length. A section of the total micro heat-sink is modeled for the initial optimization of the pin-fin shape. The model consists of two sections, the substrate and the fluid. Six different shapes: square, circle, rectangle, triangle, oval and rhombus were analyzed in the initial optimization study. Preliminary tests were conducted using the first model described above for a flow rate of 0.6ml/min. The non dimensional overall thermal resistance of the heat sink, and the nondimensional pumping power was calculated from the results. A figure of merit (FOM) was developed using the nondimensional thermal resistance and nondimensional pumping power for each structure with different pin-fin shapes. Smaller the value of FOM better the performance of the heat sink. The study revealed that the circle and ellipse structures have the best performance and the rectangle structure had the worst performance at low flow rates. At high flow rates rectangular and square structures have the best performance.
Effects of Surface Roughness on Single Phase Fluid Flow and Heat Transfer Characteristics in Microchannels
Authors: Lu Jinli , Hao Yingli
Published: July 2010

A two dimensional numerical simulation is conducted to investigate the flow and heat transfer characteristics of single phase liquid laminar flow through rough microchannels. The wall roughness is simulated in a series of cases with rectangular, triangular and trapezoidal elements, respectively. Shape factor and peak position have been used to analyze the influence of roughness elements on centerline velocity distribution, pressure drop and Nusselt number. It is found that the shape factor has a significant effect on the centerline velocity distribution, pressure drop and Nusselt number. It is also found that, for a given shape factor, the effect of peak position on pressure drop is strongly than centerline velocity distribution and heat transfer. In addition, for all considered roughness element shapes, the rectangular element displays a poor heat transfer and large pressure drop.
Modeling the Effect of Fluid-Structure Interaction on the Impact Dynamics of Pressurized Tank Cars
Authors: Yu Hailing , Tang Yim H. , Gordon Jeffrey E. , Jeong David Y.
Published: July 2010

This paper presents a computational framework that analyzes the effect of fluid-structure interaction (FSI) on the impact dynamics of pressurized commodity tank cars using the nonlinear dynamic finite element code ABAQUS/Explicit. There exist three distinct phases for a tank car loaded with a liquefied substance: pressurized gas, pressurized liquid and the solid structure. When a tank car comes under dynamic impact with an external object, contact is often concentrated in a small zone with sizes comparable to that of the impacting object. While the majority of the tank car structure undergoes elastic-plastic deformations, materials in the impact zone can experience large plastic deformations and be stretched to a state of failure, resulting in the loss of structural integrity. Moreover, the structural deformation changes the volume that the fluids (gas and liquid) occupy and consequently the fluid pressure, which in turn affects the structural response including the potential initiation and evolution of fracture in the tank car structure. For an event in which the impact severity is low and the tank car maintains its structural integrity, shell elements following elastic-plastic constitutive relations can be employed for the entire tank car domain. For events in which the impact severity is higher and the tank car is expected to be punctured, an equivalent plastic strain based fracture initiation criterion expressed as a function of stress triaxiality is adopted for the material in the tank car’s impact zone. The fracture initiation is implemented for ductile, shear and mixed fracture modes and followed by further material deterioration governed by a strain softening law. Multi-layered solid elements are employed in the impact zone to capture this progressive fracture behavior. The liquid phase is modeled with a linear Us–Up Hugoniot form of the Mie-Gru¨neisen equation of state, and the gas phase is modeled with the ideal gas equation of state. Small to moderate amounts of fluid sloshing are assumed for an impacted tank car in this study. As such, the FSI problem can be solved with the Lagrangian formulation of ABAQUS, and appropriate contact algorithms are employed to model the multi-phase interactions. The force, displacement and impact energy results from the finite element analysis show good correlations with the available shell (side) impact test data. The puncture energy of a tank car in a shell impact scenario is further analyzed. It is demonstrated that the FSI effect needs to be adequately addressed in an analysis to avoid overestimating the puncture resistance of a tank car in an impact event.
High Strain-Rate Response of Polyurethane-Clay Nanocomposites and Their Use for Blast Applications
Authors: Kaushik Amit K. , Arruda Ellen M.
Published: July 2010

The dispersion of strong nanoscale building blocks into polymers may result in nanocomposites that can mimic the structural and mechanical properties of advanced materials found in nature. In this study, exceptionally high strength and stiffness (in-plane modulus: 270 GPa) clay nanoparticles are used to synthesize polyurethane-clay nanocomposites with enhanced mechanical properties using a layer-by-layer (LBL) technique. The LBL technique allows spatial and orientational control of these clay nanoparticles within the polymer matrix at the nano-scale. Moreover, the structure of LBL manufactured nanocomposites resembles the structure of naturally occurring tough biocomposite Nacre. A series of nanocomposite films with a wide range of volume fractions of clay nanoparticles was manufactured and investigated at low and high strain rates in uniaxial tension and compression deformation states respectively. The growth of these films in the thickness direction was enhanced by replacing alternate layers of MTM nanoparticles with (poly) acrylic acid. Thick samples for the uniaxial compression tests were made by hot-pressing several of these films together. The nanocomposites demonstrated an increasing yield strength and stiffness with volume fractions of MTM nanoparticles. The nanocomposites, at high-strain rate compression, showed a rapid strain hardening with true stresses as high as 0.45 GPa at a strain of 0.8. The incorporation of clay nanoparticles resulted in a plastic deformation leading to large energy dissipation which makes these materials suitable for applications in increasing the survivability of structures under blast loadings.
Flow Maldistribution in Multichanneled Microdevices With In-Line Manifolds
Authors: Soman J. , Mathew B. , John T. J. , Hegab H.
Published: July 2010

This paper deals with the analyses of fluid flow distribution in a microfluidic device with in-line manifolds. The analysis was performed using commercially available microfluidic simulation software called CoventorWare™. The number of channels in the microfluidic device considered for this study was kept at ten due to limitations on the number of nodes and computational time. Channels with only square profile were analyzed for flow rates varying between 1 to 60 ml/min. The length of the channels was maintained at 1.5 cm for all simulations. The fluid flow distribution characteristics for different channel widths/depths (200, 100, and 75 μm) were investigated. It was observed that the flow rate decreased from the central channels to the outer channels. The flow per channel was symmetric about the geometric centre of the microdevice. The uniformity in flow was accessed using the root mean square value of flow per channel and it decreased with decrease in channel width/depth for a specific flow rate. The difference in the flow rate through the channels increased with increase in total flow rate. Similarly, the spacing between the channels was varied (300, 200, and 100 μm) for a microdevice with channel width/depth of 100 μm and its corresponding flow characteristics were studied for flow rate ranging between 1 ml/min and 60 ml/min. Finally, the length of each manifold was varied between 2500 μm and 1000 μm for understanding the effect of manifold length on flow distribution. The standard deviation of flow per channel did not show much variation with changes in spacing and manifold length. In addition each design of the manifolds was analyzed on the basis of pressure and flow rate as well as velocity profile in each of the channels.
Extended Exergy Analysis Applied to an Offshore Platform Flare Stack
Authors: Diaz-Mendez Sosimo E. , Hernandez-Guerrero Abel , Sciubba Enrico , Rangel-Hernandez Victor Hugo
Published: July 2010

An original procedure based on the EEA method (Extended Exergy Accounting) is described and implemented in this paper. The goal is the quantification of the environmental externality linked to the chemicals released by an offshore platform flare stack (SOX and NOX). The extended exergy calculations provide a measure of both the exergy flux released into the environment by the offshore platform flare stack and its “cost” in primary resource equivalents. Idealized processes are assumed for the effluent treatment, and this bears a non-negligible influence on the final resource cost. As a further example of the application, it is shown that both the environmental damage and the product costs can be reduced if hot gas recycling is enforced.
Investigation of Oxide-Removal of Various Metal Particles for Fabricating MEMS-Based Corrosion Sensor
Authors: Pan Feng , Huang Adam
Published: July 2010

Recently, our research group has proposed a MEMS-based solid state corrosion sensor, which is based on embedding metal particle into elastomeric polymers to form a composite-based sensing material. The chemical and dimensional properties of the metal particles and polymer matrix will provide the tailorability in sensor sensitivity, selectivity, time response, and operating life-span. However, the oxidization of metallic particles prior to embedding is adverse for electrical transduction of such sensor. This paper will be based on the investigation of chemical etching protocols used to remove the oxide coating from metal particles without adversely alter the particle itself. The etching process must also be compatible with common MEMS fabrication processes and not limited by the wide range of particle sizes used (30nm–100um). More specifically, metal particles such as Titanium, Aluminum, Nickel, and Stainless Steel are currently being used and investigated.
Control Design and Passivity Analysis for Scaled One-Dimensional Bilateral Teleoperated Nanomanipulation
Authors: Motamedi Mohammad , Ahmadian Mohammad Taghi , Vossoughi Gholam Reza , Tajaddodianfar Farid
Published: July 2010

In this paper, a novel control approach for one-dimensional bilateral teleoperated nanomanipulation system is proposed. While manipulating objects with a nanomanipulator, real time visual feedback is not available. So, force feedback is used to compensate for the lack of visual information. Since nanometer scale forces are dominated by surface forces instead of inertial forces as in macro world, scaling of nanoforces is one of the major issues of teleoperation system. The Hertz elastic contact model is used to model the interactions between the slave robot and the environment. The proposed approach uses the simple proportional derivative control, i.e., the master and slave robots are connected via a virtual spring and damper. The passivity of the combination of control blocks and communication is demonstrated via the control passivity concept. The outcome is a robust platform to enforce master-slave position coordination and perform teleoperated nanomanipulation on a broad range of materials. Simulations are performed to confirm the proposed control approach.
A Numerical Model for Non-Isothermal Flow Induced Crystallization in Thermoplastic Polymers
Authors: Zinet Matthieu , El Otmani Rabie , Boutaous M’hamed , Chantrenne Patrice
Published: July 2010

In industrial forming processes such as extrusion or injection molding, polymeric materials experience severe thermomechanical conditions: high pressure, high deformation rates, very fast cooling kinetics and important temperature gradients. In semi-crystalline thermoplastics, such as polypropylene, these phenomena have a major influence on the crystallization occurring during cooling, which determines the final microstructure. Predicting the solidified part properties by numerical simulation requires the implementation of a crystallization kinetics model including both the thermally and flow induced effects. In this work, a numerical model simulating polymer crystallization under non-isothermal flows is developed. The model is based on the assumption that the polymer melt elasticity, quantified by the first normal stress difference, is the driving force of flow-induced extra nucleation. Two sets of Schneider equations are used to describe the growth of thermally and flow induced nuclei. The model is then coupled with the momentum equations and the energy equation. As an application, a simple shear flow configuration between two plates (Couette flow) is simulated. The relative influence of the mechanical and thermal phenomena on the crystallization development as well as the final morphology distribution is finally analyzed as a function of the shearing intensity, in terms of nucleation density and crystallite mean sizes.
Adaptive Control of Regenerative Chatter in Turning Process With Tool Wear Effect
Authors: Hajikolaei Kambiz Haji , Moradi Hamed , Alasty Aria , Vossoughi Gholam-Reza , Movahhedi Mohammad-Reza
Published: July 2010

Chatter suppression is of great importance for achieving high precision and surface quality in machining processes. A single degree of freedom model of orthogonal turning process is used to set up the nonlinear delay differential equation of motion. Tool wear effect is considered as the contact force between the workpiece and tool flank surfaces. Uncertainties in parameters of dynamic model and machining conditions are included in the model. An adaptive control strategy is applied for chatter suppression in cutting process. The force provided by a piezo-actuator is the control input of the system. Results of stability analysis and adaptive control for two distinct cases of sharp and worn tools are presented and compared.
A New Planar 3-DOF Parallel Mechanism With Continuous 360-Degree Rotational Capability
Authors: Seo Tae Won , In Woosung , Kim Jongwon
Published: July 2010

This paper presents a novel 3-DOF planar parallel mechanism with 360-degree rotational capability, which can be used as a positioning device. A high rotational capability is necessary to reduce process time and to apply the mechanism to various fields such as micro machining and PCB depaneling. The proposed mechanism has the advantage of a continuous rotational capability over existing planar parallel mechanisms with limited rotation. The position and velocity kinematics are derived, and the singularities are analyzed based on the Jacobian matrices. The workspace can be determined not to have a singularity inside, and the kinematic variables for enlarging the singularity-free workspace are determined.
Mathematical Model of Solidification in Continuous Cast Low Carbon Steel Billets
Authors: Putta Ramesh N. , Srinivasan Malur N.
Published: July 2010

This paper describes the relation between the Secondary Dendrite Arm Spacing (SDAS), Area of Mushy Zone with the Continuous Casting variables in low carbon steels during the solidification process in the mold zone. A Finite Element analysis of the heat flow equation, coupled with the solute distribution model and the dendrite growth model, enables the determination of the Secondary Dendrite Arm Spacing (SDAS). The CONBCAST.FOR program is developed in this work to analyze effects of process variables on the Secondary Dendrite Arm Spacing (SDAS), Area of Mushy Zone and Volume of the Bleed. Effort is also made to find the optimum casting parameters. A new concept is introduced in this work to analyze the relation between the Area of Mushy Zone and Secondary Dendrite Arm Spacing (SDAS) with the Volume of the Bleed. Quantitative work is performed by collecting the square shaped billets at two different process conditions and determined the Secondary Dendrite Arm Spacing and Volume of Bleed to analyze the relationship between SDAS, Area of Mushy zone and Volume of Bleed.
Stability Analysis of a Reach Truck
Authors: Bae Jong-Su , Kim Taewung , Jeong Hyun-Yong
Published: July 2010

There is a need for a higher mast of a reach truck in the market, but a higher mast brings a safety concern. Usually, it is more plausible to fall in the roll direction than in the pitch direction. Since a reach truck with a high mast is a heavy and its center of gravity is high, it is not easy to conduct tests to evaluate its stability. If there is a mathematical tool to evaluate the stability of a reach truck, it is easy to evaluate a design in terms of stability and to modify the design in order to increase its stability. In this study, a variational method using a total potential function was used to make a mathematical means to evaluate the stability of a reach truck. By using the mathematical means the stability of a reach truck was evaluated and compared with FE simulation results.
Application of Heat Pipes to the Uniformation of Thermal Fluxes in Industrial Exhausts
Authors: Dumas Antonio , Trancossi Michele
Published: July 2010

This work analyses the mathematical model of thermal exchange in presence of transitory subjected to unexpected thermal shocks of indefinite duration. It investigates the industrial feasibility of heat pipes heat exchanger in order to reduce the effects of thermal shocks in industrial exhausts in plants for cement production. Low cost recovered thermal energy could be dedicated to any necessary low temperature application. The solutions of the equations, which describe the problem, are obtained in a general form. They could so be easily extended to whichever exchanger, on the base of the common, verified and validated, calculation parameters, which could be found in bibliography. A Matlab code has been produced to solve the problem. It has been validated thought CFD simulations using data of thermal shocks produced by rotary kilns.
Drop Simulation and Testing in Computer Peripheral Hardware Development
Authors: Su Bin , Tiku Sanjay , Darbha Krishna
Published: July 2010

Drop is one of the most common user scenarios for computer peripherals like wired/wireless keyboards, mice, and webcams. Failures due to such impact events are typical examples of overstress types of failures that occur during the useful life of a product. The ability of computer peripheral devices to survive impact with minimal to no impact to product performance or aesthetics is a goal for the product development teams. Engineers have to choose the proper materials and use different simulation and test methods for creating product designs that will survive multiple drop events. Traditional product development process involves iterations of design-physical test-design modification cycles to meet drop requirements. To reduce iterations, expedite product development and reduce time-to-market, virtual drop simulations are conducted at an early stage in product development without the need for any physical samples. This paper presents case-studies on this approach to product development. Case-studies are presented for a keyboard and a mouse. The case-study shows how drop simulation results were used to inform design decisions and how design improvements in terms of material selection or actual feature changes were made early in the design cycle. The study illustrates the use of a high speed camera to capture movies of product performance in drop tests to further discover weaknesses and correlate actual results with simulations. Using a combination of simulation and capturing deformation information with a high speed camera during actual testing, the product development iterations were minimized in terms of cost and time.
Investigating Mass Scaling in Vehicle Crashworthiness
Authors: Reid John D.
Published: July 2010

Mass scaling is a technique used in explicit nonlinear finite element analysis that adds mass to relatively small elements in order to increase the time step, and thus, decrease the overall cpu requirements of a simulation. With multi-million element vehicle crash models becoming common, the likelihood of several very small, time step controlling elements is high. Mass scaling can provide great benefits in these cases. However, there is very little information on the actual usage and possible effects of mass scaling for vehicle crashworthiness in the literature. Inherit to explicit FEA is the well known high frequency content in accelerations. Thus, even very small addition of mass will result in different acceleration traces. Because of that, various techniques are needed to determine if the mass scaled results are the same, or at least similar enough, as the non-mass scaled results. Two applications are investigated; a crush tube and an NCAP test of a Chevy Silverado. The latter model size approaches one million elements.
Implementing a Robust, Yet Straightforward, Direct Assessment Process That Engages 100% of the Faculty
Authors: Morales Juan C.
Published: July 2010

This paper discusses a straightforward direct assessment process that has created an atmosphere in which outcomes assessment is conducted to truly strive to improve engineering education rather than to merely satisfy ABET criteria. It has been implemented only during the last 18 months but represents the latest improvement in a sustained six-year effort to implement an effective direct assessment process. The key component of the methodology is to use the learning objectives of each of the engineering courses as the performance criteria for assessment at the program-level. Each course objective is mapped to a program outcome and to the student work to be assessed. The assessment of student work is performed with rubrics. The course-level assessment measurements, that map into a specific program outcome, are then averaged in a spreadsheet to obtain program-level results for each of the program outcomes. The process is conducted every semester, including a closing-the-loop faculty meeting to evaluate the results. It is shown through a faculty survey that the response of the faculty, in general, has surprisingly been very positive, even though the average time to conduct the assessment is high: 9.22 hours per course per semester. The assessment results clearly reveal areas that need strengthening in the courses, as well as areas that can be de-emphasized. In turn, the integrated results also provide valuable information regarding the state of each outcome at the program-level. Although additional work is required to enhance the process, the results of this investigation suggest that a strong assessment component at the course-level — not directly required by ABET — can be the basis for achieving a sustainable and effective assessment process at all levels. Instead of creating a separate set of performance criteria for each outcome, the direct link between course objectives and program-level outcomes provides a straightforward and efficient mechanism to effectively manage continuous improvement efforts while fully engaging 100% of the faculty.