bluuebunny/crossref_metadata_2025 huggingface dataset:
Robot Remote Control and Mine Sweeping
Authors: Belotti Vittorio , Hemapala Manjula U. , Michelini Rinaldo C. , Razzoli Roberto P.
Published: July 2009

Demining is calamity of third world countries. The clearing is ceaseless, more expensive than the spreading, and terrorist return is obtained by weakening of the antagonistic population. The mines are cheapest weapon, built to make horrible injuries, affecting active people, with major falls-off into economic growth. The disaster is notably cruel in Sri Lanka, with anti-person mines spread in the northeast region. After the ceasefire, the international organisations started the mine sweeping, with poor issues, due to politico-economical motivations in direct bond with wants in the technical effectiveness. The pitiable situation is worsened, as most rich lands are removed from farming exploitation, with increasing of the internally displaced persons. Now, clearing is engineering duty, and the humanitarian goal comes to be technical challenge. The advanced robotics fulfils clean and reliable tasks, on condition to upgrade sophistication and cost and to loose third-world appropriateness. The challenge is to turn local machines and awareness into effective robotic aids, willingly used by the local people, and to enhance the on-going outcomes. The analysis, mainly, addresses the following points: - the engaged technologies need to provide special purpose outfits and to involve operators having adapted uniformity; - the work-flow pre-setting ought to detail the duty-cycles and to establish the standard achievements; - the planning has to specify the on-process warning/emergency management and the failure protection rules; - the operators’ instruction and training shall aim at off-process optimised work-flows to circumvent risky issues; - the effectiveness comes from organised routine agendas, in conformity with allotted tasks and emergency events. This is a mix of organisational and technologic demands, calling for responsible commitment of the involved people, so that the local Civil Service is entitled to do the clearing operations, and the all engaged community is solidly concerned. The winning solution shall look at low-cost robotic outfits, to be obtained with resort to nearby available resources and competences (e.g., drawn on from the local agricultural machinery and know-how), and full account of the cost limits, while aiming at the process effectiveness by the mix of enabling cues, principally deferred to enhancing the regional awareness and the factual dedication. The paper stresses on fairly unorthodox robots, addressing unmanned effectors facilities joined with intelligent remote-command abilities, not as advanced achievements, rather as cheapest productivity upgrading, assembled from standard farming devices, through the shared know-how and commitment of locally involved operators.
The Model Eliciting Activity (MEA) Construct: Moving Engineering Education Research Into the Classroom
Authors: Shuman Larry J. , Besterfield-Sacre Mary , Clark Renee , Yildirim Tuba Pinar
Published: July 2009

A growing set of “professional skills” including problem solving, teamwork, and communications are becoming increasingly important in differentiating U.S. engineering graduates from their international counterparts. A consensus of engineering educators and professionals now believes that mastery of these professional skills is needed for our graduates to excel in a highly competitive global environment. A decade ago ABET realized this and included these skills among the eleven outcomes needed to best prepare professionals for the 21st century engineering world. This has left engineering educators with a challenge: how can students learn to master these skills? We address this challenge by focusing on models and modeling as an integrating approach for learning particular professional skills, including problem solving, within the undergraduate curriculum. To do this, we are extending a proven methodology — model-eliciting activities (MEAs) — creating in essence model integrating activities (MIAs). MEAs originated in the mathematics education community as a research tool. In an MEA teams of students address an open-ended, real-world problem. A typical MEA elicits a mathematical or conceptual system as part of its procedural requirements. To resolve an MEA, students may need to make new connections, combinations, manipulations or predictions. We are extending this construct to a format in which the student team must also integrate prior knowledge and concepts in order to solve the problem at hand. In doing this, we are also forcing students to confront and repair certain misconceptions acquired at earlier stages of their education. A distinctive MEA feature is an emphasis on testing, revising, refining and formally documenting solutions, all skills that future practitioners should master. Student performance on MEAs is typically assessed using a rubric to measure the quality of solution. In addition, a reflection tool completed by students following an MEA exercise assists them in better assessing and critiquing their progress as modelers and problem solvers. As part of the first phase a large, MEA research study funded by the National Science Foundation and involving six institutions, we are investigating the strategies students use to solve unstructured problems by better understanding the extent that our MEA/MIA construct can be used as a learning intervention. To do this, we are developing learning material suitable for upper-level engineering students, requiring them to integrate concepts they’ve learned in foundation courses while teasing out misconceptions. We provide an overview of the project and our results to date.
Forced Convection in a Uniformly Heated Enclosure With Different Aspect Ratios: Effect of the Inlet and Two Outlet Port Locations
Authors: Botello-Arredondo A. I. , Hernandez-Guerrero A. , Rubio-Arana C. , Pen˜a-Taveras M.
Published: July 2009

This paper presents a numerical investigation on forced convection in a cavity with one inlet and two outlet ports. For the present study three different aspect ratios between height (H) and length (L), (H ≠ L)were considered (AR = H/L), AR = 1, 1.3 and 2.5. Different conditions and geometric arrays for the position of the ports are analyzed. The walls of the cavity are considered to be isothermal warming-up the incoming cold fluid. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, the aspect ratio affects the flow behavior in the cavity. An increment of vorticity leads to a heat transfer enhancement. The different aspect ratios of the cavity and the effect of the outlet ports and their location are discussed.
The Interplay Between Design and Mathematics: Introduction to Bootstrapping Effects
Authors: Reich Yoram , Shai Offer , Subrahmanian Eswaran , Hatchuel Armand , Le Masson Pascal
Published: July 2009

In spite of common perceptions, design and mathematics have much in common in the way they are practiced and in their results. Understanding the interplay between design and mathematics could therefore, lead to mutual benefits to both disciplines. This paper introduces this subject and focuses on one benefit that could arise from a tight transfer of knowledge between design and mathematics that bootstraps progress in both disciplines.
Robust Adaptive Nonlinear Controller for Robotic Systems: Linear Matrix Inequality Approach
Authors: Levy Itzhack , Berman Nadav , Ailon Amit
Published: July 2009

In this paper the tracking problem of a robotic system with model uncertainty is considered via an application of the H∞ control theory for nonlinear systems. In particular, we develop a state feedback controller which yields a global exponential stability of the underlying system and provides the closed loop system with relatively low gains. The main ingredient which facilitates our development is the choice of a particular storage function (which serves as a Lyaponov function). This particular storage function leads to certain linear matrix inequalities, the solution of which yields the desired controller. Moreover, the resulting LMIs (Linear Matrix Inequalities) turn out to be of the same form of the LMIs achieved in the analogous linear case. Simulation results and implementation of the control algorithm in a two-degree of freedom robot illustrate the controller efficiency.
Qualitative Experimental Behavior of Oscillatory Gutter Brushes
Authors: Vanegas Useche Libardo V. , Abdel Wahab Magd M. , Parker Graham A.
Published: July 2009

Cutting and flicking128 brushes are two types of gutter brushes that sweep the debris that lies in the gutter towards the main sweeping mechanism of a street sweeper. As most of the debris is commonly found in the gutter, the operation of gutter brushes is important. In this work, the concept of oscillatory gutter brushes is studied. Qualitative experimental tests are carried out to determine frequencies at which enhanced vibration patterns of the bristles of cutting and flicking128 brushes are obtained. The brushes are rotated at variable angular speed, first in free rotation, and then against a concrete test bed. The findings are analyzed in the light of previous theoretical results. The results suggest that bristle vibrations may be excited at the first natural frequency of the bristles for both brush types. Notably, the trends indicate that when the frequency is a third of the first natural frequency, a resonant condition seems to occur. The results also indicate that an equivalent length for bristle vibration has to be calculated, due to the way in which the bristles are clamped into the mounting board. This equivalent length is necessary for the comparison between the experimental and analytical results. These tests are useful in the determination of frequencies that may be potentially helpful during sweeping.
Design, Development and Characterization of a Micro-Reactor for Fast Pyrolysis of Biomass Feedstocks
Authors: Mayor J. Rhett , Williams Alex
Published: July 2009

This paper presents the latest results in the design, development and performance characterization of a novel prototype micro-reactor system that is uniquely capable of capturing the transient product evolution history of the fast pyrolysis of biomass products. With strong demand driving the technological development of sustainable energy solutions, the consideration of optimal conversion methodologies for biomass energy feedstocks has received a great deal of attention recent years. [1, 2] The pyrolysis of soft woods, in particular spruce and pine, has emerged as a credible alternative to bio-digestive strategies that are reliant on fermentation processes, typically of corn feedstocks. The design objectives for the micro-reactor system are reviewed, highlighting the multi-physics and multi-disciplinary complexity in designing for transient characterization of the pyrolized products by the micro-reactor system. One of the dominant challenges in the design of the micro-reactor for fast pyrolysis reactions is the requirement of very high heating rates for the feedstock, on the order of 100°C/s. A 1D transient thermal model of the reactor is developed that considers the average particle size and morphology, the initial surface temperature of the reaction surface within the micro-reactor, the heat loss to the ambient atmosphere in the reactor, the heat loss through the contact resistance between the sample and the reaction surface and the thermal capacitance of the reaction surface. A parametric evaluation of the design space was performed using the 1D model in order to identify a preferred range of particle size, reactor surface area and thermal input power. Based on the results for the domain reduction study, multi-physics thermo-mechanical 3D FEA was used to undertake a brute-force optimization process of the final design. The key metric considered in the FEA study was the maximum thermal gradient in the reaction surface and was driven to a minimum value. The thermal response of the prototype micro-reactor has been evaluated using infra-red thermography measurement techniques. Thermographical analysis of the results has demonstrated negligible thermal gradients in the reaction plane up to the maximum reaction setpoint of 450°C. Based on the results of the thermal testing of the micro-reactor, the achieved peak heating rates of the sample have been estimated to be on the order of 400°C/s, meeting and exceeding the design requirement.
Generating Traveling Vibration Waves in Finite Structures
Authors: Gabai Ran , Bucher Izhak
Published: July 2009

This work is concerned with a method to generate pure traveling vibration waves in finite structures. Progressing elastic deformations, i.e. waves, are not common in forced vibrating structures since a structure is naturally vibrating in its, naturally occurring, normal modes that are usually referred to standing waves. This makes the generation of traveling waves in a structure a challenging task. In this work, external excitation is applied to the structure in order to create traveling waves in one dimensional structures. Based on a model of the structure and its boundaries, it is possible to calculate, theoretically, the required excitation, in order to generate a pure traveling wave in the structure. This calculation has little merit in practice since small model uncertainties and boundary dynamics effects may alter the generated waves such that they are far from being traveling waves. An iterative in situ method to tune the applied forces, until the desired traveling wave are formed, is presented. This method relays on estimating the current wave-vibrations state in a structure from measurements and tune the external forces toward a pure traveling wave state. An experimental validation of the theory is presented to support the theory.
Study on Coupled Acoustic Wave Propagation of Circular Metal Pipe
Authors: Kim Ho-Wuk , Kim Min-Soo , Lee Sang-Kwon
Published: July 2009

The circular cylinder pipe is extensively used for the supplement of the gas. The leakage of this gas induces the catastrophic problem when it leases into open area in the city without any monitoring. This paper investigated theoretically the propagation of the acoustic wave of the circular cylinder pipe containing the gas in a pipe for the development of the leakage monitoring system. The acoustic wave is propagated through the waveguide of the circular pipe with the characteristics acoustically coupled by the gas contained in a cylinder and the shell. However, as a special case, the acoustic waves in a metal pipe containing gas are corresponded closely to the uncoupled in-vacuo shell waves and to the rigid-wall duct fluid waves. In this case, the dominant acoustic energy can be estimated at the frequencies in which coincidence between the shell modes and the acoustic modes occurs. In the paper, the characteristics of the dominant waves are theoretically investi-gated and analyzed experimentally with a long steel pipe. The measured data is clearly analyzed by the continuous wavelet transform and by spectral density analysis. Finally, a bandwidth of the frequency for a good estimation of the correlation would be suggested through the consideration of the coherence function between two sensors.
Simulated Planar Polycrystalls With Planar and Spatial Random Lattice Orientations
Authors: Cizelj Leon , Simonovski Igor
Published: July 2009

A planar multiscale model of a polycrystalline aggregate was employed in this paper to arrive at new and interesting results. The model accounted for the most important mesoscopic features including explicitly modeled random grain structure with crystal grains represented as randomly oriented monocrystals obeying anisotropic elasticity and crystal plasticity (Schmid resolved shear stress) constitutive models. The results presented include the illustrative description of simulated mesoscopic strain fields, including the development of shear bands, and a sensitivity analysis of the equivalent macroscopic response at various sizes of polycristalls smaller than Representative Volume Element (RVE). Columnar grain structure is assumed in a planar (plane strain) finite element model. The presentation of results includes the comparison of aggregate responses obtained assuming 2-D only and full 3-D random grain orientations. The material properties have been chosen to represent the German nuclear reactor pressure vessel steel 22 NiMoCr 3 7.
Architecture for Integrated Service Systems
Authors: Bo¨ttcher Martin
Published: July 2009

Even though the necessity of a holistic approach for service modeling is widely accepted no such approach is available by now. By analyzing existing service modeling approaches, service literature and by supervising an industrial project we identified several weak points within the field of service modeling. One main problem is the disregard of a clear separation of modeling levels (so called meta-levels). This leads to an unnecessary backlog within the field of service modeling as approaches are neither conformant to each other nor can they be compared. Therefore we suggest applying meta-levels (and corresponding technical spaces) within the area of service modeling, as known from other modeling domains. We outline the advantages of such an approach and we define which concepts are necessary for modeling services and what kind of impact they have on the idea of meta-levels within the service modeling domain.
Verification and Validation Method in Complex Systems: Case Study
Authors: Alperin Regina , Manor Eyal , Leibowitz Moti
Published: July 2009

The article describes a case study methodology that is applied in RAFAEL for the verification and validation (V&V) of complex and multi-disciplinary systems. Various methods of V&V are found within the nature and the type of the product. Some applications use methods that are prevalent in the electronics industry. There are other methods that are based on international standards such as V&V for airborne structures. Complex systems are characterized by a number of special issues which do not allow for a simple implementation of V&V mentioned above. The following issues are unique to complex systems: the design consists of multi-disciplinary subjects, the cost of the life cycle is high, it takes a long time for hardware production and for the completion of development, there is a demand for high reliability, the V&V process contains a multiplicity of parameters and the system has multiple interfaces. For systems of this nature there is no V&V process available in use and it is necessary to implement a tailored-made method. This method of V&V deals with the two main quantitative and qualitative questions of proof: (a) how does the system and sub-system behave under external environmental conditions?, (b) how does the system and sub-system functioning under the existence of differences between sub-systems and components which are supplied in the delivery stage of the life cycle (i.e. geometrical and performance tolerances, time depending parameters)? The new approach is to design a process of V&V in the early stages of the product life cycle. It is different from the conventional approach which performs the reliability tests at the completion of the product development via the approval examinations. The steps in building updated V&V process for complex system are: 1. Identification of the functionality specification of the system and deriving from it the V&V building blocks. 2. Breaking down the system into independent factors and connecting to each factor the relevant part of the physical structures. For each component in the structures it is necessary to identify its functionality and whether if the specification comply with demands. 3. Building computational, analytical and functional models which describe the system, sub-system and its components behavior and sensitivity analysis. 4. Experimental validation for individual sub-systems and components. The purposes are to verify reliability of the models, to validate the margin of safety needed and to find out the failure threshold. 5. Experimental validation at a higher level. The purposes of this stage are to examine the internal and external interfaces, to verify the approach of the separation of parameters and to validate the system functionality. This new approach will be demonstrated on an electromechanical system.
Heat Transfer and Temperature Distribution Outside the Borehole
Authors: Lipnicki Zygmunt , Pa˛zik Rafeł
Published: July 2009

In this paper a theoretical analysis of the non-stationary distribution of temperature outside a borehole in the ground is presented. The ground, surrounding the cylinder, is the source to heat or cool the medium flowing inside the cylinder. Direction of temperature distribution in the ground depends on the circumstance if the cylinder is responsible for heating or cooling. The discussion will concern the effect of an accumulation of heat in time by the deposit (ground) and the distance from the borehole to the place where there is no heat exchange, as well as the influence of temperature distribution on cooling or heating effects. An analytical model was designed to determine a profile of temperature in the ground and the Nusselt number in the borehole dependents on both the time and the outward radius. An attempt is made to define the radius of the thermal influence of the.
Maintaining Currency and Staying at the Cutting Edge of the Profession
Authors: Kreiner Jesa H. , Miles David J.
Published: July 2009

Educators and employers have traditionally worked together to identify engineering skills which require ongoing updating and upgrading in order to avoid obsolescence. That, along with the need to work successfully in multidisciplinary environments, has become increasingly critical in staying competitive in the face of rapidly changing technology and current trends toward outsourcing of engineering jobs. Mechanical engineers, specifically, are continuously confronted with the requirement to maintain proficiency in CAD and FEA tools, evolving multiplicity of design materials and fabrication processes and increased sophistication of design components. Another aspect of a successful engineer entails the ability to communicate with both engineers and non-engineers who frequently are in positions to approve or cancel projects which may affect success and/or survival of the company where engineers work. A recent survey was conducted of engineering alumni of the mechanical engineering program at California State University, Fullerton spanning a period of close to four decades to assess if and how these graduates managed to stay current and the degree of success achieved in this continuing endeavor. The survey evaluated ways and means of these efforts and the employers’ attitudes and support, or lack thereof, towards such efforts. Also the surveys examined alumni experiences of working in multidisciplinary and multinational teams. Relationships between continued education and success in pursuit of the career of alumni were examined. Implications of these findings to engineers, academic institutions and industry were discussed with particular interest in the roles that educational institutions and professional societies play in the career of engineers.
Cluster Formation and Growth in Flow of Dilute Particle Suspension in Microchannels
Authors: Gudipaty Tarun , Cheung Luthur S. L. , Jiang Linan , Zohar Yitshak
Published: July 2009

Microchannels are susceptible to blockage by solid particles. The lifetime of microfluidic devices depends on their ability to maintain flow without interruption, while certain applications require microdevices for transport of liquids containing particles. In this work, the phenomenon of interest is the formation and growth of clusters in the flow of a dilute suspension of hard spheres. Based on the present experiments, aggregation of clusters was observed for particle-laden flow in a microchannel with particle void fraction as low as 0.001 and particle diameter to channel height ratio as low as 0.1. The incipience and growth of a single cluster is discussed, and the spatial distribution and time evolution of clusters along the microchannel is presented. Although the cluster size seems to be independent of location, higher number of clusters is found at the inlet/outlet regions than in the microchannel center. Similar to individual cluster, the total cluster area in the microchannel grows almost linearly in time. The effects of flow rate, particle size and concentration are also reported.
Effect of Fine Sediments on the Performance of Axial Pumps
Authors: Al-Ghamdi Abdullah Saeed
Published: July 2009

This study presents experimental work done to investigate the effect of fine sediment concentration on the performance of axial pumps. The pump was tested at three different motor speeds of 1000 rpm, 1150 rpm and 1350 rpm. At each motor speed, the pump was tested at three different sediment concentrations by weight of 0%, 2.485% and 8.10%. The sediment used in the investigation consists of a mixture of fine sand, silt and clay (16% fine sand, 38% silt and 46% clay). Results show that the efficiency of the axial pump is negatively influenced by the presence of fine sediments in the flow. As the sediment concentration increases to 8.10% the maximum reduction in axial pump’s efficiency for the range tested reached about 30% for motor speed of 1350 rpm and up to 40% for the lower motor speed of 1000 rpm. The reduction in the efficiency may be attributed to the change in the viscosity of the fluid that required higher torque (hence higher input power) to produce the same discharge. These results provide an evidence of a considerable reduction of axial pumps efficiency when used to pump water with fine sediment of silt and clay. However, further investigation is recommended for commercial size pumps and at different sediment concentrations and different composition of sediment.
Conversion Methods of Efficiency for Hydraulic Machinery Using Model Under Influence of Roughness
Authors: Li Long , Wang Ze , Yang Xuelin , Li Dan
Published: July 2009

The hydraulic efficiency conversion method of Moody formula based on H. Blasius friction coefficient formula for the “Hydraulically smooth zone” was analyzed. The method of model to prototype that involves the influence of the surface roughness of hydraulic machinery was advised. The conversion result was compared among the Haaland fomula, the Swamee-Jain formula, and the different proportion of hydraulic loss type. It was contrasted with the standard method. The difference of prototype efficiency is no bigger than 0.0025 in the prototype roughness 0.025mm range. The proposed computational method is provided with the same characteristics with the flowing zone, and possessed the clear physics significance, the simple computation process and the high conversion precision. It is satisfied with the efficiency conversion under the influence of the surface roughness.
Wall Normal Jet Produced by DBD Plasma Actuator With Doughnut-Shaped Electrode
Authors: Segawa Takehiko , Yoshida Hiro , Takekawa Shinya , Jukes Timothy , Choi Kwing-So
Published: July 2009

Properties of coaxial annular jets produced by a dielectric barrier discharge (DBD) plasma actuator with a doughnut shaped electrodes were investigated under atmospheric pressure and room temperature. The actuator consists of two circular electrodes sandwiching a thin dielectric layer. By applying 0 – ±3.3 kV between the electrodes at radio frequencies, the plasma jet is formed near the inner edge of the top electrode. The radial jet runs toward the center of the electrode and then impinges at the center to generate a wall normal annular jet. The evolution of the wall normal jet was observed precisely using particle image velocimetry (PIV) system. It was found that characteristic velocities increase in proportion to the bursting frequency and inversely proportional to the inner diameter of the electrode at the surging time of the voltage at 5.0 × 10−6sec.
The Effect of Annular Fluid Loss on Optimum Meridian Profile of Impeller and Guidevane
Authors: Tsugawa Takuji
Published: July 2009

In the previous paper, the optimum meridian profile of impeller and guidevane is able to obtain by blade-to-blade fluid loss calculated with diffusion factor. In this paper, considering the effect of annular fluid loss on optimum meridian profile of impeller and guidevane, the optimum profile is calculated by means of above method. The annular fluid loss is calculated by conventional annular friction loss coefficient. The effect of the annular friction loss coefficient on optimum meridian profile is mentioned in this paper. The annular fluid loss is caused by the meridian component of shearing stress of axisymmetric walls of hub and tip. In case of the component of tangential direction flow is large, in the calculation of annular fluid loss coefficient, the component of tangential direction flow is considered. The calculation of annular fluid loss has great influence on blade height of optimum impeller and guidevane meridian profile.
Decomposition of Hexahedral Block Topology to Generate Initial Tetrahedral Grids for Complex Configurations
Authors: Bahrainian Seyed Saied
Published: July 2009

Most three dimensional tetrahedral grid generators can refine an initial grid in matter of seconds. But making an initial tetrahedral grid for complex geometry can be a tedious and time consuming task. This paper describes a novel procedure for generation of starting tetrahedral cells using hexahedral block topology. Hexahedral blocks are arranged around an aerodynamic body to fill-up a computational flow domain. Each of the hexahedral blocks is then decomposed into six tetrahedral elements to obtain an initial tetrahedral grid around the same aerodynamic body. This resulted in an algorithm that enables users to produce starting tetrahedral grids for variety of aerodynamic configurations. To construct an initial starting tetrahedral grid suitable for computational flow simulations, representing a solid surface geometry (fuselage or a wing section) attached to a plane-of-symmetry, a topology containing at least 5 hexahedral blocks is required. This results in an initial starting grid consisting of 30 tetrahedral cells with 74 faces and 16 vertices, which is the same number of vertices as for the hexahedral blocks. Since the number of vertices and their coordinate locations are kept the same, a connectivity matrix can be produced to describe the forming faces of the tetrahedral grid. This procedure was performed for a single block, 5-block, and 9-block topologies to produce starting tetrahedral cells for numerous domain size and shapes.
Computational and PIV Analysis of the Fluid Flow in a Channel With an Oscillating Finned Surface
Authors: Olayiwola Bolaji O. , Schaldach Gerhard , Walzel Peter
Published: July 2009

Experimental and CFD studies were performed to investigate the kinematics of flow resulting from oscillation of a finned surface in a duct. The experiments were performed with working fluid with a kinematic viscosity of 1.8×10−6 m2/s. A steady flow Reynolds number in the laminar range of 0 < Re < 400 was studied. The oscillation Reynolds number Reosc was between the range of 50 and 1000. Oscillation amplitude range of 0.2 mm < A < 1.0 mm together with oscillation frequency in the range of 5 Hz < f < 90 Hz were employed. The acquired images were analysed using the particle image velocimetry (PIV) software. Three experimental conditions were studied, i.e. oscillating finned surface in a fluid at rest, steady finned flow and oscillating finned flow. CFD simulations were performed using the software suit CFX11 from ANSYS GmbH, Germany. The simulation results were compared with the PIV measurements using the time averaged velocity. The results of the visualization reveal periodic recirculation eddies around the fins which enhances the fluid mixing. The flow patterns and the crossflow effects depend on the geometries of the fins and the oscillation parameters. CFD results allow for performance predictions of different geometries and flow conditions. Enhanced heat transfer was obtained at moderate flow rates when applied in cooling system. Triangular finned geometry gives better performance.
Wave-Induced Effect on the Airside Velocity Field Above the Wind-Generated Water Waves
Authors: Shaikh Nasiruddin , Siddiqui Kamran
Published: July 2009

An experimental study was conducted to investigate the influence of surface waves on the airside flow behavior over the water surface. Two-dimensional velocity field in a plane perpendicular to the surface was measured using particle image velocimetry (PIV) at wind speeds of 3.7 and 4.4 m s−1. The results show that the wave induced velocities are significant immediately adjacent to the water surface and their magnitudes decreases with height and become negligible at a height three times the significant wave height. The structure of the wave induced vorticity indicates two different type of flow pattern on the windward and leeward sides of the wave crest. Positive and negative magnitudes of the turbulent and wave induced Reynolds stress respectively, indicates upward and down transfer of momentum flux across air water interface. The results also indicate that the flow dynamics in the region two to three times significant wave heights are significantly different than that at greater heights. Higher magnitudes of the turbulent and wave induced Reynolds stresses were observed in this region which could not be predicted from the measurements at greater heights. Thus, it is concluded the understanding of the wave effects to the airflow field especially within the crest-trough region is vital to improve our knowledge about the air-water heat, mass and momentum exchange.
A Continuum Model for Simulating Mine Water Inflow and Gas Emission
Authors: Adhikary D. P. , Guo H.
Published: July 2009

This paper describes a three-dimensional numerical model, called COSFLOW. It uses a Cosserat continuum approach for the efficient description of mechanical stress changes and deformation in weak layered rock, typical of coal measures. This mechanical model is coupled with a two-phase dual porosity fluid flow model to describe flow of water and gas through porous rock, desorption of gas from the matrix and subsequent flow of water and gas through the fracture network. The coupling includes simulation of permeability and porosity changes with rock deformation. Further the rock mass consisting of many interconnected fractures is idealized as an equivalent porous continuum using an equivalent anisotropic hydraulic conductivity matrix defined in terms of mean fracture spacing and mean aperture. This formulation is amenable to easy evaluation of modifications to the hydraulic conductivities as a function of stress induced changes in fracture aperture. The numerical code is used to simulate water inflow and gas emission in two Australian coal mines. The models at the two mine sites require significant geotechnical and hydrogeological data for adequate calibration. Many parameters in the model are not directly measurable and must be inferred by back-analysis of existing deformation, stress and hydrological data obtained during previous mining. The calibrated model is then used to make predictions for future mining panels. Water inflows at Mine A were predicted to increase significantly as mining progressed and this was supported by later measurements. This increase was attributed to wider longwall panels and increased roof rock permeability as more panels are mined. At Mine B, the model used measurements of gas production from predrainage boreholes for calibration and provided accurate predictions of average gas emissions into the longwall panel and post-drainage boreholes, although transient fluctuations were seen in the measurements. These were probably caused by local variations in geology or gas content or other factors not incorporated in the model.
An Instrument for Measuring Orifice-Specific Fuel-Injection Rate From a Multi-Orifice Nozzle
Authors: Kempenaar Jason G. , Mueller Charles J. , Shollenberger Kim A. , Lakshminarasimhan Krishna
Published: July 2009

Understanding fuel-injection processes is important for improving combustion in compression-ignition engines. To understand and model injection processes in detail, it is necessary to measure the instantaneous mass flow rate of fuel through each orifice of the injector nozzle. Due to constraints from injector design and operation, injection rate is typically measured downstream from the orifice exit. Measuring injection rate from a multi-orifice nozzle adds several geometric constraints, particularly when measuring fuel flow from a single orifice. The injection ratemeter discussed in this paper is designed to fit inside an optical research engine so that the injection rate can be measured without having to place the injector in an external fixture. The injection rate is calculated from a measurement of the momentum flux of a jet of fuel impinging upon the surface of a piezoelectric force (or pressure) transducer, combined with a measurement of the quantity of fuel injected, as demonstrated previously [1–3]. The ratemeter includes a thermal shield to limit the effects of temperature fluctuations on the transducer output. Data were acquired for one injector nozzle at several different injection durations and compared to results from literature for similar injector designs. Estimates for the uncertainty of the measured injection rates are provided and the calibration technique used is presented.
Effects of Endplates on Secondary Streaming of Oscillating Flows Past a Circular Cylinder
Authors: Hsu C. T. , Su Yan
Published: July 2009

The effects of parallel endplates on the secondary streaming of oscillating flows past a circular cylinder are studied by solving the Navier-Stokes equations numerically with Direct Numerical Simulation (DNS) method. A fractional-step scheme was implemented with the incorporation of the spectral method applied along the circumferential direction in solving a set of 2-D Poisson equations. The structure of the secondary streaming flows is presented with three-dimensional fluid particle traces (streak lines) and vorticity distributions. Unlike the traditional secondary streaming of two dimensional oscillating flows that exhibits 8 closed re-circulation zones (two in each quadrant), the mean secondary streaming flows in this study are three-dimensional without closed recirculation. The fluid particle traces show that there are three-dimensional spirals in each quadrant. Fluid particles near the endplates are attracted into the spirals toward the mid-plane of the two endplates. The trace trajectories in the flow domains never interest except at the stagnation points. The effects of cylinder aspect ratio, Keulegan-Carpenter number, and Stokes number on the secondary streaming patterns are also studied. The oscillatory drag and lift coefficients are also computed and discussed. The comparison of flow patterns obtained from this study with the results of experimental visualization shows qualitative agreement.
Numerical Simulation of Rayleigh-Taylor Instability With Two-Fluid Model and Interface Sharpening
Authors: Sˇtrubelj Luka , Tiselj Iztok
Published: July 2009

The free surface flows are successfully modeled with one of the existing free surface models, such as: level set method, volume of fluid method, front tracking method, two-fluid model (two momentum equations) with modified interphase force and some others. The main disadvantage of the two-fluid model used for simulations of free surface flows is numerical diffusion of the interface, which can be significantly reduced as presented in this paper. The interface is sharpened with the conservative level set method, where after the advection step of volume fraction the numerical diffusion of the interface is reduced in such a way that the thickness of the interface is kept constant during the simulation. The reduction of the interface diffusion can also be called interface sharpening. In the present paper the two-fluid model with interface sharpening is validated with Rayleigh-Taylor instability. Under assumptions of isothermal and incompressible flow of two immiscible fluids, we simulated a system with the fluid of higher density located above the fluid of smaller density in two dimensions. Due to the gravity in the system, the fluid with a higher density moves below the fluid with a smaller density. The initial condition is not a flat interface between the fluids, but a cosine wave with small amplitude, which develops into a mushroom-like structure. Mushroom-like structure in simulation of Rayleigh-Taylor instability later develops into small droplets as result of numerical dispersion of interface (interface sharpening) or to narrow trails with interface diffusion (no interface sharpening). The results of the two-fluid model with interface sharpening are compared to two-fluid model without interface sharpening and single-fluid-model with/without interface sharpening. The analytic solution of amplitude growth can be found for small amplitudes and was also compared to simulation.
Forced Convection in Cross Flow of Power Law Fluids Over a Pair of Circular Cylinder in Tandem Arrangement
Authors: Patil Rahul C. , Bharti Ram P. , Chhabra Raj P.
Published: July 2009

Forced convection heat transfer characteristics for the flow of incompressible power law fluids over a pair of cylinders (of equal diameters) in tandem arrangement have been studied numerically in the two-dimensional, steady cross-flow regime. The field equations have been solved using a finite volume method based solver (FLUENT 6.2) over the ranges of conditions as follows: power law index (n = 0.4, 1, 1.8), Reynolds number (Re = 1, 40), Prandtl number (Pr = 1, 100), the gap between the two cylinders (G = 2) and for two thermal boundary conditions, namely constant temperature or heat flux prescribed on the surface of the two cylinders. While the upstream cylinder shows heat transfer characteristics similar to that of an isolated cylinder, the downstream cylinder displays a complex dependence on the relevant dimensionless parameters. Both the wake interference and power-law rheology influence the heat transfer characteristics to varying extents. Generally, the upstream cylinder shows higher values of the average Nusselt number than the downstream cylinder. However, the average Nusselt number values for both cylinders are seen to be smaller than that for a single cylinder otherwise under identical conditions. With reference to Newtonian fluids, the shear-thinning behaviour promotes heat transfer whereas shear-thickening lowers it.
Drag Reduction for Blunt Body With Cross Flow by Extremum-Seeking Control
Authors: Kamagata Nobuhiko , Horio Susumu , Hishida Koichi
Published: July 2009

The active flow control, which can adapt to variation of flow velocity and/or direction, is an effective technique to achieve drag reduction. The present study has investigated a separated shear layer and established two control systems; the system reduces drag force and lift force by controlling the separated shear layer to reattachment for variation of flow velocity and /or direction. The adaptive control system to the variation of flow velocity was constructed by using a hot wire anemometer as a sensor to detect flow separation. The system to flow direction was constructed by using pressure transducers as a sensor to estimate drag force and lift force. The extremum-seeking control was introduced as a controller of the both systems. It is indicated from the experimental results that adaptive drag/lift control system to various flow velocity ranging from 3 to 7 m/s and various flow direction ranging from 0 to 30 deg. was established.
Basin-Scale Internal Waves Within the South Arm of the Great Salt Lake
Authors: Spall Robert E.
Published: July 2009

The Reynolds-averaged Navier-Stokes equations were solved to predict the internal basin-scale wave motion in the south arm of the Great Salt Lake. Forcing of the wave motion was through surface stresses induced by a spatially uniform but temporally varying wind distribution. The brine distribution was initialized as an upper layer with salinity 120 ppt over a deep brine layer of salinity 240 ppt. The simulations were run for one month periods with wind data (from the Salt Lake City International Airport) for the months March, April, May, and June 2006. Results indicate the existence of a Kelvin wave propagating counter-clockwise about the perimeter of the basin with period 24 hours.
Direct Numerical Simulation of 1000 Deformable Capsules in a Channel Flow at Finite Inertia
Authors: Doddi Sai K. , Kalluri R. Murthy , Bagchi Prosenjit
Published: July 2009

Three-dimensional numerical simulations are presented on the motion of large ensembles of deformable particles (up to 1096 in number) in a channel flow in presence of inertia. Particles are modeled as capsules, that is, liquid drops surrounded by hyperelastic membranes. Unlike liquid drops where the fluid-fluid interface is characterized by isotropic surface tension, that of a capsule is governed by more complex constitutive laws. Here we assume that the membrane follows the neo-Hookean constitutive law. The particle Reynolds number, based on the centerline velocity of the undisturbed flow, the undeformed particle diameter, and suspending fluid viscosity, is in the range 0.1 to 25. The particle volume fraction considered is 9 and 26%. The ratio of the particle diameter to channel height varies from 0.08 to 0.16. The numerical methodology is based on a mixed finite-difference/Fourier transform method for the flow solver and a finite-element based fluid-structure interaction, and front-tracking method. In the simulations, the flow field is resolved using up to 2883 grid points, and each particle surface is resolved by 1280 triangular elements. Instantaneous snapshots of particle distribution from the simulations are analyzed to study the interaction between the deformable particles in a multi-particle environment. Results are presented on the time-dependent and mean quantities such as particle velocity and trajectory, deformation and orientation, rms fluctuations in lateral velocity, location, and deformation. The simulations are computation- and data-intensive, and the first of their kind in the context of deformable particle suspension. The database generated from the simulations provides a wealth of information on the dynamics of semi-dense suspension of liquid capsules, in particular, and of deformable particles, in general.
Inlet Conditions for LES of Swirl Flows
Authors: Baba-Ahmadi Mohammad H. , Tabor Gavin R.
Published: July 2009

In this paper we present a novel technique for generating swirl inlets for Large Eddy Simulation (LES). The velocity a short distance downstream of the inlet to the main domain is sampled and the flow velocity data reintroduced back into the domain inlet, creating an inlet section integrated into the main domain where turbulence can develop. Additionally, variable artificial body forces and velocity corrections are imposed in this inlet section, with feedback control to force the flow towards desired swirl, mean and turbulent profiles. The method has been applied to swirling flow in a circular pipe and in an axisymmetric sudden expansion, and for the latter case compared against experimental and literature LES data, and against similar results in the literature. The method generates excellent results, and is elegant and straightforward to implement.