bluuebunny/crossref_metadata_2025 huggingface dataset:
Fifty Years of Fluidic Injection for Jet Noise Reduction
Authors: Henderson Brenda
Published: March 2010

The paper reviews 50 years of research investigating jet noise reduction through fluidic injection. Both aqueous and gaseous injection concepts for supersonic and subsonic jet exhausts are discussed. Aqueous injection reduces jet noise by reducing main jet temperature through evaporation and main jet velocity through momentum transfer between water droplets and the main jet. In the launch vehicle environment where large quantities of fluid do not have to be carried with the vehicle, water injection is very effective at reducing excess overpressures. For in-flight use, aqueous injection is problematic as most studies show that either large quantities of water or high injection pressures are required to achieve noise reduction. The most effective noise reduction injection systems require water pressures above 2000 kPa (290 psi) and water-to-main-jet mass flow rates above 10% to achieve overall sound pressure level reductions of roughly 6 dB in the peak jet noise direction. Injection at lower pressure (roughly 1034 kPa or 150 psi) has resulted in a 1.6 EPNdb reduction in effective perceived noise level. Gaseous injection reduces noise through jet plume modifications resulting from the introduction of streamwise vorticity in the main jet. In subsonic single-stream jets, air injection usually produces the largest overall sound pressure level reductions (roughly 2 dB) in the peak jet noise direction. In dual-stream jets, properly designed injection systems can reduce overall sound pressure levels and effective perceived noise levels but care must be taken to choose injector designs that limit sound pressure level increases at high frequencies. A reduction of 1.0 EPNdB has been achieved with injection into the fan and core streams. However, air injection into dual-stream subsonic jets has received little attention and the potential for noise reduction is uncertain at this time. For dual-stream supersonic jets, additional research needs to be conducted to determine if reductions can be achieved with injection pressures available from current aircraft engines.
Parametric Constructionist Kits: Physical Design and Delivery System for Rapid Prototyping Devices
Authors: Sass Lawrence
Published: March 2010

In this paper we illustrate a design methodology based on constructionist learning principles with CAD modeling and rapid prototyping. The belief is that a constructionist approach to design development extends design possibilities beyond the visual aspects of rendering and animation to building construction by way of component-based parametric modeling. This is demonstrated by way of construction kits as a proposed system of physical design production, individually and in groups. Results of the system are data sets for model manufacturing, hand assembly and design feedback. The impact of this work is to teach physical modeling as a system of production that will allow a designer hands-on learning of building structure, material mechanics and building component behavior. Also design success is newly defined as a relationship between the visual and physical evaluation; not just the visual. The paper ends with examples of complex design models generated from elements in the construction kit and a physical design grammar used to guide element assembly. Although the examples in this paper satisfy model making for building structures we believe this system can be useful for anyone who needs to construct physical artifacts beyond traditional scales found in rapid prototyping.
Solution of Some Systems of Nonlinear Partial Differential Equations by Variational Iteration Method
Authors: Darvishi Mohammad Taghi , Khani Farzad , Hamedi-Nezhad Somayeh
Published: March 2010

This paper applies the variational iteration method to solve two systems of nonlinear partial differential equations, numerically and/or analytically. Two examples are given to illustrate the accuracy and effectiveness of the method. Comparison with Adomian decomposition method reveals that the method is easier to be implemented.
Vortex-Speed Selection within the Rotating-Disk Boundary Layer
Authors: Garrett S. J.
Published: March 2010

A theoretical investigation into the vortex-speed selection within the rotating-disk boundary layer is conducted. Two methods are used which are different to previous investigations in the literature and enable analysis of a particular vortex speed with respect to the rotating surface. Using these methods (together with arguments based on critical Reynolds numbers, unstable parameter ranges and linear growth rates) it is hypothesised that crossflow modes travelling at around 75% of the disk surface are likely to be selected in applications where smooth, clean disks are used, for example in Chemical Vapour Deposition (CVD) reactors.
Parameter Identification for a Low-Order Network Model of Combustion Instabilities
Authors: Niederberger André S.P. , Schuermans Bruno B.H. , Guzzella Lino
Published: March 2010

This paper describes the identification and modeling of a test rig designed to study thermoacoustic instabilities. Various operating conditions with different flame structures are identified. Physics-based models are used in a network model in order to advance the understanding of the phenomena involved. The parameters identified of the flame correlate well with the observed flame shapes. The transfer function from a loudspeaker input to a pressure reading is assembled and compared to measurements. Reflection coefficients are introduced to study the amplifying frequency ranges of the flame, which correspond to the highest peaks in the pressure spectrum.
Development of Optical Measurement Techniques for Thermo-Acoustic Diagnostics: Fibre-Optic Microphone, Rayleigh-Scattering, and Acoustic PIV
Authors: Konle H. , Rausch A. , Fischer A. , Doll U. , Willert C. E. , Paschereit C. O. , Röhle I.
Published: March 2010

Thermo-acoustic investigations require reliable measurement techniques in hot environments for pressure, density fluctuations with a high dynamic range and acoustic particle velocity. This paper presents recent developments of optical measurement techniques in combustion diagnostics. A fibre-optic microphone based on the interferometric detection of membrane deflections was designed to measure acoustic pressure oscillations. Due to the heat resistant design, the sensor has an upper temperature limitation of approximately 970 K. Rayleigh-Scattering measurements, using the density dependent intensity of scattered light were performed in an unconfined flame with approximately 1600 K to study amplitude and phase distribution of the flame pulsation. Acoustic particle velocity can be determined applying acoustic PIV (particle image velocimetry) technique. This paper shows a way to measure simultaneously the acoustic particle velocity and the locally resolved mean flow velocity of a turbulent flow. Together these non-invasive techniques are applicable to study thermo-acoustic processes and sound generation in combustion chambers or turbines.
Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships
Authors: Aggarwal Suresh K.
Published: March 2010

In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs) subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H2, which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter VR, defined as the ratio of coflow velocity to jet velocity. For VR ≤ 1 (low coflow velocity regime), the structures of both 0- and 1-g flames are strongly sensitive to changes in VR, while they are only mildly affected by coflow in the high coflow velocity regime (VR > 1). In addition, the spatio-temporal characteristics of the 0- and 1-g flames are markedly different in the first regime, but are essentially similar in the second regime. A more significant difference in the first regime between these flames is the presence of a flow instability that manifests itself through the self-excited oscillations of the 1-g flame and the concomitant flickering of the nonpremixed reaction zone. For VR ≤ 1, as the coflow velocity is increased, the oscillation amplitude decreases and the oscillation frequency increases, both of which are in accord with previous experimental and computational results concerning 1-g jet diffusion flames. The modified conserved scalar approach is found to be effective in characterizing the flame structure and developing state relationships for both steady and unsteady partially premixed flames. This is demonstrated by the fact that the temperature as well as the major and minor species profiles follow similar state relationships in terms of the modified mixture fraction for the 0- and 1-g flames, even though these flames have markedly different spatio-temporal characteristics.
Propagation of a Spherical Flame through a Polydisperse Fuel Spray
Authors: Greenberg J. Barry
Published: March 2010

A new evolution equation is derived for a laminar flame front propagating into air and a polydisperse liquid fuel spray cloud. The asymptotic analysis employed for developing the equation exploits the usual inverse large activation energy parameter associated with chemical reaction in the flame. It is demonstrated that the droplet size distribution in the fuel cloud can be critical in determining whether propagation or extinction of the flame front occurs, even for different size distributions initially having the same Sauter Mean Diameter (SMD).
Performance of a Hopping Rotochute
Authors: Beyer Eric , Costello Mark
Published: March 2010

A hybrid micro air/ground vehicle has been developed and is specifically tailored to explore interior spaces with complex terrain. The vehicle, called the hopping rotochute, maneuvers through intricate environments by hopping over or through impeding obstacles. A small coaxial rotor system provides the necessary lift while a moveable internal mass allows directional control. In addition, the low mass center and egg-like exterior shape of the body creates a means to passively reorient the vehicle to an upright attitude when in contact with the ground while protecting the rotating components. This paper examines basic flight performance of the device obtained through a validated simulation. Key parameters such as system weight, rotor speed, internal mass weight and location, as well as battery capacity are varied to explore air vehicle performance characteristics such as single hop height and range, number of hops, and total achievable range. In general, the total achievable range is increased as the internal mass weight, internal mass offset, and battery capacity are increased. For a given system, an optimum rotor speed and pulse width results in the maximum achievable total range for a single battery charge. The sensitivity of the hopping rotochute to atmospheric winds is also investigated and the ability of the device to perform trajectory shaping is shown.
Force Measurements and Flow Visualization for a Flexible Flapping Wing Mechanism
Authors: Massey Kevin , Flick Ashley , Jadhav Gautam
Published: March 2010

This paper describes a series of experiments using a flapping wing mechanism. Force measurements were combined with high speed photography for two sets of flexible wings. The aerodynamic forces generated by flexible membrane type wings were measured using a two degree of freedom force balance constructed during the course of these experiments which measured the aerodynamic forces of lift and thrust. Lift and thrust measurements were acquired as the mechanism flapped the flexible wings for multiple cases, and the two most interesting conditions were explored in more detail. These two conditions consisted of a zero velocity free stream condition and a forward flight condition of 5 m/s. For these two conditions, high-speed video of the flapping wing was taken. The images from the video were also correlated with cycle averaged aerodynamic forces produced by the mechanism. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles. In addition, flow visualization images were taken of the flapping wing under forward flight condition and flow field velocity vectors were calculated.
Aerodynamic Experiments on DelFly II: Unsteady Lift Enhancement
Authors: De Clercq Kristien M.E. , de Kat Roeland , Remes Bart , van Oudheusden Bas W. , Bijl Hester
Published: March 2010

Particle image velocimetry measurements and simultaneous force measurements have been performed on the DelFly II flapping-wing MAV, to investigate the flow-field behavior and the aerodynamic forces generated. For flapping wing motion it is expected that both the clap and peel mechanism and the occurrence of a leading edge vortex during the translational phase play an important role in unsteady lift generation. Furthermore, the flexibility of the wing foil is also considered of primary relevance. The PIV analysis shows a strong influx between the wings during the peel but no downward expelling jet during the clap. The force measurements reveal that the peel, oppositely to the clap, contributes significantly to the lift. The PIV visualization suggests the occurrence of a leading edge vortex during the first half of the in- and outstroke, which is supported by a simultaneous augmentation in lift. The early generation of a leading edge vortex during the flex cannot be assessed from the PIV images due to optical obstruction, but is likely to appear since the wing flexing is accompanied with a large increase in lift.
Optical Flow for Heading Estimation of a Quadrotor Helicopter
Authors: Stowers John , Bainbridge-Smith Andrew , Hayes Michael , Mills Steven
Published: March 2010

This paper demonstrates that computer vision techniques can estimate the heading of a small fixed pitch four rotor helicopter. Heading estimates are computed using the optical flow technique of phase correlation on images captured using a down facing camera. The camera is fitted with an omnidirectional lens and the images are transformed into the log-polar domain before the main computational step. The vision algorithm runs at 10 Hz on a single board computer (SBC) mounted aboard the craft. Experimental performance of this system is compared with results obtained from a traditional inertial measurement unit (IMU). It is found that the yaw rate computed from the optical flow is comparable to the IMU and thus appropriate for use in controlling the helicopter.
Towards a Long Endurance MAV
Authors: Bronz Murat , Moschetta Jean Marc , Brisset Pascal , Gorraz Michel
Published: March 2010

A conceptual design and performance analysis method (Long Endurance Conceptual Design Program) for long-endurance mini-micro UAVs is presented. Recent long endurance oriented results and achievements are looked through for possible usage for mini-micro scale. A real mission is also explained, whose objective is to accomplish a 200 km straight line flight autonomously with the smallest electric platform possible. Design phases of the platform by using the presented method, flight tests and comparison of the results are included. On the following section a design study for long-endurance MAVs using a hybrid energy system combining solar energy and Lithium batteries and the effect of size and cruise speed are investigated. We demonstrate that under a certain size, the use of solar energy becomes not useful at all. We conclude with the study of a candidate design for EMAV09 Endurance Mission in the light of the rules and scoring of the mission.
Business Model Innovation The Strategy of Business Breakthroughs
Authors: Morris Langdon
Published: March 2010

While a commonly-held mental image suggests that big corporations live very long lives, the reverse is actually true quite often, and the lifespan of companies is decreasing as the rate of change increases. The situation of accelerating change places ever greater challenges before each and every company, and while innovation is obviously a response to this dilemma, it turns out that not all types of innovation are equally valuable. Business model innovation, the subject of this paper, has proven to a tremendous source of competitive advantage. This paper examines many dimensions of business model innovation, focusing particularly on the relationship between a company and its customers, and the methods that companies use to grasp the bigger picture, or whole system perspective, that enables them to understand how their enterprise relates to the larger industry and broader economy in which it operates.
Numerical Study of Particle Interaction in Gas-Particle and Liquid-Particle Flows: Part II Particle Response
Authors: Mohanarangam K. , Tu J. Y.
Published: March 2010

In this paper the numerical model, which was presented in the first paper (Mohanarangam & Tu; 2009) of this series of study, is employed to study the different particle responses under the influence of two carrier phases namely the gas and the liquid. The numerical model takes into consideration the turbulent behaviour of both the carrier and the dispersed phases, with additional equations to take into account the combined fluid particle behaviour, thereby effecting a two-way coupling. The first paper in this series showed the distinct difference in particulate response both at the mean as well as at the turbulent level for two varied carrier phases. In this paper further investigation has been carried out over a broad range of particle Stokes number to further understand their behaviour in turbulent environments. In order to carry out this prognostic study, the backward facing step geometry of Fessler and Eaton (1999) has been adopted, while the inlet conditions for the carrier as well as the particle phases correspond to that of the experiments of Founti and Klipfel (1998). It is observed that at the mean velocity level the particulate velocities increased with a subsequent increase in the Stokes number for both the GP (Gas-Particle) as well as the LP (Liquid-Particle) flow. It was also observed that across the Stokes number there was a steady increase in the particulate turbulence for the GP flows with successive increase in Stokes number. However, for the LP flows, the magnitude of the increase in the particulate turbulence across the increasing of Stokes number is not as characteristic as the GP flow. Across the same sections for LP flows the majority of the trend shows a decrease after which they remain more or less a constant.
Wear Prediction in Fully Developed Multi-Size Particulate Flow in Horizontal Pipelines
Authors: Pagalthivarthi K. V. , Ravichandra J. S. , Sanghi S. , Gupta P. K.
Published: March 2010

Erosion wear prediction in fully developed multi-size particulate flow through horizontal pipes is carried out numerically using Galerkin finite element methodology. The predicted multi-size particulate flow field near the pipe wall is correlated with wear rates via empirically determined wear coefficients. The wear models for particle impact and sliding take into account the broad particle size distribution. The effects of various operating parameters such as flow rate, solids concentration, solids density, particle size, particle size distribution and so forth has been studied. Normalized predicted wear rates are compared with published experimental results and are found to be within an average error of 16.5% with respect to experimental observations. Different wear trends with different flow parameters indicate the existence of a very complex relationship between wear rate and the flow governing parameters. A major conclusion is that accurate wear prediction could be obtained by characterizing the particle size distribution into suitable number of size classes, and accounting for the particle-size dependence in the wear model(s).
Computational Investigation of Flow Fields and Erosion in a Dimpled Channel
Authors: Alhajeri M. H. , Alhajeri H. Alhamad
Published: March 2010

A numerical prediction of flow in a dimpled channel is reported. The flow regimes considered cover a wide range of Reynolds numbers, which range from 380 to 99000 and which are equivalent to a range of inlet velocities from very low (0.072 m/s) to very high (60 m/s). In this study, calculations were made using the standard k-e model with standard wall function. The drag coefficient, skin friction drag, pressure drag, and pressure distribution around a dimple were investigated. As the velocity increased, the drag coefficient decreased until the velocity exceeded 45 m/s, after which it increased. Furthermore, the pressure drag and skin friction drag depend on the velocity.

Particles with a density of 2440 kg/m3 and a diameter of 100 microns were tracked through the domain to estimate the frequency, velocity, and angle of impact of the particles and to estimate the resulting erosion rate. It was found that the maximum erosion rate occurred between 40 and 65 degrees from the leading edge of the dimple. Furthermore, a computational study of the flow fields of three dimples in an in-line arrangement is presented. This study showed that similar flow behaviours exist between the first and second dimples and that the flow behaviours are identical between the second and third cylindrical dimples.
Comparison of Experimental and Numerical Two-Phase Flows in a Porous Micro-Model
Authors: Crandall Dustin , Ahmadi Goodarz , Smith Duane H.
Published: March 2010

Characterizing two-phase flow in porous media is important to provide estimates of sweep efficiency in enhanced oil recovery and storage estimates in potential geological CO2 sequestration repositories. To further the current understanding of two-phase flow in porous media a micro-model of interconnected channels was designed and fabricated using stereolithography to experimentally study gas-liquid flows. This flowcell was created with a wide variability of throat dimensions to represent naturally occurring porous media. Low flow rate experiments of immiscible two-phase drainage were performed within this cell. Additionally, a computational model for analyzing two-phase flows in the same flowcell was developed and used to simulate conditions not possible with our laboratory settings. The computational model was first tested for the identical conditions used in the experimental studies, and was shown to be in good agreement with the experimentally determined fractal dimension of the invading gas structure, time until breakthrough, and fluid saturation. The numerical model was then used to study two-phase air-water flows in flowcells with the same geometry and different gas-liquid-solid contact angles. The percent saturation of air and the motion of the fluids through the cell were found to vary with changes in these parameters. Finally, to simulate flows expected during geologic carbon sequestration, the fluid properties and interface conditions were set to model the flow of CO2 into a brine-saturated porous medium at representative subsurface conditions. The CO2 flows were shown to have larger gas saturations than the previous air into water studies. Thus the accuracy of the computational model was supported by the flowcell experiments, and the computational model extended the laboratory results to conditions not possible with the apparatus used in the experiments.
The Innovation Infrastructure
Authors: Morris Langdon
Published: March 2010

In a world of progressively more difficult business conditions, the capacity to innovate remains one of the most important attributes of all organizations. It's not, however, particularly easy to do. The quest for innovation is supported through a focus on learning, and particularly
when learning is applied to increasing the productivity of knowledge tasks. To support this process, there are elements of infrastructure that are particularly important to develop, which include adoption of effective innovation methodology, as well as robust collaboration, attention to eliminating
obstacles and enhancing the enablers of innovation, and providing effective work environments.
Democratizing Innovation: The Evolving Phenomenon of User Innovation
Authors: von Hippel Eric
Published: March 2010

Almost 30 years ago, researchers began a systematic study of innovation by end users and user firms. At that time, the phenomenon was generally regarded as a minor oddity. Today, it is clear that user-centered innovation is a very powerful and general phenomenon. It is rapidly growing
due to continuing advances in computing and communication technologies. It is becoming both an important rival to and an important feedstock for manufacturer-centered innovation in many fields. In this article, I provide an overview of what the international research community now understands
about user-centered innovation.
Building New Knowledge and the Role of Synthesis in Innovation
Authors: Burnett Bill
Published: March 2010

We innovate to create competitive advantage. Competitive advantage is found in new knowledge, which solves the buyer's problem. Humans create new knowledge in three ways: through Discovery - stumbling upon something that solves a problem; through Experimentation - trying
different approaches to a problem until the solution is found; and through Synthesis - combining existing knowledge to create new knowledge. Today, Synthesis is the most common way we solve problems. Everyone synthesizes, but some people are extraordinarily good at it. They see the big
picture, and how all the pieces fit together. Their brains have the ability to reach great mental distances to find remote metaphors which presents knowledge that turns into great solutions. Mixing your experts with people who are novice super-synthesizers can create best in class solutions
and give a company a sustainable competitive advantage.
The Innovation Iteration Grid
Authors: Trusko Brett
Published: March 2010

A common misconception about innovation is that the innovation process lacks pragmatism. Innovation professionals use soft concepts applied in fuzzy ways with too much emphasis on unproven approaches to solving problems. Perhaps because of the unconventional approaches taken by practitioners
of innovation, business executives have generally segregated innovators from main stream operations, recognizing the importance of innovation, but not comfortable with the approach that innovation professionals often employ in getting to their ends. This paper discusses an approach to innovation
that has the ability to firmly tie the strategy, mission or vision of the organization to the innovation process. An approach that allows you to take the “Universal Intentions” (mission, vision, goals objectives or strategies) to an iterative process that allows innovation iteration
to optimization of a process.
Computational Modelling of Gas-Particle Flows with Different Particle Morphology in the Human Nasal Cavity
Authors: Inthavong Kiao , Tu Jiyuan , Ahmadi Goodarz
Published: March 2010

This paper summarises current studies related to numerical gas-particle flows in the human nasal cavity. Of interest are the numerical modelling requirements to consider the effects of particle morphology for a variety of particle shapes and sizes such as very small particles sizes (nanoparticles), elongated shapes (asbestos fibres), rough shapes (pollen), and porous light density particles (drug particles) are considered. It was shown that important physical phenomena needed to be addressed for different particle characteristics. This included the Brownian diffusion for submicron particles. Computational results for the nasal capture efficiency for nano-particles and various breathing rates in the laminar regime were found to correlate well with the ratio of particle diffusivity to the breathing rate. For micron particles, particle inertia is the most significant property and the need to use sufficient drag laws is important. Drag correlations for fibrous and rough surfaced particles were investigated to enable particle tracking. Based on the simulated results, semi-empirical correlations for particle deposition were fitted in terms of Peclet number and inertial parameter for nanoparticles and micron particles respectively.
Modelling of Break-up and Coalescence in Bubbly Two-Phase Flows
Authors: Lo Simon , Zhang Dongsheng
Published: March 2010

Numerical simulations of gas-liquid two-phase flow with high superficial velocity in a vertical pipe were conducted with the use of the commercial software package STAR-CD 3.27. The change in bubble size due to breakup and coalescence was modelled by the Sγ model. The applicability and performance of the Sγ model in modelling of gasliquid bubbly flow were studied. The sensitivity of the Sγ model to the distribution moment γ, and the drainage mode were investigated. The numerical results were compared with the experimental data of Hibiki et al., (2001). Good agreement was achieved for axial velocities and void fraction for all tested cases. It was found in this work that the Sγ model is capable of predicting with reasonable accuracy the bubble size and its distribution even in high void fraction. Except in the near wall region, the simulated bubble size and therefore the interfacial area density fit well with the experiment measurements. It was observed that the predicted bubble size and interfacial area density obtained from both the S0 and S2 models are more or less the same, indicating that the numerical results are independent of the distribution moment γ. It was further found that, the drainage mode greatly affects the bubble size: an increase in mobility of the bubble surface enhances the coalescence and leads to an over-prediction of the bubble size in the pipe centre. The bubble size increases with the increase of the gas phase superficial velocity while the variation of the interfacial area density is smaller as it is a combined function of the bubble size and local gas hold-up.
Estimation of Extreme Water Levels Due to Cyclonic Storms: A Case Study for Kalpakkam Coast
Authors: Rao A.D. , Jain Indu , Venkatesan R.
Published: March 2010

Numerical ocean models are considered today as an essential tool to predict spurt in the sea level rise and associated inland extent of flooding that could be generated by a cyclonic storm crossing any coastal stretch. For this purpose, the advanced two-dimensional depth-integrated (ADCIRC-2DDI) circulation model based on finite-element formulation is applied for the simulation of surges and associated water levels off Kalpakkam coast. Using the long term inventory of cyclone database, synthesized tracks are deduced for affected coastal districts of Tamil Nadu, a state bordering the Bay of Bengal encompassing the Kalpakkam region. Return periods are also computed for the intensity and frequency of cyclones at each coastal district of Tamil Nadu. Using the ADCIRC-2DDI model, validation of surges and associated water levels generated by the November 2000 cyclone, which had landfall near Pondicherry coast was initially carried out. The simulation exercise exhibits a good agreement with available observations from post-storm survey reports. Considering the importance of Kalpakkam region, extreme water levels are computed based on a 50-year return period data, for the generation of storm surges, associated water levels and extent of inland inundation. Based on experimental evidence, it is advocated that this region could be inundated from produced water levels when pressure deficit exceeds a threshold value of 66hPa. Also it is noticed that the horizontal extent of inland inundation ranges between 1–1.5 km associated with the peak surge.
Extreme Air-Gap Response below Deck of Floating Structures
Authors: Li Jing , Huang Zhenhua , Tan Soon Keat
Published: March 2010

This paper presents the findings of a study on the air gap below deck of a typical six-column, double-pontoon semi-submersible in deep water. The writers present a method to predict the extreme air-gap by establishing the distribution of extreme air-gap response. In the case of linear incident wave, the proposed air-gap distribution suggested a better fits compared with that given by Rayleigh distribution. Moreover, the proposed approach is found to be an effective way to predict air-gap extremes within a specified duration. As a comparison, the fractile-based method cum Gumbel distribution is also applied to the same floating structure. Comparisons of the numerical results from these 2 different approaches show strong agreement in extreme air-gap response below deck.
Genetic Programming for Sea Level Predictions in an Island Environment
Authors: Ghorbani M.A. , Makarynskyy O. , Shiri J. , Makarynska D.
Published: March 2010

Accurate predictions of sea-level are important for geodetic applications, navigation, coastal, industrial and tourist activities. In the current work, the Genetic Programming (GP) and artificial neural networks (ANNs) were applied to forecast half-daily and daily sea-level variations from 12 hours to 5 days ahead. The measurements at the Cocos (Keeling) Islands in the Indian Ocean were used for training and testing of the employed artificial intelligence techniques. A comparison was performed of the predictions from the GP model and the ANN simulations. Based on the comparison outcomes, it was found that the Genetic Programming approach can be successfully employed in forecasting of sea level variations.
Enhancement of a Turbulence Sub-Model for More Accurate Predictions of Vertical Stratifications in 3D Coastal and Estuarine Modeling
Authors: Huang Wenrui
Published: March 2010

This paper presents an improvement of the Mellor and Yamada's 2nd order turbulence model in the Princeton Ocean Model (POM) for better predictions of vertical stratifications of salinity in estuaries. The model was evaluated in the strongly stratified estuary, Apalachicola River, Florida, USA. The three-dimensional hydrodynamic model was applied to study the stratified flow and salinity intrusion in the estuary in response to tide, wind, and buoyancy forces. Model tests indicate that model predictions over estimate the stratification when using the default turbulent parameters. Analytic studies of density-induced and wind-induced flows indicate that accurate estimation of vertical eddy viscosity plays an important role in describing vertical profiles. Initial model revision experiments show that the traditional approach of modifying empirical constants in the turbulence model leads to numerical instability. In order to improve the performance of the turbulence model while maintaining numerical stability, a stratification factor was introduced to allow adjustment of the vertical turbulent eddy viscosity and diffusivity. Sensitivity studies indicate that the stratification factor, ranging from 1.0 to 1.2, does not cause numerical instability in Apalachicola River. Model simulations show that increasing the turbulent eddy viscosity by a stratification factor of 1.12 results in an optimal agreement between model predictions and observations in the case study presented in this study. Using the proposed stratification factor provides a useful way for coastal modelers to improve the turbulence model performance in predicting vertical turbulent mixing in stratified estuaries and coastal waters.
Identification of Swell in Nearshore Surface Wave Energy Spectra
Authors: Work Paul A. , Srisuwan Chatchawin
Published: March 2010

An approach for routine identification of swell and sea in nominally fully developed, omnidirectional, surface water wave energy spectra measured in arbitrary water depth is developed, applied, and discussed. The methodology is an extension of earlier work with deepwater spectra and involves identifying the frequency at which wave steepness is maximized and relating this to the swell separation frequency. The TMA parameterized spectrum is employed to establish a relationship between the two frequencies so that the methodology can be used when wind data are unavailable. The methodology is developed for finite water depth and tested using a dataset that includes both acoustic Doppler current profiler and wave buoy data, recorded simultaneously at the same location. For cases where the sea and swell are clearly, visually distinguishable in the omnidirectional spectra, the new method accurately distinguishes between the two, but it can also be used to identify sea and swell in unimodal spectra.
Deglaciation-Induced Spatially Variable Sea Level Change: A Simple-Model Case Study for the Greenland and Antarctic Ice Sheets
Authors: Kuhn M. , Featherstone W.E. , Makarynskyy O. , Keller W.
Published: March 2010

Some studies on deglaciation-induced sea level change provide only a global average change, thus neglecting the fact that sea level change is spatially variable. This is due mainly to the gravitational and visco-elastic feedback effects of the changing surface mass loads. In order to address this apparent misconception and raise further awareness, we provide a conceptual example based on a simulated total melt of the Greenland and Antarctic ice sheets. This would give a global average sea level change of about 64 m. However, due to the changed distribution of gravitating masses, the sea-level change depends on location, with a range of about −27 m to +79 m (i.e., sea-level will even fall in some places). This spatial dependency has several implications, such as >10% biases in global average sea-level change estimates based only on tide-gauge records, flooding of almost 10% of current land areas, an increase of the length of day by almost a half a second and a northward move of the centre of mass (geocentre) by about 20 m.
Critical Assessment of Downscaling Procedures in Climate Change Impact Models
Authors: Şen Zekâi
Published: March 2010

General Circulation (Climate) Models (GCMs) from different research centers of the world provide future replicates of various meteorological variables up to years 2100 at rather coarse mesh nodes of about 250 km apart from each other. These models are based on the physically dynamic equations of energy, momentum and mass conservation in addition to the state equation of gases. Hence, an arena of equations requires simultaneous solution by considering global initial and boundary conditions. It is necessary to downscale the GCM results at coarse nodes to locally smaller scales so as to match the historical data sequences to scenario series. Such downscaling procedures are necessary for climate change impact effect assessments including vulnerability, mitigation and adaptation works at finer scales. Various methods have been suggested so far in the literature for downscaling and still new ones are expected to come in the future. It is the main purpose of this paper to provide the critical review of available methods and then to suggest a regional dependence function based on the point cumulative semivariogram technique.
Influence of Particle Shape on Drag Coefficient for Commonly Occuring Sandy Particles in Coastal Areas
Authors: Arora Chitra , Kumar B. Prasad , Narayana A.C.
Published: March 2010

A well defined relationship connecting settling velocity with sediment geometry and ambient properties is an essential pre-requisite for coastal and hydraulic engineering studies. An established relationship for settling velocity of sandy particles assuming spherical shape geometry is available in the literature. In reality, the sediment particles need not be spherical at all times, which influences settling velocity that is strongly biased to the drag coefficient. Based on quantitative comparison with measured data collected at Oahu Islands located in the Hawaiian archipelago, USA this work provides a relationship between drag coefficient and particle shape factor for sand grains viz; sand, sandy loam and fine sandy loam typically found in coastal environment (typical size ranges from 0.05 to 2.0 mm). The particle Reynolds number and shape factor are evaluated for each grain. The drag coefficient evaluated as function of nominal diameter and Reynolds number show a positive correlation over a wide range of shape factors used in this study. A comprehensive correlation has been developed of the drag coefficient for non-spherical particles as a function of Reynolds number and particle shape. Further a regression analysis was performed on the functional dependence of drag coefficient on particle shape. Based on this study, it could be advocated the validity of Krumbien shape factor holds well for the above characterized grain size and various particle shapes considered. Hence, the settling velocity of particles has a functional dependence on estimated drag coefficient with important implications for modeling sediment transport and swash zone hydrodynamics.
Analysis of Breast Thermography Using Fractal Dimension to Establish Possible Difference between Malignant and Benign Patterns
Authors: Etehad Tavakol Mahnaz , Lucas Caro , Sadri Saeed , Ng E. Y. K.
Published: March 2010

Early detection of breast cancer by means of thermal imaging has a long and extremely controversial history. Recently, the availability of highly sensitive infrared (IR) cameras which can produce high‐resolution diagnostic images of the temperature and vascular changes of breasts, as well as a better knowledge of advanced image processing techniques, has generated a renewed interest. The objective of this study is to investigate fractal analysis of breast thermal images and to develop an algorithm for detecting benignity and malignancy of breast diseases. The study is based on IR images captured by thermal camera, in which the resolution of the results is within the state of the art of IR camera. A total of 7 malignant cases and 8 benign cases have been considered. The breast images were first segmented by fuzzy c‐means clustering. Then the first hottest regions for each image were identified and the fractal dimension of those regions was computed. It is shown that the fractal dimension results significantly differ between malignant and benign patterns, suggesting that fractal analysis may potentially improve the reliability of thermography in breast tumor detection.
Reengineering the Cardiac Catheterization Lab Processes: A Lean Approach
Authors: Raghavan Venkatesh , Venkatadri Vikram , Kesavakumaran Varun , Wang Shengyong , Khasawneh Mohammad , Srihari Krishnaswami
Published: March 2010

This paper presents a cross‐functional effort in a US community hospital for an overall process improvement in its Cardiac Catheterization Lab (CCL). One of the key system performance metrics identified was the patient turnaround time. The objective of this study was to identify the sources of delays in the system that lead to prolonged patient turnaround time using a structured lean approach. A set of qualitative recommendations were proposed and implemented. Quantification of some of these recommendations and certain additional ‘what‐if’ scenarios were evaluated using Discrete Event Simulation (DES). The simulation results showed that significant reduction in patient turnaround time could be achieved if the proposed recommendations were implemented. This study demonstrated the benefits of adopting the lean philosophy in the continuous process improvement journey in the healthcare delivery arena.
An Experimental and Numerical Study on the Behavior of High Strength Concrete Columns in Fire Subjected to High Restraint
Authors: Ali Faris , Nadjai Ali , Choi S.
Published: March 2010

The first part of this paper represents the results of an experimental research executed on 42 high strength concrete columns. The parametric study investigated high strength concrete columns under 3 loading levels 0.2, 0.4 and 0.6 subjected to high degree of axial restraint = 0.2 and exposed to two heating rates with a special attention directed to explosive spalling. The second part of the paper represents a three-dimensional finite element model of the reinforced concrete columns taking into account exposure to high temperatures. The effects of tension softening is included in the model and based on Hordijik, Cornelissen and Rienhardt curve. The concrete columns were modeled taking into account the embedded reinforcement and cracks formation and propagation using smeared cracks model which allowed a non-linear transient structural analysis to be conducted. The comparison of the results of the FE and the performed tests showed a reasonable agreement and a divergence in some cases due to concrete spalling. An assessment of the stresses generated in the high strength concrete columns under fire using the FEM model is also presented in the paper. The experimental and the FEM study showed that imposing axial restraint against concrete columns expansion may reduce explosive spalling of concrete during fire.
Thermo-Structural Analysis of an Open Section Cold-Formed Steel Beam in Contact with a Concrete Slab and a Masonry Wall in Fire Situation
Authors: Almeida Saulo , Rigobello Ronaldo , Neto Jorge , Silva Valdir
Published: March 2010

This work presents the results of numerical analyses, both thermal and structural, of a pinned-pinned open cross section of a "U-shaped" cold-formed steel beam in a fire situation. The beam was in physical contact with a concrete slab and a masonry wall. The eventual partial compartmentalisation due to the wall was disregarded. The field of temperatures for the steel-concrete-wall elements was determined using the software programs Super Tempcalc and Ansys. For structural analysis the software Ansys was used. Restrictions due to the lateral displacement, the compatibility of transversal displacements at the points of contact between the slab and the beam, local buckling and restrictions to the thermal strains at the end supports were taken into account. Material and geometrical nonlinearities were considered, as well as the variation of the stressstrain diagrams with temperature, according to Eurocode prescriptions. The variation of the resistance reducer with the time of fire exposure was also evaluated. Based on the adopted model, the structure under standard fire exposure is not adequately safe. More research is under development to consider compartmentalisation and natural fire.
Axially Loaded Stainless Steel Columns in Case of Fire
Authors: Lopes Nuno , Real Paulo , da Silva Luís , Franssen Jean-Marc
Published: March 2010

The simple model of Eurocode 3, for the fire resistance evaluation of stainless steel members, are based on the procedures used for carbon steel structural elements. However, due to the existing differences in the constitutive laws of these two materials, it is expected that it would not be possible to use, in both materials, the same formulae for the member stability calculation, as proposed in Eurocode 3. This paper aims at increasing the knowledge on the behaviour of stainless steel axially loaded columns at elevated temperatures. For this purpose, a geometrical and material non linear computer code has been used to determine the buckling load of these elements. The Eurocode formulae are evaluated and a new proposal, that ensures accurate and conservative results when compared with the numerical simulations, is presented.