bluuebunny/crossref_metadata_2025 huggingface dataset:
On Using Fast Response Pressure Sensors in Aerodynamic Probes to Measure Total Temperature and Entropy Generation in Turbomachinery Blade Rows
Authors: Mersinligil Mehmet , Brouckaert Jean-François , Courtiade Nicolas , Ottavy Xavier
Published: July 2013

This contribution addresses the possibility of exploiting the temperature dependency of piezoresistive sensors as a temperature measurement per se. This requires the characterization of the sensor, or the probe as a temperature probe, i.e. determination of the recovery factor between the sensor temperature and the flow temperature. This temperature calibration as well as the determination of the thermal response time was performed for two probe geometries: a high temperature flush-mounted and a low temperature sub-surface mounted single sensor total pressure probe, both with a probe head diameter of 2.5 mm.

Two applications are reported. The first application was performed with the flush-mounted sensor probe in the high-speed 3 1/2-stage axial compressor CREATE tested in the 2 MW test rig of LMFA at École Centrale de Lyon, in France. The probes were traversed at each inter-row section up to temperatures of 180°C and an absolute pressure of 3 bar. The second application was performed with the sub-surface mounted sensor probe in the high-speed single stage R-4 compressor test rig of the von Karman Institute in Belgium. Both applications have shown results in extremely good agreement with simultaneous total temperature measurements with a Kiel type thermocouple probe. They also underline the necessity of a very accurate temperature calibration.

Finally, considering the fact that a simultaneous temperature measurement can be obtained at the same location as the pressure measurement from the sensor, it is possible to derive entropy generation after a blade row, based on the average pressure and temperature quantities. This unveils another extremely interesting aspect of using the fast response probe technique in turbomachinery applications.
Developing Effervescent Atomisation for Alternative Fuels
Authors: Konstantinov Dancho D. , Bowen Philip J. , Marsh Richard , Kay Peter J. , Crayford Andrew P. , Derksen Marco
Published: July 2013

A wide range of atomiser types have been developed for industrial applications — such as rotary, pressure, air-assist and air-blast atomisers. Each type works on the principle of applying mechanical or kinetic energy to disintegrate a jet or sheet of liquid fuel, in preparation for combustion. The aim is to sufficiently increase the surface area to volume ratio of the fuel and presents it in a form suitable for a consistent combustion process. Traditional liquid fuels, such as fossil fuels, have been employed for some decades and combustion systems (and atomisers) have been optimised for their use. However, combustion engineers are being increasingly forced to consider the use of alternative, biologically-derived hydrocarbon fuels. Such fuels often have very different viscosities, densities and surface tensions or possess complex, non-linear properties when compared to conventional fuels. Effervescent atomisation is a promising two-phase atomisation technique offering potential improvements in fluid atomisation quality and reductions in fluid operating pressures. It appears particularly well suited to the atomisation of viscous fuels such as biofuels; this applicability to alternative fuels has led to a renewed interest in the method. After an extensive literature review of the current state of this technology [1] an adjustable geometry effervescent atomiser was designed, built and studied at the Cardiff School of Engineering. Water and air were used as the operating fluids. The sprays produced by the atomiser were characterised using a Phase Doppler Anemometry (PDA) system which allowed for simultaneous real-time droplet size and velocity data to be obtained. High quality data was achieved with data rates over 10 kHz and validation rates over 90% in 2-D LDA mode in the high density sprays. A PDA probe designed for dense spray applications was utilised. A number of important operating parameters identified during the literature review phase can be altered on the atomiser, and their effects on fuel spray quality investigated. The operating parameters investigated in this manner included air-to-liquid by mass ratio (ALR), pressure drop as well as a range of geometric parameters. This paper discusses and analyses the influence of ALR on the quality of atomisation and the associated two-phase flow field. Comparisons are made with previous studies and correlations, using earlier versions of the hardware or alternative techniques. Ongoing work will assess and optimise the performance of simulated biofuels mixtures.
Precision Temperature Detection Using a Phosphorescence Sensor Coating System on a Rolls-Royce Viper Engine
Authors: Feist J. P. , Sollazzo P. Y. , Berthier S. , Charnley B. , Wells J.
Published: July 2013

By adapting existing thermal barrier coatings a sensor coating has been developed to enhance their functionality, such that they not only protect engine components from the high temperature gas, but can now also measure the material temperature accurately and the health of the coating e.g. ageing, erosion and corrosion. The sensing capability is introduced by embedding optically active materials into the thermal barrier coating and by illuminating these coatings with excitation light phosphorescence can be observed. The phosphorescence carries temperature and structural information about the coating. Knowledge of the exact temperature could enable the design of advanced cooling strategies in the most efficient way using a minimum amount of air. The integration of an on-line temperature detection system would enable the full potential of thermal barrier coatings to be realized due to improved accuracy in temperature measurement and early warning of degradation. This in turn will increase fuel efficiency and reduce CO2 emissions.

Application: The work carried out included the successful implementation of a sensor coating system on a Rolls-Royce Viper engine. The system consists of three components: industrially-manufactured robust coatings, advanced remote detection optics and improved control and readout software. The majority of coatings were based on yttria stabilized zirconia doped with Dy, although other coatings made of yttrium aluminium garnet were manufactured as well. Coatings were produced on a production line using atmospheric plasma spraying. Parallel tests at Didcot power station revealed the durability of specific coatings in excess of 4,500 effective operating hours. It is expected that the capability of these coatings is in the range of normal maintenance schedules of industrial gas turbines of 24,000hrs or even longer. An optical energy transfer system was designed and developed permitting scanning of coated components and also the detection of phosphorescence on rotating turbine blades (13,000 RPM) at probe-to-target distances of up to 400mm. The online measurement system demonstrated precision (around ±5K) comparable to commercial thermocouples and has shown calibration accuracy of ±4K. Transient temperatures were tracked at maximum at 8Hz which is fast enough to follow a typical power generation gas turbine. Repeatable measurements were successfully taken from the nozzle guide vanes (hot), the combustion chamber (noisy) and the rotating turbine blades (moving) and compared with thermocouple and pyrometer installations.
Experimental and CFD Evaluation of the Part Load Performance of a Micro Gas Turbine Fuelled With CH4-N2 Mixtures
Authors: D’Alessandro Bruno , Laranci Paolo , Testarmata Fabio , Fantozzi Francesco
Published: July 2013

There is a strong interest in numerical and experimental research on syngas combustion in GTs however experimental studies require syngas generation which is costly and also provides a variable and dirty fuel gas. To investigate the combustion behaviour and GT performance when fuelled with low LHV syngas, nitrogen diluted natural gas can be considered.

To this aim the micro gas turbine (mGT) available at the IPRP (Integrated Pyrolysis Regenerated Plant) pilot facility of the University of Perugia, modified to use biomass pyrolysis gas, was fuelled with a CH4−N2 mixtures at different part load conditions obtained from pipeline (CH4) and cylinders (N2). The aim of the work is to analyze the functioning condition of the mGT which is monitored by a dedicated data acquisition system. Performances are evaluated and discussed showing that nitrogen dilution does not affect significantly efficiency and NOx production while CO emission increase slightly when increasing nitrogen content and this is more evident when decreasing the load.

A CFD model of the combustion chamber, which was developed and tuned in previous works by the authors, was also run to reproduce experimental data showing a good agreement and also suggesting flame detachment in the mixing tube when nitrogen is present.
Phosphor Based Temperature Indicating Paints
Authors: Heyes A. L. , Rabhiou A. , Feist J. P. , Kempf A. M.
Published: July 2013

The ability to measure temperature in extreme environments such as the hot sections of gas turbines is critically important. Several on-line techniques exist but it is often not possible to measure in real-time the temperature of all surfaces of interest. Indeed, some surfaces are so inaccessible as to require complex, costly and intrusive instrumentation for on-line temperature measurement. Here, off-line sensors, also called thermal history sensors, can be used to record the temperatures to which they are exposed, in such a way that they can be extracted later off-line, at room temperature.

Probably the best-known types of thermal history sensor are the colour changing thermal paints, that are widely used in gas turbine development. These have been valuable tools of engine developers for many years, but their use presents a number of challenges so that alternatives would be welcome.

This paper reports the latest developments of a thermal history sensor based on phosphors that undergo permanent changes in their luminescence properties when exposed to high temperatures. Such thermal history sensors have several advantages over and address many of the shortcomings of existing sensors. The paper contains details of the application of a phosphor-based temperature indicating paint based on Y2SiO5:Tb suspended in a chemical binder. The binder was found to influence the optical properties of the phosphor but despite this, a viable sensor paint for temperatures in the range 400°C to 900°C was formed.

A thermal history coating was installed using a thermal barrier coating architecture, applied on various components of a Royce-Rolls Viper 201 engine owned by STS and operated for a number of hours at Cranfield University. Post-operation analysis revealed a temperature distribution on the surfaces/components and enabled hotspots to be identified. Overall the results suggest that phosphor-based temperature indicating paints have the potential to surpass the capability of existing paints.
Sugar Cane Bagasse Gasification Using Air-Steam for Partial Oxidation and N2 as Carrier Gas
Authors: Rodriguéz Catalina , Gordillo Gerardo
Published: July 2013

Several technologies have been proposed to reduce the environmental impact caused by greenhouse emissions (CO2) from fossil fuel combustion processes. One of them is the use of biomass as feedstock in gasification processes. Biomass fuels which include energy crops, agricultural and forestry residues, and municipal, industrial, and animal wastes can serve as renewable feedstock for thermal gasification to produce gaseous and liquid fuels. The inclusion of biomass as feedstock in thermal conversion processes does not increase the CO2 concentration in the atmosphere because biomass is a carbon neutral fuel. The sugarcane agriculture industry around the world produces a great amount of wastes, e.g., only in Colombia about 9 million tons of bagasse wastes are produced per year. That great amount of bagasse wastes can cause pollution of natural sources (land, water, and air) if waste handling systems and storage and treatment structures are not properly managed. If thermal gasification technology is developed for sugarcane bagasse wastes (SCBW), the negative environmental impact from both SCBW and fossil-fuels could be mitigated. The current paper deals with i) SCBW adiabatic gasification modeling using air-steam blends for partial oxidation and ii) pyrolysis kinetic model to determine, by thermogravimetric analysis (TGA), the SCBW activation energy (E). The Chemical Equilibrium with Applications program (CEA), developed by NASA, was used to estimate the effect of both the equivalence ratio (ER) and steam to fuel ratio (S:F) on adiabatic temperature, gas quality (gas composition and energy density), and energy recovery of an unlimited number of species (∼150). Thermogravimetric analysis (TGA) was carried out using N2 as carrier gas and under different heating rates (β: 5, 10, 20, and 40 °C/min). The activation energy (E) was estimated based in the results from TGA and using the isoconversional method (i.e., free-model). In general for the range of parameters studied (0.3<S:F<0.8 and 2<ER<6), the results from equilibrium adiabatic modeling (CEA) showed that increasing ER and (S:F) ratios increases the production of H2 and CO2 but decreases the production of CO. At ER <4, the equilibrium temperature decreases with increased ER, but at ER > ∼ 4.0, it remains stable. The production of CH4 is only possible at ER>4. The average value of the activation energy, estimated from the kinetics model, was 266 kJ/kmol.
Reducing Conservatism in Aircraft Engine Response Using Conditionally Active Min-Max Limit Regulators
Authors: May Ryan D. , Garg Sanjay
Published: July 2013

Current aircraft engine control logic uses a Min-Max control selection structure to prevent the engine from exceeding any safety or operational limits during transients due to throttle commands. This structure is inherently conservative and produces transient responses that are slower than necessary. In order to utilize the existing safety margins more effectively, a modification to this architecture is proposed, referred to as a Conditionally Active (CA) limit regulator. This concept uses the existing Min-Max architecture with the modification that limit regulators are active only when the operating point is close to a particular limit. This paper explores the use of CA limit regulators using a publicly available commercial aircraft engine simulation. The improvement in thrust response while maintaining all necessary safety limits is demonstrated in a number of cases.
Solving Problems With Patterns for Heat and Flow Diagnostics Dedicated for Turbine Power Plants
Authors: Gluch Jerzy , Slezak-Zolna Justyna
Published: July 2013

The article analyses problems of defining reference states of the turbine power plants in cases of difficulties resulting from changes of operating conditions, including: changes in cycle configuration, repairs of only selected devices, and periodical replacements of measuring sensors in inter-repair time intervals. All above actions lead to time consuming corrections of the unified reference pattern. High time consumption of the correction can be reduced provided that a functional reference pattern with a modular structure is used. It was shown that in that case the effect of current operating conditions can be reconstructed when determining the reference state at relatively low time consumption for the reference pattern correction.
Development and Evaluation of a High Frequency Response Signal Conditioning Amplifier for Miniature, Silicon Bridge-Type Pressure Transducers
Authors: Ilott J. , Allan W. D. E.
Published: July 2013

In addition to their small size, miniature silicon pressure transducers offer wide-band frequency response. Taking advantage of the high-frequency response of these pressure transducers within an electrically noisy environment requires high bandwidth amplification and anti-alias filtering. This paper describes a signal conditioning amplifier that provides for linear phase filtering of a differential or single-ended input signal and outputs a differential signal. Differential signals are suitable for driving long cable runs that may be required when digital recording hardware cannot be located in close proximity to experimental apparatus. The design has also been shown to exhibit nearly constant group delay over the pass-band, reducing the need for substantial oversampling of the pressure transducer signals to avoid the nonlinear phase response typical of low-pass filters in the vicinity of their cut-off frequency. Testing has shown the module to provide a very flat pass-band response while achieving a high-order filter response at the cut-off frequency, along with excellent steady state DC accuracy.
Combined Effects of CMAS and FOD in Ceramic Matrix Composites
Authors: Choi Sung R. , Faucett D. Calvin
Published: July 2013

The combined effects of CMAS (calcium magnesium aluminosilicate) and FOD (foreign object damage) were determined in three different ceramic matrix composites (CMCs), two melt-infiltrated (MI) SiC/SiCs and one oxide/oxide. Foreign object damage was introduced at ambient temperature in CMC test targets using 1.6 mm steel ball projectiles at an impact velocity of 340 m/s utilizing a ballistic impact gun. One type of target support, partial support, was used. The impact-damaged test coupons were then CMAS-exposed at 1200°C for 10 hrs in air. Additional tests were also performed by exposing impact-damaged test coupons to a mixture of CMAS and salt (sodium sulfate) at 1200°C for 10 hrs in air. The combined effects of FOD and CMAS or CMAS/salt were quantified by determining the residual strengths of test coupons after exposures. Also, six different sands ingested into aeroengines were analyzed in their chemical compositions. The melt CMAS solid, melted at 1300°C and solidified, was assessed in its mechanical properties of microhardness and fracture toughness.
CFD Approach of Growing Cu-Particles in a ‘Kenics’ Static Mixer Reactor
Authors: van Wageningen W. F. C. , Mudde R. F. , van den Akker H. E. A.
Published: July 2013

Waste-to-waste technology can be used for the reduction of heavy metals to their metallic state with carbohydrates. The carbohydrate waste originates from the pulp or food industry. Heavy metals in the form of Cu(II) are found in wastewater from the IC-manufacturers or mine leaches. A CFD approach is used in order to develop the reactor and to determine the right reactor conditions. A uniform size distribution of the particles which are formed in the process increases the economical value of the end product. A Kenics static mixer is used to optimize the flow inside the reactor. The growth of the copper particles is investigated by Monte Carlo simulations inside the static mixer. Fluent v5.5 unstructured was used to calculate the laminar flow field (Reynolds 50–500), Cu(II) concentration and particle tracks. The resulting flow field was validated by a grid independence check and a comparison with PIV experiments. It was found that the hydrodynamics of the mixer have a profound influence on the size distribution and the ‘best’ results were achieved at Reynolds 200.
Computation of Fluid-Structure Interaction in a Static Mixer Using MpCCi
Authors: Wintergerste Torsten
Published: July 2013

Static mixers are used for the mixing of fluids with different properties like viscosity, density, temperature, etc. The Sulzer SMB mixer is designed for a high pressure drop which is e.g. the case in polymer melt blending. The deformation of the mixer caused by the fluid flow is investigated by the coupling of commercial CFD and FEA codes through a communications library called MpCCI. This loose coupling approach gives the opportunity for calculating the deformation of very complex structures which can be used for an optimization process during the phase of development of new mixers. This paper shows the use of the coupling of the two commercial codes STAR-CD and PERMAS by MpCCI for the investigation of the deformations of a mixer. It demonstrates that the use of coupling allows a more realistic calculation of stresses inside the structure.
Numerical Analysis on Wave Dynamic Processes in Pulse Detonation Devices
Authors: Jiang Z. L. , Wang C. , Hu Z. M. , Zhao W.
Published: July 2013

In this paper, wave dynamics processes occurring in pulse detonation devices are analyzed both numerically and experimentally, including the propagation of detonation fronts, the motion of rarefaction waves in gas exhausting phase and the diffraction of shock waves at thrust nozzles. Numerical results are also compared with experiments to confirm the observed wave phenomena. In order to estimate operation roles of pulse detonation engines more accurately, the initiation of the air/hydrogen mixture is also examined experimentally at certain conditions. Numerical analysis indicates that pulse detonation devices can be operated in a quite high frequency, the gas-filling phase occupies a longer time in one detonation cycle, and decreasing the length of detonation chambers for the higher operation frequency is possible, but has its limitation.
Numerical Analysis of Phase Change and Natural Convection Phenomena During Pipe Freezing Process
Authors: Jeong Gi Ho , Ahn Byung Jin , Seong Young Sik , Kim Kui Soon
Published: July 2013

A numerical analysis is performed in this study to see the characteristics of the ice plug formation and the heat transfer during pipe freezing process. The unsteady three dimensional computer code which solves incompressible Navier-Stokes equations including energy equation has been developed in this study. The computed results for verification including phase interface and flow patterns showed good agreements with others. And additional pipe freezing experiments for verification showed that maximum flow rate for the complete plug formation is highly dependent on the pipe diameter and length of jacket containing refrigerant (LN2). The results of pipe freezing experiments could be also used as a guideline and to the proper computation. It was found that the effects of pipe diameter and freezing jacket length on the ice plug formation are significant. It was also found that this bi-cellular vortex oscillates in an axial section (r – z plane) as moves to downstream. Finally, the numerical results showed that the characteristics of the flow in the mushy region influence the shape and the freezing time of ice plug formation.
The Development and Validation of Fast Numerical Method of Simulating Wet Steam Flow
Authors: Zhang Dongyang , Liu Jianjun , Jiang Hongde
Published: July 2013

A fast numerical method of simulating turbine nucleating flow is developed and calibrated. Analytical limiting subcooling degree, transition function and tabular steam properties are applied. The agreements between calculations and experimental data are well. The developed method applies some new and unique techniques and is contributed to be a tool of fast analysis and industrial design for wet steam flow.
Applying CFD for Design of Gas Conditioning Towers With Swirling Flow
Authors: Nielsen Niels F. , Lind Leif
Published: July 2013

The aim of the present study is to investigate the gas flow distribution within a Gas Conditioning Tower (GCT) used for cooling hot flue gases by means of atomized water injection. Special focus is placed on developing a design that prevents wall flow separation in the evaporation zone as well as in the tower in general. In due cause a special swirler design is presented introducing the swirling type of flow in the tower (swirl no. in the range of 0.2 to 1.0). The GCT geometry studied includes inlet ducting, swirl generator unit, conical diffuser section and tower section. The swirler is a totally new design while the inlet ducts and conical diffusers studied are modifications of the traditional design. The three-dimensional flow distribution within the GCT is calculated by standard Computational Fluid Dynamical (CFD) tools giving high resolution of the calculation domain. The presented results include intensive validation studies of the swirling flow introduced by the swirler and practical applications. The validation case shows that medium mesh resolution, second order upwind difference scheme and the high Reynolds number form of the standard k-ε turbulence model with the law of the wall representation offer a good compromise between accuracy, required number of computational cells, computer time and agreement with experimental data. Studies of practical applications include design flexibility in general, optimization of gas distribution and sensitivity to water droplet size. Depending on the actual parameter in play, the results clearly demonstrate, that the newly developed design reflects the needs of an acceptable gas distribution in GCTs and that the design can be used in other flue gas process units including large opening angle diffusers. Also, the study indicates that the swirl number is a good measure of optimum operation.
A Model for Simulation Heat Transfer in Porous Media
Authors: Reich Alton J. , Athavale Mahesh M.
Published: July 2013

The simulation of flow with heat transfer is important in several areas of current research and development interest. These areas include fuel cells and low cost, high temperature seals. This paper describes the implementation of a model for simulating the heat transfer porous media that has been incorporated into the commercial CFD-ACE+ software package. This model has been validated for both steady state and transient cases. Also presented are results for a “typical” fuel cell application.
Use of CFD to Design a Melt Blowing Die
Authors: Krutka Holly M. , Shambaugh Robert L. , Papavassiliou Dimitrios V.
Published: July 2013

Computational Fluid Dynamics (CFD) can play an important role in understanding the flow field below two converging rectangular jets. Each rectangular nozzle has a large length to width ratio, and the nozzles are parallel and very close to each other. This design is used in practical applications to produce polymeric fibers in the process known as melt blowing. In this paper we use turbulence models available in the CFD software Fluent 5.0 to study the detailed flow field. We also use experimental measurements to compare with the simulation results, and we test altemative die designs with the goal of identifying those that perform better.
Numerical Simulation of a Specialty Optical Fibre Drawing Process
Authors: Lyytika¨inen Katja , Ra˚back Peter , Ruokolainen Juha
Published: July 2013

The present study investigates the mass and heat transfer in the optical fibre fabrication process where a specialty optical preform with a non-homogeneous cross-sectional structure is drawn into a fibre. A finite element method was used to model the steady state fibre drawing process. The model included free surface calculation of the neck-down shape of the preform coupled with a two-dimensional heat transfer equation. The enclosure model was used for the radiation heat transfer. In addition to the silica preform the model took into account the graphite-resistance furnace structure and the inert gas surrounding the preform. Fibre designs with axisymmetric cross-sections with radial variations in material properties were modeled, including air silica structures. The effect of internal air structures was found to have a significant impact on temperature distribution. The effects of drawing parameters such as draw speed, preform diameter, draw temperature and furnace structure were also studied.
Advanced Hydrodynamic Design of Vertical Diffuser Pumps Using Computational Fluid Dynamics
Authors: Michaelides Kristis V. , Tourlidakis Antonios
Published: July 2013

The current paper describes an investigation into the industrial use of CFD and other computational technologies for the three-dimensional hydrodynamic design of vertical diffuser pumps and outlines the complete product development process. Detailed description of the complete design process is described and numerous CFD predictions of the flow are presented with detailed examination of the several factors affecting the hydrodynamics of impeller and diffuser and staging of the pump. Furthermore, variations of important geometrical design parameters based on the design optimisation procedure are discussed in accordance to the CFD results. The capabilities of the 3-D hydrodynamic design through CFD and the importance of the three dimensional blade geometry are demonstrated by the fact that two different pump impellers were designed based on strict design constraints affecting their basic dimensions. Finally, an overview of the functional prototypes development is described and comparisons are carried out between overall performance predictions and experimental results.
Three-Dimensional Modeling of Lime Kilns
Authors: Georgallis M. , Nowak P. , Salcudean M. , Gartshore I. S.
Published: July 2013

Rotary kilns have wide use in industry from the calcination of limestone to cement manufacturing to calcining of petroleum coke etc. Problems such as low thermal efficiency and low product quality have plagued rotary kiln operations yet these machines have survived and have been continuously improved (fuel efficiency, automation) for over a century.
Three-Dimensional Thermal-Hydraulic Analysis in Slit Finned-Tube Heat Exchangers
Authors: Jang Jiin-Yuh , Yeh Jer-Nan , Ay Her-Chang
Published: July 2013

A numerical study of laminar flow and heat transfer over a two-row and three-dimensional slit fin and tube heat exchanger is presented. The effects of two different slit numbers Sn = 2 and 4 are investigated in detail for the Reynolds number ReH (based on the fin spacing and the frontal velocity) ranging from 160 to 900. The numerical results for the velocity field, fin surface Nusselt number, Colburn and fanning factor are shown. It is found that, both the average Nusselt number and pressure drop coefficient are increased as the slit number Sn is increased. A comparison of the numerical results with the available experimental data is also presented.
Characterization of Common Carotid Artery Curvature and Its Impact on Velocity Profile Shape
Authors: Manbachi Amir , Hoi Yiemeng , Steinman David A.
Published: July 2013

Clinical and engineering studies of carotid artery disease typically assume that the common carotid artery (CCA), proximal to the bifurcation, is relatively straight, at least enough to assume the velocity profile is fully-developed (i.e., Poiseuille or Womersley profile) or at least axisymmetric. However, a recent study from our group has shown the surprising presence, in vivo, of strongly skewed velocity profiles in what appeared to be only mildly curved CCAs [1]. A computational fluid dynamics (CFD) study from our group also demonstrated strong velocity profile skewing in an idealized geometry possessing subtle wiggles similar to those observed in the CCA [2].
Cryosurgery as an Alternative Treatment for Menorrhagia and Uterine Fibroids
Authors: McCaffrey Katherine L. , Rose Karen M. , Abraham John P.
Published: July 2013

Nearly 80% of all women may suffer from uterine fibroids (leiomyomas) and/or menorrhagia, which is a condition where the uterus walls bleed abnormally. The vast majority of women whose symptoms are strong enough to require treatment obtain a hysterectomy. Other treatment options which are less invasive than hysterectomy include thermal therapies such as thermal ablation or cryosurgical removal of tissue. This project numerically evaluates the efficacy of a liquid-nitrogen-based cryotherapy for the treatment of uterine fibroids. A bioheat transfer model was utilized which included both the effects of blood perfusion and the impacts of liquid-to-solid phase change. An upper limit on the cooling rate was obtained by simulating a direct contact between the probe tip and the inner lining of the uterus. Calculations were carried out for a one-minute treatment duration with 720 calculation nodes which spanned the thickness of the uterine wall. Results obtained from the calculations allowed a determination of the cooling rate at each nodal location within the tissue. Based on data obtained from previous cell-survival studies, it was found that necrosis would occur within the tissue up to a depth of approximately 5.8 mm.
Direct Numerical Simulation of Cellular Blood Flow Through a Model Arteriole Bifurcation
Authors: Reasor Daniel A. , Clausen Jonathan R. , Aidun Cyrus K.
Published: July 2013

Blood is composed of a suspension of red blood cells (RBCs) suspended in plasma, and the presence of the RBCs substantially changes the flow characteristics and rheology of these suspensions. The viscosity of blood varies with the hematocrit (volume fraction of RBCs), which is a result not seen in Newtonian fluids. Additionally, RBCs are deformable, which can alter suspension dynamics. Understanding the physics in these flows requires accurately simulating the suspended phase to recover the microscale, and a subsequent analysis of the rheology to ascertain the continuum-level effects caused by the changes at the particle level. The direct numerical simulation of blood flow including RBC migration effects has the capability to resolve the Fåhraeus effect of observing low hematocrit values near walls, the subsequent cell-depleted layer, and the presence of velocity profile blunting due to the distribution of RBCs.
Assessment of Three Possible Criteria for Remodelling of Collagen Gels and Collagenous Tissues
Authors: Kroon Martin
Published: July 2013

Collagenous tissues are living structures, in which new material may be added and the structural organisation may change over time. The maintenance of the collagen matrix is accomplished by fibre-producing cells, such as fibroblasts. During maintenance, the extracellular matrix (ECM) influences the development, shape, migration, proliferation, survival, and function of the cells. The mobility of the fibroblasts and their ability to contract the ECM are important properties for a proper maintenance of the ECM [1,2]. The purpose of the present paper is to shed some more light on the interaction between the ECM and the fibre-producing cells. The fibroblasts remodel the collagen gel by reorienting the individual collagen fibres. This reorientation of fibres is described by an evolution law, which depends on a continuum mechanics entity. Three possible choices are assessed: reorientation towards increasing Cauchy stress, increasing elastic stretch, and increasing current stiffness of the material. The model is compared with experimental results, and the three different criteria are evaluated in terms of the predicted distribution of collagen fibres after remodeling and resulting stress-strain relations. Experimental results from tissue equivalents in the form of collagen gels are used when assessing the three criteria [3]. We consider a network of collagen fibres, where the fibres are embedded in a matrix fluid. The collagen fabric and the surrounding fluid are assumed to be the only load-carrying constituents in the material. Embedded in and attached to the collagen fabric is also a population of fibroblasts. The collagen fabric is composed of collagen fibres, which in turn are bundles of collagen fibrils. The deformation of a line element in the matrix is described by the deformation gradient F(X) = ∂x/∂X, which is decomposed according to F = FelFlfFr, see Fig. 1. The fibroblasts’ remodelling of the collagen fabric results in a new matrix configuration Ωr. This deformation of the matrix is described by Fr. The configuration Ωr does not necessarily fulfill equilibrium, and the deformation gradient Flf takes the matrix to the state Ωlf, that fulfils global equilibrium with no external loads applied. Finally, if external loads are applied to the material, the configuration Ωel is attained, and this deformation is described by the deformation gradient Fel.
Effect of Albumin Concentrations on Frictional Coefficients of Cobalt-Chromium Femoral Head From Atomic Force Microscopy
Authors: Duong CongTruyen , Lee Jae-Hoon , Lee SangSoo , Park Seonghun
Published: July 2013

Atomic Force Microscopy (AFM) has been widely used to measure frictional properties of diverse materials at the microscopic level [1, 2]. Furthermore, there has been the general agreement that albumin plays an important role as an effective lubricant in the frictional behavior of hip implant materials. Through hip simulator, it has been reported that either boundary or mixed lubrication occurs when bovine serum albumin was used as a lubricant [3, 4]. When lubricants contained proteins of albumin or globulin, the frictional properties of the rubbing surfaces were affected by the adsorption of these constituents on the bearing surfaces of the prostheses [4]. Through macroscopic pin-on-disk measurements, another study in the literature has reported the importance of albumin as an effective lubricant for reducing friction and wear of hip implant materials [5]. Although microscopic AFM measurements are very effective for exploring boundary lubrication of diverse lubricants on joint implants, because the frictional coefficients of bearing surfaces in the joint implants can be measured without being affected by the surface roughness of bearing materials, the effect of boundary lubrications of bovine serum albumin (BSA) on hip implant materials has not been well identified. Therefore, the objective of the present study is to investigate the role of BSA as a boundary lubricant in the lubrication of cobalt-chromium (CoCr) femoral head ten years after total hip arthroplasty (THA) by measuring its frictional coefficients with AFM techniques.
Theoretical Evaluation of the Feasibility of Inducing Brain Hypothermia Using a Torso Cooling Pad
Authors: Smith Katisha D. , Zhu Liang
Published: July 2013

Injuries to the brain and spinal cord are common in traumatic injury involving accidents. Clinical and animal studies have demonstrated the protective mechanisms of cooling the brain and spinal tissue for minimizing secondary tissue damage following the initial injury.1 Our previous theoretical study illustrates the feasibility of significantly reducing the temperatures of the spinal cord using a simple torso cooling pad, and the spinal fluid surrounding the spinal cord by approximately 3.5°C within 30 minutes. Since the spinal fluid connects with the cerebrospinal fluid (CSF) surrounding the brain hemisphere, brain hypothermia may be possible as the cold spinal fluid constantly replaces part of the warm CSF.
Experimental and Computational Biomechanical Characterization of the Dolphin Tracheo-Bronchial Tree During Diving
Authors: Bagnoli Paola , Zaffora Adriano , Cozzi Bruno , Fumero Roberto , Costantino Maria Laura
Published: July 2013

Marine mammals belonging to the Order of CetoArtiodactyla have developed their organs and adapted their anatomic structures to survive and better exploit the resources of the surrounding water environment. Though belonging to the Mammal Class and, hence, having a cardio-respiratory system based on the gas exchange with the atmosphere, they are able to perform long-lasting immersions and reach considerable depths during diving [1]. On the other hand, the anatomy of the tracheo-bronchial structures of the Family Delfinidae differs from that of terrestrial mammals in the lack of muscular tissue in the posterior region and the irregular shape of the cartilaginous rings (Fig.1a-b-c) [1, 2]. So far, the behavior of dolphin respiratory system during diving is not yet fully understood, since they cannot be subjected to invasive analysis being endangered and protected species. Namely, it remains to ascertain whether the tracheo-bronchial tree collapses during diving or is kept open by the peculiar material properties, the anatomical structure and the presence of entrapped air. Aim of this work is to model the dolphin Tursiops truncatus’s tracheo-bronchial tree to study its behavior during diving by coupling experimental in vitro mechanical characterization of airways tissues to finite element computational analyses. Furthermore, we performed a comparison between the mechanical behavior of tracheo-bronchial trees of dolphins and that of the goat, a terrestrial mammal whose conformation of the upper airways is similar to the human, to highlight discrepancies due to the different habitats.
Predicting Human Carotid Plaque Site of Rupture Using 3D Critical Plaque Wall Stress and Flow Shear Stress: A 3D Multi-Patient FSI Study Based on In Vivo MRI of Plaques With and Without Prior Rupture
Authors: Teng Zhongzhao , Canton Gador , Yuan Chun , Ferguson Marina , Yang Chun , Huang Xueying , Zheng Jie , Woodard Pamela K. , Tang Dalin
Published: July 2013

Atherosclerotic plaque rupture is the primary cause of cardiovascular clinical events such as heart attack and stroke. Image-based computational models of vulnerable plaques have been introduced seeking critical mechanical indicators which may be used to identify potential sites of rupture [1–5]. Models derived from 2D ex vivo and in vivo magnetic resonance images (MRI) have shown that 2D local critical stress values rather than global maximum stress values correlated better with plaque vulnerability, as defined by histopathological and morphological analyses [5]. A recent study by Tang et al. [4] using in vivo MRI-based 3D fluid-structure interaction (FSI) models for ruptured human carotid plaques, reported that mean plaque wall stress (PWS) values from ulcer nodes were 86% higher than mean PWS values from all non-ulcer nodes (p<0.0001). This study extends the “critical stress” concept to 3D and uses 3D FSI models based on in vivo MRI data of human atherosclerotic carotid plaques with and without prior rupture to identify 3D critical plaque wall stress (CPWS), critical flow shear stress (CFSS), and to investigate their associations with plaque rupture.
A Reciprocal Connection at Knee Joint
Authors: Kim Wangdo , Veloso Antonio , Tan John , Andrade Carlos
Published: July 2013

Ligaments and other soft tissues, as well as articular contacts, all contribute to the stability of the knee joint. However, precisely how these structural components of the knee joint affect joint stability is not fully understood. The extent to which geometric changes to said structure, resulting from surgical reconstruction and or replacement procedures, may affect joint movement is unclear. This paper was designed to explain connections between the instantaneous motion of the knee and restraining forces in the components that are engaged with it and responsible for such motion (i.e. the anterior cruciate ligaments (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), as well as bony contacts in the medial and lateral compartments). This instantaneous motion is characterized by a rotation about the instantaneous screw axis (ISA), governed by restraining forces along the wrench axes. Said restraining forces may be systematically explored using the principle of reciprocity [Hunt, 1990], which has previously been used to successfully explain the twists that a body may execute whilst maintaining, and not breaking, contact with other bodies. In this way, the motion coordinates may be linked to the force ones, within a novel unified screw coordinate construct. Thus, two approaches which were previously treated as separate entities may now be explained together and in simpler terms to clinicians and other practitioners.
A Simple Goniometer for Use Intra-Operatively in Total Knee Arthroplasty
Authors: Liddle Kate D. , Peter Jennifer , Currey Jovauna M. , Buckley Jenni M. , McGann William A.
Published: July 2013

Intra-operative range of motion (ROM) assessment can be challenging during total knee arthroplasty (TKA) surgery. Measurement accuracy is often compromised by patient draping and anatomy, particularly when assessing knee extension. Accurate ROM assessment is important, as ROM after total knee arthroplasty is an important indicator of clinical outcome. Computer assisted surgery has been shown to accurately determine intra-operative range of motion; however, navigation systems are costly and not readily available to many surgeons. We have developed a simple, cost-effective intraoperative device to precisely measure knee flexion and extension that is efficient and easy to use.
A Computational Model for Gut Looping
Authors: Ramasubramanian Ashok
Published: July 2013

In chick embryos, a series of complex invaginations involving the three germ layers (endoderm, ectoderm, and mesoderm) lead to the formation of the primitive gut tube. This process normally occurs during the third day of development, at the end of which the gut appears as an open cylindrical tube (Fig.1A). By the end of the fourth day, the tube is closed except in the middle section, which is connected to the yolk sac (Fig. 1B). The gut at this stage is typically divided into three sections: the foregut, midgut, and hindgut. Now starts the process of gut looping that transforms the initially straight gut tube into the complex intestinal system of the adult chick. The focus of this study is on shape changes that occur between the fourth and fifth days of incubation when the straight gut tube is transformed into an s-shaped one (Fig. 1C). This occurs as the primitive gut tube undergoes rapid elongation, twisting, and rotation causing three distinct bends (the duodenal loop, umbilical loop, and the duodenal-jejunal flexure) to appear simultaneously by the end of the fifth day. Borrowing the term used to describe a similar process in heart development, this initial phase of gut looping is referred to as “s-looping of the gut” in this study.
Critical Design Condensation Locations in Facial Masks
Authors: Al-Jumaily A. M.
Published: July 2013

Facial masks are the main interface between patients and breathing supportive devices. Condensation in these masks causes serious breath disturbance which could be life threatening. Based on temperature-driven mass and heat transfer formulations, a computer simulation fluid dynamic model is developed to compute the condensation rate and locations of a typical breathing facial mask. Condensation measurements are taken to validate the model. The effects of mask geometry and shape on condensation are elaborated on.
Drug Eluting Stents: Modelling the Physics of Mass Transport in the Arterial Wall
Authors: Denny W. , O’Connell B. , Milroy J. , Walsh M.
Published: July 2013

Coronary artery disease (CAD), which results in inadequate blood flow to the heart, is responsible for 1 in every 4.8 deaths in the USA (Lloyd-Jones et al., 2009). Currently, there are 16.5 million patients with stable angina and 500,000 new diagnoses annually (Gibbons et al., 2003). CAD has been linked with atherosclerosis since the early 20th century (McMahan et al., 2008) and refers to the localisation of the disease in the coronary arteries. Atherosclerosis is a degenerative disease that affects not only the coronary arteries, but also the carotid and other peripheral arteries in the body.
Implementation of a New Torque Device in Ox-Tails
Authors: Rizza Robert , Liu Xue-Cheng , Thometz John , Lyon Roger , Tassone Channing
Published: July 2013

In adolescent idiopathic scoliosis patients, the vicious cycle hypothesis proposed by Dr. Stokes [1] suggests, a lateral spinal curvature produces asymmetrical loading of the skeletally immature spine, which in turn causes asymmetrical growth and therefore progressive wedging deformity. Numerous studies have been done to evaluate the effect of sustained compression-tension loading on spinal growth. Despite all this research, only [2] investigated the effect of torque on segmented bodies. However, the previous study did not have independent control of torque and bending moments. Since a coupling mechanism between the torque and bending moments may be involved in the development of spinal curvature, it is important to separate the torque and bending moments so that the effect of the torque may be fully understood.