bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Heat Transfer Enhancement and Pressure Characteristics of Zig-Zag Channels
Authors: Siw Sin Chien , Chyu Minking K. , Alvin Mary Anne
Published: August 2013

Described in this paper is a study combining experiment and CFD simulation to explore the heat transfer characteristics of an internal cooling passage with different turning angles ranging from 70, 90 and 110 degrees. When adjacent passages are connected by a turn in a periodic fashion, the channel exhibits a “zig-zag” pattern, and hence the name. The test channel has a cross-section of 63.5mm by 25.4mm, corresponding to the aspect ratio of 2.5:1. This specific design with several turns will generate additional secondary vortices while providing longer flow path that allows coolant to remove a greater heat load before being discharged downstream. The computational study employs a commercially available CFD code, ANSYS CFX. As a significant finding, the numerical simulation suggested that the case with 110 degree turns has the best heat transfer performance. An experimental study thus is followed to investigate the detailed surface heat transfer distribution on the 110 degree case using the transient liquid crystal technique. The overall heat transfer coefficient characteristics except near the turning region are found to be comparable between the experimental and numerical simulation. Pressure loss in these test channels is several folds higher than that of straight smooth test channel due to the presence of turns; but is it significant lower than the limiting case with a 180-degree turn. The case with 70 degree turns has the highest pressure loss, while the case with 110 degree turns has the lowest pressure loss. Internal channels of zig-zag configurations might be a viable design for internal cooling of an airfoil mainbody or trailing edge while serving the purpose of bridging structures between the pressure and suction sides.
Influence of Friction on the Blow-Down Behavior of an Aramid Fiber Brush Seal
Authors: Ruggiero Eric J.
Published: August 2013

Aramid fiber brush seals are ultra-low leakage, compliant sealing elements for turbomachinery applications. Such seals are applicable in the Aviation, Energy, and Oil and Gas markets as either air-air seals or air-oil seals. In the present study, the influence of friction present between the front plate and upstream side of the bristle pack of an aramid fiber brush seal is experimentally investigated. With the bristle pack fully exposed on the upstream side of the seal, the bristles are shown to blow down and create a better seal compared to the same brush seal with a front plate installed.
Windage Measurements in a Rotor Stator Cavity With Rotor Mounted Protrusions and Bolts
Authors: Long C. A. , Miles A. L. , Coren D. D.
Published: August 2013

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results.

Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 × 107 ≤ Reφ ≤ 1.68 × 107 and 0.24 × 105 ≤ Cw ≤ 1.06 × 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11 mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out.

Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here.

This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixtures.
Influences on the Oil Split Between the Offtakes of an Aero-Engine Bearing Chamber
Authors: Kurz Wolfram , Dullenkopf Klaus , Bauer Hans-Jörg
Published: August 2013

The aim of the presented work was to identify factors that influence the oil split between the two offtakes of a vented aero-engine bearing chamber. The impact of different vent and scavenge offtake designs was experimentally investigated with a test rig at the ITS. The generic bearing chamber was also equipped with ten film thickness sensors. The film measurements allowed a further evaluation of the mechanisms behind different oil splits. Two of the examined offtake features ensured a very constant oil split: a protruding vent and a covered ramp offtake. The latter also decreased the oil film thickness on the bearing chamber walls significantly. Furthermore, an influence of a non-uniform seal gap was detected which altered the oil split by several percent.
Numerical Investigation on the Influence of the Fillet on Film Cooling Rotor Blades in Heavy Duty Gas Turbines With an Object-Oriented CFD Code
Authors: Mangani Luca , Launchbury David Roos , Casartelli Ernesto , Maritano Massimiliano
Published: August 2013

The present paper examines the numerical simulation of the effects of film wall cooling on rotor blades in a high-pressure-ratio axial turbine. Special attention is given to the differently shaped geometries of the fillet at the blade endwall and their influence on secondary flows, since the fillet is often neglected in CFD calculations in order to minimize the effort in grid generation.

Simulations were conducted using both sharp and radius edge fillet configurations to investigate the effects on film cooling and secondary flows. For this purpose all simulations were performed using a modified in-house 3D RANS solver based on an object-oriented open-source library. The results were compared against experimental measurements in terms of local quantities such as aerodynamic losses and adiabatic effectiveness.
Aero-Thermal Performance of a Rotor Blade Cascade With Stator-Rotor Seal Purge Flow
Authors: Barigozzi G. , Fontaneto F. , Franchini G. , Perdichizzi A. , Maritano M. , Abram R.
Published: August 2013

The present paper investigates the effects of purge flow from a stator-rotor seal gap on the aerodynamic and thermal performance of a rotor blade cascade. Particular attention is paid to thermal results in the leading edge area that is typically difficult to protect. Experimental tests have been performed on a seven-blade cascade of a high-pressure rotor stage of a real gas turbine at low Mach number (Ma2is = 0.3). To simulate the rotational effect in a linear cascade environment, a number of inclined fins have been installed inside the stator-rotor gap, making the coolant flow to exit with the right tangential velocity component. Tests have been carried out at different blowing conditions, with mass flow rate ratios up to 2.0%. Aerodynamic effects of purge flow on secondary flow structures were surveyed by traversing a 5-hole miniaturized pressure probe in a plane 0.08cax downstream of the trailing edge. Film cooling effectiveness distributions on the end wall platform were obtained by using Thermochromic Liquid Crystals technique. Results allowed to investigate the effect of purge flow injection from the upstream gap on the secondary flows development and on the thermal protection capability. Purge flow injection of 1.0% reduced secondary flow losses and was found to effectively protect the front end wall region, up to about 0.5cax downstream of the leading edge. Increasing the purge flow up to 1.5%–2.0% provided a better thermal protection not only stream wise, but also in the region close to the leading edge because of the weakened washing activity of the horseshoe vortex.
Theoretical Investigations on Water Condensation in Main Steam Pipe
Authors: Yan Xin , Fan Yizhi , Shang Xianyou , He Kun , Li Jun , Feng Zhenping
Published: August 2013

Condensation in the main steam pipe is harmful for the downstream steam turbine. If the condensation water has not been completely drained from the main pipeline, the droplet will lead to the water hammer and cause unstable operations for the power station. As a result, accurate predictions of the water condensation during the startup and stable running processes are helpful for the drainage system operations and controls. In the power station, the main pipeline consists of pipe and outside insulation layer which prevents the heat loss thus improves the thermal efficiency. In this case, complex heat transfers including heat convection, conduction and radiation occur from the water-steam side to the atmospheric environment. In the current study, by using the theoretical methods, heat transfer and water condensation rate in the main steam pipe for the nuclear power station are calculated. Firstly, heat convection from the steam to the pipe, heat conduction in the pipe and insulation layer, and natural convection outside the insulation layer are computed and analyzed based on heat transfer theory and empirical correlation expressions. Secondly, in order to visualize the wetness distributions and pressure loss, the corresponding CFD computations with equilibrium condensation model is additionally utilized. Compared to the theoretical predictions, numerical result shows the same trend of the condensation and heat transfer loss. Finally, a new theoretical method without specifying the outer wall temperature of the insulation layer is developed. It shows that this method can predict a reasonable condensation rate and is convenient for the industrial applications.
Experimental Survey on Heat Transfer in a Trailing Edge Cooling System: Effects of Rotation in Internal Cooling Ducts
Authors: Bonanni L. , Carcasci C. , Facchini B. , Tarchi L.
Published: August 2013

The high thermal loads, the heavy structural stresses and the small thickness required for aerodynamic performances make the trailing edge cooling (TE) cooling of high pressure gas turbine blades a critical challenge. The presented paper point out an experimental study focusing the aerothermal performance of a TE internal cooling system of a high pressure gas turbine blade, evaluated under stationary and rotating conditions. The investigated geometry consists of a 30:1 scaled model reproducing the typical wedge shaped discharge duct with one row of enlarged pedestals. The airflow pattern inside the device simulates a highly loaded rotor blade cooling scheme with a 90° turning flow from the radial hub inlet to the tangential TE outlet. Two different tip configurations were tested, the first one with a completely closed section, the second one with 5 holes on the tip outlet surfaces discharging at ambient pressure. To investigate the rotation effects on the trailing edge cooling system performance, a rotating test rig was purposely developed and manufactured. The test rig is composed by a rotating arm that holds the PMMA TE model and the instrumentation. A thin Inconel heating foil and wide band Thermo-chromic Liquid Crystals are used to perform steady state heat transfer measurements. A rotary joint ensures the pneumatic connection between the blower and the rotating apparatus, moreover several slip rings are used for both instrumentation power supply and thermocouple connection. Heat transfer coefficient measurements were made with fixed Reynolds number close to 20k in the hub inlet section and with variable rotating speed in order to set the Rotation number from 0 (non rotational test) up to 0.3. Six different configurations were tested: two different tip mass flow rates (the first one with a completely closed tip, the second one with the 12.5% of the inlet flow discharged from the tip) and three different surface conditions: the first one consists in the flat plate case and the others in two ribbed cases, with different angular orientation (60° and −60° respect to the radial direction). Results are reported in terms of detailed heat transfer coefficient 2D maps on the suction side surface as well as span-wise profiles inside the pedestal ducts. The reported work has been supported by the Italian Ministry of Education, University and Research (MIUR).
High Resolution Heat Transfer Measurement on Flat and Contoured Endwalls in a Linear Cascade
Authors: Laveau Benoit , Abhari Reza S. , Crawford Michael E. , Lutum Ewald
Published: August 2013

In order to continue increasing the efficiency of gas turbines, a significant effort is being made to reduce losses induced by secondary flows in turbine stages. In addition to their impact on aerodynamic losses, these vortical structures are also the source of large heat transfer variations across the passage. A substantial reduction of the secondary flow losses can be achieved with a contoured endwall. However, a change in the vortical pattern can dramatically impact the thermal loads on the endwall and lead to higher cooling requirements in those areas. This paper focuses on heat transfer measurements made in a passage with either flat or contoured endwalls. The experimental data are supplemented with numerical predictions of the heat transfer data. The measurements are carried out on an isothermal endwall equipped with symmetric NACA airfoils. The paper presents measurements at M = 0.3 corresponding to a Reynolds number ReCax = 4.6×105. An infrared camera is used to provide high-resolution surface temperature data on the endwall. The surface is equipped with an insulating layer (Kapton) allowing the calculation of heat flux through the endwall. The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are then derived from a set of measurements at different isothermal plate temperatures. The numerical predictions clarify the link between the change in the heat transfer quantities and the changes in the flow field due to endwall contouring. Finally numerically predicted heat transfer data are deducted from a set of adiabatic and diabatic simulations that are compared to the experimental data. The comparison focuses on the differences in the regions with endwall contouring, where a significant difference in the heat transfer coefficient between flat and contoured endwalls is measured, but under-predicted numerically.
Heat Transfer Characteristics of a Rotor-Stator System With Small Radial Outflow
Authors: Lin Li , Ren Jing , Jiang Hongde , Childs Peter
Published: August 2013

In some cases, the mass flow rate needed to prevent ingress through rim seals in turbine is smaller than that entrained by a free disk. In order to obtain the heat transfer features of the rotor-stator system at such a small mass flow rate, a combined computational and theoretical study has been carried out. It is found that the average Nusselt number (Nuav) on the rotor drops approximately linearly down to zero with decreasing turbulent flow parameter (λt) when λt is smaller than λt,c (λt,c < λt,fd), while Nuav almost keeps constant when λt is larger than λt,c. A correlation between Nuav and λt has been developed, which is expected to be useful in determining disk temperatures in the preliminary design of an internal air cooling system. The Eckert number, which can express the relationship between heat generated by windage and heat conducted through disk, turns out to be an important nondimensional number in describing the heat transfer features of such rotor-stator systems. Moreover, the effect of rotational speed on heat transfer when λt,c<λt<λt,fd has been studied, further identifying the significance of the Eckert number.
Coherent Structures in Trailing-Edge Cooling and the Challenge for Turbulent Heat Transfer Modelling
Authors: Schneider Hayder , Bauer Hans-Jörg , von Terzi Dominic , Rodi Wolfgang
Published: August 2013

In the present paper, we test the capability of a standard Reynolds-Averaged Navier-Stokes (RANS) turbulence model to predict the turbulent heat transfer in a generic trailing-edge situation with a cutback on the pressure side of the blade. The model investigated uses a gradient-diffusion assumption with a scalar turbulent-diffusivity and constant turbulent Prandtl number. High-fidelity Large-Eddy Simulations (LES) were performed for three blowing ratios to provide reliable reference data. Reasonably good agreement between the LES and recent experiments was achieved for mean flow and turbulence statistics. For increasing blowing ratio, the LES replicated an also experimentally observed counter-intuitive decrease of the cooling effectiveness. In contrast, the model failed in predicting this behavior and yielded significant overpredictions. It is shown that the model cannot predict the strong upstream and wall-directed turbulent heat fluxes, which were found to cause the counter-intuitive decrease of the cooling effectiveness.
Conjugate Heat Transfer Calculations on GT Rotor Blade for Industrial Applications: Part I—Equivalent Internal Fluid Network Setup and Procedure Description
Authors: Bonini A. , Andreini A. , Carcasci C. , Facchini B. , Ciani A. , Innocenti L.
Published: August 2013

Gas turbine design has been characterized over the years by a continuous increase of the maximum cycle temperature, justified by a corresponding increase of cycle efficiency and power output. In such way turbine components heat load management has become a compulsory activity and then, a reliable procedure to evaluate the blades and vanes metal temperatures, is, nowadays, a crucial aspect for a safe components design. This two part work presents a three-dimensional conjugate heat transfer procedure developed in the framework of an internal research project of GE Oil & Gas.

The procedure, applied to the first rotor blade of the MS5002E gas turbine, consists of a conjugate heat transfer analysis in which the internal cooling system was modeled by an in-house one dimensional thermo-fluid network solver, the external heat loads and pressure distribution have been evaluated through 3D CFD and the heat conduction in the solid is carried out through a 3D FEM solution.

The first part of this work is focused on the description of the procedures in terms of set up of the equivalent fluid network model of internal cooling system and its tuning through experimental measurements of blade flow function. A first computation of blade metal temperature was obtained by coupling with CFD computations carried out on a de-featured geometry of the blade. Achieved results are compared with the data of a metallographic analysis performed on a blade operated on an actual engine. Some discrepancies are observed between datasets, suggesting the necessity to improve the models, mainly from the CFD side.
Unsteady CFD Analysis of Turbulent Flow and Heat Transfer in a Gas Turbine Blade Trailing Edge Subjected to Rotation
Authors: Borello Domenico , Delibra Giovanni , Bianchini Cosimo , Andreini Antonio
Published: August 2013

Internal cooling of gas turbine blade represents a challenging task involving several different phenomena as, among others, highly three-dimensional unsteady fluid flow, efficient heat transfer and structural design. This paper focuses on the analysis of the turbulent flow and heat transfer inside a typical wedge–shaped trailing edge cooling duct of a gas turbine blade. In the configuration under scrutiny the coolant flows inside the duct in radial direction and it leaves the blade through the trailing edge after a 90 deg turning.

At first an analysis of the flow and thermal fields in stationary conditions was carried out. Then the effects of rotational motion were investigated for a rotation number of 0.275. The rotation axis here considered is normal to the inflow and outflow bulk velocity, representing schematically a highly loaded blade configuration.

The work aimed to i) analyse the dynamic of the vortical structures under the influence of strong body forces and the constraints induced by the internal geometry and ii) to study the impact of such motions on the mechanisms of heat removal. The final aim was to verify the design of the equipment and to detect the possible presence of regions subjected to high thermal loads.

The analysis is carried out using the well assessed open source code OpenFOAM written in C++ and widely validated by several scientists and researchers around the world. The unsteadiness of the flow inside the trailing edge required to adopt models that accurately reconstructed the flow field. As the computational costs associated to LES (especially in the near wall regions) largely exceed the available resources, we chose for the simulation the SAS model of Menter, that was validated in a series of benchmark and industrially relevant test cases and allowed to reconstruct a part of the turbulence spectra through a scale-adaptive mechanism. Assessment of the obtained results with steady-state k-ω SST computations and available experimental results was carried out.

The present analysis demonstrated that a strong unsteadiness develops inside the trailing edge and that the rotation generated strong secondary motions that enhanced the dynamic of heat removal, leading to a less severe temperature distribution on the heated surface w.r.t the non rotating case.
Time-Averaged and Time-Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High-Pressure Turbine: Part I—Analytical and Experimental Comparisons
Authors: Green Brian R. , Mathison Randall M. , Dunn Michael G.
Published: August 2013

The effect of rotor purge flow on the unsteady aerodynamics of a high-pressure turbine stage operating at design corrected conditions has been investigated both experimentally and computationally. The experimental configuration consisted of a single-stage high-pressure turbine with a modern film-cooling configuration on the vane airfoil as well as the inner and outer end-wall surfaces. Purge flow was introduced into the cavity located between the high-pressure vane and the high-pressure disk. The high-pressure blades and the downstream low-pressure turbine nozzle row were not cooled. All hardware featured an aerodynamic design typical of a commercial high-pressure ratio turbine, and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response, flush-mounted pressure transducers and miniature thermocouples to measure flow field parameters above and below the angel wing.

Predictions of the time-dependent flow field in the turbine flow path were obtained using FINE/Turbo, a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code that had the capability to perform both steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three blade-row computational model that incorporated the purge flow cavity between the high-pressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The time-accurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the time-averaged and time-accurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for flow field analysis that will be provided in Part II.
Time-Averaged and Time-Accurate Aerodynamic Effects of Rotor Purge Flow for a Modern, One and One-Half Stage High-Pressure Turbine: Part II—Analytical Flow Field Analysis
Authors: Green Brian R. , Mathison Randall M. , Dunn Michael G.
Published: August 2013

The detailed mechanisms of purge flow interaction with the hot-gas flow path were investigated using both unsteady CFD and measurements for a turbine operating at design corrected conditions. This turbine consisted of a single-stage high-pressure turbine and the downstream, low-pressure turbine nozzle row with an aerodynamic design equivalent to actual engine hardware and typical of a commercial, high-pressure ratio, transonic turbine. The high-pressure vane airfoils and inner and outer endwalls incorporated state-of-the-art film cooling, and purge flow was introduced into the cavity located between the high-pressure vane and disk. The flow field above and below the blade angel wing was characterized by both temperature and pressure measurements. Predictions of the time-dependent flow field were obtained using a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code and a computational model incorporating the three blade rows and the purge flow cavity. The predictions were performed to evaluate the accuracy obtained by a design style application of the code, and no adjustment of boundary conditions was made to better match the experimental data.

Part I of this paper compared the predictions to the measurements in and around the purge flow cavity and demonstrated good correlation. Part II of this paper concentrates on the analytical results, looking at the primary gas path ingestion mechanism into the cavity as well as the effects of the rotor purge on the upstream vane and downstream rotor aerodynamics and thermodynamics. Ingestion into the cavity is driven by high static pressure regions downstream of the vane, high-velocity flow coming off the pressure side of the vane, and the blade bow waves. The introduction of the purge flow is seen to have an effect on the static pressure of the vane trailing edge in the lower 5% of span. In addition, the purge flow is weak enough that upon exiting the cavity, it is swept into the mainstream flow and provides no additional cooling benefits on the platform of the rotating blade.
A Study of Deposition on a Turbine Vane With a Thermal Barrier Coating and Various Film Cooling Geometries
Authors: Davidson F. Todd , Kistenmacher David A. , Bogard David G.
Published: August 2013

Recent interest has been shown in using synthetic gaseous (syngas) fuels to power gas turbine engines. An important issue concerning these fuels is the potential for increased contaminate deposition that can inhibit cooling designs and expedite the material degradation of vital turbine components. The purpose of this study was to provide a detailed understanding of how contaminates deposit on the surface of a turbine vane with a thermal barrier coating (TBC). The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients as well as the thermal conductivity of the vane wall. Four different film cooling configurations were studied: round holes, craters, a trench and a modified trench. The contaminates used in this study were small particles of paraffin wax that were sprayed into the mainstream flow of the wind tunnel. The wax particles modeled both the molten nature of contaminates in an engine as well as the particle trajectory by properly matching the expected range of Stokes number. This study found that the presence of film cooling significantly increased the accumulation of deposits. It was also found that the deposition behavior was strongly affected by the film cooling configuration that was used on the pressure side of the vane. The craters and trench performed the best in mitigating the accumulation of deposits immediately downstream of the film cooling configuration. In general, the presence of deposits reduced the film cooling performance on the surface of the TBC. However, the additional thermal insulation provided by the deposits improved the cooling performance at the interface of the TBC and vane wall.
Feasibility Study of Film Source Coupling Transpiration and a Row of Cylindrical Film Holes
Authors: Natsui Greg , Claretti Roberto , Wolski Constantine , Ricklick Mark , Kapat Jayanta S.
Published: August 2013

The present study assesses the performance of a film cooling source, composed of a segment of permeable wallinstalled near a row of cylindrical film holes. Coolant is introduced through both the permeable wall and the film holes resulting in a downstream film composed of both transpired and discretely injected coolant. The aerodynamic performance and cooling downstream of this coupled sourceare studied analytically, experimentally andnumerically. The sensitivity of transpiration blowing ratio, discrete hole blowing ratio, discrete hole pitch, transpiration slot width, and the relative positioning of the two sources on these global parameters of interest is the end result. The analytical results are used to get a basic understanding of the issue and design the test matrix for the numerical study. A range of design parameters are studied numerically in a Box-Behnken test matrix to yield global results which are then combined into one parameter, β. A second order response surface of the parameter βallows for a more complete understanding of the coupled source. This numerical analysis is compared with experimental results from two different coupled sources in order to assess the predictions. The results indicate that coupling of the two sources allows a more efficient use of coolant by generating a more uniform initial film. One coupled case in particular shows a 170% increase in cooling over the baseline cylindrical row, a 22% reduction in aerodynamic losses over the baseline transpiration source, all with a 51% reduction in mass flow as compared with the same cylindrical row baseline. Further study and optimization will allow this technique to provide more effective thermal protection at a lower cost of aerodynamic losses and spent coolant.
Direct Calculation of Entropy Generation by Solving Reynolds-Averaged Entropy Transport Equation in an Air-Cooled Turbine Cascade
Authors: Orhan Ömer Emre , Uzol Oguz
Published: August 2013

This paper presents an implementation of directly solving Reynolds-Averaged Entropy Transport equation as a part of the CFD solution to predict entropy generation rates in a two-dimensional turbine blade stator section. The Reynolds Averaged Entropy Transport and the necessary modeling equations are implemented to a commercial CFD solver as a User Defined Scalar (UDS). The results are compared with those obtained by post-processing the temperature and velocity fields obtained by solving full Navier-Stokes equations using a k-ε closure. Results show that there could be significant differences especially in the spatial distributions of entropy fields. This type of approach could offer significant improvements in entropy and loss prediction in turbomachinery flows. However, more studies especially for accurate modeling of temperature fluctuations and temperature-velocity correlations in the entropy transport equation are needed.
Large Eddy Simulation of Film Cooling Flows Using Octree Hexahedral Meshes
Authors: Fujimoto Shu
Published: August 2013

Today, high temperatures are needed for the inlet gas of turbines to increase the efficiency of gas turbines. The vanes and blades of a turbine that are exposed to hot gas must be cooled, and film cooling is now being widely applied to gas turbines because of its high cooling effectiveness. Recently, numerous researchers have conducted numerical simulations of film cooling flows using Reynolds-averaged Navier–Stokes (RANS) simulation, detached eddy simulation (DES), and large eddy simulation (LES) turbulence models, along with structured and/or unstructured meshes. In fact, for cooling designers, both the prediction accuracy and turnaround time (TAT) of their mesh generations are important to speedily and repeatedly optimize the locations of film cooling holes and shapes. Several researchers have examined the prediction accuracy and effectiveness of film cooling flows in case of RANS in order to minimize the TAT of mesh generation such as for unstructured meshes. However, few papers have considered LES.

In this paper, the open-source computational fluid dynamics (CFD) toolkit OpenFOAM [17] is used as the solver, and LES is used to numerically simulate the film cooling flow into the zero-pressure gradient cross-flow on a flat plate from cylindrical holes, which is one of the most typical and basic test cases. LES is used because of its ability to capture the flow unsteadiness and non-uniformity observed in film cooling flows. In addition, surface-adjusted octree hexahedral meshes, which are relatively easy to generate automatically are used. The mesh generation tool used in this study is snappyHexMesh, which is included in OpenFOAM. The experimental data presented by Sinha et al. [15] are used. Because the film cooling effectiveness strongly depends on certain parameters and conditions, those of the simulated film cooling flow are set to the experimental parameters and conditions as closely as possible. In this study, the density ratio DR is set to 2.0, and the blowing ratio BR is set to 0.5 and 1.0 with the steady cross-flow inlet. In addition, a case is considered where BR = 0.5 (DR = 2.0), with an unsteady turbulent cross-flow inlet.

In the case of LES, the results obtained using the octree hexahedral meshes are compared with those of the experiment and my previous film cooling study (Fujimoto [32]), which was conducted using multiblock structured meshes. The results show that the prediction accuracy using the octree hexahedral meshes is equivalent to that using the multiblock structured meshes, even though the mesh generation TAT is significantly smaller.
Robustness and Compensation of Information Transmission of Signaling Pathways
Authors: Uda Shinsuke , Saito Takeshi H , Kudo Takamasa , Kokaji Toshiya , Tsuchiya Takaho , Kubota Hiroyuki , Komori Yasunori , Ozaki Yu-ichi , Kuroda Shinya
Published: August 2013

Simple Signals?

Cells process information about themselves and their surroundings through biochemical signaling pathways.

Uda
et al.

(p.
558
8) used a recently developed cytometric method to quantitate signaling through biochemical pathways in individual rat pheochromocytoma cells responding to growth factors. The signaling pathways studied provided about 1 bit of information, or only enough for a binary (on or off) decision. In spite of the simplicity, the results showed interactions between pathways with shared components. In some cases, information carried between inputs and intermediate outputs was less than that between the input and more “downstream” outputs, indicating that information was carried through multiple paths. Similarly, in the presence of pharmacological inhibitors of one pathway, others were able to compensate to allow robust transfer of information. Thus, in spite of noise and variation in signal intensities in individual cells, robust transfer of information from the growth factors was achieved.
Changes in Ecologically Critical Terrestrial Climate Conditions
Authors: Diffenbaugh Noah S. , Field Christopher B.
Published: August 2013

The impact of climate on terrestrial ecosystems probably will be dramatic because of the rapid pace of climate change.
Spinning the Doppler Effect
Authors: Marrucci Lorenzo
Published: August 2013

Detection of an object's rotation by exploiting the orbital angular momentum of light may find applications in remote sensing and astronomy.

[Also see Report by

Lavery
et al.

]
Top Contenders Blast Pentagon's New Bioterror Detection Prize
Authors: Servick Kelly
Published: August 2013

Scientists vying for a $1 million DNA analysis prize are crying foul.
Venturing Back Into Colombia
Authors: Regalado Antonio
Published: August 2013

In rural areas where guerrillas and drug traffickers have long been in control, researchers are now on the scene—but so are cattle ranchers, miners, and palm oil planters.
Discovery of a New Titi Monkey
Authors: Regalado Antonio
Published: August 2013

A young Colombian researcher made the find of a lifetime when he discovered the red-bearded titi monkey.
Coca Science Seeks an Answer in Kilos
Authors: Regalado Antonio
Published: August 2013

The scientists who work at the Pijaos ranch have two main goals: to perfect ways to kill the coca plant and to estimate exactly how much cocaine is produced in Colombia.
How a Fickle Climate Made Us Human
Authors: Gibbons Ann
Published: August 2013

Researchers are drilling for clues to how dramatic changes in African rainfall and vegetation shaped our species.
Tundra in Turmoil
Authors: Pennisi Elizabeth
Published: August 2013

Models and experiments only go so far in assessing the effects of climate change. For a reality check, researchers turn to historical photos.
Comparison of the FDA-Approved CDC DENV-1-4 Real-Time Reverse Transcription-PCR with a Laboratory-Developed Assay for Dengue Virus Detection and Serotyping
Authors: Waggoner Jesse J. , Abeynayake Janaki , Sahoo Malaya K. , Gresh Lionel , Tellez Yolanda , Gonzalez Karla , Ballesteros Gabriela , Guo Frances P. , Balmaseda Angel , Karunaratne Kumudu , Harris Eva , Pinsky Benjamin A.
Published: August 2013

Dengue virus (DENV) is the agent of the most common vector-borne disease worldwide. Using 199 clinical samples collected from Nicaragua and Sri Lanka, a laboratory-developed DENV multiplex real-time reverse transcription-PCR (rRT-PCR) proved more clinically sensitive than the FDA-approved CDC assay for DENV serotypes 1 to 4 when measured against a composite reference standard, with sensitivities of 97.4% versus 87.1%, respectively.
Reverse Transcription-PCR–Electrospray Ionization Mass Spectrometry for Rapid Detection of Biothreat and Common Respiratory Pathogens
Authors: Jeng Kevin , Hardick Justin , Rothman Richard , Yang Samuel , Won Helen , Peterson Stephen , Hsieh Yu-Hsiang , Masek Billie Jo , Carroll Karen C. , Gaydos Charlotte A.
Published: August 2013

Electrospray ionization mass spectrometry (ESI-MS) analysis of reverse transcription (RT)-PCR amplicons from human respiratory samples allows for broad pathogen identification approximately 8 h after collection. We investigated the performance characteristics of a high-throughput RT-PCR-coupled ESI-MS assay for distinguishing biothreat (BT) agents from common bacterial, fungal, and viral respiratory pathogens in bronchoalveolar lavage (BAL) fluid specimens from subjects with suspected respiratory infections. In a retrospective case series, 202 BAL fluid specimens were collected at the Johns Hopkins Hospital between August 2010 and February 2011 from patients with suspected acute respiratory infections. Samples were processed using standard bacterial, viral, and fungal testing in the clinical microbiology laboratory as part of routine care and then were blindly spiked with either water or nucleic acids from BT organisms (Bacillus anthracis,Yersinia pestis,Francisella tularensis,Brucellaspp.,Burkholderiaspp., andRickettsia prowazekii) and tested by RT-PCR–ESI-MS. The sensitivities and specificities of RT-PCR–ESI-MS versus standard clinical methods were as follows: for mock BT DNA, 98.5% sensitivity (95% confidence interval [CI], 94.2 to 99.7%) and 100% specificity (95% CI, 93.1 to 100.0%); for bacterial pathogens, 81.8% sensitivity (95% CI, 74.3 to 87.6%) and 73.6% specificity (95% CI, 64.2 to 81.4%); for viral pathogens, 93.3% sensitivity (95% CI, 66.0 to 99.7%) and 97.3% specificity (95% CI, 89.7 to 99.5%); for fungal pathogens, 42.6% sensitivity (95% CI, 29.5 to 56.7%) and 97.8% specificity (95% CI, 91.8 to 99.6%). Our data suggest that RT-PCR–ESI-MS is a useful adjunct to standard culture protocols for rapid detection of both BT and common respiratory pathogens; further study is required for assay validation, especially for fungal detection, and potential implementation.
Identification and Subtyping of Clinically Relevant Human and Ruminant Mycoplasmas by Use of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry
Authors: Pereyre S. , Tardy F. , Renaudin H. , Cauvin E. , Del Prá Netto Machado L. , Tricot A. , Benoit F. , Treilles M. , Bébéar C.
Published: August 2013

Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) recently emerged as a technology for the identification of bacteria. In this study, we aimed to evaluate its applicability to human and ruminant mycoplasmal identification, which can be demanding and time-consuming when using phenotypic or molecular methods. In addition, MALDI-TOF MS was tested as a subtyping tool for certain species. A total of 29 main spectra (MSP) from 10 human and 13 ruminant mycoplasma (sub)species were included in a mycoplasma MSP database to complete the Bruker MALDI Biotyper database. After broth culture and protein extraction, MALDI-TOF MS was applied for the identification of 119 human and 143 ruminant clinical isolates that were previously identified by antigenic or molecular methods and for subcultures of 73 ruminant clinical specimens that potentially contained several mycoplasma species. MALDI-TOF MS resulted in accurate (sub)species-level identification with a score of ≥1.700 for 96% (251/262) of the isolates. The phylogenetically closest (sub)species were unequivocally distinguished. Although mixtures of the strains were reliably detected up to a certain cellular ratio, only the predominant species was identified from the cultures of polymicrobial clinical specimens. For typing purposes, MALDI-TOF MS proved to cluster
Mycoplasma bovis
and
Mycoplasma agalactiae
isolates by their year of isolation and genome profiles, respectively, and
Mycoplasma pneumoniae
isolates by their adhesin P1 type. In conclusion, MALDI-TOF MS is a rapid, reliable, and cost-effective method for the routine identification of high-density growing mycoplasmal species and shows promising prospects for its capacity for strain typing.
Evaluation of the Clinical Performance of the cobas 4800 HPV Test in Patients Referred for Colposcopy
Authors: White Christine , Keegan Helen , Pilkington Loretto , Ruttle Carmel , Kerr Patrick , Sharp Linda , O'Toole Sharon , Turner Michael , Prendiville Walter , D'Arcy Tom , Fitzpatrick Myra , Lenehan Peter , Flannelly Grainne , O'Leary John J. , Martin Cara M.
Published: August 2013

The clinical performance of the cobas human papillomavirus (HPV) test for detection of high-grade disease in a colposcopy-referred population was compared with that of Hybrid Capture 2 (HC2). The overall agreement between the tests was 92.3%. Clinical sensitivity and specificity for detection of cervical intraepithelial neoplasia grade 2 or greater (CIN2+) were 90.0% and 55.5% for cobas and 90.5% and 50.2% for HC2, respectively. In conclusion, both tests showed comparable performance for detection of CIN2+.
Cellular mRNA Decay Protein AUF1 Negatively Regulates Enterovirus and Human Rhinovirus Infections
Authors: Cathcart Andrea L. , Rozovics Janet M. , Semler Bert L.
Published: August 2013

To successfully complete their replication cycles, picornaviruses modify several host proteins to alter the cellular environment to favor virus production. One such target of viral proteinase cleavage is AU-rich binding factor 1 (AUF1), a cellular protein that binds to AU-rich elements, or AREs, in the 3′ noncoding regions (NCRs) of mRNAs to affect the stability of the RNA. Previous studies found that, during poliovirus or human rhinovirus infection, AUF1 is cleaved by the viral proteinase 3CD and that AUF1 can interact with the long 5′ NCR of these viruses
in vitro
. Here, we expand on these initial findings to demonstrate that all four isoforms of AUF1 bind directly to stem-loop IV of the poliovirus 5′ NCR, an interaction that is inhibited through proteolytic cleavage of AUF1 by the viral proteinase 3CD. Endogenous AUF1 was observed to relocalize to the cytoplasm of infected cells in a viral protein 2A-driven manner and to partially colocalize with the viral protein 3CD. We identify a negative role for AUF1 in poliovirus infection, as AUF1 inhibited viral translation and, ultimately, overall viral titers. Our findings also demonstrate that AUF1 functions as an antiviral factor during infection by coxsackievirus or human rhinovirus, suggesting a common mechanism that targets these related picornaviruses.
The Surface Glycoprotein of Feline Leukemia Virus Isolate FeLV-945 Is a Determinant of Altered Pathogenesis in the Presence or Absence of the Unique Viral Long Terminal Repeat
Authors: Bolin Lisa L. , Ahmad Shamim , Lobelle-Rich Patricia A. , Ooms Tara G. , Alvarez-Hernandez Xavier , Didier Peter J. , Levy Laura S.
Published: August 2013

Feline leukemia virus (FeLV) is a naturally transmitted gammaretrovirus that infects domestic cats. FeLV-945, the predominant isolate associated with non-T-cell disease in a natural cohort, is a member of FeLV subgroup A but differs in sequence from the FeLV-A prototype, FeLV-A/61E, in the surface glycoprotein (SU) and long terminal repeat (LTR). Substitution of the FeLV-945 LTR into FeLV-A/61E resulted in pathogenesis indistinguishable from that of FeLV-A/61E, namely, thymic lymphoma of T-cell origin. In contrast, substitution of both FeLV-945 LTR and SU into FeLV-A/61E resulted in multicentric lymphoma of non-T-cell origin. These results implicated the FeLV-945 SU as a determinant of pathogenic spectrum. The present study was undertaken to test the hypothesis that FeLV-945 SU can act in the absence of other unique sequence elements of FeLV-945 to determine the disease spectrum. Substitution of FeLV-A/61E SU with that of FeLV-945 altered the clinical presentation and resulted in tumors that demonstrated expression of CD45R in the presence or absence of CD3. Despite the evident expression of CD45R, a typical B-cell marker, T-cell receptor beta (TCRβ) gene rearrangement indicated a T-cell origin. Tumor cells were detectable in bone marrow and blood at earlier times during the disease process, and the predominant SU genes from proviruses integrated in tumor DNA carried markers of genetic recombination. The findings demonstrate that FeLV-945 SU alters pathogenesis, although incompletely, in the absence of FeLV-945 LTR. Evidence demonstrates that FeLV-945 SU and LTR are required together to fully recapitulate the distinctive non-T-cell disease outcome seen in the natural cohort.