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Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by the formation of a cystic cavity (syrinx) in the spinal cord (SC), has not yet been provided. It has been hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused by subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause of syrinx formation and subsequent pain in the patient. However, paucity in detailed in vivo pressure data has made theoretical explanations for the syrinx difficult to reconcile. In order to understand the complex pressure environment, four simplified in vitro models were constructed to have anatomical similarities with post-traumatic SM and Chiari malformation related SM. Experimental geometry and properties were based on in vivo data and incorporated pertinent elements such as a realistic CSF flow waveform, spinal stenosis, syrinx, fexible SC, and flexible spinal column. The presence of a spinal stenosis in the SAS caused peak-to-peak cerebrospinal fluid CSF pressure fluctuations to increase rostral to the stenosis. Pressure with both stenosis and syrinx present was complex. Overall, the interaction of the syrinx and stenosis resulted in a diastolic valve mechanism and rostral tensioning of the SC. In all experiments, the blockage was shown to increase and dissociate SAS pressure, while the axial pressure distribution in the syrinx remained uniform. These results highlight the importance of the properties of the SC and spinal SAS, such as compliance and permeability, and provide data for comparison with computational models. Further research examining the influence of stenosis size and location, and the importance of tissue properties, is warranted. [DOI: 10.1115/1.4000089] Keywords: cerebrospinal fluid hydrodynamics, syringomyelia, Chiari malformation, hydrocephalus, fluid-structure interaction, spinal cord, subarachnoid space stenosis, syrinx, intracranial and spinal pressures, in vitro model

An infinite-line probe is commonly used to measure unsteady pressure in high-temperature environments while protecting the pressure transducer. In this study, an existing theoretical model is used to derive the response of a waveguide pressure measuring system. An ambient temperature centrifugal compressor rig acts as an experimental source of fluctuating pressure. The compressor is operated at different discrete rotational speeds, and the blade-passing frequencies are used to obtain frequency response data. In the experiments, pressure waves attenuated at a rate faster than that predicted by the theoretical model for a 0.322 m (12 in.) sensor offset. Furthermore, the decay in the magnitude of the pressure oscillations accelerated at blade-passing frequencies above 9 kHz. A unique contribution of this study is to show that whereas the experimentally observed overall attenuation is broadly consistent with the theoretical predictions, pressure oscillations corresponding to individual blade passages may be disproportionally attenuated. [DOI: 10.1115/1.3159387]

Although uplift motion of flat-bottom cylindrical shell tanks has been considered to contribute toward various damages to the tanks, the mechanics were not fully understood. As well as uplift displacement of the tanks, fluid pressure accompanying the uplift motion of the tanks may play an important role in the cause of the damage. An accurate estimate of the fluid pressure induced by the uplift motion of the tanks is indispensable in protecting the tanks against destructive earthquakes. As a first step of a series of research, this study mathematically derives the fluid pressure on a rigid rectangular tank with a unit depth accompanying angular acceleration, which acts on a pivoting bottom edge. The rectangular tank employed herein is equivalent to a thin slice of the central vertical cross section of a rigid flat-bottom cylindrical shell tank. Assuming a perfect fluid and velocity potential, a continuity equation is given by the Laplace equation in Cartesian coordinates. The fluid velocities accompanying the motions of the walls and bottom plate constitute the boundary conditions. Since this problem is set as a parabolic partial differential equation of the Neumann problem, the velocity potential is solved with the Fourier-cosine expansion. The derivative of the velocity potential with respect to time gives the fluid pressure at an arbitrary point inside the tank. A mathematical solution for evaluating the fluid pressure accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with the Fourier series. The proposed mathematical solution well converges with a few first terms of the Fourier series. Values of the fluid pressure computed by the explicit finite element (FE) analysis well agrees with those by the proposed mathematical solution. For the designers' convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. Consequently, the mathematical solution given by the Fourier series converges easily and provides accurate evaluation of the fluid pressures on a rigid rectangular tank accompanying the angular acceleration acting on the pivoting bottom edge. Irregularity in the fluid pressure distribution increases as the tank becomes taller. [DOI: 10.1115/1.4000546] Keywords: flat-bottom cylindrical shell tank, fluid pressure, angular acceleration, uplift motion, Fourier-cosine expansion, velocity potential, normalized fluid pressure, rigid rectangular tank

To protect flat-bottom cylindrical tanks against severe damage from uplift motion, accurate evaluation of accompanying fluid pressures is indispensable. This paper presents a mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank in the same manner as the procedure outlined and discussed previously by the authors (Taniguchi, T., and Ando, Y., 2010, 'Fluid Pressures on Unanchored Rigid Rectangular Tanks Under Action of Uplifting Acceleration,' ASME J. Pressure Vessel Technol., 132(1), p. 011801). With perfect fluid and velocity potential assumed, the Laplace equation in cylindrical coordinates gives a continuity equation, while fluid velocity imparted by the displacement (and its time derivatives) of the shell and bottom plate of the tank defines boundary conditions. The velocity potential is solved with the Fourier--Bessel expansion, and its derivative, with respect to time, gives the fluid pressure at an arbitrary point inside the tank. In practice, designers have to calculate the fluid pressure on the tank whose perimeter of the bottom plate lifts off the ground like a crescent in plan view. However, the asymmetric boundary condition given by the fluid velocity imparted by the deformation of the crescent-like uplift region at the bottom cannot be expressed properly in cylindrical coordinates. This paper examines applicability of a slice model which is a rigid rectangular tank with a unit depth vertically sliced out of a rigid flat-bottom cylindrical tank with a certain deviation from (in parallel to) the center line of the tank. A mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with Fourier series. It well converges with a few first terms of the Fourier series and accurately calculates the values of the fluid pressure on the tank. In addition, the slice model approximates well the values of the fluid pressure on the shell of a rigid flat-bottom cylindrical tank for any points deviated from the center line. For the designers' convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. The proposed mathematical and graphical methods are cost effective and aid in the design of the flat-bottom cylindrical tanks that allow the uplifting of the bottom plate. [DOI: 10.1115/1.4000374] Keywords: flat-bottom cylindrical tank, fluid pressure, uplift motion, Fourier--Bessel expansion, velocity potential pivoting edge, normalized fluid pressure, angular acceleration, slice model

A detailed review and analysis of the hydrodynamic characteristics of laminar developing and fully developed flows in noncircular ducts is presented. New models are proposed, which simplify the prediction of the friction factor--Reynolds product f Re for developing and fully developed flows in most noncircular duct geometries found in heat exchanger applications. By means of scaling analysis it is shown that complete problem may be easily analyzed by combining the asymptotic results for the short and long ducts. Through the introduction of a new characteristic length scale, the square root of cross-sectional area, the effect of duct shape has been minimized. The new model has an accuracy of [+ or -]10% or better for most common duct shapes when nominal aspect ratios are used, and [+ or -]3% or better when effective aspect ratios are used. Both singly and doubly connected ducts are considered. [DOI: 10.1115/1.4000377] Keywords: laminar flow, noncircular ducts, hydrodynamic entrance length, developing flow, modeling, pressure drop

This paper discussed the computational accuracy of roughsurface point-contact isothermal elastohydrodynamic lubrication (EHL) analysis by investigating the effects of differential scheme, viscosity-pressure, and shear-thinning models. An EHL experiment with multitransverse ridges was employed as simulated target. Four differential schemes, including the combined and the separate first-order and second-order backward schemes, were investigated. It is found that the separate second-order backward scheme offers the best results based on the comparison with the experimental data, with which two roughness derivatives may be fully or partially canceled each other; thus, the discretization error induced by roughness can be reduced. The consistency of differential schemes is an important issue for the separate schemes. The Yasutomi free-volume viscosity-pressure model and the Eyring rheological model are found to yield the numerical simulations the closest to experimental results. [DOI: 10.1115/1.2842245] Keywords: EHL, differential schemes, viscosity-pressure models, rheological models

Contours of surface texture of contact faces are not always parallel to the directions of the axis in solving Reynolds equations with finite difference method, and this often induces significant pressure saw-tooth effect, which results in an unignored analysis error. In this paper, pseudo-nine-point finite difference, as a new finite difference method, is introduced to solve the lubrication numerical problem of pressure saw-tooth. Also, application is carried out in gas lubrication of hard disk systems to verify the validity of the new method. In analysis, pressure distributions and gas floating forces are calculated for two different types of sliders, and the astringency and efficiency of the new method is discussed. Numerical results show that the pseudo-nine-point finite difference method can restrain pressure saw-tooth evidently, and presents better astringency and efficiency than the traditional five-point finite difference method. With the increase in mesh density, pressure distribution and gas floating force trend to steady. Also, numerical values of the floating force agree well with the experimental ones. [DOI: 10.1115/1.3195039] Keywords: pseudo-nine-point finite difference, pressure saw-tooth, gas lubrication

The burst pressure of cylinders with hillside nozzle is determined using both experimental and finite element analysis (FEA) approaches. Three full-scale test models with different angles of the hillside nozzle were designed and fabricated specifically for a hydrostatic test in which the cylinders were pressurized with water. 3D static nonlinear finite element simulations of the experimental models were performed to obtain the burst pressures. The burst pressure is defined as the internal pressure for which the structure approaches dimensional instability, i.e., unbounded strain for a small increment in pressure. Good agreement between the predicted and measured burst pressures shows that elastic-plastic finite element analysis is a viable option to estimate the burst pressure of the cylinders with hillside nozzles. The preliminary results also suggest that the failure location is near the longitudinal plane of the cylinder-nozzle intersection and that the burst pressure increases slightly with an increment in the angle of the hillside nozzle. [DOl: 10.1115/1.3147987] Keywords: burst pressure, hillside nozzle, cylinder-nozzle intersection, finite element analysis

Pressure pulsations in the piping system of the reciprocating compressor produce excessive noise and even lead to damage in piping and machinery. Therefore, it is very important to predict precisely the pressure pulsation with large amplitude in the piping system. In this paper, the finite disturbance theory is used to solve the nonlinear partial differential equations that describe the unsteady one-dimensional compressible flow in the complex piping system. The solution is then compared with experimental results. The comparison shows that the finite theory fits the large pressure disturbance more precisely than the acoustic theory. [DOI: 10.111511.3085882] Keywords: pressure pulsation, piping system, reciprocating compressor, finite disturbance theory, acoustic theory

This paper describes experimental work performed at General Electric, Global Research Center to evaluate the performance and understand the risks of using dry low N[O.sub.x] (DLN) technologies in exhaust gas recirculation (EGR) conditions. Exhaust gas recirculation is viewed as an enabling technology for increasing the C[O.sub.2] concentration of the flue gas while decreasing the volume of the postcombustion separation plant and therefore allowing a significant reduction in C[O.sub.2] capture cost. A research combustor was developed for exploring the performance of nozzles operating in low [O.sub.2] environment at representative pressures and temperatures. A series of experiments in a visually accessible test rig have been performed at gas turbine pressures and temperatures, in which inert gases such as [N.sub.2]/C[O.sub.2] were used to vitiate the fresh air to the levels determined by cycle models. Moreover, the paper discusses experimental work performed using a DLN nozzle used in GE's F-class heavy-duty gas turbines. Experimental results using a research combustor operating in a partially premixed mode include the effect of EGR on operability, efficiency, and emission performance under conditions of up to 40% EGR. Experiments performed in a fully premixed mode using a DLN single nozzle combustor revealed that further reductions in N[O.sub.x] could be achieved while at the same time still complying with CO emissions. While most existing studies concentrate on limitations related to the minimum oxygen concentration (MOC) at the combustor exit, we report the importance of C[O.sub.2] levels in the oxidizer. This limitation is as important as the MOC, and it varies with the pressure and firing temperatures. [DOI: 10.1115/1.2982158]

An ex-vessel steam explosion may occur when, during a severe reactor accident, the reactor pressure vessel fails and the molten core pours into the water in the reactor cavity. A steam explosion is a fuel-coolant interaction process where the heat transfer from the melt to water is so intense and rapid that the timescale for heat transfer is shorter than the timescale for pressure relief This can lead to the formation of shock waves and production of missiles that may endanger surrounding structures. A strong enough steam explosion in a nuclear power plant could jeopardize the containment integrity and so lead to a direct release of radioactive material to the environment. In the article, different scenarios of ex-vessel steam explosions in a typical pressurized water reactor cavity are analyzed with the code MC3D, which is being developed for the simulation of fuel-coolant interactions. A comprehensive parametric study was performed by varying the location of the melt release (central and side melt pours), the cavity water subcooling, the primary system overpressure at vessel failure, and the triggering time for explosion calculations. The main purpose of the study was to determine the most challenging ex-vessel steam explosion cases in a typical pressurized water reactor and to estimate the expected pressure loadings on the cavity walls. Special attention was given to melt droplet freezing, which may significantly influence the outcome of the fuel-coolant interaction process. The performed analysis shows that for some ex-vessel steam explosion scenarios much higher pressure loads are predicted than obtained in the OECD program SERENA Phase 1. [DOI: 10.1115/1.3078789] Keywords: steam explosion, ex-vessel, reactor cavity, pressure load, severe accident

The paper will present an analytical model for the evaluation of the pressure and flow rate oscillations in a given axial inducer test facility. The proposed reduced order model is based on several simplifying assumptions and takes into account the facility design and the dynamic properties of the tested inducer. The model has been used for evaluating the dynamic performance of a prototype of the LE-7 engine liquid oxygen (LOX) inducer, in tests carried out under given external flow rate excitations. The main results of these calculations will be shown, including the expected oscillations under a wide range of operational conditions and the influence of facility design. Calculations showed that the only way to obtain the two linearly independent test conditions, necessary for evaluating the inducer transfer matrix, is by changing the facility suction line: Any other changes in the facility design would result ineffective. Some other important design indications provided by the analytical model will be presented in the paper. [DOI: 10.1115/1.3089535]

Tekscan pressure sensors are used in biomechanics research to measure joint contact loads. While the overall accuracy of these sensors has been reported previously, the effects of different calibration algorithms on sensor accuracy have not been compared. The objectives of this validation study were to determine the most appropriate calibration method supplied in the Tekscan program software and to compare its accuracy to the accuracy obtained with two user-defined calibration protocols. We evaluated the calibration accuracies for test loads within the low range, high range, and full range of the sensor. Our experimental setup used materials representing those found in standard prosthetic joints, i.e., metal against plastic. The Tekscan power calibration was the most accurate of the algorithms provided with the system software, with an overall rms error of 2.7% of the tested sensor range, whereas the linear calibrations resulted in an overall rms error of up to 24% of the tested range. The user-defined ten-point cubic calibration was almost five times more accurate, on average, than the power calibration over the full range, with an overall rms error of 0.6% of the tested range. The user-defined three-point quadratic calibration was almost twice as accurate as the Tekscan power calibration, but was sensitive to the calibration loads used. We recommend that investigators design their own calibration curves not only to improve accuracy but also to understand the range(s) of highest error and to choose the optimal points within the expected sensing range for calibration. Since output and sensor nonlinearity, depend on the experimental protocol (sensor type, interface shape and materials, sensor range in use, loading method, etc.), sensor behavior should be investigated for each different application. [DOI: 10.1115/1.3005165] Keywords: Tekscan, pressure sensor, calibration, accuracy, prosthetic joints

The loss of the initial tightness during service is one of the major causes of failure of tube-to-tubesheet joints. The initial residual contact pressure and its variation during the lifetime of the joint are among the parameters to blame. A reliable assessment of the initial contact pressure value requires accurate and rigorous modeling of the elastoplastic behavior of the tube and the tubesheet during the expansion process. This paper deals with the development of a new analytical model used to accurately predict the residual contact pressure resulting from a hydraulic expansion process. The analytical model is based on the elastic perfectly plastic material behavior of the tube and the tubesheet and the interaction between these two elements of the expanded joint. The model results have been compared and validated with those of the more accurate finite element analysis models. Additional comparisons have been made with existing methods. [DOI: 10.1115/1.3027462]

The indicated mean effective pressure (IMEP) is typically used as an engine running quality metric. IMEP depends on cylinder pressure, which is costly to measure, therefore it is useful to estimate IMEP from currently measured crankshaft encoder data. In this paper, the difficulties in developing an optimal linear estimator from acceleration computed from crankshaft rotational speed and cylinder pressure data are discussed, and strategies are presented to reduce these difficulties. Estimating IMEP from crankshaft data requires the determination of which data to use in the estimator Without this step, the estimator can become unnecessarily complex due the inclusion of strongly correlated data points in the estimator. A strategy to determine the angular location of the acceleration points to use is presented and is shown to greatly reduce the estimator complexity without significantly affecting estimation error Additionally, while increasing the estimator order usually decreases the estimation error, it will be shown that increasing the estimator order can actually increase the estimation error. This effect is due to uncertainties in the gains of the estimator. These uncertainties in the gains can result from using limited training data to estimate the statistics necessary to compute the gains or when dealing with a nonstationary system. A method of reducing the effect of these uncertainties by optimizing the estimator order based on the number of available training data cycles is developed and demonstrated. [DOI: 10.1115/1.3023115]

An experimental investigation was conducted to study the effects of increased ambient pressure (up to 6.89 MPa) and increased nozzle pressure drop (up to 2.8 MPa) on the cone angles for sprays produced by pressure-swirl atomizers having varying amounts of initial swirl. This study extends the classical results of DeCorso and Kemeny, (1957, 'Effect of Ambient and Fuel Pressure on Nozzle Spray Angle,' ASME Transactions, 79(3), pp. 607-615). Shadow photography was used to measure cone angles at x/[D.sub.0] = 10, 20, 40, and 60. Our lower pressure results for atomizer swirl numbers of 0.50 and 0.25 are consistent with those of DeCorso and Kemeny, who observed a decrease in cone angle with an increase in nozzle pressure drop, [DELTA]P, and ambient density, [[rho].sub.air] until a minimum cone angle was reached when [DELTA]P[[rho].sub.air.sup.1.6] ~100 MPa[(kg/[m.sup.3]).sup.1.6] (equivalent to 200 psi[(lbm/[ft.sup.3]).sup.1.6]). Results for atomizers having higher initial swirl do not match the DeCorso and Kemeny results as well, suggesting that their correlation be used with caution. Another key finding is that an increase in [DELTA]P[[rho].sub.air.sup.1.6] to a value of 600 MPa[(kg/[m.sup.3]).sup.1.6] leads to continued decrease in cone angle, but that a subsequent increase to 2000 MPa[(kg/[m.sup.3]).sup.1.6] has little effect on cone angle. Finally, there was little effect of nozzle pressure drop on cone angle, in contrast to findings of previous workers. These effects are hypothesized to be due to gas entrainment. [DOI: 10.1115/1.2939004] Keywords: pressure swirl, cone angle, nozzle pressure drop, ambient pressure, entrainment

Pressure drop through anisotropic porous mediumlike cylinder bundles is experimentally examined in turbulent flow regime. Three porosities, [epsilon] = 0.66, 0.82, and 0.90, are considered. The flow blockage by the cylinder bundles is varied, with the yaw angle ([alpha]) used as an anisotropic measure. When the yaw angle is fixed while the porosity is varied, the pressure drop behaves as predicted by the force balance model, consistent with the classic observation: The pressure drop is proportional to the square of the flow velocity with the empirical proportionality as a function of (1 - [[epsilon].sup.1/2])[[epsilon].sup.2] obtained from the force balance model compared to that of (1 - [epsilon])/[[epsilon].sup.3] from the hydraulic radius theory. On the other hand, for a given porosity, topological anisotropy of the cylinder bundles causes the sinusoidal response of the pressure drop to the variation of yaw angle. At [alpha] = 0 deg with a 60 deg period, the lowest pressure drop occurs from the most open configuration of the cylinder bundle whereas the largest flow blockage at [alpha] = 30 deg causes the highest pressure drop. This variation appears to result from an increase in the drag coefficient of each cylinder element in a harmonic manner.

This study shows the results of pressure distribution measurements on a rotor blade of a horizontal axis wind turbine under various yawed operations. The experiments are carried out in a wind tunnel with a 2.4 m diameter test rotor. In the measurements, the power curve and pressure distributions are measured for different azimuth angles. By increasing yaw angle, the maximum value of power coefficient of the rotor decreases. The sign of the yaw angle does not have any effect on power performance. The aerodynamic forces are discussed using the axial and rotational force coefficients for each azimuth angle. In the case of higher tip speed ratios, the blade section passing on the upstream side in yawed operations has a greater contribution to the rotor torque than that on the downstream side. In this tip speed range, the aerodynamic forces at the 70% radius section appear proportional to the angle of attack. In the case of the lower tip speed ratios, the blade on the downstream side does not contribute to rotor torque, which appears to result from separation. [DOI: 10.1115/1.2931514] Keywords: wind turbine, performance, pressure distribution, yawed inflow

A normalized P-V curve is proposed for quantitative comparisons of quasistatic P-V curves from different sources, including data from different investigators, airway pressure-volume curves versus transpulmonary pressure-volume curves, normal versus injured respiratory system, and animal tests versus clinical data. Similarities and differences among five different data groups we analyzed are shown to be quantified through the nondimensional pressure range of an individual data set, combined with the magnitudes of two nondimensional parameters of the inflation limb, derived from a respiratory system model previously reported. [DOI: 10.1115/1.2913345] Keywords: pulmonary pressure-volume curve, respiratory system model, alveolar recruitment, lung injury, ARDS, similitude

Numerical analysis of flow distribution inside a compact ceramic high temperature heat exchanger and chemical decomposer (thereafter, heat exchanger), which will be used for hydrogen production, wherein the sulfur iodine thermochemical cycle is performed. To validate the numerical model, experimental investigation of the heat exchanger is accomplished. The study of the flow distribution in the base line design heat exchanger shows that the design has large-flow maldistribution and the reverse flow may occur at poor inlet and outlet manifold configurations. To enhance uniformity of the flow rate distribution among the heat exchanger internal channels, several improved designs of the heat exchanger manifolds and supply channels are proposed. The proposed designs have a sufficiently uniform flow rate distribution among the internal channels, with an appropriate pressure drop. [DOI: 10.1115/1.2911680] Keywords: CFD, pressure drop, fluid flow distribution, channel flow, gross flow maldistribution

A respiratory system model (RSM) is developed for the deflation process of a quasistatic pressure-volume (P-V) curve, following the model for the inflation process reported earlier. In the RSM of both the inflation and the deflation limb, a respiratory system consists of a large population of basic alveolar elements, each consisting of a piston-spring-cylinder subsystem. A normal distribution of the basic elements is derived from Boltzmann statistical model with the alveolar closing (opening) pressure as the distribution parameter for the deflation (inflation) process. An error minimization by the method of least squares applied to existing P-V loop data from two different data sources confirms that a simultaneous inflation-deflation analysis is required for an accurate determination of RSM parameters. Commonly used terms such as lower inflection point, upper inflection point, and compliance are examined based on the P-V equations, on the distribution function, as well as on the geometric and physical properties of the basic alveolar element. Keywords: pulmonary pressure-volume curve, respiratory system model, alveolar recruitment, lung injury, ARDS

A simple model is developed here to predict the pressure drop and discharge coefficient for incompressible flow through orifices with length-to-diameter ratio greater than zero (orifice tubes) over wide ranges of Reynolds number The pressure drop for flow through orifice tubes is represented as two pressure drops in series; namely, a pressure drop for flow through a sharp-edged orifice in series with a pressure drop for developing flow in a straight length of tube. Both of these pressure drop terms are represented in the model using generally accepted correlations and experimental data for developing flows and sharp-edged orifice flow. We show agreement between this simple model and our numerical analysis of laminar orifice flow with length-to-diameter ratio up to 15 and for Reynolds number up to 150. Agreement is also shown between the series pressure drop representation and experimental data over wider ranges of Reynolds number. Not only is the present work useful as a design correlation for equipment relying on flow through orifice tubes but it helps to explain some of the difficulties that previous authors have encountered when comparing experimental observation and available theories.

A single-jet water meter was modeled and simulated within a wide measuring range that included flow rates in laminar, transitional, and turbulent flow regimes. The interaction between the turbine and the flow, on which the operating principle of this kind of meter is based, was studied in depth from the detailed information provided by simulations of the three dimensional flow within the meter. This interaction was resolved by means of a devised semi-implicit time-marching procedure in such a way that the speed and the position of the turbine were obtained as part of the solution. Results obtained regarding the turbine's mean rotation speed, measurement error, and pressure drop were validated through experimental measurements performed on a test rig. The role of mechanical friction on the performance of the meter at low flow rates was analyzed and interesting conclusions about its influence on the reduction of the turbine's rotation speed and on the related change in the measurement error were drawn. The mathematical model developed was capable of reproducing the performance of the meter throughout the majority of the measuring range, and thus was shown to be a very valuable tool for the analysis and improvement of the single-jet water meter studied. Keywords: single-jet water meter, CFD, fluid-structure interaction, measurement error, pressure drop, mechanical friction

An experimental investigation has been made on a turbulent boundary layer near the trailing edge on a long flat plate. The flow was controlled by an additional splitter plate fitted to the trailing edge along the wake centerline. The length of the splitter plate, l, was varied from a half, to five times the trailing edge thickness, h. Measurements of base pressure behind the trailing edge and of mean velocity and pressure distribution in the turbulent boundary layer on the flat plate were made under the freestream zero-pressure gradient. The absolute value of the base pressure coefficient of the long flat plate was considerably smaller than that of the short flat plate without the splitter plate. A significant increase in the base pressure coefficient was achieved with the splitter plate (l/h [greater than or equal to] 1), fitted to the long flat plate. Within an inner layer in the turbulent boundary layer near the trailing edge, the mean velocity increased more than that in the upstream position in the case without the splitter plate. With the splitter plate, however, the base pressure rise made the mean velocity distribution more closely approach that of a fully developed turbulent boundary layer. Keywords: flat plate, boundary layer, separation, splitter plate, base pressure

Fundamental aspects of Common Rail (CR) fuel-injection-system dynamics were investigated, paying specific attention to the wave propagation induced pressure oscillations and to their relationships with the system control parameters and multiple-injection performance. A detailed experimental analysis of the pressure-wave propagation phenomena in a last-generation CR Multijet equipment of the solenoid type was carried out on a high performance new test-bench Moehwald-Bosch MEP2000-CA4000 under real engine simulated conditions. The experimental results include pressure time histories in the rail and at the injector inlet, as well as flow-rate patterns, for both single and multiple injection events. The measured volume of fuel injected at each injection pulse is also reported. The analysis of the system oscillating behavior was carried out with the support of a simple lumped parameter model. Such a model was shown to be capable of predicting the main frequencies of the hydraulic circuit and their dependence on the geometrical parameters. The good agreement between the outcome of this simple model and the experimental data also substantiated the reliable authors' interpretation of the primary cause and effect relations underlying the complex flow phenomena occurring in the system. A refined computational model was developed and validated in a parallel work, providing a hydrodynamic analysis tool that is complementary to experimentation and also a means of hydraulic-system layout design and optimization. Finally, the mutual fluid-dynamic interactions taking place between consecutive injection events by distinct injectors of the same system are investigated in addition to the difference in dynamics of valve covered orifice and Minisac-nozzle injectors. Cycle-to-cycle variations in system performance were also investigated. [DOI: 10.1115/1.2835353]

During these last years, passenger vehicles have been equipped with an increasing number of sensors, in an effort to monitor and control their behavior in terms of global performance and emissions. This, together with constantly increasing electronic control unit computing power and data storage capabilities, allowed the development of more efficient engine-vehicle control strategies. In this perspective, new sensors will be employed as soon as their use will be shown to be necessary to design new engine control and diagnostic strategies, and their cost and expected life will be compatible with onboard application. A sensor that has been largely studied in recent years is the in-cylinder pressure one: advanced engine control strategies that make use of the signal coming from such a sensor have been investigated, while reliable and low-cost sensors are being developed to survive for the vehicle life the harsh on-board environment. The signal coming from the in-cylinder pressure is, in fact, very rich in information and could be used, for example, to improve engine torque management (by directly computing the instantaneous indicated torque), to improve air/fuel ratio control, misfire and knock detection capabilities, engine emission estimation (to be used for DeN[O.sub.x] catalysts purging management as an example), residual gas fraction estimation, etc. Many sensor concepts have been developed, although none seems to actually fully meet both the precision and low-cost requirements necessary for on-board application. This work deals with defining the sensor precision characteristics necessary to effectively implement the aforementioned engine control and diagnostic capabilities improvements. In particular, it will be shown that only the low-frequency signal content has to be precisely measured and is critical for certain application. In addition, the importance of a correct reference of the in-cylinder pressure signal is discussed, and a novel methodology to quickly obtain this information once the engine has been setup with a proper in-cylinder pressure sensor is discussed. [DOI: 10.1115/1.2830549]

In order to explore the influence of hot streak temperature ratio on the low pressure stage of a vaneless counter-rotating turbine, three-dimensional multiblade row unsteady Navier--Stokes simulations have been performed. The predicted results show that hot streaks are not mixed out by the time they reach the exit of the high pressure turbine rotor. The separation of colder and hotter fluids is observed at the inlet of the low pressure turbine rotor. After making interactions with the inner-extending and outer-extending shock waves in the high pressure turbine rotor, the hotter fluid migrates toward the pressure surface of the low pressure turbine rotor, and most of the colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are dominated by the secondary flow in the low pressure turbine rotor. The results also indicate that the secondary flow intensifies in the low pressure turbine rotor when the hot streak temperature ratio is increased. The effects of the hot streak temperature ratio on the relative flow angle at the inlet of the low pressure turbine rotor are very remarkable. The isentropic efficiency of the vaneless counter-rotating turbine decreases as the hot streak temperature ratio is increased.

A flow analysis is carried out for an inclined slider bearing with the aim of showing the governing mechanism at conditions where an optimum in load carrying capacity is achieved. The effects of surface texture on pressure buildup and load carrying capacity are explained for a textured slider bearing geometry. Numerical simulations are performed for laminar, steady, and isothermal flows. The energy transferred to the fluid from the moving wall is converted into pressure in the initial part of the converging contact and into losses in the second part. The convergence ratio can be increased, in order to get the greatest pressure gradient, until the limiting value where flow recirculation begins to occur. The texture appears to achieve its maximum efficiency when its depth is such that the velocity profile is stretched at its maximum extent without incurring incoming recirculating flow. The wall profile shape controlling the velocity profile can be optimized for many hydrodynamic contacts. Keywords: convergent surface, texture, pressure buildup, recirculation

Friction factor data for adiabatic cross flow of water in a staggered tube array were obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000-250,000. The tubes were 12.7 mm (0.5 in.) outer diameter in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations and was found to be best matched by the Idelchik correlation. Other correlations were found to significantly vary from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry, which covers the entire Reynolds number range tested. [DOI: 10.1115/1.2903817] Keywords: friction factor, tube bundle, pressure drop, staggered array

This article deals with a phenomenon named as cavitation resonance. Cavitationassociated pressure fluctuations in hydraulic systems affect their design, operation, and safety. Under certain conditions, the amplitude of a particular component of these fluctuations will be significantly magnified, causing a resonance. Here, the observed phenomenon from three different flow systems is briefly introduced. Based on the coupling of two subsystems, a hypothesis of (macroscopic) mechanism reduced from these experimental observations is presented. [DOI: 10.1115/1.2842149] Keywords: cavitation, resonance, system instability, pressure fluctuations

Three-dimensional oscillatory airflows induced by a rotating grass-cutting blade in a cylindrical chamber are studied experimentally and numerically in this paper. Experimental pressure results are obtained using a sound pressure transducer and a data acquisition system. The measured pressure data contain background noise and high frequency sound signals due to the blade vibrations. The background noise is separately measured; its effect on the signal is determined from a spectral subtraction algorithm. A time-accurate finite volume numerical solution to the three-dimensional incompressible unsteady Navier--Stokes equations is also sought using the sliding frame technique and the unstructured tetrahedral mesh. Convergence studies are conducted using various combinations of mesh sizes and time increments to ensure the stability of the numerical scheme. The experimental and numerical pressure results are in good agreement.[DOI: 10.1115/1.2842225] Keywords: computational fluid dynamics (CFD), cutting blade, oscillatory airflow, slidingframe, air pressure, rotation

The pressure drop and heat transfer characteristics of a single-phase micropin-fin heat sink were investigated experimentally. Fabricated from 110 copper, the heat sink contained an array of 1950 staggered square micropin fins with 200 x 200 [micro][m.sup.2] cross section by 670 [micro]m height. The ratios of longitudinal pitch and transverse pitch to pin-fin equivalent diameter are equal to 2. De-ionized water was employed as the cooling liquid. A coolant inlet temperature of 25[degrees]C, and two heat flux levels, [q.sup.'.sub.eff]=50 W/[cm.sup.2] and [q.sup.'.sub.eff] = 100 W/ [cm.sup.2], defined relative to the platform area of the heat sink, were tested. The inlet Reynolds number ranged from 93 to 634 for [q.sup.'.sub.eff] =50 W/[cm.sup.2], and from 127 to 634 for [q.sup.'.sub.eff] = 100 W/[cm.sup.2]. The measured pressure drop and temperature distribution were used to evaluate average friction factor and local averaged heat transfer coefficient/ Nusselt number Predictions of the previous friction factor and heat transfer correlations that were developed for low Reynolds number (Re

Weld repairs and alterations of pressure vessels and piping built to ASME codes may require pressure testing to prove the integrity of the weld and/or design. Conventional hydrostatic pressure testing requires filling an entire vessel or piping system with water and pressurizing it to the test pressure. In recent years, several designs were developed to employ bolted devices to perform local pressure testing of flange-to-nozzle, flange-to-pipe, and nozzle-to-shell attachment welds. Due to the cost and equipment down-time associated with performing a full conventional pressure test and the desire to reduce repair costs, several petrochemical companies adopted the use of such devices. The purpose of this paper is to compare the stress values and stress distribution associated with conventional and local pressure testing techniques. The advantages and disadvantages of both approaches are discussed and the conclusions are supported by a practical example. [DOI: 10.1115/1.2767372]

This paper examines the denting response of pipes subjected to lateral (transverse) quasistatic wedge loading, in the presence of internal pressure. Pipes are modeled with nonlinear shell finite elements and a simplified analytical model The analysis focuses on the significant influence of internal pressure on the denting resistance. Furthermore, the effects of wedge denting device orientation on the denting resistance are briefly discussed. Motivated by the experimental and numerical results, a two-dimensional heuristic model is proposed, which yields closed-form expressions for the denting force in terms of the corresponding displacement. The finite element results and the model equations are in good agreement with the experimental results and illustrate pipe denting response in an elegant manner. [DOI: 10.1115/1.2767345]

Shock-tube experiments and chemical kinetics modeling were performed to further understand the ignition and oxidation kinetics of lean methane-based fuel blends at gas turbine pressures. Such data are required because the likelihood of gas turbine engines operating on C[H.sub.4]-based fuel blends with significant (> 10%) amounts of hydrogen, ethane, and other hydrocarbons is very high. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of C[H.sub.4], C[H.sub.4]/[H.sub.2], C[H.sub.4]/[C.sub.2][H.sub.6], and C[H.sub.4]/[C.sub.3][H.sub.8] in ratios ranging from 90/10% to 60/40%. Lean fuel/air equivalence ratios ([empty set]=0.5) were utilized, and the test pressures ranged from 0.54 to 30.0 atm. The test temperatures were from 1090 K to 2001 K. Significant reductions in ignition delay time were seen with the fuel blends relative to the C[H.sub.4]-only mixtures at all conditions. However, the temperature dependence (i.e., activation energy) of the ignition times was little affected by the additives for the range of mixtures and temperatures of this study. In general, the activation energy of ignition for all mixtures except the C[H.sub.4]/[C.sub.3][H.sub.8] one was smaller at temperatures below approximatelyl300 K (~27 kcal/mol) than at temperatures above this value (~41 kcal/mol). A methane/hydrocarbon-oxidation chemical kinetics mechanism developed in a recent study was able to reproduce the high-pressure, fuel-lean data for the fuel/air mixtures. The results herein extend the ignition delay time database for lean methane blends to higher pressures (30 atm) and lower temperatures (1100 K) than considered previously and represent a major step toward understanding the oxidation chemistry of such mixtures at gas turbine pressures. Extrapolation of the results to gas turbine premixer conditions at temperatures less than 800 K should be avoided however because the temperature dependence of the ignition time may change dramatically from that obtained herein. [DOI: 10.1115/1.2720543]

Electrical power generation employing pressure-driven flows is a fundamental problem in microfluidics. In the present work, analytical and numerical analyses are performed to study the interplaying effects of electrolyte motion with the associated electrical current in a flat microchannel with and without fluid reservoirs. The modified Navier--Stokes equations as well as a Poisson equation for the distribution of electric potential and the Nernst--Planck equations for the distribution of charge densities are solved for the steady flow of a Newtonian liquid. The results show that for a pressure-driven flow, an electric potential is induced due to the motion of charged particles, which increases linearly along the microchannel. This streaming potential generates an opposing conduction current in the core region of the channel as well as in the immediate vicinity of the walls, where the streaming current is negligible. The streaming potential varies in a nonlinear manner with the zeta potential at the walls such that a maximum potential exists at a certain zeta potential. The maximum potential is also observed to increase with both the applied pressure difference and the electric double layer thickness in the range studied. The presence of reservoirs adds significant complexity to this electrokinetic flow. [DOI: 10.1115/1.2776967] Keywords: electrokinetic flow, zeta potential microchannel flow, reservoir effects, streaming electric potential

The results of flow experiments performed in a row of confined cylinders designed to mimic a model of a prismatic gas-cooled reactor lower plenum design are presented. Pressure measurements between the cylinders were made. Additionally, the flow field was measured using particle image velocimetry at two different resolutions (one at high resolution and a second with wide angle that includes three cylinders). Based on these measurements, five regimes of flow behavior are identified that are found to depend on Reynolds number. It is found that the recirculation region behind the cylinders is shorter than that of half-cylinders placed on the wall representing the symmetry plane. Unlike a single cylinder, the separation point is always found to be on the rear of the cylinders, even at very low Reynolds number. [DOI: 10.1115/1.2776970]

With the rapid development of the Information Technology (IT) industry, the heat flux in integrated circuit (IC) chips cooled by air has almost reached its limit at about 100 W/cmz. Some applications in high technology industries require heat fluxes well beyond such a limitation. Therefore, the search for a more efficient cooling technology becomes one of the bottleneck problems of the further development of the IT industry. The microchannel flow geometry offers a large surface area of heat transfer and a high convective heat transfer coefficient. However, it has been hard to implement because of its very high pressure head required to pump the coolant fluid through the channels. A normal channel size could not give high heat flux, although the pressure drop is very small. A minichannel can be used in a heat sink with quite a high heat flux and a mild pressure loss. A minichannel heat sink with bottom size of 20 mm x 20 mm is analyzed numerically for the single-phase turbulent flow of water as a coolant through small hydraulic diameters. A constant heat flux boundary condition is assumed. The effect of channel dimensions, channel wall thickness, bottom thickness, and inlet velocity on the pressure drop, temperature difference, and maximum allowable heat flux are presented. The results indicate that a narrow and deep channel with thin bottom thickness and relatively thin channel wall thickness results in improved heat transfer performance with a relatively high but acceptable pressure drop. A nearly optimized structure of heat sink is found that can cool a chip with heat flux of 350 W/cm2 at a pumping power of 0.314 W. [DOI: 10.1115/1.2753887]

The effectiveness of passive flow-control devices in eliminating high surface rms pressure fluctuations at the junction of several idealized wing/body junction flows was studied. Wall-pressure fluctuation measurements were made using microphones along the line of symmetry at the wing/body junction of six different wing shapes. The wings were mounted on the wind tunnel floor at a zero degree angle-of-attack. The six wing shapes tested were: a 3:2 semi-elliptical-nosed NACA 0020 tailed generic body shape (Rood wing), a parallel center-body model, a tear-drop model, a Sandia 1850 model, and NACA 0015 and NACA 0012 airfoil shapes. Eight different fence configurations were tested with the Rood wing. The two double-fence configurations were found to be the most effective in reducing the pressure fluctuations. Two of the single fence types were nearly as effective and were simpler to manufacture and test. For this reason one of these single fence types was selected for testing with all of the other wing models. The best fence flow-control devices were found to reduce rms wall-pressure fluctuations by at least 61% relative to the baseline cases. [DOI: 10.1115/1.2746917]

The present paper provides plastic limit load solutions for axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3D) finite element (FE) limit analysis using elastic-perfectly plastic behavior. As a loading condition, axial tension, global bending moment, internal pressure, combined tension and bending, and combined internal pressure and bending are considered for circumferential through-wall cracked pipes, while only internal pressure is considered for axial through-wall cracked pipes. In particular, more emphasis is given for through-wall cracked pipes subject to combined loading. Comparisons with existing solutions show a large discrepancy in short through-wall crack (both axial and circumferential) for internal pressure. In the case of combined loading, the FE limit analyses results show the thickness effect on limit load solutions. Furthermore, the plastic limit load solution for circumferential through-wall cracked pipes under bending is applied to derive plastic [eta] and [gamma] factor of testing circumferential through-wall cracked pipes to estimate fracture toughness. Being based on detailed 3D FE limit analysis, the present solutions are believed to be meaningful for structural integrity assessment of through-wall cracked pipes. [DOI: 10.1115/1.2748828] Keywords: axial through-wall crack, circumferential through-wall crack, combined internal pressure and bending, combined tension and bending, finite element limit analysis, plastic limit load

An empirical modeling concept for the prediction of N[O.sub.x] emissions from dry low emissions (DLE) gas turbines is presented. The approach is more suited to low emissions operation than are traditional approaches (Lefebrre, A. H., 1998, Taylor and Francis, New York). The latter, though addressing key operating parameters, such as temperature and pressure drop, do not address issues such as variation in fuel/air distribution through the use of multifuel stream systems, which are commonly applied in DLE combustors to enable fame stability over the full operating range. Additionally, the pressure drop dependence of N[O.sub.x] in such systems is complex, and the exponent of a simple pressure drop term can vary substantially. The present approach derives the N[O.sub.x] model from the equations that govern the N[O.sub.x] chemistry, the fuel/air distribution and the dependence of the main reaction zone on its controlling parameters. The approach is evaluated through comparing its characteristics to data obtained from high-pressure testing of a DLE combustor fueled with natural gas. The data were acquired at a constant pressure and preheat temperature (14 Bara and 400[degrees]C) and a range of flame temperatures and flow rates. Though the model is configured to address both relatively fast and slow N[O.sub.x] formation routes, the present validation is conducted under conditions where the latter is negligible. The model is seen to reproduce key features apparent in the data, in particular, the variable pressure drop dependence without any ad hoc manipulation of a pressure drop exponent. [DOI: 10.1115/1.2718564]

Peak cylinder pressure ([P.sub.max]) of a compression-ignition engine can be affected by the engine inlet air condition, such as its inlet air temperature ([T.sub.i]) and pressure ([p.sub.i]). The variation of peak cylinder pressure due to varying inlet air temperature or pressure is analytically studied. A model is developed and simplified, and thus the variations of [P.sub.max] can be predicted along with varying inlet air temperature or pressure. The analysis and prediction indicate that cylinder active compression ratio (CR) and intake air boost ratio ([p.sub.m0]/[p.sub.i0]) play relatively significant roles in affecting the variation of [p.sub.max] over inlet air temperature and pressure, and the pressure variation is proportional to [CR.sup. k] and ratio [p.sub.mo]/[p.sub.i0]. Comparison between the predicted results using the simplified model and those from engine experiments shows a close agreement in both the trend and magnitude. The investigation and prediction also include modeling the variation in [p.sub.max] due to varying the cylinder TDC clearance volume ([V.sub.c]). The simplified model is presented and shows that the change in [p.sub.max] versus varying [V.sub.c] also depends on the cylinder compression ratio. It is indicated that for a certain change in the clearance volume, a higher compressionratio configuration would produce a greater change in [p.sub.max] than a lower one does, especially as the rest of the engine design and operating parameters remain unchanged. [DOI: 10.1115/1.2431389]

Velocity and pressure measurements are presented for a blade passage with and without leading edge contouring in a low speed linear cascade. The contouring is achieved through fillets placed at the junction of the leading edge and the endwall. Two fillet shapes, one with a linear streamwise cross-section (fillet 1) and the other with a parabolic cross-section (fillet 2), are examined. Measurements are taken at a constant Reynolds number of 233,000 based on the blade chord and the inlet velocity. Data presented at different axial planes include the pressure loss coefficient, axial vorticity, velocity vectors, and yaw and pitch angles. In the early stages of the development of the secondary flows, the fillets are seen to reduce the size and strength of the suction-side leg of the horseshoe vortex with associated reductions in the pressure loss coefficients and pitch angles. Further downstream, the total pressure loss coefficients and vorticity show that the fillets lift the passage vortex higher above the endwall and move it closer to the suction side in the passage. Near the trailing edge of the passage, the size and strength of the passage vortex is smaller with the fillets, and the corresponding reductions in pressure loss coefficients extend beyond the mid-span of the blade. While both fillets reduce pressure loss coefficients and vorticity, fillet 1 (linear fillet profile) appears to exhibit greater reductions in pressure loss coefficients and pitch angles. [DOI: 10.1115/1.2427075]

Two areas not well researched in the field of seating mechanics are the distribution of normal and shear forces, and how those forces change with seat position. The availability of these data would be beneficial for the design and development of office, automotive and medical seats. To increase our knowledge in the area of seating mechanics, this study sought to measure the normal and shear loads applied to segmental supports in 12 seated positions, utilizing three inclination angles and four levels of seat back articulation that were associated with automotive driving positions. Force data from six regions, including the thorax, sacral region, buttocks, thighs, feet, and hand support were gathered using multi-axis load cells. The sample contained 23 midsized subjects with an average weight of 76.7 kg and a standard deviation of 4.2 kg, and an average height of 1745 mm with a standard deviation of 19 mm. Results were examined in terms of seat back inclination and in terms of torso articulation for relationships between seat positions and support forces. Using a repeated measures analysis, significant differences (p < 0.05) were identified for normal forces relative to all inclination angles except for forces occurring at the hand support. Other significant differences were observed between normal forces behind the buttocks, pelvis, and feet for torso articulations. Significant differences in the shear forces occurred under the buttocks and posterior pelvis during changes in seat back inclination. Significant differences in shear forces were also identified for torso articulations. These data suggest that as seat back inclination or torso articulation change, significant shifts in force distribution occur. [DOI: 10.1115/1.2401184] Keywords: seating, posture, force, chair design, pressure sores

Air in water flow is a frequent phenomenon in hydraulic structures. The main reason for air entrainment is vortices at water intakes, pumping stations, tunnel inlets, and so on. The accumulated air, in a conduit, can evolve to a different flow pattern, from stratified to pressurized. Among different patterns, slug is most complex with extreme pressure variations. Due to lack of firm relations between pressure and influential parameters, study of slug flow is very important. Based on an experimental model, pressure fluctuations inside a circular, horizontal, and inclined pipe (90 mm inside diameter and 10 m long) carrying tow-phase air-water slug flow has been studied. Pressure fluctuations were sampled simultaneously at different sections, and longitudinal positions. The pressure fluctuations were measured using differential pressure transducers (DPT), while behavior of the air slug was studied using a digital camera. The objective of the paper is to predict the pressure variation in a pipeline or tunnel, involving resonance and shock waves experimentally. The results show that the more intensive phase interaction commences stronger fluctuations. It is shown, that the air-water mixture entering the pipe during rapid filling of surcharging can cause a tremendous pressure surge in the system and may eventually cause failure of the system (e.g., the maximum pressure inside the pipe would reach up to 10 times of upstream hydrostatic pressure as suggested by others too). Relations for forecasting pressure in these situations are presented as a function of flow characteristics, pipe geometry, longitudinal, and cross-sectional positions and head water [DOI: 10.1115/1.2375134] Keywords: two-phase flow, water tunnel, pressure fluctuation, experimental model slug flow

An advanced technique for establishing pressure boundary conditions in annular sector cascade experiments has been developed. This novel technique represents an improvement over previous methods and provides the first means by which annular sector boundary conditions that are representative of those which develop in an annular cascade can be established with a high degree of satisfaction. The technique will enable cascade designers to exploit the obvious advantages of annular sector cascade testing: the reduced cost of both facility manufacture and facility operation and the use of engine parts in place of two-dimensional counterparts. By employing an annular sector of deswirl vanes downstream of the annular sector of test vanes, the radial pressure gradient established in the swirling flow downstream of the test vanes is not disturbed. The deswirl vane exit flow--which has zero swirl velocity--can be exhausted without unsteadiness, and without the risk of separation, into a plenum at constant pressure. The pressure ratio across the annular sector of test vanes can be tuned by adjusting the throat area at the deswirl vane exit plane. Flow conditioning systems which utilize the Oxford deswirl vane technology have previously been used to set pressure boundary conditions downstream of fully annular cascades in both model and engine scale (the Isentropic Light Piston Facility at Farnborough) experimental research facilities (Povey, T., Chana, K. S., Oldfield, M. L. G., Jones, T. V., and Owen, A. K., 2001, Proceedings of the ImechE Advances in Fluid Machinery Design Seminar, London, June 13; Povey, T., Chana, K. S., Jones, T. V., and Oldfield, M. L. G., 2003, Advances of CFD in Fluid Machinery Design, ImechE Professional Engineering, London, pp. 65-94). The deswirl vane is particularly suited to the control of highly whirling transonic flows. It has been demonstrated by direct comparison of aerodynamic measurements from fully annular and annular sector experiments that the use of a deswirl vane sector for flow conditioning at the exit of an annular sector cascade represents an attractive novel solution to the boundary condition problem. The annular sector technique is now described. [DOI: 10.1115/1.2372766]

In modeling advanced steam power cycles, thermodynamic properties as functions of pressure and enthalpy (p,h) or pressure and entropy (p,s) are required in the critical and supercritical regions (region 3 of IAPWS-IF97). With IAPWS-IF97, these calculations require cumbersome two-dimensional iteration of temperature T and specific volume u from (p,h) or (p,s). While these calculations in region 3 are not frequently required, the computing time can be significant. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for T(p,h), v(p,h), T(p,s), and u(p ,s) in region 3, along with boundary equations for the saturation pressure as a function of enthalpy, [P.sub.3sat](h), and of entropy, [P.sub.3sa]t(S). Using the new equations, two-dimensional iteration can be avoided. The numerical consistency of temperature and specific volume obtained in this way is sufficient for most uses. This paper summarizes the need and the requirements for these equations and gives complete numerical information. In addition, numerical consistency and computational speed are discussed. [DOI: 10.1115/1.2181598]

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT[R]. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results. [DOI: 10.1115/1.2170121]

An experimental study has been carried out to measure the pressure loss at the side orifice of a liquid metal reactor fuel assembly. The characteristics of the pressure loss at the side orifice are investigated using the experimental data measured from 17 different types of side orifices that have different geometric shapes, dimensions, and arrangements of nozzles, and a correlation that covers the whole flow range by one equation is developed. The error range of the correlation is within [+ or -] 10%, and most of the errors occurred in a region where the Reynolds number is small. The range of Reynolds numbers based on the hydraulic diameter of the orifice is 2000-350,000. It is found that the geometric factor is the most important parameter for the pressure loss when the Reynolds number is >30,000. As the Reynolds number becomes smaller, its effect becomes larger, and when the Reynolds number is small, it is the most important parameter for the pressure loss at the side orifices. The measured data shows a trend that the pressure loss coefficient increases as the number of orifices increases, and the effect of the longitudinal arrangement is small. [DOI: 10.1115/1.1881694]

Pressure screening is an efficient means of removing various contaminants that degrade the appearance and strength of paper. A critical component of a screen is the rotor, which induces a tangential velocity to the suspension and produces pressure pulses to keep the screen apertures clear. To understand the effect of key design and operating variables for a NACA foil rotor, a computational fluid dynamic (CFD) simulation was developed using FLUENT, and the results were compared to experimental measurements. Comparing the pressure pulses obtained through CFD to experimental measurements over a wide range of foil tip speeds, clearances, angles of attack, and foil cambers, general trends of the pressure pulses were similar, but the overall computed values were 40% smaller than the measured values. The pressure pulse peak was found to increase linearly with the square of tip speed for all the angles of attack studied. The maximum magnitudes of negative pressure pulse occurred for the NACA 0012 and 4312 foils at a 5 deg angle of attack and for the NACA 8312 foil at 0 deg. The stall angle of attack was found to be ~5 deg for NACA 8312, ~10 deg for NACA 4312, and ~15 deg for NACA 0012. The positive pressure peak near the leading edge of the foil was eliminated for foils operating at a positive angle of attack. The magnitude of the negative pressure coefficient peak increased as clearance decreased. Increased camber increases both the magnitude and width of the negative pressure pulse. [DOI: 10.1115/1.1881672]