bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of R132H Mutation‐specific IDH1 Antibody Binding in Brain Tumors
Authors: Capper David , Weißert Susanne , Balss Jörg , Habel Antje , Meyer Jochen , Jäger Diana , Ackermann Ulrike , Tessmer Claudia , Korshunov Andrey , Zentgraf Hanswalter , Hartmann Christian , Von Deimling Andreas
Published: October 2009

Heterozygous point mutations of isocitrate dehydrogenase (IDH)1 codon 132 are frequent in grade II and III gliomas. Recently, we reported an antibody specific for the IDH1R132H mutation. Here we investigate the capability of this antibody to differentiate wild type and mutated IDH1 protein in central nervous system (CNS) tumors by Western blot and immunohistochemistry. Results of protein analysis are correlated to sequencing data. In Western blot, anti‐IDH1R132H mouse monoclonal antibody mIDH1R132H detected a specific band only in mutated tumors. Immunohistochemistry of 345 primary brain tumors demonstrated a strong cytoplasmic and weaker nuclear staining in 122 cases. Correlation with direct sequencing of 186 cases resulted in consensus of 177 cases. Genetic retesting of cases with conflicting findings resulted in a match of 186/186 cases, with all discrepancies resolving in favor of immunohistochemistry. Intriguing is the ability of mIDH1R132H to detect single infiltrating tumor cells. The very high frequency and the distribution of this mutation among specific brain tumor entities allow the highly sensitive and specific discrimination of various tumors by immunohistochemistry, such as anaplastic astrocytoma from primary glioblastoma or diffuse astrocytoma World Health Organization (WHO) grade II from pilocytic astrocytoma or ependymoma. Noteworthy is the discrimination of the infiltrating edge of tumors with IDH1 mutation from reactive gliosis.
Alterations in anterior chamber depth in primary open‐angle glaucoma patients during latanoprost therapy
Authors: Cankaya Ali Bulent , Teberik Pinar , Acaroglu Golge
Published: October 2009

Purpose:  The aim of this study was to evaluate changes in the anterior chamber depth (ACD) in primary open‐angle glaucoma (POAG) patients during latanoprost therapy.

Methods:  We carried out a prospective study in which we enrolled 66 newly diagnosed POAG patients treated with latanoprost 0.005% (group 1) and 50 ocular hypertensive and/or glaucoma suspect cases who were given no therapy (group 2 [control]). Measurements of the ACD were performed by A‐scan ultrasonography before and after cycloplegia at baseline and at 3 months of latanoprost therapy. Differences in ACD and their correlations with the ocular hypotensive effect of the agent as well as the clinical significance of changes in ACD were analysed using Student’s t‐test and Pearson’s correlation coefficient. Statistical significance was set at p < 0.05.

Results:  Mean baseline ACD was 3.13 ± 0.35 mm (range 2.45–3.84 mm) in group 1 and 3.14 ± 0.36 mm (range 2.54–3.80 mm) in group 2 (p = 0.89). At 1 hour after instillation of cyclopentolate 1%, mean ACD in groups 1 and 2 was 3.18 ± 0.38 mm (range 2.45–3.92 mm) and 3.19 ± 0.37 mm (range 2.56–3.91 mm), respectively (p = 0.91). After 3 months of treatment, mean ACD in group 1 both without (3.05 ± 0.36 mm, range 2.14–3.76 mm) and with (3.09 ± 0.4 mm, range 2.20–3.96 mm) cycloplegia was significantly reduced compared with baseline values (p < 0.001 for both). However, there was no significant difference between mean ACD at baseline and that at month 3 in group 2. No correlation was demonstrated between the changes in ACD and the ocular hypotensive effect of latanoprost (p = 0.96, r = − 0.006). There were no changes in refractive status or visual acuity.

Conclusions:  The overall results seem to suggest that latanoprost decreases mean ACD in patients with POAG. The clinical significance of this effect is uncertain.
Pre‐Orders for New To‐be‐Released Products Considering Consumer Loss Aversion
Authors: Zhao Xuying , Stecke Kathryn E.
Published: October 2009

Advance selling through pre‐orders is a strategy to transfer inventory risk from a retailer to consumers. A newsvendor retailer can have three strategies to choose from: no advance selling allowed (NAS), moderate advance selling with a moderate discount for pre‐orders (MAS), and deep advance selling with a deep discount for pre‐orders (DAS). This research studies how a retailer could design an advance selling strategy to maximize her own profits. We find some interesting results. For example, there exist two thresholds for the selling season profit margin and two thresholds for consumer's expected valuation. For products with higher profit margin than the high threshold on profit margin, a retailer should always use DAS. For products with medium profit margin within the two thresholds, a retailer should adopt MAS if consumer's expected valuation is lower than the high threshold and use DAS otherwise. For products with lower profit margin than the low threshold, a retailer should use NAS, DAS, or MAS, respectively, if consumer's expected valuation is lower than the low threshold, higher than the high threshold, or between the two thresholds, respectively. Through sensitivity analyses, we also show the effects of multiple consumer characteristics on a retailer's optimal advance selling strategy.
Tissue Doppler and Strain Imaging in Dogs with Myxomatous Mitral Valve Disease in Different Stages of Congestive Heart Failure
Authors: Tidholm A. , Ljungvall I. , Höglund K. , Westling A.B. , Häggström J.
Published: October 2009

Background:Tissue Doppler imaging (TDI) including strain and strain rate (SR) assess systolic and diastolic myocardial function.

Hypothesis:TDI, strain, and SR variables of the left ventricle (LV) and the interventricular septum (IVS) differ significantly between dogs with myxomatous mitral valve disease (MMVD) with and without congestive heart failure (CHF).

Animals:Sixty‐one dogs with MMVD with and without CHF. Ten healthy control dogs.

Methods:Prospective observational study.

Results:Radial motion: None of the systolic variables were altered and 3 of the diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs.Longitudinal motion: 2 systolic velocities and 3 diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Difference in systolic velocity time‐to‐peak between LV and IVS was significantly increased in dogs with MMVD with and without CHF compared with control dogs. In total, 11 (23%) of 48 TDI and strain variables differed significantly between groups. Left atrial to aortic ratio was positively correlated to early diastolic velocities, percentage increase in left ventricular internal diameter in systole was positively correlated to systolic and diastolic velocities, and mitral E wave to peak early diastolic velocity in the LV basal segment (E/Em) was positively correlated to radial strain and SR.

Conclusions and Clinical Importance:Few TDI and strain variables were changed in dogs with MMVD with and without CHF. Intraventricular dyssynchrony may be an early sign of MMVD or may be an age‐related finding.
Impulsive Motion of a Sphere at Supersonic Speeds
Authors: Chang Stephen S. H.
Published: October 2009

This paper presents an analytical transient solution to the subsonic flow near the stagnation region of a sphere which starts impulsively at a constant supersonic speed. The analysis is based upon a series expansion in time of the flow variables and of the shape of the moving shock. The coefficients of the series are determined analytically by substituting the series into the differential equations of motion and the standard Rankine-Hugoniot jump conditions. The series is extended over 30 terms at stagnation point and up to nine terms near the sonic point. The first four terms are in agreement with the known solutions. By recasting them in Euler’s transformation, the series is analytical beyond their natural region of convergence. The results match the experiments and are in agreement with the known steady-state numerical solutions.
Dependence of Shock Characteristics on Droplet Size in Supersonic Two-Phase Mixtures
Authors: Comfort W. J. , Crowe C. T.
Published: October 2009

In a dispersed two-phase flow, the mixture chokes at a velocity well below the vapor choking velocity, as shown by the velocity at the throat of a converging-diverging, two-phase, supersonic nozzle. The formation and abruptness of a normal shock wave in a two-phase mixture depends strongly on the coupling between phases, particularly upon droplet size. As droplet size becomes small, the mixture behaves as a continuum, and sharp discontinuities can occur at velocities above the two-phase choking velocity but below the vapor sonic velocity. An approximate analysis is performed to incidate the droplet size at which continuum behavior might be expected to occur. A numerical model, which includes the drag, buoyancy, Basset force, and the force associated with the virtual mass effect, is used to show droplet-size dependence in two-phase normal shock waves. For the examples presented, continuum behavior apparently is approached at droplet diameters between 1 and 2 μm, even through normal shock waves.
Predicted and Measured Pressure Drop in Parallel Plate Rotary Regenerators
Authors: Maclaine-Cross I. L. , Ambrose C. W.
Published: October 2009

The flow in the passages of parallel plate rotary heat exchangers or regenerators is laminar and fully developed. Laminar flow theory should allow an accurate prediction of heat and mass transfer and pressure drop. Previously measured values of pressure drop have been 20 percent higher than predicted. Pressure drop is predicted here by considering the passage cross section rectangular and correcting for flow acceleration, property variations, and inlet and outlet pressure drop. The pressure drops measured on a parallel plate sensible heat regenerator were within 3 percent of theory and on a prototype parallel plate total heat regenerator within 4 percent.
On the Relevance of Inviscid Subsonic Flow Calculations to Real Centrifugal Impellers Flow
Authors: Adler D. , Krimerman Y.
Published: October 2009

The results of a fully three-dimensional inviscid compressible calculation technique for the flow field inside centrifugal impellers are compared to optical measurements in an open, radial exit impeller. It is concluded from this comparison that as long as viscous influence, including its displacement effects (manifested mainly in the jetwake flow structure), are not too big, the inviscid method applied can be used with confidence. When the viscous influence is such that it distorts the flow field in certain regions but displacement effects are still insignificant, the inviscid method can be used outside regions of viscous dominance. This situation occurs about halfway downstream, through the impeller. Only when displacement effects resulting from viscous flow field distortions, become big and the jet-wake profile becomes fully developed, does the inviscid method fail to predict the correct flow field. This happens at the exit of the impeller investigated here.
An Experimental Study of the Secondary Flow in a Curved Rectangular Channel
Authors: Kelleher M. D. , Flentie D. L. , McKee R. J.
Published: October 2009

The Taylor-Gortler vortex pattern in a curved rectangular channel of high aspect ratio has been examined using hot wire anemometry. Using a two dimensional traversing mechanism, velocity surveys have been made at several radial locations across the channel for several values of Dean number. The velocity measurements show that the periodic secondary motion undergoes a phase shift as the hot wire probe crosses the midplane between the concave and convex walls. The measurements also indicate that the secondary flow wave number is constant over the range of Dean numbers examined. Complementary flow visualization photographs of the secondary motion have also been obtained.
Vortex Shedding From Two Circular Cylinders in Staggered Arrangement
Authors: Kiya M. , Arie M. , Tamura H. , Mori H.
Published: October 2009

The frequency of vortex shedding from two circular cylinders of the same diameter in staggered arrangement is experimentally investigated at a Reynolds number of 1.58 × 104. This Reynolds number is within the range where the flow around a circular cylinder is relatively insensitive to Reynolds number changes. The results are summarized in several figures from which one can obtain the Strouhal number of vortex shedding for all arrangements within distances between their centers less than 5 diameters.
Pressure Distributions Around Circular Cylinders in Oscillating Flow
Authors: Dalton C. , Chantranuvatana B.
Published: October 2009

Oscillatory motion of a circular cylinder is studied from the viewpoint of the average pressure distribution on the cylinder. Effects of Reynolds number up to 40,000, period, and Keulegan and Carpenter number on the pressure distribution are examined. Results are explained in terms of vortex shedding and its relationship to period and Keulegan-Carpenter number. The effects of flow reversal, sweeping wake vortices back over the cylinder, are discussed.
Angled Injection of Jets Into a Turbulent Boundary Layer
Authors: Lee L. H. Y. , Clark J. A.
Published: October 2009

Inclined laminar submerged plane jets were injected from a 1 cm slot into a turbulent boundary layer developed on a sidewall of a water channel. Profiles of mean velocities and longitudinal fluctuations were measured to 64 slot widths downstream of the jet exit. Length and velocity similarity scales were obtained from mean velocity data, and local values of skin friction coefficient were determined. Two maxima in the longitudinal fluctuation profiles were established and found to follow precisely loci of vortex formations. The maxima grew exponentially in the downstream direction and peaked at a location where these transverse vortices were at their full strength before coalescence. Effects of different injection angles and velocity ratios were found. Further extension of a physical model to describe the flow is validated based on correlation of mean and fluctuating velocity data with visual information.
Transonic Inlet Flow Calculations Using a General Grid-Generation Scheme
Authors: Chen L. T. , Caughey D. A.
Published: October 2009

Finite difference solutions for transonic flowfields about engine inlet nacelles are obtained by combining a general grid-generation scheme with a previously developed general solver for transonic potential flowfields (1). The grid-generation scheme is similar to Thompson’s method, but uses simpler equations to solve for the mesh coordinates. An extrapolated relaxation procedure is used to obtain improved convergence of the transonic solution to small residuals. Results obtained for flowfields with embedded supersonic regions both outside and inside the inlets compare well with experimental results.
The Influence of Inlet Conditions on the Performance of Annular Diffusers
Authors: Stevens S. J. , Williams G. J.
Published: October 2009

Low speed tests have been carried out to investigate the performance and mechanism of flow in two annular diffusers having center bodies of uniform diameter and conically diverging outer walls. In the first part of the investigation the diffusers were tested over a range of naturally developed inlet velocity profiles ranging from near-uniform to fully developed flow. Information is presented concerning the pressure recovery, total pressure loss, and characteristics of the outlet flow. Measurements have also been made of the mean velocity profile and turbulence structure at a number of stations along the length of the diffusers. The second part of the test program was devoted to studying the effects of increased inlet turbulence. The results show a marked improvement in the stability of the outlet flow and gains in pressure recovery, up to a maximum of 20 percent, with only small increases in total pressure loss.
A Theoretical Study on Air Bubble Motion in a Centrifugal Pump Impeller
Authors: Minemura Kiyoshi , Murakami Mitsukiyo
Published: October 2009

Equations of motion for air bubbles in a centrifugal pump impeller were obtained and solved numerically for a flow in a radial-flow-type impeller, and the results were compared with experiments. Governing factors for the bubble motion are the force due to the pressure gradient, the drag force due to the flow resistance of the surrounding liquid, and the inertia force due to virtual mass of the liquid. If the bubble diameter is reduced continuously, the effect of the inertia force is also reduced and trajectories of the air bubbles approach more and more to the path of the flowing water.
A Theoretical Model for the Transverse Impingement of Free Jets at Low Reynolds Numbers
Authors: Winton R. , Martin H. R.
Published: October 2009

There are many applications in industrial fluid mechanics and fluidic technology where jets of fluid interact. This paper examines the interaction of two liquid laminar free jets under low Reynolds number conditions and particularly highlights the phenomenon of the inwards deflecting jet. A potential flow solution is developed for the modelling of the control jet flow in the vicinity of the control nozzle exit plane, which demonstrates the presence of a net suction force modifying the momentum interaction of the two orthogonal jets under these low Reynolds number conditions.
The Effect of Secondary Vorticity on the Inception of Vortex Cavitation
Authors: Billet M. L.
Published: October 2009

Cavitation inception of a vortex is difficult to predict. This is due in a large part to a confusion in the type of cavitation occurring, i.e., vaporous versus nonvaporous cavitation. In addition, the vortex structure is poorly defined in many cases. These two problems are particularly important for the prediction of cavitation inception in a vortex created in the low momentum fluid near the inner wall of a rotor. The purpose of this paper is to present the results of a vortex cavitation investigation which are both experimental and theoretical. A vorticity flow analysis is developed and employed to assess the effect of vorticity on cavitation inception of a vortex. Previous investigations have shown that the minimum pressure coefficient of a vortex depends upon the vorticity associated with the vortex. Employing secondary vorticity equations, the vorticity is calculated in the blade passage. Changes in passage vorticity are used in a simple vortex model to predict trends in cavitation inception of a vortex. Theoretical results indicate that small changes in vorticity distribution near the inner wall of the rotor create rather large differences in the cavitation inception of the vortex. These small changes are primarily due to changes in the secondary vorticity. This secondary vorticity dominates the vortex structure. Comparisons are presented between the predicted and measured cavitation inception and good agreement is shown when the effects of gas on cavitation inception are reduced. Experimental data confirms that secondary vorticity dominates the vortex structure. In addition, experimental cavitation data are presented which show the dramatic influence of a gas on cavitation inception of a vortex.
Pressure and Vortex Shedding Patterns Around a Low Aspect Ratio Cylinder in a Sheared Flow at Transitional Reynolds Numbers
Authors: Rooney D. M. , Peltzer R. D.
Published: October 2009

Model tests were performed in a wind tunnel to determine vortex shedding patterns induced around a circular cylinder by spanwise shear in transitional Reynolds number flow. In addition, mean and fluctuating pressure measurements were obtained. The introduction of shear in the upstream flow generated two distinct cells of vortex frequencies behind the cylinder in the transcritical regime, thereby documenting for the first time that the re-established high Reynolds number shedding closely parallels patterns already observed in subcritical flow. The two cell pattern did not permit any correlation between shear level and cell length to be found.
Turbulent Boundary Layer Flow Through a Gap in a Wall Mounted Roughness Element
Authors: Schofield W. H. , Barber D. S. , Logan E.
Published: October 2009

The center-line development of a turbulent boundary layer flow through a gap in an isolated wall mounted roughness element has been studied experimentally. The centerline flow downstream of the gap can be divided into a distortion region followed by a readjustment region. The nature of the distortion produced by the gap varies with gap size and thus flows downstream of large gaps were found to differ significantly from those through small gaps. After distortion the layer readjusts itself and approaches equilibrium conditions of an undisturbed zero pressure gradient layer. The readjustment starts near the wall with the turbulence adjustment preceding the mean flow adjustment. For flow through all six gap sizes the growth of the centerline internal layer can be described by a single function if internal layer height and distance from the gap are non-dimensionalized with the local wall length scale. Well downstream of the gap it is shown that all six centerline flows are similar and are approaching equilibrium conditions in a similar manner.
Effects of Free-Stream Turbulence on Diffuser Performance
Authors: Hoffmann J. A.
Published: October 2009

An experimental evaluation of the effects of free-stream turbulence on the performance of a subsonic two-dimensional diffuser has been made. Increases of the diffuser’s static pressure recovery coefficient of 11.3 and 23.9 percent at total included divergence angles of 12 and 20 degrees respectively were obtained when the value of the inlet integral free-stream scale of turbulence in the flow direction was at least 7.2 times larger than the inlet boundary layer displacement thickness, when the inlet total free-stream turbulence intensity was at least 3.5 percent, and when the axes of upstream rods used to generate turbulence were perpendicular to the flow and parallel to the diverging walls of the diffuser. It is hypothesized that a larger scale of turbulence with the specified eddy axis orientation transmits the free-stream energy to the walls more effectively and, when coupled with large turbulence intensities, are mechanisms which act to decrease the distortion and delay separation within the diffuser.
Torque Characteristics of a 122-Centimeter Butterfly Valve With a Hydro/Pneumatic Actuator
Authors: Lin F. N. , Moore W. I. , Lundy F. E.
Published: October 2009

Actuating torque data from field testing of a 122-centimeter (48 in.) butterfly valve with a hydro/pneumatic actuator is presented. The hydraulic cylinder functions as either a forward or a reverse brake. Its resistance torque increases when the valve speeds up and decreases when the valve slows down. A reduction of flow resistance in the hydraulic flow path from one end of the hydraulic cylinder to the other will effectively reduce the hydraulic resistance torque and hence increase the actuating torque. The sum of hydrodynamic and friction torques (combined resistance torque) of a butterfly valve is a function of valve opening time. An increase in the pneumatic actuating pressure will result in a decrease in both the combined resistance torque and the actuator opening torque; however, it does shorten the valve opening time. As the pneumatic pressure increases, the valve opening time for a given configuration approaches an asymptotical value.
Scale Effects on Various Types of Limited Cavitation
Authors: Billet M. L. , Holl J. W.
Published: October 2009

Scale effects on limited cavitation discussed in this paper are those departures from the classical similarity relations due to variations in size and velocity. These scale effects are an important consideration in the prediction of limited cavitation in a design process. In most cases, the limited cavitation number of a model is different from that of the prototype. Some recently published results have shown that viscous effects and free-stream nuclei can cause significant scale effects. The purpose of this paper is two-fold. First, new experimental data are presented which show scale effects for several types of cavitation. Second, these data are discussed and examined for possible rational explanations. Limited cavitation data are presented and discussed for axisymmetric headforms and three families of hydrofoils. For the hydrofoils, measurement of surface cavitation for both sheet and bubble types in addition to tip-vortex cavitation were obtained over a range of Reynolds numbers. Each family of hydrofoils is geometrically similar in planform and cross section and has chord lengths of 38.1, 76.2, 152.4 and 304.8 millimeters. The cross sections of the three hydrofoil families are: (1) a modified Joukowski hydrofoil section with a maximum thickness of 10.6 percent. (2) a NACA 0015 hydrofoil section and (3) a cambered NACA 0010 section with a maximum camber of 10 percent. These hydrofoil families were tested in the 1.22 m water tunnel at ARL/PSU. It is indicated that scale effects are due to changes in the pressure field (type #1) and to bubble dynamic and nuclei effects (type #2). The various types of cavitation are examined to determine the type of scale effects which appear to be controlling the cavitation process. Approximate analyses are presented for bubble-ring, band, tip-vortex, and fixed-patch or sheet cavitation. The latter appear to be controlled by surface roughness effects.
Tilting, Stretching, Pairing and Collapse of Vortex Structures in Confined Counter-Current Flow
Authors: Humphrey J. A. C. , Li S.
Published: October 2009

Visualization observations are reported for the time evolving vortex structure at the interface of a counter-current channel flow. The results are primarily qualitative in nature, but show clearly the evolution of a two-dimensional saddle-point flow into a complex, three-dimensional, periodic vortex-pairing process. Generation, pairing and collapse of the flow structure at the free interface is attributed to tilting and stretching of transverse vorticity by the main flow in the longitudinal direction. It is suggested that the present flow configuration may prove of use for investigating mixing in chemically reacting flows due to entraining vortex motions.
An Experiment Concerning the Confluence of a Wake and a Boundary Layer
Authors: Bario F. , Charnay G. , Papailiou K. D.
Published: October 2009

Measurements have been performed at low speed in the confluent region of a two dimensional wake and turbulent boundary layer. A tandem symmetrical arrangement was used, placed in a variable pressure gradient wind tunnel. Pressure and turbulent quantities were measured and current semi-empirical laws were examined in the light of the experimental results.
Drag Reduction in Flow of Coal-Oil Suspensions
Authors: Ghassemzadeh M. R. , Carmi S.
Published: October 2009

Pipe flow characteristics of coal-oil mixtures (C.O.M.) are studied by a pipe flow facility consisting of a Tri-Rotor positive displacement pump, which draws fluid from a reservoir tank and discharges through a pipeline at regulated pressures. Pipe flow tests are carried out to study the drag reduction effect of the polymer carboxymethylcellulose (CMC) on the flow of coal-oil mixtures. Addition of CMC reduces friction drag on the average by 10 percent. Preliminary results are presented covering appropriate ranges of operating parameters (coal concentration and temperature) which influence the drag reduction. A brief discussion will evaluate the significance of these results.
Radial Vaneless Diffusers: A Re-Examination of the Theories of Dean and Senoo and of Johnston and Dean
Authors: Inoue M.
Published: October 2009

There are two different but well known theories for calculating loss in the mixing process of the nonuniform flow discharged from the impeller, into the vaneless diffuser. One is by Dean and Senoo, the other by Johnston and Dean. In this paper explanations are given why these two very different theories predict similar total pressure losses. The mixing process in the vaneless diffuser based on the Dean and Senoo theory is re-examined. It is found that the reversible work exchange makes a significant contribution to the non-uniform flow becoming axisymmetric. This process is, however, greatly accelerated by wall friction and interface shear forces between the jet and wake, which lead to loss in total pressure.
A Stall Margin Design Method for Planar and Axisymmetric Diffusers
Authors: Strawn R. C. , Kline S. J.
Published: October 2009

An inverse design method is presented which gives the user control over stall margin, or distance from detachment, along the walls of planar and axisymmetric diffusers. It is proposed that optimum diffuser designs have continuous incipient detachment along their wall boundary layers. This hypothesis is supported by experimental and computational results plus physical arguments concerning the detachment process. Several computed optimum planar diffuser shapes are presented and discussed. For short diffusers with healthy inlet boundary layers, these optimum shaped wall units can have significantly higher pressure recovery than their straight-wall counterparts (up to 40 percent higher Cp in certain favorable cases). In most cases, however, the gains from wall contouring are small when compared to optimum straight-wall designs. This paper differs from earlier discussion in two ways: (i) it employs an improved physical model and correlation of detachment, and (ii) it uses improved boundary layer procedures based on (i).
Regular Structures in a Plane Triple Jet
Authors: Schweiger G.
Published: October 2009

The mixing process in the near field of a triple rectangular jet (air-CO2-air-jet) has been investigated in this paper by number density measurements (Laser-Raman-scattering) and schlieren pictures. The mixing process was found to be dominated by the rolling-up mechanism of the free shear layer into regular vortices. Four basic types of this process could be observed and are described here. Pulsed schlieren technique was applied to measure the vortex shedding frequency. The results are presented as a function of nozzle geometry and flow conditions. Finally a second vortex system oriented perpendicular to the main system could be detected.
Aerodynamic Loads on a Darrieus Rotor Blade
Authors: Wilson R. E. , Lissaman P. B. S. , James M. , McKie W. R.
Published: October 2009

A free-vortex analysis of a Darrieus rotor blade in nonsteady motion has been developed. The method uses the circle theorem to map a moving airfoil into the circle plane. The wake is modeled using point vortices. Nascent vortex strength and position are determined from the Kutta condition so that the nascent vortex has the same strength as a vortex sheet of uniform strength. The force on the airfoil is determined by two methods, integration of the pressure over the plate and from the impulse of the wake vortices. Both methods yield the same numerical results. A comparison with an analytical solution for a plunging airfoil gives excellent agreement. Results are shown for a one-bladed Darrieus Rotor at a tip speed ratio of three and two chord sizes. The numerical results indicate that the forces and moment on a Darrieus Rotor blade may be adequately approximated by quasisteady relationships although accurate determination of the local velocity and circulation are still required.
Computer Prediction of Local Destratification Near Low-Level Release Structures of Reservoirs
Authors: Busnaina A. A. , Lilley D. G.
Published: October 2009

The Garton Pump consists of a low-energy axial flow propeller placed just below the surface so as to provide a downward directed jet of fluid and thereby locally mix reservoirs near the release structure of the dam. In this way high-quality epilimnion water is transported downwards, so obtaining local destratification and improved release water quality in the vicinity of low-level release structures. The flowfield is fully three-dimensional and a simplified numerical simulation and solution procedure has been formulated in Cartesian coordinates to include species diffusion and buoyancy forces. Comparison of predictions with experimenal data confirms that the main dynamic effects are modeled adequately and better than a previous two-dimensional simulation. This fundamental study with practical applications represents a low cost basic tool to show the influence of design parameters on the practical flowfield.
Flow Around a Normal Plate of Finite Width Immersed in a Turbulent Boundary Layer
Authors: Sakamoto H. , Arie M.
Published: October 2009

An experimental investigation was carried out on the flow around a normal plate of finite width mounted on a smooth plane wall along which a turbulent boundary layer was fully developed. Experimental data were collected to investigate the effects of (1) the aspect ratio of the plate (2) the parameters characterizing the boundary-layer on the pressure drag and the vortex shedding frequency. The pressure drag coefficient of the plate defined by CDτ = D/(1/2ρuτ2hw) was found to be expressed by a power function of huτ/ν in the range h/δ<1.0 for each aspect ratio w/h, where D is the pressure drag, uτ is the shear velocity, ρ is the density of fluid, h and w are the height and the width of the plate, respectively, ν is the kinematic viscosity, δ is the thickness of the boundary layer. Also, the Strouhal number for the plate defined by St =fc • w/ U0 was found to be expressed by a power function of the aspect ratio w/h in the range of h/δ less than about 1.0, where fc is the vortex shedding frequency, U0 is the free-stream velocity. As the aspect ratio was reduced, the type of vortex shedding behind the plate was found to change from the arch type to the Karman type at the aspect ratio of about 0.8.
A Remote Laser-Probe System for Velocity and Temperature Measurements
Authors: Fujii S. , Gomi M. , Eguchi K.
Published: October 2009

This paper demonstrates the feasibility of simultaneously making velocity and temperature measurements by the combined use of a laser Doppler velocimeter and coherent anti-Stokes Raman scattering. The test area and control room were separated to avoid hostile surroundings in the combustion area. Data on probability density functions of velocity and temperature are given for reacting flows around a bluff-body flame stabilizer.
Gas Flow Resistance Measurements Through Packed Beds at High Reynolds Numbers
Authors: Jones D. P. , Krier H.
Published: October 2009

This research study indicates that the classical Reynolds number dependency of the coefficient of drag for gases forced into packed beds is not correct at high Reynolds numbers. Care must also be taken to account for boundary layer wall effects that occur when the ratio of test chamber diameter to bead particle diameter is too small. Included is a review of the literature pertaining to gaseous flow resistance in packed beds. An existing test facility used in a previous study was found unsatisfactory, and necessary corrections were made to obtain normalized pressure gradient measurements at increasingly high Reynolds numbers. The resultant data was organized into a new correlation for the coefficient of drag, that is Fv=150+3.89Re1−φ0.87 This formula was developed for air flowing over spherical particles at Reynolds numbers ranging from 103–105.
Matched Impedance to Control Fluid Transients
Authors: Wright S. J. , Wylie E. B. , Taplin L. B.
Published: October 2009

A methodology for the use of passive elements for transient control in pipelines is outlined. The specific objective is the elimination of pressure fluctuations in a fuel delivery line that are created by fuel injector operation. This is accomplished by the appropriate sizing of resistance elements upstream and downstream of the fuel injection system in the delivery line such that no pressure wave reflections occur in the system. The concept of matching the resistance element to the characteristic impedance of the fuel delivery system is described and applied to orifice and laminar flow elements. Experimental evidence is presented to validate the concepts.
Near-Wall Similarity in a Pressure-Driven Three-Dimensional Turbulent Boundary Layer
Authors: Pierce F. J. , McAllister J. E. , Tennant M. H.
Published: October 2009

Ten of eleven three-dimensional near-wall similarity models identified in the literature are evaluated with direct wall shear, velocity field, and pressure gradient data from a three-dimensional pressure-driven boundary layer flow. In a primary focus in the interval 50<y+<300 graphical results indicate that six simpler models and the streamwise component of one complex model are adequate for profiles with monotone increasing skew up to about 15 deg. The three remaining complex models provide a better predictive capability (for the main flow component) for monotone increasing skew up to almost 20 deg but these require significantly more input. One of three transverse models shows reasonably good predictive capability. Similar general results also appear for profiles with increasing-decreasing skew as occurs with freestream streamline recurvature with the maximum skew limited to about 10 deg. In a secondary focus in the interval of y+<50 there is a very strong tendency for the data to follow the well accepted, two-dimensional like behavior often identified with a transition or buffer region below the two-dimensional log-like law.
Toward Attenuation of Self-Sustained Oscillations of a Turbulent Jet Through a Cavity
Authors: Karadogan H. , Rockwell D.
Published: October 2009

Several attenuation configurations are assessed, involving the following concepts: generating streamwise vorticity, dephasing the azimuthal coherence of the jet, and reducing rigidity of the jet separation edge. By proper design, effective attenuation of the discrete frequency components of the oscillation can be achieved. For cases where there is not complete attenuation, the phase condition corresponding to maximum relative amplitude of the oscillation is maintained, the disturbance phase speed is essentially unaltered, and there is a proportional reduction in amplitude along the jet, including the initial fluctuation level at separation.
Prediction of Aerodynamically Induced Vibrations in Turbomachinery Blading
Authors: Hoyniak D. , Fleeter S.
Published: October 2009

To predict the aerodynamically forced response of an airfoil, an energy balance between the unsteady aerodynamic work and the energy dissipated through the airfoil structural and aerodynamic damping is performed. Theoretical zero incidence unsteady aerodynamic coefficients are then utilized in conjunction with this energy balance technique to predict the effects of reduced frequency, inlet Mach number, cascade geometry and interblade phase angle on the torsion mode aerodynamically forced response of the cascade. In addition, experimental unsteady aerodynamic gust data for flat plate and cambered cascaded airfoils are used together with these theoretical cascade unsteady self-induced aerodynamic coefficients to indicate the effects of incidence angle and airfoil camber on the forced response of the airfoil cascade.
Measurement of a Recirculating, Two-Dimensional, Turbulent Flow and Comparison to Turbulence Model Predictions. I: Steady State Case
Authors: Boyle D. R. , Golay M. W.
Published: October 2009

Turbulent flow measurements have been performed in a two-dimensional flow cell which is a 1/15-scale model of the Fast Flux Test Facility nuclear reactor outlet plenum. In a steady water flow, maps of the mean velocity field, turbulence kinetic energy, and Reynolds stress have been obtained using a laser doppler anemometer. The measurements are compared to numerical simulations using both the K–ε and K–σ two-equation turbulence models. A relationship between K–σ and K–ε turbulence models is derived, and the two models are found to be nearly equivalent. The steady-state mean velocity data are predicted well through-out most of the test cell. Calculated spatial distributions of the scalar turbulence quantities are qualitatively similar for both models; however, the predicted distributions do not match the data over major portions of the flow area. The K–σ model provides better estimates of the turbulence quantity magnitudes. The predicted results are highly sensitive to small changes in the turbulence model constants and depend heavily on the levels of inlet turbulence. However, important differences between prediction and measurement cannot be significantly reduced by simple changes to the model’s constants.
Measuring Particle Transverse Velocity Using an LDA
Authors: Stock D. E. , Fadeff K. G.
Published: October 2009

Four problems encountered in making transverse velocity measurements with an LDA are alignment of the optical system, velocity bias correction, avoidance of incomplete signal bias, and collecting sufficient data. Each problem is discussed and the method used to overcome each is presented for the case of measuring particle transverse velocities in a laboratory-scale electrostatic precipitator.
The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture
Authors: Greitzer E. M.
Published: October 2009

A review is presented of the types of instabilities which are encountered in pumping systems of technological interest. These include axial and centrifugal compression systems, pumping systems involving cavitation, systems with two-phase flow, systems with combustion, hydraulic systems, and systems which have two or more pumping elements in parallel. All of the above will be seen to exhibit instabilities under certain operating conditions, although the mechanism of instability, as well as the particular system element that is responsible for the instability, will be quite different in the different systems. However, several basic concepts, such as the idea of negative damping which is associated with dynamic instability, will be seen to be common to the different systems. The review is organized around the different types of systems that are discussed, and includes descriptions of the steady-state performance, the regimes in which one would expect instability, and the mechanisms of instability. An idealized pumping system is first examined to illustrate some of the basic concepts. More realistic systems are then treated in the same manner of showing steady-state performance, regimes of instability and mechanisms. In the review attention is given mainly to those areas in which there is high current engineering interest, and an attempt is made to describe those areas of research which can be most fruitfully pursued. In general, it is suggested that efforts should be directed toward obtaining an improved understanding of the transient behavior of the active (instability causing) elements within the system, since it is lack of knowledge of this aspect that currently limits the accuracy of system stability predictions.
Review—A Review of Some Phenomena in Turbulent Flow Separation
Authors: Simpson R. L.
Published: October 2009

Although turbulent flow separation is an old topic, little credible information is available on the flow details that must be understood to predict flows of this type. Until the last decade, there was little serious effort to develop and use experimental techniques that give unambiguous results. Consequently, flow models that are based on valid data are not well developed. Furthermore, the terminology used in discussing separation has been loosely defined, adding further confusion to the subject. This brief review presents a cross-sectional view of recent experimental techniques and results, development of models for flow prediction, efforts to define a meaningful common terminology to describe the flow, unsteady effects, and efforts to control separation.
The Effect of Nuclei on the Inception of Bubble and Sheet Cavitation on Axisymmetric Bodies
Authors: Kodama Y. , Take N. , Tamiya S. , Kato H.
Published: October 2009

Hydrogen bubbles were generated as cavitation nuclei and their distributions were measured. The number and size distribution of bubble cavities generated on axisymmetric bodies was calculated and compared with experimental results. The measured size distribution of bubble cavities agreed qualitatively with the calculated value, but the total number of cavities was about one half of the calculation. The role of stream nuclei on the inception of sheet cavity was investigated experimentally. Without added nuclei, the value of the incipient cavitation number σi showed a large scattering, whereas with added nuclei the scattering became fairly small and σi converged to the upper limit of that when no nuclei were added. σi with added nuclei also coincided with the desinent cavitation number σd, and σd remained unchanged by adding nuclei.
Review—Theoretical Models of Gas-Liquid Flows
Authors: Wallis G. B.
Published: October 2009

Two-phase flow is an “insecure” science. Many factors influence the phenomena, limiting the value of theory unless supported and guided by observation. Several methods of analysis are available; they should be used carefully and often need to be adapted in an “ad hoc” way to solve particular problems. Current efforts are concentrated on the separated (two-fluid) theoretical model and the development of improved instrumentation.
Experiments on Fluidelastic Instability of Cylinder Clusters in Axial Flow
Authors: Paidoussis M. P. , Curling LI. R. , Gagnon J. O.
Published: October 2009

This paper presents a summary of the general behavior of cylinder clusters in axial flow and especially of the fluidelastic instabilities which occur at high flow velocities. Experiments were conducted in a water tunnel with three- and four-cylinder clusters, and the behavior was monitored either optically or by instrumenting one of the cylinders with strain gauges. With increasing flow, the amplitude of small random vibrations of the cylinders increased; simultaneously, the natural frequencies, as a group, decreased, which is in good agreement with theory. The cylinders eventually lost stability by buckling (divergence), and at higher flow by flutter. Agreement between theoretical and experimental critical flow velocities for these fluidelastic instabilities has been found to be good.
Curved Ducts With Strong Secondary Motion: Velocity Measurements of Developing Laminar and Turbulent Flow
Authors: Taylor A. M. K. P. , Whitelaw J. H. , Yianneskis M.
Published: October 2009

Two orthogonal components of velocity and associated Reynolds stresses have been measured in a square-sectioned, 90 degree bend of 2.3 radius ratio using laser-Doppler velocimetry for Reynolds numbers of 790 and 40,000. The boundary layers at the bend inlet were 0.25 and 0.15 of the hydraulic diameter and resulted in secondary velocity maxima of 0.6 and 0.4 of the bulk flow velocity respectively. Comparison with fully-developed inlet flow shows that the boundary layer thickness is important to the flow development (mainly in the first half of the bend), particularly so when it is reduced to 0.15 of the hydraulic diameter. Turbulent flow in an identical duct with a radius ratio of 7.0 gives rise to smaller secondary velocities than in the strongly curved bend, although their effect is more important to the streamwise flow development because of the smaller pressure gradients. The detail and accuracy of the measurements make them suitable for evaluation of numerical techniques and turbulence models. Partially-parabolic techniques are applicable to the flows studied and their reduced storage requirements seem essential if satisfactory numerical accuracy is to be achieved.
Criteria for Filling of Liquid-Carrying Pipes
Authors: Krishnakumar C. K. , Fields S. F.
Published: October 2009

Flow rate versus pressure drop relations for liquid flow in pipes are well established for the case of pipes running full. However, these relations are not applicable for pipes that run partially filled. This article summarizes an experimental study to determine criteria for establishing full-pipe flow in horizontal, open-ended pipes and submerged, downward-flow vertical pipes.