bluuebunny/crossref_metadata_2025 huggingface dataset:
Compliance With the Treatment of Hypertension: The Potential of Combination Therapy
Authors: Erdine Serap
Published: November 2009

J Clin Hypertens (Greenwich). 2010;12:40–46. ©2009 Wiley Periodicals, Inc.

Patient adherence to antihypertensive medication is vital to ensure the successful treatment of hypertension. Low levels of adherence to and persistence with prescribed therapy are major factors leading to the current poor rates of blood pressure control among patients with hypertension. There are many reasons for nonadherence to therapy including patient‐, physician‐, and therapy‐related factors. Poor tolerability has a detrimental effect on adherence, therefore reducing the apparent effectiveness of agents with dose‐dependent side effects. Various effective combination therapies are recommended by current guidelines, eg, β‐blocker plus calcium channel blocker (CCB), angiotensin receptor blocker (ARB) plus thiazide diuretic, angiotensin‐converting enzyme (ACE) inhibitor plus thiazide diuretic, CCB plus thiazide diuretic, ACE inhibitor plus CCB, and ARB plus CCB, and these have the potential to increase adherence to therapy by combining a favorable tolerability profile with once‐daily dosing.
Regional Immunity of the Eye
Authors: Mochizuki Manabu
Published: November 2009

This article reviews molecular mechanism of intraocular inflammation in animal models and in humans, and the immunological defence system of the eye with particular attention to ocular pigment epithelium. In experimental autoimmune uveitis (EAU), T lymphocytes, particularly CD4+ T lymphocytes, play a central role in its immunopathogenic mechanisms. In humans, activated CD4+ T cells also play a central role in the immunopathogenic mechanisms. This notion is demonstrated in two human diseases: one is Vogt–Koyanagi–Harada disease, and the other is human T‐cell leukemia virus type 1 (HTLV‐1) uveitis. Activated CD4+ T cells infiltrating the eye are harmful to vision‐related cells and tissues in the eye and cause sight‐threatening conditions. However, the eye has regional defence systems to protect itself from these harmful activated T cells. We focus on ocular pigment epithelium (PE) and demonstrate immunoregulatory activity of iris PE and retinal PE. Iris PE suppresses activated CD4+ T cells by cell‐to‐cell contact with a crucial role played by B7‐2 molecule on iris PE and CTLA4 on T cells. The actual immunosuppressive factor being membrane bound TGF‐β. In contrast, retinal PE suppresses activated CD4+ T cells by soluble factors, such as soluble TGF‐β and thrombospondin 1. In addition to the direct T‐cell suppression by ocular PE, ocular PE has the capacity to promote activated T cells to regulatory T cells and use them as a tool to amplify the immune down regulation in the eye. The molecular mechanisms of generation of T regulatory cells by iris PE and retinal PE is also discussed.
Molteno aqueous shunt as a primary surgical intervention for uveitic glaucoma: long‐term results
Authors: Vuori Marja‐Liisa
Published: November 2009

Purpose:  To evaluate the efficacy of Molteno aqueous shunt as a primary surgical treatment in uveitic glaucoma.

Methods:  Nonrandomized, interventional, retrospective clinical study. The intraocular pressure (IOP), survival rate and complications were analyzed in 30 patients with uveitic glaucoma treated with Molteno implant.

Results:  The mean follow‐up time was 59.3 ± 18.4 months. Preoperatively, the mean ± SD IOP was 32.8 ± 7.5 mmHg (range 20–48), and the mean number of medications was 3.1 ± 0.6. The mean IOP decreased significantly (p < 0.001) to 17.7 and 15 mmHg at 3 and 6 months postoperatively. The mean number of medications decreased statistically significantly (p < 0.001) from the preoperative number 3.1 to 1.9 three months postoperatively. The number of medications continued to decrease significantly up to 3 years postoperatively. The qualified success rate (Kaplan–Meier estimate) was 97%, 93%, 90% and 85% at 1, 2, 3 and 4 years, respectively. Two patients failed because of hypotony, two patients developed conjunctival erosion and one patient had corneal decompensation.

Conclusions:  Molteno aqueous shunt as the first glaucoma procedure decreased IOP effectively in uveitic glaucoma. Even after 4 years, the survival estimate was quite high. The IOP decreased continuously during the first year after the surgery, and the medication was slowly tapered even up to 3 years postoperatively. It is suggested that it may be possible to postpone further surgical intervention during the first postoperative year after Molteno implantation even if the IOP is not quite optimal.
Conjunctival and corneal findings in bleb‐associated endophthalmitis: an in vivo confocal microscopy study
Authors: Carpineto Paolo , Agnifili Luca , Nubile Mario , Fasanella Vincenzo , Doronzo Emanuele , Mastropasqua Alessandra , Ciancaglini Marco
Published: November 2009

Purpose:  To report the conjunctival and corneal findings in delayed onset glaucoma filtering bleb‐associated endophthalmitis (BAE), by using in vivo confocal microscopy (IVCM).

Methods:  This was an observational case series. Four eyes of four glaucomatous patients who previously underwent mytomicin C augmented filtering surgery and affected with delayed onset BAE, underwent IVCM of conjunctival bleb and cornea at diagnosis, after 2 and 8 weeks of therapy. The inflammatory status of the conjunctival epithelium and sub‐epithelium was microscopically investigated. Corneal epithelial cells, stromal and endothelial morphology were also evaluated. A group of eight patients with functioning conjunctival filtering bleb was used as control.

Results:  At diagnosis, a diffuse inflammatory cell infiltration within the conjunctival epithelium presenting evident microcysts was found; conversely, there were no such alterations in the sub‐epithelium. An evident stromal oedema, keratocytes activation and diffuse endothelial inflammatory precipitates were the major corneal hallmarks. After 2 weeks of therapy, besides a remarkable improvement of epithelial inflammation and an evident reduction in endothelial precipitates, dendritic cells appeared within conjunctival sub‐epithelium and corneal epithelium showed aspects of cellular disruption. After 8 weeks, the conjunctival and corneal features consistently improved, except for the endothelium which still presented high‐reflective residual precipitates.

Conclusions:  In vivo confocal microscopy proved valuable in the analysis of conjunctival bleb and cornea in patients affected with delayed onset BAE, permitting an evaluation of the course of the disease, the response to therapy and the modulation of dose regimen.
Prevalence and causes of visual impairment in a rural North‐east China adult population: a population‐based survey in Bin County, Harbin
Authors: Song Wulian , Sun Xian , Shao Zhengbo , Zhou Xinrong , Kang Yang , Sui Hong , Yuan Huiping
Published: November 2009

Acta Ophthalmol. 2010: 88: 669–674

Purpose:  To investigate the prevalence and causes of visual impairment in a rural population in north‐east China.

Methods:  A population‐based study was conducted within Bin County, Harbin of north‐east China. Low vision and blindness were defined using the World Health Organization categories of visual impairment. The prevalence of visual impairment was estimated, and causes were identified based on best‐corrected visual acuity (BCVA) as well as presenting visual acuity (VA).

Results:  Out of 5764 people, 4956 (86.01%) aged older than 40 participated in the study. The prevalence of visual impairment, low vision and blindness based on presenting VA was 9.6% (BCVA, 6.6%), 7.7% (BCVA, 4.9%) and 1.9% (BCVA, 1.7%), respectively. Taking the presenting VA, cataract (44%) was the most common cause for visual impairment followed by uncorrected refractive error (24%), treatable causes of visual impairment accounted for 68% of the total cases. Cataract (59%) and glaucoma (15%) were leading causes for blindness based on presenting VA. According to BCVA, cataract was the leading cause of visual impairment and blindness (58% and 60%, respectively), followed by glaucoma (17% and 15%, respectively). The prevalence of visual impairment was higher among women than men (p < 0.0001) and increasing with age (p < 0.0001) and decreasing with increasing education level (p = 0.0075).

Conclusion:  Visual impairment was a serious public health problem in this rural population, with most of it easily remedied. Results highlighted the need for visual impairment prevention programs to an increasing number of elderly people, with a special emphasis on female and those with little or no education.
Bridging of Chronic Oral Anticoagulation with Enoxaparin in Patients with Atrial Fibrillation: Results from the Prospective BRAVE Registry
Authors: Hammerstingl C. , Schmitz A. , Fimmers R. , Omran H.
Published: November 2009

Current American College of Chest Physicians (ACCP) guidelines on the perioperative management of oral anticoagulation (OAC) suggest bridging therapy with therapeutic doses of low‐molecular‐weight heparin (LMWH) in patients with atrial fibrillation (AF) if at high or moderate thromboembolic (TE) risk, and with reduced doses in patients with low TE risk. Our objective was to assess the efficacy and safety of bridging OAC with enoxaparin in AF patients. These are the results of an open, prospective monocenter register. Hospitalized and ambulatory patients with AF requiring bridging therapy at high or moderate TE risk and normal renal function were treated with therapeutic LMWH doses; all other patients received reduced doses. A total of 703 patients were enrolled, of whom 358 (50.9%) were at moderate‐to‐high and 345 (49.1%) at low TE risk. Renal impairment was detected in 308 patients (43.8%). One hundred ninety patients (27.1%) were treated with therapeutic LMWH doses and 513 (72.9%) with reduced doses. No TE events were observed during the follow‐up period (0%; 95% confidence interval [CI] 0.0–0.52). Three major bleeds (0.4%; 0.1–1.2) and 60 minor bleeds were noted (8.9%; 6.6–10.9). Age and total LMWH doses were risk factors for bleeding in the multivariate analysis. The study, under conditions of everyday clinical care, supports a predefined bridging regimen based on the individual patient's TE risk and renal function. Patients with low TE risk or with impaired renal function can be bridged effectively and safely with reduced LMWH doses.
Gender and Responses to Aspirin and Clopidogrel: Insights Using Short Thrombelastography
Authors: Hobson Alex R. , Qureshi Zeshan , Banks Phil , Curzen Nick
Published: November 2009

There is significant variability in both baseline clotting tendency and response to antiplatelet therapy. Responses are associated with outcome. We have investigated whether differences could explain the increased risk observed in women presenting with coronary artery disease. We have utilized short thrombelastography to assess (i) baseline clotting responses, (ii) response to aspirin and clopidogrel, and (iii) post‐treatment platelet reactivity in 48 young volunteers, 22 older patients and 18 patients with previous stent thrombosis. Baseline responses were significantly higher in young women than in men. While there was no difference in response to aspirin, platelet reactivity on aspirin remained higher in women (area under curve at 15 min [AUC15] of arachidonic acid channel 332 ± 122 vs. 172 ± 80, P= 0.04). Young women had less response to clopidogrel (% reduction in AUC15 with adenosine diphosphate [ADP] 36.4 ± 12.4 vs. 64.0 ± 13.2, P < 0.01) in addition to higher post‐treatment reactivity (AUC15 of ADP 714 ± 161 vs. 311 ± 146, P < 0.01) compared to men. There were no such differences between male and female patients over 50. However, young women with previous stent thrombosis had among the highest platelet reactivity observed. Compared to men, young women have greater baseline clotting tendency, reduced response to clopidogrel, and greater post‐treatment reactivity while on both aspirin and clopidogrel. Differences in clotting tendency and response to antiplatelet therapy may contribute to the excess risk observed in young women but are not observed in older female patients.
Drug–Drug Noninteractions
Authors: Greenblatt David J.
Published: November 2009

Understanding and documentation of drug–drug interactions (DDIs) are an important component of drug development, and of clinical therapeutics. Because clinical DDI studies are costly, time‐consuming, and involve some risk, not all clinical DDI questions can be realistically addressed through human DDI trials.In vitromodels have been used to identify and predict drug combinations that might interact, and combinations that are unlikely to interact. This screening or “filtration” information allows clinical resources to be targeted in a more informed way. Still, many DDI studies will end up with a negative result. Negative DDI results constitute important and clinically relevant information, and scientific reports of such studies are candidates for publication.
Performance of Butterfly Valves as a Flow Controller
Authors: Eom K.
Published: November 2009

Butterfly valves have been used for shut-off and throttling-control application. It is found that the information available on loss coefficients of butterfly valves for good throttling control is limited at present. This report investigates the performance of two different configurations of butterfly valve: perforated blades and different diameter of solid blades that allow partial opening of the valve at closed position. The experimental results support the suitability of a butterfly valve for good flow control.
Navier-Stokes Computation of Radial Inflow Turbine Distributor
Authors: Vu T. C. , Shyy W.
Published: November 2009

A two-dimensional flow analysis of a radial inflow turbine distributor using full steady-state Reynolds-averaged Navier-Stokes equations is made. The numerical prediction of the total energy loss and the wicket gate torque is compared with experimental data. Also, a parametric study is carried out in order to evaluate the behavior of the numerical algorithm.
Theoretical Calculations of the Flow Around a Rotating Circular Cylinder Placed in a Uniform Flow
Authors: Aldoss Taha K. , Mansour Awad
Published: November 2009

The rotation of a circular cylinder placed in a uniform flow is assumed to add a circulation to the flow around the cylinder proportional to the product of the angular velocity of the cylinder and the front area between upper and lower separation points. Adding the velocity due to this induced circulation to the base velocity distribution of the non-rotating cylinder the new velocity distribution on the rotating cylinder is formed. Thwaites’ method is then used to calculate the laminar boundary layer on the upper and on the lower sides of the cylinder. The stagnation point, and the upper and lower separation points are also calculated at different values of rotational speed. The calculated lift and drag coefficients using a linear pressure distribution on the wake part of the cylinder with the calculated pressure dstribution on the front part between the two separation points show the same trend as the measured values. The torque coefficient is also calculated to estimate the necessary power required to rotate the cylinder to produce the needed lift.
Sensitivity of Three Sensor Hot Wire Probe to Yaw and Pitch Angle Variation
Authors: Lakshminarayana B. , Davino R.
Published: November 2009

The use of a three sensor hot wire probe for the measurement of three-dimensional flow field is increasing rapidly. This probe is very sensitive to yaw and pitch angle variations and existing laws for single sensor wires cannot be utilized to provide the correct hotwire response equations. A systematic study at various yaw and pitch angles (maximum values of ± 40 deg, nearly 220 different yaw and pitch angles) is carried out to determine the nature of response of a triple sensor hot wire probe. These results are analyzed to provide a correlation for the hot wire response equation which includes both pitch and yaw angles as variables.
Module Friction Factors and Intramodular Pressure Distributions for Periodic Fully Developed Turbulent Flow in Rectangular Interrupted-Plate Ducts
Authors: McBrien R. K. , Baliga B. R.
Published: November 2009

This paper presents detailed time-mean pressure measurements for periodic fully developed turbulent flows in straight interrupted-plate ducts of rectangular cross section. Several combinations of plate spacing and duct aspect ratio are investigated for Reynolds numbers, based on a module hydraulic diameter, in the range 5000 to 45000. The experiments undertaken in this work establish the existence of steady, time-mean, periodic fully developed flows for all flow rates and geometric configurations investigated. The results include graphical and tabular presentations of module friction factor versus Reynolds number data, and intramodular time-mean wall static pressure distributions. The physical implications of these results are also discussed.
Effect of Separation on Partial Cavitation
Authors: Pellone C. , Rowe A.
Published: November 2009

Partially cavitating flow around a hydrofoil in a confined two-dimensional flow is presented. The calculation method, based on the singularities technique combined with a minimisation method, is adapted to open configurations. With this extension, cavity wakes not necessarily merging with the upper-side of the foil can be treated. In the case of subcavitating flow, a boundary layer calculated is made, indicating a separation point downstream of which the flow becomes separated. In this area, an imaginary streamline (wake) is introduced to simulate the effect of separation. The choice of different forms of wake clearly shows the influence of wake form on the value of results. The process is extended to the case of cavitating flow for wakes developing behind the cavity. The method is applied to a test cavitating hydrofoil placed in a tunnel. Several cavity wakes progressively diverging from the foil were tested. The results obtained, compared with experimental results, show the great importance of achieving more accurate modelling of flow conditions behind cavities.
Temperature Effects on Single Bubble Collapse and Induced Impulsive Pressure
Authors: Shima A. , Tomita Y. , Ohno T.
Published: November 2009

In relation to the temperature effect in cavitation damage, the collapse of a single bubble in water over a wide range of temperatures was experimentally studied. A spark-induced bubble was observed by using a high speed camera and the impulsive pressure caused by the bubble collapse was measured by means of a pressure transducer. As water temperature increases, the motion of a bubble tends to weaken owing to the increase in saturated vapor pressure of water, and the surface configuration of a bubble becomes highly irregular because of thermal instability. The impulsive pressure depends not only on the bubble size and its distance from a solid wall but also on the water temperature. When the water temperature approaches the boiling point of water, the impulsive pressure abruptly decreases with increasing water temperature. The evidence obtained seems to be associated with the known temperature effect on cavitation damage at high water temperature.
Comparison of Holographic and Coulter Counter Measurements of Cavitation Nuclei in the Ocean
Authors: O’Hern T. J. , d’Agostino L. , Acosta A. J.
Published: November 2009

Holographic and Coulter Counter detection techniques were jointly used to measure the concentration density distribution of cavitation nuclei in the ocean. Comparison of the two techniques indicates that Coulter Counter analysis measures particulate contents up to an order of magnitude smaller than indicated by the holographic method and may also produce a distorted concentration density distribution. Several possible explanations of the observed discrepancies are proposed and discussed, including fundamental differences between the in situ holographic samples and the collected samples examined with the Coulter Counter, differences between the unknown electrical conductivity of the measured particles in the sea water samples and the non-conductive polystyrene spheres used to calibrate the Coulter Counter, the rupture of aggregate particles in the flow through the Coulter Counter orifice, the effect of electronic noise on the Coulter Counter signal, and the influence of statistical sampling error. The particle number concentration density distributions decrease approximately with the fourth power of the particle radius in the observed size range of 10 to 50 μm radius. Both sets of data indicate an increase in particle concentration near the bottom of the thermocline, and the holographic bubble concentrations also indicate a similar behavior. Much higher concentrations of particles were detected in the ocean, according to the holographic analysis, than in typical cavitation test facilities. Consideration of the static mechanical equilibrium of individual air bubbles suggests that the average tensile strength of the ocean waters examined in this study is not larger than about 2000 Pa and occasionally as low as about 100 Pa.
Observations on the Development of a Tip Vortex on a Rectangular Hydrofoil
Authors: Francis T. B. , Katz J.
Published: November 2009

The present paper describes a flow visualization study that focuses the development of a tip vortex on a rectangular NACA-66 hydrofoil. The experiments have been performed in a towing tank. Illumination with a thin laser sheet together with distribution of dye have been utilized as a means of observation. The results demonstrate the growth of the vortex along the chord, the increase in its dimensions with increasing incidence angle and decreasing Reynolds number. They also show that the center of the vortex moves inward towards the root with increasing incidence angle, increasing chordwise location, and decreasing velocity. Empirical relations for these trends have been computed. The observations also demonstrate that the flow around the tip is dominated by muliple vortex structures that include the primary vortex, a counter rotating structure, shear layer eddies, and several other secondary vortices.
The Effect of Particle Shape on Pressure Drop in Turbulent Pipe Flow of a Gas-Solid Suspension
Authors: Coughran M. T.
Published: November 2009

The pressure drop was measured for air suspensions of spherical paricles and two types of fibrous partcles, all having mean diameters of between 8 and 20 μm, in the same apparatus and at the same operating conditions. The pipe diameter was 50.42 mm. A Reynolds number range of 61,000 to 114,000 and loading ratio range of 0.06 to 0.30 were investigated. Air-sphere suspensions showed drag reduction, in agreement with published results. Fairly uniform fibers of aspect ratio = 75 gave no drag change and drag increases resulted with “random cut” fibers of mean aspect ratio = 31, contrary to the published results for water-fiber suspensions. A relative humidity effect was also shown for fibrous particles. The flocculation of the fibers may be an important variable to address in future experiments.
Comment on the Loss of Vorticity in the Near Wake of Bluff Bodies
Authors: Zdravkovich M. M.
Published: November 2009

Fage and his co-workers [1,2] made a remarkable discovery in the 20’s that only half of the vorticity generated by bluff bodies remained concentrated in shed vortices. This belated comment reconsiders Fage’s method of “loss” calculation by examining nonlinear effects. The ignored effect of three dimensional distortion of vortex filaments before roll up might be another important cause for the “apparent” loss of vorticity.
Computational Methods With Vortices—The 1988 Freeman Scholar Lecture
Authors: Sarpkaya Turgut
Published: November 2009

A comprehensive review is presented of the computational methods based upon Helmholtz’s powerful concepts of vortex dynamics, making use of Lagrangian or mixed Lagrangian-Eulerian schemes, the Biot-Savart law or the Vortex-in-Cell methods. The ingenious approximations and smoothing schemes developed in search of predictive models, qualitative solutions, new insights, or just some inspiration in the simulation of often two-dimensional, occasionally three-dimensional, and almost always incompressible fluids are described in detail. One is forewarned at the onset that chaos awaits at the end of the road. The challenge is to produce results in the face of ever accumulating errors within a time scale appropriate for the investigation. The review is organized around two major sections: Theoretical foundations and practical applications of vortex methods. The first covers topics such as vorticity and laws of transportation, evolution equations for a vortex sheet, real vortices and instabilities, Biot-Savart law, smoothing techniques (cutoff schemes, amalgamation of vortices, subvortex methods), cloud-in-cell or vortex-in-cell methods, body representation (Routh’s rule, surface singularity distributions), operator splitting and the random walk method (description and convergence), and asymmetry introduction. The next section covers contra flowing streams, vortical flows in aerodynamics (vortex sheet roll-up; slender-body, two-vortex, multi-discrete vortex, and segment or panel methods; three-dimensional flow models, and vortex-lattice methods), separated flow about cylindrical bodies (circular cylinder, sharp-edged bodies, arbitrarily-shaped bodies), general three-dimensional flows (vortex rings, turbulent spots, temporally and spatially-growing shear layers, and other applications (vortex-blade interactions, combustion phenomena, acoustics, contour dynamics, interaction of line vortices, chaos, and turbulence). The review is concluded with a brief comparison of these methods with others used in computational fluid dynamics and a personal view of their future prospects.
Measurements in Vertical Plane Turbulent Plumes
Authors: Ramaprian B. R. , Chandrasekhara M. S.
Published: November 2009

Mean-flow and turbulence measurements have been obtained in two-dimensional vertical turbulent plumes in a nominally still ambient. The plumes were generated by injecting hot water vertically upwards from the bottom of a reservior containing cold water. A two-component Laser Doppler Anemometer (LDA) and a “cold-film” resistance thermometer were used to obtain instantaneous velocity and temperature measurements in the plume. The present mean-flow measurements have confirmed many of the earlier measurements on plane plumes, but have also indicated some important differences. The use of the two-component LDA made it possible to obtain data on turbulent intensities, turbulent fluxes and other details of the structure of turbulence in plane plumes. The turbulence measurements have shown that the eddy viscosity and turbulence are significantly higher in the plume compared to an isothermal jet. Detailed measurements of energy balance suggest that buoyant production contributes substantially to this increase.
Studies of Flow Patterns in a Diffuser Designed to Generate Longitudinal Vortices
Authors: Goenka L. N. , Panton R. L. , Bogard D. G.
Published: November 2009

This paper describes flow visualization studies on a three-dimensional diffuser that generates two longitudinal vortices. The premise is that the three-dimensional flow patterns of this diffuser may have attributes that are superior to the two-dimensional flows of conventional diffusers. The diffuser geometry consists of a wide-angle, plane-wall diffuser with a pyramid-shaped insert attached to its expansion wall. The upsweep on the insert upper surface increases the pressure of the incoming flow, which rolls over into the expansion region in the presence of a transverse pressure gradient to form two symmetric, longitudinal vortices. At low Reynolds numbers (below 6000 based on the diffuser inlet height), the flow exhibited three flow patterns with subtle distinctions. The flowfield contained longitudinal vortices that modified and reduced in extent the separated regions that were present along the diffuser expansion wall. At high Reynolds numbers (above 6000), the separated regions along the diffuser expansion wall were replaced by a turbulent vortex. The lack of closed separated regions in the flow implies the absence of low-frequency effects that are characteristic of such regions. In addition, the flowfield exhibited little or no hysteresis with respect to changes in Reynolds number. These flowfield features are desirable in certain applications, such as exhaust diffusers for turbomachinery.
Mean Flow Downstream of Two-Dimensional Roughness Elements
Authors: Logan E. , Phataraphruk P.
Published: November 2009

The response of a fully developed pipe flow to wall mounted roughness elements of rectangular cross section was investigated experimentally using a probe with a single hot-wire. Four heights of rectangular, ring-type elements were installed rigidly in a 63.5-mm diameter, smooth-walled, circular pipe in which air was flowing at a Reynolds number of 50,000. After passing over the roughness element, the flow recovery occurred in three stages. The three flow regions are delineated, and the velocity profiles for each are correlated.
Fully Developed Flow in Curved Channels of Square Cross Sections Inclined
Authors: Duh Tay-Yueh , Shih Yaw-Dong
Published: November 2009

The fully developed viscous flow in curved channels of obliquely oriented square cross section with angle of inclination is analyzed for an incompressible fluid. A nonorthogonal helical coordinate system is introduced to study the flow field for various angles of inclination. To obtain a stationary numerical solution, a primitive-variable formulation of the pressure-velocity finite-difference scheme is formulated based on an ADI method. The results for the channel at zero angle are compared with data available in the literature. Detailed predictions of secondary-flow streamlines, axial velocities and friction factor ratios show that there are significant changes at inclination angles 0, 15, 30, 45, 60, and 75 deg. At a certain Dean number, it is found that no additional pair of vortices appears near the outer wall, except for angle of inclination 0 deg. If the Dean number is less than 125 the friction factor ratio has a minimum value at zero angle. If the Dean number is greater than 125, the minimum value of the friction factor ratio occurs at the angles of rotation 15 and 75 deg.
Drying of an Initially Saturated Fractured Volcanic Tuff
Authors: Russo A. J. , Reda D. C.
Published: November 2009

The isothermal drying of an initially saturated welded tuffaceous rock was studied experimentally. Gamma-beam densitometry was used to measure the material’s effective porosity distribution prior to the drying experiment. It was then used to measure liquid saturation distributions during a 1400 hour drying period. The core selected for study was taken from the Busted Butte outcrop at the Nevada Test Site, part of the Topopah Spring Member of Paintbrush tuff. This specimen contained several microfractures transversely oriented to the direction of the water or vapor migration. These fractures were found to be regions of rapid dryout or low saturation even though they were displaced from the surface over which dry nitrogen was flowing. An imbibition experiment was performed earlier on the same core. In the imbibition experiment the presence of most of these microfractures was detected by discontinuities in the measured saturation curves, which indicated a delay in liquid transport past the microfractures. The mechanism for this “inside out” drying is believed to be capillary action that removes water from the larger-pore fracture zone. Vapor pressure lowering in the fine pore region, which would result in transport by evaporation, diffusion and condensation, is thought not to be important at room temperatures. Modeling of this dryout experiment reproduced some of the overall features of the experiment but underpredicted the saturation near the drying surfaces.
Unsteady Structure Measurement of Cloud Cavitation on a Foil Section Using Conditional Sampling Technique
Authors: Kubota A. , Kato H. , Yamaguchi H. , Maeda M.
Published: November 2009

The structure of flow around unsteady cloud cavitation on a stationary two-dimensional hydrofoil was investigated experimentally using a conditional sampling technique. The unsteady flow velocity around the cloud cavitation was measured by a Laser Doppler Anemometry (LDA) and matched with the unsteady cavitation appearance photographed by a high-speed camera. This matching procedure was performed using data from pressure fluctuation measurements on the foil surface. The velocities were divided into two components using a digital filter, i.e., large-scale (low-frequency) and small-scale (high frequency) ones. The large-scale component corresponds with the large-scale unsteady cloud cavitation motion. In this manner, the unsteady structure of the cloud cavitation was successfully measured. The experimental result showed that the cloud cavitation observed at the present experiment had a vorticity extremum at its center and a cluster containing many small cavitation bubbles. The convection velocity of the cavitation cloud was much lower than the uniform velocity. The small-scale velocity fluctuation was not distributed uniformly in the cavitation cloud, but was concentrated near its boundary.
Comparison of Computational and Experimental Unsteady Cavitation on a Pitching Foil
Authors: Stern F.
Published: November 2009

Comparisons are made between a nonlinear method for predicting unsteady sheet cavitation and available experimental data for a pitching foil for the purposes of verifying the calculations and to further analyze the flow. A dynamical approach is employed in which the form of the instantaneous cavity surface is modeled as a semiellipse. The cavity length (major axis), thickness (semiminor axis), and position are determined such that the nonlinear cavity-surface boundary conditions are satisfied approximately. The pressure on the instantaneous cavity surface is prescribed using an unsteady thick-foil potential-flow method based on Green’s second identity. The computational method yields best results in predicting the cavity dynamics, but underpredicts the cavity length. For fixed cavitation number, mean foil angle, and pitch amplitude, the cavity dynamics, such as maximum cavity size and cavity surface behavior, are shown to depend on the ratio of the cavity natural frequency for the foil fixed at the maximum pitch amplitude to the foil reduced frequency. For a certain value of this ratio, the cavitation response is shown to be a minimum. The experimental results confirm the computational trends up to the point that experimental data were obtained.
Drag of Bodies of Revolution in Supercavitating Flow
Authors: Wolfe W. P. , Hailey C. E. , Oberkampf W. L.
Published: November 2009

The drag of bodies of revolution at zero degree angle of attack in supercavitating flow has been calculated. The potential flow about the body and cavity is calculated using an axial distribution of source/sink elements and is coupled with laminar and turbulent boundary-layer solutions for the body. Excellent agreement for drag coefficient is demonstrated between theory and a water-tunnel experiment, also between theory and a high-speed water-entry experiment. Results show skin-friction drag is the dominant drag component for high-speed water entry or high-speed underwater travel.
Viscous and Nuclei Effects on Hydrodynamic Loadings and Cavitation of a NACA 66 (MOD) Foil Section
Authors: Shen Y. T. , Dimotakis P. E.
Published: November 2009

A series of experiments has been conducted on a two-dimensional NACA 66 (MOD) foil to examine the effects of viscosity and nuclei on cavitation inception. In this paper the main discussions center on two foil angles having different types of pressure loadings to represent a propeller blade section operating at design and off-design conditions. At one degree design angle of attack the foil experiences a rooftop-type gradually varying pressure distribution. At three degrees off-design angle of attack the foil experiences a sharp suction pressure peak near the leading edge. Cebeci’s viscid/inviscid interactive code is used to compute the viscous scale effects on the development of the boundary layer, lift, drag and pressure distribution on the foil. Chahine’s multibubble interaction code is used to compute the effect of nuclei, test speeds, foil size and foil surface on traveling bubble cavitation. Both computer codes are found to agree satisfactorily with the experimental measurements reported here. Two assumptions commonly used to predict full scale surface cavitation from model tests are examined experimentally and theoretically. The first assumption states that cavitation inception occurs when the static pressure reaches the vapor pressure. On the contrary, the experiments showed that the water flowing over the foil surface sustained significant amounts of tension during inception of midchord bubble cavitation as well as leading edge sheet cavitation. The second assumption states that there is no scale effect on the values of negative minimum pressure coefficient. In the case of a rooftop-type pressure loading, the second assumption is supported by the pressure numerical calculations. However, in the case of a pressure loading with a strong suction peak near the leading edge the value of negative minimum pressure coefficient is as much as 12 to 15 percent lower on a model than at full scale.
Concentration Fluctuation Spectra in Turbulent Slurry Pipeline Flow
Authors: Sumner R. J. , Shook C. A. , Roco M. C.
Published: November 2009

Using probes responding to changes of slurry electrical resistance with concentration, time spectra of longitudinal concentration fluctuations in turbulent slurry flows have been measured. The sensors, with an effective domain approximately 1 mm in diameter, showed the spectra to be relatively insensitive to location within the pipe cross section. High frequency spectra were found to be relatively insensitive to slurry concentration and particle diameter. Low frequency spectra showed fluctuation amplitudes which increased with solids concentration.
The Use of a Photoelastic Method to Study the Effects of Bubble Collapse on Surfaces
Authors: Nienaltowska E.
Published: November 2009

A photoelastic technique using two laser beams and high acquisition rate (20 MHz) has been used to investigate the dynamics of a single bubble in a fluid at rest. The bubbles are spark-generated in the vicinity of a photoelastic wall. The influence of liquid pressure, proximity of the wall and the bubble life-time on the collapse intensity is examined. The results obtained are compared qualitatively with the measurements of pressure obtained by Shima and Tomita for the liquid at atmospheric pressure.
A Modified Form of the Betz’ Wind Turbine Theory Including Losses
Authors: Dyment A.
Published: November 2009

The aim of this brief paper is to present a variant of the classical Betz’ theory concerning the flow through a wind turbine. The new model includes losses and gives more realistic maximum values of the characteristic nondimensional coefficients of the machine.
Compressible Flowfield Characteristics of Butterfly Valves
Authors: Morris M. J. , Dutton J. C.
Published: November 2009

The results of an experimental investigation into the flowfield characteristics of butterfly valves under compressible flow operating conditions are reported. The experimental results include Schlieren and surface flow visualizations and flowfield static pressure distributions. Two valve disk shapes have been studied in a planar, two-dimensional test section: a generic biconvex circular arc profile and the midplane cross-section of a prototype butterfly valve. The valve disk angle and operating pressure ratio have also been varied in these experiments. The results demonstrate that under certain conditions of operation the butterfly valve flowfield can be extremely complex with oblique shock waves, expansion fans, and regions of flow separation and reattachment. In addition, the sensitivity of the valve disk surface pressure distributions to the local geometry near the leading and trailing edges and the relation of the aerodynamic torque to flow separation and reattachment on the disk are shown.
Flow Over a Cylinder at a Plane Boundary—A Model Based Upon (k–ε) Turbulence
Authors: Solberg T. , Eidsvik K. J.
Published: November 2009

A model for two-dimensional flows over a cylinder at a plane boundary is developed. The model, based upon a (k-ε) turbulence closure, is formulated in a curvilinear coordinate system based upon frictionless flow. A length scale modification in areas of adverse pressure gradient and recirculating flow appears to be more realistic than the standard (k-ε) model. The main features of the predicted flow do not depend critically upon the details of the grid or model, which means that a well defined solution is obtained. The solution appears to be reasonable and validated to the extent that the data permits.
Asymmetrical Boundary Layer Separation at the Base of a Two Cylinder Geometry
Authors: Boyle M. T. , Langston L. S.
Published: November 2009

This paper reports on the experimental description of the three-dimensional horseshoe vortex system occurring at the base of two cylinders mounted side by side on an endwall. The spacing between the two cylinders is adjusted to generate a family of viscous flows. Flow visualization performed in a water tunnel provides a qualitative understanding of the flow over a range of flow variables. A detailed wind tunnel experiment, provides a quantitative description of the flow at a single test condition. The flow is described by the use of a five-hole pressure probe and by cylinder and endwall surface static pressure measurements. At ReD = 2.5 × 105 the measurements show an asymmetrical primary vortex with a wide flat cross section. A small counter rotating vortex is found between the primary vortex and the cylinder leading edge.
Three-Dimensional Flow Pattern Upstream of a Surface-Mounted Rectangular Obstruction
Authors: Lai K. Y. M. , Makomaski A. H.
Published: November 2009

A three-dimensional TEACH-like computer code is developed and employed to study the flow phenomena upstream of a rectangular obstruction placed in a two-dimensional turbulent boundary layer. Satisfactory comparison is obtained with the experimental results of Blair (1984, 1987). The general trends, regarding the dependence of vortex dimensions, wall static pressure distributions and saddle point positions on Re = U∞δ*/ν and on D* = D/δ*, are similar to the experimental results for circular cylinders (Eckerle and Langston, 1986 and Baker, 1980). The position of the saddle point depends on the turbulence intensity in the primary vortex. The pressure coefficient at the foot of the obstruction depends solely on D* if no corner vortex exists. This coefficient is reduced when a corner vortex is present. All the computed flow patterns are similar to the one-vortex model of Eckerle and Langston (1986). The four-vortex model reported by Baker (1980) and Hunt et al. (1978) cannot be found in any of the calculations.
Impulse Response Method for Frequency-Dependent Pipeline Transients
Authors: Suo Lisheng , Wylie E. B.
Published: November 2009

An effective numerical method is presented to compute transients in piping systems in which frequency-dependent parameters influence the response. Frequency-dependent friction is utilized as the parameter-of-concern herein, however, the procedure can accommodate other factors such as frequency-dependent wavespeed equally well. The method, a variation in the impulse response method, is developed from the frequency response analysis and incorporates the fast Fourier transform. Examples are included showing the application of the method in computing both classic waterhammer and transients in pipes with frequency-dependent friction. Computed results agree very well with those from the standard method of characteristics and with physical experiments.
Flow Induced Pulsations in Gas Transport Systems: Analysis of the Influence of Closed Side Branches
Authors: Bruggeman J. C. , Hirschberg A. , van Dongen M. E. H. , Wijnands A. P. J. , Gorter J.
Published: November 2009

A theoretical analysis is presented of the low frequency aero-acoustic behavior of closed side branches along a gas transport pipe. The theory predicts the hydrodynamic conditions for moderate and strong pulsations. A model is proposed which predicts the order of magnitude of the power generated by the aero-acoustic source. The theoretical analysis leads to the design of spoilers which reduce the pulsation level by 30 to 40 dB. The results obtained by theoretical analysis and model experiments (Reynolds number 106) have been confirmed in full scale tests (Reynolds number 108).
Evaluation of a Model for Predicting the Drift of Iceberg Ensembles
Authors: El-Tahan H. , Venkatesh S. , El-Tahan M.
Published: November 2009

This paper describes the evaluation of a model for predicting the drift of iceberg ensembles. The model was developed in preparation for providing an iceberg forecasting service off the Canadian east coast north of about 45°N. It was envisaged that 1–5 day forecasts of iceberg ensemble drift will be available. Following a critical examination of all available data, 10 data sets containing up to 404 icebergs in the Grand Banks area off Newfoundland were selected for detailed study. The winds measured in the vicinity of the study area as well as the detailed current system developed by the International Ice Patrol were used as inputs to the model. A discussion on the accuracy and limitations of the input data is presented. Qualitative and quantitative criteria were used to evaluate model performance. Applying these criteria to the results of the computer simulations, it is shown that the model provides good predictions. The degree of predictive success varied from one data set to another. The study demonstrated the validity of the assumption of random positioning for icebergs within a grid block, especially for ensembles with large numbers of icebergs. It was found that an “average” iceberg size can be used to represent all icebergs. The study also showed that in order to achieve improved results it will be necessary to account for the deterioration (complete melting of icebergs), especially during the summer months.
Finite Element Modeling of Remote-Field Eddy Current Problems for the
Nondestructive Testing of Metal Tube
Authors: Palanisamy R.
Published: November 2009

The remote-field eddy current effect refers to a low frequency eddy current nondestructive testing (NDT) phenomenon in tubular conductors (magnetic or nonmagnetic) in which the behavior of both amplitude and phase of induced magnetic field are in apparent contradiction to the conventional eddy current theory. Equal detection sensitivity across the wall thickness, linear relationship between the output signal phase-lag and the wall thickness, and absence of the lift-off problem are some of the attractive and contradicting features of this technique. Despite its early recognition and useful application in down-hole inspection of oil-well casing, no development of adequate scientific base that could explain this phenomenon has been reported. This paper describes modeling of this phenomenon using the finite element numerical analysis technique. Amplitude and phase of the sensor coil output have been predicted using this model for different axisymmetric test geometries, material properties, and excitation frequencies.
Two-Dimensional Water-Solid Impact
Authors: Cointe R.
Published: November 2009

The general problem of a two-dimensional water-solid impact is considered. The method of matched asymptotic expansions is used to solve the resulting boundary value problem for small penetration depth. The first-order solution obtained extends the classical Von Ka´rma´n and Wagner theories to non-normal impact and initially curved free surfaces. It accounts for nonlinear features such as the creation of a jet at each waterline. The application of the method to the computation of the impact loads exerted by spilling breakers on a marine structure is discussed.