bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Control of a Very Large Floating Beam Structure
Authors: Yang Jia Sheng , Gao Rui Ping
Published: November 2015

In this paper, a novel boundary control method is investigated to suppress the vertical vibration of a very large floating structure (VLFS) with regular waves. The VLFS can be described as a distributed parameter system with partial differential equation (PDE). The proposed boundary controllers are developed based on Lyapunov's direct method to act on the upstream and downstream ends of the VLFS, respectively. Along with the suitable choice of control parameters, the proposed controllers could stabilize the vertical vibration of the VLFS subjected to regular waves. This study verifies the effectiveness of the proposed control methods to the VLFS. Then, the effects of wave amplitude and bending rigidity on the hydroelastic response of the VLFS are investigated.
Optimization Design on Performance of Self-Priming Jet Pump Based on Orthogonal Test
Authors: Yawen Han , Yang Wang , Shouqi Yuan , Lifeng Zhao , Xinxin Zhu
Published: November 2015

This paper study on a JSW10 Self-priming jet pump, in order to improve the performance of the pump, using the method of orthogonal test design test [1–2] and selecting the ejector throat diameter D1, outlet diameter of the diffusion tube D2, the outlet width of impeller b2, the number of blades z as the impact factors. Then design orthogonal test of four factors and three levels. Using the k–ε turbulence model provided by CFD on the whole flow field numerical calculation. According to the Q-H curves of the tests. Only judge by the standard of head, the optimal solution is test7, followed by test2;while if only judge by the efficiency test2 is the optimal scheme, test7 is the sub-optimal solution. Application analysis of range obtained that the best level combination for head curves is A1B1C3D1 and the best level combination for hydraulic efficiency is A1B1C3D1. Then through numerical results prove the correctness.Analyzing the test data at the rated flow point.Get the order of the factor affecting on head is C>D>B>A while the order on the efficiency is C>A>B>D. This analysis method has a certain reference value for the structure optimization of self-priming jet pumps to make ejector and centrifugal impeller fit perfect to improve the performance.
Full-Scale Validation of a Comprehensive Criterion to Predict Fish-Friendliness of Pumps
Authors: Krakers L. A. , Kruyt N. P. , Rutjes H. A.
Published: November 2015

Many pumping stations in drainage & irrigation applications are currently equipped with conventional (not fish friendly designed) pumps. Field tests have been performed [1] for several pump types of a certain size at certain pumping conditions to assess survival rates of fish passing through pumps. In order to compare different pump types of different sizes at different pumping conditions, a general criterion is required.

Testing of fish friendliness of pumps is expensive and involves animal tests with living fish for which permits are required. Therefore, pump manufacturers prefer to perform fish friendliness tests for a single pump size. In order to convert such results to other pump sizes, a scaling law is desired. Van Esch [2, 3] made a first attempt to address scaling principles for fish friendliness of pumps.

In the current study a general criterion is described to predict fish friendliness of pumps by means of models of mortality rates of fish passing through pumps. The criterion is validated with literature data [1–3] and experimental full-scale test data from the newly developed fish-friendly axial flow concrete volute pump by Flowserve with an impeller diameter of 850 mm. The full-scale tests involved a total of 1800 roach, perch and eel deployed over 7 pumping conditions, including 3 different heads and 5 different rotational speeds.

The fish-friendliness criterion includes different aspects that together predict the survival rate of fish passing through pumps. The first and most important contributor is the impeller, which can have an axial, mixed or radial flow design. The criterion involves the leading edge shape of the blades. Secondly, the diffuser or volute is considered, which provides a strike probability with diffuser vanes or volute tongue(s). In case the gap between the trailing edge of the impeller vanes and the leading edge of the diffuser vanes or volute tongue(s) is small relative to the fish size, there is the possibility of a “scissor” effect. Research in the USA for fish friendliness of hydropower turbines [4–7] showed that shear velocity and pressure drops can be of importance. Also cavitation (involves pressure drop & vapor bubble implosions), recirculation and turbulence can influence survival rates. At this stage these flow effects are roughly captured using the pump performance curve. This way, extensive CFD calculations to evaluate detailed flow effects can be avoided. For open impellers, the gap between the impeller vanes and wear ring is included in the criterion. In addition, fish species-dependent effects are taken into account, since fish vary widely in their internal and external building plan. For instance salmonid, percid and cyprinid fish respond differently to the same pump design than for example eel. Sharp edges and rough surfaces (for example caused by cavitation, erosion or corrosion) can also be harmful to fish but are not included at this stage.
Analysis of High Speed Train Flow Structures Under Crosswind
Authors: Avadiar Terence , Bell James , Burton David , Cormaty Heman , Li Chao
Published: November 2015

The flow structures along the length of a High-Speed Train (HST) under crosswind are investigated in a wind tunnel, through flow visualisations and velocity measurements at various angles of yaw. Surface visualisations show the development of a streamwise vortex originating at the nose that travels longitudinally along the length of the train. In addition, the hypothesis that flow structures repeat when the boundary layer (BL) on the roof of the HST model is pushed off is tested, with a view to analysing the effectiveness of using shortened HST models to accurately represent full-length trains in a wind tunnel. It would appear that using a shortened train model cannot completely model full-scale HSTs at realistic yaw angles using this theory.
A Dual-Scale LES Subgrid Model for Turbulent Liquid/Gas Phase Interface Dynamics
Authors: Herrmann Marcus
Published: November 2015

Turbulent liquid/gas phase interface dynamics are at the core of many applications. For example, in atomizing flows, the properties of the resulting liquid spray are determined by the interplay of fluid and surface tension forces. The resulting dynamics typically span 4–6 orders of magnitude in length scales, making direct numerical simulations exceedingly expensive. This motivates the need for modeling approaches based on spatial filtering or ensemble averaging. In this paper, a dual-scale modeling approach is presented to describe turbulent two-phase interface dynamics in a large-eddy-simulation-type spatial filtering context. To close the unclosed terms related to the phase interface arising from filtering the Navier-Stokes equation, a resolved realization of the phase interface dynamics is explicitly filtered. This resolved realization is maintained on a high-resolution over-set mesh using a Refined Local Surface Grid approach [1] employing an un-split, geometric, bounded, and conservative Volume-of-Fluid method [2]. The required model for the resolved realization of the interface advection velocity includes the effects of sub-filter surface tension, dissipation, and turbulent eddies. Results of the dual-scale model are compared to recent direct numerical simulations of an interface in homogeneous isotropic turbulence [3].
Investigation of Regenerator Matrix Through Figure of Merit Analysis
Authors: Gheith Ramla , Aloui Fethi , Ben Nasrallah Sassi
Published: November 2015

To choose the adequate regenerator, that gives the highest Stirling engine performances, different compromises must be considered. The figure of Merits is a powerful tool to evaluate and compare the performance of different Stirling engine regenerator matrices. The figure of merits is usually defined as the ratio between the heat transfer performance and the pressure drop losses through the regenerator matrix. The figure of merits can be obtained too by calculating different rations of pressure drop ΔPPm of regenerator volume VdrVE and for regenerator loss Q.tQ.r

F M S C = 1 Δ P P m V d r V E Q . t Q . r

In this study the experimental results of various Gamma Stirling engine metallic wire regenerator matrices are presented. The figure of merit parameter will be estimated to determine the adequate regenerator. Then the FMSC was used to determine the best regenerator porosity and the optimal operation parameters.
Impact of Operating Parameters on Beta Type Regenerative Stirling Machine Performances
Authors: Hachem Houda , Gheith Ramla , Ben Nasrallah Sassi , Aloui Fethi
Published: November 2015

Due to its high efficiency, fast cool-down, small size, light weight, low power consumption, high reliability, Stirling cycle machine has many successful commercial applications such as heating and cooling. In the present paper, performances of a Beta type Stirling machine having a regenerative displacer were investigated. Energy analysis is reproduced taking into account complex phenomena related to compressible fluid mechanics, thermodynamics and heat transfer. A special attention is paid to the effect of such operating parameters as pressure, temperature, frequency and cooling water flow rate on Beta type regenerative Stirling machine performances. A MATLAB program was developed. Net cooling capacity, imputed work and COP inside the machine were assumed and compared to the experimental values. Comparing the results obtained by this code with experimental data, an acceptable agreement can be deduced for the predicted performance of the Stirling machine. The optimum speed is investigated.
Study of the Melting Behavior in a PCM-Based Thermal Energy Storage
Authors: Bashar Mohammad , Siddiqui Kamran
Published: November 2015

Thermal energy storages are becoming important due to their significance in energy conservation as well as for the uninterrupted supply of thermal energy from renewable energy sources. The latent heat-based thermal energy storage systems utilizing phase change material (PCM) are gaining much attention due to some inherent advantages compared to sensible heat-based storage systems. However, the heat transfer process associated with the phase change in a PCM is complex and not well understood. In the present study, the melting process in a PCM-based thermal storage is experimentally studied. Two different configurations of the heat source were considered; horizontal and U-tube heat sources. The results show that the heat source shape has a significant influence on the solid to liquid phase change process (melting). The results also show that for the horizontal heat source configuration, the solid-liquid interface has a wavy profile, which is attributed to the convective cells in the melted domain of the PCM. These convective cells also influence the heat transfer coefficient, which decreased with an increase in the melted fraction. In U-tube configuration, the heat is non-uniformly transferred to the PCM domain.
Velocity and Momentum Decay Characteristics of Submerged Yield-Pseudoplastic Jets
Authors: Hammad Khaled J.
Published: November 2015

The velocity and momentum decay characteristics of submerged yield-pseudoplastic jets are studied. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel-Bulkley rheological model, are obtained using a finite-difference scheme. A parametric study is implemented to investigate the influence of flow inertia and rheology over the following range of parameters: Reynolds number, 50 ≤ Re ≤ 200, Yield number, 0 ≤ Y ≤ 1, and shear-thinning index, 0.6 ≤ n ≤ 1. A large recirculation region exists for Newtonian and pseudoplastic non-Newtonian jets. However, the extent and strength of the recirculation region substantially diminish with the yield number and, to a lesser extent, when the shear-thinning index is reduced from 1 to 0.6. Increasing the yield number beyond a critical value eliminates flow recirculation. The centerline velocity and momentum decay of yield-pseudoplastic jets, in general, increases with the yield number. Velocity and momentum based depths of penetration, DPU and DPM, respectively, are extracted and presented. A substantial decrease in DPU and DPM is observed when the shear-thinning index is reduced from 1 to 0.6 for Y = 0. The presence of yield stress significantly reduces both DPU and DPM of submerged jets. The impact of shear-thinning on the decay characteristics of the jet is more pronounced at low yield numbers.
Optimization of Anastomotic Geometry for Vascular Access Fistula
Authors: Bao Guangyu , Chen Xiaomin , Agarwal Ramesh K.
Published: November 2015

Arteriovenous fistula (AVF) is one type of vascular access which is a surgically created vein used to remove and return blood during hemodialysis [1]. It is a long-term treatment for kidney failure. Although clinical treatment and technology have both achieved great improvements in recent years, the vascular access for hemodialysis still has significant early failure rates after the insertion of AVF in patients [2]. Studies have shown that stenosis in the vascular access circuit is the single major cause for access morbidity. Majority of efforts to understand the mechanisms of stenosis formation, and its prevention and management have largely focused on understanding and managing this complication based on the pathophysiology, tissue histology and molecular biology; however these efforts have not resulted in significant progress to date. We believe that the major impact in this area will come from continued and accurate understanding of the hemodynamics, and by development of techniques of intervention to modulate factors such as flow rates, pressures and compliance of the circuit.

The goal of this paper is to study anastomotic models of AV access using Computational Fluid Dynamics (CFD) and optimize them to minimize the wall shear stress (WSS). In order to achieve this goal, the commercial CFD software FLUENT [3] is employed in conjunction with a single objective genetic algorithm [4].

Computations for two types of AVF currently in use in clinical practice are performed. AVF with 25° angle/3–4mm diameter and 90° angle/3–5mm diameter are selected to conduct the optimization. A single-objective genetic algorithm is employed in the optimization process and a k-kl-ω turbulence model is employed in CFD simulations; this model can accurately compute transitional/turbulent flows. In order to optimize for the same flow conditions, a fixed boundary condition is used during the optimization process. Computations for 16 to 20 generations of the selected AVFs are obtained from the genetic algorithm solver. The maximum WSS in the two AVFs considered are 6997.8 and 7750 dynes/cm2; however, the maximum WSS in the shape-optimized AVFs are reduced to 3511.2 and 4293.9 dynes/cm2 respectively, which have decreased by 49.82% and 44.59% respectively. Thus, the probability of the formation of stenosis in AVFs and early failure rates of vascular access are reduced by using the optimized AVFs.
Numerical Study of Flow Through Models of Aortic Valve Stenoses and Assessment of Gorlin Equation
Authors: Agarwal Ramesh K. , Bao Guangyu
Published: November 2015

Gorlin equation has been applied in clinical practice for evaluating the aortic valve area (AVA) of vascular and aortic valve stenosis for past sixty years [1]. It was derived using the Bernoulli equation across the stenosis with the assumption that the velocity of the fluid behind the stenosis is much greater than the velocity upstream of the stenosis. Because of this assumption, the calculated stenosed area may have large error if the flow rate across the valve is low or the stenosis is mild [2]. In a recent paper, Okpara and Agarwal [3] proposed a new equation (Agarwal – Okpara equation) which significantly decreases the evaluation error compared to the Gorlin Equation. The purpose of this paper is to modify the Agarwal – Okpara equation to generalize its applicability based on additional data calculated from the commercial CFD software FLUENT as well as the clinical data obtained from the literature. A total of ten cases are computed using CFD to assess the range of validity of the Gorlin equation and the Agarwal – Okpara equation. In addition, eighty clinical data points were obtained from the papers of Minners et al. [4] and Hakii et al. [5] covering a large range of severity of stenosis. The error in AVA computed from Gorlin equation and Agarwal – Okpara equation varied from 7.44 to 82.14% and 0.06 to 27.26% respectively compared to the CFD simulation data, and 41.47 to 83.60% and 8.88 to 33.98% respectively compared to the clinical data; however, AVA calculated using the Agarwal – Okpara – Bao equation presented in this paper gives results within 0.42 to 9.6% error compared to the exact AVA used in FLUENT simulations, and from 4.76 to 24.13% compared to the clinical data. The Agarwal – Okpara – Bao equation agrees with the clinical data for all relevant flow rates and full range of severity of stenosis. Thus, the use of Agarwal – Okpara – Bao equation to evaluate AVA in clinical practice is suggested.
Cyclic Breathing Simulations: Pressure Outlet Boundary Conditions Coupled With Resistance and Compliance
Authors: Wang Xiao , Walters Keith , Burgreen Greg W. , Thompson David S.
Published: November 2015

A patient-specific non-uniform pressure outlet boundary condition was developed and used in unsteady simulations of cyclic breathing in a large-scale model of the lung airway from the oronasal opening to the terminal bronchioles. The computational domain is a reduced-geometry model, in which some airway branches in each generation were truncated, and only selected paths were retained to the terminal generation. To characterize pressure change through airway tree extending from the truncated outlets to pulmonary zone, virtual airways represented by extended volume mesh zones were constructed in order to apply a zero-dimensional airway resistance model. The airway resistances were prescribed based on a precursor steady simulation under constant ventilation condition. The virtual airways accommodate the use of patient-specific alveolar pressure conditions. Furthermore, the time-dependent alveolar pressure profile was composed with the physiologically accurate pleural pressure predicted by the whole-body simulation software HumMod, and the transpulmonary pressure evaluated based on lung compliance and local air volume change. To investigate airway flow patterns of healthy and diseased lungs, unsteady breathing simulations were conducted with varying lung compliances accounting for healthy lungs, and lungs with emphysema or interstitial fibrosis. Results show that the simulations using this patient-specific pressure boundary condition are capable of reproducing physiologically realistic flow patterns corresponding to abnormal pulmonary compliance in diseased lungs, such as the hyperventilation in lungs with emphysema, and the demand of more mechanic work for breathing in lungs with fibrosis.
Investigation of Impeller Exit Flow Field in a Highly Loaded Centrifugal Compressor
Authors: Dutta Soumya , Sato Wataru , Funazaki Kenichi , Kakudate Yukiya
Published: November 2015

Recently, the demand of a highly loaded impeller for industrial compressors is increasing due to environmental and economic reasons. In a compressor aerodynamic design including the matching of an impeller and a diffuser, it is very important to predict the impeller flow field precisely, but due to its high blade loading, a large flow separation and a strong clearance leakage flow occurring inside the impeller passage and impeller exit flow is distorted significantly. Thus it becomes difficult to predict a compressor performance with enough accuracy.

Therefore, in order to validate the prediction accuracy of CFD analysis to the highly loaded industrial compressor impeller, flow measurements at the impeller exit were conducted by using 3 holes yaw meter and hot wire anemometry traverse tests, and compared to the CFD results. CFD analysis was conducted by Iwate University using ANSYS CFX, in which SST model was applied to estimate turbulence intensity.

From the comparison between CFD results and measurements, significant difference in turbulence intensity and flow angles between measurements and CFD results could be observed at the impeller exit. These results imply that the reason behind this difference could be because CFD prediction underestimates the free stream turbulence and mixing effects between free stream and clearance flows.
Impact of Tongue Shapes on Hydraulic and Structure Performances of Double-Channel Pump Based on Fluid-Structure Interaction
Authors: Zhao Binjuan , Qiu Jing , Chen Huilong , Wang Yu , Zhao Youfei
Published: November 2015

The volute tongue has a great influence on the rotational impeller and stationary volute interaction in a pump. In this paper, the impact of tongue shapes on hydraulic and structural performances of a double channel pump with a specific speed of 110.9 is investigated, and four cases with different tongue shapes are simulated by the two-way coupling fluid-structure interaction (FSI) method. The result shows that, in the hydraulic performance aspect, the influence of tongue shapes on the efficiency is weak, and the maximum different value is 0.76%. But the maximum different value of pump-head is 0.126m. Tongue shapes mainly affect the pressure fluctuation in and after the tongue edge in the rotational direction. Pressure fluctuation near the rectangle tongue is stronger than that near the rounded tongue, and an appropriate increase of the corner radius will decrease the pressure fluctuation effectively. Because of the asymmetry of the volute, radial force on the volute is very large. It is periodical when the impeller rotates one circle and decreases obviously with an appropriate increase of the corner radius. Compared to the rounded tongue, the radial force on the volute with rectangle tongue is larger. In structural performance aspect, stress concentration of the impeller appears on the suction surface near the outlet, and the volute stress concentration appears near the tongue edge. Tongue shapes have little effect on the stress distribution of the impeller, but affect the volute stress deeply. The maximum stress near the rectangle tongue is a little larger than that near the rounded tongue, but an appropriate increase of the corner radius will decrease the maximum stress of volute obviously, and the amplitude will decrease slightly. Displacement with the magnitude 10−5 m happens in the pump, and the maximum displacement point appears in the outlet of the volute. It is periodical and mainly influenced by the blade-passing frequency. The tongue shape has little impact on the maximum displacement, but it has an obvious effect on the vibration velocity of the pump. Compared to the volute with rectangle tongue, the rounded tongue can decrease the vibration velocity, and larger corner radius can also suppress the vibration.
Large-Scale Simulation of Rod Bundles: Coherent Structure Recognition and Stability Analysis
Authors: Merzari Elia , Fischer Paul , Walker Justin
Published: November 2015

The axial flow in rod bundles has been the object of several investigations, since they are relevant for various industrial applications (e.g., heat exchangers, nuclear reactor cores). For tight configurations (pitch-to-diameter ratio smaller than 1.1) the large difference in velocity within the cross section creates the possibility of a Kelvin-Helmholtz instability and the generation of a vortex street in the gap (“gap instability”). While the presence of spacing devices may perturb the flow, simple grid spacers — grids of the type usually encountered in sodium fast reactors — do not prevent this instability.

This work seeks to improve our understanding of the gap instability in large rod bundles by using high-fidelity large-eddy simulation (LES). The application of LES methods has been historically limited to single-pin calculations because of the large cost of full-bundle calculations. However, using Nek5000, a massively parallel spectral-element computational fluid dynamics code, we are able to carry out well-resolved LES simulations for this class of geometries. Results are compared with experimental data. For the largest bundle case, over 8 billion collocation points at a polynomial order of 20 are judged necessary to achieve overall excellent accuracy. More than 500,000 processors are used to carry out the simulations (costing approximately 50,000,000 CPU-hours), and 3,000 snapshots of the flow field have been collected to apply several coherent structure recognition techniques, including one of the largest proper orthogonal decompositions carried out to date.

Also investigated here is the effect of geometry, including the (presence of spacers, changing pitch-to-diameter ratio, and canister wall. In particular, global linear stability analysis is applied to a series of simplified geometries in order to gain insight into the physics of the gap instability.
Parallel Pressure Poisson Solvers for LES of Complex Geometry Flows
Authors: Singh Krishna M. , Avital Eldad J. , Williams John J. R. , Ji C. , Munjiza A.
Published: November 2015

This paper presents an assessment of performance of parallel pre-conditioners for BICGSTAB solver for numerical solution of the pressure Poisson equation arising in large eddy simulation of turbulent incompressible flows. We explore the performance of geometric multigrid pre-conditioner for the non-uniform grid and compare its performance with additive Schwarz pre-conditioner, Jacobi and SOR(k) pre-conditioners. Numerical experiments have been performed for a wide range of non-uniformity (stretching) of the grid. The fictitious domain geometric multigrid preconditioner shows the best performance followed by the SOR(k) preconditioner.
Bubble Size Reduction Using Mesh Bubble Breakers in Two-Phase Vertical Co-Flow
Authors: Kalbfleisch Alan , Siddiqui Kamran
Published: November 2015

Bubble breakers have been shown to reduce the bubble size and hence increasing the bubble surface-to-volume ratio facilitating higher mass transfer. We report on an experimental study investigating the effect of mesh-type bubble breaker on two-phase co-flow in a vertical column. A range of gas-liquid flow rates ratios (GLR) has been considered that covers the two-phase regimes from bubbly flow to slug flow. A vertical glass tube was used as the experimental apparatus which provides full optical access. A high speed imaging system was used to capture the flow dynamics for bubble characterization. The results show that the bubble size generated by the mesh bubble breaker is greatly affected by the pore size. For a bubbly flow regime, the initial bubble size was reduced by approximately 60%–70% for a pore size of 1mm and by about 45%–50% for a pore size of 4mm. It is found that the transition from bubbly flow to slug flow can be affected by the mesh bubble breaker. The results show that in general, the mesh bubble breaker increases the GLR limit for the transition from bubbly to slug flow.
Finite Element Prediction of Multi-Size Particulate Flow Through Three-Dimensional Pump Casing
Authors: Pagalthivarthi Krishnan V. , Furlan John M. , Visintainer Robert J.
Published: November 2015

Flow through centrifugal pump casing is highly complex in nature due to the complex geometry of the casing. While simplified two dimensional modeling of pump casing reveals the overall flow pattern and pressure distribution, a complete 3D model of pump casing is essential to fully capture the interaction of the primary main stream flow and the secondary flows especially in areas of heavy recirculation.

This paper presents steady state finite element simulation of multi-size particulate slurry flow through three dimensional pump casing. The flow field and concentration distribution is presented for different cross-sectional planes. The multi-size particulate flow simulation results are compared with two mono-size particle simulations using (1) the concentration weighted mean diameter of the slurry and (b) the D50 size of the slurry. Qualitative comparison is made with the wear rate predicted by the simulations and the field data. Simulations and field data show that at low flow rates, the side-wall gouging wear near the tongue region becomes significant.
Ultrasonic Measurements of Local Particle Velocity and Concentration Within the Casing of a Centrifugal Pump
Authors: Furlan John M. , Garman Mohamed , Kadambi Jaikrishnan , Visintainer Robert J. , Pagalthivarthi Krishnan V.
Published: November 2015

In the design of slurry transport equipment used in the mining and dredging industries, the effects of solid particle velocity and concentration on hydraulic performance and wear need to be considered. Two ultrasonic techniques have been used to investigate slurry flows through a centrifugal pump casing: a local particle concentration measurement technique (Furlan et al., 2012) and a pulsed ultrasonic Doppler Velocimetry (PUDV) technique (Hanjiang, 2003, Garman, 2015).

Local particle velocities and concentrations have been obtained in a flow of soda lime glass particles (diameter of 195 μm) and water through the casing of a centrifugal slurry pump operating close to the best efficiency point using the two ultrasound techniques. For the concentration measurements, the acoustic properties of slurry flows such as sonic velocity, backscatter, and attenuation are correlated to the volume fraction of solid particles. The algorithm utilizes measurements obtained from homogeneous vertical pipe flow fields as calibration data in order to obtain experimental concentration profiles in the non-homogenous flow regimes which are encountered in the pump casing.

The PUDV technique correlates the Doppler shift in frequency associated with the movement of particles towards or away from the transducer. A two measurement (angle) technique is applied within the pump casing in order to account for the components of particle velocity which are orthogonal to the casing side wall. The techniques are utilized to obtain concentration and velocity profiles within the pump casing for overall average loop particle concentrations ranging from 7–11 % by volume.

The experimental results are compared with the concentration and velocity fields that are predicted by in-house finite element computational fluid dynamics (CFD) codes (Pagalthivarthi and Visintainer, 2009) which are used to predict wear in centrifugal slurry pump wet end components. Reasonable agreement is observed for both the concentration and velocity fields. Specifically, measurements indicate that there is a reduction of in-situ concentration and hence a corresponding radial acceleration of the particles with respect to the fluid occurring within the impeller which has also been predicted by computational predictions of flow through the impeller (Pagalthivarthi et al., 2013). Additionally, the prediction of the existence of secondary flow patterns by the casing computational code has been supported with the velocity measurements.
Evaporation Kinetics and Residue Patterns of a Nanofluid Droplet
Authors: Lee H. H. , Fu S. C. , Chao Y. H. Christopher
Published: November 2015

This paper studies how the nanoparticle size affects nanofluid droplet evaporation kinetics and residue patterns. An experiment is set up to investigate the evaporation rate of a sessile nanofluid droplet under ambient conditions using different particle sizes, with diameters of 9nm, 13nm, 20nm, 80nm and 135nm. The smaller the particle size, the higher the evaporation rate of the nanofluid droplet. After evaporation, a residue pattern is left on a substrate. The experiment shows that different particle sizes and concentrations have various residue patterns. For smaller size particles (diameters up to 13nm), a ring-shaped pattern is observed after evaporation. A uniform pattern appears for particles bigger than 13nm.
A Fully Coupled Flow and 6-DOF Motion Solver in Multiple Reference Frames
Authors: Shan Hua , Kim Sung-Eun , Rhee Bong
Published: November 2015

In many computational fluid dynamics (CFD) applications involving a single rotating part, such as the flow through an open water propeller rotating at a constant rpm, it is convenient to formulate the governing equations in a non-inertial rotating frame. For flow problems consisting of both stationary and rotating parts, e.g. the stator and the rotor of a turbine, or the hull and propeller of a ship, the multiple reference frames (MRF) approach has been widely used. In most existing MRF models, the computation domain is divided into stationary and rotating zones. In the stationary zone, the flow equations are formulated in the inertial frame, while in the rotating zone, the equations are solved in the non-inertial rotating frame. Also, the flow is assumed to be steady in both zones and the flow solution in the rotating zone can be interpreted as the phase-locked time average result. Compared with other approaches, such as the actuator disk (body-force) model, the MRF approach is superior because it accounts for the actual geometry of the rotating part, e.g. propeller blades.

A more complicated situation occurs when the flow solver is coupled to the six degrees of freedom (6-DOF) equations of rigid-body motion in predicting the maneuver of a self-propelled surface or underwater vehicle. In many applications, the propeller is replaced by the actuator disk model. The current work attempts to extend the MRF approach to the 6-DOF maneuvering problems. The governing equations for unsteady incompressible flow in a non-inertial frame have been extended to the flow equations in multiple reference frames: a hull-fixed frame that undergoes translation and rotation predicted by the 6-DOF equations of motion and a propeller-fixed frame in relative rotation with respect to the hull. Because of the large disparity between time scales in the 6-DOF rigid body motion of the hull and the relative rotational motion of the propeller, the phase-locked solution in the propeller MRF zone is considered a reasonable approximation for the actual flow around the propeller. The flow equations are coupled to the 6-DOF equations of motion using an iterative coupling algorithm. The coupled solver has been developed as part of NavyFOAM. The theoretical framework and the numerical implementation of the coupled solver are outlined in this paper. Some numerical test results are also presented.
Numerical Analysis of Dust Emission by Powder Discharge and Jet Expansion
Authors: Audard F. , Fede P. , Simonin O. , Belut E.
Published: November 2015

The paper deals with the Euler-Euler numerical simulation of an experimental study (Ansart et al., 2009 [1]) of freely falling granular jet for investigating the dispersion of dust. The configuration is a bunker, where quasi-static particulate flow takes place, and a free-fall chamber. As a first step, a frictional viscosity model developed by Srivastava and Sundaresan (2003) [2] is implemented to take into account the frictional effects occurring in the quasi-static particulate flows. Without the frictional model for the viscosity, the numerical simulations overpredict the solid mass flow rate at the outlet of the bunker. When using the frictional viscosity, the solid mass flow rate is in better accordance with the experimental value. However, the solid velocity is overestimated in numerical simulations.
Numerical Investigation of Influence of Rotor-Rotor Gap on Performances of Contra-Rotating Axial Flow Pump
Authors: Cao Linlin , Watanabe Satoshi , Furukawa Akinori , Wu Dazhuan
Published: November 2015

As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performances. However, while compared with the traditional rotor-stator combination, it suffers from more significant potential interactions between two rotating blade rows, and the gap between two rotors has to be kept large with accepting the small deterioration of head performance. In our previous studies, the different speed design was confirmed effective to weaken the blade rows interactions, and therefore indicated the possibility to pertinently reduce the gap between two rotors as well as improve the hydraulic performances of the contra-rotating axial flow pump. The present paper majorly discuss the possibility to further improve the hydraulic performances of contra-rotating axial flow pump by reducing the gap between two blade rows. The cases with original gap, increased gap and reduced gap were studied by the numerical approach. The internal flow structures between two blade rows were concentrated, and a simplified method for the pressure fluctuations investigation was applied. This study is supposed to offer more understanding about the internal flow properties and give more guidelines to determine the related parameters for contra-rotating rotor-rotor combination.
Towards Simulation of Clogging Effects in Wastewater Pumps: A Review of the State-of-the-Art in Cloth Modelling and Challenges in the Simulation of Clogging Effects
Authors: Jensen Anna Lyhne , Rosendahl Lasse , Sørensen Henrik , Lykholt-Ustrup Flemming
Published: November 2015

Simulation of clogging effects caused by cloths in wastewater pumps enables a faster and cheaper design process of wastewater pumps, which potentially leads to a reduction in the occurrence of clogging. Four potential methods for cloth simulation are reviewed and the challenges of each method are identified and compared.

These methods are the Arbitrary Lagrangian-Eulerian (ALE) method, Immersed Boundary (IB) method, Smoothed Particle Hydrodynamics (SPH) coupled with the Finite Element method (FEM), and Computational Fluid Dynamics (CFD) coupled with the Discrete Element method (DEM).

Each method has advantages and disadvantages, and each of them may prove to be applicable for the application. The CFD-DEM approach is chosen for future work.
Operational Parametric Study of a Tesla Pump: Disk Pack Spacing and Rotational Speed
Authors: Dodsworth Laura , Groulx Dominic
Published: November 2015

A Tesla pump was designed and built with the objective of being a compact and rugged pump for cooling electronics. A Tesla pump is a bladeless pump that uses spinning disks to move fluid. Due to the nature of the pump, cavitation is avoided, and the lack of conventional blades makes it rugged and easy to build. A continuous test loop was designed and used to produce pump curves at several different disk pack spacings and motor speeds. Pump curves were obtained and analyzed for this prototype Tesla pump. It was determined the smallest spacing tested proved to be the most efficient, especially at the highest motor speed. A relationship between disk pack gap and efficiency was found, as well as one between the pump’s performance and motor speed.
Predicting, Improving and Visualizing Cavitation Characteristics of First-Stage Impellers in High-Speed, High-Energy Pumps
Authors: van den Berg Nico , Bastiaansen Tim , Elebiary Kariem
Published: November 2015

This paper describes the development and verification of a new first-stage impeller using an automated and parameterized process of reshaping the vane leading edge. By utilizing Computational Fluid Dynamics (CFD), several design iterations can be performed in a short period of time driven by the numerical NPSHi curve — which is an indication of the NPSH at which the first cavitation bubbles will start to form [1].

Based on the original (parent) impeller hydraulic, five designs were created with a variety of vane leading edge shapes. To ensure the Best Cavitation Point (BCP) is located near rated condition and the NPSH3 requirement is met at maximum operating flow, the most promising design was selected and manufactured at full scale using rapid prototyping.

During full scale, reduced speed, flow visualization testing in a dedicated test loop of a reworked and a non-reworked original impeller and the new impeller design, it was confirmed that the results were in line with the numerical predictions; the field impeller showed cavitation formation that matched the observed damage pattern and the new impeller design demonstrated a significant decrease in cavity lengths. For the condition of field NPSHA at 80 and 100 percent rated flow, cavitation formation was not observed anymore for the new design.

The lesson learned from this study is that the NPSH3 requirement alone is an inappropriate criterion for high-speed, high-energy centrifugal pumps. It is advised to map the development of cavitation for all high-energy pumps having high eye peripheral speeds. Besides this, it can be concluded that CFD is a viable tool in assessing incipient cavitation behavior and can be considered an alternative to flow visualization testing.
Part Load Flow and Hydrodynamic Instabilities of a Centrifugal Pump: Part 1 — Experimental Investigations
Authors: Gros Laurent , Couzinet Anthony , Pierrat Daniel
Published: November 2015

Rotor-stator interactions have been widely studied for thirty years especially concerning part load operating points. Transient phenomena are mainly the focus of these experimental or numerical studies. Depending on type of centrifugal pumps, an unstable characteristic (saddle-type characteristic) can appear at part load; the consequence is an unstable local head drop of the performance curve and this singularity exhibits a positive slope in the decreasing performance curve. An experimental work is proposed to identify this instability and the investigations led on a high specific speed centrifugal pump have allowed to study the interaction with the upstream circuit and the cavitation, the translation on other speed of rotation and the effect on the vibrations level.
Part Load Flow and Hydrodynamic Instabilities of a Centrifugal Pump: Part 2 — Numerical Simulations
Authors: Couzinet Anthony , Gros Laurent , Pierrat Daniel
Published: November 2015

This paper - part2 presents the results of 3D CFD simulations in a centrifugal pump corresponding to the experimental tests presented in Part 1 [1]. Numerical investigations have been carried out to study the behavior of the same centrifugal pump in the range of flow rates corresponding to the saddle-type instability. The numerical results obtained from numerical simulations performed with ANSYS CFX and based on a steady state approach are compared to the experimental data.

This study aims to reproduce by numerical simulations the head drop induced by the saddle-type instability starting from industrial approaches using two-equation turbulence modeling. Moreover the analysis of the local flow provides explanations about the physical phenomenon behind this instability.

By comparing an approach taking into account the full geometry of the pump and another limited to one blade passage the limits of usual approaches in rotating machinery simulations for the representation of such instabilities are discussed.
Two Phase Flow Simulation of Water Ring Vacuum Pump Using VOF Model
Authors: Ding Hui , Jiang Yu , Wu Hao , Wang Jian
Published: November 2015

Due to the complex two phase flow, CFD simulation of liquid ring pump used to be extremely challenging. Using a recently developed Volume of Fluid (VOF) two phase flow model, this paper presents a 3D transient CFD model for a water ring vacuum pump. The test simulations show that the new VOF model is very robust and can catch most of the important physics when applied to a industrial water ring vacuum pump. Model formulation and problem setup will be presented in detail in the paper. Important issues that could affect the simulation results will be discussed. Water ring pump flow field characteristics revealed from simulation results will be summarized with explanation. And finally the simulation results will be compared with experiment test data.
A Review of Common Problems Observed in Cooling Water Intakes and the Use of Physical Models to Develop Effective Solutions
Authors: Werth David , Havice Matthew
Published: November 2015

Pump intake structures are a necessary component of the cooling water systems for power plants, process and manufacturing facilities, flood control and water/wastewater applications. Large cooling water systems often use substantial sea / river water intakes or cooling towers to provide the required cooling of the process or circulating water. These structures can be very large and often house multiple pump with capacities ranging in size from a few hundred m3/hr to 60,000 m3/hr or more. With such large flow rates care must be taken to ensure uniform flow to the pump to limit vortex activity, vibration, flow induced cavitation and performance problems. In many cases, a physical hydraulic model study is conducted to evaluate the overall approach flow and the performance of the intake. This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common design features.

This paper takes a closer look at stop log support walls, an intake design feature common to seawater intakes. This wall is often used to minimize the height of the stop logs. In applications with large variations of water level, such as a seawater intake, there are times when the support walls are submerged significantly, resulting in significant flow disturbances. A feature common to cooling towers is the use of 90-degree suction elbows to supply horizontal pumps. A review of short radius vs. long radius elbow performance is presented. Cooling towers often have another common feature which is a significant difference in depth between the cooling tower basin and the pump sump. This results in typical shallow basins and deeper sumps. A common problem is the utilization of minimum pump submergence to set the water levels without reference to the basin invert elevation. A discussion of choked flow conditions in cooling towers is presented. A final discussion is presented regarding cross-flow and the use of concentrated supply channels in cooling tower applications to facilitate the isolation of individual tower cells.

This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common intake design features. The results of several model studies are presented to demonstrate the negative impacts that these common intake features have on approach flow conditions. The intent of the paper is to provide the design engineer some additional guidance not offered in industry guidelines or standards with the hope of avoiding common problems which can be costly and difficult to remediate after the intake has been constructed.