bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Pressure Pulsation in the Stages of an Electric Submersible Pump at Best Efficiency Point Under Various Speeds
Authors: Arumugam Dhanasekaran , Sivasailam Kumaraswamy 
Published: November 2019

Abstract
Fluctuating pressures can induce vibration in the Electric Submersible Pump (ESP) and severely affect the pump components. The installation depths of ESP systems are varying from a few meters to several hundred meters. Once installed ESPs are not accessible for diagnostic measurement and maintenance activity, so it becomes necessary to obtain detailed information of mean and fluctuating pressures to attain an optimal pressure distribution inside the pump. In this paper the results obtained from an experimental investigation of stage-wise pressure pulsation at Best Efficiency Points at various speeds are presented. Tests were conducted on a five stage ESP having impellers of 121 mm diameter and 14 mm width at outlet with impeller of 8 vanes and a diffuser-return channel of 6 vanes which delivers 7 lps (litres per second) and develop 60 m total head at various speeds. Unsteady pressure signals were captured by mounting piezoresistive transducers at each stage of ESP. Captured pressure signals were converted into frequency domain to analyze the characteristics of pressure pulsation. The results have indicated that the maximum amplitude of pressure pulsation was obtained at the highest operating speed setting of 60 Hz at stage 4. The normalized frequency at which this amplitude was maximum was highest at stage 2 at all the speeds.
Large Eddy Simulation of Turbulent Combustion Flows in a Methane-Hydrogen Gasturbine Combustor and NOx Prediction by its Database
Authors: Oshima Nobuyuki , Kishine Ryosuke , Oda Takeo 
Published: November 2019

Abstract
In this research, the LES with the multiple-scalar flamelet approach is performed for an industrial gasturbine combustor, L30A, produced by Kawasaki Heavy Industries, which can appropriately simulate a partial premixed combustion by methane-hydrogen mixed fuel operation. Its instantaneous and time-averaged data by LES result are analyzed for predict NO production in thermal and prompt regime under different operation conditions. PDF statistical analysis is also applied to evaluate the effects from turbulent fluctuations of flame propagation and mixture fraction. These analyses reveal different mechanisms of turbulent fluctuations to increase or decrease NO productions.
Methane Production Strategies for Oceanic Gas Hydrate Reservoirs
Authors: Choudhary Neelam , Phirani Jyoti 
Published: November 2019

Abstract
Gas hydrates can be an efficient replacement for the conventional fossil fuels, as the large amount of methane gas is trapped in the gas hydrate reservoirs that can be used as a potential source of energy. In this study, we investigate the impact of a combination of horizontal and vertical wells on the gas production from oceanic Class-2, unconfined gas hydrate reservoirs. An In-house multicomponent, multiphase, thermal, 3-D finite volume simulator is used. Different locations of horizontal and vertical wells as warm water injectors and methane gas producers are investigated. For unconfined reservoirs, depressurization is found to be ineffective with horizontal and vertical wells. Horizontal warm water injectors are more effective for gas production. The gas production increases from 22% of original gas in place (OIGP) when vertical injector is used to 48% of OGIP when horizontal injector is used.
The Effect of Suction Pressure and Flow Rate on the Dynamic Characteristics of a Cavitating Inducer
Authors: Morimoto Yuta , Sugiura Takafumi , Horiguchi Hironori , Sugiyama Kazuyasu 
Published: November 2019

Abstract
This paper presents an experimental work on dynamic characteristics of a cavitating inducer. In the present study, the focus is placed on the cavitation compliance K and the mass flow gain factor M, which are necessary for stability analysis of a propulsion system of liquid propellant rockets. Our experiment revealed that the magnitude of K and M increased as the inlet pressure and the flow rate decreased: the volume of the cavity increased. It also clarified that K had no significant phase delay and M had the phase delay of about 90 degrees, regardless of the inlet pressure and the flow rate.
Secondary Flow Loss Reduction Method by Use of 3D-Fence in a Gas Turbine Cascade
Authors: Uehara Ryota , Mizuguchi Syohei , Kusano Kakeru , Miyabe Masahiro , Kawata Yutaka 
Published: November 2019

Abstract
The aerodynamic loss accounted to the secondary flow, or secondary loss is one of the most prominent causes of the internal losses in turbine cascades. The secondary flow losses are mostly due to the interaction between horseshoe vortex and endwall crossflow. The authors have developed a so-called endwall fence experimentally to reduce the secondary loss in a gas turbine cascade. However, it is very difficult to handle many design parameters simultaneously in experiment.
The objective of this research work is to optimize the shape of the 3D-fence with considering many design parameters and clarify the flow mechanism of loss reduction. In addition, one of the most important objectives of this paper is to show this optimization method is effective for the designer of the turbine. In this study, the optimization framework and CFD were applied to the endwall fence (3D-fence) and the effect of it on the crossflow was investigated. As a result, the optimized shape, installation position, and the setting angle of the 3D-fence to mitigate the interaction between the horseshoe vortex and endwall crossflow was specified. In order to validate the effectiveness of the optimization method, total pressure was measured and loss analysis was implemented and flow visualization using oil-film and smoke were implemented. Then, the good agreement can be seen qualitatively between the experimental results and CFD results. It is clarified the 3D-fence delays the confluence between suction side leg and pressure side leg of the horseshoe vortex. Based on both calculation and experiment, it is revealed that the 3D-fence has good effect to reduce the secondary flow loss.
Improvement of Film Cooling Effectiveness in the Gas Turbine Endwall by Use of Optimization Framework
Authors: Hata Daisuke , Kakio Kazuto , Kawata Yutaka , Miyabe Masahiro 
Published: November 2019

Abstract
Recently, the number of gas turbine combined cycle plants is rapidly increasing in substitution of nuclear power plants. The turbine inlet temperature (TIT) is constantly being increased in order to achieve higher effectiveness. Therefore, the improvement of the cooling technology for high temperature gas turbine blades is one of the most important issue to be solved.
In a gas turbine, the main flow impinging at the leading edge of the turbine blade generates a so called horseshoe vortex by the interaction of its boundary layer and generated pressure gradient at the leading edge. The pressure surface leg of this horseshoe vortex crosses the passage and reaches the blade suction surface, driven by the pressure gradient existing between two consecutive blades. In addition, this pressure gradient generates a cross-flow along the endwall. This all results into a very complex flow field in proximity of the endwall. For this reason, burnouts tend to occur at a specific position in the vicinity of the leading edge. In this research, a methodology to cool the endwall of the turbine blade by means of film cooling jets from the blade surface and the endwall is proposed. The cooling performance is investigated using the transient thermography method. CFD analysis is also conducted to investigate the phenomena occurring at the endwall and calculate the film cooling effectiveness.
Numerical Investigation of the Influence of Impeller-Diffuser Gap (A- and B-Gaps) on Unsteady Flow in a Centrifugal Pump at Part Flows
Authors: Takamine Taiki , Watanabe Satoshi 
Published: November 2019

Abstract
Because of the high energy density of multi-stage centrifugal pump, it is really important to ensure the reliability of the pumps thus the stability of rotor system in the wide flow rate range. Rotating stall is a well-known unsteady flow phenomenon in which one or several stall cell structures propagate circumferentially in impeller and/or diffuser. Rotating stall alters the peripheral pressure distribution of rotors, and therefore it is often regarded as one of the primary trigger of unstable fluid force acting on the rotor system. One possible factor which could affect the rotating stall is a geometrical relationship between the rotor and the stator. In the present study, unsteady RANS simulations of internal flow in a centrifugal pump are carried out. The pump is the partial model of the final stage of the three-stage centrifugal pump used in our previous study. In order to investigate the effect of the gap between impeller trailing edge and diffuser leading edge on the unsteady flow of the pump, three cases of impeller-diffuser gap is simulated; one is the smaller gap case with original impeller. The other cases are two larger gap cases with only cutting the impeller blades and with cutting the both impeller blades and impeller shroud walls. For all gap cases, the computations are conducted for the nominal flow rate and the low flor rate with 10% of the nominal flow rate.
As a result, the rotating stall is observed only in the larger gap case with the cut shroud walls, indicating that the key phenomenon for the stable formation of the stall cell is not only the weakened rotor-stator interaction, but also the other phenomenon attributed to the enlarged gap between the impeller shroud walls and the diffuser walls. In the shroud cut case, a part of the main flow blocked by the stalled region and the secondary flow on the diffuser walls tend to flow into the side gaps more easily than other cases. They might be the important phenomenon associated with the diffuser rotating stall in the enlarged wall gap condition.
Three Dimensional Simulation of Ventilation Flow Through a Solar Windcatcher
Authors: Abdo Peter , Taghipour Rahil , Huynh B. P. 
Published: November 2019

Abstract
Natural ventilation is the process of supplying and removing air through an indoor space by natural means. There are two types of natural ventilation occurring in buildings: winddriven ventilation and buoyancy driven or stack ventilation. The most efficient design for natural ventilation in buildings should implement both types of natural ventilation. Stack ventilation which is temperature induced is driven by buoyancy making it less dependent on wind and its direction. Heat emitted causes a temperature difference between two adjoining volumes of air, the warmer air will have lower density and be more buoyant thus will rise above the cold air creating an upward air stream. Combining the wind driven and the buoyancy driven ventilation will be investigated in this study through the use of a windcatcher natural ventilation system. Stack driven air rises as it leaves the windcatcher and it is replaced with fresh air from outside as it enters through the positively pressured windward side.
To achieve this, CFD (computational fluid dynamics) tool is used to simulate the air flow in a three dimensional room fitted with a windcatcher based on the winddriven ventilation alone, buoyancy driven ventilation alone, and combined buoyancy and winddriven ventilation. Different wind speeds between 0 up to 2.5 m/s are applied and the total air flow rate through the windcatcher is investigated with and without temperature of 350 K applied at the windcatcher’s outlet wall. As the wind speed increased the efficiency of the solar windcatcher decreased.
Effect of Pipe Inclination on Solids Distribution in Partially Stratified Slurry Flow
Authors: Matoušek Václav , Krupička Jan , Konfršt Jiří , Vlasák Pavel 
Published: November 2019

Abstract
Partially stratified flows like flows of sand-water slurries exhibit non-uniform distribution of solids (expressed as a vertical profile of local volumetric concentration) in a pipe cross section. The solids distribution in such flows is sensitive to pipe inclination. The more stratified the flow is the more sensitive its concentration profile is to the pipe slope. In general, the distribution tends to become more uniform (less stratified) if the inclination angle increases from zero (horizontal pipe) to positive values (ascending pipe) up to 90 degree (vertical pipe). In a pipe inclined to negative angles (descending pipe) the development is different. The flow tends to stratify more if it changes from horizontal flow to descending flow down to the angle of about −35 degree. If the angle further decreases towards −90 degree, then the flow becomes less stratified reaching uniform distribution at the vertical position.
This also means that the same flow exhibits a very different degree of stratification in ascending and descending pipes inclined to the same (mild) slope say between ±10 and ±40 degree. The rather complex development of the solids distribution with the variation of the inclination of pipe is insufficiently documented experimentally and described theoretically in predictive models for a concentration profile in partially stratified flow.
In order to extend the existing limited data set with experimental data for partially stratified flow of medium sand slurry, we have carried out a laboratory experiment with the slurry of narrow graded fraction of sand with the mean grain size of 0.55 mm in our test loop with an invert U-tube inclinable to arbitrary angle between 0 and 90 degree. A pipe of the loop has an internal diameter of 100 mm. Both legs of the U-tube have a measuring section over which differential pressures are measured. Radiometric devices mounted to both measuring sections sense concentration profiles across a pipe cross section. Furthermore, the discharge of slurry is measured in the test loop.
In the paper, experimental results are presented for various inclination angles with a small step between 0 and ±45 degree and a development in the shape of the concentration profiles with the changing inclination angle is analyzed. For the analysis, it is critical to distinguish between suspended load and contact load in the flow as the two loads tend to react differently to the flow inclination. The measured concentration profiles and pressure drops are compared with predictions by the layered model adapted for taking the flow inclination into account.
Characterization of Thermals in a Heated Turbulent Boundary Layer
Authors: Dennis Kadeem , Siddiqui Kamran 
Published: November 2019

Abstract
The hydrodynamic boundary layer encountered in many practical engineering systems is turbulent in nature and known to play a significant role in governing the induced friction drag and species transport. In turbulent boundary layer flows, heat transfer is often involved which increases flow complexity due to the influence of buoyancy. When the buoyant force is sufficiently large in magnitude, thermals carrying heated fluid are known to detach and rise from the wall. Literature review shows that in mixed convection, thermals have been primarily identified through qualitative flow visualizations and there is a scarcity of their quantitative assessment. Furthermore, the evolution of thermals in the boundary layer with respect to flow inertia and viscous shear is not well-understood. Hence, there is a need for a better understanding of the dynamics of thermals in mixed convection turbulent boundary layer flow.
The objective of this study is to experimentally investigate the three-dimensional nature of thermals rising from a turbulent boundary layer flow over a heated smooth horizontal flat plate. Experiments were performed in a closed loop low-disturbance wind tunnel with a test section featuring a 1 m long heated bottom wall. The multi-plane particle image velocimetry (PIV) technique was used to capture images in multiple planes with respect to the turbulent boundary layer mean flow direction for three-dimensional characterization. The measurements were conducted at Richardson numbers (Ri) of 0.3, 1.0, and 2.0. Flow visualization images are used to describe the nature of thermals and the dynamical processes involved during their interaction with bulk boundary layer flow. An image processing algorithm to detect thermals is then detailed and applied to experimental images. The performance of the new algorithm is then assessed in its ability to detect thermals.
Validation of a Developed Assessment Procedure for the Functional Performance of Wastewater Pumps
Authors: Pöhler Michael , Hasirci Ümit , Rese Tim , Thamsen Paul Uwe 
Published: November 2019

Abstract
To date, there is no standardised test available, which assesses the actual performance of a pump for wastewater (especially its clog-resistance) as well as providing references about its efficiency. The developed testing procedure presented in this paper can display the different levels of performance for different pumps. The functionality of the pump, together with its efficiency is aggregated to the Functional Efficiency Index (FEI). The developed testing procedure is validated with two pumps from the field. Both are considered to be very prone to clogging by their respective wastewater network operators.
Simulation of the Wake of the Flow Around Two Side-By-Side Circular Cylinders at Reynolds Number 5000
Authors: Jensen Anna Lyhne , Sørensen Henrik , Hærvig Jakob 
Published: November 2019

Abstract
Interaction between the wakes of two cylinders in side-by-side configuration creates interesting flow phenomena. The nature of the wake depends on the Reynolds number and the transverse pitch distance between the cylinders. The flow over two side-by-side cylinders of equal diameter is simulated in 3D at Reynolds number 5000 using Large Eddy Simulation (LES). The centre-to-centre transverse pitch ratio is varied and the flow behind the cylinders is classified into either a bi-stable flow regime with biased gap flow or a regime with parallel vortex streets. Furthermore, representative instantaneous flow fields, Strouhal number and the time varying drag coefficient C′D are presented.
Investigations Into Wet Wipe Related Clogging Phenomena of Wastewater Pumps
Authors: Mitchell Raja-Louisa , Busche Susanne , Thamsen Paul Uwe 
Published: November 2019

Abstract
To gain a better understanding of the operational problems confronting wastewater pumps due to nonwoven wet wipes, experimental data generated in a laboratory setting were compared with data collected in the field. Pump blockages from a wastewater pump operating in the field under normal conditions were collected and analysed. The types of wet wipes occurring in the blockages were identified and were categorised according to their (claimed) flushability. The clogging effect of comparable wet wipes was then investigated in the laboratory using a wastewater pump with a low resilience against clogging. Profound differences in the clogging effect of the nonwoven wet wipes could be observed. It could also be shown that wet wipes labelled as “flushable” have different clogging effects, depending on whether or not they comply with industry flushability guidelines.
DSMC Simulation of Rarefied Gas Flow Over a Wall Mounted Cube
Authors: Nabapure Deepak , Murthy Ram Chandra 
Published: November 2019

Abstract
The present study investigates the flow behavior of the rarefied gas over a wall-mounted cube. The problem is studied for different cube heights (h) of 9mm and 18mm in the slip and transition regimes. The Direct Simulation Monte Carlo (DSMC) method is employed to evaluate the properties such as velocity, pressure and temperature fields. The Reynolds number (Re) ranges from 403 to 807, and the Knudsen number (Kn) is in the range from 0.05 to 0.103. A typical shock wave is formed in front of the cube. The recirculation length of the vortices normalized with respect to the respective cube heights for Kn = 0.05 and Kn = 0.103 are about 1.11 and 1.95 respectively. Similarly, the center of the vortices is located at about 3.33 and 6.11 times the respective cube heights upstream, for Kn = 0.05 and Kn = 0.103. The local temperature and pressure variations observed upstream of the cube are two orders higher in magnitude and are primarily attributed to strong compressibility effects. The present study paves the way for benchmarking, and forms a basis for understanding the rarefied gas flows over complex geometries.
Predictive Model for Two-Phase Flow Performance of Mixed Flow Pumps
Authors: Patil Abhay , Ayyildiz Burak , Pirouzpanah Sahand , Delgado Adolfo , Morrison Gerald 
Published: November 2019

Abstract
Multiphase pumps are increasingly being used to transport gas-liquid multiphase flow in the oil and gas industry. Complexity of two-phase flow interaction and varying designs of multiphase pumps pose significant challenges to developing generalized performance prediction tool similar to the affinity laws. The goal of this study is to characterize the performance of two multiphase pumps with different specific speeds using experimental data to develop generalized prediction models. Initially, the performance is investigated in the terms of head, power input and efficiency for different Gas Volume Fractions (GVF). Dimensional analysis is performed to evaluate the effect of pump geometry and GVF. Head degradation due to the presence of gas is presented in the terms of dimensionless numbers. These numbers represent the systematic change in the energy loss due to two phase flow interaction and inherent characteristics of the pump design. This is utilized to develop a generalized model for two phase flow. The study is concluded by validating the model using experimental data.
Comparison of Field Measurements and Large Eddy Simulations of the Scaled Wind Farm Technology (SWiFT) Site
Authors: Blaylock Myra L. , Houchens Brent C. , Maniaci David C. , Herges Thomas , Hsieh Alan , Knaus Robert C. , Sakievich Philip 
Published: November 2019

Abstract
Power production of the turbines at the Department of Energy/Sandia National Laboratories Scaled Wind Farm Technology (SWiFT) facility located at the Texas Tech University’s National Wind Institute Research Center was measured experimentally and simulated for neutral atmospheric boundary layer operating conditions. Two V27 wind turbines were aligned in series with the dominant wind direction, and the upwind turbine was yawed to investigate the impact of wake steering on the downwind turbine. Two conditions were investigated, including that of the leading turbine operating alone and both turbines operating in series. The field measurements include meteorological evaluation tower (MET) data and light detection and ranging (lidar) data. Computations were performed by coupling large eddy simulations (LES) in the three-dimensional, transient code Nalu-Wind with engineering actuator line models of the turbines from OpenFAST. The simulations consist of a coarse precursor without the turbines to set up an atmospheric boundary layer inflow followed by a simulation with refinement near the turbines. Good agreement between simulations and field data are shown. These results demonstrate that Nalu-Wind holds the promise for the prediction of wind plant power and loads for a range of yaw conditions.