bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation on the Pump Suction Performance and Thermodynamic Effects
Authors: Jeong Eunhwan , Kang Byung Yun , Hong Soon Sam , Kim Dae Jin , Choi Chang Ho 
Published: October 2020

Abstract
The thermodynamic effects on the suction performance of a liquid oxygen (LOX) pump, observed during liquid rocket engine combustion tests, were investigated. Owing to the pump rotational speed and inlet pressure variation in the short duration of the engine starting, LOX pump head drops occurred occasionally depending on the initial pump inlet condition. Because the engine tests were performed at various inlet temperature and pressure settings of the LOX pump, the resulting suction performance behaviors of the LOX pump were varied. The critical cavitation number, at which the pump head drops 3%, was considered as the main parameter for representing the pump suction performance. The suction performance behaviors shown in the engine tests were investigated based on the classical theory of thermodynamic effects on cavitation. The LOX pump component test results in water, the LOX pump assembly suction performance test results in liquid nitrogen, and the J-2 LOX pump test results available in the open literature were used in the analysis and comparison. It was found that the critical cavitation number ratio of a pump could be expressed as a function of the thermodynamic parameter Σ*. For a given LOX pump flow condition, Stepanoff’s B-factor was almost constant at the specified head drop condition; as a result, Brennen’s time scale ratio βwas not constant but varying with Σ*. The argument of the geometrical similarity of pump cavitation at the critical condition of the pump head drop was addressed in conjunction with the constancy of Stepanoff B-factor.
Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe
Authors: Almheiri Ayesha , Khezzar Lyes , Alshehhi Mohamed , Salam Saqib , Goharzadeh Afshin 
Published: October 2020

Abstract
Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.
Deformation of Erythrocyte in Couette Type of Pulsatile Shear Field
Authors: Hashimoto Shigehiro 
Published: October 2020

Abstract
The experimental methodology has been designed for evaluation of the cyclic deformation of an erythrocyte in the pulsatile shear field in vitro. To observe the deformation of the suspended erythrocytes in the Couette type of the shear flow, a rheoscope system has been manufactured. The system consists of a pair of counter-rotating parallel disks and an inverted phase-contrast microscope. The human erythrocytes were suspended in the dextran aqueous solution of high viscosity. The rotating speed varies sinusoidally to make the pulsatile shear field. The deformation of each erythrocyte was measured at the video image of the rheoscope. The experimental results show that the system is available to measure the following behavior of an erythrocyte. The ellipsoidal shape of each erythrocyte varies cyclically to follow the pulsatile cyclic shear field. The delay of deformation phase of each erythrocyte in the cycle is related to the frequency of the cyclic variation of the shear field. The delay is also related to deformability of the erythrocyte.
Sand Particle Concentration Distribution Inside Vertical Pipes: A CFD and Experimental Analysis
Authors: Sedrez Thiana A. , Shirazi Siamack A. 
Published: October 2020

Abstract
The concentration of the sand inside the flowlines can directly affect the magnitude of erosion in various pipelines and pipe fittings components. The erosion models available in the literature suggest that the relationship between erosion and sand concentration is linear. Furthermore, some authors believe that for a volume concentration of sand approximately below 0.75% by volume (corresponding to about 2% by mass in liquid), the effects of sand concentration on the rate of erosion are minimal. However, one could ask how this limitation on the amount of sand concentration varies in various geometries as the local concentration at the location where the sand particles are impacting can change within a flow geometry and how this can affect the maximum local erosion rates. Therefore, the sand concentration distributions inside a vertical pipe and two elbows in series for liquid-solid and liquid-gas-solid flows are examined in this investigation by CFD simulations and experimentally. Experiments are performed in a facility with two vertical pipe sections (101.6 mm reducing to a 50.8 mm inner pipe diameters) and immediately after the first and second elbows (50.8 mm inner pipe diameter) from the inner to the outer diameter of the elbows. The concentration distributions are associated with erosion measurement results in both the first and the second elbows. Finally, the CFD simulations of the corresponding experiments in liquid-sand and liquid-gas-sand flows are conducted and compared with the experimental erosion patterns and magnitude as well as various concentration distributions.
Particle Size and Concentration Effects on Solid Particle Erosion With PIV Measurements of Particle Velocities
Authors: Rajkumar Yeshwanth R. , Shirazi Siamack A. , Karimi Soroor 
Published: October 2020

Abstract
Solid particle erosion is one of the most commonly encountered problems faced by the oil and gas industries during production and transportation processes. The severity of solid particle erosion is affected by multitude of factors such as particle properties, fluid flow properties and flow geometry, flow regime, and target material properties. The present work investigates the effect of particle size on solid particle erosion in gas flows. Sharp quartz particles with nominal sizes of 75, 150, 300 and 600 μm are used in this work. Particle Image Velocimeter (PIV) is used to measure the particles velocities distributions for various particle flow rates. An average particle velocity of 24 m/s is used to conduct erosion experiments for various particle sizes and two particle rates on Stainless Steel 316 at two different impact angles of 15 and 90 degrees. Comparison of measurements for two particle flow rates of approximately 0.02% and 0.002% by volumes demonstrates that increased particle flow rate can affect the carrier fluid’s flow field and change particle velocities within the carrying fluid. In the erosion experiments, the magnitude of erosion ratio increases as there is an increase in particle size. A preliminary erosion model is developed that can be used in CFD simulations of solid particle erosion for various particle sizes.
Theory of Uncertainty Analysis With Application to Naval Hydrodynamics (Keynote Paper)
Authors: Park Joel T. 
Published: October 2020

Abstract
The modern methodology for quantifying the quality of experimental data is uncertainty analysis. This paper is a review of current methods with some examples primarily from naval hydrodynamics. The methods described are applicable to fluids engineering. The paper discusses the history of uncertainty analysis, US and international standards on uncertainty analysis, verification and validation standards for computational fluid dynamics, and instrument calibration. One important result is that random loading in force calibration can produce a lower uncertainty estimate than sequential loading.
Physical and Rheological Properties of Active Fluids Under Shear Stress: Suspensions of Synechocystis
Authors: Mehdizadeh Allaf Malihe , Habibi Zahra , Samadi Zahra , DeGroot Christopher T. , Rehmann Lars , de Bruyn John R. , Peerhossaini Hassan 
Published: October 2020

Abstract
Design of photobioreactors (PBRs) for microalgae and cyanobacteria cultivation involves the interplay between fluid flow, microbe biokinetics, and radiative transport phenomena, in which the physical and rheological properties of the active fluid play a crucial role. In this study, we focus on the variation of physical and rheological properties of dilute suspensions of Synechocystis sp. CPCC534 with the shear stress applied to the fluid.
Experiments were carried out at three different stirring rates in well-controlled conditions and the results were compared with stationary conditions where only molecular diffusion and cell motility govern the transport phenomena, and cell growth. Our results show that the growth and biomass production of Synechocystis sp. under various shear conditions were improved significantly, and the yield was nearly doubled by adding agitation to the system.
The viscosity of Synechocystis suspensions, subjected to different shear stress levels, was measured with two different methods. The viscosity data showed shear stress independent Newtonian behavior. However, the viscosity of Synechocystis suspensions increased moderately with cell volume fraction up to 10%, beyond which it increased more rapidly. The shear stress history of the cell suspensions did not show any effect on the fluid viscosity.
CFD Simulation of Wall-Bounded Laminar Flow Through Screens: Part II — Mixing Characterization
Authors: Abou Hweij W. , Azizi F. 
Published: October 2020

Abstract
This paper characterizes the mixing behavior of laminar flows within a circular pipe equipped with plain woven meshes or screens, acting as static mixers. In this quest, their performance was numerically investigated using the Lagrangian particle method in a commercial CFD solver, whereby the effect of changing the screen geometry, number of screens, inter-screen spacing, and operating conditions were considered.
Mixing was addressed from a distributive and dispersive perspectives using both qualitative and quantitative descriptions. The distributive mixing indicated that a central injection of a single fluid should be coupled with a short inter-screen spacing to better spread the particles and enhance mixing as opposed to a larger inter-screen spacing. On the contrary, the mixing of two immiscible fluids of similar properties reveal that a large inter-screen spacing is recommended. From a dispersive mixing perspective, extensional efficiency contours revealed that the fluid would undergo all three modes of flow behavior, each of which dominating a certain region depending on the location with respect to the screen. Finally, it was interesting to find that a coarser screen geometry consistently outperformed finer screens in spreading and mixing the particles.
Stochastic Analysis of LES Atmospheric Turbulence Solutions With Generative Machine Learning Models
Authors: Rodriguez Arturo , Cuellar Carlos R. , Rodriguez Luis F. , Garcia Armando , Gudimetla V. S. Rao , Kotteda V. M. Krushnarao , Munoz Jorge A. , Kumar Vinod 
Published: October 2020

Abstract
The Large Eddy Simulations (LES) modeling of turbulence effects is computationally expensive even when not all scales are resolved, especially in the presence of deep turbulence effects in the atmosphere. Machine learning techniques provide a novel way to propagate the effects from inner- to outer-scale in atmospheric turbulence spectrum and to accelerate its characterization on long-distance laser propagation. We simulated the turbulent flow of atmospheric air in an idealized box with a temperature difference between the lower and upper surfaces of about 27 degrees Celsius with the LES method. The volume was voxelized, and several quantities, such as the velocity, temperature, and the pressure were obtained at regularly spaced grid points. These values were binned and converted into symbols that were concatenated along the length of the box to create a ‘text’ that was used to train a long short-term memory (LSTM) neural network and propose a way to use a naive Bayes model. LSTMs are used in speech recognition, and handwriting recognition tasks and naïve Bayes is used extensively in text categorization. The trained LSTM and the naïve Bayes models were used to generate instances of turbulent-like flows. Errors are quantified, and portrait as a difference that enables our studies to track error quantities passed through stochastic generative machine learning models — considering that our LES studies have a high state of the art high-fidelity approximation solutions of the Navier-Stokes. In the present work, LES solutions are imitated and compare against generative machine learning models.
Experimental Study of Evaporation Frictional Pressure Drop in Horizontal Enhanced Tube
Authors: Gu Zong-bao , Guo Yu , Ma Xiang , He Yan , Li Wei 
Published: October 2020

Abstract
An experimental investigation for evaporation frictional pressure drop in horizontal enhanced tubes with an outer diameter of 12.7 mm was studied using R410A as the working fluid. The experiment was conducted: the mass flux in the range of 100 kg/(m2s) to 200 kg/(m2s), over a vapor quality range of 0.2 to 0.8, an average saturation temperature at 279 K. The inner tubes were the tested tubes, which included a smooth tube, a three-dimensional enhanced tube (a tube enhanced by protrusions and petal arrays background patterns), respectively. The results show that the frictional pressure drop increases with the mass flux increasing. Moreover, the frictional pressure drop of the enhanced tube is 1.6∼2.4 times than that of the smooth tube. This is mainly due to the increase of the flow resistance inside the enhanced tube, which is caused by the increased interfacial turbulence, flow separation and secondary flow. It is also observed that the pressure drop increases with vapor quality increasing. In addition, some existing correlations are used to compare with our experimental data and verify their accuracy. A new modified correlation is proposed to predict the frictional pressure drop of EHT-1 tube.
Experimental and Numerical Investigation of Various Tube Geometries for Improved Heat Transfer in Solar Central Receivers
Authors: Ismail Salman M. , Rashwan Mohammed M. , Ghani Saud 
Published: October 2020

Abstract
Central receiver of Concentrated Solar Power technology constitutes 15% of the total initial cost and plays an important role in achieving high operating temperatures. Central receiver systems are composed of tubes with heat transfer fluid flowing inside that transports heat from radiation on the outer wall of tubes. This work investigates radiation heat transfer to fluid in tubes of various geometries. Experimental and numerical analysis were conducted to observe the boundary layer temperatures, bulk fluid temperatures, and fluid mixing near the tube walls. Four different samples of corrugated tubes adopted from literature were compared to a circular tube and a generic tube designed to provide larger surface area exposed to radiation without corrugation. The circular tube had high temperature in the boundary layer but low bulk fluid temperature due to lack of fluid mixing at wall. A spirally corrugated tube was found to have the highest bulk fluid temperature due to turbulent mixing and low temperature at boundary layer. The generic tube had higher bulk temperature compared to circular tube and two other corrugated tubes.
Fluid Dynamics Investigation on the Body Structure Inside a Sleeve Regulating Valve
Authors: Wu Jia-yi , Yue Yang , Yang Jia-ming , Jin Zhi-jiang , Qian Jin-yuan 
Published: October 2020

Abstract
The sleeve regulating valve is a typical flow regulating component, which is indispensable in various industrial applications. This work investigates the effects of the body structure on the overall performance and the flow characteristic of a sleeve regulating valve. The anterior cavity h, the diameter of the center cavity Dc, and the eccentricity of the center cavity e are studied in a parametric way. When the relative increment of h, Dc, and e all take the value of 0.15, the rated flow coefficient Kve of the optimized valve is promoted by 33.99% relative to the Kve of the original model. The optimized model presents less wear between the valve core and the sleeve relative to the original model. It results from the fact that the non-centrosymmetric pressure distribution is reduced on the valve core. Besides, the optimized model has smaller lateral fluid force imposed on the valve core FL than the original model when the relative travel L/Lmax &gt; 0.625, and they have close FL in the other range. Also, the optimized model has larger axial fluid force imposed on the valve core FA than the original model when L/Lmax &gt; 0.875, and they have close FA in the other range.
Investigation of Applying Physics Informed Neural Networks (PINN) and Variants on 2D Aerodynamics Problems
Authors: Tay Wee-Beng , Damodaran Murali , Teh Zhi-Da , Halder Rahul 
Published: October 2020

Abstract
Investigation of applying physics informed neural networks on the test case involving flow past Converging-Diverging (CD) Nozzle has been investigated. Both Artificial Neural Network (ANN) and Physics Informed Neural Network (PINN) are used to do the training and prediction. Results show that Artificial Neural Network (ANN) by itself is already able to give relatively good prediction. With the addition of PINN, the error reduces even more, although by only a relatively small amount. This is perhaps due to the already good prediction. The effects of batch size, training iteration and number of epochs on the prediction accuracy have already been tested. It is found that increasing batch size improves the prediction. On the other hand, increasing the training iteration may give poorer prediction due to overfitting. Lastly, in general, increasing epochs reduces the error. More investigations should be done in the future to further reduce the error while at the same time using less training data. More complicated cases with time varying results should also be included. Extrapolation of the results using PINN can also be tested.
Solids Distribution in Sediment-Laden Open-Channel Flow: Experiment and Prediction
Authors: Matoušek Václav , Krupička Jan , Picek Tomáš , Zrostlik Štěpán 
Published: October 2020

Abstract
Solid-liquid flow is studied in an open channel with a mobile bed at the condition of intense transport of solids. It is flow of high-concentrated mixture of coarse sediment and water over a plane surface of the bed eroded due to high bed shear. In the flow, solid particles are non-uniformly distributed across the flow depth. The flow develops a transport layer, adjacent to the the top of the bed, in which transported particles interact with each other.
Results are presented of experimental investigations of the sediment-laden open-channel flow in a recirculating titling flume. The experiments included measurements (using ultrasonic techniques) of the distribution of solids velocity across the transport layer. The related distribution of solids concentration was deduced from the measured distribution of velocity and from other measured flow quantities. Since recently, a direct measurement of the solids distribution across the transport layer has been added to the experiments using a measuring technique svideo camera and a laser sheet.
This work discusses results of combined measurements of the distributions of solids concentration and velocity in steady uniform turbulent flow for two lightweight solids fractions and various flow conditions (a broad range of the bed Shields parameter, discharge of solids, discharge of mixture, and the longitudinal slope of the bed). Furthermore, the camera-based measuring method and the deducing method for a determination of solids distribution are discussed and their results compared to show a good agreement in a majority of the test runs.
The experimental results are compared with predictions of a recently developed bed-load transport model. Among other outputs, the model predicts the position of the top of the transport layer and the local velocity of sediment particles at this position. The presented model predictions agree well with experimental results based on the measured distibutions.
Ball Passage and Impeller Types Do Not Characterize the Functional Performance of a Sewage Pump
Authors: Tilcher David Konstantin , Pöhler Michael , Thamsen Paul Uwe 
Published: October 2020

Abstract
During the development of sewage pumps their functionality and efficiency have been continuously improved. Different impeller types have been developed; types to reduce clogging, types for associated maintenance during the various stages of the wastewater transport system, and types to increase the efficiency of the pumps.
In the current market, energy requirements and efficiency play an increasingly important role. The design of pump impellers with the aim of improving efficiency may increase the susceptibility of clogging. So far there is no test describing both the energy efficiency and the wastewater pumping functionality. Operators can only describe in tenders, a desired efficiency and the indication of plausible experience with respect to the impeller geometry: the impeller shape and the ball passage.
It is generally assumed that the susceptibility of clogging can be derived from the impeller shape and the ball passage (or freely passable space). Under this assumption, the vortex impeller should have the lowest susceptibility to clogging. With single and dual-channel impellers, accordingly, the largest possible ball passage points to a low susceptibility of clogging. Both, the hydraulically disadvantageous form of the vortex impeller and an enlargement of the ball passages beyond the hydraulic requirements leads to a significant reduction of efficiency. Generally, it is inferred from these circumstances that clog-free pumps are associated with low efficiency. This assumption, which is also found in the literature, requires a uniform test procedure for the objective assessment of the clogging behavior of sewage pumps. Such a test did not exist.
At the Chair of fluid system dynamics, TU Berlin a test stand was developed to examine such assumptions to investigate the functionality and the clogging behavior of sewage pumps.
More than 30 different wastewater pumps were tested in this procedure. The results may suggest a correlation between the susceptibility to clogging and the shape of the impeller or ball passage of various sewage pumps. Based on investigations already carried out at the Chair of fluid system dynamics, TU Berlin, the following conclusions are drawn from the measurements:
• the superordinate impeller form (Vortex, Channel, etc.) gives no evidence about the susceptibility to blockages,
• the ball passage does not indicate the susceptibility to blockages.
From these observations it can be deduced:
• a sewage pump with an appropriate efficiency may have a low susceptibility to clogging.
It can therefore be concluded that the ball passage and the type of impeller are not appropriate parameters to characterize the functional performance of a sewage pump.