Accepted Manuscripts

Hao Tian and James D. Van de Ven
J. Fluids Eng   doi: 10.1115/1.4036711
The bulk modulus of hydraulic fluid is dependent on the quantity of entrained gas in the fluid. In this paper, an effective fluid bulk modulus model that captures dynamic gas absorption during pressure transients is derived from the overall mass transfer theory. Optical measurement of a micro gas bubble volume is used to determine the interfacial mass transport. Compared to traditional models, the proposed model is able to capture the 10% gap in the pressure profile between the first and second cycles, when simulating multiple compression cycles of an oil sample with 0.65% entrained gas by volume at 8 MPa.
TOPICS: Compressibility, Fluids, Absorption, Modeling, Cycles, Bulk modulus, Pressure, Compression, Transients (Dynamics), Bubbles, Optical measurement, Mass transfer
Yi Ma, Huashuai Luo, Tao Gao and Zhihong Zhang
J. Fluids Eng   doi: 10.1115/1.4036715
In petroleum industry, the stability of multiphase pumping is highly disturbed by the gas presence with high content and variable working conditions. This paper is focused on studying the whole working cycle of the novel three-cylinder double-acting reciprocating multiphase pump. Based on the theoretical analysis, the method of computational fluid dynamics is adopted to simulate the oil-gas flow in reciprocating multiphase pump. The numerical methodology, involving multiphase model, dynamic grid technique and user defined functions, is used to deal with in the calculation. The transient flow characteristics in pump cavity are obtained, and the flow ripples of reciprocating multiphase pump are analyzed. Furthermore, the effects of different operating parameters, such as suction and discharge pressures, inlet gas volume fraction on the capacity and stability of pump are studied. The results could help to develop and optimize the high-efficiency multiphase pump system.
TOPICS: Pumps, Cylinders, Unsteady flow, Stability, Flow (Dynamics), Suction, Computational fluid dynamics, Petroleum industry, Theoretical analysis, Cavities, Cycles
Adam Ritcey, Joesph R. McDermid and Samir Ziada
J. Fluids Eng   doi: 10.1115/1.4036717
The maximum skin friction and flow field is experimentally measured on a planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. A jet nozzle width of W = 15 mm, impingement ratios H=W = 4;6;8; 10, and a range of jet Reynolds numbers Rejet = 11000- 40000 is tested to provide a parametric map of the maximum skin friction. The maximum skin friction predictions of Phares et al. [1] for plane jets agree within 5 % of the current OFI results for H=W = 6, but deviates upwards of 28 % for other impingement ratios. The maximum skin friction is found to be less sensitive to changes in the impingement ratio when the jet standoff distance is roughly within the potential core length of the jet. PIV measurements show turbulence transition locations moving towards the nozzle exit with increasing Reynolds number, saturation in the downstream evolution of the maximum axial turbulence intensity before reaching a maximum peak upon impingement, followed by sudden damping at the plate surface. As the flow is redirected, there is an orthogonal redistribution of the fluctuating velocity components, and local peaks in both the axial and transverse turbulence intensity distributions at the plate locations of the maximum skin friction.
TOPICS: Flow (Dynamics), Skin friction (Fluid dynamics), Turbulence, Reynolds number, Nozzles, Jets, Damping, Interferometry, Particulate matter
Johan Pretorius, Gazi I. Mahmood and Josua P. Meyer
J. Fluids Eng   doi: 10.1115/1.4036671
Standard pin-fins in the heat transfer channels are shaped to reduce the pressure penalty and increase the thermal performance. The paper presents experimental results of the wall-static pressure distributions in an array of modified cylindrical short pin-fins in a channel. Standard cylindrical pin-fins with a smooth surface and a similar array configuration are also evaluated as a baseline for comparisons. The pin-fins with a height to diameter ratio of 1.28 are arranged in a staggered array consisting of 13 rows in a rectangular channel of aspect ratio 1:7.8. The cylindrical pins are modified by the machined slots at the tips. The slots in the pins are aligned in the streamwise direction. The static pressure distributions are measured on the endwall between the pin-rows and on the pin surface. The Reynolds number based on the channel hydraulic diameter ranges from 10,000 to 50,000. The slots in the pins reduce the friction factor and wall-static pressure drop between the pin-rows by up to 50%. The objectives of the investigation are to reduce the pressure penalty in the cylindrical pin-fin channel to provide increased thermal performance.
TOPICS: Pressure, Pins (Engineering), Fins, Pressure drop, Friction, Heat transfer, Reynolds number
Ajith Airody, David de Montmorency and Sean D. Peterson
J. Fluids Eng   doi: 10.1115/1.4036667
Large-scale power generation and delivery to remote locales is often expensive and can have deleterious effects on the local ecosystem. With smaller environmental footprints, small-scale run-of-river hydroelectric facilities that are capable of generating power from the modest head provided by streams and rivers are attractive alternatives. Concern remains, however, for the health and safety of the local fish population in these water ways. In order to reduce the impact of small-scale axial turbine-based hydroelectric facilities on the local fauna, AlfaStar Hydro has proposed a vaneless swirl injector to replace traditional turbine inlet guide vanes. Herein we perform a numerical study of the flow development in the vaneless swirl injector as a function of the number of revolutions and the pitch angle of the rifling in the absence of a rotor towards maximizing turbine efficiency. Swirl intensity, pressure loss in the injector, and axial and circumferential velocity distributions are incorporated as performance metrics into an objective function in order to optimize the casing design. Results indicate that the number of revolutions of the injector has considerably less influence on overall performance than does pitch angle. The casing with the best predicted performance consists of 4 revolutions at a pitch angle of 25 degrees.
TOPICS: Design, Ejectors, Optimization, Hydraulic turbines, Turbines, Energy generation, Rivers, Hydropower, Inlet guide vanes, Water, Pressure, Flow (Dynamics), Health and safety, Rotors
Technical Brief  
Hassan Iftekhar and Martin Agelin-Chaab
J. Fluids Eng   doi: 10.1115/1.4036666
This study reports the results of turbulent flows on forward facing steps (FFS) in pressure gradients using a particle image velocimetry (PIV) technique to obtain data up to 68 step heights downstream. The contours of two-point velocity correlations indicate that regardless of the pressure gradients, the physical size of the coherent structures characterized by the auto-correlations grow as the flow develops downstream along the step. Additionally, adverse pressure gradient (APG) elevates the size of the auto-correlations.
TOPICS: Turbulence, Pressure gradient, Fitness-for-service, Flow (Dynamics), Particulate matter
Phillip Limbach and Romuald Skoda
J. Fluids Eng   doi: 10.1115/1.4036673
3D simulations with ANSYS CFX 16.1 as well as measurements of the cavitating flow in a low specific speed centrifugal pump (nq = 12 1/min) are performed for different operation conditions and varying surface roughness. Surface roughness is considered by wall functions in the flow simulations. Good agreement between measured and calculated head is achieved for non-cavitating flow. NPSH3% rises towards over load due to incidence, flow separation and vapor zones at the volute tongue. The NPSH3% rise is slightly higher for rough walls according to measurements and significantly overestimated by the wall function approach, irrespective of the roughness level in the simulation. A low-Reynolds number approach at the volute tongue leads to a more accurate prediction of NPSH3% than wall functions, at cost of high computational effort.
TOPICS: Flow (Dynamics), Surface roughness, Centrifugal pumps, Experimental analysis, Simulation, Flow separation, Stress, Flow simulation, Vapors
Raquel Faria, Almerindo D. Ferreira, A.M.G. Lopes and Antonio C. M. Sousa
J. Fluids Eng   doi: 10.1115/1.4036668
In this work, the suitability of pressure probes, commonly known as Irwin probes, to determine the local wall shear stress was evaluated for steady turbulent flow in rectangular ducts. Pressure measurements were conducted in the fully developed flow region of the duct and both the influence of duct aspect ratio (from 1:1.03 to 1:4.00) and Reynolds number (from 104 to 9×104) on the mean characteristics of the flow were analyzed. In addition, the sensitivity of the longitudinal and transversal placement of the Irwin probes was verified. To determine the most appropriate representation of the experimental data, three different characteristic lengths (l*) to describe Darcy’s friction coefficient were investigated, namely: hydraulic diameter (Dh), square root of the cross-section area (vA) and laminar equivalent diameter (DL). The comparison of the present experimental data for the range of tested Re numbers against the results for turbulent flow in smooth circular tubes indicates similar trends independently of the aspect ratio. The selection of the appropriate l* to represent the friction coefficient was found to be dependent on the aspect ratio of the duct and the three tested scales present similar performance. However, the hydraulic diameter, being the commonly employed to compute turbulent flow in rectangular ducts, is the selected characteristic length scale to be used in the present study. A power function- based calibration equation is proposed for the Irwin probes, which is valid for the range of aspect ratios and Reynolds numbers tested.
TOPICS: Flow (Dynamics), Calibration, Ducts, Probes, Turbulence, Reynolds number, Friction, Pressure measurement, Shear stress, Pressure
Frank Böhnke and Sebastian Semmelbauer
J. Fluids Eng   doi: 10.1115/1.4036674
The cochlea is the most important part of the hearing system, due to the fact that it transforms sound guided through air, bone and lymphatic fluid to vibrations of the cochlear partition which includes the organ of Corti with its sensory cells. These send nerve impulses to the brain leading to hearing perception. The work presents the wave propagation in rigid ducts filled with air or water including viscous-thermal boundary layer damping. In extension a mechanical box model of the human cochlea represented by a rectangular duct limited by the tapered basilar membrane at one side is developed and evaluated numerically by the finite element method. For the tapered bm an orthotropic solid with constant Young's moduli and boundary layer damping is sufficient to simulate characteristic traveling waves for frequencies in the audible range. The results match with rare experiments on human temporal bones without using the physically unfounded assumption of Rayleigh damping. A forecast on the concept of the traveling wave parametric amplification is given to potentially explain the high hearing sensitivity and otoacoustic emissions.
TOPICS: Acoustics, Boundary layers, Ducts, Damping, Traveling waves, Bone, Young's modulus, Membranes, Water, Wave propagation, Fluids, Vibration, Brain, Finite element methods, Impulse (Physics), Otoacoustic emissions
Alessandra Borrelli, Giulia Giantesio and Maria Cristina Patria
J. Fluids Eng   doi: 10.1115/1.4036670
This paper concerns the study of the influence of an external magnetic field on the reverse flow occurring in the steady mixed convection of two Newtonian immiscible fluids filling a vertical channel under the Oberbeck-Boussinesq approximation. The two isothermal boundaries are kept either at different or at equal temperatures. The velocity, the temperature and the induced magnetic field are analytically obtained. The results are presented graphically and discussed for various values of the parameters involved in the problem (in particular the Hartmann number and the buoyancy coefficient) and are compared with those for a single Newtonian fluid. The occurrence of the reverse flow is carefully studied.
TOPICS: Fluids, Flow (Dynamics), Temperature, Magnetic fields, Mixed convection, Approximation, Buoyancy
Chang Xu, Yiwei Wang, Chenguang Huang, Chao Yu and Jian Huang
J. Fluids Eng   doi: 10.1115/1.4036669
Unstable cavitation presents an important speed barrier for underwater vehicles such as hydrofoil craft. In this paper, the authors concern about the physical problem about the cloud cavitating flow that surrounds an underwater launched hydrofoil the near free surface at relatively high Froude number, which has not been discussed in previous research. A water tank experiment and computational fluid dynamics simulation are conducted in this paper. The cavity evolution process in the experiment involves three stages, namely, cavity growth, shedding, and collapse. Numerical methods adopt large eddy simulation with Cartesian cut-cell mesh. Given that the speed of the model changes during the experiment, this paper examines cases with varying constant speeds. The free surface effects on the cavity, re-entry jet location, and vortex structures are analyzed based on the numerical results.
TOPICS: Flow (Dynamics), Hydrofoil, Cavities, Collapse, Underwater vehicles, Water, Large eddy simulation, Simulation, Cavitation, Computational fluid dynamics, Numerical analysis, Vortices
George Papadopoulos
J. Fluids Eng   doi: 10.1115/1.4036594
A dimensional analysis that is based on the scaling of the two-dimensional Navier-Stokes equations is presented for correlating bulk flow characteristics arising from a variety of initial conditions. The analysis yields a functional relationship between the characteristic variable of the flow region and the Reynolds number for each of the two independent flow regimes, laminar and turbulent. A linear relationship is realized for the laminar regime, while a non-linear relationship is realized for the turbulent regime. Both relationships incorporate mass-flow profile characteristics to capture the effects of initial conditions (mean flow and turbulence) on the variation of the characteristic variable. The union of these two independent relationships is formed utilizing the concept of flow intermittency to further expand into a generic functional relationship that incorporates transitional flow effects to fully encompass solutions spanning the laminar to turbulent flow regimes. Empirical models of some common flows are formed to demonstrate the engineering potential of the proposed functional relationship.
TOPICS: Turbulence, Modeling, Flow (Dynamics), Dimensional analysis, Reynolds number, Navier-Stokes equations
Siddharth K.S., Mahesh Panchagnula and T.J. Tharakan
J. Fluids Eng   doi: 10.1115/1.4036593
We describe a novel non-intrusive velocimetry technique for measuring the instantaneous velocity field on a liquid sheet. Short wavelength corrugations are naturally formed on the surface of a liquid sheet when the sheet interacts with ambient air. This method called Feature Correlation Velocimetry (FCV) relies on cross-correlation of such short wavelength corrugations visualized on the liquid sheet surface when captured using a high-speed camera. An experimental set-up was created for producing a liquid sheet of known thickness and velocity. After imaging the liquid sheet with a high-speed camera, cross-correlation was employed at various spatial locations on the liquid sheet. To examine the fidelity of the method, Laser Doppler Velocimetry (LDV) measurements were obtained for a range of flow rates at the same spatial locations and were compared with the FCV values. The FCV values were found to be consistently within 7% of the LDV readings with the FCV measurements being consistently less than those from the LDV. In order to examine the cause of the bias error, a theoretical model of the liquid sheet has been developed. Based on the model predictions, the bias error was observed to scale as U^(3/2), where U is the local instantaneous liquid sheet velocity. After correcting for this bias error, a good match was observed between the FCV and the LDV readings. As an application of the FCV method, the near nozzle region of an annular sheet exiting a spray injector has been characterized.
TOPICS: Flow (Dynamics), Wavelength, Ejectors, Nozzles, Sprays, Errors, Laser Doppler anemometry, Imaging
Grant M. Skidmore, Jules W. Lindau, Timothy A. Brungart, Michael J. Moeny and Michael P. Kinzel
J. Fluids Eng   doi: 10.1115/1.4036596
Computations of pulsating supercavity flows behind axisymmetric disk cavitators are presented. The method of computation is a finite volume discretization of the equations of mixture fluid motion. The gas phase is treated as compressible, the liquid phase as incompressible, and the interface accuracy enhanced using a volume of fluid approach. The reentrant, pulsating, and twin vortex modes of cavity closure are delineated and computationally resolved, including the expected hysteresis. A phase diagram of cavitation number versus ventilation rate at three Froude conditions is computationally constructed. Sample reentrant, pulsation, and twin vortex snapshots are presented. Pulsation results are compared with stability criterion from the literature as well as examined for their expected character. Computations appear to capture the complete spectrum of cavity closure conditions. A detailed comparison of computational simulation and physical experiment at similar conditions is also included as a means to validate the computational results.
TOPICS: Stability, Flow (Dynamics), Fluids, Simulation, Cavitation, Phase diagrams, Ventilation, Computational fluid dynamics, Vortices, Disks, Cavities, Computation
Osamu Akiyama and Chisachi Kato
J. Fluids Eng   doi: 10.1115/1.4036589
Mechanism of particle separation in a cyclone separator is fully clarified by one-way coupled numerical simulations of large eddy-simulation and particle tracking. The former resolves all the important vortical structures while the later inputs the computed flow fields and tracks trajectories of particles by considering Stokes drag as well as gravity. The computed axial and tangential velocities of the swirl flow in a cyclone well compare with the ones measured by particle image velocimetory (PIV). The precession frequency of the vortex rope computed for Stairmand cyclone also matches with the one measured by Darksen et al. The predicted collection efficiencies reasonably well agree with the measured equivalents for two cylindrical cyclones with different diameters and inflow conditions. Detailed investigations on the simulated vortical structures in the test cyclones and predicted trajectories of the particles have revealed that there are three major paths of trajectories for those particles that are not collected and exhausted from the cyclone. More than half of the exhausted particles are trapped by longitudinal vortices formed in the periphery of the vortex rope. Namely, the precession motion of the vortex rope generates a number of longitudinal vortices at its periphery, which trap particles and move them into the region of the upward swirl.
TOPICS: Particulate matter, Unsteady flow, Vortices, Ropes, Flow (Dynamics), Separation (Technology), Eddies (Fluid dynamics), Computer simulation, Drag (Fluid dynamics), Simulation, Inflow, Gravity (Force)
Brandon Horton, Yangkun Song, Jeffrey Feaster and Javid Bayandor
J. Fluids Eng   doi: 10.1115/1.4036590
Despite recent interests in complex fluid-structure interaction (FSI) problems, little work has been conducted to establish baseline multidisciplinary FSI modeling capabilities for research and commercial activities across computational platforms. The current work provides a stepping stone toward identifying accurate solution options for comprehensive FSI. By incorporating both monolithic and partitioned solvers, a holistic comparison of computational accuracy and time-expense is presented between Lattice-Boltzmann methods (LBM), coupled Lagrangian-Eulerian (CLE), and smoothed particle hydrodynamics (SPH). These explicit methodologies are quantitatively assessed using the square lid-driven cavity for low Reynolds numbers (100 - 3200) and are validated against an implicit Navier-Stokes solution in addition to established literature. From an investigation of grid resolution error, the Navier-Stokes solution, LBM, and CLE were all relatively mesh independent for modeling cavity flow. However, SPH displayed a significant dependence on grid resolution and required the greatest computational expense by far. Throughout the range of Reynolds numbers investigated, both LBM and CLE closely matched the Navier-Stokes solution and literature, with the average velocity profile error along the cavity centerlines at 1% and 4% respectively for Re = 3200. SPH did not provide accurate results whereby the average error for the centerline velocity profiles was 31% for Re = 3200, and the methodology was unable to represent vorticity in the cavity corners. Results indicate that while both LBM and CLE show promise for modeling complex fluid flows, commercial implementations of SPH demand further development.
TOPICS: Fluid dynamics, Flow (Dynamics), Hydrodynamics, Fluids, Particulate matter, Reynolds number, Resolution (Optics), Shear (Mechanics), Corners (Structural elements), Vorticity, Cavity flows, Modeling, Cavities, Errors, Fluid structure interaction, Lattice Boltzmann methods
Hong-Na Zhang, Dong-Yang Li, Xiao-Bin Li, Wei-Hua Cai and Feng-Chen Li
J. Fluids Eng   doi: 10.1115/1.4036592
Viscoelastic fluids are now becoming promising candidates of micro heat exchangers’ working medium due to the occurrence of elastic instability and turbulence at micro scale. This paper developed a sound solver for the heat transfer process of viscoelastic fluid flow at high Wi, and this solver can be used to design the multiple heat exchangers with viscoelastic fluids as working medium. The solver validation was conducted by simulating four fundamental benchmarks to assure the reliability of the established solver. After that, the solver was adopted to study the heat transfer process of viscoelastic fluid flow in a curvilinear channel where apparent heat transfer enhancement by viscoelastic fluid was achieved. The observed heat transfer enhancement was attributed to the occurrence of elastic turbulence which continuously mix the hot and cold fluids by the twisting and wiggling flow motions.
TOPICS: Flow (Dynamics), Heat transfer, Computer simulation, Viscoelastic fluids, Turbulence, Heat exchangers, Reliability, Design, Fluids
Anup Kumer DATTA, Yasutaka HAYAMIZU, Toshinori KOUCHI, Yasunori NAGATA, Kyoji YAMAMOTO and Shinichiro YANASE
J. Fluids Eng   doi: 10.1115/1.4036477
Turbulent flows through helical pipes with circular cross section are numerically investigated comparing with the experimental results obtained by our team. Numerical calculations are carried out for two helical circular pipes having different pitches and the same non-dimensional curvature δ (= 0.1) over a wide range of the Reynolds number, Re, from 3000 to 21000 for torsion parameter ß (= torsion /2δ = 0.02 and 0.45). We numerically obtained the secondary flow, the axial flow and the intensity of the turbulent kinetic energy by use of three turbulence models incorporated in OpenFOAM. We found that RNG k-ε turbulence model can predict excellently the fully developed turbulent flow with comparison to the experimental data. It is found that the momentum transfer due to turbulence dominates the secondary flow pattern of the turbulent helical pipe flow. It is interesting that torsion effect is more remarkable for turbulent flows than laminar flows.
TOPICS: Turbulence, Pipe flow, Torsion, Flow (Dynamics), Pipes, Axial flow, Fully developed turbulent flow, Teams, Kinetic energy, Laminar flow, Reynolds number, Momentum
Diego N. Venturi, Waldir P. Martignoni, Dirceu Noriler and Henry F. Meier
J. Fluids Eng   doi: 10.1115/1.4036444
Two-phase flows across tube bundles are very commonly found in industrial heat exchange equipment such as shell and tube heat exchangers. However, recent studies published in the literature are generally performed on devices where the flow crosses the tube bundle in only a vertical or horizontal direction, lacking geometrical fidelity with industrial models, and the majority of them use air and water as the working fluids. Also, currently, experimental approaches and simulations are based on very simplified models. This paper reports the simulation of a laboratory full-scale tube bundle with a combination of vertical and horizontal flows and, with two different baffle configurations. Also, it presents a similarity analysis to evaluate the influence of changing the fluids to hydrogen and diesel in the operational conditions of the hydrotreating. The volume of fluid (VOF) approach is used as the interface phenomena is very important. The air/water simulations show good agreement with classical correlations and are able to show the stratified behavior of the flow in horizontal regions and the intermittent flow in the vertical regions. Also the two baffle configurations are compared in terms of volume fraction and streamlines. When dealing with hydrogen/diesel flow using correlations and maps made for air/water, superficial velocity is recommended as similarity variable when a better prediction of the pressure drop is needed, and the modified superficial velocity is recommended for prediction of the volume-average void fraction and the outlet superficial void fraction.
TOPICS: Flow (Dynamics), Diesel, Hydrogen, Water, Fluids, Simulation, Porosity, Pressure drop, Shells, Experimental methods, Heat exchangers, Two-phase flow, Interface phenomena, Heat
Xin Wen and Hui Tang
J. Fluids Eng   doi: 10.1115/1.4036410
This paper presents a parametric study on the interaction of twin circular synthetic jets (SJs) that are in line with a crossflow over a flat plate. The resulting vortex structures under differ- ent actuation and flow conditions are investigated using stereoscopic color dye visualization in a water tunnel. The influence of four independent non-dimensional parameters, i.e., the Reynolds number ReL, Strouhal number St, velocity ratio V R, and phase difference ?f, on the behavior of the twin SJs is studied. It is found that the increase of Reynolds number causes the SJ-induced vortex structures more turbulent, making the twin SJ interaction less organized; The increase of velocity ratio pushes the occurrence of interaction further away from the wall, and makes the resulting vortex structures more sustainable; The Strouhal number has no obvious influence on the interaction; And three types of vortex structures are observed under different phase differences: one combined vortex, two completely separated vortices, and partially interacting vortex structures. Based on this parametric study, a simple model is proposed to predict the resulting vortex pattern for the twin SJ interaction.
TOPICS: Jets, Visualization, Vortices, Reynolds number, Flat plates, Water tunnels, Sustainability, Flow (Dynamics), Turbulence

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