Retracted: “Experimental Investigation of the Fluctuating Static Pressure in a Subsonic Axisymmetric Jet” [ASME 2020 Fluids Engineering Division Summer Meeting, Volume 2: Fluid Mechanics; Multiphase Flows, Virtual, Online, July 13–15, 2020, Conference Sponsors: Fluids Engineering Division, ISBN: 978-0-7918-8372-3, Copyright © 2020 by ASME. Paper No. FEDSM2020-20242, V002T03A040; 15 pages; doi: 10.1115/FEDSM2020-20242]

This paper was removed from publication at the author’s request. December 9, 2020. Copyright © 2020 by ASME

CFD Evaluation of Bend Angle Effects on Sand Particle Erosion in Multiphase Flows

In many industrial applications, gas-liquid-particle three-phase flows are observed. Predicting erosion damage in this type of flow is a challenging issue, and so many factors, such as the liquid film behavior have significant effects on the erosion rate. In the present study, the Eulerian-Lagrangian approach was implemented to study the process of sand particle erosion in elbows with different bend angles. For this purpose, gas and liquid phases under annular flow conditions were introduced at the pipe inlet, and the volume of fluid (VOF) method was employed to solve the governing equations. For evaluating the erosion rate, the Det Norske Veritas (DNV) model was applied. The predicted erosion results for the bend angles of 30°, 60° and 90° at different orientations were compared with those of the two-phase gas-particle flows. The simulation results indicated that for gas-liquid-particle flow, the behavior of film thickness in the bend plays a major role on the particle impact velocity and the corresponding erosion rates. By comparing the impact characteristics for gas and liquid superficial velocities of 40 and 0.4 m/s, respectively, in the 90° elbow, it was found that the impact velocities for gas-particle and gas-liquid-particle flows at the erosion hotspot are 38 and 14 m/s, respectively. In addition, among the studied geometries, the 30° elbow is the most erosion-resistant bend angle configuration among those studied for both two- and three-phase flows.

Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe

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.

Computational Analysis of Fiber Dynamics in Human Nasal Cavity

Elongated particles, such as asbestos and mineral fibers, are considered severe inhalation hazards due to their ability to penetrate into the deep lung. Frequently the dynamic behavior of the fibrous particles is attributed to their unique needle-like geometry. Therefore, understanding the interactions of the inhaled elongated particles with the airflow environment is of great significance. In this study, the transport and deposition of elongated micro-fibers in a realistic human nasal cavity is investigated numerically. The motion of the micro-fiber is resolved by solving the system of equations governing its coupled translational and rotational motions. The governing equations included the drag, the hydrodynamic torques that were evaluated using the Jeffrey model. The influence of the shear lift force was also included in these simulations. The no-slip wall boundary condition for airflow in the airways was used. Since the surface of airways is covered with mucus, when a fiber touches the surface, it was assumed to be deposited with no rebound. The study allows a close look at the non-spherical particle-flow dynamics with respect to the translation, rotation, coupling, and how the rotation affects the particle’s macroscopic transport and deposition properties. A series of simulations for different microfiber diameters and aspect ratios were performed. The simulation results are compared with the existing experimental data, and earlier computational model predictions and good agreements were obtained. The present study also seeks to provide additional insight into the transport processes of microfibers in the upper respiratory tract.

Four-Phase Flow of Oil, Gas, Water, and Sand Mixtures in Subsea Pipelines

This paper investigates issues around four-phase (Oil/CO2/water/sand) flows occurring within subsea pipelines. Multi-phase flows are the norm, as production fluid from reservoirs typically include sand with water. However, these multi-phase flow mixtures, whether three- or four-phase, are at risk of forming slug flows. The inclusion of sand in this mixture is concerning, as it not only leads to increased levels of pipeline erosion but it also has the potential, to accumulate sand at the bottom of the pipe, blocking the pipe or at the very least hindering the flow. This latter impact can prove problematic, as a minimum fluid velocity must be maintained to ensure the safe and regulated flow of particles along a pipeline. The presence of low amounts of sand particles in oil/gas/water flow mixtures can serve to reduce the pressure exerted on bends. The sand volume fraction must in this case, be relatively low such that the particles’ resistance causes only a moderate loss in pressure. Therefore, the study aims to gauge the impact of oil/gas/water/sand mixtures on various pipeline structures as well as to further investigate the phenomenon of flow-induced vibration to determine the optimal flow variables which can be applied predicting the structural responses of subsea pipelines.

Effects of Pipe Diameter and Stokes Number on Erosion in Elbows

Large diameter pipes and elbows are vastly used in industry especially in mining and oil and gas production. Solid particle erosion is a common issue in these pipelines, and it is important to predict it to avoid failures. Currently, laboratory experiments reported in the literature are limited to diameters less than 4 inches. Therefore, there is not much experimental data available for large diameter elbows. However, the erosion can be predicted by CFD simulations and applying erosion equations in such elbows. The goal of this project is to examine the effects of elbow diameter and Stokes number on erosion patterns and magnitude for various flow conditions for elbow diameters of 2, 4, 8, and 12 inches. The approach of this work is to first perform CFD simulations of liquid-solid and gas-solid flows in 2-inch and 4-inch elbows, respectively, and evaluate the results by available experimental data. Then CFD simulations are carried for 2, 4, 8, and 12-inch standard elbows for various Stokes numbers corresponding to gas dominant flows with the velocity of 30 m/s, and liquid dominant flows with the velocities of 6 m/s. For gas dominant flows erosion in air and for liquid dominant flows erosion in water is investigated. All these simulations are carried for four particle sizes of 25, 75, 150, and 300 microns. The results indicate that Stokes number and diameter of elbows have significant effects on erosion patterns as well as magnitudes in this geometry. This work will have various applications, including validating mechanistic models of erosion predictions in elbows and developing an Artificial Intelligence (machine learning) algorithm to predict erosion for various flow conditions. Such algorithms are limited to the range of conditions they are trained for. Therefore, it is important to expand the database these codes are accessing. Overall, the CFD database of large diameter elbows will reduce the computational costs in the future.

Comparison of Turbulent Boundary Layer Profiles Modified With Injection or Uniform Concentration of Drag-Reducing Polymer Solution

The current study explores the influence of polymer drag reduction on the near-wall velocity distribution in a turbulent boundary layer. The classical view is that the polymers modify the intercept constant within the log-region without impacting the von Kármán coefficient, which results in the log-region being unaltered though shifted outward from the wall. However, it has been recently shown that this is not accurate, especially at high drag reduction (> 40%). Past work examining the von Kármán coefficient and intercept constant has shown that polymer properties must impact the deviations, but without any quantification of the dependence. This work reviews the literature to make estimates of the local polymer properties and then demonstrates that the scatter at HDR can be attributed to variations in the Weissenberg number. In addition, new polymer ocean results are incorporated and shown to be quite consistent with polymer injection results using the maximum polymer concentration to define the polymer properties.

A Correction to the Barotropic Model of Gaseous Cavitation in Choked Converging-Diverging Nozzle Flows

The Barotropic Cavitation Model describes the behavior of a homogeneous mixture of liquid and gas bubbles (gaseous cavitation) as it traverses a converging-diverging (CD) nozzle. Its normal shock formulation makes reliable and accurate predictions of streamwise static pressure distribution from the nozzle inlet to just downstream of the throat and in the diverging section as the flow approaches the nozzle outlet. It fails in the intermediate portion of the divergence with maximum pressure prediction errors (as a fraction of nozzle inlet pressure) roughly equivalent to the back pressure ratio (as high as 0.46). A correction to the streamwise static pressure distributions predicted by the normal shock solution of the Barotropic Cavitation Model is proposed, applied and compared to experiments with aerated and non-aerated cavitation in several fluids. When used to simulate aerated cavitation of dodecane in a CD nozzle it predicts the location of first disagreement between the normal shock solution and experimental static pressure measurements within 4% of nozzle length. A polynomial curve fit between this predicted point (xcorr) and the normal shock location (xshock) then reduces maximum prediction error for static pressure in the correction region to no more than 0.11 (as a fraction of inlet pressure) for the aerated dodecane cases examined. For non-aerated gaseous cavitation in dodecane, water or JP8 jet fuel this error ratio does not exceed 0.13 and typical values are less than 0.07.

Impact of Bubble Size on Flow Response to Transient Pressure Drop Through Converging Nozzle

For homogenous two-phase bubbly flows, the theoretical speed of sound is dramatically reduced at moderate void fractions to speeds much lower than the speed of sound for either single phase. This theoretical speed of sound would suggest a propensity for bubbly flows to reach choked conditions when traveling through a convergent nozzle. However, for a bubbly flow to be considered homogenous requires assumptions that may not be realized in practical applications. In this experimental study, a bubbly flow was sent through a convergent nozzle before entering a large chamber. By setting steady flow conditions upstream and then reducing the chamber pressure via a vacuum pump, the transient response in terms of gas and liquid flow rates and upstream channel pressure was determined. The bubble size was carefully varied from ∼0.3–1 mm while holding gas and liquid flow rates constant in order to study how bubble size affects the transient flow characteristics. High-speed imaging was used for measuring the bubbles. Experiments were also conducted at two gas-liquid mass flow ratios. Results are presented to demonstrate the impact of bubble size and gas-liquid ratio on the transient response of upstream gas and liquid flow rates, upstream pressure and exit Mach number to the lowering of pressure downstream of the convergent nozzle. Results are presented both for flows that remained in the bubbly regime and for flows that transitioned to an annular flow regime during a trial.

Analysis of Coupled CFD-DEM Simulations in Dense Particle-Laden Turbulent Jet Flow

In this paper, coupled CFD-DEM simulations of dense particle-laden jet flow are performed using CFDEM® coupling interface that couples LAMMPS-based LIGGGHTS® DEM engine with OpenFOAM CFD framework. Suspensions of mono-sized spherical glass particles with 80 microns diameter and a mass loading of 0.23 and 0.86 are considered. Three different CFD meshes are used with an average mesh resolution dimension of 3.06, 2.67, and 1.86 particle diameters and it is determined that mesh resolution does not change results for void fraction calculation (using the divided model) of the CFD-DEM equations. Samples of particle flux are taken at 0.1, 10, and 20 nozzle diameters along the axial direction of the jet region. The numerical results for particle flux are compared with a well cited experimental data found in literature. The CFD-DEM simulations in turbulent jet flow are found to be highly sensitive to initial particle velocity inputs but the experimental data provide sufficient information to produce comparable results.