Influence of Slug Flow on Hydraulic Sand Dune Migration in Horizontal Pipelines

2008 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Peter Rodgers ◽  
Chokri Touati
Keyword(s):  
Slug Flow ◽  
High Speed ◽  
Sand Dune ◽  
Front Velocity ◽  
Sand Particle ◽  
Horizontal Pipe ◽  
Particle Mobility ◽  
Three Phase ◽  
Slug Flows ◽  
Gas Ratio

This paper presents an experimental study of three phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of slug flow. Sand dune pitch, height and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for slug flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with slug flows. The sand dune local velocity (inside the slug body) was measured to be three times higher than the averaged dune velocities.

Influence of Gas-Liquid Two-Phase Intermittent Flow on Hydraulic Sand Dune Migration in Horizontal Pipelines

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Afshin Goharzadeh ◽  
Peter Rodgers ◽  
Chokri Touati
Keyword(s):  
High Speed ◽  
Sand Dune ◽  
Front Velocity ◽  
Intermittent Flow ◽  
Sand Particle ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Particle Mobility ◽  
Three Phase ◽  
Gas Ratio

This paper presents an experimental study of three-phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of a gas-liquid two-phase intermittent flow. Sand dune pitch, length, height, and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for intermittent flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with intermittent flows. The sand dune local velocity (within the slug body) was measured to be three times higher than the averaged dune velocities, due to turbulent enhancement within the slug body.

Influence of Pipeline Inclination on Hydraulic Conveying of Sand Particles

2012 ◽  
Author(s):  
Ahmed Mohamed Nossair ◽  
Peter Rodgers ◽  
Afshin Goharzadeh
Keyword(s):  
Particle Transport ◽  
High Speed ◽  
Sand Dune ◽  
Sand Particle ◽  
Hydrocarbon Production ◽  
Production Wells ◽  
Load Transport ◽  
Bed Load Transport ◽  
Sand Particles ◽  
Dune Dynamics

The understanding of sand particle transport by fluids in pipelines is of importance for the drilling of horizontal and inclined hydrocarbon production wells, topside process facilities, infield pipelines, and trunk lines. Previous studies on hydraulic conveying of sand particles in pipelines have made significant contributions to the understanding of multiphase flow patterns, pressure drop and particle transport rate in horizontal pipelines. However, due to the complexity of the flow structure resulting from liquid-sand interactions, the mechanisms responsible for bed-load transport flow for hydraulic conveying of sand particles have not been extensively studied in inclined pipelines. This paper presents an experimental investigation of hydraulic conveying of sand particles resulting from a stationary flat bed in both horizontal and +3.6 degree upward inclined pipelines. The characteristics of sand transportation by saltation from an initial sand bed are experimentally visualized using a transparent Plexiglas pipeline and high-speed digital photography. The dune formation process is assessed as a function of pipeline orientation. Based on the visualized dune morphology, pipeline inclination is found to have a significant influence on hydraulic conveying of sand dune dynamics (i.e., dune velocity), as well as sand dune geometry (i.e., dune pitch and characteristic dune angles).

Investigations on Slug Flow in a Horizontal Pipe Using Stereoscopic Particle Image Velocimetry and CFD Simulation With Volume of Fluid Method

2012 ◽  
Author(s):  
Marek Czapp ◽  
Matthias Utschick ◽  
Johannes Rutzmoser ◽  
Thomas Sattelmayer
Keyword(s):  
Particle Image Velocimetry ◽  
Slug Flow ◽  
Particle Image ◽  
Volume Of Fluid ◽  
Stereoscopic Particle Image Velocimetry ◽  
Horizontal Pipe ◽  
Pressurized Water ◽  
Cooling Circuit ◽  
Image Velocimetry ◽  
Slug Flows

Investigations on gas-liquid flows in horizontal pipes are of immanent importance for Reactor Safety Research. In case of a breakage of the main cooling circuit of a Pressurized Water Reactor (PWR), the pressure losses of the gas-liquid flow significantly govern the loss of coolant rate. The flow regime is largely determined by liquid and gas superficial velocities and contains slug flow that causes high-pressure pulsations to the infrastructure of the main cooling circuit. Experimental and numerical investigations on adiabatic slug flow of a water-air system were carried out in a horizontal pipe of about 10 m length and 54 mm diameter at atmospheric pressure and room temperature. Stereoscopic high-speed Particle Image Velocimetry in combination with Laser Induced Fluorescence was successfully applied on round pipe geometry to determine instantaneous three-dimensional water velocity fields of slug flows. After grid independence studies, numerical simulations were run with the open-source CFD program OpenFOAM. The solver uses the VOF method (Volume of Fluid) with phase-fraction interface capturing approach based on interface compression. It provides mesh refinement at the interfacial area to improve resolution of the interface between the two phases. Furthermore, standard k-ε turbulence model was applied in an unsteady Reynolds averaged Navier Stokes (URANS) model to resolve self-induced slug formation. The aim of this work is to present the feasibility of both relatively novel possibilities of determining two-phase slug flows in pipes. Experimental and numerical results allow the comparison of the slug initiation and expansion process with respect to their axial velocities and cross-sectional void fractions.

scholarly journals Experimental Investigation of Annular Flow Behaviour in Horizontal Pipe

2021 ◽  
Vol 13 (6) ◽  
Author(s):  
Osokogwu Osokogwu ◽  
◽  
Uche Uche ◽  
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Slug Flow ◽  
High Speed ◽  
Annular Flow ◽  
Flow Behavior ◽  
Liquid Film Thickness ◽  
Experimental Investigations ◽  
Internal Diameter ◽  
Horizontal Pipe

The experimental investigations of annular flow were conducted in horizontal pipe using water/air in a 0.0504m internal diameter pipe loop with a total length of 28.68m. To understand annular flow behaviors, conductivity ring sensors, conductance probe sensors and Olympia high speed digital camera were used. In all the experiments, emphasis were on annular flow behavior, phase distribution and liquid film thickness. Liquid film thickness was observed to be thicker mostly when the superficial gas velocities were within 8.2699 m/s to 12.0675 m/s. Above the aforementioned superficial gas velocities, the flow became uniformly distributed on the walls of the internal pipe diameter hence reducing the thicker liquid film at the bottom with gas core at the center of the pipe. More so, annular-slug flow was discovered in the investigation. At superficial liquid velocity of 0.0505 m/s-0.1355 m/s on superficial gas velocities of 8.2699 m/s – 12.0675 m/s, annular-slug flow was prominent. Also discovered was at superficial liquid velocities of 0.0903 m/s - 0.1355 m/s with respect to superficial gas velocities of 13.1692 m/s – 23.4575 m/s, the pipe walls are fully covered with liquid film at very high speed at the entire walls (upper walls and bottom). Also discovered in this experiment is the wavy flow of the upper walls. The liquid film thickness that flows at the upper pipe walls, creeps in a wavy flow. Therefore, the entire flow behavior in an annular flow could be grouped into; wavy-flow at the upper walls, annular-slug flow and thicker liquid film at the bottom with gas core at the center.

Direct Current Deadbeat Predictive Controller for BLDC Motor Using Single DC-Link Current Sensor

2020 ◽  
Vol 38 (8A) ◽  
pp. 1187-1199
Author(s):  
Qaed M. Ali ◽  
Mohammed M. Ezzalden
Keyword(s):  
Control System ◽  
High Speed ◽  
Fast Response ◽  
Bldc Motor ◽  
Current Controller ◽  
Three Phase ◽  
Predictive Controller ◽  
Two Phases ◽  
Dc Current ◽  
Three Phase Inverter

BLDC motors are characterized by electronic commutation, which is performed by using an electric three-phase inverter. The direct control system of the BLDC motor consists of double loops; including the inner-loop for current regulating and outer-loop for speed control. The operation of the current controller requires feedback of motor currents; the conventional current controller uses two current sensors on the ac side of the inverter to measure the currents of two phases, while the third current would be accordingly calculated. These two sensors should have the same characteristics, to achieve balanced current measurements. It should be noted that the sensitivity of these sensors changes with time. In the case of one sensor fails, both of them must be replaced. To overcome this problem, it is preferable to use one sensor instead of two. The proposed control system is based on a deadbeat predictive controller, which is used to regulate the DC current of the BLDC motor. Such a controller can be considered as digital controller mode, which has fast response, high precision and can be easily implemented with microprocessor. The proposed control system has been simulated using Matlab software, and the system is tested at a different operating condition such as low speed and high speed.

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