The Experts below are selected from a list of 3717 Experts worldwide ranked by ideXlab platform
Arash Zakeri - One of the best experts on this subject based on the ideXlab platform.
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drag forces caused by submarine glide block or out runner block impact on suspended free span Pipelines numerical analysis
Ocean Engineering, 2013Co-Authors: Arash Zakeri, Bipul HawladerAbstract:Abstract Computational fluid dynamics (CFD) approach was employed to simulate soil–Pipe interaction behavior subjected to impact load. Numerical analysis is verified with results experimentally obtained in a geotechnical centrifuge. The physical experiments in centrifuge simulated the impact of soft to firm clay blocks (4 to 8 kPa of undrained shear strengths) on two model Pipes (0.19 and 0.29 m in diameter), at velocities ranging between 0.04 and 1.3 m/s in a direction normal to the Pipe Axis. The corresponding shear strain rates ranged from about 4 to 136 s −1 . In this paper, a relationship between shear stress and shear strain rate for the clay blocks is first established through re-analysis of the centrifuge experiments and then used to calibrate a CFD numerical model and to complement the physical test results. The present CFD analyses covered impact velocities up to 2 m/s and investigated different Pipe diameters (6.35 to 150 mm) and clay strengths. The methodology and results of the CFD analyses are discussed and compared with the observations made from the physical experiments. The experimental results were combined with the results of the CFD analyses and a simple approach is proposed to estimate the drag force caused by a glide block or out-runner block impact on a suspended (free-span) Pipeline.
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drag forces caused by submarine glide block or out runner block impact on suspended free span Pipelines
Ocean Engineering, 2012Co-Authors: Arash Zakeri, Bipul HawladerAbstract:Abstract The results of a series of physical experiments to quantify the drag force on a submarine Pipeline caused by a glide block or an out-runner block impact normal to the Pipe Axis are presented. The experiments were conducted in a geotechnical centrifuge under submerged conditions at a centrifugal force of 30 times the Earth's gravity (i.e. N=30) and simulated impact situations under steady state conditions and uniform velocities. The soil blocks (approximately 4.5 m high in prototype terms) were made of kaolin clay with undrained shear strengths between 4 and 8 kPa. The model Pipes were 6.35 and 9.52 mm in diameter (0.19 and 0.29 m in prototype terms). The impact velocities ranged between 0.04 and 1.3 m/s. The Pipe centerline was at mid-height of the block. The shear strain rates, defined as the ratio of impact velocity to Pipe diameter. The shear strain rates ranged from about 4 to 137 reciprocal seconds. Hence, the test results are applicable to a wide range of field situations. A method is presented for estimating glide or out-runner block impact drag force on submarine Pipelines based on the results of the centrifuge experiments.
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impact drag forces on Pipelines caused by submarine glide blocks or out runner blocks
2012Co-Authors: Arash Zakeri, Bipul HawladerAbstract:This paper discusses the forces resulting from the impact of an intact submarine landslide (the glide block or out-runner block region) on a suspended submarine Pipeline. Eight physical experiments were conducted using the geotechnical centrifuge facility at C-CORE. In prototype scale, clay chunks equivalent to 12 m × 6 m × 4.5 m (l × w × h) were used to model the glide blocks or out-runner blocks. They had s u ranging from 4 to 7 kPa, and impact velocities ranging from 0.1 to 1.3 m/s. The clay blocks impacted the suspended Pipes at a direction normal to the Pipe Axis. The diameters of the Pipes were 0.19 and 0.29 m. Based on these experimental results, a method to estimate the impact drag force on a Pipeline caused by a submarine glide block or out-runner block was developed.
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submarine debris flow impact on suspended free span Pipelines normal and longitudinal drag forces
Ocean Engineering, 2009Co-Authors: Arash ZakeriAbstract:Computational fluid dynamics (CFD) analysis was employed to numerically simulate impact of clay-rich submarine debris flows on a suspended (free-span) Pipeline at various angles of attack. The resultant horizontal drag force can be decomposed into two components: normal and parallel to the Pipe Axis. A method is presented for estimating the normal and longitudinal drag forces on a suspended Pipeline and is applicable to a wide of impact situations. The work presented here complements the results of an earlier investigation into the drag forces on suspended and laid-on-seafloor Pipelines. The previous investigation consisted of both physical laboratory experiments and CFD numerical analyses, for an impact situation normal to the Pipe Axis. The impact Reynolds numbers presented in this paper range between about 2 and 320. This range is considered appropriate for practical design purposes.
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submarine debris flow impact on Pipelines part i experimental investigation
Coastal Engineering, 2008Co-Authors: Arash Zakeri, Kaare Hoeg, Farrokh NadimAbstract:Estimating the impact forces exerted by a submarine debris flow on a Pipeline is a challenge, and there is room for considerably more work to advance the state of the art. To this end, an experimental program was performed to investigate the impact on two Pipeline installation scenarios: 1) suspended Pipeline and 2) laid-on-seafloor Pipeline. The results and observations from the experimental investigation are discussed. The definition of Reynolds number was modified for non-Newtonian fluids and an ad hoc method was developed to estimate the drag force exerted by an impact perpendicular to the Pipe Axis. The method may be used in prototype situations to estimate the drag force from submarine debris flow impact on Pipelines. The experimental program was complemented by Computational Fluid Dynamics (CFD) analyses, the details of which are discussed in the accompanying paper.
Yuji Tomita - One of the best experts on this subject based on the ideXlab platform.
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effect of particle size distribution on pressure drop and concentration profile in Pipeline flow of highly concentrated slurry
International Journal of Multiphase Flow, 2005Co-Authors: D R Kaushal, Kimihiko Sato, Takeshi Toyota, Katsuya Funatsu, Yuji TomitaAbstract:Abstract The experiments were conducted in 54.9 mm diameter horizontal Pipe on two sizes of glass beads of which mean diameter and geometric standard deviation are 440 μm & 1.2 and 125 μm & 1.15, respectively, and a mixture of the two sizes in equal fraction by mass. Flow velocity was up to 5 m/s and overall concentration up to 50% by volume for each velocity. Pressure drop and concentration profiles were measured. The profiles were obtained traversing isokinetic sampling probes in the horizontal, 45° inclined and vertical planes including the Pipe Axis. Slurry samples of the mixture collected in the vertical plane were analyzed for concentration profiles of each particle batch constituting the mixture. It was found that the pressure drop is decreased for the mixture at high concentrations except 5 m/s and a distinct change of concentration profiles was observed for 440 μm particles indicating a sliding bed regime, while the profiles in the horizontal plane remains almost constant irrespective of flow velocity, overall concentration and slurry type.
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particle velocity and concentration characteristics in a horizontal dilute swirling flow pneumatic conveying
Powder Technology, 2000Co-Authors: Hui Li, Yuji TomitaAbstract:An experimental study concerning particle behaviors in a horizontal dilute swirling flow pneumatic conveying was performed. Measurements of particle velocities and concentration profiles have been carried out using the photographic image technique. From the experimental results, it is found that mean particle velocity of swirling flow pneumatic conveying is lower than that of conventional pneumatic conveying in the range of high gas velocity, but the higher mean particle velocity in swirling flow pneumatic conveying can be obtained at low gas velocity. The particle concentration profiles in the swirling flow pneumatic conveying exhibit symmetric distributions with respect to the Pipe Axis and the higher particle concentration appears near the wall in the acceleration region. In developed region, the particle concentration profiles of the swirling flow pneumatic conveying show anti-symmetric distributions, and the higher particle concentration appear at the bottom of Pipe. However, the particle concentrations of the swirling flow pneumatic conveying at the bottom of Pipe are lower than that of axial flow pneumatic conveying.
Farrokh Nadim - One of the best experts on this subject based on the ideXlab platform.
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submarine debris flow impact on Pipelines part i experimental investigation
Coastal Engineering, 2008Co-Authors: Arash Zakeri, Kaare Hoeg, Farrokh NadimAbstract:Estimating the impact forces exerted by a submarine debris flow on a Pipeline is a challenge, and there is room for considerably more work to advance the state of the art. To this end, an experimental program was performed to investigate the impact on two Pipeline installation scenarios: 1) suspended Pipeline and 2) laid-on-seafloor Pipeline. The results and observations from the experimental investigation are discussed. The definition of Reynolds number was modified for non-Newtonian fluids and an ad hoc method was developed to estimate the drag force exerted by an impact perpendicular to the Pipe Axis. The method may be used in prototype situations to estimate the drag force from submarine debris flow impact on Pipelines. The experimental program was complemented by Computational Fluid Dynamics (CFD) analyses, the details of which are discussed in the accompanying paper.
Kaare Hoeg - One of the best experts on this subject based on the ideXlab platform.
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submarine debris flow impact on Pipelines part i experimental investigation
Coastal Engineering, 2008Co-Authors: Arash Zakeri, Kaare Hoeg, Farrokh NadimAbstract:Estimating the impact forces exerted by a submarine debris flow on a Pipeline is a challenge, and there is room for considerably more work to advance the state of the art. To this end, an experimental program was performed to investigate the impact on two Pipeline installation scenarios: 1) suspended Pipeline and 2) laid-on-seafloor Pipeline. The results and observations from the experimental investigation are discussed. The definition of Reynolds number was modified for non-Newtonian fluids and an ad hoc method was developed to estimate the drag force exerted by an impact perpendicular to the Pipe Axis. The method may be used in prototype situations to estimate the drag force from submarine debris flow impact on Pipelines. The experimental program was complemented by Computational Fluid Dynamics (CFD) analyses, the details of which are discussed in the accompanying paper.
Bipul Hawlader - One of the best experts on this subject based on the ideXlab platform.
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drag forces caused by submarine glide block or out runner block impact on suspended free span Pipelines numerical analysis
Ocean Engineering, 2013Co-Authors: Arash Zakeri, Bipul HawladerAbstract:Abstract Computational fluid dynamics (CFD) approach was employed to simulate soil–Pipe interaction behavior subjected to impact load. Numerical analysis is verified with results experimentally obtained in a geotechnical centrifuge. The physical experiments in centrifuge simulated the impact of soft to firm clay blocks (4 to 8 kPa of undrained shear strengths) on two model Pipes (0.19 and 0.29 m in diameter), at velocities ranging between 0.04 and 1.3 m/s in a direction normal to the Pipe Axis. The corresponding shear strain rates ranged from about 4 to 136 s −1 . In this paper, a relationship between shear stress and shear strain rate for the clay blocks is first established through re-analysis of the centrifuge experiments and then used to calibrate a CFD numerical model and to complement the physical test results. The present CFD analyses covered impact velocities up to 2 m/s and investigated different Pipe diameters (6.35 to 150 mm) and clay strengths. The methodology and results of the CFD analyses are discussed and compared with the observations made from the physical experiments. The experimental results were combined with the results of the CFD analyses and a simple approach is proposed to estimate the drag force caused by a glide block or out-runner block impact on a suspended (free-span) Pipeline.
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drag forces caused by submarine glide block or out runner block impact on suspended free span Pipelines
Ocean Engineering, 2012Co-Authors: Arash Zakeri, Bipul HawladerAbstract:Abstract The results of a series of physical experiments to quantify the drag force on a submarine Pipeline caused by a glide block or an out-runner block impact normal to the Pipe Axis are presented. The experiments were conducted in a geotechnical centrifuge under submerged conditions at a centrifugal force of 30 times the Earth's gravity (i.e. N=30) and simulated impact situations under steady state conditions and uniform velocities. The soil blocks (approximately 4.5 m high in prototype terms) were made of kaolin clay with undrained shear strengths between 4 and 8 kPa. The model Pipes were 6.35 and 9.52 mm in diameter (0.19 and 0.29 m in prototype terms). The impact velocities ranged between 0.04 and 1.3 m/s. The Pipe centerline was at mid-height of the block. The shear strain rates, defined as the ratio of impact velocity to Pipe diameter. The shear strain rates ranged from about 4 to 137 reciprocal seconds. Hence, the test results are applicable to a wide range of field situations. A method is presented for estimating glide or out-runner block impact drag force on submarine Pipelines based on the results of the centrifuge experiments.
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impact drag forces on Pipelines caused by submarine glide blocks or out runner blocks
2012Co-Authors: Arash Zakeri, Bipul HawladerAbstract:This paper discusses the forces resulting from the impact of an intact submarine landslide (the glide block or out-runner block region) on a suspended submarine Pipeline. Eight physical experiments were conducted using the geotechnical centrifuge facility at C-CORE. In prototype scale, clay chunks equivalent to 12 m × 6 m × 4.5 m (l × w × h) were used to model the glide blocks or out-runner blocks. They had s u ranging from 4 to 7 kPa, and impact velocities ranging from 0.1 to 1.3 m/s. The clay blocks impacted the suspended Pipes at a direction normal to the Pipe Axis. The diameters of the Pipes were 0.19 and 0.29 m. Based on these experimental results, a method to estimate the impact drag force on a Pipeline caused by a submarine glide block or out-runner block was developed.