Hydrodynamic Forces on Subsea Pipelines due to Orbital Wave Effects

2013 ◽  
Author(s):  
Annelise Karreman ◽  
Jeremy Leggoe ◽  
Terry Griffiths ◽  
Lisa King ◽  
Nino Fogliani
Keyword(s):  
Vertical Velocity ◽  
Large Diameter ◽  
Significant Proportion ◽  
Economic Benefits ◽  
Hydrodynamic Forces ◽  
Design Methods ◽  
Fundamental Aspect ◽  
Experimental Investigations ◽  
Rectilinear Motion ◽  
Particle Paths

Ensuring pipeline stability is a fundamental aspect of subsea pipeline design and can contribute a significant proportion of project costs in regions with large diameter trunklines, shallow water and severe geotechnical and metocean conditions [1]. Reducing the conservatism and simplifications of existing pipeline stabilisation design methods therefore offers economic benefits to hydrocarbon producers necessary to ensure the ongoing viability of projects in these regions. To realise this potential and reduce the conservatism of the existing design methods, a more accurate understanding of the hydrodynamic loads exerted by waves and currents is required. This paper investigates one of the inherent assumptions incorporated into the existing design methods through the arrangement of previous experimental investigations to determine whether rectilinear motion provides a reasonable approximation to simulate the near seabed orbital particle paths in wind-generated waves. This assumption is based on the flattening of particle paths to ellipsoids with depth and ignores the small vertical velocity components near the seabed. Based on the hydrodynamic forces calculated numerically using a validated Computational Fluid Dynamics (CFD) model for rectilinear and orbital wave modelling it is concluded that pipeline stabilisation requirements calculated in accordance with the DNV-RP-F109 absolute lateral static stability design method and rectilinear wave motion assumption are conservative. It is also concluded that the hydrodynamic force asymmetry in favour of the reverse half wave cycle caused by the vertical velocity components in orbital wave conditions requires further consideration to determine the implication for dynamic lateral stability design methods.

scholarly journals A qualitative study on the multi-level process of resilience development for adults recovering from eating disorders

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Katie Grogan ◽  
Hannah O’Daly ◽  
Jessica Bramham ◽  
Mary Scriven ◽  
Caroline Maher ◽  
...  
Keyword(s):  
Eating Disorders ◽  
Eating Disorder ◽  
Qualitative Study ◽  
Significant Proportion ◽  
Well Being ◽  
Fundamental Aspect ◽  
Increased Risk ◽  
Resilience Process ◽  
Multi Level ◽  
Level Process

Abstract Background Resilience research to date has been criticised for its consideration of resilience as a personal trait instead of a process, and for identifying individual factors related to resilience with no consideration of the ecological context. The overall aim of the current study was to explore the multi-level process through which adults recovering from EDs develop resilience, from the perspectives of clients and clinicians. The objective of this research was to outline the stages involved in the process of developing resilience, which might help to inform families and services in how best to support adults with EDs during their recovery. Method Thirty participants (15 clients; 15 clinicians) took part in semi-structured interviews, and responded to questions relating to factors associated with resilience. Using an inductive approach, data were analysed using reflexive thematic analysis. Results The overarching theme which described the process of developing resilience was ‘Bouncing back to being me’, which involved three stages: ‘Who am I without my ED?’, ‘My eating disorder does not define me’, and ‘I no longer need my eating disorder’. Twenty sub-themes were identified as being involved in this resilience process, thirteen of which required multi-level involvement. Conclusion This qualitative study provided a multi-level resilience framework for adults recovering from eating disorders, that is based on the experiences of adults with eating disorders and their treating clinicians. This framework provided empirical evidence that resilience is an ecological process involving an interaction between internal and external factors occurring between adults with eating disorder and their most immediate environments (i.e. family and social). Plain English summary Anorexia nervosa, bulimia nervosa and binge-eating disorder demonstrate high rates of symptom persistence across time and poor prognosis for a significant proportion of individuals affected by these disorders, including health complications and increased risk of mortality. Many researchers have attempted to explore how to improve recovery outcomes for this population. Eating disorder experts have emphasised the need to focus not only on the weight indicators and eating behaviours that sustain the eating disorder during recovery, but also on the psychological well-being of the person recovering. One way to achieve this is to focus on resilience, which was identified as a fundamental aspect of eating disorder recovery in previous research. This study conceptualises resilience as a dynamic process that is influenced not only at a personal level but also through the environment in which the person lives. This study gathered data from adults with eating disorders and their treating clinicians, to devise a framework for resilience development for adults recovering from eating disorders. The paper discussed ways in which these findings and the framework identified can be easily implemented in clinical practice to facilitate a better understanding of eating disorder resilience and to enhance recovery outcomes.

The Research of Large-Diameter & Energy-Saving More Medium Supplied Gravity-Fed Three-Product Heavy Medium Cyclone

2011 ◽  
Vol 211-212 ◽  
pp. 1072-1076
Author(s):  
Ping Huo ◽  
Li Qiang Zhang ◽  
Jing Bo Jia
Keyword(s):  
Energy Saving ◽  
Separation Efficiency ◽  
Simulation Analysis ◽  
New Technology ◽  
Large Diameter ◽  
Economic Benefits ◽  
Heavy Medium ◽  
Processing Ability ◽  
The One ◽  
High Processing

The characteristics and the development restrict factors in large-diameter area of the traditional three-product heavy medium cyclone are described. The paper mainly describes the structure and principles of large-diameter & energy-saving more medium supplied gravity-fed three-product heavy medium cyclone. The simulation analysis of this cyclone (DWP type) is presented. The results show that this type of more medium supplied cyclone is better than the one medium supplied cyclone for it has a faster separation speed, high processing ability and better separation efficiency. The applications in field of the 3SNWX1500/1100-Ⅳ type cyclone which using the new technology indicated that there have energy-saving, a high output, a stable separation efficiency, a high precision and a significant economic benefits.

Non-Traditional Materials, Technology and Non-Traditional Research Mode

2012 ◽  
Vol 517 ◽  
pp. 730-736
Author(s):  
Qiang Ye ◽  
Tuo Wen Ju ◽  
Na Chen
Keyword(s):  
Economic Benefits ◽  
Design Methods ◽  
New Materials ◽  
Application Method ◽  
Traditional Research ◽  
Technical Details ◽  
Short Time

In order to obtain better social and economic benefits, non-traditional materials and technologies must be closely integrated with non-traditional research mode. Traditional studies on materials and techniques are mainly undertaken by engineers of structures and materials, while architects play the role in the application of materials and technologies. Therefore, the application of new materials and technologies shall be inevitably accepted, well acquainted with and proficiently utilized by architects. The three factors that have a major impact on this process are the complexity, differentiation and timeliness, indicating that the application of new materials and technologies is simpler, similar to the application method of traditional materials and technologies and can be learned and mastered by architects in a short time. The hardcore of non-traditional research mode is the close coordination between architects and the engineers of structure and materials, the design methods and technical details that adapt to new materials and technologies.

Dynamic Stability Response of Piggyback Pipelines

2010 ◽  
Author(s):  
Hammam Zeitoun ◽  
Masˇa Brankovic´ ◽  
Knut To̸rnes ◽  
Simon Wong ◽  
Eve Hollingsworth ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Dynamic Stability ◽  
Large Diameter ◽  
Hydrodynamic Forces ◽  
Model Testing ◽  
Equivalent Diameter ◽  
Pipeline System ◽  
Hydrodynamic Coefficients ◽  
Hydrodynamic Loads

One of the main aspects of subsea pipeline design is ensuring pipeline stability on the seabed under the action of hydrodynamic loads. Hydrodynamic loads acting on Piggyback Pipeline Systems have traditionally been determined by pipeline engineers using an ‘equivalent pipeline diameter’ approach. The approach is simple and assumes that hydrodynamic loads on the Piggyback Pipeline System are equal to the loads on a single pipeline with diameter equal to the projected height of the piggyback bundle (the sum of the large diameter pipeline, small diameter pipeline and gap between the pipelines) [1]. Hydrodynamic coefficients for single pipelines are used in combination with the ‘equivalent diameter pipe’ to determine the hydrodynamic loads on the Piggyback Pipeline System. In order to assess more accurately the dynamic response of a Piggyback Pipeline System, an extensive set of physical model tests has been performed to measure hydrodynamic forces on a Piggyback Pipeline System in combined waves and currents conditions, and to determine in-line and lift force coefficients which can be used in a dynamic stability analysis to generate the hydrodynamic forces on the pipeline [2]. This paper describes the implementation of the model testing results in finite elements dynamic stability analysis and presents a case study where the dynamic response of a Piggyback Pipeline System was assessed using both the conventional ‘equivalent diameter approach’ and the hydrodynamic coefficients determined using model testing. The responses predicted using both approaches were compared and key findings presented in the paper, in terms of adequacy of the equivalent diameter approach, and effect of piggyback gap (separation between the main line and the secondary line) on the response.

Numerical Investigation of Flow Around a ROV With Crawler Based Driving System

2012 ◽  
Author(s):  
Tokihiro Katsui ◽  
Satoshi Kajikawa ◽  
Tomoya Inoue
Keyword(s):  
Hydrodynamic Forces ◽  
Point Of View ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Accurate Estimation ◽  
Remotely Operated Vehicle ◽  
Driving System ◽  
Sea Bottom ◽  
Computational Fluid Dynamics Analysis ◽  
Turn Over

The Remotely Operated Vehicle, so called “ROV” which has crawler based moving system is considered as one of the appropriate underwater vehicles for seafloor exploration or seabed resources development [1][2][3][4][5][6][7]. The advantages of crawler driven ROV are to be able to stay on a fixed sea bottom location and to be capable to do heavy works such as digging the seafloor. However, the ROV moving on the sea bottom with crawler based driving system easily turn over due to the buoyancy and hydrodynamic forces [8][9][10][11][12]. Therefore, it is important to know the moving capability of the ROV on the sea bottom for the design point of view. The authors have shown the condition for the normal running of the ROV which moves on horizontal and inclined flat sea bottom by means of a simple dynamic model [11]. Normal running means that the ROV runs without bow-up or stern-up situations and the crawlers touch the ground normally. The normal running condition of ROV indicates the constrained condition of the relation between gravity and buoyancy center locations for any given design parameters such as geometry, weight, displacement and running speed of the ROV. Though this method estimates the ROVs’ moving capability with acceptable accuracy, the hydrodynamic forces on the ROV and its application point are required for accurate estimation. In the previous research, those quantities are roughly estimated from the past experimental investigations. The present study investigated the flow around the crawler driven ROV which runs on seafloor with CFD (Computational Fluid Dynamics) analysis to evaluate the characteristics of hydrodynamic forces acting on the ROV. The open source CFD code, OpenFOAM [13] was applied for flow calculation and the results were validated with model experiments. By using the calculated hydrodynamic forces on ROV, the moving capability of ROV was evaluated with a method the authors had shown. The estimates of the running capability of the ROV by using the CFD calculations are quite different from past estimations in some running conditions.

Experimental Investigation Into the Thermal Behavior of Copper-Alloyed Dies in Pressure Die Casting

2006 ◽  
Vol 128 (4) ◽  
pp. 844-859 ◽  
Author(s):  
L. D. Clark ◽  
M. T. Alonso Rasgado ◽  
K. Davey ◽  
S. Hinduja
Keyword(s):  
Thermal Resistance ◽  
Die Casting ◽  
Significant Proportion ◽  
Casting Machine ◽  
Experimental Results ◽  
Heat Extraction ◽  
Zinc Alloy ◽  
Experimental Investigations ◽  
Spray Process ◽  
Pressure Die Casting

The rate of heat extraction during the pressure die casting process is central to both the quality and the cost of finished castings. Recent efforts to reduce the thermal resistance of dies by optimizing the effectiveness of the cooling channels have shown the potential for improvement. Reducing the thermal resistance of the coolant boundary layer means that a significant proportion of the total thermal resistance becomes attributable to the die steel. Further significant reductions in die thermal resistance can be obtained by replacing the steel with copper. This paper investigates the feasibility of using copper dies, reinforced with steel inserts and coated with a thin layer of wear resistant material, which is deposited using the thermal arc spray process. Experimental work relating to the thermal spray process has been undertaken to establish bond strengths and thermal conductivities for various process parameters. Moreover, experimental investigations have been carried out using two copper coated dies, the first of which was a pseudodie block heated by an infrared heater. The second die was tested on a die casting machine and produced zinc alloy castings at a greatly increased production rate when compared to its steel counterpart. The experimental results from the two dies are compared with those predicted by an in-house thermal-cum-stress model based on the boundary element method. Reasonable agreement between the predicted and experimental results is shown and the feasibility of copper-alloyed dies for pressure die casting is established.

Experimental Investigation of Steam Bubble Condensation in Flowing Subcooled Water With Two Different Injection Nozzle Geometries

2013 ◽  
Author(s):  
Suleiman Al Issa ◽  
Patricia B. Weisensee
Keyword(s):  
Test Section ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Bubble Diameter ◽  
Large Diameter ◽  
Low Pressure ◽  
Test Facility ◽  
Experimental Investigations ◽  
Subcooled Water

A multiphase flow test facility was built at the Department of Nuclear Engineering at the Technical University Munich. The main goal of this facility is to investigate the condensation of steam bubbles injected into a vertical large diameter pipe (104 mm) with flowing subcooled water (6–15 K) at low pressure conditions (1.1–1.45 bar). Current experimental investigations will contribute to a better understanding of subcooled boiling at low pressures, accidental conditions in nuclear power plants and low-pressure research reactors and correlations for the validation of CFD codes. The test section is a 1 m long transparent pipe that is surrounded by an 18×18 cm rectangular “aquarium” filled with distilled water for refraction correction. High-speed camera (HSC) recording was used to gather data about condensing bubbles including bubble diameter, shape and rising velocity. Steam was injected via two different vertical injection nozzles with an inner diameter of 4 and 6 mm, respectively, directly into the center of the test section. The present experiments were carried out at three different steam superficial velocities, water superficial velocities and water temperatures leading to bubble diameters up to 50 mm and bubble relative velocities around 1 m/s. The measurements enabled the calculation of bubble Reynolds and Nusselt numbers and comparison with correlations given in literature. Even though significant differences could be observed between the two injection nozzles with respect to the bubble’s diameter and velocity, the Nusselt and Reynolds numbers are in the same range of values. The bigger bubbles of the 6 mm with respect to the 4 mm nozzle are almost neutralized by the lower rising velocities.

Spatio–temporal analysis of hydrodynamic forces on the particle bed in an oscillatory flow environment

2018 ◽  
Vol 841 ◽  
pp. 167-202 ◽  
Author(s):  
Chaitanya D. Ghodke ◽  
Sourabh V. Apte
Keyword(s):  
Oscillatory Flow ◽  
Large Diameter ◽  
Pressure Fluctuations ◽  
Temporal Analysis ◽  
Hydrodynamic Forces ◽  
Generalized Extreme Value Distribution ◽  
Flow Environment ◽  
Lift Forces ◽  
Drag And Lift ◽  
Particle Bed

A numerical investigation of unsteady hydrodynamic forces on the particle bed in an oscillatory flow environment is performed by means of direct numerical simulations. Statistical descriptions of drag and lift forces for two particle sizes of diameter 372 and 125 in wall units in a very rough turbulent flow regime are reported. Characterization of unsteady forces in terms of spatial distribution, temporal autocorrelation, force spectrum as well as cross-correlations with measurable flow variables is carried out. Based on the concept of impulse, intermittency in the drag and lift forces is also investigated. Temporal correlations show drag and lift to be positively correlated with a time delay that is approximately equal to the Taylor micro-scale related to the drag/lift fluctuations. The force spectra for drag and lift reveal roughly two scaling regions, $-11/3$ and $-7/3$; the former typically represents turbulence–mean-shear interactions, whereas the latter indicates dominance of turbulence–turbulence interactions. Particle forces are strongly correlated with streamwise velocity and pressure fluctuations in the near-bed region for both flow cases. In comparison to the large-diameter particle case, the spatial extent of these correlations is 2–3 times larger in homogeneous directions for the small sized particle, a feature that is reminiscent of longer near-bed structures. For both large- and small-particle cases, it is shown that the distributions of drag (lift) fluctuations, in particular, peakedness and long tails, match remarkably well with fourth-order Gram–Charlier distributions of velocity (pressure) fluctuations. Furthermore, it is demonstrated that the intermittency is larger in the case of the lift force compared to that for the drag in both flow cases. Distributions of impulse events are heavily and positively skewed and are well described by a generalized extreme value distribution.

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