Hydrodynamic Loading on Mid Water Arch Structures

2011 ◽  
Author(s):  
Colin Russell ◽  
Bertrand Vignaud
Keyword(s):  
Shallow Water ◽  
Fluid Dynamic ◽  
Theoretical Models ◽  
Hydrodynamic Coefficients ◽  
Dynamic Simulations ◽  
Large Structures ◽  
Hydrodynamic Loading ◽  
Combined Action

In the design and analysis of subsea structures, the hydrodynamic coefficients play a significant role in determining the behaviour of the system, particularly when they are under the combined action of steady and oscillatory flow. For small regularly shaped structures and slender members there is a significant amount of literature that provides assistance in the selection of suitable values, however this is not the case for larger and irregular shaped structures where there is a scarcity of information. This paper details the results of a study to develop techniques to derive hydrodynamic coefficients for representative mid water arch configurations commonly used in shallow water flexible riser system applications. The results of a literature review are presented outlining where these structures fit into the different theoretical models. The use of the potential flow approach is verified by means of computational fluid dynamic simulations for a representative structure and both methods are utilised to assist in the generation of appropriate coefficients. A case study on a typical shallow water North Sea project is presented that demonstrates the importance of selecting appropriate hydrodynamic values to represent the structure. The influence of each of the coefficients on the arch motion, which has an impact on the riser response, is studied. It is shown that it is not always possible to be conservative and instead it is important to select appropriate coefficients for the structure in question, which may differ from those typically used. The method developed has wide ranging applicability and can in principle be applied to the determination of hydrodynamic coefficients for other large structures subject to hydrodynamic loading, including disconnectable turret buoys and hybrid riser tower systems.

Determination of the added masses and damping coefficients during coupled motions of two ships in shallow water parallel to the vertical wall

2021 ◽  
pp. 16-25
Author(s):  
В.Ю. Семенова ◽  
К.И. Баканов
Keyword(s):  
Shallow Water ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Hydrodynamic Coefficients ◽  
Damping Coefficients ◽  
Added Masses ◽  
Joint Motions ◽  
National Practice ◽  
Simultaneous Influence

В статье рассматривается определение коэффициентов демпфирования и присоединенных масс, возникающих при совместной качке двух судов в условиях мелководья параллельно вертикальной стенке на основании решения трехмерной потенциальной задачи. Определение гидродинамических коэффициентов осуществляется на основании методов интегральных уравнений и зеркальных отображений. Представленное решение в отечественной практике является новым. В статье приводятся результаты расчетов коэффициентов присоединенных масс и демпфирования, возникающих при качке двух одинаковых судов, расположенных лагом к волнению и параллельно вертикальной стенке в зависимости от изменения расстояний как между судами, так и между судами и вертикальной стенкой. Проводится исследование влияния различных фарватеров на величины гидродинамических коэффициентов, а именно: мелководного фарватера, мелководного фарватера с вертикальной стенкой, мелководного фарватера со вторым параллельно качающимся судном и мелководного фарватера с вертикальной стенкой и вторым судном. Таким образом, в работе учитывается одновременное влияния мелководья, вертикальной стенки и второго судна. Показано увеличение значений коэффициентов присоединенных масс и демпфирования при уменьшении расстояний между судами и между судами и вертикальной стенкой. Также показано значительное совместное влияние вертикальной стенки и второго судна на коэффициенты присоединенных масс и демпфирования по сравнению с другими видами стесненных фарватеров. The article discusses the determination of damping coefficients and added masses arising from the joint motions of two ships in shallow water conditions parallel to the vertical wall based on the solution of a three-dimensional potential problem. Determination of hydrodynamic coefficients is carried out on the basis of the methods of integral equations and mirror images. The solution presented in the national practice is new The article presents the results of calculating the coefficients of added masses and damping arising from the motions of two identical ships located lagged to the sea and parallel to the vertical wall, depending on the change in the distances between the ships and between the ships and the vertical wall. A study is being made of the influence of various waterways on the values ​​of hydrodynamic coefficients, namely: a shallow waterway, a shallow waterway with a vertical wall, a shallow waterway with a second parallel oscillating ship and a shallow waterway with a vertical wall and a second ship. Thus, the work takes into account the simultaneous influence of shallow water, vertical wall and the second ship. An increase in the values of the coefficients of added masses and damping with a decrease in the distances between ships and between ships and the vertical wall is shown. It also shows a significant combined effect of the vertical wall and the second ship on the added mass and damping coefficients in comparison with other types of constrained waterways.

scholarly journals Comparative analysis of the theoretical models of ideal propulsor, ideal fluid brake, ideal screw propeller and ideal axial wind turbine

2013 ◽  
Vol 20 (2) ◽  
pp. 3-12 ◽  
Author(s):  
Tadeusz Koronowicz ◽  
Jan A. Szantyr
Keyword(s):  
Wind Turbine ◽  
Ideal Fluid ◽  
Fluid Dynamic ◽  
Theoretical Models ◽  
Design Procedures ◽  
Flow Losses ◽  
Maximum Value ◽  
Screw Propeller ◽  
Effectiveness Coefficient

Abstract The article presents a detailed discussion of the theoretical models of four different fluid dynamic devices: an ideal propulsor, an ideal fluid brake, an ideal screw propeller and an ideal turbine. The four models are presented with all relevant mathematical formulae regarding the forces, the power and the efficiency. It is demonstrated that the application of the model of an ideal optimum fluid brake according to the Betz theorem for determination of the maximum effectiveness coefficient of an axial wind turbine is not correct. In the case of a turbine the inclusion of important rotational flow losses may increase the maximum value of the turbine effectiveness coefficient above the level defined by Betz. Therefore the model of an ideal turbine should be an inversion of the model of an ideal screw propeller. This conclusion is supported by numerical calculations. It may influence the design procedures of wind turbines and may lead to increase in their efficiency.

Dynamic On-Bottom Stability of Shallow Water Pipeline: A Case Study

2010 ◽  
Author(s):  
Lim Kok Kien ◽  
Lau Siew Ming ◽  
M. Fauzi B. Badaruddin
Keyword(s):  
Shallow Water ◽  
Hostile Environment ◽  
Sea State ◽  
Interaction Modelling ◽  
Concrete Coating ◽  
Water Pipeline ◽  
Subsea Pipelines ◽  
Coating Weight

Traditionally, on-bottom stability requirement of offshore subsea pipelines is often determined based on simplified forcebalance methods. Despite its’ relative ease of application and quick result time, the predicted requirement for stabilisation in shallow water and/or hostile environment can be overbearing and the practicality to install such pipes and subsequent cost becomes a major issue. This paper describes the approach of using dynamic on-bottom stability analysis as pre-requisite to achieve the requirement for stability of subsea pipeline. It was adopted for the determination of concrete coating weight requirements of a 24-inch pipeline in shallow water offshore Sabah, Malaysia, a maiden application of this approach in Malaysian waters. Citing the above as a case study, several key differences in this approach as opposed to traditional methods will be discussed such as the use of a simulated random sea-state in time-domain, advanced pipe-soil interaction modelling, realtime update of hydrodynamic forces and effects of pipeline stiffness on its overall response. The merits of a dynamic stability design approach will also be highlighted in terms of the final stabilisation requirements and its impact on installation and cost.

scholarly journals Computational fluid dynamic simulations for determination of ventricular workload in aortic arch obstructions

2013 ◽  
Vol 145 (2) ◽  
pp. 489-495.e1 ◽  
Author(s):  
Jessica S. Coogan ◽  
Frandics P. Chan ◽  
John F. LaDisa ◽  
Charles A. Taylor ◽  
Frank L. Hanley ◽  
...  
Keyword(s):  
Aortic Arch ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Dynamic Simulations

scholarly journals Energy Efficiency Analysis in Buildings using Dynamic Simulations

2017 ◽  
Vol 2 (5) ◽  
pp. 1
Author(s):  
Elena Eftimie
Keyword(s):  
Energy Efficiency ◽  
Energy Performance ◽  
Design Stage ◽  
Dynamic Simulations ◽  
Heating Systems ◽  
Use Phase ◽  
Comfort Parameters ◽  
The Impact

This paper proposes an analysis of factors that have a significant impact on energy efficiency in buildings. Thus, as a first objective proposes an analysis of the impact of rehabilitation and modernization of buildings in view of their energy performance improvement. A second followed objective consisted of the study of some production and use thermal energy systems in order to increase the thermal comfort. Based on a case study, this paper provides the opportunity for comparative analyses both among different insulation materials for buildings and among different heating systems. Determination of energy consumption for space heating and of the building comfort parameters was achieved using dynamic simulations by means of TRNSYS program; it was envisaged that the assessment of energy efficiency in buildings, the design stage or before their rehabilitation, is more economical than finding solutions in the use phase of buildings.

scholarly journals Wind Effects on a Permeable Double Skin Façade, the ENI Head Office Case Study

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 415
Author(s):  
Giulia Pomaranzi ◽  
Ombretta Bistoni ◽  
Paolo Schito ◽  
Lorenzo Rosa ◽  
Alberto Zasso
Keyword(s):  
Energy Demand ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Scale Model ◽  
Wind Loading ◽  
Wind Effects ◽  
Dynamic Simulations ◽  
Double Skin ◽  
The Impact

Currently, the energy and environmental efficiency of buildings has led to the development of cladding systems that may help to reduce the structure’s energy demand, using techniques such as the Permeable Double Skin Façade (PDSF). Given complex aerodynamic interactions, the presence of an external porous screen in addition to an inner skin may play a crucial role in the fluid-dynamic characterization of such buildings, making the definition of wind effects very complex. A new methodology for the quantitative assessment of the impact of wind-loading conditions on this particular type of cladding is presented. It is based on a combined experimental–numerical approach, essentially based on wind-tunnel tests on a rigid scale model and computational fluid dynamic simulations. A case study is proposed as an application of this methodology. Results include the design pressure values for the inner glazed façade and the permeable facade. An estimation of the flow rate across the porous skin is quantified using the numerical model.

The Effect of Stress and Warfarin on the Adrenal Gland in Relation to Spontaneous Hemorrhage, as Judged by Measurement of Adrenal Ascorbic Acid and Serum Corticosterone

1971 ◽  
Vol 26 (02) ◽  
pp. 275-288 ◽  
Author(s):  
S Chattopadhyay ◽  
D. D Johnson ◽  
G. J Millar ◽  
L. B Jaques
Keyword(s):  
Ascorbic Acid ◽  
Acid Concentration ◽  
Ascorbic Acid Concentration ◽  
Corticosterone Concentration ◽  
Serum Corticosterone ◽  
Spontaneous Hemorrhage ◽  
Combined Action ◽  
Series Of Experiments ◽  
Pituitary Adrenal Axis

SummaryRats were subjected to the following procedures: No treatment, Stressor (10% NaCl i.p.), Warfarin for 7 days, Stressor followed by Warfarin; and groups were sacrificed at intervals for assessment of spontaneous hemorrhage and of adrenal ascorbic acid concentration. There was no hemorrhage in the no treatment and stressor groups; some hemorrhage in the warfarin group; profound hemorrhage with Warfarin + Stressor. The adrenal ascorbic acid concentration was found to be lower, 8 h and again 5 days after stress, and remained lower in the warfarin + stress animals. Warfarin had no effect on adrenal ascorbic acid level.In another series of experiments in which the stress consisted of an electric current to the cage floor for 6 sec over 15 min, rats were sacrificed daily for determination of serum corticosterone concentration and occurrence of spontaneous hemorrhage. There was a statistically significant increase of serum corticosterone concentration with stress, warfarin and combined warfarin and stress treatments (P< 0.001 for all three variables). There was a significant correlation (r = 0.96 and 0.89, P< 0.01) for serum corticosterone concentration with hemorrhage score and incidence of hemorrhage in stressed rats receiving warfarin, but not in those receiving only warfarin. The results indicate an activation, rather than an exhaustion, of the pituitary-adrenal axis during the combined action of anticoagulant and stress, which results in the development of spontaneous hemorrhage.

A novel method for the determination of linting propensity of paper

TAPPI Journal ◽  
2012 ◽  
Vol 11 (10) ◽  
pp. 9-17
Author(s):  
ALESSANDRA GERLI ◽  
LEENDERT C. EIGENBROOD
Keyword(s):  
Ash Content ◽  
The Novel ◽  
Offset Printing ◽  
Excellent Correlation ◽  
End Conditions ◽  
Bottom Side ◽  
Novel Method ◽  
Total Fraction

A novel method was developed for the determination of linting propensity of paper based on printing with an IGT printability tester and image analysis of the printed strips. On average, the total fraction of the surface removed as lint during printing is 0.01%-0.1%. This value is lower than those reported in most laboratory printing tests, and more representative of commercial offset printing applications. Newsprint paper produced on a roll/blade former machine was evaluated for linting propensity using the novel method and also printed on a commercial coldset offset press. Laboratory and commercial printing results matched well, showing that linting was higher for the bottom side of paper than for the top side, and that linting could be reduced on both sides by application of a dry-strength additive. In a second case study, varying wet-end conditions were used on a hybrid former machine to produce four paper reels, with the goal of matching the low linting propensity of the paper produced on a machine with gap former configuration. We found that the retention program, by improving fiber fines retention, substantially reduced the linting propensity of the paper produced on the hybrid former machine. The papers were also printed on a commercial coldset offset press. An excellent correlation was found between the total lint area removed from the bottom side of the paper samples during laboratory printing and lint collected on halftone areas of the first upper printing unit after 45000 copies. Finally, the method was applied to determine the linting propensity of highly filled supercalendered paper produced on a hybrid former machine. In this case, the linting propensity of the bottom side of paper correlated with its ash content.

The Calculation of Turbulent Diffusion Coefficients in Aquatic Ecosystems

2019 ◽  
Vol 70 (11) ◽  
pp. 3903-3907
Author(s):  
Galina Marusic ◽  
Valeriu Panaitescu
Keyword(s):  
Transport Equation ◽  
Turbulent Diffusion ◽  
Diffusion Coefficients ◽  
Aquatic Ecosystems ◽  
Specific Area ◽  
Left Bank ◽  
The Right ◽  
Prut River

The paper deals with the issues related to the pollution of aquatic ecosystems. The influence of turbulence on the transport and dispersion of pollutants in the mentioned systems, as well as the calculation of the turbulent diffusion coefficients are studied. A case study on the determination of turbulent diffusion coefficients for some sectors of the Prut River is presented. A new method is proposed for the determination of the turbulent diffusion coefficients in the pollutant transport equation for specific sectors of a river, according to the associated number of P�clet, calculated for each specific area: the left bank, the right bank and the middle of the river.

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