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ABSTRACT In the last decade, offshore pipeline engineering extended its action field to very deep waters and continental slopes. This implied the necessity to deal with continental slopes instability and mass gravity flows. Mass gravity flows are rare and have random occurrence; therefore, considering also the technical difficulties, the direct measurement of the phenomena is practically impossible. This pushed toward the development of physical and numerical models apt to investigate the characteristics and intensity of the phenomena (Niedoroda et al., 2000a, Niedoroda et al., 2000b). In order to provide design activities with reliable predictive tools, two numerical models, one for debris flows and the other for turbidity currents, have been developed. A further diffusion model has been created to couple the above calculation method, thus allowing the complete simulation of a mass gravity flow starting as a debris flow that flowing down generates a turbidity current. INTRODUCTION In the recent years, offshore pipelines engineering has more and more dealt with continental slopes and deep waters. This brought to face new problems that were previously disregarded. Among these, the hazard of mass gravity flows could in some cases become one of the main issues having impact on costs and feasibility of projects. Mass gravity flows are essentially downslope currents of material denser than the ambient water that, due to gravity, move down continental slopes under the action of their own weight. Even if a standard classification of mass gravity flows does not exist in literature, they can be divided into two main different classes with different physical characteristics, respectively having laminar and turbulent regimes. The first class, namely debris flow, is a very dense laminar flow, up to 1800 Kg/m , with Bingham fluid characteristics
- North America > United States (0.68)
- Europe (0.68)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.48)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.40)
ABSTRACT This paper presents an experimental study on a heated jet discharged into a stagnant ambient and in a wave environment for small Richardson numbers. Improving a previous research (Di Natale and Vicinanza, 2000), extensive measurements of veloeity and temperature profiles in lateral direction have been carried out. The aim of the work was firstly to study the hehaviour of heated jet-wave interaction and secondly to work out equations to predict the variation of velocity and temperature excess correlated with some dimensionless parameters. INTRODUCTION In the last years the increase in electric power request have intensified the problem of discarding heated water rejected by the plant cooling system. When this operation is not well controlled, the receiving waterbodies (lakes, rivers, coastal areas) present induced water temperature changes, with relevant water quality modifications. The most important consequence of increased temperature is the decreased solubility of oxygen in the receiver that it is essential for many forms of aquatic life. Even though international laws give criteria on thermal discharges, fixing the temperature excess ranges, some countries still rely on it for economical reasons. Three dimensional surface heated jets discharged into a stagnant ambient have been studied experimentally by many authors (Wiegel et al., 1964; Jen et al., 1966; Hayashi and Shuto, 1967; Stefan, 1972; Pande and Rajaratnam, 1977; Wiuff, 1978) considering different outlets (circular, rectangular or square) and source Richardson numbers (small, moderate or large), Rio, where: (equation 1 shown in paper) in which g is the acceleration due to gravity, ho is the depth of outlet section, ∆ρo is the difference in mass densities of the hot water discharge ρo and the ambient ρa, and Uo is the velocity at the outlet.
- Europe (0.68)
- North America > Canada (0.28)
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
- Energy > Oil & Gas > Upstream (0.69)
- Water & Waste Management > Water Management (0.54)
ABSTRACT The authors [Tomita, 1999] El1 have shown that the temperature distribution near the plate can be estimated by calculating the heat flow of non-combustion impinging jet instead of the impinging combustion jet flame. For 2-dimensional impinging combustion jet flame, close agreement between measured and calculated temperature near the plate surface has been verified when the highest temperature within the flame, the velocity of mixed gas at the upstream side of the nozzle and the width of the actual combustion flame are employed as temperature, velocity and width of the impinging jet at the exit. The gas flame used in the actual line heating process is 3-dimensional. It is needed to measure the transient temperature distribution of 3-dimensional flame near the plate surface accurately. In this report, for 3-dimensional axial symmetry jet, the transient temperature distribution near the plate surface in the spot heating is measured in detail by a high - performance L.I.E measurement system. The temperature in this case is also calculated by the numerical method proposed in the previous paper. The calculated and experimental results are compared, and the tendency of the temperature distribution is discussed. 1. INTRODUCTION The shell plates of ships are composed of complicated 3-dimensional curved structures, which are formed using the line heating by the skilled workers. In recent years, the number of skilled workers has decreased and it becomes gradually difficult to succeed to the engineering skill of line heating. It is strongly desired to analyze the line heating process and to make automation of the line heating procedure. Analysis of the physical phenomena associated with the line heating is divided into the following two;heat transfer from impinging combustion jet flame to steel plate and heat conduction in the steel plate and thermal elasto-plastic deformation of the steel plate.
- Research Report > New Finding (0.50)
- Research Report > Experimental Study (0.40)