Efforts sur une conduite sous-marine en zone côtière

Abstract

Nous avons mesuré les efforts exercés sur un cylindre horizontal près du fond par l'action de la houle se propageant vers la côte. Celle-ci est modélisée par une plage de pente constante qui va induire une déformation progressive de la houle. Les efforts mesurés sont influencés par la hauteur et la dissymétrie de la houle ainsi que par l'écartement du cylindre par rapport au fond. Une modélisation de l'effort en ligne par la formulation de Morison est également menée et les coefficients hydrodynamiques correspondants sont présentés. Nous montrons ainsi que l'emploi d'un modèle simplifié de la vitesse horizontale, prenant en compte la dissymétrie de l'écoulement, permet d'étendre la validité du modèle de Morison aux houles pré-déferlantes. Abstract We have measured wave forces on a horizontal cylinder near the seabed in the coastal zone. A beach of constant slope induces the progressive wave deformation. The measured forces are influenced by the wave heig..'1t, the wave asymmetry and the distance between the cylinder and the bottom. Modelling of the in-line force using the Morison formulation is also performed and the resulting hydrodynamic coefficients are presented. We show that the use of a horizontal velocity model taking into account the flow asymmetry enables to extend the validity of the Morison model to shoaling waves.

On-Bottom Stability Analysis of Cylinders under Tsunami-Like Solitary Waves

“…Comparing the values of C D , the authors observed an overall good agreement with the non-linear fit carried out by Bryndum et al [14] and a slight underestimation of the present experiments as compared to those performed by Sarpkaya and Rajabi [12], Neill and Hinwood [15], and Chevalier et al [16], even if few values of C D are present in the above works. With regard to C MH , Figure 9b shows the comparison between the current dataset and the values obtained by Sarpkaya and Rajabi [12], Bryndum et al [14], Neill and Hinwood [15], Chevalier et al [16], and Aristodemo et al [19]. The present values of C MH are lower than those calculated by Sarpkaya and Rajabi [12], Bryndum et al [14] and, in particular, by Aristodemo et al [19], while they are slightly higher than those obtained by Neill and Hinwood [15] and Chevalier et al [16].…”

“…A more scattered range for KC compared to A/d can be observed since the Keulegan-Carpenter number depends on the apparent wave period which suffers from small oscillations near the free surface due to the appearance of spurious trailing waves. Figure 9a shows the present values of C D as a function of KC plotted against the experiments conducted by Sarpkaya and Rajabi [12], and Bryndum et al [14] through a non-linear fit of the laboratory data (Neill and Hinwood [15] and Chevalier et al [16]). Comparing the values of C D , the authors observed an overall good agreement with the non-linear fit carried out by Bryndum et al [14] and a slight underestimation of the present experiments as compared to those performed by Sarpkaya and Rajabi [12], Neill and Hinwood [15], and Chevalier et al [16], even if few values of C D are present in the above works.…”

“…Figure 9a shows the present values of C D as a function of KC plotted against the experiments conducted by Sarpkaya and Rajabi [12], and Bryndum et al [14] through a non-linear fit of the laboratory data (Neill and Hinwood [15] and Chevalier et al [16]). Comparing the values of C D , the authors observed an overall good agreement with the non-linear fit carried out by Bryndum et al [14] and a slight underestimation of the present experiments as compared to those performed by Sarpkaya and Rajabi [12], Neill and Hinwood [15], and Chevalier et al [16], even if few values of C D are present in the above works. With regard to C MH , Figure 9b shows the comparison between the current dataset and the values obtained by Sarpkaya and Rajabi [12], Bryndum et al [14], Neill and Hinwood [15], Chevalier et al [16], and Aristodemo et al [19].…”

“…In contrast, for horizontal cylinders under the action of currents or regular and random waves, numerous studies have researched this kind of wave-structure interaction process, adopting different degrees of external roughness of the cylinder and of the sea bed (for a comprehensive review see [8,9]). For bottom-mounted cylinders under the above kind of incident flows, values of hydrodynamic coefficients in Morison-type equations (e.g., [10]) were deduced from field tests [11] as well as smalland large-scale laboratory experiments, and for wide ranges of Keulegan-Carpenter (KC) and Reynolds (Re) numbers [12][13][14][15][16][17][18][19]. More complex models as compared to Morison-type ones and dealing with an improved description of flow-cylinder interaction processes have been also developed [20,21].…”

New model to determine forces at on-bottom slender pipelines

“…For bottom-mounted submarine pipelines, values of Morison hydrodynamic coefficients have been evaluated for different wave and current conditions based on field investigations (Grace and Zee, 1981;Lambrakos et al, 1987) and small and large scale laboratory experiments (Sarpkaya and Rajabi, 1980;Norwegian Hydrodynamic Laboratories, 1985;Cheong et al, 1987;Veritas Offshore Technology, 1988;Bryndum et al, 1983Bryndum et al, , 1992Benassai, 1993;Neill and Hinwood, 1998;Chevalier et al, 2000;Tomasicchio et al, 2007). Some authors (Sarpkaya, 1981;Bearman et al, 1984;Sarpkaya and Wilson, 1984;Chaplin and Subbiah, 1997;Sarpkaya, 2001) proposed, for limited KC and Re ranges, additional terms in the basic Morison equations in order to minimize the differences between the experimental and the simulated forces.…”