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5. Finite element model for the assessment of the mesh resistance to opening of fishing nets

Author

Morvan, Barthelemy, Priour, Daniel, Guede, Zakoua, Bles, G., Morvan, Barthelemy, Priour, Daniel, Guede, Zakoua, and Bles, G.

Abstract

The evaluation of the mesh resistance to opening of fishing nets is an important issue in assessing the selectivity of trawls by numerical methods. Sala et al. (2007) proposed a method using a relatively expensive experimental device ensuring the 2D deformation of net sample. De la Prada and Gonzales (2015) proposed a simple uni-axial experimental set-up, which stretches a sample in the transverse direction of the meshes while leaving free its deformation in the normal direction. Both authors (Sala and De la Prada) assumed that the deformation is uniform in the sample. The present study aims at developing a finite element model taking into account the mesh resistance to opening of nets, allowing the simulation of non-uniform deformation. Mechanical experimental tests were performed on a range of fishing nets commonly used in trawl codends, with varied dimensions of the sample and loading. The proposed model is in good agreement with these experimental results, and it captures the heterogeneous deformation of the netting samples. Consequently, a procedure for the assessment of the mesh resistance to opening using this model and a simple non-expensive experimental setup are proposed.

Published
2016
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6. Improvement ocean wave spectra estimation using the temporal structure of wave systems

Author

Kpogo Nuwoklo, Komlan Agbéko, Ailliot, Pierre, Olagnon, Michel, Guede, Zakoua, Arnault, Sabine, Kpogo Nuwoklo, Komlan Agbéko, Ailliot, Pierre, Olagnon, Michel, Guede, Zakoua, and Arnault, Sabine

Abstract

Sea states are usually the combination of several time-evolving wave systems whereas the classical spectral estimation methods assume stationarity. A method that adapts to the dynamical evolution of the spectral components is proposed to improve both omnidirectional and directional sea wave spectral estimations. In this method, periodograms are computed for each sea state as in the conventional methods, and rather than only smoothing individual periodograms, the overall time-history of periodograms are simultaneously smoothed in frequency and time dimensions. Since a simple two dimensional averaging would not be appropriate because the temporal evolution of the wave systems reflects typical non-stationary behaviors, we use either kriging or adaptive 2D kernel density estimators that allow the taking care of the spectral component frequency-time evolutions. The method is successfully validated on sequences of spectra typical of sea-state conditions in West Africa. The comparison with the simple 2D averaging method and individual periodogram smoothing method shows that the proposed method gives higher effective numbers of degrees of freedom, better estimates of the spectral shape and reliable spectral moments. The method also provides a tool for sea wave spectra interpolation and may thus be used to fill in missing values and improve wave systems tracking for storm identification purposes.

Published
2015
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7. Statistical processing of West Africa wave directional spectra time-series into a climatology of swell events

Author

Olagnon, Michel, Kpogo-nuwoklo, Komlan, Guede, Zakoua, Olagnon, Michel, Kpogo-nuwoklo, Komlan, and Guede, Zakoua

Abstract

Accurate estimation of long-term sea conditions is a major issue for the design of coastal and offshore structures, for the preparation of marine operations, and for other applications such as marine energy, and coastal erosion. It requires, on the one hand, proper parametric models of the sea state spectra and the statistics of the parameters, and on the other hand, representations of their time evolutions. In some locations such as West Africa, sea conditions are complex with wave spectra showing many well separated peaks corresponding to several swells and wind sea. The present study focuses on swell at a West Africa location. First, a time-consistent triangular model is assessed for the spectral shapes of the swell components. Then statistical analysis of the time-histories of those components is carried out in connection with the storms at their source. A model that is triangular for Hs and a linear trend for period and direction is found appropriate for the time-histories of those parameters within a storm event. Using the empirical distributions of the characteristics of the individual events parameters, it is shown that arbitrary long durations of the swell climate may be reconstructed preserving the main observed statistical properties.

Published
2014
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8. Validation of the Iterative Component Addition (ICA) formulas for the damage assessment of multimodal loading spectra

Author

Guede, Zakoua, Olagnon, Michel, and Pineau, Hélène

Abstract

The purpose of this study is to validate the use of the so-called Iterative Component Addition (ICA) formulas for the assessment of fatigue damage of marine structures subjected to complex (multimodal) wave loading conditions, as prevail in West Africa areas where the sea states are usually described as combinations of three wave systems (e.g. main swell, secondary swell and wind sea). In this context, operators specifications require to consider a very large set of fatigue loading cases, which lead to excessive computation times if the conventional procedure is used for fatigue assessment. The use of the ICA formulas is expected to simplify the evaluation of the damage and to allow a drastic reduction of computation time, keeping a slight level of conservatism. The present work intends to validate those formulas on an industrial application. One is especially interested in the accuracy of the ICA-based approach for fatigue damage assessment, the ease of use of this approach and the computation times it involves. The scope of the study is limited for simplicity purposes to cases where the structural dynamic response is linear. Its actual industrial application deals with the assessment of the fatigue damage induced by the vertical bending moment of an FPSO hull girder subjected to wave loading in a West Africa area. In this report, we define the occurrence probabilities of all the fatigue loading cases to be applied as required by the operator specifications. Then, to validate the use of the ICA formula, the fatigue damage is estimated according to two main approaches. The first one, which serves as a reference solution, uses a conventional method and computes the damages of the sea states from the metocean data base only. The other one uses ICA formulas and compute the damages of all possible sea states defined by the operator specifications. For this last approach, a full application of ICA formulas based on a partition of wave systems response spectra is also carried out and some analytical formulas for the damage of unimodal spectra are set up. Between both approaches, some intermediate computations are made to estimate the individual effects of the approximations introduced. The occurrence probabilities of the fatigue loading cases derived from the metocean specifications exhibit some significant discrepancies from the statistics of the metocean database. Namely, they provide a lower significant height for the sea states with only a main swell and a larger one for sea states with the three wave systems. As to the application of ICA formulas, it is shown to provide accurate results. We can note that the ICA results are close to the reference solution and that most of the conservatism comes from the discretization defined for the statistical analysis. Moreover, the implementation of the ICA-based approach is simple on the actual industrial application. With appropriate change of programming language and optimization of the procedure, dramatic improvements have been obtained in the computation time, with nearly 2 million combinations of sea states processed in less than one minute. Two main difficulties were encountered in this study. The first one concerns the two-slopes S-N curve, as a combined spectrum may have cycles amplitudes that are larger than the stress thres hold of the S-N curve while its individual components do not. That was solved by providing a method to estimate two-slope damage from the two single-slope ones. The second difficulty stems from the discrepancies observed between the statistics on the metocean database and the sea states probabilistic model derived from the metocean specifications, which raises some questions on the construction of fully relevant metocean specifications. Though some progress was made, that second difficulty is not yet satisfactorily solved. However, this study appears as a mighty step in the development of a global framework for fatigue damage assessment under multimodal loading conditions with the ICA formulas.

Published
2009

9. Statistical Analysis of Low Frequency Motions of Floating Bodies in Shallow Water

Author

Prevosto, Marc, Le Louarne, Jean-franois, and Guede, Zakoua

Subjects
second order wave loading, shallow water, extreme response, crossing rate, low frequency motion
Abstract

In this study we discuss various methods to assess the statistics of extreme response of a floating structure subjected to random waves. This issue is of great importance in the case of low frequency motion of floating bodies in shallow water. Those methods are based on the evaluation of the level crossing rate, which is easily related to the extreme value statistics for stationary random processes and large levels. Four main methods are considered, namely the Rice formula with either a Gaussian assumption or an approximation of the joint distribution of the response and its first derivative by a projection method; the Breitung's formula; the Hagberg's approaches using either an asymptotic expansion or a Monte-Carlo integration and finally the time domain simulation which serves as the reference solution. All these methods are applied to the surge motion of a floating body subjected to unidirectional waves. In that case, the Rice formula under the Gaussian assumption strongly underestimates the level crossing rate. The other methods are more or less accurate compared to the time domain simulation, but Hagberg's Monte-Carlo integration is shown to give the best approximation.

Published
2007

10. Detection potential of the KM3NeT detector for high-energy neutrinos from the Fermi bubbles

Author

Adrian-martinez, S., Ageron, M., Aguilar, J. A., Aharonian, F., Aiello, S., Albert, A., Alexandri, M., Ameli, F., Anassontzis, E. G., Anghinolfi, M., Anton, G., Anvar, S., Ardid, M., Jesus, A. Assis, Aubert, J-j, Bakke, R., Ball, A. E., Barbarino, G., Barbarito, E., Barbato, F., Baret, B., De Bel, M., Belias, A., Bellou, N., Berbee, E., Berkien, A., Bersani, A., Bertin, V., Beurthey, S., Biagi, S., Bigongiari, C., Bigourdan, Benoit, Billault, M., De Boer, R., Rookhuizen, H. Boer, Bonori, M., Borghini, M., Bou-cabo, H. M., Bouhadef, B., Bourlis, G., Bouwhuis, M., Bradbury, S., Brown, A., Bruni, F., Brunner, J., Brunoldi, M., Busto, J., Cacopardo, G., Caillat, L., Diaz-aldagalan, D. Calvo, Calzas, A., Canals, M., Capone, A., Carr, J., Castorina, E., Cecchini, S., Ceres, A., Cereseto, R., Chaleil, Th., Chateau, F., Chiarusi, T., Choqueuse, Dominique, Christopoulou, P. E., Chronis, G., Ciaffoni, O., Circella, M., Cocimano, R., Cohen, F., Colijn, F., Coniglione, R., Cordelli, M., Cosquer, A., Costa, M., Coyle, P., Craig, J., Creusot, A., Curtil, C., D'Amico, A., Damy, Gilbert, De Asmundis, R., De Bonis, G., Decock, G., Decowski, P., Delagnes, E., De Rosa, G., Distefano, C., Donzaud, C., Dornic, D., Dorosti-hasankiadeh, Q., Drogou, Jean-francois, Drouhin, D., Druillole, F., Drury, L., Durand, D, Durand, G.a., Eberl, T., Emanuele, U., Enzenhoefer, A., Ernenwein, J-p, Escoffier, S., Espinosa, V., Etiope, G., Favali, P., Felea, D., Ferri, M., Ferry, S., Flaminio, V., Folger, F., Fotiou, A., Fritsch, U., Gajanana, D., Garaguso, R., Gasparini, G. P., Gasparoni, F., Gautard, V., Gensolen, F., Geyer, K., Giacomelli, G., Gialas, I., Giordano, V., Giraud, J., Gizani, N., Gleixner, A., Gojak, Carl, Gomez-gonzalez, J. P., Graf, K., Grasso, D., Grimaldi, A., Groenewegen, R., Guede, Zakoua, Guillard, G., Guilloux, F., Habel, R., Hallewell, G., Van Haren, H., Van Heerwaarden, J., Heijboer, A., Heine, E., Hernandez-rey, J. J., Herold, B., Hillebrand, T., Van De Hoek, M., Hogenbirk, J., Hoessl, J., Hsu, C. C., Imbesi, M., Jamieson, A., Jansweijer, P., De Jong, M., Jouvenot, F., Kadler, M., Kalantar-nayestanaki, N., Kalekin, O., Kappes, A., Karolak, M., Katz, U. F., Kavatsyuk, O., Keller, P., Kiskiras, Y., Klein, R., Kok, H., Kontoyiannis, H., Kooijman, P., Koopstra, J., Kopper, C., Korporaal, A., Koske, P., Kouchner, A., Koutsoukos, S., Kreykenbohm, I., Kulikovskiy, V., Laan, M., La Fratta, C., Lagier, P., Lahmann, R., Lamare, P., Larosa, G., Lattuada, D., Leisos, A., Lenis, D., Leonora, E., Le Provost, H., Lim, G., Llorens, C. D., Lloret, J., Loehner, H., Lo Presti, D., Lotrus, P., Louis, F., Lucarelli, F., Lykousis, V., Malyshev, D., Mangano, S., Marcoulaki, E. C., Margiotta, A., Marinaro, G., Marinelli, A., Maris, O., Markopoulos, E., Markou, C., Martinez-mora, J. A., Martini, A., Marvaldi, Jean, Masullo, R., Maurin, G., Migliozzi, P., Migneco, E., Minutoli, S., Miraglia, A., Mollo, C. M., Mongelli, M., Monmarthe, E., Morganti, M., Mos, S., Motz, H., Moudden, Y., Mul, G., Musico, P., Musumeci, M., Naumann, Ch, Neff, M., Nicolaou, C., Orlando, A., Palioselitis, D., Papageorgiou, K., Papaikonomou, A., Papaleo, R., Papazoglou, I. A., Pavalas, G. E., Peek, H. Z., Perkin, J., Piattelli, P., Popa, V., Pradier, T., Presani, E., Priede, I. G., Psallidas, A., Rabouille, C, Racca, C., Radu, A., Randazzo, N., Rapidis, P. A., Razis, P., Real, D., Reed, C., Reito, S., Resvanis, L. K., Riccobene, G., Richter, R., Roensch, K., Rolin, Jean-francois, Rose, J, Roux, J, Rovelli, A., Russo, A., Russo, G. V., Salesa, F., Samtleben, D., Sapienza, P., Schmelling, J-w, Schmid, J., Schnabel, J., Schroeder, K., Schuller, J-p, Schussler, F., Sciliberto, D., Sedita, M., Seitz, T., Shanidze, R., Simeone, F., Siotis, I., Sipala, V., Sollima, C., Sparnocchia, S., Spies, A., Spurio, M., Staller, T., Stavrakakis, S., Stavropoulos, G., Steijger, J., Stolarczyk, Th., Stransky, D., Taiuti, M., Taylor, A., Thompson, L., Timmer, P., Tonoiu, D., Toscano, S., Touramanis, C., Trasatti, L., Traverso, P., Trovato, A., Tsirigotis, A., Tzamarias, S., Tzamariudaki, E., Urbano, F., Vallage, B., Van Elewyck, V., Vannoni, G., Vecchi, M., Vernin, P., Viola, S., Vivolo, D., Wagner, S., Werneke, P., White, R. J., Wijnker, G., Wilms, J., De Wolf, E., Yepes, H., Zhukov, V., Zonca, E., Zornoza, J. D., Zuniga, J., Adrian-martinez, S., Ageron, M., Aguilar, J. A., Aharonian, F., Aiello, S., Albert, A., Alexandri, M., Ameli, F., Anassontzis, E. G., Anghinolfi, M., Anton, G., Anvar, S., Ardid, M., Jesus, A. Assis, Aubert, J-j, Bakke, R., Ball, A. E., Barbarino, G., Barbarito, E., Barbato, F., Baret, B., De Bel, M., Belias, A., Bellou, N., Berbee, E., Berkien, A., Bersani, A., Bertin, V., Beurthey, S., Biagi, S., Bigongiari, C., Bigourdan, Benoit, Billault, M., De Boer, R., Rookhuizen, H. Boer, Bonori, M., Borghini, M., Bou-cabo, H. M., Bouhadef, B., Bourlis, G., Bouwhuis, M., Bradbury, S., Brown, A., Bruni, F., Brunner, J., Brunoldi, M., Busto, J., Cacopardo, G., Caillat, L., Diaz-aldagalan, D. Calvo, Calzas, A., Canals, M., Capone, A., Carr, J., Castorina, E., Cecchini, S., Ceres, A., Cereseto, R., Chaleil, Th., Chateau, F., Chiarusi, T., Choqueuse, Dominique, Christopoulou, P. E., Chronis, G., Ciaffoni, O., Circella, M., Cocimano, R., Cohen, F., Colijn, F., Coniglione, R., Cordelli, M., Cosquer, A., Costa, M., Coyle, P., Craig, J., Creusot, A., Curtil, C., D'Amico, A., Damy, Gilbert, De Asmundis, R., De Bonis, G., Decock, G., Decowski, P., Delagnes, E., De Rosa, G., Distefano, C., Donzaud, C., Dornic, D., Dorosti-hasankiadeh, Q., Drogou, Jean-francois, Drouhin, D., Druillole, F., Drury, L., Durand, D, Durand, G.a., Eberl, T., Emanuele, U., Enzenhoefer, A., Ernenwein, J-p, Escoffier, S., Espinosa, V., Etiope, G., Favali, P., Felea, D., Ferri, M., Ferry, S., Flaminio, V., Folger, F., Fotiou, A., Fritsch, U., Gajanana, D., Garaguso, R., Gasparini, G. P., Gasparoni, F., Gautard, V., Gensolen, F., Geyer, K., Giacomelli, G., Gialas, I., Giordano, V., Giraud, J., Gizani, N., Gleixner, A., Gojak, Carl, Gomez-gonzalez, J. P., Graf, K., Grasso, D., Grimaldi, A., Groenewegen, R., Guede, Zakoua, Guillard, G., Guilloux, F., Habel, R., Hallewell, G., Van Haren, H., Van Heerwaarden, J., Heijboer, A., Heine, E., Hernandez-rey, J. J., Herold, B., Hillebrand, T., Van De Hoek, M., Hogenbirk, J., Hoessl, J., Hsu, C. C., Imbesi, M., Jamieson, A., Jansweijer, P., De Jong, M., Jouvenot, F., Kadler, M., Kalantar-nayestanaki, N., Kalekin, O., Kappes, A., Karolak, M., Katz, U. F., Kavatsyuk, O., Keller, P., Kiskiras, Y., Klein, R., Kok, H., Kontoyiannis, H., Kooijman, P., Koopstra, J., Kopper, C., Korporaal, A., Koske, P., Kouchner, A., Koutsoukos, S., Kreykenbohm, I., Kulikovskiy, V., Laan, M., La Fratta, C., Lagier, P., Lahmann, R., Lamare, P., Larosa, G., Lattuada, D., Leisos, A., Lenis, D., Leonora, E., Le Provost, H., Lim, G., Llorens, C. D., Lloret, J., Loehner, H., Lo Presti, D., Lotrus, P., Louis, F., Lucarelli, F., Lykousis, V., Malyshev, D., Mangano, S., Marcoulaki, E. C., Margiotta, A., Marinaro, G., Marinelli, A., Maris, O., Markopoulos, E., Markou, C., Martinez-mora, J. A., Martini, A., Marvaldi, Jean, Masullo, R., Maurin, G., Migliozzi, P., Migneco, E., Minutoli, S., Miraglia, A., Mollo, C. M., Mongelli, M., Monmarthe, E., Morganti, M., Mos, S., Motz, H., Moudden, Y., Mul, G., Musico, P., Musumeci, M., Naumann, Ch, Neff, M., Nicolaou, C., Orlando, A., Palioselitis, D., Papageorgiou, K., Papaikonomou, A., Papaleo, R., Papazoglou, I. A., Pavalas, G. E., Peek, H. Z., Perkin, J., Piattelli, P., Popa, V., Pradier, T., Presani, E., Priede, I. G., Psallidas, A., Rabouille, C, Racca, C., Radu, A., Randazzo, N., Rapidis, P. A., Razis, P., Real, D., Reed, C., Reito, S., Resvanis, L. K., Riccobene, G., Richter, R., Roensch, K., Rolin, Jean-francois, Rose, J, Roux, J, Rovelli, A., Russo, A., Russo, G. V., Salesa, F., Samtleben, D., Sapienza, P., Schmelling, J-w, Schmid, J., Schnabel, J., Schroeder, K., Schuller, J-p, Schussler, F., Sciliberto, D., Sedita, M., Seitz, T., Shanidze, R., Simeone, F., Siotis, I., Sipala, V., Sollima, C., Sparnocchia, S., Spies, A., Spurio, M., Staller, T., Stavrakakis, S., Stavropoulos, G., Steijger, J., Stolarczyk, Th., Stransky, D., Taiuti, M., Taylor, A., Thompson, L., Timmer, P., Tonoiu, D., Toscano, S., Touramanis, C., Trasatti, L., Traverso, P., Trovato, A., Tsirigotis, A., Tzamarias, S., Tzamariudaki, E., Urbano, F., Vallage, B., Van Elewyck, V., Vannoni, G., Vecchi, M., Vernin, P., Viola, S., Vivolo, D., Wagner, S., Werneke, P., White, R. J., Wijnker, G., Wilms, J., De Wolf, E., Yepes, H., Zhukov, V., Zonca, E., Zornoza, J. D., and Zuniga, J.

Abstract

A recent analysis of the Fermi Large Area Telescope data provided evidence for a high-intensity emission of high-energy gamma rays with a E-2 spectrum from two large areas, spanning 50 above and below the Galactic centre (the "Fermi bubbles"). A hadronic mechanism was proposed for this gamma-ray emission making the Fermi bubbles promising source candidates of high-energy neutrino emission. In this work Monte Carlo simulations regarding the detectability of high-energy neutrinos from the Fermi bubbles with the future multi-km(3) neutrino telescope KM3NeT in the Mediterranean Sea are presented. Under the hypothesis that the gamma-ray emission is completely due to hadronic processes, the results indicate that neutrinos from the bubbles could be discovered in about one year of operation, for a neutrino spectrum with a cutoff at 100 TeV and a detector with about 6 km(3) of instrumented volume. The effect of a possible lower cutoff is also considered. (C) 2012 Elsevier B.V. All rights reserved.

Published
2013
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11. Life-time reliability based assessment of structures submitted to thermal fatigue

Author

Guede, Zakoua, Suldret, B, Lemaire, M, Guede, Zakoua, Suldret, B, and Lemaire, M

Abstract

A probabilistic approach of the current thermal fatigue design of nuclear components is set up. It aims at incorporating all kinds of uncertainties that affect the thermal fatigue behaviour. This approach is based on the theory of structural reliability. Two dual approaches of reliability analysis for the thermal fatigue are defined, respectively, in the time domain and in the frequency domain. Beside the probability of failure calculation, the sensitivity of the reliability index to each random variable is estimated. The proposed method is applied to a pipe submitted to thermal loading due to water flow. Both high cycles fatigue (HCF) and low cycles fatigue (LCF) regimes are investigated. The results show that it is possible to perform a complete reliability analysis to compute the failure probability. It is observed that the scatter of fatigue data and the heat transfer coefficient are the most important variables in thermal fatigue reliability. (C) 2006 Elsevier Ltd. All rights reserved.

Published
2007
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