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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (83,371 recursos)
E-prints UPC cobreix dues finalitats: per una banda, és el dipòsit institucional de la UPC que recull els articles de revista, les comunicacions de congrés i els reports de recerca generats en les activitats de recerca del personal docent i investigador de la universitat; per l'altra, és una eina que permet accelerar la producció científica, allotjant versions de documents prèvies a la publicació en una revista o a les actes d’un congrés.

Articles de revista

Mostrando recursos 1 - 20 de 164

1. Onshore sandbar migration in the surf zone: new insights into the wave-induced sediment transport mechanisms - Fernández Mora, María de los Ángeles; Calvete Manrique, Daniel; Falqués Serra, Albert; de Swart, Huib E.
We present a novel process-based morphodynamic model, which includes transport processes due to both velocity and acceleration skewness and a new formulation for intrawave motions, that successfully simulates observations of onshore sandbar migration. Results confirm findings of previous studies, in which each process was considered separately and in which sediment transport was computed from the observed water motion. However, our results indicate that accounting for the joint action of both velocity and acceleration skewnesses causes major improvement of the modeled onshore bar migration and is essential to accurately model the evolution of the entire cross-shore bottom profile, when compared with...

2. Dynamics of axially localized states in Taylor-Couette flows - López Alonso, José Manuel; Marqués Truyol, Francisco
We present numerical simulations of the flow confined in a wide gap Taylor-Couette system, with a rotating inner cylinder and variable length-to-gap aspect ratio. A complex experimental bifurcation scenario differing from the classical Ruelle-Takens route to chaos has been experimentally reported in this geometry. The wavy vortex flow becomes quasiperiodic due to an axisymmetric very low frequency mode. This mode plays a key role in the dynamics of the system, leading to the occurrence of chaos via a period-doubling scenario. Further increasing the rotation of the inner cylinder results in the appearance of a new flow pattern which is characterized...

3. Dynamics of shoreface-connected and inactive sand ridges on a shelf, Part 2: The role of sea level rise and associated changes in shelf geometry - Nnafie, Abdel; de Swart, Huib E.; Calvete Manrique, Daniel; Garnier, Roland Charles
Many inner continental shelves are characterized by the presence of large rhythmic bedforms, such as shoreface-connected ridges and the more offshore located sand ridges, which have heights of several meters and are spaced several kilometers apart. This study focuses on explaining the observed orientation difference between shoreface-connected sand ridges and the more offshore located ridges. For this, an existing idealized morphodynamic model is used, but modified such that sea level rise simultaneously induces a steepening of the inner shelf and a retreating shoreface. Different settings (rate of sea level rise; landward depth of the inner shelf) are systematically explored. For...

4. Snow bands over the Gulf of Finland in wintertime - Mazón Bueso, Jordi; Niemelä, Sami; Pino González, David; Savijärvi, Hannu; Vihma, Timo
Large shore-parallel, quasi-stationary snow bands are occasionally observed over the Gulf of Finland during wintertime when the sea is not frozen. On the basis of Weather Research and Forecasting mesoscale model experiments and radar observations of snow bands formed in January 2006 and February 2012, we show that their dynamics share common characteristics: (1) the sea gulf that produces the known lake effect, (2) cold easterly large-scale flow along the gulf and (3) a cold local flow from the two near and opposite coastlines of Estonia and Finland in the form of two land-breeze cells which collide offshore. The associated...

5. Historical, hydraulic, hydrological and meteorological reconstruction of 1874 Santa Tecla flash floods in Catalonia (NE Iberian Peninsula) - Ruiz Bellet, Josep Lluís; Balasch Solanes, Josep Carles; Tuset Mestre, Jordi; Barriendos Valve, Mariano; Mazón Bueso, Jordi; Pino González, David
A multidisciplinary methodology for historical floods reconstruction was applied to 1874 Santa Tecla floods occurred in Catalonia (NE Iberian Peninsula), using both historical information and meteorological data from 20th Century Reanalysis. The results confirmed the exceptionality of the event: the highest modeled specific peak flow was around 14.6 m3 s1 km2 in a 100 km2 catchment and all the modeled total rainfall values were above 110 mm in about six hours, with maximum intensities around 60 mm min1 . The peak-flows peak flows’ return periods were about 260 years and the rainfalls periods were between 250 and 500 years. The meteorological cause of the rainstorms was the flash...

6. Simulació numèrica de fronts costaners nocturns a la conca de la Mediterrània - Mazón Bueso, Jordi; Pino González, David
During the night, inland air cools faster than the air near the coast or above the water bodies (in our case the Mediterranean Sea). Due to this temperature difference, the colder air moves offshore driven by drainage wind following the river valleys, streams and down slope the mountain ranges. A coastal front is formed when the colder air mass interacts with the warm and moist maritime air mass. This interaction enhances the vertical movement of the warm air mass that cools and may condensate forming clouds and in some cases producing precipitation. This nocturnal coastal front formation has been analyzed...

7. Role of the nocturnal coastal-front depth on cloud formation and precipitation in the Mediterranean basin - Mazón Bueso, Jordi; Pino González, David
Ten nocturnal coastal front events formed in the Mediterranean basin are simulated and analyzed, focusing on the coastal-front depth by using version 3.3 of the WRF-ARW mesoscale model. During the night the inland air cools faster than the air over the Mediterranean Sea. Consequently, this colder air may move offshore, forming a coastal front when interacting with the warmer and moister maritime air mass, which is lifted over the colder air. Then clouds and precipitation may occur. In this mechanism the depth of the cold air mass (H) plays an important role in theformation of clouds and precipitation. Stratiform clouds...

8. Transitions between symmetric and nonsymmetric regimes in binary-mixture convection - Meca Alvarez, Esteban; Mercader Calvo, María Isabel; Ramírez de la Piscina Millán, Laureano
We present here a comprehensive picture of the different bifurcations found for small to moderate Rayleigh number in binary-mixture convection with lateral heating and negative separation ratio (S). The present work connects the symmetric regime found for pure fluid (S=0)[Mercader et al 2005] with the fundamentally nonsymmetric regime found for S=-1 [Meca et al 2004a-2004b]. We give a global context as well as an interpretation for the different associations of bifurcations found, and in particular we interpret an association of codimension-two bifurcations in terms of a higher codimension bifurcation never found, to our knowledge, in the study of an extended system.

9. Super and massive AGB stars - III. nucleosynthesis in metal-poor and very metal-poor stars - Z = 0.001 and 0.0001 - Doherty, Carolyn L.; Gil Pons, Pilar; Lau, Herbert B.; Lattanzio, John C.; Siess, Lionel; Campbell, Simon W
We present a new grid of stellar models and nucleosynthetic yields for super-AGB stars with metallicities Z = 0.001 and 0.0001, applicable for use within galactic chemical evolution models. Contrary to more metal-rich stars where hot bottom burning is the main driver of the surface composition, in these lower metallicity models the effect of third dredge-up and corrosive second dredge-up also have a strong impact on the yields. These metal-poor and very metal-poor super-AGB stars create large amounts of 4He, 13C, 14N and 27Al as well as the heavy magnesium isotopes 25Mg and 26Mg. There is a transition in yield...

10. Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings - Pietersen, Henk; Vilà Guerau de Arellano, Jordi; Augustin, P; van de Boer, Anneke; de Coster, Olivier; Delbarre, Hervé; Durand, Pierre; Fourmentin, M; Gioli, Beniamino; Hartogensis, Oskar; Lohou, Fabienne; Lothon, Marie; Ouwersloot, Huug; Pino González, David; Reuder, Joachim
We study the influence of the large-scale at- mospheric contribution to the dynamics of the convective boundary layer (CBL) in a situation observed during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. We employ two modeling ap- proaches, the mixed-layer theory and large-eddy simulation (LES), with a complete data set of surface and upper-air at- mospheric observations, to quantify the contributions of the advection of heat and moisture, and subsidence. We find that by only taking surface and entrainment fluxes into ac- count, the boundary-layer height is overestimated by 70 %. Constrained by surface and upper-air observations, we infer the large-scale vertical motions and horizontal advection of heat and moisture....

11. Spontaneous generation of a swirling plume in a stratified ambient - Marqués Truyol, Francisco; López Moscat, Juan Manuel
The transition from laminar to complex spatio-temporal dynamics of plumes due to a localized buoyancy source is studied numerically. Several experiments have reported that this transition is sensitive to external perturbations. Therefore, a well-controlled set-up has been chosen for our numerical study, consisting of a localized heat source at the bottom of an enclosed cylinder whose sidewall is maintained at a fixed temperature which varies linearly up the wall. Restricting the dynamics to the axisymmetric subspace, the first instability is to a puffing state. However, for smaller Grashof numbers, the plume becomes unstable to three-dimensional perturbations and a swirling plume...

12. Mesoscale numerical simulations of heavy nocturnal rainbands associated with coastal fronts in the Mediterranean Basin - Mazón Bueso, Jordi; Pino González, David
Three offshore rainbands associated with nocturnal coastal fronts formed near the Israeli coastline, the Gulf of Genoa and on the northeastern coast of the Iberian Peninsula, are simulated using version 3.3 of the WRF-ARW mesoscale model in order to study the dynamics of the atmosphere in each case.; The simulations show coastal fronts producing relatively high (in comparison with some other similar rainbands) 1 and 10 h accumulated precipitations that formed in the Mediterranean Basin. According to these simulations, the coastal fronts that formed near the Israeli coastline and over the Gulf of Genoa are quasi-stationary, while the one that...

13. Modeling large scale shoreline sand waves under oblique wave incidence - Van den Berg, Niels; Falqués Serra, Albert; Ribas Prats, Francesca
Postprint (published version)

14. On the mechanism of wavelength selection of self-organized shoreline sand waves - Van den Berg, Niels; Falqués Serra, Albert; Ribas Prats, Francesca; Caballería Suriñach, Miquel
Sandy shorelines exposed to very oblique wave incidence can be unstable and develop self-organized shoreline sand waves. Different types of models predict the formation of these sand waves with an initially dominant alongshore wavelength in the range 1–10 km, which is quite common in nature

15. Modeling shoreline sand waves on the coasts of Namibia and Angola - Ribas Prats, Francesca; Falqués Serra, Albert; Van den Berg, Niels; Caballería Suriñach, Miquel
The southwestern (SW) coast of Africa (Namibia and Angola) features long sandy beaches and a wave climate dominated by energetic swells from the Southsouthwest (SSW), therefore approaching the coast with a very high obliquity. Satellite images reveal that along that coast there are many shoreline sand waves with wavelengths ranging from 2 to 8 km. A more detailed study, including a Fourier analysis of the shoreline position, yields the wavelengths (among this range) with the highest spectral density concentration. Also, it becomes apparent that at least some of the sand waves are dynamically active rather than being controlled by the...

16. Dynamics of single-barred embayed beaches - Ojeda Casillas, Elena; Guillén Aranda, Jorge; Ribas Prats, Francesca
The dynamics of single submerged sandbars of two artificial embayed beaches (La Barceloneta and Bogatell, Barcelona, NW Mediterranean) has been studied with a video-recorded data set of 4.3 years. The alongshore-averaged cross-shore migration, the orientation with respect the shoreline and the sinuosity of the barlines have been analyzed and related to wave conditions, alongshore sediment transport and shoreline variability.

17. Characteristics and dynamics of surfzone transverse finger bars - Ribas Prats, Francesca; Kroon, A.
Patches of transverse finger bars have been identified in the surf zone of Noordwijk beach (Netherlands). They consisted of three to nine elongated accumulations of sand attached to the low-tide shoreline. The bars extended up to 50 m into the inner surf zone, had an oblique orientation with respect to the shore-normal, and were quasiregularly spaced in the alongshore direction.

18. The "Prediflood" database of historical floods in Catalonia (NE Iberian Peninsula) AD 1035–2013, and its potential applications in flood analysis - Barriendos Valve, Mariano; Ruiz Bellet, Josep Lluís; Tuset Mestre, Jordi; Mazón Bueso, Jordi; Balasch Solanes, Josep Carles; Pino González, David; Ayala, Jose Luis
“Prediflood” is a database of historical floods that occurred in Catalonia (NE Iberian Peninsula), between the 11th century and the 21st century. More than 2700 flood cases are catalogued, and more than 1100 flood events. This database contains information acquired under modern historiographical criteria and it is, therefore, suitable for use in multidisciplinary flood analysis techniques, such as meteorological or hydraulic reconstructions.

19. Development of a Low-Cost Weather Station to Measure in Situ Essential Climate Variables - Rojas Gregorio, José Ignacio; Diaz Gilete, Silvia; Mazón Bueso, Jordi
A weather station is proposed especially designed for developing countries, and to meet the standards of the international scientific community making research on the earth system. The station would measure in situ several ECV (essential climate variables). These data may enable an agricultural breakthrough in countries lacking meteorological infrastructure, help in climate change monitoring, and facilitate diffusion of wind energy. A pre-feasibility analysis is presented. It appears interesting that the station is supplied by a social enterprise. A research to establish the best shelter design using computational fluid dynamics is also reported. The criterion is the accuracy with which the...

20. The BLLAST field experiment: boundary-layer late afternoon and sunset turbulence - Lothon, Marie; Lohou, Fabienne; Pino González, David
Due to the major role of the sun in heating the earth’s surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The after-noon transition, the period of the day that connects the day-time dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state

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