UPCommons - E-prints UPC Universitat Politècnica de Catalunya
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 41 - 60 de 113
Non-linear response of shoreface-connected sand ridges - de Swart, Huib E.; Calvete Manrique, Daniel
A non-linear morphodynamic model of a microtidal coastal shelf is used to study the response of shoreface-connected sand ridges and the net sand balance of the shelf to large-scale interventions. The model describes the interaction between storm-driven currents and the erodible bottom. The transport of sediment comprises both bedload and suspended load contributions and is due to the joint action of waves (stirring of sediment from the bed) and net currents (causing transport). Three basic types of interventions are studied: extracting sand from ridges, nourishing sand at the shelf and constructing navigation channels. The model results indicate that for all...
Growth of large-scale bed forms due to storm-driven and tidal currents: a model approach - Walgreen, M.; Calvete Manrique, Daniel; Swart, Huib E. de
An idealized morphodynamic model is used to gain further understanding about the formation and characteristics of shoreface-connected sand ridges and tidal sand banks on the continental shelf. The model consists of the 2D shallow water equations, supplemented with a sediment transport formulation and describes the initial feedback between currents and small amplitude bed forms. The behaviour of bed forms during both storm and fair weather conditions is analyzed. This is relevant in case of coastal seas characterized by tidal motion, where the latter causes continuous transport of sediment as bed load.
The new aspects of this work are the incorporation of...
A field test of a linear stability model for crescentic bars - Tiessen, M C H; Leeuwen, S M Van; Calvete Manrique, Daniel; Dodd, N
A morphodynamical linear stability analysis is used to predict the natural development of crescentic bed patterns and rip channels. The purpose is to investigate whether this technique, which is useful for understanding the physics of emerging bed-forms, can be used to make quantitative predictions in the field, which may then be of use for coastal engineers.
To this end a morphodynamical linear stability model (Morfo60) is used to describe the development of crescentic bed patterns at the coast at the USACE Field Research Facility in Duck, North Carolina, USA. Wave, tide and alongshore-averaged bathymetry data recorded at Duck over a 2...
Effect of depth-dependent wave stirring on the final amplitude of shoreface-connected sand ridges - Calvete Manrique, Daniel; Swart, Huib E. de; Falqués Serra, Albert
A nonlinear morphodynamic model is analysed to gain fundamental knowledge about the initial growth and long-term behaviour
of observed shoreface-connected sand ridges. Themodel describes quasi-steady, depth-averaged flow on a storm-dominated inner shelf with an erodible bottom and a transverse slope. Both bed load and suspended load sediment transport are incorporated. The formulations are linear with respect to the current and account for depth dependent stirring of sediment by waves as well as for the effect of local bed slopes.
A linear stability analysis has already revealed the initial growth of bed forms that resemble observed shoreface-connected
ridges. Here, a nonlinear analysis is carried...
Linear evolution of a shoreface nourishment - Leeuwen, Van S.; Dodd, N.; Calvete Manrique, Daniel; Falqués Serra, Albert
The morphological evolution of a shoreface nourishment is investigated by interpreting the nourishment as a linear perturbation of the natural system. The nourishment is projected onto the subset of linear eigenmodes with negative growth rates of the morphodynamical system. The evolution of these linear modes then determines the temporal behaviour of the shoreface nourishment. The method is presented, and results are shown for shoreface nourishments of different length scales on a straight coast and subject to normal incidence. Shoreface nourishments are represented by their expansions according to the projection method on a 1:50 plane beach profile. All nourishments are shown...
Rhythmic surf zone bars and morphodynamic self-organization - Falqués Serra, Albert; Dodd, N.; Garnier, Roland; Ribas Prats, Francesca; Machardy, L.C.; Larroude, P.; Calvete Manrique, Daniel; Sancho, F.
Work undertaken in the EU HUMOR project on morphodynamical modelling, particularly with regard to simulating and understanding
rhythmic surf zone bars and related morphodynamic self-organization, is presented. These features are reviewed and their engineering context stated. Hydrodynamical and morphodynamical models developed and/or applied within the HUMOR project in order to address these issues are
briefly presented. The linear stability modelling concept and stability studies using fully nonlinear models are contrasted. The stability of a shoreparallel bar under normal or oblique wave incidence is chosen as a test case for the different models. The results are compared and discussed. Lastly, modelling efforts and...
Shoreline instability under low-angle wave incidence - Idier, Deborah; Falqués Serra, Albert; Ruessink, B.G.; Garnier, Roland
The growth of megacusps as shoreline instabilities is investigated by examining the coupling between wave transformation in the shoaling zone, long-shore transport in the surf zone, cross-shore transport, and morphological evolution. This coupling is known to drive a potential positive feedback in case of very oblique wave incidence, leading to an unstable shoreline and the
consequent formation of shoreline sandwaves. Here, using a linear stability model based on the one-line concept, we demonstrate that such instabilities can also develop in case of low-angle or shore-normal incidence, under certain conditions (small enough wave height and/or large enough beach slope). The wavelength and...
Instabilities and inertial waves generated in a librating cylinder - López, J.M.; Marqués Truyol, Francisco
A librating cylinder consists of a rotating cylinder whose rate of rotation is modulated.
When the mean rotation rate is large compared with the viscous damping rate, the flow may support inertial waves, depending on the frequency of the modulation. The modulation also produces time-dependent boundary layers on the cylinder endwalls and sidewall, and the sidewall boundary layer flow in particular is susceptible to instabilities which can introduce additional forcing on the interior flow with time scales different from the modulation period. These instabilities may also drive and/or modify the inertial waves. In this paper, we explore such flows numerically using...
The influence of wave direction on the morphological response of a double sandbar system - Thiebot, Jerome; Idier, Deborah; Garnier, Roland; Falqués Serra, Albert; Ruessink, B.G.
Nearshore sandbars are often characterized by three-dimensional bed patterns. To analyze the influence of wave direction on the morphological response of a double sandbar system, this paper uses the 2DH nonlinear surf zone model MORFO55. Depending on wave direction, different morphologies emerge as free instabilities. These morphological responses differ in terms of geometry (shape of the alongshore rhythmic patterns) and temporal evolution. Nearly shore-normal waves favor the emergence of crescentic patterns along both the inner and outer bars. These instabilities arise from “bedsurf” coupling, which is the positive feedback between the bed perturbations and the wave-breaking patterns resulting in rip-cell...
Dissipative solitons in binary fluid convection - Mercader Calvo, María Isabel; Batiste Boleda, Oriol; Alonso Maleta, María Aránzazu; Knobloch, Edgar
A horizontal layer containing a miscible mixture of two fluids can produce dissipative solitons when heated from below. The physics of the system is described, and dissipative solitons are computed using numerical continuation for three distinct sets of experimentally realizable parameter values. The stability of the solutions is investigated using direct numerical integration in time and related to the stability properties of the competing periodic state.
Observations and large-eddy simulations of entrainment in the sheared sahelian boundary layer - Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Pino González, David; Saïd, Frédérique
At the top of the planetary boundary layer, the entrainment of air, which incorporates
dry and warm air from the free troposphere into the boundary layer, is a key process
for exchanges with the free troposphere since it controls the growth of the boundary layer.
Here, we focus on the semi-arid boundary layer where the entrainment process is analyzed
using aircraft observations collected during the African Monsoon Multidisciplinary Analysis
experiment and large-eddy simulations. The role of the entrainment is specifically enhanced
in this region where very large gradients at the planetary boundary-layer top can be found
due to the presence of the moist, cold monsoon flow on...
Transitions to three-dimensional flows in a cylinder driven by oscillations of the sidewall - Panadès Guinart, Carles; Marqués Truyol, Francisco; Lopez, Juan M.
The transition from two-dimensional to three-dimensional flows in a finite circular
cylinder driven by an axially oscillating sidewall is explored in detail. The complete
symmetry group of this flow, including a spatio-temporal symmetry related to the
oscillating sidewall, is Z2xO(2). Previous studies in flows with the same symmetries,
such as symmetric bluff-body wakes and periodically forced rectangular cavities,
were unable to obtain the theoretically predicted bifurcation to modulated travelling
waves. In the simpler cylindrical geometry, where the azimuthal direction is physically
periodic, we have found these predicted modulated travelling waves as stable fully
saturated nonlinear solutions for the first time. A careful analysis of the base states and...
Long-term evolution of nourished beaches under high angle wave conditions - Van den Berg, Niels; Falqués Serra, Albert; Ribas Prats, Francesca
A nonlinear numerical model for large-scale dynamics of shoreline and nearshore bathymetry under wave action is applied to investigate the long-term evolution of a rectilinear coast dominated by high angle wave incidence, which is perturbed by a nourishment or an offshore borrow pit. Previous studies show that a coastline can be unstable due to high angle wave instability, which results from the feedback between shoreline changes and the wave field. In contrast to traditional one-line shoreline models, which always predict a diffusional behaviour, this instability can lead to the growth of shoreline perturbations. Model results suggest that due to high...
Application of the CORMIX model to assess environmental impact in the coastal area: an example of the ocean disposal system for sanitary sewers in the city of Fortaleza (Ceará, Brazil) - Maia, L. P.; Bezerra Menezes, María Ozilea; Pinheiro, L.; Redondo Apraiz, José Manuel
Cornell Mixing Zone Expert System-CORMIX software was used to simulate the behavior of effluents discharged by the underwater emissary in Fortaleza (Ceará, Brazil). This software is used to analyze and predict the discharge design in bodies of water. Application of the CORMIX model was determined to simulate the tracer discharge using local environmental parameters and underwater emissary discharge data. Data on wind, current and position in relation to the coast were used in the chosen case to obtain the discharge flow classification from the model since the hydrodynamic dispersion fields are differentiated by the predominance of different physical processes responsible...
Shoreline instability due to very oblique wave incidence: some remarks on the physics - Falqués Serra, Albert; Calvete Manrique, Daniel; Ribas Prats, Francesca
Previous research has shown that a very oblique wave incidence on a coast may render a rectilinear shoreline unstable. Here, we present some further insight into the physics of such instability. The obliqueness of wave incidence has two effects on the alongshore drift: (i) a direct effect on the relative angle between the wave fronts and the shoreline, and (ii) an indirect effect on the breakers height via the wave energy spreading as the waves refract when they approach the shore. The direct effect turns out to be, in all incidents, stabilizing, and the instability occurs only from the effects...
Experimental analysis of the flow dynamics in the suction chamber of an external gear pump - Ertürk, Nihal; Vernet, Anton; Castilla López, Roberto; Gámez Montero, Pedro Javier; Ferre, Josep Anton
Time-Resolved Particle Image Velocimetry (TRPIV) has been used to investigate the flow inside the suction chamber of an external gear pump where the movement of the fluid through the pump is maintained by the rotation of the gears. The main purpose of this paper is to study the characteristics of the complex flow pattern of this pump system in order to help in improving its total performance. The applied experimental techniques establish a method that allows visualising the flow inside the gear pump with a high rotational velocity system. Small micro air bubbles have been used as flow seeding. The...
On the multiple shooting continuation of periodic orbits by Newton-Krylov methods - Sánchez Umbría, Juan; Net Marcé, Marta
The application of the multiple shooting method to the continuation of periodic orbits in large-scale dissipative systems is analyzed. A preconditioner for the linear systems which appear in the application of Newton’s method is presented. It is based on the knowledge of invariant subspaces of the Jacobians at nearby solutions. The possibility of speeding up the process by using parallelism is studied for the thermal convection of a binary mixture of fluids in a rectangular domain, with positive results.
Super asymptotic giant branch stars. I - Evolution code comparison - Doherty, Carolyn L.; Siess, Lionel; Lattanzio, John; Gil Pons, Pilar
We present an extensive set of detailed stellar models in the mass range 7.7–10.5M over the
metallicity range Z = 10−5–0.02. These models were produced using the Monash University
version of the Mount Stromlo Stellar Structure Program (MONSTAR) and follow the evolution
from the pre-main sequence to the first thermal pulse of these super asymptotic giant branch
stars. A quantitative comparison is made to the study of Siess. Prior to this study, only
qualitative comparisons and code validations existed in this critical mass range, and the
large variations in the literature were largely unexplained. The comparison presented here
is particularly detailed due to the standardization of the...