5,688 research outputs found
Vulnerability of Catalan (NW Mediterranean) ports to wave overtopping due to different scenarios of sea level rise
The final publication is available at Springer via http://dx.doi.org/10.1007/s10113-015-0879-xThe overtopping of port breakwaters may affect the assets located at the breakwater lee side. If adaptation measures are not taken, the sea level rise will increase the overtopping discharges putting those assets at significant risk. This study compares, at a regional scale, overtopping discharges over port breakwaters for three storm conditions (return periods of 1, 5 and 50 years) under present climate as well as for three scenarios of sea level rise based on recent projections. The results indicate that, for the worst storm and sea level rise conditions, the overtopping discharge would not be negligible (larger than 1 l/s/m) in 35 ports (84 %), in contrast to only 18 ports (42 %) being affected under present conditions. In addition, in 28 ports (65 %) the overtopping would be at least one order of magnitude larger than for present conditions. In the case of large storms, in 2 ports the overtopping discharge exceeds 200 l/s/m (the discharge that can initiate breakwater damage) under present conditions, while in the worst scenario of sea level rise the number of ports exceeding this value would be 7. On the other hand, the vulnerability of each port for which overtopping flow is greater than an acceptable discharge flux is assessed, and regional maps of vulnerability are plotted. For the worst storm conditions, 23 % of the Catalan ports have risks associated with overtopping under present climate conditions. This percentage would increase to 47 % in the worst sea level rise scenario.Peer ReviewedPostprint (author's final draft
Modeling transitional plane Couette flow
The Galerkin method is used to derive a realistic model of plane Couette flow
in terms of partial differential equations governing the space-time dependence
of the amplitude of a few cross-stream modes. Numerical simulations show that
it reproduces the globally sub-critical behavior typical of this flow. In
particular, the statistics of turbulent transients at decay from turbulent to
laminar flow displays striking similarities with experimental findings.Comment: 33 pages, 10 figure
Collider and Gravitational Wave Complementarity in Exploring the Singlet Extension of the Standard Model
We present a dedicated complementarity study of gravitational wave and
collider measurements of the simplest extension of the Higgs sector: the
singlet scalar augmented Standard Model. We study the following issues: (i) the
electroweak phase transition patterns admitted by the model, and the proportion
of parameter space for each pattern; (ii) the regions of parameter space that
give detectable gravitational waves at future space-based detectors; and (iii)
the current and future collider measurements of di-Higgs production, as well as
searches for a heavy weak diboson resonance, and how these searches interplay
with regions of parameter space that exhibit strong gravitational wave signals.
We carefully investigate the behavior of the normalized energy released during
the phase transition as a function of the model parameters, address subtle
issues pertaining to the bubble wall velocity, and provide a description of
different fluid velocity profiles. On the collider side, we identify the subset
of points that are most promising in terms of di-Higgs and weak diboson
production studies while also giving detectable signals at LISA, setting the
stage for future benchmark points that can be used by both communities.Comment: 38 pages, 22 figures. Version published in JHE
Variational Multiscale Stabilization and the Exponential Decay of Fine-scale Correctors
This paper addresses the variational multiscale stabilization of standard
finite element methods for linear partial differential equations that exhibit
multiscale features. The stabilization is of Petrov-Galerkin type with a
standard finite element trial space and a problem-dependent test space based on
pre-computed fine-scale correctors. The exponential decay of these correctors
and their localisation to local cell problems is rigorously justified. The
stabilization eliminates scale-dependent pre-asymptotic effects as they appear
for standard finite element discretizations of highly oscillatory problems,
e.g., the poor approximation in homogenization problems or the pollution
effect in high-frequency acoustic scattering
Apollo Lightcraft Project
The ultimate goal for this NASA/USRA-sponsored Apollo Lightcraft Project is to develop a revolutionary manned launch vehicle technology which can potentially reduce payload transport costs by a factor of 1000 below the Space Shuttle Orbiter. The Rensselaer design team proposes to utilize advanced, highly energetic, beamed-energy sources (laser, microwave) and innovative combined-cycle (airbreathing/rocket) engines to accomplish this goal. The research effort focuses on the concept of a 100 MW-class, laser-boosted Lightcraft Technology Demonstrator (LTD) drone. The preliminary conceptual design of this 1.4 meter diameter microspacecraft involved an analytical performance analysis of the transatmospheric engine in its two modes of operation (including an assessment of propellant and tankage requirements), and a detailed design of internal structure and external aeroshell configuration. The central theme of this advanced propulsion research was to pick a known excellent working fluid (i.e., air or LN sub 2), and then to design a combined-cycle engine concept around it. Also, a structural vibration analysis was performed on the annular shroud pulsejet engine. Finally, the sensor satellite mission was examined to identify the requisite subsystem hardware: e.g., electrical power supply, optics and sensors, communications and attitude control systems
Parameterization of directional absorption of orographic gravity waves and its impact on the atmospheric general circulation simulated by the Weather Research and Forecasting Model
In this work, a new parameterization scheme is developed to account for the directional absorption of orographic gravity waves (OGWs) using elliptical mountain wave theory. The vertical momentum transport of OGWs is addressed separately for waves with different orientations through decomposition of the total wave momentum flux (WMF) into individual wave components. With the new scheme implemented in the Weather Research and Forecasting (WRF) model, the impact of directional absorption of OGWs on the general circulation in boreal winter is studied for the first time. The results show that directional absorption can change the vertical distribution of OGW forcing, while maintaining the total column-integrated forcing. In general, directional absorption inhibits wave breaking in the lower troposphere, producing weaker orographic gravity wave drag (OGWD) there and transporting more WMF upwards. This is because directional absorption can stabilize OGWs by reducing the local wave amplitude. Owing to the increased WMF from below, the OGWD in the upper troposphere at midlatitudes is enhanced. However, in the stratosphere of mid-to-high latitudes, the OGWD is still weakened due to greater directional absorption occurring there. Changes in the distribution of midlatitude OGW forcing are found to weaken the tropospheric jet locally and enhance the stratospheric polar night jet remotely. The latter occurs as the adiabatic warming (associated with the OGW-induced residual circulation) is increased at midlatitudes and suppressed at high latitudes, giving rise to stronger thermal contrast. Resolved waves are likely to contribute to the enhancement of polar stratospheric winds as well, because their upward propagation into the high-latitude stratosphere is suppressed
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