Prestressed vibrations of partially filled tanks containing a free-surface fluid: finite element and reduced order models

In linear vibration analysis of partially filled elastic tanks [1], even if the the structure is submitted by a gaz or a liquid pressure, the reference configuration is generally used without the effect of static loads. In the case of very thin structures or soft material, the static state is considered as prestressed, due to geometrical nonlinearities of the deformed tank. The global stiffness of the structure may change in function of the fluid volume amount [2, 3, 4]. The aim of the paper is to quantify the prestressed effets on the linearized dynamic behavior of the fluid-structure system. The chosen methodology is the following: (i) A quasi-static solution is computed from an empty to a fully filled state of the tank, by considering geometrical nonlinearities and hydrostatic follower forces [5] (no volumetric mesh of the fluid is needed for this step); (ii) after a volumetric remeshing of the fluid at each states, a linearized hydroelastic displacement-pressure formulation around the prestressed state, without gravity effects, is established; (iii) a reduced basis of the hydroelastic problem is generated by using prestressed dry modes to minimize the computation of the added mass matrix. Numerical examples are given to illustrate the proposed approaches

Projection-based reduced order model for prestressed hydroelastic vibrations

In aerospace industry, the computations of liquid-propelled launchers vibrations are based on linear elastic tanks coupled with an inviscid, incompressible fluid with free surface. In this specific case, the fluctuation of pressure on the free surface is supposed to be zero (i.e. the sloshing effects are neglected). Those vibrations are usually called hydroelastic vibrations. The discretized finite element dynamic problem is commonly expressed only in terms of displacements considering an added mass matrix, which represents the kinetic energy of the moving liquid expressed in terms of normal displacement interface. Those computations can be performed for various fluid level configurations, but no prestressing from geometrical nonlinearity is usually considered [1]. In the present study, the evaluation of the prestressed state influence on the coupled fluid structure vibrations is estimated numerically. This prestressing is supposed to be due to a gas or liquid pressurization, acting on the internal surface of the tank, inducing relatively large static displacement compared to the tank thickness. In reference [2], we have evaluated efficiently and accurately the nonlinear displacements for various filling rate with the use of an original level-set approach. We present here the hydroelastic vibrations around each known prestressed state corresponding to different level of liquid with the use of the added mass matrix. Using the open-source computing finite element platform FEniCS [3], numerical results are in very good agreements with experimental studies from the literature [4]. Comparisons with and without prestressing illustrates the contribution of the efect. To overcome an expensive added mass matrix computation, an appropriate reduced order model obtained by projection on prestressed dry modes is also proposed and show very encouraging results

Thermal evolution of the syn-tectonic Ainsa-Jaca basin (South Pyrenean Zone). New constraints from a multiproxy approach.

International audienceConstraining the Thermal history of tectonically active basins is of special importance for the petroleum industry. Indeed, the estimation of geothermal gradients and their evolution are basic parameters to understand the tectono-sedimentary evolution of fold-and-thrust belts and associated foreland basins. In this work, we focus on the turbiditic deposits of the Ainsa-Jaca basin (western part of the South Pyrenean Zone) which consist of an accreted foreland basin composed of Eocene syn-tectonic sediments. The aim is to quantify peak temperatures of the basin that underwent late diagenesis and low-grade metamorphism conditions during the Pyrenean activity. For this, turbiditic rocks and calcite veins (extensional and shear veins) were systematically sampled along a section over a thickness of 4 km through the Monte Perdido unit. In order to constrain the structures observed, sampling was accompanied with a detailed structural analysis. We have combined three thermometric indicators to evaluate peak temperature of rocks: Raman thermometry on carbonaceous material, fluid inclusion microthermometry on calcite/quartz shear and extensional veins and compositional chlorite thermometry on Fe-chlorite observed in shear veins. The Raman temperatures obtained show variations ranging from <160°C to 270°C. As the quantitative Raman thermometry calibration is limited to 200°C, the peak temperatures belonging at 140-180°C range have been determined comparing Pyrenean Raman spectra to those of Glarus area. Indeed, Raman thermometry method has been calibrated recently using samples collected from Glarus Alps. To check the reliability of the Pyrenean Raman data, we confront Raman temperature to available temperatures estimated in this study using compositional chlorite thermometry and fluid inclusion methods. Temperatures determined by the three different methods converge. This result tends to confirm the efficiency of Raman thermometry in determining the maximum burial temperature of basin infill, taking into account that chlorite thermometry has been tested successfully in samples from the Monte Perdido thrust fault. Although our results are preliminary, they suggest that the various published peak temperatures of the Ainsa-Jaca basin do not seem so obvious and need to be carefully used. In order to better constrain the thermal history of South Pyrenean Zone, we are currently working on the acquisition of more data

Maïdo observatory: a new high-altitude station facility at Reunion Island (21° S, 55° E) for long-term atmospheric remote sensing and in situ measurements

Since the nineties, atmospheric measurement systems have been deployed at Reunion Island, mainly for monitoring the atmospheric composition in the framework of NDSC/NDACC (Network for the Detection of <i>Stratospheric</i> Change/Network for the Detection of Atmospheric Composition Change). The location of Reunion Island presents a great interest because there are very few multi-instrumented stations in the tropics and particularly in the southern hemisphere. In 2012, a new observatory was commissioned in Maïdo at 2200 m above sea level: it hosts various instruments for atmospheric measurements, including lidar systems, spectro-radiometers and in situ gas and aerosol measurements. <br><br> This new high-altitude Maïdo station provides an opportunity:<br> 1. to improve the performance of the optical instruments above the marine boundary layer, and to open new perspectives on upper troposphere and lower stratosphere studies;<br> 2. to develop in situ measurements of the atmospheric composition for climate change surveys, in a reference site in the tropical/subtropical region of the southern hemisphere;<br> 3. to offer trans-national access to host experiments or measurement campaigns for focused process studies

Early invasive vulvar squamous cell carcinoma arising in a woman with vulvar pemphigus vulgaris and systemic lupus erythematosus

Pemphigus vulgaris (PV) is an autoimmune blistering disease of the skin and mucous membranes. Genital involvement occurs when most other common sites are concurrently affected or are in remission. Systemic lupus erythematosus (SLE) is an autoimmune disease that may affect many parts of the body and the skin with occasional bullous lesions. Pemphigus vulgaris and SLE may be associated, albeit rarely. Here, we report the first case of a woman affected with SLE presenting with early invasive squamous cell carcinoma (SCC) arising from Pemphigus Vulgaris of the vulva

Effects of fishery protection on biometry and genetic structure of two target sea cucumber species from the Mediterranean Sea

Sea cucumber fisheries are now occurring in most of the tropical areas of the world, having expanded from its origin in the central Indo-Pacific. Due to the overexploitation of these resources and the increasing demand from Asian countries, new target species from Mediterranean Sea and northeastern Atlantic Ocean are being caught. The fishery effects on biometry and genetic structure of two target species (Holothuria polii and H. tubulosa) from Turkey, were assessed. The heaviest and largest individuals of H. polii were found into the non-fishery area of Kusadasi, also showing the highest genetic diversity. Similar pattern was detected in H. tubulosa, but only the weight was significantly higher in the protected area. However, the observed differences on the fishery effects between species, could be explained considering the different percentage of catches (80% for H. polii and 20% for H. tubulosa)