This investigation presents a modelling strategy for wind-energy studies in complex terrains using computational fluid dynamics (CFD). A model, based on an unsteady Reynolds Averaged Navier-Stokes (URANS) approach with a modified version of the standard k-ε model, is applied. A validation study based on the Leipzig experiment shows the ability of the model to simulate atmospheric boundary layer characteristics such as the Coriolis force and shallow boundary layer. By combining the results of the model and a design of experiments (DoE) method, we could determine the degree to which the slope, the leaf area index, and the forest height of an escarpment have an effect on the horizontal velocity, the flow inclination angle, and the turbulent kinetic energy at critical positions. The DoE study shows that the primary contributor at a turbine-relevant height is the slope of the escarpment. In the second step, the method is extended to the WINSENT test site. The model is compared with measurements from an unmanned aircraft system (UAS). We show the potential of the methodology and the satisfactory results of our model in depicting some interesting flow features. The results indicate that the wakes with high turbulence levels downstream of the escarpment are likely to impact the rotor blade of future wind turbines.

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The current study describes analyses of the WINSENT wind energy test site located in complex terrain in Southern Germany by highly resolved numerical simulations. The resolved atmospheric turbulence is simulated with Delayed Detached Eddy Simulations by the flow solver FLOWer without consideration of the research wind turbines. The mean inflow and wind direction of the analysed time period is provided by precursor simulations of project partners. The simulation model chain consists of three codes with different time scales and resolutions. The model chain provides a data transfer from mesoscale WRF simulations to OpenFOAM. As a next step OpenFOAM provides inflow data in the valley of the terrain site for the present FLOWer simulations, the code with the highest resolution in space and time. The mean velocity field provided by OpenFOAM is superimposed with fluctuations that are based on measurements to obtain the small turbulent scales within the FLOWer simulations, which the previous tools of the model chain can not resolve. Comparisons with the two already installed met masts clarify that the current FLOWer simulations provide an adequate agreement with measured data. The results are verified with the application of a second simulation, in which a homogeneous velocity profile is superimposed with turbulence. Thus, comparisons with measured data showed that the benefit of using the inflow data of this model chain is especially evident near the ground.

Micrometeorological observations from a tower, an eddy-covariance (EC) station and an unmanned aircraft system (UAS) at the WINSENT test-site are used to validate a computational fluid dynamics (CFD) model, driven by a mesoscale model. The observation site is characterised by a forested escarpment in a complex terrain. A two-day measurement campaign with a flow almost perpendicular to the escarpment is analysed. The first day is dominated by high wind speeds, while, on the second one, calm wind conditions are present. Despite some minor differences, the flow structure, analysed in terms of horizontal wind speeds, wind direction and inclination angles shows similarities for both days. A real-time strategy is used for the CFD validation with the UAS measurement, where the model follows spatially and temporally the aircraft. This strategy has proved to be successful. Stability indices such as the potential temperature and the bulk Richardson number are calculated to diagnose atmospheric boundary layer (ABL) characteristics up to the highest flight level. The calculated bulk Richardson values indicate a dynamically unstable region behind the escarpment and near the ground for both days. At higher altitudes, the ABL is returning to a near neutral state. The same characteristics are found in the model but only for the first day. The second day, where shear instabilities are more dominant, is not well simulated. UAS proves its great value for sensing the flow over complex terrains at high altitudes and we demonstrate the usefulness of UAS for validating and improving models.

But : Préciser le profil épidémioclinique, étiologique et thérapeutique des thromboses veineuses portales au Maroc. Matériel et méthode : Étude rétrospective de 28 cas de thrombose portale colligés dans le service de gastroentéro-logie du CHU Mohammed-VI de Marrakech, sur une période de quatre ans entre janvier 2004 et décembre 2008.Résultats : Les dossiers de 20 femmes et huit hommes, de 40 ans de moyenne d'âge, ont été étudiés. Les signes cliniques révélateurs étaient représentés par des douleurs abdominales aiguës dans 11 cas, un tableau d'infarctus mésentérique dans un cas, une hypertension portale dans 14 cas, une ascite dans deux cas. L'échographie abdominale couplée au doppler réa-lisée chez tous les malades a objectivé une thrombose porte dans 15 cas et un cavernome portal dans l3 cas. Une cause locale était retrouvée chez 21 malades. Le bilan à la recherche d'une affection favorisant la thrombose était demandé chez 15 malades, mais il n'a été réalisé que chez cinq d'entre eux par faute de moyens, il a objectivé un déficit en protéine C et S dans trois cas, un déficit en protéine S dans un cas et un syndrome des anticorps antiphospholipides dans un cas. La thrombose était jugée aiguë chez 12 malades devant les signes clinicoradiologiques ayant justifié un traitement par anticoagulants pendant six mois, poursuivi à vie chez huit d'entre eux. L'évolution était marquée par un décès chez un malade suite à un infarctus mésentérique et une bonne évolution chez les autres malades traités. Discussion : En dehors de l'obstruction par une tumeur maligne, la thrombose est le principal mécanisme responsable de l'occlusion de la veine porte. C'est une pathologie rare ayant une prévalence entre 0,05 et 0,5 % selon les séries, dans notre série, il s'agit de 1 % des malades hospitalisés. La thrombose porte est souvent diagnostiquée à un stade tardif après la survenue d'un cavernome portal, cela en raison du caractère peu spécifique du tableau aigu dominé par les douleurs abdominales. L'échographie abdominale couplée au doppler est un examen performant qui permet le diagnostic positif dans 85 %. L'angioscanner permet actuellement une étude plus précise. La cause est souvent multifactorielle, nécessitant une enquête étiologique afin de guider la conduite thérapeutique. Conclusion : La thrombose portale est relativement fré-quente dans notre contexte, sa prise en charge thérapeutique pose des problèmes en rapport avec le coût élevé du bilan étiologique, et la survenue sur des terrains particuliers. Mots clés Thrombose veineuse portale · MarocAbstract Aim: To study clinical, epidemiological character, aetiology and treatment of portal thrombosis in Morocco. Material and method: A retrospective study of 28 cases of portal thrombosis at Gastroenterology Department of University Hospital Mohamed-VI Marrakech for a period of four years between January 2004 and December 2008. Results: Twenty women and eight men of the average age of 40 were studied. The clinical symptoms included acute abdominal pain in 11 cases, a mesenteric inf...