Numerical and experimental analysis of the hydroelastic behavior of purse seine nets

The paper presents a general three dimensional hydro-elastic tool for the analysis of different types of fishing nets and aquaculture facilities. Flexible net strands are modeled by non-linear truss elements having two nodes. Hydrodynamic loads due to relative motion of the net with the surrounding fluid are computed using the Morison equation. The coupled hydrodynamic-elastodynamic equations are solved using finite element (FE) approximations. Furthermore, experimental data are presented for the drag resistance of a purse seine net, commonly used as fishing tool in the Mediterranean sea. The measurements were conducted in the towing tank of NTUA on a sample of a net. The net was tested in three configurations: vertical, horizontal and inclined at 451. The derived drag coefficients are compared to predictions of the FEM developed model. The vertical submergence behavior of the seine in calm water is also examined, both experimentally and theoretically. Moreover, the shooting phase of the purse-seine fishing is simulated with the aim to investigate the diving behavior of the net. The flow shading effect of neighboring strands is identified as a critical parameter for the consistent predictions of the diving behavior

CFD code comparison for 2D airfoil flows

The current paper presents the effort, in the EU AVATAR project, to establish the necessary requirements to obtain consistent lift over drag ratios among seven CFD codes. The flow around a 2D airfoil case is studied, for both transitional and fully turbulent conditions at Reynolds numbers of 3 × 106 and 15 × 106. The necessary grid resolution, domain size, and iterative convergence criteria to have consistent results are discussed, and suggestions are given for best practice. For the fully turbulent results four out of seven codes provide consistent results. For the laminar-turbulent transitional results only three out of seven provided results, and the agreement is generally lower than for the fully turbulent case

Final results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents final results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Special attention is paid to the improvement of low fidelity engineering (BEM based) models with higher fidelity (CFD) models but also with intermediate fidelity free vortex wake (FVW) models. The latter methods were found to be a good basis for improvement of induction modelling in engineering methods amongst others for the prediction of yawed cases, which in AVATAR was found to be one of the most challenging subjects to model. FVW methods also helped to improve the prediction of tip losses. Aero-elastic calculations with BEM based and FVW based models showed that fatigue loads for normal production cases were over predicted with approximately 15% or even more. It should then be realised that the outcome of BEM based models does not only depend on the choice of engineering add-ons (as is often assumed) but it is also heavily dependent on the way the induced velocities are solved. To this end an annulus and element approach are discussed which are assessed with the aid of FVW methods. For the prediction of fatigue loads the so-called element approach is recommended but the derived yaw models rely on an annulus approach which pleads for a generalised solution method for the induced velocities

Latest results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents the most recent results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Measurements on a DU 00-W-212 airfoil are presented which have been taken in the pressurized DNW-HDG wind tunnel up to a Reynolds number of 15 Million. These measurements are compared with measurements in the LM wind tunnel for Reynolds numbers of 3 and 6 Million and with calculational results. In the analysis of results special attention is paid to high Reynolds numbers effects. CFD calculations on airfoil performance showed an unexpected large scatter which eventually was reduced by paying even more attention to grid independency and domain size in relation to grid topology. Moreover calculations are presented on flow devices (leading and trailing edge flaps and vortex generators). Finally results are shown between results from 3D rotor models where a comparison is made between results from vortex wake methods and BEM methods at yawed conditions

Les temps de la consultation du comité d’entreprise

The DD4HEP detector description toolkit offers a flexible and easy-to-use solution for the consistent and complete description of particle physics detectors in a single system. The sub-component DDREC provides a dedicated interface to the detector geometry as needed for event reconstruction. With DDREC there is no need to define an additional, separate reconstruction geometry as is often done in HEP, but one can transparently extend the existing detailed simulation model to be also used for the reconstruction. Based on the extension mechanism of DD4HEP, DDREC allows one to attach user defined data structures to detector elements at all levels of the geometry hierarchy. These data structures define a high level view onto the detectors describing their physical properties, such as measurement layers, point resolutions, and cell sizes. For the purpose of charged particle track reconstruction, dedicated surface objects can be attached to every volume in the detector geometry. These surfaces provide the measurement directions, local-to-global coordinate transformations, and material properties. The material properties, essential for the correct treatment of multiple scattering and energy loss effects in charged particle reconstruction, are automatically averaged from the detailed geometry model along the normal of the surface. Additionally, a generic interface allows the user to query material properties at any given point or between any two points in the detector's world volume. In this paper we will present DDREC and how it is used together with the linear collider tracking software and the particle-flow package PANDORAPFA for full event reconstruction of the ILC detector concepts ILD and SiD, and of CLICdp. This flexible tool chain is also well suited for other future accelerator projects such as FCC and CEPC

Experimental study of drag-reduction devices on a flatback airfoil

Various trailing-edge drag-reduction devices, including a new flap device, were examined experimentally on a flatback airfoil in a wind tunnel. The tests concerned a 30% thick airfoil with 10.6% thick trailing edge. Pressure, hot wire, and stereo particle image velocimetry measurements were performed at a chord Reynolds number of 1.5e6. Results show that the best-performing devices decrease drag, increase the vortex shedding frequency, and reduce flow variation downstream of the wing trailing edge. The best-performing device was a combination of the flap with an offset cavity plate. Further investigation is required for the optimization of the new device to examine its effects on noise reduction, load mitigation, and control

A ten thousand frames per second readout MAPS for the EUDET beam telescope

Designed and manufactured in a commercial CMOS 0.35 μm OPTO process for equipping the EUDET beam telescope, MIMOSA26 is the first reticule size pixel sensor with digital output and integrated zero suppression. It features a matrix of pixels with 576 rows and 1152 columns, covering an active area of ~224 mm2. A single point resolution of about 4 μm was obtained with a pixel pitch of 18.4 μm. Its architecture allows a fast readout frequency of ~10 k frames/s. The paper describes the chip design, test and major characterisation outcome