Accurate and efficient source analysis in electro- and magnetoencephalography using sophisticated realistic head geometries requires advanced numerical approaches. This paper presents DUNEuro, a free and open-source C++ software toolbox for the numerical computation of forward solutions in bioelectromagnetism. Building upon the DUNE framework, it provides implementations of modern fitted and unfitted finite element methods to efficiently solve the forward problems of electro- and magnetoencephalography. The user can choose between a variety of different source models that are implemented. The software’s aim is to provide interfaces that are extendable and easy-to-use. In order to enable a closer integration into existing analysis pipelines, interfaces to Python and MATLAB are provided. The practical use is demonstrated by a source analysis example of somatosensory evoked potentials using a realistic six-compartment head model. Detailed installation instructions and example scripts using spherical and realistic head models are appended.

The formation and dynamics of large-scale circulations in forced and mixed convection has been studied at ambient and elevated fluid pressure by means of particle image velocimetry and temperature measurements. The study has been conducted in two rectangular containers of the same shape and aspect ratios of C xz = 1 and C yz = 5. For the measurements at high fluid pressure the dimensions of the cell have been scaled down by a factor of 5. Air with Pr = 0.7 has been used as fluid in both configurations. Forced convection has been investigated at Re = 1.01 Â 10 4 and mixed convection has been studied at Ar = 3.3, Re = 1.01 Â 10 4 and Ra = 2.4 Â 10 8. In this configuration low-frequency oscillations in the heat transfer between the inlet and outlet have been found for mixed convection. Instantaneous velocity vector fields obtained from particle image velocimetry have been analysed using proper orthogonal decomposition and an algorithm to detect the core and the core centre position of large-scale circulations.

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SummaryAn experimental investigation of flow structure formation in turbulent mixed convection in a closed rectangular cavity with an aspect ratio of 1 : 1 : 5 and air as working fluid is presented. Mixed convection at Re = 1.1·104 and Ra = 3.0·10 8 is studied under welldefined conditions by combination of forced and thermal convection. The resulting flow structures strongly depend on the ratio of inertia and buoyancy forces. A 2D mean wind, which can be approximated by a solid body rotation, is found at pure forced convection. With increasing Archimedes number (Ar), realized by a temperature gradient between bottom and ceiling of the convection cell, this structure becomes instable. Leading to four convection rolls for Ar = 3.4, which are oriented in longitudinal direction of the cell, are observed.