• Home
• Program
• Authors centre
• Important dates
• Social programme & conference dinner
• Committees
• Sponsors, & Exhibitors
• Invited speakers
• Registration
• Practical information
• Contact
• Privacy policy

15:45   Computational Fluid and Solid Mechanics: Electromagnetism Chair: Kees Vuik 15:45 25 mins A comparison of boundary element and spectral collocation approaches to the thermally coupled MHD problem Canan Bozkaya, Önder Türk Abstract: The thermally coupled full magnetohydrodynamic (MHD) flow is numerically investigated in a square cavity subject to an externally applied uniform magnetic field. The governing equations given in terms of stream function, vorticity, temperature, magnetic stream function, and current density, are discretized spatially using both the dual reciprocity boundary element method (DRBEM) and the Chebyshev spectral collocation method (CSCM) while an unconditionally stable backward difference scheme is employed for the time integration. Apart from the novelty of the methodology that allows the use of two different methods, the work aims to accommodate various characteristics related to the application of approaches differ in nature and origin. The qualitative and quantitative comparison of the methods are conducted in several test cases. The numerical simulations indicate that the effect of the physical controlling parameters of the MHD problem on the flow and heat transfer can be monitored equally well by both proposed schemes. 16:10 25 mins FFT-based solution schemes for the unit cell problem in periodic homogenization of magneto-elastic coupling Felix Dietrich Abstract: The analysis and the computation of effective properties for multi-phased composite materials plays an important role in the modern industry. Usually the goal consists in combining two or more constituents in such a way that their respective properties are enhanced, sometimes out- ranking the original behaviour by several magnitudes. One class of composites makes use of magnetomechanical coupling effects, where a deformation occurs due to an external magnetic field for one thing and the magnetization of the material may change when it is subjected to mechanical stress for another. Hence, magnetic particle-filled elastomers exploiting this phenomenon can be used as sensors and actuators in a variety of dif- ferent applications, including e.g. variable stiffness devices or as artificial muscles in robotics. One way to tackle such large scale simulations efficiently is a multiscale approach, where quanti- ties computed on a smaller scale are transfered in a homogenization step to obtain the constitutive equations on the larger scale. In the case of classical periodic homogenization, instead of apply- ing standard finite element methods, the usage of FFT-based methods has proven itself to be advantageous in determining effective properties. Operating on a regular grid, this approach has no need for an otherwise costly meshing step and can be directly applied on pixel or voxel data stemming from image-based methods such as microtomography. Switching between the spatial and the spectral domain then allows for a fast and matrix-free algorithm, originally introduced two decades ago by Moulinec and Suquet. In this work, the derivation of the magneto-elastic constitutive equations will be shown. After the periodic homogenization of the underlying problem, it will then be solved by spectral meth- ods which will be elaborated in detail. To round everything off, some numerical benchmarks will be presented in the end. 16:35 25 mins Finite Difference Solutions of 2D Magnetohydrodynamic Channel Flow in a Rectangular Duct Sinem Arslan, Münevver Tezer-Sezgin Abstract: In this study, the MHD flow of an electrically conducting fluid is considered in a long channel (pipe) of rectangular cross-section along with the $z$-axis. The fluid is driven by a pressure gradient along the $z$-axis. The flow is steady, laminar, fully-developed and is influenced by an external magnetic field applied perpendicular to the channel axis. So, the velocity field $\vec{V}=(0,0,V)$ and the magnetic field $\vec{B}=(0,B_{0},B)$ have only channel-axis components $V$ and $B$ depending only on the plane coordinates $x$ and $y$ on the cross-section of the channel which is a rectangular duct. The finite difference method (FDM) is used to solve the governing equations with several type of boundary conditions such as slip or no-slip velocity $V(x,y)$ and conducting, insulated or partly conducting/partly insulated side walls for $B(x,y)$. The numerical solutions for each case of boundary conditions are simulated in terms of equivelocity contours and current lines. The effects of the slip and the wall conductivities on the behavior of the velocity $V$ and the induced magnetic field $B$ are investigated to see their physical effects on the solution mostly. Also, the numerical results obtained from the FDM discretized equations and the exact solution values are shown on the same figure for no-slip and insulated walls to see the coincidence with the exact results and we obtain the accuracy at least $10^{-2}$. Thus, the FDM which is simple to implement, enables one to depict the physical effects of the slip and wall conductivities on the behavior of both the velocity and the induced magnetic field at a small expense. 17:00 25 mins Numerical Simulation of Coupled Electromagnetic and Thermal Problems in Permanent Magnet Synchronous Machines Abdelhakim A. Lotfi, Dániel D. Marcsa, Zoltán Z. Horváth, Christophe C. Prud'homme, Vincent V. Chabannes Abstract: The main objective of our task is to develop a finite element model to analyse the thermal effects in electric machines during its various operating conditions. The application allows the predictions of simultaneous heat transfer in solid and fluid media with energy exchange between them and to determine the heat removal from the machine surface. The permanent magnets and the insulation in the stator windings are sensitive to temperature variations, so a special attention must be paid to this part because the high temperature can affect the durability of the stator winding insulation and the efficiency of the permanent magnets. The prediction of the temperature distribution inside an electric motor is required at the machine design stage in order to control the temperature rise and avoid overheating of the sensitive parts. The accuracy of the thermal model depends on the material properties and the knowledge of losses in electrical machine. In order to simplify the thermal model, the windings and the stator are treated as homogeneous medium with equivalent thermal parameters and the effective properties to characterize the thermal behaviour are calculated based on the volume-weighted average over all constituents. For heat transfer through the external surface of the machine, natural convection is considered. On the other hand the internal air gap is defined as solid and the effective conductivity to characterize the thermal behaviour of the air gap is calculated from empirical correlations. Electromagnetic computation is carried out with the aid of two 2D finite-element (FE) simulations on the cross-section of the PM motor. This computation is made by coupling transient thermal fields with the developed losses model. The temperature rises with the dissipated electromagnetic losses so causing a change in the electromagnetic material properties. The electromagnetic-thermal coupling proposed in this study is a coupling between the 2D transient electromagnetic computation with temperature-dependent material properties, which allows the estimation of the losses distribution of motor, and the 3-D thermal computation, which allows the prediction of the temperature distribution inside an electric motor. The coupling algorithm is based on separately solving of the magnetic field and the heat equations by an individual solution scheme and then exchanging coupling data between the two sub-problems at specific time points. The 2-D magnetic model is simulated in Maxwell ANSYS software and the thermal model is implemented using the open source Feel++ software. Two examples are presented to assess the accuracy of the developed coupled solvers and the numerical results are compared with the experimental ones, which are obtained from a prototype machine.