Title: Gravitational Instabilities in Partially Molten Crust
Authors: Louis Napoleon Aurelie et al.
Description: The deep roots of the Archaean to Phanerozoic continental crust reveal domed structures of kilometer to deca-kilometer sizes. These domes are typically cored by migmatites, which attest of the dynamics of the partially molten crust and associated heterogeneous mass redistribution. We model here numerically the development of gravity instabilities in a continental crust heated from below with no lateral motion, simulating the conditions prevailing at the transition between orogenic climax and collapse. The chemical and physical heterogeneity of the crust is represented by deformable inclusions of distinct viscosity and density with power-law temperature and strain-rate dependent viscosities. We use the VOF Method (Volume Of Fluid, OpenFOAM code) that reproduces well the coalescence and separation of inclusions, of sizes of a few hundred meters.
We identified three distinct flow regimes depending on two Rayleigh numbers RaUM and RaPM, which characterize the solid and molten domains, respectively. A”suspension” regime (high RaUM and RaPM) describes the entrainment of the inclusons in the convective cells. A “stratification” regime (low RaUM and high RaPM) characterizes how the light inclusions amalgamate as floating clusters under the rigid upper crust, which can then form kilometer scale dome structures. A “diapirism” regime corresponds to the segregation of the heavy and light inclusions to to form layers at the bottom and top of the molten layer, respectively.
The present study incorporates 3D models that evidence the key role of the size and concentration of the inclusions for the “stratification” regime, and pinpoint the fundamental characteristics of Earth’s rocks heterogeneity at the crustal scale.
Application of our results to the kilometer-scale subdomes within the crustal-scale migmatite dome exposed on Naxos Island (Greece) probe basal heating for 5-10 Ma, below a 45 km thick crust. There, several cycles of zircon precipitation dated from 24 to 16 Ma have been interpreted in terms of convective motion (Vanderhaeghe et al., 2018). Distinct configurations validate this scenario in which the viscosity and density distributions, and the basal heating time were varied. All configurations also lead to the final formation and preservation of domes cored by the low-viscosity-density material of a diameter of 2 to 5 km, at a depth of ca. 15 km. These results show that the efficiency of material redistribution within a partially molten crust depends on the flow regime associated to the development of gravitational instabilites and is very sensitive to the physical heterogeneity of the crust.
Title: Implementation of Discontinuous Galerkin in OpenFOAM
Authors: Hrvoje Jasak, Gregor Cvijetic, Tessa Uroic
OpenFOAM is an open source Computational Fluid Dynamics (CFD) toolbox based on the Finite Volume Method (FVM). The advantage of FVM is a straightforward and relatively easy formulation of equations and operators for computational meshes consisting of arbitrary polyhedral cells. The method is conservative and 2ndorder accurate in space, which is adequate for most engineering applications.There are some examples when FVM discretisation is insufficiently accurate such as acoustic wave propagation and highly accurate simulations of fluid flow, e.g. using the Large Eddy Simulation (LES) approach for turbulence modelling. For such cases, Discontinuous Galerkin (DG) methods are becoming a popular choice. DG represents a combination of FVM and the Finite Element Method (FEM). The unknowns are represented by polynomials which are locally defined for each cell, which is consistent with FEM. The discontinuous values on a face shared by two cells are treated by using a numerical flux, which is taken from FVM. The order of polynomials is arbitrary and can provide highly accurate solutions. The formulation presented here was derived by prof. M. Oberlack et al. and it satisfies the polyhedral cell support requirement, provided in OpenFOAM.
Title: Sustainable Corrosion Protection Based on Materials Modelling and Digitalization
Authors: VIPCOAT Team (link)
Presenters: Marko Horvat and Hrvoje Jasak
Description: The aim of the project is to create an open innovation platform that can be used by the research, industrial, political and public sectors alike. The approach facilitates an effective transfer of science and communication between all those involved. The platform serves as a database (for experimental, industry-relevant and modeling data), scientific infrastructure and simulation tool at the same time. Machine learning and physics-based modeling are combined here to optimize industry-relevant active protective coating development processes. VIPCOAT is designed to support industry in making the development of customized innovative corrosion protection technologies not only faster and more economical, but mainly to also to make them more sustainable and environmentally friendly.
Title: Lubricated Contact Analysis using The Finite Area Method
Author: Luka Balatinec
Description: Numerical modelling emerged as a valid alternative to costly experimental methods used for contact analysis in various applications (metal forming, bearing design, etc.). The existing design tools rarely focus on calculating the effects of microscopic contact and friction. Numerical methods can be a useful tool for calculating such effects, but also lubrication effects for rough surfaces in contact. A numerical framework based on the Finite Area Method (FAM) is presented as a viable tool for simulations of lubricated contact of rough surfaces. A FAM contact boundary condition was implemented for the hyperelastoplastic finite volume deformation solver, as a part of the foam-extend library. The framework combines a lubricant flow, thermal and asperity contact model, which enable the calculation of contact pressure and traction for all lubrication regimes. Moreover, the framework provides additional data, such as film thickness, temperature, contact area, etc., which is invaluable for analysing the properties of lubricants. The model was used for numerical simulations of a ball-on-disc tribometer and the results were validated against numerical and experimental data. Two sets of simulations were performed with varying entrainment speeds and contact loads: for a hydrodynamic lubrication regime (Turbo T9 oil) and a mixed lubrication regime (Turbo T68 oil). The results showing friction, film thickness, contact and hydrodynamic pressure, contact area, and film temperature, are presented.
Title: Conjugate Heat Transfer Simulation of LED Cooling Block
Author: Matej Čorak
Description: Numerical modelling has emerged as a valid alternative to costly thermography measurements used for heat dissipation measurements in electronics applications. A numerical model for conjugate heat transfer was done for the solid and the fluid region. Results were compared with the experimental results which were described in. Modern High powered LED chips range in power between 1 and 21W, whit their low volume and cross-section they are under the influence of significant heat fluxes. These chips have an area of 1mm2 with an average power of 1W, which corresponds to a heat flux of 100 W mm2. This high localized heat flux can result in a significant reduction of lighting and thermal performance while also shortening the expected operating life of LEDs. In conclusion, simulations of conjugate heat transfer showed that it is possible to use numerical simulations as a cost effective alternative to laboratory measurements.
Title: Harmonic Balance Method for Contra-Rotating Propellers
Authors: Franko Ćurčin, Tessa Uroić, Sanijo Đurašević
Description: In order to reduce the total time-to-solution, while preserving the required time resolution resulting from the periodicity of the flow in the case of a set of Contra-Rotating Propellers (CRP), it is possible to use the spectral methods. These methods are based on the conversion of the required quantities from the time domain to the frequency domain and vice versa. The Harmonic Balance Method (HB) is one of the spectral methods, which is often used in the simulations of rotating machinery (turbomachines, propellers, etc.). Harmonic balance is based on
solving a number of stationary equations, which are used to calculate the solution solved for the entire period T. The accuracy of the solution is depends on the selected number of harmonics. Simulations were performed for the purpose of validating the use of HB for simulations of contra-rotating propellers. The analysis of the results was based on the available results of steady-state and transient simulations. The analysis showed that the use of a lower number of harmonics produces higher accuracy results when compared to the steady-state simulations, while for the results to be closer to the results of transient simulations, a higher number of harmonics is required.
Title: Towards DNS of Bubble Formation and Dynamics in Water Electrolysis using a Phase-Field Method
Authors: Niloufar Bordbar, Dieter Bothe, and Holger Marschall
Description: Green hydrogen has the potential to play a crucial role in the global transition to sustainable energy to achieve a clean, secure, and affordable energy future. Regarding the generation of hydrogen, efficient, durable, robust, inexpensive, and scalable electrolysers are needed. The scientific objective of this project is to disclose the fundamental interplay of the coupled physico-chemical process governing the detachment of hydrogen bubbles from the electrodes under operating conditions in the real system, which affect the efficiency of electrolysers.
Title: Turbine Benchmarking Project
Authors: Dr. Xiaosheng Chen et al
Description: Unsteady loading and the inability to confidently predict unsteady loading and / or quantify errors drives unnecessary redundancy and design conservatism. A number of open access benchmarking datasets are available for the wind energy community, but not much is available for the tidal energy section. Hence, we proposed this tidal turbine benchmarking exercise to: 1) improve accuracy of modelling techniques, 2) improve confidence in the use of modelling techniques, 3) quantify modelling errors for different techniques under different loading scenarios, 4) development of novel measurement techniques. To achieve the targets, we are carrying out large laboratory test of a highly instrumented tidal turbine in turbulent flow and waves to provide underlying data, and we are also hosting a series of community wide (academia and industry) blind prediction exercises with staged data release, leading to an open access dataset.