The project was devoted to silicon melt flow simulations (e.g., hydrodynamic simulations) using OpenFOAM C++ library. The OpenFOAM library is widely used in both academical and industrial research groups. However, the current experience shows that the higher the number of used cores, the lower is the numerical stability of a simulation, which leads to numerical errors and divergence. Therefore, it is desirable to test OpenFOAM stability on a large number of computational cores, thus determining its scalability for large-scale HPC applications.

The simulations on MeluXina cluster showed better scalability than on the previously tested clusters in Latvia (University of Latvia and Riga Technical University). Especially good result is, for example, almost 14-fold speed-up with the mesh with 3.2 million cells, when core number increased from 2 to 16. Such speed-up is superlinear (the speed increases more than the number of cores) and demonstrates the efficient use of HPC resources. During the project, optimal type of linear matrix solver (GAMG) and at least a lower bound of acceptable solver tolerances (9 times higher than standard) were obtained.

This project has received funding from the European High-Performance Computing Joint Undertaking (JU) under grant agreement No 101101903. The JU receives support from the Digital Europe Programme and Germany, Bulgaria, Austria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Greece, Hungary, Ireland, Italy, Lithuania, Latvia, Poland, Portugal, Romania, Slovenia, Spain, Sweden, France, Netherlands, Belgium, Luxembourg, Slovakia, Norway, Turkiye, Republic of North Macedonia, Iceland, Montenegro, Serbia.

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This article presents a methodology to assess the effects of global warming on building heat demand and the resulting changes in the installed capacity of district heating (DH) systems with and without renovation of existing multi-apartment buildings by transitioning from the 3rd generation DH system towards the sustainable 4th generation DH system in the long-term perspective (by 2050) in the city of Riga. The methodology couples the system dynamics approach with the building heat balance model, thus enabling an analysis of heating degree days, heat load curves, and parametric changes in the DH system due to climate change.

The post New publication in the journal “Energy” appeared first on Institute of Numerical Modelling.

The distribution of dopants and impurities in silicon crystal determines the electrical resistivity and other important crystal properties. For the description of species transport, the segregation at the crystallization interface plays a key role. It is important to consider not only the equilibrium segregation coefficient, but also the effective segregation coefficient,  which takes the melt flow into account. 

In the publication the results of the modelling of crystal growth process are described: the shape of phase boundaries, melt flow, species distribution in the melt and, finally, the radial and axial species distributions in the crystal. It was proven that the effective segregation coefficient is not constant during the growth process, but increases with melt diameter due to less intensive melt mixing.

This research was supported by University of Latvia, “Strengthening of the capacity of doctoral studies at the University of Latvia within the framework of the new doctoral model”, grant number No. 8.2.2.0/20/I/006.

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All the most important data of submitted project applications are available on the ALTUM website, including technical documentation (heat energy consumption and its reduction, CO₂ emissions, building area, etc.), building contractors, construction supervisors, costs and application of financial correction. Researchers from the INM Stanislavs Gendelis has conducted a statistical analysis of publicly available data, the main results of which are presented below:

1.) Number of projects by regions of Latvia. Half of all projects (51%) consist of two cities – Riga and Liepāja, together with three counties – Olaine, Sigulda and Valmiera. The least number of projects, one each, have been submitted from Varakļani, Augšdaugava and Krāslava counties. It should be noted that only 3 projects have been approved from the second largest city, Daugavpils. Figure below shows number of buildings in the cities and counties.

2.) Area of buildings and year of construction. Two-thirds of the buildings are between 500 and 3,000 m², but the total range is from 190 m² up to 16,500 m². Figure below shows the number of buildings by the area.

Most of all buildings were built in the Soviet time (1955-1990) with a peak in 1970-1985. The oldest building was commissioned in 1870, and the newest in 2008. Figure below shows the number of buildings by the year of construction.

3.) Heating consumption in buildings before and after implementation of energy efficiency measures. In most of the buildings (75%) before the measures annual heating energy is within 100…160 kWh/m² range with peak between 120 and 150 kWh/m². Figure below shows the number of buildings by the heating consumption before the measures.

After the implementation of the energy efficiency improvement measures planned within the project, the heating consumption of 90% of the total number of buildings is calculated in the range of 40 to 70 kWh/m² with a pronounced maximum in the interval of 50…55 kWh/m², which will correspond to every fourth building. Figure below shows the number of buildings by the heating consumption after the measures.

4.) Heating consumption depending on the heated area. Analyzing the planned heating consumption vs. the existing consumption, a pronounced dependence is clearly visible – the greater the existing heating need, the less efficiency can be achieved with energy efficiency improvement measures (see figure below).

The main reason for this is the influence of the building’s geometry (including compactness) on the proportion of heat loss in the total heat balance. And this is also indicated by the dependence of heating consumption on the total area of the building – the smaller the size of the building, the higher the normalized heating consumption. Figure below shows annual heating energy (kWh/m²) depending on the building area before (blue dots) and after (orange dots) building renovation.

5.) Project costs. Depending on the building area and the type of planned measures, the cost of one project varies from €42,500 to €3,150,000, however, half of all projects are realized with total costs between €200,000 and €400,000. Normalized construction costs per building area (€/m²) for 60% of the projects is between 130 and 220 €/m² with a pronounced maximum in the interval of 160…190 €/m², which covers 22% of the buildings. Figure below shows the number of buildings by the project costs per m² of gross internal floor area.

6.) Trends in project costs throughout the duration of the programme. To analyze the changes over time for the ALTUM program ” Energy Efficiency in Multi-Apartment Buildings ” from 2016 to 2022, a statistical analysis of annual data was carried out. It showed that the total eligible costs of projects approved in the first year of the program ranged between 70 and 260 €/m² with an average indicator of 152 €/m² (see graph below). However, in the last year of the program, the average cost of projects has increased by 63% – up to 249 €/m², with the maximum indicator reaching even 460 €/m². First figure below shows the construction costs for all the accepted project with added time trendline; the second figure displays the yearly averaged values for all 6 project implementation years.

This analysis is a part of the project Analysis of the actual energy consumption of zero energy buildings and the development of the necessary energy efficiency improvement solutions 
(Nr. 1.1.1.2/VIAA/3/19/505).

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Andrejs Sabanskis presented research on dislocation modeling in germanium crystals. Using self-developed software, more than a hundred calculations were performed to describe the effect of various process parameters on the dislocation density distribution.

Maksims Surovovs presented the results of open melting front modeling for the floating zone crystal growth process. The new model is significantly more accurate than the previously used one, and the melting front can now be calculated with an accuracy of 0.1 mm.

Kirils Surovovs participated in the conference with a poster on impurity transfer modeling in a floating zone system. The algorithm developed in the research allows for a more accurate description of the distribution of impurities (boron, phosphorus, carbon) in the grown crystals. Kirils received the Young Scientist Award for his research.

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This publication shows the measurement of particle velocity in liquid metal flowing around a cylindrical obstacle using algorithms previously developed by INM researchers to determine particle trajectories.

The publication presents an image-processing methodology designed to detect particles in neutron radiographic images with high noise and low particle contrast, as well as the use of the MHT-X tracking algorithm to reconstruct particle trajectories.

Initial results show that the developed methods ensure consistent detection of particles and the recovery of long, representative, and plausible particle trajectories. This is achieved, among other means, by using particle image velocimetry data as additional information to predict particle motion. However, the need to introduce a better approach to extrapolation of particle position important to further increase tracking accuracy.

The article provides a number of recommendations on how to obtain better results with the existing tools. Currently, the greatest difficulty is the acquisition of data and the current development phase of neutron radiography technologies for liquid metals.

The study is a part of the ERAF project “Development of numerical modelling approaches to study complex multiphysical interactions in electromagnetic liquid metal technologies” (No. 1.1.1.1/18/A/108).

The post A new publication: Particle tracking velocimetry in liquid gallium flow around a cylindrical obstacle appeared first on Institute of Numerical Modelling.

Supercomputing or HPC is used all over the world to perform large-scale calculations and various types of simulations much faster, providing a much more efficient process than a personal computer. For example, with the help of supercomputing, it is possible to perform simulations before starting the production processes, thus saving resources, as HPC simulation allows to find the most suitable solutions for materials or technological processes.

More information and program of the event here!

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By changing relevant system parameters, such as the electric current, melt layer thickness and initial shape, development of instabilities and different free surface shape transformations were observed. The experimental results will be further analysed and interpreted, and will be used to validate complex numerical models that describe the underlying physical processes. Experimentally validated and tested numerical models can further be used to design and optimize different technological processes.

The studies are carried out in the framework of the ERDF project “Development of numerical modelling approaches to study complex multiphysical interactions in electromagnetic liquid metal technologies” (No 1.1.1.1/18/A/108).

The post Electromagnetic control of liquid metal layer dynamics appeared first on Institute of Numerical Modelling.

Multi-phase flows include complex particle, bubble and drop motion, as well as collective dynamics (e.g. collisions, coalescence, breakup, etc.). To understand the physics and characteristics of such systems, it is very often necessary to reconstruct the trajectories of the above-mentioned objects accounting for their interactions.

Multiple hypothesis tracking (MHT) is a computer vision algorithm that allows one to track the movement of objects and derive their trajectories. MHT is considered to be the most general and robust approach. Unfortunately, when working in real time with large amounts of data, this algorithm is too computationally expensive. However, unlike other sectors (military, surveillance, transport, etc.) where data recognition is required at once (online), science often does not require an immediate interpretation of data. Much more important is the accuracy and relevance of the results obtained.

The article offers a new approach to optimization of the MHT algorithm by switching to its offline form. In this form, when looking for optimal associations between objects (corresponding motion scenarios) to reconstruct trajectories, it is possible to do so with Algorithm-X. This allows for a very significant reduction in computational complexity. Then the most likely trajectories are selected using motion models.

The newly developed MHT-X algorithm is fast and universal. Using different motion models one can also study the movement of other objects.

The study is a part of the ERDF project “Development of numerical modelling approaches to study complex multiphysical interactions in electromagnetic liquid metal technologies” (No. 1.1.1.1/18/A/108).

The post A new publication in the journal “Experiments in Fluids” appeared first on Institute of Numerical Modelling.

Hempcrete is known as an environmentally friendly building material with a good specific thermal resistance. Experiments were conducted to determine the hygrothermal performance of this material and to ascertain compliance with modern standards.

Temperature and relative humidity were monitored over 8 months for the hempcrete wall and the hempcrete manufacturing process was documented in detail. The hygrothermal performance of the wall formed from this material was modeled using numerical simulations.

It was observed experimentally that hempcrete serves as a good insulation material in Latvian climate and similar conditions. Importantly, high-density hempcrete also proved resilient to mould growth even at high relative humidity.

Physical and mechanical tests of the material, as well as numerical modeling results, indicated that hempcrete could be a good alternative to traditional construction materials in the future, significantly reducing climate impact and improving energy efficiency.

The post Combined in situ and in silico validation of a material model for hempcrete appeared first on Institute of Numerical Modelling.