The supercomputers of the UL FEST Institute of Numerical Modelling are used by both researchers and companies as digital laboratories where scientists study and describe natural and technological processes—such as air and water flow, heat and energy transfer, and material behavior under various conditions—as well as develop artificial intelligence models and solutions for the analysis of these complex systems. The Institute also conducts numerical modelling of silicate crystals, which forms the foundation for the development of modern processors and microchips.

The exhibition explores the interaction between artificial intelligence, algorithmic communities, and humans, as well as how these phenomena shape and transform human relationships. From this perspective, the exhibition can be seen as an attempt to create a “portrait of our time,” reflecting the impact of technology on culture—including the process of art-making—and on society as a whole.

Gints Gabrāns is an installation and multimedia artist. In 2007, his project Paraspoguļi represented Latvia at the 52nd Venice Biennale. The exhibition is curated by Artūrs Virtmanis.

The exhibition is organized by the Riga City Municipality institution Riga Contemporary Art Space and is supported by the Riga City Municipality, Malduguns Brewery, Dateks, and the Institute of Numerical Modelling of the UL Faculty of Exact Sciences and Technology. The well-known computer assembly company Dateks.lv provides the high-performance computer required for Gints Gabrāns’ artificial intelligence installation.

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Mihails Birjukovs, UL FST INM — “A partial overview & plan for MHD, building physics and other research directions at the INM Multiphysical Processes Modelling Lab”;

Mihails Birjukovs, UL FST INM — “Applications of methods developed for multiphase MHD to active matter, organ-on-a-chip, magneto-microconvection & cell dynamics systems” (Part 1);

At the next (fifth) seminar (November 20), UL FST INM lead researcher Mihails Birjukovs will deliver the second part of the presentation “Applications of methods developed for multiphase MHD to active matter, organ-on-a-chip, magneto-microconvection & cell dynamics systems.” Meanwhile, during the following seminar (November 27), INM researcher Kirils Surovovs will speak about “Applying LLMs for launching CFD simulations and parameter optimization.”

The seminars take place every Thursday from 13:00 to 14:30 (up to 1.5 hours), both in person at INM (House of Science, room 520) and remotely via MS Teams. Participation and presentation at the seminars are open — those interested are asked to contact Mihails Birjukovs (UL email or LinkedIn), who organizes and leads the seminars, to receive notifications about future seminars, get access the seminar archive, and to register for (on-)offline participation, including presenting a talk. The language of the seminars is English.

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Out of 240 workshop participants 40 were students at differing study levels (not all were presenters). European Space Agency encourages students to step into space industry activities through ESA Academy that even provides financial support to students for participation in such workshops.

Spacecrafts often use two-phase cooling systems: heat pipes and loop heat pipes, where innovations still continue to spread. Luka works on development and testing of such systems in Allatherm company from Latvia, and he presented company’s latest development — multievaporator. Multievaporator is a component of loop heat pipes, which takes heat from electronics or other devices that need cooling. Extensive testing has shown that multievaporator loop heat pipes could provide passive thermal management solution for spacecraft where other existing solutions happen to be heavier or more difficult in integration.

Phase change processes that happen in evaporator required additional research from fluid dynamics viewpoint, which became the starting point for Luka’s doctoral studies in UL. For the ESTEW closure, visits to ESTEC laboratories were offered. Luka visited ESA Propulsion Laboratory, where spacecraft ionic thrusters are tested. Allatherm has another innovation dedicated to ionic thruster propulsion — Xenon Refuelling Compressor. The technology involves phase change (again!) and the related design and research conducts another UL INM doctoral student Igors Ušakovs.

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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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A new scientific article “Comparison of experimental and calculated thermal transmittance for timber-framed outer wall constructions” has been published by leading researcher Stanislavs Gendelis in Q1 Quartile journal “HeatTranfer”.

It describes the experimental measurements of the thermal transmittance (U-value) of widely used timber frame outer wall constructions with heat insulation filling in various cases of material combination. The agreement with the theoretical calculations is analyzed. The results of the study show differences between experimental and calculated thermal transmittance values for timber frame outher walls, which are mainly determined by the influence of moisture content, which is usually not taken into account in the calculations.

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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.

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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).

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