Search

Your search keyword '"Vuorinen, V."' showing total 307 results
Start Over Author "Vuorinen, V."
307 results on '"Vuorinen, V."'

1. A GPU-accelerated computational fluid dynamics solver for assessing shear-driven indoor airflow and virus transmission by scale-resolved simulations

Author

Korhonen, M., Laitinen, A., Isitman, G. E., Jimenez, J. L., and Vuorinen, V.

Subjects
Physics - Fluid Dynamics
Abstract

We explore the applicability of MATLAB for 3D computational fluid dynamics (CFD) of shear-driven indoor airflows. A new scale-resolving, large-eddy simulation (LES) solver titled DNSLABIB is proposed for MATLAB utilizing graphics processing units (GPUs). The solver is first validated against another CFD software (OpenFOAM). Next, we demonstrate the solver performance in three isothermal indoor ventilation configurations and the results are discussed in the context of airborne transmission of COVID-19. Ventilation in these cases is studied at both low (0.1 m/s) and high (1 m/s) airflow rates corresponding to $Re=5000$ and $Re=50000$. An analysis of the indoor CO$_2$ concentration is carried out as the room is emptied from stale, high CO$_2$ content air. We estimate the air changes per hour (ACH) values for three different room geometries and show that the numerical estimates from 3D CFD simulations may differ by 80-150 % ($Re=50000$) and 75-140 % ($Re=5000$) from the theoretical ACH value based on the perfect mixing assumption. Additionally, the analysis of the CO$_2$ probability distributions (PDFs) indicates a relatively non-uniform distribution of fresh air indoors. Finally, utilizing a time-dependent Wells-Riley analysis, an example is provided on the growth of the cumulative infection risk being reduced rapidly after the ventilation is started. The average infection risk is shown to reduce by a factor of 2 for lower ventilation rates (ACH=3.4-6.3) and 10 for the higher ventilation rates (ACH=37-64). The results indicate a high potential for DNSLABIB in various future developments on airflow prediction., Comment: 31 pages, 15 figures

Published
2022

32. Wafer Level Solid Liquid Interdiffusion Bonding

Author

Vuorinen, V., Dong, H., Ross, G., Hotchkiss, J., Kaaos, J., Paulasto-Kröckel, M., Electronics Integration and Reliability, Department of Electrical Engineering and Automation, Aalto-yliopisto, and Aalto University

Subjects
reliability, Cu-In-Sn system, Low-temperature SLID bonding, TLP bonding
Abstract

openaire: EC/H2020/826588/EU//APPLAUSE Wafer-level solid liquid interdiffusion (SLID) bonding, also known as transient liquid-phase bonding, is becoming an increasingly attractive method for industrial usage since it can provide simultaneous formation of electrical interconnections and hermetic encapsulation for microelectromechanical systems. Additionally, SLID is utilized in die-attach bonding for electronic power components. In order to ensure the functionality and reliability of the devices, a fundamental understanding of the formation and evolution of interconnection microstructures, as well as global and local stresses, is of utmost importance. In this work a low-temperature Cu-In-Sn based SLID bonding process is presented. It was discovered that by introducing In to the traditional Cu-Sn metallurgy as an additional alloying element, it is possible to significantly decrease the bonding temperature. Decreasing the bonding temperature results in lower CTE induced global residual stresses. However, there are still several open issues to be studied regarding the effects of dissolved In on the physical properties of the Cu-Sn intermetallics. Additionally, partially metastable microstructures were observed in bonded samples that did not significantly evolve during thermal annealing. This indicates the Cu-In-Sn SLID bond microstructure is extremely stable.

Published
2021

40. Review—Recent Developments in Low Temperature Wafer Level Metal Bonding for Heterogenous Integration

Author

Wernicke, T., Rebhan, B., Vuorinen, V., Paulasto-Kröckel, M., Dubey, V., Diex, K., Wünsch, D., Baum, M., Wiemer, M., Tanaka, S., Froemel, J., Aasmundtveit, K. E., Nguyen, H.-V., and Dragoi, V.

Abstract

An overview of various low-temperature (<200 °C) wafer bonding processes using metal interlayers is presented. Such processes are very attractive for novel applications in 3D heterogenous packaging as the allow for simultaneous formation of electrical interconnects, as well as hermetic encapsulation of various sensors and microelectromechanical systems-based devices. Metal wafer bonding is a generic category of processes consisting of various sub-categories, each one defined by the different principles governing the process. One can differentiate between eutectic wafer bonding (a eutectic alloy is formed as bonding layer during the process by liquid-solid interdiffusion), intermetallic wafer bonding (an intermetallic alloy is formed as bonding layer during the process by solid-liquid interdiffusion, a process known also as solid liquid intermetallic diffusion transient liquid phase, and metal thermo-compression wafer bonding. Different critical/gating parameters were investigated and their impact for generally reducing processing temperatures for the different metal bonding systems was studied.

Published
2024
Full Text
View/download PDF

43. Modelling aerosol transport and virus exposure with numerical simulations in relation to SARS-CoV-2 transmission by inhalation indoors

Author

Vuorinen, V., Aarnio, M., Alava, M., Alopaeus, Ville, Atanasova, N., Auvinen, M., Balasubramanian, N., Bordbar, H., Erästö, P., Grande, R., Hayward, N., Hellsten, A., Hostikka, S., Hokkanen, J., Kaario, O., Karvinen, A., Kivistö, I., Korhonen, M., Kosonen, R., Kuusela, J., Lestinen, S., Laurila, E., Nieminen, H. J., Peltonen, P., Pokki, J., Puisto, A., Råback, P., Salmenjoki, H., Sironen, T., Österberg, M., Vuorinen, V., Aarnio, M., Alava, M., Alopaeus, Ville, Atanasova, N., Auvinen, M., Balasubramanian, N., Bordbar, H., Erästö, P., Grande, R., Hayward, N., Hellsten, A., Hostikka, S., Hokkanen, J., Kaario, O., Karvinen, A., Kivistö, I., Korhonen, M., Kosonen, R., Kuusela, J., Lestinen, S., Laurila, E., Nieminen, H. J., Peltonen, P., Pokki, J., Puisto, A., Råback, P., Salmenjoki, H., Sironen, T., and Österberg, M.

Abstract

We provide research findings on the physics of aerosol and droplet dispersion relevant to the hypothesized aerosol transmission of SARS-CoV-2 during the current pandemic. We utilize physics-based modeling at different levels of complexity, along with previous literature on coronaviruses, to investigate the possibility of airborne transmission. The previous literature, our 0D-3D simulations by various physics-based models, and theoretical calculations, indicate that the typical size range of speech and cough originated droplets (d⩽20μm) allows lingering in the air for O(1h) so that they could be inhaled. Consistent with the previous literature, numerical evidence on the rapid drying process of even large droplets, up to sizes O(100μm), into droplet nuclei/aerosols is provided. Based on the literature and the public media sources, we provide evidence that the individuals, who have been tested positive on COVID-19, could have been exposed to aerosols/droplet nuclei by inhaling them in significant numbers e.g. O(100). By 3D scale-resolving computational fluid dynamics (CFD) simulations, we give various examples on the transport and dilution of aerosols (d⩽20μm) over distances O(10m) in generic environments. We study susceptible and infected individuals in generic public places by Monte-Carlo modelling. The developed model takes into account the locally varying aerosol concentration levels which the susceptible accumulate via inhalation. The introduced concept, ’exposure time’ to virus containing aerosols is proposed to complement the traditional ’safety distance’ thinking. We show that the exposure time to inhale O(100) aerosols could range from O(1s) to O(1min) or even to O(1h) depending on the situation. The Monte-Carlo simulations, along with the theory, provide clear quantitative insight to the exposure time in different public indoor environments., Cited By :11; Export Date: 7 December 2020; Article

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results