H11
Covid / Nanoparticle Modelling

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10:40
conference time (CEST, Berlin)
Dynamic Modeling of Heat Transfer for Syndromic PCR Testing
27/10/2021 10:40 conference time (CEST, Berlin)
Room: H
L. Drazek, J. Baer, D. Duba, P. Childs (bioMérieux, USA)
L. Drazek, J. Baer, D. Duba, P. Childs (bioMérieux, USA)
With the rise of COVID-19, a syndromic approach to diagnostic testing for infectious diseases has become increasingly pertinent and consequential. BioMérieux's BioFire FilmArray, a multiplex Polymerase Chain Reaction (PCR) based system, achieves this aim with a full respiratory panel including SARS-CoV-2 and many other pathogens that cause symptoms common to COVID-19.  From the list of PCR parameters requiring careful optimization to achieve the desired sensitivity and specificity for each pathogen, the fine tuning of sample thermocycling is critical. Given the vulnerability of PCR efficiency to small changes in temperature, thermal modeling can play an invaluable role in this process by providing a full, precise, and reliable thermal profile of the fluid containing the PCR reaction as the fluid is otherwise inaccessible to traditional thermal measurement devices. When combined with known kinetics of the chemistry, this enables fast, in silico optimization of the entire PCR process to ensure ideal efficiency. A 2D FEM-based numerical model has been developed and compared with multiple sets of experiments. The resulting model validation has Sprague and Geers error metrics (Schwer, 2007) of <0.01 for two physical points of comparison. With high confidence in the model accuracy, the resulting temperature profile of the fluid has been evaluated with various sets of thermocycling parameters to demonstrate a strong correlation between the percentage of fluid achieving desired temperatures and the threshold cycle (Ct) with a lower Ct signifying sensitive and robust detection of the pathogen. This thermal model and the observed correlation to PCR efficiency feed into the current effort to develop a comprehensive multiphysics model—coupling this thermal model with a previously developed EDP-based PCR model and a CFD/mass transport component—enabling fully in silico optimization for critical sustaining and future development efforts with the FilmArray diagnostic system.
Heat Transfer, FEM, Comsol Multiphysics, PCR, in vitro Diagnostics, Molecular Biology
11:00
conference time (CEST, Berlin)
Influence of the Positions of Air Purifiers on the Velocity Distribution in Rooms – Comparison of Different Simulation Methods
27/10/2021 11:00 conference time (CEST, Berlin)
Room: H
U. Janoske, S.Burgmann (Bergische Universität Wuppertal, DEU)
U. Janoske, S.Burgmann (Bergische Universität Wuppertal, DEU)
SARS-CoV-2 (COVID-19) led to the development of air purifiers systems for classrooms, offices and workshops. The quality and efficiency of these systems is strongly dependent on the position of the air purifier in the room, the direction of the outflow, the dimensions of the room, additional air conditioning systems, etc. Previous studies reported about the influence of volume flows of the air purifier, position of infected persons, etc, a detailed study on the influence of the position was not considered in literature so far. In this study, the impact of the position of the air purifier and the direction of the flow at the outlet on the flow distribution has been analysed. An empty and closed classroom with a volume of approx. 200 m³ was used in the simulation model. The aerosol transport was modelled with a combination of a steady-state flow simulation which is followed by the simulation of a transient solution of the aerosol transport based on a frozen flow approach. To evaluate the efficiency, two characteristic numbers are determined. First, the volume ratio of the volume in the room with velocities smaller than 0.1 m/s related to the total volume of the room was determined for various positions of the air purifier (coordinates x and y) as well as the angle of the outflow angle (), i.e. in total 25 simulations. A minimum volume ratio was found for x/l=0.7610, y/b=0.294,  =-15° with the dimensions of the room b and l. Second, the ratio of mean concentrations in the room at the beginning (t=0 s) and for 1,200 s were determined by solving the transport equation for the aerosol. The two characteristic numbers show a similar behaviour within a range between 0 and -20%, but show no direct correlation. Within this accuracy, the reduced model can be used for extended parameter studies. For the simulations the Open Source Computational Fluid Dynamics (CFD) code OpenFOAM® (version 6) was used. In next steps, different configurations of classrooms with persons including different positions of infected persons will be considered.
classroom, aerosol, air purifier, position, CFD
11:20
conference time (CEST, Berlin)
Simulation of the distribution of aerosols in public transport to determine the infection risk using Model Order Reduction
27/10/2021 11:20 conference time (CEST, Berlin)
Room: H
S. Vilfayeau, M. Cameron (ESI, FRA); S. Spring (Tplus Engineering GmbH, FRA); R. Magg, R. Almenar (ESI, DEU); A. Rayudu, A.M.N. Rao (ESI, IND); F. Mendonca (ESI-OpenCFD, GBR); M. Reiserer (Universität Kassel, DEU)
S. Vilfayeau, M. Cameron (ESI, FRA); S. Spring (Tplus Engineering GmbH, FRA); R. Magg, R. Almenar (ESI, DEU); A. Rayudu, A.M.N. Rao (ESI, IND); F. Mendonca (ESI-OpenCFD, GBR); M. Reiserer (Universität Kassel, DEU)
Scientific studies have confirmed repeatedly since the beginning of the Corona pandemic that the virus is transmitted mainly by air from person to person. Aerosols which are exhaled by humans play an overriding role as they can concentrate over time mainly in enclosed spaces like public transport. The risk of infection depends on a variety of factors leading to tremendous amount of simulations to explore all scenarios. It becomes consequently an ideal candidate for Model Order Reduction (MOR). Within the BMVI-funded research project EMILIA (Development of Measures for a Pandemic Resistant Public Transport System), we investigate how contaminated aerosols spread in public transport vehicles and the associated risk of infection. As far as possible, all essential factors related to the spread of aerosols in enclosed spaces must be considered. By means of digital methods of numerical fluidity mechanics (CFD), the concentration of exhaled aerosols in different areas of the passenger compartments of selected, representative public transport vehicles (e.g. bus, tram, S-Bahn) is to be determined according to the influencing factors and for selected scenarios. The aim is to gain the widest possible knowledge of passengers' risk of infection under different conditions, which can be transferred to different public transport vehicles. The usage scenarios to be considered should take into account, on the one hand, a different utilization of the vehicles, i.e. the number of passengers, at different times (e.g. rush hour (high), normal traffic time (medium) and low traffic time (low)) and on the other hand, seasonal temperature conditions in which the vehicles are heated, cooled or only ventilated. For each usage scenario the dispersion of aerosols should take into account the ventilation technology used in the vehicles (air change rate, air flow), the passengers’ activities (e.g. normal breathing, normal speaking, loud speaking), as well as the use of different protective masks of passengers (e.g. wearing a nose or no mouth-nose protection, filter quality). The CFD simulation is based on the open source software OpenFOAM. A special methodology developed by the ESI Group that takes physical properties such as air flow, buoyancy, heat flow, non-stationary impulses (such as breathing, coughing, speaking) into account. In order to optimize computing time, and to enable users to get results in real-time for other (unexplored) configurations or working conditions, a reduced model will be created based on the 3D Fluid Dynamic simulations performed. Model Order Reduction techniques, aimed at reducing the computing time without affecting the solution accuracy, will be used for this. Selected 3D simulations from Design of Experiment (DOE) will be used to train the reduced model following the Proper Generalized Decomposition (PGD). In comparison with other MOR techniques like POD, PGD delivers higher flexibility (enrichment, DC-PGD, integration of experimental data) and accuracy with a much lower amount of training runs (an order of magnitude lower). The design variables for such a model (parameters of the reduced model: passengers’ activities, flow rates, occupation rate, etc) will be defined based on relevant scientific questions and empirical values. The construction of such a model using ESI ADMORE App will be described, and how to make use of the reduced model will also be demonstrated.
CFD, Model Order Reduction, COVID 19, Data Analytics
11:40
conference time (CEST, Berlin)
Using Computational Fluid Dynamics for the Design of In-Vitro Testing Methods for Inhalable Micro- and Nanoparticles
27/10/2021 11:40 conference time (CEST, Berlin)
Room: H
C. Brodbeck (Fraunhofer SCAI, DEU); D. Ritter (Fraunhofer Institute for Toxicology and Experimental Medicine ITEM, DEU); C. Hoyer, F. Kiss (Technical University Berlin, DEU)
C. Brodbeck (Fraunhofer SCAI, DEU); D. Ritter (Fraunhofer Institute for Toxicology and Experimental Medicine ITEM, DEU); C. Hoyer, F. Kiss (Technical University Berlin, DEU)
The special material properties of nanomaterials are particularly interesting for various industrial applications, but they also raise questions about possible risks for humans. In particular, there is a lack of data on long-term effects and uptake and distribution in the organism. The aim of the NanoINHAL project, funded by the German Federal Ministry of Education and Research, is to develop an innovative testing system for investigating the toxic effects of airborne nanomaterials. A cell exposure system developed at the Fraunhofer Institute ITEM makes it possible to expose cell cultures and tissue sections to airborne substances and (nano)particles in order to investigate the interaction of the cells with the substances. Fraunhofer Institute SCAI supported the development of the exposure system through numerical flow simulations (CFD). The Technical University of Berlin and the company TissUse GmbH are developing so-called organ-on-a-chip systems, which allow different organ models on a chip to be simultaneously connected in a circuit and these cell and tissue models to be flowed through with medium. By combining the two technologies, the project aims to develop a test system that not only enables the investigation of direct effects of airborne nanomaterials on human respiratory models, but also the investigation of effects on other organs. In the NanoINHAL project, Fraunhofer Institute SCAI uses simulation methods to characterize and optimize the flow and the thermal conditions in the exposure system. Both the transport of nanoparticles in airborne flows and the essential thermal performance of the cell exposure system are investigated with simulation approaches using commercial and open source software. It became evident, that the simulation of the nanoparticle transport has some crucial influencing factors concerning both the numerical procedures and the necessary computation time. Due to a small temperature range the human cells require for viability and a sufficient high temperature gradient to ensure particle deposition with thermophoresis, the prediction of the thermal behavior of the exposure system with a Conjugate-Heat-Transfer simulation model gained substantial interest. Results of the simulation approaches will be demonstrated in this presentation.
In-vitro, toxicology, nanoparticles, CFD, thermal simulation
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