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  <doc>
    <id>5799</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Linking flow conditions in membrane oxygenators to arrangements of multimeric von-Willebrand-factor as indication for coagulation</title>
    <abstract language="eng">Introduction&#13;
Shear induced multimerisation of von-Willebrand-factor (vWF) is supposed to play an important role in coagulation inside extracorporeal membrane oxygenators. However, there is no proof that links observed vWF structures to computed or measured flow conditions.&#13;
&#13;
Methods&#13;
The structures of multimeric vWF fibers, observed in clinically used membrane oxygenators is examined using immunofluorescence microscopy (IFM) using Carstairs’ staining method (positive ethics committee vote). The flow around the membrane fibres inside the oxygenator is investigated in terms of shear rate, wall shear velocity and streamlines by using CFD (RANS, Carreau-Yasuda viscosity, geometry remodelled after high-resolution µCT-scans). By interpreting the histological and numerical results in this common context, indications for shear induced coagulation mechanisms can be identified.&#13;
&#13;
Results&#13;
The fibre structures of multimeric vWF build regular but not exactly symmetric formations around the contact face (CF) between the crosswise stacked oxygenator fibres (OF), see fig.1B, vWF marked red. Annular around the CF arranged, cells are likely to be found, see fig.1B, nuclei marked blue. &#13;
The computed streamlines around the OF show attached flow around the circular fibres. However, the irregular arrangement of real OF produce considerable cross flow between the interconnected neighbouring channels, in contrast to previous 2D-simulations. Thus, the CF are washed around closely by blood, also from neighbouring channels. The wall shear velocity streamlines form regular, slightly asymmetric shapes around the contact faces. The occurring maximum shear rates are in the range of 1,000 1/s.&#13;
Discussion&#13;
The shapes of vWF structures found in clinically used oxygenators match the computational results in terms of wall shear velocity and streamlines well. The accumulation of cells close to the CF can also be explained by fluid mechanics, as there are small shear gradients and slow velocities. However, occurring shear rates between OFs are too low to trigger multimerisation of vWF. That raises the question where in the circuit the actual activation of vWF is started and how, at least partly chained, vWF multimeres are attracted towards the OF surface. A next step will be the investigation of the actual shear rate triggered (or mediated) multimerisation of vWF. Towards this end, microfluidic experiments with shear triggered coagulation will be performed. Also of big interest is the computation of the flow situation in the oxygenator in proximity to chaining threads, which have been ignored in computations so far. However, first a realistic representation of the effective viscosity in computations is needed, which is not available yet.</abstract>
    <parentTitle language="eng">World Congress of Biomechanics 2018, Convention Centre Dublin, 8.-12. Juli 2018</parentTitle>
    <enrichment key="opus.source">publish</enrichment>
    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Clemens Birkenmaier</author>
    <author>Lars Krenkel</author>
    <author>Karla Lehle</author>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5794</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace>Göttingen</publisherPlace>
    <creatingCorporation>Deutsche Gesellschaft für Luft- und Raumfahrt e.V. / Arbeitsgemeinschaft Strömungen mit Ablösung, AG STAB</creatingCorporation>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">High Spatial Resolution Tomo-PIV of the Nasopharynx Focussing on the Physiological Breathing Cycle</title>
    <abstract language="eng">Investigations of complex patient-specific flow in the nasopharynx requires high resolution numerical calculations validated by reliable experiments. When building the validation base and the benchmark&#13;
of computational fluid dynamics, an experimental setup of the nasal airways was developed. The applied optical measurement technique of tomo-PIV supplies information on the governing flow field in three dimensions. This paper presents tomo-PIV measurements of the highly complex patient-specific geometry of the human trachea. A computertomographic scan of a person’s head builds the basis of the experimental silicone model of the nasal airways. An optimised approach for precise refractive index matching avoids optical distortions even in highly complex non-free-of-sight 3D geometries. A linear-motor-driven pump generates breathing scenarios, based on measured breathing cycles. Adjusting of the CCD cameras‘ double-frame-rate PIV-Δt enables the detailed analysis of flow structures during different cycle phases. Merging regions of interest enables high spatial resolution acquisition of the flow field.</abstract>
    <parentTitle language="deu">23. DGLR Fach-Symposium Strömungen mit Ablösung, 09./10. November 2022, Berlin, Deutschland</parentTitle>
    <identifier type="url">https://www.dlr.de/as/Portaldata/5/Resources/dokumente/veranstaltungen/stab_workshop/Jahresbericht2022.pdf</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="BegutachtungStatus">begutachtet</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Sandra Melina Tauwald</author>
    <author>Maurizio Quadrio</author>
    <author>Markus Rütten</author>
    <author>Christian Stemmer</author>
    <author>Lars Krenkel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Tomographic PIV</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Flow visualisation</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Physiological Breathing</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Nasal airflow</value>
    </subject>
    <collection role="ddc" number="6">Technik, Medizin, angewandte Wissenschaften</collection>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="institutes" number="RCHST">Regensburg Center of Health Sciences and Technology - RCHST</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5793</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace>Göttingen</publisherPlace>
    <creatingCorporation>Deutsche Gesellschaft für Luft- und Raumfahrt e.V. / Arbeitsgemeinschaft Strömungen mit Ablösung, AG STAB</creatingCorporation>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Generation, Distribution, and Contagiousness of Surgical Smoke during Tracheotomies</title>
    <abstract language="eng">Surgical smoke has been a little discussed topic in the context of the current pandemic. Surgical smoke is generated during the cauterization of tissue with heat-generating devices and consists of 95% water&#13;
vapor and 5% cellular debris in the form of particulate matter. In-vivo investigations are performed during tracheotomies where surgical smoke is produced during tissue electrocautery. Furthermore, in-vitro parametric studies to investigate the particle number and size distribution and the spatial distribution of surgical smoke with laser light sheet technique are conducted. The higher the power of the high-frequency-device the larger the particles in size and the higher the resulting particle counts. The images taken show the densest smoke at 40W with artificial saliva. The resulting characteristic size distribution, which may include viruses and bacterial components, confirms that the risk arising from surgical smoke should be considered. Furthermore, the experiments will provide the database for further numerical investigations.</abstract>
    <parentTitle language="deu">23. DGLR Fach-Symposium Strömungen mit Ablösung, 09./10. November 2022, Berlin, Deutschland</parentTitle>
    <identifier type="url">https://www.dlr.de/as/Portaldata/5/Resources/dokumente/veranstaltungen/stab_workshop/Jahresbericht2022.pdf</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="BegutachtungStatus">begutachtet</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Vera Stelzer</author>
    <author>Sandra Melina Tauwald</author>
    <author>Veronika Vielsmeier</author>
    <author>Fabian Cieplik</author>
    <author>Arne Kandulski</author>
    <author>Wulf Schneider-Brachert</author>
    <author>Olaf Wuensch</author>
    <author>Markus Rütten</author>
    <author>Lars Krenkel</author>
    <collection role="ddc" number="6">Technik, Medizin, angewandte Wissenschaften</collection>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="institutes" number="RCHST">Regensburg Center of Health Sciences and Technology - RCHST</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5792</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Numerical Investigation of a 3D Dragonfly Wing Captured with a High-Resolution Micro-CT</title>
    <abstract language="eng">The special wing geometry of dragonflies consisting of veins and a membrane forming a corrugated profile leads to special aerodynamic characteristics. To capture the governing flow regimes of a dragonfly wing in detail, a realistic wing model has to be investigated. Therefore, this study aimed to analyze the aerodynamic characteristics of a 3D dragonfly wing reconstructed from a high-resolution micro-CT scan. Afterwards, a spatially high discretized mesh was generated using the mesh generator CENTAUR™ 14.5.0.2 (CentaurSoft, Austin, TX, US) to finally conduct Computational Fluid Dynamics (CFD) investigations in Fluent® 2020 R2 (ANSYS, Inc., Canonsburg, PA, US). Due to the small dimensions of the wing membrane, only the vein structure of a Camacinia Gigantea was captured at a micro-CT voxel size of 7 microns. The membrane was adapted and connected to the vein structure using a Boolean union operation. Occurring  nconsistencies after combining the veins and the membrane were corrected using an adapted pymesh script [1]. As an initial study, only one quarter of the wing (outer wing section) was investigated to reduce the required computational effort. The resulting hybrid mesh consisting of 10 pseudo-structured prism layers along the wing surface and tetrahedra in the farfield area has 43 mio. nodes. The flow around the wing was considered to be incompressible and laminar using transient calculations. When the flow passes the vein structures, steady vortices occur in the corrugation valleys leading to recirculation zones. Therefore, the dragonfly wing resembles the profile of an airfoil. This leads to comparable lift coefficients of dragonfly wings and airfoil profiles at significantly reduced structural weight. The reconstructed geometry also included naturally occurring triangular prismlike serrated structures at the leading edge of the wing, which have comparable effects to micro vortex generators and might stabilize the recirculation zones. Further work aims to investigate the aerodynamic properties of a complete dragonfly wing during wing flapping.</abstract>
    <parentTitle language="eng">8th European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS Congress 2022, 5-9 June 2022, Oslo, Norway</parentTitle>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="BegutachtungStatus">begutachtet</enrichment>
    <licence>Creative Commons - CC BY-NC-SA - Namensnennung - Nicht kommerziell -  Weitergabe unter gleichen Bedingungen 4.0 International</licence>
    <author>Vera Stelzer</author>
    <author>Markus Rütten</author>
    <author>Lars Krenkel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>CFD</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Dragonfly</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Aerodynamics</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Gliding Flight</value>
    </subject>
    <collection role="ddc" number="6">Technik, Medizin, angewandte Wissenschaften</collection>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="institutes" number="RCHST">Regensburg Center of Health Sciences and Technology - RCHST</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5788</id>
    <completedYear/>
    <publishedYear>2018</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Towards a realistic model of blood viscosity and coagulation in membrane oxygenators</title>
    <abstract language="eng">Modelling blood flow an shear induced coagulation in membraene oxygenators (MO) is challenging. The relevant geometry of oxygenator fibers (OF) and chaining threads is complex and spans several length scales. In relevant scales and regimes blood shows several significant non-Newtonian effects. Existing models are only capable of accounting for some, but not all relevant effects. Additionally, coagulation processes are influencing fluid properties and geometry significantly. Due to the enormous size of the discretised geometries highly detailed viscosity and coagulation properties of blodd flow in MOs. First step is to find a gemoetry dependent viscosity representation on basis of parametric micro channel experiments with anti-coagulated blood. Next step is a statistic coagulation model, based on micro channel experiments with human (re-calcified citrated) whole blood an evaluation of clinically used osygenators. Since shear rate dependent (i.e. viscosity dependet) coagulation in return influences the viscosity, a combined model with suitable implementation in a RANS framework is necessary. Towards this end, micro channel experiments with new and used single OFs triggering coagulation are performed. Structures of multimeric von Willebrand fibers (vWF), as indicator for shear induced coagulation, are compared to computed and measured flow conditions, using immunofluorescence microscopy, RANS-computations and µPIV, respectively. Preliminary examinations in clinically used MOs show good agreement between occurring structures of vWF, cell depositions and computed flow patterns (geometry form µCT-Scans). However, computed shear rates might be to low to actually trigger activation of vWF. The complex geometry of MOs results in huge meshes, which makes RANS with statistical modelling of viscosity and coagulation a reasonable approach. Towards this end, experimental data on micro channel level with evaluation on real application level is crucial. Especially regarding clotting processes, micro fluidic experiments are powerful research tool.</abstract>
    <parentTitle language="eng">6th European Conference on Computational Mechanics (Solids, Structures and Coupled Problems) - ECCM 6; 7th European Conference on Computational Fluid Dynamics - ECFD 7 : Glasgow, Scotland, UK, June 11-15, 2018</parentTitle>
    <enrichment key="BegutachtungStatus">peer-reviewed</enrichment>
    <enrichment key="opus.source">publish</enrichment>
    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Clemens Birkenmaier</author>
    <author>Lars Krenkel</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Blood Viscosity</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Shear Raed Induced Coagulation</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Membrane Oxygenator</value>
    </subject>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5804</id>
    <completedYear/>
    <publishedYear>2019</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Feasibility of detecting thrombotic deposits in membrane oxygenators using micro computed tomography</title>
    <parentTitle language="eng">25th Congress of the European Society of Biomechanics, July 7-10, 2019, Vienna, Austria</parentTitle>
    <identifier type="url">https://esbiomech.org/conference/archive/2019vienna/Contribution_129.pdf</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="opus.doi.autoCreate">false</enrichment>
    <enrichment key="opus.urn.autoCreate">true</enrichment>
    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Clemens Birkenmaier</author>
    <author>Christian Dornia</author>
    <author>Karla Lehle</author>
    <author>Lars Krenkel</author>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5805</id>
    <completedYear/>
    <publishedYear>2019</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Elementary experimental setup for flow visualization in upper human respiratory tract</title>
    <parentTitle language="eng">25th Congress of the European Society of Biomechanics, July 7-10, 2019, Vienna, Austria</parentTitle>
    <identifier type="url">https://esbiomech.org/conference/archive/2019vienna/Contribution_195.pdf</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="opus.doi.autoCreate">false</enrichment>
    <enrichment key="opus.urn.autoCreate">true</enrichment>
    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Sandra Melina Tauwald</author>
    <author>Lars Krenkel</author>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5795</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
    <publisherPlace>Göttingen</publisherPlace>
    <creatingCorporation>Deutsche Gesellschaft für Luft- und Raumfahrt e.V. / Arbeitsgemeinschaft Strömungen mit Ablösung, AG STAB</creatingCorporation>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2023-02-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Experimental Investigation of Logitudinal Folds in Endotracheal Tube Cuffs and their Correlation to Silent Breathing</title>
    <abstract language="eng">Air leakage past High-Volume-Low-Pressure (HVLP) endotracheal tube (ETT) cuffs creates a potential infection risk for health care professionals during ventilation of patients suffering from contagious airborne diseases. However, unlike silent aspiration, a phenomenon where fluids enter the airways of intubated patients, the aspect of aerosol emergence through cuff folds -what we called accordingly “silent breathing” (SB)- has not been investigated in detail so far. &#13;
This study investigates air leakage past HVLP cuffs with varying cuff pressures under realistic artificial breathing scenarios experimentally and in addition numerically. The focus was laid on the parametric investigation of the occurrence and furthermore on different influencing factors of silent breathing. The morphology of the folds responsible for the leakage was captured using high-resolution 3D microcomputed tomography (μCT). For the numerical investigations (Com-putational Fluid Dynamics - CFD), the commercial CFD Software package FLUENT 2021 R2 (ANSYS, Inc., Canonsburg, PA, US), as well as the DLR in-house research code THETA has been used.</abstract>
    <parentTitle language="deu">23. DGLR Fach-Symposium Strömungen mit Ablösung, 09./10. November 2022, Berlin, Deutschland</parentTitle>
    <identifier type="url">https://www.dlr.de/as/Portaldata/5/Resources/dokumente/veranstaltungen/stab_workshop/Jahresbericht2022.pdf</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="BegutachtungStatus">begutachtet</enrichment>
    <enrichment key="opus.doi.autoCreate">false</enrichment>
    <enrichment key="opus.urn.autoCreate">true</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Lars Krenkel</author>
    <author>Johanna Michel</author>
    <author>Niklas Keil</author>
    <author>Jan Daschner</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Silent Breathing</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Aerosols</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>CFD</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Endotracheal Intubation</value>
    </subject>
    <collection role="ddc" number="6">Technik, Medizin, angewandte Wissenschaften</collection>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>5300</id>
    <completedYear/>
    <publishedYear>2010</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
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    <edition/>
    <issue/>
    <volume>18</volume>
    <type>conferencepresentation</type>
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    <title language="eng">Exploration of Gas Flow During High Frequency Oscillated Ventilation by 19F-Gas-MRI</title>
    <abstract language="eng">To detect convective gas flow inside the large airways during high frequency oscillated ventilation (HFOV) the fluorinated contrast gas Heptafluoropropane was used for 19F-MRI. In a first study the comparison between constant flow measurements and Computational Fluid Dynamics (CFD) simulations provided a good agreement. In a following experiment oscillated flow was applied to a lung phantom consisting of ventilation bag and long pipe. The pressure wave inside the pipe was explored point-by-point and corresponding velocities were determined. With these experiments it could be shown for the first time that flow measurement during HFOV using fluorinated contrast gas is feasible.</abstract>
    <parentTitle language="eng">Proceedings of the International Society for Magnetic Resonance in Medicine</parentTitle>
    <identifier type="url">https://archive.ismrm.org/2010/2527.html</identifier>
    <enrichment key="opus.import.date">2022-08-24T10:21:08+00:00</enrichment>
    <enrichment key="opus.source">sword</enrichment>
    <enrichment key="opus.import.user">importuser</enrichment>
    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Janet Friedrich</author>
    <author>Julien Rivoire</author>
    <author>Alexander-Wigbert K. Scholz</author>
    <author> Wiegbert</author>
    <author>Maxim Terekov</author>
    <author>Rainer Kbrich</author>
    <author>Lars Krenkel</author>
    <author>Claus Wagner</author>
    <author>Laura Maria Schreiber</author>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="othpublikationsherkunft" number="">Externe Publikationen</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16316">Produktion und Systeme</collection>
    <collection role="institutes" number="">Labor Biofluidmechanik</collection>
  </doc>
  <doc>
    <id>3512</id>
    <completedYear/>
    <publishedYear>2021</publishedYear>
    <thesisYearAccepted/>
    <language>deu</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferencepresentation</type>
    <publisherName/>
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    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>2022-04-12</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="deu">Blutdruck, Hämodynamik und Gefäßzustand: Innovative Erfassung und Bewertung – Schwerpunkt bildbasierte Verfahren</title>
    <abstract language="deu">Einleitung: &#13;
Blutdruck gilt als sogenannter Vitalparameter als einer der grundlegenden Indikatoren für den Gesundheitszustand einer Person. Sowohl zu niedriger als auch zu hoher Blutdruck kann lebensbedrohend sein, letzerer ist darüber hinaus ein Risikofaktor insbesondere für Herz-Kreislauferkrankungen, die trotz wichtiger Fortschritte in der Behandlung immer noch die häufigste Todesursache in Deutschland darstellen. Die Hämodynamik, also die raumzeitliche Dynamik des Blutflusses, und der Gefäßzustand sind eng verbunden mit dem Blutdruck und ebenfalls von hoher klinischer Relevanz, u.a. zur Identifikation von Durchblutungsstörungen und ungünstigen Druckverteilungen der Gefäßwand. Innovationen in der Messtechnik als auch in der Datenanalyse bieten heute neue Möglichkeiten der Erfassung und Bewertung von Blutdruck, Hämodynamik und Gefäßzustand [1], [2], [3], [4].&#13;
&#13;
Methodik:&#13;
In einer gemeinsamen Workshopserie der AG Medizinische Bild- und Signalverarbeitung der GMDS und des Fachausschusses Biosignale der DGBMT werden wir neue Ansätze und Lösungen für Mess- und Analyseverfahren zu Blutdruck und -fluss sowie zum Gefäßzustand vorstellen und diskutieren. Dabei stehen im ersten Workshop auf der GMDS Jahrestagung Bildbasierte Verfahren im Zentrum, während der zweite Workshop auf der DGBMT Jahrestagung den Fokus auf Biosignalbasierten Verfahren legt. Es werden aktuelle Forschungsergebnisse vorgestellt und diskutiert. Es sind jeweils mehrere Vorträge geplant mit ausreichend Zeit zur Diskussion. Folgende Vorträge sind geplant (Arbeitstitel):&#13;
&#13;
Sebastian Zaunseder: Videobasierte Erfassung des Blutdrucks&#13;
Anja Hennemuth: A Visualization Toolkit for the Analysis of Aortic Anatomy and Pressure Distribution&#13;
Lars Krenkel: Numerische Analyse der Rupturwahrscheinlichkeit zerebraler Aneurysmata&#13;
Susanne Schnell: Messung des Blutflusses und hämodynamischer Parameter mit 4D flow MRI: Möglichkeiten und Herausforderungen&#13;
&#13;
Ergebnisse: &#13;
Ziel des Workshops ist die Identifikation von innovativen Ansätzen und neuen Methoden zur qualitativen und quantitativen Bestimmung von hämodynamischen Parametern sowie deren kritische Bewertung durch die Community für die Eignung in der klinischen Entscheidungsunterstützung.&#13;
&#13;
Diskussion:&#13;
Der Workshop leistet inhaltlich einen Beitrag zu zentralen Aspekten für die Herz-Kreislauf-Medizin. Er bringt dabei Expertise aus verschiedenen Bereichen zusammen und schlägt die Brücke zwischen Kardiologie, Medizininformatik und Medizintechnik.&#13;
&#13;
Schlussfolgerung:&#13;
Innovative Technologien aus Medizintechnik und Informatik ermöglichen zunehmend einfache und raumzeitlich aufgelöste Erfassung und Bewertung wichtiger Informationen zur Unterstützung von Diagnose und Therapieverfolgung.&#13;
&#13;
[1] Zaunseder S, Trumpp A, Wedekind D, Malberg H. Cardiovascular assessment by imaging photoplethysmography - a review. Biomed Tech (Berl). 2018 Oct 25;63(5):617–34.&#13;
[2] Huellebrand M, Messroghli D, Tautz L, Kuehne T, Hennemuth A. An extensible software platform for interdisciplinary cardiovascular imaging research. Comput Methods Programs Biomed. 2020 Feb;184:105277.&#13;
[3] Schmitter S, Adriany G, Waks M, Moeller S, Aristova M, Vali A, et al. Bilateral Multiband 4D Flow MRI of the Carotid Arteries at 7T. Magn Reson Med. 2020 Oct;84(4):1947–60.&#13;
[4] Birkenmaier C, and Krenkel, L.  Flow in Artificial Lungs. In: New Results in Numerical and Experimental Fluid Mechanics XIII. Contributions to the 22nd STAB/DGLR Symposium. Springer; 2021.</abstract>
    <parentTitle language="deu">66. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie e. V. (GMDS), 12. Jahreskongress der Technologie- und Methodenplattform für die vernetzte medizinische Forschung e. V. (TMF), 26. - 30.09.2021, online</parentTitle>
    <identifier type="doi">10.3205/21gmds016</identifier>
    <identifier type="urn">urn:nbn:de:0183-21gmds0167</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Dagmar Krefting</author>
    <author>Sebastian Zaunseder</author>
    <author>Dennis Säring</author>
    <author>Thomas Wittenberg</author>
    <author>Christoph Palm</author>
    <author>Karin Schiecke</author>
    <author>Lars Krenkel</author>
    <author>Anja Hennemuth</author>
    <author>Susanne Schnell</author>
    <author>Nicolai Spicher</author>
    <subject>
      <language>deu</language>
      <type>uncontrolled</type>
      <value>Bildbasierte Verfahren</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Blutdruck</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Hämodynamik</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Blutgefäß</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Bildgebendes Verfahren</value>
    </subject>
    <collection role="ddc" number="0">Informatik, Informationswissenschaft, allgemeine Werke</collection>
    <collection role="ddc" number="6">Technik, Medizin, angewandte Wissenschaften</collection>
    <collection role="institutes" number="FakIM">Fakultät Informatik und Mathematik</collection>
    <collection role="institutes" number="FAKMB">Fakultät Maschinenbau</collection>
    <collection role="persons" number="palmremic">Palm, Christoph (Prof. Dr.) - ReMIC</collection>
    <collection role="persons" number="krenkellbfmconf">Krenkel, Lars (Prof. Dr.), Präsentationen - Labor Biofluidmechanik</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Regensburg Medical Image Computing (ReMIC)</collection>
    <collection role="institutes" number="">Labor Biomechanik (LBM)</collection>
  </doc>
  <doc>
    <id>8859</id>
    <completedYear/>
    <publishedYear>2025</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
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    <pageLast/>
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    <completedDate>2026-02-04</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Experimental Investigation of Shear-Induced Generation of Respiratory Aerosol: Simultaneous Measurements of Particle Quantities and Wave Topology</title>
    <abstract language="eng">Despite the high level of attention on infectious respiratory aerosol during the Covid19 pandemic, little is known about the processes how these particles form inside the respiratory system. Understanding the underlying fluid mechanical processes and their influencing factors would enable the development of drugs to suppress the generation of infectious aerosol. In the proposed work, we focus on the shear-induced mechanism of aerosol generation, which is supposed to occur mostly in the larger airways during coughing. In this process, high air velocities trigger Kelvin-Helmholtz waves in the mucus film, which lines the air vessels. Through a series of instabilities, particles detach from the crest of these waves.&#13;
In the proposed work, we investigate the process of shear-induced aerosol generation in idealized experiments where we vary the air-flow characteristics and the properties of the mucus fluid. Our central aim here is to deduct an empirical model of the quantity and size distribution of generated particles depending on the mucus rheology and the local shear flow. Further, we observe the wave topology to better understand the coupling between the air flow and the waves.&#13;
In our experimental setup, we measure the quantity of created particles and the emerging waves simultaneously. To ensure controllable conditions, we simplify the complex flow conditions in the airways. We use a rectangular channel with the bottom wall covered in a mucus mimetic. The mucus mimetic fluid is a synthetic hydrogel developed to recreate the viscoelastic properties and low surface tensions of the mucus. Filtered pressurized air is guided through the channel to trigger shear-induced aerosol generation. After passing the mucus mimetic, the air enters into a collection chamber from where particles are sampled continuously by an aerosol spectrometer. To measure wave topology, we use planar laser induced fluorescence. For this, we stain the mucus mimetic with fluorescent dyes and illuminate a line on the surface of the fluid film with a 532 nm laser. A high-resolution camera captures the resulting fluorescent glow of the mucus mimetic. Figure 1 presents exemplary wave topology results from the experiments, employing varying air flow volume rates, mucus mimetic gel properties, and different configurations of the laser and camera. The resulting wave topologies exhibit significant variation. For the conference, we will conduct parameter studies&#13;
of the particle quantities and wave topology while varying the mucus mimetic properties and the flow&#13;
rate of the air. Additionally, we will present grid projection-based techniques to extend the single-line wave measurements and asses the entire surface of the mucus film.</abstract>
    <parentTitle language="eng">2nd European Fluid Dynamics Conference (EFDC2), 26-29 August 2025, Dublin, Ireland</parentTitle>
    <identifier type="urn">urn:nbn:de:bvb:898-opus4-88593</identifier>
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    <enrichment key="Kostentraeger">Initiative and networking fund of the Helmholtz Association of German Research Centers under the CORAERO Project (Grant KA1-Co-06) - Labor für Biofluidmechanik</enrichment>
    <enrichment key="opus.source">publish</enrichment>
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    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Johanna Michel</author>
    <author>Lars Krenkel</author>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="DFGFachsystematik" number="1">Ingenieurwissenschaften</collection>
    <collection role="othforschungsschwerpunkt" number="">Gesundheit und Soziales</collection>
    <thesisPublisher>Ostbayerische Technische Hochschule Regensburg</thesisPublisher>
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    <publishedYear>2024</publishedYear>
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    <language>eng</language>
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    <pageLast/>
    <pageNumber>2</pageNumber>
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    <completedDate>2026-03-13</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">High-resolution flow field investigations in membrane lungs, considering the complex blood rheology</title>
    <abstract language="eng">Despite major improvements over the last years, coagulative disorders and clotting&#13;
phenomena in membrane lungs (MLs) are still considerable complications in extracorporeal&#13;
membrane oxygenation (ECMO). ECMO is an increasingly used treatment for patients with&#13;
severe respiratory failure or cardiac arrest [1]. For both, evaluation of therapeutic decisions&#13;
and fundamental research on patient specific intra-device clotting phenomena, the direct&#13;
visualization and analysis of clot formation in combination with a detailed flow field&#13;
correlation is highly desirable and therefore an intensively followed research topic.&#13;
Modelling blood flow and shear induced coagulation in MLs is challenging. The relevant&#13;
geometry of oxygenator fibers and chaining threads is complex and spans several length scales.&#13;
In relevant scales and regimes, blood shows several significant non-Newtonian effects.&#13;
Viscosity impacts shear rate, which is important in several coagulation mechanisms.&#13;
Additionally, coagulation processes are influencing fluid properties and geometry&#13;
significantly. Existing approaches of previous research work are only able to consider some,&#13;
but not all relevant effects and geometrical details. Due to the enormous size of the discretized&#13;
geometries, highly detailed viscosity and coagulations models are not applicable. Our goal is&#13;
to develop a model for combined viscosity and coagulation properties of blood flow in MLs.&#13;
In our work, we compare the influence of different levels of detail of the ML geometry as well&#13;
as the influence of considering realistic blood flow behavior (viscosity change by considering&#13;
the local hematocrit distribution within the Fåhraeus-Lindqvist-Effect) on the resulting flow&#13;
field in relevant subsections of a ML.&#13;
High-resolution micro-CT geometry reconstructions [1] are compared to idealized generic&#13;
fiber representations. For realistic blood flow modelling, Newtonian representation is&#13;
compared to the established Carreau-Yasuda and a multiphase Euler-Euler approach.&#13;
Results are presented for relevant subsections as well as for the complete ML.</abstract>
    <parentTitle language="eng">1st European Fluid Dynamics Conference (EFDC1), 16-20.September 2024, Aachen</parentTitle>
    <identifier type="urn">urn:nbn:de:bvb:898-opus4-89214</identifier>
    <identifier type="doi">10.35096/othr/pub-8921</identifier>
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    <enrichment key="Kostentraeger">DFG SPP 2014 "Towards an Implantable Lung"</enrichment>
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    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Michael Kranz</author>
    <author>Daniel Pointner</author>
    <author>Karla Lehle</author>
    <author>Matthias Lubnow</author>
    <author>Lars Krenkel</author>
    <collection role="institutes" number="RCBE">Regensburg Center of Biomedical Engineering - RCBE</collection>
    <collection role="DFGFachsystematik" number="1">Ingenieurwissenschaften</collection>
    <collection role="othforschungsschwerpunkt" number="">Gesundheit und Soziales</collection>
    <thesisPublisher>Ostbayerische Technische Hochschule Regensburg</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-oth-regensburg/files/8921/Kranz_ECMO_Abstract.pdf</file>
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