Hayder Alsaad

Short-range airborne exposure dominates indoor transmission in close contact. To quantify this exposure, short-range models require a dilution factor, S_x=C_0/C_x, that relates the source concentration to that over increasing distance x. Two definitions are commonly used. The first is the ensemble dilution from a continuous steady jet airflow. The second is the single-cycle dilution of interrupted jet. The latter generally predicts greater dilution than the classical steady-jet model. Large-eddy simulations of periodic oral jets were conducted for three activity intensities and two source waveforms, with a breathing manikin and anemometry used to evaluate the velocity field. Both dilution factors were extracted from the same simulated flow. Successive cycles were found to catch up with earlier cycles, forming a mixed leading head with concentrations approximately two to three times higher than those in the subsequent quasi-steady tail. In this tail region, the ensemble dilution, S_x^ss, followed the steady-jet law, S_x=0.32x/D, and was insensitive to activity intensity and waveform under the isothermal, still-air conditions studied. In contrast, the single-cycle dilution, S_x^sc, reproduced the interrupted jet behaviour and depended on the criterion used to truncate the low-concentration tail of each cycle. The two dilution factors can be related through the passage time of one cycle; Wells–Riley probabilities agree only when this conversion is applied. Without conversion, the interrupted jet dilution underpredicts conversation risk over the investigated distances. Thus, breathing and speaking should be modelled using the ensemble S_x^ss, whereas isolated coughs or sneezes should use the single cycle S_x^sc.

Abstrakt: Laut aktuellen Studien können Grünfassaden den Wärmetransport durch die Außenwand verringern. Doch welche Parameter dabei maßgebend sind und wie diese wechselwirken, wurde bislang noch nicht im Detail untersucht. Daher wurden in dieser Studie die Auswirkungen der Bebauungsdichte, der Orientierung der Grünfassade, des Bedeckungsgrades der Außenwand, der Substratschichtdicke, der Wärmeleitfähigkeit des Substrats und des Blattflächenindexes auf den ganzjährigen Energiebedarf eines städtischen Bürogebäudes simuliert. Grundlage der Untersuchungen bildet ein parameterbasiertes Gebäudeenergiemodell, das mit Rhino Grasshopper erstellt und über das Honeybee‐Plug‐in mit EnergyPlus simuliert wurde. Die Sensitivitätsanalyse basiert auf einem Latin Hypercube Sampling, welches anhand der Pearson‐, Spearman‐ und standardisierten Rangregressionskoeffizienten sowie Random‐Forest‐Surrogatmodellen ausgewertet wurde.

Zur Visualisierung und Messung von Luftströmungen werden oft invasive Verfahren angewendet, welche die Strömung durch das Einbringen von Sensoren (bspw. Anemometer) oder Partikeln (bspw. Particle Image Velocimetry) beeinflussen. Alternativen bilden die Schlierenverfahren, namentlich das optische Schlierenverfahren mit Schlierenspiegel sowie das Background‐Oriented Schlierenverfahren (BOS), die an der Professur Bauphysik der Bauhaus‐Universität Weimar insbesondere zur Visualisierung von Raumluftströmungen optimiert wurden. Beide Verfahren arbeiten nicht‐invasiv und visualisieren Luftströmungen, die auf Dichtegradienten im Medium beruhen. Folgend werden beide Verfahren sowie verschiedene Anwendungen und Möglichkeiten zur quantitativen Auswertung vorgestellt. Die dargestellten Studien beleuchten Strömungen, die sowohl aus natürlicher wie auch erzwungener Konvektion resultieren und reichen von der Visualisierung personalisierter Lüftungssysteme über das Mikroklima des Menschen einschließlich der Ausbreitung der Atemluft in verschiedenen Szenarien (u. a. Tragen verschiedener Mund‐Nase‐Bedeckungen, beim Blasinstrumentenspiel und Singen, bei sportlicher Betätigung und nasaler Highflow‐Therapie) bis hin zur Untersuchung des Mikroklimas verschiedener Forschungsgegenstände (Betonzylinder und Globe‐Thermometer). Es wird angeregt, die Schlierenverfahren anzuwenden, um Raumluftströmungen in weiteren bauphysikalischen und angrenzenden Fachgebieten holistisch zu untersuchen.

In recent years, there has been increased interest in natural ventilation solutions as a means to achieve sustainable and energy-efficient building design. Windcatchers, ancient Middle Eastern architectural elements, have surfaced as viable passive cooling devices in modern architecture, thereby enhancing interior air quality and reducing the reliance on mechanical ventilation systems. Integrating upper wing walls (UWWs) is hypothesized to augment a windcatcher’s effectiveness by optimizing wind capture, air circulation, and thermal regulation. Therefore, this study aimed to explore the influence of incorporating a two-sided windcatcher with UWWs, with a particular emphasis on the effect of the UWW angle on ventilation performance within building spaces. To achieve this aim, a series of numerical simulations were conducted to assess the synergy between the windcatcher and the wing wall configuration with varying UWW angles and under varying wind speed conditions. As the first step of the research methodology, the CFD model was validated through a comparison between the numerical results and the experimental data. The findings showed good agreement between these methods. In the next phase, windcatchers with different UWW angles spanning the range of 0° to 90° were subjected to rigorous evaluation. The results revealed that the configuration with a 30° angle exhibited the optimal performance concerning critical ventilation parameters encompassing the airflow rate, air change rate, and mean age of air. Finally, the selected configuration underwent an evaluation under diverse wind speed conditions, which affirmed that even under low-wind-speed conditions, the windcatcher provides ventilation levels that align with the standard requirements.

Background/Aim To test the chemoresistance of a multi-directional nebulizer (MDN) and to establish and implement a perioperative clinical safety concept for its clinical use to deliver pressurised intraperitoneal aerosol chemotherapy (MDN-PIPAC). Study design Ex-vivo nebulization of cytostatic drugs with the MDN device to assess chemoresistance/toxicological risks. Establishment of a perioperative safety concept for the clinical administration of MDN-PIPAC by ex- and in-vivo porcine simulation studies. Unicentric case series of 30 MDN-PIPACs in patients with peritoneal surface malignancies (PSM). Endpoints were intraoperative adverse events and perioperative complications (Clavien-Dindo). Results Toxicological studies/risk assessment confirm the safety of administering PIPAC with the MDN. The horizontal nozzles must protrude at least 7 mm beyond the most distal end of the trocar tip and lateral tilting should be prevented by fixation of the device in a single-arm holder. A total of 21 patients (male/female ratio: 2:1) with a mean age of 62 (range: 38-86) years underwent 30 consecutive MDN-PIPACs for peritoneal surface malignancies of different origin. ECOG 0 and 1 were seen in five and 16 patients, respectively. Thirteen, seven and one patient underwent one, two and three MDN-PIPACs, respectively. Two patients received only one cycle of MDN-PIPAC because they were considered candidates for cytoreductive surgery and heated intraperitoneal chemotherapy. There were no intraoperative technical/medical problems observed. Four patients suffered from postoperative grade I complications. Conclusions Compounds leached during chemotherapy nebulization with the MDN are toxicologically safe. MDN-PIPAC administration is safe and the postoperative course comparable to that of the conventional PIPAC nebulizer. MINI ABSTRACT Toxicological analyses confirm that doxorubicin, cisplatin and oxaliplatin nebulized with the MDN do not release leachables that pose a toxicological risk to patients. Through technical risk analysis and PIPAC simulations, a safety concept for the administration of MDN-PIPAC was established. No technical/medical intraoperative adverse events were observed. The perioperative course was comparable to that of the conventional axial single-direction nebulizer (SDN) PIPAC.