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    A complete LPM-CFD Coupling on a Dummy Aortic Model
    (IEEE, 2022) Aka, Ibrahim Basar; Yildirim, Canberk
    Computational fluid dynamics (CFD) has become a widely used method for solving complex fluid problems. However, it is still evolving in the field of biomedical engineering. The reason why the CFD method in the biomedical field lags behind other engineering fields is the complex structure of the flows in the human body. Apart from CFD analyses, using lumped parameter models (LPM), flows and pressures in the human circulation can be simulated in a computer environment by mimicking electrical analog circuits. The flows and geometries in the relevant cardiovascular structures have been solved in the CFD environment by adding LPM codes as the boundary conditions (BC). The areas where this technique has been used in the last decade can be listed as congenital heart diseases, heart failure, ventricular function, aortic diseases and modeling of diseases in the brain vessels. However, studies that analyze a full and comprehensive human circulation, are based on simplified models and are very limited in the applications of this still developing multidimensional model (LPM-CFD) technique. Therefore, this study demonstrates a complete two-way LPM-CFD coupling with a dummy aortic segment solved in CFD. This solution is coupled with a traditional LPM exchanging data at every time step of solution. Results demonstrate a good agreement with the traditional CFD technique. The methodology provides a basis for the development of many new cardiovascular devices.
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    Experimental and computational design improvement assessment of a household toast grill
    (Elsevier, 2020) Gunes, Dogan; Kukrer, Ergin; Yildirim, Canberk
    Small kitchen appliances have become very popular with increasing needs. One of the most common household appliances is the toast grills. The grills are available in every home or restaurant. It is necessary to reach a high temperature for the operation of these grills. However, some contact surfaces should also be kept within a certain temperature range for safety. In this paper, development and assessment of some design changes to reduce the high temperature on the upper (contact) surface of the grill and the overall performance effect are studied. Compliance with EU small domestic appliances standard (SDA), which states conditions that could threaten user health, overheating and electrical accidents constitute the A13 standard. Compliance of the new design proposals are also reported in this paper. Laboratory tests at several locations of the grill and infrared examination are carried out to analyze the results of the proposed changes. Temperature drops of up to 20. are observed on the top cover surfaces with the application of insulation as part of the new design proposal. Savings obtained in accordance with Electrotechnical Commission (ICE) standards and heat and energy efficiency gain are reported. Computational model of the toast grill developed in this paper is found in line with experimental and infrared results. The model may be used to improve new designs for further studies.
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    Mechanical support of pulmonary blood flow as a strategy to support the Norwood circulation-lumped parameter model study
    (Oxford Univ Press Inc, 2022) Peer, Syed Murfad; Yildirim, Canberk; Desai, Manan; Ramakrishnan, Karthik; Sinha, Pranava; Jonas, Richard; Yerebakan, Can
    OBJECTIVES: We hypothesize that mechanical assistance of the pulmonary blood flow in a Norwood circulation can increase systemic blood flow and oxygen delivery. The aim of the study was to compare haemodynamics of an unassisted Norwood Blalock-Taussig shunt circulation with a mechanically assisted pulmonary flow-based Norwood circulation, using a lumped parameter computational model. METHODS: A neonatal circulatory lumped parameter model was developed to simulate a Norwood circulation with a 3.5-mm Blalock-Taussig shunt in a 3.5-kg neonate. A roller pump circulatory assist device with an inflow bladder was incorporated into the Norwood circulation to mechanically support the pulmonary circulation. Computer simulations were used to compare the haemodynamics of the assisted and unassisted circulations. Assisted and unassisted models with normal (56%) and reduced ejection fraction (30%) were compared. RESULTS: Compared to the unassisted Norwood circulation, the systemic flow in the assisted Norwood increased by 25% (ejection fraction = 56%) and 41% (ejection fraction = 30%). The central venous pressure decreased by up to 3 mmHg (both ejection fraction = 56% and ejection fraction = 30%) at a maximum pulmonary assist flow of 800 ml/min. Initiation of assisted pulmonary flow increased the arterial oxygen saturation by up to 15% and mixed venous saturation by up to 20%. CONCLUSIONS: This study demonstrates that an assisted pulmonary flow-based Norwood circulation has higher systemic flow and oxygen delivery compared to a standard Norwood Blalock-Taussig shunt circulation.