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    An AI-Accelerated CFD Application on a Benchmark Device: FDA Nozzle
    (IEEE, 2022) Aka, Ibrahim Basar; Iscan, Mehmet
    In this study, we suggest a procedure for speeding CFD (computational fluid dynamics) analysis up by combining a conventional opensource CFD solver with a traditional AI module. The studied case is the FDA benchmark nozzle with various Reynolds numbers. The considered CFD simulations belong to a group of steady-state simulations and utilize the laminar flow solver SimpleFoam in the OpenFOAM toolbox. The proposed module is implemented as a Feed-Forward Neural Network (FFNN) supervised learning procedure. Our method distributes the data by creating a combined AI model for each quantity of the simulated phenomenon for various Reynolds numbers. The model can then be combined after the initial iteration phase to decrease the execution time or to lower memory requirements. We analyze the performance of the proposed method depending on the estimation accuracy of the data of interest, velocity, and pressure. For test data, we achieve time-to-solution discounts of nearly a factor of 10. Comparing simulation results based on the FFNN test results and 3D visualization shows the average accuracy for all the parameters over 99% for the velocity and the pressure.
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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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    Evaluation of the total hydrodynamic energy loss using 4D flow MRI in a case with Fontan failure
    (Cell Press, 2024) Odemis, Ender; Gumus, Terman; Aka, Ibrahim Basar; Ozkok, Sercin; Pekkan, Kerem
    Fontan Failure (FF) is a common problem for single-ventricle patients as they reach adulthood. Although several mechanisms may cause FF, an optimized blood flow stream through the surgical conduits is essential to avoid excessive energy loss (EL). Recent clinical studies showed EL is related to the quality of life, exercise capacity, and hepatic function since the single-ventricle feeds pulmonary and systemic circulation serially. 4D flow MRI effectively estimates EL in Fontan circulation and allows clinicians to compare the effectiveness of the treatment strategy concerning pre-intervention. Here, we present 26-year-old women with FF who had normal cardiac catheterization findings and were treated according to high EL definitions that are measured through 4D flow MRI.
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    Numerical investigation of volute tongue design on hemodynamic characteristics and hemolysis of the centrifugal blood pump
    (Springer Int Publ Ag, 2021) Aka, Ibrahim Basar; Ozturk, Caglar; Lazoglu, Ismail
    In the design of rotary blood pumps, the optimization of design parameters plays an essential role in enhancing the hydrodynamic performance and hemocompatibility. This study investigates the influence of the volute tongue angle as a volute geometric parameter on the hemodynamic characteristics of a blood pump. A numerical investigation on five different versions of volute designs is carried out by utilizing a computational fluid dynamics (CFD) software ANSYS-FLUENT. The effect of volute tongue angle is evaluated regarding the hydrodynamic performance, circumferential pressure distribution, the radial force, and the blood damage potential. A series of volute configurations are constructed with a fixed radial gap (5%), but varying tongue angles ranging from 10 to 50 degrees. The relative hemolysis is assessed with the Eulerian based empirical power-law blood damage model. The pressure-flow rate characteristics of the volute designs at a range of rotational speeds are obtained from the experimental measurements by using the blood analog fluid. The results indicate an inverse relationship between hydraulic performance and the tongue angle; at higher tongue angles, a decrease in performance was observed. However, a higher tongue angle improves the net radial force acting on the impeller. The pump achieves the optimized performance at 20 degrees of the tongue angle with the relatively high hydrodynamic performance and minor blood damage risk.