This allows for a calculation that is based upon conditions that are closer to the physiological environment, and thus improves the accuracy of FFRct calculation. Compared to the calculated value using the basic CFD model (MSE = 5.9%, accuracy rate = 80%), the FFR CFD calculated based on the coupled 3D–0D model has a smaller MSE of 1.9%.Ĭonclusion: The physics-driven coupled 3D–0D model that incorporates fluid–structure interactions not only consider the influence of the elastic vessel wall on blood flow, but also provides reliable microvascular resistance boundary conditions for the 3D FSI model. Results: The accuracy, sensitivity, specificity, and both positive and negative predictive values of FFR DC calculated based upon the coupled 3D–0D model were 86.7, 66.7, 84.6, 66.7, and 91.7%, respectively. A lumped parameter model (0D) was used as the outlet boundary condition for the 3D FSI coronary artery model to incorporate physiological microcirculation, with bidirectional coupling between the two models. Methods: Based upon a novel geometric multi-scale modeling technology, a FSI simulation approach was used. Thus, in this study, a physics-driven 3D–0D coupled model including fluid–structure interaction was established to calculate accurate FFRct values. Objective: In this study we incorporated both the influence of vascular elasticity and coronary microcirculatory structure on FFR, to improve the accuracy of FFRct calculation. It is likely that both have resulted in FFRct calculation errors. Changes in the resistance of coronary microcirculation during hyperaemia are likewise not typically incorporated using a fluid–structure interaction (FSI) algorithm. Therefore, important interactions between the elastic vessel wall and blood flow are not routinely considered. 2Cardiovascular Department, Peking University People’s Hospital, Beijing, Chinaīackground: The conventional FFRct numerical calculation method uses a model with a multi-scale geometry based upon CFD, and rigid walls.1Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China.Kira Grogg, Harvesting the Wind: The Physics of Wind Turbines, Carleton College, 2005.Xiaolu Xi 1, Jincheng Liu 1, Hao Sun 1, Ke Xu 1, Xue Wang 1, Liyuan Zhang 1, Tianming Du 1, Jian Liu 2 and Bao Li 1* Holthuijsen, Waves in oceanic and coastal waters, Cambridge University Press, 2007. Jiansong Li, Jiyun Zhao, and Xiaochun Zhang, A Novel Energy Recovery System Integrating Flywheel and Flow Regeneration for a Hydraulic Excavator Boom System, Energies 2020. Jewett, Physics for Scientists and Engineers, 6th edition, Brooks/Cole Publishing Co.,2004 Benjamin Crowell, Light and Matter – Physics, 2007. David Halliday, Robert Resnick, Jearl Walker, Fundamentals of Physics, 7th edition, John Wiley & Sons, 2004. If you want the result displayed in another unit, use the drop down list to choose and click the CALCULATE button again. The default unit of measurement for energy is Joule. The internal energy calculator allows you to calculate the change in internal energy of a system with a given input and output heat and input and output work. The system increased its internal energy by 12 J due to increase of its temperature (more heat received). In physics, a more common way to view the internal energy of a system is in terms of its macroscopic characteristics, which are very similar to atomic and molecular average values.įrom the macroscopic point of view, the change in internal energy ΔU is defined as the difference between the energy received Q (as heat) and energy lost W (as work). Internal energy includes kinetic energy of translation, rotation, and vibration of molecules, potential energy within molecules, and potential energy between molecules. In other words, internal energy is all the energy of a system that is associated with its microscopic components (consisting of atoms and molecules), when viewed from a reference frame at rest with respect to the object. Since the sum of kinetic energy and potential energy is the mechanical energy, the internal energy of a system is the sum of atomic and molecular mechanical energy. microscopic (atomic and molecular view)įrom the microscopic point of view, which examines the system on the atomic and molecular scale, the internal energy U of a system is the sum of the kinetic and potential energies of its atoms and molecules.Internal energy can be defined in two ways: Internal energy is the energy possessed by a system.
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