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Abstract The aim of this project is to produce a 2D simulation of laminar blood flow through a bicuspid aortic valve. Blood is a non-Newtonian fluid, meaning the viscosity changes with shear rate. For the purpose of simulation it is considered to be a Carreau fluid. Background The aortic valve is one of four valves in the heart. Blood flows from the heart to the aorta (largest artery). The aortic valve connects the heart to the aorta. The valve opens to allow blood flow out of the heart, then shuts (non return valve). Carreau fluid is a type of generalized Newtonian fluid. This means the shear stress is a function of the shear rate at a given time. At low shear rates a Carreau fluid behaves like a Newtonian fluid, and at high shear rate as a Power law fluid (non-Newtonian). An excel chart was plotted, confirming that the viscosity decreases as the shear rate increases. Project Goals/Objectives • Research blood flow rates/velocities through the aorta. • Model suitable geometry to carry out the flow analysis. • Use Ansys CFD to simulate blood flow through the aortic valve. • Produce visual representations of the flow. Methods/Process Initially the viscosity was determined using the Carreau equation. After further investigation it was found that ANSYS offers integrated tools for the modelling of blood as a simulation fluid. The dimensioned geometry of the aorta valve was drawn in the Ansys design modeller. After this, a default mesh was generated for the model. At the Fluent setup stage, the boundary conditions were input. The inlet was defined as a Velocity inlet, and the outlet as a Pressure outlet. Various reference values were also input. The angle, Theta, was set at 10 degrees and increased in increments of 5 degrees. The simulation was then run to determine both the fluid flow velocity and the pressure gradient present in the aorta valve. The various plots (velocity, pressure, vectors) were then generated. This was repeated up to a maximum value of 35 degrees. The program used to carry out these procedures was ANSYS Fluent. Initially the project was meant for CFX, but 2D modelling was not possible with this package. Results/Outcomes Velocity Plot Pressure Gradient Conclusions/Recommendations • Velocity increases through the centre of the valve, due to the decrease in area. The pressure gradient, upon discussion with the advisor, is adequate, given the model constraints. • More emphasis was put on 2D analysis instead of the 3D. A 3D model was made, but despite efforts, would not work. If doing this project again, more focus would be put in the 3D analysis. • The model used is quite simplified, but the dimensions used are as close as can be to real life. Preferably the leafs would be modelled with a curve. References 1. P.N. Wattona, X.Y. Luob, X. Wangc, G.M. Bernaccaa, P. Molloya, D.J. Wheatleya. Dynamic modelling of prosthetic chorded mitral valves using the. Glasgow, New Jersey : Elsevier, 2006. 2. Shawn C. Shadden, Matteo Astorino, Jean-Frédéric Gerbeau. Computational analysis of an aortic valve jet with Lagrangian coherent. Chicago, Paris (2010) 3. W.Y Chan, Y. Ding, J. Y. Tu. Modeling of non-Newtonian blood flow through a stenosed artery incorporating fluid - structure interaction. Melbourne : (2006) 4. Noreen Sher Akbar, S. Nadeem, Carreau fluid model for blood flow through a tapered artery with a stenosis, Ain Shams Engineering Journal, 2014 5. Jiang, Chiyu. 3D Bifurcating Artery. Cornell University. [Online] 09 15, 2014. [Cited: 03 25, 2015.] Blood flow through the Aortic Valve Eoin Connolly, Stefano Forte, Pavel Rosca, Jeff Whyte Advisor: Peter McCluskey 2D Model Geometry Results/Outcomes 10° 15° 20° 25° 30° 35° Acknowledgments: Peter McCluskey, Micheal O'Flaherty
