| The pattern and characteristics of blood flow inside the heart are the basis for exploring the mechanism of blood physiological parameters and lesions of heart tissue structure.Based on CT tomography data,the left ventricle of the heart is reconstructed in three dimensions and the model is optimized.Combined with the motion characteristics of the myocardial wall,a mathematical model of the overcurrent boundary motion of the left ventricular geometric model was established.Numerical simulation of the left ventricular intermittent pumping process was achieved using dynamic meshing techniques,non-Newtonian power-law blood models,and RNG κ-ε turbulence models.The amorphous blood flow characteristics inside the normal left ventricle of three cardiac cycles were obtained,the effect of aortic valve outlet pressure difference and valvular lesions on the blood flow characteristics of the left ventricle was investigated,and the relationship between blood flow velocity,pressure,and shear stress at the characteristic cross-section and monitoring points was analyzed over time.The specific findings of the study are as follows:(1)The deviation point of the left ventricular optimization model in the interval of [-1.66,088] accounts for 80% of the total interval,and the optimization changes the coarseness of the wall surface and does not affect its internal structure.A segmented mathematical model of the boundary movement of the left ventricle wall is established,and it is found that the three-dimensional model of the motion grid movement to the minimum moment is the same as the area and volume of the left ventricle contraction to the minimum position.(2)After the flow field is fully developed,when the left ventricular is diastolic,the pressure at the mitral valve inlet,the apex,and the center decreases,and the blood flow outlet rate increases at T/16 before the initial contraction,and the speed decreases nonlinearly from T/16 to the completion of contraction.When the left ventricle is diastolic,the velocity head is converted into a pressure head,the pressure in the heart cavity increases,and the inlet velocity of the blood flow increases first and then decreases,reaching the maximum of 0.45 m/s at the 13/16 T moment.During the full cardiac cycle,the shear stress present at the mitral valve is higher than in other parts of the left ventricle.(3)Studying the effect of the aortic outlet pressure difference on the blood flow characteristics of the left ventricle,it was found that the monitoring values of shear stress and velocity at a low blood pressure of 50 mm Hg were slightly less than the monitoring values of normal blood pressure of 100 mm Hg.Outlet blood pressure increases,the monitoring point velocity gradually increases,so that the local shear stress during the left ventricular contraction process increases,while the diastolic process aortic valve is in a closed state,and blood pressure has less effect on blood flow characteristics.(4)When the mitral valve stenosis of different degrees decreases,the inlet area decreases,the speed and pressure at the inlet during the systolic period increase,and the shear stress increases.During the diastolic period,the speed and pressure increase first and then decrease.When the degree of stenosis is large,the internal shear stress of the left ventricle is larger overall,reaching a maximum of 4.6Pa at 6/8T.As the degree of stenosis of the aortic valve deepens,the velocity and pressure at the outlet point gradually increase.The shear stress at the inlet is slightly higher,and the overall change is not obvious,the shear stress at the outlet point gradually increases,and when the degree of narrowing is larger,the shear stress increases significantly,and the maximum value of 0.8Pa is reached at 3/16 T.In this paper,the human left ventricular model is reconstructed,the blood flow characteristics of the left ventricle are simulated by moving grid technology,and the established valve stenosis model is compared,which can provide a reference for subsequent heart research work. |
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