A numerical and experimental investigation of the flow acceleration region proximal to an orifice

Attempts to quantify valvular regurgitation have recently been focused on the proximal orifice flow field. A complete description of the proximal orifice flow field is provided in this investigation. A steady state in vitro model accessible by both color Doppler ultrasound (CDU) and laser Doppler velocimetry (LDV) was utilized. Velocities for varying flow rates and orifices were calculated by finite element modeling (FEM), by LDV and by CDU. The steady flow model was composed of circular orifices of 3, 5 and 10 mm diameters at flow rates from 0.7 to 10 L/min. Regurgitant flow rates were calculated from the proximal CDU data by two separate methods. The first approach utilized angle corrected velocities while the second approach utilized only velocities which did not require angle correction (centerline velocities). Both methods correlated well with known flow rates (y = 0.97x -0.09, r = 0.98, SEE = 0.45, p < 0.0001; and y = 1.0x + 0.07, r = 0.99, SEE = 0.27, p < 0.0001, respectively) and were superior to results obtained by assuming a hemispherical geometry as is done in the aliasing technique. The methodology provides a complete analysis of the proximal flow field and involves fewer geometric assumptions than the aliasing approach. This may prove to be an advantage when analyzing in vivo flow fields with complex, uncertain geometry.