As part of an effort to develop efficient hollow cathodes for the International Space Station and low power electric propulsion systems, the effects of orifice length-to-diameter aspect-ratio on the performance of 0.5 to 2 A hollow cathodes were examined to compare with previous experiments and a recently developed model. Cathodes were constructed with nominally identical orifice diameters and ...

Background Due to the nature of the percutaneous prosthesis deployment process, a variation in its final position is expected. Prosthetic valve placement will define the spatial location of its effective orifice in relation to the aortic annulus. The blood flow pattern in the ascending aorta is related to the aortic remodeling process, and depends on the spatial location of the effective orific...

Objectives. In this study we Investigated the centerline velocity profile method for low computation applied to noncircular, as well as circular, orifices using digital color Row data . Ractlgroaud. Recently it been fed that low volume thrmo an orifice can be estimated more accurately by computing the axial "centerline" low velocityldistance profile proximal to the orifice. etha'. A total of se...

Background. Although Doppler echocardiography has been shown to be accurate in assessing stenotic orifice areas in native valves, its accuracy in evaluating the prosthetic valve orifice area remains undetermined. Methods and Results. Doppler-estimated valve areas were studied for their agreement with catheterderived Gorlin effective orifice areas and their flow dependence in five sizes (19/20-2...

OBJECTIVES We used the Doppler proximal flow convergence technique as a physiologic tool to explore the effects of the time courses of mitral annular area and transmitral pressure on dynamic changes in regurgitant orifice area. BACKGROUND In functional mitral regurgitation (MR), regurgitant flow rate and orifice area display a unique pattern, with peaks in early and late systole and a midsyst...

Previous investigations have shown that the size of a regurgitant jet as assessed by color Doppler flow mapping is independently affected by the flow rate and velocity (or driving pressure) of the jet. Fluid dynamics theory predicts that jet momentum (given by the orifice flow rate multiplied by velocity) should best predict the appearance of the jet in the receiving chamber and also that this ...

are presented. There are three types: (1) straddling tricuspid orifice entering both primitive ventricles with the mitral valve entering the left ventricle (nine cases), (2) displaced tricuspid orifice into the primitive left ventricle, with no A-V orifice in the primitive right ventricle (three cases), and (3) displaced tricuspid orifice with straddling mitral valve, in which the mitral valve ...

The present paper represents a methodology for investigating flow characteristics near orifice plate by using a commercial computational fluid dynamics code. The flow characteristics near orifice plate which is located in the auxiliary feedwater system were modeled via three different levels of grid and four different types of Reynolds Averaged Navier-Stokes (RANS) equations with proper near-wa...