IN-VITRO FLOW MAPPING OF REGURGITANT JETS - SYSTEMATIC DESCRIPTION OFFREE JET WITH LASER-DOPPLER VELOCIMETRY

Background Color Doppler and magnetic resonance imaging give pictures of abnormal jets within which the respective contribution of fluid mec hanics and image artifacts are difficult to establish because of curre nt technical limitations of these modalities. We conducted the present study to provide numerical descriptions of the velocity fields within regurgitant free jets. Methods and Results Laser Doppler measurements were collected in rigid models with pulsatile flow conditions, giving several series of two-dimensional flow images. The data were studied with the use of two-dimensional or M-mode flow images as well as regul ar plots. Numerical descriptions validated in steady flow conditions w ere tested at the various times of the cycle. In these free jets, the momentum was conserved throughout the cycle. The transverse velocity p rofiles were approximately similar. A central laminar core was found a t peak ejection and during the deceleration. Its length (l=4.08 d-0.03 6 mm, r=.99) and its diameter (d) were proportional to the orifice dia meter. At peak ejection, the velocity decay was hyperbolic, and the tr ansverse velocity profiles were clearly gaussian. The different relati ons that were tested could be combined in a single formula describing the velocity field: V(x,y,(peak)) . 4 . (d/x) . 10(-45(y/x)2) (r=.92). Conclusions These in vitro measurements demonstrated that presence of a central laminar core and similar transverse velocity profiles in fr ee turbulent jets. This allowed us to validate a series of numerical r elations that can be combined to described the velocity fields at peak ejection. On the other hand, further studies are needed to describe t he various singularities often encountered in pathology.