Diebold B, Delouche A, Delouche P, Guglielmi J P, Dumee P, Herment A
Department of Cardiology, Hôpital Broussais, Paris, France.
Circulation. 1996 Jul 15;94(2):158-69. doi: 10.1161/01.cir.94.2.158.
Color Doppler and magnetic resonance imaging give pictures of abnormal jets within which the respective contribution of fluid mechanics and image artifacts are difficult to establish because of current technical limitations of these modalities. We conducted the present study to provide numerical descriptions of the velocity fields within regurgitant free jets.
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 regular plots. Numerical descriptions validated in steady flow conditions were tested at the various times of the cycle. In these free jets, the momentum was conserved throughout the cycle. The transverse velocity profiles were approximately similar. A central laminar core was found at peak ejection and during the deceleration. Its length (l = 4.08 d-0.036 mm, r = .99) and its diameter (d) were proportional to the orifice diameter. At peak ejection, the velocity decay was hyperbolic, and the transverse velocity profiles were clearly gaussian. The different relations that were tested could be combined in a single formula describing the velocity field: V(x,y,t peak) = V(O,O,t peak).4.(d/x).10(-45(y/x)2) (r = .92).
These in vitro measurements demonstrated the presence of a central laminar core and similar transverse velocity profiles in free turbulent jets. This allowed us to validate a series of numerical relations that can be combined to describe the velocity fields at peak ejection. On the other hand, further studies are needed to describe the various singularities often encountered in pathology.
彩色多普勒和磁共振成像可显示异常射流的图像，但由于这些模态目前的技术限制，难以确定流体力学和图像伪影各自的作用。我们开展本研究以提供反流自由射流内速度场的数值描述。
在具有脉动流条件的刚性模型中进行激光多普勒测量，获取多组二维流动图像。使用二维或M型流动图像以及常规图表对数据进行研究。在稳定流条件下验证的数值描述在心动周期的不同时刻进行测试。在这些自由射流中，整个心动周期动量守恒。横向速度剖面大致相似。在射血峰值和减速期发现一个中央层流核心。其长度（l = 4.08d - 0.036mm，r = 0.99）和直径（d）与孔口直径成正比。在射血峰值时，速度衰减呈双曲线形，横向速度剖面明显呈高斯分布。所测试的不同关系可组合成一个描述速度场的单一公式：V(x,y,t峰值)=V(0,0,t峰值)·4·(d/x)·10^(-45(y/x)^2)（r = 0.92）。
这些体外测量结果表明自由湍流射流中存在中央层流核心和相似的横向速度剖面。这使我们能够验证一系列可组合以描述射血峰值时速度场的数值关系。另一方面，需要进一步研究来描述病理学中经常遇到的各种异常情况。
