基于叠加原理的钻柱行星运动诱发平面流场的PIV分析

为了研究钻柱行星运动诱发流体平面流动的规律，解决提高钻井液携岩能力、降低流动压耗、降低涡动对钻柱破坏等的实际工程问题，提出了基于叠加原理的求解思路，将行星运动诱发的平面流场分解为钻柱与井筒等角度旋转的离心力场和钻柱与井筒同时自转诱发的流场。为分析后者流场，设计了内杆与外筒自转诱发流体平面流场的测量实验装置，并进行了粒子图像测速（PIV）实验。结果表明：内杆与外筒自转所诱发平面流场的速度呈近似对称分布，对称轴是外筒与内杆横截面圆心的连心线；内杆偏心自转时，存在出现二次流的偏心率临界值，且二次流出现在远离内杆、近外筒壁的地方；内杆与外筒自转方向相同时，二次流的出现与偏心率以及内杆与外筒转速差都有关，且二次流分布区域随偏心率的增大、内杆与外筒转速差的增大而扩大；内杆与外筒自转方向相反时，二次流呈月牙儿状近似对称分布，分布区域随内杆或外筒转速的增大、偏心率的增大而扩大。

PIV analysis of plane flow field induced by the planetary motion of drill string based on superposition principle

To study the plane flow laws of fluid induced by the planetary motion of drilling string and tackle such practical engineering problems as improving the carrying capacity of drilling fluid, reducing the flow pressure loss and cutting down the damage to drill string caused by whirling motion, this paper proposes the solution ideas based on the superposition principle, i.e., the plane flow field induced by the planetary motion of drill string is decomposed into a centrifugal force field through an equal angle rotation of the drill string and wellbore, and a flow field induced by through the simultaneous rotation of the drill string and wellbore. In order to analyze the latter flow field, an experimental device is designed to measure the fluid plane flow field induced by the self-rotation of inner rod and outer cylinder, and carry out a PIV (particle image velocimetry)experiment. The results indicate that the speed of plane flow filed induced by the self-rotation of inner rod and outer cylinder presents the approximately symmetrical distribution, and the symmetry axis is the line connecting the centers of outer cylinder and inner rod plane section. When the inner rod self-rotates eccentrically, there is a critical value of eccentricity for secondary flow appears far away from inner rod but close to the walls of outer cylinder. When inner rod has the same rotating direction with outer cylinder, the occurrence of secondary flow is related to eccentricity and the rotation speed difference between inner rod and outer cylinder. Moreover, the distribution area of secondary flow expands with the increase of the rotation speed difference between inner rod and outer cylinder as well as eccentricity. When inner rod shows the rotating direction contrary to that of outer cylinder, secondary flow presents approximately symmetrical distribution in the shape of a crescent moon and the distribution area expands with the increase in the rotation speed of inner rod and out cylinder as well as eccentricity.