Abstract: The LES(large eddy simulation)approach has been applied to model the flow field of a jet impinging on the bottomhole.A research on the results of numerical simulation showed that the thickness of cross flow layer was hardly influenced by jet impinging distance and outlet areas of the nozzle when the impinging distance was less than the jet length of potential cone.Some new concepts,effective thickness of cross flow layer and effective cross flow velocity,were proposed to analyse the efficiency of hydraulic energy action on bottomhole cleaning.According to the analysis,it is found that it was scarcely notable by means of reducing the distance from bit body to bottomhole to improve effective cross flow velocity at the bottomhole for PDC bits.

Key words: water jet, flow field, numerical simulation, PDC bit, cross flow, cleaning

摘要： 应用大涡模拟方法对不同条件下单喷嘴垂直撞击射流的流场特性进行了数值模拟,对数值模拟结果的分析研究表明,在射流撞击距离小于射流等速核长度的条件下,射流撞击距离和喷嘴出口面积的变化对井底漫流层的厚度没有明显影响.提出了采用井底有效漫流层厚度和有效平均漫流速度研究水力作用对井底和钻头的清洗及冷却效果的新概念.研究表明,就PDC钻头而言,减小钻头面至井底的距离,对提高整个井底的有效平均漫流速度,效果并不明显.

关键词: 射流, 流场, 数值模拟, PDC钻头, 漫流, 清洗