Helical flow in the annular is a common flow pattern in drilling, and it is an important engineering problem for fast and accurate calculating of the flow field and pressure gradient.

• 环空螺旋流是钻井液在钻井作业中常见的一种流型,怎样方便、快速及高精度地计算其流速场与压力梯度是一个重要工程问题。