what is the curl test for vector fields
Curl (mathematics) In vector calculus, the curl is a vector operator that describes the infinitesimal rotation of a vector field in three-dimensional Euclidean space. At every point in the field, the curl of that point is represented by a vector. The attributes of this vector (length and direction) characterize the rotation at that point.
Saddle valve A saddle valve is a valve used to supply liquid where a low volume, low pressure stream is required. The name is derived from the fact that it is mounted in such a way that it "saddles" the line, mounting it from both sides.