An example of a velocity field arises in describing the flow of a fluid through a pipe or the flow of blood through an artery. At each point inside the pipe (or the artery), a vector is defined that represents the velocity of the flow. See Figure 6. The magnitude of each vector represents the speed of the fluid’s flow. Notice that the speed of blood flow is slower near the artery wall and is faster near the center of the artery and that the speed increases where the artery is contracted.