ABSTRACT
There exists a large class of ¡uid ¡ows in which the motion is caused by buoyancy in the ¡uid. Buoyancy is the force experienced in a ¡uid due to a variation of density in the presence of a gravitational ‡eld. According to the de‡nition of an incompressible ¡uid, as was presented in Section 1.6, variations in the density normally mean that the ¡uid is compressible, rather than incompressible. That being the case, one might expect that the material content of this chapter would be presented in Part IV of the text, rather than Part III. The rationale for this apparent contradiction is discussed below.
