Vorticity Measurements

Abstract This chapter describes the measurement of the components of the vorticity vector. The vorticity vector at a point is defined as the curl of the velocity vector. Using tensor notation this relationship can be expressed as where wi (i = 1-3) are the components of the vorticity vector, are the components of the velocity vector, and eijk is the alternating tensor. As discussed by Wallace (1986), at each point in the flow field a spherical fluid particle can be imagined the motion of which can be decom posed into translation, expansion, and rotation. The vorticity can be inter preted as being twice the instantaneous solid-body rotation rate of particles along the principal axis in the fluid, where there is no shear deformation.