Consider a two-dimensional, compressible flow field in which an initially square fluid particle moves and deforms. The fluid particle dimension is a at time t and is aligned with the x- and y-axes as sketched in Fig. P4–76. At some later time, the particle is still aligned with the x- and y-axes but has deformed into a rectangle of horizontal length 1.08a and vertical length 0.903a. (The particle’s dimension in the z-direction does not change since the flow is two-dimensional.) By what percentage has the density of the fluid particle increased or decreased?

FIGURE P4–76

I I 1 1 a I y X