A fluid flow is compressible if its density r changes appreciably (typically by a few percent) within the domain of interest Typically, this will occur when the fluid velocity exceeds Mach 0 3 Hence, low velocity flows (both gas and liquids) behave incompressibly
Capable of being pressed together or forced into a narrower compass, as an elastic or spongy substance
Containing a circle that does not serve as the boundary of a disk that lies in the surface, but does serve as boundary of a disk that lies in the ambient manifold
the ease with which a substance reduces its volume under external force Hydrometer: an instrument used to measure the density of liquids Pressure: a measure of the amount of force acting on a certain area of surface