Changes

where <math>\rho</math> is the [[density]] of the fluid, '''u''' its velocity and '''g''' the gravitational acceleration. The [[operator]] <math>D/Dt = \partial/\partial t + (\mathbf{u}\cdot\nabla)</math> is the convective derivative, the rate of change of a certain quantity ''A(t)'' of the fluid as it is carried by the fluid (hence the presence of '''u'''). Euler equation is then a differential operation explicitly relating the effects of the gravity and the gradient of pressure on the velocity of the fluid.

where <math>\rho</math> is the [[density]] of the fluid, '''u''' its velocity and '''g''' the gravitational acceleration. The [[operator]] <math>D/Dt = \partial/\partial t + (\mathbf{u}\cdot\nabla)</math> is the convective derivative, the rate of change of a certain quantity ''A(t)'' of the fluid as it is carried by the fluid (hence the presence of '''u'''). Euler equation is then a differential operation explicitly relating the effects of the gravity and the gradient of pressure on the velocity of the fluid.

As long as the [[speed of sound]] is much larger than '''u''', the density <math>\rho</math> of the fluid can be considered as constant (incompressible).

As long as the [[speed of sound]] is much larger than '''u''', the density <math>\rho</math> of the fluid can assumed to be constant (incompressible) in most situations.

==References==

==References==