The flow is inviscid, incompressible and has constant mass density . Further the fluid is assumed to be inviscid and incompressible, with a constant mass density. The relationship described by Bernoulli was found to be valid only for incompressible, inviscid flow. Helmholtz's theorems apply to inviscid flows. In inviscid flow, since the viscous forces are zero, the Reynolds number approaches infinity. The approximations to these problems are called inviscid flows. The Reynolds number of inviscid flow approaches infinity as the viscosity approaches zero. An inviscid fluid has no viscosity, formula 5. The fluid itself need not have zero viscosity for inviscid flow to occur. In practice, an inviscid flow is an idealization, one that facilitates mathematical treatment. Thus flows with high Reynolds numbers are approximately inviscid in the free stream.