Question

what is ideal flow of fluid

Answer 1

Consider a hypothetical fluid having a zero viscosity ( μ = 0). Such a fluid is called an ideal fluid and the resulting motion is called as ideal or inviscid flow. In an ideal flow, there is no existence of shear force because of vanishing viscosity

All the fluids in reality have viscosity (μ > 0) and hence they are termed as real fluid and their motion is known as viscous flow. 

Under certain situations of very high velocity flow of viscous fluids, an accurate analysis of flow field away from a solid surface can be made from the ideal flow theory.