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INSTABILITY OF INVISCID FLOW

INVISCID FLOW:-When fluid  is stationary then there is no any type of force like shear force acting along fluid layers. If fluid flow then shear force act along fluid layers. Shear forces are due to viscosity of the fluid. When fluid has no viscosity, flow is known as INVISCID FLOW.Generally a ideal fluids have no viscosity so flow of ideal fluid is known as inviscid flow. A ideal fluid is practically not possible so the analysis of inviscid flow are done by taking some assumption. We consider that viscosity of fluid is very low i.e. the value of viscous force between the layers is very small as compared to inertia force of fluid.The flow of fluid with low values of viscosity beyond the boundary layer agree the inviscid flow. There is not agree to inviscid flow in the boundary layer because here viscosity plays a significant role. The taken assumption for inviscid flow is valid where viscous forces are small in comparison to inertial forces.When Reynolds number is much greater than one, such flow can identified as inviscid flow.

INSTABILITY:-A flow can be stable or unstable. A flow said to be stable when a infinitely small disturbance create at a time does not affect the system and after a few time they will eventually die down and become stable.If a infinitely small disturbance create and continue growth the amplitude of disturbance and become turbulent in known as unstable flow. It is more sensitive at high Reynolds number and at high Reynolds number the flow is treated as inviscid flow.The instability is more pronounce to inviscid flow because inviscid flow are assume at high Reynolds number. A laminar flow or viscous flow have a value of some viscosity which fallow¬ the Navier-stokes equation.When flow with small value of viscosity i.e. in viscid flow, viscous forces are neglected in comparison to inertial force then Navier-stokes equation change to Euler’s equation.

INSTABILITY OF INVISCID FLOW:-In inviscid flow Reynolds number is much higher than one, this condition is very critical if any infinitely  small disturbance create then flow will become unstable and turn to turbulent flow, thin is known as instability of inviscid flow. Generally in the range of high Reynolds number there is a value of Reynolds number above it the flow became unstable is known as critical Reynolds number.