Streamline the flow of a liquid is that flow during which every component of the liquid passing through a point travels on a similar path and with the same speed because the preceding component passes through that point. A streamline is also defined as the path, straight or curving, the tangent to which at any point provides the direction of the flow of liquid at that time.
If a liquid is flowing over a surface with a gradual flow and moves within the type of layers of various velocities that don’t combine with each other, then the flow of liquid is termed streamline flow. In this flow, the speed of liquid flow is usually less than the critical velocity of the liquid the streamline flow is usually used.
Streamline flow in pipes (or tubes) happens when a fluid flows in parallel layers, with no disruption between the layers. At low velocities, the fluid tends to flow while not lateral combining, and adjacent layers slide past each other like playing cards. There are no cross-currents perpendiculars to the direction of flow of the fluids. Checking from streamline flow, the movement of the particles of the fluid is always in order with other particles moving in a parallel line to the pipe walls. Any lateral combining (mixing at right angles to the flow direction) happens by the action of diffusion between layers of the liquid. Diffusion combination is slow but if the diameter of the pipe of the tube is little then this diffusing combination is terribly important.
When a liquid travels with a speed greater than its crucial speed, the movement of the particles of the liquid becomes disordered or irregular. Such a flow is named a turbulent flow. In a flow, the path and also the speed of the particles of the liquid change ceaselessly and haphazardly with time from point to point.
Turbulent flow may be a flow regime characterized by chaotic property changes. This includes a speedy variation of pressure and flow rate in space and time. In distinction to streamline flow, the fluid does not travel in layers and combination across the tube is very economical. Flows at Reynolds numbers larger than 4000, are usually (but not necessarily) turbulent, whereas those at low Reynolds numbers below 2300 typically stay laminar. Flow within the range of Reynolds numbers 2300 to 4000 and called transition.