Types Of Fluid Flow

              Types of fluid flows

 (i) Steady flow and unsteady flow.

 (ii) Uniform flow and non- uniform flow.

 (iii) Laminar flow and turbulent flow.

 (iv) Compressible and in compressible flow

 (v) Rotational and irrotational flow.

 (vi) One, two and three- dimensional flow

(i) Steady & unsteady flow : If the flow characteristics like, velocity, density, 

pressure etc. at a point do not change with the passage of time, the flow is said to be steady. 

Mathematically,

 (∂v/∂t) xo yo zo =0, (∂p/∂t) xo yo zo =0, (∂ρ/∂t) xo yo zo =0

 Where (xo yo zo) is a fixed point in fluid field.

If the flow characteristics like, velocity, density, pressure etc. at a point changes with the passage of time, the flow is said to be un-steady.

 Mathematically,

 (∂v/∂t) xo yo zo ≠0, (∂p/∂t) xo yo zo ≠0 etc.

(ii) Uniform & Non - uniform flow :Uniform flow is that type of flow in which the 

velocity at any given time does not change with respect to space (i.e., length of direction of 

flow). Mathematically, for uniform flow,

 (∂v/∂s) t= constant =0, 

 

 ∂v = change in velocity

 ∂s = length of flow in the direction S

 Non-uniform flow is that type of flow in which the velocity at any given time changes with respect to space. Mathematically, for non-uniform flow,

 (∂v/∂s) t= constant ≠0,

(iii) Laminar & Turbulent flow :Laminar flow is that type of flow in which the 

fluid particles move along well-defined paths or stream line and all the stream-lines are straight and parallel. The particles move in laminas or layers gliding smoothly over the adjacent layer. This type of flow is also called stream line flow or viscous flow.

 Turbulent flow is that type of flow in which the fluid particles move in a zig-zag way, Due to the movement of fluid particles in zig-zag, the eddies formation take place which are responsible for high energy loss. For pipe flow, the type of flow is determined by non￾dimensional number VD/v called Reynold number. 

Where,

 D= diameter of pipe

 V= mean velocity in pipe

 v = kinematic viscosity of fluid

If the Reynold no. is less than 2000, the flow is called laminar. If the Reynold no. is more

than 4000, it is called turbulent flow. If the Reynold no. lies b/w 2000 and 4000, the flow

may be laminar or turbulent.