Skip to main content

Reynold's Experiment | Laminar flow's in circular pipe | Shear stress distribution

  Reynold's Experiment

• Osborne Reynolds (Mathematician & Physicist, UK)

• In 1883, he developed a laboratory set up in which he injected Dye (i.e. a fine, threadlike stream of colored liquid having the same density as water) at the entrance to a large glass tube through which water was flowing from a tank.

  

Fig: Reynold's experiment



Ad:

https://happyshirtsnp.com/



• Procedure:

✓ The water from the tank was allowed to flow through glass tube into atmosphere.

✓ The velocity of flow was varied by the valve.

✓ Dye was injected into the flow through a small tube.

• Observation:

✓ At the initial stage of flow, dye filament in the glass tube was in the form of straight line. This was a laminar flow.

✓ When increasing the velocity of flow, the dye filament was no longer a straight line. The dye filament starts to become wavy. This was a transitional flow.

✓ While further increase in velocity of flow, the wavy dye filament broke up and finally diffused in water. This was a turbulent flow.

✓ The occurrence of a laminar and turbulent flow was governed by the relative magnitude of inertia and viscous force. For low velocities, viscous force is predominant whereas for higher velocities, inertia force is predominant.

  
















Where,

V= Mean velocity, u= Coefficient of Kinematics viscosity = μ/p,

μ= Coefficient of Dynamic viscosity = up, p= Density of fluid,

L = Characteristics length, L= Diameter of Pipe (D), in pipe flow



Laminar Flow in Circular Pipe

Assumptions: incompressible, steady, developed laminar flow in a circular pipe.

A horizontal pipe of radius 'R' through which a fluid of density 'p' flows.

Let us consider, a fluid element with having radius 'r' of length 'dx' in the direction of flow.

Here,

p = Pressure intensity

't= Shear stress on the periphery of the cylinder acting in opposite direction of flow.

Forces acting on the fluid element: Pressure force, Shear force and Component of weight.

Fig: Forces acting on a fluid element


Ad:







Ad:



Labels:
Location: Kathmandu 44600, Nepal

Comments

Post a Comment

Popular posts from this blog

THREE RESERVOIRS AND PIPE NETWORK PROBLEMS

 Ad: https://happyshirtsnp.com/         THREE RESERVOIRS PROBLEM AND PIPE NETWORK   In practice, several pipes are interconnected forming various loops (or circuit) in municipal water distribution systems. There are a number of pipes connected either in series or in parallel or a combination of both. A group of interconnected pipes forming several loops (or circuit) in complex manner is called pipe networks, The complexity in a pipe networking is to determine the solution Of pipe problem (flow distribution) in such pipe network. Branched pipes: Three Reservoirs Problem Fig: Branched pipes: three inter connected Reservoir     In water supply system, Often a number of reservoirs are required to be interconnected by means Of a pipe system consisting of a number of pipes namely main and branches which meet at a junction. Figure shows three reservoirs 'B' and 'C' are interconnected by pipes 'a', 'b' and 'c' which meet at a junction 'D'. In the
Post a Comment
Read more

Hydrodynamically smooth and rough boundaries | Velocity distribution for turbulent flow

 Hydrodynamically smooth and rough boundaries Fig: Definition of smooth and rough boundaries In general, a boundary with irregularities of large average height 'K' on its surface is considered to  be a rough boundary and one with smaller 'K' value is considered as a smooth boundary. ✓ However, for a proper classification of smooth and rough boundaries, the flow and fluid characteristics are required to be considered in addition to the boundary characteristics. ✓ As the flow outside the laminar sub-layer is turbulent, eddies of various sizes are present which try  to penetrate through the laminar sublayer. But, due to greater thickness of laminar sub-layer ,   eddies can't reach the surface irregularities and thus the boundary acts as a smooth boundary. Such  a boundary is termed as " Hydro-dynamically Smooth Boundary" ✓ With the increase in Reynold's no (Re), the thickness of the laminar sub-layer  decreases and it's  can even become much smaller
Post a Comment
Read more

Water hammer and unsteady flows in pipes

             Ad: https://happyshirtsnp.com/                                                                             UNSTEADY FLOW IN PIPES When water is flowing through a pipe is suddenly stopped by the use of valve then we can see sudden rise in pressure inside the pipe and this pressure waves transmitted along the length of the pipe and it creates knocking like sound effects knows as 'water hammer'. In doing so, there are rapid pressure oscillation in the pipe, often accompanied by a hammering like sound, this phenomenon is called as 'Water hammer effect'. Sometimes the pressure may rise to the greater extent and may causes serious damage to the pipe. Therefore the 'water hammer' effects should be properly studied in the pipes. The magnitude of pressure rise depends on:   i)    Speed at which the valve is closed   (ii)     The velocity of flow (V) (iii)     The length of the pipe (L) (iv)      Elastic properties of pipe material (E) and flowing fluid (K).
Post a Comment
Read more