GATE Exam Syllabus for Civil Engineering - CE

Hydraulics: Forces on immersed bodies; Flow measurement in channels and pipes; Dimensional analysis and hydraulic similitude; Kinematics of flow, velocity triangles; Basics of hydraulic machines, specific speed of pumps and turbines; Channel Hydraulics -Energy-depth relationships, specific energy, critical flow, slope profile, hydraulic jump, uniform flow and gradually varied flow

Open Channel Flow - Video

Open Channel Flow

Unit I - PPT

Download PPT of Unit - I of Open Channel Flow & Hydraulic Machinery

Introduction to Fluid Mechanics

A Fluid is a substance that deforms continuously when subjected to a shear stress no matter how small that shear stress may be.  

Differentiate solid and fluid.Fluid
The fluid deforms continuously when subjected to a shear stress.When the shear stress disappears the fluid never regain in to original shape. 

Solid
The Solid deforms a definite amount when subjected to a shear stress. When the shear stress disappears solids gain fully or partly their original shape


Fluid Mechanics is the branch of science that studies the behavior of fluids when they are in state of motion or rest. 

Fluid mechanics deals with three aspects of the fluid: static, kinematics, and dynamics aspects:

1. Fluid statics: The fluid which is in state of rest is called as static fluid and its study is called as fluid statics.
2. Fluid kinematics: The fluid which is in state of motion is called as moving fluid. The study of moving fluid without considering the effect of external pressures is called as fluid kinematics.
3. Fluid dynamics: The branch of science which studies the effect of all pressures including the external pressures on the moving fluid is called as fluid dynamics.

Fluid Properties:
Properties of fluids determine how fluids can be used in engineering and technology. They also determine the behavior of fluids in fluid mechanics. The following are some of the important basic properties of fluids:

1.     Density is  mass per unit volume of a fluid
2.     Viscosity is an amount of resistance of the fluid to shear stress. In a liquid, viscosity decreases with increase in temperature. In a gas, viscosity increases with increase in temperature.
3.     Temperature
4.     Surface Tension 
5.     Capillarity
6.     Pressure
7.     Specific Volume  is the volume of a fluid (V) occupied per unit mass (m). It is the reciprocal of density.
8.     Specific Weight is the weight possessed by unit volume of a fluid.
9.     Specific Gravity is the ratio of specific weight of the given fluid to the specific weight of standard fluid.

Real and Ideal fluids
The main difference between an ideal fluid and a real fluid is that for ideal flow p1 = p2 and for real flow p1 > p2. Ideal fluid is in-compressible and has no viscosity. Real fluid has viscosity. Water is considered as Ideal Fluid.

Application of Fluid Mechanics:

1. Water Resource Engineering, in which water must be delivered to consumers and disposed of after use, 
2. Water Power Engineering, in which water is used to generate electric power, 
3. Flood Control and Drainage, in which flooding and excess water are controlled to protect lives and property, 
4. Structural Engineering, in which wind and water create forces on structures 

Pascal's Law states,
" The intensity of pressure at any point in a fluid at rest, is the same in all direction."

Bernoulli's principle states,
" For a perfect in-compressible liquid, flowing in a continuous stream, the total energy of a particle remains the same, while the particle moves from one point to another."

This statement is based on the assumption that there are no losses due to friction in the pipe. Mathematically,
 

 

Darcy's formula for loss of head in pipe
When the water is flowing in a pipe, it experiences some resistance to its motion, whose effect is to reduce the velocity and ultimately the head of water available. An empirical formula for the loss of head due to friction was derived by Henry Darcy.

The loss of head due to friction according to Darcy is,

The equation of continuity
The equation of continuity states that for an in-compressible fluid flowing in a pipe of varying cross-section, the mass flow rate is the same everywhere in the pipe. The mass flow rate is simply the rate at which mass flows past a given point, so it's the total mass flowing past divided by the time interval. The equation of continuity can be reduced to:

Generally, the density stays constant and then it's simply the flow rate (Av) that is constant.


A1.V1 = A2.V2