Question

Statement (I): Open channel flow in a channel is said to be critical when the specific force is maximum for a given discharge.

Statement (II): Direct integration for steady non-uniform flow by Bresse’s method was developed for very wide rectangular channels.

1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
2. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

Answer 1

Correct Answer - Option 4 : Statement (I) is false but Statement (II) is true

Statement I: False

Open channel flow in a channel is said to be critical under the following conditions:

1. Froude Number is unity i.e. F_r= 1.

2. For a given discharge, the specific energy is minimum.

3. For a given discharge, the specific force is minimum.

4. For a given specific force, the discharge is maximum.

5. For a given specific energy, discharge is maximum.

Statement II: True

The computation of gradually-varied flow or non-uniform flow profiles involves basically the solution of dynamic equation of gradually varied flow. The main objective of computation is to determine the shape of flow profile. There are three methods of computation:

1. The graphical-integration method: It is to integrate the dynamic equation of gradually varied flow by a graphical procedure. The best one is the Ezra Method.

2. The direct-integration method: In this method, the channel length under consideration is divided into short reaches, and the integration is carried out by short range steps. It is also Breese’s Method.  Assumptions made in this method are:

1. Wide rectangular channel.

2. Chezy’s formula is applicable and Chezy’s C is constant.

 3. Step method: The channel is divided into short reaches. The computation is carried step by step from one end of the reach to the other. The most commonly used step methods are:

Direct-Step Method- Applicable to prismatic channels only.

Standard-step Method: Applicable to both non-prismatic and prismatic channels. It is a trial and error process.