HYDRAULICS.pptx

Types of flow in open channel

1. HYDRAULICS Content- Types of flow in Open channel

2. Open Channel - Open Channel Flow is defined as fluid flow with a free surface open to the atmosphere. Examples include streams, rivers and culverts not flowing full.

3. Types of Flow in Open Channels 1. Steady and Unsteady Flow 2. Uniform Flow and Non-Uniform Flow 3. Laminar Flow and Turbulent Flow 4. Critical, Sub-Critical and Super - Critical Flow

4. Steady and Unsteady Flow In an open channel flow, if the flow parameters such as  depth of flow, the velocity of flow and the rate of flow  at a particular point on the fluid do not change with respect to time, then it is called as steady flow . For Steady Flow- dv/dt = 0 dQ/dt = dy/dt =

5. unsteady flow at any point on the open channel flow,if the flow parameters like depth of flow, the velocity of flow and rate of flow do change their value with respect to time, then it is called as an unsteady flow . It is hence given by : dv / dt , dQ / dt and dy / dt   not equal to Zero

6. 2. Uniform Flow The flow in the channel is said to be uniform, if, for a given length of the channel, the velocity of flow, the depth of flow remains constant. For Uniform flow dy / dS = 0 ; dv / dS =0;

7. Non-Uniform Flow In a Non-uniform flow, the flow parameters like velocity, depth of flow, etc do not remain constant for a given length of the channel. For Non-Uniform flow dy / dS and dv / dS not equal to zero The Non-uniform flow can be again defined as Rapidly varying flow (R.V.F) and Gradually Varied Flow (G.V.F). In the case of R.V.F, the depth of flow rapidly changes over a smaller length of the channel. It rises up suddenly for a short length and settles back. While in a G.V.F, the depth of flow changes gradually over a longer length of the channel.

8.  Laminar Flow & Turbulent Flow Laminar and turbulent flow in open channel flow is defined based on the Reynolds Number, Re. The Reynolds number is given by the relation : If the Reynolds number  Re  is less than 500 or 600, then the flow is called  laminar flow . If the Reynolds number is more than 2000, then the flow is said to be  turbulent .

9. 4. Critical, Sub-Critical and Super - Critical Flow The open channel flow is categorized as critical or sub-critical or super-critical based on the Froude number  Fe . Froude number is given by the relation :

10. Critical , Sub-Critical and Super - Critical Flow Open channel flow is Sub-critical if the Froude number is less than 1. Sub-Critical open channel flow is also defined as a  tranquil or streaming flow . An open channel flow with a Froude number equal to one is a critical flow . S uper-critical flow in open channel has a Froude number greater than 1. A supercritical flow is also termed as  rapid flow or torrential flow or shooting flow.

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