15.. Fluid Mechanics

Good morning all of you as we discussed in the last class introduction to open channel flow. Today I will continue open channel flow going slight bit more in depth about the open channel looking that I have been following now the best books for open channel flow which is the books on Hanif Choudhury books but it is a higher level book but I can suggest you to read either FM White book or the Senral Simbala book.

This introduction sets the stage for the lecture by summarying what was covered in the previous class and what will be the focus today. The emphasis is on exploring open channel flow in depth, referencing authoritative texts in the subject that are recommended for further study.

Think of it like preparing for a sports tournament. In your last practice, you learned the basics of your sport. In today's practice, you will dive deeper into specific strategies and techniques to improve your game, supported by expert coaches' guidance.

One very interesting things we will discuss about flow-proud numbers and the wave split which is new concept what we will introduce it. No doubt we already discussed about these mass conservation equations, linear momentum equations, energy conservation equations. These equations will apply for a control volume.

This chunk introduces critical concepts that will be explored in the course: Froude numbers and wave propagation. It reinforces that the previous equations learned—mass conservation, linear momentum, and energy conservation—will be integral to analyzing open channel flows and disturbances.

Consider the way a traffic jam develops when a sudden obstacle appears on the road. The vehicles represent the flow of water, and the equations we discuss are like traffic laws that govern how the cars (water) respond to changes in the environment.

One of the manmade channels we India is a country we are very much leader in constructing the canals if you look at the history of the Ganga canals...

This segment highlights India's historical significance in canal construction, particularly the Ganga Canal, which was built in the 19th century and continues to serve a vital role in water distribution and energy generation.

Think of historical engineering achievements like the engineering marvel of the Great Wall of China, which served both military and logistical purposes. Similarly, the Ganga Canal is an impressive infrastructure feat that supports millions of lives even today.

Now if you look at that just to think it that when you have let me have the river is flowing like this okay river is flowing and this is what you have the bed level or the canals this is the bed level... because of these disturbance what is the wave speed the speed of speed of of surface water wave okay surface water wave.

Here, the discussion moves into the technical aspects of flow in open channels, specifically analyzing how disturbances—like a stone thrown into a river—create waves that propagate through the water. It introduces mathematical factors like wave speed and flow depth.

Imagine dropping a pebble into a calm pond. The ripples that spread outward represent the wave propagation in a river after a disturbance. Just like how the ripples travel further away from where the pebble hit the water, waves in a river behave similarly when disturbances occur.

See if you look at that as we discussed earlier we talk about 3 types of the flow subcritical, critical and supercritical. In terms of the flow crowd numbers we define as if a lesser than 1...

This section categorizes flow types based on the relationship between inertia and gravitational forces, defining subcritical, critical, and supercritical flows through the Froude number. These concepts are pivotal for determining flow behavior and characteristics.

Think of these flow types as different speeds of running. A slow jog is like subcritical flow where the gravitational pull is stronger than the forward motion (inertia). Running at a steady pace might resemble critical flow, while sprinting past the finish line can be likened to supercritical flow where inertia dominates.

if you consider that you have the river and you have a gate okay... then you will have a energy dissipations like this.

This chunk describes hydraulic jumps, which represent a sudden change in flow conditions, resulting in energy dissipation and turbulence. It emphasizes the importance of hydraulic jumps in managing energy within flowing water systems.

Imagine a waterfall where water plunges down and creates turbulent splashes below. This is similar to a hydraulic jump where the energy from falling water dissipates, creating visible turbulence as it transitions from fast to slow flow.

So now the point is coming it how to derive the speed of water wave okay. How do you derive the speed of water wave which is a functions of the flow depth.

This segment addresses the derivation of water wave speed, demonstrating its dependence on flow depth and introducing key concepts of control volume. Understanding this relationship is crucial for predicting how waves interact within an open channel.

If you're swimming in a pool, the depth of water affects how quickly you can paddle. Similarly, the depth of an open channel influences how fast the surface waves travel. The deeper the water, the more substantial the wave action will be.

Now if you look it as I said it we follow the basic the integral approach concept the average conditions okay...

This portion elaborates on the concept of specific energy in open channel flow, detailing how it combines pressure and velocity heads. Specific energy helps designers understand how energy losses can affect flow conditions.

Imagine a water slide where the height from which you start affects your speed at the bottom. The specific energy describes how water's pressure and speed together influence how it flows in channels, just like how your starting elevation impacts your slide's momentum.

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