22.5. New Experiments at IIT Guwahati

Now let us come back to very interesting experiments what it happened in 1930s, okay much before the World War II okay. The Germans the professor used to do a simple experiments okay which one of classical experiment conducted in a pipe flow and which helped to make a this complex flow to a simpler empirical based energy loss quantification, velocity distributions quantification as well what could be this wall shear stress.

In the 1930s, prior to World War II, significant experiments were conducted by German professors that fundamentally changed our understanding of fluid mechanics in pipe flow. These experiments simplified the complex nature of fluid flow by providing empirical methods to quantify energy losses and velocity distributions. Essentially, they transformed our approach to measuring fluid behavior in pipes, making it easier to predict how fluids flow and the effects of different factors on that flow.

Think about how navigating through a crowded room can be complicated if many people are moving around. If you could measure how people move around with ease and difficulties—like creating a map of pathways—then this would help everyone navigate the room more effectively. Similarly, Nikuradse's experiments mapped out how fluids behave in complex scenarios.

If you look at this any of the pipe flow we can have a laminar flow, the turbulent flow or the transitional in between the laminar and the turbulent flow. What the experiment is conducted by the Nikuradse is that with having very simple concept that the pipe put it with a roughness, this equivalent roughness is from the sand grains.

Nikuradse’s experiments focused on different flow regimes: laminar, turbulent, and transitional flows. A key feature of his setup was the introduction of roughness inside pipes using sand grains. This surface roughness played a critical role in how fluids interacted with the pipe walls, affecting the flow characteristics such as energy losses and wall shear stress.

Imagine testing how water behaves when flowing through different types of straws—one smooth, one with bumps on the inside. The bumps represent roughness. Just as the rough straw will slow the water down more than the smooth one due to increased friction, Nikuradse's roughened pipes illustrated how roughness influences fluid behavior.

By conducting a series of experiments, by Nikuradse finally bring a the friction factors relations with the Reynolds numbers which is Moody chart and we have been using that for designing all this pipe flow networks for the industry, the water supplier, sewage treatment plant all where we are using the same equations.

Through his systematic experimentation, Nikuradse developed important relationships between friction factors and Reynolds numbers, encapsulated in what is now known as the Moody Chart. This chart remains a critical tool in engineering for designing efficient piping systems, applicable in various industrial scenarios like water supply and sewage treatment.

Using the Moody Chart is akin to having a recipe book for cooking. Just as you refer to recipes to get the right proportions of ingredients for a delicious meal, engineers use the Moody Chart to find the right flow characteristics to ensure efficient piping systems.

Now if you come back to that what we have been doing at IIT Guwahati, we also do similar sort of creating the roughness in open channel flow. That is what you can see this vegetations are there. Some degree of we are creating the roughness and we try to measure the velocity distribution.

At IIT Guwahati, researchers are building on the foundational work of Nikuradse by conducting their own experiments that introduce roughness in open channels, such as through vegetation. They aim to understand how this roughness affects fluid behavior, particularly focusing on measuring velocity distributions, wall shear stress, and how these aspects influence flow patterns.

Consider a river that flows smoothly in some areas and is filled with rocks and vegetation in others. By studying how fast the water moves in different sections—like the smooth and rocky parts—scientists can better predict the overall health and dynamics of the river system, similar to the experiments being conducted.

What we are conducting at IIT Guwahati is providing empirical relationship and those empirical relationship is used in generally in industry to design the pipe networks.

The research conducted at IIT Guwahati aims to quantify flow behavior and energy loss in roughened channels. The insights gained from these experiments can provide empirical relationships similar to those derived from earlier studies, which are crucial for practical applications in industrial pipe network design. This emphasizes the importance of experimental validity in engineering designs.

Imagine if you were designing an amusement park slide. By testing how fast the water flows down different slide surfaces (smooth, bumpy), you can design a slide that maximizes fun while ensuring safety, just like empirical research helps engineers create efficient systems.

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