17. Fluid Mechanics

Good morning, let us have a today class on drag and lift which is the last class of this course okay. This is lecture number 36 and drag and lift. I think discussion of the drag and lift I started from the lecture number 2 where we illustrated how we can estimate it what will be the drag and lift forces of the towers, the And also we talk about this how the bars drag and lift forces in linear momentum equations.

In this first part, the professor introduces the concepts of drag and lift, emphasizing that this lecture is a culmination of their course. Drag and lift are essential forces acting on bodies in fluid flow, such as towers affected by wind or vehicles encountering air resistance. Understanding these concepts is crucial for applications in various fields like aerodynamics and hydraulics.

Consider a car moving through the air. As it drives forward, the air pushes against the car's surface, creating a drag force that resists its motion. Similarly, lift can be seen when an airplane takes off; the shape of the wings allows the air to flow in a way that lifts the plane off the ground.

So if you look at that to really design a fuel efficient car or you talk about design wind turbine all he needs a information knowledge on this drag and the lift which actually help us to generate wind powers from wind tunnel.

This chunk discusses the application of drag and lift in designing efficient vehicles and wind turbines. It emphasizes the importance of understanding drag and lift forces to optimize designs that enhance performance and efficiency. The professor mentions wind tunnel testing and computational fluid dynamics as critical methods used for analyzing these forces.

When designing a race car, engineers carefully analyze the shape of the body to reduce drag. They often use wind tunnels to visualize how air flows over the car, allowing them to make improvements that help the car go faster with less fuel.

So most often we define the drag force is a functions of half rho v square is a dynamic pressures as we discussed earlier multiplied with a Cd this is called coefficients of drag into A is the frontal area.

Here, the professor defines the drag force mathematically. The drag force (FD) can be calculated using the formula FD = 0.5 * rho * v² * Cd * A, where 'rho' is the fluid density, 'v' is the velocity of the fluid, 'Cd' is the coefficient of drag, and 'A' is the frontal area of the object. The coefficient of drag is determined experimentally and varies based on the shape and orientation of the object.

Imagine you’re riding a bike. If you raise the handlebars and sit upright, you create more drag compared to if you lean forward into a racing position. This change in position affects your Cd value significantly, showcasing the importance of aerodynamics.

So if you look it any cyclist which is a really participating like national or international camps he try to do level best to reduce the frontal area and reduce this coefficients drag.

This part explains how competitive cyclists lower their drag by minimizing their frontal area and optimizing body position. By wearing tight-fitting clothing and adjusting their posture, they can reduce their drag coefficient (Cd), allowing them to go faster using the same amount of effort.

Think of competitive cyclists during a race; they wear streamlined helmets and clothing to reduce their drag. Just like how a paper airplane flies further when its wings are angled correctly, cyclists position themselves to cut through the air more efficiently.

Just normal to that components we can say that is that lift okay.

In this section, the professor introduces lift as the force acting perpendicular to the direction of flow. Lift can be generated through pressure differences around an object, such as an airfoil. Understanding how lift works is crucial for applications in aviation and other fluid dynamics contexts.

Consider an airplane wing flying through the air. The shape of the wing causes air to move faster over the top than underneath, creating lower pressure above the wing. This pressure difference generates lift, helping the airplane rise into the sky.

So if you look at the drag okay which is a it is a very simple definitions as you can understand it that is a force flowing fluid exerted on a body in the flow direction is called the drag okay.

The professor clarifies that drag is the force exerted by a fluid on an object in the direction of fluid flow. This foundational concept is critical for engineers who must account for drag when designing structures, vehicles, and any object that interacts with fluid environments.

When swimming, a swimmer feels drag from the water. As they push through, they must exert more energy to swim faster. Understanding drag helps swimmers refine their technique to minimize resistance, allowing them to swim more efficiently.

These drag and lift coefficients are primarily functions of shape of the body as I said it it also depends upon the Reynolds numbers and the surface roughness.

This point highlights that the drag and lift coefficients vary depending on the shape of the object, the Reynolds number (which relates to the flow regime), and the roughness of the object's surface. Engineers must consider these factors when designing objects that are subject to fluid flow to optimize drag and lift.

Think of a golf ball versus a smooth soccer ball. The dimples on a golf ball create turbulence that allows it to fly farther than a smooth ball would. Understanding these properties allows engineers to design better sports equipment.

So it is a very interesting subject. But as we have very limited time of finishing this course in this class. So let us talk about drag and lift friction and pressure drags okay which is definitions wise how the drag coefficients are common geometry as I just given some examples of and parallel flow over the flat plate which is the boundary layers.

In concluding remarks, the professor reinforces the importance of understanding fluid mechanics, particularly drag and lift. They summarize key concepts and indicate that fluid mechanics is fundamental to various engineering applications, emphasizing the daily relevance of these principles in real-world scenarios.

Every time a vehicle moves through the air, the principles of drag and lift are at work. By optimizing designs using the knowledge of fluid mechanics, we can create more efficient cars, airplanes, and structures that effectively resist wind forces, making them safer and more effective.

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