Fluid Mechanics: Principle of Buoyancy and Liquid Flow

Dealing with fluid mechanics and understanding the principle concept of buoyancy requires deep understanding of the concept. Buoyancy is mainly defined as the upward force exerted by a liquid on an immersed object. When you try to immerse an object in water, you will feel an upward force acting on the object which increases as you further try to immerse the object deeper into the liquid. 

What happens is that, when an object is already submerged in a liquid, the pressure applied to the bottom surface is higher than the pressure on the upper surface. The variation in pressure creates a buoyant force that acts against the force of gravity. This is a fundamental aspect of fluid mechanics. Let’s explore and understand this interesting field in detail.

Can you explain what the principle of Buoyancy means?

Buoyancy is a vital concept in fluid mechanics that explains the reason why the object floats or sinks in a liquid. The principle of buoyancy (known as Archimedes’ Principle) states that a body partially or wholly immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the body. 

Archimedes’ Principle: Some key points to know

1. Buoyant force: This is the upward force exerted that the fluid exerts on an  object that is submerged in it.
2. Displaced Fluid: When the object is submerged in a fluid, the volume of the fluid displaced by the object is directly proportional to the volume of the object that is submerged.  
3. Weight of displaced fluid: This refers to the principle that the buoyant force exerted on an object submerged in a fluid is equal to the weight of the fluid that the object displaces. 

Two main factors that puts an affect on the buoyant force:

• The density of the fluid
• The volume of the submerged object

What do you mean by Pascal’s Law?

Pascal's Law states that the pressure exerted at any point in an incompressible confined fluid is equally transmitted in all the directions of the fluid throughout the walls of the containing vessel. The force applied to a fluid is distributed uniformly throughout the fluid, unaffected by the container’s form. Change in pressure at any point in the fluid is transmitted equally in all directions. This is the basic principle behind hydraulic lifts and other hydraulic systems which transmit force with the use of liquid.

How is Bernoulli’s Principle different from the concept of buoyancy?

Bernoulli’s principle is an important concept in fluid mechanics that describes the relationship between the pressure and velocity in a fluid. It states that as the velocity of the fluid and its corresponding pressure is inversely proportional to each other. Whereas, buoyant force is equal to the weight of the fluid that an object displaces when it is submerged in a fluid. 

All you need to know about Fluid Mechanics: 

Fluid mechanics is a branch of physics that deals with fluids under specific conditions including change in pressure and temperature conditions. There are some fundamental theorems of fluid mechanics like it is based on the principles of mass, momentum, and conservation of energy. 

• Conservation of Mass: The mass entering a pipe is equal to the mass leaving the pipe for an incompressible fluid. 
• Conservation of Momentum: The conservation of momentum in fluid mechanics states that the momentum of a system remains constant when there is no net force acting on it. 
• Conservation of Energy: It states that the total mechanical energy of a fluid system remains constant at any point along a streamline. 

What is Fluid Flow?

Fluid flow refers to the movement of fluids, which includes both liquids and gases, driven by various gases. It encompasses how these substances move and interact within different environments.

Let’s get an idea about the various types of fluid flow:

• Steady Flow: This type of flow occurs when the characteristics of a fluid, such as velocity, pressure, and temperature, remain constant at every point over time. Essentially, the fluid’s velocity doesn’t change at any given point as time passes.
• Unsteady Flow: In this type of flow, the properties of the fluid, like velocity, pressure, and temperature change with time. This means that the velocity of the fluid varies at different points over time. 
• Incompressible Flow: This flow is defined by the constant density of the fluid, regardless of any pressure changes. In other words, the fluid’s density doesn’t fluctuate even if the pressure conditions alter.
• Compressible Flow: The flow that is significantly impacted due to the changes in pressure, i.e., the fluid density changes significantly with pressure changes. 
• Laminar Flow: This is a smooth and an orderly type of fluid flow where the fluid particles move in parallel layers, sliding past each other without any disruption or mixing.
• Turbulent Flow: In this type of flow the fluid moves chaotically with the layers mixing and creating eddies and swirls.
• Transitional Flow: This flow exists in a state between laminar and turbulent flow, where the fluid exhibits characteristics of both types as it transitions from smooth  to chaotic movement.

FAQS on Fluid Mechanics:

1.  What are the factors that affect fluid flow?

Fluid flow is affected by the following factors:

• Viscosity: It decreases the flow rate of the fluid.
• Density: Mass per unit volume of the fluid.
• Pressure: The force exerted by the fluid per unit area
• Temperature: It affects the viscosity and density of the fluid.

2. What do you mean by a compressible and an incompressible fluid?

A fluid whose density remains constant throughout despite any change in pressure is known as the incompressible fluid whereas a compressible fluid is the one whose density changes with change in pressure.

3. Describe Archimedes’ principle.

Archimedes' principle states that the upward buoyant force exerted on an object submerged in a liquid is equal to the weight of fluid displaced by the body.