In this tutorial, you will explore the fundamentals of fluid mechanics, a crucial branch of science that studies the behavior of fluids under various forces. This tutorial will guide you through the basic principles governing fluid mechanics, the unique characteristics of fluids, and the differences between fluids and solids. By the end, you will have a solid understanding of how fluids interact with their environment, setting the foundation for more advanced topics in fluid mechanics.
What is Fluid Mechanics?
Fluid mechanics is a branch of science that explores the behavior of fluids (liquids and gases) when subjected to forces. Unlike solids, fluids flow when a force is applied, and their behavior can be analyzed using the principles of mechanics. Fluid mechanics encompasses the study of fluids at rest, in motion, and their interactions with structures.
Basic Laws Governing Fluid Mechanics
Analysis of any fluid mechanics problem involves the application of basic laws to the fluid. These basic governing laws are as follows:
- Conservation of Mass: This law states that for a closed system, mass can neither be created nor be destroyed. Hence, mass in a fluid flow system remains constant. By this law, continuity equation for fluid flow system can be derived.
- First Law of Thermodynamics: This law states that the energy of the universe remains constant. It can be exchanged between the system and the surrounding.
- Newton’s Second Law of Motion: This law states that the force acting on a system is equal to mass multiplied by its acceleration. Newton’s second law is used to derive the impulse-momentum equation of fluid mechanics.
Characteristics of a Fluid
A fluid is a substance that deforms continuously under shear stress. Key characteristics include:
- Shape: Fluids do not have a definite shape and take the shape of their container.
- Deformation: Fluids continuously deform when subjected to a small shear stress, allowing them to flow.
Phases of Matter Based on Intermolecular Spacing
Matter can be categorized based on the spacing between molecules:
- Solid: In solids, the molecules are very closely packed. The intermolecular cohesive forces are large. Hence, solids have a rigid and a compact form. A solid can resist tensile, compressive and shear stress.
- Liquid: Liquids have higher intermolecular spacing compared to solids. Hence intermolecular cohesive forces are low. A liquid can resist compressive force to some extent when it is filled in a container.
- Gas: Gases have very high intermolecular spacing and very low intermolecular cohesive forces. Gas molecules can move freely within the gas mass. Hence gases fill the container completely in which they are filled.
Branches of Fluid Mechanics
Fluid mechanics is divided into three main branches:
- Fluid Statics: This branch deals with the study of incompressible fluids at rest, focusing on the forces acting on bodies in a static fluid.
- Fluid Kinematics: It involves the study of the motion and flow patterns of fluids without considering the forces that cause the motion.
- Fluid Dynamics: This branch explores the relationship between the forces and the motion of fluid flow.
Differences Between Fluids and Solids
Following table compares the difference between a fluid and a solid.
| Parameter | Fluid | Solid |
|---|---|---|
| Shape | Fluids have no definite shape. | Solids have a definite shape. |
| Deformation Force | Fluids cannot resist the deformation force in static condition. | Solids can resist the deformation force in static condition. |
| Shear Stress | Shear stress is directly proportional to shear strain rate. | Shear stress is directly proportional to shear strain. |
| Properties | Static properties and dynamic properties of fluids are different. | Static properties and dynamic properties of solids are same. |
| Intermolecular Force | Small intermolecular force of attraction. | Large intermolecular force of attraction. |
| Structure | Fluids have less compact structure. | Solids have more compact structure. |
Differences Between Liquids and Gases
A fluid can be classified as a liquid and a gas. Following table compares the difference between a liquid and a gas.
| Parameter | Liquid | Gas |
|---|---|---|
| Volume | Liquids have fixed volume. | Gases have no fixed volume. |
| Intermolecular Force | Intermolecular Force of attraction is higher. | Intermolecular Force of attraction is lower. |
| Intermolecular Spacing | Intermolecular spacing is higher compared to solids but lower compared to gases. | Intermolecular spacing is higher compared to the liquids and solids. |
| Sound Propagation | Sound propagates faster in liquids compared to gases. | Sound propagates slower in gases compared to liquids and solids. |
| Compressibility | Liquids have very low compressibility. Hence liquids are treated as incompressible fluids. | Gases have very high compressibility. |
| Fluidity | Liquid can flow from higher location to lower location only. | Gases can flow in all the directions. |
Fluid Mechanics Index
For a deeper understanding of fluid mechanics and related concepts, explore the following topics:
Basics of Fluid Mechanics
- Microscopic and Macroscopic in Fluid Mechanics
- Pressure and Stress in Fluid Mechanics
- Fluid Properties
- Viscosity in Fluid Mechanics
- Types of Fluids
Fluid Properties and Behaviors
- Surface Tension in Fluid Mechanics
- Capillarity in Fluid Mechanics
- Vapor Pressure and Cavitation in Fluid Mechanics
Hydrostatics: Fluids at Rest
- Fluids at Rest
- Pressure Measurement in Fluid Mechanics
- Manometers in Fluid Mechanics
- Mechanical Gauges in Fluid Mechanics
- Hydrostatic Thrust on Submerged Bodies
- Hydrostatic Forces on Dams
Buoyancy and Stability
