Mekanika Fluida FM01 (Lecture 1: 1/4). Definisi Fluida, Newton's Law

Introduction

This tutorial provides a foundational understanding of fluid mechanics, focusing on key concepts such as fluid definition, viscosity, and Newton's laws as they apply to fluid dynamics. It is especially relevant for students in Mechanical Engineering, Chemical Engineering, Aerospace Engineering, and Environmental Engineering. By the end of this guide, you will grasp essential principles that can be applied to practical engineering problems, particularly in internal flow scenarios.

Step 1: Understand the Definition of Fluids

• Definition: Fluids are substances that can flow, which include liquids and gases.
• Characteristics of Fluids:
  • They take the shape of their container.
  • They can be compressed (gases) or incompressible (liquids).

Practical Advice

• Visualize fluids in everyday life, like water in a bottle or air in a balloon. This context helps in understanding fluid behavior.

Step 2: Learn About Viscosity

• Viscosity Definition: A measure of a fluid's resistance to flow or deformation.
• Importance: Viscosity affects how fluids flow in different scenarios, such as through pipes or around objects.

Practical Advice

• Consider the viscosity differences between water and honey; water flows easily, while honey flows slowly due to higher viscosity.

Step 3: Apply Newton's Law of Viscosity

• Newton's Law of Viscosity: This law relates shear stress and shear rate in a fluid.
  • Shear stress is the force per unit area applied parallel to the fluid.
  • Shear rate is the rate at which adjacent layers of fluid move with respect to each other.

Practical Advice

• Use the formula for Newtonian fluids: [ \tau = \mu \frac{du}{dy} ] Where:
  • (\tau) = shear stress
  • (\mu) = dynamic viscosity
  • (du/dy) = velocity gradient

Step 4: Understand Ideal Gas Law

• Ideal Gas Law: This law describes the relationship between pressure, volume, temperature, and the number of moles of a gas.
  • Formula: [ PV = nRT ] Where:
  • (P) = pressure
  • (V) = volume
  • (n) = number of moles
  • (R) = ideal gas constant
  • (T) = temperature in Kelvin

Practical Advice

• Familiarize yourself with each variable in ideal gas scenarios, such as balloon inflation, to see real-world applications.

Step 5: Explore Hydrostatics

• Hydrostatics Overview: Study of fluids at rest.
• Key Concepts:
  • Hydrostatic Pressure: Pressure exerted by a fluid at rest due to the weight of the fluid above it.
  • Pascal’s Principle: A change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid.

Practical Advice

• Experiment with water pressure by submerging different objects in water to see how depth affects pressure.

Step 6: Analyze Bernoulli's Equation

• Bernoulli's Equation: Describes the conservation of energy in fluid flow.
  • Formula: [ P + \frac{1}{2} \rho v^2 + \rho gh = \text{constant} ] Where:
  • (P) = pressure energy
  • (\rho) = fluid density
  • (v) = fluid velocity
  • (g) = acceleration due to gravity
  • (h) = height above a reference point

Practical Advice

• Use Bernoulli's principle to analyze airfoil lift or water flow in different pipe sections.

Conclusion

This tutorial has covered essential concepts in fluid mechanics, including the definition of fluids, viscosity, Newton's laws, the ideal gas law, hydrostatics, and Bernoulli's equation. Understanding these principles is crucial for applying fluid mechanics to engineering problems. As a next step, consider exploring practical examples in your field of study, or conduct experiments that illustrate these principles in action.