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

Summary

The script is a lecture on fluid mechanics, a challenging subject for many students. It begins with defining 'fluid' as a substance that continuously deforms when stress is applied, unable to withstand shear stress. The lecture explains concepts such as force, pressure, and stress, and introduces viscosity, which relates to the velocity of fluid layers. An example is given using a thin layer of water, illustrating how viscosity can be calculated using the shear stress applied and the resulting velocity gradient. The lecture aims to deepen understanding of fluid dynamics and its practical applications.

Takeaways

• 🔬 Fluid mechanics is a challenging yet essential subject for students in fields like automotive engineering, physics, and any discipline related to fluid dynamics.
• 💧 The definition of a fluid is a substance that continuously deforms when subjected to shear stress, meaning it cannot withstand a pushing force.
• Shear stress (τ) is defined as the force applied parallel to a surface divided by the area of that surface, with units typically expressed as Newtons per square meter (N/m²).
• 📚 The concept of shear stress is fundamental to understanding fluid behavior, as it helps explain how fluids respond to applied forces.
• 📐 The relationship between shear stress and velocity is described by the equation τ = μ (∂u/∂y), where μ is the dynamic viscosity, u is the velocity, and y is the spatial coordinate in the direction perpendicular to the flow.
• 💧 The behavior of fluids near a solid surface is influenced by intermolecular forces, including cohesion (between fluid molecules) and adhesion (between fluid and solid molecules).
• 🌊 Fluids exhibit a property called no-slip condition, where the fluid velocity at the boundary with a solid is zero due to the adherence of fluid molecules to the solid surface.
• 📉 The velocity distribution of fluid molecules near a solid surface is not uniform; it varies linearly from zero at the surface to a maximum value at a certain distance, described by the velocity gradient.
• 🔄 Viscosity is a measure of a fluid's resistance to deformation and is crucial in predicting fluid flow behavior under different stress conditions.
• 🌐 Practical applications of understanding viscosity include solving engineering problems related to fluid flow, which can have significant implications in design and operation of various systems.
• 📚 The lecture introduces fundamental concepts in fluid mechanics that are essential for further studies and applications in the field.

Q & A

What is the definition of a fluid according to the script?

A fluid is defined as a substance that continuously deforms when subjected to a shear stress.

What is the difference between a fluid and sand according to the script?

While sand can flow and take the shape of a container, it is not considered a fluid because it does not continuously deform under shear stress.

What is shear stress?

Shear stress is defined as the force applied parallel to the surface divided by the area over which the force is applied.

What is the unit of shear stress?

The unit of shear stress is Newtons per square meter (N/m^2).

What is the relationship between shear stress and viscosity?

Viscosity is related to shear stress through the equation where shear stress is equal to viscosity times the rate of deformation.

What is the rate of deformation?

The rate of deformation is the velocity of a fluid at a certain point in space and time.

What is the concept of no-slip condition mentioned in the script?

The no-slip condition refers to the scenario where the fluid molecules at the boundary with a solid surface have a velocity equal to zero because they are in contact with the solid.

What is meant by the linear distribution of velocity in the script?

The linear distribution of velocity implies that the change in velocity across a thin layer of fluid is directly proportional to the distance from the solid surface, represented as a straight line in a velocity profile.

What is the significance of the term 'Dewi' in the context of the script?

In the script, 'Dewi' refers to the gradient of the velocity profile, which is the slope of the linear distribution of fluid velocity with respect to the coordinate normal to the surface.

What does the term 'Miu' represent in the script?

Miu, or dynamic viscosity, is the proportionality constant between shear stress and the rate of deformation, encapsulating the cause and effect relationship in fluid flow.

How does the script suggest applying the understanding of viscosity to practical engineering problems?

The script suggests that understanding viscosity is crucial for solving various engineering problems involving fluid flow.