Mod-01 Lec-05 Lecture-05

TL;DR

Fluid mechanics explains the behavior of fluids, which can be classified as newtonian or non-newtonian. In a static fluid, pressure is the only force acting, with a compressive and normal force per unit area.

Transcript

Welcome to this fifth lecture on this n p-tel course on fluid mechanics for undergraduate students in chemical engineering in the last lecture, we discussed the basic difference between newtonian fluids viscous fluids and elastic solids and we wrote down we said that suppose. You take two plates and place a fluid layer in between them, a layer of f... Read More

Key Insights

• ⚾ Fluids can be classified as newtonian or non-newtonian based on their behavior under shear stress.
• 📣 The stress in a fluid is proportional to the velocity and inversely proportional to the gap thickness, with viscosity as the proportionality constant.
• 🧑‍🏭 In a static fluid, the only forces acting on a volume element are compressive and normal forces.

Questions & Answers

Q: What is the difference between newtonian and non-newtonian fluids?

Newtonian fluids deform continuously upon application of shear stress, while non-newtonian fluids may not. Newtonian fluids follow a linear relationship between stress and rate of deformation, while non-newtonian fluids exhibit different behaviors.

Q: How is the stress in a fluid related to velocity and gap thickness?

The stress in a fluid is proportional to the velocity at which a plate is moving and inversely proportional to the gap thickness. The proportionality constant is the viscosity of the fluid.

Q: What forces act on a volume element in a static fluid?

In a static fluid, the only forces acting on a volume element are surface forces, which are purely normal and compressive in nature.

Q: Does the pressure in a static fluid depend on the orientation of the surface?

No, the pressure in a static fluid is independent of the orientation of the surface. Regardless of the orientation, the pressure remains the same at a given point in the fluid.

Key Insights:

• Fluids can be classified as newtonian or non-newtonian based on their behavior under shear stress.
• The stress in a fluid is proportional to the velocity and inversely proportional to the gap thickness, with viscosity as the proportionality constant.
• In a static fluid, the only forces acting on a volume element are compressive and normal forces.
• The pressure in a static fluid is independent of the orientation of the surface at which it is measured.

Summary & Key Takeaways

• Fluids can be classified as newtonian or non-newtonian based on their behavior when subjected to shear stress. Newtonian fluids deform continuously, while non-newtonian fluids may not.

• The stress in a fluid is proportional to the velocity at which a plate is moving and inversely proportional to the gap thickness, with viscosity as the proportionality constant.

• The volume element in a static fluid experiences only normal forces, which are compressive in nature and can be measured as pressure.

• Pressure is a scalar that does not depend on the orientation of the surface at which it is measured.