Viscosity Concepts in Fluid Mechanics

<p>Cubic meter per second (m³/s) (D)</p> Signup and view all the answers

<p>They are directly proportional (D)</p> Signup and view all the answers

<p>Materials exhibiting both viscous and elastic properties (D)</p> Signup and view all the answers

<p>Newtonian fluids have a constant viscosity regardless of stress, while non-Newtonian fluids do not. (A)</p> Signup and view all the answers

<p>High loss modulus, G’’ (B)</p> Signup and view all the answers

<p>G’ = Stress × Cos(θ) (B)</p> Signup and view all the answers

<p>Structured liquids such as polymer gels that show both viscous and elastic behavior (A)</p> Signup and view all the answers

<p>It is proportional to the loss modulus divided by frequency. (C)</p> Signup and view all the answers

<p>It creates a complex viscoelastic behavior indicating increased flow properties. (C)</p> Signup and view all the answers

<p>Their viscosity remains consistent regardless of the rate of deformation. (A)</p> Signup and view all the answers

<p>Shear stress increases linearly after the yield stress is reached. (B)</p> Signup and view all the answers

<p>They show time-dependent shear-thinning properties. (A)</p> Signup and view all the answers

<p>The fluid behaves like a Newtonian fluid. (B)</p> Signup and view all the answers

<p>The time taken for the sphere to fall. (A)</p> Signup and view all the answers

<p>They have a constant viscosity regardless of shear rate. (D)</p> Signup and view all the answers

<p>The degree of thixotropic behavior. (A)</p> Signup and view all the answers

<p>Dynamic viscosity equals shear stress divided by shear rate. (B)</p> Signup and view all the answers

<p>They display variable viscosity depending on shear rate. (B)</p> Signup and view all the answers

<p>Newtonian fluids do not have a yield stress, while non-Newtonian fluids do. (A)</p> Signup and view all the answers

<p>The temperature of the fluid. (A)</p> Signup and view all the answers

<p>The measure of a liquid's resistance to shear stress (B)</p> Signup and view all the answers

<p>The internal resistance related to the velocity gradient (B)</p> Signup and view all the answers

<p>It is the displacement divided by the height of the sample (D)</p> Signup and view all the answers

<p>The shear stress applied (A)</p> Signup and view all the answers

<p>As the velocity of the top layer over the height of the sample (B)</p> Signup and view all the answers

<p>The viscoelastic properties of a sample under different stress conditions (C)</p> Signup and view all the answers

<p>Shear stress is proportional to shear rate (D)</p> Signup and view all the answers

<p>The spreadability and adhesion characteristics of the formulation (A)</p> Signup and view all the answers

<p>Their viscosity can change based on the rate of shear applied (D)</p> Signup and view all the answers

<p>It will exhibit both elastic and viscous behavior during deformation (C)</p> Signup and view all the answers

A measure of a material's stiffness and ability to deform, calculated by dividing stress by strain amplitudes.

The viscous component of the complex modulus, indicating a material's ability to dissipate energy through friction.

The elastic component of the complex modulus, representing a material's ability to store energy reversibly.

A measure of a material's resistance to flow under shear stress, related to the loss modulus and frequency.

A rheometer test mode that measures a material's ability to deform when subjected to a constant force or stress.

A material's ability to exhibit both elastic and viscous properties.

A material that exhibits both elastic and viscous properties, but exhibits a more liquid-like behavior.

A material that exhibits primarily elastic properties, meaning it deforms reversibly and returns to its original shape.

The resistance to flow experienced by a liquid when its layers move relative to each other.

The deformation or displacement of a material caused by applied force.

The rate at which a material deforms under stress, expressed as the change in strain over time.

The measure of a material's resistance to flow under shear stress.

A type of test that measures a material's flow behavior under changing conditions, especially under oscillations or vibrations.

A material's property of exhibiting both elastic and viscous behaviors, meaning it can both store and dissipate energy.

The use of rheological testing to assess and control the quality of a product, ensuring desired consistency and functionality.

Newton's experiment demonstrates the concept of shear stress by visualizing layers of liquid moving at different speeds due to the force applied to a top plate.

The force per unit area acting parallel to the surface of an object.

The ratio of shear stress to shear rate, a constant for Newtonian fluids.

The ratio of the displacement (change in distance) to the gap (initial distance) between two points on a material subjected to a shearing force. Represents the degree of distortion in the material.

Force applied per unit area acting parallel to the surface of a material under shearing. Represents the intensity of shearing forces.

The rate of change of shear strain over time. How quickly the material is being deformed by the shearing force.

The measure of a fluid's resistance to flow under shear stress. High viscosity means the fluid is resistant to flow (thick), while low viscosity means it flows easily (thin).

A type of fluid where viscosity remains constant regardless of the applied shear stress. Simple liquids like water behave this way.

Dynamic viscosity (represented by η) is a measure of a fluid's resistance to flow under shear stress. It's calculated by multiplying the fluid's density (ρ) by its relaxation time (t) * It represents the internal friction of the fluid on a molecular level, affecting how easily it moves past itself. * This relationship can be visualized through the equation η = K ρ t, where K is a constant value.

A falling-sphere viscometer works by measuring how long it takes for a ball to fall through a specific distance in a fluid. By analyzing the ball's descent time, the viscosity of the fluid can be calculated. * A larger ball will take longer to fall through a viscous fluid. * The difference in the descent time is directly proportional to the viscosity level.

Shear stress (σ) is the force per unit area acting on a fluid's internal planes. It's responsible for creating deformation within a fluid. * Shear stress is measured in Pascals (Pa). * The greater the force applied, the higher the shear stress.

Shear rate (γ') is the rate of deformation of a fluid, reflecting how quickly its shape changes under shear stress. It's measured in reciprocal seconds (s-1). * A high shear rate represents a rapid change in shape caused by the force. * The higher the shear rate, the faster the flow of the fluid.

Newtonian fluids like water and air exhibit a linear relationship between shear stress and shear rate. Their viscosity remains constant, independent of the applied force or rate of deformation. * Think of a straight line on a graph. * These fluids flow smoothly.

Bingham fluids require a minimum force (yield stress σy) to start flowing. * Once overcome, they behave like Newtonian fluids, with a linear relationship between shear stress and shear rate. * These fluids exhibit a 'yield point' before flowing.

Thixotropic behavior refers to fluids that become less viscous over time when subjected to continuous shear stress (like stirring). * Their viscosity decreases with time of shearing, acting like a 'shear thinning' effect. * Once the stress is released, they regain their viscosity slowly.

Shear-thinning behavior occurs when a fluid's viscosity decreases with an increase in the shear rate. * This occurs in non-Newtonian fluids. * The higher the shear rate, the lower the viscosity becomes.

Hysteresis Loop is a graphical representation of thixotropic behavior, showcasing the change in stress over time. * The upward slope represents the increase in stress with time. * The downward slope represents the decrease in stress with time.

The area within the hysteresis loop (upward and downward slopes on the graph) indicates the degree of thixotropy present in a fluid. * A larger area represents a higher degree of thixotropy. * This means a fluid becomes less viscous at a faster rate.