Kinematic Viscosity

Definition

Kinematic viscosity is a measure of the resistance to flow of a fluid under the influence of gravity. It is the ratio of the dynamic viscosity of a fluid to its density, and it describes the ease with which a fluid can flow through a pipe or around an object.

5 Must Know Facts For Your Next Test

1. Kinematic viscosity is measured in units of square meters per second (m²/s) or square centimeters per second (cm²/s).
2. Kinematic viscosity is an important factor in determining the behavior of fluids in both laminar and turbulent flow regimes.
3. Kinematic viscosity is inversely proportional to the fluid's density, meaning that as the density of a fluid increases, its kinematic viscosity decreases.
4. Kinematic viscosity is a crucial parameter in the design and analysis of fluid systems, such as in the study of boundary layers and the motion of objects in fluids.
5. Kinematic viscosity can be used to calculate the Reynolds number, which is a dimensionless quantity that describes the ratio of inertial forces to viscous forces in a fluid flow.

Review Questions

• Explain how kinematic viscosity is related to the concept of laminar flow.
  • Kinematic viscosity is an important factor in determining the behavior of fluids in laminar flow. Laminar flow is a smooth, steady flow of a fluid in parallel layers, with no disruption between the layers. Kinematic viscosity, which is the ratio of dynamic viscosity to fluid density, affects the ease with which a fluid can flow through a pipe or around an object. Fluids with higher kinematic viscosity tend to exhibit more laminar flow characteristics, as the viscous forces are more dominant compared to the inertial forces.
• Describe how kinematic viscosity is used in the context of Poiseuille's Law.
  • Poiseuille's Law describes the relationship between the flow rate, pressure drop, and the radius of a pipe for a fluid flowing in laminar flow. Kinematic viscosity is a key parameter in this law, as it directly affects the flow rate of the fluid. Specifically, Poiseuille's Law states that the volumetric flow rate of a fluid through a pipe is proportional to the pressure difference and the fourth power of the pipe radius, and inversely proportional to the dynamic viscosity of the fluid. Since kinematic viscosity is the ratio of dynamic viscosity to fluid density, it can be used in Poiseuille's Law to determine the flow characteristics of a fluid in a pipe.
• Explain how kinematic viscosity influences the motion of an object in a viscous fluid, as described in the context of Section 12.6 (Motion of an Object in a Viscous Fluid).
  • In the context of Section 12.6, which discusses the motion of an object in a viscous fluid, kinematic viscosity plays a crucial role. Kinematic viscosity, being the ratio of dynamic viscosity to fluid density, determines the ease with which an object can move through the fluid. Fluids with higher kinematic viscosity will exert more resistance to the motion of an object, resulting in a lower terminal velocity and a higher drag force acting on the object. Conversely, fluids with lower kinematic viscosity will offer less resistance, allowing the object to move more freely. Understanding the relationship between kinematic viscosity and the motion of an object in a viscous fluid is essential for analyzing and predicting the behavior of objects, such as in the design of hydraulic systems or the study of sedimentation processes.

Related terms

Dynamic Viscosity: Dynamic viscosity is a measure of the internal friction of a fluid, which determines the fluid's resistance to flow.

Laminar Flow:

Laminar flow is a smooth, steady flow of a fluid in parallel layers, with no disruption between the layers.

Poiseuille's Law: Poiseuille's law describes the relationship between the flow rate, pressure drop, and the radius of a pipe for a fluid flowing in laminar flow.