Stokes

Definition

Stokes is a unit of dynamic viscosity, which is a measure of a fluid's resistance to flow. It is named after the English mathematician and physicist Sir George Gabriel Stokes, who derived the equations governing the motion of viscous fluids.

5 Must Know Facts For Your Next Test

1. The Stokes unit is defined as 1 dyne-second per square centimeter (1 dyne-s/cm^2), which is equivalent to 0.1 Pascal-seconds (0.1 Pa·s).
2. Stokes is commonly used to measure the viscosity of liquids and gases, particularly in the context of fluid mechanics and transport phenomena.
3. The Stokes unit is often used in the study of sedimentation and the motion of small particles in a fluid, as described by Stokes' law.
4. Stokes' law relates the viscous drag force on a small, spherical object moving through a fluid to the fluid's dynamic viscosity, the object's radius, and its velocity.
5. The Stokes number is a dimensionless parameter that compares the inertia of a particle to the viscous forces acting on it, and is used to predict the behavior of particles in fluid flows.

Review Questions

• Explain how the Stokes unit is related to the measurement of dynamic viscosity.
  • The Stokes unit is a measure of dynamic viscosity, which describes a fluid's internal resistance to flow. Specifically, one Stoke is defined as one dyne-second per square centimeter (1 dyne-s/cm^2), which is equivalent to 0.1 Pascal-seconds (0.1 Pa·s). This unit is used to quantify the viscosity of liquids and gases, and is particularly important in the study of fluid mechanics and transport phenomena, such as sedimentation and the motion of small particles in a fluid.
• Describe the relationship between Stokes' law and the behavior of particles in fluid flows.
  • Stokes' law relates the viscous drag force on a small, spherical object moving through a fluid to the fluid's dynamic viscosity, the object's radius, and its velocity. This law is used to predict the behavior of particles in fluid flows, as the Stokes number, a dimensionless parameter that compares the inertia of a particle to the viscous forces acting on it, can be used to determine how the particle will interact with the fluid. For example, particles with a low Stokes number will closely follow the fluid flow, while those with a high Stokes number will be less affected by the viscous forces and may deviate from the flow.
• Analyze the role of Stokes' law and the Stokes unit in the context of viscosity and turbulence.
  • Stokes' law and the Stokes unit are fundamental concepts in the study of viscosity and turbulence. Dynamic viscosity, as measured in Stokes, is a key factor in determining the behavior of fluids, particularly in the transition from laminar to turbulent flow. The Stokes number, which incorporates the Stokes unit, is used to predict how particles will interact with a fluid flow, with implications for phenomena such as sedimentation and the motion of suspended particles. Additionally, the Stokes unit is used to characterize the viscosity of fluids, which is an important parameter in understanding the onset of turbulence and the overall flow behavior of a system. By understanding the Stokes unit and its relationship to Stokes' law, you can better analyze the role of viscosity and its influence on fluid dynamics and turbulence.

Related terms

Dynamic Viscosity: The measure of a fluid's internal resistance to flow, which depends on the cohesive forces between the fluid's molecules.

Kinematic Viscosity: The ratio of a fluid's dynamic viscosity to its density, which describes the fluid's resistance to flow under the influence of gravity.

Reynolds Number: A dimensionless quantity that describes the ratio of inertial forces to viscous forces within a fluid flow, and is used to predict flow patterns.