Applied Fluid Mechanics Unit 2 - Viscosity of Fluids

The resistance of a fluid to flow, caused by internal friction between its layers.

The force per unit area that a fluid exerts on a surface due to its internal friction.

The rate at which the velocity of a fluid changes with distance.

The proportionality constant between shear stress and velocity gradient, representing the fluid's resistance to flow.

The ratio of dynamic viscosity to density, representing the fluid's resistance to flow due to its internal friction and mass.

The viscosity measured in Pascal-seconds (Pa.s) or Newton-seconds per square meter (Ns/m²), also known as absolute viscosity.

Measured in units of square meters per second (m²/s) or Stokes (St).

The application of viscosity in designing oil and gas extraction systems, considering the fluid's resistance to flow at high pressure and low temperatures.

Viscosity is the measure of a fluid's resistance to flow. It describes how easily a fluid flows under stress.

Newton's Law of Viscosity states that the shear stress (force per unit area) in a fluid is directly proportional to the rate of change of velocity with respect to distance (velocity gradient).

Newtonian fluids obey Newton's Law of Viscosity, meaning their viscosity is constant regardless of the applied shear rate. Examples include water, air, and gasoline.

Non-Newtonian fluids do not obey Newton's Law of Viscosity, meaning their viscosity changes with the applied shear rate. Examples include ketchup, blood, and paint.

The viscosity of many fluids changes significantly with temperature. Generally, liquid viscosity decreases with an increase in temperature.

Viscosity can be measured using a variety of methods, such as capillary viscometers, rotating viscometers, and falling sphere viscometers. Each method has its own advantages and disadvantages depending on the fluid type, viscosity range, and desired accuracy.

A unit of viscosity equal to 10^-4 m^2/s or 0.001 cm^2/s. Often seen in engineering applications.

A unit of viscosity equal to 10^-6 m^2/s or 0.000001 cm^2/s. Used for very viscous fluids.

A hypothetical fluid with zero viscosity and surface tension. It's an idealized concept used in fluid dynamics.

All real-world fluids have some viscosity.

A type of non-Newtonian fluid where some stress must be applied before it starts to flow (like toothpaste).

A measure of how much a fluid's viscosity changes with temperature.

Devices used to measure the viscosity of fluids.

A type of viscometer that measures the time it takes for a specific volume of fluid to flow through a calibrated orifice.

A system for classifying engine oils and lubricants based on viscosity.

A single viscosity grade, typically used for a specific temperature range.

A lubricant with multiple viscosity grades, suitable for a wider range of temperatures.

An international standard used to classify oils based on their viscosity. It uses the prefix "ISO VG" followed by a number representing the nominal kinematic viscosity in centistokes (cSt) at 40°C. For example, ISO VG 22 indicates a viscosity grade of 22 cSt ± 10% at 40°C.

A measure of a fluid's resistance to flow. Higher viscosity means a fluid flows more slowly. For hydraulic fluids, the viscosity must be sufficient for lubrication, but not too high to hinder fluid movement.

The ability of a fluid to reduce friction between moving parts, preventing wear and tear. It is crucial for hydraulic systems to ensure smooth operation and longevity.

The cleanliness of a hydraulic fluid is essential to prevent clogging and damage to system components. Impurities can cause wear, reduce efficiency, and lead to malfunctions.

The ability of a hydraulic fluid to withstand changes in chemical composition over time, ensuring it maintains its desired properties. Chemical stability prevents degradation and ensures proper performance.

A hydraulic fluid should not corrode or damage metal parts in the system. This characteristic ensures the longevity and performance of the system.

The ability of a hydraulic fluid to resist the growth of bacteria, which can hinder performance and lead to system contamination.

Hydraulic fluid should have minimal impact on the environment, minimizing harmful emissions and waste. This consideration ensures sustainability and responsible operation.