In other words, the fluid with high viscosity requires much more forces.Ībsolute viscosity gives the absolute size of the degree of stickiness that resists the direction of the substance’s motion in the state of a flowing fluid. As shown in Figure below, if the upper slab is moved to the right side when a fluid is filled between two slabs, the magnitude of force needed to move the slab differs depending on the type of fluid. Viscosity is defined as a fluid’s internal resistance to flow. Water being a fluid, specifically liquid, is vicious.Viscosity is the most important property governing the functions of a fluid and a measure of “sticky property” that represents the fluidity. What are the Types of Viscosity?Įngineering fluid mechanics provides two types of viscosity Dynamic Viscosity and Kinematic Viscosity. So, the resistance force against the flow by water will be less as compared to honey. Among, the two fluids, water, and honey, honey has high viscosity as compared to water. Let’s describe the term high-viscosity with an example. The fluid with high viscosity offers greater flow resistance. High viscosity usually means the liquid is thicker. Blood circulation inside our body depends on the viscosity of blood.Gums, coolants, petrol as a cleaner, brake fluid, cosmetics, food products, etc all require viscosity data during production to work smoothly.Cooking oils, fats, butter, etc are manufactured to provide a specific viscosity.For preparing various medicines like syrups viscosity data is required.For example, light machines use low viscous liquids whereas highly viscous oils are used in heavy machines. In lubrication engineering viscosity data and its variation with temperature is an absolute necessity to decide suitable lubrication for specific equipment.The molecular weight of organic liquids is determined using the knowledge of viscosity.The following examples can easily substantiate the applications of viscosity: The concept of Viscosity is used widely in science and technology. Equation 1 mentioned above is basically a mathematical representation of Newton’s law of viscosity. Dynamic viscosity is the coefficient of viscosity as defined in Newton’s law of viscosity. Non-Newtonian fluids do not follow Newton’s law of viscosity and hence their viscosity varies and is dependent on the shear rate. Newtonian fluids obey Newton’s law of viscosity. In another way, it can be stated that the ratio of shear stress to shear rate in a fluid is a constant, and is defined as the coefficient of viscosity. For a given temperature and pressure, Newton’s viscosity law states that the shear stress between two adjacent layers in a fluid is proportional to the velocity gradients between those layers. The relationship between the shear stress and the shear rate of fluid under mechanical stress is established by Newton’s law of viscosity. The following table states the viscosity of some popular substances. Temperature (☌) Kinematic Viscosity (m 2/s X 10 -6) 10 1.3059 20 1.004 30 0.801 50 0.553 70 0.413 90 0.326 100 0.294 Table 2: Kinematic Viscosity of water with respect to temperature Viscosity of Some Common Substances Table 2 below provides the kinematic viscosity of water. The kinematic viscosity of water can easily be obtained by dividing the above dynamic viscosity values by the water density. The following table provides the dynamic viscosity of water with respect to various temperatures. As for liquids, the viscosity decreases with an increase in temperature, the same is true for water. The viscosity of water at 20 0 C is 1 centipoise or 1 cP. Suspended Particles: Suspended materials increases viscosity.Multiphase flow: The viscosity of multiphase flow is affected by the volume of each phase.Liquids being incompressible does not have much impact. Pressure: With an increase in pressure, the viscosity of gases usually increases.Flow Conditions: For laminar flow, the viscosity of liquid remains constant while for turbulent flow viscosity changes.On the contrary, the viscosity of gases increases with an increase in temperature. Fluid Temperature: Usually the viscosity of liquids decreases with an increase in temperature.

Define viscosity in oil