What is Stokes law and its derivation?
The law is derived considering the forces acting on a particular particle as it sinks through the liquid column under the influence of gravity. The force that retards a sphere moving through a viscous fluid is directly proportional to the velocity and the radius of the sphere, and the viscosity of the fluid.
What are the four conditions of Stokes law?
1) The law applies to a fluid of infinite extent . 2) The law does not hold good if the spherical body is moving so fast that conditions are not streamline. 3) The spherical body must be rigid and smooth .
What is the importance of Stokes law?
Stokes law is important for understanding the swimming of microorganisms and sperm; also, the sedimentation of small particles and organisms in water, under the force of gravity.
What do you mean by Stokes law in laminar flow?
Stokes Law, named after George Gabriel Stokes, describes the relationship between the frictional force of a sphere moving in a liquid and other quantities (such as particle radius and velocity of the particle).
What is the SI unit of viscosity * 1 point?
The SI unit of viscosity is the pascal second (Pa·s) or kg·m−1·s−1. The SI unit of kinematic viscosity is square meter per second or m2/s.
Which is not unit of viscosity?
1 Poise= 1 dyne-s/cm2 and 1 Stokes= 1 cm2/s. Thus, Stokes is not an unit of μ, rather it is a unit of kinematic viscosity υ. Pascal is N/m2.
Is poise unit of viscosity?
A poise is the centimetre-gram-second (cgs) unit of viscosity. It expresses the force needed to maintain a unit… …still often used is the poise (1 Pa · s = 10 poise). At 20° C the viscosity of water is 1.0 × 10-3 Pa · s and that of air is 1.8 × 10-5 Pa · s.
What is dynamic viscosity and its unit?
The dynamic viscosity η (η = “eta”) is a measure of the viscosity of a fluid (fluid: liquid, flowing substance). The higher the viscosity, the thicker (less liquid) the fluid; the lower the viscosity, the thinner (more liquid) it is. SI unit of dynamic viscosity: [η] = Pascal-second (Pa*s) = N*s/m² = kg/m*s.
What is the instrument used to measure viscosity?
viscometer
Why do we measure viscosity?
Why Should You Measure Viscosity? Gathering viscosity data on a material gives manufacturers the ability to predict how the material will behave in the real world. For example: if toothpaste does not have the correct viscosity, it can either be too difficult to pump out from the tube, or pump out too much.
What are the factors that affects viscosity?
Viscosity denotes opposition to flow. Viscosity describes how thick and sticky the lava is, which influences how fast it flows. The two main factors that affect viscosity are temperature and silica content.
How is viscosity measured in liquids?
The viscosity of a liquid (see Viscosity) is measured using a viscometer, and the best viscometers are those which are able to create and control simple flow fields. Most modern viscometers are computer- or microprocessor-controlled and perform automatic calculations based on the particular geometry being used.
What are some liquids with low viscosity?
The viscosity of a liquid is a measure of its resistance to flow. Water, gasoline, and other liquids that flow freely have a low viscosity. Honey, syrup, motor oil, and other liquids that do not flow freely, like those shown in Figure 1, have higher viscosities.
What are two examples of viscous liquids?
Some examples of highly viscous liquids are oils, honey, glycerin, tar and sulfuric acid. Viscosity is the ability of substances, especially fluids, to resist flow. It can also be referred to as the measure of the ability of a liquid to resist being deformed by extensional stress.
What are the types and units of viscosity?
Units of Viscosity Using SI units, since shear stress was in N/m2 and shear rate was in (m/s)/m = 1/s, then dynamic viscosity has units of Ns/m2 = Pa s (pascal-second). However, the most common unit of viscosity is the dyne-second per square centimeter (dyne s/cm2) where 1 dyne = 10-5 N.
What are five properties of fluids?
Ans: Thermodynamic properties of fluids are density, temperature, internal energy, pressure, specific volume and specific weight.
What is the formula for dynamic viscosity?
Dynamic viscosity is the resistance to movement of one layer of a fluid over another and is defined by Formula F7. 8. Kinematic viscosity is dynamic viscosity divided by density (Formula F7. 9) and is the ratio of viscous forces to inertia forces.
What are the units of dynamic viscosity?
The dynamic viscosity has the dimension ML-1T-1 and the unit of kg/m.s (or, N.s/m2 or Pa. s). A common unit of dynamic viscosity is poise which is equivalent to 0.1 Pa.
What is the difference between dynamic and kinematic viscosity?
Viscosity is a fundamental material property when studying fluid flow for any application. Dynamic viscosity (also known as absolute viscosity) is the measurement of the fluid’s internal resistance to flow while kinematic viscosity refers to the ratio of dynamic viscosity to density.
What is dynamic viscosity of water?
The dynamic viscosity of water is 8.90 × 10−4 Pa·s or 8.90 × 10−3 dyn·s/cm2 or 0.890 cP at about 25 °C. Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C.
Which viscosity is used in Reynolds number?
The ratio μ/ρ is called v, the kinematic viscosity, also depending on the fluid density and temperature. For dry air at standard sea level conditions the value of v is 14.6 × 10–6. The higher the Reynolds number, the lesser the viscosity plays a role in the flow around the airfoil.