# Density and viscosity relationship

### How to Calculate Density From Viscosity | Sciencing

The more usual form of this relationship, called Newton's equation, states that the by the Greek letter ν "nu") is the ratio of the viscosity of a fluid to its density. There is no relationship between the viscosity and density of a fluid. While viscosity is the thickness or thinness of a fluid, density refers to the space between its. The viscosity of a fluid is the measure of its resistance to gradual deformation by shear stress or .. Newton's law of viscosity is a constitutive equation (like Hooke's law, Fick's law, and Ohm's law): it is not a fundamental .. is typically inversely proportional to density and increases with temperature, μ {\displaystyle \ mu } \mu.

Rheopectic dilatant liquids, that become more viscous over time when shaken, agitated, or otherwise stressed.

Bingham plastics that behave as a solid at low stresses but flow as a viscous fluid at high stresses. Shear-thinning liquids are very commonly, but misleadingly, described as thixotropic.

For gases and other compressible fluidsit depends on temperature and varies very slowly with pressure. The viscosity of some fluids may depend on other factors.

A magnetorheological fluidfor example, becomes thicker when subjected to a magnetic fieldpossibly to the point of behaving like a solid. In solids[ edit ] The viscous forces that arise during fluid flow must not be confused with the elastic forces that arise in a solid in response to shear, compression or extension stresses.

While in the latter the stress is proportional to the amount of shear deformation, in a fluid it is proportional to the rate of deformation over time. For this reason, Maxwell used the term fugitive elasticity for fluid viscosity. However, many liquids including water will briefly react like elastic solids when subjected to sudden stress. Conversely, many "solids" even granite will flow like liquids, albeit very slowly, even under arbitrarily small stress.

The extensional viscosity is a linear combination of the shear and bulk viscosities that describes the reaction of a solid elastic material to elongation.

It is widely used for characterizing polymers. In geologyearth materials that exhibit viscous deformation at least three orders of magnitude greater than their elastic deformation are sometimes called rheids. Viscometer Viscosity is measured with various types of viscometers and rheometers. A rheometer is used for those fluids that cannot be defined by a single value of viscosity and therefore require more parameters to be set and measured than is the case for a viscometer. For some fluids, the viscosity is constant over a wide range of shear rates Newtonian fluids.

The fluids without a constant viscosity non-Newtonian fluids cannot be described by a single number.

## Difference Between Viscosity and Density

Non-Newtonian fluids exhibit a variety of different correlations between shear stress and shear rate. One of the most common instruments for measuring kinematic viscosity is the glass capillary viscometer. A non-newtonian fluid is one in which the viscosity is a function of some mechanical variable like shear stress or time. Non-newtonian fluids that change over time are said to have a memory.

Some gels and pastes behave like a fluid when worked or agitated and then settle into a nearly solid state when at rest. Such materials are examples of shear-thinning fluids.

House paint is a shear-thinning fluid and it's a good thing, too. Brushing, rolling, or spraying are means of temporarily applying shear stress.

### Difference Between Viscosity and Density - knifedirectory.info

This reduces the paint's viscosity to the point where it can now flow out of the applicator and onto the wall or ceiling. Once this shear stress is removed the paint returns to its resting viscosity, which is so large that an appropriately thin layer behaves more like a solid than a liquid and the paint does not run or drip. Think about what it would be like to paint with water or honey for comparison. The former is always too runny and the latter is always too sticky.

Toothpaste is another example of a material whose viscosity decreases under stress. Toothpaste behaves like a solid while it sits at rest inside the tube. It will not flow out spontaneously when the cap is removed, but it will flow out when you put the squeeze on it. Now it ceases to behave like a solid and starts to act like a thick liquid. You don't have to worry about it flowing off the brush as you raise it to your mouth.

viscosity to density

Shear-thinning fluids can be classified into one of three general groups. A material that has a viscosity that decreases under shear stress but stays constant over time is said to be pseudoplastic. A material that has a viscosity that decreases under shear stress and then continues to decrease with time is said to be thixotropic. If the transition from high viscosity nearly semisolid to low viscosity essentially liquid takes place only after the shear stress exceeds some minimum value, the material is said to be a bingham plastic.

Materials that thicken when worked or agitated are called shear-thickening fluids.