A
non-Newtonian fluid is a
fluidIn physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
whose flow properties differ in any way from those of
Newtonian fluidA Newtonian fluid is a fluid whose stress versus strain rate curve is linear and passes through the origin. The constant of proportionality is known as the viscosity.-Definition:...
s. Most commonly the
viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
(resistance to deformation or other forces) of non-Newtonian fluids is not independent of
shear rate or shear rate history. However, there are some non-Newtonian fluids with shear-independent viscosity, that nonetheless exhibit normal stress-differences or other non-Newtonian behaviour. Many
saltIn chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as
ketchupKetchup is a sweet-and-tangy condiment typically made from tomatoes, vinegar, sugar or high-fructose corn syrup and an assortment of...
,
custardCustard is a variety of culinary preparations based on a cooked mixture of milk or cream and egg yolk. Depending on how much egg or thickener is used, custard may vary in consistency from a thin pouring sauce , to a thick pastry cream used to fill éclairs. The most common custards are used as...
,
toothpasteToothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...
,
starchStarch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
suspensions,
paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
,
bloodBlood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, and
shampooShampoo is a hair care product used for the removal of oils, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair...
. In a Newtonian fluid, the relation between the
shear stressA shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
and the
shear rate is linear, passing through the
originIn mathematics, the origin of a Euclidean space is a special point, usually denoted by the letter O, used as a fixed point of reference for the geometry of the surrounding space. In a Cartesian coordinate system, the origin is the point where the axes of the system intersect...
, the constant of proportionality being the coefficient of
viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
. In a non-Newtonian fluid, the relation between the
shear stressA shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
and the
shear rate is different, and can even be time-dependent. Therefore a constant coefficient of viscosity cannot be defined.
Therefore, although the concept of viscosity is commonly used in
fluid mechanicsFluid mechanics is the study of fluids and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest; fluid kinematics, the study of fluids in motion; and fluid dynamics, the study of the effect of forces on fluid motion...
to characterize the
shearA shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
properties of a fluid, it can be inadequate to describe non-Newtonian fluids. They are best studied through several other
rheologicalRheology is the study of the flow of matter, primarily in the liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force....
properties which relate
stressIn continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
and
strain rate tensors under many different flow conditions, such as
oscillatoryOscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
shear, or extensional flow which are measured using different devices or rheometers. The properties are better studied using
tensorTensors are geometric objects that describe linear relations between vectors, scalars, and other tensors. Elementary examples include the dot product, the cross product, and linear maps. Vectors and scalars themselves are also tensors. A tensor can be represented as a multi-dimensional array of...
-valued constitutive equations, which are common in the field of
continuum mechanicsContinuum mechanics is a branch of mechanics that deals with the analysis of the kinematics and the mechanical behavior of materials modelled as a continuous mass rather than as discrete particles...
.
Summary
Comparison of non-Newtonian, Newtonian, and viscoelastic properties
| Viscoelastic |
Kelvin material |
"Parallel" linearstic combination of elastic and viscous effects |
|
| Anelastic |
Material returns to a well-defined "rest shape" |
|
| Time-dependent viscosity |
Rheopectic Rheopecty or rheopexy is the rare property of some non-Newtonian fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shearing force, the higher its viscosity. Rheopectic fluids, such as some lubricants, thicken or solidify when shaken...
|
Apparent viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
increases with duration of stress |
Some lubricant A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
s, whipped creamWhipped cream is cream that has been beaten by a mixer, whisk, or fork until it is light and fluffy. Whipped cream is often sweetened and sometimes flavored with vanilla, in which case it may be called Chantilly cream or crème Chantilly ....
|
| Thixotropic Thixotropy is the property of certain gels or fluids that are thick under normal conditions, but flow over time when shaken, agitated, or otherwise stressed...
|
Apparent viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
decreases with duration of stress |
Some clayClay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s, some drilling mud, many paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s, synovial fluidSynovial fluid is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its yolk-like consistency , the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement.-Overview:The inner membrane of synovial joints...
|
| Time-independent viscosity |
Shear thickening (dilatant) |
Apparent viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
increases with increased stress |
Suspensions of corn starch or sand in waterQuicksand is a colloid hydrogel consisting of fine granular matter , clay, and water.Water circulation underground can focus in an area with the optimal mixture of fine sands and other materials such as clay. The water moves up and then down slowly in a convection-like manner throughout a column...
|
| Shear thinning Shear thinning is an effect where a fluid's viscosity—the measure of a fluid's resistance to flow—decreases with an increasing rate of shear stress. Another name for a shear thinning fluid is a pseudoplastic. This property is found in certain complex solutions, such as lava, ketchup, whipped cream,...
(pseudoplastic) |
Apparent viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
decreases with increased stress |
Paper pulp in water, latex paint, ice Ice sheet dynamics describe the motion within large bodies of ice, such those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity-driven activity is controlled by two main variable factors: the temperature and strength of their bases...
, bloodBlood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, syrup, molasses |
| Generalized Newtonian fluid A generalized Newtonian fluid is an idealized fluid for which the shear stress, τ, is a function of shear rate at the particular time, but not dependent upon the history of deformation.\tau = F\left where:...
s |
Viscosity is constant
Stress depends on normal and shear strain rates and also the pressure applied on it |
Blood plasmaBlood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
, custardCustard is a variety of culinary preparations based on a cooked mixture of milk or cream and egg yolk. Depending on how much egg or thickener is used, custard may vary in consistency from a thin pouring sauce , to a thick pastry cream used to fill éclairs. The most common custards are used as...
|
Shear thickening fluids
Shear thickening fluidsA dilatant material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the acronym STF, is an example of a non-Newtonian fluid....
are also used in all wheel drive systems utilising a
viscous coupling unitA viscous coupling is a mechanical device which transfers torque and rotation by the medium of a viscous fluid. It is made of a number of circular plates with tabs or perforations, fitted very close to each other in a sealed drum. Alternate plates are connected to a driving shaft at one end of the...
for power transmission.
Shear thinning fluid
A familiar example of the opposite, a
shear thinning fluidShear thinning is an effect where a fluid's viscosity—the measure of a fluid's resistance to flow—decreases with an increasing rate of shear stress. Another name for a shear thinning fluid is a pseudoplastic. This property is found in certain complex solutions, such as lava, ketchup, whipped cream,...
, or pseudoplastic fluid, is
paintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
: one wants the paint to flow readily off the brush when it is being applied to the surface being painted, but not to drip excessively.
Bingham plastic
There are fluids which have a linear shear stress/shear strain relationship which require a finite yield stress before they begin to flow (the plot of shear stress against shear strain does not pass through the origin). These fluids are called
Bingham plasticA Bingham plastic is a viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. It is named after Eugene C. Bingham who proposed its mathematical form....
s. Several examples are clay suspensions, drilling mud, toothpaste, mayonnaise, chocolate, and mustard. The surface of a Bingham plastic can hold peaks when it is still. By contrast Newtonian fluids have flat featureless surfaces when still.
Rheopectic
There are also fluids whose strain rate is a function of time. Fluids that require a gradually increasing shear stress to maintain a constant strain rate are referred to as rheopectic. An opposite case of this, is a fluid that thins out with time and requires a decreasing stress to maintain a constant strain rate (thixotropic).
Oobleck
An inexpensive,
non-toxicToxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
example of a non-Newtonian fluid is a suspension of
starchStarch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
(e.g.
cornstarchCorn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...
) in water, sometimes called "oobleck" or "ooze" (1 part of water to 1.5–2 parts of corn starch). Uncooked
imitation custardBird's Custard is the original version of what is known generically as custard powder. It is a cornflour -based powder which thickens to form a custard-like sauce when mixed with milk and heated to a sufficient temperature...
, being a suspension of primarily cornflour, has the same properties. The name "oobleck" is derived from the children's book
Bartholomew and the OobleckBartholomew and the Oobleck is a 1949 book by Dr. Seuss . It follows the adventures of a young boy named Bartholomew, who must rescue his kingdom from a sticky substance called "oobleck". The book is a sequel of sorts to The 500 Hats of Bartholomew Cubbins...
.
Flubber
Flubber is a non-Newtonian fluid, easily made from
polyvinyl alcoholPolyvinyl alcohol is a water-soluble synthetic polymer .-Properties:...
based
glueThis is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....
s and
boraxBorax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. It is usually a white powder consisting of soft colorless crystals that dissolve easily in water.Borax has a wide variety of uses...
, that flows under low stresses, but breaks under higher stresses and pressures. This combination of fluid-like and solid-like properties makes it a Maxwell solid. Its behaviour can also be described as being
viscoplasticViscoplasticity is a theory in continuum mechanics that describes the rate-dependent inelastic behavior of solids. Rate-dependence in this context means that the deformation of the material depends on the rate at which loads are applied...
or gelatinous.
Chilled caramel topping
Another example of this is chilled caramel
ice creamIce cream is a frozen dessert usually made from dairy products, such as milk and cream, and often combined with fruits or other ingredients and flavours. Most varieties contain sugar, although some are made with other sweeteners...
topping. The sudden application of
forceIn physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
—for example by stabbing the surface with a finger, or rapidly inverting the container holding it—leads to the fluid behaving like a
solidSolid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
rather than a liquid. This is the "shear thickening" property of this non-Newtonian fluid. More gentle treatment, such as slowly inserting a spoon, will leave it in its liquid state. Trying to jerk the spoon back out again, however, will trigger the return of the temporary solid state. A person moving quickly and applying sufficient force with their feet can literally walk across such a liquid.
Silly Putty
Silly Putty is a silicone polymer based
suspensionIn chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...
which will flow, bounce, or break depending on strain rate.
Ketchup
KetchupKetchup is a sweet-and-tangy condiment typically made from tomatoes, vinegar, sugar or high-fructose corn syrup and an assortment of...
is a
shear thinningShear thinning is an effect where a fluid's viscosity—the measure of a fluid's resistance to flow—decreases with an increasing rate of shear stress. Another name for a shear thinning fluid is a pseudoplastic. This property is found in certain complex solutions, such as lava, ketchup, whipped cream,...
fluid. Shear thinning means that the fluid viscosity decreases with increasing
shear stressA shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
. In other words, fluid motion is initially difficult at slow rates of deformation, but will flow more freely at high rates.
See also
- Bingham plastic
A Bingham plastic is a viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. It is named after Eugene C. Bingham who proposed its mathematical form....
- Complex fluid
- Dissipative particle dynamics
Dissipative particle dynamics is a stochastic simulation technique for simulating the dynamic and rheological properties of simple and complex fluids. It was initially devised by Hoogerbrugge and Koelman to avoid the lattice artifacts of the so-called lattice gas automata and to tackle...
- Newtonian fluid
A Newtonian fluid is a fluid whose stress versus strain rate curve is linear and passes through the origin. The constant of proportionality is known as the viscosity.-Definition:...
- Herschel–Bulkley fluid
- Navier–Stokes equations
- Pseudoplastic
- Dilatant
A dilatant material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the acronym STF, is an example of a non-Newtonian fluid....
- Quicksand
Quicksand is a colloid hydrogel consisting of fine granular matter , clay, and water.Water circulation underground can focus in an area with the optimal mixture of fine sands and other materials such as clay. The water moves up and then down slowly in a convection-like manner throughout a column...
- Rheology
Rheology is the study of the flow of matter, primarily in the liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force....
- Superfluids
External links