Viscosity refers to the internal friction between molecules when the fluid is subjected to an external force. Dynamic viscosity is also referred to as absolute viscosity, simple viscosity, and dynamic viscosity. It refers to the ratio of stress to strain rate. When two plates with an area of 1 square meters and a distance of 1 m are immersed in a liquid, they move relative to each other at a speed of 1 m/s. The internal friction force generated by the interaction between the fluids, the unit is Newton second per square, and Pa·s Pa·s.
What is kinematic viscosity? Kinematic viscosity is also called kinematic viscosity, which refers to the ratio of hydrodynamic viscosity to fluid density ρ, in square meters/s. There are multiple unit expressions for kinematic viscosity, and the conversion unit is converted to: 1㎡/s=104St=106cSt. cSt is centistokes. The instrument for measuring kinematic viscosity is called a kinematic viscometer.
Формула за израчунавање кинематског вискозитета:
The force exerted on the unit area of the liquid layer is called the shear stress τ (N/m2).
Стопа смицања (Д) Д=дв /дк (С-1)
Напон смицања и брзина смицања су два основна параметра која карактеришу реолошка својства система
Два паралелна флуида са различитим равнима имају исту површину "А", одвојену растојањем "дк", и теку у истом правцу при различитим брзинама протока "В1" и "В2". Њутн је претпоставио да је сила која одржава ове различите брзине протока пропорционална релативној брзини течности или градијенту брзине, наиме:
τ= ηdv/dx = ηD (Newton's formula) where η is the dynamic viscosity, which is related to the material properties.
Newtonian fluid: a fluid that conforms to Newton's formula. Viscosity is only related to temperature and has nothing to do with shear rate. τ is proportional to D.
Non-Newtonian fluid: does not conform to the Newtonian formula τ/D=f(D), and ηa represents the viscosity under a certain (τ/D), which is called the apparent viscosity.
Вискозност је својство које ствара унутрашње трење између молекула унутар течности. Динамички вискозитет се односи на однос силе унутрашњег трења по јединици контактне површине течности и стопе промене брзине протока управно на смер кретања. Кинематички вискозитет се односи на динамички вискозитет на истој температури. Однос густине течности под притиском. Вискозност се обично изражава кинематичком вискозитетом, а јединица је мм2/с.
Конверзија јединице динамичког вискозитета:
1 поис (1П)=100 центипоис (100цП)
1 centipoise (1cP) = 1 mPa·s (1mPa·s)
1 mPa·s (1mPa·s)=1000 microPa·s (1000μPa·s)
Конверзија динамичког вискозитета и кинематичког вискозитета
μ=ν·ρ
Where μ---dynamic viscosity of the sample (mPa·s)
ν－－- Kinematic viscosity of sample (mm2/s)
ρ－－- The density of the sample at the same temperature as the measured kinematic viscosity (g/cm3)
Вискозитет има одличан однос са температуром течности, а не много са притиском.
What does the higher the kinematic viscosity indicate? The greater the kinematic viscosity, the greater the viscosity value, and the greater the friction between the internal molecules. When the fluid moves under the action of external force, the energy consumed will be greater. If the external force acts on a certain situation, the distance of fluid circulation will be smaller. Falling ball viscometers, viscosity cups, and Ubbelohde viscometers are based on the characteristics of fluid kinematic viscosity, and use gravity as an external force to promote relative movement between fluids, which can be converted into fluid viscosity values by measuring time. Rotary viscometers and vibrating viscometers both use electrical energy to convert the friction between fluids into resistance or damping, and then convert them into viscosity values and display them on the display of the instrument. The greater the kinematic viscosity, the greater the displayed value, which represents the greater the viscosity of the fluid.