Newtonian and non newtonian fluids

newtonian and non newtonian fluids

1. Newtonian and non – newtonian fluids

2. MUHAMMAD AREEB UL HAQ 15053323-004 NAJAM ALI 15053323-003 SAMIULLAH 15053323-001 GROUP 1

3. WHAT IS FLUID? A fluid is a substance that continually deforms (flows) under an applied shear stress or in simpler terms, a fluid is a substance which cannot resist any shear force applied to it .

4. PROPERTIES OF FLUIDS Density Viscosity Temperature Pressure

5. VISCOSITY Viscosity is a quantitative measure of a fluid’s resistance to flow. It is defined as the internal friction of fluid. Lack of slipperiness is called as viscosity. Dynamic (or Absolute) Viscosity: The dynamic viscosity(η) of a fluid is a measure of the resistance it offers to relative shearing motion. η= F/ [A×(u/h)] η= τ /(u/h) N-s/m²

6. EFFECTS OF TEMPERATURE The viscosity of liquids decreases with increase the temperature. The viscosity of gases increases with the increase the temperature.

7. EFFECTS OF PRESSURE Lubricants viscosity increases with pressure. For most lubricants this effect is considerably largest than the other effects when the pressure is significantly above atmospheric.

8. NEWTON’S LAW OF VISCOSITY Newton’s law of viscosity states that “ shear stress is directly proportional to velocity gradient ”. That is the shear stress between the two adjacent layers of fluid is directly proportional to the negative value of the velocity gradient between the same two adjacent fluid layers. (Further mathematically described in Newtonian fluid topic)

9. TYPES OF VISCOSITY

10. Newtonian fluids And Non - Newtonian fluids TWO BASIC TYPES OF FLUIDS REGARDING THIER VISCOSITY BEHAVIOUR

11. NEWTONIAN FLUIDS

12. WHAT ARE NEWTONIAN FLUIDS? W here stress is directly proportional to rate of strain or Fluid with a constant viscosity at a fixed temperature and pressure . A Newtonian fluid's viscosity remains constant, no matter the amount of shear applied for a constant temperature.. These fluids have a linear relationship between viscosity and shear stress.

13. Continue….. They obey the Newton’s law of viscosity, which is τ= µdu/ dy The constant of proportionality is known as the viscosity. τ = shear stress exerted by the fluid ("drag") μ = fluid viscosity - a constant of proportionality du/ dy = velocity gradient perpendicular to the direction of shear.

14. WHAT IS STRAIN AND STRAIN RATE? Strain The ratio of extension to original length is called strain it has no units as it is a ratio of two lengths measured in meters. Strain rate is the change in strain (deformation) of a material with respect to time.

15. WHAT IS STRESS AND SHEAR RATE? Stress The stress applied to a material is the force per unit area applied to the material. The maximum stress a material can stand before it breaks is called the breaking stress or ultimate tensile stress . Shear rate is the rate at which a progressive shearing deformation is applied to some material

16. GRAPH OF NEWTONIAN FLUID

17. Continue….. This type of flow behavior Newton assumed for all fluids is called Newtonian. It is, however, only one of several types of flow behavior you may encounter. Graph A shows that the relationship between shear stress and shear rate is a straight line. Graph B shows that the fluid's viscosity remains constant as the shear rate is varied. Typical Newtonian fluids include water and thin motor oils.

18. EXAMPLES Water Mineral oil Gasoline Alcohol

19. NON - NEWTONIAN FLUID

20. WHAT ARE NON NEWTONIAN FLUIDS? Where stress is proportional to rate of strain, its higher powers and derivatives (basically everything other than Newtonian fluid ). Non-Newtonian fluids are the opposite of Newtonian fluids. When shear is applied to non-Newtonian fluids, the viscosity of the fluid changes .

21. Continue…. A non-Newtonian fluid is broadly defined as one for which the relationship   is not a constant. It means that there is non-linear relationship between shear rate & shear stress. In other words, when the shear rate is varied, the shear stress doesn't vary in the same proportion (or even necessarily in the same direction). E.g. Soap Solutions & cosmetics, Food such as butter, jam, cheese, soup, yogurt, natural substances such as lava, gums, etc. 

22. THE BEHAVIOR OF THE FLUID CAN BE DESCRIBED IN FOUR WAYS. Dilatant Pseudoplastic Thixotropic Fluid Rheopectic fluid

23. DILATANT PSEUDOPLASTIC TIME INDEPENDENT

24. DILATANT Viscosity of the fluid increases when shear is applied. Examples Quicksand Corn flour Starch in water Potassium silicate in water.

25. GRAPH

26. Continue… Increasing viscosity with an increase in shear rate characterizes the dilatant fluid. Although rarer than pseudo plasticity, dilatancy is frequently observed in fluids containing high levels of deflocculated solids, such as clay slurries, candy compounds and sand/water mixtures. Dilatancy is also referred to as shear-thickening flow behavior.

27. PSEUDOPLASTIC Pseudoplastic is the opposite of dilatant i.e. the more shear applied, the less viscous it becomes . Example Ketchup Polymer solutions greases starch suspensions biological fluids, detergent slurries etc.

28. GRAPH

29. Continue… This type of fluid will display a decreasing viscosity with an increasing shear rate. Probably the most common of the non-Newtonian fluids, pseudo-plastics include paints, emulsions, and dispersions of many types. This type of flow behavior is sometimes called "shear-thinning.

30. PSEUDOPLASTIC VS DILATANT

31. THIXOTROPIC FLUID RHEOPECTIC FLUID TIME DEPENDENT

32. THIXOTROPIC FLUID Fluids with thixotropic properties decrease in viscosity when shear is applied. EXAMPLES Inks Paints Cosmetics Asphalt Glue Drilling muds .

33. GRAPH

34. Continue… These fluids exhibit a reversible decrease in shear stress with time at a constant shear rate. Examples Some polymer solutions Some food materials and paints.

35. RHEOPECTIC Rheopectic is very similar to dilatant in that when shear is applied, viscosity increases. The difference here, is that viscosity increase is time-dependent . EXAMPLES Gypsum paste Cream Bentonite clay suspensions, certain sols and clay suspensions.

36. GRAPH

37. RHEOPECTIC VS THIXOTROPIC

38. GRAPHICALLY DIFFERENCE

39. COLLECTIVE GRAPH

40. THANKS