What is Non-newtonian fluid: Definition and 12 Discussions

A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid. Many salt solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as custard, honey, toothpaste, starch suspensions, corn starch, paint, blood, melted butter, and shampoo.
Most commonly, the viscosity (the gradual deformation by shear or tensile stresses) of non-Newtonian fluids is dependent on shear rate or shear rate history. Some non-Newtonian fluids with shear-independent viscosity, however, still exhibit normal stress-differences or other non-Newtonian behavior. In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, passing through the origin, the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress and the shear rate is different. The fluid can even exhibit time-dependent viscosity. Therefore, a constant coefficient of viscosity cannot be defined.
Although the concept of viscosity is commonly used in fluid mechanics to characterize the shear properties of a fluid, it can be inadequate to describe non-Newtonian fluids. They are best studied through several other rheological properties that relate stress and strain rate tensors under many different flow conditions—such as oscillatory shear or extensional flow—which are measured using different devices or rheometers. The properties are better studied using tensor-valued constitutive equations, which are common in the field of continuum mechanics.

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  1. S

    How can we prevent clogging in a drum dryer used for drying liquid digestate?

    I am working on a project to dry liquid digestates (residue from the fermentation process of biogas plants). The liquid digestate has a dry matter (DM) content of about 3%. The digestate is primarily made up of animal manure and maize silage. It is a non-Newtonian fluid having a viscosity of 4...
  2. A

    Is Air a Non-Newtonian Fluid at High Speeds?

    Hi guys, I came upon a definition of Non Newtonian fluid that is any fluid which doesn't deform linearly with increasing stress. But then if you think about fluids, pretty much every fluid acts like this, depending on whether you're actually capable of generating enough force to see it happen...
  3. T

    Working Out Shaft Torque in a Stirred Tank with a Cylindrical Shape

    Here is some background to the problem (in a stirred tank): "With yield stress non-Newtonian (viscoplastic) fluids, it is possible to generate an agitated volume around the impeller, defined as a cavern, surrounded by a stagnant region where the shear stress is insufficient to overcome the...
  4. thebosonbreaker

    I Non-Newtonian fluids at the quantum level

    I am intrigued by the diversity of Non-Newtonian fluids and need to ask a question. Can anyone provide me with a breakdown of what goes on at the quantum level as the Non-Newtonian fluid bounces up and down on top of the speaker in the video I have embedded. What I would like to know is...
  5. C

    Stress tensor for non-Newtonian fluid

    How does one setup the stress tensor for a non-Newtonian fluid? I know that for any fluid the normals should be the pressure and for a power law fluid the shear stress in the direction of flow is related by K(du/dy)^n. Does this mean that all other components are 0 for a symmetric pipe or...
  6. duhuhu

    Non-Newtonian Fluid as MMOD and Radiation Protection?

    So everyone has made non-Newtonian fluid at some point in their lives (when you mix corn starch and water and get that awesome liquid/solid) well in one of my classes last semester we were asked to think of ways to aid in shielding from radiation and MMOD's (Micro Meteoroids and Orbital Debris)...
  7. S

    Mechanism of Oobleck - Non-Newtonian Fluid

    Hi, What is the molecular-level mechanism of shear-thickening of oobleck (cornstarch-water paste)?
  8. A

    Help with getting a non-Newtonian fluid to react

    This is my first posting on this forum. I apologize if this is the wrong place. My friend is trying the experiment where corn starch is placed on a speaker at low frequencies and forms strange shapes. There are videos on youtube but I cannot add links yet. It's for our physics class as a final...
  9. C

    What are typical values for 'K' in the Ostwald model for non-Newtonian fluids?

    I need to make a simple model of a strain-hardening fluid flow, basically to find shear force on a wall. I'm looking at the Ostwald model http://www.answers.com/topic/power-law-fluid but I can't find any values for "K" for any material. I don't really care too much what material I'm looking...
  10. E

    Can Non-Newtonian Fluids Predict Pole (De)acceleration in Oobleck?

    Here is the problem. I drop a pole (say length L, mass M, radius R) on a non-Newtonian fluid (corn starch and water) with impact velocity v. The density and viscosity of the oobleck is known, and I know the dimensions of the oobleck container (a square box of length S filled up to height H...
  11. A

    Newtonian or Non-Newtonian fluid?

    I would like to calculate pressure drop rate across a valve,... Material is a "non-soluble" polymer melt dispersed in water...When the solution is released at high temperature from a valve I would like to calculate pressure drop rate... Question is should we be using non-Newtonian...
  12. C

    What Happens When Non-Newtonian Fluid Is Placed on a Speaker?

    Hi guys, to the point, I watched this video in youtube about how the guy put non-Newtonian fluid on a speaker and when they turn the speaker on, the fluid just went wild. as I'm still a high school student, i don't really understand this phenomenon, and I'm interested to know what will happen...