Oh, so if the viscosity becomes a function of the strain rate. In that case, it would violate Newtonian fluid?boneh3ad said:No. The shear stress is still linearly proportional to the strain rate through the viscosity. It's simply the case that viscosity may not be constant. That said, viscosity varies quite slowly with temperature so the Mach number has to be relatively high to start getting the kind of heating required for the effect to be all that noticeable.
Yes. We call such fluids non-Newtonian fluids.charlies1902 said:Oh, so if the viscosity becomes a function of the strain rate. In that case, it would violate Newtonian fluid?
But even if the viscosity varies with temperature, it doesn't necessarily mean it is a non-Newtonian fluid right?Chestermiller said:Yes. We call such fluids non-Newtonian fluids.
Incidentally, for liquids, the viscosity varies pretty rapidly with temperature. Typical values are a few percent per degree C.
Chet
There are all sorts of fluids where the viscosity varies with temperature and these fluids are Newtonian. Many heavy oils are heated to make them easier to pump by reducing their viscosity.charlies1902 said:But even if the viscosity varies with temperature, it doesn't necessarily mean it is a non-Newtonian fluid right?
As long as the viscosity does not vary with the strain rate, the shear stress is still a linear function of the strain rate, even if the viscosity is varying with other parameters?
Right (like SteamKing said).charlies1902 said:But even if the viscosity varies with temperature, it doesn't necessarily mean it is a non-Newtonian fluid right?
As long as the viscosity does not vary with the strain rate, the shear stress is still a linear function of the strain rate, even if the viscosity is varying with other parameters?
A Newtonian fluid is a type of fluid that follows Newton's law of viscosity, which states that the rate of deformation of the fluid is directly proportional to the shear stress applied to it. This means that the viscosity, or resistance to flow, of a Newtonian fluid remains constant regardless of the shear rate.
Compressible flow is a type of fluid flow in which the density of the fluid changes as a result of pressure and temperature variations. This type of flow is typically observed in gases, where changes in pressure and temperature can significantly affect the fluid's density.
In compressible flow, the density of the fluid is not constant, which can affect its viscosity. For Newtonian fluids, this means that the viscosity can change as a result of changes in pressure and temperature. In some cases, this can cause the fluid to become non-Newtonian, meaning it no longer follows Newton's law of viscosity.
Some common examples of Newtonian fluids in compressible flow include air, water vapor, and some types of oil and gas. These fluids are typically encountered in everyday life, such as in weather patterns, gas pipelines, and hydraulic systems.
Scientists and engineers use mathematical equations and computational models to study the behavior of Newtonian fluids in compressible flow. These models take into account factors such as pressure, temperature, and fluid properties to predict how the fluid will behave under different conditions.