It is, on one-dimensional flow:, physically defined as:
![](https://impeller.net/wp-content/uploads/2020/12/NewtonianFluid.png)
Of Newtonian fluid characteristics are e.g. the following:
- water
- oils
- gases
- mercury
- alcohol
- petrol
If it is not known whether a fluid is of Newtonian flow characteristics or not, it should be laboratory-tested.