Physical significance of kinematic viscosity
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Physical significance of kinematic viscosity of fluids:
As a first point, I want to say that the significance of 'kinematic viscosity' is much relevant to transient situations like 'thermal diffusivity' in heat transfer analysis.
We can say it as a measure of diffusivity of momentum in that fluid. That means " how fast momentum can be transferred in that fluid between various layers and particles".
[math] \nu = \frac{\mu}{\rho} [/math]
First, let us see the 'numerator', the dynamic viscosity.
You may get a doubt that how can a property that is proportional to viscosity (resistance to relative motion between layers) represents fastness of momentum transfer?
It is an obvious doubt. But, the answer is also very obvious.
The friction arises between two surfaces because of van der Waals forces of attraction (in case of very smooth surfaces, as we are dealing with fluids).
The more the attraction, the higher the resistance to
relative motion. So, they do not accept to move
relatively, instead, they want to move with each other .
That's the way of momentum transfer..!!
I think you got it.
Now let us see the 'denomenator', the 'mass density'.
The denser is the fluid, the higher is its inertia. So, the lower is its response to the momentum wave from adjacent layers. So, lower is the momentum diffusivity.
As a first point, I want to say that the significance of 'kinematic viscosity' is much relevant to transient situations like 'thermal diffusivity' in heat transfer analysis.
We can say it as a measure of diffusivity of momentum in that fluid. That means " how fast momentum can be transferred in that fluid between various layers and particles".
[math] \nu = \frac{\mu}{\rho} [/math]
First, let us see the 'numerator', the dynamic viscosity.
You may get a doubt that how can a property that is proportional to viscosity (resistance to relative motion between layers) represents fastness of momentum transfer?
It is an obvious doubt. But, the answer is also very obvious.
The friction arises between two surfaces because of van der Waals forces of attraction (in case of very smooth surfaces, as we are dealing with fluids).
The more the attraction, the higher the resistance to
relative motion. So, they do not accept to move
relatively, instead, they want to move with each other .
That's the way of momentum transfer..!!
I think you got it.
Now let us see the 'denomenator', the 'mass density'.
The denser is the fluid, the higher is its inertia. So, the lower is its response to the momentum wave from adjacent layers. So, lower is the momentum diffusivity.
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