Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion

There are two types of viscosity one is kinematic viscosity and other one is dynamic viscosity.

Kinematic viscosity is the dynamic viscosity divided by his dense. And mercury has high denser than water. Therefore kinematic viscosity of mercury is less than water. That's why if you fall down mercury from glass it is speedy falls down than water.

In mercury, molecules are more cohesion than water molecules however water molecules have hydrogen bond while mercury have metallic bond. And metallic bond is strong than hydrogen bond. So mercury molecules resist force more than water molecules. That's why dynamic viscosity of mercury is greater than water.

Hello, guys.

Viscosity is internal fluid friction which causes to flow, and also an origin of viscosity is due to cohesive force (in liquid) & molecular momentum transfer (in gas).

So by this, cohesive force in mercury is greater than in water, it means that molecule of mercury offers more resistance to flow as compare to water, that's why absolute viscosity of mercury is greater than water.

For kinematic, its just reverse because in kinematic viscosity, density divide the absolute viscoty

If I'm wrong, please suggest me.

Shear stress developed in Mercury is more, not water. If you understand the definition of viscosity keenly. It is resistance offered between layers of liquid. Not between ground and liquid. Shear stress developed i.e resistance offered in Mercury so strong that it will not split into layers when compared water. So absolute viscosity of Mercury is more. Water's kinematic viscosity is more not dynamic viscosity.

Viscosity means Dynamic viscosity, according to which, Hg is more viscous than water, But when it comes to kinematic viscosity (viscosity/ density), Hg has less kinematic viscosity. In the asked question, it is given as viscosity, meant Dynamic viscosity for which, Hg is more viscous. Hence answer is wrong.

The kinematic viscosity is the dynamic viscosity divided by the density.

Mercury is a lot denser than water, so its kinematic viscosity is lower than the kinematic viscosity of water. But that's just because mercury is very dense. But The dynamic viscosity of mercury is greater than water.

Viscosity is due to the adhesive force.

Lesser the adhesive force lesser will be the viscosity.

As mercury has lower adhesive force than water, so water is more viscous than mercury.

Also, by experience, we know that mercury can flow easily than water. So its viscosity is lower.

Dynamic viscosity of mercury is higher than that of water but a kinematic viscosity of mercury is lower than water because of their density.

Value of dynamic and kinematic viscosity of water is 1*10^-3 and 1*10^-6 but of mercury 1. 56*10^-3 and 1. 15*10^-7 in Ns/m^2 and m^2/s.

There are two types of viscosities they need to mention.

1. Kinematic viscosity.
2. Dynamic viscosity.

Kinematic viscosity of water is greater than kinematic viscosity of mercury.

Dynamic viscosity of mercury is greater than dynamic viscosity of water.

Viscosity of mercury is lesser than that of water because shear stress developed in water is more than Mercury this is taken from the relation viscosity is directly proportional to the shear stress and inversely proportional to the velocity gradient.

The viscosity of mercury is lesser than the water because shear stress developed in water is more than mercury, this is taken from the relation viscosity is directly proportional to the shear stress and inversely proportional to velocity gradient.