Question

1. What is a fluid? How does it differ from a solid? How does a gas differ from a liquid?

2. What is the no-slip condition? What causes it?

3. What is a boundary layer? What causes a boundary layer to develop?

4. What is a Newtonian fluid? Give an example.

5. Consider two identical small glass balls dropped into two identical containers, one filled with water and the other with oil. Which ball will reach the bottom of the container first? Why?

Answer 1

1.A substance that has no fixed shape and easily changed by the external pressure it is smooth and continuous.Afluid can be a gas or liquid type.

2.A no slip condition states that the flow velocity around the body is zero and at the body surface the velocuty is zero.

3.Boundary layer is a thin layer of a viscous fluid formed at the solid surface in contact with the incoming stream with some velocity v.Shear stress develops on the solid wall and this shear stress causes drag on the plate .

4.In newtonian fluids the shear stress coming from the flow is linearly proportional to the local strain rate.example water is a newtanian fluid.

5.As we know that the oil has more density than the water.So when the two balls are dropped at the same time and same height in the containers, the ball dropped in the water will reach the bottom first as in this case there will be less bouyancy force.lesser the density of the fluid easily the ball can reach the bottom of the surface.