Fluid mechanics viva questions answers 

Part-3

31. What happens when a ship enters into a river from the sea?

It will sink little because the density of river water is less than seawater.

32. What is the lagrangian method?

It is an exact analysis of single fluid particle motion. Whose motion is traced throughout the flow and its various property such as velocity, acceleration, etc. are observed at different points.

33. What is the eulerian method?

In this method, any point in the space occupied by the fluid is selected and observations are made of whatever changes in velocity, density, and pressure which take place at that point. We take a finite volume, called control volume, through which fluid flows in and out. Instead of tracking individual fluid particles, we define field variable functions of space and time within the control volume.

34. What are the types of fluid flow?

• steady flow and unsteady flow.
• uniform and non-uniform flow.  
• One, two, and three-dimensional flow.
• Rotational flow and irrotational flow. 
• Laminar flow and turbulent flow.  
• compressible flow and incompressible flow

35. What is steady and unsteady flow?

Steady flow– when the fluid properties such as velocity, density, acceleration, etc. do not change with time at any particular location in a fluid flow, then the fluid flow is known as steady flow.
Example-flow from a vessel in which constant level is maintained.
Unsteady flow-if one or more fluid properties or anyone changes with time, then the fluid flow will be called unsteady flow.
Example-liquid falling under gravity out an opening in the bottom of a vessel.

36. What are uniform and non-uniform flow?

Uniform flow– when the velocity of the fluid does not change, both in magnitude and direction, from point to point, at any given instant of time the flow is said to be uniform flow.
Example-fluid flow under pressure through long pipelines of constant diameter.
Non-uniform flow– If the velocity of fluid changes from point to point at any instant, the flow is said to be non-uniform.

37. What is streamline?

A streamline is an imaginary curve drawn through a flowing fluid in such a way that the tangent to it at any point gives the direction of the instantaneous velocity of flow at that point.

38. What is a pathline?

A pathline represents the trace or trajectory of a fluid particle over a period of time.it shows the directions of the velocity of the same fluid particle at successive instants of time.

39. What is streakline?

A streak line is the instantaneous picture of the positions of all the fluid particles that have passed through a fixed point in the flow field.