Question

In the context of fluid flow, which of the following statement(s) is/are correct?

• A. Streamline is a line, tangent to which at any point gives the direction of the velocity vector
• B. Streakline is the actual path traversed by a given fluid particle in an unsteady flow
• C. Streakline and streamline are same for a steady flow
• D. Pathline and streamline are same for a steady flow

Answer 1

The Correct Option is A, C, D

Step 1: Understand the terms. 
Streamline: A curve that is tangent to the velocity vector at every point, representing the instantaneous direction of fluid flow. 
Streakline: The locus of all particles that have passed through a given point in the flow field. 
Pathline: The trajectory traced by an individual fluid particle over time. 
Steady flow: A flow where the fluid properties (velocity, pressure, etc.) do not change with time at any point in the flow field. 

Step 2: Analyze each option. 
(1) Streamline is a line, tangent to which at any point gives the direction of the velocity vector: Correct. This is the definition of a streamline. 
(2) Streakline is the actual path traversed by a given fluid particle in an unsteady flow: Incorrect. A streakline is the locus of particles that have passed through a specific point, not the actual path of a single particle. 
(3) Streakline and streamline are same for a steady flow: Correct. In steady flow, streaklines and streamlines coincide as the flow properties do not change with time. 
(4) Pathline and streamline are same for a steady flow: Correct. In steady flow, pathlines and streamlines coincide as the flow properties do not change with time.