Question Details

The velocity field in a fluid is given to be  V = ( 4 x y ) i ^ + 2 ( x 2 y 2 ) j ^ Which of the following statement(s) is/are correct?

Options

A

The velocity field is one-dimensional.

B

The flow is incompressible.

C

The flow is irrotational.

D

The acceleration experienced by a fluid particle is zero at (𝑥 = 0, 𝑦 = 0).

Correct Answer :

The acceleration experienced by a fluid particle is zero at (𝑥 = 0, 𝑦 = 0).

Solution :

The correct statement is: The acceleration experienced by a fluid particle is zero at (𝑥 = 0, 𝑦 = 0).

Let us analyze the velocity field and calculate the acceleration of a fluid particle step-by-step to understand why this statement is correct.

The given velocity field is:
V = u i^ + v j^ = ( 4 x y ) i^ + 2 ( x2 y2 ) j^
From this expression, the horizontal velocity component (u) and the vertical velocity component (v) are:
u = 4 x y
v = 2 ( x2 y2 )

For a steady two-dimensional flow, the acceleration components in the x and y directions (ax and ay) are given by the convective acceleration formulas:
ax = u ux + v uy
ay = u vx + v vy

First, let us compute the required partial derivatives:
ux = x ( 4 x y ) = 4 y
uy = y ( 4 x y ) = 4 x
vx = x [ 2 ( x2 y2 ) ] = 4 x
vy = y [ 2 ( x2 y2 ) ] = 4 y

Now, substitute these derivatives into the acceleration equations:
ax = ( 4 x y ) ( 4 y ) + 2 ( x2 y2 ) ( 4 x ) = 16 x y2 + 8 x3 8 x y2 = 8 x3 + 8 x y2
ay = ( 4 x y ) ( 4 x ) + 2 ( x2 y2 ) ( 4 y ) = 16 x2 y 8 x2 y + 8 y3 = 8 x2 y + 8 y3

Evaluating the acceleration components at the origin (x=0,y=0):
ax |(0,0) = 8 (0)3 + 8 ( 0 ) (0)2 = 0
ay |(0,0) = 8 (0)2 ( 0 ) + 8 (0)3 = 0
Since both the x and y components of the acceleration vector are zero at the origin, the total acceleration experienced by a fluid particle at (x=0,y=0) is indeed zero.

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