ANS:A - Fluid flow at the inlet to a nozzle

The example that exemplifies a three-dimensional fluid flow is: Viscous fluid flow between converging plates

Explanation:

1. Fluid flow at the inlet to a nozzle:
   • This typically represents a two-dimensional flow situation where the flow can be considered to occur primarily in two dimensions (axial and radial in the case of a nozzle).
2. Fluid flow between parallel plates:
   • This example usually involves a two-dimensional flow scenario where the fluid flows predominantly in the gap between the plates with uniform conditions along the direction perpendicular to the plates.
3. Viscous fluid flow between converging plates:
   • In this case, the plates are converging, which introduces a variation in the flow across the span of the plates. The flow field in this situation can vary significantly in all three dimensions (x, y, and z directions), especially if the plates are not infinitely long. Therefore, this scenario exemplifies three-dimensional fluid flow where the flow varies in all spatial directions.
4. None of these:
   • This option would be correct if none of the given examples exemplified three-dimensional fluid flow. However, viscous fluid flow between converging plates does demonstrate three-dimensional characteristics.

Conclusion: