Flow is laminar inside the boundary layer and turbulent outside

The statement that flow is laminar inside the boundary layer and turbulent outside is true. This is a characteristic of boundary layer flow, which is the thin layer of fluid that forms along a solid surface when it is exposed to a moving fluid. The boundary layer is divided into two regions: the laminar sublayer and the turbulent layer.

Explanation:

1. Boundary Layer Flow:
- When a fluid flows over a solid surface, such as air flowing over an aircraft wing or water flowing over a ship's hull, a boundary layer is formed.
- This boundary layer is a thin layer of fluid that adheres to the surface due to viscous effects.
- The boundary layer flow can be divided into two regions: the laminar sublayer and the turbulent layer.

2. Laminar Sublayer:
- The laminar sublayer is the region of flow closest to the solid surface.
- In this region, the flow is smooth and ordered, with the fluid particles moving in parallel layers.
- The fluid viscosity dominates in this region, and the flow is characterized by low velocity gradients and smooth streamlines.
- The flow in the laminar sublayer is called laminar flow.

3. Turbulent Layer:
- Outside the laminar sublayer, there is a region called the turbulent layer.
- In this region, the flow is characterized by chaotic motion, with the fluid particles moving in irregular patterns.
- The velocity gradients are higher, and the streamlines become more complex and unpredictable.
- The flow in the turbulent layer is called turbulent flow.

4. Transition from Laminar to Turbulent Flow:
- As the fluid flows over the surface, the laminar flow in the boundary layer may transition to turbulent flow.
- This transition occurs due to factors such as flow velocity, surface roughness, and pressure gradient.
- Once the flow becomes turbulent, it remains turbulent as it moves away from the surface.

5. Flow Characteristics:
- Inside the boundary layer, where the fluid is close to the surface, the flow is influenced by the smooth and ordered laminar sublayer.
- Therefore, the flow inside the boundary layer is laminar.
- Outside the boundary layer, where the flow is further away from the surface, the flow is influenced by the chaotic and irregular turbulent layer.
- Therefore, the flow outside the boundary layer is turbulent.

In conclusion, the statement that flow is laminar inside the boundary layer and turbulent outside is true. This is a characteristic of boundary layer flow, where the flow is smooth and ordered inside the laminar sublayer and chaotic and irregular outside the boundary layer.