Can you explain the concept of boundary layer separation and its impact on flow behavior?

Sample interview questions: Can you explain the concept of boundary layer separation and its impact on flow behavior?

Sample answer:

Boundary Layer Separation occurs when the boundary layer flow adjacent to a surface transitions from laminar (smooth and orderly) to turbulent (characterized by chaotic eddies and mixing). This separation is triggered by an adverse pressure gradient, where the local pressure increases along the flow direction.

Impact on Flow Behavior:

• Increased Drag: Turbulent boundary layers exhibit higher skin friction drag compared to laminar counterparts, leading to increased overall drag forces.
• Flow Instability: Boundary layer separation can cause flow instability, such as flow separation bubbles or stall, where the flow detaches from the surface and reattaches further downstream.
• Vorticity Generation: The separation point acts as a source of vorticity, resulting in the formation of vortices and turbulent eddies.
• Pressure Recovery: The separated flow region generates a pressure deficit, which can lead to pressure recovery downstream of reattachment.

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