Which mechanism causes increased drag on a high-speed train exceeding a critical velocity?

💡 Explanation

Increased drag is a consequence of the transition to turbulence. At high velocities, the Reynolds Number exceeds a critical value, and laminar flow transitions to turbulent flow. The increased mixing of high velocity fluid with low velocity fluid near the surface through turbulent eddies increases the drag rather than compressibility or skin friction effects because of how kinetic energy dissipates.

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