How do elbows, bends, and internal obstacles affect turbulence and run-up distance?

Elbows, bends, and internal obstacles in piping systems are crucial in influencing fluid dynamics within those systems. When fluid flows through a pipe and encounters any of these features, the flow direction changes, which leads to increased turbulence. This turbulence is caused by the disruption of the streamline flow, creating chaotic and swirling eddies as the fluid navigates around the obstacles.

Moreover, turbulence can lead to an increase in mixing and energy dissipation within the fluid, which affects how the material behaves in terms of pressure and velocity. The increased turbulence can also have implications for the run-up distance—the distance that a gas or vapor may travel before the combustion or explosion occurs. In confined spaces, the presence of elbows and bends may reduce the effective run-up distance by causing changes in pressure and flow velocity, contributing to premature ignition or explosion scenarios.

Thus, the presence of elbows, bends, and internal obstacles tends to enhance turbulence while potentially reducing the distance that combustible gases can travel effectively before igniting, confirming why the correct answer is that they increase turbulence and reduce run-up distance. This dynamic plays a key role in understanding explosion hazards in process safety management, particularly in designing piping systems to mitigate risks.