1.8. Stacktip Downwash

Try these first

1. 1.

   What is stacktip downwash?

   Hint

   Think about how wind interacts with stacks.

2. 2.

   Why should the gas velocity be at least 1.5 times the wind speed?

   Hint

   Consider the relationship between gas and wind speeds.

3. 3.

   What happens during stacktip downwash?

   • Gases disperse into the atmosphere
   • Gases recirculate back to the surface
   • Gases are contained within the stack

   Hint

   Remember the interaction of wind and stack emissions.

4. 4.

   Stack gas velocity should be higher than wind speed to reduce downwash. True or False?

   • True
   • False

   Hint

   Consider the relationship between gas and wind speeds.

5. 5.

   A new factory is proposed to be built in an urban area. The stack’s gas velocity is expected to be 10 m/s, and the average wind speed is 5 m/s. Evaluate whether this design prevents stacktip downwash, and recommend changes if needed.

   Hint

   Evaluate the relationship between the gas velocity and wind speed.

6. 6.

   Discuss how a tall building positioned near a factory stack might impact local air quality. What strategies should be employed to mitigate potential negative effects?

   Hint

   Consider the phenomenon of building downwash.