GATE 2021 CE (CE2) – Question 62
A grit chamber is 0.5 m wide and carries peak flow 9720 m³/day at depth 0.75 m. Horizontal velocity is 0.3 m/s and target particle settling velocity 0.025 m/s (diameter 0.25 mm, SG2.70). Find minimum length in m (integer).
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 9 to 9
Explanation
A particle entering at the surface requires settling time $t=H/v_s=0.75/0.025=30$ s. It travels horizontally $L=v_ht=0.3(30)=\mathbf{9}$ m. The flow is consistent: 0.5×0.75×0.3=0.1125 m³/s=9720 m³/day.