3D numerical simulation of the separation zone at the channel-pipe junction

Area of Science:

• Fluid mechanics
• Environmental engineering
• Hydraulic engineering

Background:

• Confluence zones significantly impact channel flow, pollutant transport, and structural integrity.
• Understanding separation zone dynamics is critical for hydraulic structure design and environmental management.

Purpose of the Study:

• To investigate the geometric characteristics of the separation zone at a 90° channel-pipe junction.
• To analyze the tailwater effect in relation to the separation zone.
• To differentiate these characteristics from those observed in channel or river junctions.

Main Methods:

• Experimental investigation of flow dynamics.
• Numerical simulations to model the separation zone and tailwater effects.
• Analysis of geometric parameters and flow patterns.

Main Results:

• The separation zone is detached from the sidewall, exhibiting an elliptical shape with internal depression.
• Helical flow cells with opposing directions near the sidewall influence the separation zone's geometry.
• Separation zone volume correlates with discharge ratio and water-surface height, primarily driven by the momentum ratio.
• Tailwater effect is influenced by discharge ratio and water-surface height, showing a positive correlation with separation zone volume.

Conclusions:

• The 90° channel-pipe junction exhibits distinct separation zone features compared to traditional junctions.
• Momentum ratio is identified as the key factor governing separation zone volume.
• A significant relationship exists between the tailwater effect and the separation zone volume, impacting hydraulic processes.