Effect of manhole molds and inlet alignment on the hydraulics of circular manhole at changing surcharge

ABSTRACT

Head loss coefficient of a manhole is dependent on various hydraulic and structural characteristics. This study analyses the effect on manhole head loss coefficients using numerical VOF model due to three factors: manhole structural mold shapes, small changes in inlet orientations and changes in the manhole to inlet pipe ratios. Head loss coefficients showed a strong dependence on the available surcharge. Presence of sump created the maximum head loss while benching provided the best efficiency. Within small deviation of inlet pipe orientations, two different hydraulic regimes were observed indicating effects on both head loss coefficients and threshold surcharge heights. Change of manhole to inlet pipe diameter ratios (Φ_m/Φ_p) showed three head loss characteristics. Head loss in small manholes (Φ_m/Φ_p<3) did not change with surcharge. Medium manholes (3 < Φ_m/Φ_p< 4.0) showed high head losses up to a specific surcharge. Big manholes (Φ_m/Φ_p>4.5) showed a high head loss at all the surcharges.

KEYWORDS:

• CFD
• head loss coefficient
• manholes
• OpenFOAM®
• urban drainage
• VOF

Acknowledgements

The work presented is part of the QUICS (Quantifying Uncertainty in Integrated Catchment Studies) project which received funding from the European Union’s Seventh Framework Programme (Grant agreement No. 607000). Cluster computing system used in this study is supported by the Laboratory for Advanced Computing of the University of Coimbra. Authors acknowledge the support of FCT (Portuguese Foundation for Science and Technology) through the Project UID/MAR/04292/2019, financed by MEC (Portuguese Ministry of Education and Science) and FSE (European Social Fund), under the program POCH (Human Capital Operational Programme).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the FP7 People: Marie-Curie Actions [607000];Fundação para a Ciência e a Tecnologia [UID/MAR/04292/2019].