Investigation of Flow in Truncated-Helicoidal-Ramp Dropshafts

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A dropshaft filled with helical vanes of fixed helix angle has been developed. These produce swirl and a resulting inward centrifuging effect for entrapped air in the dropshaft flow. Simultaneously, the vanes act as an effective, continuously distributed source of friction to dissipate energy. Dropshafts connect collection elements in municipal surface drainage systems to large underground conveyance tunnels. Air venting and energy dissipation are key requirements. The new design integrates both features effectively. The project is to explore a variation of this design for the case of very deep dropshafts in which energy dissipation must be limited. This is accomplished with shafts only partially filled with vanes, with a variable helix angle entrance section. The flow structure in such a configuration, and optimization of the configuration, will be determined experimentally. A simple analytical model of the flow will also be developed. The design holds the potential for elimination of very large deaeration chambers and separate energy dissipators, leading to much smaller and more economical installations.