Computational studies on design optimization for Saccardo nozzle in tunnel ventilation

Joo Guan Hang, Hui An, Peng Cheng Wang, Simon Ching Man Yu, Samuel Chan, Melvyn Thong, Lean Wan Lim, Mun Kit Cheong, Gerald Louis

Research output: Journal article publicationJournal articleAcademic researchpeer-review


Longitudinal ventilation system with Saccardo nozzles has been widely used to ventilate long road tunnels to maintain acceptable air quality and thermal comfort. The design of Saccardo nozzle impacts the ventilation power consumption, nozzle efficiency and momentum exchange in the tunnel, which inherently affects the tunnel air temperature. This paper presents a detailed study of the performance of an optimised Saccardo Nozzle design using Computational Fluid Dynamics (CFD) simulation. The CFD model was combined with a mono-dimensional temperature prediction model to evaluate the carry-over effects in the tunnel. The impact of various tunnel design parameters was parametrically evaluated to identify the key important geometric parameters that affect the Saccardo nozzle performance. The design of the nozzle was finally optimized under constant power consumption conditions and compared against that in an existing baseline road tunnel. The optimized nozzle design shows a significant reduction in the overall maximum tunnel air temperature. The nozzle efficiency shows a 9% improvement. In addition, an alternative nozzle design was also proposed by introducing air bleeds underneath the Saccardo nozzle. The air bleeds design could further reduce the tunnel air temperature by 6% with a 5% improvement in the nozzle efficiency. The air bleeds design is considered to be a feasible solution to be adopted into the existing tunnel with minimal modification work required.

Original languageEnglish
Article number104185
JournalTunnelling and Underground Space Technology
Publication statusPublished - Dec 2021


  • CFD
  • Nozzle efficiency
  • Optimization study
  • Saccardo nozzle
  • Tunnel ventilation

ASJC Scopus subject areas

  • Building and Construction
  • Geotechnical Engineering and Engineering Geology

Cite this