Mosen Ltd Developed the Ground Breaking Mojet Tunnel Ventilation System with ANSYS CFD


A Wilde Analysis client, Mosen Ltd., a leader in engineering consulting services, specialises in tunnel ventilation, fire safety engineering, risk management and tunnel safety.

Using ANSYS computational fluid dynamics (CFD) simulation, Mosen developed the reversable MoJet® tunnel ventilation system, which delivers up to 25 percent more in-tunnel thrust than other jet fans.

ANSYS CFD optimised the shape of the nozzles, to direct the airstream away from the tunnel’s soffits and walls. This reduced surface friction, minimizing the Coandặ effect (the tendency of a fluid jet to remain attached to a convex surface) as a result. Simulation also helped reduce the number of fans (significantly lowering maintenance costs), sound pressure levels and system weight.

The Story

The use of Ansys and its benefits are discussed by the owner of Mosen in the following video:


Jet fans installed in the confined space of a tunnel pose a unique design challenges: safety requirements in case of fire (including smoke control) and maintaining acceptable air quality and visibility during normal operations. The closer the fan is to the tunnel soffit (roof) and walls the better, however, such placements lead to greater aerodynamic friction on the discharge side and choking of the inlet flow, which negatively impacts jet fan performance.

Engineering Solution

Using Ansys CFD tools, Ansys CFX and Ansys Fluent, MoJet Ventilation can simulate the performance of the MoJet® both in the factory during bench thrust tests, which are crucial steps for factory certification, and when installed in the actual tunnel environment. The airflow modelling capability within Ansys CFD tools means that MoJet Ventilation is able to test the entire flow domain, including the tunnel and the rotating blades mounted on the rotor, to ensure that each MoJet® is suitable for the specific job requirements.

With simulation, MoJet Ventilation can test engineering challenges and environments that were previously difficult to achieve.


  • By using Ansys CFX and Ansys Fluent, MoJet Ventilation markedly decreases the number of MoJet® prototypes, as well as the need for full-scale testing.
  • The diverse range of tunnels worldwide makes it difficult to accurately test the MoJet®. With Ansys CFD, MoJet Ventilation has the confidence to simulate tunnel environments with excellent accuracy, while also testing how the air flow from the jet fan reacts in different scenarios.
  • With the help of the Ansys CFX and Ansys Fluent, the MoJet® delivers up to 100% more thrust than other jet fans by reducing friction and improving airflow away from the soffit and walls.
  • MoJets® are more energy efficient than competitors, reducing energy consumption by up to 50%.

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Article courtesy: Ansys Inc.



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