Ducted Fan: Noise and Thrust CFD Study, ANSYS Fluent

Description

The present project simulates a ducted fan employed in a room. The study aims to investigate the acoustic condition & performance. There is a flow inlet from the door with 0.5 m/s velocities. Also, an outlet on the wall where the ducted fan is implemented. The fan is rotating with 1000 rpm angular velocity.

The 3D model is designed in Ansys Design Modeler software. A 2*3m rectangular room with 2.5-meter height and a 30cm in diameter fan. Moreover, the mesh grid is carried out in Ansys Meshing software. In the first step, a tetrahedron mesh grid is generated; then converted to Polyhedra elements to reduce the number of elements and computational cost. In total, 699432 elements are generated.

Methodology: Ducted Fan Noise & Thrust

The gravitational acceleration is considered in the negative direction of the Y direction by 9.81 m/s^2. The k-epsilon realizable model is used in order to capture the foreseeable wakes and turbulence. In addition, a separated zone is defined for the fan to apply Frame motion (MRF) and Ffowsc Williams & Hawkings (FW-H) Acoustic model determines the acoustic effects.

Conclusion

Two sound receivers are located in the room to investigate the noise effect of the fan. One is in front of the fan(receiver 1) and the other one at the entrance, near the door (reciever2). As seen in the contours, air enters the domain with 0.5 m/s, forms wake around the fan zone, and then leaves the domain. Furthermore, the duct acts like a silencer and limits the sound distribution.

Hence, although the sound pressure level is high in receiver 1, it is an acceptable range near receiver 2 that won`t cause any problem for the residents. The A-weighted pressure level backs up the claim and shows 80 dB at its maximum point, less than 120dB. After all, the thrust force is reported as 54.113455N.