Acoustic in a Turbojet Intake Fan CFD Simulation

Acoustic CFD Simulation in a Turbojet (Intake Fan), ANSYS Fluent Training

The present problem simulates the airflow inside a turbojet and examines the acoustic wave and the sound produced inside this turbojet by ANSYS Fluent software. The software uses the acoustic model to study sound or acoustic waves.

Also, the pressure and temperature of the airflow are 85416.92 pascals and 283.9524 K, respectively, obtained according to the related equations.

Turbojet Methodology

The model includes a turbojet that has a fan in its inlet. This fan rotates at 2000 rpm and around the X-axis in the current model. Therefore, an airflow area is defined around the fan, modeled using frame motion (MRF).

This turbojet is moving in the air with a Mach number of 0.5, which indicates that the flow can be considered compressible; Because the value of the Mach number is more than 0.3. Mach number is equal to the ratio of the object’s velocity in the fluid to the velocity of sound in the same fluid.

Therefore, a density-based solver is used in this model, and the density is defined as the ideal gas for the airflow in the material section. In the present simulation, the defined airflow around the turbojet has a pressure far-field boundary condition of Mach number of 0.5.

The Broadband Noise Sources model is also used to define the acoustic model. Definitive density is equivalent to air density, i.e., 1.225 kg/m3; sound speed is equivalent to sound speed in the air, i.e., 340 m/s and reference acoustic power is equal to 1e-12.

The current model is designed in three dimensions using Design Modeler software. The model consists of two parts, which include the body of a turbojet with a fan inside it, which is located inside a computational domain for airflow in the form of a cylinder.

The area around the fan is defined as an independent computational area so that the area under rotation of the fluid due to the fan rotation can be defined using the frame motion method.

Also, the entire defined cylindrical space around the turbojet body is defined as a pressure far-field boundary condition. The meshing is done in three dimensions using the ANSYS Meshing software. The mesh type is unstructured, and the element number is 3723166.

Turbojet Conclusion

For the current simulation, we present the contour and vector of velocity, pressure, temperature, Acoustic Power Level(dB), and Surface Acoustic Power Level(dB) of the Domain to give much insight into the problem.

Briefly, as the air hits the fan and fan wall, the acoustic parameters of the solution are visible more precisely behind it. Also, the amount of Surface Acoustic Power Level(dB) can be seen on the fan surface as the noise resource.

In conclusion, the plots of Acoustic Power Level(dB) and Surface Acoustic Power Level(dB) through the centerline are achieved, which helps more to understand the exact amount of acoustic parameters behind the fan.