[BlackEagle]

Hello All,

I will try to solve open water marine propeller hydro-acoustic performance in Star CCM. But I have lots of questions about the FW-H module.

The Star CCM user guide explains the aeroacoustic cylinder solution but there is no information about the hydroacoustic. Because the air and water are so different. The Star CCM+ user guide recommends that IASPL IF97 should be used in hydroacoustic simulation and speed of sound must be 1500 m/s.

The FW-H module composes of the receivers and surfaces. But the pressure probes are used in order to calculate to sound pressure during the analyses. In addition, the receiver also are put the same location like pressure probes. To calculate the sound pressure level, I can just select the pressure points which are added in derived part. I can not make FFT for receivers. There is no option for that. How can I make this?

The other question, I choose propeller blades as sound source. But I m not sure the FW-H module use this one. I choose the impermeable surface for propeller blades. I will wonder that how the FW-H module calculate the noise for defined acoustic surfaces.?

Another question is about the noise decrasing with the distance. For example, I put the pressure probes behind the propeller at x=4D and x=8D. After the analyses, I make FFT to obtain the SPL-f spectrum. But it is interesting that, the sound pressure level is not decreasing with the distance in far field. they are almost same. But according to theory, the noise must descrase as 6 dB if the distance doubled.

It is so annoying. Does anyone want to help me about the subject? (

[kiranv]

Dear Kashan,

Thank you for posting query. As you must be aware of that Aero/Hydro Acoustics demands high resolution of mesh to achieve the meaningful results and degree of accuracy. In fact no CFD can address Hydro Acoustics and can not claim single set of tool can address your real time problems. FW-H is said to be better option for especially Hydro acoustics and is not just recommended to capture dipole source of noise that is radiated from Propeller but also to measure the far field propagated noise at the microphone locations.

You can refer the paper "Verification of FW-H Method for Estimations of Pressure Fluctuation induced by Cavitating Marine Propeller".

Regards
Kiran Voonna