CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Keep Getting Negative Sound Pressure Levels on Wind Turbine Simulations

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 6, 2023, 08:03
Question Keep Getting Negative Sound Pressure Levels on Wind Turbine Simulations
  #1
New Member
 
Join Date: May 2023
Posts: 1
Rep Power: 0
Enrique Lin is on a distinguished road
Hi everyone,

This problem has been troubling me for some weeks. I hope to find some suggestions or solutions. Thanks!

I am trying to simulate the noise generated by an NREL Phase VI wind turbine with FLUENT (ANSYS ver. 19R1).

Problem description:
The sound pressure level (SPL in dB) values over a wide range of frequencies are negative (please refer to the image). I am comparing my acoustic results to this paper:
A. Tadamasa and M. Zangeneh, 2011, "Numerical prediction of wind turbine noise," Renewable Energy, 36(7), 1902-1912.
DOI: https://doi.org/10.1016/j.renene.2010.11.036

Mesh Comparison v230606-1812 for CFDOnline.jpg


My settings:
The flow fluid geometry is similar to this paper but without the turbine tower and nacelle:
J.-O. Mo and Y.-H. Lee, 2011, “Numerical simulation for prediction of aerodynamic noise characteristics on a HAWT of NREL phase VI,” Journal of Mechanical Science and Technology, 25(5), 1341-1349.
DOI: https://doi.org/10.1007/s12206-011-0234-1

Turbulence model: k-omega SST
Acoustic model: FW-H
Noise source: turbine blade surface
Acoustic receiver: located downstream of the turbine at a distance of H+D/2 on the ground. Where H is the tower height, and D is the blade diameter.
Methods: SIMPLE. Other spatial discretization settings are all set to 2nd-order.
Transient Formulation: Bounded 2nd-order
Initialization: Hybrid
Time step size: 0.000333 sec
Number of time steps: 5000
The simulation was initially calculated in steady state. After the results converged, the simulation was converted to transient state. Then continue to calculate the aerodynamic performance and acoustic results.


What actions have I tried to resolve the issue:
1. Use finer mesh: the SPL values crept toward positive, but most are still negative. Overall, no significant changes to the results.
2. Used Polyhedra-Hex mesh (in FLUENT 20R2). Can only use "Frame Motion" in steady state. And the results are even worst.
3. smaller time step size: only changes the range of the calculated frequency (as mentioned by online sources and the FLUENT user manual.)
4. larger number of time steps: only increase the acoustic resolution.
5. Google for solutions and suggestions: the following are my findings (or lack thereof)
5-1. I checked a thread titled "Why negative decibels" on this website. No replies.
5-2. A post on ANSYS Official Forum. A reply mentioned "reference pressure" of 2e-5 However, this value cannot be changed, as this IS the reference value of my case.
https://forum.ansys.com/forums/topic...stic-function/


Thank you all for your time.
Enrique Lin is offline   Reply With Quote

Reply

Tags
aeroacoustics, phase vi, wind turbine

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
viscosity udf don't use correct temperature and strain rate rezvani Fluent UDF and Scheme Programming 8 May 27, 2021 06:40
Wind tunnel Boundary Conditions in Fluent metmet FLUENT 6 October 30, 2019 13:23
Assessing spanwise pressure coefficients on a wind turbine blade Seervan STAR-CCM+ 1 July 10, 2019 21:12
why doesn't ansys allow a negative pressure when cavitation is included vysje CFX 16 December 11, 2016 18:18
Negative lift in Modeling an airfoil design for wind turbine Ram209e Main CFD Forum 3 August 8, 2012 23:39


All times are GMT -4. The time now is 18:57.