请教各位大虾： 风机、流场、噪音

lbl600

请教各位大虾：
1。 计算风机流场及噪音用什么软件最好？
        是fluent、STARcd、cfx？
2。这噪音能计算吗？ 用什么软件？
3。哪位朋友有相关代码（网格划分，计算、后处理）吗？
           
   
           ^o^  感谢不尽，拜托拜托。
          邮箱：   lbl600@21cn.com

cfdzou

fluent、STARcd、cfx均称具有计算风机等叶片机流场的能力。
FLuent6.0菜单中已有叶片机模块，但原来没有专用模块也能算风机的。
cfx-tascflow有叶片机模块，STARcd不知有无此模块。
可以去它们的网站查查。

对于噪音的模拟，这些软件好象都还不能达到工程的需求。你可到cfd-online网站上查寻一下，这里给出其中一篇的链接，希望能有所帮助。
http://www.cfd-online.com/Forum/main_archive_2000.cgi?read=8730

cfdzou

补充:
尽管模拟噪音很困难,但计算气动声学发展也很快的.有些软件宣称能模拟风机噪音的.
现从cfd-online上摘录几篇,供参考.咱也通过你的提问了解了一下行情,谢谢.
***1. We have recently coupled standard CFD codes with our computational aeroacoustics module. You will find information (papers, animations) in my web page "http://www.gre.ac.uk/~k.pericleous/".
***2. PAM-FLOW from ESI Group is a finite element based explicit solver that is used extensively for aeroacoustics simulations within the automotive industry. PAM-FLOW can handle both low frequency and high frequency phenomena.
Proven automotive applications include sunroof and side window buffeting, wind rush noise due to side mirrors, A-pillar, wipers, roof-racks etc., and internal components such as intake manifolds, engine cooling fans and HVAC systems.
We provide an integrated auto-mesher that facilitates boundary layer meshing, even for ultra-complex geometries. CPU requirements are addressed by highly scalable parallel solvers.
Please visit our website (www.esi-group.com) or contact me for additional details.
***3. Our software RADIOSS-CFD is mostly used for aeroacoustic numerical simulations. RADIOSS-CFD ios a FE code that solves the NS equations (LES turbulence) fully coupled with the structure in the time domain (explicit time integrator). We provide boundaries with prescribed acoustic impedance as well. So far, the code has been used successfully for problems like exhausts, intakes, centrifugal and axial fans, side mirrors and generally speaking components. Full car simulations require *lots* of CPU ressources. You can check our website for examples and published papers: www.mcube.fr <http://www.mcube.fr>
***4. STAR-CD offers a tool which claims to be able to do such analyses. But as far as I know this tool is "only" a post processing tool which generates pressure fluctuations based on the calculated turbulence field. May be this is sufficient to solve engineering problems like the reduction of buffeting.
***5. The Fluent6.0 version would be able to do aero-acoustic modeling. This can be done through use of udf built by FLuent. Lighthill-Curle analogy is used for noise computation in which it was not necessary to have grid upto the observers point.
***6. I'll give you three references. First, the classic Sir James Lighthill paper: M.J. Lighthill (1952). "On sound generated aerodynamically: General theory." Proc. Roy. Soc. A211, 1107. (For those who hadn't heard, Sir James drowned this year while making what was for him a routine swim around an island off the coast of England--a great loss.)
Second, a paper describing what is referred to as the "MGB method" after its developers, Ramani Mani, Phil Gliebe, and Tom Balsa: T.F. Balsa (1976), "The far field of high frequency convected singularities in sheared flows, with application to jet noise prediction," J. Fluid Mech., 330, 193.
And finally a more recent paper describing the implementation of this method using CFD results to prescribe the flow field: A.Khavaran, E.A.Krejsa, & C.M.Kim (1994), "Computation of supersonic jet mixing noise of an axisymmetric convergent-divergent nozzle," J. Aircraft, 31(3), 603.
***7. Use of CFD codes for acoustic wave propagation can be carried out succesfully. However, a very fine grid and timestep are required. Typically, with a second order code like Fluent you require at least 50 gridpoints per acoustic wavelength. This is due to the excessive dispersion and dissipation characteristics of the scheme used. Upwind differencing schemes are inherently dissipative, so very efficient at damping out acoustic waves. Not good if that's what you're trying to capture.
Also, in order to obtain a reasonable spectrum you will need to run the unsteady simulation for long enough to be able to capture several periods of the oscillation.
A MAJOR problem is that of non-reflecting boundary conditions. For an internal flow this isn't really a problem, but if any of the grid extends to freespace you will require a special non-reflecting condition. Otherwise acoustic waves will reflect from the boundary. You will not see these waves when plotting pressure contours, as acoustic waves are up to 5 orders of magnitude less than hydrodynamic pressuures. To try and get around this without specifically writing a new boundary condition, you can just put a stretched block at the outer boundary that goes to a very coarse resolution at the far edge. This will then use artificial viscosity to damp out any outgoing waves. The symptoms for this not working are that the simulation works for a transient period but then blows up.

lbl600

非常感谢cfdzou的大力支持，五一玩了几天，该书归正传了，看了你的指导，我就先决定用Fluent 算流场吧。噪音计算先看看上面这些软件，但愿能得到，实在不行——哎，自己编程-——只有辛苦了，还不知正确性。——愿经常能得到你的指导和交流。
我的邮件:  lbl600@21cn.com
谢谢

liao

本人用Numeca算过一些风机流场，效果还可以，不妨一试。

lbl600

请教Numeca能算风机噪音吗？谢谢

liao

不能,好象其他的也不能

talyer

呵呵,风机的噪音的计算只能是模拟而已

frank

fluent 最新版本号称已经有了噪声和振动计算模块

redboy

噪声的计算不是根据流场结果然后再根据噪声理论进行二次计算么？

fangzi

最新版本的fluent软件已经能够模拟风机的气动噪声，是在计算流场的基础上计算的

112

下面引用由lbl600在 2002/05/10 09:24am 发表的内容：
请教Numeca能算风机噪音吗？谢谢

limiaomiao

下面引用由lbl600在 2002/04/28 01:03pm 发表的内容：
请教各位大虾：
1。 计算风机流场及噪音用什么软件最好？
        是fluent、STARcd、cfx？
2。这噪音能计算吗？ 用什么软件？
...

thereuwillbe

请教Numeca能算风机噪音吗？谢谢

通流

商业软件是算不了噪音的。主要是，噪音的来源比较复杂，如果是由于大的流动结构，还有可能算对。可实际上，很大一部分噪音与紊流，以及小的流动结构有关。就是噪音的来源没有办法靠CFD计算。在知道了声源的基础上，由于声波是小扰动，一般需要在已知的流场中计算。如果把一般的CFD计算与声音的计算混起来，那么舍入误差就有可能影响声波的计算。所以有不少商业软件有专门的噪音模型。准不准是另外一个问题。我想，算准的可能性不大。