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Search took 0.00 seconds. Search: Posts Made By: huangxianbei
Forum: Main CFD Forum June 9, 2014, 02:29
Replies: 19
Views: 5,554
Posted By huangxianbei
While, u(x,t)=sum(e^ikx*u(k,t)) ,here k[/m],x[m],...

While, u(x,t)=sum(e^ikx*u(k,t)) ,here k[/m],x[m], so the u(k,t)[m/s] which is the same as u(x,t). So if energy spectrum is calculated, that's E(k)=u(k,t)*u-(k,t)[m^2/s^2]. Considering the FFT, as you...
Forum: Main CFD Forum June 8, 2014, 23:29
Replies: 19
Views: 5,554
Posted By huangxianbei
velocity is made dimensionless before FFT, so...

velocity is made dimensionless before FFT, so this is the nondimensional spectrum
Forum: Main CFD Forum April 27, 2014, 05:30
Replies: 19
Views: 5,554
Posted By huangxianbei
I have clarified the method by comparing with the...

I have clarified the method by comparing with the database of Moin and Kim with Ret=180. In fact , the velocity in the calculation should be non-dimensional divided by ut. So in the fft,...
Forum: Main CFD Forum April 26, 2014, 09:08
Replies: 19
Views: 5,554
Posted By huangxianbei
After numerous trying, I think I get the...

After numerous trying, I think I get the right(seems) spectrum.
clear all;
[x y z Ux Uy Uz]=textread('Uzyplus35.txt','%f%f%f%f%f%f');
[xx yy zz Uxm Uym...
Forum: Main CFD Forum April 24, 2014, 12:21
Replies: 19
Views: 5,554
Posted By huangxianbei
I think It's due to the data structure. My plane...

I think It's due to the data structure. My plane is 128*128 grid. While the output contains twice the points value(32768 values). I'll try to figure out a better way to output. I have just tried the...
Forum: Main CFD Forum April 24, 2014, 06:43
Replies: 19
Views: 5,554
Posted By huangxianbei
Unhappy Hi,Filippo: Sorry for my late. I tried...

Hi,Filippo:
Sorry for my late. I tried similar as you say to calculate the two-point correlation(just to simply see if it's right), however, the correlation exceeds 1:(
clear all;
[x y z Ux Uy...
Forum: Main CFD Forum April 22, 2014, 06:07
Replies: 19
Views: 5,554
Posted By huangxianbei
Thank you very much for your details. I'll try...

Thank you very much for your details. I'll try it:)
Forum: Main CFD Forum April 22, 2014, 04:12
Replies: 19
Views: 5,554
Posted By huangxianbei
so If I want to plot the spanwise spectrum(z...

so If I want to plot the spanwise spectrum(z direction in channel flow), is that means I should do average of each z position, with all the x positions(z fixed, and average the values at different...
Forum: Main CFD Forum April 21, 2014, 22:51
Replies: 19
Views: 5,554
Posted By huangxianbei
I find a big mistake in my process. The velocity...

I find a big mistake in my process. The velocity used in the energy spectrum should be the fluctuating velocity other than the temporal velocity, I think this should lead to the wrong shape
Forum: Main CFD Forum April 21, 2014, 20:35
Replies: 19
Views: 5,554
Posted By huangxianbei
Thank you for your suggestion, yes, I forgot to...

Thank you for your suggestion, yes, I forgot to use the loglog scale:(
Here, I have another question: I have read some papers about this and found that the usual method is to do the spectrum average...
Forum: Main CFD Forum April 21, 2014, 08:47
Replies: 19
Views: 5,554
Posted By huangxianbei
Usually,the spectrum is averaged in time. How...

Usually,the spectrum is averaged in time. How long should the time period be? As soon as the curve becomes smooth?
Forum: Main CFD Forum April 21, 2014, 07:23
Replies: 19
Views: 5,554
Posted By huangxianbei
Energy spectrum-wrong spectrum shape

Hi,all
Recently I got stuck with energy spectrum. I sampled the data across the spanwise direction(z) in channel flow, Uz, then I want to plot the energy spectrum, I adopt the method here...
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