40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  COMSOL elog  Not logged in ELOG logo
Entry  Tue Jul 23 18:26:04 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23.bmpTE_calc_Jul23.zipJul_23.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:37 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
    Reply  Tue Jul 23 20:53:45 2013, Deep Chatterjee, Optics, General, Comparison between Liu and Thorne Results and COMSOL results for TE noise Jul_23_bettermesh2.eps
Message ID: 65     Entry time: Tue Jul 23 20:53:37 2013     In reply to: 61
Author: Deep Chatterjee 
Type: Optics 
Category: General 
Subject: Comparison between Liu and Thorne Results and COMSOL results for TE noise 

Quote:

In this post I report of the results of TE noise simulated by COMSOL for the TE noise of Infinite test masses.

The aim was to follow the procedure by Liu and Thorne in their analytic calculations so that the same model could be used for the other
geometries.

The simulation is done in a different way than the TR simulations. It was observed that the output given by COMSOL by the use of commands
like mphinterp() or taking an export resulted in certain discrepancies between the results computed in COMSOL and that read by MATLAB.

Thus, the volume integration of the temperature gradient is performed in COMSOL itself and the results of the integration for each time
are sent to files. Matlab read these values and time averages them to get the result as in the paper (Sec. 2 of Liu and Thorne).

The errors expected are
> Fourier analysis is not done at all. This would have involved exporting data which, as mentioned before is giving errors

> The numerical errors by COMSOL are therefore not filtered off.

> The plot differs from the analytic solution for larger frequencies over 3000 Hz.

> It is to be noted from the paper by Liu and Thorne that the TE noise for the finite and infinite case are not very different. In
fact the correction factor goes as O(1). Thus, differences between finite and inifinte cases are unlikely to be prominent
in the log scale plots

 

 The codes are put as a zip file. Corrections made to the codes will be uploaded as a reply.

Jul_23.bmp


 Here is another plot with a mesh size slightly finer than the default Extra fine mesh in COMSOL.

One may notice that the value for the final frequency i.e. 10000Hz is different from the previous plot. 
It maybe that the error for the higher frequencies is a result of the FEA. However, it may also be that
the appropriate boundary conditions required for an infinite model break down at high frequencies.

Attachment 1: Jul_23_bettermesh2.eps  17 kB  | Hide | Hide all
Jul_23_bettermesh2.eps
ELOG V3.1.3-