Discussion Groups

## Simulation Mechanical and Multiphysics

Member
Posts: 3
Registered: ‎02-06-2012

# Simulating Radiation between Sun and a telescope mirror

172 Views, 6 Replies
02-09-2012 07:59 AM

Hi All,

For designing the thermal control of a mirror, I need to find the temperature distribution across the mirror surface.

The mirror is for telescope and it will be facing sun. Please give me some tips to how to simulate this in Autodesk Simulation.

Please use plain text.
Employee
Posts: 492
Registered: ‎03-25-2010

# Re: Simulating Radiation between Sun and a telescope mirror

02-09-2012 11:14 AM in reply to: natarajanv

Lucky you that the telescope is facing the sun; thus, you do not need to get into sines and cosines when the sun is off axis.

For the primary mirror, just apply a heat flux/source to the surface. You need to look this up, but my memory is that the flux rate is 1400 W/m^2 (above the atmosphere). But that number needs to be adjusted by the amount of heat that actually enters the mirror versus being reflected.

For secondary and tertiary mirrors, you would need to adjust the heat flux so that the total amount of heat reflected off the previoius mirror is applied to the new surface area.

Naturally, you need to account for convection, possibly radiation, and your cooling mechanism to the mirror also.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
Please use plain text.
Member
Posts: 3
Registered: ‎02-06-2012

# Re: Simulating Radiation between Sun and a telescope mirror

02-09-2012 08:35 PM in reply to: INACTIVE_AstroJohn

Dear John,

As you said I simulated the mirror, with applied heat flux/source. But I am getting some unreasonable temperatures. I am attaching archive file here. Could you please look in to it?

Thanks.

Natarajan

Please use plain text.
Employee
Posts: 492
Registered: ‎03-25-2010

# Re: Simulating Radiation between Sun and a telescope mirror

02-10-2012 06:24 AM in reply to: natarajanv

Hi Natarajan,

Something went wrong when you uploaded the file. Please try again.

Also, in case you did not do this before, what you should be doing is creating an archive file ("File > Archive > Create", or "Application button in top left corner > Archive > Create") and attaching the .ACH file.

I do not remember whether the board will accept .ACH files, so you may need to rename the file to .ZIP.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
Please use plain text.
Employee
Posts: 492
Registered: ‎03-25-2010

# Re: Simulating Radiation between Sun and a telescope mirror

02-10-2012 09:10 AM in reply to: INACTIVE_AstroJohn

UPDATE.

I just noticed that ALL attachments are now listed as 1 KB in size, and clicking on them gives a 404 error. So when I mentioned that something was wrong with the upload, it appears to be on our end.

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)
Please use plain text.
Member
Posts: 3
Registered: ‎02-06-2012

# Re: Simulating Radiation between Sun and a telescope mirror

02-11-2012 05:05 AM in reply to: INACTIVE_AstroJohn

Dear John,

The files are bit a high size (2.5MB) that I couldn't attach them in the forum. I you can share you email ID. I can send you those files through email. Thanks.

Please use plain text.
Contributor
Posts: 18
Registered: ‎01-11-2012

# Re: Simulating Radiation between Sun and a telescope mirror

02-17-2012 06:15 AM in reply to: natarajanv

Hi,

This simply looks like a situation where your inputs and outputs aren't properly defined. You need to be sure that the amount of heat entering and leaving the mirrior can equal each other as the temperature of the mirrior rises or falls. One way to do this is to add a temperature dependant convection coefficient on the outside surface of the mirrior to simulate how the air will cool the mirrior off as it gets hotter. Hope that helps

-C

Please use plain text.