Average coordinate of a boundary face
Posted 2023年6月6日 GMT-4 08:30 General, Geometry Version 6.0 9 Replies
Please login with a confirmed email address before reporting spam
Dear all,
I am looking for a method to compute the average coordinate (centroid) of a complete boundary face. While I found built-in functions to compute the mean or centroid of an expression on a mesh element, there doesnt seem to be a function to do that for a boundary.
Since I need to do that for 256 boundary faces non-local-couplings or integration operators are not an option since they need to be defined for each face separately.
Any help or idea you can provide is greatly appreciated.
Best regards, André.
PS: I have 16x16 individual domains with the a certain boundary condition on the top face of the domain. To implement the boundary condition with a general expression I want to use the coordinate of the domain/face to compute the array indices for each of the faces and use these in the equation for the bc. If there is a different method to do that, I also appreciate other ideas. Thanks!
Please login with a confirmed email address before reporting spam
Hello Andre,
If you are only considering using the coordinates of the centroid as a proxy for the face number, then an option would be to use "dom" to get the face number. In the attached file, I set up an array of cubes where the temperature on the top face of each cube equals that face's number.
Best,
Jeff
-------------------Jeff Hiller
Attachments:
Please login with a confirmed email address before reporting spam
Hello Jeff,
I do not use the face number but derive the array index in x and y direction. This way I can "identify" each array by a couple of integer, i. e. 2,2 for the second face in the x and y direction. Since I know the the geometric parameters of the array I can then compute the distance to a focal point taking into account the steering direction of the array and subsequently compute appropriate time delay for each face.
Hope this makes what I intend clearer. If there is another way to achieve what I want I am open to suggestions.
Thanks in advance, André.
Please login with a confirmed email address before reporting spam
Wouldn't you prefer to compute the distance to the focal point by using the actual x and y coordinates of individual points on the faces, rather than via the coordinates of the centroids of those faces?
Jeff
-------------------Jeff Hiller
Please login with a confirmed email address before reporting spam
Hello Jeff,
you are absolutely correct, why not use the coordinates directly, my mistake. Probably a case of not seeing the forrest because of all the trees.
Regarding your point of using the points on the faces directly. The faces are oscillating membranes of sufficiently small diameter. Therefore I intend to model them as point sources as an approximation.
However, the problem remains the same since I still need the face centroid and not the mesh element centroid.
Best regards, André
Please login with a confirmed email address before reporting spam
Hello Jeff,
just checked the manual regarding the built-in dom variable. It apparently returns the boundary face number as you said. Would something like centroid(dom(x)) return the x coordinate of the boundary?
I am currently on my phone and cannot test it.
Best regards, André
Please login with a confirmed email address before reporting spam
My question is whether you wouldn't be better off NOT making the approximation of replacing the actual coordinates of the points of each face with the coordinates of the centroid of that face.
Jeff
-------------------Jeff Hiller
Please login with a confirmed email address before reporting spam
Hello Jeff,
first off all I want to thank you for your comments.
Regarding your last comment, it is certainly easier to implement.
Maybe more details are required to understand what I am doing. I have a phased array of 16x16 ultrasonic transducers at 40kHz. I model the transducer using a normal acceleration boundary condition with a and pressure acoustics (implemented using the PDE interface) in a frequency domain study. The phase of each transducer is computed from a time delay that is derived from the distance difference from a reference point on the array (RR) and the respective transducer point (RT) to the focal point: deltaT = (RT-RR)/c0 where c0 is the speed of sound. Then in the frequency domain the bc for the transducer should be pressureAmplitudeexp(- i omega deltaT), where omega is the angular frequency and i the imaginary unit.
Since each transducer has just one delay, IMO the entire boundary must have the same delay in each point on it. Using the x-coordinate of each mesh point on the boundary would compute different time delays for each point and hence different phases for them, which IMO is too far from the actual behavior of the array.
Hope I could make the problem I am facing and the reason why I want to follow this approach clearer.
Best regards and thank you again for your help, André
Please login with a confirmed email address before reporting spam
Thanks, André, now I think I get the gist of it.
Is your array a simple one (plane, with the shifts in the x and y directions constant)? If so, would you be able to use the mod, floor and ceil operators to determine from the coordinates of each point on a face the 2 indices for the face and from there the coordinates of the centroid of that face?
Jeff
-------------------Jeff Hiller
Please login with a confirmed email address before reporting spam
Hello Jeff,
yes the array has constant pitch in both directions and consist of transducers of constant size.
And what you suggested using the mod/ceil/floor operator I just thought off on my way home after work, but think I found another solution, that might work as well.
Seting up a piecwise function in the definitions of the component with intervals of the coordinates in x and y direction and use the centroid as the function value should work. Testing it now and waiting for the results to check if this does work as intended.
Best regards and thanks again for your valuable comments and advice, André
Edit: Just thought to let anyone know, who is interested, that my approach worked fine.
Reply
Please read the discussion forum rules before posting.
Discussion Forum Rules and Guidelines
The goal of COMSOL Access is to provide a forum for you to communicate effectively with COMSOL as well as your colleagues within the multiphysics simulation community. This involves providing you with access to technical support and downloads of the latest {:comsol} software releases, as well as the ability to share your comments and work with other users of the {:comsol} software through forums such as the blog, discussion forum, and Application Exchange. In order to make this an efficient and pleasant experience for you and other members of COMSOL Access, we ask that you follow a few rules and guidelines.
When registering for COMSOL Access, you agree to provide your complete and truthful information for all fields requested on your COMSOL Access account registration page. You also agree to maintain the accuracy of all information associated with you on your COMSOL Access account. You agree to maintain your COMSOL Access account for use solely by you, not to share your username and password with anyone else, and to take appropriate precautions to restrict access to your username and password from others. Furthermore, you agree not to submit any information relating to your employer through your COMSOL Access account without your employer’s authorization. Should you use a COMSOL Access account associated with an employer, you agree to immediately discontinue using that account upon termination of that employment.
The moderators of the forums will remove any generally objectionable material as quickly as possible. You acknowledge that all posts made to these forums express the views and opinions of the author and not the administrators, moderators, or webmaster (except for posts by these people). Hence, they will not be held liable.
You agree not to post or link to any material that is abusive, obscene, vulgar, slanderous, hateful, threatening, sexually oriented, or that infringes upon or violates any third-party rights or any other material that may violate any applicable laws. You agree that you will not otherwise use your COMSOL Access account to violate or to assist anyone in violating any law. Engaging in any activity in violation of these COMSOL Access rules and guidelines may lead to you being immediately and permanently banned from COMSOL Access. The IP address of all posts is recorded to aid in enforcing these conditions. You agree that the webmaster, administrator, and moderators of the forums have the right to remove, move, or close any topic at any time as they see fit. As a user of COMSOL Access, you agree to any information you have entered into any of the forums being stored in a database.
You agree that you will not use your COMSOL Access account in violation of any applicable export control laws. You represent and warrant that you are not subject to any comprehensive sanction or embargo by the U.S. or any other country, nor are you identified on any list maintained by the U.S. government that identifies persons for which the U.S. maintains restrictions. Further, you represent and warrant that you are not subject to any restriction on the receipt of technology or products under the export control laws of the U.S. or any other country.
Basic Rules
- Flaming: Do not post any messages that harass, insult, belittle, threaten, or flame another member or guest. Debates are fine, but argue with the point, not the person.
- Trolling: Do not post with the purpose of starting a dispute. Note that a person disagreeing with your opinion is not considered trolling; keep it civil, even if you are sure that the other person is wrong. Anything seen as trolling will result in you being banned.
- Spamming: Posts without content or containing nonsense waste space and everyone's time. Spam will be removed from the forum.
- Offensive Posts, Links or Images: Do not use profanity, racial, ethnic, religious, or other slurs or any other offensive material.
- Advertising: Posting of advertisements for products or services, links to auctions, affiliate links, links to promote websites, and so forth is not allowed.
- Disclosure of Personal Information: Do not disclose any other member's email, real name, address, phone number, IP address, or other personal information. This includes posting contents of emails and private messages without the sender's consent. Do not bring personal disputes into the forums. Bans and warnings issued to other users are considered personal information.
- Misleading Titles: The subject line of the post should be as informative as possible about the content of the post. This also reduces the amount of duplicate posts.
- Thread Hijacking: Taking a thread off-topic to pursue one's own agenda is not permitted.
- Piracy: Do not upload, post, email, transmit, or otherwise make available any content that infringes upon any patent, trademark, trade secret, copyright, or other proprietary rights ("Rights") of any party. This includes COMSOL model files created by a forged or illegitimate license.
- Honesty: Users must provide truthful information in creating their COMSOL Access account.
These rules are subject to change. The moderators reserve the right to remove, edit, or move posts at their discretion. The COMSOL Access administrators will reserve the right to permanently remove a user account without notice if any of the rules are not followed. Particular services accessible with your COMSOL Access account may be subject to additional rules. You agree to comply with all rules applicable to each service you access through your COMSOL Access account.
Posting Guidelines
When posting, understand that you are trying to communicate with other people. Although many COMSOL Access members are not fluent in English, the official language of this forum is English.
Here are some important guidelines of language:
- Write in English.
- If you are familiar with LaTeX, please use this to write mathematical equations.
- Always do a quick check for spelling/grammar mistakes.
- Format your post in a legible manner. Use the Preview button often.
- Be concise and articulate as much as possible.
- Use the Enter key to create paragraphs.
- Capitalize correctly. It is difficult to read posts that are written entirely in uppercase or lowercase.
- Use correct punctuation. Avoid run-on sentences.
- Try to avoid using “text speak”, “net speak”, or slang. The purpose of language is to be understood.
- Never invent acronyms and use as few acronyms as possible. For example, write "COMSOL Multiphysics" and not "CMP".
- Review your post before publishing it. Try to catch typos.
- Please check to see if a topic has already been posted. Do not post multiple threads on the same topic.
Disclaimer
By submitting content to the forums, you hereby grant COMSOL a nonexclusive, royalty-free, perpetual, worldwide, and unrestricted license to reproduce, publicly display, publicly distribute, and prepare derivative works of the content. COMSOL hereby grants you a license to copy and/or use content from the forums solely for your own internal purposes. COMSOL provides the forum service for the benefit of our users to share content with the community. All content is provided "as is" without warranty of any kind, express or implied, including without limitation, warranties of merchantability, noninfringement, design, operation, and fitness for a particular purpose, and the entire risk as to the quality and performance of the programs is with you.
Neither COMSOL, the authors, nor the copyright owners of submitted materials warrant that the programs will be error-free, uninterrupted, virus-free, secure, and suitable for your needs, produce specific results, or that errors or failures will be corrected. Comments on supplied content should be sent to the author or copyright owner through the tools provided in the forums.
Please log in to post a reply.
Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.