this post was submitted on 30 Jul 2023
91 points (100.0% liked)

Ask Me Anything

2001 readers
4 users here now

Ask Me Anything (AMA) Community Rules and Guidelines

This is the lemmy.ca AmA.

Welcome to the Ask Me Anything (AMA) community! This is a space where individuals from various backgrounds come together to engage in open and informative discussions. To ensure a respectful, enjoyable, and inclusive experience for everyone involved, we have established the following rules and guidelines:

  1. Be Civil and Respectful:

    • Treat all participants with respect, regardless of their background, expertise, or opinions. Personal attacks, insults, or derogatory language will not be tolerated.
    • Engage in constructive conversations, even if you disagree with the person answering the questions. Focus on addressing their responses or providing alternative viewpoints without resorting to hostility.
    • Remember that the participants are sharing their knowledge and experiences voluntarily. Appreciate their time and effort.
  2. Practice Politeness and Courtesy:

    • Use polite and considerate language when asking questions or engaging in discussions.
    • Be patient and understanding if the person answering takes time to respond. They may receive a high volume of questions.
    • Avoid spamming or repeating the same question multiple times. Give others a chance to ask their questions as well.

-Use NSFW and trigger warning TW in brackets if you talk about sensitive subject.

  1. Respect Boundaries and Privacy:

    • Do not ask personal or invasive questions unless the participant explicitly invites such queries.
    • If a participant declines to answer a question or requests to move on from a topic, respect their boundaries without pressuring them for a response.
    • Avoid sharing personal information or disclosing sensitive details about yourself or others.
  2. Be Inclusive and Stand Against Discrimination:

    • Respect diverse perspectives and backgrounds. Discrimination, including racism, homophobia, and transphobia, will not be tolerated.
    • Foster an environment that welcomes individuals of all races, genders, sexual orientations, religions, and identities.
    • Be mindful of your language and the potential impact it may have on others. Avoid offensive slurs or derogatory terms.
  3. Avoid Spam and Irrelevant Questions:

    • Ensure your questions are relevant to the participant's expertise or field of knowledge.
    • Avoid posting low-quality or repetitive questions that add little value to the discussion.
    • Respect the purpose of the AMA and avoid using it solely for self-promotion or advertising.
  4. Engage in Meaningful Discussions:

    • Prioritize thought-provoking and insightful questions that foster engaging conversations.
    • Be open to different perspectives and use the AMA as an opportunity to learn and broaden your understanding.
    • Jokes are allowed as long as they are respectful, appropriate, and do not target or marginalize specific individuals or groups. -If you are sarcastic, we recommend to use /s to be sure there is no confusion about your intention. Fake sarcasm will be found.

Remember, these rules and guidelines are in place to ensure a positive and informative environment for all participants. Failure to comply may result in 3 strikes warnings, temporary restrictions, or permanent bans at the discretion of the moderators.

in the future, a mod check and balance system might be implemented . Subject to change : [You might appeal your ban by contacting a special appointed moderator to judge if the ban was abusive.

Special appointed mod can create jury like conversation with randomly chosen users with jury votes to decide if bans are legit or not.]

Thank you for being a part of the Ask Me Anything (AMA) community. Let's engage in enlightening discussions, share knowledge, and create an inclusive space that values respect and diversity!

Friendly communities :

founded 1 year ago
MODERATORS
 

cross-posted from: https://discuss.tchncs.de/post/479621

Hi all! I defended my Ph.D. thesis back in 2019 and I also served as the creator and moderator for the subreddit r/FluidMechanics for a long time. I think with that I have gathered enough experience and courage to answer some of your queries. Some broad topics that I can answer questions on are:

  • computation fluid mechanics
  • scientific programming and HPC
  • nonlinear shallow water equations
  • statistical description of turbulence: spectra, energy budget etc.
  • experimental methods: PIV
  • stratified turbulence
  • academia
  • navigating your career pre- and post-Ph.D.

Ask away!

you are viewing a single comment's thread
view the rest of the comments
[–] jet@hackertalks.com 11 points 1 year ago (1 children)

What is the difference between a solid and a fluid? Is it a discreet thing, or a spectrum?

I'm thinking of the pitch drop experience, and non-newtonian fluids.

[–] jadelord@discuss.tchncs.de 9 points 1 year ago (1 children)

It is a discreet thing if you consider pure materials. Phase transitions are sharp for all materials.

Non-newtonian fluids are usually a mixture of fine solid particles and liquid creating funky physics. Stress and shear rate are not linear as Newton's law dictates. They can be shear thickening like corn starch in water or shear thining like blood. Shear thinning fluids are considered pseudo plastics, which is also a property in some solids.

[–] jet@hackertalks.com 2 points 1 year ago (1 children)

That's super interesting. Where does vibrating sand to make it look like a liquid fall in the spectrum? Is sand considered a mixture of materials because sand is so large and mixing with air?

https://www.youtube.com/watch?v=My4RA5I0FKs

What does shear rate mean for a liquid? How attractive each particle is to each other? What would you consider a good resource for people to learn the basics or at least the basic vocabulary of fluid dynamics?

[–] jadelord@discuss.tchncs.de 2 points 1 year ago (1 children)

I have also wondered the same and I don't have an answer to why sand behaves as such.

In solids, for one talks of displacement a.k.a shear. Since fluids are often in a state of motion shear rate means the gradient of velocity (for example for a flow over a solid flat plate how horizontal velocity changes as you move away from a flat plate, du/dy).

Liquids have both fairly strong cohesive (liquid-liquid) and adhesive (liquid-solid) forces. This is why surface tension exists allowing drops to form. But these forces are weak compared to the shear forces a typical Newonian fluid experiences.

Kundu and Cohen is my go to book. Feynman Lectures also has some Fluid Mechanics sections.

What you should aim to understand is how the Navier-Stokes equation work and what different terms represent.

[–] jet@hackertalks.com 1 points 1 year ago

Does this mean a consistent fluid can't have a shear rate against itself? And one of your other comments you mentioned the different layers of the ocean mixing do the different layers have shear rates with respect to each other?

Mentally I can see how different salinity levels would act as different surfaces in terms of velocity interaction. I suppose flow turbulence would be a fluid internal shear force. It's really interesting way of looking at things thank you for defining it