A Is fluid mechanics (aerodynamics) still being discovered?

[Jurgen M]

Is fluid mechanics,particularly aerodynamics still being discoverd (like math for example) or everything has already done long time ago?

 

[Baluncore]

Aerodynamics is well understood.
Finding ways to numerically model fluid flow more accurately or more quickly continues.

 

[vanhees71]

Is the notorious turbulence problem considered solved now?

 

[InkTide]

Is the notorious turbulence problem considered solved now?

Most of the 'solutions' to it that I've seen invoke chaos theory and talk about pendulums for some reason.

Division of a fluid into dynamic zones of differing behaviors is very difficult mathematically if you want the same set of equations to work everywhere at all times. There is no guarantee such a model even exists that isn't... well, observation of experiment.

IMO the 'turbulence problem' is more a side effect of a belief that all parts of reality can eventually be represented by predictive mathematical formulations - perhaps that is indeed true, but that seems to often be paired with a belief that the mathematical formulation is always going to be easier to deal with than experimental setups. Sometimes the most efficient way to analyze a thing might just be recreating the thing and observing it.

 

[wrobel]

https://www.claymath.org/millennium-problems

 

[Jurgen M]

Navier-stokes equation are not solved, they are basics for flow simulation CFD.

 

[Chestermiller]

Most of the 'solutions' to it that I've seen invoke chaos theory and talk about pendulums for some reason.

Division of a fluid into dynamic zones of differing behaviors is very difficult mathematically if you want the same set of equations to work everywhere at all times. There is no guarantee such a model even exists that isn't... well, observation of experiment.

IMO the 'turbulence problem' is more a side effect of a belief that all parts of reality can eventually be represented by predictive mathematical formulations - perhaps that is indeed true, but that seems to often be paired with a belief that the mathematical formulation is always going to be easier to deal with than experimental setups. Sometimes the most efficient way to analyze a thing might just be recreating the thing and observing it.

I very strongly disagree with this assessment. The very purpose of mathematically modeling systems is to save the cost (sometimes very expensive) of constructing numerous configurations of equipment to manufacture and improve products or provide other functionality. Although crude CFD models are now available to analyze systems involving turbulence, they are still often somewhat inaccurate, and substantial improvement of. these models would be very desirable. Anyone who has had to design or analyze a real world system involving turbulent flow, where real money is at stake in the outcome, is well aware of the potential value of more accurate CFD models that include turbulence.

 

[InkTide]

I very strongly disagree with this assessment. The very purpose of mathematically modeling systems is to save the cost (sometimes very expensive) of constructing numerous configurations of equipment to manufacture and improve products or provide other functionality. Although crude CFD models are now available to analyze systems involving turbulence, they are still often somewhat inaccurate, and substantial improvement of. these models would be very desirable. Anyone who has had to design or analyze a real world system involving turbulent flow, where real money is at stake in the outcome, is well aware of the potential value of more accurate CFD models that include turbulence.

I don't mean to say that such a model would be useless - quite to the contrary, for all the reasons you stated.

All I'm saying is that there is no guarantee that such a model must exist. That said, I also don't mean to imply that trying to create one is a waste, even if one doesn't exist.

My main worry is that a focus on mathematical modeling might ironically distract from the eventual creation of such a model by de-emphasizing the necessity of observation and experiment. At the end of the day, that's what the models have to match.

 

[anorlunda]

a belief that the mathematical formulation is always going to be easier to deal with than experimental setups. Sometimes the most efficient way to analyze a thing might just be recreating the thing and observing it.

That is excellent. We frequently get posters who think they can calculate in cases where they should experiment. If you could reduce it to a memorable quote short enough to print on a Tee-shirt, we could quote it again and again.

 

[InkTide]

That is excellent. We frequently get posters who think they can calculate in cases where they should experiment. If you could reduce it to a memorable quote short enough to print on a Tee-shirt, we could quote it again and again.

Maybe something like, "If the math must model reality, a real model might be easier"? I think that still contains the gist of the idea.

I'm sure someone else can come up with a better formulation (and I'm sure there's some concise theorem in philosophy of science somewhere that expresses the idea).

 

[Chestermiller]

I don't mean to say that such a model would be useless - quite to the contrary, for all the reasons you stated.

All I'm saying is that there is no guarantee that such a model must exist. That said, I also don't mean to imply that trying to create one is a waste, even if one doesn't exist.

My main worry is that a focus on mathematical modeling might ironically distract from the eventual creation of such a model by de-emphasizing the necessity of observation and experiment. At the end of the day, that's what the models have to match.

My experience is that it is not an either-or prospect. Experience has shown that, for best results, modeling and experimentation go hand-in-hand in an overall development, and are complementary, rather than competing. It is up to the judgment of the researcher to determine the extent to which each is used in a particular development.

 

[boneh3ad]

Is fluid mechanics,particularly aerodynamics still being discoverd (like math for example) or everything has already done long time ago?

There are many, many areas of active research in fluid mechanics/aerodynamics. More specific examples would need more specific questions, however.

Here is a link to the proceedings with list of talks and their abstracts at a recent meeting of the American Physical Society (APS) Division of Fluid Dynamics (DFD). That should give you a good idea of the sorts of things being studied. You can find a similar list of talks at the recent meeting of the American Institute of Aeronautics and Astronautics (AIAA) here (you'll probably want to use the filters to narrow down categories since there are many).

Aerodynamics is well understood.
Finding ways to numerically model fluid flow more accurately or more quickly continues.

This is categorically false. There are many open problems in fluid mechanics. One avenue to solving them is through new numerical models and algorithms, but those models and algorithms themselves are far from the only active areas of research.

Is the notorious turbulence problem considered solved now?

No.

 

[sysprog]

That is excellent. We frequently get posters who think they can calculate in cases where they should experiment. If you could reduce it to a memorable quote short enough to print on a Tee-shirt, we could quote it again and again.

Y'mean something like this?

(maybe without accidentally chopping off the $\lambda$ on the lhs)

 

[boneh3ad]

That is excellent. We frequently get posters who think they can calculate in cases where they should experiment. If you could reduce it to a memorable quote short enough to print on a Tee-shirt, we could quote it again and again.

I think back to my high school physics class where we were basically given a bunch of formulae that covered various situations with very little context for why they applied. Obviously this was rectified later in my education when taking calculus-based physics and learning first principles, but not everyone has that or escapes the original mindset. I think that's why we get a lot of posters who think they can find a simple formula for anything.

 

[anorlunda]

I think that's why we get a lot of posters who think they can find a simple formula for anything.

I agree, but there's another factor. Even if you have a formula, you're still stuck if you don't know the values of the coefficients. Finding the coefficient with a bit of experimentation is the best advice sometimes.

In real life science, we call it model validation & verification using experimental data.

 

[vanhees71]

Sure, there are many quantities one can only get from experiment, among them on what's considered the most fundamental level today, all the free parameters of the standard model of elementary particle physics, as well as Newton's gravitational constant.

 

[boneh3ad]

I agree, but there's another factor. Even if you have a formula, you're still stuck if you don't know the values of the coefficients. Finding the coefficient with a bit of experimentation is the best advice sometimes.

In real life science, we call it model validation & verification using experimental data.

I think that's wrapped up in the same issue as before, though. My favorite example is when we get someone asking about calculating drag on an object. They say things like "I found the drag equation, $D = 0.5 C_D A \rho v^2$, but how do I calculate the drag coefficient?" That's a good example of an equation where students and other curious minds are deceived by its simplicity without realizing the amount of complicated physics baked into $C_D$. Like you said, that isn't something that can generally be calculated, but must be measured in an experiment.

 

[gmax137]

If you could reduce it to a memorable quote

How's this?

If it disagrees with experiment it's wrong.