Turbulence

[Yo-Yo]

2 hours ago, MadMonty said:

Dear @Yo-Yo,

thank you for your detailed answer.

Since my platform provides a very good output of turbulence, I have made a few tests based on your explanations.

I have given strong winds in very different (partly opposite) directions via the possible altitude levels. I set the turbulence value to 25.

Result:
Flying very low, I did not feel any turbulence over level terrain. As soon as I flew into a mountainous terrain, the turbulence increased noticeably just above the ground.
When climbing up to 10,000 feet, I didn't notice any turbulence at all as I crossed different altitudes with different winds; above a few 100 feet, it simply stops.

 

I then selected Summer Thunderstorms in Basic Weather, set Turbulence to the maximum value of 197, and again specified very strong winds (50-60 knots) in opposite directions.

Result:
Flying very low, I now noticed quite strong turbulence over level terrain, which increased again over mountainous terrain (this was then a hell of a ride on the platform).
However, when I leave the immediate vicinity of the ground, the turbulence stops again. I do notice that when crossing the different wind directions (with the same course) my Velocity Vector indicator moves from right to left and thus the aircraft (A10) is exposed to the different winds, but this is a very smooth process without any turbulence.

What we are looking for is gusts / turbulence even across all air layers. It should be possible to set a value for this - e.g. per air layer. The current value for turbulence is obviously only valid for the immediate vicinity of the ground.

Yes, the turbulence, as you feel it, becomes lower as you climb. It is well known phenomena, because the correlation length of the turbulence becomes longer with altitude.
Tests conducted shows that strong (for pilot's opinion) turbulence at 300-500 m feels like very light at ~2000 m and higher.  It is not relevant for in-cloud thunderstorm turbulence because it has very different nature and velocity distribution.

 

[MadMonty]

2 hours ago, Yo-Yo said:

Yes, the turbulence, as you feel it, becomes lower as you climb. It is well known phenomena, because the correlation length of the turbulence becomes longer with altitude.
Tests conducted shows that strong (for pilot's opinion) turbulence at 300-500 m feels like very light at ~2000 m and higher.  It is not relevant for in-cloud thunderstorm turbulence because it has very different nature and velocity distribution.

 

Of course are turbulences at higher altitudes lighter than close to the ground, but we are not talking about lighter turbulences but no turbulences at all. It simply isn´t realistic that in stormy conditions there are no gusts at all at higher altitudes. We all know them when travelling with even heavier Airbus and Boeings and I am not talking about flying through a thunderstorm cloud. So great your turbulences are close to the ground, so much I miss them at higher altitudes (happy to have them "lighter", but I just can´t see any of them).

[Bremspropeller]

On 4/27/2023 at 2:09 PM, MadMonty said:

It simply isn´t realistic that in stormy conditions there are no gusts at all at higher altitudes. We all know them when travelling with even heavier Airbus and Boeings and I am not talking about flying through a thunderstorm cloud.

That's not quite true. Turbulence is always a result of wind shear. Either vertically or horizontally. If there's no shear, there'll be no turbulence.

Near the ground, shear is mostly a result of obstacles. Higher aloft, it's more dependant on frontal activities (that includes jetstreams), but gravity-waves may fravel downrange of ground-obstacles (eg. mountain waves) for up to a thousand miles, so it's a mixed bag. Hence if you travel at high wind-speeds, but no shearing layers, you'll be fine and won't have any turbulence at all.

For thermals, you'll need a good representaion of atmspherical dynamics (such as convective potential vs capping layers, etc) and ground-air interaction. So far, our "beautiful clouds" (TM) are mostly stratus or cirrus type. The real fun, however, only starts with convection and multilayer CB clouds and associated atmospheric dynamics.

At the end, you'll have to compromise between fidelity and game-code limitations. It would be cool if DCS could depict actual weather conditions, though.

 

 

 

 

[Dragon1-1]

As far as code goes, the modeling of air is surprisingly deep, as evidenced by how wake turbulence is implemented. It's a bit of a performance hog, but it works. I think that a lot of great things could be done with it, the vector field (representing air movement) needed for complex effects is already there, it just needs a way to disturb it according to more complex rules.

[Bremspropeller]

Wakes aren't modelled deeply at all. They'll give you a nice downstream-effect, but up close, they're a good deal off. The leading airplane will actually suck you forward if you're in a sweet-spot position (you'll need less and less power to stay in place). You'll also be flying sideways if you're hugging somebody's wingtip.

This shows that the mesh is quite coarse, which makes sense as you don't want to run DCS as a CFD calculation.

 

Edited April 29, 2023 by Bremspropeller

[MadMonty]

2 hours ago, Bremspropeller said:

That's not quite true. Turbulence is always a result of wind shear. Either vertically or horizontally. If there's no shear, there'll be no turbulence.

Near the ground, shear is mostly a result of obstacles. Higher aloft, it's more dependant on frontal activities (that includes jetstreams), but gravity-waves may fravel downrange of ground-obstacles (eg. mountain waves) for up to a thousand miles, so it's a mixed bag. Hence if you travel at high wind-speeds, but no shearing layers, you'll be fine and won't have any turbulence at all.

For thermals, you'll need a good representaion of atmspherical dynamics (such as convective potential vs capping layers, etc) and ground-air interaction. So far, our "beautiful clouds" (TM) are mostly stratus or cirrus type. The real fun, however, only starts with convection and multilayer CB clouds and associated atmospheric dynamics.

At the end, you'll have to compromise between fidelity and game-code limitations. It would be cool if DCS could depict actual weather conditions, though.

 

 

 

 

We both mean the same. However - it is all too quite from 300ft above ground on.

[Dragon1-1]

1 hour ago, Bremspropeller said:

This shows that the mesh is quite coarse, which makes sense as you don't want to run DCS as a CFD calculation.

It's still more than any other sim does, and a very sensible, physics-based simulation. You don't need a very dense mesh unless you're flying very close in, which most of the time you aren't. It's good for what it's for, and the mesh density was presumably chosen so that it doesn't completely kill performance (it's a bad enough hit as it is). 

[Bremspropeller]

4 minutes ago, Dragon1-1 said:

It's still more than any other sim does, and a very sensible, physics-based simulation.

Free energy isn't sensible physics.

It's going to become interesting with buddy-pod tankers. Just plug four jets in line and tail end Charlie gets to ride in idle.

 

 

[Dragon1-1]

It's not free energy, it's a drag reduction. Flying that close does, in fact, reduce drag by quite a bit IRL. It's probably not that strong an effect (coarse simulation could exaggerate it), but it's good enough for geese and the like (why do you think they fly in those massive vics?). It'd be interesting to look at the visualization for the field, this should be an emergent effect stemming from the wake simulation. You're absolutely supposed to need less throttle while riding another ship's wake.

Aerodynamic effects from vortices can be quite counterintuitive. I never experienced the flying sideways thing, but the air is, in fact, moving sideways at several points near the wingtip. Wingtip vortices are modeled really nicely in DCS, there are some old ED pics from when they first developed them.

Edited April 29, 2023 by Dragon1-1

[Bremspropeller]

1 hour ago, Dragon1-1 said:

It's not free energy, it's a drag reduction. Flying that close does, in fact, reduce drag by quite a bit IRL. It's probably not that strong an effect (coarse simulation could exaggerate it), but it's good enough for geese and the like (why do you think they fly in those massive vics?). It'd be interesting to look at the visualization for the field, this should be an emergent effect stemming from the wake simulation. You're absolutely supposed to need less throttle while riding another ship's wake.

Aerodynamic effects from vortices can be quite counterintuitive. I never experienced the flying sideways thing, but the air is, in fact, moving sideways at several points near the wingtip. Wingtip vortices are modeled really nicely in DCS, there are some old ED pics from when they first developed them.

 

The effect in game is different to RL.

In game, the lateral offset that benefits from the drag reduction is too large. Also, the rotation-onset when flying into the wake field is rather large, instead of a gradual increase with a defined core. It's close to impossible to stay at a determined position inside the wake-field. Especially for similar sized aircraft the effect is too pronounced.

NASA flight testing of two Hornets shows a FF reduction of 13 to 20% depending on flight-condition (slower leads to greater reductions) - and this only when large throttle-movements to maintain longitudinal position aren't made:

https://ntrs.nasa.gov/api/citations/20030075684/downloads/20030075684.pdf

https://www.nasa.gov/centers/armstrong/multimedia/imagegallery/AFF/index.html

The effect IRL takes place over pronounced longitudinal distances, but requires rather precise lateral and vertical position (as one would expect).

In game, my observation has been rather the opposite: A very strong dependency on a defined longitudinal distance and a rather large influenced lateral field. My observation has also been throttle-reductions of about 30% and possibly more, when very close. Keep in mind that thrust and FF doesn't scale linearly in turbojets, so the actual FF-reduction was probably more.

 

It would be cool if anybody could manage to refly the test-setup in game and show their observed data.

[Dragon1-1]

Again, remember that the resolution of the vector field is somewhat coarse, mostly due to hardware limitations, and it's still a significant CPU load. To me it looks like a good physics model limited by the size of the cells. Maybe now that MT is a thing, we could eventually see that bit handed off to a separate core, and then resolution could go up. With this kind of thing, it's always a balance between keeping it realistic and keeping it usable on non-superpowered CPUs (and back when they first made it, DCS absolutely sucked at making good use of the CPU).

Either way, the point was that this vector field already exists and can be used for other kinds of turbulence. Even with limited resolution, it should be able to provide things like thermals and vortices near the clouds. We're not simulating gliders, some inaccuracy can be lived with.

[sthompson]

I'm not a real life pilot but I've flown as a passenger in plenty of turbulence. A lot of comments are about what you "feel" in turbulence. I don't see how you can really model it in DCS since the key sensations are all about G forces. In a passenger jet with severe turbulence you might also hear things rattling around in the overhead bins. But mostly it's about the lateral and vertical accelerations. Visually, at altitude, there really isn't much to see unless you are near another plane, or your head is bobbing around. So what exactly would better turbulence modeling be like given that we can't feel G forces?

[Dragon1-1]

Usually, DCS does that by airframe shaking. Thermals will show on your altimeter and VSI, causing you to rise when you'd expect to be flying level (this is how gliders get up to altitude). Being in formation would make that particularly obvious. And of course, there are those who have shakers and motion platforms to enhance the effect. There's plenty of options.

[Bananabrai]

On 4/30/2023 at 12:47 AM, Bremspropeller said:

The effect in game is different to RL.

In game, the lateral offset that benefits from the drag reduction is too large. Also, the rotation-onset when flying into the wake field is rather large, instead of a gradual increase with a defined core. It's close to impossible to stay at a determined position inside the wake-field. Especially for similar sized aircraft the effect is too pronounced.

NASA flight testing of two Hornets shows a FF reduction of 13 to 20% depending on flight-condition (slower leads to greater reductions) - and this only when large throttle-movements to maintain longitudinal position aren't made:

https://ntrs.nasa.gov/api/citations/20030075684/downloads/20030075684.pdf

https://www.nasa.gov/centers/armstrong/multimedia/imagegallery/AFF/index.html

The effect IRL takes place over pronounced longitudinal distances, but requires rather precise lateral and vertical position (as one would expect).

In game, my observation has been rather the opposite: A very strong dependency on a defined longitudinal distance and a rather large influenced lateral field. My observation has also been throttle-reductions of about 30% and possibly more, when very close. Keep in mind that thrust and FF doesn't scale linearly in turbojets, so the actual FF-reduction was probably more.

 

It would be cool if anybody could manage to refly the test-setup in game and show their observed data.

 

On 4/30/2023 at 1:01 AM, Dragon1-1 said:

Again, remember that the resolution of the vector field is somewhat coarse, mostly due to hardware limitations, and it's still a significant CPU load. To me it looks like a good physics model limited by the size of the cells. Maybe now that MT is a thing, we could eventually see that bit handed off to a separate core, and then resolution could go up. With this kind of thing, it's always a balance between keeping it realistic and keeping it usable on non-superpowered CPUs (and back when they first made it, DCS absolutely sucked at making good use of the CPU).

Either way, the point was that this vector field already exists and can be used for other kinds of turbulence. Even with limited resolution, it should be able to provide things like thermals and vortices near the clouds. We're not simulating gliders, some inaccuracy can be lived with.

My personal sensation is, it is also different for different planes. 

The F1 seems to be pretty susceptible to be sucked towards the leader. F-16 also does it.
In the Tomcat and Mirage 2000 on the other hand it doesn't feel that bad.

The rest I don't fly very often at the moment.

[Dentedend10]

Adding to this discussion. I do have a motion platform, and I notice that the ride feels better in the civil sim. There is turbulence at different altitudes, regardless of plane size: I feel it in small turboprops as well as large airliners. In real life, you can certainly feel the turbulence in big airliners, and it does not have to be a huge storm. This makes me think that fighter jets should also be experiencing a rough ride. Unfortunately I don't feel it in DCS at the moment. And while you might think it's because my motion platform isn't tuned properly - I feel the bumps while taxiing especially in the Mustang, so heave telemetry is set properly. I wonder if turbulence could be strengthened to feel some bumps in the air as well? 

[GOZR]

On 4/26/2023 at 8:23 AM, Yo-Yo said:

It is not correct to say that turbulence in DCS works only with wind. Yes,  setting the wind speed sets a small amount of turbulence that allows to fly in relatively comfort conditions. But the turbulence itself can be set independently. In this case plane acceleration can jump very severe.  

For example, if the dispersion of g-load is 0.3 and more,  pilots describe it as "very strong", so it's possible in DCS have the same dispersion, especially at lower altitudes, because the size of turbulence (correlation range) increases with altitude that leads to decreasing "bumps".

If you want to encounter turbulence at higher altitudes you need to set wind speed in the layers quite different (speed and/or direction).
These are a sample how DCS turbulence works, and what is correlation length or range. Please keep in mind, that the turbulence in DCS is not a function of time affecting a plane, it is SPATIAL function that means that the planes flying in close formation will be affected by the similar (correlated) vectors (but not identical) depending on the correlation length.
And, by the way, it's not static - hovering helicopter will be bumping as well.
null
null

null

DSC need to work on this..  . in VR which there is a disconnection turbulences are not felt much at all and badly done... various physics aspects are very limited in DCS at the moment and make the flight very dull  

This need to be seriously addressed , we do have some high hope .. it would be great! after so many years

 

Edited February 13 by GOZR

[Nodak]

Plowing around long enough in a low level Herc you eventually figure out where the turbulence is visually, black field to green field, lake to forest, shady side of hill to sunny, your going to catch a wicked thermal.  Even the birds know this. 

[GOZR]

On 2/14/2024 at 9:52 AM, Nodak said:

Plowing around long enough in a low level Herc you eventually figure out where the turbulence is visually, black field to green field, lake to forest, shady side of hill to sunny, your going to catch a wicked thermal.  Even the birds know this. 

No period.. Turbulences in DCS are just like a very small area and altitude like 600m that's about it.. in RL when you fly through mountains.. valleys etc you really feel them even to a much high altitude  until you are high enough for smoother..  Many pilots are avoiding areas of fear or uncomfortable .. DCS alas feel dull. has nothing todo with aircraft performances but the weather atmospheric that is almost inexistent .. alas .. if they work on it it would be the great ! but not now.  But it is true that in DCS those external reactions are disconnected on VR.. felp more visually on 2D and it need to be addressed more emergently than a missiles reaction at 500 miles away.

[twistking]

13 hours ago, GOZR said:

No period.. Turbulences in DCS are just like a very small area and altitude like 600m that's about it.. in RL when you fly through mountains.. valleys etc you really feel them even to a much high altitude  until you are high enough for smoother..  Many pilots are avoiding areas of fear or uncomfortable .. DCS alas feel dull. has nothing todo with aircraft performances but the weather atmospheric that is almost inexistent .. alas .. if they work on it it would be the great ! but not now.  But it is true that in DCS those external reactions are disconnected on VR.. felp more visually on 2D and it need to be addressed more emergently than a missiles reaction at 500 miles away.

I don't know why you want to drag VR into this. Turbulence is equally dull in 2D/pancake. What we have in DCS, i wouldn't even call turbulence: It feels more like small gusts...

[GOZR]

21 hours ago, twistking said:

I don't know why you want to drag VR into this. Turbulence is equally dull in 2D/pancake. What we have in DCS, i wouldn't even call turbulence: It feels more like small gusts...

When you fly in 2D there are more visual clues.. in VR they are far less. so there is a visual discrepancy ..  and I agree 100% Turbulences in DCS are limit to nothing.. 

[draconus]

11 minutes ago, GOZR said:

When you fly in 2D there are more visual clues.. in VR they are far less.

What makes you think that?

[GOZR]

On 3/13/2024 at 2:25 AM, twistking said:

I don't know why you want to drag VR into this. Turbulence is equally dull in 2D/pancake. What we have in DCS, i wouldn't even call turbulence: It feels more like small gusts...

When you fly in 2D there are more visual clues.. in VR they are far less. so there is a visual discrepancy ..  and I agree 100% Turbulences in DCS are limit to nothing.. 

 

 

Well it's simple try    you will see when you will be aware.

 

[draconus]

1 hour ago, GOZR said:

When you fly in 2D there are more visual clues.. in VR they are far less.

I'd argue it's the other way around depending on your fov in 2d and headset fov, but still the added benefit of depth perception in VR makes it more obvious.

[Dragon1-1]

On 2/13/2024 at 2:50 AM, Dentedend10 said:

Adding to this discussion. I do have a motion platform, and I notice that the ride feels better in the civil sim. 

Do note, I've heard opinions that the planes in the civil sim feel too lightweight, as if they had no inertia at all. It does have a vastly superior air current system, including modeling of thermals, but for that to work in DCS, a lot of optimization would have to be done on the turbulence system. We already have a vector field simulation of wake turbulence, and that's pretty good, but it's underutilized, presumably because something like, say, a WWII bomber formation bogs down the sim immensely with it turned on. Before a more complex turbulence system is added, those performance issues would have to be addressed.

It would be a great thing if we had it, not just for aircraft, but also for things like bombs. We'd get more realistic accuracy with unguided ordnance, particularly high altitude level bombing. It'd be important for low level helo ops, too, as you'd have to react to updrafts and downdrafts acting on your helo. Good old flying in bad weather, or air support in mountains, would become more exciting, too.

[GOZR]

On 3/13/2024 at 2:25 AM, twistking said:

I don't know why you want to drag VR into this. Turbulence is equally dull in 2D/pancake. What we have in DCS, i wouldn't even call turbulence: It feels more like small gusts...

When you fly in 2D there are more visual clues.. in VR they are far less. so there is a visual discrepancy ..  and I agree 100% Turbulences in DCS are limit to nothing.. 

 

 

Well it's simple try    you will see when you will be aware.

-

 

First do you have VR ?