Paul MilenkovicThat looks like a photo of the "Hush-Hush" British 4-6-4 locomotive with the marine-type water-tube boiler.
Keep in mind that the Hush-Hush had some very weird ducted preheating arrangements inside the boiler 'clothing' which did not show up in the model testing but most certainly did on the road, where reported turbulence in the ducts produced a visible 'breathing' ripple at speed.
No, neither of these approaches to duct the slipstream worked particularly well at 'smoke lifting' even though extremely well crafted to channel air directionally. None of the amazing variety of vanes, strakes, ports, little airfoils before or behind the stack, etc. particularly worked either.
On the other hand it is dramatically easy to visualize the flow from 'ears' with little more than an array of thin nozzled pipes connected to a heavy fluid, arranged at the trailing edge of, say, an ear on UP 844. In theory flow could also be followed by laser illumination or fast camera tracking of sequentially-released small or even 'smart' particles, as in looking at front-end action analytically.
That looks like a photo of the "Hush-Hush" British 4-6-4 locomotive with the marine-type water-tube boiler?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
BigJim I have seen photos showing just that somewhere. I think that it was done in England.
I have seen photos showing just that somewhere. I think that it was done in England.
This photo came up quickly:
Not elephant ears, but in an English wind tunnel. It says. Wonder who got to take the model home afterwards!
Here's a short but interesting article on smoke deflectors. It mentions wind tunnel testing:
https://en.wikipedia.org/wiki/Smoke_deflectors
and here is an undoubtedly interesting article on the subject, should you wish to invest $40:
https://journals.sagepub.com/doi/pdf/10.1243/JILE_PROC_1941_031_047_02
Ed
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Lots of speculation, here.
I would expect, back in the day when an answer would have been useful, that there were (or should have been) wind tunnel experiments to see what worked and what didn't.
Without that, you don't even know what worked, let alone HOW it worked.
Judging from the extent of these devices on US steam locomotives, the need wasn't pressing.
timz Lithonia Operator I've never understood how attaching vertical plates to each side of the smokebox causes the smoke to be blown upward. That's a puzzle, all right. Answer is, there's no need to blow the smoke upward. It's high enough already -- just need to keep it up there, at stack level. On an ordinary no-wing locomotive at speed, the flat front of the engine shoves air aside, creating low-pressure areas along the side of the engine. Which suck exhaust smoke downward into the engineers eyes. The wings are supposed to extend forward, ahead of the smokebox front, to channel air alongside the boiler, eliminating the low pressure.
Lithonia Operator I've never understood how attaching vertical plates to each side of the smokebox causes the smoke to be blown upward.
That's a puzzle, all right. Answer is, there's no need to blow the smoke upward. It's high enough already -- just need to keep it up there, at stack level.
On an ordinary no-wing locomotive at speed, the flat front of the engine shoves air aside, creating low-pressure areas along the side of the engine. Which suck exhaust smoke downward into the engineers eyes. The wings are supposed to extend forward, ahead of the smokebox front, to channel air alongside the boiler, eliminating the low pressure.
Thanks so much timz, for explaining it in a way the average person can understand.
The vortices as I saw them explained for Witte were large-scale, a bit similar to the tip vortices in the absence of winglets, arranged to provide organized high-pressure regions back along the upper sides of the tubular boiler where slipstream was causing the vacuum effect pulling the smoke down there. I suspect the effect from 'elephant ears' is a bit more like turbulent entrainment in the front end, with 'burbles' of pressure turbulence providing the envelope of high pressure held close to the boiler by slipstream but 'holding the smoke up'... if that picture makes sense.
There were attempts to provide ducting with multiple strakes. I got the impression these were an attempt at laminar flow shaping, like turning vanes in HVAC ducting, rather than small-scale turbulence for flow separation as in aircraft or the now-somewhat-discredited Airtab-style vortex generation to enhance Kamm effect behind van trailers or containers. (See the GTW version of the 'scientific' 6400-style steam streamlining for a possible evolutionary example). To my knowledge none of the straked systems worked as intended (or by accident either). I remember reading, although I don't remember where, about at least one experiment that used horizontal braces between 'outside' ears and the boiler shell, creating the effect of stacked rectangular ducts (but crippling the ability of crews to pass through behind the ears on the 'running board') and not, as an airfoil flow shaper would do, greatly compromise forward visibility.
Perhaps ironically, the specialized vacuum exhaust I designed for high-speed reciprocating locomotives used both 'feathers' active in the ejected gas plume behind the economizer train and vanes in the slipstream around the duct exits to raise the line of the exhaust above the boiler. So it's not as if defined laminar high pressure is either unworkable or wrong, just that I doubt the effect of airflow exiting behind a baffle of that kind would stay either laminar or follow the right theoretical 'streamlines' back along the barrel to accomplish the lifting rather than 'vacuum destruction' in the right areas far removed from just those keeping the forward cab-window-level view clear.
It would be easy to prove or disprove much of this with a simple arrangement of instrumented 'yaw strings' on a skeleton framework behind the ear on a locomotive like 844 equipped with a known-effective functional deflector setup. Even in the presence of quartering wind or other effects this would quickly show much of the nature of flow in the regions of peak interest... like an inside-out wind tunnel
I lean towards timz explanation.
If the plates worked by creating vortices, wouldn't they have a bank of small fins -- those of you old enough to have flown on the 707 may have seen such small fins on the wing. These vortex generators were meant to generate a small amount of roughness so the airflow would not separate from the top surface of the wing and cause a stall under slower flight and higher angle-of attack of the wing?
I think the "strakes" (fins) you see on the sides of the wide-fan jet engines on newer planes do a similar thing?
On the other hand, such fins or strakes generating vorticity could have the same effect of preventing the airflow from separating from the sides of the boiler, preventing suction drawing smoke downward towards the faces of the locomotive crew?
The use of a flat surface, however, to keep air flowing past a blunt surface such as a locomotive smokebox door, has a precedent in efforts to reduce drag of radial piston engines for aircraft.
The early radials had the cylinder sticking out into the airstream for engine cooling, which creates a lot of drag. One of the early drag reductions was to place a ring around the cylinders, essentially, a curved version of the flat-plate locomotive "smoke deflectors." That ring was refined into a cowling that was open in the front, streamlined along the sides, and had a way of expelling cooling air towards the back.
In my opinion, laminar flow doesn't exist behind most North American ears, and I think the experimental results (including the failure to work even at massive size on UP articulated power) are largely explained better with turbulent flow and vortices than with an assumption of simplistic air displacement and pressurized laminar flow in the absence of aerodynamic flow shaping.
If you look at most of the Witte deflectors you can see the model of 'scooping high-pressure air' from the displaced bowshock or whatever is not particularly optimized, yet the devices are said to work well to keep smoke away from cabs.
OM and timz: So now we have two pretty thorough technical answers about elephant ears, the second more cogent. Are both right, just different sides of the same coin?
Lithonia OperatorI've never understood how attaching vertical plates to each side of the smokebox causes the smoke to be blown upward.
Overmod... I have been hoping many years now for one of the folks doing modeling on YouTube to put up a visualization of CFD results from various types of ear to assess the actual airflow patterns involved in what, back in the day, was largely a black art using the wrong basic aerodynamics...
I have been hoping many years now for one of the folks doing modeling on YouTube to put up a visualization of CFD results from various types of ear to assess the actual airflow patterns involved in what, back in the day, was largely a black art using the wrong basic aerodynamics...
Just see if you can find a YT concerning the aerodynamics being used in auto racing - amongst all the various aero devices, wickers, flaps, airfoils and everything else - the black art gets explained to some degree.
Never too old to have a happy childhood!
I'm sure there are videos on YouTube that show the shape and magnitude of the vortices and their action above the boiler.
Perhaps the best-designed version from a scientific perspective was the German Witte design and its design-approach clones; these used shaped plates relatively high on the smokebox explicitly as tailored-vortex generators with minimal cross-sectional visible area in the engineer's or fireman's view of important areas forward. I think the tight B&M deflectors were intended to have similar induced effect but carried further inboard in the wider loading gage to 'work' just as well but not block the view forward. While most of the mature deflector designs used on American road power had minimal 'visible metal obstruction fore-and-aft (the thickness of the stiffened ear and of the braces holding the top to the boiler, jacket or smokebox), I suspect that in poor weather conditions the vortices made forward vision a trying thing all too much of the time ...
I've never understood how attaching vertical plates to each side of the smokebox causes the smoke to be blown upward. Seems like wind would enter the slots in front, exit in back, and that would be that. Is it the steps that actually deflect the wind, and the "ears" just keep that force concentrated?
Boston & Maine late model P4a and P4b Pacifics and R1a and R1b Mountains had small smoke lifters as delivered from Lima.
Western Pacific GS-64 Northerns also had them, as well as the Wabash P1 Hudsons.
Several USA steamers had smoke lifter 'elephant ears', notably the New York Central S1b Niagara 4-8-4, some of the NYC's 4-8-2's and the several FEF 4-8-4's on the Union Pacific. There were others. I would not include Canada as a place where they were widely used.
https://images.app.goo.gl/dQXTCeSUQebiCo3V8
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