Should we have 'Mythbusters' highlight the state of railroad aero?
Boyd I think a model railroader with a fair amount of technical knowledge and a home built wind tunnel could do some tests of various types of model RR cars.
I think a model railroader with a fair amount of technical knowledge and a home built wind tunnel could do some tests of various types of model RR cars.
Never too old to have a happy childhood!
As long as that modeler was conversant with the "Reynolds Number", i.e. the effects of turbulence don't necessarily scale well. Since aero drag is largely an issue of turbulence, this is not an inconsequential matter.
- Erik
Modeling the "Fargo Area Rapid Transit" in O scale 3 rail.
For what it's worth, one member - Tim O'Connor - of the "modelintermodal" group on Yahoo! posted the following yesterday evening about this:
"Railroads tested fuel efficiency years ago and found that trains ofplain old box cars are the most efficient by far, consuming less than1/2 as much fuel as intermodal trains and even less than trains ofempty hopper cars, which use more than 50% as much as loaded hoppers."
Unfortunately, he didn't provide any further details, references, citations, etc. to support those assertions.
- Paul North.
Paul_D_North_Jr oltmannd: Dakguy201: Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train? The carrier DO think so....in a perfect world, that is how it would be. But loading intermodal trains has more pragmatic considerations that take precedence over train aerodynamics. Blocking and switching are the two biggies. BaltACD: In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind. ----------------------------------------------------------------------------------------------------------------------- [From here on down is PDN's post - this new editing and formatting 'dys-function' is a pain !!!] Just when we (including me) might think that it's all settled and static and nothing's going to change: Link to a blog post by Marc Gunther (a contributing editor to Fortune magazine) from yesterday, December 7, 2010 titled "The Power of One: Union Pacific" with a description and photos of how Mike Iden, UP's General Director of Car and Locomotive Engineering, and Wayne Kennedy of UP's "Continuous Improvement" group developed and are testing a wedge-shaped airfoil to take the place of the top first container behind the locomotives, to improve fuel performance: (Thanks to Chris Butts of the "modelintermodal" group at yahoogroups.com for first posting the link to this ! ) http://theenergycollective.com/marcgunther/48227/power-one-union-pacific An excerpt pertinent to the above, in that some problems may not be as big as they first seem: "The fuel savings appeared to be meaningful, but a new problem arose. Says Mike: “The first questions that people in the company had was, why would we give up a revenue box on the train?” It turns out, though, that there’s often at least one empty container on a train, so if the cars could be arranged properly, the wedge would not displace a full container." [emphasis added - PDN] - Paul North.
oltmannd:
Dakguy201: Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train? The carrier DO think so....in a perfect world, that is how it would be. But loading intermodal trains has more pragmatic considerations that take precedence over train aerodynamics. Blocking and switching are the two biggies. BaltACD: In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind. ----------------------------------------------------------------------------------------------------------------------- [From here on down is PDN's post - this new editing and formatting 'dys-function' is a pain !!!] Just when we (including me) might think that it's all settled and static and nothing's going to change: Link to a blog post by Marc Gunther (a contributing editor to Fortune magazine) from yesterday, December 7, 2010 titled "The Power of One: Union Pacific" with a description and photos of how Mike Iden, UP's General Director of Car and Locomotive Engineering, and Wayne Kennedy of UP's "Continuous Improvement" group developed and are testing a wedge-shaped airfoil to take the place of the top first container behind the locomotives, to improve fuel performance: (Thanks to Chris Butts of the "modelintermodal" group at yahoogroups.com for first posting the link to this ! ) http://theenergycollective.com/marcgunther/48227/power-one-union-pacific An excerpt pertinent to the above, in that some problems may not be as big as they first seem: "The fuel savings appeared to be meaningful, but a new problem arose. Says Mike: “The first questions that people in the company had was, why would we give up a revenue box on the train?” It turns out, though, that there’s often at least one empty container on a train, so if the cars could be arranged properly, the wedge would not displace a full container." [emphasis added - PDN] - Paul North.
Dakguy201: Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train?
The carrier DO think so....in a perfect world, that is how it would be. But loading intermodal trains has more pragmatic considerations that take precedence over train aerodynamics. Blocking and switching are the two biggies.
BaltACD: In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind.
-----------------------------------------------------------------------------------------------------------------------
[From here on down is PDN's post - this new editing and formatting 'dys-function' is a pain !!!]
Just when we (including me) might think that it's all settled and static and nothing's going to change:
Link to a blog post by Marc Gunther (a contributing editor to Fortune magazine) from yesterday, December 7, 2010 titled "The Power of One: Union Pacific" with a description and photos of how Mike Iden, UP's General Director of Car and Locomotive Engineering, and Wayne Kennedy of UP's "Continuous Improvement" group developed and are testing a wedge-shaped airfoil to take the place of the top first container behind the locomotives, to improve fuel performance:
(Thanks to Chris Butts of the "modelintermodal" group at yahoogroups.com for first posting the link to this ! )
http://theenergycollective.com/marcgunther/48227/power-one-union-pacific
An excerpt pertinent to the above, in that some problems may not be as big as they first seem:
"The fuel savings appeared to be meaningful, but a new problem arose. Says Mike: “The first questions that people in the company had was, why would we give up a revenue box on the train?” It turns out, though, that there’s often at least one empty container on a train, so if the cars could be arranged properly, the wedge would not displace a full container." [emphasis added - PDN]
Interesting, kind of reminds me of the Aerodynamic shrouding on the early well cars operated by Espee (or was it ATSF).......
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Dakguy201: Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train? The carrier DO think so....in a perfect world, that is how it would be. But loading intermodal trains has more pragmatic considerations that take precedence over train aerodynamics. Blocking and switching are the two biggies. BaltACD In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind. ----------------------------------------------------------------------------------------------------------------------- [From here on down is PDN's post - this new editing and formatting 'dys-function' is a pain !!!] Just when we (including me) might think that it's all settled and static and nothing's going to change: Link to a blog post by Marc Gunther (a contributing editor to Fortune magazine) from yesterday, December 7, 2010 titled "The Power of One: Union Pacific" with a description and photos of how Mike Iden, UP's General Director of Car and Locomotive Engineering, and Wayne Kennedy of UP's "Continuous Improvement" group developed and are testing a wedge-shaped airfoil to take the place of the top first container behind the locomotives, to improve fuel performance: (Thanks to Chris Butts of the "modelintermodal" group at yahoogroups.com for first posting the link to this ! ) http://theenergycollective.com/marcgunther/48227/power-one-union-pacific An excerpt pertinent to the above, in that some problems may not be as big as they first seem: "The fuel savings appeared to be meaningful, but a new problem arose. Says Mike: “The first questions that people in the company had was, why would we give up a revenue box on the train?” It turns out, though, that there’s often at least one empty container on a train, so if the cars could be arranged properly, the wedge would not displace a full container." [emphasis added - PDN] - Paul North.
BaltACD In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind.
jeffhergert Paul_D_North_Jr: zardoz: [snip] . . . I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest. I wonder what the "accelerometer" function in a modern locomotive's speedometer would show with such a train when hit by a sudden gust of wind. In theory, it would register a slowdown of maybe a couple tenths of an MPH . . . That might be a good way to get a handle on the' real-life' significance of aerodynamics to freight trains. - Paul North. I've had many of those empty hopper trains across Iowa, too. A bit longer now and usually with 2 engines. Even so, the wind blowing hard affects the train. More than once, I've noticed a change of up to 5 mph when going from the open areas (farmland with few trees) to more protected areas (towns/wooded non crop land). As I recall reading, the rounded corners did provide a very, very small fuel savings. It wasn't enough though to offset the higher manufacturing costs for the rounded corners. Jeff
Paul_D_North_Jr: zardoz: [snip] . . . I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest. I wonder what the "accelerometer" function in a modern locomotive's speedometer would show with such a train when hit by a sudden gust of wind. In theory, it would register a slowdown of maybe a couple tenths of an MPH . . . That might be a good way to get a handle on the' real-life' significance of aerodynamics to freight trains. - Paul North.
zardoz: [snip] . . . I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest.
I wonder what the "accelerometer" function in a modern locomotive's speedometer would show with such a train when hit by a sudden gust of wind. In theory, it would register a slowdown of maybe a couple tenths of an MPH . . . That might be a good way to get a handle on the' real-life' significance of aerodynamics to freight trains.
I've had many of those empty hopper trains across Iowa, too. A bit longer now and usually with 2 engines. Even so, the wind blowing hard affects the train. More than once, I've noticed a change of up to 5 mph when going from the open areas (farmland with few trees) to more protected areas (towns/wooded non crop land).
As I recall reading, the rounded corners did provide a very, very small fuel savings. It wasn't enough though to offset the higher manufacturing costs for the rounded corners.
Jeff
Yeah, you got them soon after I got rid of them at Yard 9 Proviso.
Back in my day (gee, that sure makes me sound old), the coal trains came in from Clinton with three units, but one was always taken off at Proviso, so we had two SD40-2's on the northbound trains; needless to say we didn't set any speed records getting to Pleasant Prairie or Oak Creek (two units wasn't enough power to climb West Allis hill). But back then the CNW was a real stickler for isolating units. That was when the CNW installed those "fuel saver" switches on the 6800's and 6900's.
In today's railroad world, the loading and unloading of intermodal cars is rarely done by railroad employees, it is generally done by a hired contractor....the only thing the contractor is paid to care about is getting boxes on and off equipment and lining up the boxes on the right cars for the proper destination. Location of single and double stacks in the tracks they are loading is the furthest thing from their mind.
oltmannd Dakguy201: Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train? The carrier DO think so....in a perfect world, that is how it would be. But loading intermodal trains has more pragmatic considerations that take precedence over train aerodynamics. Blocking and switching are the two biggies.
Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train?
Dakguy201 Many times when you see a container train, it will seem to consist of a few cars of single stack, followed by some double stacks, followed by more single stacks and so on. Wouldn't it be much more fuel efficient to segregate the double stacks? Obviously the carriers don't seem to think so. Is the intercar spacing long enough that each doublestack is affected as if it were the only one in the train?
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Thanks, jeff ! I had you in mind, hoping you'd be able to provide that data and those observations. A 5 MPH change doesn't surprise me, such as when running into the teeth of 30 MPH gusts out of the northwest.
Aerodynamics starts to effect an automobile at about 40 mph. One government study in the 80s showed a significant fuel savings if semis drove 40 mph. Not to mention the effects of semis being on the road longer, clogging up lanes, adding costs, delaying deliveries and rotting food faster,,, which I think would cost more than the amount of fuel costs saved. Anyone on here ever driven a compact car down the highway and passed a cabover (flatnose) semi? You can really feel the air pushing the car to the side away from the semi.
I bet there could be a measured difference in fuel consumption of a 100 car mixed car type train going 40mph into a 30mph headwind compared to no wind at all.
Paul_D_North_Jr zardoz: [snip] . . . I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest. I wonder what the "accelerometer" function in a modern locomotive's speedometer would show with such a train when hit by a sudden gust of wind. In theory, it would register a slowdown of maybe a couple tenths of an MPH . . . That might be a good way to get a handle on the' real-life' significance of aerodynamics to freight trains. - Paul North.
The German Neubaustrecke with 300 kph top speeds are all slab track. Older Neubaustrecke and all Ausbaustrecke with 250 kph top speeds use concrete ties with ballast. The slab track has ballast shoulders, but the slab rests directly on the sub-grade, the shoulders are ballasted to control sideways movement and for drainage. Remember the HSR trainsets have fairly low axle loadings, and are relatively light in total weight.
samfp1943 Cricketer, you mentioned that the German HSR's traveled on unballasted tracks ? How do they manage drainage within the track structures?
Cricketer, you mentioned that the German HSR's traveled on unballasted tracks ? How do they manage drainage within the track structures?
I don't believe that is true. HSR's in Germany (ICE's) largely run on right of way that has concrete sleepers on well-maintained stone ballast. Same for French TGVs and Japanese Bullet trains: all run on ballast bound tracks. Their way of avoiding the problem of stones being sucked up is having the underside of coaches enclosed and smooth and reducing the number of smaller loose stones in the track bed. Concrete slab track beds are used on some stretches in Germany and quite heavily used in China.
C&NW, CA&E, MILW, CGW and IC fan
I'm afraid I don't know - sorry.
Cricketer Wind resistance increases with the square of the velocity, so when trains get quick aerodynamics start to matter, and really matter over 100mph. I'm afraid I don't know the formal symbols, but doing the maths is salutory. Imagine a train with a resistance of 2. Travelling at 50mph resistance is 2x50squared ie 5,000. At 100mph is 2x100squared ie 20,000. Double speed, quadruple resistance. At 125mph it's 2x125squared - 31,250. Add a quarter to the speed and resistance goes up by over half. At 200mph it's 2x200 squared - 80,000. So comparing 50mph with 200mph speed has quadrupled, wind resistance has increased sixteeen times. Clearly one can shove vast amounts of horsepower at something and speed will increase, but at diminishing returns if aerodynamics aren't re-worked. Also while it's less important with trains than cars much of high speed car aerodynamics (eg Formula 1) is designed to keep the car down, ie on the road so the wheels can transmit energy from engine to road. One further point is that all aerodynamics need to be catered for - pressure sealing vehicles so that they can pass in tunnnels without truly horrible pressure waves. 125mph (ie 250mph closing speed) is about as quick as unsealed trains can pass in a tunnel, and even then passengers will notice their ears popping. Some of the German high speed lines have especially wide tunnel mouths to try allow air to escape as a train enters them. All aerodynamics also means the bottom of the train - really high speeds can generate forces big enough to move ballast, and stones hitting metal at 200mph is not welcomed. Caused a problem with German high speed trains on French high-speed lines. The latter are ballasted, the German high speed lines have concrete track formations with no ballast. My conclusion is that even if you could put enough grunt in front of a superliner (which would need an electric engine) redesign would be needed.
Wind resistance increases with the square of the velocity, so when trains get quick aerodynamics start to matter, and really matter over 100mph. I'm afraid I don't know the formal symbols, but doing the maths is salutory. Imagine a train with a resistance of 2. Travelling at 50mph resistance is 2x50squared ie 5,000. At 100mph is 2x100squared ie 20,000. Double speed, quadruple resistance. At 125mph it's 2x125squared - 31,250. Add a quarter to the speed and resistance goes up by over half. At 200mph it's 2x200 squared - 80,000. So comparing 50mph with 200mph speed has quadrupled, wind resistance has increased sixteeen times.
Clearly one can shove vast amounts of horsepower at something and speed will increase, but at diminishing returns if aerodynamics aren't re-worked. Also while it's less important with trains than cars much of high speed car aerodynamics (eg Formula 1) is designed to keep the car down, ie on the road so the wheels can transmit energy from engine to road.
One further point is that all aerodynamics need to be catered for - pressure sealing vehicles so that they can pass in tunnnels without truly horrible pressure waves. 125mph (ie 250mph closing speed) is about as quick as unsealed trains can pass in a tunnel, and even then passengers will notice their ears popping. Some of the German high speed lines have especially wide tunnel mouths to try allow air to escape as a train enters them.
All aerodynamics also means the bottom of the train - really high speeds can generate forces big enough to move ballast, and stones hitting metal at 200mph is not welcomed. Caused a problem with German high speed trains on French high-speed lines. The latter are ballasted, the German high speed lines have concrete track formations with no ballast.
My conclusion is that even if you could put enough grunt in front of a superliner (which would need an electric engine) redesign would be needed.
Having never experienced European HSR, I had never given the effect of the ballast being sucked up, much thought, but I have experienced a somewhat similar experience a couple of times while fishing. The IC RR thoughtfully provided a raised,dry ROW through a swampy area in North Mississippi to fish from ( those were a lot simpler times).
Late at night the Panama would come through at a terrible speed and we would be pelted with rocks. We always suspected it was people on the train throwing them ( too you to realize what was happening!) . One could also see the trash swirling in the air as one of the IC passenger trains would go through the local communities (this was when the ICRR was truly the"Mainline of Mid America", and it was really well maintained, double tracked) .
Cricketer Wind resistance increases with the square of the velocity, so when trains get quick aerodynamics start to matter, and really matter over 100mph. I'm afraid I don't know the formal symbols, but doing the maths is salutory. Imagine a train with a resistance of 2. Travelling at 50mph resistance is 2x50squared ie 5,000. At 100mph is 2x100squared ie 20,000. Double speed, quadruple resistance. At 125mph it's 2x125squared - 31,250. Add a quarter to the speed and resistance goes up by over half. At 200mph it's 2x200 squared - 80,000. So comparing 50mph with 200mph speed has quadrupled, wind resistance has increased sixteeen times.
Also recall that the power required to generate a given tractive effort scales with speed, so quadrupling speed will increase the amount of power to overcome aero drag by a factor of 64. IIRC, aero drag is just starting to become significant with American passenger equipment at around 50 MPH.
FWIW, the earliest UP streamliners had smooth bottoms, but the increase in maintenance costs outweighed fuel savings. These were not particularly high speed trains.
All aerodymics also means the bottom of the train - really high speeds can generate forces big enough to move ballast, and stones hitting metal at 200mph is not welcomed. Caused a problem with German high speed trains on French high-speed lines. The latter are ballasted, the German high speed lines have concrete track formations with no ballast.
This touches on a question that has always been in the back of my mind regarding Superliner equipment. Recalling that, after some early experimantation with lower slung and articulated, streamlined passenger equipment (M-10000, Pioneer Zephyr, Land O' Corn, etc.) higher speeds of the 30's and 40's were frequently attained with non-steamlined equipment in consists or (as in the case of the early 400's) none at all.
So, aside from the design of the locomotive such as on French, Chinese and other HSR trainsets is there any particular aerodynamic problem with operating Superliners at HSR (180-200mph+) speeds? Or would it pay to redesign from the rail up?
zardoz [snip] . . . I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest.
zardoz Murphy Siding: Does train aerodynamics have a big effect on locomotive performance? I thought a moving vehicle had to be moving somewhat over 100 m.p.h., before aerodynamics made much difference in performance? I'm not sure if this addresses your question, but I remember running empty 112-car coal trains that would not get much above 35mph with only one SD40-2 locomotive, even though the train weighed only 3500 tons. All the empty hoppers acted like parachutes. I would guess the same (but to a smaller degree) would apply to a train of empty bulkhead flats. I would also guess that aerodynamics would be much more of a factor on IM trains rather than on a manifest.
Murphy Siding: Does train aerodynamics have a big effect on locomotive performance? I thought a moving vehicle had to be moving somewhat over 100 m.p.h., before aerodynamics made much difference in performance?
Does train aerodynamics have a big effect on locomotive performance? I thought a moving vehicle had to be moving somewhat over 100 m.p.h., before aerodynamics made much difference in performance?
Johnny
Rounded hood corners weren't for aerodynamics, but surely helped to make a lot of railfans love the Alco RSI-2-3's. Along with their cleaner looking trucks, smokier exhausts, and burbling/galloping/comforting sound at rest, they were more friendly or even cuddlier to be with. Baldwin did a litle of the same thing on it' AS's,
FM trainmasters were ugly here on the Reading.
As a child, the only EMD geep I liked was the American Flyer one with the wire couplers. It could pull the whole yard or the paper off the walls.
Wow, cuddly for a locomotive, and now there's Thomas and friends.
RIX
rixflix aka Captain Video. Blessed be Jean Shepherd and all His works!!! Hooray for 1939, the all time movie year!!! I took that ride on the Reading but my Baby caught the Katy and left me a mule to ride.
Murphy Siding Does train aerodynamics have a big effect on locomotive performance? I thought a moving vehicle had to be moving somewhat over 100 m.p.h., before aerodynamics made much difference in performance?
I too used to lament about how all the art deco era E-8s and F-7s were more streamlined than later GP and SD offerings.
But, if you position yourself above locos like the GP 7, etc, you can see that they are streamlined, like a wedge splitting the air in front of them.
Look at the leading edge of this one, as an example:
Perhaps not as pretty as a covered wagon, but still "streamlined" to a degree
Murphy,
I was an aircraft mechanic for the last thirty years of my working life so I think I have a handle on aerodynamics.
Airplanes are designed to have proper airflow around the wings to develop lift and to smooth the flow over the fuselage.
Trains are not designed with consideration of airflow. Depending on the consist they may be dragging many 'barn doors' against prevailing winds. Flat cars are not much of a consideration, but cars of height and square ends can surely cause more drag at higher speeds.
As far as aerodynamics are concerned rounded corners on locomotives are of little help. That may not apply to passenger trains where all cars are closely coupled.
Norm
If my memory serves me right, only the 60-series demos (GP59, GP60, SD60) were the only ones that had the rounded edges on the cab.
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