Streamlining efficiency?

 
  Stafford Station Master

Location: Kalgoorlie
This is probably a long shot but here is as good a place to ask as any.

I'm curious to know what the effectiveness of streamlining was, in particular if any studies have been published on the subject.
In particular I'm interested in the bulldog nose streamlining, although as I understand it that was more done for aesthetic effect rather than function.

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  justapassenger Minister for Railways

Probably quite low, until you get to the 1980s when Siemens used scale models in the Mercedes-Benz wind tunnel during development of the ICE 1 and the Japanese got their automotive industry involved in the design of second generation Shinkansen sets.
  Gman_86 Chief Commissioner

Location: Melton, where the sparks dare not roam!
I expect the streamlining seen on early diesels was mostly for aesthetics, but what is the reason behind abandoning this entirely.

Since the 1960's the designs of pretty much all diesel locomotives have completely ignored any sort of attempt at streamlining. Why is this?
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
I expect the streamlining seen on early diesels was mostly for aesthetics, but what is the reason behind abandoning this entirely.

Since the 1960's the designs of pretty much all diesel locomotives have completely ignored any sort of attempt at streamlining. Why is this?
Gman_86
Practicality, ease of maintenance, perhaps weight saving(?).

Streamlining is largely all spin and little substance for most rail applications.

EDIT 15/6 at 1935:
I should have said for most rail applications in Australia.
  Valvegear Oliver Bullied, CME

Location: Richmond Vic
There comes a point at which streamlining is helpful but, as YM suggests, it is probably above normal train speeds like ours.
If you look at aircraft, there are four factors influencing flight; lift, thrust, weight and drag. A box-shaped aircraft would suffer from enormous drag which would need to be compensated by more lift and/or thrust. The higher the speed of the aircraft, or, in our case, the  train, the more drag is generated. Look at the European and Japanese trains as examples; they are very streamlined  and go like the clappers. In other words, drag would be a serious problem if it were not not reduced by streamlining.
Somebody better at this type of physics than I am  could probably tell us a speed at which streamlining/drag mitigation becomes a serious factor.
  justapassenger Minister for Railways

Look at the European and Japanese trains as examples; they are very streamlined and go like the clappers …
Valvegear
The aerodynamicists responsible for those high speed designs would probably correct you and point out that streamlining is to aerodynamics as alchemy is to chemistry.

In other words, drag would be a serious problem if it were not not reduced by streamlining.
Valvegear
So far as I understand, a fair amount of the effort these days surrounds making sure they work well in tunnels and door openings don’t get compromised. Punching a hole through the air is no less important than how the air is managed once it is displaced.

There comes a point at which streamlining is helpful but, as YM suggests, it is probably above normal train speeds like ours.

Somebody better at this type of physics than I am  could probably tell us a speed at which streamlining/drag mitigation becomes a serious factor.
Valvegear
In general, the braking force of drag (the combination of frontal air resistance and base drag at the back of a vehicle) is proportional to the square of velocity.

Lower speeds don’t make aerodynamics completely irrelevant though, they just change the scale of the efforts involved. Rather than a whole ‘streamline’ body design, you’ll see all sorts of relatively minor things - such as the aerodynamic nose fairings on the Adelaide A-City which are a major change from the Perth B-Series which were in turn an update from the Vlocity.

For freight vehicles, the big advantage I could see from aerodynamics would be a focus on how they behave in cross winds. The result might be a small but welcome reduction in wheel wear.
  neillfarmer Chief Train Controller

A lot of work was done on the effect of streamlining of trains and locomotives in the 1930s. Much of this work still applies. At around 70mph the air resistance (drag) from a locomotive is about 280hp. If the locomotive is streamlined in the most effective way this can be reduced to about 210 hp. This compares with the power needed to drive the train along at 70 mph, about 2,000 hp. The air resistance increases with the speed squared, but there are other components in the resistance equation that increase with speed and weight. The ferrochronologists, common in the steam era, used these equations to work out theoretical locomotive horsepowers on various runs. These seemed to give good agreement with the few dynomometer car readings. I think the equations are to be found by googling.
  Stafford Station Master

Location: Kalgoorlie
Weird, I made a reply on this the other day but it seems to have been eaten. Confused

Thanks for the info gents, it has been enlightening. What would really be a bonus would be to see hard test data, but I guess any R&D into the subject is going to be kept secret by any given manufacturer.
  neillfarmer Chief Train Controller

Fortunately the low viscosity of air means that tests done on models can be scaled up to full size. All that is needed is a wind tunnel and a means of measuring the air speed. Similar to aircraft. What the experimenter will find is that the shape of the locomotive doesn't matter much until speeds over 100 mph are reached. A HO or O scale model would suffice. Really good project for a high school physics class. Text books also publish the drag coefficients for different shapes, but the F7 nose is not quite generic. In the steam era technical information was often freely circulated, and in the USA manufacturers often made use of the competition's products. A good example is that of ALCO who published the ground breaking work of Francis Cole in 1913.
  speedemon08 Mary

Location: I think by now you should have figured it out
Look at the European and Japanese trains as examples; they are very streamlined and go like the clappers …
The aerodynamicists responsible for those high speed designs would probably correct you and point out that streamlining is to aerodynamics as alchemy is to chemistry.

In other words, drag would be a serious problem if it were not not reduced by streamlining.
So far as I understand, a fair amount of the effort these days surrounds making sure they work well in tunnels and door openings don’t get compromised. Punching a hole through the air is no less important than how the air is managed once it is displaced.

There comes a point at which streamlining is helpful but, as YM suggests, it is probably above normal train speeds like ours.

Somebody better at this type of physics than I am  could probably tell us a speed at which streamlining/drag mitigation becomes a serious factor.
In general, the braking force of drag (the combination of frontal air resistance and base drag at the back of a vehicle) is proportional to the square of velocity.

Lower speeds don’t make aerodynamics completely irrelevant though, they just change the scale of the efforts involved. Rather than a whole ‘streamline’ body design, you’ll see all sorts of relatively minor things - such as the aerodynamic nose fairings on the Adelaide A-City which are a major change from the Perth B-Series which were in turn an update from the Vlocity.

For freight vehicles, the big advantage I could see from aerodynamics would be a focus on how they behave in cross winds. The result might be a small but welcome reduction in wheel wear.
justapassenger
The gaps between wagons/carriages is more of an aerodynamic concern than the frontal profile of a locomotive funnily enough. Case in point was the Freight Australia log trains: empty wagons one way but the train was full throttle both ways due to drag, and then adding load on the return.


And to a point to show you how little streamlining you can get away with: the Siemens ES64. OBB uses these at 230km/h on the regular, and the max anyone has had one topped out was at 357km/h.

https://www.flickr.com/photos/143492776@N05/49110654741

https://www.flickr.com/photos/126584084@N05/26529546754
  justapassenger Minister for Railways

And to a point to show you how little streamlining you can get away with: the Siemens ES64. OBB uses these at 230km/h on the regular, and the max anyone has had one topped out was at 357km/h.
speedemon08
I bet that Siemens weren't mucking around with what aerodynamic engineering they did do on it.

I'm no expert, but I do see a number of key features there:
1. Sloped front rather than pointed front, should be good for displacing air upwards rather than laterally.
2. Looks like very deliberate curvature on the piece of fairing between the front/top and side, I bet that is the result of high performance CFD modelling.
3. Good exploitation of the boundary layer effect on the sides, with the piece behind the buffer there to push the air well clear of all the messy mechanical components that can't be fully faired in.
4. Side fairing comes down quite low.
5. Protrusions from the side of the body are minimised, even the handrails for the doors are partially recessed.
6. Windscreen wipers mounted on a rail, keeping the airflow over the front nice and clean.

And all that while keeping a largely conventional body configuration instead of creating a streamline body that would be a pain in the rear end to work with on a day to day basis - though with it being Siemens you can also bet that the electrics are reliable enough that day to day access is not necessary.
  petan Chief Commissioner

Location: Waiting to see a zebra using a zebra crossing!
That 357kmh loco even does it while using hook not auto couplers. I know lots of Europe has hook couplers, so I am just making an observation on what I see.
  justapassenger Minister for Railways

That 357kmp loco even does it while using hook not auto couplers. I know lots of Europe has hook couplers, so I am just making an observation on what I see.
petan
Yes, the Taurus (ÖBB marketing name for their fleet of Siemens EuroSprinter model ES64U2) uses hook couplers to couple to the Siemens coaches used on a Railjet service.

Outside of the specially arranged record run on a German high speed line with German high speed rolling stock, Taurus locos are restricted to 230 km/h by the accreditation of the Railjet coaches. If they had coaches rated for higher speeds, the Taurus locos could run at up to 249 km/h before their non-certification for high speed service would limit them.

TGV locos have hook couplings on the back to couple to their coaches (Scharfenberg coupler behind the retractable nose fairing for coupling two sets together) and run at even higher service speeds up to 320 km/h.

Intercity operators in Europe can run loco hauled trains with hook couplings because any line important enough to have a loco-hauled intercity service is also important enough to be maintained to a standard that it won't break couplings.

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