rossiHowever, the Arrowedge generates an additional/extra/delta tail wake/vacuum resistance for the total combined resistance(of all combined containers).
Please explain better what you mean in this sentence. I think we have discussed the general pointlessness of putting a 'legacy' Arrowedge on the front of a train with no container(s) immediately behind its trailing edge, but that is because all the benefits of the leading streamlining would be lost by the time the deflected airflow reached the front of the next following container (leaving only the drags produced by the device as the net effect on train resistance). There is likely to be some trailing resistance due to the gap between the rear of the older Arrowedge and the front of the immediately following container, but presumably the high shaped airflow coming off the forebody shape is expected to persist over that gap. What is pointedly not discussed is whether the vacuum effect behind the forebody induces relatively high-pressure air or wind to move up as well as laterally into the gap, or where the collapsing flow from the forebody may be inducing larger vortices or flow instability/buffeting that might actually increase mean aerodynamic resistance on following containers.
I despaired of the UP team having a good knowledge of aerodynamics when they added the transom to make the Arrowedge easier to handle with a traditional crane and spreader. It would be interesting to see video of an array of yaw strings behind that set of struts. On the other hand, it can easily be interpolated that the transom didn't impair the actual overall train resistance very much...
It should be noted here that the "Arrowedge 3.0" has very little in common with the devices we have been discussing so far: it's a normal 53' container with the front 13' chopped off and fashioned into a fairly simple wedge beak. Here is a description of the system. This is said to have about 88% of the efficiency of the original at much lower cost (and, although it is not said, ease in handling the device with standard intermodal equipment).
I had thought that the use of wedge beaks to streamline the front of railroad equipment had been discredited long, long ago. Perhaps the BYU kids thought that because it wasn't on a locomotive, and they calculated the wind pressure as the resultant of so many psi incident over the whole of the flat (and corrugated) leading end, it would produce meaningful resistance reductions.
Where they may be missing something is in applying some form of abbreviated beaks, or probably better, parabolic deflectors, to the fronts of containers in the train, sized to deflect the vortices generated off the previous container end. One historical problem with the Airtab approach was that, while those devices were supposed to produce a set of clean trailing vortices, unlike the situation with a trailer those vortices may drift into incidence, perhaps more highly drag-inducing incidence, with the bluff fronts of the following containers, and this would be particularly troublesome when adding to the effect of a quartering wind.
(I have yet to relocate the Canadian report on the Airtab devices; can someone please provide a reference?)
Something I have requested, but not yet seen, is the actual dynamometer-car testing with and without an Arrowedge 3.0 device that shows the actual reduction in overall train resistance produced by the device over, say, a 'control' empty 53' in that position. (I have little doubt that instrumentation showing a substantial percentage of drag reduction on the modified container, measured relative to the twistlocks holding it to the container underneath, would show a reduction, but that's not the concern here.)
Aerodynamics can get really complicated.
Witness the not-entirely-scientific study done by "Mythbusters" regarding driving a pick-up with the tailgate open or closed.
As I recall, they found that having the tailgate closed was actually more aerodynamic. It has to do with a circulating cushion of air in the truck bed that is not there with the tailgate open. This rather flies in the face of what one may think would happen with the tailgate closed and blocking the perceived airflow through the bed.
I know that before I put a bed cover on one of my pick-ups, anything loose in the bed would tend to end up behind the cab, rather than flying out of the bed.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68Aerodynamics can get really complicated. Witness the not-entirely-scientific study done by "Mythbusters" regarding driving a pick-up with the tailgate open or closed.
Yes, and even more interesting was the situation with the 'aerodynamic' tailgates with mesh, holes, or slats advertised as having 'lower air resistance' than solid ones. Those produced almost epic levels of turbulence and associated drag, while relieving some of the circulation and pressure rise that create the high-pressure volume and circulation patterns that actually streamline the airflow past the bed area.
Another interesting observation is the high pressure that builds up in the windshield root area of conventional automobiles... the thing exploited by cowl-induction systems, which seem counterproductive when first examined using 'folk aerodynamics'.
Current F1 aerodymanic nose design
Never too old to have a happy childhood!
BaltACDCurrent F1 aerodynamic nose design
I suspect that what you have there is an adaptation of wing slots/slats to control downforce and shape airflow around the required suspension and steering elements. Doing active aerodynamic flow shaping via airfoil elements is a different thing from just blunt streamlining.
RME BaltACD Current F1 aerodynamic nose design I suspect that what you have there is an adaptation of wing slots/slats to control downforce and shape airflow around the required suspension and steering elements. Doing active aerodynamic flow shaping via airfoil elements is a different thing from just blunt streamlining.
BaltACD Current F1 aerodynamic nose design I suspect that what you have there is an adaptation of wing slots/slats to control downforce and shape airflow around the required suspension and steering elements. Doing active aerodynamic flow shaping via airfoil elements is a different thing from just blunt streamlining.
F1 aerodynamics have 3 purposes - maximize down force, minimize drag and create the most turbulent air possible behind the car.
Personally, I doubt UP's aero device is worth what it costs to construct it as well as the container space it occupies. I hope UP has factual data to support their position and it would be informative if they would make it public. To my mind the overall aerodynamics of a 10K to 20K foot intermodal train mitigate any benefits of a device at the lead of the train, since rarely are trains fully double stacked with 53 foot boxes so as to minimize the distance between boxes throughout the train.
Balt,
Maybe it has more value as a P/R stunt for UP with the "huggers" of the world.
Is that Quantum Physics ?
Y6bs evergreen in my mind
BaltACD F1 aerodynamics have 3 purposes - maximize down force, minimize drag and create the most turbulent air possible behind the car.
Thanks to Chris / CopCarSS for my avatar.
Murphy Siding BaltACD F1 aerodynamics have 3 purposes - maximize down force, minimize drag and create the most turbulent air possible behind the car. Create turbulent air behind the car? Is that to mess with the guy racing behind?
Create turbulent air behind the car? Is that to mess with the guy racing behind?
You've got it. Make the area behind the car so turbulent that the front wing of the following car loses its effective downforce. Keeping a following car far enough back that an effective overtaking manouver cannot be mounted.
F1 rules makers to combat this have implemented DRS (Drag Reduction System) where an element of the rear wing can be opened, reducing drag from the rear wing, and permitting a following car to attain a 10 to 12 MPH faster speed on the segment of track where DRS is implemented. The following car must be within 1 second of the lead car at specified detection points for DRS to be activated on specific straights. This applies to all cars in the field and their relation to each other. The lead car cannot open that rear wing segment, while those within 1 second of the preceeding car can.
BaltACD RME BaltACD Current F1 aerodynamic nose design I suspect that what you have there is an adaptation of wing slots/slats to control downforce and shape airflow around the required suspension and steering elements. Doing active aerodynamic flow shaping via airfoil elements is a different thing from just blunt streamlining. F1 aerodynamics have 3 purposes - maximize down force, minimize drag and create the most turbulent air possible behind the car. Personally, I doubt UP's aero device is worth what it costs to construct it as well as the container space it occupies. I hope UP has factual data to support their position and it would be informative if they would make it public. To my mind the overall aerodynamics of a 10K to 20K foot intermodal train mitigate any benefits of a device at the lead of the train, since rarely are trains fully double stacked with 53 foot boxes so as to minimize the distance between boxes throughout the train.
This purely a personal observation; and a question. The conversations in this Thread all seems to revolve around various components of 'drag' as relates to container stacker trains, and racing cars.
The one thing that seems to be missing is how all this will effect the economies of a stacker train as it goes across the railroad. What kind of transit speed will a stack train have to maintain to gain the economies of a 'streamlining system' acroos the railroad?
No one seems to have mentioned the speed element in the effectiveness of attempting to 'streamline' (?) the profile of a stacker, or would one have to put an Arrowedge device in eack singled container stack position?
I have been watching some of the stackers around here (both East and Westbounds. The faster ones seem to be at track speed of about 45 to 50 mph(at my guess). I am just guessing, No benefits at thoise speeds, but at what speed would the railroad get a positive return for the efforts and expenses of 'streamling the air flow, on the trains. I would think that the train would have to maintain a speed in excess of 50 mph for quite a distance to make the effort pay back to the railroad?
The distance between container stacks on a solid move of domestic 53' containers seems to be something less than 10' (?). While a solid stacker of export cans (mixes of 40' and 45'ers) looks to be closer to 15 '+ between the stacks(?)
[I have not measured those distances, but I think my guesses are fairly close?]
I would tend to agree with other Posters that say the UP's 'Arrowedge' device may provide interesting data; If, they do not test another bridge( height over track) with another one. The expenses whole project seems to be one, to garner some 'feel good' publicity, while getting their photo published; the whole effort aimed at making someone 'feel good' while making a show at being 'green'? .
For aerodynamics, it isn't just the train speed. It may only be doing 40mph but if facing a 30mph headwind across the plains the effective wind force is 70mph. But am among the skeptics as far as the arrowwedge is concerned.
As another thought some containers (perhaps older ones?) have corrugated sides instead of smooth. They probably add a tiny bit of turbulence and wind resistance to the train. Of course, like the wedge, the difference is most likely almost immeasurable.
John
Proof would be comparative fuel use on equivalent trains over the same route; one with the Arrowedge and one without.
My gut feeling is that fuel used differences would not be statistically signifigant and probably not repeatable.
"Tweaking" the C-17
http://www.aerotechnews.com/blog/2016/04/01/c-17-drag-reduction-testing-aims-at-saving-fuel/
Public relations is of some importance but is UP likely to spend its resources, etc. on a "feel good" exercise with little hope of improved efficiency and some savings?
C&NW, CA&E, MILW, CGW and IC fan
cx500 For aerodynamics, it isn't just the train speed. It may only be doing 40mph but if facing a 30mph headwind across the plains the effective wind force is 70mph. But am among the skeptics as far as the arrowwedge is concerned. As another thought some containers (perhaps older ones?) have corrugated sides instead of smooth. They probably add a tiny bit of turbulence and wind resistance to the train. Of course, like the wedge, the difference is most likely almost immeasurable. John
Not sure what all the expermental 'evolutions' UPRR went through to achieve the building of the Arrowsedge for real world testing?
About the time the new ROW was opened in Abo Canyon, the website "friends of bnsf.com" had some photos of the installation of anemometers on some engines, to run tests; but the photos had no further explanations of 'the why' or ' the what' they were looking for? It seemed sort of unusual to see locomotive mounted Anemometers, at the time.
schlimm Public relations is of some importance but is UP likely to spend its resources, etc. on a "feel good" exercise with little hope of improved efficiency and some savings?
Jeff
http://www.up.com/aboutup/community/inside_track/arrowedge-redesign-04-27-2016.htm
this is the pet project of a proven innovator at UP (he claims to have developed --with NRE -- the gen set for example). Look for continued tinkering till his funds run out.
Wind resistance is a function of velocity squared so at 20 mph is is four time that at 10 mph and it gets worse the faster the vehicle is moving.
jtm
Met one last night and it seemed like the next platform behind the wedge was a single container, then a few double stacks. Behind them were a short mix of double and singles, then the remainder of the train were doubles.
The other day it was windy and I had an empty coal hopper train. Speed would pick up about 5 mph when going through towns or other areas where trees and vegetation would block the wind. Once back out in the open going by farm fields, speed would drop off about 5 mph. Not unusual during periods when the winds are blowing hard.
jeffhergertMet one last night and it seemed like the next platform behind the wedge was a single container, then a few double stacks. Behind them were a short mix of double and singles, then the remainder of the train were doubles. The other day it was windy and I had an empty coal hopper train. Speed would pick up about 5 mph when going through towns or other areas where trees and vegetation would block the wind. Once back out in the open going by farm fields, speed would drop off about 5 mph. Not unusual during periods when the winds are blowing hard. Jeff
Can understand wind resistance with empty hoppers - any noticable wind resistance with a loaded coal train?
BaltACD jeffhergert Met one last night and it seemed like the next platform behind the wedge was a single container, then a few double stacks. Behind them were a short mix of double and singles, then the remainder of the train were doubles. The other day it was windy and I had an empty coal hopper train. Speed would pick up about 5 mph when going through towns or other areas where trees and vegetation would block the wind. Once back out in the open going by farm fields, speed would drop off about 5 mph. Not unusual during periods when the winds are blowing hard. Jeff Can understand wind resistance with empty hoppers - any noticable wind resistance with a loaded coal train?
jeffhergert Met one last night and it seemed like the next platform behind the wedge was a single container, then a few double stacks. Behind them were a short mix of double and singles, then the remainder of the train were doubles. The other day it was windy and I had an empty coal hopper train. Speed would pick up about 5 mph when going through towns or other areas where trees and vegetation would block the wind. Once back out in the open going by farm fields, speed would drop off about 5 mph. Not unusual during periods when the winds are blowing hard. Jeff
There was some work in the late 80s with air foils on the ends and cross braces of hopper cars after it was noticed that it took more fuel to get the empty train back to the PRB than to get the loaded one out of there. Much of the work was done by BN, some in a wind tunnel in Georgia (Lockhead?) under the direction of Steve Ditmeyer. He then turned his attention to Aries and Rockwell.
From my personal experance from a number of years ago ridiing a boxcar with the doors open tends to shake the boxcar at certain speeds
CandOforprogress2 From my personal experance from a number of years ago ridiing a boxcar with the doors open tends to shake the boxcar at certain speeds
Back in the boxcar era, I recall there was a short-lived effort by one of the Class-1s (I forget which) to close boxcar doors in order to lower wind resistance.
John Timm
desertdog CandOforprogress2 From my personal experance from a number of years ago ridiing a boxcar with the doors open tends to shake the boxcar at certain speeds Back in the boxcar era, I recall there was a short-lived effort by one of the Class-1s (I forget which) to close boxcar doors in order to lower wind resistance. John Timm
Rules on CSX, for the past several decades have required car doors to be closed. Not because of wind resistance but because of safety issues that a falling door can present.
https://www.youtube.com/watch?v=OPNmJ23WhsI
It is stupid as quoted. Missed a container right after Arrowedge. It does NOT help in any Wind Resistance Reduction, but add another more frontal impact resistance and trail-side Vacuum/Wake resistances..
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