Micro-Riblet Film

[IMAMONKEY!]

Hey guys it's been a while since I've last posted here. I was wondering If anyone has heard of Micro-riblet film or its applications?

 

I was doing research for my High School Engineering Class and I came upon this idea while searching for a way to make our project more aerodynamically efficient. The idea is that a slightly grooved surface creates a smoother airflow than a flat surface. I have heard of V-grooves and U-grooves and bar grooves...

 

It's slightly sparse. The information on the Internet is limited and I can't find much.

 

Groovy,

 

IMAMONKEY!

[Turtle]

Hey guys it's been a while since I've last posted here. I was wondering If anyone has heard of Micro-riblet film or its applications?

 

I was doing research for my High School Engineering Class and I came upon this idea while searching for a way to make our project more aerodynamically efficient. The idea is that a slightly grooved surface creates a smoother airflow than a flat surface. I have heard of V-grooves and U-grooves and bar grooves...

 

It's slightly sparse. The information on the Internet is limited and I can't find much.

 

Groovy,

 

IMAMONKEY!

 

The term you might try searching is 'laminar flow'. I'm still looking for a good link on the grooves, but I have an anecdote.

 

I did a stint taking care of some kids for a week and during that time I helped them build those little cars that Scouts race. On mine, I covered the surface with small parallel grooves running the length of the body. In the adult competition my car came in second to a Scout leader who had cheated and used oil on the axles. :D As I understand it, the grooves break up turbulence and so reduce drag.

 

Good luck. ;)

 

PS Here's the best I've found for a link; it references the grooves skin of sharks. Note that at high speeds, the effect disappears.

Turbulent flow in tubes with and without longitudinal grooves is examined. The discovery of fine grooves forming a sort of streamline pattern on the body of sharks led to the expectation that the grooves on a surface reduce the momentum change, and thus the drag. To test this thesis, drag law, velocity profile and the profile of the velocity fluctuation were determined. Results show that for moderate Reynolds numbers the drag coefficient for grooved tubes is about 3 percent smaller than that of the smooth tubes. At higher Reynolds numbers, however, the drag coefficient for grooved tubes becomes larger than that for smooth tubes. No significant differences in the velocity profiles between grooved tubes and smooth tubes are found.

Experimental investigation of turbulent flow in smooth and longitudinal grooved

 

I'm not familiar with 'Reynolds numbers', but it is mentioned as a limiting factor so here's a Wicki on the topic. >> Reynolds number - Wikipedia, the free encyclopedia

[IMAMONKEY!]

I looked at Reynolds number and it said that turbulent flow occurs at a higher number which means (according to the formula) the faster you go the less effect it has. B)

 

I need to figure out that equation because it gave me some VERY important numbers, namely 2100- is laminar which is what I want... and 2300+ is turbulent which im trying to avoid.

 

Now when u said parallel grooves do u mean like this?:

 

front

____

____

____

back

 

or like this:

front

| | |

| | |

| | |

back

 

basically did your lines run front to back or side to side? Because I believe how these grooves work is they create minute low pressure eddies on the surface allowing smooth laminar flow by disrupting the transition point and setting it back a good 10 or 12% behind the original.

 

Which means obviously you are going to get a 10-12% decrease in drag. :D

 

Which in a milage contest is quite significant. ;)

 

Good night,

 

IMAMONKEY!

 

:headdesk:

[Turtle]

I looked at Reynolds number and it said that turbulent flow occurs at a higher number which means (according to the formula) the faster you go the less effect it has. :)

 

I need to figure out that equation because it gave me some VERY important numbers, namely 2100- is laminar which is what I want... and 2300+ is turbulent which im trying to avoid.

 

Now when u said parallel grooves do u mean like this?:

 

front

| | |

| | |

| | |

back

basically did your lines run front to back or side to side? Because I believe how these grooves work is they create minute low pressure eddies on the surface allowing smooth laminar flow by disrupting the transition point and setting it back a good 10 or 12% behind the original.

 

Which means obviously you are going to get a 10-12% decrease in drag. B)

 

Which in a milage contest is quite significant. :D

Good night,

IMAMONKEY!

:headdesk:

 

I can't help you with any formulae; my bad. :(

 

I boldened the arrangement of grooves that I used. The link I quoted put the gain at only 3%, but even that is nothing to sneeze at. Good luck & good night! ;)

[IMAMONKEY!]

Wait so you made longitudinal riblets?

 

Because The theory supports latitudinal riblets. Although I'll bet the reason longitudinal worked on your car was because It straightened airflow which meant you car would go straight down with less wobble (hence u went faster didnt ya:D?)

 

Idk. I contacted the company that produced MRF but they are still in a research/developmental stage with it. So I can't acquire any from them... that and "We don't sponsor schools that are not in our area." :hyper:

 

It's 3M for god's sake... They should be in every freaking area of the U.S.

 

But yeah. I'm thinking about trying to produce my own version of MRF, but it would help if i knew how it was produced.

 

Ugh so many things to accomplish and only 7/8 of a school year to do them all! GAH!

[Turtle]

Wait so you made longitudinal riblets?

Yes; parallel grooves running front to back.

...

But yeah. I'm thinking about trying to produce my own version of MRF, but it would help if i knew how it was produced. :hyper:

 

Ugh so many things to accomplish and only 7/8 of a school year to do them all! GAH!

 

Beginning about post #15 in this thread, http://hypography.com/forums/science-projects-homework/2103-fairy-fountain-complete-internal-reflection-2.html?highlight=laminar+flow , I describe some of my experiments with laminar flow in fluid. There are also some links in there to more information on the topic. All we have is time. :turtle:

[IMAMONKEY!]

I just wish there was more information available on this subject. Unlike almost everything else I discover (in life) this topic seems relatively new. Which is surprising because I'm one of those people that is always behind the times.:note:

 

So far I think I can break this down into 4 search queries:

 

1. Laminar/Turbulent Flow

2. Micro-Riblets

3. Aerodynamic "gloves"

4. Fluid Flow Control

 

All 4 of which I have googled, dogpiled, allthewebbed, askjeevesed, and Hypographyed and found Diddly/Squat.

 

I found one article and I'm going to contact the Military Division that ran this project and see if they would be willing to release some classified Military information to a random anonymous 16 year old boy from hick-town Indiana.

 

:lol::hyper::lol::hyper: haha... yeah right... Maybe they'll help me though.

 

Who knows. Here's the link to it. I got this from one of Buffy's posts:

 

NASA - NASA Dryden Fact Sheet - F-16XL Laminar Flow

 

Gah how I love hidden information... :headdesk:

[Turtle]

Hey guys it's been a while since I've last posted here. I was wondering If anyone has heard of Micro-riblet film or its applications?

 

I was doing research for my High School Engineering Class and I came upon this idea while searching for a way to make our project more aerodynamically efficient. The idea is that a slightly grooved surface creates a smoother airflow than a flat surface. I have heard of V-grooves and U-grooves and bar grooves...

 

It's slightly sparse. The information on the Internet is limited and I can't find much.

 

Groovy,

 

IMAMONKEY!

 

Going back to this initial post, I'm curious about the exact nature of your project. What are you making? Where exactly did you encounter the term 'micro-riblet'?

 

I found one article and I'm going to contact the Military Division that ran this project and see if they would be willing to release some classified Military information to a random anonymous 16 year old boy from hick-town Indiana.

 

haha... yeah right... Maybe they'll help me though.

 

Who knows. Here's the link to it. I got this from one of Buffy's posts:

NASA - NASA Dryden Fact Sheet - F-16XL Laminar Flow

 

From the article I see no mention of grooving or ribbing as a passive approach to reducing turbulence. The active system using arrays of tiny holes using suction brought to mind the dimples on golf balls, which also serve to reduce turbulence. You might also look into Nike's work making 'shark suits' for swimmers. Keep us posted! :eek2:

[TheBigDog]

No links, but some history. I first heard of riplets, or riblets, in the early eighties. They are a natural part of the skin of sharks, and other fish. The first engineering application of them that I heard of was on the drop tanks used on fighter jets, as they reduced the drag by about 10% increasing fuel efficiency.

 

The next place I saw them in action was a place I actually predicted. During the America's Cup races, the first ones in Australia, the US boat used laminates of riblet material to decrease the drag of the boat. I had mentioned to my dad that I though it would be a good idea, and why didn't they do it. The next night they showed the crew applying the square laminates to the hull and explained what they did to improve surface flow. I never felt more like a genius.

 

Bill

[IMAMONKEY!]

Going back to this initial post, I'm curious about the exact nature of your project. What are you making? Where exactly did you encounter the term 'micro-riblet'?

 

 

 

From the article I see no mention of grooving or ribbing as a passive approach to reducing turbulence. The active system using arrays of tiny holes using suction brought to mind the dimples on golf balls, which also serve to reduce turbulence. You might also look into Nike's work making 'shark suits' for swimmers. Keep us posted! :hihi:

 

The project is a High School Engineering Tech. Class project. We are trying to design a super-efficient one person car. I encountered the term Micro-Riblet Film after I found out 3M was testing such a product.

 

And I could've sworn the article mentioned passive Aerodynamics through grooves. Ah well. In any case the tiny suction holes is not a bad idea considering active may be more effective than passive.

 

And I've never heard of those shark suits. I'll have to look into that.

 

...and TBG, do you know where I could aquire such a material as the boat laminates? :hihi:

[TheBigDog]

The project is a High School Engineering Tech. Class project. We are trying to design a super-efficient one person car. I encountered the term Micro-Riblet Film after I found out 3M was testing such a product.

 

And I could've sworn the article mentioned passive Aerodynamics through grooves. Ah well. In any case the tiny suction holes is not a bad idea considering active may be more effective than passive.

 

And I've never heard of those shark suits. I'll have to look into that.

 

...and TBG, do you know where I could aquire such a material as the boat laminates? :shrug:

I have no idea. :eek_big: Sorry.

 

Bill

[DougF]

I found these links for you, they may hold some of your answers. :hihi: :D

 

Laminar flow' date=' without viscosity, is governed by Bernoulli's principle: the sum of the static and dynamic pressures in a fluid remains the same. A fluid at rest in a pipe exerts static pressure on the walls. If the fluid now starts moving, some of the static pressure is converted to dynamic pressure, which is proportional to the square of the speed of the fluid. The faster a fluid moves, the greater its dynamic pressure and the smaller the static pressure it exerts on the sides.

 

Bernoulli's principle works very well far from the surface. Near the surface, however, the effects of viscosity must be considered since the air tends to stick to the surface, slowing down the flow nearby. Thus, a boundary layer of slow-moving air is formed on the surface of an airplane or automobile. This boundary layer is laminar at the beginning of the flow, but it gets thicker as the air moves along the surface and becomes turbulent after a point.

Aerodynamics - Skin Friction And Pressure Drag, Airfoil, Supersonic Flight - Basic air flow principles

 

 

I Think you will like this link also, it may hold the answers you seek! :hihi:

Scientists have been speculating for many years whether there is any surface having less drag of a flat plate. The drag of a flat plate is reported in the figure below' date=' for both laminar (Blasius) and turbulent flow. [/quote']

See link below for described figure.

Experimental studies in the 1970s showed that small grooves (riblets) aligned with the flow had the property of modifying the near-wall structure of the boundary layer. In particular' date=' the riblets proved to work as a constraint to the production of the Reyonlds stresses associated with the growth and eruption of the eddies in the the low-speed regions of the boundary layers.

[/quote']

See link below for described figure.

 

Later research was aimed at investigating the properties of such grooves' date=' by studying the wall boundary conditions and the flow properties at corner regions.

 

A number of studies of zoologic nature was added to the fluid dynamic problem, by studying the characteristics of fast-swimming sharks and dolphins, from where some ideas were derived.

 

On of the main practical concerns was (and it is) the amount of drag reduction that can be achieved, and studies were directed to investigating the optimum ratio fin-height/riblet spacing, physical dimensions of the riblets, along with the optimum shape (L- U- V-grooves and others, Fig. 2 above).

 

Drag Reduction

The skin friction drag reduction data published in the technical literature is variable, but converging to a figure of 8 %, with more conservative values of 5 % to the most optimistic figures of 10-11 %, obtained in laboratory conditions. While these numbers do not seem excessively high, they do lead to enourmous savings.

 

Take for example a subsonic jet transport, for which the skin friction drag is of the order of 45 % at cruise conditions. If half of the surface could be covered by efficient riblets that provide an 8 % skin friction saving, the total saving would be just less than 4 %, a remarkable amount. [/quote']

 

Surface Riblets for Aerodynamic Drag Reduction

 

 

I hope this is helps you out some. :lol: :cup: