Wrong, spin will push the ball the same direction whether smooth or dimpled.
The dimples increase turbulence in the boundary layer adjacent to the balls surface,
allowing higher speed air to mix in, and therefore helping the air to follow the contour
of the ball farther around to the back, so adding pressure to the backside.
More pressure in the back, that is less difference in pressure between front and back,
that is less drag.
You are correct that scale models do not always predict the full scale.
However, the Reynolds number is a measure of the ratio of momentum forces to viscous forces,
the size of the air molecules doesn't enter into it at all: the assumption is made that fluids are continuous.
There are ways around this, by using fluids with different densities and viscosities.
There are many scaling problems, nonetheless, in trying to get all forces and geometries to match the full scale.
In supersonic flow compressibility effects are most important, measured by the Mach number.
Many interesting problems occur near the surface, where the fluid is slowed by contact with the surface and
a lot of parameters interact in hard to predict ways.
It sounds like that those are the kinds of thing they will be investigating.
Just to disagree with one more thing: "I do not believe that there is anything at all in the entire universe that science could not explain given all the facts." Given all the facts, (which is a pretty outlandish assumption, considering the uncertainty principle, black holes, etc.) science still could not explain "all the facts". That is, the one thing that science does not even try to explain is existence. This is why as long as people have been intelligent and self-aware they have had a need for religion.
But I do know what UL is, and it is a testing agency, Not a regulatory body. And in many instances, even if the consumer doesn't know what UL is, they still can't buy an item that isn't listed or labeled by UL, CSA, ASME, ASTM or one of the other standards or testing bodies. I work in the construction industry and I know for sure that in Chicago you can't install lighting, and many other items or equipment, that isn't UL listed. This is not because UL has any regulatory power, but because the local codes and government regulations require certain items to obtain listing to ensure that they are safe.
Strictly speaking, those two issues from the arctilce are not bugs. I believe OO.org would call reports on them an enhancement request and a feature request, respectively.
I just inserted a note into a cell in Calc (OOo 2 beta, running on a fedora core 3 laptop) and it DID wrap the text and it DID show spaces typed at the end of the line. In Writer, the notes are, for some reason, handled differently and show up in a text input form without automatic word wrap, however it does preserve the spaces typed at the end of the line.
I also find that a when typing a line, a lot of word processors, including MS Word in some situations at least, truncate the spaces off at the end of sentences or in front of returns/line feeds. This irritates me more than the way Writer prevents you from typing spaces that would wrap to the next line. I guess these are (dumb) features, not a bugs.
I would be much more impressed if they just published their file formats and opened them up for interoperability. As it is, in an attempt to force upgrades, they no longer support saving to their own file formats when those formats are more than a few years old. And they change the formats almost every year. And they've even started adding weak encryption in places for no reason other than to make the format harder to reverse engineer.
I don't know for sure any details about a deal, but there is the appearance of a quid pro quo. Apparently at the time Microsoft bought Visio, Visio owned Intellicad (basically an AutoCAD clone), a product directly competing with Autodesk. Visio promptly spun off the product and Microsoft did not compete with Autodesk.
Couple of points: I read the article, and it is not talking about mandating waterless urinals, it is about allowing them. Also, this is about the Uniform Plumbing Code, which is historically reticent to allow anything that will be easier to install or use less materials. Most of the other codes already allow waterless urinals. The Uniform, Standard(Southern), and BOCA model codes have recently been merged into a single model code - the International Codes. Most of the country follows the International codes (with notable exceptions of some jurisdictions that have historically had their own codes). Part of the Uniform code split off and refused to join. I work for a consulting engineer, and we have used these in a couple of instances where it was important to be "green". There is a growing trend to have buildings certified as green, see www.usgbc.org for info on LEED ratings. Without that kind of incentive, most engineers and contractors will not try anything new. Never heard any complaints about the installations, but never designed any others. I have pissed in some waterless urinals in my travels, and didn't find any problems. However there are concerns without flushing about lack of carry thru the pipes and the corrosivity of undiluted urine in metal piping.
Waterless urinals save construction costs. The reason they're not used is that they're relatively new in the market, and the construction industry is very conservative about spec'ing things without a long history of success, or a code mandate. New technology only gets adopted very slowly because it is much easier and faster to do what you already know how to do. Also, the estimated savings of most innovations is trivial compared to the percieved potential costs of demolition and reconstruction if something doesn't work.
Many hot water systems are not set at a high enough temperature to kill Legionella, especially the temperature at a shower head. You need to keep the temperature above 160F(70+C) for a some minutes in order to kill most bacteria, including Legionella. If I recall correctly, 140F(60C) can kill Legionella if kept over a long period of time. Many water heaters in the US are set at 140F by default, but this has been changing because of scalding problems. From the quoted article: "The optimum growth temperature range for this bacteria is 20-45 degrees Celsius." The high side of this optimum range is right around the 110F to 115F maximum temperature mandated by many codes to prevent scalding. Without expensive, high maintenance thermostatic mixing valves, you would need to maintain the tank temperature below 120F(49C) to prevent scalding. Even with thermostatic mixing valves the shower head, where Legionella is most likely to be found, would never see high enough temperatures to kill the bacteria, whether storage tank or tankless. Chlorination, corrosion, biolfilms, etc. all have an impact too, so if you're susceptible or paranoid, clean your shower head regularly.
The trade deficit with China (US spending more buying goods from China than we make selling to them) is largely offset by selling US Treasury bonds to them. These bonds are the borrowing that I was referring to as enabling our consumption economy. They enable the government to increase spending while cutting taxes, stimulating our economy on both ends and encouraging consumers to spend. They are a real debt owed by the US that could cause our, and possibly their, economy big problems in the long run.
The only reason we can afford to spend so much and save so little is that we've borrowed trillions from our friends such as the People's Republic of China.
Seems like a recipe for short term gain and long term pain.
Phones are an essential aid in responding to needs of Healthcare, Natural Disasters, etc. Cell phone infrastructure is a lot cheaper than adding land lines in a developing country.
You recall almost correctly.
Per ASHRAE, for light office work an average adult puts out about 70 to 75 watts of sensible heat - radiation, cunduction, and convection. But they also put out about 60 watts of latent heat - due to the evaporation of water in sweat and breath. IIRC moderate exercise would put out about 200 watts of sensible heat and about 250 watts of latent heat.
Using smaller, cooler processors does not result in easier cooling problems. It results in packing more processors in each rack, keeping the cooling problem consistently near, but hopefully not over, the edge of disaster.
Energy contained in the air velocity is proportional to density times the velocity squared, known as the velocity pressure. Depending on how your changes in direction are being made, the pressure loss at each 90 deg turn can be anywhere between 0.1 times the velocity pressure to 3 or 4 times the velocity pressure. More important in an underfloor supply plenum than 90 deg turns is the effect of blockages from cables, etc.
What yuou need is an enforced corporate policy of removing all obsolete cables. I recently worked on changes and expansion to a server room, including phased relocation of many services to another building. Discovering which cables could be disconnected when was a huge headache, many of them were obsolete and just getting in the way.
In the expanded server room, which was a testing lab and so could be expected to undergo lots of changes, they ran underfloor data and power alternately in every other aisle. This seemed to work out OK.
We would expect power changes in any data center, and, in fact, in this case there were already several changes to the power requirements even before construction was completed.
Slashdot Mirror
It wasn't a proof. It was a simile.
Wrong, spin will push the ball the same direction whether smooth or dimpled. The dimples increase turbulence in the boundary layer adjacent to the balls surface, allowing higher speed air to mix in, and therefore helping the air to follow the contour of the ball farther around to the back, so adding pressure to the backside. More pressure in the back, that is less difference in pressure between front and back, that is less drag.
You are correct that scale models do not always predict the full scale. However, the Reynolds number is a measure of the ratio of momentum forces to viscous forces, the size of the air molecules doesn't enter into it at all: the assumption is made that fluids are continuous. There are ways around this, by using fluids with different densities and viscosities. There are many scaling problems, nonetheless, in trying to get all forces and geometries to match the full scale. In supersonic flow compressibility effects are most important, measured by the Mach number. Many interesting problems occur near the surface, where the fluid is slowed by contact with the surface and a lot of parameters interact in hard to predict ways. It sounds like that those are the kinds of thing they will be investigating.
So you're sayting that that fruit salad I ordered in place of soup is a vegetable?
Just to disagree with one more thing: "I do not believe that there is anything at all in the entire universe that science could not explain given all the facts."
Given all the facts, (which is a pretty outlandish assumption, considering the uncertainty principle, black holes, etc.) science still could not explain "all the facts". That is, the one thing that science does not even try to explain is existence. This is why as long as people have been intelligent and self-aware they have had a need for religion.
I agree with most of what you say.
But I do know what UL is, and it is a testing agency, Not a regulatory body. And in many instances, even if the consumer doesn't know what UL is, they still can't buy an item that isn't listed or labeled by UL, CSA, ASME, ASTM or one of the other standards or testing bodies. I work in the construction industry and I know for sure that in Chicago you can't install lighting, and many other items or equipment, that isn't UL listed. This is not because UL has any regulatory power, but because the local codes and government regulations require certain items to obtain listing to ensure that they are safe.
I give up.
How many?
Strictly speaking, those two issues from the arctilce are not bugs. I believe OO.org would call reports on them an enhancement request and a feature request, respectively.
I just inserted a note into a cell in Calc (OOo 2 beta, running on a fedora core 3 laptop) and it DID wrap the text and it DID show spaces typed at the end of the line. In Writer, the notes are, for some reason, handled differently and show up in a text input form without automatic word wrap, however it does preserve the spaces typed at the end of the line.
I also find that a when typing a line, a lot of word processors, including MS Word in some situations at least, truncate the spaces off at the end of sentences or in front of returns/line feeds. This irritates me more than the way Writer prevents you from typing spaces that would wrap to the next line. I guess these are (dumb) features, not a bugs.
The bugs seem to be in the article.
I would be much more impressed if they just published their file formats and opened them up for interoperability.
As it is, in an attempt to force upgrades, they no longer support saving to their own file formats when those formats are more than a few years old. And they change the formats almost every year. And they've even started adding weak encryption in places for no reason other than to make the format harder to reverse engineer.
I don't know for sure any details about a deal, but there is the appearance of a quid pro quo. Apparently at the time Microsoft bought Visio, Visio owned Intellicad (basically an AutoCAD clone), a product directly competing with Autodesk. Visio promptly spun off the product and Microsoft did not compete with Autodesk.
http://cadence.advanstar.com/newsletter/aec/1201_Couple of points:
I read the article, and it is not talking about mandating waterless urinals, it is about allowing them.
Also, this is about the Uniform Plumbing Code, which is historically reticent to allow anything that will be easier to install or use less materials. Most of the other codes already allow waterless urinals.
The Uniform, Standard(Southern), and BOCA model codes have recently been merged into a single model code - the International Codes. Most of the country follows the International codes (with notable exceptions of some jurisdictions that have historically had their own codes). Part of the Uniform code split off and refused to join.
I work for a consulting engineer, and we have used these in a couple of instances where it was important to be "green".
There is a growing trend to have buildings certified as green, see www.usgbc.org for info on LEED ratings. Without that kind of incentive, most engineers and contractors will not try anything new.
Never heard any complaints about the installations, but never designed any others. I have pissed in some waterless urinals in my travels, and didn't find any problems. However there are concerns without flushing about lack of carry thru the pipes and the corrosivity of undiluted urine in metal piping.
Waterless urinals save construction costs.
The reason they're not used is that they're relatively new in the market, and the construction industry is very conservative about spec'ing things without a long history of success, or a code mandate. New technology only gets adopted very slowly because it is much easier and faster to do what you already know how to do. Also, the estimated savings of most innovations is trivial compared to the percieved potential costs of demolition and reconstruction if something doesn't work.
Many hot water systems are not set at a high enough temperature to kill Legionella, especially the temperature at a shower head.
You need to keep the temperature above 160F(70+C) for a some minutes in order to kill most bacteria, including Legionella.
If I recall correctly, 140F(60C) can kill Legionella if kept over a long period of time. Many water heaters in the US are set at 140F by default, but this has been changing because of scalding problems.
From the quoted article: "The optimum growth temperature range for this bacteria is 20-45 degrees Celsius." The high side of this optimum range is right around the 110F to 115F maximum temperature mandated by many codes to prevent scalding.
Without expensive, high maintenance thermostatic mixing valves, you would need to maintain the tank temperature below 120F(49C) to prevent scalding. Even with thermostatic mixing valves the shower head, where Legionella is most likely to be found, would never see high enough temperatures to kill the bacteria, whether storage tank or tankless. Chlorination, corrosion, biolfilms, etc. all have an impact too, so if you're susceptible or paranoid, clean your shower head regularly.
How the hell is this patentable?
The trade deficit with China (US spending more buying goods from China than we make selling to them) is largely offset by selling US Treasury bonds to them. These bonds are the borrowing that I was referring to as enabling our consumption economy. They enable the government to increase spending while cutting taxes, stimulating our economy on both ends and encouraging consumers to spend. They are a real debt owed by the US that could cause our, and possibly their, economy big problems in the long run.
or more software used.
The only reason we can afford to spend so much and save so little is that we've borrowed trillions from our friends such as the People's Republic of China.
Seems like a recipe for short term gain and long term pain.
Phones are an essential aid in responding to needs of Healthcare, Natural Disasters, etc.
Cell phone infrastructure is a lot cheaper than adding land lines in a developing country.
won't work due to humidity problems (too much in summer, too little in winter)
You recall almost correctly. Per ASHRAE, for light office work an average adult puts out about 70 to 75 watts of sensible heat - radiation, cunduction, and convection. But they also put out about 60 watts of latent heat - due to the evaporation of water in sweat and breath. IIRC moderate exercise would put out about 200 watts of sensible heat and about 250 watts of latent heat.
Using smaller, cooler processors does not result in easier cooling problems. It results in packing more processors in each rack, keeping the cooling problem consistently near, but hopefully not over, the edge of disaster.
Some planning is in order for football field-sized datacenters.
Distribute your AC units throughout the space in the first place.
Energy contained in the air velocity is proportional to density times the velocity squared, known as the velocity pressure. Depending on how your changes in direction are being made, the pressure loss at each 90 deg turn can be anywhere between 0.1 times the velocity pressure to 3 or 4 times the velocity pressure. More important in an underfloor supply plenum than 90 deg turns is the effect of blockages from cables, etc.
Every turn creates eddies which dissipate energy, lowering the pressure available to push the air.
What yuou need is an enforced corporate policy of removing all obsolete cables. I recently worked on changes and expansion to a server room, including phased relocation of many services to another building. Discovering which cables could be disconnected when was a huge headache, many of them were obsolete and just getting in the way. In the expanded server room, which was a testing lab and so could be expected to undergo lots of changes, they ran underfloor data and power alternately in every other aisle. This seemed to work out OK. We would expect power changes in any data center, and, in fact, in this case there were already several changes to the power requirements even before construction was completed.