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JC August 2, 2001 11:01

I'm modelling the flow around tyres but I'd like to know how the direction of the rotational speed is defined around the rotation axis (clockwise, anticlockwise) ?



Tae Sang Park August 2, 2001 19:54

Re: Tyres
anticlockwise !

John C. Chien August 2, 2001 23:17

Re: Tyres
(1). There is counterclockwise, clockwise, but there is no "anticlockwise". (2). It is defined by the coordinates system, which is normally based on the right-hand rule. (3). The exception is, computer graphics field sometimes uses left-hand rule, with the positive z-axis pointing into the computer screen.

Jeremy August 6, 2001 04:30

Re: Tyres, John C Chien is wrong, please apologise
There is an anticlockwise, I just looked it up:

Main Entry: an·ti·clock·wise
Pronunciation: "an-ti-'kläk-"wIz, "an-"tI-
Function: adjective or adverb
Date: 1898
chiefly British : COUNTERCLOCKWISE

so you are wrong, please apologise to the world for spouting forth without basis or knowledge.

John C. Chien August 6, 2001 11:33

Re: Tyres, John C Chien is wrong, please apologise
(1). Perhaps "Counter-anti-clockwise" is "clockwise"? (2). From my side, I see only the computer monitor screen and my dictionary. (3). "Could you show me a technical text book which uses anti-clockwise?"

Jeremy August 7, 2001 03:06

Re: Tyres, John C Chien is wrong, please apologise
[/b]You are so blinkered! In you reply you say:

From my side, I see only the computer monitor screen and my dictionary.

Let's analyse this:
  1. My computer finds thousands of hits for anticlockwise so we assume that even if you see the screen you ignore it.
  2. I find a dictionary definition but you don't, we have to assume your dictionary is useless

We therefore have proof positive that you have two external reference sources both of which have no value, so we assume that the world according to John C Chien is the world of John C Chien, not the real world in which we all work.
Could you please do us all a favour and creep back into your box and stay there.

John C. Chien August 7, 2001 03:23

Re: Tyres, John C Chien is wrong, please apologise
(1). You are free to try, if your keyboard has a button you can press to make me disappear. (2). My world on Internet is "always not real". It is part of my brain exercise I have stated many times already. (3). If anti-clockwise is not in my dictionary or my brain, it is not there. My comment is always my personal experience. And you don't have to accept it at all.

John C. Chien August 7, 2001 04:06

Re: Tyres, John C Chien is wrong, please apologise
(1). The Harcourt Brace School Dictionary, 1968 edition, supervisory board: Chairman Albert H. Marckwardt, Professor of English and Linguistics, Princeton University. The dictionary does not have the word "anticlockwise" in it. It does have the word "counterclockwise" on page 163, it says In the opposite direction from that in which the hands of a clock turn. (2). A New English-Chinese Dictionary, 1975. It does not have the word "anticlockwise", but it has the word "counterclockwise" on page 278. (3). It seem to me that "anticlockwise" is currently not being used in US and Far-east. (4). And I have not seen it used in my life time in the engineering field. (based on the books published in US.) (5). I can only guess that it was and is being used in the old British Empire(?).

Mark Richardson August 7, 2001 07:14

Re: Tyres, John C Chien is wrong, please apologise
Very amusing gentlemen, now please calm down. Anti-clockwise is the english equivalent of counter clockwise and is in current regular usage. Whenever I hear the word counter-clockwise I always assume the user has an american education.

Perhaps we are a little old fashioned over here but we do accomodate variations in our language. many words that I use have an american variation: e.g. UK version --> American "english" colour --> color vapour --> vapor aluminium --> aluminum pavement --> sidewalk anti-clockwise --> counterclockwise

This is often troublesome when searching bibliography on publication sites.


Jeremy August 7, 2001 10:06

Re: Tyres, John C Chien is wrong, please apologise
Hey, and I thought the ball was just rolling nicely. Lets summarise:[*]A question is asked[*]Tae Sang Park answers correctly[*]John C Chien answers better (it rotates in a positive sense using the right handed rule) but cannot resist a cheap flame at the guy[*]I ask that he retracts the flame[*]John starts to squirm but cracks have begun[*]A movement starts ... lets keep it up All in good spirit John

John C. Chien August 7, 2001 13:43

Re: Tyres, John C Chien is wrong, please apologise
(1). I must say that I know very little about the British English. (2). The American English seems to make more sense in this silly "anti-clockwise" issue. (3). My personal feeling is: "anti-" is "against", "to stop", or to "destroy", like "anti-biotic", "anti-tank gun", "anti-trust", etc. (4). On the other hand, "counter-" is "to reverse the direction of movement, or process", "to overcome". It has a clear change of direction. (5). With this personal understanding, "anti-clockwise" will be interpreted as " against clockwise movement", "to stop the clockwise motion", or "to destroy the clockwise motion". It does not have the clear indication of "reverse in direction". (6). But I guess, language is part of culture, and there is nothing wrong about using a particular word. (7). There could be a problem, say in case of emergency with a fire in the building, where you are trying to save a person by telling him to go in the "counterclockwise" direction to escape from the burning building. Instead, you say "anticlockwise", and it is likely that he will stop moving in the clockwise direction and take the hall way normal to it. (8). Anyway, It is interesting to know that "anticlockwise" is not in the American English dictionary. Perhaps, it is the consequence of the great American revolution? Would you say "anti-revolution" is the same as "counter-revolution"? (By the way, it is not a CFD question.)

stephen davis August 7, 2001 15:26

Re: Tyres, John C Chien is wrong, please apologise

Old Chinese saying goes:

"Before you criticize someone, walk a mile in his shoes. Then when you do criticize that person, you'll be a mile away and have his shoes!"

John C. Chien August 7, 2001 17:51

Re: Tyres, John C Chien is wrong, please apologise
(1). As a matter of fact, I have never heard of it before. (2). Perhaps, I have never been to China before. (3). Anyway, it is hard to criticize a person on Internet. You are basically writing to yourself on the screen, and then press a button. And hoping that it will reach the person. And you are waiting for his answer. (that's part of the definition of love)(4). You will have to know the person before you can criticize the person. And if you do criticize the person, "YOU ARE HIS FRIEND". signed by John C. Chien. (5). Your enemy does not criticize you, he just wipe you out without telling you.

Stephen Davis August 8, 2001 11:47

Re: Tyres, John C Chien is wrong, please apologise

Work on your grammar.


John C. Chien August 8, 2001 13:04

Re: Tyres, John C Chien is wrong, please apologise
(1). Good suggestion! The grammar of which language? (2). It is possible that the grammar of a language is the key to the success of CFD. Has anybody done any research in this area? (3). The failure of a Martian Probe was linked to the different languages (between the metric system and the English system) used in the software. (4). Do you think we need to study grammar more to attract more CFD readers? any suggestion? Even if I say "ME NO ENGLISH", I think, people will still come here and talk about CFD. (5). The CFD forum is basically "YOUR BRAIN ACTIVITIES" (not mine) The interaction is "BY ACCIDENT".

John C. Chien August 8, 2001 14:21

A sunny day in a flea market
(1). I have been busy collecting small toy characters at the weekend flea market for my 3-D OPenGL model project. (2). At one spot, a lady said something. Then the guy in front of me asked "What is she saying?". And I didn't open my mouth. The other gentlemen looked at me waiting for answer. No one understood the lady. She walked away. (3). I saw a Rolex watch in a glass case. I looked at it for a while, and the guy said if you like it I will give it to you for fifty dollars. He quickly changed his mind and said forty dollars cash. I asked "Is it real". He answered,"No". I saw another similar Rolex watch selling at the same price. (4). Most items were selling at one dollar. It's cheaper after three pm. That's the time they were leaving. I collected several toy characters for a total of dollar and a half. (5). In the flea market, people speak different languages among themselves. But they rarely speak to you. They don't have to invest in the time speaking to you, when most items are selling at one dollar a piece. (6). In a sunny day, it is a good exercise to walk in a flea market. It is a place where you are the outsider, and it is a place where language is useless. Even though they are speaking different languages. (7). In a crowded flea market in a sunny Sunday, they were very happy, because they can forget about their languages.

Lanre August 8, 2001 15:26

Re: Tyres
Having worked in the US and Canada with an early educational background in a former British colony (in addition to being an avid Scrabble player), switching between the many variants of the English languange is quite normal. At this juncture, I conclude my deviation into the discussion on language.

Back to the direction of rotation...Using the righthand rule (clench your fist and stick your thumb out): the thumb points along the axis of rotation while the fingers represents the direction of angular motion. If you are modelling the right, front tire, and the vehicle is rolling forward, and the axis of rotation starts, say, at the hubcap and ends at the engine, the direction of rotation would be positive, or clockwise.

stephen davis August 8, 2001 16:27

Re: A sunny day in a flea market
Hey John,

What does "Gargle the Nuts mean" mean to you?

John C. Chien August 8, 2001 16:37

Re: A sunny day in a flea market
(1). I must say that it is "solid/liquid multi-phase flows". Trying to keep the answer consistent with the forum. (2). Anything fluid dynamics is fine here.

An Modh Coinniolach August 10, 2001 11:37

Re: Tyres, John C Chien is wrong, please apologise
I say use "anti-" to show off the old Greek, like Tennyson and his "Lotos" Eaters, Latin being such a pedestrian language by comparison.

De mortuis nil nisi bonum, my eye!

And for CFD relevance:

De Nihilo Nihil Fit

The Consise Oxford English Dictionnary:

anti- prefix. 1. against; opposing: anticlerical; antisocial. 2. opposite to: anticlimax; antimere. 3. rival; false: antipope. 4. counteracting, inhibiting, or neutralising: antifreeze; antihistamine. [from Greek anti]

anticlockwise adv., adj. in the opposite direction to the rotation of the hands of a clock. U.S. equivalent: counterclockwise.

counterclockwise or contraclockwise adv., adj. the U.S. and Canadian equivalent of anticlockwise.

counter- prefix. 1. against; opposite; contrary: counterattack. 2. complementary; corresponding: counterfoil. 3. duplicate or subsitiute: counterfeit. [via Norman French from Latin contra against, opposite; see CONTRA-]

contra- prefix 1. against; contrary; opposing; contrasting: contraceptive; contradistinction. 2.(in music) pitched below: contrabass. [from Latin, from contra against]

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