Angle two vectors.

May 12, 2004, 13:54

Good morning,

I am looking to calculate the angle between two 3D vectors in my CFD results. I can do this mathematically, but I don't know how to implement it in code for a general coordinate system. Has anyone any ideas were I can learn how to use standard CFD code to calculate such quantities??

May 13, 2004, 02:28

<html xmlns

="urn:schemas-microsoft-com

ffice

ffice" xmlns:w="urn:schemas-microsoft-com

ffice:word" xmlns="http://www.w3.org/TR/REC-html40">

<head> <meta http-equiv=Content-Type content="text/html; charset=windows-1255"> <meta name=ProgId content=Word.Document> <meta name=Generator content="Microsoft Word 10"> <meta name=Originator content="Microsoft Word 10"> <link rel=File-List href="dot_files/filelist.xml"> <title>This actually is just basic vector analysis</title>  <style>

</style>  </head>

<body lang=EN-US style='tab-interval:.5in'>

<div class=Section1>

<p class=MsoNormal>This actually is just basic vector analysis. The scalar product of two vectors, a and b <span class=GramE>is<span style='mso-spacerun:yes'>* </span>a</span> · b = |a| |b| <span class=SpellE>cos<span style='font-family:Symbol'>f , </span>from</span> which <span style='font-family:Symbol'>f</span> – the angle between a and b – may be solved.

<p class=MsoNormal><o

>*</o

>

<p class=MsoNormal><o

>*</o

>

</div>

</body>

</html>

May 13, 2004, 09:33

I know that, but how do I implement it numerically. How do I implement it numerically? How do I calculate that angle using code?

May 13, 2004, 10:15

Fortran implementation:

real a(3), b(3)

AdotA = a(1)*a(1) + a(2)*a(2) + a(3)*a(3)

BdotB = b(1)*b(1) + b(2)*b(2) + b(3)*b(3)

den = AdotA*BdotB

if(den .gt. 0.) then

AdotB = a(1)*b(1) + a(2)*b(2) + a(3)*b(3)

cosphi = AdotB / sqrt(den)

phi = acos(cosphi)

endif

May 16, 2004, 07:48

Thank you.

If I have two grid lines, which are not orthogonal, how can I find the angle between them? What term do I use to describe their direction? Also, how is this done in a general curvilinear coordinate system? How can I find the angle between a grid line and a velocity field for example.

May 19, 2004, 13:58

give me ur email i will drop u an email how to calculate what u need. (i understood that u want to use that in calculation for CFD, say for angle between the faces etc.)

May 20, 2004, 05:06

Hi zxaar,

This is my email account address as requested: cfd_user_uk@yahoo.co.uk

I would appreciate any help you can give me for this problem.

Thank you.

"give me ur email i will drop u an email how to calculate what u need. (i understood that u want to use that in calculation for CFD, say for angle between the faces etc.) "

May 12, 2004, 13:54	Angle two vectors.	#1
Guest Guest Posts: n/a	Good morning, I am looking to calculate the angle between two 3D vectors in my CFD results. I can do this mathematically, but I don't know how to implement it in code for a general coordinate system. Has anyone any ideas were I can learn how to use standard CFD code to calculate such quantities??

May 13, 2004, 02:28	Re: Angle two vectors.	#2
Rami Guest Posts: n/a	<html xmlns="urn:schemas-microsoft-comfficeffice" xmlns:w="urn:schemas-microsoft-comffice:word" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content="text/html; charset=windows-1255"> <meta name=ProgId content=Word.Document> <meta name=Generator content="Microsoft Word 10"> <meta name=Originator content="Microsoft Word 10"> <link rel=File-List href="dot_files/filelist.xml"> <title>This actually is just basic vector analysis</title> <!--[if gte mso 9]><xml> <w:WordDocument> <w:SpellingState>Clean</w:SpellingState> <w:GrammarState>Clean</w:GrammarState> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> <style> </style> <!--[if gte mso 10]> <style> /* Style Definitions / table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} </style> <![endif]--> </head> <body lang=EN-US style='tab-interval:.5in'> <div class=Section1> <p class=MsoNormal>This actually is just basic vector analysis. The scalar product of two vectors, a and b <span class=GramE>is<span style='mso-spacerun:yes'> </span>a</span> · b = \|a\| \|b\| <span class=SpellE>cos<span style='font-family:Symbol'>f , </span>from</span> which <span style='font-family:Symbol'>f</span> – the angle between a and b – may be solved. <p class=MsoNormal><o></o> <p class=MsoNormal><o></o> </div> </body> </html>

May 13, 2004, 09:33	Re: Angle two vectors.	#3
Guest Guest Posts: n/a	I know that, but how do I implement it numerically. How do I implement it numerically? How do I calculate that angle using code?

May 13, 2004, 10:15	Re: Angle two vectors.	#4
Rami Guest Posts: n/a	Fortran implementation: real a(3), b(3) AdotA = a(1)a(1) + a(2)a(2) + a(3)a(3) BdotB = b(1)b(1) + b(2)b(2) + b(3)b(3) den = AdotABdotB if(den .gt. 0.) then AdotB = a(1)b(1) + a(2)b(2) + a(3)b(3) cosphi = AdotB / sqrt(den) phi = acos(cosphi) endif

May 16, 2004, 07:48	Re: Angle two vectors.	#5
Guest Guest Posts: n/a	Thank you. If I have two grid lines, which are not orthogonal, how can I find the angle between them? What term do I use to describe their direction? Also, how is this done in a general curvilinear coordinate system? How can I find the angle between a grid line and a velocity field for example.

May 19, 2004, 13:58	Re: Angle two vectors.	#6
zxaar Guest Posts: n/a	give me ur email i will drop u an email how to calculate what u need. (i understood that u want to use that in calculation for CFD, say for angle between the faces etc.)

May 20, 2004, 05:06	Re: Angle two vectors.	#7
Guest Guest Posts: n/a	Hi zxaar, This is my email account address as requested: cfd_user_uk@yahoo.co.uk I would appreciate any help you can give me for this problem. Thank you. "give me ur email i will drop u an email how to calculate what u need. (i understood that u want to use that in calculation for CFD, say for angle between the faces etc.) "

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
InterFoam contact angle	JoaoMiranda	OpenFOAM Running, Solving & CFD	7	October 20, 2016 06:27
[Netgen] Import netgen mesh to OpenFOAM	hsieh	OpenFOAM Meshing & Mesh Conversion	32	September 13, 2011 05:50
What does velocity angle mean?	wateraction	FLUENT	0	May 19, 2011 03:01
Normal vector, slope and aspect angle	g_niro	Main CFD Forum	0	February 2, 2011 17:24
Integration Points and normal area vectors	Bloshchitsyn Vladimir	CFX	0	November 26, 2007 07:35