# Orbital velocity Inlet expressions

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 July 8, 2008, 15:33 Orbital velocity Inlet expressions #1 rc2v07 Guest   Posts: n/a Hi Im trying to simulate a wave in water on CFX, I have the following expressions for the X and Z velocity components: U = w*a*Exp(k*z)*sin(wt-kz) W = w*a*Exp(k*z)*sin(wt-kz) w = ang. freq.(rads/s) a = apm.(m) t = time(s) k = wave no. Im not sure as to how to specify the x and z distances in CEL expressions, do I create a local co-ord frame in Pre at the inlet boundary? Also the time, do I use 't' or 'atstep' or neither. The domain is a 2D rectangle with a foil at the centre, it is 3 (long) by 1.5 (wide) meters with openings at top and bottom and symmetry on front and back. Currently my results with both t and atstep with and without creating a co-ord frame show almost parallel flow to the inlet and vertical flow thoughout the domain! Thanks for the help!

 July 11, 2008, 07:14 Re: Orbital velocity Inlet expressions #2 MAB Guest   Posts: n/a are you working in deep water scenario. Your equations for velocity components are wrong. it should be U= w*a*exp(k*z)*sin(w*t-k*x) and W=w*a*exp(k*z)*sin(w*t-k*x) this expression is only true for deep water.

 July 11, 2008, 07:45 Re: Orbital velocity Inlet expressions #3 rc2v07 Guest   Posts: n/a yeah sorry mis-typed them the second z is x. but your eqtns are both the same the W components should be Cos. yeah Im doing deep water alright.

 July 11, 2008, 08:51 Re: Orbital velocity Inlet expressions #4 MAB Guest   Posts: n/a yes it should be cos. just leave it as x , z and time as t , the velocities should work.

 July 11, 2008, 10:43 Re: Orbital velocity Inlet expressions #5 rc2v07 Guest   Posts: n/a yeah but where are x and z measured from?

 July 11, 2008, 11:47 Re: Orbital velocity Inlet expressions #6 MAB Guest   Posts: n/a examine your geometry file in design modeller. you can note where the origin of these coordinate was. for example if you have created your wave tank with the left bottom corner at the origin (0,0,0) than thats where these coordinates are measured from. i hope it helps.

 July 11, 2008, 14:21 Re: Orbital velocity Inlet expressions #7 rc2v07 Guest   Posts: n/a yeah great thanks!

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