# expression in CFX POST

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 July 9, 2016, 12:26 expression in CFX POST #1 Member   Join Date: May 2016 Posts: 40 Rep Power: 9 Hello I want to create expression to find Froude number (v/(gy)^0.5) at a certain location using line, from expression avgvelocity()@line1/(areaInt(water.vf)@line1/area()@line1)*g )^0.5 but it showed error. also I used the same expression for plane, the same problem occur thanks for your help

 July 9, 2016, 20:22 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 Showing the error message might help..... Note there is no function "avgvelocity()@line1".

July 10, 2016, 02:34
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 Originally Posted by ghorrocks Showing the error message might help..... Note there is no function "avgvelocity()@line1".
now the expression contain, function variable and location but still it gives error if bracket and SQRT removed only error from (Velocity) other wise error occur in all term under root.
areaAve(Velocity)@line1/[(areaInt(Water.Volume Fraction)@line1/area()@line1)*g]^0.5
I used velocity same as in the CFX documentation

 July 10, 2016, 09:03 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 CEL does not use square brackets. They need to be normal brackets. You cannot do areaInt() of a line object. Or maybe you can - but the answer is zero as it has no area. Likewise the area() of a line is zero as well. You still have not posted the error message you are getting.... Red Ember and zryan civil like this.

July 10, 2016, 11:47
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Quote:
 Originally Posted by ghorrocks CEL does not use square brackets. They need to be normal brackets. You cannot do areaInt() of a line object. Or maybe you can - but the answer is zero as it has no area. Likewise the area() of a line is zero as well. You still have not posted the error message you are getting....
the follow error occur for line and plane
thanks

 July 10, 2016, 19:25 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 The error message says exactly what the problem is. There is no variable called "Velocity", there is "U Velocity", "V Velocity" and "W Velocity", or the short version u, v, w. zryan civil likes this.

July 11, 2016, 07:53
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Quote:
 Originally Posted by ghorrocks The error message says exactly what the problem is. There is no variable called "Velocity", there is "U Velocity", "V Velocity" and "W Velocity", or the short version u, v, w.
I used U Velocity, and change bracket to normal the same error occur!!!
areaAve(U Velocity)@Plane 1/((areaInt(Water.Volume Fraction)@Plane 1/area()@Plane 1)*g)^0.5

 July 11, 2016, 08:48 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 Look in the CFX reference guide for the variable names. You need to get the variable names correct or it won't accept them. It is also case sensitive.

July 14, 2016, 07:23
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Quote:
 Originally Posted by ghorrocks Look in the CFX reference guide for the variable names. You need to get the variable names correct or it won't accept them. It is also case sensitive.
thanks
I used the velocity variable as cited in CFX reference but same error happen, just for test I used pressure (p) it gives a result as in attached pictures.