[divoone1985]

Hello.
This is a buoy in a water tank.

i want to find the rotation angle of buoy in cfx-post
i use this expression to find the angle

(probe(Total Mesh Displacement Y)@Point 2 -probe(Total Mesh Displacement Y)@Point 1 )/(1[m]+probe(Total Mesh Displacement X)@Point 2 -probe(Total Mesh Displacement X)@Point 1 )

Point 1 is middle point of the right edge of buoy and point 2 is the middle point of the left edge of buoy.
1[m] is width of buoy
after this i make a transient chart in location point 3 (0,0,0). x axis is time and y axis is the variable of this expression.
is this correct?
can you help me to find the correct way?

[ghorrocks]

Why not use the built in angle variable, contained in variable "rbstate"?

[divoone1985]

Originally Posted by ghorrocks

Why not use the built in angle variable, contained in variable "rbstate"?

I didn't hear about it.
what's that?
how can i use it?

[ghorrocks]

The CFX documentation is your friend. Have a look in the reference manual.

[divoone1985]

Originally Posted by ghorrocks

The CFX documentation is your friend. Have a look in the reference manual.

Is there any taturial or example about it?

[ghorrocks]

Have a look at the floating buoy simulation in the CFX tutorials. There are probably more on the ANSYS Customer web page.

[divoone1985]

Originally Posted by ghorrocks

Have a look at the floating buoy simulation in the CFX tutorials. There are probably more on the ANSYS Customer web page.

thank you.
I have 2 questions.
1. Why this expression don't work in cfx-post?
2. why my results from this expression and the expression I said above are different?

[singer1812]

rbstate isnt passed to the results file, so Post doesnt have access to that. You would have to monitor those while the run is in solution.

rbstate returns angle in radians of rotation around global axis.

I think you need an atan in your expression and why are you adding 1[m] to the X? I dont think that is needed. In addition, you will have issues when your denominator is 0 (X displacement of both points is same).

[rasool motamedi]

i think
it is true.
atan( (probe(Total Mesh Displacement Y)@Point 1)/(1[m]-probe(Total Mesh Displacement X)@Point 1 ))

[divoone1985]

Originally Posted by singer1812

rbstate isnt passed to the results file, so Post doesnt have access to that. You would have to monitor those while the run is in solution.

rbstate returns angle in radians of rotation around global axis.

I think you need an atan in your expression and why are you adding 1[m] to the X? I dont think that is needed. In addition, you will have issues when your denominator is 0 (X displacement of both points is same).

You are right.
I forget to write atan.
But 1[m] is the width of buoy.
because two points have 1[m] distance.
and with this 1[m] in expression , the issue you noticed doesn't exist anymore.

[divoone1985]

anyone Knows how I can change the charts units from radian to degree in solver?

[rasool motamedi]

sorry divoone
atan( (probe(Total Mesh Displacement Y)@Point 1)/(0.5[m]-probe(Total Mesh Displacement X)@Point 1 ))

[divoone1985]

Originally Posted by rasool motamedi

sorry divoone
atan( (probe(Total Mesh Displacement Y)@Point 1)/(0.5[m]-probe(Total Mesh Displacement X)@Point 1 ))

Thanks. But both expressions you said have different results with solver results (rigid body euler angle)

[rasool motamedi]

Originally Posted by divoone1985

Thanks. But both expressions you said have different results with solver results (rigid body euler angle)

this is right
0.5[m] is true
atan( (probe(Total Mesh Displacement Y)@Point 1)/(0.5[m]-probe(Total Mesh Displacement X)@Point 1 ))

[divoone1985]

Originally Posted by rasool motamedi

this is right
0.5[m] is true
atan( (probe(Total Mesh Displacement Y)@Point 1)/(0.5[m]-probe(Total Mesh Displacement X)@Point 1 ))

But results of this expression differ from results of rigid body euler angle in solver environment.
Do you Know why?
which one is correct?