Vector directions on scaled (X to Y Ratio) grid?

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jtong
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Joined: Wed Jul 25, 2012 6:37 am
Location: Australia

Vector directions on scaled (X to Y Ratio) grid?

Postby jtong » Tue Oct 09, 2012 2:56 am

Hi all,

I am new to Tecplot and have been playing around with the demo version before I actually buy the package for my research.
I have been able to make 2d contour/vector plots of flow over ocean topography, based off a finite element grid and was happy with the result, until I checked the vectors more closely...

You see, I am plotting a 2d flow field in the x-z plane.
Along my "x" axis I am plotting Distance (m) and on the "y" axis I am plotting Depth (m). Under Plot->Axis I am using a X to Y Ratio=0.1 in order to scale the axes. Therefore I can represent 160m in the vertical and 1.6km in the horizontal, rather than a long narrow strip at 1:1 ratio.

However, due to the scaling of the axes, I find that Tecplot can not draw the vectors how I would wish with accurate DIRECTION.

I have tried the 3 Vector Length methods and none of the methods seem to produce what I am after.
1) Uniform (%) - Vectors all the same length, so not what I am after.

2) Relative (grid units/magnitude) - draws the vectors taking into account the grid scaling, hence a 0.5m/s vector purely in the horizontal and a 0.5m/s vector purely in the vertical are displayed with different lengths, in my case, the horizontal vector is much much smaller. This is not what I want as I want to be able to look at a vector and know whether it is big or small flow.

3)Relative (grid cm/magnitude) - I initially thought this was giving me the correct vectors, but the direction is not correct for a scaled grid as I have described. The vector magnitudes are correct, but when I checked manually with a protractor, the vector DIRECTION (or angle of flow) was correct for a 1:1 scale grid. NOT for my scaled grid! So if there was flow flowing down steep topography, the vector would not follow the topography closely (topography is drawn with X to Y ratio=0.1 too), but instead the vector is drawn with shallower angle which would be correct on unscaled 1:1 axes.

I am surprised that Tecplot does not have an option to draw the vectors with correct angle in relation to the scaled grid, but at the same time draw magnitude not in relation to the grid. I am wondering if there is an option I am missing?

Any help would be very appreciated.
Or confirmation that Tecplot actually doesnt handle this.

Thanks,

Judy.

straton
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Location: Bellevue, Washington
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Re: Vector directions on scaled (X to Y Ratio) grid?

Postby straton » Fri Dec 14, 2012 10:42 am

Thanks in great part to Judy's hard work describing this issue in detail, we will be releasing a new version -- Tecplot 360 2012 R2 -- in a few days which includes the fix for this issue: "have vectors show adjusted magnitudes as well as directions, not uniform in length".

Thank you Judy.

--Straton, on behalf of the Support and Development teams at Tecplot
Straton Spyropoulos


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