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-   -   Calculate Cp,CN,CT & calculate coefficient in sections (https://www.cfd-online.com/Forums/numeca/126166-calculate-cp-cn-ct-calculate-coefficient-sections.html)

 Ali T November 9, 2013 18:24

Calculate Cp,CN,CT & calculate coefficient in sections

Dear all my friends
How can I calculate Cp distribution (Pressure coefficient distribution) , CN (normal force coefficient), CT( tangential force coefficient ) in cfview of NUMECA?

Another question is that , I want to show Cp,CT,CN and Relative velocity contours with streamlines in different sections of blade , for example: in span 10% , 40% ,... 95%.
How can I do this?
Thank you all for your attention

 amianjan February 11, 2014 15:26

Quote:
 Originally Posted by Ali T (Post 461348) Dear all my friends How can I calculate Cp distribution (Pressure coefficient distribution) , CN (normal force coefficient), CT( tangential force coefficient ) in cfview of NUMECA? Another question is that , I want to show Cp,CT,CN and Relative velocity contours with streamlines in different sections of blade , for example: in span 10% , 40% ,... 95%. How can I do this? Thank you all for your attention
I am facing the same problem. Did you find any solution to this problem?

 colinda1 February 17, 2014 10:32

To plot the pressure coefficient in CFView you can define a new derived quantity (Quantity/Field Data/Define New Quantity...) with the new name Cp and its definition (Static Pressure - 101325)/0.5/1.2 for example in the case of a reference surface of 1.0 m^2
This new quantity can then be plotted e.g. in color contour and/or a Cartesian plot.

In CFView you have also access to the Force (in the Quick Access Pad on the left under Quantities/Mechanics). This is a vector field on your solid surfaces so in the "Define new Quantity" menu you can select under Quantity type "surface" and then define your new quantity n for example as the scalar product of the force vector and the normalized vector indicating the normal direction. For an airfoil under angle of attach alpha this could look like this in 2D:
Force_X*sin(alpha)+Force_Y*cos(alpha)
Instead of n you can of course also define the Cn coefficient instead in the same way as for the pressure coefficient.

It is not necessary to define each time you open CFView such new quantity. The first time you do this you first make sure to activate File/Macro/Record. Then you define your new quantity and when it's finished you go back to the File/Macro menu and select the option to Save. This will save the step you have just recorded in a .py file that you can relaunch in the GUI every time you open a project in CFView: use the short-cut: 6 to open the macro script. Or you can launch CFView with the -macro argument to run immediately at start-up the recorded macro.

Alternatively you can copy this command into a module and load this automatically when launching CFView: in this way the computing of the new quantity becomes available in the Macros menu at the top right of the CFView GUI.

 colinda1 February 17, 2014 10:39

Once you have created the new quantity Cn for example, you can select it from the list on the left and create a Cartesian plot e.g. at 10% of the span by drawing the section or entering the coordinates at which location you want to see the plot. In FINE/Open such section is a straight line between two points in XYZ space. If the computation was done in FINE/Turbo, you have also access to the Blade-to-blade view in which you can then draw a constant plot e.g. at constant span (normalized from 0 to 1=100%) .

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