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-   -   simulating flutter characteristic for AGARD 445-6 wing planform (http://www.cfd-online.com/Forums/ansys/110937-simulating-flutter-characteristic-agard-445-6-wing-planform.html)

acd December 26, 2012 10:21

simulating flutter characteristic for AGARD 445-6 wing planform
 
Hi all,
I am trying to simulate flutter characteristics for AGARD 445-6 wing planform following the boundary conditions used in the experiment in which the data provided is the Mach # dynamic pressure and density in ANSYS 14 workbench using coupled CFX and trainsent structural.
My question is using the parameters speicifed I am not able to simulate the damped, normal and divergent condition from the specified parameters.
As per the experiments conducted the dynamic pressure was gradually increased keeping the Mach # constant until the flutter point was achieved.
Does anyone know what parameters need to be changed to simulate the three conditions in ANSYS.
Any help and guidance is greatly appreciated.

kure87 February 19, 2013 06:31

You can use mixed or supersonic BC for inlet and rise dynamic pressure manualy. When you using CFX. Because dynamic pressure depends on the density and speed of the free stream. And when you preserve same temperature you still have a same mach number.

acd February 20, 2013 00:48

Quote:

Originally Posted by kure87 (Post 408660)
You can use mixed or supersonic BC for inlet and rise dynamic pressure manualy. When you using CFX. Because dynamic pressure depends on the density and speed of the free stream. And when you preserve same temperature you still have a same mach number.

Thanks for the suggestion, when using Mixed/supersonic I get the option for defining the normal speed and pressure or total pressure. For a given time step do I keep changing the pressure value and run the analysis. Can you explain in more detail?

I am running this analysis on Workbench. And the other point is that the Mach number's I am trying to analysis is all less than M0.960. So will the option of Mixed/supersonic effect the analysis since the Mach # is in subsonic range.

kure87 February 21, 2013 11:26

No you must define for each dynamic pressure separate case. In each case you calculate dynamic wing respond on this BC and evaluate results. Personally for the first three cases I will use the flutter dynamic pressure and +/- 20% of this value. You determine the wing response (deflection, damping coeficents etc.) on this BC and can aproximate calculated flutter boundary.

acd February 22, 2013 01:09

Quote:

Originally Posted by kure87 (Post 409337)
No you must define for each dynamic pressure separate case. In each case you calculate dynamic wing respond on this BC and evaluate results. Personally for the first three cases I will use the flutter dynamic pressure and +/- 20% of this value. You determine the wing response (deflection, damping coeficents etc.) on this BC and can aproximate calculated flutter boundary.

I think I understand what you are trying to say. So for example for Mach # 0.901, data from experiment I have rho-0.099468 kgm^-3, velocity 296.69 m/s, dynamic pressure 4275.707 Pa.
From these values I calculated the speed of sound a=329.2923 m/s and using gamma=1.4 and R=287.058 found temperature T=269.8145 and pressure P=7704.046 Pa

Currently I am using the reference pressure value of 7704.046 Pa velocity of 296.69 and temperature of 269.8145 with reference density of 0.099468 kgm^-3 in Ansys setting.
So for the three different case recalculate the density (+/-20%) along with the pressure and run the analysis for corresponding different pressure and density values. Is this what you are suggesting.

If yes then after the run how will I check the dynamic pressure is as per my set values over the wing?

Appreciate your help and thanks a lot for your input.


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