Hi everyone. I have to estimate the dynamic coefficients of aircraft such as Cmq, Calha_dot, Clr etc. I need to know the analytical as well as the experimental procedures in use. Please can anybody also comment on the feasibility of such calculation from CFD . Regards
From the CFD point of view it will not be a problem. This can be made also with opensource free softwares such as OpenFOAM.
Franco
I would recommend you to have a look to the following references:
- https://arc.aiaa.org/doi/abs/10.2514/1.C031674
- https://arc.aiaa.org/doi/pdf/10.2514/1.J051304
@ Franco Connli. Thanks for responding.
Can i use ANSYS Fluent tool to compute these derivatives. What will be the strategy to model the flow. Sliding meshes or remeshing scheme..what is prefered....Can you please elaborate or suggest any reading material to undertake the task.
For aerodynamic parameter estimation, you can use Ward and Bodson's excellent paper
Development and Flight Testing of a Parameter Identification Algorithm for Reconfigurable Control
Read More: https://arc.aiaa.org/doi/abs/10.2514/2.4329
I have consulted few references on the subject. I know a forced oscillation motion in CFD is used to estimate summation of Cmalha_dot and CM_q but how these can be separated.
It is almost impossible to separate the two. Usually you measure (Cmalpha_dot + CM_q). This is because pitch and alfa rates are intrinsically coupled.
i have consulted one reference in which the author has suggested use of linear regression approach to separate two. Obviously then it would be an approximate solution which minimizes square of error.
Depends if we can measure pitch and angle of attack rates separately. If possible, then yes, a simple LMS will work.
@ sir Bilal. In a flight dynamic model, in state space form, we have the information of states such as q. but alha_dot how we can we measure it. By derivating the alha state?
Another way is to use the sum of (Cmq,C_alpha_dot) and take alhpa_dot=q
What you suggest. I am building a flight dynamic model and i dont have dynamic derivatives. I have chosen DATCOM for initial estimates and then i can embed more accurate dynamic data afterwards.
Regards.
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