OPTIMIZATION DOUBTS
Altair EmployeeHi,
I am a new user of hyperworks. I am currently working on topology optimization of inner structure of airfoils and trying to get a good setup of the settings available in the software.I have a few doubts that i couldn't get cleared by reading the hyperworks help:
1. The use of DISCRETE option regarding the value of it and the phases involved with it.
2. How can the OBJ REFERENCE and DESVAR LINK be used in the setup?
3. Usually to avoid computational cost we go from discrete to continuous design variables and that is the general way. Then how can the given option of discrete DVs be fruitful as compared to contnuous DVs ?
4. It is written in the help site that 'DUAL' solver is used where the number of design variables is large compared to the number of constraints applied. It is advised for a general topology optimization problem. In ANSYS generally 'optimality criteria' is used´similar to 'DUAL' but when stress constraint is applied it leads to an increase in the number of constraints thus it is better to prefer a solver with capability to handle large number of constraints like sequential convex programming in ANSYS. So is the same true in hyperworks as well that if I change from a less constraint problem to a large constraint problem I would have to change from 'DUAL' as a solver to other solver? If so then which would be the best?
Answers
-
Hi ayushsharma812,
I suggest you to go through the below e_book on the optimization. In which each optimization technique is explained in detail.
Thank you
0 -
Thankyou sir for the response the book helped me in clearing my doubts but still i couldn't figure out what are the uses of DESVAR LINK and OBJ REFERENCE. One more thing, it is mentioned in the book about multiple start points optimization and obviously that's useful to get a more optimal result in a non convex problem, how can i implement that? is this connected to choosing the MATINIT option to change the starting values of mass fraction?
0 -
DLINK, links between one design variable and one or more design variables.
OBJ REFERENCE is used for minmax or maxmin problems. Please refer to the EBook for more information about minmax or maxmin problems.
Multiple starting points or GSO can activated through DGLOBAL card. Go to Control cards and enable DGLOBAL card.
0 -
Thank you sir for the response I have figured out the DLINK, OBJ REFERNECE and MULTIPLE STRATING POINTS by following your response. I have been trying to study topology optimization and set a good setup with custom settings and learning how the settings would influence my results, I just have two more doubts:
1. MATINIT is used to set the initial mass fraction values. When the constraint on mass it automatically adjusts to the constraint and thats understandable as well as the best choice for that case but when my response is not mass how changing the initial mass fraction would influence my result?
2.I studied a little about constraint screening and it is a very helpful tool introduced by you guys to reduce the computational time,I am just wondering if it affects the final results in anyway?
3. How can i apply cyclic symmetry condition on a geometry i have a airfoil blade of a turbine, i looked on net and found maybe periodic condition might work i guess but with search option in hyperworks there was no PERBC option
0 -
Hi Ayush,
Only mass will affect and for the mass fraction, the constrained value will be used.
Constraint Screening, maybe or may not be... If too many constrained responses are screened, it may take considerably longer to reach a converged solution or, in the worst case, it may not be able to converge on a solution if the number of retained responses is less than the number of active constraints for the given problem
You can use pattern grouping to get a cyclic symmetric pattern.
0 -
Hi @Prakash Pagadala thankyou for the response,
pattern grouping symmetry can be used when we have the full circular ring with us but i want to setup just one airfoil with cyclic symmetry conditions in static analysis and then do its optimization. I just want to know how can i setup the cyclic symmetry for static analysis?
I read the hyperworks paper on load and boundary conditions and the example for axi symmetric analysis, they both indicate to constraint the tangential displacement but i couldn't understand how it would make my cyclic symmetry possible because according to my understanding on a single sector of cyclic symmetry if i can enforce same mesh and same displacements on opposite faces then i should be able to get cyclic symmetry but how can i do that for each node?
0 -
OK, if the part is not continuous, you can use pattern repetition, instead.
But for this each segment should be a different DESVAR.
0 -
Hi @Prakash Pagadala i respect your help but you are thinking about topology optimization and i am asking about how to setup cyclic symmetry in a static analysis ?(nothing related to topology optimization)
I am attaching a geometry for example
A geometry similar to this but not same and i want to setup the static structural simulation
0