ioda project - esr 9 - open...
TRANSCRIPT
IODA projectESR 9 - Open CASCADE
Salvatore Auriemma
9th December 2016
Salome day, EDF Lab, Saclay
1 / 13
IODA Project
IODA1: Industrial Optimal Design using Adjoint CFD:
• European Commission project that follows other two ECprojects (FlowHead2 and AboutFlow3).
• 15 Early Stage Researchers (ESR) displaced around severalEuropean Institution to develop new methods for the designoptimisation.
• Institutions: Universities (Queen Mary University of London,University of Paderborn) and Companies (Open CASCADE,Rolls Royce D., Volkswagen..).
Main GoalAerodynamic shape optimisation.
1http://ioda.sems.qmul.ac.uk/2http://flowhead.sems.qmul.ac.uk/3http://aboutflow.sems.qmul.ac.uk/
2 / 13
Aerodynamic Shape Optimisation
Given a CAD-model, change the Shape to maximize/minimize athermo-fluid dynamics component (ex. velocity in a pipe, deltapressure, lift of a wing..)
• Two different approaches are possible:
CAD-free methodsResult is an optimised mesh7 No link to CAD
CAD-based methodsX Result is a CAD model with optimised design parameters
3 / 13
CAD-based Shape Optimisation
CAD-model with design parameters α
Mathematical formulation for gradient-based optimisation
minα
J(U(X (α)),X (α), α) (1)
R(U(X (α)),X (α)) = 0 (2)
dJ
dα=
dJ
dXS
dXS
dα(3)
CFD Sensitivity dJdXS
: Efficient adjoint method
CAD Sensitivity dXSdα : FD, Analytical, AD
4 / 13
CAD-based Shape optimisation
ESR 9 tasks
• Evaluate the CAD sensitivities using an AlgorithmicDifferentiation tool (ADOL-C, provided by University ofPaderborn (UPB) - close collaboration with ESR9 @ UPB).
• Design(Parametrise) the Industrial applications (U-bend pipe,car mirror, compressor stator blade..).
• Optimise the industrial applications using Open CASCADE +CFD tool from QMUL (close collaboration with ESR12 @QMUL).
Presentation Outline
Calculation CADsensitivities
Test case design(Parametrisation)
CAD sensitivities,Optimisation results Shaper application
5 / 13
Calculating the CAD sensitivities
An exact way of calculating the shape sensitivities w.r.t. designparameters is to apply the Automatic Differentiation (AD) to theCAD sources. AD tool integrated to OCCT is ADOL-C.
Automatic Differentiation by OverLoading in C++
ADOL-C uses operator overloading concept to compute first andhigher derivatives of vector functions that are written in C or C++.
Concept of AD by operator overloading
All variables that may be considered as differentiable quantitiesmust be of an active type, which is named adouble in ADOL-C.
Original codeDifferentiated
code
adouble
injection
6 / 13
Test Case under Investigation: U-bend
To test the differentiated OCCT in an optimisation, the IODA testcase U-bend was parametrised.
The U-bend pipe is a typical cooling channel used in turbine bladeapplication:
The parametrisation allows to deform the U-part and is based on across-sectional design approach which takes N-slices as inputs inorder to construct a final surface.
7 / 13
U-bend Parametrisation
The generic slice (shown on the left) consists of 4 Bezier curves; itis orthogonal to a planar line named ”pathline”.
Each control point of the section is characterized by a law ofevolution along the pathline. In particular every law is B-splinecurve whose control points coordinates are the design parametersof the simulation.
8 / 13
CAD Sensitivities
Example of sensitivities calculated using AD
9 / 13
Optimisation Results
Cost function:Total pressure lossesbetween inlet/outlet
Design improvement:
16%
10 / 13
Shaper application
Limit of this approach: All the code for the optimisation iswritten in c++; this is difficult for the designer:
• not all the designers are programmers.
• time consuming approach.
SolutionParametrise (design) the test cases in Shaper4 and involve it in theoptimisation loop.
4Under development (for SALOME CEA/EDF platform) ,to be published in LGPL in 2017.
11 / 13
Further work and Conclusions
Current stateX AD tool ADOL-C coupled to Open CASCADE CAD kernel.X developed an approach to design/parametrise the U-bend testcase.X Performed the U-bend optimisation.
Future steps
7 Apply ADOL-C tool to Shaper7 Design (parametrise) a test case in Shaper and perform itsoptimisation.7 Application of the optimisation tool to the test cases provided byindustrial partners of IODA project.
12 / 13
Research is conducted within IODA5 projectIndustrial Optimisation using Adjoint CFD
5http://ioda.sems.qmul.ac.uk/ Grant Agreement No. 642959.13 / 13