JSM Aircraft Model

CFD Validation - 3rd AIAA CFD High Lift Prediction Workshop

SUMMARY

In recent years, computational fluid dynamics (CFD) has become an essential tool for the design and optimization of various engineering systems, including vehicles and transportation means in the aerospace sector. However, predicting the airflow around complex geometries in aerial vehicles remains a challenging task. To address this issue, the “AIAA CFD High Lift Prediction Workshop” was established to evaluate the predictive capabilities of CFD codes for vehicle geometries in the aerospace domain. This workshop provides a set of mandatory geometries, boundary conditions, and computational meshes to enable a fair comparison among different CFD codes and establish best practices for modeling and simulation.

In this context, we have conducted a CFD validation case for the aircraft model JSM from the third “AIAA CFD High Lift Prediction Workshop” based on the paper paper “Verification and Validation of OpenFOAM for High-Lift Aircraft Flows”, using the Symula software. The main objective of our study has been to evaluate the accuracy and predictive capabilities of Symula’s virtual wind tunnel module for this aerial vehicle geometry, particularly regarding turbulence models, meshing, and numerical schemes. To this end, we obtained results for the three available precision levels in Symula and compared them with the reference experimental data provided by the workshop, as well as with the results obtained by various commercial CFD software and other participants in this CFD workshop.

Through this validation case, we aim to demonstrate the performance and reliability of Symula’s CFD simulation software for aerospace applications. The results of our study could potentially contribute to the development of more accurate and efficient CFD tools for the design and optimization of aerial vehicle geometries, with implications for enhancing performance, fuel efficiency, and safety in the aerospace industry.

3D MODEL

The geometry of this simulation case corresponds to the JSM (Jaxa highlift configuration Standard Model) air vehicle model. This study model is a scale model that has a mean aerodynamic chord value of 529.2 mm, a wing span of 4600 mm and an “Aspect Ratio” of 9.42. It should be noted that in the case studies in wind tunnel and for the rest of the participants, symmetry condition has been used, since the airplane model used has been a simplified version that only had half of the geometry. We have used the complete model since the Symula software does not allow applying a symmetry condition.

RESULTS

DRAG FORCE VALUES

The values obtained for the calculation of the force of resistance are shown in the following graph. Results for the 3 levels of precisions offered in the Symula platform are compared with respect to experimental data obtained in wind tunnel facilities, as well as with respect to the rest of the participants, CFD software and turbulence models.

“Conceptual” Precision: The error obtained, averaged for the different angles of attack, for this precision is 38% compared to experimental data from the wind tunnel and 16% compared to the average results obtained by the rest of the participants. Although it is a high error value if we compare it with the exact experimental value, at this level of precision, an order of magnitude is offered by Symula.
“Accurate” Precision: In this case, the error is reduced to 32% with respect to experimental values and 11% compared to the average results obtained by the rest of participants.
“Realistic” Precision: For the maximum precision offered by the Symula platform, the error is reduced up to 14% with respect to experimental values and up to 5% compared to the average results obtained by the rest of the participants.

LIFT FORCE VALUES

“Conceptual” Precision: The error obtained, on average for the different angles of attack, for this precision is 15% compared to experimental data from the wind tunnel. Although it is a high error if we compare it with the exact experimental value, at this level of precision an order of magnitude is offered with respect to said real value.
“Accurate” Precision: In this case, the error is maintained on average at 15% with respect to experimental values. Both in conceptual and precise precision, for high angles of attack the error increases considerably. In order to adequately capture boundary layer detachment phenomena, it will be necessary to make use of the realistic precision.
“Realistic” Precision: For the maximum precision offered by the Symula platform, the error is reduced to 5% with respect to experimental values. In this case, the accuracy is kept constant with respect to the angle of attack. Thanks to the LES turbulence model and a higher mesh refinement, this accuracy manages to capture detachment phenomena for high angles of attack without problem.

AERODYNAMIC RESULTS

Some images of results obtained for the fluid-dynamic behavior of air are also shown. Results of velocity contours, wind pressure over the vehicle, stream lines, and drag contours are displayed.

These results are the ones we offer automatically on the Symula web platform, in addition to allowing the download of results to work with programs like Paraview to be able to perform any type of post-processing operation locally.