Recent Experiences of Modeled-Stress Depletion Using DDES and IDDES for the 30P30N Three-Element Airfoil

Speaker: Neil Ashton, University of Oxford
May 3, 2016

Presentation

Abstract

This talk will focus on recent work for the BANC III workshop using the 30P30N three-element airfoil. DDES & IDDES simulations were conducted using both multi-block structured grids and unstructured grids using a commercial unstructured code. During the course of this work, problems were encountered with the boundary layer shielding functions of the DDES/IDDES models when the near-wall grid was refined. This led to grid-induced separation (GIS) and spurious noise which compromised the accuracy of the simulations.

Further investigations on a flat-plate using multiple codes, on a range of grids, exposed an underlying problem with the DDES and IDDES shielding functions when the grid (and corresponding filter width) becomes fine (typically in the streamwise direction). Recent discussions with other DDES/IDDES users using a variety of codes and grids (e.g unstructured, structured, overset) has confirmed that this has been more widely observed for different flows, often for cases where it is not possible to have ‘boundary-layer’ type grids in the near-wall region.

Whilst it is commonly expected that DDES and IDDES methods are protected from modeled-stress depletion and GIS by the fd shielding function, this work shows that this is not always the case and suggests a combination of more robust shielding functions and meshing guidelines for DDES/IDDES methods are required.

Biography

Neil Ashton completed his Masters and Ph.D. at the University of Manchester in 2012 where his thesis focused on the development of a new DDES model based upon elliptic relaxation. He has since been involved in a number of EU-funded turbulence modelling projects (such as the ATAAC & Go4hybrid projects) which looked at developing hybrid RANS-LES approaches suitable for the aerospace industry. He is now a researcher at the University of Oxford’s e-Research Centre where his work is focused on developing improved RANS and hybrid RANS-LES methods for the automotive and aerospace industry. He is actively involved with the AIAA Turbulence Modelling Benchmark group and is currently a STC visiting scholar at NASA Ames within the Computational Aerosciences branch.

Seminar Participation

Attending In Person

For select seminars, you may wish to attend in-person if you are in the vicinity of NASA Ames Research Center. These AMS seminars are held in Building N258 in Room 127, just off the front lobby. Sessions available to attend in-person will be indicated in the announcement information. In-person participants without NASA badges will need a valid visitor badge (US citizenship or permanent residency is required) to enter the facility.

Join Us Online

To attend an AMS seminar, click on the Microsoft Teams link in the seminar description. You can connect through the desktop Teams App if you have it, or you can select "Watch on the Web Instead" to enter the meeting as a guest. Please ensure that you've muted your microphone in Teams before you select "Join Now" to enter the meeting lobby.