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DESIDER
Detached Eddy Simulation for Industrial Aerodynamics

Background

The DESider project is motivated by the increasing demand of the European aerospace industries to improve analysis on turbulent, unsteady aerodynamic flows exhibiting massive separation. However, for complex, turbulent separated flows, RANS modelling has proved to be a poorly adapted approach. While LES has shown viable capabilities of resolving the flow structures, it is too costly to be used at present in aeronautical applications. To close the gap between RANS and LES, hybrid RANS-LES methods will be investigated, among which the so-called detached eddy simulation (DES) serves as a basis.

Project objectives

Based on the previously developed DES approach, the objectives are:

  • To investigate and develop advanced modelling approaches for unsteady flow simulations as a compromise between URANS and LES, which are able to produce LES-comparable results for real aeronautical applications, yet with less costly computational resources compared to LES for an employment in industrial design environments.
  • To demonstrate capabilities of hybrid RANS-LES approaches in solving industrially relevant applications with a focus on aerodynamic flows characterised by separation, wakes, vortex interaction and buffeting, i.e. all flows which are inherently unsteady.
  • To investigate further that RANS-LES methods can be well applied to multidisciplinary topics as there are aero-acoustics (noise reduction) and aero-elastics (reduced A/C weight, unsteady loads, fatigue issues, improved A/C safety), improving this as a cost-effective design.
  • To facilitate co-operation between the European industries, research establishments and universities and to foster co-operation between the different industries (as there are airframe, turbo-machinery, helicopters and power generation, as well as turbo-engines and ground transportation) with the help of an ‘observer group’.


Description of the work

Work in the DESider project has been split into four Work Packages:

Work package 1: ‘General management’ is dedicated to the overall management of the project. Coordination work includes the set-up of a project website and web-server, http://cfd.me.umist.ac.uk/desider/ with a public part that is not password protected and which provides a more elaborate overview about the DESider project.

Work package 2: ‘Experiments’ is assembled around available experimental results and will be finished around the end of the second year of the project. Although test cases have been defined at the start they are going to be adjusted during the course of the project. Moreover, a new experiment will be carried out – a channel bump – that can be used for validating the hybrid RANS-LES methods that will be investigated. The set-up of these measurements was conducted by CFD computations in order to ensure that the experimental results will exhibit all flow-specific data needed for a proper validation of the highly sophisticated CFD methods. A specific post-processing will be carried out to extract typical structures from the measurement data.

Work package 3: ‘Modelling’ is a major task as it is needed to overcome current weaknesses in the different approaches, i.e. to improve both the predictive accuracy and code robustness to make sure that industrially relevant tools are available at the end of the project.

Work package 4: ‘Applications’ is split into two main tasks dealing with ‘pure’ aerodynamics and with multidisciplinary topics. In the aerodynamics task, work started with investigations on so-called ‘underlying flow regime’ cases, and is followed by ‘real-world’ application challenges. It will be finished with an assessment of URANS, LES and hybrid RANS-LES methods to demonstrate the successful outcome, as well as to show ways for both improvements and exploitation of the approaches used. Work on the aero-elasticity as well as the aero-acoustic tasks have been started at the beginning of the second year. Both applications are of much interest in order to demonstrate how methods and approaches can offer improved prediction capabilities for the structural behaviour (safety aspect) and noise propagation (environmental aspect).

Expected results

Advanced URANS and hybrid RANS-LES methodologies will be improved and their implementation in industrial approaches facilitated. Based on modification of turbulence scales in respect of flow unsteadiness, the theoretical approaches are going to be validated by detailed physical experiments. Moreover, as improved aerodynamics results will directly influence the accuracy of multi-disciplinary industrial challenges, non-linear aero-elasticity and aero-acoustics problems will be treated, fostering the predictive capabilities in CFD and improving industrial design processes.

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