High-order detached-eddy simulation of external aerodynamics over an SAE notchback model

2017 ◽  
Vol 121 (1243) ◽  
pp. 1342-1367 ◽  
Author(s):  
A. Islam ◽  
B. Thornber
Keyword(s):  
Coherent Structures ◽  
Separated Flow ◽  
High Order ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Wind Tunnel Measurements ◽  
Flow Features ◽  
External Aerodynamics ◽  
Coarse Meshes ◽  
Automotive Aerodynamics

ABSTRACTThis research explores the modification and implementation of a Detached-Eddy Simulation (DES) in a high-order compressible solver and its application to automotive aerodynamics. This was conducted on a 20° SAE Reference Notchback Model with a Reynolds number of 2.23 × 105. This DES algorithm implemented within FLAMENCO, which is finite-volume research code operating over multi-block meshes, was used for all the simulations. The primary objectives were to capture unsteady flow features, separated coherent structures and also relax the meshing requirements to improve accessibility to turbulence-resolving methods for realistic configurations. This also aims to better understand the separated flow physics, especially around the base surfaces of the car. Simulations for three mesh refinement levels were compared to wind-tunnel measurements. Even on relatively coarse meshes (~7 m cells) for DES, time-averaged Cp was obtained with maximum errors of <8%.

Detached-Eddy Simulations Over a Simplified Landing Gear

2002 ◽  
Vol 124 (2) ◽  
pp. 413-423 ◽  
Author(s):  
L. S. Hedges ◽  
A. K. Travin ◽  
P. R. Spalart
Keyword(s):  
Stokes Equations ◽  
Separated Flow ◽  
Flow Fields ◽  
Equation Model ◽  
Landing Gear ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Navier Stokes Equations ◽  
Instantaneous Flow ◽  
Eddy Simulation

The flow around a generic airliner landing-gear truck is calculated using the methods of Detached-Eddy Simulation, and of Unsteady Reynolds-Averaged Navier-Stokes Equations, with the Spalart-Allmaras one-equation model. The two simulations have identical numerics, using a multi-block structured grid with about 2.5 million points. The Reynolds number is 6×105. Comparison to the experiment of Lazos shows that the simulations predict the pressure on the wheels accurately for such a massively separated flow with strong interference. DES performs somewhat better than URANS. Drag and lift are not predicted as well. The time-averaged and instantaneous flow fields are studied, particularly to determine their suitability for the physics-based prediction of noise. The two time-averaged flow fields are similar, though the DES shows more turbulence intensity overall. The instantaneous flow fields are very dissimilar. DES develops a much wider range of unsteady scales of motion and appears promising for noise prediction, up to some frequency limit.

Numerical Investigation of Energy Saving Device Effects on Ships With Propeller-Hull Interactions

2018 ◽  
Author(s):  
Ravi Chaithanya Mysa ◽  
Le Quang Tuyen ◽  
Ma Shengwei ◽  
Vinh-Tan Nguyen
Keyword(s):  
Energy Saving ◽  
Full Scale ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Propulsion Efficiency ◽  
Operational Conditions ◽  
Ship Resistance ◽  
The Past ◽  
Eddy Simulation ◽  
Flow Features

Energy saving devices (ESD) such as propeller ducts, pre-swirl stators, pre-nozzles, etc have been explored as a more economic and reliable approach to reduce energy consumption for both in-operation and newly design ships over the past decades. Those energy saving devices work in the principle of reducing ship resistance and improving propulsion efficiency as well as hull-propeller interactions. Potential saving from various types of ESD have been reported in literature from the range of 3–9% [1] for propulsion efficiency dependent on different measures. Deployment of those devices on actual full-scale ships has been limited over the past years. One of the key obstacles in application of ESD is the lack of confidence in measuring its efficiency on full-scale ships in actual operational conditions. Advances in computational fluid dynamics (CFD) has provided an alternative approach from model scale test to better understand uncertainties in prediction of ESD efficiency in full-scale ship operations [Shin et al, 2013]. In this work a high fidelity CFD model is presented for investigation effects of pre-nozzles on propulsion efficiency and ship resistance. The model is based on the Reynolds Average Navier-Stokes (RANS) solver with different turbulent models including a hybrid detached eddy simulation (DES) approach for predictions of complex near body flow features as well as in the wake regions from hull and propeller. The model is validated with model test for both towing and self-propulsion conditions. Finally a study of pre-nozzle effects on propeller efficiency as well as hull-propeller interaction is presented and compared with available experimental data (Tokyo 2015 Workshop). The current work constitutes a fundamental approach towards designing more efficient ESD for a specific hull form and propeller.

Zonal Detached-Eddy Simulation of Separated Flow Around a Finite-Span Wing

AIAA Journal ◽  
2015 ◽  
Vol 53 (11) ◽  
pp. 3157-3166 ◽  
Author(s):  
F. Richez ◽  
A. Le Pape ◽  
M. Costes
Keyword(s):  
Separated Flow ◽  
Detached Eddy Simulation ◽  
Finite Span ◽  
Eddy Simulation

A DDES study of the flow past a prolate spheroid using a high-order U-MUSCL scheme

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040075
Author(s):  
Yu-Chen Yang ◽  
Zhen-Ming Wang ◽  
Ning Zhao
Keyword(s):  
Flow Separation ◽  
Vortex Structure ◽  
Prolate Spheroid ◽  
High Order ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow Past ◽  
Delayed Detached Eddy Simulation ◽  
Flow Phenomena

Flow past a prolate spheroid, which is a representative simplified configuration for vehicles such as maneuvering ships, submarines and missiles, comprises a series of complex flow phenomena including pressure-induced flow separation, which results in unsteady forces and movements that may be detrimental to vehicles’ performance. In this paper, a Delayed Detached Eddy Simulation (DDES) method combined with a new high-order U-MUSCL scheme is proposed to more precisely and accurately capture the flow separation and vortex structure. This method is applied to simulate the aerodynamic performance of the 6:1 prolate spheroid at an AOA of [Formula: see text] with the Reynolds number of [Formula: see text]. Axial pressure distribution of five individual chord wise sections and flow field structure of the aft body are analyzed. Numerical results agree well with the experimental data. It can be concluded that DDES combined with three-order U-MUSCL scheme demonstrates reliable performance since it captures the vortex structure of aft body distinctly and predicts the separation and reattachment points of the secondary vortex precisely.

A comparative study of DES type methods for mild flow separation prediction on a NACA0015 airfoil

2017 ◽  
Vol 27 (11) ◽  
pp. 2528-2543 ◽  
Author(s):  
Liang Wang ◽  
Liying Li ◽  
Song Fu
Keyword(s):  
Separated Flow ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Detached Eddy Simulation ◽  
Reynolds Stresses ◽  
Content Type ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Flow Phenomena ◽  
Critical Dynamic

Purpose The purpose of this paper is to numerically investigate the mildly separated flow phenomena on a near-stall NACA0015 airfoil, by using Detached-Eddy Simulation (DES) type methods. It includes a comparison of different choices of underlying Reynolds-averaged Navier–Stokes model as well as subgrid-scale stress model in Large-Eddy simulation mode. Design/methodology/approach The unsteady flow phenomena are simulated by using delayed DES (DDES) and improved DDES (IDDES) methods, with an in-house computational fluid dynamics solver. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. Dynamic mode decomposition (DMD) method is applied to uncover the critical dynamic modes. Findings Among all the DES type methods investigated in this paper, only the Spalart–Allmaras-based IDDES captures the separation point as measured in the experiments. The classical vortex-shedding and the shear-layer flapping modes for airfoil flows with shallow separation are also found from the IDDES results by using DMD. Originality/value The value of this paper lies in the assessment of five different DES-type models through the detailed investigation of the Reynolds stresses as well as the separation and reattachment.

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