Assessment of RANS and DES turbulence models for the underwater vehicle wake flow field and propeller excitation force

2021 ◽  
Author(s):  
Yichen Jiang ◽  
Yongkun Li ◽  
Chongjian Wu ◽  
Wang Qing ◽  
Guiyong Zhang
Keyword(s):  
Flow Field ◽  
Turbulence Models ◽  
Underwater Vehicle ◽  
Wake Flow ◽  
Excitation Force

Computational Analysis of a Inverted Double-Element Airfoil in Ground Effect

2006 ◽  
Vol 128 (6) ◽  
pp. 1172-1180 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Near Field ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Navier Stokes ◽  
Main Element ◽  
Ride Height ◽  
Navier Stokes Equations

The flow around an inverted double-element airfoil in ground effect was studied numerically, by solving the Reynolds averaged Navier-Stokes equations. The predictive capabilities of six turbulence models with regards to the surface pressures, wake flow field, and sectional forces were quantified. The realizable k−ε model was found to offer improved predictions of the surface pressures and wake flow field. A number of ride heights were investigated, covering various force regions. The surface pressures, sectional forces, and wake flow field were all modeled accurately and offered improvements over previous numerical investigations. The sectional forces indicated that the main element generated the majority of the downforce, whereas the flap generated the majority of the drag. The near field and far field wake development was investigated and suggestions concerning reduction of the wake thickness were offered. The main element wake was found to greatly contribute to the overall wake thickness with the contribution increasing as the ride height decreased.

Collaborative CFD Exercise for a Submarine in a Steady Turn

2012 ◽  
Author(s):  
Serge Toxopeus ◽  
Paisan Atsavapranee ◽  
Eric Wolf ◽  
Stefan Daum ◽  
Richard Pattenden ◽  
...  
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Rotational Motion ◽  
Turbulence Models ◽  
Underwater Vehicle ◽  
Accurate Prediction ◽  
Drift Angle ◽  
Wall Functions ◽  
Ship Hulls ◽  
Long Time

The application of viscous-flow solvers to calculate the forces on ship hulls in oblique motion has been studied for a long time. However, only a few researchers have published work in which the flow around ships in steady turns was studied in detail. To predict ship manoeuvres, an accurate prediction of the loads due to rotational motion is also required. In a collaborative CFD exercise, the Submarine Hydrodynamics Working Group (SHWG) performed calculations on the bare hull DARPA SUBOFF submarine to investigate the capability of RANS viscous-flow solvers to predict the flow field around the hull and the forces and moments for several steady turns. In the study, different commercial as well as bespoke flow solvers were used, combined with different turbulence models and grid topologies. The work is part of a larger study aiming to improve the knowledge and understanding of underwater vehicle hydrodynamics. In this paper, the results of the exercise will be presented. For several cases, verification studies are done to estimate the uncertainties in the results. Flow fields predicted by the different members of the SHWG are compared and the influence of the turbulence model will be discussed. Additionally, the computed forces and moments as a function of the drift angle during the steady turns will be validated. It will be demonstrated that using sufficiently fine grids and advanced turbulence models without the use of wall functions will lead to accurate prediction of both the flow field and loads on the hull.

Effect of RANS Method on the Stall Onset Prediction by an Eigenvalue Approach

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Zhe Xie ◽  
Yangwei Liu ◽  
Xiaohua Liu ◽  
Lipeng Lu ◽  
Xiaofeng Sun
Keyword(s):  
Flow Field ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Wake Flow ◽  
Spatial Discretization ◽  
Eigenvalue Approach ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Rans Simulation ◽  
Grid Independence

The eigenvalue approach is a recently developed compressor stability model used to predict stall onset. In this model, the flow field from a Reynolds-averaged Navier–Stokes (RANS) simulation provides the basic flow. This paper presents the effect of the RANS methods (including the computational grid, the turbulence model, and the spatial discretization scheme) on the eigenvalue and investigates the most influencing flow structures to the eigenvalue. The test compressor was the transonic compressor of NASA Rotor 37. Three individual meshes with different grid densities were used to validate the grid independence, and the results indicated that RANS simulation and eigenvalue calculation obtain grid independence at the same grid density. Then, the effect of four turbulence models (including Spalart–Allmaras (SA) turbulence model, two different k–ε models with the extended wall function model (EWFKE), and the Yang–Shih model (YSKE), and k–ω shear stress transport (SST) model), and three spatial discretization schemes (the central scheme, the flux difference splitting (FDS) scheme, and the symmetric total variation diminishing (STVD)) was also studied. Further investigation showed that the SA turbulence model combined with the STVD scheme provided the best stall point prediction, with a relative error of 0.05%. Detailed exploration of the three-dimensional flow field revealed that there were two flow patterns near the blade tip necessary for precisely predicting stall onset: the flow blockage generated by the shockwave-tip leakage vortex (TLV) interaction, and the trailing edge separation and corresponding wake flow. The effect of the blockage was greater than the effect of the trailing edge flow.

Numerical analysis for wake flow field of Ahmed model based on a nonlinear-LRN/DES turbulence model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Le Dian Zheng ◽  
Yi Yang ◽  
Guang Lin Qiang ◽  
Zhengqi Gu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Wake Flow ◽  
Field Analysis ◽  
Content Type ◽  
Des Model

Purpose This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately. Design/methodology/approach As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases. Findings Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately. Research limitations/implications The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model. Practical implications This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles. Originality/value Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

Computational Analysis of Pressure and Wake Characteristics of an Aerofoil in Ground Effect

2004 ◽  
Vol 127 (2) ◽  
pp. 290-298 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Surface Pressure ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Suction Surface ◽  
Ride Height ◽  
Surface Pressure Distribution ◽  
Wake Characteristics

The pressure and wake of an inverted cambered aerofoil in ground effect was studied numerically by solving the Reynolds-averaged Navier-Stokes equations. Efforts were focused on the setting up of an accurate numerical model and assessing the abilities of various turbulence models in capturing major physical features associated with the flow, such as surface pressure distribution, separation, level of downforce, and wake. A number of ride heights were studied covering various force regions. Surface pressures, sectional forces, and wake characteristics were compared to experimental data. The k−ω SST and Realizable k−ε turbulence models were found to offer good overall simulations, with the k−ω SST performing better for the surface pressure and the Realizable k−ε better for the wake. The simulations at various ride heights correctly captured the trends in flow-field variations with ride height. The surface pressures, wake flow field, and region of separation on the suction surface of the aerofoil, at lower ride heights, were all modeled accurately.

Viscous Flow Field Computations for the VKI–1 Turbine Cascade Using Different Turbulence Models

1995 ◽  
Author(s):  
L. J. Lenke ◽  
A. W. Reichert ◽  
H. Simon
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Measurement Data ◽  
Turbulence Models ◽  
Algebraic Model ◽  
Turbulence Modelling ◽  
Wake Flow ◽  
Field Calculation ◽  
Wall Functions ◽  
Viscous Flow Field

The influence of the turbulence modelling on viscous flow field calculation results has often been discussed in the past. For a meaningful comparison of different turbulence models the access to reliable measurement data is necessary. The plane VKI–1 turbine profile has been investigated experimentally in many publications. Therefore this turbine profile is chosen for transonic 2D flow field calculations using three different turbulence models. The algebraic model of Baldwin and Lomax, the Standard k–ϵ model with wall functions and a low–Reynolds number model are considered in this investigation. The main differences between the models become apparent in the trailing edge region. The turbulence modelling influences the boundary layer thickness and the shape of the shear layers and the separation region in the wake flow. For the high Mach numbers appearing in this region, a strong influence on the flow field due to small shear layer changes has been found.

The Effect of Different Turbulence Models on the Emitter Discharge by Using Computational Fluid Dynamics

2013 ◽  
Vol 662 ◽  
pp. 586-590
Author(s):  
Gang Lu ◽  
Qing Song Yan ◽  
Bai Ping Lu ◽  
Shuai Xu ◽  
Kang Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Turbulence Models ◽  
Experimental Results ◽  
Turbulent Model ◽  
Simulation Results ◽  
Rsm Model ◽  
Dynamics Method ◽  
Emitter Discharge

Four types of Super Typhoon drip emitter with trapezoidal channel were selected out for the investigation of the flow field of the channel, and the CFD (Computational Fluid Dynamics) method was applied to simulate the micro-field inside the channel. The simulation results showed that the emitter discharge of different turbulent model is 4%-14% bigger than that of the experimental results, the average discharge deviation of κ-ω and RSM model is 5, 4.5 respectively, but the solving efficiency of the κ-ω model is obviously higher than that of the RSM model.

EFD and CFD Study of Forces, Ship Motions, and Flow Field for KRISO Container Ship Model in Waves

2020 ◽  
Vol 64 (01) ◽  
pp. 61-80
Author(s):  
Ping-Chen Wu ◽  
Md. Alfaz Hossain ◽  
Naoki Kawakami ◽  
Kento Tamaki ◽  
Htike Aung Kyaw ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Flow Field ◽  
Flow Simulation ◽  
Wake Flow ◽  
Ship Motions ◽  
Container Ship ◽  
Added Resistance ◽  
Ocean Engineering ◽  
Ship Model ◽  
Calm Water

Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools. However, validation of the computational flow field still remains a challenge. In the previous study, the flow field around the Korea Research Institute for Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 tanker model with and without propeller condition and without rudder condition was measured by the authors, as well as the resistance and self-propulsion tests in waves. In this study, the KRISO container ship model appended with a rudder was used for the higher Froude number .26 and smaller block coefficient .65. The experiments were conducted in the Osaka University towing tank using a 3.2-m-long ship model for resistance and self-propulsion tests in waves. Viscous flow simulation was performed by using CFDShip-Iowa. The wave conditions proposed in Computational Fluid Dynamics (CFD) Workshop 2015 were considered, i.e., the wave-ship length ratio λ/L = .65, .85, 1.15, 1.37, 1.95, and calm water. The objective of this study was to validate CFD results by Experimental Fluid Dynamics (EFD) data for ship vertical motions, added resistance, and wake flow field. The detailed flow field for nominal wake and self-propulsion condition will be analyzed for λ/L = .65, 1.15, 1.37, and calm water. Furthermore, bilge vortex movement and boundary layer development on propeller plane, propeller thrust, and wake factor oscillation in waves will be studied.

Sign in / Sign up

Export Citation Format

Share Document