scholarly journals Turbulence Model Sensitivity and Scour Gap Effect of Unsteady Flow around Pipe: A CFD Study

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Abbod Ali ◽  
R. K. Sharma ◽  
P. Ganesan ◽  
Shatirah Akib
Keyword(s):  
Transient Flow ◽  
Flow Behavior ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Turbulence Models ◽  
Horizontal Velocity ◽  
Gap Effect ◽  
Navier Stokes ◽  
Flow Equations ◽  
Continuity Equations

A numerical investigation of incompressible and transient flow around circular pipe has been carried out at different five gap phases. Flow equations such as Navier-Stokes and continuity equations have been solved using finite volume method. Unsteady horizontal velocity and kinetic energy square root profiles are plotted using different turbulence models and their sensitivity is checked against published experimental results. Flow parameters such as horizontal velocity under pipe, pressure coefficient, wall shear stress, drag coefficient, and lift coefficient are studied and presented graphically to investigate the flow behavior around an immovable pipe and scoured bed.

Partially Cavitating Hydrofoils: Experimental and Numerical Analysis*

2000 ◽  
Vol 44 (01) ◽  
pp. 40-58
Author(s):  
Christian Pellone ◽  
Thierry Maître ◽  
Laurence Briançon-Marjollet
Keyword(s):  
Numerical Models ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Navier Stokes ◽  
Viscous Effects ◽  
Local Pressure ◽  
Two Phase ◽  
Complete Study ◽  
Flow Configurations ◽  
Potential Methods

The numerical modeling of partially cavitating foils under a confined flow configuration is described. A complete study of previous numerical models highlights that the presence of a turbulent and two-phase wake, at the rear of the cavity, has a nonnegligible effect on the local pressure coefficient, the cavitation number, the cavity length and the lift coefficient; hence viscous effects must be included. Two potential methods are used, each being coupled with a calculation of the boundary layer developed downstream of the cavity. So, an "open cavity" numerical model, as it is called, was developed and tested with two types of foil: a NACA classic foil and a foil of which the profile is obtained performing an inverse calculation on a propeller blade test section. On the other hand, under noncavitating conditions, for each method, the results are compared with the results obtained by the Navier-Stokes solver "FLUENT." The cavitating flow configurations presented herein were carried out using the small hydrodynamic tunnel at Bassin d'Essais des Carènes [Val de Reuil, France]. The results obtained by the two methods are compared with experimental measurements.

scholarly journals Comparative Study on CFD Turbulence Models for the Flow Field in Air Cooled Radiator

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1687
Author(s):  
Chao Yu ◽  
Xiangyao Xue ◽  
Kui Shi ◽  
Mingzhen Shao ◽  
Yang Liu
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Compartment Model ◽  
Navier Stokes ◽  
Engine Compartment ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Relevant Calculation

This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.

scholarly journals The Effect of a Pressure-Containing Correlation Model on Near-Wall Flow Simulations With Reynolds Stress Transport Models

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Svetlana V. Poroseva
Keyword(s):  
Flow Behavior ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Correlation Model ◽  
Transport Models ◽  
Wall Functions ◽  
Wall Flow ◽  
Model Equations ◽  
Rotating Pipe Flow

It is accustomed to think that turbulence models based on solving the Reynolds-averaged Navier–Stokes (RANS) equations require empirical functions to accurately reproduce the behavior of flow characteristics of interest, particularly near a wall. The current paper analyzes how choosing a model for pressure-strain correlations in second-order closures affects the need for introducing empirical functions in model equations to reproduce the flow behavior near a wall correctly. An axially rotating pipe flow is used as a test flow for the analysis. Results of simulations demonstrate that by using more physics-based models to represent pressure-strain correlations, one can eliminate wall functions associated with such models. The higher the Reynolds number or the strength of imposed rotation on a flow, the less need there is for empirical functions regardless of the choice of a pressure-strain correlation model.

A Methodology for Simulating Compressible Turbulent Flows

2005 ◽  
Vol 73 (3) ◽  
pp. 405-412 ◽  
Author(s):  
Hermann F. Fasel ◽  
Dominic A. von Terzi ◽  
Richard D. Sandberg
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Bluff Body ◽  
Turbulence Modeling ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Fine Grid ◽  
Local Flow

A flow simulation Methodology (FSM) is presented for computing the time-dependent behavior of complex compressible turbulent flows. The development of FSM was initiated in close collaboration with C. Speziale (then at Boston University). The objective of FSM is to provide the proper amount of turbulence modeling for the unresolved scales while directly computing the largest scales. The strategy is implemented by using state-of-the-art turbulence models (as developed for Reynolds averaged Navier-Stokes (RANS)) and scaling of the model terms with a “contribution function.” The contribution function is dependent on the local and instantaneous “physical” resolution in the computation. This physical resolution is determined during the actual simulation by comparing the size of the smallest relevant scales to the local grid size used in the computation. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that it approaches direct numerical simulations (DNS) in the fine-grid limit and such that it provides modeling of all scales in the coarse-grid limit and thus approaches a RANS calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in large eddy simulation (LES). However, FSM is distinctly different from LES in that it allows for a consistent transition between RANS, LES, and DNS within the same simulation depending on the local flow behavior and “physical” resolution. As a consequence, FSM should require considerably fewer grid points for a given calculation than would be necessary for a LES. This conjecture is substantiated by employing FSM to calculate the flow over a backward-facing step and a plane wake behind a bluff body, both at low Mach number, and supersonic axisymmetric wakes. These examples were chosen such that they expose, on the one hand, the inherent difficulties of simulating (physically) complex flows, and, on the other hand, demonstrate the potential of the FSM approach for simulations of turbulent compressible flows for complex geometries.

scholarly journals Computation of Axisymmetric Turbulent Viscous Flow Around Sphere

2009 ◽  
Vol 1 (2) ◽  
pp. 209-219 ◽  
Author(s):  
M. M. Karim ◽  
M. M. Rahman ◽  
M. A. Alim
Keyword(s):  
Viscous Flow ◽  
Pressure Coefficient ◽  
Axisymmetric Flow ◽  
Turbulence Models ◽  
Skin Friction Coefficient ◽  
Axisymmetric Body ◽  
Navier Stokes ◽  
Viscous Drag ◽  
Reynolds Averaged Navier Stokes ◽  
Flow Around Sphere

Axisymmetric turbulent viscous flow around sphere is computed using finite volume method based on Reynolds-averaged Navier-Stokes (RANS) equations. Two-dimensional axisymmetric flow solver has been used to analyze flow at Reynolds number of 5×106. Spalart-Allmaras (S-A) and shear stress transport (SST) k-ω turbulence models are used to capture turbulent viscous flow. The numerical results in terms of the skin friction coefficient, pressure coefficient and drag coefficient for different Reynolds numbers have been shown either graphically or in the tabular form. Velocity vectors have been displayed graphically. The computed results show good agreement with published experimental measurements.  Keywords: Axisymmetric body of revolution; Sphere; Viscous drag; CFD; Turbulence model; Reynolds-averaged Navier-Stokes (RANS) equations. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1286

Development of Accelerating Pipe Flow Starting From Rest

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Ivar Annus ◽  
Tiit Koppel ◽  
Laur Sarv ◽  
Leo Ainola
Keyword(s):  
Pipe Flow ◽  
Large Scale ◽  
Transformation Method ◽  
Transition To Turbulence ◽  
Navier Stokes ◽  
Axial Velocity Component ◽  
Flow Equations ◽  
Continuity Equations ◽  
Start Up ◽  
Experimental Findings

A uniformly accelerated laminar flow in a pipe, initially at rest, is analyzed. One-dimensional unsteady flow equations for start-up flow were derived from the Navier–Stokes and continuity equations. The dynamical boundary layer in a pipe is described theoretically with the Laplace transformation method for small values of time. A mathematical model describing the development of the velocity profile for accelerating flow starting from rest up to the point of transition to turbulence is given. The theoretical results are compared with experimental findings gained in a large-scale pipeline. Particle image velocimetry (PIV) technique is used to deduce the development of accelerating pipe flow starting from rest. The measured values of the axial velocity component are found to be in a good agreement with the analytical values.

scholarly journals A comparative study of URANS, DDES and DES simulations of Jetstream 31 aircraft near the compressibility limit

2021 ◽  
Vol 16 (2) ◽  
pp. 159-172
Author(s):  
Hrishabh Chaudhary ◽  
Nicolas Ledos ◽  
László Könözsy
Keyword(s):  
Comparative Study ◽  
Turbulence Modeling ◽  
Pressure Coefficient ◽  
Turbulence Models ◽  
Flight Test ◽  
Scale Model ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Fluent Software ◽  
Lift And Drag

This work presents a comparative study of Unsteady Reynolds–Averaged Navier–Stokes (URANS), Detached Eddy Simulations (DES) and Delayed Detached Eddy Simulations (DDES) turbulence modeling approaches by performing numerical investigation with the ANSYS-FLUENT software package on a full-scale model of the Jetstream 31 aircraft. The lift and drag coefficients obtained from different models are compared with flight test data, wind tunnel data and theoretical estimates. The different turbulence models are also compared with each other on the basis of pressure coefficient distributions and velocity fluctuations along various lines and sections of the aircraft. For the mesh and the conditions presented in this study, the DDES Spalart–Allmaras model gives the best overall results.

scholarly journals Numerical determination of hydrodynamic characteristics of a submerged airfoil

2020 ◽  
pp. 32-38
Author(s):  
М.А. Ливеринова ◽  
Н.В. Тряскин
Keyword(s):  
Free Surface ◽  
Pressure Coefficient ◽  
Independent Solution ◽  
Navier Stokes ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Relative Depth ◽  
Early Design Stage ◽  
Continuity Equations ◽  
Volume Method

В работе рассмотрено влияние параметров профиля на его гидродинамические характеристики. Задача решена методом, учитывающем вязкость, расчёты произведены в открытом пакете OpenFOAM методом контрольного объема, и потенциальным, численная реализация осуществляется методом граничного элемента. Оценка вихреволнового взаимодействия в потенциальном методе выполняется с помощью распределения гидродинамических особенностей по поверхности профиля и свободной поверхности, и численного решения системы уравнений нелинейной нестационарной задачи о движении крыла вблизи раздела сред вода-воздух. В вязкостном методе совместно решены уравнения Навье-Стокса и неразрывности, осреднённые по Рейнольдсу. Решена плоская задача, движение рассмотрено обращенное. Произведена верификация математической модели и найдено сеточно-независимое решение. Рассмотрено влияние относительной глубины погружения, различных скоростей движения, малых углов атаки, формы профиля в плане на его основные эксплуатационные характеристики: коэффициент подъемной силы и коэффициент сопротивления. Выбраны три профиля в плане: сегментный, Вальхнера, симметричный. Сделаны выводы о влиянии параметров профиля на гидродинамические характеристики (ГДХ), построены зависимости ГДХ от исследуемых параметров и распределение коэффициента давления по поверхности профиля. Рассмотренные методы хорошо согласуются между собой, позволяют оценить ГДХ крыла, построить волновую поверхность, подобрать оптимальные параметры движения для СПК численно на стадии проектирования. In this article, the influence of the profile parameters on the hydrodynamic characteristics of a submerged airfoil is reviewed. A home-made code based on boundary element method and hypotheses of the potential theory was used. The interaction between free surface and airfoil generated vortexes was estimated by distribution of hydrodynamic singularities on the airfoil and free surface. To consider viscosity effects, an open-source packet OpenFOAM based on finite-volume method was used to solve the Navier-Stokes and continuity equations averaged by Reynolds method. The mathematical model was verified and validated, and a grid-independent solution was found. The influence of the relative depth of immersion, speed, angle of attack, and the shape of the profile on its main hydrodynamic characteristics was considered. Three profiles were selected: segmental, Walchner, and symmetrical. The dependences of coefficients on the studied parameters and the distribution of the pressure coefficient over the profile are studied and analyzed. The considered methods are in a good agreement with each other. Obtained results allow to estimate the wing hydrodynamic characteristics and resulting wave surface which give possibility to select the optimal motion parameters for the hydrofoil at the early design stage.

scholarly journals Comparative study between flows around sphere and pod using finite volume method

2011 ◽  
Vol 8 (1) ◽  
pp. 49-58
Author(s):  
M. M. Karim ◽  
M. M. Rahman ◽  
M. A. Alim
Keyword(s):  
Comparative Study ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Pressure Coefficient ◽  
Turbulence Models ◽  
Skin Friction Coefficient ◽  
Navier Stokes ◽  
Structured Grid ◽  
Volume Method ◽  
The Comparative Study

Two-dimensional Finite Volume Method (FVM) based on Reynolds-averaged Navier-Stokes (RANS) equations is applied to solve the turbulent viscous flow around sphere and pod. Unstructured grid with boundary layer treatment is constructed around sphere whereas structured grid is generated around pod. Spalart-Allmaras (S-A) and Shear Stress Transport (SST) k-? turbulence models are used for sphere but SST k-? turbulence model is used only for pod to solve turbulent viscous flows at Reynold’s number of 5×106 and 3×106 respectively.  The numerical results in terms of the skin friction coefficient, pressure coefficient and drag coefficient are shown either graphically or in the tabular form. Velocity vectors as well as contour of pressure and velocity distribution are also displayed. Finally, the comparative study between flows around sphere and pod is done.DOI: http://dx.doi.org/10.3329/jname.v8i1.7388

scholarly journals Effects of Micro-Tab on the Lift Enhancement of Airfoil S-809 with Trailing-Edge Flap

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 547
Author(s):  
Jianjun Ye ◽  
Shehab Salem ◽  
Juan Wang ◽  
Yiwen Wang ◽  
Zonggang Du ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Flow Behavior ◽  
Air Flow ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Lower Surface ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Trailing Edge Flap

Recently, the Trailing-Edge Flap with Micro-Tab (TEF with Micro-Tab) has been exploited to enhance the performance of wind turbine blades. Moreover, it can also be used to generate more lift and delay the onset of stall. This study focused mostly on the use of TEF with Micro-Tab in wind turbine blades using NREL’s S-809 as a model airfoil. In particular, the benefits generated by TEF with Micro-Tab may be of great interest in the design of wind turbine blades. In this paper, an attempt was made to evaluate the influence of TEF with Micro-Tab on the performance of NREL’s S-809 airfoils. Firstly, a computational fluid dynamics (CFD) model for the airfoil NREL’s S-809 was established, and validated by comparison with previous studies and wind tunnel experimental data. Secondly, the effects of the flap position (H) and deflection angle (αF) on the flow behaviors were investigated. As a result, the effect of TEF on air-flow behavior was demonstrated by augmenting the pressure coefficient at the lower surface of the airfoil at flap position 80% chord length (C) and αF = 7.5°. Thirdly, the influence of TEF with Micro-Tab on the flow behaviors of the airfoil NREL’s S-809 was studied and discussed. Different Micro-Tab positions and constant TEF were examined. Finally, the effects of TEF with Micro-Tab on the aerodynamic characteristics of the S-809 with TEF were compared. The results showed that an increase in the maximum lift coefficient by 25% and a delay in the air-flow stall were accomplished due to opposite sign vortices, which was better than the standard airfoil and S-809 with TEF. Therefore, it was deduced that the benefits of TEF with Micro-Tab were apparent, especially at the lower surface of the airfoil. This particularly suggests that the developed model could be used as a new trend to modify the designs of wind turbine blades.

Sign in / Sign up

Export Citation Format

Share Document