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 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 Numerical and Experimental Investigation of the Wake Flow Downstream of a Linear Turbine Cascade

1998 ◽  
Author(s):  
Wolfgang Sanz ◽  
Arno Gehrer ◽  
Jakob Woisetschläger ◽  
Martin Forstner ◽  
Wolfgang Artner ◽  
...  
Keyword(s):  
Turbulence Modeling ◽  
Turbulence Models ◽  
Wake Flow ◽  
Navier Stokes ◽  
Laser Doppler Velocimeter ◽  
Turbine Cascade ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
And Performance ◽  
Transonic Cascade

In turbomachinery the wake flow together with the inherent unsteadiness caused by interaction between stator and rotor has a significant impact on efficiency and performance. The prediction of the wake flow depends largely on the turbulence modeling. Therefore in this study the evolution of a viscous wake downstream of a linear turbine cascade is experimentally and computationally investigated. In a transonic cascade test stand Laser Doppler Velocimeter (LDV) measurements of velocity and turbulent kinetic energy are done in several axial planes downstream of the blade trailing edge. Two different turbulence models are then incorporated into a two-dimensional Navier-Stokes solver to calculate the turbulent wake flow and the results are compared with the experimental data to test the quality of the turbulence models. The large discrepancies between measurement and Calculation are assumed to be caused by the periodic vortex shedding from the blunt trailing edge which is not taken into account by the turbulence models. But further research is needed to resolve this issue.

scholarly journals Effect of Leading-Edge Bulges on Aerodynamic Characteristics of Bionic Wingsail

2021 ◽  
Author(s):  
Chen Li ◽  
Peiting Sun ◽  
Hongming Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Suction Surface ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Extension Direction ◽  
Lift And Drag

The leading-edge bulges along the extension direction are designed on the marine wingsail. The height and the spanwise wavelength of the protuberances are 0.1c and 0.25c, respectively. At Reynolds number Re=5×105, the Reynolds Averaged Navier-Stokes equations are applied to the simulation of the wingsail with the bulges thanks to ANSYS Fluent finite-volume solver based on the SST K-ω models. The grid independence analysis is carried out with the lift and drag coefficients of the wingsail at AOA = 8° and AOA=20°. The results show that while the efficiency of the wingsail is reduced by devising the leading-edge bulges before stall, the bulges help to improve the lift coefficient of the wingsail when stalling. At AOA=22° under the action of the leading-edge tubercles, a convective vortex is formed on the suction surface of the modified wingsail, which reduces the flow loss. So the bulges of the wingsail can delay the stall.

scholarly journals Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

2020 ◽  
Vol 01 (02) ◽  
pp. 29-36
Author(s):  
Md Rhyhanul Islam Pranto ◽  
Mohammad Ilias Inam
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Numerical Results ◽  
Ansys Fluent ◽  
Coefficient Increase ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.

scholarly journals Application of different turbulence models for improving construction of small-scale boiler fired by solid fuel

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 809-823
Author(s):  
Nebojsa Manic ◽  
Vladimir Jovanovic ◽  
Dragoslava Stojiljkovic ◽  
Zagorka Brat
Keyword(s):  
Turbulence Model ◽  
Solid Fuel ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Experimental Tests ◽  
Computer Hardware ◽  
Small Scale ◽  
Heat Output ◽  
Ansys Fluent ◽  
Model Fluid

Due to the rapid progress in computer hardware and software, CFD became a powerful and effective tool for implementation turbulence modeling in defined combustion mathematical models in the complex boiler geometries. In this paper the commercial CFD package, ANSYS FLUENT was used to model fluid flow through the boiler, in order to define velocity field and predict pressure drop. Mathematical modeling was carried out with application of Standard, RNG, and Realizable k-? turbulence model using the constants presented in literature. Three boilers geometry were examined with application of three different turbulence models with variants, which means consideration of 7 turbulence model arrangements in FLUENT. The obtained model results are presented and compared with data collected from experimental tests. All experimental tests were performed according to procedures defined in the standard SRPS EN 303-5 and obtained results are presented in this paper for all three examined geometries. This approach was used for improving construction of boiler fired by solid fuel with heat output up to 35 kW and for selection of the most convenient construction.

Aerodynamics of plunging airfoil in wind gust

2018 ◽  
Vol 90 (7) ◽  
pp. 1050-1064 ◽  
Author(s):  
Arpan Das ◽  
Shaligram Tiwari
Keyword(s):  
Navier Stokes ◽  
Wind Gust ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Freestream Velocity ◽  
Content Type ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Aerial Vehicle ◽  
Lift And Drag

Purpose Growing application of micro aerial vehicle (MAV) sets in demand for accurate computations of low Reynolds number flows past their wings. The purpose of this study is to investigate the effect of unsteady freestream velocity or wind gust on a harmonically plunging symmetric NACA0012 airfoil at Re = 1,000. The influence of unsteady parameters, such as reduced frequency of plunging motion (0.25 < k < 1.5), non-dimensional plunging amplitude (ho = 0.2) and non-dimensional amplitude of wind gust (0.1 = λ = 0.4) has been studied. Design/methodology/approach Computations have been carried out using commercial software ANSYS Fluent 16.0. To incorporate the plunging motion, the entire reference frame is oscillating, and thereby, a source term is added in the Navier–Stokes equation. Findings The results have been presented in the form of streamlines, vorticity contours, lift and drag signals and their spectra. It is observed that the ratio of plunging frequency to gust frequency (f/fg) has strong influence on periodic characteristics of unsteady wake. It has also been observed that for a fixed plunging amplitude, an increase in value of k results into a change from positive drag to thrust. Practical implications The research has implications in the development of MAV. Originality/value This study is intended to get a better understanding of unsteady parameters associated with gusty flow in flapping wing applications and possible ways to alleviate its adverse effect on it.

scholarly journals Turbulence Modeling a Review for Different Used Methods

2021 ◽  
Vol 39 (1) ◽  
pp. 227-234
Author(s):  
Khelifa Hami
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Simulation Models ◽  
Navier Stokes ◽  
Future Research ◽  
Detached Eddy Simulation ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Complicated Geometries

This contribution represents a critical view of the advantages and limits of the set of mathematical models of the physical phenomena of turbulence. Turbulence models can be grouped into two categories, depending on how turbulent quantities are calculated: direct numerical simulations (DNS) and RANS (Reynolds Averaged Navier-Stokes Equations) models. The disadvantage of these models is that they require enormous computing power, inaccessible, especially for large and complicated geometries. For this reason, hybrid models (combinations between DNS and RANS methods) have been developed, for example, the LES (“Large Eddy Simulation”) or DES (“Detached Eddy Simulation”) models. They represent a compromise - are less precise than DNS, but more precise than RANS models. The results presented in this contribution will allow and facilitate future research in the field the choice of the model approach necessary for the case studies whatever their difficulty factor.

scholarly journals COMPARISON OF NUMERICAL WAVE TANKS WITH VARIOUS TURBULENCE MODELS IN APPLICATION TO LONG WAVE MOTION AND ITS INTERACTION WITH A VERTICAL WALL

2018 ◽  
pp. 29
Author(s):  
Gizem Ezgi Cinar ◽  
Hasan Gokhan Guler ◽  
Taro Arikawa ◽  
Cuneyt Baykal ◽  
Ahmet Cevdet Yalciner
Keyword(s):  
Wave Motion ◽  
Turbulence Modeling ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Computational Time ◽  
Long Wave ◽  
Large Eddy ◽  
Numerical Wave

In this study, performances of interFoam solver of OpenFOAM and CADMAS-SURF computational tools with several turbulence modelling approaches on the numerical modelling of long wave motion and its interaction with a vertical wall based on the physical model experiments presented by Arikawa (2015) are investigated and compared. IHFOAM is used as wave generation and absorption boundary condition (Higuera et al., 2013). Three-dimensional simulations are carried out solving Reynolds Averaged Navier Stokes (RANS) with no-turbulence model and with k-ε and k-ω SST (Shear Stress Transport) turbulence models in addition to Large Eddy Simulations (LES). The aim of this study is to understand the contribution from turbulence modeling and compare the numerical wave tanks in long wave motion and their interaction with a vertical wall. The results are further discussed in scope of required accuracy in such engineering applications focusing on computational time.

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.

Prediction of Viscous Ship Roll Damping by Unsteady Navier-Stokes Techniques

1997 ◽  
Vol 119 (2) ◽  
pp. 108-113 ◽  
Author(s):  
R. A. Korpus ◽  
J. M. Falzarano
Keyword(s):  
Potential Flow ◽  
Turbulence Modeling ◽  
Numerical Technique ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Ship Motions ◽  
Ship Hulls ◽  
Unsteady Rans ◽  
Flow Effects ◽  
Real Flow

This paper describes a numerical technique for analyzing the viscous unsteady flow around oscillating ship hulls. The technique is based on a general Reynolds-averaged Navier-Stokes (RANS) capability, and is intended to generate viscous roll moment data for the incorporation of real-flow effects into potential flow ship motions programs. The approach utilizes the finite analytic technique for discretizing the unsteady RANS equations, and a variety of advanced turbulence models for closure. The calculations presented herein focus on viscous and vortical effects without free-surface, and utilize k-epsilon turbulence modeling. Series variations are presented to study the effects of frequency, amplitude, Reynolds number, and the presence of bilge keels. Moment component breakdown studies are performed in each case to isolate the effects of viscosity, vorticity, and potential flow pressures.

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