Turbulence model formulation and dispersion modelling for the CFD simulation of flows around obstacles and on complex terrains

2019 ◽  
Author(s):  
A. Parente ◽  
R. Longo ◽  
M. Ferrarotti
Keyword(s):  
Turbulence Model ◽  
Cfd Simulation ◽  
Dispersion Modelling ◽  
Model Formulation

CFD Simulation of Gas Distributor with Two Chambers

2014 ◽  
Vol 989-994 ◽  
pp. 2264-2267
Author(s):  
Dong Fang Zhao ◽  
Feng Guo Liu
Keyword(s):  
Natural Gas ◽  
Mass Flow Rate ◽  
Turbulence Model ◽  
Mass Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Second Order ◽  
Gas Distributor ◽  
New Type ◽  
Simulation Results

This paper investigated a new type of gas distributor with two chambers by CFD software. The distributor has a natural gas inlet and nine nozzle outlets. For the investigation of this project, the mass flow rate of the distributor was analyzed in this paper to provide a way to optimize the structure of distributor. The N-S equations approached with the RNG k-ε turbulence model and the discretization were employed second order upwind. The simulation results will provide a number of useful suggestions and references for the further design.

MODIFICATION OF THE SPALART–ALLMARAS MODEL FOR HEMOLYTIC SHEAR FLOW SIMULATION WITH PIV EXPERIMENT

2020 ◽  
Vol 20 (02) ◽  
pp. 2050002
Author(s):  
ZHEQIN YU ◽  
JIANPIN TAN ◽  
SHUAI WANG
Keyword(s):  
Shear Flow ◽  
Turbulence Model ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Simulation ◽  
Simulation Accuracy ◽  
Nozzle Orifice ◽  
Comparison Results ◽  
Model Coefficient ◽  
Simulation Results

Hemolysis in blood-contacting devices severely affects the health of users, and computation fluid dynamics (CFD) simulation is a crucial method for hemolysis analysis. Medical equipment has high requirements for simulation accuracy. Modification of the turbulence model is one of the most effective ways to improve efficiency. In this study, we designed nozzle models to simulate hemolytic shear flow, varying the degree of shear flow through different nozzle orifice sizes. The study acquires microscopic flow results through Particle Image Velocimetry (PIV) experiments, and the Sparlart–Allmaras (S–A) model was modified based on the experimental results. In the study, we obtained the influence characteristics of the model coefficients on the simulation results and completed the accuracy correction. The results showed that the model coefficient [Formula: see text] has the most significant effect on the simulation results. Correcting [Formula: see text] to about 200% of the standard value can significantly improve the simulation accuracy, and the high shear flow intensity corresponds to a slightly lower correction value. The model modification eliminates the simulation error in the high-speed area, and the comparison results show that it is superior to the standard turbulence model.

scholarly journals HISTORY OF UTILIZATION OF THE COMPUTATIONAL FLUID DYNAMICS METHOD FOR STUDY PICO HYDRO TYPE CROSS-FLOW

2021 ◽  
Vol 2 (1) ◽  
pp. 017-024
Author(s):  
Dendy Adanta ◽  
Dewi Puspita Sari ◽  
Nura Muaz Muhammad ◽  
Aji Putro Prakoso
Keyword(s):  
Relative Error ◽  
Turbulence Model ◽  
Rural Areas ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Electrical Power ◽  
Cross Flow ◽  
Moving Mesh ◽  
Absolute Relative Error ◽  
The Absolute

Energy crisis in particular, electricity in the isolated rural areas of Indonesia is a very crucial issue that needs to be resolve through  electrification . Compared to other options, pico hydro cross-flow turbine (CFT) is the better option to provides electrical power for the isolated rural areas. Studies to improve CFT performance can be undertaken analytically, numerically, experimentally, or a combination of those methods. However, the development of computer technology makes numerical simulation studies have become increasingly frequent. This paper describes the utilization of the computational fluid dynamic (CFD) approach in the pico hydro CFT method. This review has resulted that the recommended Renormalization Group (RNG) k-ε turbulence model for CFT CFD simulation because its absolute relative error is lower than standard k-ε and transitional Shear Stress Transport (SST). The absolute relative error for the RNG k-ε turbulence model of 3.08%, standard k-ε of 3.19%, and transitional SST of 3.10%. While for the unsteady approach, the six-degrees of freedom (6-DoF) are considered because more accurate than moving mesh. The absolute relative error for 6-DoF of 3.1% and moving mesh of 9.5%. Thus, based on the review, the RNG k-ε turbulence model and 6-DoF are proposed for the pico hydro CFT CFD study.

scholarly journals CFD Simulation Strategy for Hypersonic Aerodynamic Heating around a Blunt Biconic

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Shutian Yu ◽  
Xinyue Ni ◽  
Fansheng Chen
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Thermal Protection ◽  
High Reliability ◽  
Aerodynamic Heating ◽  
Discretization Scheme ◽  
Wall Cell ◽  
Simulation Strategy ◽  
Cell Reynolds Number

The design of the thermal protection system requires high-precision and high-reliability CFD simulation for validation. To accurately predict the hypersonic aerodynamic heating, an overall simulation strategy based on mutual selection is proposed. Foremost, the grid criterion based on the wall cell Reynolds number is developed. Subsequently, the dependence of the turbulence model and the discretization scheme is considered. It is suggested that the appropriate value of wall cell Reynolds number is 1 through careful comparison between one another and with the available experimental data. The excessive number of cells is not recommended due to time-consuming computation. It can be seen from the results that the combination of the AUSM+ discretization scheme and the Spalart-Allmaras turbulence model has the highest accuracy. In this work, the heat flux error of the stagnation point is within 1%, and the overall average relative error is within 10%.

Efficient Computation and Modeling of Viscous Flow Effects in ComFLOW

2013 ◽  
Author(s):  
Henri J. L. van der Heiden ◽  
Peter van der Plas ◽  
Arthur E. P. Veldman ◽  
Roel W. C. P. Verstappen ◽  
Roel Luppes
Keyword(s):  
Reynolds Number ◽  
Viscous Flow ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Second Order ◽  
Efficient Computation ◽  
Flow Effects ◽  
High Reynolds

In offshore applications, details of viscous flow effects can become relevant when predicting e.g. drag forces on the columns of oil drilling rigs, or the flow around a semisubmersible in figure 1. This motivates a novel approach for efficiently simulating viscous flow effects at high Reynolds numbers with the CFD simulation tool ComFLOW. In ComFLOW, the Navier–Stokes equations can be solved for one-phase and for two-phase flow. The equations are discretized second-order in space, and second-order in time. An Improved Volume-of-Fluid (IVOF) algorithm is used for free-surface advection and reconstruction [1, 2]. Modeling viscous flow effects in high Reynolds number flows requires a turbulence model that provides accurate results on coarse grids. We pursue to achieve a high local grid resolution in a computationally efficient manner. Both approaches are tested for flows around a square cylinder: grid refinement at Reynolds numbers 10 and 100, and the turbulence model at Reynolds number 22,000.

CFD Performance Analysis of a Stirred Tank Flowmaker

2006 ◽  
Author(s):  
Lasse A. Rosendahl ◽  
Xiaopeng Wang ◽  
Christian B. Jacobsen
Keyword(s):  
Steady State ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Stirred Tank ◽  
Mean Flow ◽  
Solution Quality ◽  
Transient Simulations ◽  
Multiple Frame ◽  
Steady State Simulation

In the present work, the mean flow field in a stirred tank equipped with a commercially available Grundfos AFG.40.230.35 flowmaker is investigated using both steady-state and transient CFD simulation, in order to provide information on the interaction between flow, propeller and wall proximity as well as information on aspects of using numerical tools for this type of fluid machinery. The simulations, carried out with Ansys CFX 10, used a multiple frame of reference (MFR) approach to include a full representation of the flowmaker blade and motor geometry, in order to fully include the effects of the blade shape and variable pitch for both stationary and transient simulations. The influence of grid type, turbulence model and steady vs transient setup on solution quality has been investigated, and the steady state calculations are compared with LDA measurements. The results show that for the steady state calculations, the choice of grid type is decisive in terms of quality of results, and that the transient simulations using the SST turbulence model yields a superior prediction of flow characteristics; however, the computational expenses for transient simulation is around 10 times than steady-state simulation.

scholarly journals An unsteady, moving mesh CFD simulation for Harrier hot-gas ingestion control analysis

2007 ◽  
Vol 111 (1117) ◽  
pp. 133-144 ◽  
Author(s):  
G. A. Richardson ◽  
W. N. Dawes ◽  
A. M. Savill
Keyword(s):  
Model Calculation ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Impinging Jets ◽  
Moving Mesh ◽  
Scale Model ◽  
Control Analysis ◽  
Test Rig ◽  
Hot Gas ◽  
Flow Domain

Hot gas ingestion (HGI) can be a problematic feature of short take-off vertical landing (STOVL) aircraft during the descent phase of landing, or while on the ground. The hot exhaust gases from the downwards pointing nozzles can be re-ingested into the engine intakes, causing power degradation or reduced engine surge margin. The flow-fields that characterise this phenomenon are complex, with supersonic impinging jets and cross-flows creating large ground vortices and fountain up-wash flows. A flow solver has been developed to include a suitable linear mesh deformation technique for the descending aircraft configuration. The code has been applied to predict the occurrence of HGI, by simulating experimental results from a 1/15th scale model of a descending Harrier. This has enabled an understanding of the aerodynamic mechanisms that govern HGI, in terms of the near-field and far-field effects and their impact on the magnitude of temperatures at the engine intake. This paper presents three sets of CFD results. First a validation exercise shows predicted results from the twin-jet with intake in crossflow test-case. This is an unsteady Reynolds averaged Navier Stokes (URANS) solution for a static geometry (there is no moving mesh). This allows comparison with experiment. Secondly, a full descent phase URANS Spalart-Allmaras (SA) turbulence model calculation is done on an 8·5m cell mesh for half the flow domain of the Harrier model and test-rig without dams/strakes. This shows how the HGI flow mechanisms affect the engine intake temperature profiles, for the case where there are no flow control methods on the underside of the aircraft. Thirdly, the full descent phase URANS SA turbulence model calculation is done on a 22·4m cell mesh for the full flow domain of the Harrier model and test-rig, with the dam/strake geometry included in the structured mesh region.

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