Numerical Simulation of Flow Around a Simplified Car Body

2003 ◽  
Author(s):  
Emmanuel Guilmineau
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Turbulence Models ◽  
Test Case ◽  
Slant Angle ◽  
Acceptable Limit ◽  
Numerical Errors ◽  
Car Body ◽  
Ahmed Body

Simulations have been carried out for the generic car body (Ahmed body) for 25° and 35° slant angle. At a previous Workshop [1, 2], the results of different groups showed significant variations, even when the same turbulence models were used. This indicates that either the grids used in the investigation are too coarse to reduce the numerical errors below an acceptable limit, or that other factors, like boundary conditions, model implementation had a significant effect on the simulations. In any case, the results of the simulations were inconclusive, leading to a revaluation of this test case. In this study, we investigate numerically the flow around the Ahmed body for 25° and 35° slant angle. Results are compared with experimental data of Becker et al. [3].

CFD Analysis of Effects of Damage Due to Bird Strike on Fan Performance

2010 ◽  
Author(s):  
Baizura Bohari ◽  
Abdulnaser Sayma
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Structural Integrity ◽  
Operating Point ◽  
Computational Techniques ◽  
Test Case ◽  
Base Line ◽  
Bird Strike ◽  
Stall Margin ◽  
Speed Characteristic

Bird ingestion has been a hazard that affects the structural integrity and survivability of turbofan engines. It can result in deformation of one or more fan blades, in which case, the engine is likely to surge and not recover. Numerical studies and simulations of bird strikes have become essential to optimize the design of engine components simultaneously to increase the engine capabilities for acceptable damage tolerance. Good understanding of these phenomena and the implications on the behaviour of the flow field with respect to the damage affecting the fan blades are usually investigated using computational techniques and/or experimental methods. The purpose of this paper is to present a Computational Fluid Dynamics (CFD) method for the analysis of the aerodynamic behaviour of an aero-engine fan affected by a bird strike. NASA rotor 67 was used as a test case because of the availability of experimental data that can be used to calibrate the model for the undamaged fan. The undamaged fan characteristic was mapped using a modification to the methodology developed by Sayma (2007). In this method a downstream variable throttle is added which allows changing the operating point on the speed characteristic without having to change downstream boundary conditions. This approach allows for changes in fan operating point to come out of the calculation as opposed to those dictated by the downstream static pressure boundary conditions used in typical computations. The methodology is automated allowing for a sweep along a speed characteristic or along a working line in one calculation in the same way as a rig test is conducted. Agreement with experimental data when available was excellent. This provided the base line for the undamaged blades. A damaged blade was inserted among undamaged blades in the fan assembly and the fan characteristic was mapped for a range of rotational speeds. Two different degrees of damage were analysed in an attempt to establish a correlation between the extent of the damage and the locus of the stall boundary. It was found that small increments on the damage lead to significant reduction in stall margin particularly at higher rotational speeds.

scholarly journals The Computation of Adjacent Blade-Row Effects in a 1.5 Stage Axial Flow Turbine

1997 ◽  
Author(s):  
Rolf Emunds ◽  
Ian K. Jennions ◽  
Dieter Bohn ◽  
Jochen Gier
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Axial Flow ◽  
The Other ◽  
Navier Stokes ◽  
Blade Row ◽  
Flow Through ◽  
The University

This paper deals with the numerical simulation of flow through a 1.5 stage axial flow turbine. The 3-row configuration has been experimentally investigated at the University of Aachen where measurements behind the first vane, the first stage and the full configuration were taken. These measurements allow single blade row computations, to the measured boundary conditions taken from complete engine experiments, or full multistage simulations. The results are openly available inside the framework of ERCOFTAC 1996. There are two separate but interrelated parts to the paper. Firstly, two significantly different Navier-Stokes codes are used to predict the flow around the first vane and the first rotor, both running in isolation. This is used to engender confidence in the code that is subsequently used to model the multiple bladerow tests, the other code is currently only suitable for a single blade row. Secondly, the 1.5 stage results are compared to the experimental data and promote discussion of surrounding blade row effects on multistage solutions.

Evaluation of RANS Models in Predicting Low Reynolds, Free, Turbulent Round Jet

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Shahriar Ghahremanian ◽  
Bahram Moshfegh
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Diffusion Term ◽  
Turbulent Region ◽  
Round Jet ◽  
Rans Models ◽  
Low Reynolds

In order to study the flow behavior of multiple jets, numerical prediction of the three-dimensional domain of round jets from the nozzle edge up to the turbulent region is essential. The previous numerical studies on the round jet are limited to either two-dimensional investigation with Reynolds-averaged Navier–Stokes (RANS) models or three-dimensional prediction with higher turbulence models such as large eddy simulation (LES) or direct numerical simulation (DNS). The present study tries to evaluate different RANS turbulence models in the three-dimensional simulation of the whole domain of an isothermal, low Re (Re = 2125, 3461, and 4555), free, turbulent round jet. For this evaluation the simulation results from two two-equation (low Re k-ɛ and low Re shear stress transport (SST) k-ω), a transition three-equation (k-kl-ω), and a transition four-equation (SST) eddy-viscosity turbulence models are compared with hot-wire anemometry measurements. Due to the importance of providing correct inlet boundary conditions, the inlet velocity profile, the turbulent kinetic energy (k), and its specific dissipation rate (ω) at the nozzle exit have been employed from an earlier verified numerical simulation. Two-equation RANS models with low Reynolds correction can predict the whole domain (initial, transition, and fully developed regions) of the round jet with prescribed inlet boundary conditions. The transition models could only reach to a good agreement with the measured mean axial velocities and its rms in the initial region. It worth mentioning that the round jet anomaly is still present in the turbulent region of the round jet predicted by the low Re k-ɛ. By comparing the k and the ω predicted by different turbulence models, the blending functions in the cross-diffusion term is found one of the reasons behind the more consistent prediction by the low Re SST k-ω.

Numerical Simulation of Flow over Aerators on the Chute with an Anti-Arc Section by Turbulence Flow Model

2012 ◽  
Vol 256-259 ◽  
pp. 2543-2547
Author(s):  
Yi Min Xu ◽  
Yao Wang ◽  
Ji Rui Hou ◽  
Hua Qiang Wu ◽  
Xian Dong Liu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Flow Model ◽  
Velocity Fields ◽  
Aerated Flow ◽  
Turbulence Flow ◽  
Calculation Results ◽  
Complex Boundary ◽  
Simulation Results

For a flow chute with complex boundary conditions, such as with an anti-arc section, the flow behaviors and characteristics of aeration after the aerator are more complex than that in the straight chute. Based on the k~ε turbulence flow model together with VOF method, flow velocity fields over the aerator on the chute with anti-arc section were numerical simulated. Model experiments were investigated to verify the simulation results. Comparison shows that the calculation results agree well with the observed experimental data. Some factors including radius of the anti arc, aerator’s height and takeoff angel which influence aerated flow are discussed.

scholarly journals Numerical Simulation of Flow in Parshall Flume Using Selected Nonlinear Turbulence Models

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 151
Author(s):  
Mehdi Heyrani ◽  
Abdolmajid Mohammadian ◽  
Ioan Nistor
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Standard Error ◽  
Physical Modeling ◽  
Hydraulic Structure ◽  
Turbulence Models ◽  
Computational Fluid Dynamics Cfd ◽  
The Right

This study uses a computational fluid dynamics (CFD) approach to simulate flows in Parshall flumes, which are used to measure flowrates in channels. The numerical results are compared with the experimental data, which show that choosing the right turbulence model, e.g., v2−f and LC, is the key element in accurately simulating Parshall flumes. The Standard Error of Estimate (SEE) values were very low, i.e., 0.76% and 1.00%, respectively, for the two models mentioned above. The Parshall flume used for this experiment is a good example of a hydraulic structure for which the design can be more improved by implementing a CFD approach compared with a laboratory (physical) modeling approach, which is often costly and time-consuming.

Comparison of experimental data and numerical simulation of two-phase flow pattern in vertical minichannel

2012 ◽  
Vol 33 (1) ◽  
pp. 63-71
Author(s):  
Jarosław Sowiński ◽  
Marek Krawczyk ◽  
Marek Dziubiński
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Computational Domain ◽  
Two Phase ◽  
Ansys Fluent ◽  
Satisfactory Description

Comparison of experimental data and numerical simulation of two-phase flow pattern in vertical minichannel The aim of the study was the implementation of a numerical simulation of the air-water two-phase flow in the minichannel and comparing results obtained with the values obtained experimentally. To perform the numerical simulations commercial software ANSYS FLUENT 12 was used. The first step of the study was to reproduce the actual research installation as a three-dimensional model with appropriate and possible simplifications - future computational domain. The next step was discretisation of the computational domain and determination of the types of boundary conditions. ANSYS FLUENT 12 has three built-in basic models with which a two-phase flow can be described. However, in this work Volume-of-Fluid (VOF) model was selected as it meets the established requirements of research. Preliminary calculations were performed for a simplified geometry. The calculations were later verified whether or not the simplifications of geometry were chosen correctly and if they affected the calculation. The next stage was validation of the chosen model. After positive verification, a series of calculations was performed, in which the boundary conditions were the same as the starting conditions in laboratory experiments. A satisfactory description of the experimental data accuracy was attained.

Factorial Design Applied to CFD

2004 ◽  
Vol 126 (5) ◽  
pp. 791-798 ◽  
Author(s):  
Michel J. Cervantes ◽  
T. Fredrik Engstro¨m
Keyword(s):  
Boundary Conditions ◽  
Factorial Design ◽  
Draft Tube ◽  
Turbulence Models ◽  
Test Case ◽  
Unknown Boundary ◽  
Experimental Uncertainty ◽  
Complex Flow ◽  
Input Parameters ◽  
Unknown Boundary Conditions

Factorial design, a statistical method widely used for experiments, and its application to CFD are discussed. The aim is to propose a systematic, objective, and quantitative method for engineers to design a set of simulations in order to evaluate main and joint effects of input parameters on the numerical solution. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid, differencing schemes, and turbulence models. The complex flow of the Turbine-99 test case, a hydropower draft tube flow, is used to illustrate the method, where four factors are chosen to perform a 24 factorial design. The radial velocity at the inlet (not measured) is shown to have an important influence on the pressure recovery (7%) and the energy loss factor (49%).

Large Eddy Simulation of the Flow Around an Ahmed Body

2004 ◽  
Author(s):  
Sinisˇa Krajnovic´ ◽  
Lars Davidson
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Test Case ◽  
Ground Vehicles ◽  
New Approach ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Resolution Requirements ◽  
Surface Comparison ◽  
Ahmed Body

A new approach for large eddy simulation (LES) of the flows around ground vehicles is demonstrated. It is based on the character of the flow with large regions of recirculations rather than on traditional resolution requirements for the LES of wall bounded flows. Recommendations for preparing and realization of LES for vehicle flows are presented and validated on a test case of the flow around an Ahmed body with the 25° angle of the rear slanted surface. Comparison of the LES results with the experimental data proved the validity of this new method.

Numerical Simulation of Submerged Flows With Baffles Using v2-f- and k-e Turbulence Models

2006 ◽  
Author(s):  
A. Mehdizadeh ◽  
B. Firoozabadi ◽  
S. A. Sherif
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Fluid Flows ◽  
Complex Flow ◽  
Flow Features ◽  
Elliptic Relaxation ◽  
Surface Jet ◽  
Submerged Hydraulic Jump

This paper introduces the concept of a submerged hydraulic jump being used for energy dissipation. A baffle wall is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model ([Equation] - f model) has been used to simulate this submerged flow. During the last few years, the [Equation] - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the [Equation] - f model is superior to other RANS methods in many fluid flows where complex flow features are present. In this study, we compared the results of both models with each other and with available experimental data. In addition, based on a series of numerical simulations, a diagram was developed that predicts the effect of baffle position on the friction coefficient over the bed. This feature should help preventing or reducing erosion over the bed. Moreover, we have shown that in numerical simulation, like experimental data, in some cases the flow regimes of submerged flow with baffles can either be a deflected surface jet or reattached wall jet.

Sign in / Sign up

Export Citation Format

Share Document