Large Eddy Simulations of Turbofan Engine Exhaust Plume Dispersion on Take-Off Runway

2013 ◽  
Author(s):  
Apostolos Spanelis ◽  
Kevin Garry ◽  
Mark Savill
Keyword(s):  
Experimental Data ◽  
Computational Cost ◽  
Passive Scalar ◽  
Algebraic Model ◽  
Plume Dispersion ◽  
Engine Exhaust ◽  
Exhaust Plume ◽  
Large Eddy ◽  
Lift Off ◽  
Validation Tests

The pollution generated by the aircraft engines at the start of the take-off run is an important contributor to the local air quality in proximity to airports. The installation of an array of baffles in the runway strip behind the start of the runway, a configuration aiming to accelerate the lift-off of the exhaust plume, is numerically investigated. Validation tests are carried out in an effort to limit the computational cost. In this way, experimental data, including mean and RMS velocity profiles, as well as passive scalar concentrations, have been referenced. Additionally, a Dynamic Response Algebraic Model for Baffle Imitation (DRAMBI) has been devised. The numerical model is presented and tested. Experimental data obtained in the Atmospheric Boundary Layer Wind Tunnel (ABLWT) of Cranfield University, including drag force measurements and passive scalar concentrations, are used for the validation of the model. The predictions of DRAMBI are also compared to the results of conventional simulations including the baffle geometries. In this way, two-dimensional volume sections of mean and RMS contours of velocity and passive scalar, are presented and analysed. Finally, the axial momentum reduction required so that buoyancy becomes dominant and the plume naturally lifts-off, is investigated.

scholarly journals Large Eddy Simulation of Scalar Mixing in Jet in a Cross-Flow

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Asela Uyanwaththa ◽  
Weeratunge. Malalasekera ◽  
Graham Hargrave ◽  
Mark Dubal
Keyword(s):  
Experimental Data ◽  
Velocity Field ◽  
Large Eddy Simulation ◽  
Cross Flow ◽  
Passive Scalar ◽  
Scalar Mixing ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fuel Mixing ◽  
Good Agreement

Jet in a cross-flow (JICF) is a flow arrangement found in many engineering applications, especially in gas turbine air–fuel mixing. Understanding of scalar mixing in JICF is important for low NOx burner design and operation, and numerical simulation techniques can be used to understand both spatial and temporal variation of air–fuel mixing quality in such applications. In this paper, mixing of the jet stream with the cross-flow is simulated by approximating the jet flow as a passive scalar and using the large eddy simulation (LES) technique to simulate the turbulent velocity field. A posteriori test is conducted to assess three dynamic subgrid scale models in modeling jet and cross-flow interaction with the boundary layer flow field. Simulated mean and Reynolds stress component values for velocity field and concentration fields are compared against experimental data to assess the capability of the LES technique, which showed good agreement between numerical and experimental results. Similarly, time mean and standard deviation values of passive scalar concentration also showed good agreement with experimental data. In addition, LES results are further used to discuss the scalar mixing field in the downstream mixing region.

scholarly journals Wall Modeled Large Eddy Simulation of Flow Over a Wall-Mounted Hump

2014 ◽  
Author(s):  
Deepu Dilip ◽  
Danesh Tafti
Keyword(s):  
Experimental Data ◽  
Pressure Coefficient ◽  
Boundary Layer Equation ◽  
Computational Cost ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Fine Mesh ◽  
Large Eddy

Large Eddy Simulations (LES) of wall-bounded flows at high Reynolds numbers demand an extremely fine mesh resolution in the wall proximal inner layer. Accurate modeling of near wall turbulence is therefore crucial in reducing the computational cost of LES at practical Reynolds numbers. One approach is the implementation of a two-layer model that solves for a reduced one-dimensional boundary layer equation in the inner wall layer. A wall modeled LES thus allows for a coarser grid resolution than a wall resolved LES. This work evaluated the performance of a wall modeled LES against a wall resolved LES as well as experimental data for the flow over a wall mounted hump at Reynolds number 9.36×105. Results from the wall modeled LES were in good agreement with both wall resolved LES and experimental data in parameters such as surface pressure coefficient, skin friction, mean velocity profiles, Reynolds stresses and flow reattachment. It was observed that the wall modeled LES required only a fifth of the computational resources required for the wall resolved LES.

Large eddy simulation of evolution of a passive scalar in plane jet

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 1509-1516 ◽  
Author(s):  
C. Le Ribault ◽  
S. Sarkar ◽  
S. A. Stanley
Keyword(s):  
Large Eddy Simulation ◽  
Passive Scalar ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Plane Jet

scholarly journals A study of computational methods for wake structure and base pressure prediction of a generic SUV model with fixed and rotating wheels

2017 ◽  
Vol 231 (9) ◽  
pp. 1222-1238 ◽  
Author(s):  
David Forbes ◽  
Gary Page ◽  
Martin Passmore ◽  
Adrian Gaylard
Keyword(s):  
Experimental Data ◽  
Computational Methods ◽  
Large Scale ◽  
Ground Plane ◽  
Computational Cost ◽  
Rear Wheel ◽  
Base Pressure ◽  
Detached Eddy Simulation ◽  
Wake Structure ◽  
Wake Interactions

This study is an evaluation of the computational methods in reproducing experimental data for a generic sports utility vehicle (SUV) geometry and an assessment on the influence of fixed and rotating wheels for this geometry. Initially, comparisons are made in the wake structure and base pressures between several CFD codes and experimental data. It was shown that steady-state RANS methods are unsuitable for this geometry due to a large scale unsteadiness in the wake caused by separation at the sharp trailing edge and rear wheel wake interactions. unsteady RANS (URANS) offered no improvements in wake prediction despite a significant increase in computational cost. The detached-eddy simulation (DES) and Lattice–Boltzmann methods showed the best agreement with the experimental results in both the wake structure and base pressure, with LBM running in approximately a fifth of the time for DES. The study then continues by analysing the influence of rotating wheels and a moving ground plane over a fixed wheel and ground plane arrangement. The introduction of wheel rotation and a moving ground was shown to increase the base pressure and reduce the drag acting on the vehicle when compared to the fixed case. However, when compared to the experimental standoff case, variations in drag and lift coefficients were minimal but misleading, as significant variations to the surface pressures were present.

Larger-Eddy Simulation of Velocity Fluctuation in a Mixing T-Junction

2012 ◽  
Vol 152-154 ◽  
pp. 1313-1318
Author(s):  
Tao Lu ◽  
Su Mei Liu ◽  
Ping Wang ◽  
Wei Yyu Zhu
Keyword(s):  
Experimental Data ◽  
Velocity Fluctuation ◽  
Flow Model ◽  
Numerical Results ◽  
Mean Square ◽  
Main Duct ◽  
Velocity Fluctuations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

Velocity fluctuations in a mixing T-junction were simulated in FLUENT using large-eddy simulation (LES) turbulent flow model with sub-grid scale (SGS) Smagorinsky–Lilly (SL) model. The normalized mean and root mean square velocities are used to describe the time-averaged velocities and the velocities fluctuation intensities. Comparison of the numerical results with experimental data shows that the LES model is valid for predicting the flow of mixing in a T-junction junction. The numerical results reveal the velocity distributions and fluctuations are basically symmetrical and the fluctuation at the upstream of the downstream of the main duct is stronger than that at the downstream of the downstream of the main duct.

Thrust Measurements using Acoustic Sensing on a Turbofan Engine Exhaust Plume

2021 ◽  
Author(s):  
John Gillespie ◽  
Kevin T. Lowe ◽  
Wing Ng ◽  
Loren Crook ◽  
Victor Oechsle
Keyword(s):  
Engine Exhaust ◽  
Turbofan Engine ◽  
Acoustic Sensing ◽  
Exhaust Plume

Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations

2021 ◽  
Author(s):  
Gaston Latessa ◽  
Angela Busse ◽  
Manousos Valyrakis
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Large Scale ◽  
Large Eddy Simulations ◽  
Flow Conditions ◽  
Mean Flow ◽  
Protection Measures ◽  
Practical Applications ◽  
Particle Entrainment ◽  
Large Eddy

<p>The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.</p><p>In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.</p><p>Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle’s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.</p><p>The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.</p><p>A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.</p><p>Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.</p>

scholarly journals Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation

2020 ◽  
Vol 8 (9) ◽  
pp. 728
Author(s):  
Said Alhaddad ◽  
Lynyrd de Wit ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Eddy Simulation ◽  
Failure Evolution ◽  
Large Eddy ◽  
Flow Slides

Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.

scholarly journals Wave Propagation in Thin-Walled Aortic Analogues

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
C. G. Giannopapa ◽  
J. M. B. Kroot ◽  
A. S. Tijsseling ◽  
M. C. M. Rutten ◽  
F. N. van de Vosse
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Frequency Domain ◽  
Analytical Model ◽  
Viscoelastic Properties ◽  
Numerical Models ◽  
Computational Cost ◽  
One Dimensional ◽  
Arterial Blood

Research on wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flows. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one-dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models, well defined in vitro experiments are of great importance. The objective of this paper is to present a frequency domain analytical model based on the one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogs. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, volumetric flow rate, and wall distention obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account.

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