An In-depth Comparison of Experimental and Computational Turbulence Parameters for In-cylinder Engine Flows PDF Download

Author: Charles Owen Funk
Publisher:
ISBN:
Category :
Languages : en
Pages : 458

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Author: Stephen Jay Kline
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 528

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Author: W. Rodi
Publisher: Elsevier
ISBN: 008053094X
Category : Mathematics
Languages : en
Pages : 1029

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Book Description
Turbulence is one of the key issues in tackling engineering flow problems. As powerful computers and accurate numerical methods are now available for solving the flow equations, and since engineering applications nearly always involve turbulence effects, the reliability of CFD analysis depends increasingly on the performance of the turbulence models. This series of symposia provides a forum for presenting and discussing new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. The papers in this set of proceedings were presented at the 5th International Symposium on Engineering Turbulence Modelling and Measurements in September 2002. They look at a variety of areas, including: Turbulence modelling; Direct and large-eddy simulations; Applications of turbulence models; Experimental studies; Transition; Turbulence control; Aerodynamic flow; Aero-acoustics; Turbomachinery flows; Heat transfer; Combustion systems; Two-phase flows. These papers are preceded by a section containing 6 invited papers covering various aspects of turbulence modelling and simulation as well as their practical application, combustion modelling and particle-image velocimetry.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722919252
Category :
Languages : en
Pages : 50

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A low Reynolds number k-epsilon turbulence model was presented which yields accurate predictions of the kinetic energy near the wall. The model is validated with the experimental channel flow data of Kreplin and Eckelmann. The predictions are also compared with earlier results from direct simulation of turbulent channel flow. The model is especially useful for internal flows where the inflow boundary condition of epsilon is not easily prescribed. The model partly derives from some observations based on earlier direct simulation results of near-wall turbulence. The low Reynolds number turbulence model together with an existing curvature correction appropriate to spinning cylinder flows was used to simulate the flow in a U-bend with the same radius of curvature as the Space Shuttle Main Engine (SSME) Turn-Around Duct (TAD). The present computations indicate a space varying curvature correction parameter as opposed to a constant parameter as used in the spinning cylinder flows. Comparison with limited available experimental data is made. The comparison is favorable, but detailed experimental data is needed to further improve the curvature model. Kaul, Upender K. Unspecified Center NAS2-11555...

Author: Andreas Dillmann
Publisher: Springer Nature
ISBN: 3030252531
Category : Technology & Engineering
Languages : en
Pages : 867

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This book gathers contributions to the 21st biannual symposium of the German Aerospace Aerodynamics Association (STAB) and the German Society for Aeronautics and Astronautics (DGLR). The individual chapters reflect ongoing research conducted by the STAB members in the field of numerical and experimental fluid mechanics and aerodynamics, mainly for (but not limited to) aerospace applications, and cover both nationally and EC-funded projects. Special emphasis is given to collaborative research projects conducted by German scientists and engineers from universities, research-establishments and industries. By addressing a number of cutting-edge applications, together with the relevant physical and mathematics fundamentals, the book provides readers with a comprehensive overview of the current research work in the field. The book’s primary emphasis is on aerodynamic research in aeronautics and astronautics, and in ground transportation and energy as well.

Author: Wei Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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A computational investigation of engine flow in an optical water analog engine has been carried out using KIVA. Three cases (20 RPM, 40 RPM and 60 RPM) are examined and discussed. Among the cases, simulation results of 20 RPM case are compared with previous PIV experiment results. The comparison indicates a good agreement between simulation and experiment. However, the simulation results highlight the ambiguity with regard to the velocity direction in experiment and provide a correct velocity profile at the latter part of intake stroke. A confined jet is identified in both the simulation and experiment, however, the experimental jet oscillates spatially three dimensionally, while the computationally determined jet retains constant boundaries. The study concludes that the Reynolds stress transport is the dominant component of the equation of motion near the piston surface and causes the turbulent mixing which is responsible for the mixing and combustion efficiency in an engine. For the comparison of the three different cases, there are obvious cyclic variations for different piston velocities. The discrepancies in the cases demonstrate that the transition to turbulence occurs at the lower RPM (' e.g'. 20 RPM) while the fully developed turbulence seems to occur at the higher RPM ('e.g'. 40 and 60 RPM). These, therefore, suggest that 2D PIV used in previous measurement is valid at lower RPM because the measurement actually measures the jet or the turbulence transition from jet, but 3D stereoscopic PIV is certainly better and necessary at higher RPM due to the 3D character of the turbulence.

Author: Jean Piquet
Publisher: Springer Science & Business Media
ISBN: 3662035596
Category : Technology & Engineering
Languages : en
Pages : 767

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obtained are still severely limited to low Reynolds numbers (about only one decade better than direct numerical simulations), and the interpretation of such calculations for complex, curved geometries is still unclear. It is evident that a lot of work (and a very significant increase in available computing power) is required before such methods can be adopted in daily's engineering practice. I hope to l"Cport on all these topics in a near future. The book is divided into six chapters, each· chapter in subchapters, sections and subsections. The first part is introduced by Chapter 1 which summarizes the equations of fluid mechanies, it is developed in C~apters 2 to 4 devoted to the construction of turbulence models. What has been called "engineering methods" is considered in Chapter 2 where the Reynolds averaged equations al"C established and the closure problem studied (§1-3). A first detailed study of homogeneous turbulent flows follows (§4). It includes a review of available experimental data and their modeling. The eddy viscosity concept is analyzed in §5 with the l"Csulting ~alar-transport equation models such as the famous K-e model. Reynolds stl"Css models (Chapter 4) require a preliminary consideration of two-point turbulence concepts which are developed in Chapter 3 devoted to homogeneous turbulence. We review the two-point moments of velocity fields and their spectral transforms (§ 1), their general dynamics (§2) with the particular case of homogeneous, isotropie turbulence (§3) whel"C the so-called Kolmogorov's assumptions are discussed at length.

Author: G. Biswas
Publisher: Narosa Publishing House
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 476

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Book Description
This book allows readers to tackle the challenges of turbulent flow problems with confidence. It covers the fundamentals of turbulence, various modeling approaches, and experimental studies. The fundamentals section includes isotropic turbulence and anistropic turbulence, turbulent flow dynamics, free shear layers, turbulent boundary layers and plumes. The modeling section focuses on topics such as eddy viscosity models, standard K-E Models, Direct Numerical Stimulation, Large Eddy Simulation, and their applications. The measurement of turbulent fluctuations experiments in isothermal and stratified turbulent flows are explored in the experimental methods section. Special topics include modeling of near wall turbulent flows, compressible turbulent flows, and more.

Author: Volker Sohm
Publisher: Cuvillier Verlag
ISBN: 3736922809
Category : Technology & Engineering
Languages : en
Pages : 186

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Book Description
Since the first passenger car with internal combustion (IC) engine was developed over 120 years ago, the device has been significantly improved regarding efficiency, emissions, smoothness and ease of use. Today IC-engines are used in roughly 850 million passenger cars worldwide. Even though many other concepts as e.g. fuel cells are investigated, it seems that no system can replace IC-engines in the near and intermediate future. Two different combustion concepts are considered to have the potential to full fill future requirements with respect to fuel consumption and emission standards: turbo-charged diesel and stratified spark ignition (SI) engines with high pressure direct injection (DI) systems. Both systems can operate with overall lean air/fuel mixtures. The first DISI-engine in a passenger car used a homogeneous air/fuel mixture. It was implemented in 1951 in the models Gutbrod Superior and Goliath GP 700 leading to a significant reduction in fuel consumption. The first application in mass production of direct injection systems in SI-engines was in 1997 in the Mitsubishi Carisma GDI (gasoline direct injection). The greatest issues of stratified DISI-engines today, which give a much higher potential in fuel consumption economy compared to the homogeneous combustion concept, are combustion stability and emissions. Cycle-to-cycle variations of the gas motion have been identified to play a key role in the further optimization of the device since they have a great impact on the combustion process. Engine parameters are set according to the behavior of the mean cycle. However, the extreme engine cycles, cycles of greatest and slowest burning rates, determine the operating range of the engine. Consequently, the optimal spark timing, equivalence ratio and compression ratio are a compromise. A critical issue in stratified DISI-engines is that cyclic variations are substantial to the combustibility of the air/fuel mixture at the time of the discharge of the spark plug leading to partial burning or even misfire, which is undesirable in terms of engine roughness, efficiency and unburned hydrocarbon emissions. Computational fluid dynamics (CFD) with common Reynolds averaged Naviers-Stokes (RANS) turbulence modeling has been established to be a very efficient and reliable tool within the design process of IC-engines. I. e. optimization of engine geometries can be accomplished with a short turnaround time. Additionally, insights into various physical processes can be gained that are difficult to study experimentally. However, this approach is limited by definition if unsteady features such as cycle-to-cycle variations are investigated and cannot capture this kind of phenomenon. On the other hand, large eddy simulation (LES) provides the ability to predict cyclic variations because smaller spatial scales and temporal fluctuations are resolved. Since in LES a significantly smaller range of turbulent length scales needs to be modeled compared to the RANS approach, the accuracy of LES is superior to RANS. However, resolving smaller temporal and spatial scales requires higher order numerical schemes, smaller time steps and higher resolutions of the computational grids. This can lead to a significant increase of CPU time compared to RANS. For wall-bounded turbulent flows at high Reynolds number and in complex geometries hybrid RANS/LES approaches have become more and more popular in the recent years. They combine attractive features of both methods. These methods provide the opportunity to use LES in regions, where its performance is known to be essentially superior to RANS. In other regions, where the accuracy and the averaged information on turbulent properties is sufficient, RANS can be used in order to save CPU-time. In contrast to pure RANS temporal fluctuations can be resolved in the LES regions in hybrid methods giving these approaches the potential to predict cycle-to-cycle variations or other turbulent flows of highly unsteady nature. The present work focuses on unsteady turbulent flow phenomena in IC-engines such as cyclic variations of the gas motion and investigates the ability of subgrid turbulence modeling to predict those. In Chapter 2 the basic physical principles of fluid dynamics and turbulent flows are described both phenomenologically and based on the underlying governing equations. Furthermore, a review of filtering operations applied to the Navier Stokes equations and state of the art turbulence modeling is given. The different methods as well as the corresponding specific treatment of the boundary conditions of conventional RANS simulation and LES are presented and the hybrid RANS/LES method is introduced. The numerical requirements for the hybrid approach in terms of spatial and temporal schemes as well as the meshing method that is needed for the computation of flows in complex geometries with moving boundaries as in IC-engines are described in Chapter 3. Different numerical schemes of the CFD code CFX, which is used in this work, are evaluated and tested against the numerics of other commercial and academic codes. In Chapter 4 the hybrid method is tested against measurements and data of direct numerical simulation (DNS) for simple flow cases. For a fundamental evaluation of the approach classic turbulence test cases such as the decay of homogeneous isotropic turbulence and the flow past a backward-facing step are used. The most relevant flow configurations in engine development are the steady flow through an intake port/valve assembly and the transient flow in a reciprocating engine. However, before the hybrid method is applied to these complex turbulent flows in IC engines at high Reynolds number, simplified configurations of theses cases are investigated. The hybrid RANS/LES method is compared to RANS and LES computations in terms of accuracy and level of information on turbulence properties. Chapter 5 is dedicated to flows in IC-engines. The specific flow characteristics are described and quantified and key issues in engine design are discussed. The hybrid RANS/LES method is used for the computation of the steady flow through an intake port and the multi-cycle simulation of the flow in a series production BMW engine. Optical measurements are used to evaluate the quality of the averaged flow field of the simulation as well as the ability to predict cyclic variations of the gas motion in IC-engines.

Author: Alain Dervieux
Publisher: Springer Science & Business Media
ISBN:
Category : Mathematics
Languages : en
Pages : 604

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Book Description
This volume contains contributions to the BRITE-EURAM 3rd Framework Programme ETMA and extended articles of the TMA-Workshop. It focusses on turbulence modelling techniques suitable to use in typical flow configurations, with emphasis on compressibility effects and inherent unsteadiness. These methodologies are applied to the Navier-Stokes equations, involving various turbulence modelling levels from algebraic to RSM. Basic turbulent flows in aeronautics are considered; mixing layers, wall-flows (flat-plate, backward-facing step, ramp, bump), and more complex configurations (bump, aerofoil). A critical assessment of the turbulence modelling performances is offered, based on previous results and on the experimental data-base of this research programme. The ETMA results figure in the data-base constituted by all partners and organized by INRIA