The proceedings include papers dealing with the following areas of turbulence:
?Eddy-viscosity and second-order RANS models
?Direct and large-eddy simulations and deductions for conventional modelling
?Measurement and visualization techniques, experimental studies
?Turbulence control
?Transition and effects of curvature, rotation and buoyancy on turbulence
?Aero-acoustics
?Heat and mass transfer and chemically reacting flows
?Compressible flows, shock phenomena
?Two-phase flows
?Applications in aerospace engineering, turbomachinery and reciprocating engines, industrial aerodynamics and wind engineering, and selected chemical engineering problems
Turbulence remains one of the key issues in tackling engineering flow problems. These problems are solved more and more by CFD analysis, the reliability of which depends strongly on the performance of the turbulence models employed. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation. As in other fields of Science, in the rapidly developing discipline of turbulence, swift progress can be achieved only by keeping up to date with recent advances all over the world and by exchanging ideas with colleagues active in related fields."
Proceedings of the world renowned ERCOFTAC (International Symposium on Engineering Turbulence Modelling and Measurements).The proceedings include papers dealing with the following areas of turbulence:* Eddy-viscosity and second-order RANS models * Direct and large-eddy simulations and deductions for conventional modelling * Measurement and visualization techniques, experimental studies * Turbulence control * Transition and effects of curvature, rotation and buoyancy on turbulence * Aero-acoustics * Heat and mass transfer and chemically reacting flows * Compressible flows, shock phenomena * Two-phase flows * Applications in aerospace engineering, turbomachinery and reciprocating engines, industrial aerodynamics and wind engineering, and selected chemical engineering problems Turbulence remains one of the key issues in tackling engineering flow problems. These problems are solved more and more by CFD analysis, the reliability of which depends strongly on the performance of the turbulence models employed. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation. As in other fields of Science, in the rapidly developing discipline of turbulence, swift progress can be achieved only by keeping up to date with recent advances all over the world and by exchanging ideas with colleagues active in related fields.
Front Cover 1
Engineering Turbulence Modelling and Experiments 6 4
Copyright Page 5
Contents 8
Preface 20
Part 1: Invited Lectures 22
Chapter 1. Rapid techniques for measuring and modeling turbulent flows in complex geometries 24
Chapter 2. Large-Eddy-Simulation of complex flows using the immersed boundary method 38
Chapter 3. Transition modelling for general purpose CFD codes 52
Chapter 4. Possibilities and limitations of computer simulations of industrial turbulent multiphase flows 70
Part 2: Turbulence Modelling 86
Chapter 5. (v2/k) – f Turbulence Model and its application to forced and natural convection 88
Chapter 6. Calibrating the length scale equation with an explicit algebraic Reynolds stress constitutive relation 98
Chapter 7. Near-wall modification of an explicit algebraic Reynolds stress model using elliptic blending 108
Chapter 8. Assessment of turbulence models for predicting the interaction region in a wall jet by reference to LES solution and budgets 118
Chapter 9. Eddy collision models for turbulence 128
Chapter 10. A stress-strain lag eddy viscosity model for unsteady mean flow 138
Chapter 11. Turbulence modelling of statistically periodic flows: the case of the synthetic jet 148
Chapter 12. Behaviour of turbulence models near a turbulent / non-turbulent interface revisited 158
Chapter 13. Behaviour of nonlinear two-equation turbulence models at the free-stream edges of turbulent flows 168
Chapter 14. Extending an analytical wall-function for turbulent flows over rough walls 178
Chapter 15. Bifurcation of second moment closures in rotating stratified flow 188
Chapter 16. Turbulence Model for wall-bounded flow with arbitrary rotating axes 196
Chapter 17. Application of a new algebraic structure-based model to rotating turbulent flows 206
Chapter 18. k–e modeling of turbulence in porous media based on a two-scale analysis 216
Part 3: Direct and Large-Eddy Simulations 226
Chapter 19. Effect of a 2-D rough wall on the anisotropy of a turbulent channel flow 228
Chapter 20. Direct numerical simulation of rotating turbulent flows through concentric annuli 238
Chapter 21. Numerical simulation of compressible mixing layers 248
Chapter 22. LES in a U-bend pipe meshed by polyhedral cells 258
Chapter 23. Large eddy simulation of impinging jets in a confined flow 268
Chapter 24. LES study of turbulent boundary layer over a smooth and a rough 2D hill model 278
Chapter 25. Flow features in a fully developed ribbed duct flow as a result of LES 288
Chapter 26. Coherent structures and mass exchange processes in channel flow with spanwise obstructions 298
Chapter 27. Large Eddy Simulation of natural convection boundary layer on a vertical cylinder 308
Chapter 28. Development of the subgrid-scale models in large eddy simulation for the finite difference schemes 318
Chapter 29. Assessment of the digital filter approach for generating large eddy simulation inlet conditions 328
Part 4: Hybrid LES/RANS Simulations 338
Chapter 30. Hybrid LES-RANS : Computation of the flow around a three-dimensional hill 340
Chapter 31. Applications of a renormalization group based hybrid RANS/LES model 350
Chapter 32. Application of zonal LES/ILES approaches to an unsteady complex geometry flow 360
Chapter 33. Interface conditions for hybrid RANS/LES calculations 370
Chapter 34. Approximate near-wall treatments based on zonal and hybrid RANS-LES methods for LES at high Reynolds numbers 380
Chapter 35. LES, T-RANS and hybrid simulations of thermal convection at high RA numbers 390
Part 5: Application of Turbulence Models 400
Chapter 36. Industrial practice in turbulence modelling: An evaluation of QNET-CFD 402
Chapter 37. Three-dimensional flow computation with Reynolds stress and algebraic stress models 410
Chapter 38. Comparison of turbulence models in case of jet in crossflow using commercial CFD code 420
Part 6: Experimental Techniques and Studies 430
Chapter 39. Time resolved PIV measurements for validating LES of the turbulent flow within a PCB enclosure model 432
Chapter 40. Skin friction measurements in complex turbulent flows using direct methods 442
Chapter 41. Reynolds number dependence of elementary vortices in turbulence 452
Chapter 42. Near-wake turbulence properties in the high Reynolds incompressible flow around a circular cylinder by 2C and 3C PIV 462
Chapter 43. Single- and two-point LDA measurements in the turbulent near wake of a circular cylinder 472
Chapter 44. Aerodynamics of a half-cylinder in ground effect 482
Chapter 45. Turbulent wall jet interaction with a backward facing step 492
Chapter 46. The role of pressure-velocity correlation in oscillatory flow between a pair of bluff bodies 502
Chapter 47. Turbulent structures in a supersonic jet-mixing layer interaction 512
Chapter 48. Turbulent properties of twin circular free jets with various nozzle spacing 522
Chapter 49. LDA-masurements of the turbulence in and around a venturi 532
Part 7: Transition 542
Chapter 50. Modelling of unsteady transition with a dynamic intermittency equation 544
Chapter 51. Transition to turbulence and control in the incompressible flow around a NACA0012 wing 554
Part 8: Turbulence Control 564
Chapter 52. Some observations of the Coanda effect 566
Chapter 53. Active control of turbulent separated flows by means of large scale vortex excitation 576
Chapter 54. Large-eddy simulation of a controlled flow cavity 586
Chapter 55. Parametric study of surfactant-induced drag-reduction by DNS 596
Chapter 56. Effect of non-affine viscoelasticity on turbulence generation 606
Chapter 57. Experimental and numerical investigation of flow control on bluff bodies by passive ventilation 616
Part 9: Aerodynamic Flows 626
Chapter 58. Application of Reynolds stress models to high-lift aerodynamics applications 628
Chapter 59. Turbulence modelling in application to the vortex shedding of stalled airfoils 638
Chapter 60. The computational modelling of wing-tip vortices and their near-field decay 648
Chapter 61. URANS computations of shock induced oscillations over 2D rigid airfoil: Influence of test section geometry 658
Chapter 62. Zonal multi-domain RANS/LES simulation of airflow over the Ahmed body 668
Chapter 63. Numerical simulation and experimental investigation of the side loading on a high speed train 678
Chapter 64. Large-scale instabilities in a STOVL upwash fountain 688
Part 10: Aero-Acoustics 698
Chapter 65. Direct numerical simulation of large-eddy-break-up devices in a boundary layer 700
Chapter 66. Blade tip flow and noise prediction by large-eddy simulation in horizontal axis wind turbines 710
Chapter 67. A zonal RANS/LES approach for noise sources prediction 720
Chapter 68. Aerodynamics and acoustic sources of the exhaust jet in a car air-conditioning system 730
Chapter 69. Characterization of a separated turbulent boundary layer by time-frequency analyses of wall pressure fluctuations 740
Part 11: Turbomachinery Flows 750
Chapter 70. Study of flow and mixing in a generic GT combustor using LES 752
Chapter 71. An evaluation of turbulence models for the isothermal flow in a gas turbine combustion system 762
Chapter 72. Large Eddy Simulations of heat and mass transfers in case of non isothermal blowing 772
Chapter 73. Turbulence modelling and measurements in a rotor-stator system with throughflow 782
Part 12: Heat and Mass Transfer 792
Chapter 74. Impinging jet cooling of wall mounted cubes 794
Chapter 75. Numerical and experimental study of turbulent processes and mixing in jet mixers 804
Chapter 76. Effects of adverse pressure gradient on heat transfer mechanism in thermal boundary layer 814
Chapter 77. Stochastic modelling of conjugate heat transfer in near-wall turbulence 824
Chapter 78. Study of the effect of flow pulsation on the flow field and heat transfer over an inline cylinder array using LES 834
Chapter 79. Large eddy simulation of scalar mixing 844
Part 13: Combustion Systems 854
Chapter 80. Experimental characterization and modelling of inflow conditions for a gas turbine swirl combustor 856
Chapter 81. On the sensitivity of a free annular swirling jet to the level of swirl and a pilot jet 866
Chapter 82. Prediction of pressure oscillations in a premixed swirl combustor flow and comparison to measurements 876
Chapter 83. Interaction between thermoacoustic oscillations and spray combustion 886
Chapter 84. Dynamics of lean premixed systems: Measurements for large eddy simulation 896
Chapter 85. White in time scalar advection model as a tool for solving joint composition PDF equations: Derivation and application 906
Chapter 86. The effects of micromixing on combustion extinction limits for micro combustor applications 916
Chapter 87. Joint RANS/LES approach to premixd flames modelling in the context of the TFC combustion model 926
Chapter 88. Optical observation and discrete vortex analysis of vortex-flame interaction in a plane premixed shear flow 936
Part 14: Two-Phase Flows 948
Chapter 89. Simulation of mass-loading effects in gas-solid cyclone separators 950
Chapter 90. On Euler/Euler Modeling of turbulent particle diffusion in dispersed two-phase flows 960
Chapter 91. Influence of the gravity field on the turbulence seen by heavy discrete particles in an inhomogeneous flow 970
Chapter 92. Modelling turbulent collision rates of inertial particles 980
Chapter 93. Large eddy simulation of the dispersion of solid particles and droplets in a turbulent boundary layer flow 990
Chapter 94. Dynamic self-organization in particle-laden turbulent channel flow 1000
Author Index 1010
Rapid Techniques for Measuring and Modeling Turbulent Flows in Complex Geometries
G. Iaccarino; C.J. Elkins Department of Mechanical Engineering, Stanford University, Stanford CA 94305
ABSTRACT
An approach to measure and model turbulent flows in complex configurations is presented. It is based on the synergistic use of two novel techniques: the experiments are based on magnetic resonance velocimetry, which allows the collection of a large three-dimensional volume of three-component velocity measurements in a short period of time. The numerical predictions are based on the immersed boundary technique that enables simulations to be carried out on Cartesian grids even for realistic, industrial configurations. Computer models of realistic geometries are used without modification in the simulations, and they are accurately reproduced for the experiments using rapid prototyping manufacturing. These two techniques enable analysis of flow systems in great detail by quickly providing a wealth of experimental and numerical data. Moreover, direct comparison between these datasets gives indications of the uncertainties in the data from both methods. Results are presented for the flow in a pipe and in a rib-roughened serpentine. In addition, preliminary measurements and simulations of the flow around a coral reef are included.
KEYWORDS
Magnetic resonance velocimetry
immersed boundary technique
ribbed serpentine
coral reef
INTRODUCTION
The analysis of the turbulent flow in complex, industrial configurations is of great importance for improving the design and the performance of a wide variety of engineering devices.
Traditionally, such analysis is based on an experimental investigation that involves the construction of the device (typically in a reduced scale) and the direct measure of a few performance parameters. The detailed instrumentation of an industrial device can be extremely time-consuming and expensive. It is common to use only few probes for measuring pressure, flow rates, temperature, etc. and, as a consequence, their position plays a critical role in the significance of the collected data. Although these data yield valuable information, they do not provide enough information to identify areas of separation or other problematic regions that can cause performance reduction.
Several methodologies are available to collect more detailed measurements in flows. Laser Doppler anemometry (LDA) and Particle Image Velocimetry (PIV) (Stanislas Kompenhans and Westerweel, 2000) are two non-invasive techniques. While LDA provides pointwise velocity measurements, PIV provides instantaneous two-dimensional velocity fields, and stereoscopic PIV provides three-component velocities in two-dimensional planes. All of these measurement techniques require optical access in the studied device and this limits their applications to simpler geometries. In addition, these measurements may be available only in selected positions or planes. In many realistic geometries, full coverage of the flow domain by LDA or PIV may be impossible or extremely time consuming.
Recently, a technique has been implemented in modern Magnetic Resonance Imaging (MRI) scanners to measure three-component velocity fields in three-dimensional complex geometries. This technique is called Magnetic Resonance Velocimetry (MRV). The method is based on the same principles used in MRI, now routinely employed in medical imaging. MRV is becoming popular in the study of blood flow in vascular medicine, and it has applications in the study of engineering flows as well. The typical fluid used in MRV experiments contains water since medical MRI scanners measure radio frequency signals from excited hydrogen nuclei in the presence of strong magnetic fields. More detailed discussion of MRV can be found in Elkins et al. (2003) and Markl et al. (2003).
One advantage of MRV is that it provides detailed three-dimensional data very quickly; a typical scan of a volume of size 32 × 200 × 200 mm with a resolution of about 1 mm can be obtained in less than 30 minutes. Another major advantage of MRV is its ability to measure data in complex geometries without the need for optical access. Flow models are typically fabricated using rapid prototyping manufacturing processes (i.e. stereo-lithography). There are several well-documented drawbacks to the MRV technique including signal dephasing due to turbulence and spatial misregistration due to strong accelerations in the flow. In addition, MRV provides only mean velocity measurements and knowledge of turbulence quantities can be important. These shortcomings are being investigated by the authors in an effort to improve MRV.
The other existing approach to study and design engineering systems is Computational Fluid Dynamics (CFD). Numerical flow simulations have become a common tool and several software tools are available in the industrial community. CFD calculations are carried out in two steps: the first is the geometry acquisition and mesh generation, and the second is the actual flow simulation. The geometry acquisition requires the transfer of a configuration, typically generated in a Computer-Aided-Design (CAD) environment, into a CFD mesh generation system. This process is very time consuming as the operating principles (geometry definition, tolerances, etc.) of the two software environments can be quite different. Once a watertight definition of the device to be studied is available in the mesh generator, the air-solid has to be defined. The air-solid represents the volume that is effectively occupied by the fluid (typically it is just the negative of the real device). A computational grid, i.e. a collection of small Computational Volumes (CV) covering the entire air-solid, is then generated in a semi-automatic way. Control on the resolution and the quality - the size and shape of the CVs, respectively – of the grid requires substantial user-intervention and might be very time-consuming. Once a grid is available, the solution of the equations governing the flow can be carried out.
For complex applications, the use of CFD is still challenging as the first phase of the process described above can be quite difficult and time consuming. Techniques that simplify and automate the grid generation have great potential in sustaining the widespread use of CFD. The Immersed Boundary (IB) method eliminates the need for the construction of the air-solid thus simplifying substantially both the geometry acquisition and the mesh generation phases. The IB method (Mittal and Iaccarino, 2005) uses a mesh that covers the entire computational domain (typically a large box) without the device of interest; the effect of this on the flow is then accounted for by modifying the governing equations through source terms that mimic the presence of the solid boundaries. Cartesian mesh techniques were introduced for fluid flow simulation in the 70s (Peskin, 1972) but only recently have been applied to complex, industrial flows and in the turbulent regime (Iaccarino and Verzicco, 2003).
The availability of the MRV and IB techniques to study turbulent flows in realistic configurations creates an opportunity for a new paradigm in engineering design as measurements and simulations can be used together. The combined MRV-IB approach provides a wealth of information for the designer at a resolution that is well above what is usually available. The data are typically complementary as the two techniques have different strengths and weaknesses but provide enough overlap to create confidence in the results.
In this paper some applications of the MRV-IB approach are presented with the objective of illustrating the advantages of the techniques. Comparisons of the results obtained using the two methods to more conventional PIV measurements are presented to evaluate their accuracy. As the two techniques are relatively new, further research is currently ongoing to fully evaluate their capabilities; this aspect is discussed at the end of the paper.
MEASURING TECHNIQUE: MAGNETIC RESONANCE VELOCIMETRY
MRV is a non-invasive experimental method for measuring mean velocities using modern medical Magnetic Resonance Imaging (MRI) systems. All of the measurements presented in this paper were made using a 1.5 T GE Signa CV/I system (Gmax = 40mT/m, rise time = 268 microsecs). For a discussion of the principles of MRI, the reader is referred to Stark and Bradley (1999), von Schultess and Hennig (1998), and Haacke et al. (1999). In addition, a brief discussion of MRV principles is found in Elkins et al. (2003) where the MRV technique is described in detail.
Most MRI systems image hydrogen protons which are abundant in the fluids and tissues in living things. Protons have magnetic moments (spins) that align with the direction of a strong magnetic field. If knocked out of alignment with the external magnetic field, the spins will relax back into alignment and precess about the field direction with a frequency proportional to the strength of the magnetic field. Hence, when a spatial magnetic field gradient is applied to create a continuously varying magnetic field, the spins along the direction of the gradient have different precession frequencies. This principle can be exploited to image an object. In imaging, the spins are knocked out of alignment with a strong, constant field. Then a magnetic field gradient is applied. As the spins relax back into alignment with the constant field, they broadcast RF signals, each...
| Erscheint lt. Verlag | 5.5.2005 |
|---|---|
| Sprache | englisch |
| Themenwelt | Sachbuch/Ratgeber |
| Informatik ► Software Entwicklung ► User Interfaces (HCI) | |
| Mathematik / Informatik ► Mathematik | |
| Naturwissenschaften ► Chemie ► Technische Chemie | |
| Naturwissenschaften ► Physik / Astronomie ► Angewandte Physik | |
| Technik ► Bauwesen | |
| Technik ► Luft- / Raumfahrttechnik | |
| Technik ► Maschinenbau | |
| Technik ► Umwelttechnik / Biotechnologie | |
| ISBN-10 | 0-08-053095-8 / 0080530958 |
| ISBN-13 | 978-0-08-053095-6 / 9780080530956 |
| Haben Sie eine Frage zum Produkt? |
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