Download or read book Development of a Turbulent Separated Flow Validation Test Case written by Madeline Cary Samuell and published by . This book was released on 2020 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new validation test case for CFD of turbulent separated flows is investigated through a combination of experiments and simulations. This work is part of an ongoing collaboration between the University of Washington and Boeing, which aims to contribute to the development of a high-quality validation test case for turbulent separated flows and the improvement of RANS modeling for turbulent separated flows. A three-dimensional speed-bump-like geometry, which causes separation as a result of the surface curvature, was chosen for this study. Tests were conducted to determine the influence of Reynolds number and confinement on the flowfield and to test the ability of common RANS turbulence models to accurately predict the flow. Experimental data was used to formalize the required inflow length so that the bump inflow matched between the simulations and experiments. The parameter used to match the inflows was the Reynolds number based on momentum thickness, Re theta, of the incoming boundary layer. The experimental data collected from the incoming boundary layer was also used to prove that the flow upstream of the bump was fully turbulent for all levels of confinement. Five Reynolds numbers were tested in the experiments and the simulations, corresponding to a freestream velocity range of 60 m/s - 20 m/s and four vertical confinement levels were analyzed in the experiments. Six turbulence models were examined: k-omega SST, two versions of Spalart-Allmaras (SA and SARC) and three versions of k-epsilon. The geometry was determined to be a challenge to RANS models, which was demonstrated by the pressure coefficient data because the simulations predicted an opposite Reynolds number trend to the experiments in the separated region. Furthermore, the simulations were not able to predict distinctive pressure coefficient profiles seen in the experimental results, such as an inflection point along the streamwise centerline in the separated region and a double-peak in the spanwise direction across the top of the bump. However, the simulations did predict that the flowfield is insensitive to Reynolds number at and above ReL = 2.46 x 106, which is in agreement with the Reynolds number insensitivity determined experimentally. Increasing confinement increased the magnitude of the pressure coefficients over the bump, and the pressure at the peak of the bump went from about -1.2 in the least confined case to about -1.5 in the most confined case. However, there was no change in the shape of the profile. The examination of the various RANS turbulence models concluded that, for this curved geometry, the turbulence models with the curvature correction, k-omega SST and SARC, corresponded more closely to the experimental flow than those without a curvature correction. None of the k-epsilon models predicted separation, but SARC, SA and k-omega SST all did. It was determined that SARC, SA and k-omega SST all displayed similar flow features to those observed in the experimental flow visualizations, such as the general shape of the separated region and counter-rotating surface vortices that were symmetric across the streamwise centerline. However, the extent, location and width of the separated region varied. Along with variation in the size of the separation bubble predicted by each turbulence model, they also all predicted different values and profiles for pressure and skin friction coefficient in the separated region. From this experimental and computational analysis, it is clear that this geometry poses a sufficient challenge to current RANS models, due to their inability to accurately predict the location, size and values of pressure coefficients within the separated region. Therefore, is a good choice for a turbulent separated flow validation test. Future work on this project will focus on detailed flowfield comparisons between experiments and simulations.

Download or read book Development of an Axisymmetric Afterbody Test Case for Turbulent Flow Separation Validation written by Kevin J. Disotell and published by . This book was released on 2017 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Examination of New Separated Turbulent Flow Validation Test Geometry written by E. Sage Sarwas and published by . This book was released on 2019 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational fluid dynamics (CFD) is a powerful tool for aeronautic design, however current simulations are challenged by turbulent separated flows due to their complexity. A new series of experiments are required to provide insights into the simulation challenges of this flow and to assist with the validation of future turbulence models. In this thesis, initial qualification experiments are conducted for a newly proposed separated flow geometry. This validation test used an elongated hill, "speed-bump", shaped model, which was chosen because it allowed for the largest feasible Reynolds number, is longer in the spanwise direction making it more applicable to wing-like applications, is tapered at the sides to minimize side wall effects, and allows for adjustment of the flow separation via multiple parameters (i.e. incoming boundary layer, bump height, and splitter plate position). Tests were conducted over a range of Reynolds numbers, 58, 000 [less than or equal to] Re[subscript]h [less than or equal to] 301, 000, where h is the height of the bump. Wind tunnel qualification showed high uniformity and less than 0.2% freestream turbulence, ensuring the flow was suitable for the remainder of the study. The upstream boundary layer was examined to ensure a clean inflow onto the bump. Multiple tripping devices were tested and a strip of 240-grit sandpaper was chosen for future tests. Once the trip was chosen, the experimental momentum thickness Reynolds number was used to determine the corresponding simulation inflow length, which was set to 1.5L. China clay flow visualization and surface pressure measurements were used to examine the separated region. China clay revealed the presence of surface vortices surrounding a strongly separated three-dimensional flow. Static surface pressure measurements also indicate slight three-dimensionality at the centerline as well as insensitivity of the separation region at higher Reynolds number. However, at lower Reynolds numbers, separation appeared to be greatly reduced. A comparison of experimental and 2D RANS simulation data showed the magnitude of the simulated pressures were similar to the experimental data, however they exhibited an opposite Reynolds number trend in the separated and recovery regions. This suggests the proposed validation geometry is a suitable challenge for current RANS models of turbulent separated flows.

Download or read book Turbulence Modeling Validation Testing and Development written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this work is to provide accurate numerical solutions for selected flow fields and to compare and evaluate the performance of selected turbulence models with experimental results. Four popular turbulence models have been tested and validated against experimental data often turbulent flows. The models are: (1) the two-equation k-epsilon model of Wilcox, (2) the two-equation k-epsilon model of Launder and Sharma, (3) the two-equation k-omega/k-epsilon SST model of Menter, and (4) the one-equation model of Spalart and Allmaras. The flows investigated are five free shear flows consisting of a mixing layer, a round jet, a plane jet, a plane wake, and a compressible mixing layer; and five boundary layer flows consisting of an incompressible flat plate, a Mach 5 adiabatic flat plate, a separated boundary layer, an axisymmetric shock-wave/boundary layer interaction, and an RAE 2822 transonic airfoil. The experimental data for these flows are well established and have been extensively used in model developments. The results are shown in the following four sections: Part A describes the equations of motion and boundary conditions; Part B describes the model equations, constants, parameters, boundary conditions, and numerical implementation; and Parts C and D describe the experimental data and the performance of the models in the free-shear flows and the boundary layer flows, respectively. Bardina, J. E. and Huang, P. G. and Coakley, T. J. Ames Research Center...

Download or read book Detailed Characterization of Flowfields and Uncertainty in a Speed bump Turbulent Separated Flow Validation Experiment written by Matthew Lloyd Robbins (Robbins, Matthew Lloyd) and published by . This book was released on 2021 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental examinations of incompressible flow over a novel speed-bump geometry were conducted towards the development of a turbulence model validation dataset for separated flows. Efforts to characterize the boundary conditions of the experiment were performed including a survey of flow uniformity and side-wall boundary layers at the inflow plane of an empty test section, and measurement of the as-built test model. Surface pressures over the speed-bump were examined and revealed a series of favorable and adverse pressure gradients in the streamwise direction with features associated with a quasi-two-dimensional line of flow separation. Statistical measurements of the flowfield were obtained with planar particle image velocimetry to ascertain model-installed inflow properties, the extent of relaminarization on the upstream slope of the speed-bump, and the size and shape of the separated region. The features of separation, in both the flowfield and on the surface, exhibited a dependency in Reynolds number below ReL = 2.55 x 106 and generally poor agreement with corresponding RANS simulations. Extensive documentation of the experimental facility, instrumentation, signal processing procedures, and treatment of uncertainty is provided to establish a high level of validation completeness. In accordance with the framework of Oberkampf and Smith, the model validation completeness of this experiment meets at least level one completeness and is at or approaching level two for most attributes.

Download or read book Differential Reynolds Stress Modeling for Separating Flows in Industrial Aerodynamics written by Bernhard Eisfeld and published by Springer. This book was released on 2015-03-24 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents recent progress in the application of RANS turbulence models based on the Reynolds stress transport equations. A variety of models has been implemented by different groups into different flow solvers and applied to external as well as to turbo machinery flows. Comparisons between the models allow an assessment of their performance in different flow conditions. The results demonstrate the general applicability of differential Reynolds stress models to separating flows in industrial aerodynamics.

Download or read book Engineering Turbulence Modelling and Experiments 5 written by W. Rodi and published by Elsevier. This book was released on 2002-08-21 with total page 1029 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Turbulence Modeling Validation Testing and Development written by and published by . This book was released on 1997 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 29th AIAA Fluid Dynamics Conference written by and published by . This book was released on 1998 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modelling Turbulence in Engineering and the Environment written by Kemal Hanjalić and published by Cambridge University Press. This book was released on 2022-11-30 with total page 535 pages. Available in PDF, EPUB and Kindle. Book excerpt: This standard work has new chapters devoted to unsteady RANS and to how LES and RANS strategies are effectively combined.

Download or read book Physics of Separated Flows Numerical Experimental and Theoretical Aspects written by Klaus Gersten and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains 37 contributions in which the research work is summarized which has been carried out between 1984 and 1990 in the Priority Research Program "Physik abgeloster Stromungen" of the Deutsche Forschungsgemeinschaft (DFG, German Research Society). The aim of the Priority Research Program was the inten sive research of the whole range of phenomena associated with separated flows. Physi cal models as well as prediction methods had to be developed based on detailed experi mental investigations. It was in accordance with the main concept of the research program that scientists working on problems of separated flows in different technical areas of application participated in this program. The following fields have been represented in the program: aerodynamics of wings and bodies, aerodynamics of auto mobiles, turbomachinery, ship hydrodynamics, hydraulics, internal flows, heat exchan gers, bio-fluid-dynamics, aerodynamics of buildings and structures. In order to concentrate on problems common in all those areas the emphasis of the program was on basic research dealing with generic geometric configurations showing the fundamental physical phenomena of separated flows. The engagement and enthusiasm of all participating scientists are highly appreciated. The program was organized such that all researchers met once a year to report on the progress of their work. Special thanks ought to go to Prof. E. A. Muller (Gottingen), Prof. H. Oertel jun. (Braunschweig), Dr. W. Schmidt (Dornier), Dr. H. -W. Stock (Dornier) and Dr. B. Wagner (Dornier), who had the functions of referees on those annual meetings.

Download or read book A Selection of Test Cases for the Validation of Large eddy Simulations of Turbulent Flows written by and published by . This book was released on 1998 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings of the 5th International Conference on Jets Wakes and Separated Flows ICJWSF2015 written by Antonio Segalini and published by Springer. This book was released on 2016-07-18 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume collects various contributions from the 5th International Conference on Jets, Wakes and Separated Flows (ICJWSF2015) that took place in Stockholm during June 2015. Researchers from all around the world presented their latest results concerning fundamental and applied aspects of fluid dynamics. With its general character, the conference embraced many aspects of fluid dynamics, such as shear flows, multiphase flows and vortex flows, for instance. The structure of the present book reflects the variety of topics treated within the conference i.e. Jets, Wakes, Separated flows, Vehicle aerodynamics, Wall-bounded and confined flows, Noise, Turbomachinery flows, Multiphase and reacting flows, Vortex dynamics, Energy-related flows and a section dedicated to Numerical analyses.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1992 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1991 with total page 1380 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book River Flow 2016 written by George Constantinescu and published by CRC Press. This book was released on 2016-06-22 with total page 3703 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding and being able to predict fluvial processes is one of the biggest challenges for hydraulics and environmental engineers, hydrologists and other scientists interested in preserving and restoring the diverse functions of rivers. The interactions among flow, turbulence, vegetation, macroinvertebrates and other organisms, as well as the transport and retention of particulate matter, have important consequences on the ecological health of rivers. Managing rivers in an ecologically friendly way is a major component of sustainable engineering design, maintenance and restoration of ecological habitats. To address these challenges, a major focus of River Flow 2016 was to highlight the latest advances in experimental, computational and theoretical approaches that can be used to deepen our understanding and capacity to predict flow and the associated fluid-driven ecological processes, anthropogenic influences, sediment transport and morphodynamic processes. River Flow 2016 was organized under the auspices of the Committee for Fluvial Hydraulics of the International Association for Hydro-Environment Engineering and Research (IAHR). Since its first edition in 2002, the River Flow conference series has become the main international event focusing on river hydrodynamics, sediment transport, river engineering and restoration. Some of the highlights of the 8th International Conference on Fluvial Hydraulics were to focus on inter-disciplinary research involving, among others, ecological and biological aspects relevant to river flows and processes and to emphasize broader themes dealing with river sustainability. River Flow 2016 contains the contributions presented during the regular sessions covering the main conference themes and the special sessions focusing on specific hot topics of river flow research, and will be of interest to academics interested in hydraulics, hydrology and environmental engineering.