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Teryn DalBello

Bio: Teryn DalBello is an academic researcher from University of Toledo. The author has contributed to research in topics: Turbulence & Transonic. The author has an hindex of 2, co-authored 3 publications receiving 44 citations.

Papers
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Book
02 Aug 2013
TL;DR: In this paper, the axisymmetric circular-arc boattail nozzles operating off-design at transonic Mach numbers have been analyzed and a range of turbulence models were examined, including the Explicit Algebraic Stress model.
Abstract: Computational Fluid Dynamics (CFD) analyses of axisymmetric circular-arc boattail nozzles operating off-design at transonic Mach numbers have been completed. These computations span the very difficult transonic flight regime with shock-induced separations and strong adverse pressure gradients. External afterbody and internal nozzle pressure distributions computed with the Wind code are compared with experimental data. A range of turbulence models were examined, including the Explicit Algebraic Stress model. Computations have been completed at freestream Mach numbers of 0.9 and 1.2, and nozzle pressure ratios (NPR) of 4 and 6. Calculations completed with variable time-stepping (steady-state) did not converge to a true steady-state solution. Calculations obtained using constant timestepping (timeaccurate) indicate less variations in flow properties compared with steady-state solutions. This failure to converge to a steady-state solution was the result of using variable time-stepping with large-scale separations present in the flow. Nevertheless, time-averaged boattail surface pressure coefficient and internal nozzle pressures show reasonable agreement with experimental data. The SST turbulence model demonstrates the best overall agreement with experimental data.

22 citations

Book
23 Jul 2013
TL;DR: In this article, the separation and reattachment behavior of a 2D asymmetric subsonic diffuser is analyzed using the wind computational fluid dynamics code to predict the separation.
Abstract: A computational study of the separated flow through a 2-D asymmetric subsonic diffuser has been performed. The Wind Computational Fluid Dynamics code is used to predict the separation and reattachment behavior for an incompressible diffuser flow. The diffuser inlet flow is a two-dimensional, turbulent, and fully-developed channel flow with a Reynolds number of 20,000 based on the centerline velocity and the channel height. Wind solutions computed with the Menter SST, Chien k-epsilon, Spalart-Allmaras and Explicit Algebraic Reynolds Stress turbulence models are compared with experimentally measured velocity profiles and skin friction along the upper and lower walls. In addition to the turbulence model study, the effects of grid resolution and use of wall functions were investigated. The grid studies varied the number of grid points across the diffuser and varied the initial wall spacing from y(sup +) = 0.2 to 60. The wall function study assessed the applicability of wall functions for analysis of separated flow. The SST and Explicit Algebraic Stress models provide the best agreement with experimental data, and it is recommended wall functions should only be used with a high level of caution.

21 citations

01 Nov 2003
TL;DR: In this paper, the effects of high-speed nozzle geometries on the nozzle internal flow and the surrounding boattail regions were investigated in support of NASA's Next Generation Launch Technology Program.
Abstract: Computational Fluid Dynamics (CFD) analyses of axisymmetric circular-arc boattail nozzles have been completed in support of NASA's Next Generation Launch Technology Program to investigate the effects of high-speed nozzle geometries on the nozzle internal flow and the surrounding boattail regions. These computations span the very difficult transonic flight regime, with shock-induced separations and strong adverse pressure gradients. External afterbody and internal nozzle pressure distributions computed with the Wind code are compared with experimental data. A range of turbulence models were examined in Wind, including an Explicit Algebraic Stress model (EASM). Computations on two nozzle geometries have been completed at freestream Mach numbers ranging from 0.6 to 0.9, driven by nozzle pressure ratios (NPR) ranging from 2.9 to 5. Results obtained on converging-only geometry indicate reasonable agreement to experimental data, with the EASM and Shear Stress Transport (SST) turbulence models providing the best agreement. Calculations completed on a converging-diverging geometry involving large-scale internal flow separation did not converge to a true steady-state solution when run with variable timestepping (steady-state). Calculations obtained using constant timestepping (time-accurate) indicate less variations in flow properties compared with steady-state solutions. This failure to converge to a steady-state solution was found to be the result of difficulties in using variable time-stepping with large-scale separations present in the flow. Nevertheless, time-averaged boattail surface pressure coefficient and internal nozzle pressures show fairly good agreement with experimental data. The SST turbulence model demonstrates the best over-all agreement with experimental data.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, three two-equation turbulence models developed specifically to improve prediction of jet flowfields are investigated and compared for a reference nozzle producing heated and unheated jets at a low acoustic Mach number of 0.5 to avoid complications of large compressibility effects.
Abstract: Three two-equation turbulence models developed specifically to improve prediction of jet flowfields are investigated. These models are the Tam-Ganesan k-e formulation, a standard k-e model with modification for heated jets referred to as the PAB temperature correction, and a standard k-e model employing variable diffusion for the k and e equations. Two standard two-equation models are also investigated for comparison with the modified formulations. The standard models are the Chien k-e and Menter shear stress transport formulations. All of the models were investigated for a reference nozzle producing heated and unheated jets at a low acoustic Mach number of 0.5 to avoid complications of large compressibility effects. The primary deficiency of the standard models was the delayed initial jet mixing rate. All of the modified turbulence model formulations provided improved mean flow predictions relative to the standard models. The improved mixing rate enabled by the Tam-Ganesan model and the variable diffusion correction resulted from increased turbulent diffusion enabled by both models. The Tam-Ganesan model and PAB temperature correction improved predictions of mean axial velocities for the heated jet, but did not improve prediction of the calculated turbulent kinetic energy fields.

95 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a computational study of the separated flow in a planar asymmetric diffuser using the steady RANS equations for turbulent incompressible fluid flow and six turbulence closures.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the current status of computational fluid dynamics (CFD) methods as applied to the simulation of turbulent jet flowfields issuing from aircraft engine exhaust nozzles is presented.

68 citations

Dissertation
01 Aug 2004
TL;DR: In this article, the authors compared the mean velocity and turbulent quantities with the experimental test case of Obi et al. (1993a), which involves separation from a plane wall and subsequent reattachment in the downstream duct of an asymmetric diffuser.
Abstract: A computational study has been performed to compare the mean velocity and turbulent quantities with the experimental test case of Obi et ai. (1993a) which involves separation from a plane wall and subsequent reattachment in the downstream duct of an asymmetric diffuser. The diffusing section has a length of 21H, where H is the inlet channel height, and overall expansion ratio 4.7. The Reynolds number, based on an upstream reference velocity and H, is 21200. The incompressible Navier-Stokes equations for fully developed turbulent flow has been solved by using a standard finite volume CFD code. The convection and diffusion terms of all the equations, including the momentum equations in two directions and the model transport equations for turbulence quantities, have been approximated by the higher order differencing scheme. The SIMPLE algorithm has been used to obtain the pressure field. Standard k E model and Hybrid turbulence model (Basara and Jakirlic, 2001) have been tested. The Hybrid turbulence model demonstrates an improved result for the mean velocity and turbulence quantities while standard k E model fails to capture the downstream flow behavior. There are, however some shortcomings in these models particularly in the development of flow after reattachment, which is always predicted to be too slow.

50 citations

Proceedings ArticleDOI
04 Jan 2010
TL;DR: The NPARC Alliance was begun in 1993 with the goal of providing a first-class CFD analysis tool to the US aerospace community through a joint effort of NASA, DoD, industry, and academia, resulting in the NPARC Flow Simulation System, centered on the Wind-US flow solver.
Abstract: The NPARC Alliance was begun in 1993 with the goal of providing a first-class CFD analysis tool to the US aerospace community through a joint effort of NASA, DoD, industry, and academia. Because this effort involves diverse teams at multiple sites, it has required the development and use of internetbased tools for communication and version management, as well as adherence to programming standards and practices. This approach has been very successful, resulting in the NPARC Flow Simulation System, centered on the Wind-US flow solver. Wind-US is a general Navier-Stokes flow solver with a wide variety of numerical algorithms and physical models to choose from. Major features include the ability to solve on structured grids, unstructured grids, or both. Ideal gas, equilibrium air, frozen multi-species flows, and reacting flows can be modeled. Recent enhancements include an improved unstructured grid solver, improved chemistry modeling, and improved stability of the structured grid solver. In addition to the flow solver, the NPARC Flow Simulation System consists of numerous utilities to prepare the grid and input files, modify these files, and process the resulting data. The extensive capabilities of the code have been demonstrated through the many simulations of diverse, physically and geometrically complex, real-world applications conducted by government, industrial, and academic organizations around the United States.

44 citations