Navier-Stokes Computation of Compressible Turbulent Flows with a Second Order Closure
Navier-Stokes Computation of Compressible Turbulent Flows with a Second Order Closure

Author: National Aeronautics and Space Adm Nasa

Publisher:

Published: 2018-11-03

Total Pages: 70

ISBN-13: 9781730800474

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A second order closure turbulence model for compressible flows is developed and implemented in a 2D Reynolds-averaged Navier-Stokes solver. From the beginning where a kappa-epsilon turbulence model was implemented in the bidiagonal implicit method of MACCORMACK (referred to as the MAC3 code) to the final stage of implementing a full second order closure in the efficient line Gauss-Seidel algorithm, numerous work was done, individually and collectively. Besides the collaboration itself, the final product of this work is a second order closure derived from the Launder, Reece, and Rodi model to account for near wall effects, which has been called FRAME model, which stands for FRench-AMerican-Effort. During the reporting period, two different problems were worked out. The first was to provide Ames researchers with a reliable compressible boundary layer code including a wide collection of turbulence models for quick testing of new terms, both in two equations and in second order closure (LRR and FRAME). The second topic was to complete the implementation of the FRAME model in the MAC5 code. The work related to these two different contributions is reported. dilatation in presence of stron shocks. This work, which has been conducted during a work at the Center for Turbulence Research with Zeman aimed also to cros-check earlier assumptions by Rubesin and Vandromme. Haminh, Hieu and Kollmann, Wolfgang and Vandromme, Dany Unspecified Center...

Second-Order Closure Modeling of Variable Density Turbulent Flows
Second-Order Closure Modeling of Variable Density Turbulent Flows

Author: Ashok Kumara Varmer

Publisher:

Published: 1979

Total Pages: 37

ISBN-13:

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Mixing and Chemical reactions under turbulent flow conditions are a basic feature of the energy release processes in many combustion and propulsion systems. The development of predictive calculation procedures for these systems requires the understanding and modeling of coupling between turbulence and various physical and chemical processes. Second-order closure modeling of turbulent flows provides a rational framework for studying these interactions. Models for the scalar probability density function (pdf) have to be developed to achieve closure of turbulent transport equations for mixing and reacting flows. A delta function 'typical eddy' pdf model for two species flows has been developed and incorporated into a complete second-order closure computer program. The program has been used to study uniform and variable density flowfields and the model predictions have been compared to experimental measurements. The modeling of turbulence dynamics for variable density flows requires further improvement. However, the importance of modeling the higher-order scalar correlations has been demonstrated. A number of statistical constraints on three species flowfields have also been derived. These will be useful in the development of the 'typical eddy' pdf modelfor reacting flows. (Author).

Variable Density Fluid Turbulence
Variable Density Fluid Turbulence

Author: P. Chassaing

Publisher: Springer Science & Business Media

Published: 2013-06-29

Total Pages: 387

ISBN-13: 9401700753

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The first part aims at providing the physical and theoretical framework of the analysis of density variations in fully turbulent flows. Its scope is deliberately educational. In the second part, basic data on dynamical and scalar properties of variable density turbulent flows are presented and discussed, based on experimental data and/or results from direct numerical simulations. This part is rather concerned with a research audience. The last part is more directly devoted to an engineering audience and deals with prediction methods for turbulent flows of variable density fluid. Both first and second order, single point modeling are discussed, with special emphasis on the capability to include specific variable density / compressibility effects.

Second Moment Closure Modeling of Complex Turbulent Flows
Second Moment Closure Modeling of Complex Turbulent Flows

Author: Sharath Girimaji

Publisher:

Published: 2007

Total Pages: 48

ISBN-13:

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Turbulence subject to unsteady forcing can exhibit novel features that cannot be explained using the well-known steady-turbulence paradigm. Modeling and prediction of such statistically unsteady flows are important in many practical AFOSR applications: turbine flows, wake-flows with vortex shedding, etc. Further, many flow control strategies depend upon the knowledge of unsteady turbulence dynamics to achieve the desired objectives. However, our understanding of unsteadily-forced turbulence dynamics or our ability to predict them is inadequate.

Turbulence Models and Their Application
Turbulence Models and Their Application

Author: Tuncer Cebeci

Publisher: Springer Science & Business Media

Published: 2003-12-04

Total Pages: 140

ISBN-13: 9783540402886

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After a brief review of the more popular turbulence models, the author presents and discusses accurate and efficient numerical methods for solving the boundary-layer equations with turbulence models based on algebraic formulas (mixing length, eddy viscosity) or partial-differential transport equations. A computer program employing the Cebeci-Smith model and the k-e model for obtaining the solution of two-dimensional incompressible turbulent flows without separation is discussed in detail and is presented in the accompanying CD.

Computation of Turbulent Flows Using an Extended K-Epsilon Turbulence Closure Model
Computation of Turbulent Flows Using an Extended K-Epsilon Turbulence Closure Model

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-26

Total Pages: 30

ISBN-13: 9781724264602

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An extended kappa-epsilon turbulence model is proposed and tested with successful results. An improved transport equation for the rate of dissipation of the turbulent kinetic energy, epsilon, is proposed. The proposed model gives more effective response to the energy production rate than does the standard kappa-epsilon turbulence model. An extra time scale of the production range is included in the dissipation rate equation. This enables the present model to perform equally well for several turbulent flows with different characteristics, e.g., plane and axisymmetric jets, turbulent boundary layer flow, turbulent flow over a backward-facing step, and a confined turbulent swirling flow. A second-order accurate finite difference boundary layer code and a nearly second-order accurate finite difference elliptic flow solver are used for the present numerical computations. Chen, Y.-S. and Kim, S.-W. Unspecified Center NASA-CR-179204, NAS 1.26:179204 NAS8-35918