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  • 1
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    Direct numerical simulation of reacting flows (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The objectives of this work are: (1) to extend the technique of direct numerical simulations to turbulent, chemically reacting flows, (2) to test the validity of the method by comparing computational results with laboratory data, and (3) to use the simulations to gain a better understanding of the effects of turbulence on chemical reactions. The effects of both the large scale structure and the smaller scale turbulence on the overall reaction rates are addressed. The relationship between infinite reaction rate and finite reaction rate chemistry is compared with some of the results of calculations with existing theories and laboratory data. The direct numerical simulation method involves the numerical solution of the detailed evolution of the complex turbulent velocity and concentration fields. Using very efficient numerical methods (e.g., pseudospectral methods), the fully nonlinear (possibly low pass filtered) equations of motion are solved and no closure assumptions or turbulence models are used. Statistical data are obtained by performing spatial, temporal, and/or ensemble averages over the computed flow fields.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center Combust. Fundamentals Res.; p 199-221
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  • 2
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    Numerical modeling of turbulent flow (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Three dimensional combustor calculations are currently stretching the computer hardware capabilities and the computing budgets of gas turbine manufacturers. One of the main reasons for this relates to the large number of complex physical processes occurring in the combustor. Airflow, fuel spray, reaction kinetics, flame radiation, and not the least of which, turbulence must be modeled and the related differential equations solved. Discussions in this conference will address methods to improve the accuracy of combustor flow field calculations and methods to speed the convergence of the modeled equations. This report will focus on aspects of merging these two new technologies. The improved accuracy discretization schemes have a negative impact on the speed of convergence of the modeled equations that the improved solution algorithms may not overcome. A description of the causes of this problem and potential solutions will be examined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Combust. Fundamentals Res.; p 97
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  • 3
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    Research study: Organization and development of organized convection in the boundary layer (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The status of a study to investigate the convective structures found in Doppler lidar windfield data is reported. Projected research is mentioned briefly.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-171115 , NAS 1.26:171115 , MPR-19
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  • 4
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    A strongly implicit procedure for the compressible Navier-Stokes equations (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The strongly implicit procedure of Stone is used to obtain numerical solutions of the compressible Navier-Stokes equations in conservative form. In contrast to the spatially split Douglas-Gunn type methods, the method is shown to be numerically stable for the three-dimensional wave equation. The method is applied to a variety of external and internal two-dimensional flow problems involving shock wave boundary-layer interaction for both laminar and turbulent flows. The results are in good agreement with other methods and/or experiments. The storage penalty associated with the method is discussed and a simple, yet effective, means of minimizing the problem is presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 84-0424
    Format: text
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  • 5
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    Solution of the Navier-Stokes equations for flow within a 2-D thrust reversing nozzle (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Implicit numerical procedures have been developed to solve the Reynold's Averaged Navier-Stokes equations for the flowfield within a two-dimensional thrust reversing engine nozzle. The procedures have been tested on four different thrust reverser nozzle geometries with both fixed and moving walls. The results have compared well with available experimental data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 84-0344
    Format: text
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  • 6
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    Film-cooling effectiveness with developing coolant flow through straight and curved tubular passages (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The data were obtained with an apparatus designed to determine the influence of tubular coolant passage curvature on film-cooling performance while simulating the developing flow entrance conditions more representative of cooled turbine blade. Data comparisons were made between straight and curved single tubular passages embedded in the wall and discharging at 30 deg angle in line with the tunnel flow. The results showed an influence of curvature on film-cooling effectiveness that was inversely proportional to the blowing rate. At the lowest blowing rate of 0.18, curvature increased the effectiveness of film cooling by 35 percent; but at a blowing rate of 0.76, the improvement was only 10 percent. In addition, the increase in film-cooling area coverage ranged from 100 percent down to 25 percent over the same blowing rates. A data trend reversal at a blowing rate of 1.5 showed the straight tubular passage's film-cooling effectiveness to be 20 percent greater than that of the curved passage with about 80 percent more area coverage. An analysis of turbulence intensity detain the mixing layer in terms of the position of the mixing interface relative to the wall supported the concept that passage curvature tends to reduce the diffusion of the coolant jet into the main stream at blowing rates below about. Explanations for the film-cooling performance of both test sections were made in terms differences in turbulences structure and in secondary flow patterns within the coolant jets as influenced by flow passage geometry.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-2062 , E-1206 , NAS 1.60:2062
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  • 7
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    Calculation of pressure statistics in turbulent free shear flows by direct numerical simulation (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Accurate numerical simulations of turbulent free shear flows were performed in order to study the behavior of certain critical turbulence quantities which have been difficult to measure in the laboratory. The three-dimensional time-dependent nonlinear Navier-Stokes equations are solved by the direct numerical simulation technique without turbulence modeling or ad hoc closure assumptions. The pressure interaction terms were factored into diffusion and return-to-isotropy components according to two models. Simulations of the evolution of a turbulent wake with and without swirl present were performed at sufficiently high Reynolds numbers to insure that the flows were strongly nonlinear and turbulent, but low enough so that all scales of motion containing significant energy are adequately resolved. It is noted that the presence of swirl tends to enhance the amplitude of the rms pressure levels.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 8
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    Curved film cooling admission tube (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Effective film cooling to protect a wall surface from a hot fluid which impinges on or flows along the surface is provided. A film of cooling fluid having increased area is provided by changing the direction of a stream of cooling fluid through an angle of from 135 deg. to 165 deg. before injecting it through the wall into the hot flowing gas. The 1, cooling fluid is injected from an orifice through a wall into a hot flowing gas at an angle to form a cooling fluid film. Cooling fluid is supplied to the orifice from a cooling fluid source via a turbulence control passageway having a curved portion between two straight portions. The angle through which the direction of the cooling fluid is turned results in less mixing of the cooling fluid with the hot gas, thereby substantially increasing the length of the film in a downstream direction.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 9
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    Asymptotic features of shock-wave boundary-layer interaction (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A semi-implicit method is applied to solve the Navier-Stokes equations numerically and to evaluate the features of the free-interaction phenomenon that occurs when a shock wave impinges on a Blasius boundary layer. Comparisons are made with predictions of the triple-deck theory and experiment. Results include pressure and skin-friction distribution in the free-interaction region for various values of Reynolds number.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 18; Aug. 198
    Format: text
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  • 10
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    Turbofan forced mixer-nozzle internal flowfield. Volume 1: A benchmark experimental study (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation of the flow field within a model turbofan forced mixer nozzle is described. Velocity and thermodynamic state variable data for use in assessing the accuracy and assisting the further development of computational procedures for predicting the flow field within mixer nozzles are provided. Velocity and temperature data suggested that the nozzle mixing process was dominated by circulations (secondary flows) of a length scale on the order the lobe dimensions which were associated with strong radial velocities observed near the lobe exit plane. The 'benchmark' model mixer experiment conducted for code assessment purposes is discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-3492 , NAS 1.26:3492
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