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  • 1995-1999  (7)
  • 1
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    PAR Analysis of HSR Nozzles (1999)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Only recently has computational fluid dynamics (CFD) been relied upon to predict the flow details of advanced nozzle concepts. Computer hardware technology and flow solving techniques are advancing rapidly and CFD is now being used to analyze such complex flows. Validation studies are needed to assess the accuracy, reliability, and cost of such CFD analyses. At NASA Lewis, the PARC2D/3D full Navier-Stokes (FNS) codes are being applied to HSR-type nozzles. This report presents the results of two such PARC FNS analyses. The first is an analysis of the Pratt and Whitney 2D mixer-ejector nozzle, conducted by Dr. Yunho Choi (formerly of Sverdrup Technology-NASA Lewis Group). The second is an analysis of NASA-Langley's axisymmetric single flow plug nozzle, conducted by the author.
    Keywords: Aircraft Propulsion and Power
    Type: First NASA/Industry High Speed Research Program Nozzle Symposium; 18-1 - 18-21; NASA/CP-1999-209423
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  • 2
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    Validation of the NPARC code for nozzle afterbody flows at transonic speeds (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NPARC code, a Reynolds-averaged full Navier-Stokes code, was validated for nozzle afterbody (boatail) flow fields at transonic speeds. The flow fields about three geometries were studied: an axisymmetric nozzle with attached flow; an axisymmetric nozzle with separated flow: and a two-dimensional (rectangular) nozzle with separated flow. Three turbulence models, Baldwin-Lomax, Baldwin-Barth, and Chien k-epsilon, were used to determine the effect of turbulence model selection on the flow field solution. Static pressure distributions on the nozzle surfaces and pitot pressure measurements in the exhaust plume were examined. Results from the NPARC code compared very well with experimental data for all cases. For attached flow fields, the effect of the turbulence models showed no discernable differences. The Baldwin-Barth model yielded better results than either the Chien k-epsilon or the Baldwin-Lomax model for separated flow fields.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106971 , E-9732 , NAS 1.15:106971 , AIAA PAPER 95-2614 , AIAA, ASME, SAE, and ASEE; Jul 10, 1995 - Jul 12, 1995; US
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  • 3
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    Grid resolution and turbulent inflow boundary condition recommendations for NPARC calculations (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effects of grid resolution and specification of turbulent inflow boundary conditions were examined using the NPARC code with the Baldwin-Lomax and Chien k-e turbulence models. Three benchmark turbulent test cases were calculated: two were wall bounded flows and the third was a compressible mixing layer. The wall bounded flows were essentially insensitive to axial grid density; however, the location of the first point off the wall had a substantial effect on flow solutions. It was determined that the first point off the wall must be in the laminar sublayer (y+ less than or equal to 5) for the entire boundary layer. For the compressible mixing layer cases, the axial grid density affected the capturing of oblique shock waves in the mixing region, but the overall mixing rate was not strongly dependent on grid resolution. In specifying the inflow turbulent boundary conditions, it was very important to match the boundary layer and momentum thicknesses of the two flows entering the mixing region; calculations obtained with smaller or no boundary layers resulted in substantially reduced mixing. The solutions were relatively insensitive to freestream turbulence level.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106959 , E-9711 , NAS 1.15:106959 , AIAA PAPER 95-2613 , Joint Propulsion Conference and Exhibit; Jul 10, 1995 - Jul 12, 1995; San Diego, CA; United States
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  • 4
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    Implementation of a two-equation k-omega turbulence model in NPARC (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The implementation of a two-equation k-omega turbulence model into the NPARC flow solver is described. Motivation for the selection of this model is given, major code modifications are outlined, new imputs to the code are described, and results are presented for several validation cases: an incompressible flow over a smooth flat plate, a subsonic diffuser flow, and a shock-induced separated flow. Comparison of results with the k-epsilon model indicate that the k-omega model predicts simple flows equally well whereas, for adverse pressure gradient flows, the k-omega model outperforms the other turbulence models in NPARC.
    Keywords: AERODYNAMICS
    Type: NASA-TM-107080 , NAS 1.15:107080 , E-9955 , AIAA PAPER 96-0383 , NIPS-96-08118 , Aerospace Sciences Meeting and Exhibit; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
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  • 5
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    A Comparison of Three Navier-Stokes Solvers for Exhaust Nozzle Flowfields (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A comparison of the NPARC, PAB, and WIND (previously known as NASTD) Navier-Stokes solvers is made for two flow cases with turbulent mixing as the dominant flow characteristic, a two-dimensional ejector nozzle and a Mach 1.5 elliptic jet. The objective of the work is to determine if comparable predictions of nozzle flows can be obtained from different Navier-Stokes codes employed in a multiple site research program. A single computational grid was constructed for each of the two flows and used for all of the Navier-Stokes solvers. In addition, similar k-e based turbulence models were employed in each code, and boundary conditions were specified as similarly as possible across the codes. Comparisons of mass flow rates, velocity profiles, and turbulence model quantities are made between the computations and experimental data. The computational cost of obtaining converged solutions with each of the codes is also documented. Results indicate that all of the codes provided similar predictions for the two nozzle flows. Agreement of the Navier-Stokes calculations with experimental data was good for the ejector nozzle. However, for the Mach 1.5 elliptic jet, the calculations were unable to accurately capture the development of the three dimensional elliptic mixing layer.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA/TM-1999-209184 , E-11693 , NAS 1.15:209184 , AIAA Paper 99-0748 , Aerospace Sciences; Jan 11, 1999 - Jan 14, 1999; Reno, NV; United States
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  • 6
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    Implementation and Validation of the Chien k-epsilon Turbulence Model in the Wind Navier-Stokes Code (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The two equation k-epsilon turbulence model of Chien has been implemented in the WIND Navier-Stokes flow solver. Details of the numerical solution algorithm, initialization procedure, and stability enhancements are described. Results obtained with this version of the model are compared with those from the Chien k-epsilon model in the NPARC Navier-Stokes code and from the WIND SST model for three validation cases: the incompressible flow over a smooth flat plate, the incompressible flow over a backward facing step, and the shock-induced flow separation inside a transonic diffuser. The k-epsilon model results indicate that the WIND model functions very similarly to that in NPARC, though the WIND code appears to he slightly more accurate in the treatment of the near-wall region. Comparisons of the k-epsilon model results with those from the SST model were less definitive, as each model exhibited strengths and weaknesses for each particular case.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA/TM-1999-209080 , NAS 1.15:209080 , E-11662 , AIAA Paper 99-0745 , Aerospace Sciences; Jan 11, 1999 - Jan 14, 1999; Reno, NV; United States
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  • 7
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    Parametric Studies of the Ejector Process within a Turbine-Based Combined-Cycle Propulsion System (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Performance characteristics of the ejector process within a turbine-based combined-cycle (TBCC) propulsion system are investigated using the NPARC Navier-Stokes code. The TBCC concept integrates a turbine engine with a ramjet into a single propulsion system that may efficiently operate from takeoff to high Mach number cruise. At the operating point considered, corresponding to a flight Mach number of 2.0, an ejector serves to mix flow from the ramjet duct with flow from the turbine engine. The combined flow then passes through a diffuser where it is mixed with hydrogen fuel and burned. Three sets of fully turbulent Navier-Stokes calculations are compared with predictions from a cycle code developed specifically for the TBCC propulsion system. A baseline ejector system is investigated first. The Navier-Stokes calculations indicate that the flow leaving the ejector is not completely mixed, which may adversely affect the overall system performance. Two additional sets of calculations are presented; one set that investigated a longer ejector region (to enhance mixing) and a second set which also utilized the longer ejector but replaced the no-slip surfaces of the ejector with slip (inviscid) walls in order to resolve discrepancies with the cycle code. The three sets of Navier-Stokes calculations and the TBCC cycle code predictions are compared to determine the validity of each of the modeling approaches.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1999-209172 , NAS 1.15:209172 , AIAA Paper 98-0936 , E-11679 , Aerospace Sciences; Jan 12, 1998 - Jan 15, 1998; Reno, NV; United States
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