Multigrid calculations of a jet in crossflow
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Claus, R. W.↗
Engineering topics
Claus, R. W.
Publications and source records attributed to Claus, R. W..
Time-accurate simulations of a shear layer forced at a single frequency
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Claus, R. W.↗
Multigrid Calculations of a Jet in Crossflow
A series of numerical calculations are made of a jet in crossflow using progressive mesh refinement up to 2.4 million grid points. A solution algorithm that combined the features of a point-coupled solution of the momentum and continuity equations with multigrid acceleration demonstrated efficient convergence of the governing equations. In comparisons with experimental data, some features of the jet flow field were found to be predicted reasonably well, but the results still remain affected by numerical diffusion.
Claus, R. W.↗
Mesh refinement in a two-dimensional large eddy simulation of a forced shear layer
A series of large eddy simulations are made of a forced shear layer and compared with experimental data. Several mesh densities were examined to separate the effect of numerical inaccuracy from modeling deficiencies. The turbulence model that was used to represent small scale, 3-D motions correctly predicted some gross features of the flow field, but appears to be structurally incorrect. The main effect of mesh refinement was to act as a filter on the scale of vortices that developed from the inflow boundary conditions.
Claus, R. W.↗
Response of a chemically reacting shear layer to streamwise vorticity
A series of Direct Numerical Simulations are performed of a temporally evolving shear layer subject to both harmonic (2D) and streamwise (3D) forcing. The interaction and coupling of these various 2D and 3D modes is shown to significantly alter the development of the flow. The scale of the 3D modes is quite important to the coupling process with greatly enhanced mixing and product formation resulting from 3D modes that are rapidly amplified by the spanwise vorticity. In general, the longer wavelength 3D modes are found to be highly efficient at increasing the momentum transport while the shorter wavelengths increase mass transport.
Claus, R. W.↗
Direct numerical simulations of a temporally evolving mixing layer subject to forcing
The vortical evolution of mixing layers subject to various types of forcing is numerically simulated using pseudospectral methods. The effect of harmonic forcing and random noise in the initial conditions is examined with some results compared to experimental data. Spanwise forcing is found to enhance streamwise vorticity in a nonlinear process leading to a slow, secondary growth of the shear layer. The effect of forcing on a chemical reaction is favorably compared with experimental data at low Reynolds numbers. Combining harmonic and subharmonic forcing is shown to both augment and later destroy streamwise vorticity.
Claus, R. W.↗
Time-dependent calculation of a forced mixing layer using a k-epsilon turbulence model
A two-dimensional-dependent calculation of a forced turbulent mixing layer is reported. The approach employs a k-epsilon turbulence model to represent the effects of motions which are three dimensional or out of phase with the forcing cycle. Calculations that correspond to conditions of the measurements of Weisbrot (1984) and Weisbrot and Wygnanski (1988) indicate that the main features of the mixing layer development are captured by the computation. The effect of grid refinement on the computed result indicates the importance of adequate resolution of the near field in correctly reproducing the flow evolution. The inlet boundary condition, similarly, is shown to play a decisive role in determining subsequent development.
Macinnes, J. M.↗
Time-accurate simulations of a shear layer forced at a single frequency
Calculations are presented for the forced shear layer studied experimentally by Oster and Wygnanski, and Weisbrot. Two different computational approaches are examined: Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES). The DNS approach solves the full three dimensional Navier-Stokes equations for a temporally evolving mixing layer, while the LES approach solves the two dimensional Navier-Stokes equations with a subgrid scale turbulence model. While the comparison between these calculations and experimental data was hampered by a lack of information on the inflow boundary conditions, the calculations are shown to qualitatively agree with several aspects of the experiment. The sensitivity of these calculations to factors such as mesh refinement and Reynolds number is illustrated.
Claus, R. W.↗
Time-accurate simulations of a shear layer forced at a single frequency
This report presents calculations of the forced shear layer studied experimentally by Oster and Wygnanski (1982) and Weisbrot (1984). Two different computational approaches are examined: Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES).The DNS appraoch solves the full three-dimensional, Navier-Stokes equations for a temporally evolving mixing layer, while the LES approach (as used in this report) solves the two-dimensional, Navier-Stokes equations with a subgrid scale turbulence model. While the comparison between these calculations and experimental data was hampered by a lack of information on the inflow boundary conditions, the calculations are shown to qualitatively agree with several aspects of the experiment. The sensitivity of these calculations to factors such as mesh refinement and Reynolds number is illustrated.
Claus, R. W.↗
SSME fuelside preburner two-dimensional analysis
The flow field within the fuelside preburner of the Space Shuttle Main Engine is calculated using a reacting flow code (REACT2D). Inlet and modeling parameters involved in the numerical calculation are systematically varied to establish the sensitivity of the calculated exit temperature profile. It is found that differences in the inlet equivalence ratio have a large effect on the turbine inlet temperature profile. A variety of preburner inlet modeling changes such as inlet turbulence level, modeling the gases as burned, unburned, premixed, or unmixed, are shown to have a smaller effect on the calculated turbine inlet temperature profile. Also, the form of finite differencing used is shown to have an effect on the temperature profile.
Vanoverbeke, T. J.↗
Flame radiation and linear heat transfer in a tubular-can combustor
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Claus, R. W.↗
Numerical calculation of subsonic jets in crossflow with reduced numerical diffusion
A series of calculations are reported for two, subsonic jet in crossflow geometries. The parametric variation examined are the lateral spacing of a row of jets. The first series of calculations corresponds to a widely space jet geometry, S/D = 4, and the second series corresponds to closely spaced jets, S/D = 2. The calculations are done with alternate differencing schemes to illustrate the impact of numerical diffusion. The calculated jet trajectories agreed well with experimental data in the widely spaced jet geometry, but not in the closely spaced geometry.
Claus, R. W.↗
Combustion research for gas turbine engines
Research on combustion is being conducted at Lewis Research Center to provide improved analytical models of the complex flow and chemical reaction processes which occur in the combustor of gas turbine engines and other aeropropulsion systems. The objective of the research is to obtain a better understanding of the various physical processes that occur in the gas turbine combustor in order to develop models and numerical codes which can accurately describe these processes. Activities include in-house research projects, university grants, and industry contracts and are classified under the subject areas of advanced numerics, fuel sprays, fluid mixing, and radiation-chemistry. Results are high-lighted from several projects.
Mularz, E. J.↗
Numerical calculation of subsonic jets in crossflow with reduced numerical diffusion
A series of calculations are reported for two, subsonic jet in crossflow geometries. The parametric variation examined are the lateral spacing of a row of jets. The first series of calculations corresponds to a widely space jet geometry, S/D = 4, and the second series corresponds to closely spaced jets, S/D = 2. The calculations are done with alternate differencing schemes to illustrate the impact of numerical diffusion. The calculated jet trajectories agreed well with experimental data in the widely spaced jet geometry, but not in the closely spaced geometry.
Claus, R. W.↗
Accelerated convergence for incompressible flow calculations
Two improved algorithms which solve the steady-state Navier-Stokes equations, PISO and SIMPLER, are studied. Computations were carried out on progressively finer grids for the driven cavity and flow over a backward-facing step. The effects of relaxation factor, number of grid nodes and number of sweeps through the pressure equations are studied to evaluate the performance of the PISO and SIMPLER schemes. Results show that these improved schemes accelerate the convergence rate of the solution generally by a factor of two as compared to the SIMPLE method.
Neely, G. M.↗
Combustion research for gas turbine engines
Research on combustion is being conducted at Lewis Research Center to provide improved analytical models of the complex flow and chemical reaction processes which occur in the combustor of gas turbine engines and other aeropropulsion systems. The objective of the research is to obtain a better understanding of the various physical processes that occur in the gas turbine combustor in order to develop models and numerical codes which can accurately describe these processes. Activities include in-house research projects, university grants, and industry contracts and are classified under the subject areas of advanced numerics, fuel sprays, fluid mixing, and radiation-chemistry. Results are high-lighted from several projects.
Mularz, E. J.↗
Numerical modeling of turbulent flow
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.
Claus, R. W.↗
Flame radiation and linear heat transfer in a tubular can combustor
Heat transfer within a combuster were examined. Total and spectral flame radiation in a tubular can combustor at a series of parameteric operating conditions was measured. Radiation measurements were taken for a range of inlet air pressures from 0.34 to 2.0 MPa, inlet air temperatures from 533 to 700 K, with two different fuels, Jet-A and ERBS. Measurements of linear temperatures combined with the parametric radiation results allowed a calculation of the combustor linear heat loads. Flame emissivity was determined from the spectral measurements. Previously announced in STAR as N84-13188
Claus, R. W.↗