NASA Scientific and Technical Aerospace Reports

20040111228 NASA Langley Research Center, Hampton, VA, USA
Navier-Stokes Computations and Experimental Comparisons for Multielement Airfoil Configurations
Anderson, W. Kyle; Bonhaus, Daryl L.; McGhee, Robert; Walker, Betty; [1993]; 9 pp.; In English; Aerospace Sciences
Meeting, 1993, Reno, NV, USA
Report No.(s): AIAA Paper 93-0645; No Copyright; Avail: CASI; A02, Hardcopy
A two-dimensional unstructured Navier-Stokes code is utilized for computing the flow around multielement airfoil
configurations. Comparisons are shown for a landing configuration with an advanced-technology flap. Grid convergence
studies are conducted to assess inaccuracies caused by inadequate grid resolution. Although adequate resolution is obtained
for determining the pressure distributions, further refinement is needed to sufficiently resolve the velocity profiles at high
angles of attack. For the advanced flap configuration, comparisons of pressure distributions and lift are made with
experimental data. Here, two flap riggings and two Reynolds numbers are considered. In general, the trends caused by
variations in these quantities are well predicted by the computations, although the angle of attack for maximum lift is
overpredicted.
Author
Airfoils; Computational Fluid Dynamics; Navier-Stokes Equation; Aerodynamic Configurations; Two Dimensional Flow;
Unstructured Grids (Mathematics)
20040111229 NASA Langley Research Center, Hampton, VA, USA
Dual-Code Solution Strategy for Chemically-Reacting Hypersonic Flows
Wood, William A.; Eberhardt, Scott; [1995]; 16 pp.; In English; Copyright; Avail: CASI; A03, Hardcopy
A new procedure seeks to combine the thin-layer Navier-Stokes solver LAURA with the parabolized Navier-Stokes solver
UPS for the aerothermodynamic solution of chemically-reacting air flow fields. The interface protocol is presented and the
method is applied to two slender, blunted shapes. Both axisymmetric and three-dimensional solutions are included with
surface pressure and heat transfer comparisons between the present method and previously published results. The case of Mach
25 flow over an axisymmetric six degree sphere-cone with a non-catalytic wall is considered to 100 nose radii. A stability
bound on the marching step size was observed with this case and is attributed to chemistry effects resulting from the
non-catalytic wall boundary condition. A second case with Mach 28 flow over a sphere-cone-cylinder-flare configuration is
computed at both two and five degree angles of attack with a fully-catalytic wall. Surface pressures are seen to be within five
percent with the present method compared to the baseline LAURA solution and heat transfers are within 10 percent. The effect
of grid resolution is investigated in both the radial and streamwise directions. The procedure demonstrates significant, order
of magnitude reductions in solution time and required memory for the three-dimensional case in comparison to an all
thin-layer Navier-Stokes solution.
Author
Hypersonic Flow; Aerothermodynamics; Reacting Flow; Flow Distribution; Upwind Schemes (Mathematics); Algorithms;
Computer Programs
20040111230 NASA Langley Research Center, Hampton, VA, USA
Airfoil Design and Optimization by the One-Shot Method
Kuruvila, G.; Taasan, Shlomo; Salas, M. D.; [1995]; 15 pp.; In English; 33rd Aerospace Sciences Meeting and Exhibit, 9-12
Jan. 1995, Reno, NV, USA
Contract(s)/Grant(s): NAS1-19672; NAS1-19680
Report No.(s): AIAA Paper 95-0478; Copyright; Avail: CASI; A03, Hardcopy
An efficient numerical approach for the design of optimal aerodynamic shapes is presented in this paper. The objective
of any optimization problem is to find the optimum of a cost function subject to a certain state equation (governing equation
of the flow field) and certain side constraints. As in classical optimal control methods, the present approach introduces a costate
variable (Lagrange multiplier) to evaluate the gradient of the cost function. High efficiency in reaching the optimum solution
is achieved by using a multigrid technique and updating the shape in a hierarchical manner such that smooth (low-frequency)
changes are done separately from high-frequency changes. Thus, the design variables are changed on a grid where their
changes produce nonsmooth (high-frequency) perturbations that can be damped efficiently by the multigrid. The cost of
solving the optimization problem is approximately two to three times the cost of the equivalent analysis problem.
Author
Airfoils; Aerodynamic Configurations; Optimization; Multigrid Methods; Flow Distribution; Methodology
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