NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
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self-sustained due to the low Reynolds-number, <strong>and</strong> the flow does not reach a turbulent state within the computational domain.<br />
In contrast, in the higher Reynolds-number case, boundary-layer fluctuations persist after the wake has decayed (due, in part,<br />
to the higher values of the local Reynolds number Re(sub theta) achieved in this case); some evidence could be observed that<br />
a self-sustaining turbulence generation cycle was beginning to be established.<br />
Author<br />
Boundary Layers; Flat Plates; Wakes; Direct Numerical Simulation; Large Eddy Simulation; Circular Cylinders<br />
20040111290 Maryl<strong>and</strong> Univ., College Park, MD, USA<br />
Numerical Simulations Using the Immersed Boundary Technique<br />
Piomelli, Ugo; Balaras, Elias; [1997]; 12 pp.; In English<br />
Contract(s)/Grant(s): NAG1-2285; No Copyright; Avail: CASI; A03, Hardcopy<br />
The immersed-boundary method can be used to simulate flows around complex geometries within a Cartesian grid. This<br />
method has been used quite extensively in low Reynolds-number flows, <strong>and</strong> is now being applied to turbulent flows more<br />
frequently. The technique will be discussed, <strong>and</strong> three applications of the method will be presented, with increasing<br />
complexity. to illustrate the potential <strong>and</strong> limitations of the method, <strong>and</strong> some of the directions for future work.<br />
Author<br />
Computational Fluid Dynamics; Numerical Analysis; Computational Grids; Flow Distribution; Laminar Boundary Layer<br />
20040111291 <strong>NASA</strong> Langley Research Center, Hampton, VA, USA<br />
Inverse Design of Nacelles Using Multi-Block Navier Stokes Codes<br />
Naik, D. A.; Krist, S. E.; Campbell, R. L.; Vatsa, V. N.; Buning, P. G.; Gea, L. M.; [1995]; 10 pp.; In English<br />
Contract(s)/Grant(s): NAS1-19672<br />
Report No.(s): AIAA Paper 95-1820; No Copyright; Avail: CASI; A02, Hardcopy<br />
The objective of this work is to reshape a nacelle to achieve a specified nacelle pressure distribution. The nacelle may be<br />
either isolated or installed on an airplane. There are no restrictions on the attitude (toe, incidence, <strong>and</strong> roll) <strong>and</strong> position of<br />
the nacelle. The design algorithm is coupled to two different multi-block 3-D Navier Stokes flow solvers. The coupling<br />
between design <strong>and</strong> analysis is automated to the point where the design proceeds with minimal user input.<br />
Author<br />
Nacelles; Navier-Stokes Equation; Multiblock Grids; Three Dimensional Flow; Computer Programs; Aircraft Design<br />
20040111292 <strong>NASA</strong> Langley Research Center, Hampton, VA, USA<br />
Exhaust Gas Modeling Effects on Hypersonic Powered Simulation at Mach 10<br />
Tatum, Kenneth E.; Huebner, Lawrence D.; [1995]; 11 pp.; In English<br />
Report No.(s): AIAA Paper 95-6068; Copyright; Avail: CASI; A03, Hardcopy<br />
A numerical study was performed to investigate the accuracy <strong>and</strong> validity of cold-gas simulation of actual hot scramjet<br />
exhaust within a Mach 10 free stream over a representative single-stage-to-orbit airbreathing configuration. In particular,<br />
exhausts of various noncombusting chemistry models were studied to characterize their effects on the vehicle aftbody<br />
performance <strong>and</strong> the plume flow field definition. Two approximations of the hot scramjet combustion products were utilized<br />
to determine the requirement for expensive, multi-species numerical modeling, <strong>and</strong> to establish a baseline for the validation<br />
of cold-gas simulation. Cold-gas simulation at Mach 10 is shown to be a viable technique using an appropriate thermally<br />
perfect gas mixture for reproducing hot scramjet exhaust effects.<br />
Author<br />
Exhaust Gases; Hypersonic Speed; Mathematical Models; Supersonic Combustion Ramjet Engines; Computational Fluid<br />
Dynamics; Computerized Simulation; Free Flow<br />
20040111296 <strong>NASA</strong> Langley Research Center, Hampton, VA, USA<br />
Efficiency <strong>and</strong> Accuracy of Time-Accurate Turbulent Navier-Stokes Computations<br />
Rumsey, Christopher L.; Sanetrik, Mark D.; Biedron, Robert T.; Melson, N. Duane; Parlette, Edward B.; [1995]; 15 pp.; In<br />
English; 13th AIAA Applied Aerodynamics Conference, 19-22 Jun. 1995, San Diego, CA, USA<br />
Report No.(s): AIAA Paper 95-1835; Copyright; Avail: CASI; A03, Hardcopy<br />
The accuracy <strong>and</strong> efficiency of two types of subiterations in both explicit <strong>and</strong> implicit Navier-Stokes codes are explored<br />
for unsteady laminar circular-cylinder flow <strong>and</strong> unsteady turbulent flow over an 18-percent-thick circular-arc (biconvex)<br />
airfoil. Grid <strong>and</strong> time-step studies are used to assess the numerical accuracy of the methods. Nonsubiterative time-stepping<br />
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