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  • FLUID MECHANICS  (50)
  • MATERIALS, METALLIC  (42)
  • EARTH RESOURCES AND REMOTE SENSING
  • 1995-1999
  • 1980-1984
  • 1970-1974  (94)
  • 1973  (94)
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  • 1995-1999
  • 1980-1984
  • 1970-1974  (94)
Year
  • 1
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    Calculation of transitional boundary-layer flows. (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The results of a finite-difference calculation of hypersonic transitional boundary-layer flow are presented. Precursor-transition and low Reynolds number turbulence effects are included. These calculation results are compared with data from a source where profiles are available at the beginning, middle and end of the hypersonic transitional flow. The results indicate that the low Reynolds number effect is the most important.
    Keywords: FLUID MECHANICS
    Type: AIAA Journal; 11; Apr. 197
    Format: text
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  • 2
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    A local eddy viscosity model for turbulent shear flow (1973)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In the model described, the eddy viscosity is assumed to be a fluid property dependent on the state of the fluid locally, namely the local density, turbulent kinetic energy, turbulence scale, and Mach number. An empirical law was found which related eddy viscosity to these properties satisfactorily for free jets. This law is used without modification for a set of test cases in free shear layers, free-jet decay, coaxial mixing, and wakes. The scale of turbulence is taken as a constant at any axial location equal to the width of the shear layer. By utilizing the boundary-layer order-of-magnitude analysis, a coupled set of fluid dynamic equations is formulated, which of necessity includes the equation for the production of turbulent kinetic energy.
    Keywords: FLUID MECHANICS
    Type: NASA. Langley Res. Center Free Turbulent Shear Flows, Vol. 1; p 529-547
    Format: application/pdf
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  • 3
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    A rational approach to the use of Prandtl's mixing length model in free turbulent shear flow calculations (1973)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Prandtl's basic mixing length model was used to compute 22 test cases on free turbulent shear flows. The calculations employed appropriate algebraic length scale equations and single values of mixing length constant for planar and axisymmetric flows, respectively. Good agreement with data was obtained except for flows, such as supersonic free shear layers, where large sustained sensitivity changes occur. The inability to predict the more gradual mixing in these flows is tentatively ascribed to the presence of a significant turbulence-induced transverse static pressure gradient which is neglected in conventional solution procedures. Some type of an equation for length scale development was found to be necessary for successful computation of highly nonsimilar flow regions such as jet or wake development from thick wall flows.
    Keywords: FLUID MECHANICS
    Type: Free Turbulent Shear Flows, Vol. 1; p 67-137
    Format: application/pdf
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  • 4
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    Use of ERTS-1 data to access and monitor change in the west side of the San Joaquin Valley and central coastal zone of California (1973)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: There are no author-identified significant results in this report.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E75-10216 , NASA-CR-142402
    Format: application/pdf
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  • 5
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    Effect of diffusional creep on particle morphology of polycrystalline alloys strengthened by second phase particles (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Diffusional creep in a polycrystalline alloy containing second-phase particles can disrupt the particle morphology. For alloys which depend on the particle distribution for strength, changes in the particle morphology can affect the mechanical properties. Recent observations of diffusional creep in alloys containing soluble particles (gamma-prime strengthened Ni base alloys) and inert particles have been reexamined in light of the basic mechanisms of diffusional creep, and a generalized model of this effect is proposed. The model indicates that diffusional creep will generally result in particle-free regions in the vicinity of grain boundaries serving as net vacancy sources. The factors which control the changes in second-phase morphology have been identified, and methods of reducing the effects of diffusional creep are suggested.
    Keywords: MATERIALS, METALLIC
    Type: NASA-TN-D-7177 , E-7248
    Format: application/pdf
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  • 6
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    Effects of high temperature brazing and thermal cycling on mechanical properties of Hastelloy X. (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Data are presented on the effects of brazing alloy, brazing operation, thermal cycling, and combinations of these on the yield strength, elongation, ultimate tensile strength, and fatigue life of thin gage Hastelloy X. These data show that brazing with a Ni-Pd-Au alloy at 1461 K resulted in reductions of 35 percent in yield strength and elongation, 6 percent in ultimate tensile strength, and 18 percent in fatigue limit of Hastelloy X, as compared with as-received material. Subsequent exposure to 200 thermal cycles between 533 K and 1144 K after brazing caused further losses of 4 percent in yield strength, 8 percent in ultimate tensile strength, and 6 percent in fatigue limit.
    Keywords: MATERIALS, METALLIC
    Type: NASA-TM-X-2704 , L-8561
    Format: application/pdf
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  • 7
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    Mixing of multiple dilution jets with a hot primary airstream for gas turbine combustors (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The mixing of multiple air jets with a subsonic heated crossflow in a constant area duct was studied experimentally. The jet-to-mainstream momentum flux ratio was varied from 6 to 60. Temperature and pressure surveys were made at several downstream locations for orifice geometries with parametric variation of orifice size and spacing. A mixing efficiency parameter was defined which characterized the effectiveness of the mixing over the range of conditions examined. It was found that for a given momentum flux ratio, there exists a ratio of orifice spacing to duct height which provides the best mixing.
    Keywords: FLUID MECHANICS
    Type: AIAA PAPER 73-1249 , Propulsion Conference; Nov 05, 1973 - Nov 07, 1973; Las Vegas, NV; US
    Format: text
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  • 8
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    Shock wave-turbulent boundary layer interactions in rectangular channels. II - The influence of sidewall boundary layers on incipient separation and scale of the interaction. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Keywords: FLUID MECHANICS
    Type: AIAA PAPER 73-234 , Aerospace Sciences Meeting; Jan 10, 1973 - Jan 12, 1973; Washington, DC
    Format: text
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  • 9
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    Introduction to boundary-layer theory (1973)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The pressure ratio across a turbine provides a certain amount of ideal energy that is available to the turbine for producing work. The portion of the ideal energy that is not converted to work is considered to be a loss. One of the more important and difficult aspects of turbine design is the prediction of the losses. The primary cause of losses is the boundary layer that develops on the blade and end wall surfaces. Boundary-layer theory is used to calculate the parameters needed to estimate viscous (friction) losses.
    Keywords: FLUID MECHANICS
    Type: Turbine Design and Appl., Vol. 2; p 57-92
    Format: text
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  • 10
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    A new criterion for failure of materials by environment-induced cracking (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A new criterion has been developed for predicting failure of materials by environment-induced cracking. The criterion has been developed by the use of fracture mechanics concepts and assumes that the relationship between crack-growth rate and stress intensity can be described by three separable regions of behavior as first suggested by Wiederhorn. The analytical form of the criterion relates failure time to the initial crack length and the critical crack length or alternatively, to the initial stress intensity and the fracture toughness for various conditions of stress and the environmental variables. The analytical expression is examined by the use of some experimental data on the hydrogen-induced cracking of Ti-5Al-2.5 Sn, and it is demonstrated that the expression predicts the general expected form of the relationship between the normalized stress intensity parameter and the failure time.
    Keywords: MATERIALS, METALLIC
    Type: International Journal of Fracture; 9; Mar. 197
    Format: text
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