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  • 1
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    Summary of all cycle II.5 shear and boundary layer measurements, aerodynamics (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The two measurement systems were used to measure mean velocity and velocity, mass flux, and total temperature fluctuations in the turbulent boundary on the fuselage of a KC-135 aircraft. The boundary layer thickness ranged between about 20 and 30 cm for the range of flight Mach numbers from about 0.25 to 0.85 and Reynolds numbers between 3 and 6 x 10 to the 6th power/m. The adaptation of each system for use in airborne applications is discussed. The data obtained from each system are given and compared with each other and they indicate that the two systems represent viable ones for use in future airborne turbulence experiments.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 459-464
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Unsteady density and velocity measurements in the 6 foot x 6 foot wind tunnel (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The methods used and the results obtained in four aero-optic tests are summarized. It is concluded that the rather large values of density fluctuation appear to be the result of much higher Mach number than freestream and the violent turbulence in the flow as it separates from the turret. A representative comparison of fairing on-fairing off rms density fluctuation indicates essentially no effect at M = 0.62 and a small effect at M = 0.95. These data indicate that some slight improvement in optical quality can be expected with the addition of a fairing, although at M = 0.62 its effect would be nil. Fairings are very useful in controlling pressure loads on turrets, but will not have first order effects on optical quality. Scale sizes increase dramatically with increasing azimuth angle for a reprensentative condition. Since both scale sizes and fluctuation levels increase (total turbulence path length also increases) with azimuth angle, substantial optical degradation might be expected. For shorter wave lengths, large degradations occur.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Proc. of the Aero-Optics Symp. on Electromagnetic Wave Propagation from Aircraft; p 153-181
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    A new turbulence closure model for boundary layer flows with strong adverse pressure gradients and separation (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A new turbulence closure model designed specifically to treat two-dimensional, turbulent boundary layers with strong adverse pressure gradients and attendant separation, is presented. The influence of history effects are modeled by using an ordinary differential equation (ODE) derived from the turbulence kinetic-energy equation, to describe the streamwise development of the maximum Reynolds shear stress in conjunction with an assumed eddy-viscosity distribution which has as its velocity scale the maximum Reynolds shear stress. In the outer part of the boundary layer, the eddy viscosity is treated as a free parameter which is adjusted in order to satisfy the ODE for the maximum shear stress. Because of this, the model s not simply an eddy-viscosity model, but contains features of a Reynolds-stress model. Comparisons with experiments are presented which clearly show the proposed model to be superior to the Cebeci-Smith model in treating strongly retarded and separated flows. In contrast to two-equation, eddy-viscosity models, it requires only slightly more computational effort than simple models like the Cebeci-Smith model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 84-0175
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Separated skin-friction measurements - Source of error: An assessment and elimination (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Potential sources of error in the use of heated surface gages for separated-skin-friction measurement are studied. Emphasis is placed on the interpretation of local skin-friction measurements in two- and three-dimensional separated turbulent-shear flows before they are used to test the validity of current and proposed computer codes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 80-1409 , Fluid and Plasma Dynamics Conference; Jul 14, 1980 - Jul 16, 1980; Snowmass, CO
    Format: text
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