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  • 1
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    Vortex simulation of forced/unforced mixing layers (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 25; 1417
    Format: text
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  • 2
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    A theory for turbulent curved wall jets (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An attempt is made to formulate the simplest possible model for the flow of a wall jet emanating from a two dimensional source into quiescent surroundings in the presence of a wall of arbitrary shape. The method used self similar profiles for the mean velocity together with a simple eddy viscosity model. The streamwise and radial momentum equations are integrated across the wall jet flow to give an expression for the momentum balance including the effect of the pressure gradient induced by the rate of change of surface curvature. The streamwise momentum equation is also evaluated at the point of maximum velocity to provide a second equation and thereby permit a solution for the two unknown quantities, the jet half width and the maximum velocity. This approach provides approximate closed form solutions for the flow of the wall jet over surfaces of various shapes, and in particular permits a direct comparison with the available experimental results for plane, cylindrical or logarithmic spiral surfaces.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center Proceedings of the Circulation-Control Workshop, 1986; p 99-112
    Format: application/pdf
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  • 3
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    Numerical simulation of vortex breakdown by the vortex-filament method (1983)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The vortex-filament method was applied to the simulation of vortex breakdown. The principal vortex region was represented by multiple filaments, and an axial velocity component was induced by a spiral winding of the filaments. An accuracy check was performed for a cylindrical swirling flow with simple analytical expressions for the axial and theta velocities. The result suggests that the flow field can be simulated to any accuracy by increasing the number of filaments. An axisymmetric-type vortex breakdown was simulated, with experimental data serving as upstream conditions. The calculated axial- and theta-velocity contours show the breakdown of the vortex, including a rapid change in the vortex core, followed axially by a recovery zone and then a second breakdown. When three dimensional initial data are used the second breakdown appears to be of the spiral type in correspondence with experimental observations. The present method can easily be used to simulate other types of vortex breakdown or other vortex flows with axial velocity.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 13 p
    Format: text
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  • 4
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    Thickness Measurement Device for Ice/Water Mixture (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A device and method are provided for determining the thickness of an ice and water mixture accumulated on the outer surface of an object. First and second total impedance sensors are operated at first and second frequencies over which the dielectric constants for water and ice are substantially the same. Corresponding first and second AC total impedance measuring circuits are coupled to the first and second sensors to produce output voltages based on the total impedance changes sensed by the sensors. A processor is coupled to the first and second measuring circuits to generate a voltage ratio using the measured output voltages. The voltage ratio is indicative of the thickness of the ice and water mixture. The novelty of the present invention is the use of two frequencies and dual geometry impedance sensors in order to be sensitive to the formation of ice. Thus, critical situations created by the presence of solid ice can be averted. The device is simple and is easily incorporated into current technology thereby making its realization cost- effective.
    Keywords: Instrumentation and Photography
    Type: NAS 1.71:LAR-15061-1
    Format: application/pdf
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  • 5
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    Navier-Stokes computation of wing/rotor interaction for a tilt rotor in hover (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method has been developed to analyze the wing/rotor interaction of tilt rotor aircraft in hover. The unsteady, thin-layer compressible Navier-Stokes equations are solved using an implicit, finite difference scheme that employs LU-ADI factorization. The rotor is modeled as an actuator disk which imparts a radial and azimuthal distribution of pressure rise and swirl to the flowfield. The 'chimera' approach of grid point blanking is used to update the rotor boundary conditions. Results are presented for both a rotor alone and for wing/rotor interaction where the thrust coefficient is 0.0164 and wing flap deflection is 67 degrees. Many of the complex flow features are captured including the fountain effect, leading and trailing edge separation, and the unsteady wake beneath the wing. Wing surface pressures compare fairly well with experimental data although the time-averaged download is about twenty percent higher than the measured value. This discrepancy is due to a combination of factors that are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0707
    Format: text
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  • 6
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    High speed transport cruise drag (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report provides scaling laws for the cruise aerodynamics of high speed transport wings based on the results of Navier-Stokes computations. Expressions for the various drag components are found, together with the corresponding values (L/D)(sub m) for various values of the geometric parameter s/l which allow for simple optimization of the wing configurations with respect to the span. It is found that linear theory expressions can be used for this purpose provided the coefficients of these experiments for C(sub D) and (L/D)(sub m) are available using Navier-Stokes results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-190248 , NAS 1.26:190248 , JIAA-TR-106
    Format: application/pdf
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  • 7
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    Vaporizing particle velocimeter (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A velocimeter measures flow characteristics of a flow traveling through a chamber in a given direction. Tracer particles are entrained in the flow and a source of radiant energy produces an output stream directed transversely to the chamber, having a sufficient intensity to vaporize the particles as they pass through the output stream. Each of the vaporized particles explodes to produce a shock wave and a hot core, and a flow visualization system tracks the motion of the hot cores and shock waves to measure the velocity of each tracer particle and the temperature of the flow around the tracer.
    Keywords: AERODYNAMICS
    Format: application/pdf
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  • 8
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    Vortex simulation of forced mixing layers (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two-dimensional, spatially growing, turbulent mixing layers are simulated numerically by a vortex method and the results are compared with those determined experimentally. The effects of artificial forcing on flow development are also studied. Many of the flow features which have been observed experimentally are reproduced, and good quantitative agreements between experiments and computations are obtained.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88235 , A-86191 , NAS 1.15:88235
    Format: application/pdf
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  • 9
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    Control of vortical separation on conical bodies (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.
    Keywords: AERODYNAMICS
    Type: NASA-CR-181206 , NAS 1.26:181206 , JIAA-TR-78
    Format: application/pdf
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  • 10
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    Reflection type skin friction meter (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A housing block is provided having an upper surface conforming to the test surface of a model or aircraft. An oil film is supplied upstream of a transparent wedge window located in this upper surface by an oil pump system located external to the housing block. A light source located within the housing block supplies a light beam which passes through this transparent window and is reflected back through the transparent window by the upper surface of the oil film to a photo-sensitive position sensor located within the housing. This position sensor allows the slope history of the oil film caused by and aerodynamic flow to be determined. The skin friction is determined from this slope history. Internally located mirrors augment and sensitize the reflected beam as necessary before reaching the position sensor. In addition, a filter may be provided before this sensor to filter the beam.
    Keywords: AERODYNAMICS
    Format: application/pdf
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