Unsteady measurement techniques including surface and flowfield pressure measurement systems, laser light sheet tests, liquid crystal techniques, laser Doppler anemometry and hot-wire measurement systems are treated in the present report. in particular, the hot-wire calibration and measurement techniques concerning cross-wire probes, triple-wire probes and a newly developed, reverse flow indicating four-wire probe are described. Selected results from two quantitative experimental investigations documenting both the low-speed flow environment over a 76 deg swept delta wing and over a delta-canard-configuration and the flow over a NACA 0012 airfoil in sinusoidal dynamic stall motion are presented. Results obtained include detailed flowfields of the time-dependent velocity components and distributions of the unsteady delta wing surface pressure. The structure of the highly turbulent flow is clearly depicted by time-averaged, root-mean-square and spectral distributions. Thus detailed insight in the delta wing vortex substructure as well as the breakdown phenomenon is obtained. The influence of flowfield turbulence intensity causing severe unsteady aerodynamic loads is shown by the corresponding surface pressure fluctuations. At the delta-canard-configuration strong interference effects of the vortex systems are found. Peaky velocity spectra are revealed in the vorticity sheets at burst flow conditions related to a narrow-band concentration of kinetic turbulent energy. The dynamic stall results provide strong evidence in the correct operation of the advanced four-wire probe to quantify streamwise and reverse velocity components in two-dimensional flow. This results in substantiating a refined description of unsteady separation phenomena.


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    Title :

    Application of unsteady measurement techniques to vortical and separated flows


    Additional title:

    Instationäre Meßtechniken für anliegende und abgelöste Strömungen


    Contributors:
    Laschka, B. (author) / Ranke, H. (author) / Breitsamter, C. (author)


    Publication date :

    1995


    Size :

    19 Seiten, 21 Bilder, 41 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English





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