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On 3D Structure of Wake Behind an Inclined Plate
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
The flow-field behind an inclined plate was investigated experimentally using stereo PIV method providing all 3 velocity vector components in the measuring plane. Flow structure in several measuring planes perpendicular to the main flow was studied. Statistical characteristics were evaluated in the measuring planes. The downwash angle was assessed as well to consider its effect on the lift generation mechanism. The dynamical behavior was studied using Proper Orthogonal Decomposition of velocity fields in measuring planes. The dominant (most energetic) structures were evaluated and presented. The detected structures are of the form of streamwise vortices combined with high-and low-velocity streaks.
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Flow field of the valve model I
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
This report is dealing with the measurement on the valve model. The model design is based on the real steam turbine valve used for steam regulation in an inlet pipe. The main goal of this investigation was to describe the physical principles related with the non-stationarities which are related with the stability of shear layers of the flow field inside the valve.
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Pod analysis of stereo PIV data from wake behind an inclined plate
Uruba, Václav ; Procházka, Pavel P.
The motivation of the experiments is to study the flow dynamics and topology behind an airfoil. The airfoil is modeled by a simple flat plate with rounded leading and trailing edges. To obtain an information about the 3D structure of the flow the stereo PIV method is applied in the plain behind the plate oriented perpendicularly to the main flow. The flow dynamics topology could be studied using POD method revealing the most energetic fluctuation topologies. The POD is typically applied on a 2-component vector fields. In the presented paper the POD will be used for 3-component vector field resulting from the stereo PIV method.
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Coanda effect in valves
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
Coanda effect takes place in flow within valves diffuser for certain conditions. The valve plug in\nhalf-closed position forms wall-jet, which could be stable or instable, depending on geometry and other\nconditions. This phenomenon was subject of experimental study using time-resolved PIV technique. For the acquired data analysis the special spatio-temporal methods have been used.
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On the recirculation zone suppression behind HUMP profile using the DBD actuator
Procházka, Pavel P. ; Uruba, Václav
Previously, the DBD (dielectric barrier discharge) plasma actuator was used in rectangular channel to modify the properties of the boundary layer in spanwise and in streamwise orientation. The actuator was redesigned for using on the surface of the Glauert-Goldschmied body in different position to influence the point of the separation and the reattachment point as well as the total extent of the separation bubble. The most intensive effect occurs when the actuator takes effect in the point of separation. Further downstream, the ionic wind produced by DBD causes complex coherent structures in the wake for spanwise orientation in both direction. The effect of streamwise orientation is studied also. Actuator is operated in steady regime to produces continuous ionic wind as well as in unsteady regime when the vortex street is generated. The properties of vortex street is given by modulation parameters (frequency and duty cycle). The effect of these parameters on the wake is evaluated. This experiment is realized in the perspex channel connected to the blow-down wind tunnel. The HUMP profile is flush-mounted to the bottom side. The wire electrode of the actuator is situated in x/L = 0.63, 0.66, 0.69 and 0.72 of the chord length. The time-resolved PIV (Particle Image Velocimetry) is used as a main measurement technique. The flow field behind the profile is captured in longitudinal plane as well as in cross-section planes using 3D PIV. The results based on statistical quantities will be presented in this paper. More, next part will be devoted to the decomposition analysis of the flow dynamics (BOD, OPD).
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