1. Nondimensional chordwise breakdown location is plotted as a function of angle of attack in Figures 7-10for a pitching cycle, along with static data obtained over the same angle of attackrangeandfreestreamvelocity. Thestaticdataisan average of the increasing and decreasing static angle of attack cases shown in Figure 6.Therefore the statichysteresis at the lower anglesof attack isnot shown.
2. Phase angle difference between chordwise breakdown location andmodel position wasobtained forthedynamiccases presented in Figures 7-10, in which the Reynolds number was constant at 260,000andthereducedfrequencyvariedbetweenk =0.05 and 0.30, and for the reduced frequency constant at k = 0.20 and Reynolds number varied between Re = 90,000 and 350,000. Avalueforthephaselagwasobtainedbyplotting both the breakdownlocationandmodel angularposition againsttime foracycleof motion. Thephaseanglewascalculatedgraphically by determining the time between maximum and minimum amplitudes.
3. 100000 200000 300000 400000
4. Re =90,000, 175,000,260,000,and 350,000. The curves in Figures 14 and 15 are reploned using reduced velocity, and are shownin Figures 16and 17. From the plots, the effects of reduced frequency and Reynoldsnumber can beseen.Theeffectofreducedfrequencyisminimalthroughoutmostof the pitching cycle as seen in Figure 16, and the maximum reducedvelocityin eachcaseisapproximately 1.2whichoccm in the angleof attackrange of 30" to 33". There appearsto be littledependenceuponreducedfrequency,exceptintheregionat the beginping of the upstroke where the angle of attack starts increasing. Morespecifically,thechangetakesplacebetweena =29" anda=35". Inthisregionthereducedvelocitybecomes morenegativewith decreasingreducedfrequency. Therefore,the reduced velocity with which the burst moves up the model increases. Thisincreaseisrelatedto the shapeof the hysteresis loopsas illustratedpreviouslyin Figures 7-10. Overtherange of angle of attack in which the change occurs, the location of vortex breakdown is further downstream in the lower reduced frequenciescases,andthedistancebetweendatapointsisgreater. Thisgreaterdistanceresultsinahighervalueofreducedvelocity.