1. locations of the pressure ports alongside it. Thus a simple, easily maneuverable method was needed to complete the setup for each subsequent change of location of SJA2. To solve this, a set of plastic plates dimensioned to match the width of the actuator were used with the pressure ports printed along the center line. For example, for the first location for SJA2, the actuator is located between 0-1h and the first plastic plate is located between 1h-2h. As the actuator is moved downstream h, the first plastic plate is moved to 0-1h while the actuator is between 1h-2h. Fig. 5 contains a 3-D CAD model of the actuators and plastic inserts. The plastic pressure port inserts were printed using an objet polyjet rapid prototype printer with layer resolution of 16 m.
2. The tests were conducted using a 48-channel scanivalve with a Sensor-Technics differential lowpressure sensor with a range of 0-50 Pa. The data was acquired using a National Instruments data acquisition unit. To obtain sufficient time averaged pressure measurements, 1000 samples were acquired over 10 secondsfor eachport.
3. Results from the tests are shown in Fig. 7a-e. As mentioned earlier, Fig. 7a illustrates the baseline case without actuation for which decreases in the reattachment length will be assessed from. In Fig. 7b, the actuator is placed 1.07h upstream and the drastic effect the presence of the actuator has on the step can clearly be seen. Immediately downstream of the actuator there is a small recirculation region located at the edge of the step which alters the streamwise pressure gradient, pulling the boundary layer down towards the floor and promoting mixing of the shear layer. In Fig. 7c-7e. the actuator is moved further upstream and the effect is slightly diminished; however, there is still a noticeable reduction. This can be attributed to the increase in turbulence upstream of the step as a resultofthe actuatorslocated there.
4. The second set of tests involved the study of two actuators, one located before and the other after a backward facing step, using time averaged static pressure data. It was shown in the previous section that the actuator location closest to the step had the largest influence on the separated flow at the step. Using these results, SJA1 for this study was placed 15mm(.75h) before the step, which corresponds to the same physical location used in the previous study discussed above, except for the change in step height. The location of SJA1 was held constant. The location of SJA2 was then varied in increments of ~20mm from .75h - 4.625h (15mm - 92.5mm) downstream of the step. For all subsequent results, the location of SJA2 will be referred to as X1-X5, X1 being the closest to the step, X5 the furthestaway.