School of Mechanical Engineering Seminar
Wednesday, July 1, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Steady Streaming Created by a Piezoelectric

Cantilever for Particle Manipulation

Roni Amit

MSc Student of Dr. Gábor Kósa  

With the growing use of ”Lab on a chip” devices the interest in problems of arranging, sorting and trapping micro scale particles has increasingly grown.

In our work, we used steady streaming effect, achieved by an oscillating piezoelectric cantilever in a viscous fluid to create a hydrodynamic particle manipulator.

We started by examining a previous work by Ori Ehrenberg – an actuated micropump based on the motion of a propagating wave.

We operated the pump on a highly viscous fluid and achieved no outflow. Trying to understand the findings, we decided to investigate the flow field created inside the pump.

We understood that the flow created by the beam is a steady streaming, and that we can utilize it to design a particle manipulation system.

In this study we characterize the steady streaming flow field created around an oscillating cantilever (200 Hz, creating the shape of the first mode). Using numerical analysis we simulated the streamlines and characterized the velocity field.  The analysis validation was done using particle image velocimety experiments. We proved the concept of our particle manipulation system by controlling a particle path in the XY plane.

School of Mechanical Engineering Seminar
Wednesday, July 1, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Interaction of Suction and Pulsed Blowing with a Laminar Boundary Layer

Liad Marom

MSc Student of Prof. Avi Seifert

The work presents a fundamental study of active flow control (AFC) using steady suction and oscillatory blowing actuator (SaOB, figure 1), identifying its effect on a laminar boundary layer. Recent experiments showed this effective and efficient actuator as a drag reduction device. However, improved fundamental understanding of the boundary layer interaction with suction and oscillatory blowing and the combination of these two effects in close proximity is lacking. This experimental work, performed in a laminar flow alongside a turbulent BL interaction and CFD studies will result in improving the efficiency of the actuator and will develop a reliable predictive capability of this flow control method.

    The interaction with a laminar BL is crucial for the project due to the lack of interaction with the random turbulence, the thicker BL and lower skin-friction that enables greater effect of the controlled BL. Furthermore, fundamental interaction principles could be easier to identify and understand in laminar flows, where critical trends will not be masked by turbulence, and the averaging process will better represent time dependent flow.

The results demonstrate that while the oscillatory blowing is robust and has a strong effect on the flow evolution, the steady suction introduced upstream has a crucial role in the efficient operation of the AFC system.

Figure 1: A schematic view of the SaOB (Suction and Oscillatory Blowing) actuator operation