Patar Ebenezer Sitorus

The Role of Elytra in Beetle Flight: I.Generation of Quasi-Static Aerodynamic Forces

We conducted a comprehensive study to investigate the aerodynamic characteristics and force generation of the elytra of a beetle, Allomyrina dichotoma. Our analysis included wind tunnel experiments and three-dimensional computational fluid dynamics simulations using ANSYS-CFX software. Our first approach was a quasi-static study that considered the effect of induced flapping flow due to the flapping motion of the forewings (elytra) at a frequency of around 30 Hz to 40 Hz. The dihedral angle was varied to represent flapping motion during the upstroke and downstroke. We found that an elytron produces positive lift at 0° geometric angle of attack, negative lift during the upstroke, and always produces drag during both the upstroke and downstroke. We also found that the lift coefficient of an elytron does not drop even at a very high geometric angle of attack. For a beetle with a body weight of 5 g, based on the quasistatic method, the forewings (elytra) can produce lift of less than 1% of its body weight.

Progress on development of a lab-scale flapping-type tidal energy harvesting system in KIOST

A flapping-type turbine extracts power from the kinetic energy of water stream by heaving up and down. A nose-up pitch angle will create an upstroke motion of the flapping arm and vice versa for nose-down pitch. These upstroke and downstroke motion will then be converted into a continuous rotary motion of an output shaft by a transmission system. In this work, we describe our current progress on the development of design and prototype implementation of a flapping-type tidal energy harvester and introduce the dynamic model and its experimental validation together with power and efficiency.

Study on Flow Velocity Control of a Multiple Hydrofoil Duct via Flow Visualization Techniques

In this work, we investigate the flow velocity controllability of a diffuser-type multiple hydrofoil duct by experimental and numerical flow visualization approaches. The flow velocity controllability is analyzed by changing the angle of the hydrofoil near the outlet, which is the diffuser, while the incoming flow velocity is 0.6 m/s in the experiment. When the diffuser angle is changed from 0 to 7.5 degree, the maximum velocity inside the duct is varied from 1.35 m/s to 1.52 m/s. Also, it is shown from the numerical analysis that the maximum velocity is varied from 1.09 m/s to 1.17 m/s in the same condition. Thus, the aspect of the acceleration in the duct due to the increase of the diffuser angle is similar between the both approaches. Therefore, the multiple hydrofoil duct can be used to control the flow speed inside the duct for continuously extracting power close to a rated capacity.