Abstract: Mineral product, waste concrete (fine aggregates),
waste in the optical field, industry, and construction employ separators
to separate solids and classify them according to their size. Various
sorting machines are used in the industrial field such as those operating
under electrical properties, centrifugal force, wind power, vibration,
and magnetic force. Study on separators has been carried out to
contribute to the environmental industry. In this study, we perform
CFD analysis for understanding the basic mechanism of the separation
of waste concrete (fine aggregate) particles from air with a machine
built with a rotor with blades. In CFD, we first performed
two-dimensional particle tracking for various particle sizes for the
model with 1 degree, 1.5 degree, and 2 degree angle between each
blade to verify the boundary conditions and the method of rotating
domain method to be used in 3D. Then we developed 3D numerical
model with ANSYS CFX to calculate the air flow and track the
particles. We judged the capability of particle separation for given size
by counting the number of particles escaping from the domain toward
the exit among 10 particles issued at the inlet. We confirm that
particles experience stagnant behavior near the exit of the rotating
blades where the centrifugal force acting on the particles is in balance
with the air drag force. It was also found that the minimum particle
size that can be separated by the machine with the rotor is determined
by its capability to stay at the outlet of the rotor channels.
Abstract: The propulsion of a bacterial flagellum in a viscous fluid has attracted many interests in the field of biological hydrodynamics, but remains yet fully understood and thus still a challenging problem. In this study, therefore, we have numerically investigated the flow around a steadily rotating micro-sized spring to further understand such bacterial flagellum propulsion. Note that a bacterium gains thrust (propulsive force) by rotating the flagellum connected to the body through a bio motor to move forward. For the investigation, we convert the spring model from the micro scale to the macro scale using a similitude law (scale law) and perform simulations on the converted macro-scale model using a commercial software package, CFX v13 (ANSYS). To scrutinize the propulsion characteristics of the flagellum through the simulations, we make parameter studies by changing some flow parameters, such as the pitch, helical radius and rotational speed of the spring and the Reynolds number (or fluid viscosity), expected to affect the thrust force experienced by the rotating spring. Results show that the propulsion characteristics depend strongly on the parameters mentioned above. It is observed that the forward thrust increases in a linear fashion with either of the rotational speed or the fluid viscosity. In addition, the thrust is directly proportional to square of the helical radius and but the thrust force is increased and then decreased based on the peak value to the pitch. Finally, we also present the appropriate flow and pressure fields visualized to support the observations.
Abstract: In this paper, the shape design process is briefly discussed emphasizing the use of topology optimization in the conceptual design stage. The basic idea is to view feasible domains for sensitivity region concepts. In this method, the main process consists of two steps: as the design moves further inside the feasible domain using Taguchi method, and thus becoming more successful topology optimization, the sensitivity region becomes larger. In designing a double-eccentric butterfly valve, related to hydrodynamic performance and disc structure, are discussed where the use of topology optimization has proven to dramatically improve an existing design and significantly decrease the development time of a shape design. Computational Fluid Dynamics (CFD) analysis results demonstrate the validity of this approach.