[Vol. 1] The Fluid Machinery Laboratory at Kogakuin University uses the SC/Tetra thermal-fluid simulation tool. The tool is vital for deepening the understanding of fluid characteristics by faculty and students in the laboratory, and helps advance the research at the laboratory where experiments and simulations are performed simultaneously. Professor Kotaro Sato explains that, thanks to the tool's easy operability and highly extensive support from the developer, student interest in research has expanded.
Aiming to deepen the understandings of fluid characteristics in fluid machinery, the Fluid Machinery Laboratory at Kogakuin University studies axial fans, heat pumps, and synthetic jets. Synthetic jets can be formed with miniaturized or simplified actuators. Professor Sato explains that SC/Tetra has been used in much of their research, and the tool has been extremely useful.
One of Professor Sato’s research interests is synthetic jets. A synthetic jet can be likened to a very tiny jet engine. A basic jet engine functions by ingesting air at the front of the engine, burning fuel in the combustion chamber, and emitting the exhaust through a nozzle out the back of the engine to create thrust. A turbofan engine adds a fan, compressor, and turbine to the basic jet engine and creates thrust by combining the hot engine exhaust with the cooler, high volume air from the fan. Jet engines can be very large; for instance, the engine fan for a Boeing 777 is approximately 3 m in diameter. In contrast, miniaturizing a jet engine is very difficult. Professor Sato explains that the smallest jet engine developed in their research is still as large as a few centimeters.
One of the essential research activities at Professor Sato’s laboratory is the study of a speaker-driven synthetic jet (Fig 1). A speaker is attached below the device, and oscillating flow is generated at a 5-mm-wide slot. Fig 2 shows the visualization using smoke, and Fig 3 shows the results from an SC/Tetra CFD analysis. Fig 4 shows a comparison between the experiments and the CFD simulations for the velocity measured at various distances from the outlet. As can be seen, the results from the CFD simulation agree well with the experimental results.
Professor Sato’s laboratory also aims to control flow direction by changing frequencies. Controlling the direction of the flow just by changing frequencies would enable the device to be made even smaller. Professor Sato explains that SC/Tetra is used in this research as well, along with experiments.
Professor Sato’s laboratory is also investigating how to make a synthetic jet work like a pump (Fig 5). When a typical pump transfers fluids, a vane wheel is directly in contact with the fluids. The effect of bearing oil must be considered if the fluid being transferred is either a chemical or food. When transferring fluids like these, a synthetic jet will be more appropriate. Although the efficiency may not be as high, the synthetic jet ensures complete isolation of the moving parts and the working fluid. Professor Sato says that they are trying to identify the ideal vibrational conditions for optimal fluid transfer.
One possible target application of a synthetic jet is a capsule endoscope. The capsule endoscope is self-propelled and adjusts its orientation by itself. Most mainstream research focuses on a non-contact tail-fin method for orienting the device, where the fin moves by varying the external magnetic force. Professor Sato’s Laboratory is investigating whether a synthetic jet can replace this method.
Synthetic jets are used in vehicles, where the drag force needs to be minimized. Flow that separates from the vehicle body contributes to the drag force. A jet can be used to promote flow attachment on the vehicle body and shift the flow separation point rearwards.
Before synthetic jet research was recognized fifteen years ago, synthetic jets were confused with flow acoustics. The applications for synthetic jets have great potential because of their unique characteristics.
|Type of university||Private|
|Professor||Kotaro Sato (Doctor of Engineering)|
|Location||Shinjuku-ku, Tokyo, Japan|
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