An unsteady flow visualization and force measurement were carried out in order to investigate the effects of the reduced frequency of a dragonfly-type model. The flow visualization of the wing wake region was conducted by using a smoke-wire technique. An electronic device was mounted below the test section in order to find the exact position angle of the wing for the visualization. A load-cell was employed in measuring aerodynamic forces generated by a plunging motion of the experimental model. To find the period of the flapping motion in real time, trigger signals were also collected by passing laser beam signals through the gear hole. Experimental conditions were as follows: the incidence angles of the foreand hind-wing were 0° and 10°, respectively, and the reduced frequencies were 0.150 and 0.225. The freestream velocities of the flow visualization and force measurement were 1.0 and 1.6m/sec, respectively, which correspond to Reynolds numbers of 3.4 × 10 3 and 2.9 × 10 3 . The variations of the flow patterns and phase-averaged lift and the thrust coefficients during one cycle of the wing motion were presented. Results showed that the reduced frequency was closely related to the flow pattern that determined flight efficiency, and the maximum lift coefficient and lift coefficient per unit of time increased with reduced frequency.
Nanofluids have been attracting great attention as new working fluids that can improve the heat transfer performance of cooling devices, leading to energy saving in many mechanical systems owing to their special properties. Therefore, many researchers have investigated the properties of nanofluids, such as thermal conductivity, convective heat transfer coefficient, and viscosity. In addition to these properties, the specific heat and density of nanofluids also play a crucial role in improving their heat transfer performance as these properties are closely related to the heat transfer capacity and thermal storage. Therefore, in this chapter, the experimental characteristics and prediction correlations, including the mechanisms of the specific heat and density of nanofluids, are introduced, based on the results at the present stage. Moreover, state-of-the-art technology for further increasing the specific heat and density of nanofluids is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.