Measurement of Aerodynamic Characteristics Using Cinder Models through Free Fall Experiment

• Published in: Atmosphere Vol. 12; no. 5; p. 608
• Main Authors: Liu, Meizhi, Maruyama, Takashi, Sasaki, Kansuke, Inoue, Minoru, Iguchi, Masato, Fujita, Eisuke
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.05.2021
• Subjects: Acceleration; Aerodynamic characteristics; Aerodynamics; Altitude; Angular velocity; Camcorders; Cameras; cinder model; Cinders; Coefficient of variation; Deviation; deviation angle between wind direction and wind force direction; Drag; Drag coefficient; Drag coefficients; Experiments; Fluid flow; Free fall; free fall experiment; Posture; Pressure sensors; Reynolds number; Rocks; Sensors; Velocity; Volcanic activity; Volcanic eruptions; Volcanic rocks; Volcanoes; Wind; Wind direction; Wind forces; Wind pressure; Japan
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos12050608

Rocks ejected from a volcanic eruption often cause loss of lives and structures. Aerodynamic characteristics are needed for evaluating motions of volcanic rocks for the reduction of damage. Falling motions of volcanic rock were measured by using models imitated the configuration of cinders collected at the site of the experiment, Sakurajima volcano. Two types, one with sharp edges and one without sharp edges, were selected as representative of cinder and a sphere was selected as reference model. The falling motions of the models dropped down from a drone were recorded by video camera and a stand-alone measuring system that included a pressure sensor, acceleration and angular velocity sensors in the models. The motion, posture, velocity and acceleration of the model were obtained in order to measure the three-dimensional falling trajectory. The drag and the deviation angle between relative wind direction and wind force direction were examined. The variation of the drag coefficient and the deviation angle with Reynolds number was clarified.