[MIS06-P04] 風洞実験による高速度カメラを用いた飛砂によるスプラッシュ現象の計測
キーワード：アジアダスト、黄砂、乾燥地、運動エネルギー、PTV解析、ゴビ砂漠
Saltation is one of the process for sand and dust transportations. Sand movement makes geomorphological changes in not only desert and coastal area but other planets. In this study, we focus on the saltation splash. When saltation sand particles hit grounds, not only dust but other sands are newly emitted to the atmosphere. The new sand emission from grounds induced by saltation is known as ˝splash˝. The splash particles receive energy from impacting saltation particles and can move as creeping or new saltation. The emitted new sand particles (splash particles) directly get energy from wind and accelerate the particle velocity. Then, they might behave as new impacting (saltation) particles. By repeating saltation and splash, large amount of sand and dust are supplied to the atmosphere more and more.
In order to clarify the mechanism of splash, wind tunnel experiments are conducted in Forestry and Forest Products Research Institute, Tsukuba, Japan. Toyoura sand is used as saltation particle and three soils are used as a target soil, 1) Mongol soil which has both finer and larger particles (Loam) sampled at Tsogt-Ovoo in the northern Gobi Desert, Mongolia, 2) Toyoura sand, and 3) Kasaoka clay. Sand splash is measured by using a high-speed camera. The frame rate is set to 30000 fps in order to capture particles as clearly as possible. PTV (Particle Tracking Velocimetry) method is used to analyze the particles motion. As a result, when the velocity of saltation particle is about 7.0 m s-1, the mean velocity of splashing particles is 2.8 m s-1. A reduction of kinetic energy of saltation particle is evaluated after hitting the ground surface. These findings are fundamental for elucidating the process of saltation and will link to improve dust forecasting accuracy of atmospheric dust transport models.
In order to clarify the mechanism of splash, wind tunnel experiments are conducted in Forestry and Forest Products Research Institute, Tsukuba, Japan. Toyoura sand is used as saltation particle and three soils are used as a target soil, 1) Mongol soil which has both finer and larger particles (Loam) sampled at Tsogt-Ovoo in the northern Gobi Desert, Mongolia, 2) Toyoura sand, and 3) Kasaoka clay. Sand splash is measured by using a high-speed camera. The frame rate is set to 30000 fps in order to capture particles as clearly as possible. PTV (Particle Tracking Velocimetry) method is used to analyze the particles motion. As a result, when the velocity of saltation particle is about 7.0 m s-1, the mean velocity of splashing particles is 2.8 m s-1. A reduction of kinetic energy of saltation particle is evaluated after hitting the ground surface. These findings are fundamental for elucidating the process of saltation and will link to improve dust forecasting accuracy of atmospheric dust transport models.