水滴於靜止空氣中自由落下加速過程之量測與數值模擬

MEASUREMENT AND NUMERICAL SIMULATION FOR THE ACCELERATION OF A WATER DROPLET FALLING IN STAGNANT AIR

張文詔(Wen-Jaur Chang)

《中華水土保持學報》 25卷2期 (1994/06) Pp. 103-119

https://doi.org/10.29417/JCSWC.199406_25(2).0005

摘要

土壤表面受水滴之撞擊而產生土壤顆粒分離之現象，一向被認爲是導致土壤沖蝕的主要因素之一。決定水滴沖蝕力之主要參數有水滴大小、水滴撞擊土壤表面時之速度與形狀等。本研究應用以閃光測頻儀爲光源之攝影法爲基礎，加以擴充改良以爲水滴形狀與加速過程量測之主要工具。改良後之定頻閃光攝影法是將閃光測頻儀配合一般使用之單眼照像機，結合成一套設備費用低廉，操作簡易且精準度令人滿意之完整攝影技術。目前應用此技術已可將水滴自由落下時一連串相等時間間隔之影像「凍結」於相片中，相片之精準度足以提供水滴落下速度及形狀演變計算分析使用。此外本研究並從基本理論著手，配合實測數據，推導出一組簡易但精確度合理之數值模式，以供相關學者應用。

關鍵字

水滴 ； 加速 ； 定頻閃光攝影法 ； 量測 ； 數值模擬

並列摘要

The detachment of soil particles due to water droplet impact on soil surface was considered to be a major factor that affected the amount of soil erosion. The major parameters that describe the erosivity of a water droplet are size, shape and impact velocity of the water droplet when impacting on soil surface. In this study a strobe-photography was modified and utilized for measuring droplet shape and acceleration. The modified strobe-photography combined a set of stroboscope and a common usage single-lens-camera to form a complete photographic equipment of low cost, easy to operate, and with sufficient precision. The photograpic technique was utilized to ＂freeze＂ a series of equal time interval images on a picture for a free falling water droplet. The quality of water droplet pictures talking with this technique was good enough for water droplet falling velocity measurement and shape evolution analysis. Besides, a numerical simulation model based on physical principles was developed for the utilization of related study. The model was accurate in theory, simple in algorithm and easy to apply. The model then was tested with measured data, and satisfactory results were obtained.

並列關鍵字

Water Droplet ； Acceleration ； Strobe-Photography ； Measurement ； Numerical Simulation