沙丘型底床泥砂顆粒躍移模式研究

以往研究的成果，主要是針對二維泥砂顆粒與平底床顆粒的碰撞行為以及泥砂顆粒的運動型態作探討（Garcia and Nin(1994,1998)、陳彥旭(1998)、游景雲(1999)），已獲得不錯之成果。在有關三維泥砂運行與躍移之研究，本研究群（林穎典(2000)、李博甯(2001)、王筱雯(2002)），均假設底床為規則顆粒組成之平坦床形，建立一包含底床碰撞與空間碰撞之三維多顆粒連續躍移數值模式，藉此模式探討顆粒躍移之運動特性。然而一般明渠中，底床床型會依流速的不同而呈現包括平整(flat bed)、沙紋(ripple)、沙丘(dune)、沙浪(antidune)及急灘與深潭(chutes and pools)等不同型式，不同型式的床型會對近床區域的流況造成影響，進而影響到推移載顆粒的運動情形。本研究針對沙丘(dune) 底床型態的三維泥砂顆粒躍移行為及其間的碰撞機制進行探討，藉助三維動態影像數位元化系統來建立一套在沙丘底床型態下之二維單顆粒躍移模式，並和過去所發展相互比較，希望能對泥砂顆粒躍移運動有更進一步的瞭解。

關鍵字

推移載；躍移；碰撞機制；三維動態影像數位化系統；沙丘

並列摘要

A series of studies regarding the two dimensional collision mechanism with the channel bed and among the saltating particles were conducted by Garcia and Nino(1994, 1998) and our group (Chen 1998, You 1999). The simulation results are satisfactory. For past years, our group (Lin 2000, Lee 2001, Wang 2002) had extended the experiments to three dimensional conditions. The bed forms of our previous experiments were flat bed and formed by uniformly distributed sediment particles. However, the bed forms in natural rivers vary with different flow conditions. Different types of bed forms, were observed, namely, flat bed, ripple, dune, antidune, and chutes and pools. Particles saltation characteristics will definitely be different under different bed formation. The purpose of this study is to investigate the three dimensional saltation characteristics on a dune bed, with special attention on the collision behaviors between the saltating particles and the channel bed and interparticle collision behaviors. A three dimensional flow visualization technique will be modified and upgraded in this study to measure the three dimensional saltation trajectories on a dune bed. Basing on these data, a two dimensional saltation model for single sediment particle will then be developed. This model will be very helpful in the study of bed load transport.

並列關鍵字

Bed load ； Saltation ； 3-D flow visualization technique ； Dune

參考文獻

1. Abbott J.E., and Francis J.R.C., ”Saltation and Suspension Trajectories of Solid Grains in a Water Stream,” Proc. Royal Soc. London, England, Vol.284, A, 1977, pp.225-254.

2.A. Li and G. Ahmadi. ”Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow.” Aerosol Science and Technology,1992, 16:209-226

3.Anderson, R.S. and Hallet, B., ”Sediment Transport by wind,”Geological Society of American Bulletin, Vol.97, 1986.

4.B. E. Launder and D. B. Spalding. ” Lectures in Mathematical Models of Turbulence,”Academic Press, London, England, 1972.

8.Engelund, F. , Hydraulic Resistance of Alluvial Streams, J.

國際替代計量

沙丘型底床泥砂顆粒躍移模式研究

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