Akademik Bilişim '10 10 - 12 Şubat 2010 Muğla

Akademik Bilişim’10 - XII. Akademik Bilişim Konferansı Bildirileri10 - 12 Şubat 2010 Muğla ÜniversitesiDesert Dune Dynamics And ProcessesLevent YılmazTechnical University of Istanbul, Civil Engineering Faculty, Hydraulic Division, 80626, Maslak, Istanbul, Turkey(visited Professor at Louisiana State University, Coastal Studies Institute, Baton Rouge, LA, 70803, USA)lyilmaz@itu.edu.trAbstract: The development of the dunes are governed by the effects of turbulence. Turbulence isa type of fluid flow that is strongly rotational and apparently chaotic. Turbulence separates nearbyparcels of air and thus mixed fluid properties . The evolution of sand dunes is determined by theinteractions between the atmosphere, the surface and the transport and deposition of sand. We areconcerned with this physical process and its computational simulation from three perspectives;namely, (1) flow structure; (2) sand transport and deposition and (3) interactions between flowstructure and sand transport-deposition, which determine the dune morphology.Keywords: Coastal management, dunes, sediment supply.IntroductionThe system of moving bedforms in a flow fieldcan be explained by the sediment-continuityequation and the sediment-transport equation.It yields∂h(x,t)1 ∂q(x,t)= −∂ts ∂x(1)q(x,t)= f ( t ( x,t) ) (2)where h is the height of the bedforms or topographicheight, t is the time, σ is the sedimentdensity, q is the sediment transport capacity inkg.m -1 . s-1 , τ is the shear stress due to saltation.Mathematical ModelEquation (2) shows that the sediment transportvaries linearly with the shear stress ( Stam,1994) asconstant basic term (τ o), and a correction term(τ 1) that varies with space and time:τ(x,t)= τ o+ τ 1(x,t) (4)If, in a first approximation, this correctionis assumed to be linear with the topographicheight:τ 1(x,t)=A 2h(x,t) (5)the sediment-transport equation becomes:q(x,t)=q o+A 1τ o+A 3h(x,t) (6)where A 3=A/A 2Taking the derivative of Equation (6), it yields∂ q(x,t)∂h(x,t= A)3 (7)∂x∂x496q(x,t)=q o+A 1τ (x,t) (3)where q ois a constant basic sediment-transportand A 1is the linearity constant. If topographicvariations are relatively small, it can be generallystated that the shear stress is formed of a497which, substituted in the continuity equationbecomes∂h( x,t)A3 ∂h(x,t)+ = 0∂ts ∂x(8)