【摘 要】
：
An experimental investigation on the initiation and development of bed forms on a bed of fine silica sand was conducted under alluvial flow conditions in a labo
【机 构】
：
Hydro-environmental Research Centre
【基金项目】
：
The UK’s Natural Environment Research Council(NERC);The Engineering and Physical Sciences Research Council(EPSRC)
论文部分内容阅读
An experimental investigation on the initiation and development of bed forms on a bed of fine silica sand was conducted under alluvial flow conditions in a laboratory flume with a diverging channel.The main aims of the study were to assess:I)the steepness of bed forms in the transition stage of development;and ii)the threshold height of wavelets(nt)that triggered the start of ripple development.Detailed bed profile measurements were carried out using an acoustic Doppler probe,traversed longitudinally over the sediment bed at various experimentation times.The bed form dimensions were extracted from such bed profile records and analysed for the wavelet,transition and equilibrium stages.It was found that the steepness of ripples in the transition and equilibrium stages were similar,confirming predictions of previous mathematical model simulations.A lognormal distribution fitted the wavelet length data.The wavelet threshold height was estimated as ηt≈7 mm,or y+≈80 in wall units.Such a height magnitude suggested that ripple development could be triggered by the wavelets reaching the outer flow zone of a turbulent boundary layer.The ηt value obtained corresponded generally to the intersection point between two predictive equations for bed form dimensions.A formulation was developed to predict ηt as a function of the sediment grain size,which was confirmed for the fine sand used in this study.
其他文献
Numerical simulation of TNT underwater explosion was carried out with AUTODYN software.Influences of artificial viscosity and mesh density on simulation results
Dispersion copolymerization of acrylonitrile-vinyl acetate (AN-VAc) has been successfully performed in supercritical carbon dioxide (ScCO2) with a series of lip
Impulse systems do not undergo the multi-path destructive interference that manifests itself as Ray-leigh fading prevalent in continuous wave systems, but rathe
Sphalerite banding is a common texture in Jinding (金顶) Pb-Zn deposit, Yunnan (云南), southwestern China. The frequency distribution and irregularity of sphale
The digital baseband predistorter is an effective technique to compensate for the nonlinearity of power amplifiers (Pas) with memory effects. However, most avai
The almost equal height dual peak spontaneous Brillouin scattering spectrum of a piece of micro-structure fiber with a small core was investigated at various te
The robust H∞ control problem was considered for a class of fuzzy hyperbolic model (FHM) systems with parametric uncertainties and multiple delays. First, FHM
A two-dimensional mesoscopic numerical method to simulate the failure process of concrete under compression was developed based on the discrete element method b
According to a type of normal nonlinear system, an indirect adaptive fuzzy (IAF) controller has been applied to those systems where no accurate mathematical mod