关键词: 空气动力学粗糙度, 砾石覆盖度, 预测模型

Abstract: The nature of interactions between surface winds and gravel beds that can be characterized by aerodynamic roughness length has important implications for sediment mobilization,transport and sedimentation.We report here the wind tunnel results of systematic tests of the aerodynamic roughness lengths of different gravel size and gravel coverage beds at various free-stream wind velocities.The aerodynamic roughness of gravel beds is a function of gravel size,gravel coverage and free-stream wind velocity.The 1/30 law proposed by Bagnold or simply assuming the aerodynamic roughness as fixed ratio of roughness element height in aeolian study is not hold true for gravel beds.Aerodynamic roughness of gravel beds decreases with free-stream wind velocity.The variation of aerodynamic roughness with gravel coverage can be expressed by quadric curves:Z₀=F₁+F₂C+F₃C^1.5+F₄C²,that bear the maximum aerodynamic roughness length at gravel coverage range from 40% to 75%,increasing with gravel size.The muti-variate models based on free-stream wind velocity and gravel coverage have been developed for predicting the aerodynamic roughness of different gravel-sized beds.

Key words: aerodynamic roughness, gravel coverage, prediction model