Experimental study on settlement of rod coral sand in stagnant water
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摘要: 沉降速度是珊瑚砂的一个重要物理参数。由于柱状珊瑚砂与其他形状的珊瑚砂有着明显的差异,套用现有珊瑚砂的沉速公式进行计算并不合适。本文选取柱状珊瑚砂进行单颗粒沉降试验,研究静水中柱状珊瑚砂沉降速度及其影响因素,通过讨论分析不同的等效粒径和形状系数对柱状珊瑚砂沉降速度的影响,发现柱状珊瑚砂的沉降速度与等容粒径和Corey形状系数密切相关,基于本文试验数据推求了适用于计算柱状珊瑚砂沉降速度的经验公式,丰富了海岸泥沙理论。Abstract: The settling velocity is an important physical parameter of coral sand. Because of the rod coral sand is obviously different from other shapes of coral sand, it is not suitable to apply the settling velocity formula of the existing coral sand for calculation. The rod coral sand was selected to study the settling velocity and its influencing factors for single particle settlement experiment in stagnant water in this study. By analyzing the effects of different equivalent particle sizes and shape coefficients on the settling velocity of rod coral sand, it is found that the settling velocity of rod coral sand is strongly correlated with the diameter of the volume-equivalent sphere and Corey shape coefficient. Based on the experimental data, an empirical formula suitable for calculating the settling velocity of rod coral sand is deduced, which enriches the theory of coastal sediment.
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Key words:
- rod coral sand /
- settling velocity /
- drag coefficient /
- shape coefficient
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表 1 不同等效粒径和形状系数方案设计
Tab. 1 Programmes of different equivalent particle sizes and shape coefficients
组次 等效粒径 形状系数 1 轴平均粒径 Corey形状系数 2 轴平均粒径 Wang形状系数 3 等容粒径 Corey形状系数 4 等容粒径 Wang形状系数 5 投影粒径 Corey形状系数 6 投影粒径 Wang形状系数 表 2 Corey形状系数离散程度
Tab. 2 Dispersions of Corey shape coefficient
粒径大小 Dn<0.20 Dn <0.25 Dn <0.30 Dn <0.35 第25百分位数 0.635 0.637 0.623 0.511 第75百分位数 0.685 0.685 0.684 0.680 四分位差 0.050 0.048 0.059 0.169 注:Dn单位:cm。 表 3 不同形状系数与沉降速度相关系数
Tab. 3 Correlation coefficients of shape coefficients and settling velocitys
形状系数 粗颗粒沉降速度/(cm·s−1) 细颗粒沉降速度/(cm·s−1) Corey形状系数 0.634 0.277 Wang形状系数 0.562 0.238 表 4 柱状珊瑚砂不同等效粒径和形状参数拟合公式对照
Tab. 4 Comparison of fitting formulas for rod coral sand with different equivalent particle sizes and shape coefficients
组次 V/A拟合公式 R2 沉降速度拟合公式 1 ${\dfrac{V}{ { {A_p} } } = 0.381S_{ f}^{0.434}{D_n} }$ 0.735 ${ {\omega ^2} = 0.762\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.434}{D_n} }$ 2 $ {\dfrac{V}{{{A_p}}} = 0.366{\psi ^{0.243}}{D_n}} $ 0.726 $ {{\omega ^2} = 0.732\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.243}}{D_n}} $ 3 ${\dfrac{V}{ { {A_p} } } = 0.473S_{ f}^{0.428}{D_v} }$ 0.897 ${ {\omega ^2} = 0.946\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.428}{D_v} }$ 4 $ {\dfrac{V}{{{A_p}}} = 0.452{\psi ^{0.234}}{D_v}} $ 0.886 $ {{\omega ^2} = 0.904\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.234}}{D_v}} $ 5 ${\dfrac{V}{ { {A_p} } } = 0.380S_{ f}^{0.765}{D_p} }$ 0.735 ${ {\omega ^2} = 0.760\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.765}{D_p} }$ 6 $ {\dfrac{V}{{{A_p}}} = 0.355{\psi ^{0.435}}{D_p}} $ 0.708 $ {{\omega ^2} = 0.710\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.435}}{D_p}} $ 表 5 不同等效粒径和形状参数拟合公式对照
Tab. 5 Comparison of fitting formulas for rod coral sand with different equivalent particle sizes and shape coefficients
组次 阻力系数Cd拟合公式 沉降速度ω拟合公式 1 $ {{C_d} = {\left( {\dfrac{{ - 403 \nu }}{{D_n^{1.5} \times {g^{0.5}}}} + 3.34} \right)^{ - 4.58}} + {\left( {\dfrac{{ - 205 \nu }}{{D_n^{1.5} \times {g^{0.5}}}} + 1.13} \right)^{0.405}}} $ ${ {\omega ^2} = 0.762\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.434}{D_n} }$ 2 $ {{C_d} = {\left( {\dfrac{{ - 725 \nu }}{{D_n^{1.5} \times {g^{0.5}}}} + 4.82} \right)^{ - 2.77}} + {\left( {\dfrac{{ - 226 \nu }}{{D_n^{1.5} \times {g^{0.5}}}} + 1.14} \right)^{0.416}}} $ $ {{\omega ^2} = 0.732\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.243}}{D_n}} $ 3 $ {{C_d} = {\left( {\dfrac{{ - 108 \nu }}{{D_v^{1.5} \times {g^{0.5}}}} + 2.39} \right)^{ - 11.60}} + {\left( {\dfrac{{ - 74.5 \nu }}{{D_v^{1.5} \times {g^{0.5}}}} + 1.03} \right)^{0.601}}} $ ${ {\omega ^2} = 0.946\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.428}{D_v} }$ 4 $ {{C_d} = {\left( {\dfrac{{ - 172 \nu }}{{D_v^{1.5} \times {g^{0.5}}}} + 2.95} \right)^{ - 13.50}} + {\left( {\dfrac{{ - 95.3 \nu }}{{D_v^{1.5} \times {g^{0.5}}}} + 1.05} \right)^{0.486}}} $ $ {{\omega ^2} = 0.904\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.234}}{D_v}} $ 5 $ {{C_d} = {\left( {\dfrac{{ - 210 \nu }}{{D_p^{1.5} \times {g^{0.5}}}} + 2.00} \right)^{ - 15.70}} + {\left( {\dfrac{{ - 182 \nu }}{{D_p^{1.5} \times {g^{0.5}}}} + 1.09} \right)^{0.533}}} $ ${ {\omega ^2} = 0.760\dfrac{ {\left( { {\rho _s} - \rho } \right)g} }{ {\rho {C_d} } }S_{ f}^{0.765}{D_p} }$ 6 $ {{C_d} = {\left( {\dfrac{{ - 778 \nu }}{{D_p^{1.5} \times {g^{0.5}}}} + 4.57} \right)^{ - 14.12}} + {\left( {\dfrac{{ - 249 \nu }}{{D_p^{1.5} \times {g^{0.5}}}} + 1.14} \right)^{0.436}}} $ $ {{\omega ^2} = 0.710\dfrac{{\left( {{\rho _s} - \rho } \right)g}}{{\rho {C_d}}}{\psi ^{0.435}}{D_p}} $ 表 6 沉降速度计算误差表
Tab. 6 Calculation error of the settling velocity
Eave RMSE Wang公式[18] 0.1346 3.1869 本文公式训练组 0.0714 1.7608 本文公式验证组 0.1191 2.6018 -
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