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This paper reports an experimental investigation of open channel turbulent flow over hemispherical ribs. A row of ribs consists of hemispheres closely placed to one another in the spanwise direction and cover the entire span of the channel. The pitch-to-height ratio is varied to achieve the so-called d-type, intermediate and k-type roughness. The Reynolds numbers based on water depth, h, and momentum thickness, θ, of the approach flow are respectively, Reh = 28,100 and Reθ = 1800. A particle image velocimetry is used to obtain detailed velocity measurements in and above the cavity. Streamlines, mean velocity and time-averaged turbulent statistics are used to study the effects of pitch-to-height ratio on the flow characteristics and also to document similarities and differences between the present work and prior studies over two-dimensional transverse rods. It was observed that interaction between the outer flow and the shear layers generated by ribs is strongest for k-type and least for d-type ribs. The results also show that hemispherical ribs are less effective in augmenting flow resistance compared to two-dimensional transverse ribs. The levels of the Reynolds stresses and budget terms increase with increasing pitch-to-height ratio inside the roughness sublayer. 相似文献
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P. Z. Lugovoi V. F. Meish B. P. Rybakin G. V. Sekrieru 《International Applied Mechanics》2006,42(5):536-540
Dynamic problems for cylindrical shells reinforced with discrete ribs are examined. A numerical algorithm based on Richardson
extrapolation is developed. Specific problems are solved, and the results are analyzed
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Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 50–56, May 2006. 相似文献
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A technique is proposed to determine the natural frequencies of rib-reinforced cylindrical shells with low shear stiffness. The equations of motion based on the Timoshenko model are used. The influence of the transverse shear moduli of the shell and ribs on the minimum natural frequencies and corresponding modes is studied by way of numerical examples. It is shown that the effect of the discrete ribs is different from that predicted by the classical theory of ribbed shells__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 4, pp. 66–74, April 2005. 相似文献
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E. K. Ankyanets 《International Applied Mechanics》2005,41(10):1177-1181
The vibrations of a cylindrical shell reinforced with circular ribs attached to it by means of discrete elastic elements are
studied. The problem is solved by the finite-element method. The shell and ribs are modeled by a plane four-node finite element,
which is a combination of a four-node plane stress element and a four-node flexural element. The effect of the stiffness of
the elastic elements on the natural frequencies and modes is examined
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 108–113, October 2005. 相似文献
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板结构功率流的参数研究 总被引:1,自引:0,他引:1
板以及肋板结构在工程中有着广泛的应用,其振动嗓声问题一直受到理论和工程领域的关注。本文在板结构功率流理论的基础上 ̄[1],对板的损耗因子和不同加肋形式对其功率流的影响进行了分析和测量。 相似文献
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The paper studies the effect of the discrete arrangement of ribs and their number on the number of dispersion curves for harmonic waves that have a deflection node on a rib's axis and propagate along a cylindrical shell. It is found out that these curves split and the distance between the split curves depends strongly on the torsional stiffness of the ribs 相似文献
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受自然界毛竹微观结构的启发,在传统圆管与六边形管的基础上引入内管及双菱形肋骨,通过拓扑衍生方法设计了两种新型仿生蜂窝结构。在此基础上利用有限元软件ABAQUS对新型仿生蜂窝的耐撞性进行数值模拟,研究了蜂窝单胞构型、蜂窝壁厚、双菱形肋骨夹角对仿生蜂窝耐撞性能的影响。此外,基于超折叠单元理论,建立了仿生蜂窝结构的理论分析模型。结果表明:仿生蜂窝的面外压缩耐撞性能优于传统圆形蜂窝和传统六边形蜂窝。新型仿生六边形蜂窝的比吸能相比传统六边形蜂窝提高51.18%,压缩力效率提高53.14%。仿生蜂窝结构的平均压缩力理论预测结果与数值模拟结果吻合,两者间的误差均在10%以内。单胞构型为六边形的仿生蜂窝的耐撞性能优于圆形仿生蜂窝。适当增加仿生蜂窝壁厚或增大双菱形肋骨夹角,均有利于提高结构的耐撞性能。 相似文献
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