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FLOW REGIMES BELOW AERATORS FOR DISCHARGE TUNNELS

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Journal of Hydrodynamics 2012年第3期24卷 378-382页

作者： MA Fei wu jian-hua College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

The flow regimes below an aerator influence directly the air entrainment and the cavitation damage control. Based on the theoretical considerations, the experiments of the aerator for a discharge tunnel were conducted, and the relationships between the flow regime and hydraulic and geometric parameters were investigated. The results showed that, there are two kinds of threshold values for the flow regime conversions. One is Fr1-2 standing for the conversion from the fully filled cavity to the partially filled cavity, and the other is Fr2-3 which shows the change from the partially filled cavity to the net air cavity. Two empirical expressions were obtained for the conversions of the flow regimes, which can be used in the designs of the aerators.

关键词： aerator discharge tunnel flow regime filling water jet length

Inception point of air entrainment over stepped spillways

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Journal of Hydrodynamics 2013年第1期25卷 91-96页

作者： wu jian-hua ZHANG Bin MA Fei College of Water Conservancy and Hydropower Engineering Hohai University

The location of the inception point of the air entrainment directly affects the energy dissipation ratio, the cavitation damage control, and the training wall height designs for a stepped spillway and a stilling basin. In this paper, the boundary layer theory of plates is used to predict the location of the inception point of the air entrainment over the stepped spillways by assuming the steps on the spillways as a kind of roughness. An empirical formula is presented based on the physical model experiments, with the maximum error less than 1% except at one point where the error is 1.6%, as compared to the experimental data. Meanwhile, it is shown that the location of the inception point of the air entrainment for the stepped spillway is much nearer to the top of the spillway than that for a smooth spillways, which explains why the high ratio of the energy dissipation is provided for the stepped spillway.

关键词： air entrainment cavitation energy dissipation inception point stepped spillway unit discharge

EFFECTS OF ENTRAINED AIR MANNER ON CAVITATION DAMAGE

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Journal of Hydrodynamics 2011年第3期23卷 333-338页

作者： wu jian-hua LUO Chao College of Water Conservancy and Hydropwer Engineering Hohai University Nanjing 210098 China

Early in 1953 the experiments by Peterka proved that air entrainment has effects on decreasing cavitation damage. This technology has been widely used in the release works of high dams since the inception of air entrainment in the Grand Goulee Dam in 1960. Behavior, mechanism and application of air entrainment for cavitation damage control have been investigated for over half century. However, severe cavitation damage happened due to complex mechanism of air entrainment. The effects of air entrainment are related to many factors, including geometric parameters, hydraulic parameters and entrained air manners. In the present work an experimental set-up for air entrainment was specially designed, the behavior of reducing cavitation damage was experimentally investigated in the three aspects of entrained air pressure, air tube aera and air tube number. The results show that magnitude of reduction of cavitation damage is closely related to the entrained air tube number as well as entrained air pressure, air tube aera, and that the effect through three air tubes is larger than that through single air tube although the entrained air tubes have the same sum of tube aera, that is, 1 ＋ 1 ＋ 1 〉 3. Therefore, it is important to design an effective manner of air entrainment.

关键词： air entrainment air pressure air tube area cavitation damage entrained air manner

Degenerate Orbit Flip Homoclinic Bifurcations with Higher Dimensions

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Acta Mathematica Sinica,English Series 2006年第6期22卷 1651-1656页

作者： Ran Chao wu jian hua SUN Department of Mathematics Nanjing University Nanjing 210093 P. R. China

Bifurcations of a degenerate homoclinic orbit with orbit flip in high dimensional system are studied. By establishing a local coordinate system and a Poincare map near the homoclinic orbit, the existence and uniqueness of 1-homoclinic orbit and 1-periodic orbit are given. Also considered is the existence of 2-homoclinic orbit and 2-periodic orbit. In additon, the corresponding bifurcation surfaces are given.

关键词： Orbit flip Homoclinic bifurcations Poincaré map

HYDRAULIC CHARACTERISTICS OF SLIT-TYPE ENERGY DISSIPA-TERS

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Journal of Hydrodynamics 2012年第6期24卷 883-887页

作者： wu jian-hua MA Fei YAO Li College of Water Conservancy and Hydropower Engineering Hohai University

Slit-Type Energy Dissipater （STED） has been a kind of important devices for energy dissipation. The flow through the STED is longitudinally extended and the velocity is decreased by means of the cross-section increase of the flow, which is closely related to geometric and hydraulic parameters of the STED. Therefore, it is necessary to investigate and control the hydraulic condi- tions through the STED, including the nappe section form, the conversion condition, and the effect of energy dissipation with the geometric and hydraulic parameters. In the present work, ＂I-type＂ and ＂T-type＂ nappe forms were experimentally classified, the con- version conditions of the nappe forms were empirically provided, and the effects of geometric parameters of the STED on energy dissipation were roughly analyzed. It is concluded that the contraction angle of the STED is a key factor influencing the hydraulic characteristics of the STED.

关键词： contraction angle energy dissipation fin nappe form shock wave Slit-Type Energy Dissipater (STED)

牙周基础治疗对甲状腺功能减退伴慢性牙周炎患者促甲状腺激素的影响

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临床口腔医学杂志 2024年第9期40卷 548-551页

作者：邬建华吴军郭凤芹合肥市口腔医院安徽医科大学第二附属医院

目的:评估牙周基础治疗(nonsurgical periodontal therapy, NSPT)对甲状腺功能减退伴慢性牙周炎患者血清促甲状腺激素(thyroid-stimulating hormone, TSH)水平的影响。方法:纳入42名受试者，其中21例已知甲状腺功能减退伴慢性牙周炎受... 详细信息

目的:评估牙周基础治疗(nonsurgical periodontal therapy, NSPT)对甲状腺功能减退伴慢性牙周炎患者血清促甲状腺激素(thyroid-stimulating hormone, TSH)水平的影响。方法:纳入42名受试者，其中21例已知甲状腺功能减退伴慢性牙周炎受试者服用相同的左甲状腺素钠片，且TSH在正常范围内(实验组)和21名健康受试者(对照组),评估两组患者在基线以及实验组NSPT前后的临床参数，包括血清TSH水平、简化口腔卫生指数(oral hygiene indexsimplified, OHIS)、牙龈乳头出血指数(papillary bleeding indexm, PBI)、牙周筛查和记录指数(periodontal screening and recording index, PSR)和临床附着丧失(clinical attachment loss, CAL)。采用Pearson相关性分析实验组治疗前血清TSH水平与牙周临床参数的关联。结果:Pearson相关性分析表明实验组治疗前血清TSH平均水平与牙周临床参数呈正相关。基线时，实验组患者TSH水平为(3.49±1.40)μIU/mL,对照组TSH为(2.61±1.10)μIU/mL,差异无统计学意义(P=0.092),但OHI-S、PBI、PSR、CAL临床参数大于对照组(P<0.05)。实验组患者NSPT前后TSH显著降低(P=0.014)、牙周临床指标显著改善(P<0.05)。结论:甲状腺功能减退伴慢性牙周炎患者的TSH水平与牙周临床参数相关，且NSPT改善牙周状况后，可能因炎症因子减少从而降低促甲状腺激素水平。

关键词：甲状腺功能减退牙周基础治疗慢性牙周炎促甲状腺激素

HYDRAULIC CHARACTERISTICS OF BOTTOM UNDERLAY-TYPE PIER FOR WATER-WING CONTROL

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Journal of Hydrodynamics 2008年第6期20卷 735-740页

作者： wu jian-hua YAN Zhong-min College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

The pier, placed at the outlet of the pressure flow section, is an effective design to deal with the problems of the manufacture and operation of the gates fbr a discharge tunnel with high water head. It is crucial to control the water-wing, induced by this type of the pier. Through observing the phenomena of the water-wing, the reason of the water-wing inception, i.e., the concave of the flow surface, was presented, and a type of the new pier with bottom underlay was designed. The hydraulic characteristics of the pier, including the variations of the water-wing features, both length and height, with the water head, as well as with the concave depth, and with the height of the bottom underlay, and the variations of the concave depth with the height of the bottom underlay, were investigated by physical model experiments. The results show that the approach of the modification of the concave through the structures with the bottom underlay-type pier is remarkably effective in the water-wing control.

关键词： bottom underlay-type pier concave of flow surface discharge tunnel water-wing

FLOWS THROUGH ENERGY DISSIPATERS WITH SUDDEN REDUCTION AND SUDDEN ENLARGEMENT FORMS

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Journal of Hydrodynamics 2010年第3期22卷 360-365页

作者： wu jian-hua AI Wan-zheng College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

The energy dissipation of flood discharges has been one of important problems that affect directly the safety of hydropower projects. The energy dissipater with sudden reduction and sudden enlargement forms, used widely in large-scale projects has been a kind of effective structure for energy dissipation. The concept of critical thickness was defined, which is related to both the geometric parameters and the hydraulic parameters of the energy dissipater, and the factors affecting the critical thickness, were analzsed by means of dimensional analysis. The empirical expression about the critical thickness was obtained and could be used as the criterion to distinguish the flows through the energy dissipater, i.e., the plug flow and the orifice plate flow. The error analysis showed that the critical thickness calculated by the expression has the errors of smaller than 10% in the estimation of the flows for the energy dissipater mentioned above.

关键词： critical thickness energy dissipater orifice plate plug reduction ratio sudden reduction sudden enlargement

Critical size effect of sand particles on cavitation damage

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Journal of Hydrodynamics 2013年第1期25卷 165-166页

作者： wu jian-hua GOU Wen-juan College of Water Conservancy and Hydropower Engineering Hohai University

The critical size of the sand particles in liquid is determined by means of the special vibratory apparatus, and it is related to various effects on the cavitation damage. The increase of the sand size or concentration would aggravate the cavitation damage if their sizes are larger than this critical size, conversely, this damage would be relieved.

关键词： cavitation damage sand particle sand size abrasion