Experimental Study on Vortex-Induced Vibration of Rough Risers with Coupling Interference Effect Under Side-by-Side Arrangement

A vortex-induced vibration(VIV)experiment of rough risers with coupling interference effect under a side-by-side arrangement was carried out in a wave-current combined flume.The roughness of the riser was characterized by arranging different specifications of surface attachments on the surface of the riser.Rough risers with three different roughnesses were arranged side by side with smooth risers to explore the VIV response of the riser under the combined action of roughness and interference effect,and to reveal the coupling mechanism between roughness and interference effect.The experimental results show that,compared with that of a smooth riser,the VIV of a rough riser under the coupling interference effect has a wider"lock-in"region,and the displacement decreases more significantly at a high reduced velocity,which is more likely to excite higher-order modes and frequency responses.In addition,the displacement response and frequency response of the smooth riser are not significantly affected by wake interference from the rough riser,which is caused by the decrease of the wake region due to the delay of the boundary layer separation point of the rough riser.

Use of Helical Strakes for FIV Suppression of Two Inclined Flexible Cylinders in A Side-by-Side Arrangement

The experimental studies on flow-induced vibrations(FIV) reduction of two side-by-side flexible cylinders inclined at 45° by using the helical strakes were carried out in a towing tank. The main aim of the experiment is to check whether the helical strakes with a pitch of 17.5 D and a height of 0.25 D, which is considered as the most effective vibration suppression device for the isolated cylinder undergoing vortex-shedding, still perform very well to reduce FIV of two inclined flexible cylinders in a side-by-side arrangement. The vibration of two identical inclined cylinders with a mass ratio of 1.90 and an aspect ratio of 350 was tested in the experiment. The center-to-center distance between the two cylinders was 3.0 D. The uniform flow was simulated by towing the cylinder models along the tank.The towing velocity varied from 0.05 to 1.0 m/s with an interval of 0.05 m/s. The maximum Reynolds number can be up to 1.6×104. Three cases were experimentally studied in this paper, including two side-by-side inclined smooth cylinders, only one smooth cylinder fitted with helical strakes in the two side-by-side inclined cylinders system and both two cylinders attached with helical strakes. The variations of displacement amplitude, dominant frequency, FIV suppression efficiency and dominant mode for the two side-by-side inclined cylinders with reduced velocity were shown and discussed.

Response of Two Unequal-Diameter Flexible Cylinders in A Side-by-Side Arrangement:Characteristics of FIV

Till now,little information is available on the flow-induced vibration(FIV)of multiple flexible cylinders with unequal diameters.Some FIV characteristics of unequal-diameter cylinders can be predicted based on the knowledge of equal-diameter cylinders,while there are still other features remaining unrevealed.In this paper,the FIV characteristics of two flexible cylinders with unequal diameters arranged side-by-side are experimentally investigated.The diameter ratio of the small cylinder(Small Cyl.)to the large cylinder(Large Cyl.)is nearly 0.5.The aspect ratios and mass ratios of the two flexible cylinders are 350/181 and 1.90/1.47,respectively.The centre-tocentre spacing ratio in the cross-flow(CF)direction is kept constant as 6.0 and the two cylinders can oscillate freely in both the CF and in-line(IL)directions.The towing velocity varies from 0.05 m/s to 1.00 m/s.The dominant modes and frequencies,CF and IL displacement amplitudes and response trajectories are discussed.Compared with the case of two identical cylinders in our previous study,the FIV responses demonstrate some similarities and differences.The similarities are as follows.Both cylinders exhibit multi-mode vibration features and they interact with each other.Meanwhile,the IL FIV shows a more complex behaviour than that in the CF direction.The difference is that as the diameter of one cylinder is increased,the effect on the smaller cylinder becomes more significant.For Large Cyl.,the FIV response is similar to its isolated counterpart,which indicates that Small Cyl.has a negligible effect on the FIV of the larger one.Whereas Large Cyl.perplexes the FIV of Small Cyl.during the vibration process.The spacing would change when both cylinders are oscillating.Proximity interference between the two cylinders and wake shielding effect of the Large Cyl.may occur.The dominant frequencies of Small Cyl.are reduced and the wake-induced flutter of Small Cyl.is observed from the response trajectories at different measuring points.

FLOW PAST TWO ROTATING CIRCULAR CYLINDERS IN A SIDE-BY-SIDE ARRANGEMENT

Measurements were performed using Particle Image Velocimetry （PIV） to analyze the modification of flow by the combined effects of the rotation and the Reynolds number on the flow past two rotating circular cylinders in a side-by-side-arrangement at a range of 425 〈 Re ≤ 1130,0 ≤α ≤4 （ α is the rotational speed） at one gap spacing of T / d = 1.11 （T and d are the distance between the centers of two cylinders and the cylinder diameter, respectively）. A new Immersed-Lattice Boltzmann Method （ILBM） scheme was used to study the effect of the gap spacing on the flow. The results show that the vortex shedding is suppressed as rotational speed increases. The flow reaches a steady state when the vortex shedding for both cylinders is completely suppressed at critical rotational speed. As the rotational speed further increases, the separation phenomenon in the boundary layers disappears at the attachment rotational speed. The critical rotational speed and attachment rotational speed become small as Reynolds number increases. The absolute rotational speed of cylinders should be large at same critical rotational speed and attachment rotational speed in the case of large Reynolds number. The gap spacing has an important role in changing the pattern of vortex shedding. It is very different in the mechanism of vortex shedding suppression for the flows around two rotating cylinders and single rotating cylinder.

WAKE PATTERNS OF FLOW PAST A PAIR OF CIRCULAR CYLINDERS IN SIDE-BY-SIDE ARRANGEMENTS AT LOW REYNOLDS NUMBERS

A flow past two side-by-side identical circular cylinders was numerically investigated with the unstructured spectral element method. From the computational results at various non-dimensional distances between cylinder centers T/D and the Reynolds number Re, a total of nine kinds of wake patterns were observed： four steady wake patterns, including single bluff-body steady pattern, separated double-body steady pattern and transition steady pattern for sub-critical Reynolds numbers and biased steady pattern for super-critical Reynolds numbers, and five unsteady wake patterns, including single bluff-body periodic pattern, biased quasi-steady pattern, quasi-periodic （flip-flopping） pattern, in-phase-synchronized pattern and anti-phase-synchronized pattern. Time evolution of lift and drag coefficients corresponding to each unsteady wake pattern was given.

NUMERICAL COMPUTATION OF THE FLOW AROUND TWO SQUARE CYLINDERS ARRANGED SIDE-BY-SIDE

The numerical method is used to calculate the flow around two square cylinders arranged side-by-side and the mean and fluctuating aerodynamic forces, and Strouhal numbers and power spectrum of lift force and drag force are obtained. An improved MAC method proposed by Chen Suqin et al.,which uses three order upwind scheme to discretize the convection term and uses multigrid method to solve the Poisson equation for pressure is applied to simulate the flow around two square cylinders arranged side-by-side. Results show that the interference characteristic of two square cylinders arranged side-by-side is completely different with the different spacing ratio. When the spacing ratio is smaller than a certain critical value, the gap flow between two cylinders is biased to one side in a stable or unstable manner.

Experimental Study on Vortex-Induced Vibration of Rough Risers Coupling with Interference Effect in Tandem Arrangement

In order to study the response law of vortex-induced vibration(VIV)of marine risers under the combined action of roughness and interference effects,and to reveal the coupling mechanism of roughness and interference effects on the riser,a VIV experiment of rough risers in tandem arrangement was conducted in a wave−current combined flume.The experiment characterized the risers’roughness by arranging different specifications of attachments on the surface of the risers.Three rough risers with different roughness and smooth risers were arranged in tandem arrangement,with the rough risers arranged downstream.The experimental results indicate that the suppression of the attachments on the downstream risers’vibration are more significant both in the CF and IL directions as the reduced velocity increases.For the downstream riser,the amplitude response of rough riser is more significantly weakened compared with the smooth one at high reduced velocity.For the upstream risers,changes in the roughness and spacing ratio have an impact on their‘lock-in’region.When the roughness of downstream risers is relatively large(0.1300)and the spacing between risers is small(S/D=4.0),the reduced velocity range of‘lock-in’region in the CF direction of upstream risers is obviously expanded,and the displacement in the‘lock-in’region is severer.

Interaction Mechanisms between Natural Debris Flow and Rigid Barrier Deflectors:A New Perspective for Rational Design and Optimal Arrangement

Rigid barrier deflectors can effectively prevent overspilling landslides,and can satisfy disaster prevention requirements.However,the mechanisms of interaction between natural granular flow and rigid barrier deflectors require further investigation.To date,few studies have investigated the impact of deflectors on controlling viscous debris flows for geological disaster prevention.To investigate the effect of rigid barrier deflectors on impact mechanisms,a numerical model using the smoothed particle hydrodynamics(SPH)method with the Herschel–Bulkley model is proposed to simulate the interaction between natural viscous flow and single/dual barriers with and without deflectors.This model was validated using laboratory flume test data from the literature.Then,the model was used to investigate the influence of the deflector angle and multi-barrier arrangements.The optimal configuration of multi-barriers was analyzed with consideration to the barrier height and distance between the barriers,because these metrics have a significant impact on the viscous flow pile-up,run-up,and overflow mechanisms.The investigation considered the energy dissipation process,retention efficiency,and dead-zone formation.Compared with bare barriers with similar geometric characteristics and spatial distribution,rigid barriers with deflectors exhibit superior effectiveness in preventing the overflow and overspilling of viscous debris flow.Recommendations for the rational design of deflectors and the optimal arrangement of multi-barriers are provided to mitigate geological disasters.

The Application of Piano in Chinese Pop Music Arrangements

By exploring the application of piano in Chinese pop music arrangements,this article aims to enhance the understanding of the position of piano in pop music and provide useful insights and references for the future development of Chinese pop music.Starting from the unique position of piano in Chinese pop music arrangements,the article analyses in detail the specific applications of piano in Chinese pop music arrangements.The analysis finds that the piano has been deeply integrated into the bloodline of Chinese popular music and become an indispensable part.From simple melodic embellishments to complex arrangement ideas,the piano has injected endless vitality and vigor into popular music with its unique timbre and expressive power.

An Experimental Study on Dynamics Features of Three Side-by-Side Flexible Risers Undergoing Vortex-Induced Vibrations in A Uniform Flow

A vortex-induced vibration(VIV)experiment on three side-by-side risers subjected to a uniform flow was carried out in a combined wave-current flume.The dynamic features of interference effect on three side-by-side risers were investigated by varying fluid velocity and inter-riser spacing.The distributions of dimensionless displacement,dominant frequency,and displacement trajectory of the model risers were measured using mode decomposition and wavelet transform techniques.The coupled interference of inter-riser fluid to adjacent risers at different spacings was disclosed by introducing the"interference ratio"concept.The results show that at spacings smaller than 6.0 D,the three model risers display appreciable deviations in their displacement responses in cross-flow or in-line direction,attributable to the strong proximity disturbance and wake interference between the risers.When the spacing is increased to 8.0 D,wake interference still makes great difference to the dynamic response of the risers in both directions.As reduced velocity increases,the three risers show higher agreement with an isolated riser in overall dominant vibration frequency in CF direction than that in IL direction at all spacings and the side risers,although symmetrically placed,do not vibrate symmetrically,as a result of the steady deflection of clearance flow within the riser group.Interference effect results in a remarkable unsteady mode competition within the risers;quantitation of the interference levels for the three risers at different spacings with interference ratio revealed that under low flow velocities and large spacing ratios,clearance flow constitutes a non-neglectable interferer for three side-by-side risers.

Influence of Fruit Tree Types and Arrangements on Yield, Quality and Economic Returns of Cotton of Intercropping System in Southern Xinjiang

[Objective] The aim was to provide a theoretical basis for stable and highly effective intercropping arrangements and scientific management measures by selecting apple, pear, peach, apricot, walnut, jujube and other fruit trees to study their influence on yield, fiber quality and economic returns of intercropped cotton in southern Xinjiang. [Method] Based on major cropping pattern in production, randomized block design was adopted to explore growth indicators, canopy micrometeorological indicators, yield and fiber quality in key growth stage. [Result] Shading has a significant effect on cotton canopy micro-environment and canopy diameter is proportional to shading effect. According to comparisons of the same tree type, the change of canopy micro-environment was as follows： under canopyouter canopymiddle points and peachpearapplewalnutjujube for comparisons among different tree types. Canopy diameter is directly proportional to the number of tree branch and boll weight reductions and shading is the main cause of yield reduction. The canopy expansion is the major cause of decline of light intensity, temperature and humidity of cotton canopy. [Conclusion] Fruit trees, which will promote cotton yield,quality and canopy-environment, are as follows： jujube walnut apple pear peach trees. In practice, trees, which are small in canopy or well trimmed, are popular in production, such as jujube trees, to improve cotton yield and fiber quality.

Classification and Nomenclature of Plant Metallothionein-like Proteins Based on Their Cysteine Arrangement Patterns

随着植物基因组研究的进展 ,在基因文库和蛋白文库登录的植物类金属硫蛋白基因已超过 5 0个 ,接近金属硫蛋白总数的 1/ 3,而且有不断上升的趋势。鉴于目前植物类金属硫蛋白命名与分类随意性太大 ,很有必要建立一个统一合理的命名与分类法。对植物类金属硫蛋白一级结构进行详细分析后 ,发现该蛋白两端富含半胱氨酸的区域内半胱氨酸的排列方式颇具规律性 ,进而提出了以半胱氨酸排列方式为基础的分类及命名法 ,并阐述了采用这种方法的理由及其可行性。

Restraints and Countermeasures for the Sustainable Development of China's Modern Flower Arrangement Art

Factors that influence the development of China's modern flower arrangement art are analyzed in this study,countermeasures and suggestions are proposed for the future development.

The Structural Transformation of Nucleolar DNA and Its Arrangement in Nucleolus of Allium cepa Cells

By using the DNA specific cytochemical staining method (NAMA_Ur) and conventional electron microscopic technique, the authors examined the configuration of intranucleolar DNA in Allium cepa L. cells and found that nucleolar DNA within the fibrillar center (FC) underwent a structural transformation process from condensed to extended state. The authors' observations also displayed a continuous arrangement process of nucleolar DNA, i.e., the extranucleolar DNA entered FC through the nucleolar organizer region (NOR) channel, then extended to the periphery of FC or to the border between FC and dense fibrillar component (DFC), and distributed along the periphery of FC. Thence, by passing through the NOR channel between FCs, the nucleolar DNA continued to transfer to other FCs and arranged in the same above_mentioned forms.

Research on Arrangement of Urban Garden Plants in the Perspective of Ecological Adaptability

With the increasing deterioration of urban environment, strengthening construction of garden green land was one of the effective ways to ameliorate urban environment. However, as designers only focused on the landscape effect of garden plant arrangement and neglected the relationship between plants and natural environment, it resulted in poor growth of some plant community even the disappearance of some communities. Therefore, good landscaping effect could be achieved only when garden layout requirement was considered and suitable cultivation environment was selected based on plants ecological feature, giving full play to its landscaping and ecological function. The study discussed the arrangement of garden plants mainly in the perspective of temperature, light, water, atmosphere and soil environmental factors which were suitable for garden plants, so as to realize the high unity of scientificity and artistry garden plants arrangement, provide a save, comfortable and healthy living and working environment for residents, achieve virtuous cycling development of urban ecological system and promote sustainable development of the city.

Arrangement of High-standard Basic Farmland Construction Based on Village-region Cultivated Land Quality Uniformity

As an important constitute of land consolidation, high-standard basic farmland construction is an important means to protect the quantity, quality and ecological environment of cultivated land. Its target not only lies in the increase of cultivated land quantity, but also the improvement of cultivated land quality, agricultural production conditions and ecosystem environments. In the present study, the quality evaluation method and construction arrangement of cultivated land were explored to facilitate the process of decision-making and implementation for high-standard basic farmland construction(HSBFC) with administrative village as the unit. Taking the land comprehensive improvement project area in Quzhou County, Handan City, Hebei Province as a case study, the whole process of the study comprised of three steps: 1) establishment of the evaluation model of cultivated land quality uniformity based on regional optimum cultivated land quality, and construction of the uniformity evaluation index system from the aspects of soil fertility quality, engineering quality, spatial quality and eco-environment quality, according to the new concept of cultivated land quality; 2) calculation of cultivated land quality uniformity by grading indicators, assigning scores and weighting sums, exploring the local homogenization characteristics of regional cultivated land quality through spatial autocorrelation analysis, and analyzing the constraints and transformative potential of barrier factors; 3) arrangement of HSBFC according to the principle of concentration, continuity and priority to the easy operation. The results revealed that the value of farmland quality uniformity for the administrative villages in the study area was between 7.76 and 21.96, and there was a difference between various administrative villages. The regional spatial autocorrelation patterns included High-High(HH), Low-Low(LL), High-Low(HL) and Low-High(LH). These indicate that regional cultivated land quality has local homogenization characteristics. The most restrictive factors in the study area were the medium and low transformation difficulty indexes, including soil organic matter content, farmland shelterbelt network density, field regularity and scale of the field. In addition, there were also high transformation difficulty indicators in some areas, such as sectional configuration. The project area was divided into four partitions: major construction area, secondary construction area, general construction area, and conditional construction area. The cultivated land area of each subarea was 1538.85 ha, 1224.27 ha, 555.93 ha, and 1666.63 ha, respectively. This comprised of 30.87%, 24.56%, 11.15% and 33.42% of the total project area, respectively. The evaluation model and index system could satisfy the evaluation of farmland quality and diagnosis of obstacle factors to facilitate the subsequent construction decision. The present study provides reference for the practice of regional HSBFC, and a new feasible idea and method for related studies.

Effects of Irrigation Water Quality and Drip Tape Arrangement on Soil Salinity,Soil Moisture Distribution,and Cotton Yield (Gossypium hirsutum L.) Under Mulched Drip Irrigation in Xinjiang,China

More and more attention is being focused on saline water utilization in irrigation due to the shortage of fresh water to agriculture in many regions. For purpose of reducing the risks of using of saline water for irrigation, the mechanism of soil moisture and salinity distribution and transport should be well understood for developing optimum management strategies. In this paper, field experiments were carried out at Junggar Basin, China, to study the effects of drip irrigation water quality and drip tape arrangement on distribution of soil salinity and soil moisture. Six treatments were designed, including two drip tape arrangement modes and three irrigation water concentration levels （0.24, 4.68, and 7.42 dS m^-l）. Results showed that, soil moisture content （SMC） directly beneath the drip tape in all treatments kept a relatively high value about 18% before boll opening stage; the SMC in the narrow strip in single tape arrangement （Ms） plot was obviously lower than that in the double tapes arrangement （Md） plot, indicating that less sufficient water was supplied under the same condition of irrigation depth, but there was no significant reduction in yield. Mulching had not significant influence on salt accumulation but the drip tape arrangement, under the same condition of irrigation water depth and quality, compared with Md, Ms reduced salt accumulation in root zone and brought about relatively high cotton yield.

The Supersolvable Order of Hyperplanes of an Arrangement

This paper mainly gives a sufficient and necessary condition for an order of hyperplanes of a graphic arrangement being supersolvable. In addition, we give the relations between the set of supersolvable orders of hyperplanes and the set of quadratic orders of hyperplanes for a supersolvable arrangement.

Effects of Magnetic Particles Entrance Arrangements on Mixing Efficiency of a Magnetic Bead Micromixer

In this study, a computer code is developed to numerically investigate a magnetic bead micromixer under different conditions. The micromixer consists of a microchannel and numerous micro magnetic particles which enter the micromixer by fluid flows and are actuated by an alternating magnetic field normal to the main flow. An important feature of micromixer which is not considered before by researchers is the particle entrance arrangement into the micromixer. This parameter could effectively affect the micromixer efficiency. There are two general micro magnetic particle entrance arrangements in magnetic bead micromixers: determined position entrance and random position entrance. In the case of determined position entrances, micro magnetic particles enter the micromixer at specific positions of entrance cross section. However, in a random position entrance,particles enter the microchannel with no order. In this study mixing efficiencies of identical magnetic bead micromixers which only differ in particle entrance arrangement are numerically investigated and compared.The results reported in this paper illustrate that the prepared computer code can be one of the most powerful and beneficial tools for the magnetic bead micromixer performance analysis. In addition, the results show that some features of the magnetic bead micromixer are strongly affected by the entrance arrangement of the particles.

Experimental Study on Molecular Arrangement of Nanoscale Lubricant Films——A Review

In order to understand lubrication mechanism at the nanoscale, researchers have used many physical experimental approaches, such as surface force apparatus, atomic force microscopy and ball-on-disk tribometer. The results show that the variation rules of the friction force, film thicknessand viscosity of the lubricant at the nanoscale are different from elastohydrodynamic lubrication （EHL）. It is speculated that these differences are attributed to the special arrangement of the molecules at the nanoscale. However, it is difficult to obtain the molecular orientation and distribution directly from the lubricant molecules in these experiments. In recent years, more and more attention has been paid to use new techniques to overcome the shortcomings of traditional experiments, including various spectral methods. The most representative achievements in the experimental research of molecular arrangement are reviewed in this paper： The change of film structure of a liquid crystal under confinement has been obtained using X-ray method. The molecular orientation change of lubricant films has been observed using absorption spectroscopy. Infrared spectroscopy has been used to measure the anisotropy of molecular orientation in the contact region when the lubricant film thickness is reduced to a few tens of nanometers. In situ Raman spectroscopy has been performed to measure the molecular orientation of the lubricant film semi-quantitatively. These results prove that confinement and shear in the contact region can change the arrangement of lubricant molecules. As a result, the lubrication characteristics are affected. The shortages of these works are also discussed based on practicable results. Further work is needed to separate the information of the solid-liquid interface from the bulk liquid film.