Vertical distribution of the Kuroshio velocity in the Pollution Nagasaki section and its formative mechanism

The seasonal and interannual variations of the vertical distribution of the Kuroshio velocity and its formative mechanism were studied by analyzing the Global Ocean Reanalysis Simulation 2 （GLORYS2） dataset in the Pollution Nagasaki （PN） section （126.0°E-128.2°, at depths less than 1000 m）. The results indicated that： 1） the maximum transport in the PN section occurs in summer, followed by spring, and the minimum transport occurs in fall and winter; the maximum velocities are located at the subsurface in both winter and summer and velocities are relatively larger and at a shallower depth in summer; and the velocity core is located at the surface in spring and fall. The isopycnic line has a clear depression around the Kuroshio axis in winter. The depth of maximum velocity and the zero horizontal density gradients both exhibit substantial seasonal and interannual variations, and the interannual variations are larger. 2） The distributions of velocity and density are in accordance with the therma~ wind relation. Although Kuroshio transport is determined by the large-scale wind field and mesoscale motion in the Pacific Ocean; local heat flux and thermohaline circulation influence the density field, modify the vertical structure of the Kuroshio velocity, and adjust the allocation of water fluxes and nutrients transport. 3） Shelf-water offshore transport into the Kuroshio upper layer induced by southwest monsoons might contribute to the maximum velocity up to the surface in summer. Nonlinear and nongeostrophic processes are not considered in the present study, and the thermal wind relation accounts for part of the vertical structure of the Kuroshio velocity.

Numerical investigation of velocity distribution of turbulent flow through vertically double-layered vegetation

The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence model,using the computational fluid dynamics(CFD)code FLUENT.The detailed velocity distribution was explored with a varying initial Froude number(Fr),with consideration of the steady subcritical flow conditions of an inland tsunami.In VDLV flows,the numerical model successfully captured the inflection point in the profiles of mean streamwise velocities in the mixing-layer region around the top of short submerged vegetation.An upward and downward movement of flow occurred at the positions located just behind the tall and short vegetation,respectively.Overall,higher streamwise velocities were observed in the upper vegetation layer due to high porosity,with Pr=98%(sparse vegetation,where Pr is the porosity),as compared to those in the lower vegetation layer,which had comparatively low porosity,with Pr=91%(dense vegetation).A rising trend of velocities was found as the flow passed through the vegetation region,followed by a clear sawtooth distribution,as compared to the regions just upstream and downstream of vegetation where the flow was almost uniform.In VDLV flows,a rising trend in the flow resistance was observed with the increase in the initial Froude number,i.e.,Fr?0.67,0.70,and 0.73.However,the flow resistance in the case of SLV was relatively very low.The numerical results also show the flow structures within the vicinity of short and tall vegetation,which are difficult to attain through experimental measurements.

Group velocity distribution of Rayleigh waves and crustal and upper mantle velocity structure of the Chinese mainland and its vicinity

Based on the long period digital surface wave data recorded by 11 CDSN stations and 11 IRIS stations, the dispersion curves of the group velocities of fundamental mode Rayleigh waves along 647 paths, with the periods from 10 s to 92 s, were measured by multi-filter. Their distribution at 25 central periods within the region of 18~54N, 70~140E was inverted by Dimtar-Yanovskaya method. Within the period from 10 s to 15.9 s, the group velocity distribution is laterally inhomogeneous and is closely related to geotectonic units, with two low velocity zones located in the Tarim basin and the East China Sea and its north regions, respectively. From 21 s to 33 s, the framework of tectonic blocks is revealed. From 36.6 s to 40 s, the lithospheric subdivision of the Chinese mainland is obviously uncovered, with distinct boundaries among the South-North seismic belt, the Tibetan plateau, the North China, the South China and the Northeast China. Four cross-sections of group velocity distribution with period along 30N, 38N, 90E and 120E, are discussed, respectively, which display the basic features of the crust and upper mantle of the Chinese mainland and its neighboring regions. There are distinguished velocity differences among the different tectonic blocks. There are low-velocity-zones (LVZ) in the middle crust of the eastern Tibetan plateau, high velocity featured as stable platform in the Tarim basin and the Yangtze platform, shallow and thick low-velocity-zone in the upper mantle of the North China. The upper mantle LVZ in the East China Sea and the Japan Sea is related to the frictional heat from the subduction of the Philippine slab and the strong extension since the Himalayan orogenic period.

Velocity distribution of flow with submerged flexible vegetations based on mixing-length approach

By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.

Analytical solution of velocity distribution for flow through submerged large deflection flexible vegetation

An analytical solution for predicting the vertical distribution of streamwise mean velocity in an open channel flow with submerged flexible vegetation is proposed when large bending occurs. The flow regime is separated into two horizontal layers： a vegetation layer and a free water layer. In the vegetation layer, a mechanical analysis for the flexible vegetation is conducted, and an approximately linear relationship between the drag force of bending vegetation and the streamwise mean flow velocity is observed in the case of large deflection, which differes significantly from the case of rigid upright vegetation. Based on the theoretical analysis, a linear streamwise drag force-mean flow velocity expression in the momentum equation is derived, and an analytical solution is obtained. For the free water layer, a new expression is presented, replacing the traditional logarithmic velocity distribution, to obtain a zero velocity gradient at the water surface. Finally, the analytical predictions are compared with published experimental data, and the good agreement demonstrates that this model is effective for the open channel flow through the large deflection flexible vegetation.

In situ measurement on nonuniform velocity distributionin external detonation exhaust flow by analysis ofspectrum features using TDLAS

Instantaneous and precise velocity sensing is a critical part of research on detonation mechanism and flow evolution.This paper presents a novel multi-projection tunable diode laser absorption spectroscopy solution,to provide a real-time and reliable measurement of velocity distribution in detonation exhaust flow with obvious nonuniformity.Relations are established between overlapped spectrums along probing beams and Gauss velocity distribution phantom according to the frequency shifts and tiny variations in components of light-of-sight absorbance profiles at low frequencies analyzed by the fast Fourier transform.With simulated optical measurement using H2O feature at 7185.6 cm-1 carried out on a phantom generated using a simulation of two-phase detonation by a two-fluid model,this method demonstrates a satisfying performance on recovery of velocity distribution profiles in supersonic flow even with a noise equivalent absorbance up to 2×10^(-3).This method is applied to the analysis of rapidly decreasing velocity during a complete working cycle in the external flow field of an air-gasoline detonation tube operating at 25 Hz,and results show the velocity in the core flow field would be much larger than the arithmetic average from traditional tunable diode laser doppler velocimetry.This proposed velocity distribution sensor would reconstruct nonuniform velocity distribution of high-speed flow in low cost and simple operations,which broadens the possibility for applications in research on the formation and propagation of external flow filed of detonation tube.

Velocity distribution of the flow field in the cyclonic zone of cyclone-static micro-bubble flotation column

Laboratory experiments have been conducted to study the flow field in a cyclone static micro-bubble flotation column. The method of Particle Image Velocimetry (PIV) was used. The flow field velocity distribution in both cross section and longitudinal section within cyclonic zone was studied for different circulating volumes. The cross sectional vortex was also analyzed. The results show that in cross section as the circulating volume increases from 0.187 to 0.350 m 3 /h, the flow velocity ranges from 0 to 0.68 m/s. The flow field is mainly a non-vortex potential flow that forms a free vortex without outside energy input. In the cyclonic region the vortex deviates from the center of the flotation column because a single tangential opening introduces circulating fluid into the column. The tangential component of the velocity plays a defining role in the cross section. In the longitudinal section the velocity ranges from 0 to 0.08 m/s. The flow velocity increases as does the circulating volume. Advantageous mineral separation conditions arise from the combined effects of cyclonic flow in cross and longitudinal section.

Prediction of boundary shear stress distribution in straight open channels using velocity distribution

Conventional methods for measuring local shear stress on the wetted perimeter of open channels are related to the measurement of the very low velocity close to the boundary.Measuring near-zero velocity values with high fluctuations has always been a difficult task for fluid flow near solid boundaries.To solve the observation problems,a new model was developed to estimate the distribution of boundary shear stress from the velocity distribution in open channels with different cross-sectional shapes.To estimate the shear stress at a point on the wetted perimeter by the model,the velocity must be measured at a point with a known normal distance to the boundary.The experimental work of some other researchers on channels with various cross-sectional shapes,including rectangular,trapezoidal,partially full circular,and compound shapes,was used to evaluate the performance of the proposed model.Optimized exponent coefficients for the model were found using the multivariate Newton method with the minimum of the mean absolute percentage error(MAPE)between the model and experimental data as the objective function.Subsequently,the calculated shear stress distributions along the wetted perimeter were compared with the experimental data.The most important advantage of the proposed model is its inherent simplicity.The mean MAPE value for the seven selected cross-sections was 6.9%.The best results were found in the cross-sections with less discontinuity of the wetted perimeter,including the compound,trapezoidal,and partially full circular pipes.In contrast,for the rectangular cross-section with an angle between the bed and walls of 90°,MAPE increased due to the large discontinuities.

Measurement of oil volume fraction and velocity distributions in vertical oil-in-water flows using ERT and a local probe

This paper presents the use of a high performance dual-plane electrical resistance tomography (ERT) system and a local dual-sensor conductance probe to measure the vertical upward oil-in-water pipe flows in which the mean oil volume fraction is up to 23.1%. A sensitivity coefficient back-projection (SBP) algorithm was adopted to reconstruct the flow distributions and a cross correlation method was applied to obtain the oil velocity distributions. The oil volume fraction and velocity distributions obtained from both measurement techniques were compared and good agreement was found, which indicates that the ERT tech- nique can be used to measure the low fraction oil-water flows. Finally, the factors affecting measurement precision were discussed.

Effect of number density on velocity distributions in a driven quasi-two-dimensional granular gas

The motion of mono-disperse spherical steel particles in a vibration driven quasi-two-dimensional （2D） square cell is studied. The cell is horizontally vibrated to eliminate the effect of gravity compaction. The velocity distributions at different particle number densities are studied and found to obey the form exp[-β（｜Vy｜/σy）α], in which Vy and （σy are velocity and its variance in the transverse direction, and α and β are fitting parameters. The value of α is found to decrease with the number density of particles increasing. To investigate the effect of the bottom plate, the molecular dynamics simulation without considering any bottom friction is performed. The accordance between the simulation result and the experimental result shows that the influence of bottom plate friction force on the high energy tail of the velocity distribution can be neglected.

Prediction of Fluid Velocity Distribution near a Rising Bubble

A model is presented for predicting the fluid velocity distribution around a rising bubble which startsfrom rest on a distillation column tray by considering the unsteady fluid flow based on the method of streamfunction. Experimental measurement of the velocity distribution by using whole field digitized PIV (particle imagevelocimetry) method is briefly described. The velocity distribution predicted by the present model is in betteragreement with the measurements than the others models published in literature.

Analytical solutions for transverse distributions of stream-wise velocity in turbulent flow in rectangular channel with partial vegetation

The theory of poroelasticity is introduced to study the hydraulic properties of the steady uniform turbulent flow in a partially vegetated rectangular channel. Plants are assumed as immovable media. The resistance caused by vegetation is expressed by the theory of poroelasticity. Considering the influence of a secondary flow, the momentum equation can be simplified. The momentum equation is nondimensionalized to obtain a smooth solution for the lateral distribution of the longitudinal velocity. To verify the model, an acoustic Doppler velocimeter （ADV） is used to measure the velocity field in a rectangular open channel partially with emergent artificial rigid vegetation. Comparisons between the measured data and the computed results show that the method can predict the transverse distributions of stream-wise velocities in turbulent flows in a rectangular channel with partial vegetation.

Analytical Models for Velocity Distributions in Compound Channels with Emerged and Submerged Vegetated Floodplains

The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term to account for the effects of vegetation.The three cases considered for open channels were two-stage rectangular channel with emerged vegetated floodplain,rectangular channel with submerged vegetated corner,and two-stage rectangular channel with submerged vegetated floodplain,respectively.To predict the depth-averaged velocity with submerged vegetated floodplains,we proposed a new method based on a two-layer approach where flow above and through the vegetation layer was described separately.Moreover,further experiments in the two-stage rectangular channel with submerged vegetated floodplain were carried out to verify the results.The analytical solutions of the cases indicated that the corresponding analytical depth-averaged velocity distributions agree well with the simulated and experimental prediction.The analytical solutions of the cases with theoretical foundation and without programming calculation were reasonable and applicable,which were more convenient than numerical simulations.The analytical solutions provided a way for future researches to solve the problems of submerged vegetation and discontinuous phenomenon of depth-averaged velocity at the stage point for compound channels.Understanding the hydraulics of flow in compound channels with vegetated floodplains is very important for supporting the management of fluvial processes.

Design and Structure Optimization of Plenum Chamber with Airfoil Baffle to Improve Its Outlet Velocity Uniformity in Heat Setting Machines

The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.

Evolution of Electron Velocity Distribution during ECRH and Heating Effect Analysis

1 Electron velocity distributions and energy deposition of ECW Two set of soft X-ray spectra detection system consist of high performance sillicon drift detectors （SDD） , high speed A/D transform and processing software, software pulse height analyzer （SPHA）. They are installed at mid plane （ r=0 ） and undermid plane （ r=-16.4 cm ） of HL-2A tokamak respectively to measure the time evolution of soft X-ray spectra. According to spectrum, the thermal electron and superthermal electron temperatures are derived. Because of the ratio of peak counts to background counts is very high （p/b 〉1 400-3000 ） ,

Distribution and characteristics of initial PSA and PSA velocity in men younger than 50 years without prostate cancer

Objective To explore the distribution and characteristics of initial PSA and PSA velocity in men younger than years without prostate cancer. Methods PSA in men younger than 50 years without prostate cancer from January 2001 to November 2009 were retrieved retrospec-

Boulder-induced form roughness and skin shear stresses in a gravel-bed stream

Boulder spacing in mountain rivers and near-wake flow zones within the boulder array is very useful for fish habitat and growth of aquatic organisms.The present study aims to investigate how the boulder array and spacing influence the near-bed flow structures in a gravel-bed stream.Boulders are staggered over a gravel-bed stream with three different inter-boulder spacing namely(a)large(b)medium and(c)small spacing.An acoustic Doppler velocimeter was used for flow measurements in a rectangular channel and the results were compared with those acquired from numerical simulation.The time-averaged velocity profiles at the near-wake flow zones of boulders experience maximum flow retardation which is an outcome of the boulder-induced form roughness.The ratio of velocity differences associated to form and skin roughness and its positive magnitude reveals the dominance of form roughness closest to the boulders.Form roughness computed is 1.75 to 2 times higher than the skin roughness at the near-wake flow region.In particular,the collective immobile boulders placed at different inter-boulder spacings developed high and low bed shear stresses closest to the boulders.The low bed shear stresses characterised by a secondary peak developed at the trough location of the boulders is attributed to the skin shear stress.Further,the spatial averaging of time-averaged flow quantities gives additional impetus to present an improved illustration of fluid shear stresses.The formation of form-induced shear stress is estimated to be 17%to 23%of doubleaveraged Reynolds shear stress and partially compensates for the damping of time-averaged Reynolds shear stress in the interfacial sub-layer.The quadrant analysis of spatial velocity fluctuations depicts that the form-induced shear stresses are dominant in the interfacial sub-layer and have no significance above the gravel-bed surface.

Analysis on Velocity Characteristics of Cavitation Flow Around Hydrofoil

The time-averaged velocity distributions in flows around a hydronautics hydrofoil were measured by using a digital particle image velocimeter(DPIV) system.The results show that the velocity distribution in the whole flow field depends on the development of cavitation structures with the decreasing of cavitation number.The high-fluctuation region with lower velocity relates to the cavitation area.The lowest velocity distribution in the cavity core becomes more uniform,and its influence becomes smaller gradually as moving to downstream.The main-stream velocity distribution is even,then fluctuate and even at last.In the supercavitation stage,the fluid velocity in the cavitation region,corresponding to the front of the hydrofoil's suction surface,has a distribution close to the main stream,while the fluid velocity in other cavitation area is lower.

An improved particle tracking velocimetry(PTV) technique to evaluate the velocity field of saltating particles

Velocity is a key parameter characterizing the movement of saltating particles. High-speed photography is an efficient method to record the velocity. But, manually determining the relevant information from these photographs is quite laborious. However, particle tracking velocimetry（PTV） can be used to measure the instantaneous velocity in fluids using tracer particles. The tracer particles have three basic features in fluids： similar movement patterns within a small region, a uniform particle distribution, and high particle density. Unfortunately, the saltation of sand particles in air is a stochastic process, and PTV has not yet been able to accurately determine the velocity field in a cloud of blowing sand. The aim of the present study was to develop an improved PTV technique to measure the downwind（horizontal） and vertical velocities of saltating sand. To demonstrate the feasibility of this new technique, we used it to investigate two-dimensional saltation of particles above a loose sand surface in a wind tunnel. We analyzed the properties of the saltating particles, including the probability distribution of particle velocity, variations in the mean velocity as a function of height, and particle turbulence. By automating much of the analysis, the improved PTV method can satisfy the requirement for a large sample size and can measure the velocity field of blowing sand more accurately than previously-used techniques. The results shed new light on the complicated mechanisms involved in sand saltation.

Electrical Conductivity in a Non-Maxwellian Plasma with Adjustable High-Energy-Tail Distribution

In this paper, a solution to the Fokker-Planck equation is presented, which is extended to the field particles＇ high-energy-tail non-Maxwellian velocity distribution function in transport theory. Based on the correct physical concept of collision intensity, introduced by CHANG and LI, the electrical conductivities for like-particles collisions are obtained in different conditions. The modified Fokker-Planck coefficients for non-Maxwellian scattering are applied in the study. It is found that the parallel part of the collision operator plays an important role. The non-Maxwellian scattering will stimulate the transport processes in various degrees with mutative deviation parameters.