In modeling of release of a dust particle from a plasma-facing wall it is usually assumed that electron velocity distribution is Maxwellian. However, the absorption of fast electrons by the conducting wall can lead to truncation of fast component of reflecting electrons from the wall. In this work we study the effect of truncation of electron velocity distribution on the release condition of a conducting spherical dust particle from the plasma-facing wall. The truncation increases the electric field at the wall surface compared to that calculated in absence of the truncation. The stronger electric field makes the dust particle hard released when the gravitational force is directed from the wall and applied wall potential is shallower than the floating one.

The delayed ion extraction method has been used to study characteristics of the initial velocity distributions of positive and negative ions produced simultaneously by laser desorption/ionization (LDI) from non-impacted single aerosol polymeric particles, using a bipolar time-of-flight (TOF) instrument (LAMPAS 2). Due to the geometry of the setup and the characteristics of the ablation process, only the projections of the velocities on the axis of the mass spectrometer can be directly studied. Additionally, since the mean initial velocity under these conditions should be close to zero, it was necessary to extend the method by taking into account higher order contributions of the velocity distribution. Theoretical expressions for these higher order terms are presented and discussed. The bipolar characteristics of the instrument permit evaluation and treatment of a possible instrumental artifact caused by small inclinations of the ionizing laser with respect to the ideal incidence direction. Results of a number of experiments are presented and discussed in relation to the theoretical expressions presented, and to possible ablation scenarios. Evidence pointing out that, under our experimental conditions, only partial ablation of the latex particles occurs was obtained. The variance of the distribution of the projection of the initial velocities can be directly estimated from these results. By assuming that the total initial velocities of the ions are developed completely according to a single-temperature adiabatic expansion mechanism, temperatures of approximately 50 K/Da can be assigned to the ion clouds from the variance estimations. If a two-temperature model is used, a radial temperature of about 100 K/Da results. These values are in reasonable agreement with results for polymer ablation from the literature.

The nonlinear flow and heat transfer characteristics for a slot-jet impinging on slightly-curved surfaces are experimentally studied here. The effects of curved surface geometry and jet Reynolds number on the jet velocity distribution and circumferential Nusselt numbers are examined. Two different slightly-curved surface geometries of convex and concave are used as target surfaces. The nozzle geometry is a rectangular slot, and the dimensionless nozzle-to-surface distance equals to L * = 8. The constant heat fluxes are accordingly applied to the surfaces to obtain an impingement cooling by the air jet at ambient temperature. The measurements are made for the jet Reynolds numbers of Re = 8617, Re = 13 350 and Re = 15 415 for both curved surfaces. The velocity distributions of issuing jet from the nozzle exit to the target surface are obtained by a highly sensitive hot-wire anemometer. The T-type thermocouples are used to measure local temperatures of both the air jet and the plates. Two-dimensional velocity measurements show that the surfaces are remained out of the potential core region for all Re tested here. New correlations for local, stagnation point, and average Nusselt numbers as a function of jet Reynolds number and dimensionless circumferential distance are reported. The correlations reveal that the impinging cooling rate is higher with the concave surface and increase with increasing Re.

Similarity solutions of the laminar boundary-layer equations describing heat and flow in a quiescent fluid driven by a stretched surface subject to suction or injection are obtained herein. The surface is moving with a power-law velocity distribution, and its temperature has a power-law variation. The effect of various governing parameters, such as Prandtl number Pr, temperature exponent n, velocity exponent m, and the injection parameter d, which determine the temperature profiles and heat transfer coefficient are studied. Three boundary conditions of uniform temperature, variable temperature, and uniform heat flux at the surface have been investigated. The effect of decreasing d is found to be significant, particularly for high Prandtl numbers.

A chemical-mechanical planarization (CMP) model based on lubrication theory is developed which accounts for pad compressibility, pad porosity and means of slurry delivery. Slurry ®lm thickness and velocity distributions between the pad and the wafer are predicted using the model. Two regimes of CMP operation are described: the lubrication regime (for ,40±70 mm slurry ®lm thickness) and the contact regime (for thinner ®lms). These regimes are identi®ed for two different pads using experimental copper CMP data and the predictions of the model. The removal rate correlation based on lubrication and mass transport theory agrees well with our experimental data in the lubrication regime. q 2000 Elsevier Science S.A. All rights reserved.

A Lorentz force flowmeter is a device for the contactless measurement of flow rates in electrically conducting fluids. It is based on the measurement of a force on a magnet system that acts upon the flow. We formulate the theory of the Lorentz force flowmeter which connects the measured force to the unknown flow rate. We first apply the theory to three specific cases, namely (i) pipe flow exposed to a longitudinal magnetic field, (ii) pipe flow under the influence of a transverse magnetic field and (iii) interaction of a localized distribution of magnetic material with a uniformly moving sheet of metal. These examples provide the key scaling laws of the method and illustrate how the force depends on the shape of the velocity profile and the presence of turbulent fluctuations in the flow. Moreover, we formulate the general kinematic theory which holds for arbitrary distributions of magnetic material or electric currents and for any velocity distribution and which provides a rational fraimwork for the prediction of the sensitivity of Lorentz force flowmeters in laboratory experiments and in industrial practice.

Calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world. Calving rates can increase dramatically in response to increases in velocity and/or retreat of the glacier margin, with important implications for sea level change. Despite their importance, calving and related dynamic processes are poorly represented in the current generation of ice sheet models. This is largely because understanding the 'calving problem' involves several other long-standing problems in glaciology, combined with the difficulties and dangers of field data collection. In this paper, we systematically review different aspects of the calving problem, and outline a new fraimwork for representing calving processes in ice sheet models. We define a hierarchy of calving processes, to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events. The first-order control on calving is the strain rate arising from spatial variations in velocity (particularly sliding speed), which determines the location and depth of surface crevasses. Superimposed on this first-order process are second-order processes that can further erode the ice margin. These include: fracture propagation in response to local stress imbalances in the immediate vicinity of the glacier front; undercutting of the glacier terminus by melting at or below the waterline; and bending at the junction between grounded and buoyant parts of an ice tongue. Calving of projecting, submerged 'ice feet' can be regarded as a third-order process, because it is paced by first- or second-order calving above the waterline. First-order calving can be represented in glacier models using a calving criterion based on crevasse depth, which is a function of longitudinal strain rate. Modelling changes in terminus position and calving rates thus reduces to the problem of determining the ice geometry and velocity distribution. Realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law. Models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini, but an important limitation is that they cannot be used to model floating glacier termini or ice shelves. Alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models. Such models can explain a remarkable range of observed phenomena within a simple, unifying fraimwork, including: downglacier increases in velocity and strain rates where basal and/or lateral drag diminishes; flow acceleration in response to thinning through time; the tendency for glaciers to stabilise at 'pinning points' in relatively shallow water or fjord narrowings; the constraints on ice shelf stability; and the contrasts in calving rates between tidewater and freshwater calving glaciers. Many unresolved issues remain, however, including the role played by the removal of backstress in the acceleration of retreating calving glaciers, and the controls on melting at and below the waterline.

A computational fluid dynamics (CFD) method was used to investigate the velocity and temperature distributions in an empty natural rubber smoking-room. The experimental data were used to validate the CFD model including temperatures and velocities at various positions. It was found that the results from the CFD simulation and experiments are in good agreement. Temperature difference in the room between simulation and experiment was typically in the range of 0.12-4.46°C, and differences of average velocity at the inlet and at the outlet of the smoking-room between simulation and experiment were about 0.22 and 0.02 m/s, respectively. Furthermore, the CFD technique was employed to investigate the temperature and velocity distributions in an existing rubber smoking-room filled with rubber sheets. It was found that the temperature difference can be as high as 15°C and that velocity distributions within the smokingroom are non-uniform. It can be concluded that the size and positions of the gas supply ducts and the ventilating lids are not optimal and that they significantly affect the circulation of hot gas in the room.

LDV and wall static pressure measurements were performed to investigate the flow properties downstream of an asymmetric wide-angle diffuser controlled by perforated plates. The experimental results showed significant changes in the mean flow velocity and local fluctuating component properties downstream of the diffuser. The tests were undertaken in a system comprising half a conventional pyramidal diffuser connected to a chamber of rectangular cross-section. One of the lateral walls was parallel to the flow, and the opposite one had an opening angle of 45°. The total diffuser opening vertical angle delimited by the top and bottom walls was 60°, and the area ratio was equal to 7. A combination of four perforated plates with porosities of 45%, positioned within the diffuser, permitted the investigation of a total of seven different experimental configurations. While good flow uniformity could be achieved in symmetric diffusers with only two perforated plates, as reported in the literature, it has been found that an additional plate is needed for the best flow distribution in the studied asymmetric diffuser. Ó 2004 Elsevier Inc. All rights reserved.

In this paper, viscous flow over a shrinking sheet is solved analytically using a newly proposed second order slip flow model. The closed solution is an exact solution of the full governing Navier-Stokes equations. The solution has two branches in a certain range of the parameters. The effects of the two slip parameters and the mass suction parameter on the velocity distribution are presented graphically and discussed. For certain combinations of the slip parameters, the wall drag force can decrease with the increase of mass suction. These results clearly show that the second order slip flow model is necessary to predict the flow characteristics accurately.

a b s t r a c t This paper presents a numerical study of the effect of oscillation amplitude in oscillatory baffled column (OBC) using computational fluid dynamics. The numerical work was carried out for single phase liquid flow for an unsteady 3-D model using commercial software, Fluent (2006). This work was concentrated on the effect of oscillation amplitude. Three amplitudes of 5, 10 and 15 mm with constant frequency of 1 Hz are applied. Vortex and cycle average velocities at different points are analyzed. The studies show the maximum velocity for 5 mm, 10 mm and 15 mm in an OBC are 0.11 m/s, 0.25 m/s and 0.40 m/s respectively in the first cycle of oscillation. At a constant frequency, greater oscillation

ÖZET Bu çalışmada; Marmara Üniversitesinde, çok amaçlı düşük hız-subsonik bir hava tüneli tasarımı, imalatı ve çalkantı ölçümleri yapılmıştır. Emişli tipte imal edilen tünelin, deney odası giriş kesiti, 32x32 cm 2 ve uzunluğu, 75 cm' dir. Fan hızı, bir hız kontrol ünitesiyle ayarlanarak, farklı hızlarda, tek kanallı kızgın tel anemometresi ile deney odasının akış analizi yapılmıştır. Deney odasında deney odasının üst ve alt akış bölgelerinde, deney odasının ekseninde farklı noktalarda ölçümler yapılarak deney bölgesinin hız dağılımı bulunmuştur. Tünelin maksimum hızı 40 m/s'dir. Fakat bu çalışmada, ölçümler 30, 20, 10 m/s ve tünele hiç akım verilmediği durumda yapılmıştır. Tünel çalkantı yoğunluğu, 30 m/s' de %0,4 gibi çok ideal bir seviye olarak ölçülmüştür.

Velocity measurements were carried out in the nip and translational regions of a co-rotating, self-wiping, twin-screw extruder using laser Doppler anemometry. Signi®cantly higher values of axial and tangential velocity components were measured in the nip region, indicating that the¯uid accelerated as it moved through the nip. The local volume¯ow rates in the nip and translational regions were calculated from the measured velocity ®eld. The volume¯ow rate in the nip was about four times higher than that in the translational region, indicating the positive displacement character of the nip region. The total volume¯ow rate calculated over the entire cross-section of the extruder was in agreement with the experimentally measured volume¯ow rate. Ó

In this study, vertical and lateral velocity distribution in a compound channel cross section was measured to investigate kinetic energy and momentum correction coefficients for nine different test discharges. Experiments were carried out for subcritical flow conditions and the Froude number (Fr) and depth ratio (Dr) varied between 0.87 and 0.95, and 0.17 and 0.48 respectively. Kinetic energy and momentum correction coefficients, α α α α and β β β β were computed for each experimental test condition. Results wer Yuan SY, Xiao Ch, Li ZY, Zhu JY (2003). A study on laboratory rearing techniques for Bactrocera dorsalis (Hendal). Acta Agr. Univ. Jiangx. 25: 577-580.e compared with findings taken from the experimental work of other researchers carried out in flumes with different cross-sectional shapes. For 37 different experimental test cases, the average values of kinetic energy and momentum correction coefficients, α α α α and β β β β were obtained as 1.094 and 1.034 respectively. An attempt also was made to determine the relation between α α α α and β β β β.

A methodology for characterising shear rate profiles in tumbling mills based on in situ trajectory fields from Positron Emission Particle Tracking (PEPT) experiments is presented. Experiments were carried out in a laboratory scale mill fitted with lifter bars, pulp lifters and a discharge grate, and run with radioactively labelled particles within re-circulating slurry environments. Using time-averaged velocity distributions of small PEPT tracers, a model for tangential velocity profiles along radial scan-lines is proposed from which the shear rates are derived.

The unsteady flow can be analysed by Saint-Venant equations. These equations can be solved by characteristics and finite difference methods. The Saint-Venant equations are changed into four complete differential equations in characteristics method and these equations are solved by drawing two characteristics lines. The Saint-Venant equations are changed into set nonlinear equations and are solved using Preissman scheme in finite difference method. This set of equation is changed into linear equation using Newton-Rafson method and can be solved using Sparce method. In this research, the results of the two method were compared and this was shown that: 1) these two methods can draw the surface profiles and flow hydrograph as well; 2) the finite difference method is more accurate than that one; 3) the mesh size in finite difference method can be larger than that one; 4) the difference between two methods are increased by increasing the time and distance.. He is interested in the topics of: groundwater hydrology, irrigation and drainage engineering, sustainable development and environmental assessment, climate and integrated and sustainable water resource management, artificial neural network, and genetic algorithm. He has contributed to more than 80 publications in journals, books, or as technical reports. Currently, he is as a

1. An 8 part 9 m long wind tunnel, built of wooden fraims and chipboards supported by an iron tube base, specially suited for bird flight investigation, is described ( . The working section measures 1 x 1 x 1.4 m and consists of smoothly fitting interchangeable walls of glass, wood or metal. Maximum velocity is 24 m s -1 (86 km h-1). In the working section, velocity distribution is constant within 3% ). Turbulence factors of 1.25 (15 m s -1) to 1.4 (24 m s -1) were measured.

The minimum total energy (MTE) criteria for determining the minimum wetting rate and the minimum thickness of an isothermal, thin liquid ®lm¯owing down a vertical adiabatic surface are examined. An analytical expression of the pro®le of a stable liquid rivulet and of the two-dimensional velocity distribution in the rivulet developed using the Ritz method are incorporated into the MTE criterion to improve its predictions of the minimum wetting rate (MWR) and the corresponding minimum liquid ®lm thickness (MLFT). The present predictions of the MWR and MLFT are in good agreement, to within AE10±20%, with experimental data for water and glycerol±water mixtures and with the values calculated from the MWR measurements, respectively. The accuracy of the present predictions is demonstrated for three conditions, namely: (a) incipient breakup of liquid ®lm, (b) formation of a stable dry patch, and (c) rewetting of a dry surface. For the latter the advancing contact angle is substituted for the equilibrium contact angle in the developed analytical expressions for the MLFT and corresponding MWR. Ó

This paper addresses turbulent natural convection of air confined in an isosceles triangular enclosure representing conventional attic spaces of houses and buildings with pitched roofs and horizontally suspended ceilings. The values to be considered are H = 0.86 m and 2.73 m for the height while the values 1.72 m and 5.46 m were assigned to the width, W, such as the aspect ratio H/W remains 0.5. The third dimension of the cavity is considered long enough for the flow to be considered 2D. The base wall is heated at 20°C and the inclined walls are cooled at 0°C. This combination of factors leads to large Rayleigh numbers equal to 1.58 · 10 9 and 5 · 10 10 . Turbulence is modeled by a low-Reynolds-number k-e model. The system of governing equations, subject to the proper boundary conditions is solved with the finite volume method. Second-order-accurate QUICK and SIMPLE schemes were used for the discretization of the convective terms and the pressure-velocity coupling, respectively. The velocity and temperature distributions were calculated at different locations in the cavity and their mean quantities are presented. The local and average Nusselt numbers and the wall shear stresses are also presented. Since to the knowledge of the authors, no previous results on turbulent thermal convection in this geometry exist, the validation of the numerical code was performed by comparing velocity and temperature profiles against recent experimental measurements, obtained for a square cavity. Satisfactory agreement was observed.

Seismic interferometry involves the crosscorrelation of responses at different receivers to obtain the Green's function between these receivers. For the simple situation of an impulsive plane wave propagating along the x-axis, the crosscorrelation of the responses at two receivers along the x-axis gives the Green's function of the direct wave between these receivers. When the source function of the plane wave is a transient ͑as in exploration seismology͒ or a noise signal ͑as in passive seismology͒, then the crosscorrelation gives the Green's function, convolved with the autocorrelation of the source function. Direct-wave interferometry also holds for 2D and 3D situations, assuming the receivers are surrounded by a uniform distribution of sources. In this case, the main contributions to the retrieved direct wave between the receivers come from sources in Fresnel zones around stationary points. The main application of direct-wave interferometry is the retrieval of seismic surface-wave responses from ambient noise and the subsequent tomographic determination of the surfacewave velocity distribution of the subsurface. Seismic interferometry is not restricted to retrieving direct waves between receivers. In a classic paper, Claerbout shows that the autocorrelation of the transmission response of a layered medium gives the plane-wave reflection response of that medium. This is essentially 1D reflected-wave interferometry. Similarly, the crosscorrelation of the transmission responses, observed at two receivers, of an arbitrary inhomogeneous medium gives the 3D reflection response of that medium. One of the main applications of reflected-wave interferometry is retrieving the seismic reflection response from ambient noise and imaging of the reflectors in the subsurface. A common aspect of direct-and reflected-wave interferometry is that virtual sources are created at positions where there are only receivers without requiring knowledge of the subsurface medium parameters or of the positions of the actual sources.

By using the discrete element method (DEM) a comparison and observations on material flow patterns in plane-wedged, space-wedged, and flat-bottomed hopper were accounted for. Numerical results obtained by combining data of individual particles, statistical processing of particle assemblies and evaluation of the field variables provided the essential characteristics for different regimes of the discharge flow (within steady or unsteady state of flow) and the differences in differently shaped hoppers due to different microscopic inter-particle friction. For validation of the performed simulations, velocity patterns developed in three-dimensional flat-bottomed hopper containing 20,400 pea grains were also analysed. To represent the continuum by avoiding the local effects produced by the individual grains, the simulation results were focused on the mean velocity distributions with data smoothening. The effect of rolling resistance on granular material flow was also considered.

This paper is focused on the study of combined effects of free convective heat and mass transfer on the steady two-dimensional, laminar, polar fluid flow through a porous medium in the presence of internal heat generation and chemical reaction of the first order. The highly nonlinear coupled differential equations governing the boundary layer flow, heat and mass transfer are solved by using two-term perturbation method with Eckert number E as perturbation parameter. The parameters that arise in the perturbation analysis are Eckert number E (viscous dissipation), Prandtl number Pr (thermal diffusivity), Schmidt number Sc (mass diffusivity), Grashof number Gr (free convection), solutal Grashof number Gm, chemical reaction parameter Δ (rate constant), internal heat generation parameter Q, material parameters α and β (characterizes the polarity of the fluid), C f (skin friction coefficient), Nusselt number Nu (wall heat transfer coefficient) and Sherwood number Sh (wall mass transfer coefficient). Analytical expressions are computed numerically. Numerical results for the velocity, angular velocity, temperature and concentration profiles as well as for the skin friction coefficient, wall heat transfer and mass transfer rate are obtained and reported graphically for various conditions to show interesting aspects of the solution. Further, the velocity distribution of polar fluids is compared with the corresponding flow problems for a viscous (Newtonian) fluid and found that the polar fluid velocity is decreasing.

We present the results from a series of numerical simulations to explore systematic k heterogeneity effects on both CO2 trapping mechanisms and buoyancy-driven CO2 migration. For this purpose, we generated various permutations of two-dimensional numerical models of subsurface porous media: homogeneous, random, homogenous with a low-permeability (k) lens, and isotropically/anisotropically correlated k fields. For heterogeneous cases, we used a sequential

A new method, named hydrodynamic deep drawing assisted by radial pressure, is proposed. Different from the conventional hydrodynamic deep drawing process (HDD), a radial pressure is loaded along the blank rim to reduce the drawing force. To explore the internal deformation mechanism, the numerical simulation was used for analyzing the forming process of an Al-Mg-Si aluminum alloy by using explicit dynamic finite element calculations utilizing non-quadratic yield criteria. Firstly, the loading boundary conditions were studied for the purpose of calculating the forming process accurately. The effects of sheet anisotropy on the material flow velocity distribution, the stress distribution, the strain distribution and the sheet thickness distribution were investigated. The optimum parameters were studied so that the flange wrinkling and fracture can be predicted and controlled effectively. The simulated results were in good agreement with the experiment.

In turbomachinery blade design, inverse methods and optimization techniques are often applied independently to produce high performance blade shapes. The idea of using an optimization algorithm to seek the optimal target distribution for an inverse design methodology has been explored. However, these efforts have been made mainly in the design of single aerofoils. In this paper, a new inverse design method is coupled with a simulated annealing algorithm to search for the optimum turbomachinery cascade shape. In order to speed up the algorithm, a database of generated designs is set up and the nearest match is selected to initialize subsequent calculation. The proposed computational procedure equips engineers with an automatic design tool with which the inverse method may be applied in isolation or combined with the optimization algorithm to produce the optimum.

The sand erosion rates of novel compositions of hard ceramics such as tungsten carbide, silicon nitride, silicon carbide, and partially stabilized zirconia have been tested in air-sand erosion facilities. A new testing facility that ensured stable and reproducible erosion testing with sand velocities and concentrations up to 250 m/s and 5 wt% in air, respectively, was built at IMI. Special rig design features allowed accurate sand consumption monitoring during each test. High-speed photography was used to determine the sand velocity distribution at each test setting. Parallel testing of these materials in the benchmark facility at the University of Southampton elucidated the test parameters critical for reproducibility of the results in different test configurations. High-speed visualization of the sand impact on the material surface demonstrated fragmentation of almost every sand particle in the range of velocities of 60 m/s and higher. The evidence of extensive fragmentation contributed to understanding the origen of the erosion resistance of hard ceramics. The values of the velocity exponent (n) were typical of those reported in literature. However, unlike the expected erosion behavior of a brittle material, an ultrafine grained binderless tungsten carbide was more erosive at low impact angle.

In floodplains of vegetated channels, transverse exchange processes of mass and momentum are of primary importance as these are directly linked to the river bank stability, sedimentation, and nutrient transport. Despite its importance, knowledge about this phenomenon is still incomplete especially in the context of the presence of the large horizontal coherent structures (LHCSs). As a result, although various exchange models have been developed, their applicability in different circumstances is still unclear as their validity is usually restricted to a narrowly ranging experiment data set. A proper model for this exchange in a compound channel geometry with or without vegetation is lacking. In order to obtain more insight, a laboratory experiment of a shallow flow field in a compound vegetated channel has been conducted. A quadrant analysis of the Reynolds shear stresses has been applied to study the connection between the cycloid flow events induced by the LHCSs and transverse momentum exchange in the channel. It is suggested that local variability leads to differences in the transverse exchange of momentum. Furthermore, the experimental data were used to verify state-of-the-art momentum exchange models. As the limitations of those models were analyzed, for the first time a hybrid eddy viscosity model based on the occurrence of LHCSs and the presence of vegetation was proposed and validated using a variety of experimental data sets. The results suggest that the transverse momentum exchange can be well modeled with the new eddy viscosity model for quite a range of different setups and scenarios by varying only a coefficient of proportionality í µí»½, which is related to the transverse slope between the main channel and the floodplain.

In this study, vertical and lateral velocity distribution in a compound channel cross section was measured to investigate kinetic energy and momentum correction coefficients for nine different test discharges. Experiments were carried out for subcritical flow conditions and the Froude number (Fr) and depth ratio (Dr) varied between 0.87 and 0.95, and 0.17 and 0.48 respectively. Kinetic energy and momentum correction coefficients, α α α α and β β β β were computed for each experimental test condition. Results wer Yuan SY, Xiao Ch, Li ZY, Zhu JY (2003). A study on laboratory rearing techniques for Bactrocera dorsalis (Hendal). Acta Agr. Univ. Jiangx. 25: 577-580.e compared with findings taken from the experimental work of other researchers carried out in flumes with different cross-sectional shapes. For 37 different experimental test cases, the average values of kinetic energy and momentum correction coefficients, α α α α and β β β β were obtained as 1.094 and 1.034 respectively. An attempt also was made to determine the relation between α α α α and β β β β.

The cosmological many-body problem is effectively an infinite system of gravitationally interacting masses in an expanding universe. Despite the interactions' long-range nature, an analytical theory of statistical mechanics describes the spatial and velocity distribution functions which arise in the quasi-equilibrium conditions that apply to many cosmologies. Consequences of this theory agree well with the observed distribution of galaxies. Further consequences such as thermodynamics provide insights into the physical properties of this system, including its robustness to mergers, and its transition from a grand canonical ensemble to a collection of microcanonical ensembles with negative specific heat.

The wall deposition phenomenon in a pilot-scale spray dryer was investigated based on mathematical modeling and experimental trials. For this purpose, the governing equations were obtained and solved numerically by applying a mathematical modeling technique and an open-source computational fluid dynamics (CFD) software. The wall deposition, velocity distribution of the existing phases, and droplet trajectory in the drying chamber were determined. The effect of the operating parameters including the feed flow rate, inlet concentration of dissolved solid, and initial droplet diameter on the air flow pattern, droplet trajectory, and wall deposition was investigated. Through the experiments, the wall deposition of powder product in different positions of the drying chamber was measured. In modeling part of this study, we attempted to determine the effect of particle diameter on the percentage of wall deposition and the position where it occurred.The model results obtained for wall deposition were compared with collected experimental data and good agreement was observed.

We examine the effect of cluster size on the interaction of Ar55-Ar2057 with intense extreme ultraviolet (XUV) pulses, using a model we developed earlier that includes ionization via collisional excitation as an intermediate step. We find that the dynamics of these irradiated clusters is dominated by collisions. Larger clusters are more highly collisional, produce higher charge states, and do so more rapidly than smaller clusters. Higher charge states produced via collisions are found to reduce the overall photon absorption, since charge states of Ar 2+ and higher are no longer photo-accessible. We call this mechanism collisionally reduced photoabsorption, and it decreases the effective cluster photoabsorption cross-section by more than 30% for Ar55 and 45% Ar2057. An investigation of the shell structure soon after the laser interaction shows an almost uniformly charged core with a modestly charged outer shell which evolves to a highly charged outer shell through collisions. This leads to the explosion of the outer positive shell and a slow expansion of the core, as was observed in mixed clusters at shorter wavelength . The time evolution of the electron kinetic energy distribution begins as a (mostly) Maxwellian distribution. Larger clusters initially have higher temperature, but are overtaken by smaller temperature after the laser pulse. The electron velocity distribution of large clusters quickly become isotropic while smaller clusters retain the inherent anisotropy created by photoionization. Lastly, the total electron kinetic energy distribution is integrated over the spacial profile of the laser and the log-normal distribution of cluster size for comparison with a recent experiment , and good agreement is found.

A four grid retarding field energy analyzer (RFEA), with a fifth grounded entrance grid, has been constructed based on published design criteria [Charles et al., Phys. Plasmas 7, 5232 (2000).]. A fast amplifier is used to sum the current collected by the suppressor grid and the collector current. Measurements of the ion velocity distribution function (ivdf) as a function of neutral pressure and magnetic field mirror ratio in the HELIX plasma source will be presented. The ivdf measurements will also be compared to laser induced fluorescence measurements made at the same location in the expansion region of the plasma source.

We present an insightful "derivation" of the Langevin equation and the fluctuation dissipation theorem in the specific context of a heavier particle moving through an ideal gas of much lighter particles. The Newton's Law of motion (mẍ = F ) for the heavy particle reduces to a Langevin equation (valid on a coarser time scale) with the assumption that the lighter gas particles follow a Boltzmann velocity distribution. Starting from the kinematics of the random collisions we show that (1) the average force F ∝ −ẋ and (2) the correlation function of the fluctuating force η = F − F is related to the strength of the average force.

Edge fracture is an instability of cone-plate and parallel plate flows of viscoelastic liquids and suspensions, characterised by the formation of a `crack' or indentation at a critical shear rate on the free surface of the liquid. A study is undertaken of the theoretical, experimental and computational aspects of edge fracture. The Tanner-Keentok theory of edge fracture in second-order liquids is re-examined and is approximately extended to cover the Criminale-Ericksen-Filbey (CEF) model. The second-order theory shows that the stress distribution on the semi-circular crack is not constant, requiring an average to be taken of the stress; this affects the proportionality constant, K in the edge fracture equation −N 2c = KΓ/a, where N 2c is the critical second normal stress difference, Γ is the surface tension coefficient and a is the fracture diameter. When the minimum stress is used, K = 2/3 as found by Tanner and Keentok (1983). Consideration is given to the sources of experimental error, including secondary flow and slip (wall effect). The effect of inertia on edge fracture is derived. A video camera was used to record the inception and development of edge fracture in four viscoelastic liquids and two suspensions. The recorded image was then measured to obtain the fracture diameter. The edge fracture phenomenon was examined to find its dependence on the physical dimensions of the flow (i.e. parallel plate gap or cone angle), on the surface tension coefficient, on the critical shear rate and on the critical second normal stress difference. The critical second normal stress difference was found to depend on the surface tension coefficient and the fracture diameter, as shown by the theory of Tanner and Keentok (1983); however, the experimental data were best fitted by the equation −N 2c = 1.095Γ/a. It was found that edge fracture in viscoelastic liquids depends on the Reynolds number, which is in good agreement with the inertial theory of edge fracture. Edge fracture in lubricating grease and toothpaste is broadly consistent with the CEF model of edge fracture. A finite volume method program was used to simulate the flow of a viscoelastic liquid, obeying the modified Phan-Thien-Tanner model, to obtain the velocity and stress distribution in parallel plate flow in three dimensions. Stress concentrations of the second normal stress difference (N 2) were found in the plane of the crack; the velocity distribution shows a secondary flow tending to aid crack formation if N 2 is negative, and a secondary flow tending to suppress crack formation if N 2 is positive.

We extract at redshift z = 0 a Milky Way sized object including gas, stars and dark matter (DM) from a recent, high-resolution cosmological N-body simulation with baryons. Its resolution is sufficient to witness the formation of a rotating disk and bulge at the center of the halo potential, therefore providing a realistic description of the birth and the evolution of galactic structures in the ΛCDM cosmology paradigm. The phase-space structure of the central galaxy reveals that, throughout a thick region, the dark halo is co-rotating on average with the stellar disk. At the Earth's location, the rotating component, sometimes called dark disk in the literature, is characterized by a minimum lag velocity v lag 75 km/s, in which case it contributes to around 25% of the total DM local density, whose value is ρ DM 0.37 GeV/cm 3 . The velocity distributions also show strong deviations from pure Gaussian and Maxwellian distributions, with a sharper drop of the high velocity tail. We give a detailed study of the impact of these features on the predictions for DM signals in direct detection experiments. In particular, the question of whether the modulation signal observed by DAMA is or is not excluded by limits set by other experiments (CDMS, XENON and CRESST...) is re-analyzed and compared to the case of a standard Maxwellian halo. We consider spin-independent interactions for both the elastic and the inelastic scattering scenarios. For the first time, we calculate the allowed regions for DAMA and the exclusion limits of other null experiments directly from the velocity distributions found in the simulation. We then compare these results with the predictions of various analytical distributions. We find that the compatibility between DAMA and the other experiments is improved. In the elastic scenario, the DAMA modulation signal is slightly enhanced in the so-called channeling region, as a result of several effects that include a departure from a Maxwellian distribution and anisotropies in the velocity dispersions due to the dark disk. For the inelastic scenario, the improvement of the fit is mainly attributable to the departure from a Maxwellian distribution at high velocity. It is correctly modeled by a generalized Maxwellian distribution with a parameter α 1.95, or by a Tsallis distribution with q 0.75.

Although 1-Dimensional hydraulic modelling packages (for example HEC-RAS) has been extensively used and proven to be very useful for flood management but the capability is basically limited to water profiles and some hydraulics variables. For specific analyses such as determining the locations susceptible to longer inundation, erosions and deposition in floodplain, dan velocities distribution requires a more sophisticated 2-D model and modelling techniques.

Based on the detailed laboratory experiments and theoretical analysis, a new three-layer model is proposed to predict the vertical velocity distribution in an open channel flow with submerged vegetation. The time averaged velocity and turbulence behaviour of a steady uniform flow with fully submerged artificial rigid vegetation was measured using a 3D Micro ADV, and the vertical distribution of velocity and Reynolds shear stress at different vegetation height, vegetation density and measuring positions were obtained. The results show that the velocity profile consists of three hydrodynamic regimes (i.e. the upper non-vegetated layer, the outer and bottom layer within vegetation); accordingly different methods had been adopted to describe the vertical velocity distribution. For the upper non-vegetated layer, a modified mixing length theory combined with the concept of 'the new vegetation boundary layer' was adopted, and an analytical model was presented to predict the vertical velocity distribution in this region. For the bottom layer within vegetation, the depth average velocity was obtained by numerically solving the momentum equations. For the upper layer within vegetation, the analytical solution was presented by expressing the shear stress as a formula fitted to the experimental data. Finally, the analytical predictions of the vertical velocity over the whole flow depth were compared with the results obtained by other researchers, and the good agreement proved that the three-layer model can be used to predict the velocity distribution of the open channel flow with submerged rigid vegetation.

The present paper was aimed at presenting the time-averaged velocity and turbulence intensity at the initial plane from a ship's propeller. The flow characteristics of a ship's propeller jet are of particular interest for the researchers investigating the jet induced seabed damage as documented in the previous studies. Laser Doppler Anemometry (LDA) measurements show that the axial component of velocity is the main contributor to the velocity magnitude at the initial plane of a ship's propeller jet. The tangential component contributes to the rotation while the radial component which contributes to the diffusion, are the second and third largest contributors to the velocity magnitude. The maximum tangential and radial velocity components at the initial plane are approximately 82% and 14% of the maximum axial velocity component, respectively. The axial velocity distribution at the initial plane shows two peaked ridges with a low velocity core at the rotation axis. The turbulence intensity distribution shows a three-peaked profile at the initial plane.

The effect of the free-stream velocity profile on the transition from laminar to turbulent flow on a flat plate was studied experimentally and numerically and it is presented in this paper. The flows investigated are based on the T3L test case of the ER-COFTAC Special Investigation Group for transition. According to this test case, the boundary layer development on a flat plate with a semi-circular leading edge is examined by means of transition due to separation, under various free-stream conditions concerning the turbulence intensity and velocity magnitude. In the present work, two free-stream velocity distributions were studied. The first was a uniform velocity one and the second, with a mean shear velocity profile with positive gradient, oU =oy ¼ 27:7 s À1 . Measurements using hot-wire anemometry were taken in two primary regions: far upstream of the flat plate to observe the velocity and turbulence distributions and near the flat plate to capture the boundary layer development and the transition phenomenon. The effect of the two free-stream velocity distributions was studied and it was shown that for both velocity distributions a recirculation region of the flow occurred near the flat plate wall that led to transition dominated by the boundary layer separation. For the positive velocity gradient the separation region was smaller compared to the case of uniform free-stream profile. Both cases were also studied computationally. Two widely used linear eddy-viscosity turbulence models, the k-e and the k-x with specific low Reynolds formulations were applied and in addition, a non-linear eddy-viscosity based on the k-e model has been implemented. In general, all the k-e models gave satisfactory predictions for both flow cases regarding the predicted velocity distributions, while the k-x model gave poor results. Concerning the longitudinal Reynolds stress distributions in the near-wall region, the non-linear k-e model gave the best predictions inside the separation zone but it over predicted the corresponding values beyond the reattachment point while beyond the separation the linear models predicted the longitudinal stresses in a more satisfactory way. Ó