Average Velocity Data Research Articles

Hybrid datasets: Incorporating experimental data into Lattice‐Boltzmann simulations

SummaryA novel method, which combines both fluid‐mechanical experimental and numerical data from magnetic resonance velocimetry and Lattice‐Boltzmann (LB) simulations is presented. The LB method offers a unique and simple way of integrating the experimental data into the simulation by means of its equilibrium term. The simulation is guided by the experimental data, while at the same time potential outliers or noisy data are physically smoothed. In addition, the simulation allows to increase the resolution and to obtain further physical quantities, which are not measurable in the experiment. For a benchmark case, temporally averaged velocity data is included into the simulation. The proposed model creates a hybrid dataset, which satisfies the Reynolds‐averaged Navier‐Stokes equations, including the correctly deduced contribution from the Reynolds stress tensor.

Vertical axis wind turbine analysis using MATLAB

Wind Turbines have become one of the feasible power plants to replaced fossil fuels. Because this plant is affordable cost and did not produce pollutants as an output. Vertical Axis Wind Turbine can be placed at points with high wind intensity such as; toll roads, ships, railroads, airports. The energy produced can be distributed for the civilian house light, the street lights, the fishing boats light, others. The hope is that wind turbines can generate 100 watts of power, so that charging time can be at least 6 hours. But, the average velocity data in the field is worth under 2.85 m/s (minimum wind speed to get 100 watt). Resulting in a turbine charging time more than 6 hours. In this case, The Turbine needed more than one accu as a place to store the energy even the accu take more than 6 hours to be charged.

CFD simulation and experimental validation of a horizontal pump intake system

In the present study, the numerical simulation of a horizontal pump intake system with multiple pumps has been presented. Simulations were performed using a commercially available computational fluid dynamics (CFD) software code FLUENT, which included estimation of variables such as velocity distribution at the cross section of draft tube inlet, swirl angle in the pump suction pipe and streamline patterns in the sump chamber. Four different cases given by three different sets of discharges and three different operating conditions defined by number of pumps running both symmetrically and asymmetrically were tested. Numerically computed average velocity data, vertical velocity profiles at the draft tube inlet and swirl angle at the pump suction pipe are in good agreement with the experimentally obtained ones. CFD also predicted the formation of a circulation zone in the forebay, which is in good agreement with the experimental observations although its size was greater than that estimated by CFD.

Turbulent Stresses and Secondary Currents in a Tidal-Forced Channel with Significant Curvature and Asymmetric Bed Forms

Acoustic Doppler current profilers are deployed to measure both the mean flow and turbulent properties in a channel with significant curvature. Direct measurements of the Reynolds stress show a significant asymmetry over the tidal cycle where stresses are enhanced during the flood tide and less prominent over the ebb tide. This asymmetry is corroborated by logarithmic fits using 10 min averaged velocity data. A smaller yet similar tendency asymmetry in drag coefficient is inferred by fitting the velocity and estimated large-scale pressure gradient to a one-dimensional along-channel momentum balance. This smaller asymmetry is consistent with recent modeling work simulating regional flows in the vicinity of the study site. The asymmetry in drag suggests the importance of previously reported bed forms for this channel and demonstrates spatial and temporarily variations in bed stress. Secondary circulation patterns observed in a relatively straight section of channel appear driven by local curvature rather th...

Some Studies on Water Permeability of Nonwoven Fabrics

In this paper we report on the water permeability behavior of nonwoven fabrics produced from flax fibers. Three different types of needle punched nonwoven fabrics are produced by varying the depths of needle penetration during the needle punching process. The pore size and its distribution in the nonwoven fabrics are measured by liquid extrusion porometry. Water permeability is measured by the water permeability testing instrument working on the principle of falling hydraulic head method. A finite element analysis is employed to predict the flow velocity through the nonwoven fabrics. A good correlation is achieved between the average velocity data obtained from water permeability test and theoretical prediction based on finite element analysis. The pore size and its distribution play an important role in water permeability characteristics.

Water flow through the polypropylene‐based geotextiles

AbstractThis article presents the results from a study on the cross‐plane water flow through the needle punched nonwoven geotextiles produced from polypropylene fibers. Different types of nonwoven geotextiles are produced by varying the processing parameters during the needle punching process. The pore characteristics and the cross‐plane water flow (or permeability) through the nonwoven geotextiles are measured by liquid extrusion porometry and water permeability tester, respectively. The water flow velocities through the geotextiles are predicted by the finite element analysis. There is a good correlation between the average velocity data obtained from water permeability test and theoretical prediction based on finite element analysis. The pore characteristics play an important role in water permeability behavior of nonwoven geotextiles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

THE FLOW CHARACTERISTICS OF A REDESIGNED 50cc PENN STATE LVAD

Recent measurements in the original Penn State 50cc LVAD found a strong flow field dependence on mitral valve (MV) orientation and areas of low wall shear. The inflow through the MV is the controlling factor in adequately maintaining washout throughout the cardiac cycle. Here, we investigate the flow fields in a new design of our 50cc pump, with focus on the impact of MV orientation and the nature of the blood analog fluid. Planar particle image velocimetry (PIV) is used to quantify the pump flow field characteristics. A Bjork-Shiley Monostrut MV is rotated in 15° increments from -15° to 45°, relative to the horizontal axis of the pump. Both Newtonian and non-Newtonian blood analog solutions are used. Flow field data are acquired over three planes parallel to the pusher plate. Phase averaged velocity data is measured over the entire cardiac cycle. The data shows better overall flow penetration and washout characteristics along the perimeter of the device during mid to late diastole at the larger valve angle orientations. The Non-Newtonian blood analog creates a more coherent inlet jet through the mitral valve than the Newtonian fluid suggesting that the overall rotational flow pattern will lead to improved washout.

An experimental study of electro-osmotic flow in rectangular microchannels

Experimental studies were carried out on fully developed and steady electro-osmotic flow in a rectangular channel where the channel height $h$ is comparable to its width and the thickness of the electric double layer characterized by the Debye length is much less than $h$ . The nano-particle image velocimetry technique was used to measure the two components of the velocity field parallel to and within about 100 nm of the channel wall for $h\,{\leq}\,25\,\umu$ m. The mobility of the particle tracers was calculated from averaged velocity data for various electric field strengths. The experimentally determined mobility values are compared with analytical predictions for dilute aqueous solutions of sodium tetraborate.

Steady and unsteady computation of impeller‐stirred reactors

AbstractA general computational approach is presented for numerical modeling of viscous flow in baffled, impeller‐stirred‐tank reactors. A multiblock, body‐fitted grid structure facilitates modeling of various impeller and baffle designs, and a new procedure offers averaged velocity data from a complex 3‐D CFD dataset. Impellers are modeled precisely, eliminating the need for inputting experimental velocity data for boundary conditions. The method can be used quickly to obtain extremely detailed flow computations at a fraction of the cost of computing unsteady moving grid solutions. A steady‐state computational approach that neglects the relative motion between impeller and baffles yields numerical results comparably accurate to full unsteady computations for laminar flow at a fraction of the time and expense. The approximate steady‐state method is used to predict power requirements of a Rushton turbine in laminar flow.An unsteady, moving grid technique provides time‐accurate solutions for the flow inside an impeller‐stirred reactor with side‐wall baffles. These computed results are compared with those using the approximate steady‐state method and with experimental measurements. The unsteady, moving grid method uses two different initial conditions: one starting from rest and the other starting from an approximate steady‐state solution obtained at the starting position of the impeller relative to the baffles. For unsteady simulations of laminar flow in stirred vessels, the final operating condition can be achieved much more efficiently if the solution obtained from the steady‐state procedure is used as an approximate initial condition.

On the flow in the unobstructed space between shrouded corotating disks

A model of a computer hard disk drive was constructed and measurements of the air flow in the unobstructed space between a pair of disks were obtained. The disks were centrally clamped to a common hub, and rotated within an axisymmetric (cylindrical) enclosure or shroud. Measurements of the circumferential velocity component were made at five radial locations and three rotation rates (Ω=300, 1200, and 3600 rpm) using a laser-Doppler velocimeter. The resulting mean and rms circumferential velocity profiles are presented and discussed. The data show that the circumferential velocity component profiles are fairly uniform in the axial direction in the space between the disks, except near the shroud where the flow is strongly sheared. The circumferential velocity peaks at a critical radius. Between the hub and the critical radius location the flow is in solid body rotation. Between the critical radius and the shroud the circumferential velocity decreases to zero, gradually at first and then very quickly as the shroud is approached. Analysis based on simplified force balance considerations facilitates the interpretation of the experimental observations and leads to improved understanding of the complex flow phenomena. Numerical calculations of the present configuration assuming axisymmetric steady flow were performed by Chang et al. (submitted to Int. J. Heat Mass Transfer). These calculations show reasonable agreement with the averaged velocity data but, for the reasons discussed, fail to reproduce features of the rms distribution associated with nonturbulent flow unsteadiness.

Steady Shear Rheology and Fluid Mechanics of Four Semi‐Solid Foods

ABSTRACTThe steady shear rheology of four semi‐solid food materials (ketchup, mustard, apple sauce and tomato paste) was studied by generating and comparing flow data using cone and plate, parallel plate and capillary measurements over the shear rate range of 0.05–1600 see−1. Super‐position of flow data was demonstrated and correlations obtained; using the power law, Bingham Plastic, Herschel‐Bulkley and Casson models were compared. In the low shear rate range (y = 0.05 – 1.0 set−1), the Bingham Plastic model and in the high shear rate range (y = 1.0 – 1600 sec−1), the Herschel‐Bulkley model were shown to be most successful. Comparison of average velocity data with mathematical predictions using the power law, Herschel‐Bulkley and Cas‐son models showed that the equation using the Herschel‐Bulkley model was best and should be used in the design of flow processes for the foods studied.

S.A.W. reflecting arrays

It is shown that metal surface-acoustic-wave reflecting arrays on piezoelectric substrates with a range of ratios t of electrode width to period can be modelled by a cascade of equal-length transmission-line sections. Measurements were made on short- and open-circuited arrays with various t ratios; impedance ratio r and average velocity data are presented against t.