The exact measurement of feed water flow is the major factor in nuclear power plant efficiency. However, due to the fouling problem, the venturi nozzle used in feed water measurement frequently causes a decrease in the efficiency of the nuclear power plant. To avoid this problem, ultrasonic technology is a reasonable candidate. The temperature of the feed water is about 300 °C. The commercial piezoelectric element used in an ultrasonic transducer preserves its characteristics up to a temperature of 120 °C. This problem must be overcome in order to use an ultrasonic flowmeter to measure the feed water flow. To address this issue, we designed a thermal block to insulate the high temperature from the pipe line. The method we used included a clamp-on type transducer and a driving circuit with a transit time difference method. The signals from the driving circuit were measured and the ultrasonic transducer assembly was tested at room temperature and at a high temperature of 300 °C. The test results revealed that the transit time difference was reasonably proportional to the flow velocity at room temperature, and the signals of the transducer installed on the pipe line were the same at 300 °C as those at room temperature. This result confirmed that the ultrasonic pulse was working well through the thermal block and in the high temperature fluid.

Research has been completed in a pilot scale, eight foot diameter tank to investigate blending, using a pump with dual opposing jets. The jets re-circulate fluids in the tank to promote blending when fluids are added to the tank. Different jet diameters and different horizontal and vertical orientations of the jets were investigated. In all, eighty five tests were performed both in a tank without internal obstructions and a tank with vertical obstructions similar to a tube bank in a heat exchanger. These obstructions provided scale models of several miles of two inch diameter, serpentine, vertical cooling coils below the liquid surface for a full scale, 1.3 million gallon, liquid radioactive waste storage tank. Two types of tests were performed. One type of test used a tracer fluid, which was homogeneously blended into solution. Data were statistically evaluated to determine blending times for solutions of different density and viscosity, and the blending times were successfully compared to computational fluid dynamics (CFD) models. The other type of test blended solutions of different viscosity. For example, in one test a half tank of water was added to a half tank of a more viscous, concentrated salt solution. In this case, the fluid mechanics of the blending process was noted to significantly change due to stratification of fluids. CFD models for stratification were not investigated. This paper is the fourth in a series of papers resulting from this research (Leishear, et.al. [1–4]), and this paper documents final test results, statistical analysis of the data, a comparison of experimental results to CFD models, and scale-up of the results to a full scale tank.

This paper presents a three-dimensional unsteady numerical simulation of a turbulent plunging liquid jet without artificial surface disturbance impinging on a quiecent liquid pool. The focal point of the study is the initial impact and air entrainment process. The multiphase, Volume of Fluid Model is used in combination with the Reynolds Averaged k-ε turbulence model. The process of the initial impact of the jet on the free surface, the subsequent formation of an air cavity and the subsequent break-down of the cavity into small bubbles are captued and analyzed. These simulations show clearly and in detail the process of air carryunder by the liquid-liquid jet. The air cavity caused by the intial jet impact stretches deeply under the pool surface untill break down due to the shear created by a torroidal vortex. The predicted maximum height of the developing air cavity shows very good agreement with existing semi-empirical correlations from the literature and experiments. The velocity of the front of the air cavity is equal to about half the jet valocity at impact as shown by previous works and the predicted penetration depth shows acceptable agreement with previous correlations. The VOF model shows a strong capability of tracking the interface between two phases.

This paper presents a novel control structure to mitigate the mechanical fatigue in towers of onshore and offshore wind turbines. A general wind turbine dynamic model for both, (1) onshore and (2) offshore systems with the effects of ice and tide is included. These weather conditions further contribute to the uncertainties in the model, most importantly, in the values of tower equivalent mass, stiffness, and damping and increase the amplitude of the velocity of tip-tower vibrations at some particular frequencies, which creates greater mechanical fatigue. A novel control technique to attenuate such a mechanical fatigue is presented in the paper. It is based on the variation of the generator torque in the above rated wind speed region. The control strategy, designed by using Quantitative Feedback Theory (QFT), decreases the velocity of the nacelle movement due to the wind turbulences, thus reducing the associated mechanical fatigue. The new strategy is validated with a realistic nonlinear simulator under a set of different input scenarios and a Monte Carlo method for the uncertainty selection.

The problem of water-in-oil emulsion destruction is related to many technological processes in the oil-and-gas industry, especially in extracting and processing of oil, preparation and transportation of oil, and liquidation/recycling of oil-sludge barns. High stability of water-in-oil emulsions is principally conditioned by the presence in oils of heavy high-molecular polar components that envelope water droplets and prevent coalescence of these droplets. Using conventional techniques to destroy the emulsions yields no positive results. Employing electromagnetic field energy is one of the ways to address this problem. The paper presents the results of an experimental study of the water-in-oil emulsion destruction in radio-frequency and microwave electromagnetic fields. A mathematical model is also proposed to describe the process of electromagnetic impact on water-in-oil emulsions.

Jet and Vortex Actuator (JaVA) is a zero-net-mass flux device for active flow control of boundary layers and transition. JaVA produces various jets which can be used to delay flow separation or to “steer” the boundary layer velocity profile. In this study, numerical simulations of JaVA-boundary layer interactions are analyzed using Proper Orthogonal Decomposition (POD). JaVA-induced flow regimes are governed by the plate width ( b ), the amplitude ( a ) and the operating frequency ( f ). In this study the frequency is changed between 2/3 Hz and 8/3 Hz keeping the plate width and the amplitude constant. A commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver has been used to study the flow fields generated by JaVA. Then, POD is applied to time dependent snapshots of velocity fields at each operating frequency. The POD modes revealed the behavior of the flat plate boundary layer under the effect of active flow control. Traveling modes can be captured in the successive modes for high frequencies.

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers ( 1.01 × 10 6 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

A nonlinear viscoelastic damper is designed for several industrial applications. The damper is structurally similar to typical commercial dampers and the design is based on the choice of the viscoelastic material used as damping agent in the damper. Given the rheological parameters of certain material known from experiments, the coefficients of Johnson-Segalman constitutive equation model for the material are evaluated by fitting the data. The problem is first formulated by writing the governing equations for the flow between two parallel flat plates, i.e. Couette flow. The velocity and stress are represented by symmetric and antisymmetric Chandrasekhar functions in space. Both inertia and normal stress effects are included. A numerical scheme is applied to solve the governing equations in time domain projected by Galerkin method. For given Reynolds number and viscosity ratio, two critical Weissenberg numbers are found at which an exchange of stability occurs between the Couette and other steady flows. The model is capable of predicting the nonlinear amplitude-dependent behavior of viscoelastic dampers under single and multiple-frequency excitations.

Ribbon Growth on Substrate (RGS) has emerged as a promising method for growing multicrystalline silicon wafer directly on a substrate for photovoltaic applications. In this method, the wafer forms as a substrate contacts molten silicon for a controlled period of time. Due to the surface roughness, a thin layer of air is trapped at the interface of the substrate and molten silicon, leading to a contact resistance to heat transfer. The interfacial heat transfer plays an important role in determining the subcooling rate and nucleation, which defines the structural characteristics of the wafer. The contact resistance has been identified as an important phenomenon that affects solidification at the interface. It is dependent on many factors such as the roughness and wetting of the substrate as well as the substrate pre-heating temperature. Quantitative knowledge of the interfacial heat transfer resistance is essential for control of the solidification process. A mathematical model is presented for quantification of the interfacial heat transfer resistance during the initial stage of the solidification for RGS process. A three dimensional unit cell is constructed to represent the contact geometry and interface characteristics. The surface roughness, the mean trapped air layer between the substrate and the liquid, the parameters of area density and the radius of contact spots will be included in the geometry of the unit cell. A microscale heat transfer model is developed to describe conduction and radiation across the interface to quantify the contact heat transfer resistance as a function of surface roughness, morphology and preheating temperatures of the substrate. The contact resistance is incorporated into a heat transfer model and predicts the temperature variation with time in the substrate during the initial stage of contact. The presented model provides a valuable tool to predict the effect of various process parameters and substrate surface roughness on wafer growth during the RGS process.

The wettability of reservoir rocks plays a critical role in oil recovery operations. This property is traditionally defined in terms of the contact angle between the fluid-fluid interface and the solid surface. In natural porous media, it has been preferred to characterize the wettability and its effects on fluid flow behavior in terms of Amott indices, through the capillary pressure-fluid saturation relationship. This “bulk” definition is based on the steady states reached by the two phases, the wetting one and the non-wetting one, upon drainage (removal of the wetting fluid) and imbibition (removal of the non-wetting fluid). These indices provide some indirect indication of the rock surface chemistry and porosity structure. Previous studies on Amott indices have mostly focused on numerical modeling of rocks. In this paper, we present an experimental study on two phase flow in regular lattices of glass microchannels. A wet etching technique is used to fabricate 2 D networks composed of hundreds of repeat units. The repeat units are square, hexagonal, or triangular, with a lattice parameter of about 100 micrometers. Controlling and varying the microchannel wettability, network geometry, and fluid properties allow correlating the physical chemistry of the system and the characteristics of the multiphase flow. We perform drainage-imbibition cycles by controlling the pressure difference across the device. For each pressure difference, we record and characterize the distribution of the two phases at equilibrium. Our results capture the dependance of the Amott index on both fluid and network properties. The values obtained are consistent with previous studies on wetting phenomena at the pore level. The drainage-imbibition cycles also provide information on the patterns of invasion. We show that the study of the cycles can further predictability of Amott indices.

The interface between intersecting microfluidic flows is investigated experimentally. Two microchannel configurations are studied. Each configuration has a main channel and an intersecting daughter channel. The channel cross sections are equal and square with the intersection either at 90 or 45 degrees. Flow visualization is achieved using confocal fluorescence microscopy. The flow interface is examined for equal and unequal viscosities and a range of Reynolds numbers. Viscosity differences and Reynolds numbers influence the three-dimensional nature of the interface. As the Reynolds number increases, the increased flow inertia produces curvature in the interface surface perpendicular to the flow. Curvature is also evident in flows with unequal viscosities. The interface location at fixed flow ratios is independent of the Reynolds number, but varies significantly with unequal viscosity ratios. Viscosity and Reynolds number effects are similar in both the 45 and 90 degree configurations.

Flow in a special designed multi-rotor hydro turbine was simulated using the immersed-boundary method. Thanks to the immersed-boundary method, the complicated flow-driven motion of the turbine components can be simulated. The Smagorinski-Lilly turbulence model was implemented in order to simulate the practical high-Reynolds-number cases. The rotor rotating speeds (RPM’s) of cases with different multirotor configurations were compared to obtain the optimal designs. The configurations studied include the size and position of the flow blocker, as well as the number of rotors. Detailed flow characteristics around the turbine was revealed from the simulation results.

It is desired to perform accurate Near Infrared sensor measurements of slurries flowing in pipes leaving large batch reactors. A concern with these measurements is the degree to which the slurry sensed is representative of the material in the reactor and flowing through the pipe. Computational Fluid Dynamics (CFD) has been applied to the flow in the pipe to determine the flow fields and the concentration profiles seen by the sensors. The slurry was comprised of a xylene liquid phase and an ADP (2-amino-4, 6-dimethylpyrimidine) solid phase with a density ratio of 1.7. Computations were performed for a horizontal pipe with diameter 50.8 mm, length 2.032 m, and 1.76 m/s and 3.26 m/s mixture velocities. The corresponding pipe Reynolds numbers were 1.19E+05 and 2.21E+05. The flow through a slotted cylindrical probe inserted radially in the pipe also was considered. Spherical slurry particles with diameters from 10 μm to 1000 μm were considered with solid volume fractions of 12%, 24%, and 35%. Computations were performed with ANSYS FLUENT 12 software using the Realizable k-ε turbulence model and the enhanced wall treatment function. Comparisons of computed vertical profiles of solid volume fraction to results in the literature showed good agreement. Symmetric, nearly flat solid volume fraction profiles were observed for 38 μm particles for all three initial solid volume fractions. Asymmetric solid volume fraction profiles with greater values toward the bottom were observed for the larger particles. Changes in the profiles of turbulent kinetic energy also were observed. These changes are important for optical measurements which depend upon the mean concentration profiles as well as the turbulent motion of the slurry particles.

The particle method is a useful approach to simulate fluid flows within micro/nano spaces such as micro-electromechanical systems, nano-in-print processes, and head-disk interfaces of hard disk drives. Particle methods are based on continuum dynamics, and some studies have recently extended the scope of these methods to approaches within micro/nano spaces. Surface tension is a dominant force in the fluid flow within micro/nano spaces. However, surface-tension models used in the particle methods need to be improved to achieve more stable and accurate simulation. In the present study, we developed a new surface tension model for the particle method using inter-particle force to improve the stability and accuracy of simulation; the inter-particle force was given by the derivation of potential energy in space. The developed surface tension model was verified using simple benchmark tests: pressure in a round droplet and oscillation period of a square liquid-droplet. The predicted pressure in a round droplet agreed well with that given by the Young-Laplace equation, and the predicted oscillation period of a square droplet agreed well with that given by Lamb’s theory. The wall-adhesion was also verified at various contact angles; heights of droplets on the wall agreed well with those given theoretically. We found that our new surface tension model was useful for simulating fluid flow within micro/nano spaces for particle method.

This paper deals with the longitudinal flight control for a novel Airborne Wind Energy (AWE) system: the EAGLE System. It is a tethered lighter-than-air flyer wind turbine composed of a blimp, several aerodynamic airfoils (wings) with specific aerodynamic control surfaces (ailerons, elevator, rudder), a counter-rotating aerodynamic rotor for the wind turbine (four identical sections, symmetrically arranged, with three blades each), an electrical synchronous generator attached to the counter-rotating rotors, and a tether to secure the airship and to transmit the generated power. Additional information can be found in US Patent, Provisional Application No. 61/387,432 developed by the authors. The designed system proposed here supports a 2.5 kW generator and flies at approximately 100 meters. The mathematical model developed for the AWE system incorporates a hybrid blimp-airfoil design, modeled using a hybrid Cartesian-polar coordinate system to capture the dynamics of both the airship and the tether, and includes the effect of the counter-rotating aerodynamic rotor of the wind turbine, as well as the aerodynamic control surfaces. This paper presents the design of a robust Multi-Input Multi-Output (MIMO) controller for the 3×3 longitudinal flight dynamics of the tethered airborne wind energy system. The control system is designed by applying sequential MIMO robust Quantitative Feedback Theory (QFT) techniques.

Stress analysis of Pseudo-Plastic flow between rotating cylinders is studied in the narrow gap limit. The Galerkin projection method is used to derive dynamical system from the conservation of mass and momentum equations. Flow parameters were obtained using IMSL and also verified by Mathematica Software. Stresses are computed in a wide range of the Pseudo-Plastic effects. Azimuthal stress was found to be far greater than other stress components. All stress components increased as Pseudo-Plasticity decreased. Furthermore, complete stress and viscosity maps are presented for different scenarios in the flow regime.

Microwave heating is extremely popular as a household method for warming up foodstuffs quickly. However the industrial application of this convenient, pollution free heating technique is very limited because of its non-uniform temperature distribution with hot and cold spots. The temperature distribution in microwave heating depends on the electromagnetic frequency, processing time, size and shape, and dielectric properties of the object being heated. In this paper, we present a close form analytic solution for temperature distribution in a three dimensional rectangular block under microwave processing. With the knowledge of electric field distribution from Maxwell’s equation, a three dimensional, unsteady, non-homogenous energy equation containing a microwave source term is solved by the integral transform technique. The effects of various parameters such as sample thickness, electromagnetic frequencies, dielectric properties, and processing time are studied for a salmon fillet. The results indicate that the proper integration of incident frequencies, dielectric properties, sample thickness and processing time could provide homogenous temperature distribution in a salmon fillet under microwave heating.

Numerical simulations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature. The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature is fixed at 300 K and the computations were done for wall temperature, which ranges from 305 K to 350 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The obtained Reynolds number ranges widely up to 10081 and the Mach number at the outlet ranges from 0.1 to 0.9. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy.

This paper presents an experimental study of air flow through open cell metal foams for use as a thermal energy dissipating system. The goal of this paper is to identify the optimum configuration of metal foam design parameters for maximum flow. Four foam blocks were used in the study, representing a range of design parameters: material (copper or aluminum), pore size (5–10 pores per inch), and relative density (ε = 0.875–0.952). The effects of pore size were isolated by comparing air flow through three aluminum foam blocks with constant density and varied pore size. A series of wind tunnel tests were performed to measure the velocity of air flowing through the foam as a function of the free stream air velocity, ranging from 0 to 17.4 mph (7.5 m/s). Results indicated smaller pore sizes and larger densities decreased the amount of airflow through the foam. However, one foam sample produced results that did not fit this trend. Further investigation found this was likely due to the differences in the cross-sectional geometry of the foam ligaments. The ligament geometry, affected by density and manufacturing method, was not constant and not initially considered as a variable of interest. The cross-section shape of the ligaments was found to vary from a rounded triangular shape to a triangle shape with concave surfaces, increasing the amount of drag in the airflow through the sample.

Large electronics systems such as telecom racks and VME bus systems contain arrays of several cards where fan trays consisting of multiple fans are employed to provide forced convective cooling. Typically, flow distributors such as slotted plates are used to distribute the flow evenly through the cards. Thus, a typical telecom rack system contains a large number of parts, with a wide range of length scales. Thus, modeling such large electronic systems with all components can be challenging in terms of solution time and computational resources. In this paper, we presented two techniques to create compact board models that capture the overall physical behavior of detailed boards: 1) the Lumped Block (LB) method, which is a geometry based simplification technique, 2) the Calibrated Porous Medium (CPM) method, which is based on wind tunnel calibrations. Although different in concept, both schemes showed similar behavior when compared to the detailed card, where the maximum difference from pressure drop across the board was less than 10% and less than 30% for the thermal resistance. Moreover, both schemes resulted in mesh reduction that is greater than 83%. Despite the relatively large deviation in the thermal part, both techniques provide good choices for system level analysis where general information about the flow structure and thermal behavior of the system is required.