Abstract A combined experimental and numerical approach is employed to study the hydrodynamic performance and characterize the flow features of thunniform swimming by using a tuna-inspired underwater vehicle in forward swimming. The three-dimensional, time-dependent kinematics of the body-fin system of the underwater vehicle is obtained via a stereo-videographic technique. A high-fidelity computational model is then directly reconstructed based on the experimental data. A sharp-interface immersed-boundary-method (IBM) based incompressible flow solver is employed to compute the flow. The primary objective of the computational effort is to quantify the thrust performance of the model. The body kinematics and hydrodynamic performances are quantified and the dynamics of the vortex wake are analyzed. Results have shown significant leading-edge vortex at the caudal fin and unique vortex ring structures in the wake. The results from this work help to bring insight into understanding the thrust producing mechanism of thunniform swimming and to provide potential suggestions in improving the hydrodynamic performance of swimming underwater vehicles.

Abstract Flapping wings of insects can passively maintain a high angle of attack due to the torsional flexibility of wing basal region without the aid of the active pitching motion. However, the lift force generated by such passive pitching motion has not been well explored in the literature. Consequently, there is no clear understanding of how torsional wing flexibility should be designed for optimal performance. In this work, a computational study was conducted to investigate the passive pitching mechanism of flapping wings in hovering flight using a torsional spring model. The torsional wing flexibility was characterized by Cauchy number. The impacts of the inertial effect of wings were evaluated using the mass ratio. The aerodynamic forces and associated unsteady flow structures were simulated by an in-house immersed-boundary-method based computational fluid dynamic solver. A parametric study on the Cauchy number was performed with a Reynolds number of 300 at a mass ratio of 1.0, which covers a wide range of species of insect wings. According to the analysis of the aerodynamic performance, we found that the optimal lift can be achieved at a Cauchy number around 0.16, while the optimal efficiency in terms of lift-to-power ratio was reached at a Cauchy number around 0.3. All the corresponding wing pitching kinematics had a pitching magnitude around 60 degrees with slightly advanced rotation. In addition, 3D wake structures generated by the passive flapping wings were analyzed in detail. The findings of this work could provide important implications for designing more efficient flapping-wing micro air vehicles.

Abstract In this paper, the effect of wing aspect ratio and kinematics on wing-wake interaction at Re∼10 4 , which matched the flight regime of flapping-wing micro air vehicle (FWMAV), was investigated. The dynamically scaled-up robotic model submerged in a water tank environment revealed that the wing-wake interaction augmented lift across a decrease in both aspect ratio and wing pitching duration. At such high Re, a time-course digital particle image velocimetry (DPIV) measurement showed the entire flow was strongly dominated by trailing-edge vortices (TEV). A pair of counter-rotating TEV was found to induce a jetlike flow towards the windward side of the wing at stroke reversal. The transfer of momentum from the accelerated flow to the wing caused the enhanced lift. The size of the pair vortex decreased for an increase in both aspect ratio and wing pitching duration. The size of the TEV pair was the key feature found to generate the observed aerodynamic force characteristics.

Abstract Ventricular assist devices (VAD) are designed to provide circulatory support to patients suffering from advanced-stage heart failure. While not pulsatile, the advantages of continuous axial flow VADs include a compact size and low mechanical failure rate. However, being compact, they operate at high speed, resulting in adverse effects, such as hemolysis caused by high flow shear and thrombosis formation in stagnant regions are common and threaten the successful use of the device. While state-of-the-art computational fluid dynamics (CFD) is widely used in designing these devices, detailed high-resolution experimental measurements of the flow within them are not readily available in the literature. Such experimental data is crucial for understanding the flow inside the VAD and its interaction with blood cells as well as for validating the CFD predictions. The present study investigates the flow inside a 1:1 exact replica of a VAD – ReliantHeart HeartAssist5 ® . This 12mm diameter device consists of an inlet guide vane (IGV), a rotor and a stator. However, unlike in the real machine, the rotor is driven by a thin shaft that penetrates through the center of the IGV. Refractive index-matching is used to facilitate optical measurements. Hence, all the blades and housing of the pump are made of transparent acrylic. The working fluid is a mixture of water, sodium iodide and glycerin, which matches the refractive index of acrylic, and the kinematic viscosity of blood. Performance tests have been carried out at speeds ranging from 7000 to 9000 RPM. Trends of the results are consistent with those of the actual machine. While scaled data for the pressure rise across the rotor at different speeds collapse, the total head rise across the entire machine does not. High-resolution 2D PIV measurements with vector spacing of 30μm have been conducted in meridional planes of the rotor passage at several blade orientations. They have been performed at 8000RPM and flowrate of 4.5L/min, consistent with physiological requirements. They show that near the rotor front end, the flow in the tip region is dominated by the tip leakage vortex (TLV), associated blockage effects, and very high turbulence level. The upstream end of this domain remains aligned with the leading edge, implying that blades persistently dissect the remnants of a previous TLVs. Interaction of the hub boundary layer with the blades also generates secondary flows. Downstream of the helical section of the rotor, the axial flow is high near the hub and low in the outer part of the passage due to leakage flow-related blockage. Hub boundary layer separation occurs upstream of the stator, generating a large circumferential vortex that occupies nearly half of the rotor span. The complexity of the flow structure and turbulence in this machine would be a challenge to model.

Abstract Inside an automobile engine, there are a camshaft, a crankshaft, a chain sprocket, etc. that transmit driving force. There are many rotating parts installed there. For example, there are gears soaking in engine oil, and bubbles are generated by rotating gears which drag air into engine oil. That raises void fraction of the engine oil. The void fraction is the gas phase fraction per unit volume. In general, high void fraction causes decreasing performance of the engine oil, such as lubrication, cooling and pressure transmission. Although it is required to reduce void fraction and establish a defoaming technique, the processes of bubble generation have not been clarified. One of the reasons is difficulty to measure void fraction and other physical parameters in oil flow using a real engine. Therefore, the influence of rotating speed, number of teeth, and kinematic viscosity of test fluid on bubble generation behavior is not grasped in detail. In this study, the motivation is to understand the mechanism of bubble generation behavior around a rotating body. Detailed visualization was conducted around a rotating body soaking in fluid. The actual phenomena were reproduced by using silicone oil having the same kinematic viscosity of real engine oil. From the visualization using a high speed video camera, there are some characteristic phenomena such as dragging air, subdividing bubbles, and bubbles coalescence. By using observed images, we measured bubble diameter and bubble number density with image processing. Rotating speed, shapes of the rotating bodies, and kinematic viscosity of the test fluids affected on bubble generation behavior. In particular, as the rotating speed increased, the bubble diameter decreased and the bubble number density increased.

The fluid dynamics of air flow in the pharynx is critical to the vibration of the uvula and to the generation of the snoring sound. In this work, a combined experimental and computational approach was conducted to study the aerodynamics of the flow field in the human airway. An anatomically accurate pharynx model associated with different uvula kinematics was reconstructed from human magnetic resonance images (MRI) and high-speed photography. An immersed-boundary-method (IBM)-based direct numerical simulation (DNS) flow solver was used to simulate the corresponding unsteady flows in all their complexity. Analysis has been performed on vortex dynamics and pressure oscillation at various points of interest. Computations with varying airway obstructions, uvula kinematics, and vibrating frequencies were conducted to study the effect of the three factors on the vortex formation and pressure oscillation, respectively. It is found that the vortex formation is significantly affected by the airway width. The fast Fourier transformation (FFT) analysis of the pressure time history revealed the existence of higher order harmonics of the base frequency at significant amplitudes. It was also found that the pressure tended to oscillate more violently at higher uvula vibrating frequencies. Results from this work are expected to bring novel understanding on the sound producing in patients with sleep apnea and provide guidance for surgical interventions.

Dorsoventral undulation is adopted by aquatic mammals for propulsion. However, it is not too common to find invertebrate aquatic animals that undulate their bodies in the vertical plane, which results from antiphasic contractions of dorsal and ventral muscles. To explore the mechanisms of the soft-bodied propulsion, in this work, an annelid swimmer employing up and down undulatory swimming mode is chosen, and the related kinematics and hydrodynamics are studied using a combined experimental and computational approach. A fully calibrated photogrammetry system with three highspeed cameras from different views is used to record the forward swimming motion of this invertebrate swimmer, namely leech. The vertically undulating kinematics are then reconstructed from those videos. With the detailed reconstruction, the undulating wavelength and amplitude distribution the swimmer exhibits during propulsion are quantified. Kinematics analysis results show that the invertebrate swimmer swims in a vertical anguilliform mode and the wavelength is about 0.7 BL (body length) when it swims at a velocity of 1.5 BL /s. An in-house immersed-boundary-method based flow solver is used to conduct the numerical simulations, with which the hydrodynamic performance and wake structures are investigated. The thrust generation and power consumption of the undulating body are described quantitatively. Furthermore, along the undulating body, the pressure distributions are studied.

Flexible cylinders surrounded by a fluid flow that is dominantly aligned with the axis of the cylinders can be found in several applications. Examples with a flow confined to a narrow region around the cylinder(s) can be found in tube bundles of heat exchangers and reactor cores and also in air-jet weaving machines. This research analyses the flow-induced vibration of these two different cases with flexible cylinders in confined axial flow using numerical fluid-structure interaction (FSI) simulations. The FSI simulations of both cases use a partitioned framework, meaning that a computational fluid dynamics (CFD) solver is coupled with a finite element analysis (FEA) structural solver. The dynamic and kinematic equilibrium conditions at the contact surface between the fluid and the structure are satisfied by performing coupling iterations between both solvers in each time step. Convergence of these iterations is accelerated using quasi-Newton coupling techniques. For the case of the tube bundle, the modal characteristics have been identified for a tube bundle when they are submerged in an axial fluid flow. Furthermore, different types of flow-induced vibration have been studied. The flow speed has been increased in an FSI simulation of a single cylinder surrounded by an annular fluid domain, resulting first in static buckling and then in flutter at higher flow speeds. For the case of the air-jet weaving machines, the cylinder represents a smooth yarn which is accelerated by an air jet in the main nozzle of the machine, consisting of a long tube with small diameter. FSI simulations of a yarn clamped at the upstream end have been performed using the arbitrary Lagrangian-Eulerian formulation with deforming grids in the fluid domain. This work demonstrates the feasibility of analyzing and predicting flow-induced vibration of cylinders in confined axial flow by performing FSI simulations. The results of simulations are compared with those of experiments for tubes in axial flow and for a yarn in a nozzle of an air-jet weaving machine.

This work investigates the special case of in-plane fluid flow of a Newtonian incompressible fluid at low Reynolds numbers across a paper-thin porous medium in a confined conduit. Fluid transport in sheets with these characteristics are used in emerging devices such as microscale paper-based analytical devices (μPADs) and “e-paper” displays. Darcy’s law is applied and tested to determine if experimentally measured pressures at two flow rates of 5 μL/min and 10 μL/min agree with predicted values. A test device was designed using kinematic design principles to ensure a deterministic 318 μm gap that directs prescribed flow, unidirectionally across porous filter paper. The paper used was Grade 50 Whatman filter paper with an average pore size of 2.7 μm. Pressure was measured along the direction of flow over a 125 mm distance by six pressure ports placed at uniform increments of 25 mm to determine a profile of pressure along the flow path. Measurements were recorded at discrete time intervals over a period up to 48 hours with at least four replicates. Experimental measurements of the pressure profile show a linear relationship as predicted by Darcy’s law, allowing material permeability to be calculated. Among replicates measured under the same set of controllable conditions, experimental data also show a nonlinear relationship. The nonlinearity suggests evidence of transition into an inertia region, providing insight into the factors and behavior of the Darcy-Forchheimer transition for this special case of porous media flow.

This paper presents an empirical approach for flapping-wing aerodynamics using a servo-driven towing tank and a dynamically scale-up robotic manipulator. Time-varying aerodynamic force and moment were measured, and digital particle image velocimetry in multiple cross-sections were conducted. Three case studies showed that the towing tank experiment could be an effective way to investigate the aerodynamic characteristics in detail, which are difficult to be predicted by other conventional approaches. The force and moment measurements clarified that an advance ratio has significant role in governing the LEV behavior and consequent aerodynamic performance of flapping wings. Results for moving sideways showed the effects of the wing-wing and wing-body interaction, and the usefulness of the towing tank experiments for analyzing the flight dynamic characteristics. It was also shown that the towing tank experiments can be applicable to realistic wing motions; test results using the wing kinematics of a living insect in forward flight were well compatible with the trim condition of the insect.

Bees sustain flight at extremely low Reynolds Numbers (500<Re<10,000) using three degrees of freedom and a flap frequency between 100 and 200 Hz. These combined mechanics create a complex vortex field that results in extraordinary agility and flight efficiency. In addition to agility and efficiency, bees are able to carry loads up to 80% of their body weight for miles making bee flight a very interesting subject area for drone and UAV related development. In order to better understand these complex fluid dynamics, Fluent is utilized to resolve the flow fields during forward flight for 4 anatomically accurate cross-sections of the bee wing at a speed of 1 m/s in two-dimensional flow. Each of the four cross-sections are taken at regular 1/6th wingspan intervals from the anatomically accurate bee wing model. The bee wing model was generated from a μCT scan of Bombus pensylvanicus with generalized bee kinematics presented in the literature. The kinematics applied to each cross-section are adjusted for the change in radial distance from the wing base. The presented analysis and discussion investigates the effects of the variation in cross-section and kinematics over the wing on vortex-shedding dynamics, and instantaneous aerodynamic forces.

Bioinspired designs offer a viable solution to the design challenges of micro air vehicles (MAVs) desired to operate in the same size region under similar conditions as flying vertebrates and insects. Inspired by our previous studies of tethered live dragonflies, here, a quantitative characterization of the unsteady aerodynamic features of a live, freely flying dragonfly under well-established level flight condition will be presented. In particular with regard of the span-wise features of vortex interactions between the fore- and hind-pairs of wings, that highly contributes to the flight agility and efficiency of dragonflies. Flow fields of free flying dragonflies in still air have been measured by time-resolved stereo particle image velocimetry (TRS_PIV). A specifically designed dark flight chamber has been built, where hand hold dragonflies (Pantala flavescens) were released and made to fly nearly parallel to the measurement plane toward a guiding light. Realistic kinematics of the dragonfly wings in free flight were measured by filming with 2 synchronized high-speed video cameras. Using the recorded images, several dozens of landmarks on the fore- and hind-wing surfaces and several landmarks on the body were traced with high precision and the three-dimensional coordinates were then reconstructed with a direct linear transformation (DLT) method. Using the reconstructed wing-body model, Navier-Stokes-based computational fluid dynamics (CFD) analyses, with wing shapes prescribed based on the experimental measurement, dynamically moving multi blocked, and an overset-grid system were conducted. The numerical results are in overall agreement with the PIV data, and the combined numerical and experimental approach offers valuable insight into aerodynamic analyses. The results show that the interaction with the forewing leading edge vortex (LEV) strongly influences the flow structures around the inner spanwise region of the hindwing, while aerodynamic enhancement via vortex capture in the outer span is observed. The interaction depends not solely on wing phasing, geometrical arrangement, but also the flight mission.

Theory of molecular Taylor-Aris dispersion (TAD) is an accepted framework describing tracer dispersion in suspension flows and determining effective diffusion coefficients. Our group reported a pseudo-Lagrangian method to study dispersion in suspension flows at FEDSM-2000. Tracer motions were studied in a steadily moving inertial reference frame (SMIRF) aligned with the flow direction; increments of change of axial position of individual tracers were collected to demonstrate how the tracer moved as they, individually, interacted with similar collections of other bodies brought to and from the region. First, individual tracers with no apparent axial velocity component (NAAVC) were identified; they exhibited fixed positions in video recordings of images collected in the SMIRF. Then, time increments were measured for tracers to pass at least 5, but usually 10 pre-selected, nested distances in the up- or downstream direction laid out with respect to the zero-site in the SMIRF. Such data were richer than measurements of tracer spread over time because stations along each path were serial first-passages (FP) with probabilistic meaning. Dispersion of various types of suspension and two transformation rules for combining velocity components are discussed herein. Traditional low-speed continuum theory and particle dynamics use Galilean transforms. Yet, to recognize the limited speed in laws for channel flows, Lorentzian transformations may be appropriate. In a four-space, deterministic paths would begin at NAAVC sites and continue in time-like conical regions of four-space. Distances in this space are measured using Minkowski’s metric; at the NAAVC site and on the boundary of the space-time cone, this metric has the format of the Fürth, Ornstein, and Taylor (FOT) equation when only terms to order t 2 are used. Data shown at FEDSM-2000 can be reinterpreted as “prospective paths” in time-like regions that were consolidated in normalized cumulative probability distributions to provide retrospective descriptions. The ad hoc sign alteration of the FOT equation to fit the data of FEDSM-2000 is now taken as a part of measuring lengths using a Minkowski metric, which signifies a hyperbolic geometry, for which an inherent scaling constant is a negative curvature. The space also has an intrinsic distance of ℓ = S τ, obtained from fitting parameters ( S , τ) for the FOT equation. Integrals of the area under the FOT curve have units of volume, which are considered as describing an average volume of dispersion on S 3 , the 3-sphere. Path motion through this volume was kinematic dispersion, S 2 τ, which was the form for effective diffusivity in continuum theory used in FEDSM-2000. Weiner and Wilmer describe transformations in four-spaces in terms of commutating rotations on orthogonal planes, a concept readily linked to symmetries in the hyperbolic space typical of Lorentzian transformations; they also describe a second order ODE like the FOT equation.

The aerodynamic performance of an oscillating pitching and plunging foil operating in the energy harvesting mode is experimentally investigated. Experiments are conducted in a closed-loop recirculating wind tunnel at Re of 24,000 to 48,000, and reduced frequencies (k) of 0.04 to 0.08. Foil kinematics are varied through the following parameter space: heaving amplitude of 0.3c, pitching amplitudes of θ 0 = 45° to 75°, as well as phase lag between sinusoidal pitching and heaving motions of Φ = 30° to 120°. Aerodynamic force measurements are collected to show the energy extraction performance (power coefficient and efficiency) of the foil. Coupled with the force measurements, flow fields are collected using particle image velocimetry. The flow field characteristics are used to supplement the force results, shedding light into flow features that contribute to increased energy extraction at these k values. In addition, inertia-induced passive chord-wise flexibility at the leading edge (LE) of the foil is investigated in order to assess its feasibility in this application. Results indicate that favorable performance occurs near θ 0 = 45°, Φ = 90° and k = 0.08. When k is decreased (through increased U ∞ ) to 0.04, overall extraction performance becomes insensitive to θ 0 and Φ. This is supported by the flow field measurements, which show premature leading edge vortex (LEV) evolution and detachment from the foil surface. Although overall performance was reduced with the passive LE flexibility, these results indicate that a proper tuning of the LE may result in a delay of the LEV detachment time, yielding increased energy harvesting at this otherwise inefficient operating parameter space.

Computational fluid dynamics (CFD) was used to investigate the fluid mechanics for undulatory stingray locomotion. This method of undulatory propulsion can be utilized to generate non-turbulent thrust with minimal disturbance to the immediate environment, ideal for exploratory vehicles for underwater environments. Undulatory locomotion was modeled as a two-dimensional fin in free flow with a deforming non-slip boundary to represent a propagating sinusoidal wave with a linearly increasing amplitude, constant frequency, wavelength and flow velocity. In the presented computational study, we varied the amplitude, wavelength, frequency, and flow velocity parametrically and examined the effect on thrust, lift, and pitching moment. Average net thrust was found to increase with wavelength and frequency, whereas for this two-dimensional case amplitude showed negligible effects. For the parametric cases, a theoretical efficiency for forward propulsion was then calculated for a continuous fin. The amplitude was found to increase the input power required for actuation, but decreased output power for forward thrust. Variation of the other parameters showed that the output power depends nearly linearly on the input power, regardless of the particular kinematics or swimming speed.

An experimental investigation is carried out to evaluate the performance of bi-directional pumping ring for dual mechanical seals. An experimental setup is constructed, and appropriate instrumentation are employed to measure the pressure, temperature, and flow rate of the barrier fluid. The experimental study focused on the influence of the kinematic viscosity of the barrier fluid on the performance of the pumping ring. This is done by monitoring Q-Δ P curves for various barrier fluids and temperature ranges. The tests are conducted for industrial barrier fluid compositions which are recommended by vendors of dual mechanical seals, such as Propylene Glycol-water mixtures and Diesel fuel (Grade D2). Despite the importance of the measured performance curves for process control purposes, indicated experimental curved are generalized so that they can be employed in prediction of pumping ring performance for different sizes and operational conditions. Moreover, they can be utilized for numerical models validation.

Insects, sustaining flight at low Reynolds numbers (500<Re<10,000), fly utilizing mechanically simple kinematics (3 degrees of freedom) at an extremely high flap frequency (150–200 Hz), resulting in a complicated vortical fluid field. These flight characteristics result in some of the most agile and maneuverable flight capabilities in the animal kingdom and are considered to be far superior to fixed wing flight, such as aircraft. Bees are of particular interest because of the utilization of humuli to attach their front and hind wings together during flight. A Cartesian-based adaptive meshing implementation of the Lattice-Boltzmann Method is utilized to resolve the complex flow field generated during insect flight and is verified against experimental and computational results present in the literature in two dimensions. The Lattice-Boltzmann Method was found to agree well in both qualitative and quantitative comparisons with both two-dimensional computational and three-dimensional experimental results.

Three-dimensional numerical simulations are used to investigate the hydrodynamic performance and the wake patterns of a sunfish in steady swimming. Immersed boundary method for deformable attaching bodies (IBM-DAB) are used to handle complex moving boundaries of one solid body (fish body) attached with several membranes (fins). The effects of the vortices shed from both the dorsal and anal fins on the hydrodynamic performance of the caudal fin are analyzed by prescribing an undulatory swimming kinematics to a full body sunfish model. Results show that both the dorsal fin vortices and the anal fin vortices can increase the thrust and efficiency of the caudal fin comparing to caudal fin only case. This is because the dorsal/anal fin not only can feed vorticity into the caudal fin wake via vortex shedding, but also can modulate the flow in the downstream in a way of forming a jet with stronger backward component.

The looped airfoil wind turbine (LAWT™) is a patented new technology by EverLift Wind Tecnology, Inc. for generating power from wind. It takes advantage of the superior lift force of a linearly traveling wing compared to the rotating blades in conventional wind turbine configurations. Compared to horizontal and vertical axis wind turbines, the LAWT™ can be manufactured with minimal cost because it does not require complex gear systems and its blades have a constant profile along their length [1]. These considerations make the LAWT™ economically attractive for small-scale and decentralized power generation in rural areas. Each LAWT™ is estimated to generate power in the range of 10 kW to 1 MW. Due to various advantages, it is meaningful to determine the maximum power generation of a LAWT™ by optimizing the structural layout. In this study, CFD simulations were conducted using ANSYS Fluent to determine the total lift and drag coefficient for a cascade of airfoils. The k-kl-ω turbulence model was used to account for flow in the laminar-turbulent transition region. Given the lift and drag coefficients and the kinematics of the system, an analytical formula for the power generation of the LAWT™ was developed. General formulas were obtained for the average lift and drag coefficients so that the total power could be predicted for any number of airfoils in LAWT™. The spacing between airfoils was identified as the key design parameter that affected the power generation of the LAWT™. The results show that a marked increase in total power can be achieved if the optimum spacing between the airfoils is used.

Million-gallon double-shell tanks at Hanford are used to store transuranic, high-level, and low-level radioactive wastes. These wastes consist of a large volume of salt-laden solution covering a smaller volume of settled sludge primarily containing metal hydroxides. These wastes will be retrieved and processed into immobile waste forms suitable for permanent disposal. Retrieval is an important step in implementing these disposal scenarios. The retrieval concept evaluated is to use submerged dual-nozzle jet mixer pumps with horizontally oriented nozzles located near the tank floor that produce horizontal jets of fluid to mobilize the settled solids. The mixer pumps are oscillated through 180° about a vertical axis so the high velocity fluid jets sweep across the floor of the tank. After the solids are mobilized, the pumps will continue to operate at a reduced flow rate producing lower velocity jets sufficient to maintain the particles in a uniform suspension (concentration uniformity). Several types of waste and tank configurations exist at Hanford. The jet mixer pump systems and operating conditions required to mobilize sludge and maintain slurry uniformity will be a function of the waste type and tank configuration. The focus of this work was to conduct a 1/12-scale experiment to develop an analytical model to relate slurry uniformity to tank and mixer pump configurations, operating conditions, and sludge properties. This experimental study evaluated concentration uniformity in a 1/12-scale experiment varying the Reynolds number (Re), Froude number (Fr), and gravitational settling parameter (Gs) space. Simulant physical properties were chosen to obtain the required Re and Gs where Re and Gs were varied by adjusting the kinematic viscosity and mean particle diameter, respectively. Test conditions were achieved by scaling the jet nozzle exit velocity in a 75-in. diameter tank using a mock-up of a centrally located dual-opposed jet mixer pump located just above the tank floor. Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time in-situ ultrasonic attenuation probe and post-test analysis of discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (≤ ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless parameters. The parameters that best describe the maximum solids volume fraction that can be suspended were found to be 1) the Fr based on nozzle average discharge velocity and tank contents level and 2) the dimensionless particle size based on nozzle diameter. The dependence on the jet Re does not appear to be statistically significant.