Inlet Corner Research Articles

Research on erosion wear law of four-way flow channel of wellhead fracturing in ultra-deep wells

Abstract This paper establishes a 1/2 three-dimensional finite element model that considers multiple factors affecting the erosion rate of the four-way fracturing structure on site. The model can simulate the effects of different inlet velocities, dynamic viscosities, outlet quantities, outlet pressures, and channel wall angles on the velocity and streamline distribution of the four-way channel. It is also possible to analyze the effects of different factors such as inlet velocity, sand carrying mass flow rate, inlet quantity, fluid dynamic viscosity, fracturing fluid particle density, fracturing fluid particle diameter, four-way wall hardness, and channel wall inclination angle on the erosion of the inner wall. Through the established model calculation, it was found that as the inlet flow velocity increases, the maximum flow velocity in the channel also increases, and the value is close to 1.8 times the inlet velocity, with the maximum value appearing at the inlet corner. When the inlet velocity of the four-way valve is low, a significant vortex-like flow field appears in the closed flow channel of the four-way valve, which will lead to the accumulation of particles in the fracturing fluid. The calculation shows that the number and velocity of sand containing fracturing fluid inlets have the greatest impact on the erosion rate of the four-way flow channel, and the optimal inclination angle of the flow channel is 9 degrees. Increasing the hardness of the four-way wall can improve the maximum erosion rate of the flow channel wall, but changing the sand particle density and diameter has little significance in reducing the erosion rate of the four-way flow channel. It is recommended to perform corresponding heat treatment on the inner wall of the four-way valve to reduce the impact of sand containing fracturing fluid on wall erosion. This article provides a theoretical basis and guidance for controlling or avoiding erosion and thinning failure of four-way valves and also provides a theoretical basis for the design of wellhead four-way valves and various safe construction operations.

CFD Characterization and Field Test Study on Plugging Air Leakage with Time-Varying Viscosity Solidified Foam to Prevent Coal Spontaneous Combustion

ABSTRACT From the perspective of plugging air leakage paths and preventing coal spontaneous combustion in the goaf of coal mines, filling and plugging the ends of the working face is crucial. Generally speaking, rapidly solidified foam slurry is beneficial to plugging air leakage paths. However, researchers have not yet clarified the accumulation and diffusion rules of rapidly solidified foam, resulting in low efficiency in plugging air leakage paths. To solve the above problems, this study takes the goaf of 1301 working faces of the Shandong Lilou Coal Industry as the research object, uses the computational fluid dynamics modeling method to construct a physical model of pressure injection foam slurry, and optimizes the on-site application process parameters of plugging the end of the working face. The numerical simulation results show that coagulant can improve the accumulation characteristics and plugging efficiency of foam slurry, and the optimal addition amount is 3 wt%. In addition, as the perfusion flow increases from 5 to 15 m3/h, the airflow rates on the working face gradually increases and the oxidation zone gradually shrinks. Therefore, the grouting flow is preferably 15 m3/h. Field test results show that rapid-setting inorganic solidified foam blocks the airflow at the air inlet corner from leaking into the goaf and weakens the composite reaction of coal and oxygen. The temperature at each monitoring point first decreased, then stabilized, and the final temperature was maintained at 27-28°C. The CO concentration gradually decreased and finally remained below 20 ppm. The CO concentration of the mine’s total return airflow is stable below 10 ppm. This study can provide theoretical guidance for the technological design of using solidified foam to rapidly plug the air leakage paths at the end of the fully mechanized caving working face.

Physically Realistic Inlet-Velocity Profiles in Duct Flows

A uniform inlet velocity profile is widely used in the numerical simulations of fluid flow and heat transfer in ducts for both incompressible and compressible flows. In incompressible flows, the calculated fluid pressure at the inlet edge is extremely high and affects the calculation of the average pressure. In compressible flows, the fluctuation of pressure in the flow direction results in the fluctuation in the velocity. This has motivated this study to numerically investigate a physically realistic velocity profile at the inlet of a pipe rather than using a uniform velocity profile. The numerical simulations were based on the control volume-based power law scheme and the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The continuity and momentum equations for a flow in a pipe with the rounded inlet corner were solved to obtain a physically realistic inlet velocity profile. The obtained inlet velocity profile was expressed by a simple expression in the range of Reynolds number from 100 to 2000. Using this velocity profile, both the incompressible and compressible flows in a pipe were numerically investigated. The results resolved the previously observed inconsistencies in the pressure that were previously observed in the numerical simulations with uniform inlet velocity profiles.

Computational Fluid Dynamics Analysis and Experimental Results for the Dynamic Performance of Two Long Smooth Surface Annular Seals Operating With a Liquid in Air Mixture

Abstract Compressors in subsea oil and gas production must handle wet gases to reliably operate for extended periods of time. Annular clearance seals contribute to compressor performance and do affect system rotordynamic stability. Prior experimental work with two smooth surfaces, uniform clearance seals supplied with a light oil in air mixture and undergoing similar operating conditions produced direct stiffnesses (K) with distinct trends as the liquid content increased to 8% in volume. Both seals differ in length and diameter albeit having similar radial clearance. Other force coefficients for both seals, namely, cross-coupled stiffness (k) and direct damping (C) increase as the inlet liquid volume fraction (LVF) grows. Rationale for the peculiar differences in centering stiffness (K) is missing. Hence, a computational fluid dynamics (CFD) model and its predictions, the thrust of this paper, unveil flow field details (pressure, velocity fields, and liquid content evolution) for the oil in air mixture. Besides the CFD model, an enhanced bulk-flow model (BFM) also predicts the seals' leakage and dynamic force coefficients. Both models predict through flows agreeing well with the measured ones, the maximum difference is less than 16%. The BFM direct stiffness (K) does reproduce closely the experimental K whereas the direct damping coefficient (C) is up to ∼41% lower than the test result. The CFD model captures the variation trend of K versus inlet LVF for the first seal, albeit its magnitude is thrice the experimental stiffness. The CFD C agrees well with the test data for both seals, the largest difference is less than 10%. In spite of the complexity of the CFD model, significant differences with the experimental results persist, in particular for K. When considering the seal inlet corner as round, the CFD model produces a significant reduction in K to better approach the test result for a seal supplied with air. Attention to the seal geometry is paramount to produce accurate predictions.

Homogeneous Field Measurement and Simulation Study of Injector Nozzle Internal Flow and Near-Field Spray

The homogeneous field measurement of internal flow and spray of internal combustion engine injector nozzles under high pressure has always been one of the difficulties in experimental research. In this paper, an actual-size aluminum alloy nozzle is designed, and the simultaneous measurement of internal flow and near-field spray is successfully realized with the help of synchrotron radiation X-ray phase contrast imaging technology under an injection pressure of 30~90 MPa. For a 0.25 mm aperture nozzle, different radii of the inlet corner can induce different cavitation layer thicknesses, and the measured flow section shrinkage ratio is 0.70. The flow characteristics in the nozzle are entirely connected to the jet characteristics, indicating a tight correlation between internal flow and jet morphology. Finally, the internal cavitation of the nozzle was studied by the CFD simulation, and the simulation results are in good agreement with the experiment.

Air Flow Movement Law in Working Face and Gob with Roof-Cutting and Pressure-Releasing Mining: A Numerical Simulation and Engineering Verification.

In comparison to traditional longwall mining, "roof-cutting and pressure-releasing" mining along gob-side entry retaining changes the permeability of the gob, as well as the pressure-relief characteristics and caving mode of the overlying strata. These changes are a result of the interaction of these factors, which also changes the boundary condition of the gob and the airflow movement law of the working face and the gob. In order to study the law of air flow movement in the working face and gob under the "roof-cutting and pressure-releasing" mining along gob-side entry retaining, the permeability model of gob was established under the engineering background of the 21,304 experimental working face of Chengjiao coal mine, then using fluent numerical simulation software, the movement law of air flow in working face and gob is simulated. The results show that the law of air leakage is much different from that of traditional longwall mining, and there are two main air leakage routes, First, most of the airflow will flow directly into the gob-side entry retaining under the action of inertia, and it will collide with the air flow provided by the fan at the end of the gob-side entry retaining, and the air will leak in the gob along the airflow direction; second, when the remaining airflow flows to the working face, the air leakage is serious in the air inlet corner, and most of the air flow flows into the gob. In view of the air leakage area, the air leakage prevention measures are put forward, such as setting the baffle plate, hanging the wind shield at the corner, and blocking the wall of the roadway with guniting; the simulation results show that the air leakage area is obviously reduced, and it is consistent with the measured data. The simulation results can generally describe the law of air flow movement in the face and gob with "roof-cutting and pressure-releasing".

3D-CFD Study of Oblique Streamlining Membranes on the Roof-Top of a Low-Rise Building, Targeting Pedestrian Comfort-A Case Study

Considering the cubic nature of the most frequent geometries among the urban elements and their configurations, the manipulation of the free stream wind flow around the enormous objects, as well as within relatively narrow corridors, such as street canyons is significant in many regards. One of its instances could be mentioned as pedestrian comfort. In this case study, the implementation of an Oblique Streamlining Membrane (OSM) has been studied on a sub-branch of a low rise, but bulky, building, over which a roof-top outdoor food court area has been primarily designed. The OSM serves as the streamlining mechanism, preventing the roof-top area from the intense fluctuations of the wind flow after the flow is separated from the inlet corner side of the building in question. The optimization of sub-geometries and the proof of the concept for the OSM flow controlling mechanism were the subject of the current manuscript, for which a 3D numerical Reynolds Average Navier-Stokes (RANS) scheme has been used. An unstructured computational grid has been applied around the 3D geometry of the entire building and its sub-branching details, which is in contrast with most studies on full-scale geometries, tending to have simplifications on the body to reach a more generalized set of results. All cases have been numerically tested with and without the presence of the OSM. This comparison has been the grounds for proving the effectivity of the said flow controlling mechanism to eliminate high gradient fluctuations of the separated flow off the roof corners. This has led to pedestrian/resident comfort on the roof-top food court area located on top of the building.

Development and validation of the cavitation-induced erosion risk assessment tool

This work presents the development of a cavitation-induced erosion risk assessment (CIERA) tool that links multiphase flow simulation predictions with the progress towards material erosion. To develop a robust erosion modeling tool, the cavitation and erosion predictions for pressurized diesel fuel flow within a channel geometry were validated over a range of Reynolds and cavitation number conditions in two different aluminum channel geometries, one featuring a rounded inlet corner and the other with a sharp inlet corner. The multiphase flow development within the channel was modeled using a compressible mixture model, where phase change was represented with the homogeneous relaxation model and the turbulent flow evolution was modeled using a dynamic structure approach for Large Eddy Simulations. To improve representation of the incubation period before material rupture over existing approaches, a physics-based metric was derived based on the cumulative energy absorbed by the solid material from repeated hydrodynamic impacts. When the average peak pressure was related to the incubation period, the incubation period and its sensitivity to changes in flow conditions were found to be overpredicted. In contrast, predictions from CIERA provided a more accurate means to qualitatively and quantitatively predict the influence of flow conditions on the incubation period before material erosion. When the predicted stored energy was related to the solid material properties to estimate the incubation period, multiphase flow simulations demonstrated accurate representation of the sensitivity of erosion severity to changes in flow conditions. The use of CIERA led to quantitative agreement of the predicted incubation period within 5% of the experimentally measured incubation period.

Time-resolved 3D imaging of two-phase fluid flow inside a steel fuel injector using synchrotron X-ray tomography

The multiphase flow inside a diesel injection nozzle is imaged using synchrotron X-rays from the Advanced Photon Source at Argonne National Laboratory. Through acquisitions performed at several viewing angles and subsequent tomographic reconstruction, in-situ 3D visualization is achieved for the first time inside a steel injector at engine-like operating conditions. The morphology of the internal flow reveals strong flow separation and vapor-filled cavities (cavitation), the degree of which correlates with the nozzle’s asymmetric inlet corner profile. Micron-scale surface features, which are artifacts of manufacturing, are shown to influence the morphology of the resulting liquid-gas interface. The data obtained at 0.1 ms time resolution exposes transient flow features and the flow development timescales are shown to be correlated with in-situ imaging of the fuel injector’s hydraulically-actuated valve (needle). As more than 98.5% of the X-ray photon flux is attenuated within the steel injector body itself, we are posed with a unique challenge for imaging the flow within. Time-resolved imaging under these low-light conditions is achieved by exploiting both the refractive and absorptive properties of X-ray photons. The data-processing strategy converted these images with a signal-to-noise ratio of ~ 10 into a meaningful dataset for understanding internal flow and cavitation in a nozzle of diameter 200 μm enclosed within 1–2 millimeters of steel.

Numerical simulation of sediment deposition and trapping efficiency estimation in settling basins, considering secondary flows

In this paper, sediment deposition and trapping efficiency in shallow rectangular reservoirs were numerically estimated considering secondary flows. In order to do this, three dimensional (3D) steady, incompressible, Reynolds-averaged Navier-Stokes (RANS) equations with the standard k−ε turbulence model were used as the governing equations. The drift-flux model also was used to model the solid phase. In the next step, the developed model was validated using the available data. Then it was used to simulate the sediment deposition and trapping efficiency in shallow rectangular reservoirs, considering secondary flows. The results show the sediment is trapped in the inlet corner of the reservoir, and two pairs of large vortices on the sides and two pairs of small vortices at the inlet corner of the reservoir are observed. Finally, the effects of the input angle of the reservoir to the trapping efficiency are evaluated and the results are discussed.

Numerical simulation study on the coupling mechanism of composite-source airflow–dust field in a fully mechanized caving face

The dust produced during the process of coal mining is the main cause of the lung disease pneumoconiosis in miners. The study using Fluent software to perform a numerical study of the multi-source dust field in a fully mechanized caving face. The results of the simulation showed that the airflow velocities at the inlet and return air corners increase considerably, and that the overall air velocity in the coal mining face first decreases, from 2.33 to 0.41 m/s, before increasing to 1.91 m/s. The diffusion laws of dust produced by coal-cutting and the advancing of the hydraulic support at the working face tend to be consistent. Following dust superposition, a high-concentration dust belt is formed to the downwind side of the coal mining machine; this dust belt is about 16 m in length, about 1.2 m high, and with an average mass concentration of 1640 mg/m3.

Effect of rotor spinning transfer channel modification on fiber orientation and yarn properties

The vortices are generated at the conventional transfer channel, having adverse effects on fiber configuration. In a former research, a conventional transfer channel was modified via rounding the transfer channel inlet corner and adding a bypass channel. The simulation results obtained with the modified transfer channel showed that the vortices were eliminated and the inlet air velocity increased. We present the impact of this modification on the yarn properties and fiber straightness. Four groups of yarn samples were spun using the conventional and modified spinning system. Yarn properties and fiber straightness along the rotor groove were evaluated. Results revealed that tenacities of the yarns spun on the modified system, increased in comparison to that of the conventionally spun yarns. The number of nearly straight fibers is increased by 25.55% by using the modified system, which was mainly attributed to the decrease in the number of fibers with trailing and leading hooks.

Numerical study of liquid nitrogen cavitating flow through nozzles of various shapes

The cavitating flow of cryogenic liquid through a spray nozzle is influenced by many factors, such as unique thermophysical properties of cryogenic liquid, the inflow temperature and the complicated geometrical structure of the spray nozzle. The geometrical parameters of liquid nitrogen spray nozzles have a profound impact on cavitating flow which in turn affects spray atomization characteristics and cooling performance. In present study, CFD simulations are performed to investigate influence of the nozzle geometry on the liquid nitrogen cavitating flow. The mixture model is used to describe the liquid-vapor two phase flow, and both the cavitation and evaporation are considered for the phase change. The predictions of mass flow of liquid nitrogen spray are validated against experimental results. The effects of geometric parameters, including the outlet orifice diameter and the length of nozzle, the inlet edge angle of orifice, the inlet corner radius of orifice, the orifice shape and different positions of swirl vanes, are investigated under a wide range of pressure difference and inflow temperature. The results show that the effects of geometric parameters on cavitating flow show different trends under subcooled conditions compared with saturated temperature conditions. The flow characteristics are more affected by the changes of the inlet edge angle, the inlet corner radius, and the orifice shape. The insert of swirl vanes has an effect on the distribution of the cavitated vapor within the orifice, but it has little influence on flow characteristics. The results could enrich our knowledge of liquid nitrogen cavitating flow in spray nozzles of various shapes.

High-resolution X-ray tomography of Engine Combustion Network diesel injectors

The flow inside direct-injection diesel nozzles is strongly influenced by the local geometry. Deviations from the design geometry and nonuniformities along the fuel’s flow path can alter the expected spray behavior. The influence of small-scale variations in the internal geometry is not well understood due to a lack of data available to experimentalists and modelers that resolve such features. To address the need for more accurate geometry measurements that also quantify the error bounds on manufacturing variability, the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory has been customized to obtain high-resolution X-ray tomography of injection nozzles. In this article, we present results for several diesel injectors provided by the Engine Combustion Network. The imaging setup was optimized to measure dense metallic samples at high signal-to-noise ratio using projection imaging. To improve contrast, multiple images were recorded at each rotation angle. Phase shifting effects, which amplify the uncertainty in locating nozzle boundaries, were minimized by reducing the propagation distance of the X-rays between the nozzle and detector. Such improvements to the imaging technique enabled the nozzle hole diameter to be measured with an accuracy of 1.8 µm, which takes into account the pixel resolution as well as the properties of the imaging setup and the geometric analysis. The high spatial resolution allows the nozzle hole inlet corner radius to be azimuthally resolved. For the sample set under consideration, these new measurements reveal that non-hydroground injectors have a distribution of radii which typically vary by more than a factor of two. An azimuthally varying radius of curvature at the hole inlet is expected to result in highly asymmetric cavitation. Skeletal wireframe models of the nozzle hole geometries suitable for computational fluid dynamics mesh generation have been developed, in addition to full three-dimensional isosurfaces; these data have been made publicly available online.

S-shaped Inlet Flow Characteristics Test Rig Design and Experimental Research

An inlet flow characteristics test bench was designed for the high offset s-shaped inlet. Parametric design method was used in the design of direct-connect contraction. Numerical simulation results showed export velocity of the designed contraction distributed uniformly, the boundary layer was thin, which had good air contraction effect. Steady state flow characteristics test of the s-shaped inlet was carried out on the inlet test bench, and effectively verified the performance indicators of it. Test results showed that an obvious low pressure area existed on the bottom wall after the first corner of the s-shaped inlet. With the increase of inlet Mach number, the exit flow field quality deteriorated. When the inlet Mach number was 0.72, the export distortion index DC60 was over 17%, which could not meet the needs of normal work of the engine.

Effects of nozzle configuration on internal flow and primary jet breakup of flash boiling fuel sprays

Fuel spray plays more vital role in governing fuel economy and emission quality of IC engines due to the wide application of direct injection system in automotive engines. High temperature fuel spray, namely flash boiling spray, has been documented to improve fuel atomization and evaporation with less energy consumption compared with high pressure fuel spray. It is because the hot exhaust gas and coolant are two potential energy sources can be used to heat the fuel. Most of existing research works of flash boiling spray focus on investigating the spray behavior outside the nozzle, and limited studies can be found about the in-nozzle superheated flow. In this study, a two-dimensional transparent slit nozzle was designed to reveal the in-nozzle flow under various superheated conditions. Both internal flow and near-nozzle fuel jet were investigated using high-speed backlit imaging technique to acquire a better understanding of the primary breakup process of flash boiling sprays. The slit thickness was 40μm with well-adjusted nozzle length and inlet corner radius to investigate the effects of nozzle configuration. The ambient pressure ranged from 40kPa to 190kPa, and fuel temperature varied from 41°C to 71°C, which produced a wide range of superheated conditions. N-pentane was chosen as test fluid with an injection pressure of 0.6MPa. Experimental results showed that the bubbles occurring inside the nozzle near the nozzle exit affected the near-nozzle fuel jet characteristics. Stronger superheated conditions resulted in larger in-nozzle bubbles, which facilitated the jet break-up process significantly. Longer nozzle and nozzle with sharp inlet corner led to larger inner bubble volume fraction and narrower liquid core of near-nozzle fuel jet. In summary, the effects of nozzle configuration on in-nozzle flow and near-nozzle fuel jet were revealed with more fundamental understanding of the primary breakup process of flash boiling sprays.

Rotor spinning transfer channel design optimization via computational fluid dynamics

The conventional rotor spinning unit generates flow vortices in the transfer channel upstream region which affect the fiber configuration and consequently yarn properties. Geometry and spinning parameters such as transfer channel length, inlet width, rotor outlet pressure, opening roller speed, and diameter were found to be key parameters influencing airflow characteristics. To reduce the flow vortices in the upper stream region, modifications of the transfer channel were proposed, and their airflow fields were analyzed using computational fluid dynamics. Three designs were studied: a round transfer channel inlet, a bypass channel for extra air supply, and one with both the bypass and the round inlet. Analysis of airflow revealed that the design with both round transfer channel inlet and a bypass proved to be very effective in properly directing the flow and minimizing vortices. The design was also characterized by smoother velocity streamlines and maximum mass flow across the transfer channel. A conventional rotor spinning unit was modified in which a round transfer channel inlet corner and a bypass channel were utilized to conduct the experimental tests. Three sets of yarn samples were produced using the conventional and modified rotor spinning units under different rotor speed conditions. Yarn properties were tested. Properties such as tenacity, CVm%, and thin and thick places of the spun yarns produced by the new design improved compared to that of the conventional yarn.

Numerical investigation of the flow over a model transonic turbine blade tip

Direct numerical simulations (DNS) are used to investigate the unsteady flow over a model turbine blade tip at engine-scale Reynolds and Mach numbers. The DNS are performed with an in-house multiblock structured compressible Navier–Stokes solver. The particular case of a transonic tip flow is studied since previous work has suggested that compressibility has an important effect on the turbulent nature of the separation bubble at the inlet to the tip–casing gap and subsequent flow reattachment. The flow is simulated over an idealized tip geometry where the tip gap is represented by a constant-area channel with a sharp inlet corner to represent the pressure side edge of the turbine blade. The effects of free-stream disturbances, cross-flow and the pressure side boundary layer on the tip flow aerodynamics and heat transfer are studied. For ‘clean’ inflow cases we find that even at engine-scale Reynolds numbers the tip flow is intermittent in nature, i.e. neither laminar nor fully turbulent. The breakdown to turbulence occurs through the development of spanwise streaks with wavelengths of approximately 15 %–20 % of the gap height. Multidimensional linear stability analysis confirms the two-dimensional base state to be most unstable with respect to spanwise wavelengths of 25 % of the gap height. The linear stability analysis also shows that the addition of cross-flows with 25 % of the streamwise gap exit velocity increases the stability of the tip flow. This is confirmed by the DNS, which also show that the turbulence production is significantly reduced in the separation bubble. For the case when free-stream disturbances are added to the inlet flow, viscous dissipation and the rapid acceleration of the flow at the inlet to the tip–casing gap cause significant distortion of the vorticity field and reductions of turbulence intensity as the flow enters the tip gap. The DNS results also suggest that the assumption of the Reynolds analogy and a constant recovery factor are not accurate, in particular in regions where the skin friction approaches zero while significant temperature gradients remain, such as in the vicinity of flow reattachment.

Fracture strength of glass chips for high-pressure microfluidics

High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10−5 m s−1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

Experimental Investigation of Flow Distortion in an Auxiliary-Power-Unit-Style Inlet System

The flowfield inside a rectangular-sectioned 90 deg bend was studied using laser Doppler velocimetry. The bend used in the present study was part of an auxiliary power unit for helicopter engines. The results showed strong tangential velocity gradients near the inlet of the 90 deg bend and reverse flow at the inlet corner near the top wall and the outer wall. Rapid mixing was observed as the flow traveled through the bend. Additionally, measurements were acquired at constant-theta planes with a high spatial resolution to better resolve the secondary flow structures. The geometric asymmetry in the circular-to-rectangular transition duct was measured, and the effect of this asymmetry on the downstream flowfield was characterized. Results showed that the asymmetry of the transition duct led to asymmetric flow through the bend. This was one of the few studies that showed how a small change in the upstream geometry yielded very different flow patterns, which were eventually mixed out by the exit of the bend, and thus provided some guidance on acceptable manufacturing tolerances.