Flow Angle Research Articles

Research on Energy Loss of Optimization of Inducer–Impeller Axial Fit Dimensions Based on Wave-Piercing Theory

With the development of modern fluid machinery, the energy density of pumps is gradually being improved, and at the same time, higher demands are being placed on the cavitation performance, hence the introduction of the inducer and centrifugal impeller to form a dynamic–dynamic series structure. However, there are strict constraints on the axial size of pumps in fields such as firefighting and aerospace. The traditional empirical formula no longer satisfies the need to fit the axial dimensions between the induced wheel and the impeller at high velocities. Therefore, based on the wave-piercing theory, the drag reduction coefficient is introduced to explore the optimal axial fit size from the perspective of energy characteristics. This paper focuses on the influence of the inducer’s wake on the energy characteristics of downstream impellers, and conducts the following research: by adjusting the axial matching dimensions between the upstream inducer and the centrifugal impeller in the initial model, ten sets of axial distance models with matching dimensions of KD are designed, and the drag reduction coefficient is embedded to determine the optimal axial distance. The results show that the optimal axial distance is 0.2D, which is far lower than the axial distance value of 0.42D obtained from the traditional empirical formula for axial matching dimensions. Meanwhile, this paper uses tangential velocity, the inlet flow angle of the impeller, entropy production theory, and other indicators to analyze the internal energy loss of the high-speed vehicular fire pumps one by one. All of them confirm that the impeller in the high-speed vehicular fire pump has the lowest energy loss and optimal performance at an axial distance of 0.2D. Specifically, at this axial distance, the head can reach 259 m, and the hydraulic efficiency is as high as 83.62%. Thus, the feasibility of determining the axial placement of the impeller using the drag coefficient is validated. This research provides new insights into determining the axial coordination dimensions between the inducer and the impeller.

An interlaboratory study for assessing repeatability and reproducibility of the data generated by rotating drum powder rheometers

The National Institute of Standards and Technology (NIST) organized an interlaboratory study to assess the repeatability and reproducibility of the data generated by two commercially available rotating drum powder rheometers namely, Granudrum and Revolution Powder Analyzer. Part 1 of this interlaboratory study focuses on the Granudrum rheometer. In total, thirteen laboratories comprised of industry, academia, and a national laboratory participated in this study. A nickel-based alloy, a titanium alloy, and a stainless-steel alloy in powder forms were tested, and an analysis of variance (ANOVA) model was used to rank the contributions of the study factors to the observed variability in the data. First, a maximum of five study factors were considered: material, sample, rotation speed, test, and participant (lab), which provides the ability to assess interactions, such as between lab and rotation speed and lab and material. The ANOVA results indicate that the ‘Flow Angle’ data showed 6% of its variation attributable to repeatability and 5% to reproducibility, whereas the ‘Cohesive Index’ data showed 21% of its variation attributable to repeatability and 17% to reproducibility. Next, because using the different rotation speeds and materials can add significant variability to the overall data, we also present separate ANOVA results for each combination of rotation speed and material. These results provide further insight into the repeatability and reproducibility of the Granudrum-generated data.

Non-Zero Power Flow Angles in Surface Acoustic Wave Resonators for Transverse Mode Suppression

Non-Zero Power Flow Angles in Surface Acoustic Wave Resonators for Transverse Mode Suppression

Shape optimization of annular transonic thrust nozzles via genetic algorithm and adjoint method

In this research, the idea of combining the genetic algorithm and adjoint method was proposed to leverage the benefits of both approaches to improve the accuracy of thrust nozzle shape optimization. Although the genetic algorithm can search the entire design space to approach the global optimum, its computational cost increases considerably with the number of design variables. Meanwhile, the adjoint method is unaffected by the design variables, but it cannot achieve the global optimum directly and relies on the initial guess geometry. To address these challenges, a genetic algorithm was initially employed to approximate the global optimal geometry of a thrust nozzle with a conical center body parameterized by a Bezier curve. A MATLAB code integrated the geometry parameterization, genetic algorithm, and Fluent R2 2021 flow solver. The resulting geometry was then considered as the initial guess for the adjoint method, which accurately achieved the final optimal geometry with increased control points. The genetic algorithm aimed to maximize the thrust coefficient as the objective function, while the adjoint solver aimed to minimize the axial velocity variance at the nozzle outlet as the cost function. Three distinct constraints were incorporated in the optimization process, and the influence of the center body shape on the results was thoroughly examined to consider all possible geometries throughout the optimization procedure. The findings revealed that the conical center body effectively adjusted the flow angle at the exit, significantly affecting the thrust force. Both optimization steps reduced the average velocity and increased the average pressure at the nozzle exit, enhanced the mass flow rate, and finally increased the thrust force. The genetic algorithm and adjoint method contributed to 3 % and 0.6 % increases, respectively, in the thrust force, resulting in a thrust coefficient of 96.15 % for the final optimized nozzle.

PRODUCTION OF Ni-HARD ALLOY POWDERS BY GAS ATOMIZATION

Ni-Hard cast iron materials are frequently used in equipment where high wear resistance is required in industrial applications. Generally, Ni-Hard is produced by conventional casting techniques. In this study, it was aimed to produce Ni-Hard powders to produce Ni-Hard cast iron materials with additive manufacturing techniques. To produce spherical and fine raw materials for additive manufacturing techniques, the gas atomization technique with a close-coupled nozzle system was preferred for the production of Ni-Hard powders. Ni-Hard alloy was melted in a high-frequency 10kW induction furnace under a protective atmosphere integrated into the gas atomization system. During the atomization process, 150 °C superheating was applied to prevent the liquid metal from freezing and clogging the melt delivery tube. In terms of the continuity of the atomization process, the negative pressure (aspiration pressure) values formed at the end of the melt delivery tube at different gas pressures were measured. An aspiration pressure of -50 mbar was obtained under an atomization pressure of 35 bar. Particle size distributions, hall flow behaviour and angle of repose properties of the produced powders were determined. Finally, the characterization of the powders was carried out by scanning electron microscopy. It was determined that the powders obtained as a result of atomization exhibited a spherical morphology and a narrow size range. The Hall flow rate test result of Ni-Hard powders was measured as 22 seconds for 50 g.

A comparative study of two fish farm layouts under pure current conditions

High-value finfish, such as the Atlantic Salmon (Salmo Salar), are typically raised in multi-cage fish farms. The fish farm needs to be designed with sufficient strength and water exchange. A coupling algorithm between two open-source numerical toolboxes, OpenFOAM and Code_Aster, is utilized in this work for fluid-structure interaction analysis of fish farms. The two different fish farm layouts, i.e., the 2 × 3 array layout and the Honeycomb layout, are investigated in this study under pure current conditions with different flow angles. The fluid and structure responses of the two fish farm layouts are compared, in terms of flow field in and around fish farms, tensions in anchor lines, drag force, and total cultivation volume. The present results suggest that, compared to the 2 × 3 array layout, the Honeycomb layout has a smaller covered area and reduced environmental loads, which are making this layout advantageous for fish farming.

DESIGN, MULTI-POINT OPTIMIZATION AND ANALYSIS OF DIFFUSIVE STATOR VANES TO ENABLE TURBINE INTEGRATION INTO ROTATING DETONATION ENGINES

Abstract Pressure gain combustion is considered a possible path toward improved thermal cycle efficiency and reduced carbon emissions. However, ad-hoc turbine designs are required to maximize the thermodynamic potential; the new turbomachinery should be suited for the oscillations in flow conditions generated by the detonation combustor, which are very different from conventional gas turbines. This manuscript investigates the design, optimization, and analysis of diffusive stator vanes operating under large inlet flow angles in the high subsonic regime. First, the design methodology is outlined, focusing on the geometric requirements to ingest high Mach number flow and the parametric modeling of the endwall and the 3D vane pressure and suction sides. Then, the impact of the inlet flow angle on the flow field and vane design is studied through a multi-point, multi-objective optimization with three different inlet angles, performed using steady Reynolds Averaged Navier Stokes simulations. Remarkable reductions in pressure loss and stator-induced rotor forcing are attained while maintaining an extensive operating envelope and high flow turning. Moreover, several design guidelines are provided based on the analysis of the optimized geometries. Finally, the effectiveness of the proposed methodology is verified with an unsteady assessment of the baseline and optimized vane designs

Improving the Hydrodynamic Performance of Underwater Tags for Blue Shark Monitoring

The use of tag devices in marine environments has become indispensable in attaining a better understanding of marine life and contributing to conservation efforts. However, the successful deployment and operation of underwater tags both depend significantly on their hydrodynamic characteristics, particularly their resistance to motion and stability in various environmental conditions. Herein, a comprehensive study on the hydrodynamic characteristics and optimization of an underwater tag designed for monitoring blue sharks is presented. Firstly, a validation process is conducted by comparing the computational fluid dynamics (CFD) results with the experimental data from Myring’s study, focusing on the resistance characteristics of the tag’s body and the impact of various operational conditions. Subsequently, the validated CFD model is applied to assess the hydrodynamic performance of the tag under different flow conditions, velocities, and angles of attack. Through iterative simulations, including mesh independence studies and boundary condition adjustments, the study identifies key parameters influencing the tag’s resistance and stability. Furthermore, the paper proposes and implements design modifications, including the incorporation of stabilizing fins, aimed at minimizing resistance and improving the tag’s equilibrium position. The effectiveness of these design enhancements is demonstrated through a comparative analysis of resistance and pitching moments for both preliminary and optimized tag configurations. Overall, the study provides valuable insights into the hydrodynamic behavior of underwater tags and offers practical recommendations for optimizing their design to minimize interference with the movement of tagged marine animals.

A shock loss reduction method for the low-pressure rotor of a vaneless counter-rotating turbine using circulation redistribution

This paper proposes the circulation redistribution for the low-pressure (LP) rotor of a highly-loaded vaneless counter-rotating turbine (VCRT) to reduce the LP shock losses. The method is to decrease the mid-span circulation and increase the tip circulation at the exit of the LP rotor with unchanged high-pressure (HP) and LP power output. The LP Blade-to-Blade flow field can be considered as a Laval nozzle model. And the high static pressure drop from the throat to the exit results in strong trailing edge (TE) shocks near the LP mid-span. Also, the suction side TE shock (ST) and the reflected shock of the pressure side TE shock (RPT) near the LP mid-span merge into a relatively strong shock very close to the TE. These two factors result in high shock losses. To reduce the shock losses under the design condition, decreasing the stagger angle and the blade exit angle near the LP mid-span are adopted to reduce the LP mid-span exit circulation. This changes the throat area to exit area ratio near the LP mid-span, prompting the actual static pressure drop from the throat to the exit to be reduced and closer to the theoretical value, so that the TE shock strength is reduced. Besides, the intersection of the RPT and the ST is delayed owing to the improved flow angle distributions near the TE, further contributing to the LP mid-span shock loss reduction. Since the LP power output is decreased and the LP tip-leakage flow (TLF) losses are far lower than the HP TLF losses, increasing the stagger angle and the blade exit angle in LP tip regions are employed to increase the LP exit circulation and decrease the HP exit circulation in tip regions. Then the HP and LP efficiency are both raised with unchanged HP and LP power output after optimizing the blade profiles near the mid-span and in tip regions of the LP rotor. The remarkable thing is that the TE shock strength in LP tip and root regions are both reduced after improved because of the decreased ratio of the exit area to the throat area. And the intersection of the RPT and the ST in LP tip and root regions are also both delayed, leading to reduced shock losses. The reduced TE shock losses along the whole LP span appreciably raise the LP and VCRT efficiency by 0.96% and 0.32% respectively.

Numerical study of the distribution of sprayed particle deposition in different human nasal cavity

This article numerically investigates the propagation of nasal sprayer particles to improve drug delivery through the nasal cavity. Topical nasal sprays are among the generally dictated therapeutic agents for sinus disorders in humans. However, the inconsistency of instructions indicates a lack of definitive knowledge of the best methods for nebulizing drugs. This study suggested nasal spray angles that could improve local drug delivery to the affected area compared to common spray methods. In this study, various particle diameters and aerosol flow angles are examined to evaluate the optimal efficiency of drug supply into the nasal cavity. Computational simulation of a particle-laden flow is performed in the nasal cavity of a healthy patient and a patient with rhinitis. The numerical results of this work open up new possibilities for proposing an alternative user-friendly plan that can essentially improve local drug delivery to the human nasal cavity.

A study of angle parametric optimization of the composite honeycomb on turbine blade tip

To reduce the secondary flow loss of the high-pressure turbine caused by the tip leakage flow, the design of the composite honeycomb tip has been experimentally and numerically examined in this study. The arrangement angle of the composite honeycomb is defined and optimized using the radial basis function and genetic algorithm. The tip flow field of the high-pressure turbine blade with a 2.128 mm clearance is simulated by CFX 18.0, and the arrangement angle of the composite honeycomb is optimized to obtain a lower loss. Moreover, the flat tip, basic honeycomb tip, and optimized honeycomb tip are tested in a low-speed cascade test facility. The results show that the vortices and radial velocity induced by the honeycomb structure cavity increase the kinetic energy loss of the leakage flow and reduce the leakage flow rate. Compared with the basic honeycomb, the optimized honeycomb has a supplemental blocking effect on the tip leakage flow by reducing the crosswise pressure gradient in the blade tip. The optimized honeycomb also changes the outlet angle of the leakage flow in the tip clearance, reduces the leakage vortex, and the total pressure loss is further reduced by 2.5%.

Endwall Contouring for Improving Aerodynamic Performance in a High-Pressure Turbine Cascade

Abstract The endwall contouring has proven to be an effective technique in controlling the impacts of secondary flow within turbomachinery. A baseline cascade with the original axisymmetric endwall (BASE) has been redesigned with a non-axisymmetric contoured shroud endwall (EW-B1), and both configurations are investigated through experimental and numerical methods. The endwall is profiled through the B-spline surface method with the purpose of reducing the overall total pressure loss at the exit. The experimental studies involve flow field traverses at the exits of both cascades. Numerical calculations are conducted to gain a deeper understanding of the effects of endwall contouring. The numerical results exhibit good agreement with the experimental results, both in loss and flow angle. The results demonstrate a significant reduction in losses and secondary kinetic energy in EW-B1. The causes of the high-loss region and the overturning near the shroud are analyzed using computational fluid dynamics (CFD), as well as the changes in pressure fields and vortex structures within the cascade passage. The weakening of the horseshoe vortex and the radial movement of the passage vortex are confirmed to be the primary reasons for losses reduction.

Erosion Resistance of Casing with Resin and Metallic Coatings in Liquid–Solid Two-Phase Flow

Protective coatings are typically applied to enhance their resistance to corrosion. There is considerable research on the corrosion resistance of coated casings. However, few research studies have focused on the erosion resistance on coated casings. In this work, the erosion resistance of resin- and metallic-coated casings in liquid–solid two-phase fluids were investigated using a self-made erosion facility. The results show that the resin coating tends to peel off the material base in the form of brittle spalling or coating bulge in the high-speed sand-carrying liquid. Both resin and metallic coatings were broken through within 20 min in a liquid–solid two-phase flow environment. Compared to resin coatings, metallic coatings exhibit weaker erosion resistance in similar liquid–solid flow. Through the analysis of experimental results and fitted curves, empirical constants for materials and sand content influencing factors were determined using non-dimensional processing. The erosion prediction model of metallic coatings and resin coatings was established based on the ECRC/Zhang model with the change in flow rate, angle, and sand content. This research contributes to a better understanding of the erosion resistance performance of casings used in oil and gas fields, thereby contributing to potential improvements in their production.

Observation of Kinetic Alfvén Waves inside an Interplanetary Coronal Mass Ejection Magnetic Cloud at 1 au

Recent advancements have significantly enhanced our grasp of interplanetary coronal mass ejections (ICMEs) in the heliosphere. These observations have uncovered complex kinematics and structural deformations in ICMEs, hinting at the possible generation of magnetohydrodynamic (MHD) and kinetic-scale waves. While MHD-scale waves in magnetic clouds have been explored, understanding the dynamics of kinetic-scale mode waves remains challenging. This article demonstrates the first in situ observation of kinetic Alfvén waves (KAWs) within an ICME’s magnetic cloud, notably near the heliospheric current sheet–ICME interaction region, close to the reconnection exhaust. Analysis indicates a distinctive negative bump in the estimated normalized magnetic helicity (σ m = −0.38) around the gyrofrequency spread, indicating a right-handed polarization of the wave. Furthermore, examination across flow angle (θ VB) within the frequency domain reveals a specific zone (90°–135°) showcasing negative helicity fluctuations, confirming the presence of KAWs. Moreover, we noted a significant rise in temperature anisotropy in the vicinity, indicating the role of KAWs in plasma heating. Identifying KAW challenges established notions about ordered magnetic clouds and raises questions about energy transfer processes within these structures. This finding opens the door to a deeper understanding of energy transfer mechanisms within traditionally nondissipative regions and invites further exploration of low-beta plasma heating and the interactions between waves and particles in magnetic clouds.

Influence of wind directionality on the three-dimensional distortion of buffeting force on a streamlined bridge deck: Insight into the pylon interference effect

The present work aims to experimentally investigate the influence of wind directionality on the three-dimensionality of buffeting force on a streamlined bridge deck, considering the pylon interference effect (PIE). The pylon has an obvious impact on the downstream flow structure under the skew wind, influencing the aerodynamic loads acting on the bridge deck. The results show that the most dangerous wind direction exists at 30° for the downstream bridge deck, indicating the invalidation of the traditional “cosine rule.” It indicates that the lift force will be amplified due to the PIE, depending on the yaw angle of the oncoming flow. When turbulence passes through the pylon, the large-scale eddies in the wake region will be broken into small-scale eddies, attenuating the integral length scale in comparison with that of the free-stream turbulence. Consequently, the lift spectrum and corresponding three-dimensional aerodynamic admittance (AAF) increase in the high-frequency domain, resulting in the decrease in the spanwise correlation under the skew wind. Notably, the two-dimensional (2D) AAF indicates that the 2D distortion effect of turbulence on the lift increases in the wake region, causing the 2D AAF to decay rapidly in the high-frequency domain.

Development of the Universal Air Collector Design for Measuring the Flow Rate of Swirling Air Flow Using an Integral Thermoanemometer

Measurement of the swirling air flow rate and average speed of air at air distribution units of ventilation systems is a rather difficult task due to the fact that the air flow enters the measuring device at different angles. As a result, significant measurement errors can occur when using point thermoanemometers or other flow meters. The use of integral anemometers facilitates the measurement process. However, it is necessary to eliminate the errors associated with changes in the angle of the air flow to the sensing element of the measuring device. To do this, it is necessary to ensure a rectilinear structure of the air flow using a transitional air collector and rectifier. The aim of this paper is to develop a design of an air collector device that will allow to measure the flow rate of a swirling air flow. The objectives of the paper are to optimize the geometrical parameters of the air collector to ensure a rectilinear flow, minimize its dimensions and aerodynamic drag. The correctness of the air collector design was evaluated by matching the calibration characteristic of the probe of an integral thermoanemometer in the presence of a vortex diffuser in front of the air collector and in its absence. The proposed device has a rectangular shape and consists of a receiver, a rectifying grid, a chamber, an accelerating and stabilizing section, at the outlet of which a thermoanemometer probe is installed. The receiver and the accelerating section are tapered along their length, while the chamber and the stabilizing section have a constant cross-section. The rectifying grid is installed inside the chamber and has a square-shaped honeycomb structure. Several options of the air collector design with different geometrical parameters were studied using computer modelling. The dependence of aerodynamic drag on air flow was plotted. The optimal design of the air collector was chosen, for which a life-size physical model was created. The calibration characteristics of the measuring probe with an air collector were experimentally obtained when a swirling air flow was applied. The developed universal air collector allows the air flow rate measurement at the outlets of almost any air distribution devices of ventilation systems of buildings.

Transient Characteristics of Fluidic Pintle Nozzle in a Solid Rocket Motor

The fluidic pintle nozzle, a new method to control the thrust of a solid rocket motor, has been proposed in recent years by combining the pintle with the aerodynamic throat (fluidic throat). The study of static characteristics has proved that it has a remarkable effect on thrust control. To study the transient characteristics of the fluidic pintle nozzle, 2D transient simulations of a fluidic pintle nozzle propulsion system were conducted, employing dynamic meshing techniques. The Reynolds-averaged Navier–Stokes equations were meticulously solved, implementing a k–ω SST turbulence model. The thrust control principle of the fluid pintle nozzle was studied, and the wave structure was summarized. The transient characteristics of the secondary flow opening, secondary flow closing, pintle moving forward (pressure rise), and pintle moving backward (pressure drop) were obtained, and the effects of the injection angle and injection port position were studied. The response process after injection can be roughly divided into three stages: pressure propagation, pressure oscillation, and equilibrium stability, with time distributions of 0.4%, 5.39%, and 94.21%, respectively. In the process of the pintle moving forward, the rate of combustion chamber pressure increases and thrust decreases gradually because of the arc wall of the nozzle throat upstream, and the process of throats moving backward is just the opposite. Compared with the condition with a maximum throat opening and no secondary flow, the thrust of the condition with a minimum throat opening and a 0.3-flow-ratio secondary flow is increased by 80.95%. Under conditions of constrained flow ratio, the injection angle of the secondary flow ostensibly exerts negligible influence on the dynamic modulation of thrust. Nevertheless, it remains evident that a reduction in throat opening accentuates the impact of reverse injection. Furthermore, the proximity of the injection port to the head of the pintle is directly proportional to the efficacy of thrust control.

Heat Transfer and of Flow Structure of a Turbine Blade’s Air-cooled Leading Edge Considering Different Hole Shapes and Additional Flow Angles

Heat Transfer and of Flow Structure of a Turbine Blade’s Air-cooled Leading Edge Considering Different Hole Shapes and Additional Flow Angles

Application of cohesive soil flow limit and slope critical flow angle

To investigate the relationship between moisture content in cohesive soils during spontaneous liquefaction and their corresponding critical slope failure angles. This study modified the liquid limit test apparatus originally developed by A. Atterberg in 1911, adapting it into a liquid-flow limit test apparatus. On-site soils from three actual cases of slope failures in Xiaolin Village, Jiasian District, Kaohsiung City, as well as soils from slope failures along the banks of Meilong River and Zengwun River were used for experiments involving different soil moisture content and slope failure angles. Based on the experimental findings, the moisture content which cohesive soils undergo spontaneous liquefaction was designated as the Flow Limit (FL), corresponding to the downslope angle at which circular failure occurs. This value represents the critical sliding angle at which spontaneous liquefaction occurs as a results of soil saturation. It also represents the maximum slope angle for exposed mudrock or clay slopes, and establishes the critical slope angle for vegetated slopes. Beyond this critical FL angle, all vegetation is susceptible to loss due to soil liquefaction. Furthermore, this study conducted FL tests on soils from thirteen tree holes in Kaohsiung City, two mountain slopes in Fengshan District, and the silty clay responsible for property damage and injuries during a landslide in Yanchao District on September 29, 2016, as a means of validation. The consistent test results observed reaffirm that different soils exhibit similar spontaneous liquefaction angles and flow limit behavior. These FL test results demonstrate a consistent pattern, reinforcing the notion of distinct curve characteristics that can be replicated across diverse soil compositions.

Design, Modeling, and Control of a Composite Tilt-Rotor Unmanned Aerial Vehicle

Tilt-rotor unmanned aerial vehicles combine the advantages of multirotor and fixed-wing aircraft, offering features like rapid takeoff and landing, extended endurance, and wide flight conditions. This article provides a summary of the design, modeling, and control of a composite tilt-rotor. During modeling process, aerodynamic modeling was performed on the tilting and non-tilting parts based on the subcomponent modeling method, and CFD simulation analysis was conducted on the entire unmanned aerial vehicle to obtain its accurate aerodynamic characteristics. In the process of modeling the motor propeller, the reduction of motor thrust and torque due to forward flow and tilt angle velocity is thoroughly examined, which is usually ignored in most tilt UAV propeller models. In the controller design, this paper proposes a fusion ADRC control strategy suitable for vertical takeoff and landing of this type of tiltrotor. The control system framework is built using Simulink, and the control algorithm’s efficiency has been verified through simulation testing. Through the proposed control scheme, it is possible for the composite tiltrotor unmanned aerial vehicle to smoothly transition between multirotor and fixed-wing flight modes.