Steady Reynolds-averaged Navier-Stokes Equations Research Articles

Effects of interface model on performance of a vortex pump in CFD simulations

That the predicted head of a vortex pump is higher than that measured experimentally is very common in simulations of turbulent flow in such pumps. To identify why, reported here is a study of the turbulent flow of water in a vortex pump with a specific speed of 76 and fluid domains with 1/8-impeller and whole-impeller geometrical models and smooth walls using the 3D steady Reynolds-averaged Navier–Stokes equations, the standard k–ɛ model, and a scalable wall function in ANSYS CFX 2019 R2. The results show that the aforementioned phenomenon is related to the choice of interface model. With the 1/8-impeller model, the head predicted by the frozen rotor model agrees with the experimental head. By contrast, the transient rotor model provides a reasonably accurate head against the experimental head but requires huge computing resources and overestimates the pump efficiency, and the stage model is unsuitable for predicting the head of the pump. The flow patterns in the vaneless chamber and impeller predicted with the 1/8-impeller model are more uniform because of artificial fluid mixing on the interface than those predicted with the whole-impeller model by using the frozen rotor model, and the flow patterns predicted with the whole-impeller model by using the transient rotor model are in between. The hydraulic performance of the pump is predicted with the 1/8-impeller model and frozen rotor model at various viscosities, and the flow-rate, head, and efficiency correction factors are determined and correlated with the impeller Reynolds number.

Heat transfer enhancement of supercritical carbon dioxide in eccentrical helical tubes

A type of eccentrical helical tube (EHT) was proposed for more efficient and compact supercritical carbon dioxide (SCO2) heat exchangers in refrigeration systems. The forced convective heat transfer of SCO2 flowing in three designed eccentrical helical tubes with pitches of 25, 50 mm and eccentricities of 0.9, 1.5 mm was simulated by using the three-dimensional steady Reynolds-averaged Navier-Stokes equations, shear stress transport turbulence model and energy equation in ANSYS CFX 2019 R2 at mass fluxes of 200, 400 kg/m2s, inlet pressures of 8, 9 MPa, outwards wall heat fluxes of 12, 24 kW/m2. The flow and heat transfer models were validated in the plain tube with experimental mean heat transfer coefficient and empirical Darcy friction factor. Influences of pitch, eccentricity and operational conditions on heat transfer enhancement were identified. Flow pattern, heat transfer mechanism and vortex kinematics were clarified. Heat transfer enhancement of SCO2 in the EHT was compared with water and air in the EHT, twisted elliptical tube and conical tube, respectively. A pitch of 25 mm and eccentricity of 1.5 mm at 6 mm tube diameter can achieve a better thermal-hydraulic performance. A higher SCO2 mass flux raises Nusselt number and reduces friction factor, a higher inlet pressure and a larger wall heat flux reduces Nusselt number but increases friction factor. The ratio f/f0 is ranged in 2.52–1.68 and drops off with increasing inlet pressure and nominal Reynolds number, the ratios Nu/Nu0, ψ and η curves show a concave shape near the pseudocritical point ranged in 1.68–1.06 and 1.06–1.55, 1.23–0.83 and 0.83–1.30, 0.67–0.50 and 0.50–0.92 at the pitch of 25 mm and eccentricity of 1.5 mm, inlet pressure of 8 MPa, mass flux of 400 kg/m2s, and wall heat flux of 12 kW/m2. A helical flow pattern with a core flow occurs in the EHT, the local heat transfer coefficient can be correlated to absolute helicity. The high-wall shear stress on the ridge of the EHT is responsible for the heat transfer enhancement. The f/f0 value of the EHT is in between the twisted elliptical tube and the conical tube, but the Nu/Nu0 and ψ values are comparable.

Mechanisms of lobed jet mixing: Comparison of bilinear, rectangular, and circular lobed mixers

In this study, bilinear lobed mixers (BLMs), rectangular lobed mixers (RLMs), and circular lobed mixers (CLMs), with two sectional area ratios of the bypass channel to the core channel, were configured while maintaining the same lobe angle, lobe height, lobed nozzle length, mixing duct length, and core sectional area. Using three-dimensional steady Reynolds-averaged Navier–Stokes equations and the SST k–ω turbulence model, numerical simulations of jet mixing in these lobed mixers at three velocity ratios of the bypass stream to the core stream were performed. The jet mixing characteristics and performances of the three types of lobed mixers were analyzed. Through a comprehensive and in-depth analysis of the jet-mixing flow fields of the three types of lobed mixers, more universal mechanisms of lobed jet mixing were revealed. Systematic and meaningful conclusions were drawn from four aspects: the formation and evolution mechanisms of the cross flow, longitudinal vortices, heat and mass convection, and orthogonal vortex strip. The findings from this study hold significant implications for the development of lobed mixers and exploration of lobed jet-mixing mechanisms.

Impact of eave and roof pitch on cross ventilation for an isolated building with sawtooth roof

An eave refers to an extension attached to the building roof to protect the interior space from direct solar radiation and improve the performance on cross ventilation. In this study, the impact of eave inclination angle and roof pitch of an isolated sawtooth roof building on cross ventilation were investigated. The eave configurations at either windward or leeward openings were included. 3D steady Reynolds-Averaged Navier-Stokes (RANS) equation in combination with the Shear-Stress Transport model (SST k-ω model) was used for the Computational Fluid Dynamics (CFD) simulations. Grid sensitivity study was carried out and the performance of cross ventilation was evaluated based on the non-dimensional velocity magnitude, spatial distribution of pressure coefficient as well as the ventilation rate of the building. For the simulation model with 55° roof pitch, it is observed that a region with high velocity magnitude formed on top of the leeward eave due to the higher roof pitch and presence of the leeward eave. Results also indicated that the building model with 90° leeward eave and 55° roof pitch has the highest increment in ventilation rate which is 7.16%. On the other hand, the building model with 90° windward eave has the highest pressure coefficient because more blockage of airflow is caused by a steeper roof as the roof pitch of the building increases. Furthermore, the building model with 90° leeward eave shows a larger region with negative pressure at the leeward façade indicating higher airflow leaving the leeward opening. Therefore, the airflow behavior and characteristic are both dependent on the roof pitch and eave inclination angle for a naturally ventilated building.

Parametric optimization of vortex generator configuration for flow control in an intake duct for waterjet propulsion

Vortex generators (VG) are simple miniature devices that suppress flow separation in aeronautical elements. In this study, VG device operation in a submerged flush waterjet inlet was numerically investigated to improve the flow quality entering the jet pump at low Inlet Velocity Ratio (IVR). Steady Reynolds-averaged Navier-Stokes equations are solved using the SST k-ω turbulence model and used to simulate the flow field, with the effects of the orientation, angle of attack, height and installation position of VGs thoroughly analyzed. The hydrodynamic performance of the intake duct was assessed over the operational range. The results show that VGs arranged in a divergent configuration better suppress flow separation. The zonal magnitude of the high turbulent kinetic energy on the ramp side was reduced, with the non-uniformity in the pump face plane reduced from 0.41 to 0.26. Excessive angles of attack and VG heights have negative effects. Through parametric studies, VGs were found to have best performance in the target duct with an angle of attack of 40⁰ and a height measuring 20% of the bottom boundary layer thickness. In addition, VGs installed along the keel of a ship can effectively suppress the flow distortion and improve the overall efficiency of the intake duct.

Convective heat transfer in a thermal chimney for freshwater production in geothermal total flow systems

The convective heat transfer of air in a laboratory-scale thermal chimney with rectangular cross-section of constant area and two row electrical heaters simulating two heat exchangers was studied experimentally and numerically at 60–200 ℃ nominal temperatures of the top row heaters, 100 ℃ of the low row heaters and 20 ℃ ambient temperature to verify our design concept on freshwater production in geothermal total flow systems. Computational fluid dynamics simulations of air convective heat transfer were performed in ANSYS 2019R CFX based on the three-dimensional, steady Reynolds-averaged Navier-Stokes equations, Boussinesq buoyancy model, k-ω turbulence model, and energy equation. The thermal radiation between heater surfaces and chimney walls was considered. The overall thermal and heat transfer characteristics, temperature and flow fields in the chimney were obtained. Effects of boundary condition of heater surface and thermal radiation between two row heaters on heat transfer were discussed. The thermal characteristics of the chimney with two row heaters are better than that with single row heaters. The predicted thermal power and convective Nusselt number agree with the experimental data, and the convective Nusselt number of the low row heaters is enhanced by (11.6–29.8) % compared with the single row heaters. The optimal operating nominal temperature of top row heaters should be higher than 140 ℃, and the optimal centre-to-centre row gap ratio is 5. Multiple jets in the gaps among the heaters and temperature jump crossing each row were observed. The maximum velocity and temperature jump rise with increasing heater nominal temperature.

Relative Importance of Certain Factors Affecting Air Exchange in a High-Altitude Single-Heading Tunnels Based on the Numerical Simulation Method

Single-heading tunnels in underground metal mines have high air pollutant concentrations, chaotic airflow, and low pollutant diffusion efficiency in high-altitude areas, resulting in poor air exchange. Based on Pulang copper mine (China), a computational fluid dynamics case using the steady Reynolds-averaged Navier–Stokes equations with a k-omega turbulence model was developed to study certain factors influencing the air exchange of single-heading tunnels, and was combined with an orthogonal experimental method to simulate the mean age of air (MAA) under different working conditions. This study revealed the ranking of the importance of some factors on the air exchange via sensitivity analysis. The MAA generally increases with the increasing distance between the duct and the heading face and the increasing diameter of the oxygen supply duct. This study’s optimal distance and diameter can reduce MAA by 14.7% and 9.9%, respectively. Placing the oxygen supply duct and the duct on the same side and using an 800/1000 mm inner diameter duct can effectively reduce the MAA by 6.7% and 4.2%, respectively, in this study. The findings of this study can optimize air exchange in the Pulang copper mine, and can also be referenced for the optimization of air exchange in high-altitude highway or railway tunnels being excavated.

Gas turbine endwall film cooling and heat transfer characteristics with a multi-cavity slashface gap design

A novel multi-cavity slashface gap with different cavity obstruction modes, compared with a typical single-cavity slashface, is designed to arrange coolant flow on a gas turbine endwall. Solving the steady Reynolds averaged Navier–Stokes equations, the interaction condition between the coolant jet and cascade secondary vortices is studied. The corresponding film cooling and aero-thermal performances of the endwall are evaluated. The obtained results indicate that the dual-cavity slashface urges the coolant from the fore cavity to stagnate on the obstruction and to be redirected toward the spanwise direction. Consequently, the coolant downstream migration tendency near the obstruction is restricted, and the cooling effectiveness downstream of the obstruction increases. When the blowing ratio (M) is 0.5, the cavity obstruction is most effective when placed at 30%Ls and 50%Ls in redirecting the coolant to eject out more quickly. The endwall cooling effectiveness in the vicinity is increased from 0.2 to 0.4. The influence of the obstruction is the most moderate when M=1.0. The cooling effectiveness upstream of the obstruction is only increased by 0.06 in the DC-10% case. Another mainstream ingestion region appears downstream of the obstruction, and the lack of coolant decreases the average endwall cooling effectiveness by 0.04. At a high blowing ratio (M=1.5), the ingestion and ejection velocities at the slashface are the highest, and the obstruction can only influence the region of z/Cax < 0.4. After penetrating directly into the mainstream of the coolant, an uncovered region is formed on the endwall, and its average cooling effectiveness is increased by up to 0.08 with an increasing net heat flux reduction of 0.2 in the DC-30% case. This paper provides insights into elaborate purge flow control for turbine cooling designers.

Impingement Heat Transfer Enhancement in Crossflow by V-Shaped Protrusion Vortex Generator

This paper numerically studies the effect of a V-shaped protrusion vortex generator on flow and heat transfer of impingement cooling in crossflow. The simulations are performed by solving three-dimensional steady Reynolds-Averaged Navier-Stokes equations with shear stress transport k-Omga turbulence model. Four crossflow ratios, five locations and heights of the V-shaped protrusion vortex generator are discussed. Results indicate that (1) the V-shaped protrusion vortex generator effectively improves the peak value of Nusselt number and widens the high heat transfer range at the crossflow ratios of 0.3 and 0.4 due to the decrease of actual crossflow ratio and the generation of an additional counter-rotating vortex pair, while it has little effect at the crossflow ratios of 0.1 and 0.2; (2) as the distance between vortex generator and jet hole increases from 2.5 to 4.5 times of diameter, the Nusselt number increases and the jet total pressure drop decreases, thus the thermal performance factor increases with a maximum increasement of 22.57%; and (3) the Nusselt number increases with the increase of vortex generator height, and when the crossflow ratio is large enough, the impingement heat transfer can be improved even that a shallow V-shaped protruding vortex generator is used.

CFD evaluation of mean and turbulent wind characteristics around a high-rise building affected by its surroundings

This study comprehensively investigated the accuracy of computational fluid dynamics (CFD) simulations for predicting the mean and turbulent wind characteristics around a high-rise building surrounded by low-rise street canyons. The flow field was characterized based on the complicated interaction between a high-rise building and its surrounding buildings, which has rarely been examined in previous CFD studies. We obtained the CFD results using steady Reynolds averaged Navier-Stokes equation (RANS) models and large eddy simulations (LES), which were compared with the measurement results obtained via wind tunnel experiments. Furthermore, we quantitatively investigated the impact of the presence of a high-rise building on the prediction accuracy of pedestrian wind environments, including the gust wind velocity. The results showed that the performance of both LES and RANS decreased in the presence of a high-rise building, indicating that predicting the flow around a high-rise building is more challenging than predicting the flow of a simple street canyon. Additionally, the prediction accuracies of RANS and LES for the mean wind velocity at the pedestrian level were similar in regions with high wind velocity. However, the prediction accuracy of LES in the medium- and low-wind-velocity regions was significantly better than that of RANS, which is closely related to the superior prediction accuracy of turbulent kinetic energy in LES. Although LES can predict the gust wind velocity directly with higher accuracy than that of RANS by using a gust factor, RANS can be used to predict the gust wind velocity with a certain accuracy using a peak factor.

CFD assessment of wind energy potential for generic high-rise buildings in close proximity: Impact of building arrangement and height

High-rise building complexes are of great importance for enabling sustainable urban development in large parts of the world. Earlier studies have indicated that high wind speed regions can be present along the passage between two high-rise buildings as well as above the roofs. At such locations, urban wind energy could be harvested by installing wind turbines between and/or above the roof of the buildings. However, the available wind energy potential around an array of generic high-rise buildings in close proximity has not yet been assessed for different building configurations. This paper conducts a detailed evaluation of the impacts of the building arrangement and height for a 2 × 2 array with a building height-to-street width ratio of 30 on the mean wind velocity and the wind energy potential along the passages between both upstream and downstream buildings as well as on their roofs. The following parameters are analyzed: (i) the passage width between the two upstream buildings (w), (ii) the streamwise distance between the upstream and downstream buildings (d), and (iii) the height difference between the upstream and downstream buildings (ΔH). The 3D steady Reynolds-averaged Navier-Stokes (RANS) equations are solved using the Reynolds stress model (RSM) turbulence model for closure. The CFD results are validated using wind-tunnel measurements of mean wind speed and turbulence intensity performed for the same building array. The results show elevated wind power density along the upstream passages for small w (=0.15B), high d (=0.6B), and equal building height (ΔH = 0). In contrast, comparatively high values of w, small d, and ΔH < 0 yield high wind power densities between the downstream buildings. Among the different wind turbine types considered, horizontally-mounted vertical axis wind turbines seem the most promising option for wind energy harvesting between the buildings.

CFD Analysis of Wind Distribution around Buildings in Low-Density Urban Community

The computational fluid dynamics (CFDs) models based on the steady Reynolds-averaged Navier–Stokes equations (RANSs) using the k−ω two-equation turbulence model are considered in order to estimate the wind flow distribution around buildings. The present investigation developed a micro-scale city model with building details for the Hail area (Saudi Arabia) using ANSYS FLUENT software. Based on data from the region’s meteorological stations, the effect of wind speed (from 2 to 8 m/s) and wind direction (north, east, west, and south) was simulated. This study allows us to identify areas without wind comfort such as the corner of the building and the zones between adjacent buildings, which make this zone not recommended for placement of restaurants, pedestrian passages, or gardens. Particular attention was also paid to the highest building (Hail Tower, 67 m) in order to estimate, along the tower height, the wind speed effect on the turbulence intensity, the turbulent kinetic energy (TKE), the friction coefficient, and the dynamic pressure.

Numerical Investigation of the Hydrodynamic Characteristics of 3-Fin Surfboard Configurations

Surfing is a popular sport, with the associated market forecast to reach 2.6 billion US dollars by 2027. In the published literature, there is a range of investigations into the performance of surfboard fins. Some studies model a single fin or review the performance of different fin layouts and surface designs. However, the effects of individual fin design features on flow dynamics are not well understood. This study provides numerical analysis into the thruster fin aspects (rake, depth, and base length) and resultant key performance indicators (i) lift and drag coefficients, and (ii) turbulent kinetic energy. The models were simulated in Ansys Fluent R19.1, solving steady Reynolds-averaged Navier–Stokes equations using the SST k−ω turbulence model at a velocity of 7 m/s. The results indicate the performance of fins varies more post-stall. The variations in rake showed the biggest impact on the turbulence intensity at an angle ≥20°. The variations in base length exhibited coefficient trends with greater lift at small angles but significant lift losses at high angles of attack. The variations in depth affected the forces on the fins rather than the performance indicators. Based on these simulations, a proposed fin set was developed that presented the lowest lift losses after the stall point.

Impacts of urban morphology on improving urban wind energy potential for generic high-rise building arrays

Previous findings have indicated better performance attained by modified urban morphologies for wind energy utilization only in single and pair buildings, or medium-dense low-rise building arrays. Hence, the main purpose of this study is to address the research gaps to complete a fundamental understanding of the influences of urban morphology in compact high-rise urban areas on enhancing urban wind energy harvest for sustainable urban development. A comprehensive parametric study is conducted using the computational fluid dynamics tool to analyze the impacts of urban morphologies on the wind energy potential for a 6 × 6 array of generic high-rise buildings, including (i) urban density altered from compact to sparse urban layouts, (ii) building corner shapes of sharp and rounded corners, (iii) urban layouts of in-line and staggered patterns, and (iv) wind directions of 0° and 45°. This investigation implements the three-dimensional steady Reynolds-averaged Navier-Stokes equations with the Reynolds stress model to explore the distributions of wind speed, power density, and turbulence intensity over the building array. The results indicate that decreasing urban plan area density reduces the unacceptable turbulence areas with relatively higher wind power density on the roof. Besides, round corners can produce elevated power densities up to 201% greater than sharp corners beside the building. Even under the oblique wind direction of 45°, the rounded corner still shows better wind energy potentials than the sharp corner. The in-line urban layout demonstrates more significant areas with higher power densities and low turbulence intensities than the staggered urban layout.

Multi-fidelity shape optimization methodology for pedestrian-level wind environment

In this study, a multi-fidelity shape optimization framework is proposed for the pedestrian-level wind environment (PLWE). In the proposed framework, low-fidelity computational fluid dynamics (CFD) models based on steady Reynolds-averaged Navier–Stokes equations (RANS) models and high-fidelity CFD models based on large-eddy simulation (LES) are efficiently integrated into the optimization process to improve the optimization reliability while maintaining its computational speed in an affordable range for practical engineering applications. The optimization solver is coupled with an approximation model generated by low-fidelity CFD samples obtained using a design of experiments (DOE) technique. The optimal candidates are then evaluated according to the degree of improvement of the objective function compared to the reference case. If the degree of improvement shows significant deviations between the low-fidelity and high-fidelity models, suitable corrections and modifications are applied to improve the reliability of the optimization process. The applicability of the proposed method was investigated in terms of minimizing the high-wind-speed area, as the optimization objective, around a high-rise building considering (a) uniform urban blocks and (b) real urban blocks with different frequency distributions of wind directions associated with two different local wind climates. In summary, a significant reduction in the critical strong-wind area around the target building was realized using the proposed optimization framework. Furthermore, the application of the proposed multi-fidelity optimization framework highlighted the importance of considering the local wind climate in architectural design.

Validation Process for Rooftop Wind Regime CFD Model in Complex Urban Environment Using an Experimental Measurement Campaign

This research presents a validation methodology for computational fluid dynamics (CFD) assessments of rooftop wind regime in urban environments. A case study is carried out at the Donadeo Innovation Centre for Engineering building at the University of Alberta campus. A numerical assessment of rooftop wind regime around buildings of the University of Alberta North campus has been performed by using 3D steady Reynolds-averaged Navier–Stokes equations, on a large-scale high-resolution grid using the ANSYS CFX code. Two methods of standard deviation (SDM) and average (AM) were introduced to compare the numerical results with the corresponding measurements. The standard deviation method showed slightly better agreements between the numerical results and measurements compared to the average method, by showing the average wind speed errors of 10.8% and 17.7%, and wind direction deviation of 8.4° and 12.3°, for incident winds from East and South, respectively. However, the average error between simulated and measured wind speeds of the North and West incidents were 51.2% and 24.6%, respectively. Considering the fact that the upstream geometry was not modeled in detail for the North and West directions, the validation methodology presented in this paper is deemed as acceptable, as good agreement between the numerical and experimental results of East and South incidents were achieved.

Numerical investigation of cavity-induced enhanced supersonic mixing with inclined injection strategies

In this study, an inclined injection system with a cavity and grooves arranged in series is developed to enhance the supersonic mixing in a scramjet combustor. Three-dimensional steady Reynolds-averaged Navier–Stokes equations, the two-equation shear stress transport k-ω model, and the finite-rate/no turbulence-chemistry interaction model are used to simulate the flow field structures with and without grooves at different inclination angles. The numerical method used in the study has been verified using experimental data from the open literature, and the static wall pressure distribution of the numerical simulation is in good agreement with the experimental data. The numerical results reveal that the grooved configuration has a significant influence on the flow field structure. The downstream streamline of the structure with grooves is more turbulent and produces more streamwise vortices because the geometry of the grooves enhances the shear effect between the vortex and the high-speed incoming flow. In the case of the grooved configuration, the mixing coefficient at the fuel orifices is slightly lower, but the fuel mixing effect in the downstream is enhanced and gradually exceeds the grooveless configuration. Moreover, the grooved configuration can obtain the best mixing coefficient at a jet angle of 30°. The grooved configuration has a greater stagnation pressure loss than the grooveless configuration.

Improving pedestrian micro-climate in urban canyons: City Center of Alexandria, Egypt

Due to the accelerated pace of urbanization, the study of the local urban microclimate has acquired significance. A detailed and accurate prediction of outdoor ventilation and thermal comfort is required for a healthy environment, particularly in densely built areas, due to the complex interaction of physical phenomena across different length and time scales. Engineering approaches are critical for solving the issues of wind discomfort. These approaches can however not be applied independently of the architectural context. An interdisciplinary approach can bridge the gap between architectural design and engineering wind-comfort solutions in a coastal city of developing countries with a temperate climate. The current study aims to evaluate the effect of urbanization on an asymmetrical historical canyon in the city center of Alexandria, Egypt. Challenges and limitations are imposed regarding applying retrofitting techniques to improve pedestrian comfort without changing the historical features of these areas.This paper provides a Computational Fluid Dynamics (CFD) simulation of a residential district in the modern city of Alexandria which contains the library of Alexandria and the two oldest paved roads in the world which still in use until today. The 3D steady Reynolds-averaged Navier-Stokes (RANS) equations and the standard k-ε model are used to calculate the aerodynamic flow field. These computational settings were validated with previously published wind-tunnel results. The indices of thermal comfort were calculated using a Predicted Mean Vote (PMV) model utilizing Custom Field Functions (CFF). On-site measurements of air velocity, temperature, and humidity were conducted to validate the thermo-flow characteristics with the numerical simulation and they were in a good agreement.To reach the comfort level which contributes to a pedestrian-friendly environment, it brings a range of measures that covers qualitative design guidelines on street and building level to mitigate wind discomfort and excessive solar access in urban canyons. One of these measures presents (CFD) simulations for comparing the model of the modern city with a visualized model of the ancient city of Alexandria at the end of Cleopatra's reign. This comparison aims to give a close vision on how urbanization has influenced the aerodynamics and thermal comfort in this region. The current study helps urban planners and architects to enhance the current situation for better urban microclimate at the pedestrian level, without setting up new developments during hot summer days.

Optimization Design of a Two-Vane Pump for Wastewater Treatment Using Machine-Learning-Based Surrogate Modeling

This paper deals with three-objective optimization, using machine-learning-based surrogate modeling to improve the hydraulic performances of a two-vane pump for wastewater treatment. For analyzing the internal flow field in the pump, steady Reynolds-averaged Navier-Stokes equations were solved with the shear stress transport turbulence model as a turbulence closure model. The radial basis neural network model, which is an artificial neural network, was used as the surrogate model and trained to improve prediction accuracy. Three design variables related to the geometry of blade and volute were selected to optimize concurrently the objective functions with the total head and efficiency of the pump and size of the waste solids. The optimization results obtained by using the model showed highly accurate prediction values, and compared with the reference design, the optimum design provided improved hydraulic performances.

Effects of inlet guide vane and blade pitch angles on the performance of a submersible axial-flow pump

This study investigates the effects of inlet guide vane (IGV) and blade pitch angles on the steady and unsteady performance of a submersible axial-flow pump. To analyze the interaction between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations were used with shear stress transport turbulence closure. Hexahedral meshes were used in the computational domain. The numerical results for performance curves showed good agreement with experimental data. The results showed that the steady and unsteady performance characteristics were dependent on both the IGV and blade pitch angles. Adjusting these angles affected the total pressure rise and thus caused variation in the efficiency in overload conditions. But adjusting these angles affected the unsteady pressure fluctuations in partial-load conditions. Detailed flow analyses were performed to find the root-cause of these phenomena.