Numerical Computational Fluid Dynamics Research Articles

Numerical Simulation and Computational Fluid Dynamics Analysis of Two-Dimensional Lid-Driven Cavity Flow Within the Weapon Bay of an Autonomous Fighter Drone

The efficient deployment of weapons in military operations is critical for mission success, and the flow of air within the weapon bay of an autonomous fighter drone plays a vital role in achieving this objective. In this paper, we present a comprehensive numerical simulation and computational fluid dynamics (CFD) analysis of the three-dimensional lid-driven cavity flow within the weapon bay of an autonomous fighter drone. To address this challenging problem, we employ CFD analysis and a multigrid approach to solve the Navier-Stokes equations for the aerodynamic problem. Our simulations include high Reynolds numbers of up to 10,000, which demonstrates the potential of CFD analysis in optimizing the design of autonomous fighter drones for military operations. We evaluate the effectiveness of the linked strongly implicit multigrid technique in estimating high-Re fine-mesh flow solutions using the vorticity-stream function formulation of the two-dimensional incompressible Navier-Stokes equations. The model issue is the driven flow in a square cavity, and we consider meshes up to 1024 x 1024 points and combinations with Reynolds numbers as high as 1000. To further improve the accuracy of our simulations, we employ one-dimensional grid clustering coordinate transformations instead of uniform mesh refinement, as the flow field exhibits one or more secondary vortices. Our findings demonstrate that CFD analysis can provide valuable insights into the complex flow dynamics within the weapon bay of autonomous fighter drones, which can lead to the optimization of their design for enhanced mission capabilities. Overall, our study highlights the significance of numerical simulations and CFD analysis in the design and optimization of autonomous fighter drones for military applications. Our results can serve as a basis for future research in the field of UAV aerodynamics and contribute to the development of more efficient and effective military operations.

Quantification of uncertainty in linear wave energy hydrodynamic models from experimental data

Considerable testing and modeling are required in order to fully realise, efficiently develop, and successfully industrialise the wave energy converters (WECs). Numerical modeling, full-scale measurements, and scaled prototype testing are the various methodologies that can be applied to model WECs and predict the dynamic response. Mathematical WEC models form the basis of model-based energy maximising control and directly affect the ability of model-based controllers to maximise energy capture. Linear WEC models are attractive in leading to simpler control designs, but may not cover the complete operational space. One solution is to identify a range of linear models at different operating points, which give a measure of the underlying nonlinear behaviour [1], [2]. This model set can then be used to extract a nominal model, and an associated uncertainty region, which can be used as a basis for a robust WEC controller synthesis process, such as articulated in [3].
 Recently, such an approach has been adopted using data generated from a high-fidelity numerical computational fluid dynamics (CFD) model [4]. However, numerical wave tanks (NWTs) and physical wave tanks differ significantly in terms of the range of tests which can be performed, and the contamination which can affect the measurements used to determine the data-based models e.g. measurement noise, numerical effects, wave reflections, etc [5]. As a result, the determination of nominal models and uncertainty regions in a physical wave tank may provide some advantages (and disadvantages) which need to be examined carefully. In addition, the range of post-processing techniques which could, or should, be applied to the different experimental/numerical domains, to improve the fidelity of the identified models, may differ between domains.
 In this paper, experimental testing of a WEC, by recreating a wave field similar to real-life conditions and a small-scale version of the device, is used to understand the hydrodynamic behaviour and to obtain an accurate dynamic model for WECs, which are considered to be essential towards optimal WEC design. Physical wave tank experiments, even though having their own disadvantages, overcome some difficulties of CFD-based NWT experiments, most notably huge computation time, problems in accurate representation of viscous fluids, uncertainty in the specification of an appropriate turbulence model, and propagation of incident waves [6]. 
 In this study, representative linear models of a point-absorber type WEC from a physical wave tank in the wave basin at Aalborg University are determined which give insight into the system dynamics and provide a basis for robust control of WECs. Among different stimulation techniques to excite the system dynamics in physical wave tank tests, the particular types of excitation signals covering the complete range of frequencies and amplitudes of the system dynamics, while considering limitations on the range of excitation signals or the wave tank reflections, are adopted for the determination of representative linear models. Moreover, a full investigation is carried out to ascertain the appropriate post-processing needed to optimise the signals as the basis for model identification. The model identification includes the non-parametric frequency response by means of empirical transfer function estimate (ETFE). 
 

Numerical investigation of the effect of altitude on diesel engine combustion and soot emissions

It is increasing concerned that the plateau environment will potentially increase fuel consumption in engines. Despite this, the current state of research on high altitude engines is still inadequate in providing sufficient and detailed information to counteract the decrease in engine efficiency. In addition, one of the novelty of this study was that the investigated altitudes is up to 4500 m, of which the previous studies was limited. Therefore, this study aims to investigate the effect of altitude on in-cylinder spray, combustion, and soot formation processes in diesel engines. A calibrated three-dimensional (3D) computational fluid dynamics (CFD) model of a single-cylinder, four-strokes, direct injection (DI) compression ignition, intake boost research diesel engine is established. The numerical CFD model used in this study has been validated through comparison with experimental data. It effectively investigates the in-cylinder activities and provides insights into the causes behind combustion and soot emission deterioration. The simulation is operated at altitudes of 0, 1500, 3000, 4500 m with corresponding intake pressure. It has been observed that engine performance and soot emissions deteriorate as altitude increases, and a sharp drop occurs when the altitude exceeds 3000 m, which can be attributed to the dramatic decline in combustion efficiency. The extended spray leads to a decrease in air utilization, which ultimately results in a sudden drop in combustion efficiency at altitudes above 3000 m. Overall, this study has identified that the extended penetration of the spray, caused by reduced pressure and air density, leads to poor air utilization, resulting in decreased performance and increased emissions. Hence, it is recommended that optimization of the combustion chamber geometry and injection strategies of diesel engines operating at high altitudes be undertaken to improve air utilization and combustion quality. This will serve as an avenue for further research in the future.

Experimental and Numerical CFD Modelling of the Hydrodynamic Effects Induced by a Ram Pump Waste Valve

The hydraulic ram pump or hydram is a machine capable of lifting water to a hydraulic head higher than the level of the supply source. It is a sustainable and self-sufficient device: the working principle is based on the rise of abrupt pressure variations occurring in the feeding pipeline when the liquid inside it undergoes a locally sharp change in velocity as a consequence of the sudden closure of the waste valve. Invented in 1772, the pump has been improved over the decades. Due to its simplicity, low cost and reliability, it has been widely used worldwide to provide adequate domestic water supplies, especially before the spreading of electricity and internal combustion engines. In recent years, the new attention placed on sustainability and energy transition from fossil fuels to renewable energy devices has brought a growing interest to this basic machine, essentially forgotten and abandoned in the last century; it seems promising especially in developing countries. The hydram is, in fact, a very simple machine, with only two moving parts, the waste and delivery valves. The efficiency of the hydraulic ram pump is mainly influenced by the characteristics of the waste valve. However, sufficient data are not available for the design of the hydram and the waste valve. In this work, the behaviour of the waste valve of a hydram was simulated by means of Computational Fluid Dynamics (CFD). Velocity and pressure values were analysed for different scenarios with different closing times of the valve. The data obtained from the developed numerical model were compared, in order to verify the validity of the simulations, with those collected during the operation of the hydram placed at the Laboratory of Environmental and Marine Hydraulics (LIDAM) of the University of Salerno, Italy. The numerical model thus obtained can, therefore, be used to identify the ideal configuration of the valve in order to ensure the best performance of the hydram.

Effects of Volute Structure on Energy Performance and Rotor Operational Stability of Molten Salt Pumps

A double-volute molten salt pump with two outlet pipes is proposed based on the original pump model. A numerical approach coupling finite element analysis and computational fluid dynamics (CFD) is implemented to investigate the operational stability and energy performance of two molten salt centrifugal pumps for high-temperature molten salt. The entropy production of the single-volute and double-volute molten salt pumps is investigated. The effects of the volute structures on the mechanical behavior of the impeller and shaft are considered. According to the findings, the local entropy production in the molten salt pump is dominated by the local pulsating entropy production (Spro-T), with the double-volute scheme achieving reduced energy loss. A visualization of the flow field and the local entropy production rate (LEPR) distributions indicate that the LEPR is positively correlated with the complexity of the flow, and higher levels of turbulence intensity lead to greater LEPR. The double-volute scheme enhances the complexity of the flow in the impeller, resulting in an increase in the LEPR compared with the single-volute design. However, the LEPR in the whole double-volute molten salt pump is reduced compared with the single-volute design. It is discovered that the double-volute molten salt pump experiences a less radial hydraulic force. Although the double-volute design has a slightly higher maximum equivalent stress on the impeller than the single-volute scheme, the rotor deformation is significantly less. In general, the double-volute scheme reduces energy loss and ensures better structural stability.

Machine Learning and IoT Trends for Intelligent Prediction of Aircraft Wing Anti-Icing System Temperature

Airplane manufacturers are frequently faced with formidable challenges to improving both aircraft performance and customer safety. Ice accumulation on the wings of aircraft is one of the challenges, which could result in major accidents and a reduction in aerodynamic performance. Anti-icing systems, which use the hot bleed airflow from the engine compressor, are considered one of the most significant solutions utilized in aircraft applications to prevent ice accumulation. In the current study, a novel approach based on machine learning (ML) and the Internet of Things (IoT) is proposed to predict the thermal performance characteristics of a partial span wing anti-icing system constructed using the NACA 23014 airfoil section. To verify the proposed strategy, the obtained results are compared with those obtained using computational ANSYS 2019 software. An artificial neural network (ANN) is used to build a forecasting model of wing temperature based on experimental data and computational fluid dynamics (CFD) data. In addition, the ThingSpeak platform is applied in this article to realize the concept of the IoT, collect the measured data, and publish the data in a private channel. Different performance metrics, namely, mean square error (MSE), maximum relative error (MAE), and absolute variance (R2), are used to evaluate the prediction model. Based on the performance indices, the results prove the efficiency of the proposed approach based on ANN and the IoT in designing a forecasting model to predict the wing temperature compared to the numerical CFD method, which consumes a lot of time and requires high-speed simulation devices. Therefore, it is suggested that the ANN-IoT approach be applied in aviation.

Thermodynamic performance and heat and mass transfer analysis of air source absorption heat pump for heating

To lower CO2 emission and obtain better heating efficiency compared with conventional gas boilers, this paper proposed a solar air source absorption heat pump (SAAHP) with falling film heat exchanger for district heating. The thermodynamic model is established to analyze the performance of the proposed system. The falling film generator as the key heat exchange component has been designed carefully, and then the numerical models of the falling film generation process which include one and two-dimensional numerical models are developed. According to the thermodynamic analysis, the primary energy efficiency (PEE) and heating capacity of the system are 1.65 and 45.02 kW at the generation temperature of 190 °C and ambient temperature of −7 °C, respectively, which can save 41.69 t of CO2 emissions from heating. The two-dimensional numerical model indicates the main heat and mass transfer occur between the falling film height x = 0 mm and x = 200 mm, and the interface heat transfer decreases from 74.6 kJ/(m2·s) to 40.5 kJ/(m2·s) in a typical vertical falling film generation process. In addition, the energy transfer as the inter-diffusion is corrected in the energy equation which improves the prediction accuracy by about 1.5% of the two-dimensional model. The research provides a reference for the optimization design of the generator, where one-dimensional models can quickly guide the design and selection of equipment, modified two-dimensional numerical models and Computational fluid dynamics (CFD) models can provide references for the refined optimization design, which attributes to the improvement of thermodynamic performance of the solar absorption heat pump system.

RANS CFD Model for Global Performance Evaluation of Floating Vessel in Extreme Head Waves

Extreme waves acting on the floating vessel would cause serious physical behavior and could cause a catastrophic incident. Such phenomena should be put of high interest during the designing step of the floating vessel. The numerical CFD (Computational Fluid Dynamics) viscous fluid approach along with the recent development of computer hardware gives us advantages to simulate a huge number of scenarios in the very early design phase. The current study will explain the CFD method to investigate the global performance of stationer floating vessel Fn = 0 on its motion and green water occurrence due to extreme waves λ/L = 2.0. Based on the simulation results, the CFD model can handle well the green water on deck phenomenon during extreme head waves. The water on deck affected vessel pitch motion amplitude not symmetric under regular waves i.e. 8 degrees by stern and 6 degrees by bow. Similar results were also found in heave motion amplitude by the maximum +4 centimeter and minimum -12 centimeter. Those asymmetric results of heave & pitch motion amplitude under regular waves indicate the contribution of green water to the vessel motion. In addition, green water on deck only affects the motion amplitude but not the motion frequency.

Flow-Induced Forces for a Group of One Large and Several Small Structures in the Sheared Turbulent Flow

Evaluating the hydrodynamic force fluctuations acting on each structure in a group of subsea objects of different cross-section shapes, sizes and relative positions represents a challenge due to the sensitivity of the vortex shedding process, especially for a variety of sheared flows. The present study uses the numerical 2D computational fluid dynamics model to estimate the flow-induced forces on a group of small circular and D-shaped cylinders in the linear and parabolic sheared flow, which are placed in proximity to a larger structure of the squared cross-section. This allows us to evaluate loads, which are affected by the presence of subsea equipment located on the seabed. The average Reynolds number of the considered linear flow profile is 3900, while the parabolic flow profile has the maximum Reynolds number of 3900. The k-ω SST turbulence model is used for simulations. The work demonstrates the effect of the cross-sectional shape of smaller cylinders on hydrodynamic coefficients, explores the effect from the spacing in between the structures and highlights differences between loads in the linearly sheared and parabolic flow. The results obtained show that the presence of the squared cylinder notably influences the mean drag coefficient on the first cylinder, for both circular and D-shaped cylinders. The parabolic sheared flow profile in this series leads to the highest mean drag and the highest amplitudes of the fluctuating drag and lift coefficients.

A numerical investigation on thermal analysis of RPC based solar thermochemical reactor for two-step H2O splitting cycle for hydrogen production

Ceria based solar thermochemical cycle is a high-temperature based redox chemical reactions to split H2O or CO2to produce hydrogen and/or syngas. The redox reactions are carried out in a reactor cavity thus the analysis and optimization of design as well as thermal analysis is a crucial factor to improve the solar-to-fuel conversion efficiency. This paper proposes the hybrid design of cylindrical and hemispherical cavity and its effects of geometrical parame-ters such as reticulated porous ceria (RPC) thickness (15 mm, 20 mm, and 25 mm) and gas flow gap (5 mm&10 mm) on temperature and flux distribution and solar-to-fuel efficiency for both steady-state and transient condition. A numerical computational fluid dynamics (CFD) analysis is carried out to study heat and mass transfer as well as geometrical design consid-eration of the STCR cavity under SolTrace generated Gaussian distributed concentrated solar flux. Two-step water-splitting reaction in the Solar Thermochemical cavity reactor (STCR) using ceria (CeO2) has been modeled to explore the oxygen evolution/reaction rate and to estimate solar-to-fuel efficiency and its relationship with geometrical factors. The RPC of 25 mm thickness yields the highest oxygen evolution rate of 0.34 mL/min/gCeO2 and solar-to-fuel efficiencies are 7.82%, 12.07% and 16.18% for 15 mm, 20 mm and 25 mm of RPC thickness, respectively without heat recovery. The operating conditions and optimized geometric factors, based on result analysis and comparison, are discussed in detail.

Experimental and Numerical Computational Fluid Dynamics Analysis on the Flow at Pelton Turbine Nozzle with Various Opening Settings

This paper refers to the flow analysis of nozzle with spear for different nozzle opening of Pelton turbine. Experimental test was performed by using model turbine to find out the parameters during testing period. The flow rate, head and the rotational speed on the turbine shaft are measured for various nozzle openings covering a wide operation range. The best efficiency is 86% and output power of the model turbine is 110W. For water flow simulation of nozzle with spear by applying Computational Fluid Dynamics (CFD) software ANSYS CFX-14.5 are presented. The pressure and velocity distribution have also been obtained to study the effect of nozzle on flow pattern. The flow simulation has been carried out the standard k - ? turbulence model. And then, CFD simulation results with experimental value have been compared in this research.

Evaluation of System Identification Methods for Free Vibration Flutter Derivatives of Long-Span Bridges

The significance of long-span bridges being susceptible to wind-induced vibrations and the need for evaluating their aerodynamic performance is the focus of this study. The main emphasis is on experimental methods for assessing the bridges’ aerodynamic stability, using sectional model tests with the free vibration technique. The dynamic properties of the model are determined from the measured response, using various system identification methods, including the modified Ibrahim time domain (MITD) and iterative least squares (ILS) for two-degree-of-freedom systems and the logarithmic decrement method (LDM) and the Hilbert transform method (HTM) for single-degree-of-freedom (SDOF) systems. A new dynamic testing setup was designed to facilitate single-degree-of-freedom (heave and pitch) and coupled two-degree-of-freedom (2DOF) motion in a wind tunnel section model. The vertical and torsional stiffnesses of the model were adjusted with elastic springs. A Great Belt Bridge section model was selected for testing due to its streamlined aerodynamic shape. The direct and crossflow derivatives were extracted from the measured response using the system identification methods mentioned. Additionally, analytical studies and numerical computational fluid dynamics simulations were conducted to validate the experimental results. The study found that HTM is most effective in SDOF due to its ability to extract both damping and frequency from the nonlinear response, whereas the MITD method is faster in converging system parameters in 2DOF system tests. The experimental and numerical results are comparable to the flat plate, which confirms the streamlined behavior of the Great Belt section from an aerodynamic perspective.

Influence of fuel distribution on co-combustion of sludge and coal in a 660 MW tangentially fired boiler

The distribution method of coal and sludge is an important factor affecting co-combustion, but few studies have been carried out in most papers. The influence of different fuel distribution methods for municipal sewage sludge and coal on co-combustion in a furnace was studied using numerical computational fluid dynamics simulations in this paper. In the considered cases, the burners that inject sludge were artificially altered, while the masses and contents of sludge and coal remained unchanged. The combustion temperature, combustion characteristics, and the heat of the boiler were analysed. The concentrations of CO, CO2, and volatile matter were used as characteristic parameters. The conclusion shows that the co-combustion temperature in the main combustion region inevitably decreases compared to coal mono-combustion regardless of the fuel distributions being used. When coal and sludge are premixed, the furnace temperature distribution is more uniform. However, premixing has a greater influence on the boiler heat flux. Feeding sludge into the furnace from the top layer of burners individually can effectively reduce the adverse impact of premixed combustion, and the total heat flux of the furnace is reduced by 4.8%, the heat flux decreased by about 6% for other distribution methods. Considering the broad prospects of sludge co-disposal in boilers, these findings provide guidance and suggestions for the co-combustion of sludge and coal, and they provide theoretical support for the efficient operation of boilers.

Numerical Simulation of Flow Over Airfoil and Its Optimization

Airfoils are one of the most important factors in determining an airplane’s ability to fly. As such, their optimization holds important ramifications for the continual need to improve airplane performance. In this paper, the optimization of airfoil design is explored through numerical computational fluid dynamics. This paper first investigates the effects of Angle of Attack on airfoil lift/drag ratios, which is shown to have a significant influence on the performance of airfoils. Then, the effects from thickness are explored, and it is found that the influence of thickness is highly dependent on the specific shape of airfoil. In addition, in order to further improve airfoil aerodynamic performance, a type of modified airfoil with an additional tip is developed and simulated. The results indicate that airfoils with additional tips can perform better, but only with the proper combination of tip parameter values. For example, the modified airfoil with a tip of 0.03 L length at a 25° tip angle bested that same airfoil without an additional tip. Finally, it is found that the Backpropagation machine-learning algorithm, when trained with prior simulation data, can quickly predict lift and drag coefficients of airfoils. The results in this paper could facilitate the further optimization of airfoil design.

Investigation of steam ejector parameters under three optimization algorithm using ANN

Several industries have adopted Steam ejectors as promising energy-saving devices. The steam ejector is used extensively in the HVAC, refrigeration, and desalination industries because it harnesses surplus heat. Numerous computational fluid dynamics (CFD) and thermodynamic models have been addressed in the academic literature. Predictions for steam ejector parameters using these models are fairly accurate. However, considerable discrepancies between experiments and models are sometimes as high as 20 %. Contrarily, CFD simulations for an ejector are computationally expensive and necessitate careful selection and tweaking of the turbulence model. ANN-based data-driven techniques are now used for complicated mechanical system modeling. The advantages of a well-trained ANN model include low computational costs and adaptability for integration with real-time control systems. In this study, we developan artificial neural network (ANN) model of a steam ejector and analyzes how different training strategies affect the ANN model's ability to make accurate predictions. The model is trained using a sizable experimental library with various geometrical and operational conditions. Using a typology of four input factors (Nozzle Throat Diameter (Ntd), Diffuser Outlet Diameter (Dod), Ejector Area Ratio (σp), and Entrainment Ratio (ER)) that capture geometry and operating conditions characteristics, the framework predicts two output parameters: (a) Coefficient of performance (COP) and (b) Pressure reduction ratio (PRR) of the steam ejector. Among the three optimizers tested for algorithm training, the ANN model trained using the ADAM optimizer performed the best. The model's hidden layer contains 102 neurons, and a split ratio of 0.2 is used during dataset training. The average error for COP and PRR predictions made by the ANN model is ± 1.8 % and ± 2.4 %, respectively. As a result, the ANN model can be used to improve the steam ejector system's configuration and operation.

Numerical simulation of pneumatic throttle check valve using computational fluid dynamics (CFD)

The article presents a numerical CFD simulation of a throttle-check valve used in an innovative control system for two pneumatic drives. This type of control is used in an innovative rehabilitation device for lower limbs. In order to determine the boundary conditions, experimental tests were carried out. The throttle valves on the test stand were scaled and the air flow rate values were read for different valve opening heights. The purpose of this article is to present a CFD simulation of a pre-adjusted check valve throttle. Numerical simulation (CFD) makes it possible to study the flow phenomena inside a pneumatic throttle-check valve, with different sizes of flow gaps. The obtained results made it possible to determine the distribution of physical quantities of static pressure, the velocity of the medium flowing through the valve, or the vector velocity distribution. The throttle valve assembly has been scaled for a suitable degree of synchronization of the movement of the piston actuators independently of the different external loads acting on each of them. The authors investigated airflow phenomena for different valve opening heights. The simulation provided information on the occurrence of supersonic and subsonic flow velocities at specific valve opening heights.

Experimental and numerical study on seakeeping performance of a benchmark ASD tug in head seas

Today’s modern ports are undergoing a wave of digital transformation to achieve higher efficiencies and better management of resources. The automation of harbour tugs are one example of concomitant developments for future-ready smart ports. Automating navigation and vessel operations implicitly requires a digital twin, which can be realized as a maneuvering model that incorporates the hydrodynamic behaviour and response of the tug. With the aim of building a maneuvering model, the present work investigates the seakeeping performance of a benchmark azimuthing-stern drive (ASD) tug using both experimental and numerical means. Experimental tests were performed in a towing tank using a 1:9.78 scale model at Fr = 0.378 and 0.165. Added resistance and hydrodynamic responses in head seas were measured in a captive setup. Some of the test cases were repeated in a free-sailing mode. Experiments provided validation data for numerical computational fluid dynamics (CFD) simulations, which were performed using a Reynolds-Averaged Navier–Stokes (RANS) solver, k-ω turbulence model, and a Volume of Fluid approach. Numerical results generally correlate well with experimental results. In addition to model-scale analysis, CFD simulations were also performed at full-scale to study scale effects.

Numerical computational fluid dynamics (CFD) simulation study based on plunger gas lift test

In order to explore the feasibility of the Computational Fluid Dynamics (CFD) method for plunger gas lift and the flow pattern in a long wellbore, a lab simulation test was conducted to verify the reliability of the CFD simulation results. Verification data were provided for CFD simulation through carrying out a plunger gas lift lab test for vertical wells, identifying the plunger movement patterns and delivery rates under different flow pressures, and determining the minimum plunger startup pressure or differential pressure and leakage, and an identical CFD physical model was created on the basis of the lab test model, CFD dynamic grid programming and CFD simulation were conducted under test conditions, and a comparison of the simulation and test results was made to identify the calculation accuracy and the rationality of the CFD model and method; finally, boundary conditions such as temperature and pressure were set according to the actual long wellbore (200 m) conditions, the CFD simulation was performed, and the impacts of the downhole conditions on the gas lift performance were analyzed, so as to develop CFD calculation methods to predict the bottom-hole flow pressure, plunger speed, and delivery rate. The results show: the average plunger speed range is 7.74–22.5 m/s when the flow pressure varies from 199.77 to 632.93 kPa, and the leakage rate increases in a nearly linear way with the speed; compared with the lab test results, the simulation results from the created dynamic grid model and multi-phase turbulent flow model have the leakage error of 7.2% and the plunger speed average error is smaller than 11.1%; under long-wellbore conditions, the plunger lift speed shows the change pattern of increasing and then decreasing, the wellbore pressure has a wave-like drop, and in addition to this pressure drop characteristic, the fact that the plunger startup pressure differential increases with the wellhead pressure should be considered (when the bottom-hole pressure is 15 MPa, the wellhead pressure must not exceed 10 MPa).

HEAT TRANSFER FROM A SLIGHTLY CURVED CONVEX SURFACE

This study is prepared to analyze the heat transfer from a uniformly heated, slightly curved convex (SCX) surface numerically using computational fluid dynamics (CFD) code of commercial software ANSYS-CFX. Some experimental results are also obtained by means of a wind tunnel setup to confirm the results of numerical study. After a good agreement is achieved between the experimental and numerical results, the effects of some major parameters on heat transfer around the SCX surface are determined by using numerical results. Effects of Prandtl number (Pr = 0.237 to 3431), Reynolds number (Re = 40,000 and 400,000), and curvature ratio (CR = 1,2, and 4) on local Nusselt number (Nu) along the circumference of SCX are the extracted results. Additionally, new correlations of Nu depending on Re, Pr, and CR are obtained. The prime outcomes of this mathematical investigation are provided here. An exact numerical CFD solution is provided for the turbulent external flow around the curved surface appearing in this study. The graphical solutions of Nu number that show the heat transfer rate of the system can be divided into three regions for various Re numbers. The maximum average heat transfer is observed in the case of higher curvature ratio.

Effect of Blade Number on the Performance of a Centrifugal Pump Using Commercial Tool ANYS 91.2

Computational fluid dynamics (CFD) is frequently used in centrifugal pump design. The characteristics of the flow fields around turbomachinery can be simulated using tools for numerical computational fluid dynamics in three dimensions. Numerical simulation, which also provides significant information for the hydraulic design of the centrifugal pump, can be used to visualize the internal flow condition of a centrifugal pump. The purpose of this study was to examine the effect of blade number on the hydraulic performance curve using a commercial instrument. ANSYS 91.2. code commercial.The geometric model of the pump was built using CF turbo, and the flow domain was meshed using the commercial programme ICEM. The results demonstrated that an increase in the number of blades significantly improved the hydraulic performance of the centrifugal pump’s head. The findings also revealed that the area of the low-pressure zone at the blade’s input suction grew and that the static pressure distribution homogeneity in the diffusion section was significantly better than that in the spiral section. The design flow of 35 m3 per hour is where the best efficiency point (BEP) is located. At Z = 6 and Z = 7, the head values were 51.58 m and 53.13 m, respectively, while the efficiency values were 50.32% and 53.35%. The comparison of the H-Q curve for estimated head discharge indicates that all impeller efficiency curves share the same fundamental tendency.