Computational Fluid Dynamics Module Research Articles

Research on Short-Term Prediction Methods for Small-Scale Three-Dimensional Wind Fields

The accurate prediction of small-scale three-dimensional wind fields is of great practical significance for aviation safety, wind power generation, and related fields. This study proposes a novel method for predicting small-scale three-dimensional wind fields by combining the mesoscale Weather Research and Forecasting (WRF) model with Computational Fluid Dynamics (CFD). The method consists of three components: the WRF module, the hybrid neural network prediction module, and the CFD module. First, mesoscale meteorological fields are simulated using the WRF module to establish a historical inflow boundary dataset for the CFD domain. Next, deep separable convolutions are incorporated, and convolutional long short-term memory (ConvLSTM) is combined with a deep separable convolution-gated recurrent unit (DSConvGRU) to construct a hybrid neural network prediction module named ConvLSTM-DSConvGRU. This module is employed for predicting inflow boundary data. Finally, the predicted inflow boundary conditions drive the CFD module to predict small-scale three-dimensional wind fields. The effectiveness of the WRF and CFD downscaling coupling method was validated using observed data from meteorological stations within the simulated domain, along with statistical indicators of errors. Additionally, a comparative evaluation was conducted between the proposed hybrid network model and the four commonly used spatiotemporal prediction models to assess its prediction performance. The results demonstrate that our proposed wind field prediction method achieves accurate simulation and short-term prediction of small-scale three-dimensional wind fields, and the hybrid network model exhibits comprehensive advantages in terms of model complexity and prediction accuracy.

Hydrodynamic behaviour improvement of check valves through CFD analysis

In this article, the computer assisted design, flow simulation, optimization of production parameters and unique design prototype manufacturing of a check valve with 16 bar pressure, 5 m/s flow rate and 52000 m3/h flow coefficients, which have never been achieved before in the valve sector, were presented to the attention of the readers. Check valves have a critical role that do not allow reverse flow of the fluid passing through them and are generally designed to secure the pipeline. A small mistake in design may cause great damage in the system. For this reason, a new product of which the disc material exposed to 5 m/s fluid velocity, the body subjected to 16 bar pressure and the system with a flow coefficient of 52000 m3/h were designed by the Solidworks, the flow was simulated with CFD (Computational Fluid Dynamics), and the mechanical resistance was analysed by FEA (Finite Element Analysis). Fluent, CFD and mechanical modules of ANSYS were used to define the parameters of the design. The manufactures of the products designed in the computer environment have been produced by casting method with a 45% ferritic microstructure and impact resistance twice as high as the standard requirements have been implemented.

Exergy performance assessment of a novel air-cooled photovoltaic thermal collector with a double serpentine runner

Despite the various technologies are used in enhancing the air-cooled photovoltaic thermal (PVT) collector through ranging baffles on the chamber, it still leads to a greater pressure loss, resulting in increasing the energy consumption of the fan. This problem is addressed in this work by rearranging the baffle to form a double serpentine runner for improving heat transfer characteristic and reducing the pressure drop of the air in the structure of the serpentine runner. A CFD (Computational Fluid Dynamics) module has been carried out to analyze the collector performance and verified by the experiments. Influences of the structural and operating parameters are studied to optimize the performance of the PVT collector and the results indicated that: (a) Large flow stagnation zones may result from improperly arranged baffles, significantly affecting heat transfer and producing considerable pressure loss. And the recommended values of the structural parameters are given: baffle height is in the range of 75–95 mm, baffle number is in the range of 10–14, and baffle length is in the range of 700–800 mm. (b) although the thermal and electrical efficiency are improved with increasing flow rate, the exergy efficiency increases first and then reduces. The value of the air mass rate is suggested in the range of 0.02–0.03 kg/s. (c) the value ranges of the thermal, electrical, total, and exergy efficiency of the collector for Lasa in November can be 37.2–42.3 %, 11.3–12.5 %, 41.3–51.1 %, and 9.8–11.8 %. (d) comparing this collector with previous studies, the thermal and electrical efficiency of this collector is similar to other collectors, and the pressure drop is significantly lower.

A New Thermal Elasto-Hydrodynamic Lubrication Solver Implementation in OpenFOAM

Designing effective thermal management systems within transmission systems requires simulations to consider the contributions from phenomena such as hydrodynamic lubrication regions. Computational fluid dynamics (CFD) remains computationally expensive for practical cases of hydrodynamic lubrication while the thermo elasto-hydrodynamic lubrication (TEHL) theory has demonstrated good accuracy at a lower computational cost. To account for the effects of hydrodynamic lubrication in high-power transmission systems requires integrating TEHL into a CFD framework such that these methodologies can be interfaced. This study takes an initial step by developing a TEHL solver within OpenFOAM such that the program is prepared to be interfaced with a CFD module in future versions. The OpenFOAM solver includes the Elrod–Adams cavitation model, thermal effects, and elastic deformation of the surfaces, and considers mixing between the recirculating flow and oil feed by applying energy and mass continuity. A sensitivity study of the film mesh is presented to show the solution variation with refinement along the circumferential, axial and radial directions. A validation case is presented of an experimental single axial groove journal bearing which shows good agreement in the pressure and temperature results. The peak pressure in the film is predicted within 12% and the peak temperature in the bush is predicted within 5% when comparing the centerline profiles.

Numerical investigation of variable-mass seepage mechanism of broken rock mass in faults

The continuous migration and loss of small particles in fractured rock mass with water flow is the main cause of water inrush in fault zones. In this study, a fluid–solid coupling model for fault zone was established to study the complex coupling between the groundwater seepage and migration of broken rock mass, and reveal the mechanism of erosion-induced water inrush. The rock skeleton and broken rock mass in the fault zone were modelled by large skeleton particles and small filling particles, respectively, in 3D particle flow software while the fluid flow through the fault was modelled by the built-in computational fluid dynamics module. The numerical results show that: (1) with the increase of water pressure, the loss of filling particles increases continuously, and the whole seepage process can be divided into three stages: slow seepage, abrupt seepage and steady seepage, (2) the mass loss, porosity and permeability first increase slowly, then increase rapidly, and finally tend to be stable, (3) higher fine particle content are more likely to cause structural instability due to mass loss, thus increases the risk of water inrush and mud outburst.

Focus on software, data acquisition, and instrumentation

Focus on software, data acquisition, and instrumentation

A computational fluid dynamics analysis on Fe3O4–H2O based nanofluid axisymmetric flow over a rotating disk with heat transfer enhancement

In present times modern electronic devices often come across thermal difficulties as an outcome of excessive heat production or reduction in surface area for heat exclusion. The current study is aimed to inspect the role of iron (III) oxide in heat transfer enhancement over the rotating disk in an axisymmetric flow. Water is utilized as base fluid conveying nano-particle over the revolving axisymmetric flow mechanism. Additionally, the computational fluid dynamics (CFD) approach is taken into consideration to design and compute the present problem. For our convenience, two-dimensional axisymmetric flow configurations are considered to illustrate the different flow profiles. For radial, axial, and tangential velocity profiles, the magnitude of the velocity, streamlines, and surface graphs are evaluated with the similarity solution in the computational fluid dynamics module. The solution of dimensionless equations and the outcomes of direct simulations in the CFD module show a comparable solution of the velocity profile. It is observed that with an increment in nanoparticle volumetric concentration the radial velocity decline where a tangential motion of flow enhances. Streamlines stretch around the circular surface with the passage of time. The high magnetization force 0 le {{mathrm{m}}_{1}}le 6 resist the free motion of the nanofluid around the rotating disk. Such research has never been done, to the best of the researchers’ knowledge. The outcomes of this numerical analysis could be used for the design, control, and optimization of numerous thermal engineering systems, as described above, due to the intricate physics of nanofluid under the influences of magnetic field and the inclusion of complex geometry. Ferrofluids are metallic nanoparticle colloidal solutions. These kinds of fluids do not exist in nature. Depending on their purpose, ferrofluids are produced using a variety of processes. One of the most essential characteristics of ferrofluids is that they operate in a zero-gravity environment. Ferrofluids have a wide range of uses in engineering and medicine. Ferrofluids have several uses, including heat control loudspeakers and frictionless sealing. In the sphere of medicine, however, ferrofluid is employed in the treatment of cancer via magneto hyperthermia.

Deep-learning-based aerodynamic shape optimization of rotor airfoils to suppress dynamic stall

The use of computational fluid dynamics (CFD) to optimize the aerodynamic shape of rotor airfoils with the aim of suppressing dynamic stall is computationally expensive and inefficient. To address this issue, a surrogate model based on deep learning (DL) is employed to replace a CFD module of optimization process in this study. The optimization framework is demonstrated by optimizing a SC1095 rotor airfoil in subsonic flow. The airfoil shapes are parameterized using the class function/shape function transformation method, and an airfoil dataset for a deep neural network (DNN) is generated by Latin hypercube sampling. The surrogate model for predicting the aerodynamic coefficients of the airfoils is established by training the DNN, which can get the predicted results within a second. This surrogate model is then combined with the multi-island genetic algorithm for rotor airfoil optimization. Finally, the aerodynamic performance of a rotor with the optimized airfoil is investigated to verify the dynamic stall suppression effect. The results demonstrate that the peak drag and moment coefficients of the optimized airfoil can be reduced by 82.5% and 88.6%, respectively, compared with the baseline airfoil, while the lift coefficients increase during almost all of the pitching period. This means that the optimized airfoil has significantly improved dynamic stall characteristics. Moreover, by suppressing the dynamic stall, the rotor with the optimized airfoil achieves better aerodynamic performance than the baseline rotor. Statistical data show that our use of a DL-based surrogate model instead of the CFD module will reduce the optimization time by at least one order of magnitude.

Design analysis and modeling of a floating wave power plant in the coastal zone using the module of computational fluid dynamics

The features of modeling a floating wave power plant (FWPP) in the computational fluid dynamics module are considered. A description of the computational fluid dynamics module is given and its application is shown in optimizing the design of FWPP. The stages of modeling, the order of construction, the necessary initial and boundary conditions, the goals and results of calculations are given. Keywords: floating wave power plant, hydraulic structure, computational fluid dynamics, modeling, power generation, kinematic parameters, internal and surface waves, energy. noreas@mail.ru

Computational fluid dynamics analysis of the natural circulation system in vertical heater horizontal cooler (VHHC) molten salt loop

Molten salt has attracted the attention of researchers, especially as a coolant because of its characteristics. This study aimed to analyse the transient and steady-state of the natural circulation system in the molten salt loop with vertical heater and horizontal cooler using computational fluid dynamics. The computational fluid dynamics module in the COMSOL Multiphysics software was used to solve governing equations. Experimental data from several references were used as input data in modelling. The loop was modelled as a rectangular loop with Inconel 625 as the pipe material and molten salt (NaNO3+KNO3) as the working fluid. The variation of heater power was also carried out in modelling. The modelling results showed a good agreement with the experimental results. The results provided that the molten salt natural circulation loop with vertical heater and horizontal cooler showed good flow stability without reversal of flow direction.

Coupled Numerical Method for Modeling Propped Fracture Behavior

Hydraulic fracturing is a well-known production intensification technique in the petroleum industry that aims to enhance the productivity of a well drilled mostly in less permeable reservoirs. The process’s effectiveness depends on the achieved fracture conductivity, the product of fracture width, and the permeability of the proppant pack placed within the fracture. This article presents an innovative method developed by our research activity that incorporates the benefit of the Discrete—and Finite Element Method to describe the in situ behavior of hydraulic fractures with a particular emphasis on fracture conductivity. DEM (Discrete Element Method) provided the application of random particle generation and non-uniform proppant placement. We also used FEM (Finite Element Method) Static Structural module to simulate the elastic behavior of solid materials: proppant and formation, while CFD (Computational Fluid Dynamics) module was applied to represent fluid dynamics within the propped fracture. The results of our numerical model were compared to data of API RP-19D and API RP-61 laboratory measurements and findings gained by publishers dealing with propped fracture conductivity. The match of the outcomes verified the method and encouraged us to describe proppant deformation and embedment and their effect as precisely as possible. Based on the results, we performed sensitivity analysis which pointed out the impact of several factors affecting proppant embedment, deformation, and fracture conductivity and let one be aware of a reasonable interpretation of propped hydraulic fracture operation. However, DEM–CFD coupled models were introduced regarding fracturing before, to the best of our knowledge, the developed workflow of coupling DEM–FEM–CFD for modeling proppant-supported fracture behavior has not been applied yet, thus arising new perspectives for explorers and engineers.

Nonlinear dynamics of Z-shaped morphing wings in subsonic flow

Morphing wing aircraft have generated increasing interest in recent years owing to their ability to alter the shape and configuration of the wings to retain optimum flight performance under different flight conditions. However, while theoretical approaches have greatly advanced our understanding of the nonlinear vibrational characteristics of morphing wings during the morphing process, little effort has been made to verify the results of theoretical studies based on corresponding experimental results. The present work addresses this issue by first investigating the nonlinear dynamic behaviors of Z-shaped morphing wings during the morphing process in subsonic flow based on thin airfoil theory under ideal incompressible fluid conditions. First, the steady aerodynamic lift on the morphing wing is derived and the nonlinear partial differential equations governing the morphing wing motion are established. The influence of the folding angle on the nonlinear responses of the morphing wing is investigated via numerical simulations. Then, the aeroelastic characteristics of the morphing wing, including the flutter displacements of edge points on the outer plate of the wing, are investigated using the computational fluid dynamics module in ANSYS. Finally, the results of theoretical analysis are verified by experiments conducted with a corresponding Z-shaped morphing wing model.

Development of a Modularized Virtual Flight Simulator based on Multiple Discipline Coupled Method

The problem of aircraft control involves multiple subjects and has always been extremely complicated in mechanics modelling. Virtual flight simulation was put forward in order to reduce the cost of full-scale airplane flying test and wind tunnel experiment. A typical virtual flight simulator includes a computational fluid dynamics (CFD) solver, a structure dynamics (FD) function, and a flight controller. However, existed virtual flight solver usually ignores the universal modelling of dynamics for complex aircraft configuration and the modularization of CFD, FD and flight controller module, which makes it very inconvenient for many in-house virtual flight codes for engineering application and commercial software development. A new framework of virtual flight simulation platform is established with a parallel Reynolds Averaged Navier-Stokes (RANS) solver, a structured moving overlapping grid function, a generic multiple body dynamics (MBD) solver, and a plug-in type flight controller platform. A universal data exchange interface between MBD and flight controller is presented. An X-wing missile flying forward and pitching-up maneuvering validation case is conducted with the current virtual flight simulator, the result is compared with Matlab Simulink solver based on steady aerodynamic database and good agreement is obtained.

Study on the evolution process of recast layer for fast EDM drilling based on observation experiment and a novel thermal-fluid coupling model

The existence of a recast layer of film cooling holes on turbine blades imposes a crucial problem that affects the quality of fast electrical discharge machining (EDM) drilling. This paper focuses on an evolution process from molten material generation to recast layer formation. Single pulse discharge observation experiments with a high speed camera and a self-built observation platform were carried out to observe the formation and movement of the molten material. A novel thermal-fluid coupling model is proposed to combine fast EDM drilling methods with special materials and geometric properties of film cooling hole machining. A heat transfer module, a turbulent flow computational fluid dynamics module, a phase change module and a level set method are combined in this model. The complete process of generation, flow and solidification of molten materials is investigated by simulation with a single pulse discharging. The simulation results agree well with the experimental observation results. A thermal-mechanical coupling analysis of a molten material evolution process is carried out based on the temperature, velocity and pressure fields from the thermal-fluid model. Simulation results show that the molten material is generated at 1 μs after the starting of a discharge, and solidifies within 20 μs after the ending of the discharge. Under the influence of a high-speed flushing fluid, molten materials will not splash into a gap channel along the radial directions. Most of the molten material enters the gap channel along the workpiece surface with a velocity of over 25 m s−1. The moving direction of the molten material is consistent with that of a flushing fluid. The thickness of a recast layer gradually increases from bottom to top in the fast EDM drilling.

A numerical comparative study of axial flow turbines for solar chimney power plant

In sunny regions, solar chimney power plants (SCPP) is a promising technology depends mainly on renewable energy sources. This requires an efficient design of the SCPP components to enhance its reliability and expansibility. Since the turbine is the key component of the SCPP, this article presents a comparative simulation study of three different designs of the SCPP turbine in order to substantiate which one is the most suitable. These designs are based on: the so-called matrix through flow method (MTFM), the classic blade element theory (BET), and a modification of the BET based design to consider the enclosure duct of the turbine. The analysis is based on numerical simulations of the whole SCPP unit using the computational fluid dynamics module ANSYS CFX v18.1. The numerical results of the three designs showed that the modified BET based design gives the highest output power, compared to the two other designs. This study provides recommendations for the design and implementation of SCPPs.

Coupled CFD-FEM simulation for the wave-induced motion of a CALM buoy with waves modeled by a level-set approach

The Finite-Analytic Navier-Stokes (FANS) computational fluid dynamics (CFD) code was coupled with an in-house nonlinear finite element (FEM) mooring analysis program, MOORING3D, to study the dynamic responses of a catenary anchor leg mooring (CALM) buoy system in waves. The hydrodynamic loading on the moored buoy was estimated by the CFD module, in which large eddy simulation (LES) was used as the turbulence model. The FANS code was solved in conjunction with the level-set (LS) formulation to model waves. A motion solver in six degrees of freedoms (DoFs) was coupled with the MOORING3D and the CFD to achieve the coupled analysis. Model-scale simulations of free-decay motions of the buoy were performed and validated by experimental comparison. Simulations of the wave-induced motion of the buoy were performed, and the response amplitude operators (RAOs) were compared to experiments. The agreement with experiments manifested the advantages of the coupled CFD-mooring method in addressing viscous and turbulent effects and nonlinear hydrodynamic effects due to free surface. The sensitivity study of the skirt demonstrates the skirt exerting limited influence on the buoy RAOs, which appeared to be dominated by the inertial and viscous effects of the buoy hull. The conclusions demonstrate that the coupled FANS-MOORING3D code provides accurate prediction of wave-induced motion of floating systems.

Thermal Hydraulics Analysis of the Distribution Zone in Small Modular Dual Fluid Reactor

The Small Modular Dual Fluid Reactor (SMDFR) is a novel molten salt reactor based on the dual fluid reactor concept, which employs molten salt as fuel and liquid lead/lead-bismuth eutectic (LBE) as coolant. A unique design of this reactor is the distribution zone, which locates under the core and joins the core region with the inlet pipes of molten salt and coolant. Since the distribution zone has a major influence on the heat removal capacity in the core region, the thermal hydraulics characteristics of the distribution zone have to be investigated. This paper focuses on the thermal hydraulics analysis of the distribution zone, which is conducted by the numerical simulation using COMSOL Multiphysics with the CFD (Computational Fluid Dynamics) module and the Heat Transfer module. The energy loss and heat exchange in the distribution zone are also quantitatively analyzed. The velocity and temperature distributions of both molten salt and coolant at the outlet of the distribution zone, as inlet of the core region, are produced. It can be observed that the outlet velocity profiles are proportional in magnitude to the inlet velocity ones with a similar shape. In addition, the results show that the heat transfer in the center region is enhanced due to the velocity distribution, which could compensate the power peak and flatten the temperature distribution for a higher power density.

Numerical simulation of the dimensional transformation of atomization in a supersonic aerodynamic atomization dust-removing nozzle based on transonic speed compressible flow

To simulate the transonic atomization jet process in Laval nozzles, to test the law of droplet atomization and distribution, to find a method of supersonic atomization for dust-removing nozzles, and to improve nozzle efficiency, the finite element method has been used in this study based on the COMSOL computational fluid dynamics module. The study results showed that the process cannot be realized alone under the two-dimensional axisymmetric, three-dimensional and three-dimensional symmetric models, but it can be calculated with the transformation dimension method, which uses the parameter equations generated from the two-dimensional axisymmetric flow field data of the three-dimensional model. The visualization of this complex process, which is difficult to measure and analyze experimentally, was realized in this study. The physical process, macro phenomena and particle distribution of supersonic atomization are analyzed in combination with this simulation. The rationality of the simulation was verified by experiments. A new method for the study of the atomization process and the exploration of its mechanism in a compressible transonic speed flow field based on the Laval nozzle has been provided, and a numerical platform for the study of supersonic atomization dust removal has been established.

Computational fluid dynamics (CFD) modelling of hybrid photovoltaic thermal system

In this paper an attempt has been made to simulate and evaluate the distribution of temperature and heat flux for the hybrid photovoltaic thermal system with CFD (computational fluid dynamics) module in ANSYS 19.1 software. The simulation was carried to determine the temperature and heat flux across the different layers of HPVT (hybrid photovoltaic thermal) system. The temperature and heat flux were found to gradually decrease from the top glass layer to the bottom tedlar layer. The temperature varied from 36.4 °C (ambient) to 26.8 °C across the layers from top glass layer to bottom tedlar layer. The heat flux of (561.2 W/m2) at the glass layer due to solar insolation was also found to gradually decrease with the increasing thickness. The reduction in temperature and heat flux with increasing thickness is attributed to fluid flowing beneath the system. The water flowing beneath the tedlar layer takes the excess heat out of the photovoltaic layer, thereby increasing the efficiency of the hybrid photovoltaic thermal system.

Modification of natural waterway shape as a river trash interceptor–an approach model for Citarum River recovery

The Citarum River is the most polluted river in Indonesia. The river irrigates three cascade reservoir such as Saguling, Cirata and Jatiluhur, which serve for hydroelectric power plant, drinking water, agricultural irrigation and fishery. Solid municipal waste and agricultural debris that is dumped into the river cause destruction of river habitats, flooding and shallowing especially in cascade reservoirs. This study aims to develop an idea of river recovery from waste, by using namely river trash interceptor (RTI) located at the Citarum river tributaries due to the economic consideration and efficiency. By using CFD (Computational Fluid Dynamics) and Particle Tracing module, the form of the interceptor is simulated based on the mostly general form of the Citarum River waterway; straight line shape, bend shape and U-type shape. The parameters used are river depth, river width, water discharge, particle size and density. These results of this study could be used as a reference for decision makers and developers on further development of the RTI in the near future.