CFD Simulation Results Research Articles

RANS based CFD Simulations for Urban Wind Prediction –Field Verification against MoTUS

The current paper presents an investigation, which has its main objective in the verification of outdoor wind flow CFD simulation results (ANSYS R Fluent) with real environment measurements in urban setting. The details of the simulation set-up are discussed in the paper including the inlet boundary conditions, surface roughness parameters and the source/sink terms to represent the effect of trees. The simulation results are compared with the high-resolution on-site wind velocity measurements from the Measurement of Turbulence in an Urban Setup (MoTUS) project of Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland. Multiple simulations were conducted to evaluate the performance of the model based on different wind direction and speeds. At the end of the current study, the highly consistent and accurate results were observed from all 18 verification cases; with the RMSEs of the simulated wind velocities in range of 0.21 and 0.59 m/s only.

STRESS AND FATIGUE LIFE PREDICTION OF THE H-TYPE DARRIEUS VERTICAL AXIS TURBINE FOR MICRO-HYDROPOWER APPLICATIONS

The present study aims to analyze the structural behavior of the Darrieus Hydro-kinetic turbine at different upstream velocity values and rotational rates. For that purpose, one-way fluid-structure interaction is performed to predict stresses, deformation and fatigue life of the turbine. To determine real-time fluid loads three-dimensional fluid flow simulations were performed, the obtained fluid loads were transferred to the structural finite element analysis model. CFD simulation results were validated with experimental results from literature where the close agreement was noticed. Structural analysis results revealed that the highest stresses are produced in the struts and at the joint where the shaft is connected with struts. Moreover, it was also found that the stress produced in the turbine is highly non-linear against Tip Speed Ratio (TSR) i.e inflow water velocity. Finite Element Analysis (FEA) results showed that maximum values of stresses were found in the turbine strut having a value 131.99MPa, which lower than the yield strength of the material, the fatigue life of 117520 cycles and factor of safety 1.89. The study also found that increased inflow velocity results increase in stress and deformation produced in the turbine. Additionally, the study assumed Aluminum Alloy as turbine blade material, further; it was found that the blade which confronts flow, experience higher stresses. Moreover, the study concluded that strut, blade-strut joint and strut-shaft joint are the critical parts of the turbine, require careful design consideration. Furthermore, the study also suggests that the turbine blade may be kept hollow to reduce turbine weight; hence inertia and turbine struts and shaft should be made of steel or the material having higher stiffness and strength.

Experimental Verification of CFD Simulation When Evaluating the Operative Temperature and Mean Radiation Temperature for Radiator Heating and Floor Heating

The assessment of heating systems is not only interested in the efficiency of the heating system itself, but also in the quality of the environment that the heating system creates. The quality of the environment and the heat-humidity microclimate is closely related to thermal comfort. A suitable environment has a positive effect, for example, on the efficiency of work at the workplace. The range of temperatures, humidity and operating temperatures in workplaces is often also legally prescribed in such a way that there is no thermal discomfort for users in the heated space. In terms of savings, it is therefore best to use heating systems that can create a comfortable environment with the lowest possible energy costs. During their development, variations are possible with temperature gradients, the size of the heat exchange area, or the ratio of the radiant and convective components of heat transfer. When developing such systems, it is appropriate to consider CFD simulations. The comparison of the results of CFD simulation and experimental measurement is also in the following article, where the comparison of the operating temperature and the mean radiation temperature of two different heating systems in the model office is monitored.

Exhaust Prototype Design of L12B Engine

The CFD simulation test carried out on the prototype exhaust, produce an average fluid flow velocity value of 8.36 m/s, and the experimental test results using a flowbench engine on the prototype exhaust, produce an average fluid flow velocity value of 8.49 m/s, so the errorcomparison from themeasurement results on the prototype exhaust between the CFD simulation and experimental results is 1.53%. Fluid flow velocity is a measurement reference in this study because it directly affectsthe scavenging effect on the internal combustion engine, which of course will directly affect the level of power generated by the engine.

Exploring the feasibility of predicting contaminant transport using a stand-alone Markov chain solver based on measured airflow in enclosed environments

Correctly predicting contaminant transport in enclosed environments is crucial for improving interior layouts to reduce infection risks. Using the measured airflow field as input to predict the contaminant transport may overcome the challenges of measuring complex boundary conditions and inaccurate turbulence modeling in the existing methods. Therefore, this study numerically explored the feasibility of predicting contaminant transport from the measured airflow field. A stand-alone Markov chain solver was developed so that the calculations need not rely on commercial software. Airflow information from CFD simulation results, including the three-dimensional velocity components and turbulence kinetic energy, was used as surrogate for experimental measurement based on the spatial resolution of ultrasonic anemometers. Three cases were used to assess the feasibility of the proposed method, and the calculation results were compared with the benchmark calculated by the commercial CFD software. The results show that, when the airflow was simple, such as that in an isothermal ventilated chamber, the stand-alone Markov chain solver based on the measured airflow field predicted the trend of contaminant transport and peak concentrations reasonably well. However, for complex airflow, such as that in non-isothermal chambers with heat sources or occupants, the solver can reasonably predict only the general trend of contaminant transport.

Prediction of the Acoustic Reflection in a Realistic Aeroengine Intake With Three Numerical Methods to Analyze Fan Flutter

Abstract For a particular range of frequencies, an acoustic coupling between the fan and the air intake can modify fan stability regarding flutter. Previous works have shown that characterizing the reflection on the intake opening might be a cru- cial element to target operating points for which the risk of acoustic driven flutter is high. To do so, three methodologies are compared in this paper: an aeroelastic CFD simulation, an acoustic potential simulation and an analytical model. Each of them has a different fidelity level and computational cost, what makes their usage more beneficial at some step in the design process. It is shown that results of aeroelastic CFD and acoustic potential simulations are in excellent agreement. Fast acoustic simulations are then a good option in the early design process. The analytical model presents an important error mainly on the phase, and should be adapted before usage.

An adaptive approach to duct optimization of an industrial boiler air supply system using airfoils

The purpose of this paper is to examine the pressure drop caused by placing an airfoil at different angles of attack in the straight part of the rectangular air duct, as the first step of investigating the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow in radial elbows of an air supply system used in industrial boilers. The initial problem was approached by using the commercial CFD code based on the finite volume method to numerically simulate a 2-D incompressible turbulent flow and by conducting direct experimental measurements in the wind tunnel. The results of CFD simulations have been compared to experimentally measured data for two considered cases of inlet velocities and five different angles of attack. Numerical solutions show an adequate level of agreement with experimental measurements. The obtained results indicate the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow.

Design and Flow Analysis of an Adjustable Check Valve by Means of CFD Method

The article presents results of research on an adjustable check valve. In particular, the article deals with improvement of flow characteristics and reduction in pressure losses of an existing valve design. The subject of the research was the valve body in the form of a steel block intended for mounting a typical cartridge valve insert. Two variants of the valve body were analysed: a standard one, which is currently in production, and the proposed new solution, in which the geometry was modified based on the results of CFD simulations. The main research task was to properly shape and arrange holes and flow channels inside the body, between the cartridge valve and the connecting plate. Using CFD analyses, a solution for minimising the flow resistance was sought and then the method of modifying flow channels geometry was developed. The CFD simulation results showed a significant reduction in pressure loss, up to 40%. The obtained simulation results were verified on a test bench using a prototype of the proposed valve block. A high degree of consistency in the results of CFD simulations and laboratory experiments was achieved. The relative difference between simulation and experimental results in the entire considered range of the flow rate did not exceed 6.0%.

Upgrading the performance of a new shell and helically coiled heat exchanger by using longitudinal fins

Shell and helically coiled tube heat exchangers are comprised of curved tubes inside a shell and they are usually utilized in different sectors such as refrigeration systems, chemical processes, food industry, heat recovery systems and thermal storage systems. Improving the efficiency of heat exchangers could result in improve in the total performance of energy systems. The main purpose of the present research is to specify the effect of adding fins over helically coiled tube on thermal performance of a horizontal shell and helically coiled tube heat exchanger. In the first step of this study, CFD method was utilized to simulate finned and finless heat exchangers and determining the influence of adding fins. In the next step, manufactured finless and finned heat exchangers were tested experimentally. CFD simulation and empirical results of the present work exhibited the positive effect of integrating fins on the coil. Integrating fins over the helically coiled tube led to increase in turbulence intensity and consequently improved the heat transfer. The effectiveness of finned and finless heat exchangers was attained between 0.59 and 0.93. Integrating fins led to obtain an average improvement of 10% in the heat transfer coefficient. Furthermore, adding fins led to achieve a mean improvement of 10.6% in the overall heat transfer coefficient. While, the highest improvement in the overall heat transfer coefficient obtained as 15%.

Results of CFD-simulation of a solar photovoltaic-thermal module

Currently, in the energy supply of agroindustrial complex facilities there is an increasing interest in the development of structures and engineering systems using renewable energy sources, including combined photovoltaic-thermal modules (PVT-modules), combining photovoltaic modules (PV-modules) and solar collectors in one design. The use of PVT-modules technology makes it possible to increase the electrical performance of solar cells due to their cooling during operation, while the use of PVT-modules integrated into the roofs and facades of buildings can significantly reduce the need for centralized electricity and heat supply. The purpose of this work is to develop a CFD model of a solar PVT module for producing an estimate of the thermal performance of a PVT module. Using the ANSYS Fluent software package, a CFD model of the PVT module was developed. The contours of the temperature distribution, the coolant pressure in the PVT module channel at different values of the coolant flow at the entrance to the PVT module were obtained. The paper presents the daily variation of thermal power and total insolation calculated using the solar calculator built into ANSYS. The verification of the developed CFD-model of the PVT-module showed the comparability of the calculated values with the data obtained analytically and experimentally - the relative error of the results was no more than ± 1%. ANSYS is an effective software package that allows simulating thermal processes in PVT-modules.

Numerical Simulation of Carbon Black Plasma Synthesis From Wood Sawdust

This article presents the results of numerical CFD simulation of carbon black (CB) plasma synthesis from wood sawdust. The data on the content of sawdust pyrolysis products at different nitrogen plasma temperatures, different particle size distributions, and changes in the carbon-containing raw material consumption are presented. The obtained results could be used for the engineering of plasma systems for CB production from wood sawdust.

Modelling of turbulent shear controllable co-precipitation synthesis of lithium ion battery cathode precursor micro-particles in a Taylor-Couette flow reactor with variable configurations of inner cylinder

Turbulent shear controllable co-precipitation synthesis of lithium ion battery cathode precursor micro-particles, Ni0.6Co0.2Mn0.2(OH)2 (NCM622), in a Taylor-Couette flow (TC) reactor has been investigated using both CFD simulation and experimental validation. The experimental co-precipitation in TC reactor was conducted using two types of inner cylinder, circular and lobed cross-sections (referred to as CTC and LTC), focusing on the effects of processing time and local turbulent shear rate. CFD simulation was employed to reveal the difference of flow field at various operating conditions. Both CFD simulation and experimental results show that the increased shear rate can lead to the decrease of the final synthesised micro-particle size due to the suppression of particle growth by turbulence eddy induced shear. Taylor-Couette flow by using the lobed inner cylinder can achieve an enhanced shear rate in the impinging jet regions formed in the vicinity of the inner cylinder surface due to the occurrence of a large radial velocity gradient. Consequently, the synthesised micro-particle properties such as morphology and specific surface area in the LTC are much more improved than those in the CTC. The mixing was also assessed and characterised by two variables, mean mixture fraction and its variance, predicted by CFD modelling with user-defined scalar (UDS), and correlating with the effect of shear rate for both the CTC and LTC. CFD simulation reveals that effective mixing at both the macro-scale and micro-scale can be quickly achieved in the LTC.

Site Test Performance and Numerical Study of Vertical Axis Hydrokinetic Turbine Straight Blade Cascaded (VAHT–SBC)

The Vertical Axis Hydrokinetic Turbine – Straight Blade Cascaded (VAHT-SBC) is a type of energy generation technology developed to meet the increasing demand for renewable energy. Previous studies have been carried out to enhance the efficiency of the turbine through several aspects. To deploy a turbine on site, a study on its power generation and conversion is needed. In this research, the VAHT–SBC was integrated with a permanent magnet synchronous generator (PMSG) by a pulley and belt transmission system. This study was conducted by experimental and numerical analysis. The CFD simulation result showed that the highest torque of the turbine was found at 0° and 360°, with an average value of 23.923 Nm and with current velocity at 0.92 m/s. The experimental data showed that the voltage and frequency were proportional to the generator rotational speed and inversely correlated with the load given to the integration system. In the inverter, the voltage and frequency values were stable at 230 V and 56 Hz respectively. The VAHT-SBC prototype was able to produce a maximum power of 50 W on site, with a current velocity of 0.82 and 0.92 m/s.

Оценка эффективности сжигания аммиаксодержащего газа в реакционных печах установки Клауса с использованием методов вычислительной гидродинамики

Based on the computational fluid dynamics method using ANSYS Fluent software, we carried out a simulation of acid gases combustion process in the Claus furnaces with further combustion of ammonia containing gas originated from sour water stripper. The sulphur recovery unit of the heavy residue conversion complex owned by TAIF-NK was considered as a research subject. As per the results of CFD-simulation, the optional scenarios were defined for utilization of ammonia containing acid gases in the sulphur recovery unit by adjustment of gas composition, thermodynamic conditions, as well as by controlling the flow pattern in the Furnace. The data obtained agree quite well with the actual performance parameters of the existing unit and the findings in the public domain.

Teorijsko i eksperimentalno istraživanje zone rezanja nastale primenom AWJ procesa

The aim of this paper is to make a theoretical and experimental study to evaluate the water jet influence on a metallic material used in oilfield manufacturing, using AWJ process. It was investigated how the scattering of the jet has influenced the width of the kerf and neighboring area. The metallic material is P275NL2 which is a low temperature quality steel alloy specially used in petrochemical industry. The experimental tests were made on the waterjet cutting machine model YCWJ-380-1520 using preestablish working conditions. Theoretical investigations were performed using CFD simulation with planar 2D fluid flow on the geometrical model. Graphical correlation was performed between theoretical outcomes given by CFD simulation and experimental results on the regarded material, overlapping on the theoretical searching for the cutting velocity and the hardening velocity limits nearby the kerf.

Influence of the limited room space on inlet conditions and fan operation at the rotating test rig

The limited space of the laboratory room allows maintaining the selected ambient air parameters in the required ranges. It can be, however, a source of many problems in the case of rotating test rigs that blow a large amount of air. The aim of the paper is to examine the influence of limited space and its shape on the working conditions of axial fans test stand. The focus was particularly on the conditions prevailing at the inlet to the test rig and their potential impact on the tested fan operation. The article presents the results of CFD simulations for two rooms of different volumes and the results of experimental measurements carried out for the smaller one. Good qualitative agreement between the simulations and the experiment was obtained. The limited space around the test rig causes the unsteadiness of the axial velocity profile and introduces an unsteady swirl at the inlet. This leads, in turn, to local changes in the angle of attack of the fan blades and the resulting consequences related to the off-design working conditions. The paper proves the need to minimise the effects of the induced airflow in the test room and proposes some methods to accomplish this task.

Modelling of complex boron dilution transients in PWRs—Validation of CFD simulation with ANSYS CFX against the ROCOM E2.3 experiment

This paper compares CFD simulation results of a boron dilution scenario with experimental results. The simulation was carried out with ANSYS CFX using the SST turbulence scheme, experimental data were produced in the ROCOM test facility, experiment E2.3. The main features of the scenario are asymmetric, transient mass flow conditions in the affected loops 1 and 2 of a KONVOI-type reactor vessel and reduced density of the underborated coolant slugs fed into the reactor trough the cold legs of both loops. The CFD simulation was able to capture the density stratification in the loops affected by underboration and the mixing in the downcomer and in the lower plenum. Good agreement with the experiment was obtained for the temporal evolution of average boron concentration in several measuring sections of the reactor vessel and of the boron distribution in the core inlet. In general, minimum values of boron concentration were found to be lower in the simulation than in the experiment.

CFD analysis of pylon equipped by plasma module for combustion in supersonic airflow

Two new geometrical configurations of pylon equipped by plasma module for combustion in supersonic airflow were developed and discussed. This paper presents the results of three-dimensional CFD simulation of the flow around the pylon. The simulation was performed for two modifications of pylon and two possible geometries of set of three pylons. No fundamental difference was found between the two pylon geometries. It was shown that in one case of the installation of three pylons it provides continuous flow around the pylons, which should ensure stable operation of the plasma generator. In the second case of the arrangement of the pylons, the obtained flow structure promotes faster mixing of fuel with air; however, a significant separation zone is formed behind the pylons, which may impede the stable operation of the discharge.

Cross verification of a simplified model of pure steam condensation in a tube bundle using experimental and CFD-simulation data

This paper presents an analysis of a simplified model of pure steam condensation in a bundle of smooth horizontal tubes. The model was based on classical recommendations for calculating the condensation process in tube bundles. Two different approaches were used to calculate the condensation heat transfer coefficient in the model. First, the inundation effect was not considered, and the average heat transfer coefficient was calculated for condensation on a single cylinder using the Nusselt equation. Second, condensation drainage which is asymmetric to the vertical diameter of the tube was considered. The results of these calculations were verified using available experimental data. The analysis of distributions of condensation local characteristics was presented. The results of detailed CFD simulation using a previously developed author’s model was employed for additional cross-verification of closing equations used in the simplified model.

CFD Simulation and Analytical Validation of Rectangular and Square microchannel heat sink with liquid water as cooling medium

In present work, both analytical and CFD investigation was performed to check the microchannel heat sink cooling performance, made up of copper with two different microchannel cross sections with shape of rectangle and square. CFD analysis is conducted with water as working fluid for both of the cross sections and Reynolds number ranging from 600 to 1000. A copper microchannel heat sink with bottom size of 25.4mm×25.4mm and height of 2.384mm is selected and CFD analysis was carried out and at bottom constant heat flux boundary condition is assumed. For comparison between two cross sections, the hydraulic diameter used is same for both. Rectangular cross section microchannel showed better cooling performance as compared to square cross section microchannel. Both analytical and CFD simulation results of pressure drop in rectangular microchannel heat sink are in good agreement with a difference of 18.9%.