CFD Program Research Articles

Galloping Simulation of the Power Transmission Line under the Fluctuating Wind

Since the power transmission line (PTL) passes through the high mountain and heavy snowfall region, it is necessary to keep the stability of the PTL. In this study, PTL is modeled as the mass-spring-damper system by using multi-body dynamics analysis program. In order to analyze the dynamic behavior of PTL, a damping coefficient for a multi-body model is derived by using the free vibration test and Rayleigh damping theory. The icing cross section of the transmission line is considered by ellipse and triangle shape. The aerodynamic coefficient for each cross sections are derived by using the commercial CFD program, ANSYS Fluent. The fluctuating wind velocity is regenerated with time history by using Kaimal spectrum. Galloping simulations are performed for the elliptical and triangular iced sections by using the generated fluctuating wind velocity. There is an attack angle which showed the maximum vertical displacement according to the icing section. As a results, the triangular icing shape on the fluctuating wind velocity is more dangerous for the galloping phenomenon. This results can be available to the tower design for the power transmission line.

Multibody dynamics study on galloping of power transmission line

When the power transmission line (PTL) passes through a region of high mountains and heavy snowfall, maintaining the stability of the PTL and avoiding sleet jump and galloping are necessary. In this study, PTL is modeled as the mass-spring-damper system by using the multi-body dynamics analysis program, RecurDyn. The lumped mass model is compared with the finite element model based on deflection. To analyze the dynamic behavior of the PTL under icing and wind conditions, we obtained a damping coefficient for a multibody model from the free vibration test and Rayleigh damping theory. The icing cross-section of the transmission line is assumed to have ellipse and triangle shapes. The aerodynamic coefficients for each cross-section are derived by using the commercial CFD program, ANSYS Fluent. The occurrence of galloping is simulated for each shape according to the attack angle. Results indicate that the dynamic behavior of the PTL and the galloping conditions such as the icing shape, thickness, and attack angle, can be analyzed. Furthermore, the effects of each factor are evaluated. In the elliptical icing section, the effect of icing thickness is high; whereas in the triangular icing section, the wind velocity highly affects galloping.

Numerical and experimental evaluation of a centrifugal compressor

The present paper provides a comparative study in the development of a centrifugal compressor impeller designed for methane (CH4) and tested in similitude conditions, using air as working fluid. The rotor was designed in maximum efficiency conditions and will be part of compression equipment used for underground gas storage for inaccessible areas, experiencing difficulties in gas supply. Optimization of the geometrical shape of the impeller was made using CFD programs based on the finite volume method. Since the experimental tests have taken place at the similitude, the rotating speed had to be adapted to 14915 rpm, to compensate for the change in working fluid. Redundant pressure and temperature probes have been placed on each radial location in order to minimize experimental errors. For the CFD side, the established best practices were employed, using the k-omega SST model with a y+<1 along the walls, with a growth ratio of ~1.2:1. Overall, the global performances were in good agreement with each other

Modeling water flow on Façade

Abstract This study aims to develop a novel method by which visually to simulate water flow paths on building facades. Rainwater runoff affects the designs of facades in terms of safety and aesthetics because runoff leaves dirt and stains on an aesthetic facade. The first step is to review flow simulation algorithms and identify its limitations in fluid visualization research on flow path simulations. The second step is to review an existing CFD program to identify its limitations, and then establish the goals of the newly proposed method. The third step is to identify the properties and behaviors of water on a surface, including basic fluid mechanics to establish the mechanical relationship between the water and the facade material. The fourth step involves an experiment with water flows to reveal their characteristics based on the literature. The fifth step is to develop an algorithm which visually simulates water flows on a building facade. As a result, “Rainflow01” and “Rainflow02” are developed based on the open-source Grasshopper component “Drainage Polysurface” and Rhino. Rainflow01 and Rainflow02, which work based on the angle variation and critical sliding angle of the water path, present an innovative approach for predictions of water paths over a facade.

On numerical methods; optimization of CFD solution to evaluate fluid flow around a sample object at low Re numbers

Computational fluid dynamic methods are applied to survey numerical approximations of partial differential equations. In this area, there is a wide range of numerical methodologies, algorithms, schemes, simulation strategies as well as software programs for solution.In most experimental studies, these complicated numerical methods are used to simulate a problem without enough regard to the communication between the problem, advanced software and the nature of the solution methods. In this study, this scientific gap was considered to discuss most used numerical methodologies, their accuracy and the way numerical methods are used to solve engineering problems. In this research, governing equations and formula of numerical methods are introduced; then a 2-D sample object (cylindrical shape) is simulated in the incompressible flow as an example for simulation in CFD program (ANSYS Fluent 16).

An innovative personalized displacement ventilation system for airliner cabins

In airliner cabins, mixing ventilation systems with gaspers are not efficient in controlling contaminant transport. To improve the cabin environment, this investigation proposed an innovative ventilation system that would reduce contaminant transport and maintain thermal comfort. We manufactured and installed the proposed ventilation system in an occupied seven-row, single-aisle aircraft cabin mockup. Air velocity, air temperature, and contaminant distribution in the cabin mockup were obtained by experimental measurements. The investigation used the experimental data to validate the results of CFD simulation. The validated CFD program was then used to study the impact of the locations and number of exhausts on contaminant removal and thermal comfort in a one-row section of a fully occupied Boeing-737 cabin. Although the diffusers in the proposed system were close to the passengers' legs, the air velocity magnitude was acceptable in the lower part of the cabin and the leg area. The proposed system provided an acceptable thermal environment in the cabin, although passengers could feel cold when placing their legs directly in front of the diffusers. The four-exhaust configuration of the new ventilation system was the best, and it decreased the average exposure in the cabin by 57% and 53%, respectively, when compared with the mixing and displacement ventilation systems.

Modeling of Anisotropic Scattering of Thermal Radiation in Pulverized Coal Combustion

In this work, the effect of applying different approximations for the scattering phase function on radiative heat transfer in pulverized coal combustion is investigated. Isotropic scattering, purely forward scattering, and a δ-Eddington approximation are compared with anisotropic scattering based on Mie theory calculations. To obtain suitable forward scattering factors for the δ-Eddington approximation, a calculation procedure based on Mie theory is introduced to obtain the forward scattering factors as a function of temperature, particle size, and size of the scattering angle. Also, an analytical expression for forward scattering factors is presented. The influence of the approximations on wall heat flux and radiative source term in a heat transfer calculation is compared for combustion chambers of varying size. Two numerical models are applied: A model based on the discrete transfer method (DTRM) representing the reference solution and a model based on the finite volume method (FVM) to also investigate the validity of the obtained results with a method often applied in commercial CFD programs. The results show that modeling scattering as purely forward or isotropic is not sufficient in coal combustion simulations. The influence of anisotropic scattering on heat transfer can be well described with a δ-Eddington approximation and properly calculated forward scattering factors. Results obtained with both numerical methods show good agreement and give the same tendencies for the applied scattering approximations.

CFD Modelling of Adsorption Behaviour in AGN Tank with Polyethylene Terephthalate Plastic Waste Based Activated Carbon

Indonesia imports fuel (fuel oil) in large quantities. Indonesia has reserves of methane gas in the form of natural gas in large numbers but has obstacles in the process of storage. To produce a storage tank to a safe condition then proclaimed to use ANG (Adsorbed Natural Gas) technology. Manufacture of activated PET based activated carbon for storage of natural gas where technology has been widely studied, but still has some shortcomings. Therefore to predict the performance of ANG technology, modeling of ANG tank with Fluent CFD program is done so the condition inside the ANG tank can be known and can be used to increased the performance of ANG technology. Therefore, in this experiment natural gas storage test is done at the ANG tank model using Fluent CFD program. This experiment is begin with preparation tools and material by characterize the natural gas and activated carbon followed by create the mesh and model of ANG tank. The next process is state the characteristic of activated carbon and fluid in this experiment. The last process is run the simulation using the condition that already been stated which is at 27°C and 35 bar during 15 minutes. The result is at adsorption contour we can see that adsorption is higher at the top of the tank because the input of the adsorbent is at the top of the ANG tank so the adsorbate distribution is uneven that cause the adsorbate concentration at the top of the ANG tank is higher than the bottom tank.

Analysis of Flettner Rotor ships in beam waves

Flettner Rotors are spinning cylinders which produce lift force by utilizing wind power. Today, due to global warming and necessity of reducing emissions, renewable energy resources such as wind energy become more significant than ever before. This study presents the influence of Flettner Rotors on roll motion of ships and the effects of roll motion on performance of Flettner Rotors in beam waves. The calculations are carried out by using XFlow CFD program. The sample rotor has a 4 m diameter, 27 m height and a Thom disc. The calculations are performed with 0°, 20°, 40° and 60°heel angles to obtain the heeling moment function and driving force function with respect to heeling angle. The results of roll responses of the sample ship with and without Flettner rotors are presented in time and frequency domain comparatively. The results from the calculations show that the lift power performance of Flettner Rotors decreased with increasing of heeling angle. After adding Flettner Rotor contribution on heeling moment function, it is seen that Flettner rotors do not increase the nonlinearity of roll motion. Also, it was found that at large heel angles the driving force becomes almost zero.

Studies of turbulent coolant mixing flows in the new generation reactors

Due to studying of the flow parameters in the downcomer the bottom plenum of the nuclear reactor can be carried out with the help of CFD programs, the work is devoted to experimental researches in the field of pressurized water reactor with the purpose of creation of benchmarks for verification of domestic codes of computational hydrodynamics. Such data must have high spatial resolution, high resolution and high accuracy of the measurements. It makes necessary to apply complex experimental methodologies, measurement instrumentation and careful adjustment of experimental methodology. So a brief description of the experimental stand and its research methodology is given. A spatial conductometric measuring system that allows to study the processes of turbulent mixing of flows in the complex geometry of the nuclear reactor is presented. The description of experimental research and their results are presented. Conclusions are drawn about the prospects of using spatial conductometry as a vortex-resolving measurement method.

Development and Verification of CFD Program by Central Difference Calculus for Incompressible Fluid

Development and Verification of CFD Program by Central Difference Calculus for Incompressible Fluid

Assessment of the performance for a new design of storage solar collector

This research includes a numerical study for a new design of a storage solar collector to confirm its convenience for household use. This novel collector is called the wedge storage collector and can be utilized as storage water reservoirs to substitute the common cubical or cylindrical container commonly used for domestic application. The study includes storage collector derived from cutting a cylinder at two planes, the first plane is a vertical and the other is an inclined plane at 45 o . Fluent software was used to achieve the numerical study. The free convection process in the space of these storage collectors was investigated based on the finite volume method. From the results of CFD program (Fluent), the distributions of the temperature and velocity during the day were obtained. The maximum value of mean storage temperature inside the storage collector (its volume 666 liter) is 18 o C at 4 p.m. during winter (21 December) when the tap water temperature was 7 o C. During summer, the mean storage temperature inside the storage collector reaches 41 o C when the tap water temperature is 25 o C. It is observed that the mean storage temperature of the water inside the collector decreased with increasing the volume of collector, also the results show there is no obvious influence of the barrier on the mean storage temperature of water inside the collector. This storage collector was better than the previous design of collectors because of the high sunlit ratio area to storage volume which is an important significant parameter affecting the performance of this type of storage solar collector.

Modeling the Design Flow Coefficient of a Centrifugal Compressor Impeller

In calculating gas-dynamic characteristics by the universal modeling method it is necessary to determine a non-incidence flow rate through the blades of an impeller because of its relationship with the magnitude of incidence losses. The flow area decreased by the blades of finite thickness and the blades load have impact on the critical streamline direction. The universal modeling method in primary designing uses for this a scheme of replacing the influence of the blade load by the vortex effect with identical circulation. Finally, calculating the inviscid flow around the blades allows selecting a value of the inlet blade angle. For impellers with small design flow coefficients, the condition of the non-incidence inlet for the primary design and for the calculation of the inviscid flow is significantly different. The calculating correctness of the non-incidence regime for the non-viscous flow was checked earlier by measurements of the flow in the impellers. The paper presents CFD calculations of twenty impellers in a tenfold range of design flow coefficients. To provide correct comparison, it takes into account the differences in the value of the loading factor calculated by the programs of inviscid quasi-three-dimensional calculation and CFD programs. Shows the identity of inlet conditions for both methods. To increase primary design accuracy, the calculation model was refined. The formula for calculating vortex-induced velocity involves an empirical coefficient. The analysis of data for 32 impellers with different blade profiling allowed working out formulas for calculating empirical coefficient, depending on the type of an impeller, the blade load and the width of the throat at an impeller inlet. The new scheme-based calculation with the empirical coefficient is accurate enough for the primary design.

Performance evaluation of passive heat barrier system in Latvian climatic conditions

Lately significant amount of research is being directed towards novel external building walls with embedded pipe systems where a fluid is circulating. Most of presented systems require additional power to function. We present a novel pipe embedded external wall with utilisation of ground heat and the performance evaluation of the system. Main advantage of the system – no auxiliary power is required. The system is called Passive Heat Barrier (PHB). The extracted energy is low grade and it’s applied for reducing heat losses instead of heating internal environment.The performance of the PHB is assessed using CFD program ANSYS CFX 16.2. Result show the PHB can reduce heat flux up to 3.5 times In Latvian climatic conditions. Therefore, such system can improve energy efficiency of the whole building.

Features of Convective Turbulent Flows Behind the Mixing Spacer Grids of the TVS-Kvadrat of The PWR-Type Reactor

This paper presents the results of experimental investigations of the influence of mixing spacer grids with different types of deflectors on the coolant flow in the TVS-Kvadrat fuel assembly of the PWR-type reactor. Investigations were conducted on an aerodynamic stand with the use of a multichannel pneumometric probe. Analysis of the spatial distribution of projections of the absolute flow velocity permitted detailing the coolant flow pattern behind the mixing spacer grid with various types of deflectors of mixing grids. The results obtained in the present paper are used to verify three-dimensional CFD programs, and in applied cell by cell codes they also serve as a database in calculations of thermotechnical reliability of the cores of PWR-type reactors with the TVS-Kvadrat.

Numerical Investigation of Electroosmotic Flow in Microchannels

Electrokinetic micropumps receive increasing attention due to their applications in pumping of biological and chemical fluids; such as blood, DNA, and saline PBSs. In this paper, the electroosmotic flow in square microchannels has been numerically investigated by developing a model from the basic governing equations (continuity, momentum, energy, Laplace and Poisson- Boltzmann equations). These equations were numerically solved by CFD program for two fluids (water and PBS). The study considered the external applied electric field and zeta potential to interrogate their potential effects on electroosmotic flow. Thermal characteristics of electroosmotic flow have been also studied by calculating the temperature distribution through electroosmosis micropump region. The results confirm the considerable effect of applied electric field, concentration of electrolyte fluid and zeta potential on microflow velocity and flow rate. The PBS gave higher velocity and flow rate values compared with water, and there was only a slight increase in temperature due to Joule heating effect.

Discrete element method for the prediction of the onset velocity in a spouted bed

Spouted Bed Reactors (SBRs) are currently receiving a lot of attention due to their properties: thanks to the enhanced mass and energy transfer rates and the unique configuration of these reactors, solid particles can be handled with very high efficiency, making them suitable for several applications, such as biomass gasification. Spouted Bed Reactors can also give positive responses to the problem of segregation, which strongly compromises the efficiency of processes involving the handling of heterogeneous mixtures.The aim of this work is to study the behaviour of a spouted bed facility, both experimentally and via simulations performed with the CFD program ANSYS FLUENT, in view of a possible employment of it to assess the scale up criteria or segregation phenomena in spouted beds. The solid phase is simulated enabling the DDPM-DEM model (Dense Discrete Phase Model - Discrete Element Method), commonly known as the Eulerian-Lagrangian approach. The influence of the following physical properties of the particles on the onset velocity was assessed: diameter, sphericity and density. The results of the simulations were compared with those obtained experimentally, for a single solid phase using three different types of inert material (glass, sand and PET) and also for a binary mixture. The model has been proved to be a useful tool to evaluate the performance and estimate the onset gas velocity of the spouted bed.

Fully coupled fluid-structure interaction model of reed valves in a multi-cylinder reciprocating piston compressor

For years compressor researchers have tried to account for the fluid interaction effect of the working fluid on valve motion in displacement compressors. In recent years, the computing capacities and available CFD and FEA programs have allowed fully coupled interaction of fluids and moving structures to be modelled more comprehensively. This paper describes our experience and results from developing a model of a multi-cylinder reciprocating piston compressor with suction and discharge valve systems that are fully coupled with the pressure pulsation in the adjacent plenum. Valve dynamics are captured by the model that affects compressor performance. The results show that higher running speed causes more discharge valve delay on closing due to higher pressure pulsation in discharge plenum. The acoustic property of the discharge plenum as it relates to valve motion is studied by the developed cost-effective standalone model.

Kinetic energy based model assessment and sensitivity analysis of vortex induced vibration of segmental bridge decks

In this paper, semi 3D models for segmental Bridge decks are created in ABAQUS CFD program with the support of MATLAB codes to simulate and analyze vortex shedding generated due to wind excitation through considering the stationary position of the deck. Three parameters (wind speed, deck streamlined length and dynamic viscosity of the air) are dedicated to study their effects on the kinetic energy of the system in addition to the shapes and patterns of the vortices. Two benchmarks from the literature Von Karman and Dyrbye and Hansen are considered to validate the vortex shedding aspects for the CFD models. Good agreement between the results of the benchmarks and the semi 3D models has been detected. Latin hypercube experimental method is dedicated to generate the surrogate models for the kinetic energy of the system and the lift forces. Variance based sensitivity analysis is utilized to calculate the main sensitivity indices and the interaction orders for all the three parameters. The kinetic energy approach performed very well in revealing the rational effects and the roles of each parameter in the generation of vortex shedding and predicting vortex induced vibration of the deck.

A research of heat transfer enhancement of rectangular channel with dimples

this thesis is aimed to do numerical simulations on rectangular channel with a new model of dimple in different condition of channel height, dimple depth, dimple distance by using CFD program and RNG k-e model. It is concluded that, the existence of dimple has changed the velocity and direction of the fluid, as well as the original flow status. Dimple increased the heat exchange area of rectangular channel and broke the boundary layer, enhanced the flow rate of fluid, as a result of enhanced heat transfer performance.