Finite Control Volume Research Articles

A Computational Investigation of Unsteady Aerodynamics of Insect-Inspired Fixed Wing Micro Aerial Vehicle’s 2D Airfoil

A Micro air vehicle (MAV) is defined as class of unmanned air vehicle (UAV) having a linear dimension of less than 15 centimeters and a mass of less than 100 grams with flight speeds of 6 to 12 meters per second. MAVs fall within a Reynolds number (Re) range of 50,000 and 120,000, in which many causes of unsteady aerodynamic effects are not fully understood. The research field of low Reynolds number aerodynamics is currently an active one, with many defence organizations, universities, and corporations working towards a better understanding of the physical processes of this aerodynamic regime. In the present work, it is proposed to study the unsteady aerodynamic analysis of 2D airfoil using CFD software and Xfoil panel code method. The various steps involved in this work are geometric modelling using CATIA V5R17, meshing using ICEM CFD, and solution and postprocessing through FLUENT. The finite control volume analysis and Xfoil panel code method has been carried out to predict aerodynamic characteristics such as lift coefficients, drag coefficients, moment coefficients, pressure coefficients, and flow visualization. The lift and drag coefficients were compared for all the simulations with experimental results. It was observed that for the 2D airfoil, lift and drag both compared well for the midrange angle of attack from −10 to 15 degree AOA.

Modelling of the transmission system in conveying equipment based on Euler method with application

This paper presents an approach to predict and evaluate the dynamic characteristics of the transmission system in conveying equipment under various working conditions. To solve the problems of varying mass and load, the space, which the transmission system locates, is divided into multiple space-fixed finite control volumes according to the material distribution as well as motion pattern. Each volume is further discretized into a series of finite elements. System-governing equations are obtained by the assembly of all the individual elements’ dynamic equations and the topological structure of the transmission system. Karnopp model is utilized as the basis to render the duty resistance induced by friction. As an illustrative example, the present method is applied to model a large-scale armoured face conveyor, and the corresponding simulation code is developed based on Matlab/Simulink. Simulation results show that the start-up and stop processes with empty load are relatively smooth, which is beneficial to protect the components of the system, especially the chains. Furthermore, the resulted chain-steady velocity, chain-load spectrum and minimum tension force can be directly used to predict the conveying capacity, evaluate chain strength and optimise the pretension force.

Water Level Rise Upstream a Permeable Barrier in Subcritical Flow: Experiment and Modeling

This work addresses the dependence of water depth upstream a permeable barrier, h1, with discharge per unit channel width, Q/W, in sub-critical flow regime. The barrier, that extends over the entire width of the channel, is composed by smooth cylinders of small aspect ratio vertically mounted on the bottom in a staggered pattern and fully submerged in the flow. The height of the cylinders above the bottom was kept constant for all runs. Several configurations were considered by varying systematically the cylinders diameter, dv, the number of cylinders per unit area of the bed, or density, m, and the length of the barrier in the stream direction, Lv. A one-dimensional model was developed to predict the observed values of h1 and to obtain a sound basis taking into account the incidence of Q/W, m, dv and Lv. This model is based on fluid mechanics equations applied on a finite control volume for the flow in the test section, and it was deduced under simplifying assumptions physically-based. Finally, and based on the experimental results and the model predictions, the mechanical energy losses of the flow are analyzed. The main role played by a dimensionless number R, that takes into account the barrier's resistance to the flow, is highlighted.

Generalized shell heat transfer element for modeling the thermal response of non-uniformly heated structures

A generalized shell heat transfer element is formulated in isoparametric coordinates to simulate the 3D thermal of non-uniformly heated shells with curved geometries. The element uses a combination of finite element and control volume methods to discretize the domain of the element into 2D layers that are coupled by a finite difference calculation. As demonstrated in previous work, the finite element-control volume formulation allows the thermal response to be evaluated with minimal computational expense and the temperature field is calculated in a manner that is compatible with distributed plasticity elements for structural analysis. Although the formulation uses a mixture of finite element and finite difference equations, the element equations are in a form that can readily be implemented in a commercial finite element code. The nine-node quadratic element considered here is implemented in Abaqus as a user-defined element. One-, two-, and three-dimensional verification cases are presented to demonstrate the capabilities of the element. Comparisons between the shell heat transfer element and traditional continuum heat transfer elements illustrate that the shell element converges rapidly and results in significant savings in computational expense.

High Temperature Fatigue Tests of Cu-be and 40CrMoV13.9 Alloys

The present paper summarizes the results from uniaxial-tension stress-controlled fatigue tests performed at different temperatures up to 650°C on Cu-Be and 40CrMoV13.9 specimens. Two geometries are considered: hourglass shaped (both materials), plates weakened by a central hole (Cu-Be alloy). The motivation of the present work is that, at the best of authors’ knowledge, only a limited number of works on these alloys under high-temperature fatigue are available in the literature and no results deal with notched components.In the present contribution, after a brief review of the recent papers, material properties and experimental procedure are described. The new data from un-notched and notched specimens are summarized in the corresponding fatigue curves.The Cu-Be specimens fatigue data are re-analysed in terms of the mean value of the Strain Energy Density (SED). The approach, successfully used by the same authors to summarise fatigue data from notched specimens made of different materials tested at room temperature, is extended here for the first time to high-temperature fatigue. In the plates with central holes the SED is evaluated over a finite size control volume surrounding the highly stressed zone at the hole edge. A value of the radius equal to 0.6mm seems to be appropriate to summarize all fatigue data in a quite narrow scatter-band. Thanks to the SED approach it is possible to summarise in a single scatter-band all the fatigue data, independent of the specimen geometry.

Characteristics of Homogeneous Nucleation Boiling in Ethanol during Rapid Linear Boundary Heating

The characteristics of homogeneous boiling in ethanol subjected to rapid heating with a linearly increasing boundary temperature condition have been studied by applying a theoretical model. A finite liquid control volume or cluster at the liquid boundary hasbeen considered in this model where energy is stored due to external heating while some energy is consumed due to bubble nucleation and subsequent growth. A particular state of liquid heating has been defined as the boiling explosion condition when massive scale vaporization causes the liquid sensible energy to decrease. As the size of liquid cluster, two different length scales have been adopted such as, size of a critical vapor embryo (2rc) and thermal penetration depth ▪. For ethanol heating with initial and boundary conditions identical to those reported in the literature, the model predicts the time of the homogeneous boiling explosion with reasonable agreement with the experiments with the liquid cluster size being assumed to be that of a critical vapor embryo (2rc); while the consideration of the thermal penetration depth ▪ results in late prediction of the occurrence of boiling explosion. However, the temperature at the boiling explosion essentially corresponds to the same for both sizes of the liquid cluster. The obtained results have been presented and discussed in terms of the average liquid temperature rise inside the liquid cluster, maximum attainable cluster temperature and time to reach the boiling explosion condition for a wide range of boundary heating rates (10-109 K/s).

Prediction of Asphalt Pavement Temperature Profile with Finite Control Volume Method

The accurate prediction of the pavement temperature profile and history is critical for the calculation of the viscoelastic response of asphalt concrete pavements under traffic and thermal loadings. An accurate prediction is also essential in the estimation of the asphalt binder oxi-dative aging. A sound alternative approach is proposed to predict the pavement temperature profile with the finite control volume method in a fully implicit scheme. The model for the finite control volume method provides a fundamental and clear understanding of the heat energy balance, including the incoming and outgoing thermal energies, in addition to the dissipated heat in the system. Also, the variability in the materials’ thermal properties in a multilayered pavement structure can be remedied by assigning appropriate thermal properties to each control volume or cell. The fully implicit scheme improved the time efficiency of the calculation significantly. Moreover, enhancements were made by defining the accurate heat balance equations for the pavement surface and the bottom boundary conditions. With reliable meteorological data, solar radiation, and monthly variable pavement surface radiation properties, accurate prediction of the pavement temperature profile was made possible as validated by comparison with field measurements. Consequently, Windows-compatible software has been developed on the basis of the proposed model, which is capable of effectively predicting the pavement temperature profile and history.

High-temperature fatigue strength of a copper–cobalt–beryllium alloy

This article summarizes the results from uniaxial tension stress-controlled fatigue tests performed at 650°C on Cu-Be specimens. Two geometries are considered: hourglass-shaped specimens and plates weakened by a central hole. The motivation of this present study is that, at the best of the authors knowledge, only a limited number of studies on copper alloys under high-temperature fatigue are available in the literature, and no results from these alloys deal with notched components. In the present contribution, after a brief review of the recent literature, material properties and experimental procedure are described. The new data from un-notched and notched specimens are summarized in the corresponding fatigue curves. By analyzing the fatigue behavior of the plates weakened by central holes, a reduction of the fatigue strength about equal to 40% at 2 million cycles can be noted, whereas the inverse slope, k, is very close to that of un-notched specimens. All fatigue data from un-notched and notched specimens are reanalyzed here in terms of the mean value of the strain energy density. The approach, successfully used to summarize fatigue data from notched specimens tested at room temperature, is extended here for the first time to high-temperature fatigue. In the plates with central holes, the strain energy density is evaluated over a finite size control volume surrounding the highly stressed zone at the hole edge. A value of the radius equal to 0.6mm seems to be appropriate to summarize all fatigue data in a quite narrow scatter band.

Process simulation for a large composite aeronautic beam by resin transfer molding

This paper presents the numerical process analysis and the experimental investigation for the manufacturing of a reinforced carbon-fiber demonstrator of a large aeronautic beam by resin transfer molding (RTM). The component is a primary structure characterized by several thick sections with abrupt changes in shape that complicates the resin impregnation of the preform. Process simulations based on a finite element method-modified control volume (FEM-CV) were conducted to investigate the resin flow front patterns and find the injection scheme that guarantees both a good impregnation of the preform and a filling time compatible with the resin gel time. The beam component was successfully manufactured, and a good agreement between the numerical analysis and the fabrication process was demonstrated.

Numerical study on the thermal performance of a ventilated facade with PCM

A new type of ventilated facade (VF) with macro-encapsulated phase change material (PCM) in its air cavity is presented in this paper. Two identical house-like cubicles located in Puigverd de Lleida (Spain) were monitored during 2012, and in one of them, the VF with PCM was implemented in the south wall. The versatility of the facade allows the system to reduce both heating and cooling loads. During winter, the PCM increases the heat storage capacity of the system exposed to solar radiation and during summer the system can be used as a cold storage unit or as a night free cooling device. From the experimental winter campaign, important net electrical energy savings were registered due to the use of the VF. On the other hand, no net energy savings were achieved during summer due to excessive use of mechanical ventilation. In this paper, an own developed numerical model, based on finite control volume approach, was validated against experimental data and it is used to select the operational schedule of both solidification and melting processes in order to achieve net electrical energy savings. During the mild summer period the system presents a net energy supply of 2.49 MJ/day. This value would be increased by 61.6% if a wooden structure would have been used instead of the current metallic structure. Moreover, the high hysteresis of the PCM limits strongly the potential of the system in supplying cooling during the severe summer period.

Numerical study on thermo-hydraulic performance of an offset-bubble primary surface channels

In this paper, the thermo-hydraulic performance of an offset-bubble primary surface channel is presented. The idea of the present design comes from the cross corrugated (CC) primary surface channel and offset-strip plate-fin channel, which imports the transverse disturbance of plate-fin channel into the primary surface channel. The analysis is accomplished by the finite control volume method and the low Reynolds k–w turbulent model is used. Under the similar geometrical parameters, the comprehensive performance of the offset-bubble primary surface channel is the best, whose averaged area goodness factor is enhanced by 41% and 71% compared to the CC3.1-60 (pitch-over-height ratio of 3.1 and inclined angle of 60°) and offset-strip plate-fin channels. The comprehensive performance of the offset-bubble primary surface channel with the baseline dimension is superior to the CC4-45 (pitch-over-height ratio of 4 and inclined angle of 45°) and CC3.1-60 primary surface channels. The geometrical parameter studies indicate that variation of the comprehensive performance is very small when the wave length is greater than 18 mm and the effect of wave height is very small.

Double criterion optimisation of transparent façades based on solar thermalprocesses

This work aimed to find the best possible solution for transparent façades. The evaluation was formulated to assure the highest user comfort criteria corresponding to energy efficiency—two criterion optimisation. The analyses were based on BESTEST, south-oriented zone geometry. Computer model was designed using Finite Control Volume Techniques with assumptions for applied materials and specified boundary conditions, plus reference year for energy calculation (WYEC2). The natural ventilation façade system was designed to determine airflow network inside the façade. The adjustable size of openings (inlets and outlets) was selected at the level of 80% for the cold season and totally closed during the hot season. Environmental parameters for thermal comfort evaluation were: zone resultant temperature and solar radiation in zone space. Energy efficiency was assessed based on heat flux between the zone with controlled temperature and external environment. Results showed that well selected design of buffer zone section could improve energy efficiency of adjacent zones for both winter and summer periods. The most profitable Double Skin Façade solution is DGC (double glazing with low-e coating) combined with single glazing with internal blinds (SGB) or coloured glazing.

Laminar Mixed Convection in the Entrance Region of Horizontal and Inclined Semicircular Ducts

Laminar mixed convection in the entrance region of horizontal and inclined semicircular ducts has been investigated. The governing momentum and energy equations were solved numerically using a marching technique with finite control volume approach following the SIMPLER algorithm. Results were obtained for thermal boundary condition of uniform heat input axially and uniform wall temperature circumferentially, incorporating Pr = 7, Re = 500, inclination angles (α = 0° and 20°), and a wide range of Grashof numbers. These results include velocity and temperature distributions at different axial locations as well as axial distribution of local Nusselt number and local wall friction factor. It was found that Nusselt number is close to the forced convection values near the entrance region, then decreases to minimum value as the distance from the entrance increases, and then rises due to the effect of free convection before reaching a constant value (fully developed). As Grashof number increases Nusselt number and wall friction factor increase in both developing and fully developed regions for horizontal and inclined ducts. A comparison with the experimental data in the thermal entrance region was also conducted and the comparison was satisfactory.

Numerical Investigation of a PCM Heat Exchanger for Latent Cool Storage

Latent cool storage system for air conditioning is largely used in coolness systems. This system includes phase change materials (PCMs) contained in plate type capsules. Solidification of PCMs inside these capsules has been formulated by using a conduction model. An enthalpy method with finite control volume approach is used. This model has been validated by comparison with available experimental results of the literature. The model is then used for numerical study on ice banks of the parallel plate type. The temperature and enthalpy history, the heat flow rate and the evolution of the solidified mass fraction are presented and discussed. In the extreme conditions, complete loading of the cool storage tank is achieved within 3h 37 mn. 81% of loaded energy is done in 57% of the total solidification time.

A Finite Element Simulation of Mold Filling Process in Resin Film Infusion Based on Material Properties and Mechanics Properties

A finite element method (FEM) has been developed to simulate the isothermal resin infusing process in resin film infusion. The FEM is based on conservation of resin mass at any instant of time and is objective of resin film infusion (RFI) fiber impregnation and mold filling. The developed computer code was able to simulate the resin infusing visually. A numerical example presented here demonstrated that compared with traditional finite element/ control-volume (FE/CV), FEM is physically accurate and computationally efficient.

Heat transfer element for modeling the thermal response of non-uniformly heated plates

This paper presents a novel heat transfer element for modeling the 3D thermal response in plates and shells exposed to non-uniform heating. The formulation uses a combination of finite element and control volume techniques to discretize the governing equations into a series of 2D layers that are linked by a finite difference calculation. While a combination of techniques are used in the element formulation, the governing element equations are in a form that can readily be implemented into a commercial finite element code. The nine-node quadratic element considered here is implemented in ABAQUS as a user-defined element. Two- and three-dimensional verification cases are presented to demonstrate the capabilities of the element. Comparisons between the proposed shell heat transfer element and traditional continuum elements demonstrate that the proposed model exhibits a high level of accuracy and requires minimal computational power. The layered formulation offers the additional advantage of simplifying the transfer of temperature data from a thermal analysis to a structural analysis because both models can have the same mesh.

Dynamic modeling for vapor compression systems—Part II: Simulation tutorial

This two-part article provides an introduction to dynamic modeling for vapor compression systems. Part II presents example physics-based models for each component with a discussion on common assumptions and model variations. For two-phase heat exchangers, examples for both moving boundary and finite-control volume approaches are given, along with their associated advantages and limitations. Particular modeling challenges, such as model initialization, validation, and numerical simulation, are also addressed, and sample simulation results are utilized to compare modeling paradigms and illustrate key issues. Rather than advocating the use a particular software tool, this article provides a general tutorial on constructing dynamic simulations of vapor compression systems, outlining potential challenges and possible solutions.

Dynamic modeling for vapor compression systems—Part I: Literature review

This two-part article provides an introduction to dynamic modeling for vapor compression systems. Part I provides a detailed review of current literature in this area. Both physics- and data-based approaches are discussed with their associated advantages and limitations. Physics-based modeling paradigms include (1) lumped parameter approaches that qualitatively capture gross pressure and cooling transients, (2) moving boundary approaches that seek to model the dynamic variations in phase transition points, and (3) finite-control volume approaches that use discretized models that include temperature and parameter gradients in an effort to achieve greater accuracy. These models are based on first principles, but yet require time-consuming tuning and validation with experimental data. Data-based approaches offer faster model generation but are specific to the system and conditions from which the data originated.

Heat transfer through fibrous assemblies incorporating reflective interlayers

Fibrous insulation has many applications including functional protective clothing, sleeping bags, buildings and construction, and aircrafts, particularly under extreme climatic conditions. It has been realized that reflective interlayers can be incorporated into the fibrous materials to block radiative heat transfer. However, since reflective interlayers generally have greater thermal conductivity than the bulk fibrous materials, the optimization of the construction of the fibrous insulation is important in maximizing the overall thermal insulation. In order to analyze this complex optimization problem, a two-flux radiative heat transfer model was built for the heat transfer through fibrous assemblies incorporating reflective interlayers. By using finite control volume method, the solution was obtained. After validation it was applied to predict the optimum constructional parameters of such an assembly for maximizing thermal insulation. It was found that (1) although extinction coefficient of Al-coated interlayer fibers decrease unidirectionally as the fiber diameter increases, the total heat flux first decreases and then increases with minimum heat flux at the fiber diameter of about 2μm; Consequently, the thermal resistance reaches a maximum value when the fiber diameter d is about 2μm; (2) the optimum construction is determined by the balance of the weakening of conductive thermal resistance and enhancement of the radiative thermal resistance as a result of incorporating thin reflective interlayers. For relatively thick reflective interlayer, the assembly with lower interlayer fiber volume fraction has a higher thermal resistance. On the other hand, for very thin reflective interlayers, relatively high fiber volume fraction is beneficial to the overall thermal insulation.

Transient natural convective heat transfer in porous medium with solidification of binary mixture

In this paper an enthalpy porosity method associated with finite control volume scheme and SIMPLE iteration was employed to solve Navier–Stokes equation coupled with energy equation through Ergun equation and Boussinesq approximation for studying the effect of two-dimensional transient natural convective heat transfer from a closed region of porous medium with the different porosity on solidification in carbon–iron system. As shown in the results, it is fund that the thickness of solidification layer is increased with time due to thermal coupled flow induced by natural convection; and the wall temperature is faster changed in porous medium with larger porosity, which corresponds to slow the growth of the solidification layer in binary system.