• Mechanics and materials in the design of a buckling diaphragm wave energy converter

      Le, Huirong; Collins, Keri M.; Greaves, Deborah M.; Bellamy, Neil; University of Plymouth (2015-08-15)
    • Meshing strategy for PEM fuel cells CFD modelling – a systematic approach

      Choopanya, Pattarapong; Yang, Zhiyin; University of Sussex, Brighton, UK; University of Derby, Derby, UK (DEStech Publications, Inc., 2016-01)
      Typical PEM fuel cell models usually involve more than one million mesh elements making the computation very intense. This necessitates an effective way to mesh the computational domain with a minimum number of mesh points while, at the same time, maintaining good accuracy. The meshing strategy in each flow direction is investigated systematically in the current study and it has been found that mesh resolution in different directions has a different degree of influence on the accuracy of solutions. The proposed meshing strategy is capable of greatly reducing the number of mesh elements, hence computation time, while preserving the characteristics of important flow-field variables
    • A method for detecting abnormal program behavior on embedded devices

      Xiaojun, Zhai; Ehsan, Shoaib; Howells, Gareth; Dongbing, Gu; McDonald-Maier, Klaus; Appiah, Kofi; Hu, Huosheng; University of Leicester; University of Essex; University of Kent; University of Derby (IEEE, 2015-04-13)
      A potential threat to embedded systems is the execution of unknown or malicious software capable of triggering harmful system behavior, aimed at theft of sensitive data or causing damage to the system. Commercial off-the-shelf embedded devices, such as embedded medical equipment, are more vulnerable as these type of products cannot be amended conventionally or have limited resources to implement protection mechanisms. In this paper, we present a self-organizing map (SOM)-based approach to enhance embedded system security by detecting abnormal program behavior. The proposed method extracts features derived from processor's program counter and cycles per instruction, and then utilises the features to identify abnormal behavior using the SOM. Results achieved in our experiment show that the proposed method can identify unknown program behaviors not included in the training set with over 98.4% accuracy.
    • Methodologies for data collection and model documentation in computer simulation

      Liyanage, Kapila; The Open University of Sri Lanka (Siam Technology College, Bangkok, Thailand, 2005-10)
      In recent years, computer simulation has become a mainstream decision support tool in an industry. In order to maximise the benefits of using simulation within businesses, simulation models should be designed, developed and deployed in a shorter time span. A number of factors, such as excessive model details, inefficient data collection, lengthy model documentation and poorly planned experiments, increase the overall lead-time of simulation projects. Among these factors, input data modeling and model documentation are seen as major obstacles. Input data identification, collection, validation and analysis typically take more than one-third of project time. This paper presents an IDEF (Integrated computer-aided manufacturing DEFinition) based approach to accelerate identification and collection of input data. A functional module library and a reference data model, both developed using the IDEF family of constructs, are the core elements of the methodology. In addition, this paper also intends to give a methodological approach that helps and motivates the project team to document simulation projects.
    • Methodology for rapid identification and collection of input data in the simulation of manufacturing systems

      Perera, Terrence; Liyanage, Kapila; Sheffield Hallam University (Elsevier, 2000-02)
      Computer simulation is a well-established decision support tool in the manufacturing industry. The rapid development and deployment of simulation models however, are inhibited by factors such as inefficient data collection, lengthy model documentation, and poorly planned experimentation. Typically, more than one third of project time is spent on identification, collection, validation, and analysis of input data. Whilst most research work has been focused on statistical techniques for data analysis, less attention has been paid to the development of systematic approaches to input data gathering. This paper presents a methodology for rapid identification and collection of input data in batch manufacturing environments. A functional module library and a reference data model, both developed using the IDEF (Integrated computer aided manufacturing DEFinition) family of constructs, are the core elements of the methodology. The paper also identifies the major causes behind the inefficient collection of data.
    • Micro- climate adaptation of whole building energy simulation in large complexes.

      Zoras, Stamatis; Veranoudis, Sotiris; Dimoudi, Argyro; University of Derby; Democritus University of Thrace (Elsevier, 2017-09-01)
      The purpose of this study was to evaluate the cooling demand during a summer day over a large city area before and after bioclimatic interventions in outdoor spaces by using whole building thermal simulation. This kind of interventions ultimately leads to a microclimatic change in a city. Prediction of microclimate data for a whole day in a large area due to changes in outdoor spaces is time and cost demanding. A model for prediction of hourly microclimatic data in a region for a whole day by employing Fourier analysis of past (measured) and future (simulated from a CFD analysis) microclimate data of a limited period (sunlight hours) was also developed. The whole building energy simulation software TAS-EDSL was applied for a quite large built space (∼500 m × 500 m), for simultaneous simulations in all buildings in the area, and took into account detailed building construction data, mutual shading between buildings and local climatic conditions. In this context, strategies and practices that a building complex should follow in the future in relation to climate change could be investigated. Simulation estimations of cooling loads of building spaces were related to buildings’ age, orientation and height. Main outcome of the study was the ability to assess building energy performance due to exterior micro- climate improvement, simultaneously, for about 200 buildings.
    • Micro/Nanostructure and tribological characteristics of pressureless sintered carbon nanotubes reinforced aluminium matrix composites

      Manikandan, Paramasivan; Sieh, Raymond; Elayaperumal, A.; Le, Huirong; Basu, Sourajyoti; Anna University, India; Plymouth University, United Kingdom; University of Derby (2016-03-30)
      This study reports the manufacture, microstructure, and tribological behaviour of carbon nanotube reinforced aluminium composites against pure aluminium. The specimens were fabricated using powder metallurgy method. The nanotubes in weight percentages of 0.5, 1.0, 1.5, and 2.0 were homogeneously dispersed and mechanically alloyed using a high energy ball milling. The milled powders were cold compacted and then isothermally sintered in air. The density of all samples was measured using Archimedes method and all had a relative density between 92.22% and 97.74%. Vickers hardness increased with increasing CNT fraction up to 1.5 wt% and then reduced. The microstructures and surfaces were investigated using high resolution scanning electron microscope (SEM). The tribological tests showed that the CNT reinforced composites displayed lower wear rate and friction coefficient compared to the pure aluminium under mild wear conditions. However, for severe wear conditions, the CNT reinforced composites exhibited higher friction coefficient and wear rate compared to the pure aluminium. It was also found that the friction and wear behaviour of CNT reinforced composites is significantly dependent on the applied load and there is a critical load beyond which CNTs could have adverse impact on the wear resistance of aluminium.
    • Micromechanical modeling of 8-harness satin weave glass fiber-reinforced composites.

      Choudhry, Rizwan Saeed; Khan, Kamran A.; Khan, Sohaib Z.; Khan, Muhammad A.; Hassan, Abid; Capital University of Sciences and Technology; University of Manchester; National University of Science and Technology; Khalifa University of Science and Technology (Sage, 2016-05-26)
      This study introduces a unit cell (UC) based finite element (FE) micromechanical model that accounts for correct post cure fabric geometry, in-situ material properties and void content within the composite to accurately predict the effective elastic orthotropic properties of 8-harness satin weave glass fiber reinforced phenolic (GFRP) composites. The micromechanical model utilizes a correct post cure internal architecture of weave, which was obtained through X-ray microtomography (XMT) tests. Moreover, it utilizes an analytical expression to up-date the input material properties to account for in-situ effects of resin distribution within yarn (the yarn volume fraction) and void content on yarn and matrix properties. This is generally not considered in modeling approaches available in literature and in particular, it has not been demonstrated before for FE micromechanics models of 8-harness satin weave composites. The UC method is used to obtain the effective responses by applying periodic boundary conditions. The outcome of the analysis based on the proposed model is validated through experiments. After validation, the micromechanical model was further utilized to predict the unknown effective properties of the same composite.
    • Microstructural analysis of TRISO particles using multi-scale X-ray computed tomography

      Lowe, Tristan; Yue, Sheng; Bari, Klaudio; Gelb, Jeff; Rohbeck, Nadia; Turner, Joel; Withers, Philip; University of Derby (Elsevier, 2015-06)
      TRISO particles, a composite nuclear fuel built up by ceramic and graphitic layers, have outstanding high temperature resistance. TRISO fuel is the key technology for High Temperature Reactors (HTRs) and the Generation IV Very High Temperature Reactor (VHTR) variant. TRISO offers unparalleled containment of fission products and is extremely robust during accident conditions. An understanding of the thermal performance and mechanical properties of TRISO fuel requires a detailed knowledge of pore sizes, their distribution and interconnectivity. Here 50 nm, nano-, and 1 μm resolution, micro-computed tomography (CT), have been used to quantify non-destructively porosity of a surrogate TRISO particle at the 0.3–10 μm and 3–100 μm scales respectively. This indicates that pore distributions can reliably be measured down to a size approximately 3 times the pixel size which is consistent with the segmentation process. Direct comparison with Scanning Electron Microscopy (SEM) sections indicates that destructive sectioning can introduce significant levels of coarse damage, especially in the pyrolytic carbon layers. Further comparative work is required to identify means of minimizing such damage for SEM studies. Finally since it is non-destructive, multi-scale time-lapse X-ray CT opens the possibility of intermittently tracking the degradation of TRISO structure under thermal cycles or radiation conditions in order to validate models of degradation such as kernel movement. X-ray CT in-situ experimentation of TRISO particles under load and temperature could also be used to understand the internal changes that occur in the particles under accident conditions.
    • Modelling in ranking procedures: A case study of infrastructure failures in Nigeria

      Omoregie, Alohan; Ebohon, Obas John; Radford, Dennis; De Montfort University (International Council for Research and Innovation in Building and Construction, 2005-11-17)
      The lack of a scientific approach as to which factors are considered or chosen in a decision-making process can seriously influence the effectiveness of that process. Using the example of infrastructure failures in Nigeria, this paper presents a severity index in matrix order (SIMO) model that unambiguously ranks factors and also defines a threshold that demarcates between major variable factors that should not be compromised in policy and less important ones. Infrastructures failures in Nigeria have hindered economic processes which were meant to alleviate poverty. Constraints responsible for this situation are identified from a carefully conducted survey in Nigeria. Severity of these constraints is empirically ranked using a developed severity index in matrix order (SIMO) model. However, the investigation reveals that corruption, misallocation of investments, inadequate maintenance, lack of transparency and accountability, insufficient funding for infrastructure, lack of supportive institutions, inconsistent political, social and economic policies and the lack of suitable technical and managerial skill are the major variable factors responsible for infrastructure failures in Nigeria.
    • Modelling of the buckling of a diaphragm–spine structure for a wave energy converter

      Collins, Keri M.; Meng, Maozhou; Le, Huirong; Greaves, Deborah M.; Bellamy, Neil; Plymouth University; University of Derby; Sea Energy Associates Ltd. (Elsevier, 2017-01-15)
      A wide range of wave energy converter (WEC) designs exists, and the SeaWave WEC uses an unstable buckled spine mode of operation. The SeaWave consists of a hose and buckled spine-diaphragm, which pumps air along the device under wave action. A physical model and finite element analysis (FEA) is compared to a previous theoretical model in this paper. The FE model was developed in ABAQUS 6.14 using shell, solid and contact elements and the analysis was done with a quasi-static approach to reduce the computational costs. The physical model was a scale version of the novel arrangement of the spine and diaphragm made from steel, polycarbonate and latex rubber. Geometry of the deformed device was investigated results showed an increase in transverse and longitudinal curvature as the compression rate increased. The FEA tended to overestimate the bending stiffness of the model, and hence the transverse curvature, because certain behaviours of the physical model were not captured. The force required to switch from one buckled state to another was measured both in the physical and FEA models and the potential energy storage was estimated to be 0.5 J/m of device at a compression rate of 0.1%.
    • Modelling of waste material costs on road construction projects.

      Waty, Mega; Alisjahbana, Sofia W.; Gondokusumo, Onnyxiforus; Sulistio, Hendrik; Hasyim, Cholil; Setiawan, M. Ikhsan; Harmanto, Dani; Ahmar, Ansari Saleh; Tarumanagara University; Bakrie University; Darul Ulum University; Narotama University; University of Derby; Universitas Negeri Makassar (Science Publishing Corporation, 2018)
      Material waste is a term from the amount of waste material percentage and is one of the serious problems in the implementation of road construction project. The research objective is to calculate the average percentage of waste material in road construction projects and obtain waste material influencing profit and make a regression model of % material waste to % profit contractors. The data obtained are 158 projects in East and North Kalimantan divided into 51 road building projects and 107 road improvement projects. The percentage of waste material on road building project is B aggregate as the largest (26%) and ready mix concrete (5.3%) as the smallest. The percentage of waste material on road improvement project is B aggregate as the largest (24.2%) and ready mix concrete (6.14%) as the smallest. The influencing waste material on the road construction project is B aggregate, lean concrete and ready mix concrete with regression equation to determine the estimated % profit contractor as a function of % material waste is Y = 7.363 -0.032 X3 - 0.078 X4 - 0.066 X6. The influenced waste material on road improvement projects are cement, B aggregate, and Land Fill with the regression equation to determine the estimated % profit of contractor as a function of % material waste is Y = 8,702- 0,037 X4- 0,054 X5- 0,044 X7.
    • Moisture effects on the bending fatigue of laminated composites

      Meng, Maozhou; Le, Huirong; Grove, Stephen; Jahir Rizvi, M.; Plymouth University; University of Derby (Elsevier, 2016-07-19)
      This paper investigated the effect of moisture ingress on the bending fatigue of laminated composites. An accelerated testing method was developed to investigate the correlation between composite fatigue and moisture diffusion effects. Unidirectional and cross-ply laminated CFRP composites were manufactured in autoclave, and then submerged in both fresh and seawater for various periods until moisture saturation. Quasi-static and cyclic tests were carried out in both air and wet environment, and the failure mechanisms were investigated using visual and microscopic methods. Additionally, a robust 2D Finite Element model (FEA) was developed to simulate the fatigue crack propagation based on Virtual Crack Closure Technique (VCCT), while a 3D FEA model was developed to investigate the edge effect on fatigue crack propagation. The experimental observations gave a good agreement with the FEA models. The study showed that the bending fatigue failure was due to the so-called buckling-driven delamination, and the fatigue life was reduced significantly owing to the combination of edge effect and capillary effect. The fatigue test indicated that the fatigue resistance was degraded one stress level due to the water ingress. Therefore, a 4-step fatigue failure theory was proposed to explain the moisture effects on the crack propagation under bending fatigue.
    • Multi-scale analysis of moisture diffusion coupled with stress distribution in CFRP composites

      Meng, Maozhou; Le, Huirong; Rizvi, M.J.; Grove, Stephen; University of Plymouth (Composites UK, 2015-06)
    • Multi-scale modelling of moisture diffusion coupled with stress distribution in CFRP laminated composites

      Meng, Maozhou; Rizvi, Jahir; Le, Huirong; Grove, Stephen; University of Derby; University of Plymouth (2016-03-15)
      Laminated composite structures operating in a marine environment are subject to moisture ingress. Due to the slow diffusion process of moisture, the distribution of moisture is not uniform so that the laminates can develop hygrothermal stresses. An accurate prediction of the moisture concentration and the associated hygrothermal stress is vital to the understanding of the effect of marine environment on failure initiation. The present paper investigates the time-dependent moisture diffusion and the stress distribution in carbon fibre reinforced polymeric (CFRP) composites by means of experimental study and Finite Element Analysis (FEA). Samples were made from CFRP pre-preg autoclave-cured, and then immersed in fresh water and sea water at a constant 50 °C for accelerated moisture diffusion. Laminates with [0]16, [90]16, [±45]4s lay-up sequences were investigated. A multiscale 3D FEA model was developed to evaluate the interfacial stresses between polymer matrix and carbon fibre and the stress distribution in the composite laminates. The analysis revealed that both the stress distribution and stress level are time-dependent due to moisture diffusion, and the interphase between fibres and matrix plays an important role in both the process of moisture diffusion and the stress/strain transfer. The interlaminar shear stresses of the laminates induced by hygrothermal expansion exhibited a significant specimen edge effect. This is correlated with the experimental observations of the flexural failure of laminates.
    • Multiphase computational fluid dynamics–conjugate heat transfer for spray cooling in the non-boiling regime.

      Langari, Mostafa; Yang, Zhiyin; Dunne, Julian F.; Jafari, Soheil; Pirault, Jean-Pierre; Long, Chris A.; Jose, JT; University of Sussex; University of Derby; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK; Department of Engineering, College of Engineering and Technology, University of Derby, Derby, UK; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK; Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, UK (Sage, 2017-12-11)
      A numerical study is described to predict, in the non-boiling regime, the heat transfer from a circular flat surface cooled by a full-cone spray of water at atmospheric pressure. Simulations based on coupled computational fluid dynamics and conjugate heat transfer are used to predict the detailed features of the fluid flow and heat transfer for three different spray conditions involving three mass fluxes between 3.5 and 9.43 kg/m2s corresponding to spray Reynolds numbers between 82 and 220, based on a 20 mm diameter target surface. A two-phase Lagrange–Eulerian modelling approach is adopted to resolve the spray-film flow dynamics. Simultaneous evaporation and condensation within the fluid film is modelled by solving the mass conservation equation at the film–continuum interface. Predicted heat transfer coefficients on the cooled surface are compared with published experimental data showing good agreement. The spray mass flux is confirmed to be the dominant factor for heat transfer in spray cooling, where single-phase convection within the thin fluid film on the flat surface is identified as the primary heat transfer mechanism. This enhancement of heat transfer, via single-phase convection, is identified to be the result of the discrete random nature of the droplets disrupting the surface of thin film.
    • Multiscale modelling of fluid and solute transport in soft tissues and microvessels

      Lu, Yiling; Wang, Wen; University of Derby (2010)
      This study focuses on the movement of particles and extracellular fluid in soft tissues and microvessels. It analyzes modeling applications in biological and physiological fluids at a range of different length scales: from between a few tens to several hundred nanometers, on the endothelial glycocalyx and its effects on interactions between blood and the vessel wall; to a few micrometers, on movement of blood cells in capillaries and transcapillary exchange; to a few millimetres and centimetres, on extracellular matrix deformation and interstitial fluid movement in soft tissues. Interactions between blood cells and capillary wall are discussed when the sizes of the two are of the same order of magnitude, with the glycocalyx on the endothelial and red cell membranes being considered. Exchange of fluid, solutes, and gases by microvessels are highlighted when capillaries have counter-current arrangements. This anatomical feature exists in a number of tissues and is the key in the renal medulla on the urinary concentrating mechanism. The paper also addresses an important phenomenon on the transport of macromolecules. Concentration polarization of hyaluronan on the synovial lining of joint cavities is presented to demonstrate how the mechanism works in principle and how model predictions agree to experimental observations quantitatively.
    • Music Festivals: How are people encouraged to be mindful in their uses of finite resources and not waste water? Where does water go after use?

      Tracada, Eleni; Adeyeye, Kemi; Sephton, Neil; University of Derby; University of Bath; First Wessex, Assets & Sustainability (2016-07)
      During the last few months, People and Communities Technical Committee in Water Efficiency network has been interested in and selected specific case studies to be proposed for further analysis and discussion by members of this committee. Most members decided to bring to the attention of the committee one case study for further development. Some case studies, such as, for example, ‘Water and its use by people at a music festival’ appeared to be triggering further investigation from members of the committee with the potential to become new and original research projects; this particular case study is going to be analysed through videos to be produced on the occasion of next Reading Festival. Organised by Festival Republic (FR), this annual event is held over the August Bank Holiday weekend. Thus, this paper intends to discuss some large performance venues and sites’ planning and organisation on methods and solutions having an immediate impact to people’s behaviours in relation to the uses of water and the impact to the environment through water management. The researchers and members of this technical group wish to understand how organisers can plan water uses, how they may be contributing to specific guidance of the public by introducing specific guides on water management at outdoor events and by also creating plans to overcome some unexpected outcomes of overflows or failure of provision at times. The team working on this project hopes to get some detailed overview on water and its use by people during these events; they hope to be able to do some recommendations and draw some important conclusions at the end. Amongst other relevant outcomes the research team is hoping to help organisers to develop useful guides for the public and enhance the people’s awareness on the water uses and management. The organisers and the audience should be able to build confidence and joint support also in extreme cases when something could happen unexpectedly, such as failure to drainage or supply systems. They should be able to be putting on place a relevant plan of emergency and this could be feasible by contributing to important reports in progress, such as, for example, ‘The show must go on’ report. By documenting this coming event via filming the team hopes to create a freely available resource that demonstrates globally how people interact with water, a precious and essential source. Whenever possible the team aims to show how water can be used carefully, mindfully and efficiently during large size events, such as music festivals through their chosen case study in the UK. A short video will be shown during the Conference as well.
    • Music festivals: how are people encouraged to be mindful in their uses of finite resources and not waste water? Where does water go after use?

      Tracada, Eleni; Adeyeye, Kemi; Sephton, Neil; University of Derby; University of Bath; Water Efficiency Network (2016-09)
      During the last few months, People and Communities Technical Committee in Water Efficiency network has been interested in and selected specific case studies to be proposed for further analysis and discussion by members of this committee. Most members decided to bring to the attention of the committee one case study for further development. Some case studies, such as, for example, ‘Water and its use by people at a music festival’ appeared to be triggering further investigation from members of the committee with the potential to become new and original research projects; this particular case study is going to be analysed through videos to be produced on the occasion of next Reading Festival. Organised by Festival Republic (FR), this annual event is held over the August Bank Holiday weekend. Thus, this paper intends to discuss some large performance venues and sites’ planning and organisation on methods and solutions having an immediate impact to people’s behaviours in relation to the uses of water and the impact to the environment through water management. The researchers and members of this technical group wish to understand how organisers can plan water uses, how they may be contributing to specific guidance of the public by introducing specific guides on water management at outdoor events and by also creating plans to overcome some unexpected outcomes of overflows or failure of provision at times. The team working on this project hopes to get some detailed overview on water and its use by people during these events; they hope to be able to do some recommendations and draw some important conclusions at the end. Amongst other relevant outcomes the research team is hoping to help organisers to develop useful guides for the public and enhance the people’s awareness on the water uses and management. The organisers and the audience should be able to build confidence and joint support also in extreme cases when something could happen unexpectedly, such as failure to drainage or supply systems. They should be able to be putting on place a relevant plan of emergency and this could be feasible by contributing to important reports in progress, such as, for example, ‘The show must go on’ report. By documenting this coming event via filming the team hopes to create a freely available resource that demonstrates globally how people interact with water, a precious and essential source. Whenever possible the team aims to show how water can be used carefully, mindfully and efficiently during large size events, such as music festivals through their chosen case study in the UK. A short video will be shown during the Conference as well.
    • Neutral thermal sensation or dynamic thermal comfort? Numerical and field test analysis of a thermal chair.

      Shahzad, Sally; Calautit, John Kaiser; Aquino, Angelo I.; Nasir, Diana S. N. M.; Hughes, Ben; University of Derby; University of Nottingham; University of Sheffield (Elsevier, 2018-01-31)
      Neutral thermal sensation is considered as the measure of thermal comfort in research, as when participants report feeling neutral regarding the thermal environment, they are considered as thermally comfortable. This is taken for granted, and although a few researchers have criticised the matter, still researchers use thermal sensation and the neutral point to assess the thermal conditions in their studies. This study questions the application of thermal neutrality and consequently poses a question on the findings of all the studies that only rely on it. Field studies of thermal comfort were applied in an open plan office in the UK in the winter of 2014. Participants were provided with a thermal chair and before and after using the chair, their views of comfort were recorded, including the ASHRAE seven point scale of thermal sensation, thermal preference, comfort, and satisfaction. The thermal environment was measured and compared against the ASHRAE Standard 55-2013. In addition, numerical modelling was also conducted to investigated the airflow and thermal distribution around the proposed thermal chair with a seated occupant. The results indicated that overall, 72% of the respondents, who did not feel neutral (thermal sensation) before or after using the thermal chair reported to feel comfortable and 65% reported to be satisfied. The results indicated that a neutral thermal sensation does not guarantee thermal comfort of the occupants and that thermal comfort is dynamic and other thermal sensations need to be considered. This study recommends the use of multiple methods (e.g. thermal, preference, decision, comfort, and satisfaction) to assess thermal comfort more accurately. Also, it questions the findings of any research that solely relies on thermal sensation and particularly on the neutral thermal sensation to assess thermal comfort of the occupants. The results also emphasised the importance of the application of numerical modelling in evaluating the thermal performance of the chair.