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The flow behavior of many multiphase flow applications is greatly influenced by wetting properties and the presence of surfactants. We present a numerical method for two-phase flow with insoluble surfactants and contact line dynamics in two dimensions. The method is based on decomposing the interface between two fluids into segments, which are explicitly represented on a local Eulerian grid. It provides a natural framework for treating the surfactant concentration equation, which is solved locally on each segment. An accurate numerical method for the coupled interface/surfactant system is given. The system is coupled to the Navier-Stokes equations through the immersed boundary method, and we discuss the issue of force regularization in wetting problems, when the interface touches the boundary of the domain. We use the method to illustrate how the presence of surfactants influences the behavior of free and wetting drops.

We present a numerical method for suspensions of spheroids of arbitrary aspect ratio, which sediment under gravity. The method is based on a periodized boundary integral formulation using the Stokes double layer potential. The resulting discrete system is solved iteratively using generalized minimal residual accelerated by the spectral Ewald method, which reduces the computational complexity to O(N log N), where N is the number of points used to discretize the particle surfaces. We develop predictive error estimates, which can be used to optimize the choice of parameters in the Ewald summation. Numerical tests show that the method is well conditioned and provides good accuracy when validated against reference solutions. 

The cooling system of a DC-motor is examined in this thesis. A change of direction of the cooling air is desired to prevent the generated coal dust from entering into the windings of the machine. Ultimately this will have a negative effect on the cooling in the machine and the loss of cooling needs to be compensated through other ways. The purpose of this thesis is to work for an improved operational safety and performance of the DC-motor and to make it more competitive in the market. By modelling the interior geometry of the machine and defining the boundaries in the software programs Gambit and FLUENT respectively, the motion and the heat transfer of the airflow could be simulated. The simulation results would give us an understanding of the flow pattern which later could be used to develop design modifications on the cooling system of a DC-motor. In this thesis the main focus lies on creating a simulation model with a sufficiently fine mesh size.

This paper presents an experimental investigation of the concept of using the combustor transition duct wall to shield the nozzle guide vane leading edge. The new vane is tested in a high-speed experimental facility, demonstrating the improved aerodynamic and thermal performance of the shielded vane. The new design is shown to have a lower average total pressure loss than the original vane, and the heat transfer on the vane surface is overall reduced. The peak heat transfer on the vane leading edge–endwall junction is moved further upstream, to a region that can be effectively cooled as shown in previously published numerical studies. Experimental results under engine-representative inlet conditions showed that the better performance of the shielded vane is maintained under a variety of inlet conditions.

In gas turbines with can combustors the trailing edge of the combustor transition duct wall is found upstream of ev- ery second vane. This paper presents an experimental and numerical investigation of the effect of the combustor wall trailing edge on the aerothermal performance of the nozzle guide vane. In the measurements carried out in a high speed experimental facility, the wake of this wall is shown to in- crease the aerodynamic loss of the vane. On the other hand, the wall alters secondary flow structures and has a protective effect on the heat transfer in the leading edge-endwall junc- tion, a critical region for component life. The different clock- ing positions of the vane relative to the combustor wall are tested experimentally and are shown to alter the aerothermal field. The experimental methods and processing techniques adopted in this work are used to highlight the differences be- tween the different cases studied. 

The remarkable developments in gas turbine materials and cooling technologies haveallowed a steady increase in combustor outlet temperature and, hence, in gas turbine efficiencyover the last half century. However, the efficiency benefits of higher gas temperature,even at the current levels, are significantly offset by the increased losses associatedwith the required cooling. Additionally, the advancements in gas turbine cooling technologyhave introduced considerable complexities into turbine design and manufacture.Therefore, a reduction in coolant requirements for the current gas temperature levels isone possible way for gas turbine designers to achieve even higher efficiency levels. Theleading edges of the first turbine vane row are exposed to high heat loads. The high coolantrequirements and geometry constraints limit the possible arrangement of the multiplerows of film cooling holes in the so-called showerhead region. In the past, investigatorshave tested many different showerhead configurations by varying the number of rows, inclinationangle, and shape of the cooling holes. However, the current leading edge coolingstrategies using showerheads have not been shown to allow a further increase inturbine temperature without the excessive use of coolant air. Therefore, new coolingstrategies for the first vane have to be explored. In gas turbines with multiple combustorchambers around the annulus, the transition duct walls can be used to shield, i.e., to protect,the first vane leading edges from the high heat loads. In this way, the stagnationregion at the leading edge and the showerhead of film cooling holes can be completelyremoved, resulting in a significant reduction in the total amount of cooling air that is otherwiserequired. By eliminating the showerhead the shielding concept significantly simplifiesthe design and lowers the manufacturing costs. This paper numerically analyzes the potentialof the leading edge shielding concept for cooling air reduction. The vane shape wasmodified to allow for the implementation of the concept and nonrestrictive relative movementbetween the combustor and the vane. It has been demonstrated that the coolant flowthat was originally used for cooling the combustor wall trailing edge and a fraction of thecoolant air used for the vane showerhead cooling can be used to effectively cool both thesuction and the pressure surfaces of the vane.

Fouling on gas turbine blades is detrimental to process operation as it may, over a period of time, reduce the blade efficiency and consequently the turbine’s efficiency. With the limitation of today’s technology, experimental study or real-life observation of fouling in a gas turbine is beyond imagination of maintenance engineers. Hence, the effect of fouling cannot be fully quantified for the engineers to come out with mitigation or intervention plans. Nevertheless, computational fluid dynamics (CFD) may provide a good simulation to understand the phenomena. In this chapter, recent effort involving CFD study on the influence of fouling on gas turbine performance is presented. Firstly, the nature of fouling on the gas turbine and the general consequences are discussed. This is followed by an elaboration on how CFD study has been conducted by the authors. Finally, the findings from the study are discussed.

The objective of this thesis work was to construct and implement an algorithm into the programADAPDT to calculate the zero-lift drag profile for defined aircraft geometries. ADAPDT, shortfor AeroDynamic Analysis and Preliminary Design Tool, is a program that calculates forces andmoments about a flat plate geometry based on potential flow theory. Zero-lift drag will becalculated by means of different hand-book methods found suitable for the objective andapplicable to the geometry definition that ADAPDT utilizes.

Drag has two main sources of origin: friction and pressure distribution, all drag acting on theaircraft can be traced back to one of these two physical phenomena. In aviation drag is dividedinto induced drag that depends on the lift produced and zero-lift drag that depends on the geometry of the aircraft.

How reliable and accurate the zero-lift drag computations are depends on the geometry data thatcan be extracted and used. ADAPDT‟s geometry definition is limited to flat plate geometrieshowever although simple it has the potential to provide a huge amount of data and also delivergood results for the intended use. The flat plate representation of the geometry proved to beleast sufficient for the body while wing elements could be described with much more accuracy.

Different empirical hand-book methods were used to create the zero-lift drag algorithm. Whenchoosing equations and formulas, great care had to be taken as to what input was required sothat ADAPDT could provide the corresponding output. At the same time the equations shouldnot be so basic that level of accuracy would be compromised beyond what should be expectedfrom the intended use.

Finally, four well known aircraft configurations, with available zero-lift drag data, weremodeled with ADAPDT‟s flat plate geometry in order to validate, verify and evaluate the zeroliftdrag algorithm‟s magnitude of reliability. The results for conventional aircraft geometriesprovided a relative error within 0-15 % of the reference data given in the speed range of zero toMach 1.2. While for an aircraft with more complicated body geometry the error could go up to40 % in the same speed regime. But even though the limited geometry is grounds foruncertainties the final product provides ADAPDT with very good zero-lift drag estimationcapability earlier not available. A capability that overtime as ADAPDT continues to evolve hasthe potential to further develop in terms of improved accuracy.

Wave energy conversion is a renewable energy technology with a promising potential. Although it has been developed for more than 200 years, the technology is still far from mature. The survivability in extreme weather conditions is a key parameter halting its development. We present here results from two weeks of measurement with a force measurement buoy deployed at Uppsala University’s test site for wave energy research at the west coast of Sweden. The collected data have been used to investigate the reliability for two typical numerical wave energy converter models: one low fidelity model based on linear wave theory and one high fidelity Reynolds-Averaged Navier–Stokes model. The line force data is also analysed by extreme value theory using the peak-over-threshold method to study the statistical distribution of extreme forces and to predict the return period. The high fidelity model shows rather good agreement for the smaller waves, but overestimates the forces for larger waves, which can be attributed to uncertainties related to field measurements and numerical modelling uncertainties. The peak-over-threshold method gives a rather satisfying result for this data set. A significant deviation is observed in the measured force for sea states with the same significant wave height. This indicates that it will be difficult to calculate the force based on the significant wave height only, which points out the importance of more offshore experiments.

We present Auxtrument, a prototype instrument that allows audiences to experience the acoustic qualities of remote locations. Using the metaphor of a reverberation chamber, artists send signals from the mixers, bus, or aux via the Auxtrument's network connections from a concert hall to a few different locations. At each location the signal is played through loudspeakers and captured, colored by the acoustics and noises of the place, via a stereo or ambisonics microphone. The signal is sent back and played for the audience in a surround sound system conveying the spatial qualities of the places. The Auxtrument allows us to merge and layer the different locations in the concert hall. However, this arrangement places great demands on the network. The audio signals need to be high-resolution to preserve the inherent quality of the sounds, which creates large streams. The system must be equipped to work over different types of networks, and to enable any location, the system must work with mobile devices. After ruling out several commercial and opensource solutions, we built the Auxtrument with web technologies: mainly node.js, WebSockets, WebRTC, and WebAudio. 

A theoretical model of an electroacoustic gas sensor has been designed and compared with experimental data. The sensor includes a piezoelectric element coupled to an acoustic resonator depending on the average molecular weight of the gas with respect to resonance frequency. The model is based on a transmission line coupled to a Butterworth van Dyke model of the piezoelectric element. The frequency characteristics of the sensor impedance was both simulated and measured on prototype sensors. The results indicate that the model provides an adequate description of overall sensor behaviour, and will constitute a useful design tool. Due to interdependencies of the model parameters, the precise quantification of sensor characteristics will either require highly accurate parameter data, or a considerably more complex model.

This report is written on commission by WSP Acoustics. The report studies the outdoor sound levels on school yards in Stockholm. The questions given by the company to be answered was what are the actual sound levels at diffrent school yards with low traffic noise and how can you construct a facade element that reduces the sound level from the outside and meet the indoor requirements. Mesurements for four hours was done at eight schools set north and south of the city centre. The measurement period included one school break and one lunch break. The results of the measurements were that the equivalent and maximum sound level had small variations between the schools with some exceptions.The equivalent sound level was Leq 58-62 dB(A) and this shows a small variation. The school with the highest equivalent sound level of 67 dB was Maria skolan. This high level can be explained by more children on the school yard together at the same time etc. The maximum sound level was 85-89 dB(A), this if the level for Sofia skolan 82 dB was ignored. The level 85-89 dB(A) also shows a small variation. Calculations of the sound reduction index (R'w) for facade elements were also carried out for all the schools. The resulting sound reduction index for the whole facade was 34-41 dB. After assuming a 200 mm thick concrete facade for Sjöstadsskolan another calculation of building elements gives that the window have to reduce R'w 32 dB to meet the indoor requirements. In the future WSP Acoustics will use this report to choose building elements such as windows when building or rebuilding schools. It can also be used if any of the eight schools in this report needs a window changed to improve the acoustics.

Emerging offshore renewable energy technologies are expected to become an important part of the futureenergy system, and reliability for these new technologies in different metocean scenarios must be guaranteed.This poses a challenge in extreme weather scenarios like storms, in particular for less mature technologiessuch as wave energy. Not only the offshore survivability must be controlled; the restoration after disruptiveevents and failures should be addressed and optimized. Offshore operations are costly and cannot be carriedout if the weather is too harsh, and the resulting downtime after failures may be financially devastating forprojects. In this paper, the resilience of large wave energy systems is studied with respect to wave conditions,metocean dependent failure rates, and weather windows available for offshore repair operations. A metocean-and time-dependent failure rate is derived based on a Weibull distribution, which is a novelty of the paper.The performance of the farm is assessed using the varying failure rates and metocean data at different offshoresites. Critical metocean thresholds for different offshore vessels are considered, and the resilience is quantifiedusing relevant measures such as unavailability and expected energy not supplied. The resilience analysis iscoupled to an economic assessment of the wave farm and different repair strategies. Our results show thatthe commonly used assumption of constant failure rates is seen to overestimate the annual energy productionthan when a more realistic varying failure rate is used. Two offshore sites are compared, and the availabilityis found to be higher at the calmer site. Most of the evaluated repair strategies cannot be considered to beeconomically justified, when compared to the cost of the energy not supplied.

The drag approximations done in the initial design phase needed to be verified. A model of the aircraft has been analyzed with CFD and results examined to see how accurate the estimations were. A step by step analysis was made and then a simulation was run. The drag results of the CFD analysis did not meet the goal of the initial design study. Several reasons for this are discussed. The analysis shows that the aircraft design works well aerodynamically but also shows a few areas where the design can be improved.

Runout Table (ROT) cooling is one of the most important factors for controlling quality of hot rolled steel. ROT cooling uses large quantities of water to cool the steel plate. Optimizing heat transfer in the ROT would reduce the amount of water used, which will lower the amount of energy needed for pumping, filtering, storage and use of water. Optimization will therefore result in a direct energy saving as well as increasing the product quality.

This study investigates heat transfer by turbulent water jets impinging on a hot flat steel plate at temperatures below the boiling point in order to understand convection heat transfer phenomena. This is an important stage that precedes the boiling and addresses the applicability of the heat transfer correlations available in the literature.

A single axisymmetric jet and a pair of interacting jets are simulated using Computational Fluid Dynamics (CFD). The Reynolds Averaged Navier Stokes (RANS) model under steady and transient conditions and the k–ɛ turbulence model are used in both 2D axisymmetric and 3D simulations. We investigate the influence of the water flow rate on the jet cooling characteristics and develop a correlation for the radial position of the maximum Nusselt number based on numerical results.

Two sets of boundary conditions – constant temperature and constant heat flux – are applied at the surface of the steel plate and evaluated. The single jet numerical results compare favourably with published data based on measurements and analytical models. The thermal performance of a two-jet system was found to be no better than a single jet because the jets were too far from each other to generate any additional thermal interaction.

One of the most important steps to control the quality in steel hot rolling is the Runout Table (ROT) Cooling. In this investigation, the heat transfer of water jets impinging on a hot flat steel plate was studied under temperatures below the boiling point to understand the convection heat transfer phenomena which is a major step preceding the boiling. Single axisymmetric jet and a pair of interacting jets are simulated using Computational Fluid Dynamics (CFD). The RANS model under steady and transient conditions as well as the k-Ɛ turbulence model are used for both 2D axisymmetric and 3D simulations. The water flow rate influence on the jets cooling characteristics is investigated.Two sets of boundary conditions, constant temperature and constant heat flux were applied at the surface of the steel plate and evaluated. The single jet numerical results are successfully compared to published data based on measurements and analytical models. The two jets thermal performance was found to be unaffected because the jets are too far from each other to generate any additional thermal interaction.

Fluid flow and heat transfer in small channels have a wide range of engineering and medical applications. It has always been a topic of numerous theoretical, numerical and experimental studies. Several numerical methods have been used to simulate such flows. The most common approaches are the finite volume method (FVM) and the direct numerical simulation (DNS), which are numerically expensive to solve cases involving complex engineering problems. The main purpose of this work is to investigate the usability of the mesh-free particle based Smoothed Particle Hydrodynamics (SPH) method to simulate convective heat transfer. To validate our approach, as a starting point, we choose to solve a simple well-established problem which is the laminar flow and heat transfer through an infinitely long mini-channel. The solution obtained from SPH method has been compared to the solution from FVM method and analytical solution with good accuracy. The results presented in this paper show that SPH is capable to solve laminar forced convection heat transfer, however, turbulent flow cases need to be considered to be able to utilize the SPH method for engineering thermal applications.

Smoothed Particle Hydrodynamics (SPH) is a mesh-free particle method that has been widely used in the last years to model some complex flows. SPH was mainly used to investigate problems related to hydrodynamics and maritime engineering where heat transfer is of no importance. Thermal problems have seldom been addressed due to the limitation of the main commercial and open-source SPH codes.

In this article, the energy equation is implemented in the SPH based open-source code DualSPHysics to solve conduction and forced convection heat transfer problems. Laminar flow cases are simulated as the first validation cases of the implemented model. The studied cases include conduction in an aluminum block, conduction in still water in a cavity, laminar water flow between two infinite parallel plates and tube bank heat exchanger. The thermal solutions obtained from SPH are benchmarked with the solutions from Finite Volume Method (FVM) and also validated using available analytical solutions. The obtained results are in good agreement with FVM and available analytical models, which combined with the advantages of the meshless approach, show the high potential for industrial heat transfer applications.

This development is an important step towards thermal optimization of several industrial applications that can’t benefit from the conventional FVM approach due to geometry or process complexities. The demonstrated SPH simulation and visualization capabilities contribute to build the future reliable energy-saving solutions.

Thermal management of the rotating electrical machines is a very challenging area which needs appropriate solutions for each machine and operating condition. The heat is generated by the electromagnetic losses and the mechanical friction during the rotation. Computational Fluid Dynamics (CFD) is used in this study to predict and analyze the thermal performance of a rotating electrical machine where high speed rotation is coupled with small flow gaps. The investigation presented in this paper is based on a geometry used for model assessment and verification purposes. However, the approach outlined and the observations made are transferrable to other geometries. ANSYS Fluent has been used to perform CFD simulation where both the air velocity field and the temperature distribution are obtained. The results are qualitatively highly interesting to understand the thermal behavior within an electrical machine operations. The results show a periodic temperature distribution on the stator surface with similar periodic pattern for the heat transfer coefficient on the rotor surface. The simulated average heat transfer coefficient at the rotor surface is compared with the correlations from published literature with an overall good agreement.

Electrically driven ducted fans (e-fans), either underwing-mounted or located at the aft-fuselage, can potentially improve the system overall efficiency in hybrid-electric propulsion architectures by increasing their thrust share over the thrust generated by the main engines. However, the low design pressure ratio of such e-fans make them prone to operability issues at off-design conditions, i.e., takeoff, where nozzle pressure ratio is close or below the critical value. This paper investigates the operational limitations of such e-fans, proving the necessity of variable geometry. A component zooming approach is deployed by integrating a streamline curvature method within an aero-engine performance tool to investigate the e-fan installed performance and operability. The concepts of variable pitch fan (VPF) and variable area nozzle (VAN) are systematically explored to quantify any performance benefits, while the unavoidable added-weight challenges due to variable geometry are taken into account. Although e-fans with low design pressure ratio (PR) are more susceptible to operability issues compared to higher PR e-fans, the former show improved overall efficiency levels, mainly dominated by propulsive efficiency. It is found that variable geometry not only tackles operability but it can improve the off-design overall efficiency of e-fans even more. VPF mostly affects the component efficiency by reshaping the e-fan performance maps, while VAN has a greater impact on propulsive efficiency by moving the operating points.

In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.

This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.

In Part I of this two-part publication, a comprehensiveanalysis of thermo-fluid modelling for gas turbines is presentedand the fluid models developed are discussed in detail.Common technical models, used for calculating caloricproperties, are compared while typical assumptions made influid modelling, and the uncertainties induced, are examined.Several analyses, which demonstrate the effects of composition,temperature and pressure on caloric properties of workingmediums for gas turbines, are presented. The working mediumsexamined include dry air and combustion products for variousfuels and H/C ratios. The errors induced by ignoringdissociation effects are also discussed.

In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.

This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.

In Part II of this two-part publication, the uncertaintyinduced in performance calculations by common technicalmodels, used for calculating caloric properties, is discussed atengine level. The errors induced by ignoring dissociation areexamined at 3 different levels: i) component level, ii) enginelevel, and iii) aircraft system level. Essentially, an attempt ismade to shed light on the trade-off between improving theaccuracy of a fluid model and the accuracy of a multidisciplinarysimulation at aircraft system level, againstcomputational time penalties. The results obtained demonstratethat accurate modelling of the working fluid is not alwaysessential; the accuracy/uncertainty for an overall engine modelwill always be better than the mean accuracy/uncertainty of the individual component estimates as long as systematic errors arecarefully examined and reduced to acceptable levels to ensureerror propagation does not cause significant discrepancies.Computational time penalties induced by improving theaccuracy of the fluid model as well as the validity of the idealgas assumption for future turbofan engines and novelpropulsion cycles are discussed.

To develop an equation of state with simple structure and reasonable accuracy for engineering application, Redlich-Kwong equation of state was modified for gaseous CO₂ and CO₂-H₂O mixtures. In the new modification, parameter a of gaseous CO₂ was regressed as a function of temperature and pressure from recent reliable experimental data in the range: 220-750 K and 0.1-400 MPa. Moreover, a new mixing rule was proposed for gaseous CO₂-H₂O mixtures. To verify the accuracy of the new modification, densities were calculated and compared with experimental data. The average error is 1.68% for gaseous CO₂ and 0.93% for gaseous mixtures of CO₂ and H₂O. Other thermodynamic properties, such as enthalpy and heat capacities of CO₂ and excess enthalpy of gaseous CO₂-H₂O mixtures, were also calculated; results fit experimental data well, except for the critical region.

This paper describes a new modular experimental facility that was purpose-built to investigateflow interactions between the combustor and first stage nozzle guide vanes (NGVs)of heavy duty power generation gas turbines with multiple can combustors. The first stageturbine NGV is subjected to the highest thermal loads of all turbine components andtherefore consumes a proportionally large amount of cooling air that contributes detrimentallyto the stage and cycle efficiency. It has become necessary to devise novel coolingconcepts that can substantially reduce the coolant air requirement but still allow theturbine to maintain its aerothermal performance. The present work aims to aid this objectiveby the design and commissioning of a high-speed linear cascade, which consists oftwo can combustor transition ducts and four first stage NGVs. This is a modular nonreactiveair test platform with engine realistic geometries (gas path and near gas path), coolingsystem, and boundary conditions (inlet swirl, turbulence level, and boundary layer).The paper presents the various design aspects of the high pressure (HP) blow down typefacility, and the initial results from a wide range of aerodynamic and heat transfermeasurements under highly engine realistic conditions.

Computational Fluid Dynamics (CFD) simulations are extensively used to model indoor environments, including airflow patterns, temperature distribution, and contaminant dispersion. These simulations provide valuable insights for improving indoor air quality, enhancing thermal comfort, optimizing energy efficiency, and informing design decisions. The recent global pandemic has emphasized the importance of understanding airflow patterns and particle dispersion in indoor spaces, highlighting the potential of CFD simulations to guide strategies for improving indoor air quality and public health. Consequently, there has been a significant increase in research focused on studying the transport and dispersion of pollutants in indoor environments using CFD techniques. These simulations are vital in advancing engineers' understanding of indoor environments; however, achieving accurate results requires careful method selection and proper implementation of each step. This paper aims to review the state-of-the-art CFD simulations of indoor environments, specifically focusing on strategies employed for three main simulation components: geometry and grid generation, ventilation strategies, and turbulence model selection. Researchers can select suitable techniques for their specific applications by comparing different indoor airflow simulation strategies.

The recent epidemic of the coronavirus disease showed the increased importance of controlling the transmission of contamination in the ward areas more than before. The performance of the ventilation systems in healthcare facilities can significantly impact the overall healthcare quality. This paper aims to compare two ventilation designs in an isolation room of a hospital and study the indoor airflow pattern. Computational fluid dynamics using ANSYS Fluent software was employed for the numerical simulation of the fluid flow. The simulation included the prediction of flow patterns and particle trajectories with the additional investigation into the impact of considering human thermal plume and modeling particle trajectories considering the turbulent fluctuations using the discrete random walk method in the simulation.  

We propose a novel technique that combines physics-informed machine learning (PIML) with the wall-adapting local eddy viscosity model for predicting flow patterns over time. In order to generate loss functions for turbulence flow and calculate dissipation rates within the domain, a new form of machine learning-based WALE-LES model includes updating the boundary matrix and tensor of component velocity and pressure tensors over time. By utilizing boundary conditions, Navier-Stokes-based equations will be discretized via automatic differentiation in PIML. We present a novel point cloud-based method for pore-scale porous media (PSPM) for the first time. This method transforms complex geometry into a matrix of data based on a point cloud. As a result of this method, boundary conditions are included in transient calculations. We modified the standard form of momentum equations to obtain the loss function for flows passing through a PSPM. According to the findings, high-fidelity numerical simulation and PIML prediction results are very similar in pressure and velocity. Additionally, this method can reduce calculation costs by up to 41% compared to the standard method.

In this paper, the numerical modeling of condensation processof water vapor from a flue gas with high CO2 concentration is studied. Tosimplify the study and focus on the physical model, a simple vertical platewas chosen. Two condensation models are developed. A numericalapproach is considered to implement these models. The main objective inthe current paper was to study the capability of numerical model inprediction of complex process. Results showed that developedcondensation models in combination with numerical approach can predictthe trends in condensation behavior of binary mixture very well. Resultsfrom this study can be developed further to be used in designing ofcondenser which are suitable for oxy-fuel power plants.

Pulping digester including the channelling phenomenon and chemical reactions in the channel is modelled using the CFD, finite volume method, FLUENT. The objective of this paper is to predict the chemical and hydraulic behaviour of the digester under the hazardous situations.

A 2D geometry of the digester is built and symmetric planes are defined in the Gambit. The mesh is then exported to the FLUENT and then the created half geometry was treated by axisymmetric function to establish a complete model of the digester. The Eulerian scheme is applied which    represent the multiphase flows in the digester. A heterogeneous porous media is defined for the compressible bed. Species transport is applied to define a mixture template of the wood chips components. The kappa number is predicted in the channel and around it to characterize the cooking development under hazardous conditions.               

This paper describes the use of a CFD multiphase model using commercial FLUENT software to aid understanding of the physical behavior of solid and liquid flows in the digester of the pulping process. We take into consideration the mass balance of the multi-inlets, outlets and circulation flows in the digester. We also look at the application of a Porous media model to describe the dynamic behavior of the liquor flow through a bed of solid particles.

The cylindrical Korsnas/vallvik pulping digester in Sweden is represented in the models as an axisymmetric two-dimensional model, which includes multiple feeds, outlets, pressure adjustment valves and circulation pipes.

Separation of the phases is an important part of the pulping process. A number of multiphase models are evaluated for their potential use in phase separation.

For this evaluation we constructed the two-dimensional digester model in the Gambit software package, a pre- processor tool for FLUENT 

Physical strainers at the entrances of outlet pipes were designed in Gambit, in order to investigate the possibility of physically separating large solid particles from the liquid flow where both phases are subject to suction into the circulation pipes.

The compaction of the wood chips is also considered in the modeling. In the Porous model, the digester is divided into sections of different porosity, and the behavior of individual suspension particles  is not considered. The bulk of this paper concerns modeling mass balances and phases of the mixture in the digester using Eulerian and Mixture strategies.

A dynamic model is developed for a continuous pulping digester to characterize the channeling phenomenon. The commercial CFD codes, FLUENT, are used to compute the hydraulic behavior of the digester under the normal and particular operational conditions. All the circulation flows, extractions, multiple inlets and outlets are included in this model. The digester is designed in the Gambit and an axisymmetric 2d model is applied. A porous scheme is implemented in the model in order to design the fluid flow and channelling phenomenon inside the digester. A heterogeneous porous media is specified in order to take the compression of the pulp into account. The simulation can serves as a prognosis model to predict the risk situations and probably to hinder high economical damage. The k- model contributes to compute the flow “regimes” or eventual eddies in some turbulent zones of the digester.

The following project has been carried out in collaboration with Abstracta AB (AAB), a company based in Lammhult with specialization in sound landscapes for indoor environments. The company manufactures different types of products with sound-absorbing properties where sustainability and design are in great focus. A new product idea of the company is based on developing an A-classified discreetly designed wall absorber that is considered more as a "wall" than a "wall with mounted absorbent on". The purpose of the project was to develop the following product on a conceptual level.

A main research question with two underlying issues was developed that served as a support during the project.

Question 1: How can an A-rated discreetly designed sound wall absorber be developed?

1.a: How can an A-rated sound wall absorber be developed?

1.b: How can a sound wall absorber achieve a discreetness in its design?

The project followed a product development process where the mainly focus was on concept development and concept testing. The concept was developed based on data collected from a literature study and with the use of a sound absorption calculator. A sound absorption test and an examination form regarding the discrete modeling and design of the absorbent were performed for the final concept that the project resulted in.

The project showed that an A-rated discreetly designed sound wall absorber can be developed through a process where design-critical specifications that affect the absorber's discrete design control how the object can be modeled. Via a sound absorption calculator, concepts can be designed that theoretically indicate an A-rate while the design-critical specifications are not exceeded. Based on the concept, a prototype is manufactured that can undergo a sound absorption test to determine the absorbent's actual sound absorption capacity. Finally, an examination is made to analyze whether the absorbent is considered a discrete alternative or not.

Based on the project's results, the work process proved to be advantageous as the concept indicated a sound absorption capacity that exceeded the requirements of the A-rating and at the same time obtained a discreet design and modeling. This was achieved in connection with the manufacturing materials achieving their technical specifications and a square meter cost lower than expected.

Based on the project's results, the work process proved to be advantageous as the concept indicated a sound absorption capacity that exceeded the requirements of the A-rating and at the same time obtained a discreet design and modeling. This was achieved in connection with the manufacturing materials achieving their technical specifications and a square meter cost lower than expected.

In the further development of the final concept, a solution for how the absorbent is to be mounted on the wall must be developed as this was not focused on in the project based on its boundaries. To achieve a valid A-rate, an additional sound absorption test must also be performed where a larger object area of 10–12 m² is tested. In future work, the concept's discrete modeling and design should also be examined based on physical treatment to review how the examination form's response results relate to this.

In subcooled flow boiling, heat transfer mechanism involves phase change between liquid phase to the vapour phase. During this phase change, a large amount of energy is transferred, and it is one of the most effective heat transfer methods. Subcooled boiling heat transfer is an attractive trend for industrial applications such as cooling electronic components, supercomputers, nuclear industry, etc. Due to its wide variety of applications for thermal management, there is an increasing demand for a faster and more accurate way of modelling. 

In this work, a supervised deep neural network has been implemented to study the boiling heat transfer in subcooled flow boiling heat transfer. The proposed method considers the near local flow behaviour to predict wall temperature and void fraction of a sub-cooled mini-channel. The input of the network consists of pressure gradients, momentum convection, energy con- vection, turbulent viscosity, liquid and gas velocities, and surface information. The output of the model is based on the quantities of interest in a boiling system i.e. wall temperature and void fraction. The network is trained from the results obtained from numerical simulations, and the model is used to reproduce the quantities of interest for interpolation and extrapolation datasets. To create an agile and robust deep neural network model, state-of-the-art methods have been implemented in the network to avoid the overfitting issue of the model. The results obtained from the deep neural network model shows a good agreement with the numerical data, the model has a maximum relative error of 0.5 % while predicting the temperature field, and for void fraction, it has approximately 5 % relative error in interpolation data and a maximum 10 % relative error for the extrapolation datasets. 

In the non-intrusive measurement of swirling air flow, helium-filled soap bubbles (HFSBs) are ideal neutrally buoyant tracer particles However, there are some researchers that do not use HFSBs in the non-intrusive measurement of swirling air flow, leading to some kind of measurement inaccuracy. Since the flow velocity data has been implicitly included in the physical equations of any kind of tracer particles, it is possible to extract such hidden flow velocity from particle trajectory. In this study we propose a physics-informed procedure of adopting SINDy algorithm to identify the hidden physical equations of non-neutrally buoyant particle dynamics, so that the implicit flow velocity can be discovered. First of all, the numerical experiment is conducted to generate particle trajectory in a 2D swirling air flow in small cyclone separator. Based on the numerical experiment trajectory data, the input variables for SINDy algorithm are properly constructed. The output of SINDy algorithm, which are the identified physical equations, are evaluated and validated on two different-density particle trajectory data. Our results show that the physical equations of tracer particle dynamics can be identified and the discovered flow velocity data has a maximum deviation of 1.4% from the truth (R2≥0.999). The proposed method may remove the requirement of NB tracer particle in non-intrusive measurement of swirling air flow, and may be applied to recognize the physical equations of complex particle laden flow.