The use of chemical scale inhibitors in the oil and gas industry for subsea installations has been presented for a long time, but the ever-increasing exploration of HPHT (high pressure high temperature) wells put demands on knowledge of how the rheological properties such as viscosity of scale inhibitors behave under large pressures. This work reports new experimental data of high-pressure viscosity using a rotational rheometer, measured across a pressure range of 0.1 MPa to 15 MPa, at temperatures from 273 K to 298 K, and a broad range of shear rates, 100 s(-1) to 1000 s(-1) for a scale inhibitor. The experimental data are used to construct a power-law regression model with fitting parameters. Results indicate that the inhibitor shows a near Newtonian behavior.

Existing thermal condition and indoor air quality have a big impact on our work performance, comfort, and health in an indoor environment. Apart from many other parameters, door motions and human movements play crucial role in mass and thermal exchange affecting safety and/or energy management issues in various situations. An isolation room in a hospital setup, for instance, helps to protect patients and staff against the risk of infection by airborne pathogens. Another example is cold storage room facilities, where temperature and moisture control are the key parameters for an optimal operation and energy usage. In this study, we present a transient flow analysis of door motions in indoor environment. The flow physics is resolved by solving 3D compressible RANS (Reynolds-averaged Navier-Stokes) equations together with the energy and species transport equations and two-equation turbulence models utilizing an overset mesh strategy to address the rigid body motion of doors in a relevant fluid domain involving air and sulfur hexafluoride (SF6). Simulations are performed for three different types of doors, namely a hinged door, a two-way sliding door, and a sliding door considering door opening and closing phases. Transient flow-field data through the door opening area have been processed and a comparative analysis is performed considering the mass flux of the constituents, normal velocity, cumulative mass exchange through the different doors.

For the last couple of years, the world has faced the global pandemic COVID-19. The viral transmission could occur via different modes like large respiratory droplets, direct contact with contaminated surfaces and airborne microdroplets or aerosol. This work revisits and focuses on human cough, and breathing sequence together with cough in confined spaces. We consider the Eulerian dispersion medium as a multicomponent ideal gas mixture consisting of oxygen, nitrogen and water vapor and the Lagrangian dispersed phase of human cough/breathe is modeled as pure liquid water. The unsteady complex flow is resolved with an advanced three-dimensional multiphase flow solver utilizing adaptive mesh refinement (AMR). A simplified rectangular block with a rectangular mouth area is considered to mimic human beings to inject exhaled gas and liquid droplets associated with cough and or breathing instances. The evaporation model is switched off for the particles of diameter less than 5 μm to resolve the dynamics of the airborne particles. The results clearly demonstrate the efficacy of the novel approach toward gaining more knowledge about viral transmission in indoor environments.

The main objective of this work is to investigate the energy and exergy performance of a solar assisted ground source heat pump for a school building designed according to Norwegian passive house standard. The system is designed in such a way that the solar collector prioritizes to provide heat to the hot water tank and whenever there is excess heat from the solar collector it can be used to charge the ground borehole. A detailed thermodynamic analysis of the system has been carried out in Engineering Equation Solver (EES). Isobutane (R600a), propane (R290), ammonia (R717) and solstice (R1234ze(E)) have been investigated as working fluid for the heat pump. The result revealed that the solar collector and the different working media have affected both the COP and the exergy of the system. Moreover, the mass flow rate of the brine and the length of the borehole affect the performance of the system.

Phase change material (PCM) is an attractive solution for improvement of thermal performance in buildings, and have excited a vast amount of research in recent years. There are however practical challenges with ensuring adequate phase transitions of the PCM to exploit the passive heat storage benefits. Night ventilation (NV) with free cooling have surfaced as one of the most promising methods to properly utilize PCMs and maximize energy savings. This work deals with a novel spackling compound enhanced with microencapsulated PCM. The product is intended for use at inner walls and ceiling surfaces of buildings and is suited for new and retrofitting building applications. Ensuing former experimental studies, a validated simulation model is developed and used to study the PCM with natural and hybrid NV strategies in an office building during summer conditions in Oslo, Norway. Cooling load reduction and energy savings are analyzed with varying air flow rates of 0.5–5 air changes per hour (ACH) and 2–4 mm PCM layer thickness. It is shown how increasing air flow rates and PCM thickness greatly enhances energy performance, but at a diminishing rate. Although the NV alone can reduce the cooling load by 11.5% at 1 ACH, 40.2% at 3 ACH and 59.8% at 5 ACH, one can achieve further reduction up to 19.5%, 78.2% and 95.5% for the respective ACHs with 4 mm PCM. The natural NV provides more energy savings compared to the hybrid strategy. As energy requirement by fans increases with the increase of air flow rates in the hybrid strategy, the energy savings eventually start to reduce. The hybrid strategy can save 38% energy at most with 3 ACH, and the savings is increased to 50% with the inclusion of 4 mm PCM. On the other hand, the natural strategy saves 56% of energy at the same air flow rate, and 69% with 4 mm of PCM.

This study reports a numerical analysis of the performance of green façades in different geographical locations and seasonal conditions.A mathematical model from a previous study is implemented and combined with the modified convective heat transfer coefficients from a recent study of the literature to simulate the transient heat transfer through bare walls and green facades with climbing vegetation.An implicit Finite Difference Method (FDM) based solver is used to perform the numerical simulations.Climate data are taken from relevant weather stations in Oslo and Rome and typical meteorological year (TMY) values are used for this purpose together with variable thermo-physical properties of air.An energy budget analysis reveals that the short-wave radiation term and convective heat transfer term are predominating compared to the other terms involved in the energy balance equation for summer time.The results show that the green walls are most effective in summer seasons with high levels of solar radiation, as most of the cooling effect is credited to the vegetation blocking the solar radiation.In cooler seasons, the benefit is less prominent.Furthermore, an analysis of the effects of the different models of convective heat transfer coefficients is presented.

This article presents an ongoing research project regarding blended education; Flexible Digital Class­room (FlexiDig), and a survey on full-time and part-time students’ experiences with blended education in a master’s degree programme in Art and Design Education. To optimise educational resources, the lectures for the full-time students were recorded, including the dialogue between the students and the lecturers, and made digitally available for all students. Generally, both the part- and full-time students participating in the questionnaire expressed their experience as “satisfactory” for the availability of the recorded lectures. Moreover, the capture of dialogues in the recording was found to be extremely useful for better understanding and learning, according to the students. This idea forms a basis to develop FlexiDig as simple as possible with a transfer value to other educational situations based on the approach of Student-Centered Learning and Teaching in Higher Education (SCLT).

Shock-wave diffraction over double concave cylindrical surfaces has been numerically investigated at different flow regimes by varying the incident-shock-wave Mach number from Ms=1.6 (transonic) to Ms=4.5 (supersonic regime). The purpose of this study is to better understand the dynamics of shock-wave structure and the associated wave configurations. A mesh-independent solution is obtained and the flow is assessed through different physical quantities (transition angles, triple points trajectories, wall-pressure and skin-friction distributions, velocity and shock location). It is found that the transition angles, from regular to Mach reflection, increase with the Mach number. This phenomenon remains almost the same over both concave surfaces for weak Mach numbers (up to Ms=2.5) and becomes relatively larger on the second surface for high Mach numbers. In terms of shock dynamics, it is found that by increasing the incident incident-shock-wave Mach number to Ms=4.5, unlike the first reflector, the transition from a single-triple-point (STP) wave configuration to a double-triple-point (DTP) wave configuration and back occurred on the second reflector, indicating that the flow is capable of retaining the memory of the past events over the entire process. For the shock velocity, the velocity deficit is found to be increasing with increase in Ms. A best fitting scaling law is derived, to ensure a universal decay of the shock velocity depending on the flow parameters.

The unsteady aspect of turbulent flow structures generated by a shock-wave diffraction over double cylindrical wedges, with initial diffracting angle of 75∘, are numerically investigated by means of two-dimensional high-fidelity numerical simulation. Different incident-shock-Mach numbers, ranging from transonic to supersonic regimes, are considered. Unlike previous studies where only the total vorticity production is evaluated, the current paper offers more insights into the spatio-temporal behavior of the circulation by evaluating the evolution of the instantaneous vorticity equation balance. The results show, for the first time, that the diffusion of the vorticity due to the viscous effects is quite important compared to the baroclinic term for low Mach numbers regimes, while this trend is inverted for higher Mach numbers regimes. It is also found that the stretching of the vorticity due to the compressibility effects plays an important role in the vorticity production. In terms of pressure impulses, the effect of the first concave surface on the shock strength has been quantified at both earlier and final stages of the shock diffraction process. Unlike the overpressure, the static and the dynamic pressure impulses are shown to be significantly reduced at the end of the first concave surface.

Thermal energy storage with phase change materials (PCM) is a promising candidate to promote resource sustainability in buildings. The intelligent selection and usage of a PCM within the structure of a building poses a challenging engineering task due the highly dynamic nature of occurring heat transfers. This work features a step-by-step FEM modeling guideline to assist the design of building structures by means of a 1D heat conduction scheme. The phase change functionality is based on the apparent heat capacity method and extended by ordinary differential equations to account for the thermal hysteresis of materials with different melting and freezing temperatures. The set of equations is solved alongside with logical expressions representing a thermostat functionality to assess the external energy demand. Two proof-of-concept examples for PCM usage in typical Swiss and Greek wall structures are given.

Shock-wave propagation through obstacles or internal ducts involves complex shock dynamics, shock-wave shear layer interactions and shock-wave boundary layer interactions arising from the associated diffraction phenomenon. This work addresses the applicability and effectiveness of the high-order numerical scheme for such complex viscous compressible flows. An explicit Discontinuous Spectral Element Method (DSEM) equipped with entropy-generation-based artificial viscosity method was used to solve compressible Navier–Stokes system of equations for this purpose. The shock-dynamics and viscous interactions associated with a planar moving shock-wave through a double-bend duct were resolved by two-dimensional numerical simulations. The shock-wave diffraction patterns, the large-scale structures of the shock-wave-turbulence interactions, agree very well with previous experimental findings. For shock-wave Mach number M s = 1.3466 and reference Reynolds number Re f = 10 6 , the predicted pressure signal at the exit section of the duct is in accordance with the literature. The attenuation in terms of overpressure for M s = 1.53 is found to be ≈0.51. Furthermore, the effect of reference Reynolds number is studied to address the importance of viscous interactions. The shock-shear layer and shock-boundary layer dynamics strongly depend on the Re f while the principal shock-wave patterns are generally independent of Re f .

The turbulent structures and long-time flow dynamics of shock diffraction over 90° convex corner associated with an incident shock Mach number Ms = 1.5 are investigated by large eddy simulation (LES). The average evolution of the core of the primary vortex is in agreement with the previous two dimensional studies. The Type-N wall shock structure is found to be in excellent agreement with the previous experimental data. The turbulent structures are well resolved and resemble those observed in the experimental findings. Subgrid scale dissipation and subgrid scale activity parameter are quantified to demonstrate the effectiveness of the LES. An analysis based on turbulent-nonturbulent interface reveals that locally incompressible regions exhibit the universal teardrop shape of the joint probability density function of the second and third invariants of the velocity gradient tensor. Stable focus stretching (SFS) structures dominate throughout the evolution in these regions. Stable node/saddle/saddle structures are found to be predominant at the early stage in locally compressed regions, and the flow structures evolve to more SFS structures at later stages. On the other hand, the locally expanded regions show a mostly unstable nature. From the turbulent kinetic energy, we found that the pressure dilatation remains important at the early stage, while turbulent diffusion becomes important at the later stage. Furthermore, the analysis of the resolved vorticity transport equation reveals that the stretching of vorticity due to compressibility and stretching of vorticity due to velocity gradients plays an important role compared to diffusion of vorticity due to viscosity as well as the baroclinic term.

This work reports analysis of complex shock wave diffraction and longtime behavior of shock-vortex dynamics over splitter geometry encountered in both external and internal compressible flows. The simulation resolved the experimental findings of literature, and the insight of the flow topology is being presented with the probability density functions (PDFs) of various contributing terms of enstrophy transport equation and the invariants of the velocity gradient tensor. We use an artificial viscosity (AV)-based explicit discontinuous spectral element method (DSEM)-based compressible flow solver for this purpose. The numerical scheme utilizes entropy generation-based artificial viscosity and thermal conductivity to simulate the conservative form of the governing compressible flow equations. A shock sensor-based switch is used to reduce the addition of AV coefficients in rotation-dominated regions.

This paper reports the numerical analysis of shock wave diffraction over a convex sharp splitter geometry, focusing on the mechanism of the shock diffraction and the longtime behavior of shock–vortex dynamics. The flow evolution with shock–vortex dynamics for incident shock Mach number, \({M}_{{\mathrm {s}}} = 1.59\), is found to be in excellent agreement with the previous experimental results. We use a recent entropy-generation-based artificial viscosity (AV) method in conjunction with a high-order explicit discontinuous spectral element method (DSEM) to resolve these complex interactions. The AV is coupled with a shock sensor switch to attain optimal dissipations. Simulations capture the essential wave diffraction, transverse wave interaction with the deforming and growing primary vortex, and weaker secondary vortices arising from the Kelvin–Helmholtz instability. A quantification of the artificial dissipation of the numerical scheme is made by comparing the components of the kinetic energy dissipation rate and the pressure dilatation term. A new detailed transient flow analysis is also presented to address the shock dynamics, shock–vortex interaction, and the evolution of the flow topology with the probability density functions of various parameters of the enstrophy transport equation and the invariants of the velocity gradient tensor. The analysis reveals the mechanism of unwinding of vortices and its link with the divergence of the Lamb vector. A positive correlation is found between enstrophy and the imaginary part of the eigenvalues. Real parts of the two eigenvalues are associated with high dilatation shock regions and the outer edges of the vortices, respectively.

We present numerical analysis of a cold storage room with a product load, a fan, and a sliding door by solving compressible form of the conservative 3D Navier-Stokes equation (without Boussinesq approximation) together with the energy and mass fraction equations.The commercial computer program StarCCM+ is used for this purpose.The sliding door is treated with an overset mesh on a suitable background mesh.A rigid body translation is applied by a field-function to model the opening and closing of the door.The preliminary study captures essential features of the effect of the energy transport and the cooling of the product load by the fan and the hot, moist air exchange through the doorway.The airflow behavior and heat/mass transfer mechanisms are studied and presented for several numerical experiments.

This work presents a numerical analysis of a planar moving shock wave with Mach number M s = 1.3, travelling through a square cavity geometry with rigid boundaries.A high-order artificial viscosity based Discontinuous Spectral Element Method (DSEM) is used for this purpose.The explicit numerical scheme utilizes entropy generation based transport coefficients to solve the conservative form of the viscous compressible fluid flow equations.Numerical prediction of the shock propagation and diffraction is found to be in excellent agreement with the experimental results of the literature.The stable numerical scheme resolves the detail of the complex flow dynamics for varying reference Reynolds number (Re f ).The range of values of the artificial coefficients and the relative contribution of the components of the artificial energy dissipation rate are investigated and compared for different cases.Artificial energy dissipation is less for low Re f .The dilatational dissipation dominates over other components till the incident shock wave resides in the flow domain.

We present numerical analysis of a cold storage room with a product load, a fan, and a sliding door by solving compressible form of the conservative 3D NavierStokes equation (without Boussinesq approximation) together with the energy and mass fraction equations. The commercial computer program StarCCM+ is used for this purpose. The sliding door is treated with an overset mesh on a suitable background mesh. A rigid body translation is applied by a field-function to model the opening and closing of the door. The preliminary study captures essential features of the effect of the energy transport and the cooling of the product load by the fan and the hot, moist air exchange through the doorway. The airflow behavior and heat/mass transfer mechanisms are studied and presented for several numerical experiments.

The present study conceives a numerical model for phase change materials following the apparent heat capacity method where the phase change occurs within a chosen temperature interval.A multiphysical modeling approach to satisfy the coupled momentum, energy and continuity conservation equations whilst avoiding numerical singularities is applied.By means of a 2D test-case geometry with variable boundary heating the influence of natural convection within the melted liquid zone is visualized.Corresponding non-dimensional governing equations are analysed to quantify the dominant contributing terms.It turns out that for sufficiently small Grashof number, or consequently small Rayleigh numbers the influence of natural convection can be neglected, thus simplyfing the problem substantially.The modeling approach has been adapted to a 2D-axisymmetric geometry within the scope of experimental validation.The simulation results and experimental data show reasonably good agreement.The model is numerically stable and suitable to facilitate design of latent heat storage systems.

This work conceives a numerical modeling approach for the practical application of phase change materials (PCM). Momentum, energy and mass conservation are implemented in a coupled manner including auxiliary algebraic equations for phase change functionality. Key element of the modeling approach is the introduction of a socalled mushy zone at the interface between solid and liquid where the thermophysical properties are smeared out over an user-defined range of melting temperature. A 2D square cavity test-case shows the influence of natural convection on the melting front propagation. For practical application the model has been adapted to an 1D case representing the wall-crosssection of a typical Norwegian wooden cabin. The model can quickly reveal energetic optimization potential as well as provide orientation among the vast selection of PCM for the target-oriented choice of a suitable material.

The ability of large-eddy simulations (LES) to resolve the most energetic coherent structures of a spatially-evolving supersonic turbulent boundary layer over a flat plate at M∞=2 and Reθ≈6000 is analyzed using three different local subgrid scale models. Additionally, an Implicit LES (ILES), which relies on the intrinsic numerical dissipation to act as a subgrid model, is investigated to assess the consistency and the accuracy of the method. Direct comparison with data from high resolution DNS calculations (Pirozzoli and Bernardini, 2011) provides validation of the different modeling approaches. Turbulent statistics up to the fourth-order are reported, which help emphasizing some salient features related to near-wall asymptotic behavior, mesh resolution and models prediction. Detailed analysis of the near-wall asymptotic behavior of all relevant quantities shows that the models are able to correctly reproduce the near-wall tendencies. The thermodynamic fluctuations, Trms and ρrms, show a lack of independence from SGS modeling and grid refinement in contrast to the velocity fluctuations. The pressure fluctuations, which are associated with the acoustic mode, are not significantly affected by the modeling and the mesh resolution. Furthermore, the comparison of different contributions to the viscous dissipation reveals that the solenoidal dissipation plays the most dominant role regardless of the model. Finally, it is found that the ILES is more likely to produce consistent near-wall behavior even with a numerical scheme that has a small amount of numerical dissipation to emulate the effects of unresolved scales.