In this paper, collaborative aeroelastic analyses of the Pazy Wing are presented, which support the activities of the Large Deflection Working Group, a sub-group of the 3rd Aeroelastic Prediction Workshop (AePW3). The Pazy Wing is a benchmark for the investigation of nonlinear aeroelastic effects at very large structural deflections. Tip deformations on the order of 50% semi-span were measured in wind tunnel tests at the Technion - Israel Institute of Technology. This feature renders the model highly attractive for the validation of numerical aeroelastic methods for geometrically nonlinear, large deflection analyses. A distinguishing feature of the Pazy Wing is that its flutter speed is a function of the static deformation, and capturing this effect requires a nonlinear aeroelastic framework which allows for stability (flutter) analyses about steady states of large deformations. In particular, the flutter characteristics of the model are dominated by a hump mode which develops due to the coupling of the first torsion and the second out-of-plane bending mode; this hump mode moves towards lower airspeeds as the steady structural deformation increases. Different nonlinear aeroelastic solvers were applied by the authors to obtain static coupling and flutter results for a series of airspeeds and angles of attack. The results reveal that the decisive nonlinear effects were captured very well by the applied methods and computational tools.

AbstractSimulating entire wind farms with an actuator line model requires significant computational effort, especially if one is interested in wake dynamics and wants to resolve the tip vortices. A need to explore unconventional approaches for this kind of simulation emerges. In this work, the actuator line method is implemented within a lattice‐Boltzmann flow solver, combined with a sliding mesh approach. Lattice‐Boltzmann solvers have advantages in terms of performance and low dissipation, while the sliding mesh allows for local refinement of the blade and tip vortices. This methodology is validated on a well‐documented case, the NREL Phase VI rotor, and the local refinement is demonstrated on the NREL 5 MW rotor. Results show good agreement with reference Navier–Stokes simulations. Advantages and limitations of the sliding mesh approach are identified.

Numerical simulations of a wind turbine blade with and without trailing-edge serrations are validated with full-scale field test of a 130 m diameter onshore wind turbine. Simulations focus on trailing-edge noise and are conducted on extruded airfoil sections of the blade using the lattice-Boltzmann method and very large eddy simulations, which are then propagated to the far-field using the Ffowcs Williams-Hawkings approach, simulating the rotation of the sections and the noise of the entire rotor. Far-field noise spectra at two mean wind speeds are used for validation, with the sound power level of the simulations being within 2.5 dB of field test and the total noise reductions attributed to the serrations being captured within 0.6 dB.

With distributed propulsion and electric vertical take-off and landing aircraft on the rise, fast and accurate methods to simulate propeller slipstreams and their interaction with aircraft components are needed. In this work, we compare results obtained with a filament-based free wake panel method to experimental and previously validated numerical data. In particular, we study a propeller-wing configuration at zero angle of attack and the aerodynamics of the blade-resolved slipstream interaction with the wing. We use a prescribed wake on the wing and a free wake on the propeller, which greatly accelerate the computations. Results indicate that, while forces are overpredicted due to the inviscid nature of the panel method, the free wake is able to capture the slipstream deformation and shearing with remarkable success. We find that a filament-based free wake panel method can be a useful tool for propeller-wing interaction in preliminary aircraft design.

The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater treatment (WWT) sewage sludge through plasma gasification. Effective syngas production hinges on precise equipment design which, in turn, depends on the detailed feedstock used for characterization. Key components of plasma gasification include the plasma torch, reactor, heat exchanger, scrubber, and cyclone, enabling the generation of inert slag for landfill disposal and to ensure clean syngas. Designing these components entails considerations of sludge composition, calorific power, thermal conductivity, ash diameter, and fusibility properties, among other parameters. Accordingly, this work entails the development of an experimental setup for the plasma gasification of sewage sludge, taking into account a comprehensive sludge characterization. The experimental findings reveal that domestic WWT sewage sludge with 40% humidity exhibits a low thermal conductivity of approximately 0.392 W/mK and a calorific value of LHV = 20.78 MJ/kg. Also, the relatively low ash content (17%) renders this raw material advantageous for plasma gasification processes. The integration of a detailed sludge characterization into the equipment design lays the foundation for efficient syngas production. This study aims to contribute to advancing sustainable waste-to-energy technologies, namely plasma gasification, by leveraging sewage sludge as a valuable resource for syngas production.

Vertical axis wind turbines (VAWTs) have been identified as a technology that, in association with wake steering, can increase power density of wind farms. In this study, we validate a free wake method for VAWT wake prediction, which leads to satisfactory results. We then use this method to simulate wake steering by means of fixed pitched blades and struts. We demonstrate that combining pitched wakes and struts can lead to very advantageous wake behavior, but only when the interactions between the tip vortices are taken into account. The possibility to inject more high momentum flow into the wake while moving the vortex system away from the next turbine could make pitched blades and struts a powerful tool for future wind farms.

In this work, the interaction of grid-generated turbulence with airfoils of different thicknesses, namely, a National Advisory Committee for Aeronautics (NACA) 0008 and a NACA 0018, is investigated, leading to a deeper understanding of the influence of the airfoil geometry on the near-field flow and on the far-field pressure fluctuations. Experimentally validated lattice-Boltzmann simulations are used to analyze the flow properties in the leading-edge (LE) vicinity. The analysis of the velocity fluctuations near the LE shows that momentum is transferred from the streamwise to the transverse velocity for the NACA 0008 airfoil interacting with a large turbulence length scale. This mechanism changes with the increase in the airfoil thickness because the inflow turbulence length scale becomes comparable to the airfoil thickness in the LE region, resulting in a higher concentration of vortices near the LE oriented in the transverse direction, creating high-velocity fluctuations in the spanwise direction. The near- and far-field pressure fluctuations are analyzed to understand the impact of the inflow turbulence distortion on these parameters and the limitations of analytical methods for real airfoils. Results show that the wall-pressure fluctuations are affected by the turbulence distortion in the LE region. Thick airfoils have noise directivity patterns significantly different compared to the Amiet predictions for higher frequencies, radiating higher noise levels upstream of the LE than the thin airfoil. This is likely associated with a drastic change in the pressure fluctuation distribution near the airfoil LE region, attributed to the change in the distortion of the vortical structures in the LE area.

Green roofs are made up of several components, including those belonging to the waterproofing and drainage layers, substrate, and vegetation. Of these, the substrate is undoubtedly one of the most important layers of a green roof, contributing not only to the healthy growth of vegetation but also to the water retention capacity and thermal behaviour of the whole solution. Although green roofs are widely recognized as sustainable solutions, it is possible to further improve their environmental performance by developing more ecological substrates that contain industrial by-products. Bearing this objective in mind, sixteen newly developed substrates were characterized in terms of thermal conductivity, specific heat, emissivity, water vapour transmission, hygroscopic sorption, and water retention/drainage capacity. These properties are extremely relevant when solving heat and mass transfer problems as well as for water management prediction. Two reference substrates were also studied for comparison purposes. The results showed that the new ecological substrates have properties that make them comparable to conventional substrates already available on the market. Additionally, the results showed that temperature, moisture content, and density play an important role in the behaviour of substrates of this kind and have a significant influence on many of the studied properties.

The current environmental policies of the EU regarding waste management focus on a circular economy concept with an emphasis on the reduction of the waste that goes to landfills. In this context, the reuse of sewage sludges as an energy resource can be an attractive solution, mainly for the sector of paper and wastewater treatment plants. The plasma gasification of sewage sludges, even challenging, is pointed out as an option for waste valorization. However, several technical aspects must be investigated in order to make this solution attractive to the market. The conversion of the chemical energy contained in this raw material into the desired syngas depends on several factors such as the adequate configuration of the gasification system, its dimensioning, as well as the correct definition of the gasifier operating conditions. To provide a solution, this work focus on the design of a plasma gasifier for the valorization of sewage sludges. Data is provided regarding the sewage sludge composition and origin, using a DSC-TGA technique and the selection of the different elements that compose the gasification system in function of the expected operating conditions is provided. Also, a first approach related to a mass and energy balance estimation was performed. Moreover, a numerical simulation is conducted in order to characterize the flow dynamics inside the reactor and the evolution of the temperatures that have a critical impact on the raw material gasification.

Waste management is a major challenge for contemporary societies, requiring urgent attention since population growth combined with widespread consumerism and industrialization has led to an alarming increase in waste production. To avoid harmful environmental impacts and the misuse of resources, it is urgent to combat this scourge. A potential solution involves the creation of industrial symbioses, characterized by the practical application of circular economy principles. The use of collaborative platforms is a possible way to promote industrial symbiosis. Addressing these pressing concerns and responding to these challenges, the Upcycle4Biz project envisions establishing a digital platform called Upvalue, conceived as a marketplace where companies can exchange waste and by-products. This article aims to provide a comprehensive overview of the challenges and benefits associated with the development of this innovative platform, as well as a presentation of the platform itself.

The use of integral solutions to the acoustic-analogy-based Ffowcs Williams-Hawkings (FW-H) formulation is the de facto industrial and academic approach for assessing far-field acoustic behavior from airframe noise simulations. The methodology utilizes time-accurate flow variables obtained at arbitrary data surfaces to determine far-field spectra. The solid surface approach, where the time history of pressure is recorded on the surface of the aircraft, is generally preferred. Permeable surfaces, where pressure and velocity are recorded on a user-defined surface enclosing the aircraft, are also used. This paper seeks to share some of the valuable lessons we learned over the past several years on the limitations of the FW-H formulation and best practices for its successful application. We show results for various configurations comprising isolated landing gears, a business jet, a large commercial transport, and a generic low boom supersonic prototype, all at landing conditions. We demonstrate that the solid FW-H approach has significant accuracy limitations for most realistic cases and that the permeable FW-H approach may also fail in specific scenarios, requiring additional costly steps to extract the correct far-field noise spectra. Suggested guidelines for proper FW-H calculations are also given.

Abstract. We investigate the aerodynamics of a surging, heaving, and yawing wind turbine with numerical simulations based on a free wake panel method. We focus on the UNAFLOW case: a surging wind turbine which was modelled experimentally and with various numerical methods. Good agreement with experimental data is observed for amplitude and phase of the thrust with surge motion. We achieve numerical results of a wind turbine wake that accurately reproduce experimentally verified effects of surging motion. We then extend our simulations beyond the frequency range of the UNAFLOW experiments and reach results that do not follow a quasi-steady response for surge. Finally, simulations are done with the turbine in yaw and heave motion and the impact of the wake motion on the blade thrust is examined. Our work seeks to contribute a different method to the pool of results for the UNAFLOW case, while extending the analysis to conditions that have not been simulated before.

The recent increased interest in distributed propulsion and electric vertical take-off and landing vehicles have made propeller wake interactions with the aircraft more relevant. The interaction between high-lift wings and propeller slipstreams are still not fully understood and several research efforts are being carried out to improve that knowledge. Lattice-Boltzmann, very large eddy simulations of a propeller-wing-flap configuration are conducted in this work. The simulations are validated with experimental data, with very good agreement of surface static pressure, surface shearlines, and wake total pressure. The complex separation patterns on the flap and their interaction with the slipstream of the propeller are well captured. The effects of grid resolution and laminar-to-turbulent transition are demonstrated. With the simulations validated, they are used to better understand the flow field of this configuration. We find that the angle of attack has a strong effect on how the slipstream is split over the wing, that the tip vortices wrap around the wing leading-edge instead of being cut by it, and that increased circulation stabilizes the tip vortices on the suction side, while making the tip vortices on the pressure side more unstable.

Due to the energy crisis that some countries are facing nowadays, the gasification process appears to be a good alternative to produce some energy from solid materials. Increasingly, gasification involves using wastes as a solid fuel, making the process green and reusing some materials that otherwise could end up in a landfill. However, the process of finding the best gasification parameters of a sample can be very expensive and time-consuming. In this sense, a refuse-derived fuel (RDF) char produced from an original RDF under 30 min at 400 °C was tested on a small-scale reactor using macro thermogravimetric analysis (TGA), as presented in this paper. The goal was to study and evaluate the devolatilization and residual carbon rate of the sample under several conditions and, at the same time, quantify and analyze the released gas. In the first round of tests, 5, 10, and 20 g of samples were tested at 750 °C with an excess of air coefficient (λ) = 0 and 0.2. It was possible to conclude that the lower the mass, the higher the devolatilization rate. The λ only had an influence on the devolatilization rate with a 20 g sample. Regarding the gas, CO, CO2, and H2 had no variation in the sample mass in contrast to CH4, which increased with the increase in the sample mass. The second round of tests was performed with samples of 10 g of mass at temperatures of 700, 800, and 900 °C and λ values of 0.15, 0.2, and 0.25. The tests indicated that the temperature influenced the devolatilization rate but not the residual carbon combustion rate. Regarding the gas composition, CH4, CO2, and CO followed the same trend, decreasing the concentration with the increase in temperature; in contrast, H2 increased in concentration with an increase in temperature. The heating value of the gas followed the same behavior as CH4.

We investigate the aerodynamics of a surging, heaving, and yawing wind turbine with numerical simulations based on a free-wake panel method. We focus on the UNAFLOW (UNsteady Aerodynamics of FLOating Wind turbines) case: a surging wind turbine which was modeled experimentally and with various numerical methods. Good agreement with experimental data is observed for amplitude and phase of the thrust with surge motion. We achieve numerical results of a wind turbine wake that accurately reproduce experimentally verified effects of surging motion. We then extend our simulations beyond the frequency range of the UNAFLOW experiments and reach results that do not follow a quasi-steady response for surge. Finally, simulations are done with the turbine in yaw and heave motion, and the impact of the wake motion on the blade thrust is examined. Our work seeks to contribute a different method to the pool of results for the UNAFLOW case while extending the analysis to conditions that have not been simulated before and providing insights into nonlinear aerodynamic effects of wind turbine motion.

This paper presents low speed fluid structure interaction simulations of a highly flexible wing at various flow conditions, including flutter and excitation from sinusoidal gusts. Such wings are becoming more relevant in recent years, due to their potential for improving aerodynamics and reducing weight, while their flutter characteristics are particularly challenging to address, as the modal properties of the wings change as deflections increase. Calculations are based on time domain coupling of a geometrically exact beam structural model and a 3D free wake panel method, modeling the outer sur-face of the wing, which allow for nonlinear effects in terms of geometrical deformations and the flow at low computational cost. Static and aeroelastic wing deflections are in line with experimental data of the Pazy wing, which is a benchmark for highly flexible wings from Technion. Two flutter mechanisms are predicted within 1 to 3 m/s of the experimental range. An analysis of the flutter modes is performed, showing that the second torsion mode plays a role in flutter, something that had not been published before. Limit cycle oscillations are achieved and are shown to compare well with reference data, with the frequency being within 1% of the experimental value. Finally, results of gust simulations of the Pazy wing are compared to data from experiments and corrections for the wind tunnel measurements are proposed, which should facilitate future validation efforts. This work serves as a contribution to the Pazy wing dataset and is a step towards mid-fidelity simulations for more complex configurations.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Thermochemical conversion of solid fuels depends on the devolatilization rate of the volatile compounds. Depending on the process, the temperature is the key variable that controls such a process. Refuse Derived Fuels (RDFs) are fuels that can have a positive impact on the energy mix while contributing to the reduction of landfill material. Due to its variable composition, to design the conversion facility, it is of utmost relevance to have an accurate understanding of the actual behaviour of the fuel. Although gasification is the preferred route for energy conversion of RDF, carbonization appears to be an attractive pre-treatment process to reduce the corrosive compounds such as chloride RDF. For this purpose, samples were selected from a waste treatment plant in the north of Portugal, and the char was obtained after 30 min carbonization at 400 ℃. Vegetable char was also tested to be used as the main reference. To understand the influence of other materials on the process, biomass and sewage sludge were used. Mixed with the RDF char on a weight percentage of 20

According to the European standard EN ISO 21640:2021, Solid Recovered Fuels (SRF) is defined as solid fuel made from non-hazardous waste used for energy recovery, that can be produced by specific waste, municipal solid waste, industrial waste, commercial waste, construction and demolition waste and sewage sludge. These fuels can be used to generate electricity and/or thermal energy, promoting a low-carbon and circular economy. In recent years, the use of SFR has expanded to other interesting and promising fields, such as gasification or combined gasification and pyrolysis. This work aims to clarify the terminology of SRF, identify the production of different fractions of SRF in Portugal (industrial or municipal-waste source), classify each fraction, according to its potential and identify the main barriers to the gasification of SRF. For that, it was performed several physical-chemical analyses on SRF samples from different origins and locations. Results showed that in Portugal, SRF production can be divided into two typologies considering their origin: SRF from urban wastes or SRF from industrial wastes. Regarding the urban wastes SRF, in 2019 it was produced 683 tons in Portugal. The main physical-chemical characteristics demonstrate levels of moisture between 33.9% and 39.14%, low heating values (LHV) in order of 12 MJ/kg, and high content of heavy metals, sulfur, and chlorine. Regarding the SRF from industrial wastes, it was identified an annual production of above 200 thousand tons in 2019. The characteristics or physical-chemical composition of this type of SRF, namely low percentage of humidity (15‒17.3%), LHV in order of 19.43 MJ/kg, and also the low concentration of heavy metals, confirm the potential use of this product in gasification processes.

In search of a more sustainable society, humanity has been looking to reduce the environmental impacts caused by its various activities. The energy sector corresponds to one of the most impactful activities since most energies produced come from fossil fuels, such as oil and coal, which are finite resources. Moreover, their inherent processes to convert energy into electricity emit various pollutants, which are responsible for global warming, eutrophication, and acidification of soil and marine environments. Biofuels are one of the alternatives to fossil fuels, and the raw material used for their production includes vegetable oils, wood and agricultural waste, municipal waste, and waste cooking oils (WCOs). The conventional route for WCO valorization is the production of biodiesel, which, as all recovery technologies, presents advantages and disadvantages that must be explored from a technical and economic perspective. Despite its successful use in the production of biodiesel, it should be noticed that there are other approaches to use WCO. Among them, thermochemical technologies can be applied to produce alternative fuels through cracking or hydrocracking, pyrolysis, and gasification processes. For each technology, the best conditions were identified, and finally, projects and companies that work with this type of technology and use WCO were identified.

Climate change and environmental sustainability are among the most prominent issues of today. It is increasingly fundamental and urgent to develop a sustainable economy, capable of change the linear paradigm, actively promoting the efficient use of resources, highlighting product, component and material reuse. Among the many approaches to circular economy and zero-waste concepts, biochar is a great example and might be a way to push the economy to neutralize carbon balance. Biochar is a solid material produced during thermochemical decomposition of biomass in an oxygen-limited environment. Several authors have used life cycle assessment (LCA) method to evaluate the environmental impact of biochar production. Based on these studies, this work intends to critically analyze the LCA of biochar production from different sources using different technologies. Although these studies reveal differences in the contexts and characteristics of production, preventing direct comparison of results, a clear trend appears. It was proven, through combining life cycle assessment and circular economy modelling, that the application of biochar is a very promising way of contributing to carbon-efficient resource circulation, mitigation of climate change, and economic sustainability.