https://research.chalmers.se/ 2026-04-23 01:36:25 Visar de 30 senaste forskningspublikationerna för Hållbar utveckling https://research.chalmers.se//Images/chalmers_bldmrk.jpg Buses are essential for urban transport and generally considered safe. However, accidents involving buses, particularly in urban areas, often result in severe injuries and fatalities for vulnerable road users (VRUs). This study introduces a novel method to compute a safety envelope using reachability analysis and set-volume optimization. The research examines how the size of the safety envelope is influenced by simultaneous steering and braking maneuvers, factoring in perceived risk constraints for both standing bus passengers and VRUs. It also evaluates the relationship between minimum safety distance (MSD) and unsafe distances recorded in real-world bus-VRU collision. Key findings include the impact of VRU-perceived safety risk on a critical zone, with MSD increasing by 5 cm to 4.2 m for different maneuvers and initial speeds. Passenger-perceived safety risk also significantly affects MSD, with increases ranging from 0.05–1 m at 20 km/h to 4.8–12 m at 50 km/h, depending on the lateral offset. A comparison of MSD with crash data reveals that braking distances recorded for most of the crashes, align within the critical zone. Given levels for dangerous VRUs’ and passengers’ risk, the proposed method provides the interval when automated system should engage, as the set difference between the critical zones between the dangerous and highest risk levels. Paper i proceeding 2026-04-22 10:51:10 https://research.chalmers.se/publication/cee9657f-7f27-4ac3-8372-287283182213 2026-04-22T10:51:10Z In situ vibrational spectroscopy (Raman, FTIR) is used at temperatures of 120-430 degrees C under oxidative dehydration conditions to study the effect of CeO x , NbO x , and SbO x modifiers, as well as the effect of thermal aging, on the structural and configurational properties of titania(anatase)-supported vanadia catalysts. The study pertains to catalysts with low vanadium coverage (i.e., similar to 0.5 V nm-2) and an M/V molar ratio (M = Ce, Nb, Sb) equal to one. The dispersed (VO x )n phase consists of three species with distinct configurations: a majority Species-I with an O=V(-O-Ti)3 configuration (V=O terminal mode at 1024-1027 cm-1) followed by Species-II with an O=V(-O-Ti)4 configuration (V=O terminal mode at 1014-1016 cm-1) and a minority Species-III with an (O=V)2(-O-Ti) x configuration (symmetric stretching mode at similar to 1000 cm-1). Lowering of the temperature in the 430-120 degrees C range results in reversible temperature-dependent structural transformations. First, in the 430-250 degrees C range, a Species-II to Species-I transformation takes place, followed by a Species-I to Species-III transformation at lower temperatures. Modifying the VO x /TiO2(anatase) catalysts with CeO x , NbO x , or SbO x results in the increased presence of Species-I at the expense of Species-II. Thermal aging of the studied catalysts at 580 degrees C for 100 h gives rise to structural transformation of the anatase carrier, resulting in an increased presence of (101) facets and severe lowering of the specific surface area, thereby causing an increase in Species-I at the expense of Species-II and in the formation of V-O-V and/or V-O-M linkages. The results are deemed important for gaining insight into the structure and the behavior of anatase-supported vanadia catalysts. Artikel i vetenskaplig tidskrift 2026-03-20 21:28:46 https://research.chalmers.se/publication/551207 2026-03-20T21:28:46Z Polymer nanocomposites are attractive for HVDC insulation applications, especially for HVDC cables, due to their ability to suppress space charge accumulation through interfacial effects. However, direct evidence to support the existence of interfacial effects at the nanoscale is still lacking. Therefore, rational design and molecular engineering of the interfaces to improve the insulation properties of polymer nanocomposites remain unavailable. Here, we show that efficient space charge suppression can be achieved in polymer nanocomposites at temperatures up to 100 °C by introducing local deep traps through carefully designed nanoparticle/polymer interfaces. The local interfacial deep traps are directly detected at the nanoscale using intermodulation electrostatic force microscopy (ImEFM). This work provides a deep understanding of the interfacial effects in polymer nanocomposites and will enable the rational design of interfaces for high-performance insulation materials. Artikel i vetenskaplig tidskrift 2023-12-11 09:46:08 https://research.chalmers.se/publication/9642a607-c0ae-46a3-a18a-2570980c6ac1 2023-12-11T09:46:08Z Many people spend most of their time in an indoor environment. A positive relationship exists between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air-cleaning devices are commonly marketed as benefiting the removal of air pollutants and, consequently, improving indoor air quality. Depending on the type of cleaning technology, air cleaners may generate undesired and toxic byproducts. Different air filtration technologies, such as electrostatic precipitators (ESPs) have been introduced to the market. The ESP has been used in buildings because it can remove particles while only causing low pressure drops. Moreover, ESPs can be either in-duct or standalone units. This review aims to provide an overview of ESP use, methods for testing this product, the performance of existing ESPs concerning removing pollutants and their byproducts, and the existing market for ESPs. Artikel i vetenskaplig tidskrift 2026-03-25 09:16:53 https://research.chalmers.se/publication/545972 2026-03-25T09:16:53Z The contested nature of knowledge about sustainable development makes it difficult to embed sustainable development in engineering curricula, which tend to have a deterministic approach to understanding theoretical concepts. Such an approach does not align well with the emergent thinking of sustainable development, where thinking about the future requires dealing not only with what is known, but also with what is unknown and at times unknowable. Text-based approaches that privilege explicit and codified knowledge are limited in helping students visualise what a sustainable future might look like. To facilitate such visualisation would require expansion of the repertoire of tools and artefacts beyond text-based materials. In this article, we critically reflect on a series of student-centred 'Open-space' workshops over the past several years aimed at promoting debate and co-production of knowledge around developing sustainable futures using a range of artefacts such as pictorial illustrations, wiki terms, art materials and chill-out music. Attention is paid on critically appraising the role artefacts play in developing knowledge to empower students to collectively reflect on, imagine and visualise sustainable futures. Artikel i vetenskaplig tidskrift 2018-01-22 18:41:14 https://research.chalmers.se/publication/698ceb65-7be8-427b-95cb-dff276f94816 2018-01-22T18:41:14Z The demand for sustainable ship design has driven the use of high-strength steel to reduce structural weight, although this introduces buckling challenges due to unchanged elastic properties. Supported by the ISSC 2025 Ultimate Strength Committee, this study evaluated the ability of numerical simulations to predict the nonlinear response and ultimate strength of stiffened panels subjected to transverse compression. The benchmark consisted of full-scale blinded experimental tests that were conducted in parallel using a deck-like structure with thin plating prone to elastic buckling. The finite element models produced by participating researchers were compared, focusing on the complete end-shortening curve rather than just ultimate strength. Despite identical input geometry and minimal modeling guidance, results varied widely, revealing the significant influence of user-defined assumptions. The inclusion of additional data on material properties in the second study phase led to greater result dispersion due to the different strategies adopted for the hardening model. Key variability sources included the modeling of initial imperfections, material constitutive laws, and residual stresses from welding. The study highlights the need for consistent modeling and improved experimental data collection, particularly regarding boundary conditions and residual stress effects. While including welding stresses improved stiffness predictions, uncertainty in boundary behavior limited the assessment of ultimate strength impacts. The study also evaluated compliance with classification society rules (e.g., CSR, DNV, UR-S35), offering insights into how nonlinear numerical analyses complement or challenge regulatory frameworks based on closed-form expressions. Recommendations are made for improving simulation reliability and result validation. Artikel i vetenskaplig tidskrift 2025-11-24 11:15:43 https://research.chalmers.se/publication/cd8cd3e5-aed1-4618-b0eb-16ff95e66d69 2025-11-24T11:15:43Z Background: The biodistribution of PSMA-ligands is of interest in radionuclide therapy planning. We investigated the variability of [18F]PSMA-1007 uptake in organs at risk and in relation to tumour burden in prostate cancer patients. Methods: A total of 1086 patients who underwent PSMA PET-CT for staging or recurrence of prostate cancer were included. Total lesion volume (TLV) and total lesion uptake (TLU) were calculated from manual segmentations. The mean standardized uptake value (SUVmean) in the organs at risk kidneys, liver, parotid glands and spleen was obtained. Correlations between TLV/TLU and SUVmean in normal tissues were calculated using Spearman rank correlation. SUVmean in normal tissues was stratified into groups based on TLV. Results: The median (IQR) SUVmean of the kidneys, liver, parotid glands, and spleen was 13.1 (IQR 4.6), 11.8 (4.4), 18.6 (6.8) and 11.3 (5.8), respectively. The median TLV was 3.8 cm3 (9.7) and median TLU was 31.2 cm3 (106.3). There was no significant correlation between TLV or TLU and SUVmean for the liver, parotid glands, or spleen, but a weak negative correlation between TLV/TLU and SUVmean in the kidneys (r = −0.011, p = 0.0005; r = −0.09, p = 0.003). There was a tendency towards a lower SUVmean in the kidneys and parotid glands in patients with a very high TLV. Conclusions: There was a large uptake variability in organs at risk, which demonstrates the need for individual pretherapy dosimetry. There may be a tumour sink effect in the kidneys and parotid glands in patients with a very high TLV. Artikel i vetenskaplig tidskrift 2025-06-26 10:04:12 https://research.chalmers.se/publication/547076 2025-06-26T10:04:12Z This paper presents the development of a high-performance slot-liner solution based on thermoplastic PEEK Films tailored for the next generation of 800 V+ oil-cooled electric drive units in automotive applications. The work highlights the critical role of slot-liners as a fundamental component of primary insulation systems to enable the design of electric motors that achieve high efficiency and torque without compromising reliability. To meet the demanding dielectric performance requirements for 800 V+ e-motors, a material development study has been conducted. The results undermine the suitability of PEEK Films for high-voltage slot-liner applications upon meeting the oil compatibility and dielectric performance criteria for passenger cars and heavy-duty vehicles. Artikel i vetenskaplig tidskrift 2026-02-25 10:00:21 https://research.chalmers.se/publication/0523945a-779d-4fbc-9937-188993ab66a8 2026-02-25T10:00:21Z The maturation and scalability of unmanned aerial vehicle (UAV) technology offer transformative opportunities to revolutionize prompt delivery. This study explores integrating UAVs with public transportation vehicles (PTVs) to establish a novel delivery paradigm that enhances revenue for public transit operators and improves transport system efficiency without compromising passenger convenience or operational efficiency. Employing hexagonal planning technology, this study identifies and quantifies the available spatio-temporal resources of PTVs for UAV integration. This involves aligning the spatio-temporal dynamics of prompt delivery orders with PTV ridership, based on field data from Beijing's Haidian District. Utilizing these outputs, we quantitatively analyze the benefits of integrating UAVs with PTVs on increasing public transit revenue, and potentials of reducing carbon emissions and mitigating congestion. Furthermore, we quantify the long-term benefits of UAV-PTV integration by predicting future increases in delivery demand. Based on obtained quantitative results, this study discusses practical and policy implications to support the sustainable integration of UAVs with PTVs. Artikel i vetenskaplig tidskrift 2024-05-30 16:18:03 https://research.chalmers.se/publication/541280 2024-05-30T16:18:03Z Installing an energy saving device such as a pre-swirl duct (PSD) is a major investment for a ship owner and prior to an order a reliable prediction of the energy savings is required. Currently there is no standard for how such a prediction is to be carried out, possible alternatives are both model-scale tests in towing tanks with associated scaling procedures, as well as methods based on computational fluid dynamics (CFD). This paper summarizes a CFD benchmark study comparing industrial state-of-the-art ship-scale CFD predictions of the power reduction through installation of a PSD, where the objective was to both obtain an indication on the reliability in this kind of prediction and to gain insight into how the computational procedure affects the results. It is a blind study, the KVLCC2, which the PSD is mounted on, has never been built and hence there is no ship-scale data available. The 10 participants conducted in total 22 different predictions of the power reduction with respect to a baseline case without PSD. The predicted power reductions are both positive and negative, on average 0.4 %, with a standard deviation of 1.6 %-units, when not considering two predictions based on model-scale CFD and two outliers associated with large uncertainties in the results. Among the variations present in computational procedure, two were found to significantly influence the predictions. First, a geometrically resolved propeller model applying sliding mesh interfaces is in average predicting a higher power reduction with the PSD compared to simplified propeller models. The second factor with notable influence on the power reduction prediction is the wake field prediction, which, besides numerical configuration, is affected by how hull roughness is considered. Artikel i vetenskaplig tidskrift 2025-11-20 09:38:22 https://research.chalmers.se/publication/27441bf7-64f2-4174-a5ac-f644ac0c462d 2025-11-20T09:38:22Z Tremendous efforts have been devoted to boosting the power conversion efficiency (PCE) of organic solar cells (OSCs) via the introduction of cathode interlayers (CILs). However, CIL materials have limited diversity and the development of multifunctional devices is largely neglected. Herein, an acidochromic organic photovoltaic integrated device is firstly proposed by introducing an acid-sensitive stimulating-reaction organic molecule as both the CIL of OSCs and the sensor of monitoring environmental acidity. The oxazolidine unit of acidochromic molecule can form a ring-opening structure after acid treatment, resulting in the remarkable color change with the direct reflection of pH value of ecological environment. The additive-free PM6:Y6 OSCs using the acidochromic molecule as the CIL achieve an excellent PCE of above 15.29 %, which is 47 % higher than that of the control device. The PCE can even maintain above 92 % after treating CIL with various strong acids (pH = 1). Moreover, the color of acidified films and the degraded performance of acidified OSCs can be easily restored by alkaline treatment. The successful application of CIL in other highly efficient photovoltaic systems proves its good universality. This work triggers the promising application of acidochromic molecules in solar cells as CIL with the additional function of recognition of acid environment. Artikel i vetenskaplig tidskrift 2022-10-24 14:54:11 https://research.chalmers.se/publication/532539 2022-10-24T14:54:11Z Ridesplitting promises to reduce emissions. Previous studies mainly compared ridesplitting with single rides like taxis, leaving its impact on other modes unclear. This study quantifies the reduction or increase in CO2 emissions due to ridesplitting from a modal substitution perspective and explore the nonlinear impacts of built environment factors on emission reductions. Considering different urban contexts, we choose Chengdu and Xi'an as representative examples for analysis. The results indicate that most ridesplitting trips lead to an increase in CO2 emissions when compared to other modes. In Chengdu, a mere 8.92% of ridesplitting trips result in emission reduction, whereas in Xi'an, this figure stands at 4.68%. Emission reduction is predominantly linked to taxi substitution. Moreover, many built environment factors exhibit positive relationship with the increase in emission resulting from ridesplitting, and present nonlinear and threshold effects. The findings offer a framework to assess ridesplitting's environmental benefits, aiding urban planners and policymakers. Artikel i vetenskaplig tidskrift 2024-08-06 15:19:04 https://research.chalmers.se/publication/542147 2024-08-06T15:19:04Z This paper aims to enhance ship collision awareness by providing decision support in collision avoidance. To enable real-time computation in navigation, a Non-iterative Action Distance Determination Algorithm (NADDA) is developed. NADDA reduces the time complexity from O ( T log n ) to O ( T) by eliminating iterative processes, while maintaining the same space complexity as conventional bisection-based methods. This improvement significantly enhances computational efficiency, facilitating real-time applications. Based on NADDA, a robust and interpretable method for quantifying collision stages is developed by incorporating operational uncertainties, ship man-euverability, and the International Regulations for Preventing Collisions at Sea (COLREGs), thereby providing proactive colli-sion avoidance timing. Simulation experiments and a historical collision accident validated the effectiveness of the proposed methods. The results demonstrate that NADDA reduces computa-tion time by up to 93.1% compared to existing bisection-based methods, and the proposed collision stages quantification method achieves higher accuracy due to the consideration of operational uncertainties. The proposed method exhibits strong robustness and can provide real-time decision support in multi-ship encounter scenarios involving up to four target ships. Artikel i vetenskaplig tidskrift 2025-10-15 08:01:45 https://research.chalmers.se/publication/c1edbf7b-76e9-411d-ac4c-343468abed8d 2025-10-15T08:01:45Z Gas turbines powered by hydrogen offer a promising route to cleaner energy production. However, the use of austenitic stainless steel AISI 321, a common material for fuel supply pipes presents challenges due to its susceptibility to hydrogen embrittlement,which is often linked to deformation-induced martensite formation and the presence of δ-ferrite. While deformation-induced martensite is suppressed above the alloy’s Md temperature, the embrittlement role of δ-ferrite at elevated temperatures remains unclear. in this study, slow strain rate tensile tests were conducted in both air andpressurized H2 gas environments at room temperature (RT) and at 150 °C. Hydrogen embrittlement was observed at room temperature, as evidenced by a relative reductionin area of 0.44, whereas specimens tested at 150 °C exhibited no measurable embrittlement. Fractographic and microstructural analysis revealed that cracking of δ-ferrite phase boundaries at room temperature is associated with the formation of deformation-induced martensite. These findings demonstrate that hydrogen embrittlement in AISI 321 during tensile testing is primarily governed by the presence of deformation-induced martensite, and that δ-ferrite alone is insufficient to cause embrittlement at elevated temperatures. in addition, the effect of loading mode on HE behaviours is also discussed. The insight provided in this study is crucial for guiding material selection in hydrogen-fuelled gas turbines. Artikel i vetenskaplig tidskrift 2026-04-21 07:27:34 https://research.chalmers.se/publication/551723 2026-04-21T07:27:34Z Corporate purpose has seen a resurgence of interest in recent years and is increasingly portrayed as a potential driver of innovation, adaptability, and renewal. At the same time, we still know little about how organizations organize for purpose in ways that make renewal possible. This licentiate thesis examines how corporate purpose shapes strategic renewal through organizational design and business model innovation. Drawing on two qualitative studies, the thesis finds that when purpose introduces multiple commitments, organizations face a performance–complexity trade-off in which they may choose between alternative design approaches with different implications for performance across commitments, coordination demands, managerial effort, and renewal potential. At the business model level, the thesis distinguishes between two patterns of purpose-driven business model innovation: reinforcing innovation within an existing value logic and renewing innovation involving broader business model reconfiguration around new value logics. Taken together, the studies suggest that purpose-driven renewal is influenced by how organizations translate multiple commitments into organizational and business model arrangements, and the trade-offs they make between performance towards goals and the complexity required to sustain it. The thesis concludes by outlining two directions for future research towards a systems understanding of purpose-driven strategic renewal: how purpose evolves over time, and how organizational actors interpret and mobilize purpose in pursuit of renewal. Licentiatavhandling 2026-04-20 14:55:55 https://research.chalmers.se/publication/551722 2026-04-20T14:55:55Z Since the introduction of Industry 4.0, digital twin technology has significantly evolved, laying the groundwork for a transition toward Industry 5.0 principles centered on human-centricity, sustainability, and resilience. Through digital twins, real-time connected production systems are anticipated to be more efficient, resilient, and sustainable, facilitating communication and connectivity between digital and physical systems. However, environmental performance and integration with virtual reality (VR) and artificial intelligence (AI) of such systems remain challenging. Further exploration of digital twin technologies is needed to validate the real-world impact and benefits. This paper investigates these challenges by implementing a real-time digital twin based on the ISO 23247 standard, connecting the physical factory and simulation software with VR capabilities. This digital twin system provides cognitive assistance and a user-friendly interface for operators, thereby improving cognitive ergonomics. The connection of the Internet of Things (IoT) platform allows the digital twin to have real-time bidirectional communication, collaboration, monitoring, and assistance. A lab-scale drone factory was used as the digital twin application to test and evaluate the ISO 23247 standard and its potential benefits. Additionally, AI integration and environmental performance Key Performance Indicators (KPIs) have been considered as the next stages in improving VR-integrated digital twins. With a solid theoretical foundation and a demonstration of the VR-integrated digital twins, this paper addresses integration issues between various technologies and advances the framework of digital twins based on ISO 23247. Preprint 2025-10-31 10:48:27 https://research.chalmers.se/publication/548140 2025-10-31T10:48:27Z Hydropower is the largest carbon-neutral electricity source worldwide and a key flexibility resource in electricity systems, capable of adjusting its output across time scales from seconds to years. Yet its operational capabilities are constrained by, among other factors, the physics of how water flows through networks of dams and reservoirs and the technical characteristics of turbines. Moreover, hydropower operations affect river ecosystems, creating a tension between decarbonization and the protection of aquatic biodiversity. Understanding what hydropower can realistically deliver requires both improved modeling and analysis of these limits and their consequences.This thesis aims to advance both the modeling approaches and substantive understanding of hydropower in electricity systems. To situate this work, the thesis first examines how another flexibility strategy, potential transmission expansion, affects the cost of low-carbon electricity systems. It then turns to hydropower, addressing three research questions: How does hydropower modeling detail affect the realism of modeled operations, and does the choice of representation affect electricity system model results such as costs and electricity prices? How do physical, technical and regulatory constraints affect hydropower's operational capabilities? And what are the electricity system implications of regulatory constraints on hydropower? While the modeling approaches and insights are general, the case study applications focus on Swedish hydropower within the Nordic and Northern European electricity system.The thesis builds on four appended papers as well as additional analyses. New models are developed that represent individual hydropower plants at high technical detail, both standalone and embedded within an electricity system dispatch model. Using these models, the representation of hydropower in energy system models is scrutinized by comparing formulations ranging from fully aggregated national representations to individual turbines, showing that the choice of modeling approach is consequential for the results obtained. Hydropower's ability to sustain high output during prolonged periods of high demand is quantified under real physical, technical and regulatory constraints. The effects of environmental regulations on Swedish hydropower, including minimum flow requirements and restrictions on rapid flow changes, are assessed both in terms of hydropower operations and electricity system costs. The findings are discussed in light of ongoing regulatory processes for environmental adaptation of hydropower in Sweden. Doktorsavhandling 2026-04-20 11:03:15 https://research.chalmers.se/publication/551661 2026-04-20T11:03:15Z With growing global energy demand and the need to ensure energy security, meet climate goals, and support sustainable development, nuclear energy has experienced a renewed global interest. However, the safe disposal and management of high-level radioactive waste, particularly spent nuclear fuel (SNF), remains a significant scientific, societal and political challenge on a global scale.  One Proposed solution is the long-term isolation of the SNF in deep geological repositories (DGRs), where SNF is enclosed in copper canisters with an iron insert, surrounded by bentonite clay, and placed ~500 meters underground in granitic bedrock. While deep geological repositories (DGR) are designed to rapidly evolve towards anoxic, reducing conditions after closure, a potential breach of the canister containment followed by groundwater intrusion to the SNF can generate localized oxidizing conditions through the formation of radiolytic oxidants produced through water radiolysis. Such conditions can induce oxidative dissolution of UO2 matrix, potentially resulting in the mobilization and release of highly radiotoxic radionuclides into the biosphere. Metallic iron, a key component of the engineered barrier system, can simultaneously undergo anoxic corrosion upon contact with groundwater producing Fe(II) and H2.These species could inhibit the oxidative dissolution of the spent fuel matrix. In addition, metallic iron and Fe(II) may also play a crucial role in reducing U(VI) to U(IV) in groundwater systems, thereby limiting its solubility and mobility. Furthermore, the  co-precipitation UO2(s) with minor components of  the SNF may serve as a retention mechanism for radionuclides, further enhancing repository safety. Therefore, a detailed understanding of fuel matrix dissolution, radionuclide migration, and interactions with engineered barrier materials is essential for assessing repository performance over extended timescales. This thesis investigates key chemical processes influencing the behaviour of SNF under DGR conditions.  The findings indicate that anoxic corrosion of metallic iron significantly suppresses radiolytically induced oxidative dissolution of the fuel, leading to lower actinide releases. The coprecipitation studies infer that the concentrations of other actinides, lanthanides and fission products released by the fuel matrix during oxidative dissolution will not be determined by their individual solubilities when they coprecipitate with UO2(s) at the iron surface of the canister insert but will be orders of magnitude lower. Additionally, metallic iron efficiently reduces U(VI) to U(IV), promoting its sorption and precipitation on iron corrosion products. Overall, this thesis provides new insights and a better understanding of uranium redox behaviour in groundwater systems, spent fuel redox stability and actinide oxides co-precipitation processes under repository relevant conditions. Doktorsavhandling 2026-04-17 16:20:23 https://research.chalmers.se/publication/551693 2026-04-17T16:20:23Z Access to safe drinking water is essential for public health and for the functioning of modern societies. Water distribution networks (WDNs) play a vital role in ensuring the reliable delivery of drinking water to consumers. However, ageing WDNs, increasing pipe failure rates, and constrained renewal budgets are placing growing pressure on water utilities and driving a shift from reactive maintenance towards more proactive asset management. Data-driven methods can support such proactive management by providing outputs that are meaningful to water utilities. This thesis focuses on the development and evaluation of practical data-driven methods for pipe failure prediction and risk-based prioritization in WDNs. Using data obtained from water utilities in Sweden, the thesis investigates how data-driven methods can be used to support utility decision-making. This is done by estimating the likelihood of pipe failures and integrating failure likelihood with the consequences of pipe failures to generate outputs that are useful for maintenance planning, renewal decisions, and risk reduction. In addition, the thesis explores how such methods can be used under real-world deployment conditions by predicting future pipe failures and comparing the predictions with failures observed in the following years. Licentiatavhandling 2026-04-17 15:28:42 https://research.chalmers.se/publication/551660 2026-04-17T15:28:42Z The current study summarizes findings of the RoughProp project aiming to develop and utilize controlled surface roughness to mitigate tip vortex cavitation (TVC). The analysis is conducted through numerical and experimental investigations of tip vortex flows over an elliptical foil and a high-skewed propeller by focusing on how the roughness should be applied to have an optimum balance between TVC mitigation and hydrodynamic performance degradation. To model the tip vortex, LES is employed on a proper grid resolution having at least 32 grid points across the tip vortex diameter. The CFD analysis is supported by new sets of experiments conducted in the cavitation tunnel at Kongsberg Hydrodynamic Research Centre. The outcome of CFD results and experimental observations clarify the capability of roughness application in TVC mitigation with a reasonable performance degradation. For the propeller, it is found that the combination of having roughness on the blade tip and a limited area on the leading edge is the optimum roughness pattern that can provide a reasonable balance between tip vortex cavitation mitigation and performance degradation over a wide range of operating conditions. This pattern leads to an average TVC mitigation of 21% with an average performance degradation of 1.5%. Paper i proceeding 2022-02-03 13:20:46 https://research.chalmers.se/publication/527094 2022-02-03T13:20:46Z The marine propeller design process runs under strict time limitations and even if it entails contradicting requirements from different stakeholders and complex physical phenomena, the analysis tools must be very fast. Cavitation nuisance is such a complex phenomenon that is hard to predict accurately from these tools and requires additional evaluation by the blade designer. Thus, a good blade design depends on approximate analysis tools and on the expertise of an experienced blade designer. Therefore, we previously developed an interactive optimisation methodology, where interactive genetic algorithms were utilised for blade design optimisation and cavitation was manually evaluated by the blade designer. However, since blade design involves a large design space, the optimisation requires populations of thousands of individuals, something that makes the manual evaluations by the blade designer very laborious. Accordingly in this study, a machine learning pipeline has been developed with the aim to reduce the number of manual evaluations and classify the cavitation nuisance automatically. Nested-cross validation has been used in order to identify the best classification algorithms combined with the most suitable hyperparameters for three different propellers with both suction and pressure side cavitation. The results have shown that using machine learning can be very beneficial in order to reduce user fatigue in interactive optimisation processes. Paper i proceeding 2023-03-16 16:12:44 https://research.chalmers.se/publication/533535 2023-03-16T16:12:44Z Wind-assisted ship propulsion (WASP) has received much attention lately with research focusing on the different sail technologies, ship-hull design optimisation and weather route optimisation. However, the traditional propulsion system is still needed for wind-assisted vessels and is associated with several challenges, related to the wide range of operating conditions and propeller loads due to the varying degree of wind-assistance that will occur. In this study we use an interactive design and optimisation methodology applied on propellers of wind-assisted vessels. The methodology involves handling the complete operating profile of the propeller, an optimisation method for interactive cavitation evaluation by the blade designer, and the use of a new objective, the total energy consumption (TEC) of the expected operation. We use a case study where the KVLCC2 tanker is retrofitted with six Flettner rotor sails, operating between two fixed destinations at constant speed. The purpose is to investigate to what extent a new propeller design can offer a significantly lower TEC when compared to the existing design. Based on the results of this study, approximately 0.9% further reduction in TEC was achieved with the WASP adapted propeller compared to the existing one. Övrigt konferensbidrag 2022-12-26 14:51:43 https://research.chalmers.se/publication/533534 2022-12-26T14:51:43Z In recent years, there has been a growing interest in gaining in-depth understanding of ship hydrodynamics at full-scale conditions. Currently, there are only well-established procedures and guidelines for scaled models provided by the ITTC and supported through research findings. Although model testing and simulations give an insight into understanding ship hydrodynamics such as wake, resistance, propeller cavitation, and noise; scale effects create variations relative to actual operating conditions. In geometrically relative terms, it is well known that the boundary layer at full scale is generally thinner than model scale with delayed separation and weaker bilge vortices. Therefore, one can only obtain an accurate understanding of ship hydrodynamics under actual operation by conducting full-scale studies. However, such investigation raises additional considerations and challenges such as surface roughness modeling. The development of robust numerical methods aided by the continuous increase of available computational power has now opened the opportunity to perform such analysis.  For this reason, the aim of this research is to showcase numerical considerations for full-scale simulations together with comparisons of model-scale results. Övrigt konferensbidrag 2024-08-16 10:32:43 https://research.chalmers.se/publication/538707 2024-08-16T10:32:43Z Reynolds-Transport Theorem can be employed for analysing the conservation of energy equation over a control volume. Through this approach we can decompose the propeller delivered power into mechanical and thermal energy components. This approach not only enables us to qualitatively describe the flow but also makes it possible to quantify different energy flux components and understand the energy loss mechanisms within the studied system. Employing this method, the effect of free-surface on propeller-hull interaction is studied for an axisymmetric body in the vicinity of free-surface relative to a deeply submerged body. The required flow quantities for the control volume analysis are obtained from a Reynolds- Averaged Navier-Stokes approach together with a Volume-of-Fluid method for capturing the free-surface. The mechanical and thermal energy flux components have been computed for control volumes of different sizes, even including the free-surface. These results deviate less than 0.5% from the propeller delivered power which verifies the applicability of the method for further analysis of the interaction effects. The self-propelled hull is studied in two different depths and thus the propeller loadings and efficiencies are different. The analysis of energy flux components quantitatively explains the reasons for the differences. Paper i proceeding 2021-04-16 17:25:29 https://research.chalmers.se/publication/510612 2021-04-16T17:25:29Z The role of waterjet pump is to generate thrust by increasing the flow head. Details of the flow inside waterjet pump are important when pump performance is of the main interest. However, in waterjet self-propulsion, pump induced effects are of the main interest rather than the details of the flow inside the pump. This permits sim- plification of pump models when using numerical methods for simulating the flow. In order to find a robust and yet accurate pump model suitable for Computational Fluid Dynamics based methods, models of different so- phistication level are studied in this paper. First, a Sliding Mesh approach, which is capable of capturing the flow details, is validated against a set of cavitation tunnel measurements. Then a series of simpler models, i.e. Moving Reference Frame technique and three different body-force models, are studied and their results are compared to the ones obtained from the Sliding Mesh approach. The results indicate that one of the body-force models which takes the guide vanes as well as the impeller induced flow swirl into account has the best compromise between the robustness and accuracy among the investigated pump models. Artikel i vetenskaplig tidskrift 2019-07-10 17:48:53 https://research.chalmers.se/publication/6d7fc5e7-4588-46fa-a736-bceb66f9f73a 2019-07-10T17:48:53Z Open water testing for model scales is a universally accepted method to evaluate the thrust, torque, and efficiency of a propeller. Even so, due to the Reynolds number dissimilarity in tests, the development of the boundary layer and the natural transition to turbulence is not the same. This creates discrepancies in the force ratios known as scale effects. To overcome this issue, the standardized ITTC 78 method was developed as an extrapolation procedure to estimate the full scale propeller delivered power and performance. With the development of Computational Fluid Dynamics numerical tools, the scaling issue could be avoided by modeling the geometry in its real sea conditions. This paper aims at studying the scaling effects of a marine propeller in uniform open water condition. The geometry can be described as a moderately skewed 4-bladed controllable pitch propeller mounted on a simplified hub, and the geometrical scaling ratio for the model λ = 27.143. A comparison of the propeller performance across a range of advance ratios J at varying scales will be presented. Results of the numerical simulations will be compared with model scale experimental measurements carried out at Kongsberg’s research facility. The overall aim of this study is to gain a perception of how the scaling effects will influence the performance of this specific propeller. Paper i proceeding 2024-11-20 10:53:23 https://research.chalmers.se/publication/538708 2024-11-20T10:53:23Z This study investigates cavitation erosion in a commercial water jet pump through numerical methods, with comparison to experimental paint test. The multiphase flow is modelled using a mixture modelling approach within an unsteady Reynolds Averaged Navier-Stokes (RANS) framework. The erosion model used, identifies and stores the "collapse cells" that contribute to erosion together with a measure of their erosion aggressiveness. This algorithm checks all cells at the end of each time step to avoidincorrect identification of erosion areas. The comparison with experiments indicates that the proposed methodology is a reliable tool to assess cavitation erosion. Övrigt konferensbidrag 2025-05-10 11:37:37 https://research.chalmers.se/publication/544728 2025-05-10T11:37:37Z The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested and effects on cavitation inception, drag, and lift, are studied. Implicit Large Eddy Simulation (ILES) is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Centre, for the rough foil are presented.The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region and trailing edge of the suction side are acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The analysis of boundary layer characteristics shows a separation line caused by roughness is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition leading to a reduction in vortexstrength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33 % compared to the smooth foil condition with a drag force increase observed to be less than 2 %. Artikel i vetenskaplig tidskrift 2022-04-06 15:02:43 https://research.chalmers.se/publication/178df453-dcf1-4269-bb33-f31fd9c6068e 2022-04-06T15:02:43Z Tip vortex cavitating flow is known as challenging to study. The objective of this paper is to investigate the effective parameters in numerical modelling of tip vortex cavitation (TVC) inception through the comparison of three different models. The models are (1) a commonly used homogenous mixture model, in which inception is based on pressure drop criterion; (2) a Lagrangian bubble model, in which cavitation is initiated from free nuclei in the liquid; and (3) a hybrid Eulerian-Lagrangian model, in which the cavities are initiated based on the pressure drop criterion, but the growth of initially small cavities are modelled using the more accurate Lagrangian equations. The simulations are conducted on the tip vortex flow around an elliptical foil. The results show that the commonly applied pressure drop assumption is not a sufficient criterion for cavitation inception. Also, it is seen that the water quality and nuclei transport towards the vortex core influence the cavity pattern at inception. Paper i proceeding 2022-01-20 13:48:27 https://research.chalmers.se/publication/524708 2022-01-20T13:48:27Z In this paper, a numerical method to assess the risk of cavitation erosion is proposed, which can be applied to incompressible simulation approaches. The method is based on the energy description of cavitation erosion, which considers an energy transfer between the collapsing cavities and the eroded surface. The proposed framework provides two improvements compared with other published methods. First, it is based on the kinetic energy in the surrounding liquid during the collapse instead of the potential energy of collapsing cavities, which avoids the uncertainty regarding the calculation of the collapse driving pressure in the potential energy equation. Secondly, the approach considers both micro-jets and shock-waves as the mechanisms for cavitation erosion, while previous methods have taken into account only one of these erosion mechanisms. For validation, the proposed method is applied to the cavitating axisymmetric nozzle flow of Franc et al. (2011), and the predicted risk of cavitation erosion is compared with the experimental erosion pattern. This comparison shows that the areas predicted with high erosion risk agree qualitatively well with the experimental erosion pattern. Furthermore, as the current method can be used to study the relationship between the cavity dynamics and the risk of cavitation erosion, the hydrodynamic mechanism responsible for the high risk of cavitation erosion at the inception region of the sheet cavity is investigated in detail. It is shown for the first time that the risk of cavitation erosion in this region is closely tied to the separation of the flow entering the nozzle. Artikel i vetenskaplig tidskrift 2021-01-19 12:49:09 https://research.chalmers.se/publication/7182a044-7122-496d-875c-6367731dbdc5 2021-01-19T12:49:09Z