bluuebunny/crossref_metadata_2025 huggingface dataset:
Flood resilience: Response of an Australian sub‐tropical riparian rainforest to catastrophic flooding
Authors: Martiniello Léandra , Baker Andrew G. , Grant John Campbell , Palmer Graeme
Published: August 2024

Riparian taxa are subject to dynamic, intense, flood‐related stressors, and have evolved traits to persist in this environment. Climate change‐induced intensification of flood regimes pose a threat to these ecosystems, and little is understood about their resilience to this intensification. Following two consecutive major floods (the first flood record‐breaking) along the subtropical coast of eastern Australia in March 2022, we used methods based on persistence (resprouting, seedling recruitment), and floristic structure (height, DBH) and assemblage, to assess the resilience of an old growth riparian rainforest to severe flooding in the 12‐month post‐flooding window. Smallerwoody plants (stems <10 m tall, <30 cm DBH) were the most impacted and were significantly impacted by flooding. Native species richness and plant density (plants/m−2) significantly decreased between before and 3 months post‐flooding, after which they continued to significantly increase to surpass pre‐flood values. Overall, ~35% of taxa exhibited resprouting, ~28% of taxa exhibited seedling recruitment, and ~11% exhibited both resprouting and recruitment. An additional ~21% native taxa were introduced to the site via seedling recruitment, along with 65 invasive species. Model‐based multivariate analysis showed flooding significantly altered community floristics (p = 0.026) at 3 months. At 12 months post‐flooding the community was recovering, becoming more floristically similar to its pre‐flood composition. The riparian rainforest exhibited high resilience to intense flooding. Impact, persistence, and resilience varied amongplots, and the community took 12 months to move into recovery. We found that persistence, and floristic structure and composition weighted against impact were effective measures of ecosystem resilience. In the absence of further consecutive events, mature‐phase riparian rainforests are likely to be structurally and floristically resilient to climate change‐induced amplification of flood regimes. Further studies should build on this framework to include invasive weed species impacts, for a more accurate assessment of impacts.
Civilian behavior on social media during civil war
Authors: Gohdes Anita R. , Steinert‐Threlkeld Zachary C.
Published: August 2024

Recent research emphasizes social media's potential for citizens to express shared grievances. In active conflict, however, social media posts indicating political loyalties can pose severe risks to civilians. We develop a theory that explains how civilians modify their online behavior as part of efforts to improve their security during conflict. After major changes in territorial control, civilians should be more likely to post positive content, and more content that supports the winning side. We study social media behavior during and after the siege of Aleppo in November 2016. We match Aleppo‐based Twitter users with users from other parts of Syria and use large language models to analyze changes in online behavior after the regime's retaking of the city. Results show that users in Aleppo post more positive and pro‐Assad content, but only when self‐disclosing their location. The findings have important implications for our understanding of digital communication in civil conflict.
Communication, coordination, and surveillance in the shadow of repression
Authors: Chau Tak‐Huen , Hassan Mai , Little Andrew T.
Published: August 2024

Communication technology helps protesters organize, but also allows the government to monitor and repress their actions. We study this trade‐off in a model where protesters want to show up at the same time and place, but also want to avoid government forces. If leaders of a movement can send messages observed only by other protesters, they can successfully coordinate on a variety of sites and force the government to spread resources thin, helping the success of the movement. If the government always observes the messages too, protesters can do no better than always going to a “focal site” knowing that the government will send all resources there as well, and thus experience higher levels of repression for the sake of coordinating tactics. Intermediate cases where messages are partially observed generate dynamics where new technologies and media that are relatively known to other protesters and not the government are used until the government can reliably infiltrate them and the protesters move on to a new medium. When some protesters are more informed than others, the model can explain protest tactics observed in recent prominent cases like having smaller “parallel” protests at the same time but different location of the main gathering.
The enhancing effect of social reward on inhibitory control in smokers: Evidence from behaviour and ERP studies
Authors: Zhang Yuhan , Chen Haide , Li Weijian , Gao Lingfeng , Zhao Boqiang , Zhao Wan
Published: August 2024

Objective

Prior research has revealed impaired inhibitory control as a pivotal factor contributing to smokers' struggle to control smoking impulses. However, few studies focus on enhancing smokers' inhibitory control. This study investigates the potential of social rewards to bolster inhibitory control among smokers and elucidates the underlying mechanisms.

Methods

In Experiment 1, a reward‐based Go/Nogo paradigm assessed error rates and reaction times for 30 smokers exposed to social reward and neutral feedback in distinct contexts (smoking‐related and neutral). Experiment 2 used a modified paradigm, incorporating cognitive load manipulation, to investigate error rates, reaction times, N2, and P3 ERPs among 32 smokers facing social reward and neutral feedback under different cognitive loads (high and low).

Results

Smokers exhibit lower Nogo error rates with social reward feedback; higher error rates occur with smoking cues and high cognitive load; increased N2, P3 amplitudes under social reward versus neutral feedback; low cognitive load enhances P3 amplitude under social reward.

Conclusion

Social reward improves smokers' inhibitory control, but this effect weakens with exposure to smoking cues; higher cognitive load further diminishes the enhancement of smokers' inhibitory control by social reward under smoking cues.
Lightening the load for paediatric ITP: The importance of health‐related quality of life
Authors: Neunert Cindy E. , Lambert Michele P.
Published: August 2024

In their paper, Klaassen et al. present their findings on the revised Kids ITP Tools (KIT). This important work provides an update to the validated measure for evaluating health‐related quality of life (HRQoL) in children with immune thrombocytopenia (ITP). ITP, an acquired autoimmune disorder, results in thrombocytopenia and places children at risk for significant bleeding. Thankfully, the majority of children with ITP will have a brief disease course and no or mild bleeding symptoms. The rarity of severe bleeding events or the development of chronic disease provides a challenge with regard to clinical trial design, making alternative measures of pharmacological efficacy extremely important.

Commentary on: Dhir et al. Quality of life in childhood immune thrombocytopenia: Revision of the Kids' ITP Tools (KIT). Br J Haematol 2024 (Online ahead of print). doi: 10.1111/bjh.19662.
Inkblots, Psychotherapy and the Tavistock Clinic
Authors: Sayers Janet
Published: August 2024

The purpose of this article is to recount the early history of the Rorschach's inkblots test in Europe and the USA; its subsequent application in highlighting the ill effects on children of bombing during the Second World War; its wartime use in selecting military personnel; its post‐war use in selecting patients for psychotherapy at the Tavistock Clinic in London and subsequent decline in this use of Rorschach's inkblots in favour of focus on the psychotherapy patient's transference experience of the psychotherapist treating them. The article ends with evidence of interest, beyond psychotherapy, in Rorschach's inkblots and with the implications of this for the author's principal conclusion regarding the value of these inkblots in evoking the free association and conversation crucial to psychotherapy.
Dairy versus non‐dairy cheese texture: Sensory and instrumental contrasts
Authors: Hutchings Scott , Alfante Renna , Jacob Noby , Loveday Simon M.
Published: August 2024

With growing consumer demand for plant‐based products that mimic the eating experience of animal‐based products, there is a need for improvement in instrumental measurements of sensory texture. This study aimed to characterize textural differences between dairy and non‐dairy cheeses, and to investigate whether Large Amplitude Oscillatory Shear (LAOS) rheometry could discriminate sensory texture better than Texture profile analysis. Commercial dairy and non‐dairy cheddar, mozzarella, and cream cheese were selected to provide a wide range of textures. Sensory evaluation used the check‐all‐that‐apply methodology with 73 consumers. Texture profile analysis force‐distance data were analyzed empirically, and also converted to stress and strain (see https://shiny.csiro.au/texture_dash). The major textural differences between dairy and non‐dairy cheddar were related to structural cohesion, according to both instrumental measures (dairy cheddar had 1.5‐fold higher failure stress and 2.2‐fold higher failure strain) and sensory measurements (dairy cheddar was more chewy and less crumbly). In contrast, cream cheeses showed similar textural properties using sensory testing but significant instrumental differences (non‐dairy cream cheese had 5.7‐fold higher modulus of deformability, 4.7‐fold higher failure stress). For mozzarella, there were large differences in both sensory attributes (chewy, crumbly, jelly‐like, stretchy) and instrumental parameters (13.6‐fold difference in modulus, 2.7‐fold difference in failure stress). LAOS rheometry gave insights into the mechanisms by which samples absorbed or dissipated mechanical energy at nonlinear strains. The LAOS parameter correlated well with sensory attributes creamy, fatty/oily, and moist, indicating the potential of this technique to measure structural phenomena linked to sensory attributes that resonate with consumers.
Genetic and telomeric variability: Insights from a tropical avian hybrid zone
Authors: Vernasco Ben J. , Long Kira M. , Braun Michael J. , Brawn Jeffrey D.
Published: August 2024

Telomere lengths and telomere dynamics can correlate with lifespan, behaviour and individual quality. Such relationships have spurred interest in understanding variation in telomere lengths and their dynamics within and between populations. Many studies have identified how environmental processes can influence telomere dynamics, but the role of genetic variation is much less well characterized. To provide a novel perspective on how telomeric variation relates to genetic variability, we longitudinally sampled individuals across a narrow hybrid zone (n = 127 samples), wherein two Manacus species characterized by contrasting genome‐wide heterozygosity interbreed. We measured individual (n = 66) and population (n = 3) differences in genome‐wide heterozygosity and, among hybrids, amount of genetic admixture using RADseq‐generated SNPs. We tested for population differences in telomere lengths and telomere dynamics. We then examined how telomere lengths and telomere dynamics covaried with genome‐wide heterozygosity within populations. Hybrid individuals exhibited longer telomeres, on average, than individuals sampled in the adjacent parental populations. No population differences in telomere dynamics were observed. Within the parental population characterized by relatively low heterozygosity, higher genome‐wide heterozygosity was associated with shorter telomeres and higher rates of telomere shortening—a pattern that was less apparent in the other populations. All of these relationships were independent of sex, despite the contrasting life histories of male and female manakins. Our study highlights how population comparisons can reveal interrelationships between genetic variation and telomeres, and how naturally occurring hybridization and genome‐wide heterozygosity can relate to telomere lengths and telomere dynamics.
Practice Guidelines for Bipolar Disorder by the JSMD (Japanese Society of Mood Disorders)
Authors: Kato Tadafumi , Ogasawara Kazuyoshi , Motomura Keisuke , Kato Masaki , Tanaka Teruaki , Takaesu Yoshikazu , Nio Shintaro , Kishi Taro , So Mirai , Nemoto Kiyotaka , Suzuki Eiji , Watanabe Koichiro , Matsuo Koji ,   JSMD Bipolar Disorder Guidelines Revision Working Group,   JSMD Bipolar Disorder Committee,   JSMD Guidelines Committee
Published: August 2024

The Japanese Society of Mood Disorders (JSMD) published treatment guidelines of bipolar disorder in 2011. The present guidelines incorporating new findings were developed to comply to the guidelines of the National Academy of Medicine (NAM) by utilizing systematic reviews and meta‐analysis and taking patient and family opinions as well as insights from multiple professional fields into account. They support combination therapy using mood stabilizers and second‐generation antipsychotics in many aspects. They also have limitations, including the grouping of mood stabilizers and second‐generation antipsychotics when meta‐analysis was performed despite their distinct properties, due to the scarcity of drug‐specific evidence. Despite the limitations, these guidelines provide clinical decision support for psychiatrists in Japan.
The impact of financial inclusion on rural–urban households welfare inequality in Ghana: A decomposition analysis
Authors: Tawiah Thompson Ogajah , Sakyi Daniel , Ayibor Raphael Edem , Amanor Kofi
Published: August 2024

This article examined the impact of financial inclusion on rural–urban households' welfare inequality in Ghana using nationally representative survey data sourced from the seventh round of the Ghana Living Standard Survey. The article used a multidimensional financial exclusion index and the real per adult equivalent measures of total annual household consumption expenditure as measures of financial inclusion and welfare, respectively. The article employed the instrumental variable estimation technique to account for the issues of endogeneity and sample selectivity bias associated with measuring financial inclusion. The estimated results from recentered influenced function‐Ordinary Least Squares of the unconditional quantile regression and the Oaxaca‐Blinder techniques show significant rural–urban welfare gaps in favor of urban households at the mean and across the selected quantiles. The study also found that differences in financial inclusion between rural and urban households contribute significantly to the welfare gaps, while the economic returns to financial inclusion reduce the welfare gaps both at the mean and the selected quantiles. The study recommends that policies aimed at improving financial inclusion as well as strengthening financial institutions in rural areas be put in place to help reduce the rural–urban welfare inequality in Ghana.
Theorizing Sexuality Politics of Neoliberalism: A Queer Sociological Approach
Authors: Jung Minwoo
Published: August 2024

This article provides a critical overview of neoliberalism scholarship from a queer sociological perspective. Despite mainstream neoliberalism scholarship neglecting sexuality as a system of intersecting power relations, sociologists of sexualities have explored how neoliberalism reshapes the state, market, society, and subjectivity concerning sex, intimacy, and sexual politics. Highlighting the intersection of the sociology of sexualities with transnational feminist and queer studies, as well as critical race studies, I advocate for a refined understanding of sexuality as integral to neoliberalism's operations with empire, colonialism, and racial capitalism. I suggest areas for future research to further develop this understanding, including the emphasis on the variegated nature of neoliberalism, its ambivalence and contradictions, and its promiscuous convergence with other political, social, and cultural formations. This article ultimately calls for a queer political economic analysis in the continued engagement with neoliberalism and its interactions with sexuality politics to understand new global challenges and social transformations, including shifting geopolitics, digital and platform economies, and climate and reproductive crises.
An examination of the development of a secondary mathematics preservice teacher's use of effective questioning
Authors: Nolan Edward C.
Published: August 2024

This case study explores how one secondary mathematics preservice teacher develops his use of questioning for instruction over the course of a year. The article explores how experiences in a secondary mathematics methods course and student teaching provide opportunities for the preservice teacher to use questioning to elicit, interpret, and respond to student thinking. Using classroom activities, plan‐teach‐reflect cycles of instruction, and recordings and transcripts of instructed lessons, the preservice teacher creates, revises, and reflects on his use of questioning over the year. The study shows that preservice teachers can improve their questioning to help elicit, interpret, and respond to student thinking.
Transient Simulation and Characterization of Conjugate Heat Transfer at Hydro Generator Polewindings
Authors: Dauch Thilo F. , Diebel Bastian , Jester-Zürker Roland
Published: August 2024

The analysis and the design of effective cooling schemes is essential for the integrity of turbomachinery components. Therefore, an accurate prediction of temperatures in critical devices is a necessity. This also applies to electrical turbomachinery such as hydropower generators. Focus of the current paper is on the prediction of the heat and fluid flow at the polewindings of such a machine. Three different numerical setups enabling the computation of winding temperatures are presented and benchmarked to each other. One of the approaches is the Bi-Fo scaling methodology, which demonstrates to perform best in terms of accuracy and computational effort. Finally, the impact of unsteadiness and turbulence modeling on the accuracy of the prediction is presented. In contrast to previous studies, the local distribution of fluctuations and its impact on the thermal boundary layers at the windings is highlighted yielding new fundamental insights into the local heat transfer mechanisms in hydro generators.
Towards New Insights in Gas Turbine Aerothermodynamics With Wall-Modeled LES and Immersed Boundary Method
Authors: De Vanna Francesco , Benini Ernesto
Published: August 2024

This paper introduces a novel methodology for investigating and analyzing the aerothermal dynamics of high-loaded gas turbine vanes. The method combines an advanced wall-modeled Large Eddy Simulation technique with an immersed boundary method, allowing for treating complex geometries on Cartesian grids and accurately handling high Mach and Reynolds flows. Compared to other similar solutions available in the literature, the method’s significant strength is its high compatibility with high-order numerical schemes and explicit algorithms. This allows efficient computing on modern GPU-based architectures, enabling scale-resolved simulations within a reasonable time frame, mainly comparable to more standard unsteady Reynolds-Averaged Navier-Stokes simulations. The effectiveness and accuracy of the method are demonstrated through testing and validation in various canonical scenarios, typical of wall turbulence studies. Here, for the first time, its ability to replicate experimental data associated with a gas turbine nozzle in the transonic regime is verified, testing numerical results compatibility with a precursor and well-established experimental campaign.
A Data Driven Method for the Derivation of Explicit Algebraic Reynolds Stress Models Applied to the Wake Losses of Low-Pressure Turbine Cascades
Authors: Deutsch Johannes , Fard Afshar Nima , Henninger Stefan , Jeschke Peter
Published: August 2024

This paper introduces and validates a data-driven approach to improve the prediction of linear eddy viscosity models (LEVMs). The general approach is adopted in order to improve the wake mixing of low-pressure turbine (LPT) cascades. The approach is based on the modification of the Boussinesq assumption. It follows the rationale applied in the derivation of explicit algebraic Reynolds stress models (EARSMs) by including additional second-order tensors, as suggested by Pope [1]. The unknown scalar functions that determine the contributions of each second-order tensor to the Reynolds stresses are approximated as polynomials. A metamodel-assisted multi-objective optimization determines the value of each of the polynomial coefficients. The optimization minimizes the difference between the result of the EARSM simulation and reference data provided by a high fidelity large eddy simulation (LES).

In this study, tailor made EARSMs are calibrated in order to improve the prediction of the kinetic energy loss distribution in the wake of the T106C LPT cascade with an isentropic Reynolds number of 80 000. We showed that the wake losses predicted by state of the art Reynolds-averaged Navier-Stokes (RANS) turbulence models cannot reproduce the reference LES data. In the following, we investigated the influence of each polynomial coefficient of the EARSM on the flow solutions within a sensitivity study. The models generated by the approach reduced the deviations in turbulent kinetic energy loss between the LES reference solution and the baseline model by approximately 70 %. The turbulent quantities are analyzed to identify the physical correlations between the model inputs and the improvement. The transferability of the models to unseen test cases was assessed using the MTU-T161 LPT cascade with an isentropic Reynolds number of 90 000. A decrease of up to 80% is achieved regarding the deviations between the LES reference and the baseline RANS model.

In summary, the suggested approach was able to generate tailor made EARSM models that reduce the deviations between RANS and LES for the mixing of turbulent wake flows.
A Review of Secondary Combustion on Turbine Blade Cooling
Authors: Ngwenya Tinashe , Nava Antonino , Ireland Peter T.
Published: August 2024

The gas turbine engine is the powerhouse of most large modern military and civil aircraft. These engines operate at temperatures above the melting point of the materials that the combustor and turbine components are made from. Film cooling is used extensively to cool the hot surfaces and extend the life of the gas turbine’s hot end components. In some modern and future engines, the average turbine inlet temperature is increased to about 2,400K and the length of the combustor is reduced. The turbine inlet temperature is increased to improve the thermal efficiency while the combustor is shortened to increase the thrust-to-weight ratio. Both developments are meant to reduce the amount of fuel burnt and the operational cost of the power plant. Increasing the turbine inlet temperature to above 1,850 K CO2 dissociation starts to compete with CO oxidation. Reducing the combustor length reduces the residence time of fuel and increases the likelihood of unburnt hydrocarbons entering the turbine. When carbon monoxide and/or unburnt hydrocarbons enter the turbine, they could react with oxygen in the cooling air and potentially increase the blade metal temperature. An increase of about 30 K can reduce the blade life by half: secondary combustion of reactive species entering the turbine section could therefore lead to serious durability concerns. In a review of the literature, it was found that an estimated 10% of fuel energy is available for combustion in the turbine section and a maximum heat flux augmentation of 18% due to secondary combustion occurs. Secondary combustion in the turbine components is reviewed through a discussion of the analysis of reactive film cooling, developments driving the need to develop an in-depth understanding of reactive film cooling, scaling of reaction kinetics and heat release potential, performance of cooling hole geometries and configurations and mitigation strategies.
A Review of Numerical Methodologies for Predicting Rotating Stall and Surge in High-Speed Centrifugal Compressors
Authors: Neri Francesco , Hickel Stefan , Pini Matteo
Published: August 2024

High-speed supersonic radial compressors are a critical enabling technology for meeting the requirements of future aviation-propulsion and thermal-management systems. These turbomachines must be designed to be both efficient and robust on the widest possible operating range. Flow instabilities in the form of rotating stall and surge are therefore phenomena that must be accurately predicted early in the design process. Unsteady full-annulus computational fluid dynamics can be used to get accurate information about the onset of instabilities, but at the expense of costly simulations. As a result, the design of new compressors continues to rely on existing correlations for the prediction of the critical mass flow rate. This approach, however, leads to sub-optimal compressor designs.

This article provides a review of the numerical methodologies that can be used for the accurate prediction of the critical mass flow rate in high-speed centrifugal compressors. Methods of different fidelity level and computational cost are described. Two particularly promising models, namely those proposed by Spakovszky and Sun, are subsequently examined in more detail. Exemplary applications of these two models are finally discussed.
Combustor Design From a Turbine Perspective to Minimize the Effect of Turbulence
Authors: Miklaszewski Jennifer A. , Folk Masha B. , Hamlington Peter E.
Published: August 2024

During the gas turbine design process, control and optimization of turbulence characteristics at the combustor-turbine interface can lead to improved specific fuel consumption. Here, we use computational large-eddy simulations to explore the turbulent flow characteristics at the exit plane of two combustor designs: a baseline design corresponding to an idealized non-reacting combustor simulator and a design that has been optimized to minimize turbulence intensity at the combustor exit while maintaining good mixing uniformity and low pressure drop. By comparing the two designs, we demonstrate that the size, orientation, and positioning of the primary zone and dilution jets are the primary drivers determining turbulence characteristics at the combustor exit. We show that by modifying the combustor geometry we can shift the energy-containing eddies to larger scales, affecting both the turbulence decay rate and the interaction of turbulence with the turbine boundary layer. In the optimized design, turbulence decays at a faster rate towards isotropic flow and we observe that Reynolds stresses are substantially decreased. We introduce a flat plate with a tapered leading edge downstream of the combustor exit to quantify the subsequent boundary layer profile, skin friction, and boundary layer dissipation for each design. This work illustrates how understanding the mechanisms responsible for decreased turbulence at the combustor exit can aid designers in maximizing performance of gas turbines, as well as demonstrating the potential of computational optimization for combustor design.
Innovative Synergies in Aircraft Propulsion: the Concept of Hybrid Power Systems With Contra-Rotating Propellers
Authors: Hazeri Majid , Moradkhani Mohsen , Rashid Jafari Javad , Asadi Davood
Published: August 2024

In an era characterized by escalating emphasis on fuel economy and the mitigation of greenhouse gas emissions within the aerospace industry, this paper presents an innovative paradigm including the hybrid electric engine with contra-rotating propellers. This article unveils a pioneering technological achievement, exemplified by our patented invention registered under the identifier IB/2021/060538, which received a gold medal at the ICAN 2022 International Invention competition in Toronto, Canada, represents a noteworthy advancement in the domain of hybrid engine technology. It is imperative to acknowledge that the concept is currently in the conceptual design phase, necessitating further refinement to attain its maximum potential. The engine, characterized as a contra-rotating propeller system, engenders an efficiency gain ranging from 6% to 16% relative to single-fuel engines, with one internal combustion engine providing half of the required power and the electric motor complementing the remaining share. This innovative system comprises two distinct configurations: a system with two electric motors and one fuel engine in which one of the electric engines is used as a backup engine. In case of user preference or fuel engine failure, the backup electric is engaged in place of the fuel engine. This paradigm-shifting innovation effectively changes the conventional internal combustion engine into a multi-engine anti-torque system, facilitating augmented thrust generation while simultaneously reducing fuel consumption by an impressive margin of 40% to 60% when compared with conventional engine models. Beyond its commendable fuel efficiency, the hybrid engine is characterized by a satisfactory level of reliability. This is related to the inclusion of a backup electric motor. In addition to the internal combustion engine, supporting the system with the ability to manage system failures and maintain power output even under emergency circumstances. Notably, the fundamental concept of the contra-rotating propeller system is not entirely novel, however, our innovative approach harmoniously synchronizes two electric motors, thereby containing the advantages inherent in the contra-rotating system with the reliability attributed to electric propulsion.
Effects of Localized Non-Gaussian Roughness on High Pressure Turbine Aero-Thermal Performance: Convective Heat Transfer, Skin-Friction and the Reynolds’ Analogy
Authors: Jelly Thomas O. , Nardini Massimiliano , Sandberg Richard D. , Vitt Paul , Sluyter Greg
Published: August 2024

Compressible direct numerical simulations are conducted to investigate how surface roughness affects the aero-thermal performance of a high pressure turbine vane operating at an exit Reynolds number of 0.59 × 106 and exit Mach number of 0.92. The roughness under investigation here was synthesized with non-Gaussian statistical properties and an amplitude that varies over its chord length — representative of what truly occurs on an in-service vane. Particular attention is directed towards how systematically changing the axial extent of leading edge roughness affects convective heat transfer (Nusselt and Stanton numbers) and aerodynamic drag (skin-friction coefficient) on the pressure and suction surfaces. The results of this investigation demonstrate that moving the larger amplitude roughness further along the suction surface can alter the blade boundary-layer state. In fact, towards the trailing-edge of one of the rough vanes investigated here, the local skin-friction coefficient increases by a factor of twenty-two compared to smooth-vane levels, whereas the local Nusselt number increases by a factor six. The disproportionate rise of drag compared to heat transfer is explored in further detail by quantifying the Reynolds’ analogy and by calculating the fractional contributions of pressure drag and viscous drag to the total drag force. The effect of varying the inlet turbulence intensity and integral length-scale for a fixed roughness topography is also investigated, and the Reynolds-number scaling of heat transfer and drag is examined in the context of the Chilton-Colburn analogy.
Effect of Blockages on Film Effectiveness on the Pressure Surface of a Turbine Blade
Authors: von Mueller Tassilo , Bacci David , Wambersie Augustin , Wong Tsun Holt , Ireland Peter , Jackson Dougal
Published: August 2024

An experimental and numerical study was conducted on fan-shaped holes on the pressure surface of a high-pressure turbine blade. Blockages in these film holes can arise through dirt accumulation as well as erosion of the thermal barrier coatings. The objective was to study the effects of partial blockages on film cooling effectiveness. Similar studies have been conducted on flat surfaces. This study includes the effect of curvature, which has been shown to be influential on film cooling performance. A blade with a single row of nominal fan-shaped holes at a lateral inclination of 30° was tested and used as the baseline performance. Blockage cases were then tested at various blowing ratios, with partial blockages in the throat as well as partial lidding in the fan exit of the film hole. The experiments were carried out using Pressure Sensitive Paint (PSP) in the high velocity 2D linear cascade experimental facility at the Oxford Thermofluids Institute, using engine representative Mach and Reynolds numbers. The results show that lidding with up to 0.5 blocking ratio (defined as the ratio of lidded length to the length of the film hole exit, in the film hole plane) only has a minor impact on film effectiveness, while lidding with 0.75 blocking ratio as well as throat blockage both result in significant deterioration of film cooling effectiveness. The effect of blockages on discharge coefficient was also studied and only blockages in the throat were found to reduce discharge coefficient.
Robust Design Optimization of a Compressor Rotor Using Recursive Cokriging Based Multi-Fidelity Uncertainty Quantification and Multi-Fidelity Optimization
Authors: Wiegand Marcus , Prots Andriy , Meyer Marcus , Schmidt Robin , Voigt Matthias , Mailach Ronald
Published: August 2024

This work focuses on the application of multi-fidelity methods for the robust design optimization of engine components. The robust design optimization approach yields geometric designs that have high efficiencies and are less sensitive to uncertainties from manufacturing and wear. However, the uncertainty quantification techniques required to evaluate the robustness are computationally expensive, which limits their use in robust optimization. Multi-fidelity methods offer a promising solution to reduce the computational cost while maintaining the accuracy in both uncertainty quantification and optimization.

A Kriging and a multi-fidelity recursive Cokriging framework are developed, implemented, and applied to a test function. In addition, a multi-fidelity super efficient global optimization algorithm is developed. The optimizer is surrogate model-based and can handle constraints. The developed methods are then applied to a compressor test case of a high pressure compressor blade row with 9 uncertainty and 24 design parameters of the geometry. The 2.5 % quantile of the stage efficiency is used as a robustness measure and it is therefore optimized. Design bounds and performance constraints are applied. In addition, various uncertainty quantification techniques are analyzed. A multi-fidelity uncertainty quantification approach is developed that combines simplified coarse-grid low-fidelity results with high-fidelity results to reduce the computational cost while maintaining a high accuracy. Uncertainty quantification techniques of three fidelity levels are then developed and used for the multi-fidelity approach in the design space. The robust design optimization of the compressor is performed and the optimal designs obtained from the multi-fidelity approach show superior performance compared to existing robust design optima in the literature.
Analysis of Pumped Hydro Storage Using Mines As Hydro Reservoirs
Authors: Castorino Giulia Anna Maria , Dahlquist Erik , Kyprianidis Konstantinos , Losi Enzo , Manservigi Lucrezia , Pinelli Michele , Renuke Avinash , Spina Pier Ruggero , Venturini Mauro
Published: August 2024

Pumped hydro storage (PHS) is the most mature and widely used technology for large-scale energy storage. Hydropower plants are in fact also employed for this aim. However, most hydraulic sites suitable for this purpose have been already exploited. Therefore, the use of abandoned mines represents an alternative solution to take advantage of the availability of underground volumes as hydro storages.

This paper investigates the potential of PHS plants integrated within a power generation system that comprises both programmable (e.g., hydropower and nuclear power plants) and non-programmable (e.g., wind and solar power plants) energy systems. All systems are connected with the power grid.

To this purpose, this paper develops a methodology aimed at identifying the optimal sizing of the PHS plant as well as the optimal operation of the whole power generation system at Country level, with the goal of minimizing the imported energy.

The methodology is validated by using Sweden as the case study, to assess the energy and economic feasibility of PHS plants in 2050. Different future scenarios of electricity production, demand, and cost are analyzed.

The analyses carried out in this paper demonstrate that PHS plants are highly recommended if the cost of imported energy is expected to increase. In such a scenario, PHS is mainly employed to meet domestic electricity demand.
GPU Accelerated LES-FGM Modelling for Industrial Combustion Applications
Authors: McManus Liam , Goldin Graham , Zhang Yongzhe , Veljkovic Ivana , Sadasivuni Suresh , Liu Kexin
Published: August 2024

Due to the ever-increasing use of Large Eddy Simulation (LES) for assessing gas turbine combustor flow and mixing fields, flame position and flame dynamics, methods to reduce the computational costs of such simulations are desirable. One such method to achieve this is to utilize advanced High Performance Computing (HPC) architectures such as General Purpose Graphical Processing Units (GPGPUs).

In this paper, the Simcenter STAR-CCM+® solver, with the ability to run LES and flamelet based combustion models using GPUs, is used to assess the benefits of using GPU architecture compared to traditional Central Processing Units (CPUs). LES simulations using the Flamelet Generated Manifold (FGM) combustion model are assessed across a series of test cases: A diffusion jet flame, a pressurized annular combustor and a swirl stabilized industrial gas turbine Dry Low Emission (DLE) combustor provided by Siemens Energy Industrial Turbomachinery Ltd, Lincoln, UK.

Numerical simulations using GPUs and CPUs are compared in terms of solution similarity, accuracy in relation to experimental data, computational cost and power consumption. The computational performance of the FGM model with GPU is quantified through comparison to a non-reacting simulation on the same computational grid.

It is demonstrated that the use of GPU architectures can result in high-fidelity combustion modelling within the required turn-around times of engineering design cycles whilst maintaining a similar solution and level of accuracy as a traditional CPU based simulation.
Supercritical Carbon Dioxide Mixing Loss Characteristics Near the Critical Point
Authors: Wang Jinhong , Cao Teng , Martinez-Botas Ricardo
Published: August 2024

This paper aims to study the mixing loss characteristic of sCO2 near the critical point and shed light on the non-ideal fluid effect on the mixing losses. As a simplified model of the mixing process in the trailing edge or tip leakage flow in turbomachines, a case of mixing in a constant area adiabatic duct involving two streams of parallel flows is studied by control volume analysis. Both perfect gas and non-ideal fluid calculations are carried out for comparisons. The isolated and coupled effects of the two mixing streams’ temperature, velocity, and pressure differences on the loss are investigated. The study shows that non-ideal fluid mixing produces significantly higher losses when compared to the equivalent perfect gas estimation. It also reveals that the non-ideal fluid mixing loss is sensitive to the average thermodynamic states of the mixing streams. A general trend is that the closer the temperature is to the critical point, the higher the loss is observed. This is particularly apparent for the temperature and pressure mixings, while the mixing loss due to the velocity difference is less affected. A significant variation of the mixing loss coefficient is reported if the static state of any of the two streams is near the critical point, which is mainly caused by the significant variation of the temperature gradient regarding the entropy along the isobar. In addition, a positive combined effect of the temperature, velocity, and pressure differences was found for mixing loss. The results also show that the change in the mixing loss due to the variation of one property difference between mixing streams is almost independent of the other property difference. This behaviour matches the conclusion drawn in literature for perfect gases [1]. The results from this simple case contribute to understanding the mixing loss behaviour differences between perfect gas and non-ideal fluids in sCO2 turbomachinery and hold significance for the development of mean-line models.
Numerical Modelling Approach for Wet Humid Air Flows in Hydrogen E-Turbos
Authors: Tosun Adem , Fuhrer Christopher , Hughes Stephen , Vogt Damian M.
Published: August 2024

A numerical modeling approach for predicting phase transition in rapid expansions of humid air is derived. For this purpose, the well-established classical theory of condensation in wet steam flows is extended to the multicomponent flow environment. The proposed model equations for nucleation and droplet growth in humid air account for the presence of a non-condensable flow component. An Euler-Euler framework is used alongside the commercial flow solver ANSYS CFX to calculate the two phase flow. The model is validated against supersonic nozzle test cases with pressure measurements available in open literature. The onset and thermodynamic impact of phase transition is predicted with reasonable accuracy regarding the pressure distributions. Finally, the phase transition model is applied to the radial turbine stage of a fuel cell e-turbo. Droplet formation inside the turbine and the impact of phase transition on the turbine performance are discussed.
Smoke Point Is Adequate for Engineering Soot Prediction: A Demonstration
Authors: Krishnasamy Bharathi Arvind , S. Varunkumar
Published: August 2024

A semi-empirical Laminar Smoke-Point (LSP) model is used to compare soot predictions against the experimental Laser-Induced Incandescence (LII) based measurements in a lab-scale CFM-56 aircraft combustor with liquid jetA1 as fuel and dilution jets. The soot model, which has so far been used in the fire dynamics domain for laminar flames, has now been extended to an industrial burner using LES. Comparison of the averaged Discrete Phase Model (DPM) droplet distribution against the backlight spray imaging shows a good comparison. The simulation displays some degree of spray asymmetry similar to the data due to the wall confinement effect. A comparison of the thermal field with the instantaneous flame image shows a good match in terms of the radial and axial extent of the flame front. Finally, a comparison of the soot volume fraction predicted by the model with the LII data shows an acceptable qualitative and good quantitative match. The soot field immediately downstream of the swirler shows a near-uniform soot field at an angle of about 98° which is close to the measured spray angle. The radial extent of the soot at the widest section matches closely with the data. However, the model predicts an axial extension of the soot further downstream and up to the dilution jets which is not observed in LII. This could be due to the presence of Poly-Aromatic Hydrocarbons (PAH) in these regions which are not picked up in LII due to the spectral filter or could be due to the laser sheet attenuation by the liquid fuel on the quartz window.
Impact of the Wall-Parallel Length Scale of Roughness on the Development of Turbulent Boundary Layers in Turbines
Authors: Berhane Abigail M. , Longley John P.
Published: August 2024

The detrimental effects of surface roughness on the growth of turbulent boundary layers in turbines, and compressors, are well known. However, robust prediction of these effects can be problematic, especially for surfaces which are not similar to sand grains. Several publications have proposed that additional parameters such as slope, skew, etc. can be used to augment a wall-normal measure such as Sa to correlate surface roughness. Here, we introduce a new roughness parameter, the mean separation, which explicitly measures the average separation between each local minima and its closest local maxima. Scans of turbine blade surfaces showed that they can have mean separations which are up to six times that of the sand grain surface which has the same wall-normal length scale.

The availability of high resolution, typically < 0.1 μm, area scanning tools and 3-D printing techniques have enabled the development of a “Scan-Scale-Print-Measure” methodology. A surface scan is scaled-up, 3-D printed, applied to a flat-plate and then the turbulent boundary layer is measured. The surface roughness-loss is the additional momentum thickness, above that of the datum smooth surface.

The Scan-Scale-Print-Measure methodology has enabled parametric studies to be undertaken where the mean separation was increased whilst keeping either the Sa value or the feature size constant. Both studies demonstrated a surface roughness-loss that was strongly dependent on the mean separation and different to a Schlichting based sand grain correlation. It also showed that for large mean separations the roughness-loss decreased to zero. A parametric study into pits-and-peaks surface features showed that, at the same wall-normal length scale, peaks generated a surface roughness-loss twice that of pits.

An engine representative surface produced only half the roughness-loss that would be attributed to a sand grain surface. The measured surface roughness-loss could be estimated within 5% using the aforementioned parametric studies.
Status of Gas Turbine Performance Degradation
Authors: Kurz Rainer , Brun Klaus , Pinelli Michele , Suman Alessio
Published: August 2024

Any prime mover exhibits the effects of wear and fouling over time. The degradation affects the performance of such a machine. For a industrial gas turbine, the problem includes predicting the effects of wear and fouling on the performance of such an engine, as well as the description and determination of the mechanisms that cause wear and in particular fouling. The degradation effects can be classified in several categories, for example recoverable vs. non-recoverable degradation, alluding to the fact that cleaning the engine is possible for some types of degradation. Another differentiation is fouling, where fine particles adhere to blade surfaces as opposed to material removal from heavier particles or rubbing. The systematic attempts to determine degradation mechanisms, their impact on gas turbine performance, and mitigation methods go back several decades. More recently, simulation methods have closed the gap between observed contamination and numerical results. The deterioration of gas turbine components, such as the compressor or turbine sections result in a performance reduction that depends on the operating conditions of the engine, and is, for example dependent on the prevailing ambient conditions and the load of the gas turbine. This paper attempts to reflect the state of the art theoretical and practical results.