Full-scale Conditions Research Articles

Icing on Full-Scale Swept Wings in Flight and Icing Wind Tunnel

Inflight ice accretion on aircraft wings has been critically important for development and certification of transport category aircraft. With recent efforts toward certification by analysis, it is becoming increasingly important to characterize ice accretions in icing wind tunnels, the primary source of validation data for higher-fidelity three-dimensional ice shape analysis codes to be used in aircraft certification, in comparison with those in natural icing environments. In this study, a series of natural icing flight tests and icing wind tunnel tests were conducted on a transport category aircraft. The results were compared at similar test conditions on protected and unprotected surfaces of swept wings and empennage. For unprotected surfaces, both tests resulted in scallop ice, with natural icing flight test resulting in significantly smaller ice accretions. For protected surfaces, runback ice was formed on the lower wing surface in both tests, with natural icing flight test resulting in significantly less and sparser runback ice. Differences in scallop ice structures, limitations of icing wind tunnels, and scaling methods are considered the potential contributing factors to the differences. The results indicate a need for further studies on case-to-case comparison of ice accretions in the two test methods focusing on full-scale aircraft conditions.

Influence of Different Bifurcation Angles on the Flame Propagation of Gas Explosions in Three-Way Bifurcated Pipes

Exploring the flame propagation law in the process of gas explosion under different bifurcation angles is of great significance to the design of coal mine roadway and the prevention of gas explosion accidents. To study the variation of flame propagation law with bifurcation angle, an in-house experimental system based on a small scale three-way bifurcated pipe was developed to perform gas explosion experiments using mixtures of premixed methane-air with a methane concentration of 9.5%. Numerical simulations were conducted to study the propagation of the explosion flame. The results show that, (i) during the flame propagation process, the flame morphology evolves in the following manner: hemispherical, concave entrainment-deformation-flattening; (ii) in the case of gas explosion of three-way bifurcated pipes, there are significant differences in damage at different positions, and the damage at the pipe connection is the most serious. (iii) Although the parameters of the explosion flame in the bifurcated pipe exhibit similar trends across four different bifurcation angles, the values of the flame parameters obtained by the experiments and numerical simulations were not completely consistent. (iv) When the bifurcation angle is between the 45 and 75° bifurcation range, the area of the turbulent vortex formed by the air flow increases as the angle of the pipe widens. The research results analyze the propagation law of gas deflagration flame in the bifurcated pipeline, providing reference for the propagation mechanism of gas deflagration in underground bifurcated roadway and the formulation of prevention measures, which is conducive to preventing the propagation of gas explosion, reducing the intensity, and reducing the loss caused by gas explosion. However, large-scale tests are needed to determine the applicability of small-scale tests and calculations in this paper to full-scale mine conditions.

The effects of digestate pyrolysis liquid on the thermophilic anaerobic digestion of sewage sludge — Perspective for a centralized biogas plant using thermal hydrolysis pretreatment

The use of pyrolysis process to valorize digestate from anaerobic digestion (AD) of municipal sewage sludge for biochar production was piloted in a central biogas plant. The pyrolysis also generates pyrolysis liquid with high organics and nutrient contents that currently has no value and requires treatment, which could potentially be done in AD. As the pyrolysis liquid may contain inhibitory compounds, we investigated the effects of adding the pyrolysis liquid on AD of sewage sludge and thermal hydrolysis pretreated sewage sludge (THSS) simulating the full-scale centralized biogas plant conditions. In batch assays, the pyrolysis liquid as such did not produce any methane, and the 1% and 5% (v/w) shares suppressed the methane production from THSS by 14–19%, while a smaller decrease in methane production was observed with sewage sludge. However, in the semi-continuous reactor experiments, pyrolysis liquid at a 1% (v/w) share was added in sewage sludge or THSS feed without affecting the methane yields or digestate characteristics. The laboratory results indicated that pyrolysis liquid can be treated in AD, while extrapolating the results to the centralized biogas plant indicated minor increase in the overall methane production and an increased potential for ammonium recovery.

Prediction of Durability of Thermal Insulating Epoxy Coatings with Regard to Climatic Ageing.

It is generally accepted that the color and performance characteristics of liquid thermal insulation coatings are affected by the combined effect of various climatic factors such as solar radiation, temperature fluctuations, moisture, precipitation and others. This work presents the results of a scientific study of the full-scale exposure of coatings with regard to climatic ageing. Methods have been carried out, such as: spectrophotometry and direct scanning; determining adhesion, determining the adhesion strength of facing and protective coatings; and thermal conductivity and thermal resistance. As the results of the research work have shown, only in situ climatic tests, accompanied by the obligatory recording of the aggressive factors affecting the coating, make it possible to assess changes in the properties of epoxy coatings in full-scale conditions and, consequently, their climatic resistance by the methods of spectrophotometry and direct scanning. The ageing of polymer composites is known to be accompanied by a change not only in elasticity but also in color. Of the epoxy coatings tested, Etal-45M showed the greatest color variation during the in situ climate test. The most decorative resistant coatings are obtained using epoxy resin ED-20 + modified epoxy resin Etal-1440N.

다상유동 RANS법을 이용한 수상 함정 주위 기포 층 두께 예측

This paper shows the numerical analysis of bubbly flows generated by an air bubble masking belt installed in the midships of a surface ship. Numerical simulations were performed using the Reynolds Averaged Navier-Stokes(RANS) Eulerian multiphase(EMP) flow method and the bubble layer thickness around the model and full scale ship, bubble diameter distribution, and changes in hull resistance were investigated. The layer of bubbles became thicker downstream of the both hulls as the air flow rate increased. Since the large bubbles moving downstream of the hulls rose to the free surface due to the buoyancy, the average diameter of the bubbles inside the bubble layers tended to decrease as it went downstream. Although the thickness of bubble layers according to the air flow rates at the model and full scale conditions showed a tendency to roughly follow the scale ratio, a further study on the accurate correlation should be conducted in the future. Both the model and full scale ship showed an increase in pressure resistance after air injection, and a decrease in friction resistance. The distribution of air bubbles in the propeller planes followed the nominal wake characteristics, showing more bubbles at the full scale conditions.

Application of dynamic mechanical analysis and linear dilatometry in the study of the mechanisms of climatic aging of transparent thermoplastics in natural conditions

The volume, assortment and application areas of transparent thermoplastics, including as construction materials in modern hightech products and devices, are expanding every year. At the same time, parts of products made from these materials are one of the most sensitive elements of the product exposed to the environment. Assessment of material performance under the influence of environmental factors is carried out by conducting tests in full-scale and laboratory conditions. The use of physical research methods makes it possible to understand the mechanism and kinetics of the aging processes of thermoplastic materials and to increase the reliability of predicting performance under natural conditions. In addition, the use of the proposed research methods makes it possible to more reliably evaluate and, if necessary, correct the methods of accelerated climatic tests when comparing the aging mechanisms in natural and artificial conditions.

Optimization solution substantiation for resource-saving maintenance of workings

Purpose. Substantiate the expediency of optimizing decision-making in resource-saving maintenance of mine workings. Methods. The concept of ensuring the conditions for the repeated use of mine working is based on modern methods of managing the rock pressure manifestations, conducting multifactorial computational experiments, experimental verification of the principles’ implementation during effective use of resources in full-scale conditions. Findings. The directions of improving the fastening and protection structures, which ensure the stability of reused mine workings, have been determined. In this case, the most lightweight protection structure is proposed, the functions of which are transferred to the collapsed and compacted rocks of the uncontrolled collapse zone. Originality. The basic concept of repeated use of mine workings, taking into account resource-saving technologies, has been formulated and implemented. The stress-strain state of the “mass – support – protection elements” system has been studied, and its rational parameters have been optimized. An example of an optimization solution based on the stated methodology is presented. Practical implications. The schemes have been developed for calculating the parameters of loading the fastening and protection structures in reused mine workings with a geomechanical substantiation of the adopted provisions and assumptions, which is the basis for issuing recommendations to ensure the mine working stability.

Метод пересчета результатов модельных испытаний гребного винта на натурные условия

Object and purpose of research. This paper discusses numerical method for simulation of propeller parameters in model and full-scale conditions. The purpose is to develop a similar methods for extrapolation of propeller model test data to the full-scale. Materials and methods. Propeller parameters are simulated as per the improved numerical method of E. Papmel. The flow around cylindrical section profiles of blades and hub is simulated as per the methods of boundary integral equations and integral calculation methods for the boundary layer with consideration of laminary-to-turbulent transition. Main results. Development of the method taking into account scale effect for propellers. The method has been applied to extrapolate model test data to the full scale. Conclusion. The method is of practical value for modern propeller design.

Development of a test-rig for advanced rotor–stator seals used in jet engines: Part II

Advanced rotor–stator seals are becoming more and more common in the latest generation of jet engines. In order to develop new radial seals and fully understand existing ones, testing needs to be done under full-scale conditions. It is necessary to be able to evaluate a new seal concept at “scale one”, under representative operating temperatures, pressure and rotational speed. This article – published in two instalments – presents details of an advanced new test-rig that is able to achieve this goal. It describes many facets of its design, construction, commissioning and use, and the challenges associated with its development.

Evaluation of the anaerobic degradation of food waste collection bags made of paper or bioplastic

The amount of compostable bioplastics collected with the food waste is constantly growing, particularly due to the bags used for collection. According to the Italian legislation, compostable bioplastics must be accepted by all biological treatment plants, including aerobic and anaerobic facilities. Anyway, the compostability standard requires only the assessment of the aerobic degradability, while it is generally not required to test the behaviour under anaerobic conditions. This aspect is evaluated in the paper, where the anaerobic degradability of bioplastic bags used for the food waste collection is assessed. First, Biochemical Methane Potential (BMP) tests were performed on four commercial types of bioplastic bags, including those designed only for the collection of food waste and the shoppers, that can be reused for the same purpose. Subsequently, an innovative approach for this kind of substrate was applied, subjecting two bags to semi-continuous co-digestion tests together with the food waste. Both tests were performed by comparing the behaviour of bioplastic bags with that of an alternative collection paper bag. Finally, tests to evaluate the influence of physical phenomena on the degradation of bioplastics were performed to better understand the results of biological tests. BMP tests indicated a good degradability (>71%) of bioplastic bags, while semi-continuous tests showed a much lower degradability (<27%), confirmed by the observation of the undigested bag pieces. On the contrary, the paper bag presents interesting characteristics, because its degradability in the semi-continuous tests (82%) resulted even higher than that observed in the BMP tests (74%). These results highlight an important difference between the bags mono-digestion by means of BMP tests and the semi-continuous co-digestion tests with food waste, which better simulate the full-scale operational conditions.

Development of a test-rig for advanced rotor–stator seals used in jet engines: Part I

Advanced rotor–stator seals are becoming more and more common in the latest generation of jet engines. In order to develop new radial seals and fully understand existing ones, testing needs to be done under full-scale conditions. It is necessary to be able to evaluate a new seal concept at “scale one”, under representative operating temperatures, pressure and rotational speed. This article – published in two instalments – presents details of an advanced new test-rig that is able to achieve this goal. It describes many facets of its design, construction, commissioning and use, and the challenges associated with its development. The first instalment, which appears here, looks at key characteristics of the test-rig, provides an overview of its mechanical design and airflow loop, and lists associated references. The second instalment will be published in the January 2022 issue of Sealing Technology.

Granulometric composition research of mine rocks as a material for backfilling the mined-out area in coal mines

Purpose. Determination of the granulometric characteristics and loosening coefficient of mine rocks formed during stope operations from undercutting the bottom rocks as a potential backfill material based on a set of mine and laboratory research. Methods. To do research, a complex methodology is used, which includes a photographic surveying the mass of destroyed rocks from undercutting the bottom rocks in mine conditions, digital processing and determining the granulometric composition in the software package, sampling the mine rocks at the surface complex, and reconstructing the granulometric composition, similar to the full-scale mine conditions in the laboratory. Sieve analysis, laboratory balance and laboratory container are used to determine the granulometric composition and loosening coefficient. Findings. The dependence between the granulometric composition and loosening coefficient of rocks, which increases by 33% within fractions of 0-50 mm and by 8% within fractions of 50-140 mm, has been revealed. It has been determined that the destroyed rocks in the face within fractions of 0-140 mm have a bulk density of 1.28 g/cm3, loosening coefficient of 1.7, the voidness of and the maximum reserve for the backfill mass compaction with mine rocks is 41.9%. An analytical assessment of the volumes of the formed cavities of the mined-out area in the longwall face and gobed mine workings, as well as the prospects and completeness of their filling with mine rocks have been performed. Originality. It has been determined that the loosening coefficient of mine rocks destroyed in the stope face by KA-200 shearer changes according to the logarithmic dependence on their granulometric composition. This makes it possible to control the granulometric characteristics of the backfill material to achieve the maximum density of the backfill mass. Practical implications. Further research can serve as a basis for determining the rational parameters for the formation and placement of backfill masses during complex-mechanized selective mining of coal seams using various methods of backfilling operations.

Experimental validation of a simplified numerical model to predict train-induced ground vibrations

This study evaluates the effect of high-speed train (HST)-induced environmental vibrations using simplified computational models and validates the test results in full-scale field conditions. Experimental investigations and in-situ measurements were performed at the Istanbul-Ankara high-speed railway section to examine the effect of ground vibrations from HSTs on the surrounding residential lands. In this study, ground-borne free-field surface motion at different distances from the railway track was realized using accelerometers. The experimental results of vertical and horizontal ground vibration accelerations induced by HSTs with a velocity of 250 km/h were analyzed. In the first part of the study, a two-dimensional (2D) numerical model based on finite element method (FEM) was used to investigate ground vibrations and validate the experimental results. To minimize artificial reflections and dissipate vibrational energy at the boundaries, the lateral extension of an infinite domain was modeled with viscous absorbing boundaries. A dynamic analysis of the proposed railway-soil coupled model was performed in the time domain under plain-strain conditions using Plaxis 2D, a commercial FEM software. For the verification, the experimental results were compared with those obtained from the numerical analysis. The simplified computational model validated by the test results may help researchers determine further investigation strategies to develop cost-effective mitigation measures for structures with sensitive devices near the railway track and significantly contribute to understanding complex wave propagation problems. In the second part of the study, train-induced environmental ground vibrations were analyzed for different types of soil conditions using a 2D FE model. Computational analyses were performed with four types of soil: soft, medium, dense, and rock, based on the Turkish Earthquake Code. The HST was used as a dynamic source to observe the differences in vibration generation and wave transmission in different types of soil. The HST load on the slab track was simulated to study the effect of operational loads on ground-borne vibrations. Based on the dynamic analysis results, the response of the free-field motion was investigated to obtain the relative acceleration time histories for different points of soil. According to the results, the peak acceleration values of train-induced vibrations at soft, medium, and dense soil sites increased dramatically when compared to the rock site. Vibration measurement data collected from parametric experiments with a simple numerical model for various soil characteristics can be particularly useful when planning residential and industrial facilities at new locations near railroads, to avoid the adverse effects of environmental vibrations caused by HSTs.

DEM modeling of the effects of external loads and material properties on the stability of nickel ore in a cargo hold

Cargo liquefaction leading to the serious loss of ship stability is attracting more attention from the international community. However, due to the complexity of external loads and the properties of the cargo, the mechanism of cargo liquefaction has not been revealed for every situation. In this study, considering the effects of the moisture content, particle size grading, initial porosity and motions of a typical cargo hold, a three-dimensional full-scale numerical model based on the discrete element method is established, and numerical investigations are carried out. To better ensure that the full-scale model conditions are consistent with the reality and the rationality of particle amplification, a static incline test and a cargo loading test are also simulated and verified. The results show that the effect of the moisture content on the cargo stability can be estimated using the friction coefficients between particles. Additionally, the moisture content is the key factor that affects the stability of the cargo and promotes its liquefaction. Furthermore, there are critical values for fine particle content, at which cargo fluidity is greatly enhanced. For external loads, the cargo stability is greatly weakened with the increase of the motion amplitude. Furthermore, there is a critical frequency, beyond which the cargo stability will be further damaged.

Determination of the optimal modes of filling and emptying the chamber of the navigational lock of a low-pressure hydroelectric complex

The construction of the low-pressure Nizhny Novgorod hydroelectric complex covered by the Strategy for the Development of Inland Water Transport of the Russian Federation for the period up to 2030 envisages a ship lock as part of the hydroelectric system to ensure ships passage. One of the options under consideration is a ship lock with a head power system, which uses short bypass water-circulating culvert for filling and emptying the chamber. At the same time, an important task is to select the optimal modes ensuring movement of the gates of the filling and emptying systems, in which the normative values of the hydrodynamic forces influencing the vessel in the chamber during the lock process would not be exceeded. The article describes the experience of performing laboratory hydraulic studies of the ship lock model and presents the results of determining the optimal modes of locks movement in the ship lock filling and emptying systems. The studies were carried out on a model located in the hydrotechnical laboratory named after Professor V.E. Timonov of the State University of Maritime and River Fleet named after Admiral S.O. Makarov. The article describes the experience of performing laboratory hydraulic studies of the ship lock model and presents the results of determining the optimal modes of gates movement in the ship lock filling and emptying systems. The studies were carried out on a model located in the hydrotechnical laboratory named after Professor V.E. Timonov of the State University of Maritime and River Fleet named after Admiral S.O. Makarov. The studies included three series of measurements taken at different speeds of gates movement. The speeds were assigned based on the following idea: the maximum hydrodynamic forces of one of the series were close to the permissible values, and of the other two – 30–50 % smaller and larger, respectively. The experimental results determined the optimal operating modes of the systems for filling and emptying the lock chamber. It is recommended to select of the optimal modes of gates movement in full-scale conditions on the newly built ship locks immediately after their construction.

Life cycle assessment of sewage sludge pretreatment for biogas production: From laboratory tests to full-scale applicability

In this work, different pretreatment technologies (low temperature thermal treatment, ultrasonication, alkali treatment, combined alkali-thermal treatment, icing-thawing) were investigated together with biochar addition to increase biogas yield from sewage sludge. The aim of the work was to develop a standardized protocol, including physicochemical characterization, biochemical methane potential (BMP) tests, digestate characterization, life cycle assessment (LCA) and economic analysis, to verify the techno-economic suitability and the related environmental impacts of upgrading conventional full-scale anaerobic digesters. Low-temperature (65–85 °C) thermal pretreatment showed the best performances in enhancing sludge solubilization and methane yield (up to 110%), followed by ultrasonication (up to 53%) and biochar addition (about 16%). The solubilization rate obtained after each pretreatment was similar for municipal and industrial sludge; however, it did not correspond to a proportional increase in methane yield. LCA showed that ultrasonication led to the worst environmental impacts at laboratory scale, due to the huge electricity request; however, at full-scale conditions, green-house gases (GHG) emissions could be reduced by 22%, fossil depletion by 25% and stratospheric ozone depletion by 18%, when compared to the baseline scenario (raw sludge anaerobic digestion). The economic analysis proved that the high ultrasonication capital costs could not be recovered in the considered timeframe (15 yr), while biochar price should be significantly lowered (down to 6.5 €/ton) to give an overall positive outcome. Finally, the thermal scenario would be convenient only when considering waste heat recovery. The proposed protocol, including physicochemical sludge characterization, BMP tests, digestate characterization, LCA and economic analysis, could be extended to other existing digesters to compare alternative pretreatment strategies, enhancing renewable energy generation in biogas form.

Legal aspects of conducting clinical trials and military trials with the participation of military personnel

Currently, the procedure for conducting clinical trials and military trials is regulated by a number of regulatory documents ranging from Federal laws to local orders of medical organizations. The article analyzes the regulatory documents of the Russian Federation in relation to conducting clinical trials and military trials with the participation of military personnel. It is noted that the legal status of a volunteer (military personnel) when conducting research in full-scale conditions is not fixed. In addition, in the case of conducting research with the involvement of military personnel as volunteers, it should be borne in mind that a serviceman has the right to engage in scientific, pedagogical and other creative activities. There is no regulatory document defining payments to volunteers participating in clinical trials. These organizational aspects require legislative permission to exclude legal conflicts in the planning, organization and conduct of research involving military personnel as volunteers (patients) (bibliography: 9 refs).

Прогнозирование объема каверн на вращающихся лопастях и масштабные эффекты

Object and purpose of research. Pressure pulsations induced by cavitating blades substantially contribute to flowinduced loads and amplify structural vibration. These pulsations depend on oscillation of the volume of cavities over blades. Prediction of them usually involves model tests and there are three kinds of scale effects influencing the cavity volumes. The first one is associated with the non-uniform inflows. The second one is associated with the combined influence of the blade boundary layer and surface tension on the cavity surface. The third one is associated with the cavity buoyancy. Materials and methods. Because of complexity of blade flows, a qualitative analysis of similar unsteady non-uniform flows around 3D hydrofoils is useful. This paper presents such an analysis for a hydrofoil with the sections copied from a marine propeller blade. The inflows correspond to the wakes of a ship and of her model. Computations carried out using an analysis of viscous-inviscid interaction. Main results. The qualitative explanation of observed trends and scale effects is obtained due to this analysis. In particular, the role of pressure side cavitation in full scale conditions is pointed out. Conclusion. The difference of model and ship wakes results in the substantial difference in blade section angles of attack at the same blade loading. Therefore, in model tests the suction side cavitation is more extensive, whereas the pressure side cavitation may not appear, though it exists on full-scale ship propeller blade. This substantial scale effect has been usually out of previous considerations.

Ship resistance when operating in floating ice floes: Derivation, validation, and application of an empirical equation

With the effects of global warming, the Arctic is presenting a new environment where numerous ice floes are floating on the open sea surface. Whilst this has improved Arctic shipping navigability in an unprecedented way, the interaction of such floes with ships is yet to be understood to aid the designing of ships and route planning for this region. To further explore this topic, the present work develops a procedure to derive an empirical equation that can predict the effects of such floes on ship resistance. Based on a validated computational approach, extensive data are extracted from simulations of three different ships with varying operational and environmental conditions. The ice-floe resistance is shown to strongly correlate with ship beam, ship buttock angle, ship waterline angle, ship speed, ice concentration, ice thickness and floe diameter, and the regression powers of each of the parameters on resistance are ascertained. This leads to a generic empirical equation that can swiftly predict ice-floe resistance for a given ship in a given condition. Subsequently, demonstrations are given on the incorporation of the derived equation into a set of real-time Arctic ship performance model and voyage planning tool, which can predict a ship's fuel consumption in ice-infested seas and dynamically suggest a route with the least safety concern and fuel consumption. Moreover, the equation is validated by providing ice resistance prediction for experimental and full-scale conditions from multiple sources, showing high accuracy. In conclusion, the empirical equation is shown to give valid and rapid estimates for ice-floe resistance, providing valuable insights into ship designs for the region, as well as facilitating practical applications for polar navigation.

Recent research challenges in constructed wetlands for wastewater treatment: A review

The review paper sis based on the analysis or nearly 700 research papers published during 2019 and the first half of 2020 and indexed by Web of Science under the password “constructed wetlands for wastewater treatment”. Out of this number 132 papers dealing with “new” topics such as new wastewaters treated in constructed wetlands (CW), new filtration materials, role of vegetation, floating treatment wetlands, microbiology of CW, greenhouse gas emissions from CWs, sustainability and secondary benefits of CWs. For the deeper analysis the supporting literature from previous periods has been cited. The analysis indicates increasing popularity and diversification of types and tasks of CWs. This supports the need for further research of processes and design-related properties of CWs. The research in full scale CWs and long-term studies are only rare and in order to upgrade the CWs technology, research must be also carried out in the field under full-scale conditions.