Sloping Plate Research Articles

Mechanical Performance Investigation of a Flat-Roof and Four-Slope Folded Plate Structure

The flat-roof and four-slope folded plate structure is a space thin-walled structure composed of four trapezoidal plates and a rectangular plate parallel to the bottom surface, which is widely used in various engineering applications. In order to clarify the force transmission path and stress distribution law under the action of this structural load, the folded plate structures were made by utilizing the plexiglass with the thicknesses of 3 and 4 mm, respectively, and had the simple support on opposite sides and fixed support on another opposite side. Then, the static load tests and ANSYS finite element analysis were implemented, and the results were compared. It shows that the test results are basically consistent with the finite element calculation results, the maximum stress values of the folded plate structure along the X and Y directions appear in the same position, and the maximum stress value of a 3 mm thick folded plate structure is greater than that of 4 mm. The junction position of the roof and the slope plate is the dangerous section, and the special treatment should be made for this section to prevent the damage of folded plate structure in the practical engineering. Moreover, some reasonable measures also should be taken to meet the design requirements of the plate–plate junction position.

Towards high performance Al–Si–Fe alloy castings via rheo-diecasting: Effect of injection velocity and heat treatment on microstructure evolution and property

The mechanical properties and thermal conductivity of Al–Si–Fe castings must meet high requirements in the automobile, aerospace, and communication fields. Traditional high-pressure diecasting (HPDC) castings often have dendritic structures and pore defects that deteriorate their overall performance. Therefore, an advanced rheo-diecasting (RDC) technique assisted by a vibrating contraction sloping plate was proposed to address this problem. However, the process optimization strategy, microstructural evolution, and performance improvement mechanisms remain unclear. The influence of the injection velocity on the microstructure, mechanical properties, and thermal conductivity of the RDC tensile specimens was first investigated. A high-performance cover plate was fabricated via RDC using an optimized injection velocity. The results showed that when the injection velocity increased to 2.8 m/s, the porosity decreased to a minimum value, and the mechanical performance and thermal conductivity of the RDC tensile specimens reached their maximum values. Furthermore, spherical eutectic Si phases and nanosized Mg2Si precipitates for the RDC cover plate were observed after T6 heat treatment, which further improved the mechanical properties and thermal conductivity owing to Orowan strengthening and decreased lattice distortion, respectively. The ultimate tensile strength, yield strength, elongation, and thermal conductivity for the RDC cover plate were 358.2 MPa, 279.9 MPa, 12.5%, and 180.72 W/(m·K), respectively, which were higher than that of reported similar alloys. From engineering perspectives, this study had the application value for produce of high-quality RDC castings.

The effect of cooling plate, mechanical vibration, and grain refinement on the microstructure and hardness of A380 produced by sand mold

ABSTRACT The mechanical properties of aluminium alloys can be increased by controlling the grain size and morphology of the alloy. In these studies, mechanical vibration, cooling slope plate (CSP), and grain refiner were applied on sand mould casting using A380 alloys. The hardness, and microstructure of the cast samples are investigated. These processes lead to the refinement of grain structures and a decrease in the tendency for dendritic structure formation. The Effect of the solidification time (modulus) on the microstructure is investigated. It was determined that the solidification time varies depending on the section thickness, which affects the SDAS values. It was observed that the lowest SDAS values were in CSP and the highest values were in grain refiners added casting. The lowest hardness value was recorded at CSP casting. Meanwhile, the grain refiner added vibration casting exhibits the highest hardness.

Modeling of wavy water film by application of artificial neural network - a state of art study

Nowadays, artificial intelligence (AI) tools have attained a state of maturity and have advanced at a quick rate of achievement in various fields of study. Thus, the predictive and classification of artificial intelligence AI capabilities in manufacturing, commercial, and scientific research applications have resulted in remarkable success. It is widely known that two-phase flow is such a complex problem, and it has a vital state of study due to its importance and wide range of applications. Such as water film phenomena are critical for various industries, including nuclear protection, energy generation, absorption processes, internal combustion engines, chemical reactors, and spray cooling. The present study presented a realistic model for a particular two-phase flow problem of water film thickness. Also, we used neurotic networks for prediction and classification, such as the conventional neural network (CNN) and Long Short-Term Memory (LSTM). The proposed model was evaluated using various raw data, including the input liquid Reynolds number, the Reynolds gas number, the angle of inclination, and the thickness of the water film. The water film thickness was determined using a planar laser-induced fluorescence (PLIF) technique on the various inclination platforms. The current experimental work's inclination angle varied between 0 and 50 degrees. However, when the Reynolds number of the input water changed from 175 to 435, the thickness of the water film was determined; Reynolds gas numbers range from 6950 to 34800.The current study findings indicate an effective alternative method for detecting and forecasting water films on a sloping plate. Nash-Sutcliffe Efficiency (NSE) affected 99 %, 97 %, and 94 % of forecasts, respectively. The findings show tremendous improvement when deep learning uses both LSTM and CNN. The gravitational pressure and air share tension push the water film.

The bioaerosols generated from the sludge treatment process: Bacterial and fungal variation characteristics, source tracking, and risk assessment

Bioaerosols generated from sludge treatment processes in wastewater treatment plants (WWTPs) may spread infectious diseases. This study investigated the generation characteristics, source, and associated risks of bioaerosols produced during sludge treatment processes. The results showed that the concentration range of total suspended particles was 49 ± 3 to 354 ± 10 μg/m3, and the primary water-soluble ions in bioaerosols were NH4+, SO42− and Cl−. The bacterial concentration in bioaerosols was 50 ± 5 to 1296 ± 261 CFU/m3, with the highest concentration in the biochemical reaction tank. The dominant bacteria in bioaerosols included Bacteroides, Cetobacterium, Romboutsia, Lactobacillus and Turicibacter, while the dominant fungi were Aspergillus, Alternaria, Cladosporium and Fusarium. Pathogenic microorganisms such as Escherichia and Aspergillus were detected in all treatment processes. The results of principal component analysis showed that the bacterial composition in bioaerosols was similar of different technological processes, while the fungal species composition was different. The dominant microbial composition of sludge and bioaerosols was relatively close. The Source Tracker results indicated that sludge was the main source of airborne bacteria in the sludge dewatering house, as well as the main source of airborne fungi in the plate-frame pressure filtration tank and the sloping plate sedimentation tank. The non-carcinogenic risk in each stage was low (1.22 × 10−9–3.99 × 10−2). However, Bugbase phenotype prediction results showed that the bioaerosols in the anaerobic sedimentation tank may have potential pathogenicity. Therefore, the management and control of bioaerosols from the sludge treatment should be strengthened.

Enhanced comprehensive performance via alloying and rheo-diecasting in a semi-solid Al–Si–Fe–Mg–Cu–Sr alloy

A semi-solid Al alloy with superior comprehensive performance was obtained via alloying design concept and rheo-diecasting (RDC). The semi-solid alloy slurry was obtained via the vibrating contraction sloping plate. As the contents of Cu and Mg elements increased, the secondary dendrite arm spacing (SDAS) decreased and solubility of Cu and Mg elements increased, which improved the mechanical property and decreased the thermal conductivity of as-cast alloys. The effect of microstructure evolution induced by pouring temperature on mechanical properties at room and elevated temperatures, thermal conductivity, and corrosion behavior of the RDC alloy was investigated. The results demonstrated that the low porosity and refined primary α1-Al grains, secondary α2-Al grains, β-Al5FeSi phases, eutectic Si phases played a significant role in enhancing mechanical properties of the alloy at room temperature. Meanwhile, some submicron β-Al5FeSi phases effectively hindered grain boundary sliding, resulting in the increased mechanical properties of the alloy at elevated temperatures. The improvement in thermal conductivity was related to the decreased electron scattering due to the reduced porosity and small-sized secondary phases. The decrease in the potential difference between the β-Al5FeSi phase and matrix helped improve the corrosion resistance of the alloy.

Morphology-dependent quasi 2D/2D point-flat-plate ternary CdS/MoS2/WS2 heterojunction with improved visible photocatalytic degradation of tetracycline

The morphology of CdS affects its photocatalytic properties and assembly efficiency of CdS-based heterojunction. In this study, various morphologies of CdS, including sloping plate, spherical, flower, lamellar and leaf were synthesized by adjusting different solvents and crystal control agents in solvothermal process. By comparison of geometric matching and photocatalytic activity of the multi-shaped CdS assembling with MoS2, the concept of point-flat-plate microstructure assembly was firstly introduced into construction of ternary quasi 2D/2D CdS/MoS2/WS2 heterojunction. Owing to better geometric configuration, quasi 2D/2D CdS/MoS2/WS2 heterojunction exhibited excellent characteristics of photocatalytic degradation of tetracycline. In this work, 97.2% of tetracycline (20 mg/L, 0.1 g/L dosage) was degraded within 60 min under the irradiation of 150 W Xenon light power, which was superior to other previously reported CdS heterojunctions.The enhancement of photocatalytic performance was due to the faster separation of photogenerated electrons and the lower recombination of electron-hole pairs in point-flat-plate CdS/MoS2/WS2 heterojunction. This study provides a promising way to construct highly efficient photocatalyst and other micro-nano structures for different applications.

Solidification behavior and enhanced properties of semi-solid Al–8Si–0.5Fe alloys fabricated by rheo-diecasting

Compared with the high pressure diecasting, rheo-diecasting has an advantage in decreasing defects, refining microstructure and improving properties. In the present work, an Al–8Si–0.5Fe alloy with a good combination of mechanical property and thermal conductivity was obtained by rheo-diecasting. The solidification behavior, mechanical properties, and thermal conductivity of the alloy under rheo-diecasting were discussed. The results demonstrated that the chilling effect and shearing vibration not only affected the primary solidification on the vibrating contraction sloping plate, but also the secondary solidification in the remaining liquid during rheo-diecasting. The rheo-diecasting alloy possessed spherical primary α1-Al grains and secondary α2-Al grains, small-sized Al5FeSi phases, eutectic Si phases, and low porosities, and thus exhibited the high mechanical properties and thermal conductivity. With decreasing pouring temperature from 690 °C to 670 °C, the size of primary α1-Al grains, secondary α2-Al grains, Al5FeSi phases and eutectic Si phases was decreased due to high cooling rate, which further improved the mechanical properties and thermal conductivity of the alloy.

Efficient fabrication of semisolid nondendritic Al alloy slurry with high quality

Subjecting a normal mechanical vibration to a cooling slope plate, is a proposed method for preparing semisolid nondendritic slurry, named shear-vibration coupling sub-rapid solidification (SCS). Taking Al-8Si alloy as model material, the temperature field and distribution field of solid or liquid phase during SCS were simulated using COMSOL Multiphysics software to primarily choose the optimal processing parameters. Subsequently, the slurries were prepared with the parameters selected according to the simulation results and the microstructures of the slurries were experimentally investigated. Results indicate that the simulation results could provide a basis for roughly choosing the processing parameters, although the calculated solid fractions are always higher than the experimental ones. The processing parameters affect the primary grain size, shape factor and solid fraction mainly through altering the contact duration of melt on the plate, and thus affecting the cooling effect on the melt, nucleation rate, and grain dissociation and proliferation. Experiments with optimized processing parameters show that the primary grains in the slurry have an average size of about 32 µm and shape factor of 1.38, and are quite uniform, even at the highest pouring rate of 2.81 kg·s-1, the size and shape factor are about 46 µm and 1.7, respectively, which implies that the proposed SCS is a promising technology for efficient fabrication of high-quality Al slurry available for engineering applications.

Research on Mechanical Model of Canal Lining Plates under the Effect of Frost Heaving Force

Frost heaving damage of canal lining in cold and dry areas is one of the important causes of canal leakage. In this paper, based on the bending theory of thin plate, a mechanical model of canal lining under the action of frost heaving force is established and solved. Through parametric and engineering case analysis, the following conclusions are drawn: under the action of frost heaving force, the bending moment, shear force, and internal force of the slope plate show a nonuniform distribution, and the maximum values of bending moment Mx and normal stress σx are close to the bottom third of the slope, which is consistent with the existing research and engineering practice. Compared with the theory of beam, the results of the theory of thin plates show that the internal forces and stresses increase at the free boundary (longitudinal expansion joint). The bending moment Mxy and stress τxy are maximum at the four corners of the plate: although the numerical magnitude is lower than that of Mx, it may cause stress concentration to damage the lining plate and thus cause break. The shear force at the longitudinal expansion joint may lead to fracture of the joint material, which needs to be considered in the design process. Due to the uniform distribution of the frost heaving force on the bottom plate lining, its deflection, internal forces, and stresses also show a uniform distribution. The research results can provide scientific reference for the design and operation and maintenance of water transmission canal lining in cold areas.

Microstructure evolution of semi-solid Mg2Si/A356 composites during remelting process

The semi-solid processed Mg2Si/A356 composites were fabricated using a sloping plate, and the phase and morphology evolution of the semi-solid Mg2Si/A356 slurry during the remelting process was investigated. Results indicate that compared to as-cast microstructure, the size of primary α-Al phase and Mg2Si phase of semi-solid microstructure fabricated by using a sloping plate decreases and the morphology of α-Al phase becomes fine and globular. With increasing the reheating temperature and prolonging the holding time, the primary α-Al phase spheroidizes, the liquid fraction in semi-solid microstructure increases, and the Chinese script Mg2Si phase embedded in the primary α-Al phase cannot be observed. The Chinese script Mg2Si phase is distributed in the secondary α-Al phase and becomes smaller. The net-shaped eutectic phase also becomes finer after reheating. The optimum remelting parameters suitable for thixoforming in this study are remelting at 580 °C for 30 min.

The Combined Effect of Cooling Slope Plate Casting and Mold Vibration on Microstructure, Hardness and Wear Behavior of Al–Si Alloy (A390)

Semisolid casting using the cooling slope plate method (CSP) is known to refine the microstructure of hypereutectic aluminum alloys and enhance their mechanical properties. The current research investigates the combined effect of casting using the CSP and mechanical vibration of the mold on microstructure and wear behavior of A390 alloy. After pouring the alloy on the CSP, the mold (sand/metallic) was vibrated mechanically at 50 Hz during filling and up to solidification. Conventional casting with the same mold vibration conditions was also done for comparison. During CSP casting with mechanical vibration of the mold, the crystal nucleus multiplication inhibits the grain growth, and the dendrite break-up takes place simultaneously, leading to refinement of the microstructure. The double effect of the shear force by melt flow and vibrational turbulence is responsible for fragmentation of the particles. This finding was more pronounced in case of using the sand mold. The quantitative measurements showed that the size of primary Si reduced from ~ 184 μm for the conventional casting in the sand mold without vibration to ~ 70 μm when the mold was vibrated and from ~ 30 μm in case of CSP down to ~ 20 μm when CSP was followed by mechanical vibration of the mold. However, applying the mechanical vibration after CSP in case of the metallic mold increased the size of primary Si from ~ 21 to 36 μm. Accordingly, the improvement in the hardness and wear resistance of the CSP samples due to vibration was more significant in case of using the sand mold.

Optimizing the Pouring Temperature for Semisolid Casting of a Hypereutectic Al–Si Alloy Using the Cooling Slope Plate Method

This work investigates the optimum pouring temperature during semisolid casting (rheo-casting) of Al–17%Si alloy (A390) to obtain the best combination of microstructure modification and wear resistance. Pouring semisolid slurry was done in both metallic and sand molds to observe the effect of cooling rate on the optimum pouring temperature. The molten metal/slurry was poured into the specified mold type through a cooling slope plate which was continuously water cooled. Different pouring temperatures: 670, 690, 710 and 730 °C, were applied, and their influence on the microstructure and alloy properties was analyzed. Based on the obtained results, the optimum pouring temperature for semisolid casting was decided for the two mold types. Conventional casting was conducted at the optimum temperature in both metallic and sand molds for comparison. It was observed that rheo-casting using the cooling plate is an effective process in microstructure modification of A390 alloy in terms of refining and redistributing the primary Si and fragmenting the coarse AlFeMnSi phase. The optimum temperatures to obtain small particle size of primary Si, uniform distribution and regular shape using the cooling plate technique were 690 °C and 710 °C for the metallic and sand molds, respectively. This refinement and homogenization of the microstructure enhanced the hardness and wear resistance of alloy A390.

Self-cleaning poly(L-dopa)-based coatings with exceptional underwater oil repellency for crude oil/water separation

As a new derivative material of polydopamine, poly(L-dopa) (PDopa) possesses abundant catechol, carboxyl and amino groups, endowing a new platform for construction of multifunctional coatings. In the present work, negatively charged PDopa was synthesized on a large scale by self-polymerization of L-3,4-dihydroxyphenylalanine (L-Dopa) in aqueous solutions. The PDopa-based coatings were fabricated via layer-by-layer assembly of positively charged polyelectrolyte and negatively charged PDopa. The as-obtained coatings demonstrate excellent underwater oil repellency with oil contact angles of 165 ± 2° and ultra-low contact angle hysteresis arising from electrostatically-induced and hydrogen bonding-induced hydration layers formed between functional groups of PDopa and water. Unlike traditional underwater superoleophobic coatings realized by introducing hydrophilic nano/microstructures, the smooth PDopa-based coatings can clean up oil fouling simply by water action. The coatings applied onto steel meshes facilitate high-performance separation of both phase-separated and emulsified oil/water mixtures with high flux and separation efficiency solely driven by gravity. By employing the separation apparatus with a sloping plate structure, crude oil/water mixture collected from oilfield with 75–80% of water can be effectively separated under mixture temperature of 35–50 °C, with oil content in water of ~20 to ~70 ppm, and water content in oil of 1.9–4.3%.

Effect of docosahexaenoic acid on the recovery of motor function in rats with spinal cord injury: a meta-analysis.

Objective:Studies have shown that docosahexaenoic acid (DHA) has a beneficial effect in the treatment of spinal cord injury. A meta-analysis was used to study the effect of DHA on the neurological recovery in the rat spinal cord injury model, and the relationship between the recovery of motor function after spinal cord injury and the time and method of administration and the dose of DHA.Data source:Published studies on the effect of DHA on spinal cord injury animal models from seven databases were searched from their inception to January 2019, including PubMed, MEDLINE, EMBASE, the China National Knowledge Infrastructure, Wanfang, VIP, and SinoMed databases. The search terms included “spinal cord injury” “docosahexaenoic acid”, and “rats”.Data selection:Studies that evaluated the influence of DHA in rat models of spinal cord injury for locomotor functional recovery were included. The intervention group included any form of DHA treatment and the control group included treatment with normal saline, vehicle solution or no treatment. The Systematic Review Centre for Laboratory animal Experimentation’s risk of bias assessment tool was used for the quality assessment of the included studies. Literature inclusion, quality evaluation and data extraction were performed by two researchers. Meta-analysis was then conducted on all studies that met the inclusion criteria. Statistical analysis was performed on the data using RevMan 5.1.2. software.Outcome measures:The primary outcome measure was the score on the Basso, Beattie, and Bresnahan scale. Secondary outcome measures were the sloping plate test, balance beam test, stair test and grid exploration test.Results:A total of 12 related studies were included, 3 of which were of higher quality and the remaining 9 were of lower quality. The highest mean Basso, Beattie, and Bresnahan scale score occurred at 42 days after DHA treatment in spinal cord injury rats. At 21 days after treatment, the mean difference in Basso, Beattie, Bresnahan scores between the DHA group and the control group was the most significant (pooled MD = 4.14; 95% CI = 3.58–4.70; P < 0.00001). In the subgroup analysis, improvement in the Basso, Beattie, and Bresnahan scale score was more significant in rats administered DHA intravenously (pooled MD = 2.74; 95% CI = 1.41–4.07; P < 0.0001) and subcutaneously (pooled MD = 2.99; 95% CI = 2.29–3.69; P < 0.00001) than in the groups administered DHA orally (pooled MD = 3.04; 95% CI = –1.01 to 7.09; P = 0.14). Intravenous injection of DHA at 250 nmol/kg (pooled MD = 2.94; 95% CI = 2.47–3.41; P < 0.00001] and 1000 nmol/kg [pooled MD = 3.60; 95% CI = 2.66–4.54; P < 0.00001) significantly improved the Basso, Beattie, and Bresnahan scale score in rats and promoted the recovery of motor function.Conclusion:DHA can promote motor functional recovery after spinal cord injury in rats. The administration of DHA by intravenous or subcutaneous injection is more effective than oral administration of DHA. Intravenous injection of DHA at doses of 250 nmol/kg or 1000 nmol/kg is beneficial. Because of the small number and the low quality of the included studies, more high-quality research is needed in future to substantiate the results.

Numerical Simulations of the Hydraulic Performance of a Breakwater-Integrated Overtopping Wave Energy Converter

OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples.

Experimental study on bed pressure around geotextile mattress with sloping plate.

A geotextile mattress with sloping curtain is a newly proposed countermeasure against river and estuarine scour. In previous laboratory experiments, a geotextile mattress with sloping curtain was capable of protecting the bed downstream from scour and stimulating sediment deposition on both sides. However, the seepage scour under its geotextile mattress is inadequately researched at present. In this study, the Geotextile Mattress with Sloping Plate (GMSP) is proposed based on the simplification of the geotextile mattress with sloping curtain with the construction feasibility considered. A series of experiments was conducted to investigate the pressure distribution around the GMSP and the averaged seepage hydraulic gradient beneath its mattress. The results indicate remarkable pressure difference on two sides of the GMSP. The minimum bed pressure appears about 1.3 times the plate height downstream to the GMSP. The averaged seepage hydraulic gradient beneath the mattress increases with the sloping angle increasing from 35° to 60° in general. The averaged hydraulic gradient also ascends as the relative plate height increases, but reduces as the opening ratio increases at opening ratios greater than 0.143. The safety boundary for the averaged hydraulic gradient under the geotextile mattress of the GMSP could get much smaller than the critical hydraulic gradient of piping and can easily be overwhelmed. This phenomenon can mainly be attributed to the discontinuous contact between the mattress and the seabed. A suggestion for the parametric design of the GMSP is to extend the width of the mattress to reduce the risk of seepage failure.

Temperature distribution and its influence on microstructure of Mg–3Sn–1Mn alloy during rheo-rolling process

ABSTRACTIn this paper, an innovative semisolid rheo-rolling process of Mg–3Sn–1Mn alloy was proposed; the temperature distribution and its influence on microstructure of Mg–3Sn–1Mn alloy during the semisolid rheo-rolling process were studied. The alloy temperature decreased gradually from the entrance to the exit of the slope plate, and the alloy velocity increased gradually. The temperature of the alloy near the slope plate surface was lower than that of melt surface. The alloy temperature decreased gradually from the entrance to the exit of the roll gap. In the roll gap, the nearer the roll was, the lower the alloy temperature was. With the increment of casting temperature, the semisolid zone increased and moved forward from the filling mouth to the exit of the roll gap. When the casting temperature was 670°C and the roll speed was 0.052 m/s, Mg–3Sn–1Mn alloy strip with good surface quality was obtained. Homogeneous microstructure was obtained. Mechanical properties of the present product at room temperature or 150°C are higher than that of Mg–3Sn–1Mn–0.87Ce prepared by casting.

КОНСТРУКЦИЯ И РАСЧЕТ ТЕРМОЭЛЕКТРИЧЕСКОГО ГЕНЕРАТОРА ДЛЯ СУДОВЫХ ЭНЕРГЕТИЧЕСКИХ УСТАНОВОК

The article presents the design of a thermoelectric generator (TEG) for utilizing heat energy of exhaust gases of ship diesel engines. There have been chosen a TEG basic design and a technique for its efficiency raising. Geometric, heat and electric parameters of TEG have been calculated using RSD 49 ship project. Calculation of heat and electric parameters of TEG with intensive heat exchange on the surface of a hot node was made using sloping plates. The relation between TEG position (before and after exhaust boiler) and a Wartsila 6L20 main engine exhaust system has been determined. According to the analysis result, in case of TEG position after exhaust boiler and 100% load of main engine, estimates increased compared to a basic design: performance - 4%, capacity - 5%; output gas temperature decreased to 1%. At combined operation of TEGs positioned in the exhaust system of one main engine with exhaust boiler shut down and TEG positioned after exhaust boiler, estimates grew: capacity - 35%, performance - 14%; output gas temperature decreased to 19%. Total maximum capacity of TEGs positioned in the main engine exhaust systems makes 42.78 kW which is 1.78% of a ship power plant capacity.

Modeling of Molecular Diffusion in Non-Homogeneous Media

Background. Due to combined effects of medium inhomogeneity and action of external forces, i.e. Earth’s gravitation, electro-magnetic forces, global rotation, etc., a number of specific fluid motions appear in the environmental and life systems even in absence of pure mechanical reasons. Among them are so called diffusion-induced flows which always exist around obstacles with arbitrary geometry due to breaking of natural molecular flux of a stratifying agent on an impermeable surface. Objective. The aim of the paper is to analyze numerically a diffusion induced flow structure and dynamics around motionless obstacles immersed into a stably stratified medium, including a sloping plate, a wedge-shaped obstacle, a disc, and a circular cylinder. The numerical results obtained are compared with the available analytical and experimental data. Methods. The problem is solved numerically using two different algorithms based on the finite difference and finite volume methods. The first approach is implemented in the specially developed Fortran program codes, and the second one is based on the open source package OpenFOAM with the use of C++ programming language for developing special own solvers, libraries, and utilities, which enable solving the problems under consideration. Results. The numerical simulation reveals a complex multi-level vortex system of compensatory circulating flows around a motionless obstacle, which structure is strongly dependent on its position relative to the horizon. The most intensive and extended high-gradient horizontal interfaces attached to sharp edges or poles of obstacles are clearly observed in the numerical computations and laboratory experiments. Diffusion-induced flows form intensive pressure deficiency zones around an obstacle, which may lead to generation of propulsion mechanism resulting in self-movement of neutral buoyancy bodies in a continuously stratified fluid, e.g. horizontal movement of a wedge, rotation of a sloping plate, etc. Conclusions. Diffusion-induced flows are a wide-spread phenomenon in biology, medicine, and environmental systems, since such flows inevitably occur in any inhomogeneous media, including different solutions, suspensions, mixtures, etc. A complex multilevel vortex structure of diffusion-induced flows on an obstacle becomes even more compli­­cated due to self-motion of the obstacle itself and displacement of various admixtures, suspended particles, additives, etc., which are always present in the real systems.