This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in...This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.展开更多
The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine conve...The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine convergent nozzle,such configuration offers increased design flexibility with additional parameters,leading to heightened interactions among these parameters.As such,it is crucial to reveal the influence of design parameters on the aerodynamic performance of the serpentine convergent-divergent nozzle and the multifactor interaction,as well as its mechanism.Therefore,the influence,interaction and sensitivity of parameters on the aerodynamic performance of the nozzle were numerically investigated using the orthogonal test method.Additionally,the influence mechanism of the convergence angle,throat aspect ratio,and axial length to inlet diameter on the flow characteristics of the nozzle was investigated in detail.The results show that the convergence angle is identified as the main factor affecting the aerodynamic parameters of the nozzle.As the convergence angle increases,the thrust coefficient,total pressure recovery coefficient and discharge coefficient gradually decrease.The interaction between throat aspect ratio and other parameters is obvious.Different design parameters affect the local loss and the friction loss by affecting the curvature and wetted perimeter area,resulting in different aerodynamic characteristics of serpentine convergent-divergent nozzle.展开更多
The paper provides an overview of geometric solutions of marking all types of serpentine by the method of internal circular curve in designing forest roads directly in the field. The main objective of presenting this ...The paper provides an overview of geometric solutions of marking all types of serpentine by the method of internal circular curve in designing forest roads directly in the field. The main objective of presenting this original method for marking all serpentine types in one place is to show similarities and differences in marking different types of serpentine, and identify opportunities for further research of this type. The method is based on the establishment of the minimum number of elements necessary to mark the serpentine on the forest roads and other budget elements and their design in the field. By using this method, construction errors or the number of attempts of serpentine marking are reduced, which increases the effects of design compared to the ones reached by the previous method of marking the serpentine on forest roads.展开更多
Serpentine structured Co_(3)Si_(2)O_(5)(OH)_(4) is inexpensive,chemically stable,and electrochemically active in oxygen evolution reactions(OER).However,the OER activity of Co_(3)Si_(2)O_(5)(OH)_(4) materials is still...Serpentine structured Co_(3)Si_(2)O_(5)(OH)_(4) is inexpensive,chemically stable,and electrochemically active in oxygen evolution reactions(OER).However,the OER activity of Co_(3)Si_(2)O_(5)(OH)_(4) materials is still unfavorable due to the low active sites.Here,Mn^(2+)-doped Co_(3)Si_(2)O_(5)(OH)_(4) serpentine nanosheets with tuned d-band centers are achieved for efficient oxygen evolution in alkaline and neutral electrolytes.The Co_(x)Mn_(3−x)Si_(2)O_(5)(OH)_(4) serpentine nanosheets are synthesized by a simple hydrothermal method.The optimized Co_(2.4)Mn_(0.6)Si_(2)O_(5)(OH)_(4) serpentine nanosheets showed favorable OER overpotentials as well as stable durability in KOH solution and phosphate buffer solution,which were superior to most of the Co-based and Mn-based OER electrocatalysts.The in situ Raman spectroscopy shows that the materials are kept well in the electrochemical OER environments.Further density functional theory shows that the d-band center of Co_(x)Mn_(3−x)Si_(2)O_(5)(OH)_(4) serpentine nanosheets is shifted more upward in comparison with pristine Co_(3)Si_(2)O_(5)(OH)_(4).The changes in the d-band center increase the adsorption of intermediates,optimize the reaction steps,and lower the energy barriers of the OER.That is the main reason for the OER enhancement Mn^(2+)-doped Co_(3)Si_(2)O_(5)(OH)_(4).This work gives an efficient strategy to design cheap and stable electrocatalytic materials for OER in a broad pH environment.展开更多
The effect of sodium hexametaphosphate（SHMP） on the separation of serpentine from pyrite and its mechanism were studied systematically through flotation tests,sedimentation tests,surface dissolution,ζ potential tes...The effect of sodium hexametaphosphate（SHMP） on the separation of serpentine from pyrite and its mechanism were studied systematically through flotation tests,sedimentation tests,surface dissolution,ζ potential tests,adsorption measurements,and infrared spectroscopic analyses.The results show that the SHMP could significantly reduce the adverse effect of serpentine on the flotation of pyrite and make the mixed sample of pyrite and serpentine more disperse in the alkaline condition,thus improve the adsorption of xanthate on pyrite.The action mechanism of the SHMP is that it lowers the pH value at the isoelectric point of serpentine and enhances the negative charge through the dissolution of magnesium from the surface of serpentine and adsorbing on the surface of serpentine.It changes the total interaction energy between serpentine and pyrite from gravitational potential energy to repulse potential energy,according to the calculation of the EDLVO theory.展开更多
The electrokinetic behavior and surface dissolution of serpentine mineral were studied through Zeta potential measurements, dissolution experiments and X-ray photoelectron spectroscopy. The results show that serpentin...The electrokinetic behavior and surface dissolution of serpentine mineral were studied through Zeta potential measurements, dissolution experiments and X-ray photoelectron spectroscopy. The results show that serpentine has an iso-electric point （IEP） of 11.9, which is higher than that of other phyllosilicate minerals. Dissolution experiments show that the hydroxyl is easy to dissolve with respect to the magnesium cations in the magnesium oxide octahedral sheet. As a result of hydroxyl dissolution, the magnesium ions are left on serpentine surface, which is responsible for serpentine surface charge. The removal of magnesium ions from serpentine surface by acid leaching results in a decrease of serpentine IEP. Therefore, it has been clearly established that the surface charge developed at the serpentine/aqueous electrical interface is a function of the serpentine surface incongruent dissolution.展开更多
An innovative one-step semi-solid processing technique of A356 Al alloy,the serpentine channel pouring rheo-diecasting process （SCRC）,was explored.The mechanical properties and microstructures of the tensile samples...An innovative one-step semi-solid processing technique of A356 Al alloy,the serpentine channel pouring rheo-diecasting process （SCRC）,was explored.The mechanical properties and microstructures of the tensile samples made by the SCRC technique were tested in the as-cast and T6 heat treatment conditions.The experimental results show that the as-cast ultimate tensile strength can reach about 250MPa and the elongation is 8.6%？13.2%.The ultimate tensile strength can increase approximately 30% higher than that of the as-cast one but there is some slight sacrifice of the plasticity after T6 heat treatment.Under these experimental conditions,the semi-solid A356 Al alloy slurry with primary α1（Al） grains,which have the shape factor of 0.78？0.89 and the grain diameter of 35？45μm,can be prepared by the serpentine channel pouring process.The primary α2（Al） grains are very fine during the secondary solidification stage.Compared with the conventional HPDC process,the SCRC process can improve the microstructures and mechanical properties of the tensile test samples.The advantages of the SCRC process include easily incorporating with an existing HPDC machine,cancelling the preservation and transportation process of the semi-solid alloy slurry,and a higher cost performance.展开更多
The semi-solid slurry of 7075 aluminum alloy was prepared by a serpentine pouring channel （SCP）. Influences of pouring temperature and the number of turns on the microstructure of semi-solid 7075 alloy slurry were i...The semi-solid slurry of 7075 aluminum alloy was prepared by a serpentine pouring channel （SCP）. Influences of pouring temperature and the number of turns on the microstructure of semi-solid 7075 alloy slurry were investigated. The results demonstrated that the semi-solid 7075 aluminum alloy slurry with satisfied quality could be generated by a serpentine pouring channel when the pouring temperature was in the range of 680-700 ℃. At a given pouring temperature, the equivalent size of the primaryα（Al） grains decreased and the shape factor increased with the increase of the number of turns. During the slurry preparation of semi-solid 7075 aluminum alloy, the flow direction of alloy melt changed many times when it flowed in a curved and closed serpentine channel. With the effect of“stirring”in it , the primary nuclei gradually evolved into spherical and near-spherical grains.展开更多
The integral microstructure of semisolid A356 alloy slurry with larger capacity cast by serpentine channel was studied and the influence of cooling ability of serpentine channel on the microstructure was investigated....The integral microstructure of semisolid A356 alloy slurry with larger capacity cast by serpentine channel was studied and the influence of cooling ability of serpentine channel on the microstructure was investigated. The results indicate that ideal slurry with larger capacity can be prepared through serpentine channel with good cooling ability. When the serpentine channel was continuously cooled, both the longitudinal and the radial microstructure of the slurry was composed of granular primary phase and the integral microstructure uniformity of the slurry was good. However, uncooled serpentine channel can only produce larger slurry with fine grains in positions adjacent to its centre and with a large number of dendrites in positions close to its edge, thus, the radial microstructure of larger slurry is nonuniform. The pouring temperature is set up to 680 °C and the solid shell inside the channel can be avoided at this pouring temperature.展开更多
The semi-solid slurry of A380 aluminum alloy was prepared by the serpentine channel. The effects of pouring temperature, curve number and curve diameter of the serpentine channel on the microstructure of the semi-soli...The semi-solid slurry of A380 aluminum alloy was prepared by the serpentine channel. The effects of pouring temperature, curve number and curve diameter of the serpentine channel on the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the satisfactory semi-solid A380 aluminum alloy slurry could be obtained when the pouring temperature ranged from 630 to 650 °C. Under the same conditions, increasing the curve number or reducing the curve diameter of the serpentine channel would decrease the average diameter and increase the shape factor of the primary α（Al） grains. The ＂self-stirring＂ of the alloy melt in the serpentine channel was beneficial to the ripening of the dendrites and the spheroidizing of the primary α（Al） grains.展开更多
The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfac...The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfactants. The results showed that at pH 8.8 with the addition of 100 g/t sodium hexametaphosphate, 4.5 L/t oleic acid, and 4.5 L/t kerosene, significant amount of fine magnetite particles adhered to the pentlandite surface, while trace amount of coating was found on serpentine surfaces. Thus, the magnetism of pentlandite was enhanced and pentlandite was well separated from serpentine by magnetic separation under the magnetic field intensity of 200 kA/m. Scanning electron microscopy （SEM） and zeta potential measurement were performed to characterize changes of mineral surface properties. Calculations of the extended Derjaguin-Landau-Verwey-Ocerbeek （EDLVO） theory indicated that, in the presence of surfactants the total interaction energy between magnetite and pentlandite became stronger than that between magnetite and serpentine. This enabled the selective adhesion of magnetite particles to pentlandite surfaces, thereby enhancing its magnetism.展开更多
Semi-solid A356 aluminum alloy slurry was prepared by using serpentine channel pouring process, and the influences of the channel diameters and pouring temperatures on the semi-solid A356 aluminum alloy slurry were in...Semi-solid A356 aluminum alloy slurry was prepared by using serpentine channel pouring process, and the influences of the channel diameters and pouring temperatures on the semi-solid A356 aluminum alloy slurry were investigated. The experimental results show that when the channel diameter is 20 and 25 mm, respectively, and the pouring temperature is 640-680 ℃, the average diameter of primary α（Al） grains in the prepared A356 aluminum alloy slurry is 50-75 and 55-78 μm, respectively, and the average shape factor of primary α（Al） grains is 0.89-0.76 and 0.86-0.72, respectively. With the decline in the pouring temperature, the microstructure of semi-solid A356 aluminum alloy slurry is more desirable and a serpentine channel with smaller diameter is also advantageous to the microstructure imProvement. During the preparation of semi-solid A356 aluminum alloy slurry, a large number of nuclei can be produced by the chilling effect of the serpentine channel, and owing to the combined effect of the chilled nuclei separation and melt self-stirring, primary α（Al） nuclei can be multiplied and spheroidized finally.展开更多
Semi-solid slurry of ZL101 aluminum alloy was prepared using serpentine channel. The influences of the pouring temperature, the number of curves and the serpentine channel temperature on the microstructure of semi-sol...Semi-solid slurry of ZL101 aluminum alloy was prepared using serpentine channel. The influences of the pouring temperature, the number of curves and the serpentine channel temperature on the microstructure of semi-solid ZL101 aluminum alloy were investigated. The results show that, satisfied semi-solid slurry of ZL101 aluminum alloy was prepared with pouring at 630-680℃. The morphology of primaryα（Al） grains transforms from rosette to spheroid with the decrease of pouring temperature. At the same pouring temperature, increasing the number of curves can improve the morphology of primaryα（Al） grains and decrease the grain size. Qualified slurry can be attained with lowering the pouring temperature when the serpentine channel temperature is higher. The alloy melt has the effect of“self-stirring”in the serpentine channel, which can make the primary nuclei gradually evolve into spherical and near-spherical grains.展开更多
In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pr...In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pressure distribution measurement along the wall, the flow separation is found at the top wall of the second S duct for the baseline inlet design, which yields a high flow distortion at the exit plane. To improve the flow uniformity, a single array of vortex generators （VGs） is employed within the inlet. In this experimental study, the effects of mass flow ratio, free stream Mach number, angle of attack and yaw on the performance of a serpentine inlet instrumented with VGs are obtained. Results indicate： （1） Compared with the baseline serpentine design without flow control, the application of the VGs promotes the mixing of core flow and the low momentum flow in the boundary layer and thus prevents the flow separation. Under the design condition, the exit flow distortion （-↑△σ0） decreases from 11.7% to 2.3% by using the VGs. （2） With the descent of the free stream Mach number the total pressure loss decreases. However, the circular total pressure distortion increases. When the angle of attack rises from - 4° to 8°, the total pressure recovery and the circular total pressure distortion both go down. In addition, with the increase of yaw the total pressure recovery is fairly constant, while the circular total pressure distortion ascends gradually. （3） When Mao = 0.6-0.8, a = -4°-8° and β = 0°-6°, the total pressure recovery varies between 0.936 and 0. 961, the circular total pressure distortion coefficient varies between 1.4 % and 5.4 % and the synthesis distortion coefficient has a ranges from 3.8 % to 7.0 %. The experimental results confirm the excellent performance of the newly designed serpentine inlet incorporating VGs.展开更多
Gas–liquid flow in serpentine microchannel with different surface properties exhibits drastically different flow behavior. With water and air as working fluids, the method of numerical simulation was adopted in this ...Gas–liquid flow in serpentine microchannel with different surface properties exhibits drastically different flow behavior. With water and air as working fluids, the method of numerical simulation was adopted in this paper based on CLSVOF(coupled level set and volume of fluid method) multiphase model. After verifying the reasonability of the model through experiment, by changing wall properties and Re number(Re<1500), the influences of contact angle and surface roughness on flow regime and Po number were discussed. Moreover, the difference of pressure drop between curve and straight microchannel was also calculated. Beyond that, the combined effect of curve channel and wall properties on flow resistance was analyzed. This paper finds that wall properties have great influence on gas–liquid flow in microchannels not only on flow regime but also flow characteristics. Meanwhile, the pressure drop in curve microchannels is larger than straight. It is more beneficial for fluid flowing when the straight part of microchannel is hydrophilic smooth wall and curve part is hydrophobic with large roughness.展开更多
To inhibit the dissolution of Mg^2+ during the bioleaching process of high-magnesium nickel sulfide ore, the effect of major bioleaching factors on the dissolution of Mg^2+ from olivine and serpentine was investigated...To inhibit the dissolution of Mg^2+ during the bioleaching process of high-magnesium nickel sulfide ore, the effect of major bioleaching factors on the dissolution of Mg^2+ from olivine and serpentine was investigated and kinetics studies were carried out. The results indicated that the dissolution rate-controlling steps are chemical reaction for olivine and internal diffusion for serpentine. The most influential factor on the dissolution of Mg^2+ from olivine and serpentine was temperature, followed by p H and particle size. A novel method of bioleaching at elevated pH was used in the bioleaching of Jinchuan ore. The results showed that elevated pH could significantly reduce the dissolution of Mg^2+ and acid consumption along with slightly influencing the leaching efficiencies of nickel and cobalt. A model was used to explain the leaching behaviors of high-magnesium nickel sulfide ore in different bioleaching systems. The model suggested that olivine will be depleted eventually, whereas serpentine will remain because of the difference in the rate-controlling steps. Bioleaching at elevated pH is a suitable method for treating high-magnesium nickel sulfide ores.展开更多
Comprehensive optimization design of serpentine nozzle with trapezoidal outlet was studied to improve its aerodynamic and electromagnetic scattering performance.Serpentine nozzles with different center offsets and dif...Comprehensive optimization design of serpentine nozzle with trapezoidal outlet was studied to improve its aerodynamic and electromagnetic scattering performance.Serpentine nozzles with different center offsets and different ratios of the bases of the trapezoidal outlet were generated based on curvature control regulation.Computational Fluid Dynamics(CFD)simulations have been conducted to obtain the flow field in the nozzle,and Forward-Backward Iterative Physical Optics(FBIPO)method was applied to study the electromagnetic scattering characteristics of the nozzle.Guarantee Convergence Particle Swarm Optimization(GCPSO)algorithm based on Radial Basis Function(RBF)neural network was used to optimize the geometry of the nozzle in consideration of its aerodynamic and electromagnetic scattering characteristics.The results show that the GCPSO method based on RBF can be used to optimize the aerodynamic characteristics of the internal flow and the scattering characteristics of the cavity of the serpentine nozzle with irregular outlet.The optimized model has a higher center offset and a lower ratio of the bases of the trapezoidal outlet after optimization compared to the original model.The optimized model leads to a slight change in aerodynamic performance,with a total pressure recovery coefficient increase of 0.31%and a discharge coefficient increase of 0.41%.In addition,the Radar Cross Section(RCS)decreases also by around 83.33%and the overall performance is significantly improved,with a decrease of the optimized objective function by around 38.74%.展开更多
Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are c...Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.展开更多
Sodium hexametaphosphate(SHMP)was used to minimize the adverse effect of serpentine for improving aschariterecovery.The effects of particle size and content of SHMP,and serpentine on ascharite flotation process were i...Sodium hexametaphosphate(SHMP)was used to minimize the adverse effect of serpentine for improving aschariterecovery.The effects of particle size and content of SHMP,and serpentine on ascharite flotation process were investigated throughflotation,zeta potential tests,FT-IR analysis,XPS analysis and DLVO theory.Particles interaction and mechanism of SHMP werealso discussed.It was found that aggregation between serpentine and ascharite particles easily happened,and the particle size ofserpentine had a profound impact on the ascharite recovery.In particular,the fine serpentine with size less than38μm had thegreatest contribution to the deterioration of ascharite flotation performance.After SHMP treatment,the adverse effect of serpentinewas significantly reduced.The mechanism of SHMP showed that it could alter the surface charges of serpentine and ascharite toprevent severe interparticle aggregation,which resulted in a well-dispersed pulp and benefited ascharite flotation process.Theadsorption of SHMP on serpentine was due to hydrogen bonding and chemical adsorption,resulting in the formation of complex onserpentine surface to decrease its floatability.展开更多
Inner Mongolian serpentine ore was subjected to sulfuric acid leaching tests,and the effects of the leaching process parameters on the leaching efficiency of different metals were investigated.The leaching efficiency ...Inner Mongolian serpentine ore was subjected to sulfuric acid leaching tests,and the effects of the leaching process parameters on the leaching efficiency of different metals were investigated.The leaching efficiency of Mg,Fe,Al,Ni,and Co reaches 93.98%,60.09%,82.08%,90.58%,and 94.06%,respectively,under the leaching conditions of 5 mol/L H_(2)SO_(4),liquid/solid ratio of 4 mL/g,and leaching temperature 100℃.Hence,the valuable metals in serpentine were effectively recovered by sulfuric acid leaching.The leaching behaviors of Mg,Fe,and a small amount of Al were analyzed using X-ray diffraction.The results show that the unreacted Mg and Fe remained as MgFe_(2)O_(4),and Al formed Al_(2)Si_(2)O_(5)(OH)_(4) in the leaching residue.The kinetics of Mg and Ni in the leaching process was studied respectively.The leaching kinetics of Mg conformed to the shrinking core model with an activation energy of 16.95 kJ/mol,which was controlled by the combination of the diffusion and chemical reaction.The leaching kinetics of Ni accorded with the Avrami equation with an activation energy of 11.57 kJ/mol,which was controlled by diffusion.In the study,the valuable metal elements were extracted from serpentine minerals with high efficiency and low cost,which possessed important practical values.展开更多
文摘This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.
基金supported by the National Science and Technology Major Project of China(No.J2019-Ⅲ-0009-0053)。
文摘The serpentine convergent-divergent nozzle represents an optimal configuration for nextgeneration fighter aircraft characterized by low detectability and high thrust-to-weight ratio.In contrast to the serpentine convergent nozzle,such configuration offers increased design flexibility with additional parameters,leading to heightened interactions among these parameters.As such,it is crucial to reveal the influence of design parameters on the aerodynamic performance of the serpentine convergent-divergent nozzle and the multifactor interaction,as well as its mechanism.Therefore,the influence,interaction and sensitivity of parameters on the aerodynamic performance of the nozzle were numerically investigated using the orthogonal test method.Additionally,the influence mechanism of the convergence angle,throat aspect ratio,and axial length to inlet diameter on the flow characteristics of the nozzle was investigated in detail.The results show that the convergence angle is identified as the main factor affecting the aerodynamic parameters of the nozzle.As the convergence angle increases,the thrust coefficient,total pressure recovery coefficient and discharge coefficient gradually decrease.The interaction between throat aspect ratio and other parameters is obvious.Different design parameters affect the local loss and the friction loss by affecting the curvature and wetted perimeter area,resulting in different aerodynamic characteristics of serpentine convergent-divergent nozzle.
文摘The paper provides an overview of geometric solutions of marking all types of serpentine by the method of internal circular curve in designing forest roads directly in the field. The main objective of presenting this original method for marking all serpentine types in one place is to show similarities and differences in marking different types of serpentine, and identify opportunities for further research of this type. The method is based on the establishment of the minimum number of elements necessary to mark the serpentine on the forest roads and other budget elements and their design in the field. By using this method, construction errors or the number of attempts of serpentine marking are reduced, which increases the effects of design compared to the ones reached by the previous method of marking the serpentine on forest roads.
基金supported by the National Natural Science Foundation of China(No.22072183)the Natural Science Foundation of Hunan Province,China(No.2022JJ30690)the High Performance Computing Center of Central South University.
文摘Serpentine structured Co_(3)Si_(2)O_(5)(OH)_(4) is inexpensive,chemically stable,and electrochemically active in oxygen evolution reactions(OER).However,the OER activity of Co_(3)Si_(2)O_(5)(OH)_(4) materials is still unfavorable due to the low active sites.Here,Mn^(2+)-doped Co_(3)Si_(2)O_(5)(OH)_(4) serpentine nanosheets with tuned d-band centers are achieved for efficient oxygen evolution in alkaline and neutral electrolytes.The Co_(x)Mn_(3−x)Si_(2)O_(5)(OH)_(4) serpentine nanosheets are synthesized by a simple hydrothermal method.The optimized Co_(2.4)Mn_(0.6)Si_(2)O_(5)(OH)_(4) serpentine nanosheets showed favorable OER overpotentials as well as stable durability in KOH solution and phosphate buffer solution,which were superior to most of the Co-based and Mn-based OER electrocatalysts.The in situ Raman spectroscopy shows that the materials are kept well in the electrochemical OER environments.Further density functional theory shows that the d-band center of Co_(x)Mn_(3−x)Si_(2)O_(5)(OH)_(4) serpentine nanosheets is shifted more upward in comparison with pristine Co_(3)Si_(2)O_(5)(OH)_(4).The changes in the d-band center increase the adsorption of intermediates,optimize the reaction steps,and lower the energy barriers of the OER.That is the main reason for the OER enhancement Mn^(2+)-doped Co_(3)Si_(2)O_(5)(OH)_(4).This work gives an efficient strategy to design cheap and stable electrocatalytic materials for OER in a broad pH environment.
基金Project(2007CB613602)supported by the National Basic Research Program of China
文摘The effect of sodium hexametaphosphate（SHMP） on the separation of serpentine from pyrite and its mechanism were studied systematically through flotation tests,sedimentation tests,surface dissolution,ζ potential tests,adsorption measurements,and infrared spectroscopic analyses.The results show that the SHMP could significantly reduce the adverse effect of serpentine on the flotation of pyrite and make the mixed sample of pyrite and serpentine more disperse in the alkaline condition,thus improve the adsorption of xanthate on pyrite.The action mechanism of the SHMP is that it lowers the pH value at the isoelectric point of serpentine and enhances the negative charge through the dissolution of magnesium from the surface of serpentine and adsorbing on the surface of serpentine.It changes the total interaction energy between serpentine and pyrite from gravitational potential energy to repulse potential energy,according to the calculation of the EDLVO theory.
基金Project(51174229) supported by the National Natural Science Foundation of China
文摘The electrokinetic behavior and surface dissolution of serpentine mineral were studied through Zeta potential measurements, dissolution experiments and X-ray photoelectron spectroscopy. The results show that serpentine has an iso-electric point （IEP） of 11.9, which is higher than that of other phyllosilicate minerals. Dissolution experiments show that the hydroxyl is easy to dissolve with respect to the magnesium cations in the magnesium oxide octahedral sheet. As a result of hydroxyl dissolution, the magnesium ions are left on serpentine surface, which is responsible for serpentine surface charge. The removal of magnesium ions from serpentine surface by acid leaching results in a decrease of serpentine IEP. Therefore, it has been clearly established that the surface charge developed at the serpentine/aqueous electrical interface is a function of the serpentine surface incongruent dissolution.
基金Project(2006AA03Z115) supported by the National High-tech Research and Development Program of ChinaProject(2011CB606302-1) supported by the National Basic Research Program of ChinaProject(50774007) supported by the National Natural Science Foundation of China
文摘An innovative one-step semi-solid processing technique of A356 Al alloy,the serpentine channel pouring rheo-diecasting process （SCRC）,was explored.The mechanical properties and microstructures of the tensile samples made by the SCRC technique were tested in the as-cast and T6 heat treatment conditions.The experimental results show that the as-cast ultimate tensile strength can reach about 250MPa and the elongation is 8.6%？13.2%.The ultimate tensile strength can increase approximately 30% higher than that of the as-cast one but there is some slight sacrifice of the plasticity after T6 heat treatment.Under these experimental conditions,the semi-solid A356 Al alloy slurry with primary α1（Al） grains,which have the shape factor of 0.78？0.89 and the grain diameter of 35？45μm,can be prepared by the serpentine channel pouring process.The primary α2（Al） grains are very fine during the secondary solidification stage.Compared with the conventional HPDC process,the SCRC process can improve the microstructures and mechanical properties of the tensile test samples.The advantages of the SCRC process include easily incorporating with an existing HPDC machine,cancelling the preservation and transportation process of the semi-solid alloy slurry,and a higher cost performance.
基金Project (2011CB606302-1) supported by the National Basic Research Program of China
文摘The semi-solid slurry of 7075 aluminum alloy was prepared by a serpentine pouring channel （SCP）. Influences of pouring temperature and the number of turns on the microstructure of semi-solid 7075 alloy slurry were investigated. The results demonstrated that the semi-solid 7075 aluminum alloy slurry with satisfied quality could be generated by a serpentine pouring channel when the pouring temperature was in the range of 680-700 ℃. At a given pouring temperature, the equivalent size of the primaryα（Al） grains decreased and the shape factor increased with the increase of the number of turns. During the slurry preparation of semi-solid 7075 aluminum alloy, the flow direction of alloy melt changed many times when it flowed in a curved and closed serpentine channel. With the effect of“stirring”in it , the primary nuclei gradually evolved into spherical and near-spherical grains.
基金Project (50774007) supported by the National Natural Science Foundation of ChinaProject (20082022) supported by the Scientific Research Foundation for Doctors from Taiyuan University of Science and Technology, China
文摘The integral microstructure of semisolid A356 alloy slurry with larger capacity cast by serpentine channel was studied and the influence of cooling ability of serpentine channel on the microstructure was investigated. The results indicate that ideal slurry with larger capacity can be prepared through serpentine channel with good cooling ability. When the serpentine channel was continuously cooled, both the longitudinal and the radial microstructure of the slurry was composed of granular primary phase and the integral microstructure uniformity of the slurry was good. However, uncooled serpentine channel can only produce larger slurry with fine grains in positions adjacent to its centre and with a large number of dendrites in positions close to its edge, thus, the radial microstructure of larger slurry is nonuniform. The pouring temperature is set up to 680 °C and the solid shell inside the channel can be avoided at this pouring temperature.
基金Project(2011CB606300)supported by the National Basic Research Program of ChinaProject(5077400)supported by the National Natural Science Foundation of China
文摘The semi-solid slurry of A380 aluminum alloy was prepared by the serpentine channel. The effects of pouring temperature, curve number and curve diameter of the serpentine channel on the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the satisfactory semi-solid A380 aluminum alloy slurry could be obtained when the pouring temperature ranged from 630 to 650 °C. Under the same conditions, increasing the curve number or reducing the curve diameter of the serpentine channel would decrease the average diameter and increase the shape factor of the primary α（Al） grains. The ＂self-stirring＂ of the alloy melt in the serpentine channel was beneficial to the ripening of the dendrites and the spheroidizing of the primary α（Al） grains.
基金Project(51574061)supported by the National Natural Science Foundation of ChinaProject(N150106004)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2014SKY-WK011)supported by the Open Fund Project of Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources,China
文摘The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfactants. The results showed that at pH 8.8 with the addition of 100 g/t sodium hexametaphosphate, 4.5 L/t oleic acid, and 4.5 L/t kerosene, significant amount of fine magnetite particles adhered to the pentlandite surface, while trace amount of coating was found on serpentine surfaces. Thus, the magnetism of pentlandite was enhanced and pentlandite was well separated from serpentine by magnetic separation under the magnetic field intensity of 200 kA/m. Scanning electron microscopy （SEM） and zeta potential measurement were performed to characterize changes of mineral surface properties. Calculations of the extended Derjaguin-Landau-Verwey-Ocerbeek （EDLVO） theory indicated that, in the presence of surfactants the total interaction energy between magnetite and pentlandite became stronger than that between magnetite and serpentine. This enabled the selective adhesion of magnetite particles to pentlandite surfaces, thereby enhancing its magnetism.
基金Project (2006AA03Z115) supported by the National High-tech Research and Development Program of ChinaProject (2006CB605203) supported by the National Basic Research Program of ChinaProject (50774007) supported by the National Natural Science Foundation of China
文摘Semi-solid A356 aluminum alloy slurry was prepared by using serpentine channel pouring process, and the influences of the channel diameters and pouring temperatures on the semi-solid A356 aluminum alloy slurry were investigated. The experimental results show that when the channel diameter is 20 and 25 mm, respectively, and the pouring temperature is 640-680 ℃, the average diameter of primary α（Al） grains in the prepared A356 aluminum alloy slurry is 50-75 and 55-78 μm, respectively, and the average shape factor of primary α（Al） grains is 0.89-0.76 and 0.86-0.72, respectively. With the decline in the pouring temperature, the microstructure of semi-solid A356 aluminum alloy slurry is more desirable and a serpentine channel with smaller diameter is also advantageous to the microstructure imProvement. During the preparation of semi-solid A356 aluminum alloy slurry, a large number of nuclei can be produced by the chilling effect of the serpentine channel, and owing to the combined effect of the chilled nuclei separation and melt self-stirring, primary α（Al） nuclei can be multiplied and spheroidized finally.
基金Projects(51204147,51274175)supported by the National Natural Science Foundation of ChinaProject(2014DFA50320)supported by the Ministry of Science and Technology of ChinaProjects(2013081017,2012081013)supported by the International Science and Technology Cooperation Project of Shanxi Province,China
文摘Semi-solid slurry of ZL101 aluminum alloy was prepared using serpentine channel. The influences of the pouring temperature, the number of curves and the serpentine channel temperature on the microstructure of semi-solid ZL101 aluminum alloy were investigated. The results show that, satisfied semi-solid slurry of ZL101 aluminum alloy was prepared with pouring at 630-680℃. The morphology of primaryα（Al） grains transforms from rosette to spheroid with the decrease of pouring temperature. At the same pouring temperature, increasing the number of curves can improve the morphology of primaryα（Al） grains and decrease the grain size. Qualified slurry can be attained with lowering the pouring temperature when the serpentine channel temperature is higher. The alloy melt has the effect of“self-stirring”in the serpentine channel, which can make the primary nuclei gradually evolve into spherical and near-spherical grains.
文摘In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pressure distribution measurement along the wall, the flow separation is found at the top wall of the second S duct for the baseline inlet design, which yields a high flow distortion at the exit plane. To improve the flow uniformity, a single array of vortex generators （VGs） is employed within the inlet. In this experimental study, the effects of mass flow ratio, free stream Mach number, angle of attack and yaw on the performance of a serpentine inlet instrumented with VGs are obtained. Results indicate： （1） Compared with the baseline serpentine design without flow control, the application of the VGs promotes the mixing of core flow and the low momentum flow in the boundary layer and thus prevents the flow separation. Under the design condition, the exit flow distortion （-↑△σ0） decreases from 11.7% to 2.3% by using the VGs. （2） With the descent of the free stream Mach number the total pressure loss decreases. However, the circular total pressure distortion increases. When the angle of attack rises from - 4° to 8°, the total pressure recovery and the circular total pressure distortion both go down. In addition, with the increase of yaw the total pressure recovery is fairly constant, while the circular total pressure distortion ascends gradually. （3） When Mao = 0.6-0.8, a = -4°-8° and β = 0°-6°, the total pressure recovery varies between 0.936 and 0. 961, the circular total pressure distortion coefficient varies between 1.4 % and 5.4 % and the synthesis distortion coefficient has a ranges from 3.8 % to 7.0 %. The experimental results confirm the excellent performance of the newly designed serpentine inlet incorporating VGs.
文摘Gas–liquid flow in serpentine microchannel with different surface properties exhibits drastically different flow behavior. With water and air as working fluids, the method of numerical simulation was adopted in this paper based on CLSVOF(coupled level set and volume of fluid method) multiphase model. After verifying the reasonability of the model through experiment, by changing wall properties and Re number(Re<1500), the influences of contact angle and surface roughness on flow regime and Po number were discussed. Moreover, the difference of pressure drop between curve and straight microchannel was also calculated. Beyond that, the combined effect of curve channel and wall properties on flow resistance was analyzed. This paper finds that wall properties have great influence on gas–liquid flow in microchannels not only on flow regime but also flow characteristics. Meanwhile, the pressure drop in curve microchannels is larger than straight. It is more beneficial for fluid flowing when the straight part of microchannel is hydrophilic smooth wall and curve part is hydrophobic with large roughness.
基金financially supported by the National Natural Science Foundation of China (Nos. 51574036 and 51404033)
文摘To inhibit the dissolution of Mg^2+ during the bioleaching process of high-magnesium nickel sulfide ore, the effect of major bioleaching factors on the dissolution of Mg^2+ from olivine and serpentine was investigated and kinetics studies were carried out. The results indicated that the dissolution rate-controlling steps are chemical reaction for olivine and internal diffusion for serpentine. The most influential factor on the dissolution of Mg^2+ from olivine and serpentine was temperature, followed by p H and particle size. A novel method of bioleaching at elevated pH was used in the bioleaching of Jinchuan ore. The results showed that elevated pH could significantly reduce the dissolution of Mg^2+ and acid consumption along with slightly influencing the leaching efficiencies of nickel and cobalt. A model was used to explain the leaching behaviors of high-magnesium nickel sulfide ore in different bioleaching systems. The model suggested that olivine will be depleted eventually, whereas serpentine will remain because of the difference in the rate-controlling steps. Bioleaching at elevated pH is a suitable method for treating high-magnesium nickel sulfide ores.
基金the financial support of the Fundamental Research Funds for the Central Universities(No.31020190MS708)。
文摘Comprehensive optimization design of serpentine nozzle with trapezoidal outlet was studied to improve its aerodynamic and electromagnetic scattering performance.Serpentine nozzles with different center offsets and different ratios of the bases of the trapezoidal outlet were generated based on curvature control regulation.Computational Fluid Dynamics(CFD)simulations have been conducted to obtain the flow field in the nozzle,and Forward-Backward Iterative Physical Optics(FBIPO)method was applied to study the electromagnetic scattering characteristics of the nozzle.Guarantee Convergence Particle Swarm Optimization(GCPSO)algorithm based on Radial Basis Function(RBF)neural network was used to optimize the geometry of the nozzle in consideration of its aerodynamic and electromagnetic scattering characteristics.The results show that the GCPSO method based on RBF can be used to optimize the aerodynamic characteristics of the internal flow and the scattering characteristics of the cavity of the serpentine nozzle with irregular outlet.The optimized model has a higher center offset and a lower ratio of the bases of the trapezoidal outlet after optimization compared to the original model.The optimized model leads to a slight change in aerodynamic performance,with a total pressure recovery coefficient increase of 0.31%and a discharge coefficient increase of 0.41%.In addition,the Radar Cross Section(RCS)decreases also by around 83.33%and the overall performance is significantly improved,with a decrease of the optimized objective function by around 38.74%.
基金co-supported by the Postdoctoral Foundation of China (Nos. 2013M542525, 2014T71019)
文摘Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.
基金Project(51204033) supported by the National Natural Science Foundation of ChinaProject(L2014088) supported by Liaoning Provincial Education Department of China
文摘Sodium hexametaphosphate(SHMP)was used to minimize the adverse effect of serpentine for improving aschariterecovery.The effects of particle size and content of SHMP,and serpentine on ascharite flotation process were investigated throughflotation,zeta potential tests,FT-IR analysis,XPS analysis and DLVO theory.Particles interaction and mechanism of SHMP werealso discussed.It was found that aggregation between serpentine and ascharite particles easily happened,and the particle size ofserpentine had a profound impact on the ascharite recovery.In particular,the fine serpentine with size less than38μm had thegreatest contribution to the deterioration of ascharite flotation performance.After SHMP treatment,the adverse effect of serpentinewas significantly reduced.The mechanism of SHMP showed that it could alter the surface charges of serpentine and ascharite toprevent severe interparticle aggregation,which resulted in a well-dispersed pulp and benefited ascharite flotation process.Theadsorption of SHMP on serpentine was due to hydrogen bonding and chemical adsorption,resulting in the formation of complex onserpentine surface to decrease its floatability.
基金Project(51574286)supported by the National Natural Science Foundation of China。
文摘Inner Mongolian serpentine ore was subjected to sulfuric acid leaching tests,and the effects of the leaching process parameters on the leaching efficiency of different metals were investigated.The leaching efficiency of Mg,Fe,Al,Ni,and Co reaches 93.98%,60.09%,82.08%,90.58%,and 94.06%,respectively,under the leaching conditions of 5 mol/L H_(2)SO_(4),liquid/solid ratio of 4 mL/g,and leaching temperature 100℃.Hence,the valuable metals in serpentine were effectively recovered by sulfuric acid leaching.The leaching behaviors of Mg,Fe,and a small amount of Al were analyzed using X-ray diffraction.The results show that the unreacted Mg and Fe remained as MgFe_(2)O_(4),and Al formed Al_(2)Si_(2)O_(5)(OH)_(4) in the leaching residue.The kinetics of Mg and Ni in the leaching process was studied respectively.The leaching kinetics of Mg conformed to the shrinking core model with an activation energy of 16.95 kJ/mol,which was controlled by the combination of the diffusion and chemical reaction.The leaching kinetics of Ni accorded with the Avrami equation with an activation energy of 11.57 kJ/mol,which was controlled by diffusion.In the study,the valuable metal elements were extracted from serpentine minerals with high efficiency and low cost,which possessed important practical values.
