In this paper, the unsteady cavitating turbulent flow around a marine propeller is simulated based on the unsteady Reynolds averaged Navier-Stokes(URANS) with emphasis on the hull-propeller interaction by an integral ...In this paper, the unsteady cavitating turbulent flow around a marine propeller is simulated based on the unsteady Reynolds averaged Navier-Stokes(URANS) with emphasis on the hull-propeller interaction by an integral calculation approach, which means the propeller and hull are treated as a whole when the cavitating flow is calculated. The whole calculational domain is split to an inner rotating domain containing a propeller and an outer domain containing a hull. And the two split sections are connected together in ANSYS CFX by using the GGI interfaces and the transient rotor stator frame change/mixing model. The alternate rotation model is employed for the advection term in the momentum equations in order to reduce the numerical error. Comparison of predictions with measurements shows that the propeller thrust coefficient can be predicted satisfactorily. The unsteady cavitating flow around the propeller behind the ship hull wake shows quasi-periodic features including cavity inception, growth and shrinking. These features are effectively reproduced in the simulations which compare well to available experimental data. In addition, significant pressure fluctuations on the ship hull surface induced by the unsteady propeller cavitation are compared with experimental data at monitoring points on the hull surface. The predicted amplitudes of the first components corresponding to the first blade passing frequencies match well with the experimental data. The maximum error between the predictions and the experimental data for the pressure pulsations is around 8%, which is acceptable in most engineering applications.展开更多
An integrated calculated approach based on weakly coupled finite element(FEM)-viscoplastic selfconsistent(VPSC)model was established to simulate the texture evolution during the variable strain path extrusion process ...An integrated calculated approach based on weakly coupled finite element(FEM)-viscoplastic selfconsistent(VPSC)model was established to simulate the texture evolution during the variable strain path extrusion process of magnesium alloys.The spiral die extrusion(SDE)process with additional circumferential shear deformation was applied to investigate the effect of path control on texture adjustment and verify the accuracy of the model.The results indicated that the additional spiral shear resulting from the overall inclined flow path effectively reduced the intensity of the{0002}//ED fiber texture by suppressing basal slip activation in the core area,while the local shear deformation along the spiral equal channel strain path led to the formation of an inclined{0002}//ND plane texture on the side.Using the modified Hall-Petch relationship,the correlation between texture and yield strength was quantified.Specifically,the weakening of the texture effectively suppressed{10-12}tensile twinning,which compensated for the deficiency of compressive yield strength without significantly sacrificing tensile yield strength,and thus improved the tension-compression asymmetry.Furthermore,the strongly inclined{0002}//ND plane texture inhibited the widespread activation of basal slip during tensile yielding,thereby enhancing the yield strength.展开更多
An extremely simple formula to estimate the heat of formation of complexes between an ion and a polar molecule or between highly polar systems is presented.The formula is entirely electrostatic and the expression used...An extremely simple formula to estimate the heat of formation of complexes between an ion and a polar molecule or between highly polar systems is presented.The formula is entirely electrostatic and the expression used is verified by means of perturbation theory.This formula is test- ed for several ion-molecule and molecule-molecule pairs.It is also applied to estimate the heat of hydration of simple salts.展开更多
Refractory high-entropy alloys(RHEAs)demonstrate exceptional high-temperature performance,extending their application potential beyond superalloys.Understanding the precise phase stability in RHEAs is crucial for desi...Refractory high-entropy alloys(RHEAs)demonstrate exceptional high-temperature performance,extending their application potential beyond superalloys.Understanding the precise phase stability in RHEAs is crucial for designing materials and microstructures with optimized properties.This study establishes a thermodynamic database for the Mo–Nb–Ta–W–Hf–Zr system within a third-generation(3rd-generation)thermodynamic framework,enabling the prediction of phase stabilities in different RHEAs.Initially,a third-generation thermodynamic model was proposed for solid and liquid phases in stable and metastable states,applied to Mo,Nb,Ta,W,Hf,and Zr elements to ensure lattice stability across the temperature range.Subsequently,9 sub-binary and 10 subternary systems within the Mo–Nb–Ta–W–Hf–Zr system were thermodynamically modeled under the 3rd-generation thermodynamic framework,demonstrating that the calculated results agree well with the measurements.By leveraging the optimized binary and ternary coefficients,a thermodynamic database for Mo–Nb–Ta–W–Hf–Zr was established applying the calculation of phase diagram approach.The reliability of this database was confirmed through equilibrium thermodynamic calculations as well as non-equilibrium solidification simulations in the Mo Nb Ta WZr alloys,exhibiting agreement with the experimental data.Ultimately,the database was utilized to predict phase stability in various RHEAs within the Mo–Nb–Ta–W–Hf–Zr system.The current predictions suggest that the precipitation temperatures of hexagonal close-packed_A3 and C15 Laves phases are relatively high,mostly above 1000 K,whereas that of the B2 phase is below 928 K.With an increase in the number of elements,the precipitation behavior in the alloys tends to become more complex,leading to the formation of multiple precipitated phases.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11772239,51822903 and 91752105)the Natural Science Foundation of Hubei Province(Grant Nos.2017CFA048,2018CFA010)
文摘In this paper, the unsteady cavitating turbulent flow around a marine propeller is simulated based on the unsteady Reynolds averaged Navier-Stokes(URANS) with emphasis on the hull-propeller interaction by an integral calculation approach, which means the propeller and hull are treated as a whole when the cavitating flow is calculated. The whole calculational domain is split to an inner rotating domain containing a propeller and an outer domain containing a hull. And the two split sections are connected together in ANSYS CFX by using the GGI interfaces and the transient rotor stator frame change/mixing model. The alternate rotation model is employed for the advection term in the momentum equations in order to reduce the numerical error. Comparison of predictions with measurements shows that the propeller thrust coefficient can be predicted satisfactorily. The unsteady cavitating flow around the propeller behind the ship hull wake shows quasi-periodic features including cavity inception, growth and shrinking. These features are effectively reproduced in the simulations which compare well to available experimental data. In addition, significant pressure fluctuations on the ship hull surface induced by the unsteady propeller cavitation are compared with experimental data at monitoring points on the hull surface. The predicted amplitudes of the first components corresponding to the first blade passing frequencies match well with the experimental data. The maximum error between the predictions and the experimental data for the pressure pulsations is around 8%, which is acceptable in most engineering applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.51975146,52205344)Shandong Province Natural Science Foundation(Grant No.ZR2020QE171)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF-2021R1A2C3006662,NRF-2022R1A5A1030054).
文摘An integrated calculated approach based on weakly coupled finite element(FEM)-viscoplastic selfconsistent(VPSC)model was established to simulate the texture evolution during the variable strain path extrusion process of magnesium alloys.The spiral die extrusion(SDE)process with additional circumferential shear deformation was applied to investigate the effect of path control on texture adjustment and verify the accuracy of the model.The results indicated that the additional spiral shear resulting from the overall inclined flow path effectively reduced the intensity of the{0002}//ED fiber texture by suppressing basal slip activation in the core area,while the local shear deformation along the spiral equal channel strain path led to the formation of an inclined{0002}//ND plane texture on the side.Using the modified Hall-Petch relationship,the correlation between texture and yield strength was quantified.Specifically,the weakening of the texture effectively suppressed{10-12}tensile twinning,which compensated for the deficiency of compressive yield strength without significantly sacrificing tensile yield strength,and thus improved the tension-compression asymmetry.Furthermore,the strongly inclined{0002}//ND plane texture inhibited the widespread activation of basal slip during tensile yielding,thereby enhancing the yield strength.
文摘An extremely simple formula to estimate the heat of formation of complexes between an ion and a polar molecule or between highly polar systems is presented.The formula is entirely electrostatic and the expression used is verified by means of perturbation theory.This formula is test- ed for several ion-molecule and molecule-molecule pairs.It is also applied to estimate the heat of hydration of simple salts.
基金financially supported by the National Natural Science Foundation of China(No.52101012)the Natural Science Foundation of Hebei Province,China(No.E202302154)。
文摘Refractory high-entropy alloys(RHEAs)demonstrate exceptional high-temperature performance,extending their application potential beyond superalloys.Understanding the precise phase stability in RHEAs is crucial for designing materials and microstructures with optimized properties.This study establishes a thermodynamic database for the Mo–Nb–Ta–W–Hf–Zr system within a third-generation(3rd-generation)thermodynamic framework,enabling the prediction of phase stabilities in different RHEAs.Initially,a third-generation thermodynamic model was proposed for solid and liquid phases in stable and metastable states,applied to Mo,Nb,Ta,W,Hf,and Zr elements to ensure lattice stability across the temperature range.Subsequently,9 sub-binary and 10 subternary systems within the Mo–Nb–Ta–W–Hf–Zr system were thermodynamically modeled under the 3rd-generation thermodynamic framework,demonstrating that the calculated results agree well with the measurements.By leveraging the optimized binary and ternary coefficients,a thermodynamic database for Mo–Nb–Ta–W–Hf–Zr was established applying the calculation of phase diagram approach.The reliability of this database was confirmed through equilibrium thermodynamic calculations as well as non-equilibrium solidification simulations in the Mo Nb Ta WZr alloys,exhibiting agreement with the experimental data.Ultimately,the database was utilized to predict phase stability in various RHEAs within the Mo–Nb–Ta–W–Hf–Zr system.The current predictions suggest that the precipitation temperatures of hexagonal close-packed_A3 and C15 Laves phases are relatively high,mostly above 1000 K,whereas that of the B2 phase is below 928 K.With an increase in the number of elements,the precipitation behavior in the alloys tends to become more complex,leading to the formation of multiple precipitated phases.
