The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate ...The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.展开更多
An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curv...An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β0, which is defined by β0 = τ/（2δ）1/2 with non-dimensional torsion r, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows： The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion （toroidal pipe） to a single vortex type after one of the twin-vortex gradually disappears as β0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β0, but changes its shape as β0 increases, and attains the shape similar to that in a straight circular pipe when ,β0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as ,β0 increases for small ,β0, and then increases after taking a minimum at ,β0 ≈ 1.4 as ,β0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at ,β0 ≈ 1.4.展开更多
In order to investigate the effect of sample size on the dynamic torsional behaviour of the 2A12 aluminium alloy. In this paper, torsional split Hopkinson bar tests are conducted on this alloy with different sample di...In order to investigate the effect of sample size on the dynamic torsional behaviour of the 2A12 aluminium alloy. In this paper, torsional split Hopkinson bar tests are conducted on this alloy with different sample dimensions. It is found that with the decreasing gauge length and thickness, the tested yield strength increases. However, the sample innerlouter diameter has little effect on the dynamic torsional behaviour. Based on the finite element method, the stress states in the alloy with different sample sizes are analysed. Due to the effect of stress concentration zone （SCZ）, the shorter sample has a higher yield stress. Furthermore, the stress distributes more uniformly in the thinner sample, which leads to the higher tested yield stress. According to the experimental and simulation analysis, some suggestions on choosing the sample size are given as well.展开更多
Taking a concrete frame supporting space structure as the research object,we systematically studied its lateral-torsion coupling effect of reverse problems in consistent earthquake excitation.Firstly,based on its reve...Taking a concrete frame supporting space structure as the research object,we systematically studied its lateral-torsion coupling effect of reverse problems in consistent earthquake excitation.Firstly,based on its reverse forms and features,we put forward a mechanical analysis model(flexibility layer model) and a calculation method using the response spectrum method and the weighted average method,and verified their validity and feasibility using case analysis.The result shows that the translation displacement change trend of the space structure is basically the same whether reverse exists in the supporting structure or not,but the supporting structure torsion has an effect on the displacement with a relative increase of 10%.展开更多
We investigate the effect of torsion on DNA condensation with the covalently closed circular DNA as the torsionconstrained system, using an atomic force microscope. It is found that there are two stages in the DNA con...We investigate the effect of torsion on DNA condensation with the covalently closed circular DNA as the torsionconstrained system, using an atomic force microscope. It is found that there are two stages in the DNA condensation process under torsional constraint. At the early stage, the low torsion will accelerate DNA condensation by promoting the formation of micro-loops or intersection structures; while at the later stage, the increasing torsion will slow it down by preventing the crosslinking of cisplatin and DNA since the DNA molecule becomes more rigid. Our results show the important role of torsion in DNA condensation and sheds new light on the mechanism for DNA condensation.展开更多
Torsional instability of an incompressible thermo-hyperelastic cylindrical rod, subjected to axial stretching and large torsions, is examined within the framework of finite elasticity. When the cylinder is stretched a...Torsional instability of an incompressible thermo-hyperelastic cylindrical rod, subjected to axial stretching and large torsions, is examined within the framework of finite elasticity. When the cylinder is stretched and twisted by a sufficiently large degree, a knot may form suddenly at one point. This inherent elastic instability is analyzed with the minimum potential energy principle and the critical values of torsion are obtained. The distribution of stresses as well as the tensile force and the torque are studied. Effect of tem- perature change is specifically discussed.展开更多
Simultaneous observations of the solar eclipse on 06/01/2011 were carried out using a Foucault pendulum and a torsion balance. The instruments were installed in a salt mine, where the interference was minimal. Both in...Simultaneous observations of the solar eclipse on 06/01/2011 were carried out using a Foucault pendulum and a torsion balance. The instruments were installed in a salt mine, where the interference was minimal. Both instruments clearly reacted to the eclipse. We conclude that these reactions should not be considered as being gravitational effects.展开更多
The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional...The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional and axial vibration, the actuating force applied on the piston, the actuating torque and force applied on the propeller is included. The governing equations of the model denote a strong nonlinear and non autonomous system. By numeric simulation, the dynamic response of the system to initial displacement and initial speed, variable moment of inertia, the pressure applied on the piston by combustion gas, the torque and the axial force applied on the propeller by fluid is researched respectively. According to the research results, the variable moment of inertia and coupling effect between torsional and axial vibration are the fundamental reason for nonlinear vibration. Different actuating factors can not only result in different frequency components of the response, but make the same frequency component have different vibration amplitude. The dynamic behavior of the system is not influenced obviously by the actuating torque and force applied on the propeller. There is obvious difference in sensitivity of the dynamic response in the different direction to the same actuating factor.展开更多
A CO<sub>2</sub> capture system without supercritical CO<sub>2</sub> was optimized for mixtures of hydrophobic room temperature ionic liquids (RTILs) and propanol. We tested RTILs using bis(tri...A CO<sub>2</sub> capture system without supercritical CO<sub>2</sub> was optimized for mixtures of hydrophobic room temperature ionic liquids (RTILs) and propanol. We tested RTILs using bis(trifluoromethanesulfonyl)imide, TFSI-, anion and four quaternary ammonium cations, two quaternary phosphonium cations, and one imidazolium cation. The addition of 2-propanol into the RTILs clearly promoted the capture of normal CO<sub>2</sub>(nCO<sub>2</sub>) at ambient temperature and pressure. When combined with 2-propanol, the most efficient RTILs for nCO<sub>2</sub> capture were N-butyl-N,N,N-trimethylammonium TFSI-. This enhancement of nCO<sub>2</sub> capture was not observed in RTIL mixtures with 1-propanol or in propanol mixtures containing other phosphonium- and imidazolium-based RTILs. The torsion angle of TFSI-, which was calculated using density functional theory, is thought to be related to high nCO<sub>2</sub> capture efficiently.展开更多
In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local...In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local method in this paper. Numerical results involving the distribution of shearing stresses olt cross-section and the torsional deformation and the interlaminar stresses near to free edges are given. If necessary elements discretization may be densely carried out only in the high stress gradient, region. Obviously, it requires less computer memory and computational time so that it offers an effective way for evaluating strength of laminated bars torsion with a greet number of layers.展开更多
文摘The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.
文摘An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β0, which is defined by β0 = τ/（2δ）1/2 with non-dimensional torsion r, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows： The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion （toroidal pipe） to a single vortex type after one of the twin-vortex gradually disappears as β0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β0, but changes its shape as β0 increases, and attains the shape similar to that in a straight circular pipe when ,β0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as ,β0 increases for small ,β0, and then increases after taking a minimum at ,β0 ≈ 1.4 as ,β0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at ,β0 ≈ 1.4.
基金Financial support is from the NSFC(Grant Nos.11602257,11472257,11272300,11572299)funded by the key subject"Computational Solid Mechanics"of the China Academy of Engineering Physics
文摘In order to investigate the effect of sample size on the dynamic torsional behaviour of the 2A12 aluminium alloy. In this paper, torsional split Hopkinson bar tests are conducted on this alloy with different sample dimensions. It is found that with the decreasing gauge length and thickness, the tested yield strength increases. However, the sample innerlouter diameter has little effect on the dynamic torsional behaviour. Based on the finite element method, the stress states in the alloy with different sample sizes are analysed. Due to the effect of stress concentration zone （SCZ）, the shorter sample has a higher yield stress. Furthermore, the stress distributes more uniformly in the thinner sample, which leads to the higher tested yield stress. According to the experimental and simulation analysis, some suggestions on choosing the sample size are given as well.
基金Funded by the Research on Damage Mechanism of the Spatial Dome-Reinforced Concrete Structures and Reduce Vibration System in West Area (No. 51068019)
文摘Taking a concrete frame supporting space structure as the research object,we systematically studied its lateral-torsion coupling effect of reverse problems in consistent earthquake excitation.Firstly,based on its reverse forms and features,we put forward a mechanical analysis model(flexibility layer model) and a calculation method using the response spectrum method and the weighted average method,and verified their validity and feasibility using case analysis.The result shows that the translation displacement change trend of the space structure is basically the same whether reverse exists in the supporting structure or not,but the supporting structure torsion has an effect on the displacement with a relative increase of 10%.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11674383,11774407 and 11874415the Key Research Program of Frontier Sciences of Chinese Academy of Sciences under Grant No QYZDB-SSW-SLH045+3 种基金the National Key Research and Development Program under Grant No 2016YFA0301500the Higher Educational Science and Technology Program of Shandong Province under Grant No J16LM06the Natural Science Foundation of Shandong Province under Grant No ZR2014AQ025the Program of Shandong Provincial Government International Exchanges
文摘We investigate the effect of torsion on DNA condensation with the covalently closed circular DNA as the torsionconstrained system, using an atomic force microscope. It is found that there are two stages in the DNA condensation process under torsional constraint. At the early stage, the low torsion will accelerate DNA condensation by promoting the formation of micro-loops or intersection structures; while at the later stage, the increasing torsion will slow it down by preventing the crosslinking of cisplatin and DNA since the DNA molecule becomes more rigid. Our results show the important role of torsion in DNA condensation and sheds new light on the mechanism for DNA condensation.
基金The project supported by the National Natural Science Foundation of China （10402018, 10272069） and Shanghai Key Project Program （Y0103） The English text was polished by Keren Wang.
文摘Torsional instability of an incompressible thermo-hyperelastic cylindrical rod, subjected to axial stretching and large torsions, is examined within the framework of finite elasticity. When the cylinder is stretched and twisted by a sufficiently large degree, a knot may form suddenly at one point. This inherent elastic instability is analyzed with the minimum potential energy principle and the critical values of torsion are obtained. The distribution of stresses as well as the tensile force and the torque are studied. Effect of tem- perature change is specifically discussed.
文摘Simultaneous observations of the solar eclipse on 06/01/2011 were carried out using a Foucault pendulum and a torsion balance. The instruments were installed in a salt mine, where the interference was minimal. Both instruments clearly reacted to the eclipse. We conclude that these reactions should not be considered as being gravitational effects.
文摘The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional and axial vibration, the actuating force applied on the piston, the actuating torque and force applied on the propeller is included. The governing equations of the model denote a strong nonlinear and non autonomous system. By numeric simulation, the dynamic response of the system to initial displacement and initial speed, variable moment of inertia, the pressure applied on the piston by combustion gas, the torque and the axial force applied on the propeller by fluid is researched respectively. According to the research results, the variable moment of inertia and coupling effect between torsional and axial vibration are the fundamental reason for nonlinear vibration. Different actuating factors can not only result in different frequency components of the response, but make the same frequency component have different vibration amplitude. The dynamic behavior of the system is not influenced obviously by the actuating torque and force applied on the propeller. There is obvious difference in sensitivity of the dynamic response in the different direction to the same actuating factor.
文摘A CO<sub>2</sub> capture system without supercritical CO<sub>2</sub> was optimized for mixtures of hydrophobic room temperature ionic liquids (RTILs) and propanol. We tested RTILs using bis(trifluoromethanesulfonyl)imide, TFSI-, anion and four quaternary ammonium cations, two quaternary phosphonium cations, and one imidazolium cation. The addition of 2-propanol into the RTILs clearly promoted the capture of normal CO<sub>2</sub>(nCO<sub>2</sub>) at ambient temperature and pressure. When combined with 2-propanol, the most efficient RTILs for nCO<sub>2</sub> capture were N-butyl-N,N,N-trimethylammonium TFSI-. This enhancement of nCO<sub>2</sub> capture was not observed in RTIL mixtures with 1-propanol or in propanol mixtures containing other phosphonium- and imidazolium-based RTILs. The torsion angle of TFSI-, which was calculated using density functional theory, is thought to be related to high nCO<sub>2</sub> capture efficiently.
文摘In view of rite effective elastic moduli theory([1]), analyzing the thick composite laminated bars subjected to an externally applied torque are presented by three-dimensional finite element (3-D FEM) and global-local method in this paper. Numerical results involving the distribution of shearing stresses olt cross-section and the torsional deformation and the interlaminar stresses near to free edges are given. If necessary elements discretization may be densely carried out only in the high stress gradient, region. Obviously, it requires less computer memory and computational time so that it offers an effective way for evaluating strength of laminated bars torsion with a greet number of layers.
