Influence Of Phase Difference Research Articles

Evolution of flow structure from a coaxial synthetic jet

• Influence of phase differences (∅) on novel coaxial synthetic jet (CSJ) is studied. • Azimuthal instability widens the jet for ∅ = 45°, and 90°. • Vortex pairing results in a strong jet for ∅ = 180°. • Entrainment ability of CSJ is high compared to single cavity synthetic jets. • Modulation of CSJ can be achieved with ∅ without investing any extra power. In this work, we propose and demonstrate a novel coaxial synthetic jet (CSJ) in which two cavities are arranged coaxially with 0° orientation angle with inner and annular orifices of equal hydraulic diameter. The flow behavior of the CSJ is studied at a low Reynolds number; Re = 135. The Navier-Stokes equations are solved (Direct Numerical Simulation) with the finite volume solver of openFoam, an open-source platform for numerical simulations. During the evolution of CSJ, two vortex rings IVR (inner vortex ring), and AVR (annular vortex ring), which are single toroid and double toroid in nature, are emanated from inner and annular orifices, respectively. Both the inner and annular jets are operated at equal mass fluxes. The evolution and interaction of the IVR, and AVR are studied by providing five-phase differences (∅ = 0°, 45°, 90°, 135°, and 180°) between the inner and outer diaphragms, and also its influence on the nature of the CSJ is highlighted. The phase-averaged and time-averaged flow fields are analyzed, and the CSJ is compared with the single cavity synthetic jet (SJ) at Re = 135, which is obtained by operating the inner cavity and annular cavity alone. The CSJ with ∅ = 0° reveals a wide and strong jet as compared to the single cavity SJ. The pairing of IVR and AVR results in a narrow and strong jet for ∅ = 180° as compared to ∅ = 0°. Merging and pulling mechanisms in case of ∅ = 45° and 90° enhances the azimuthal instability resulting in a wide and strong jet as compared to ∅ = 0°. A significant increase in the integrated jet area is observed for CSJ, which evidences the increase in entrainment ability of the CSJ. This novel device may find wide applicability for various engineering applications.

Influence of Phase Differences and Frequency Ratios of Oscillating Foil in Periodic Flow on Thrust and Lift Coefficients

We investigated the phase difference and frequency ratio effect on the thrust and lift coefficient of oscillating foil in a periodic flow. The periodic flow is the freestream oscillating in the streamwise direction. The frequency ratio is the ratio of foil frequency to freestream one. The thrust and lift coefficients were obtained using OpenFOAM v8 under the conditions of Reynolds number of 4066 and frequency ratio of 1, 2, and 3. We found that the thrust increases with increasing frequency ratio. Furthermore, the effect of phase difference on lift coefficient is relatively small at the frequency ratio of 2 and 3 under the present condition. We also found the correlation between forces and wake velocity.

A stress gradient-based fatigue life prediction method for multiaxial notched specimen considering additional hardening effect

In this paper, the damage parameter considering stress field distribution near the notch root is employed to overcome the deficiency of the equivalent stress method (ESM) ignoring the influence of stress gradient, and a new multiaxial fatigue life prediction method is then developed taking into account stress gradient effects and additional hardening effects. Firstly, the equivalent stress distribution on the critical plane is analyzed using the finite element method (FEM), and the equivalent stress field intensity of fatigue damage affected area is defined as the multiaxial fatigue damage parameter to estimate the fatigue life of notched specimens. Secondly, a new non-proportional additional hardening coefficient is defined to consider the influence of phase difference and material characteristics on multiaxial fatigue life. Finally, in order to verify the reliability of the proposed model, the estimated lives using the proposed method and the equivalent stress method are compared with the test life, and the comparison results show that the accuracy of the proposed method considering stress gradient effect and additional hardening effect is higher than that of the equivalent stress method under proportional and non-proportional loading.

The influence of phase difference on the effect of multi-beam interference processing

The influence of phase difference in laser interference lithography system is often ignored by researchers. In this paper, we simulated the interference process of dual-beam, three-beam and four-beam, and the influence of phase difference on the interference effect was discussed in detail. The simulation results show that in the process of dual-beam and three-beam interference, the change of phase difference causes the shift of the interference pattern but does not change the laser intensity distribution of the interference field, and has no effect on the actual interference processing; while in the process of four-beam interference, the change of phase difference can change the laser intensity of the interference field. Based on this, we built a four-beam interference processing system with dual-channel mutual injection solid-state laser as the laser source to process aluminum materials. The phase of the beam is changed by adjusting the optical path of the output laser, and the interference processing effect is observed when there are different phase differences between the beams. The experimental results show that in the process of four-beam interference processing, when the phase difference between beams is not zero, the interference processing will be greatly affected, and the processing results will appear some phenomena, such as small depth of concave holes, irregular shape, unclear boundary between concave holes and so on.

Influence of phase difference between kinematic and inertial loads on seismic behaviour of pile foundations in layered soils

A series of dynamic centrifuge experiments was conducted on model pile foundations embedded in a two-layered soil profile consisting of soft-clay layer underlain by dense sand. These experiments were specifically designed to investigate the individual effect of kinematic and inertial loads on a single pile and a 3 × 1 row pile group during model earthquakes. It was observed that the ratio of free-field soil natural frequency to the natural frequency of structure might not govern the phase relationship between the kinematic and inertial loads for pile foundations as reported in some previous research. The phase relationship obtained in this study agrees well with the conventional phase variation between the force and displacement of a viscously damped simple oscillator subjected to a harmonic force. Further, as expected, the pile accelerations and bending moments can be smaller when the kinematic and inertial loads act against each other compared to the case when they act together on the pile foundations. This study also revealed that the peak kinematic pile bending moment will be at the interface of soil layers for both single pile and pile group. However, in the presence of both kinematic and inertial loads, the peak pile bending moment can occur either at the shallower depths or at the interface of soil layers depending on the pile cap rotational constraint.

A new multiaxial fatigue life prediction model considering additional hardening effect

The established linear fatigue life prediction model based on the Miner rule has been widely applied to fatigue life prediction under constant amplitude uniaxial and multiaxial loading. Considering the physical significance of crack formation and propagation, a multiaxial equivalent linear fatigue life prediction model is put forward based on Miner rule and critical plane method under constant amplitude loading. The essence of this approach is that the equivalent strain, which consists of the shear strain and normal strain on the critical plane, replaces the relevant parameter of uniaxial nonlinear fatigue damage model. The principal axes of stress/strain rotate under non-proportional loading. Meanwhile, the microstructure of material and slip systems change, which lead to additional hardening effect. The ratio of cyclic yield stress to static yield stress is used to represent the cyclic hardening capacity of material, and the influence of phase difference and loading condition on the non-proportional hardening effect is considered. The multiaxial fatigue life is predicted using equivalent stain approach, maximum shear stain amplitude model, CXH model, and equivalent multiaxial liner model under proportional and/or non-proportional loading. The smooth and notched fatigue specimens of four kinds of materials (Q235B steel, titanium alloy TC4, Haynes 188, and Mod.9Cr-1Mo steel) are used in the multiaxial fatigue experiments to verify the proposed model. The predicted results of these materials are compared with the test results, and the results show that these four models can achieve good effect under proportional loading, but the proposed model performs better than the other three models under non-proportional loading. Meanwhile, it also verifies that the proposed enhancement factor can reflect the influence of phase difference and material properties on additional hardening.

Investigation on the thermoacoustic conversion characteristic of regenerator

Abstract Regenerator is the core component in the regenerative heat engines, such as thermoacoustic heat engine, and Stirling heat engine. The regenerator has a porous configuration, in which the thermoacoustic effect happens between the working gas and solid wall converting heat into acoustic work. In this paper, a novel experimental setup was developed to investigate the thermoacoustic conversion characteristic of the regenerator. In this system, two linear motors acted as compressors to provide acoustic work for the regenerator and the other two linear motors served as alternators to consume the acoustic work out of the regenerator. By changing the impedance of the alternators, the phase difference between the volume velocities at the two ends of the regenerator could be varied within a large range. In the experiments, the influence of phase difference, heating temperature and different materials on the performance of the regenerator were studied in detail. According to the experimental results, the output acoustic power increased when the phase difference between velocities of the compression and expansion pistons increased within this phase angle range. And the thermoacoustic efficiency had different optimum values with different heating temperatures. Additionally, it also shows that flow resistance and heat transfer area were very important to the performance. In the experiments, a maximum output acoustic power of 715 W and a highest thermoacoustic efficiency of 35.6% were obtained with stack and random fiber type regenerators respectively under 4 MPa pressurized helium and 650 °C heating temperature. This work provides an efficient way to investigate the thermoacoustic conversion characteristic of the regenerator. It also provides some clues to the regenerator design.

Experimental Research on Isolation Vibration Effect of Engine Suspension Based on Power Flow

The acceleration and force sensors are taken as the measurement parameter,vibration power flow analysis is conducted to the data collected using MATLAB software,the results show that validity of engine suspension vibration is intuitively judged using the power flow,it is a evaluation index,moreover,it is not only convenient measurement,but also the influence of phase difference between the measured parameters to vibration isolation effect is not needed consider.

Study of the Multiaxial Fatigue Life Influencing Factors Based on the Critical Plane Approach

The tension-torsion thin walled tube specimens were used as the researching object in this paper. The method of determination to the critical plane which has the maximum normal strain and maximum shear strain was expounded. The strain state on the critical plane under non-proportional loading was analyzed, and the unified prediction model was used to calculate the fatigue life. In order to research the influence of phase difference on fatigue life under the non-proportional loading, the relation of the equivalent strain and the phase difference in different positive strain amplitude and different strain amplitude ratio were analyzed. It’s found that the dangerous phase difference which has the shortest fatigue life is in direct relation with the strain amplitude ratio. The general formula of dangerous phase difference is presented. Through the material mechanics performance and fatigue parameters of uniaxial stress state, the coefficients in the formula can be obtained and the coefficients of 15 kinds of common materials are given for practical application.

Polarization State Evolution in Fibre Polarization TransformerInfluenced by Phase Difference

In accordance with the intrinsic structure of controllably-spunbirefringent-fibre-based fibre polarization transformer (FPT), theJones vector is calculated from point to point along the polarizationtransforming fibre by the cascade differential phase retarder model. Itis the first time using this concise method to examine thephase-difference effect on the evolution of state of polarization (SOP)inside this special fibre component. Both the extinction ratio andorientation angle of SOP are calculated to give out a whole evolutionhistory from linear polarization light at the slow spun end into circularpolarization light at the fast spun end, and vice versa. The influence ofphase-difference is discussed on the polarization transformingperformance and further referential conclusion is provided for designand test of the FPT component.

Phase- and helicity-dependent effects in three-color ionization

AbstractWe study the two-photon ionization of the hydrogen atom from its ground state by a three-color electromagnetic field consisting of a superposition of an IR laser and two of its consecutive odd harmonics of order 2p−1 and 2p+1, withp a positive integer and constant relative phase difference. The ionization process due to the net absorption of the energy 2pħω (ω being the IR laser frequency) is considered. The influence of phase difference and helicity on the azimuthal angular distribution of the ejected photoelectrons is illustrated in the case in which the two harmonics have identical polarizations. Phase effect on the alignment of the differential ionization rate is also investigated.