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Centrifugal force is often used as an exciting force for fruit vibration harvest. However, the magnitude of centrifugal force varies quadratically with angular velocity. When the frequency of excitation force remains constant, the amplitude of vibration force cannot be freely adjusted. This study achieves decoupling of the amplitude and frequency of centrifugal force by varying the eccentricity of the eccentric block. Different combinations of eccentric blocks with varying quantities and parameters enable the creation of different types of centrifugal force amplitude–frequency decoupling exciters. Both the amplitude and frequency of excitation force produced by these exciters can be freely adjusted. Furthermore, a physical prototype of a symmetrical dual eccentric block exciter with centrifugal force amplitude–frequency decoupling is developed and tested. It is found that when the exciter frequency or excitation force amplitude remains constant, the vibration acceleration amplitude generated by the exciter changes by adjusting the eccentricity of the eccentric blocks. As the eccentricity of the eccentric blocks decreases, their moment of inertia and kinetic energy decrease. Utilizing mechanisms to adjust the eccentricity of the eccentric block's center of mass to the rotation axis achieves the dynamic adjustment of the size and frequency of centrifugal force. [ABSTRACT FROM AUTHOR]

Introduction. Forward plate compactors are surface soil compaction machines with a flat operating device, which are usually equipped with a single-shaft vibration exciter. Forward plate compactors may be driven by gasoline, diesel or electric engines. When designing and modernizing forward plate compactors, a problem of technical specifications justification may arise, including such parameters as exciting force, vibration exciter oscillation frequency, engine power, base plate width, etc. This statistical analysis of plate compactors with different types of engines was carried out to summarize manufacturers practices and reveal correlations between the technical specifications of forward plate compactors.Materials and methods. This research is based on the information presented on the official websites of forward plate compactors manufacturers and their dealers. 644 models of forward plate compactors were scrutinized. Regression equations and correlation coefficients were derived using Microsoft Excel software.Results. Parameters ranges for forward plate compactors with different types of engines were determined. Regression equations of correlations between oscillation frequency, exciting force, engine power, base plate width, relative exciting force and mass of forward plate compactors with different types of engines were derived, as well as the corresponding correlation coefficients. It was revealed, that most parameters have low or very low correlation coefficient, regardless of the engine type.Conclusion. The ranges of the technical specifications of diesel and gasoline forward plate compactors are quite close to each other. The parameters ranges of electric plate compactors, in most cases, are beyond the ranges of gasoline and diesel plate compactors. Low correlation coefficients and a large scatter of parameters indicate that manufacturers do not have a methodology for justification of the technical specifications of forward plate compactors. Results of the study may be used when clarify ranges of parameters and formulate requirements for a mathematical model of vibration plates behavior.

Centrifugal force is often used as an exciting force for fruit vibration harvest. However, the magnitude of centrifugal force varies quadratically with angular velocity. When the frequency of excitation force remains constant, the amplitude of vibration force cannot be freely adjusted. This study achieves decoupling of the amplitude and frequency of centrifugal force by varying the eccentricity of the eccentric block. Different combinations of eccentric blocks with varying quantities and parameters enable the creation of different types of centrifugal force amplitude–frequency decoupling exciters. Both the amplitude and frequency of excitation force produced by these exciters can be freely adjusted. Furthermore, a physical prototype of a symmetrical dual eccentric block exciter with centrifugal force amplitude–frequency decoupling is developed and tested. It is found that when the exciter frequency or excitation force amplitude remains constant, the vibration acceleration amplitude generated by the exciter changes by adjusting the eccentricity of the eccentric blocks. As the eccentricity of the eccentric blocks decreases, their moment of inertia and kinetic energy decrease. Utilizing mechanisms to adjust the eccentricity of the eccentric block’s center of mass to the rotation axis achieves the dynamic adjustment of the size and frequency of centrifugal force.

ObjectiveThe appendages of a submarine affect the wake field at the propeller disk, which in turn affects the exciting force characteristics of the propeller. Grasping the influence law of the wake field on the exciting force is helpful for the low-excitation force design of submarines and propellers. MethodBased on the Suboff Model and INSEAN E1619 propeller, the RANS method is used to numerically simulate the propeller exciting force under wake fields affected by different appendages, and the harmonic analysis method is used to quantitatively characterize the wake fields at the propeller disk. The mechanism of the linear spectrum exciting force is revealed by combining the distribution characteristics of the transient flow field of the propeller. ResultsThe results show that the distribution of each order of the harmonic components of the wake field is consistent with the distribution of a single-blade linear spectrum exciting force, and the relative amplitude of the single-blade exciting force in its main frequency is basically equal to that of a seven-blade propeller. The harmonic components of circumferential symmetrical rudders to the wake field are mainly concentrated on the fourth and eighth orders, and have little effect on the exciting force of a seven-blade propeller; however, fairwaters influence the harmonic components of the wake field and have a major effect on the exciting force of a seven-blade propeller. ConclusionThe influence of rudders on propeller exciting force is less than that of fairwaters. In order to improve the exciting force characteristics of propellers, the optimization of submarine fairwaters should be emphasized.

There are many kinds of assembly structures in heavy-duty gas turbine compressor stator blades which have significant influence on the complex damping vibration characteristics. At present, compressor design is becoming more and more compact, so it is very meaningful to accurately obtain stator blade vibration characteristics of structures with contact damping. Firstly, a fretting slip friction dynamic model was introduced, and then a vibration analysis model of the compressor stator blade with outer ring structure was established based on the slip friction theory. Then, the vibration response of the compressor stator blade was obtained according to various working conditions, and the main factors affecting the vibration characteristics of the stator blade were revealed. Finally, the vibration response of the blade under a particular exciting force condition was simulated. The results show that the damping vibration characteristics of the compressor stator blades were affected by the excitation force and the normal load of the contact surface. The vibration response curve of the stator blade and the equivalent stiffness coefficient of the contact surface were analyzed, and the friction motion of the contact surface changed with the change of the working condition. The model can simulate the nonlinear vibration characteristics of stator blades. This method provides a reference for the vibration safety analysis of compressor stator blades. [ABSTRACT FROM AUTHOR]

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We consider a device which consists of a floating structure over a cylindrical plate placed at a finite height from the impermeable ocean floor. This paper developes the interaction of linear water waves with such a device. The whole fluid domain is divided into a number of sub-domains and boundary value problems are formulated for each identified sub-domain. The channel multipoles, separation of variables and matched eigenfunction expansion methods allow us to solve boundary value problems for the diffracted velocity potentials in each sub-domain. We investigate the wave forces exerted on the proposed device. Consequently, the effects of the various parameters, e.g., drafts, radii, the gap between the cylinders and mainly channel width of the device on the wave forces exerted by the cylinders are presented graphically. We observe a small oscillation nature near the peak value of the exciting force for the particular value of channel width w=2.4m. The peak value of the exciting forces occurs near the wavenumber kr1=1.0 for different width of the channel walls. The obtained results are compared with some available results, and it shows a good agreement between the obtained and available results.

In this study, a coupling method of the higher order boundary element method and the eigenfunction expansion method is applied to investigate the diffraction and radiation problems of a floating body over an uneven seabed under the assumption of linear small-amplitude wave theory. The wave exciting forces and hydrodynamic coefficients are calculated for a floating rectangular box. It is found that the curves of the wave exciting forces and hydrodynamic coefficients versus frequency become fluctuating as the horizontal length L and vertical height D of the sloping seabed gradually increase. The period of the fluctuations decreases with the increase of L , and the magnitude of the fluctuations increases with the increase of D. The mechanism of the fluctuation phenomenon is then examined, and found that it is associated with the wave reflection from the slope seabed. With increasing horizontal scale L and vertical scale D of the sloping seabed, the amplitude and phase of the reflection wave change, which leads to the combined action of the incident, scattering and reflection waves fluctuating with the wave frequency. [ABSTRACT FROM AUTHOR]

There are many kinds of assembly structures in heavy-duty gas turbine compressor stator blades which have significant influence on the complex damping vibration characteristics. At present, compressor design is becoming more and more compact, so it is very meaningful to accurately obtain stator blade vibration characteristics of structures with contact damping. Firstly, a fretting slip friction dynamic model was introduced, and then a vibration analysis model of the compressor stator blade with outer ring structure was established based on the slip friction theory. Then, the vibration response of the compressor stator blade was obtained according to various working conditions, and the main factors affecting the vibration characteristics of the stator blade were revealed. Finally, the vibration response of the blade under a particular exciting force condition was simulated. The results show that the damping vibration characteristics of the compressor stator blades were affected by the excitation force and the normal load of the contact surface. The vibration response curve of the stator blade and the equivalent stiffness coefficient of the contact surface were analyzed, and the friction motion of the contact surface changed with the change of the working condition. The model can simulate the nonlinear vibration characteristics of stator blades. This method provides a reference for the vibration safety analysis of compressor stator blades.

The cavitation performance of an oblique flow field is different from that under a pure axial flow field. This study analyzed the hydrodynamic performance, bearing force, and tip clearance flow field under different rotating speeds and different cavitation numbers in an oblique flow field. Furthermore, this study proposed a hybrid deep learning model CNN-Bi-LSTM to quickly and accurately predict the bearing force of a pump-jet propulsor (PJP), which will solve the problem of time-consuming calculation and consumption of considerable computing resources in traditional computational fluid dynamics. The Shear–Stress–Transport model and Reynolds-averaged Navier–Stokes equations were utilized to procure the training and testing datasets. The training and testing datasets were reasonably divided in the ratio of 7:3. The results show that the propulsion efficiency decreased more obviously under higher rotating speed conditions, with a maximum decrease of up to 13.59%. The small cavitation numbers 1.4721 and high oblique angle significantly impacted the efficiency reduction; the maximum efficiency loss exceeded 20%. Thus, a small cavitation number 1.4721 is extremely detrimental to the propulsion efficiency of the PJP due to the large cavitation area. Moreover, the intensity of the tip clearance vortex continuously increased with the rotating speed. The CNN-Bi-LSTM deep model successfully predicted the phase difference and trend change of the propulsor bearing force under different conditions. The prediction difference was large at the crest and trough of the bearing force, but it is within the acceptable error range. [ABSTRACT FROM AUTHOR]

By studying dynamic characteristics of the leaf spring system, a new elastic component is designed to reduce the working load and to a certain extent to ensure the linearity as well as increase the amplitude in the vertical and horizontal directions in vibration screen. The modal parameters, amplitudes, and amplification factors of the leaf spring system are studied by simulation and experiment. The modal results show that the leaf spring system vibrates in horizontal and vertical directions in first and second mode shapes, respectively. It is conducive to loosening and moving the particles on the vibration screen. In addition, it is found that the maximum amplitude and amplification factor in the horizontal direction appear at 300 r/min (5 Hz) while those in the vertical direction appear at 480 r/min (8 Hz), which are higher than those in the disc spring system. Moreover, the amplitude of the leaf spring system increases proportionally with the increase of exciting force while the amplification factors are basically the same under different exciting forces, indicating the good linearity of the leaf spring system. Furthermore, the minimum exciting force occurs in the leaf spring system under the same amplitude by comparing the exciting force among different elastic components. The above works can provide guidance for the industrial production in vibration screen. [ABSTRACT FROM AUTHOR]

As an important component in the automobile drive system，the performance of drive shaft has influence on NVH performance of the whole vehicle. In order to improve the influence of drive shaft on NVH performance，a design scheme to replace the intermediate universal joint of the drive shaft with Birfield CV joint is proposed based on the transmission characteristics analysis of universal joint and Birfield CV joint. The exciting forces at the inter-mediate support of three universal joint for two kinds of the drive shaft are solved and analyzed respectively. Results show that， due to the stable additional bending moment，the Birfield CV joint can reduce the exciting force at the intermediate support as well as the body of the vehicle，thus the NVH performance of the whole vehicle is improved.

Here, we examine the exciting forces for an arrangement of two coaxial vertical cylinders—a riding porous cylinder and a submerged bottom-mounted solid rigid cylinder. We take up two cases: first we consider a hollow porous cylinder at the top and secondly a solid porous cylinder at the top, and for both the cases, there is a solid rigid cylinder placed at the bottom. The present configuration may be observed as a wave energy device which can tap and transfer ocean wave energy to be used as non-conventional energy. A three-dimensional representation of the problem is developed, based on the familiar method of eigenfunction expansion under the assumption of linear water wave theory. The important porous boundary condition on the porous boundary can be defined by means of Darcy's law. The matching conditions across the linear interface between the adjacent fluid domains can be obtained through the continuity of pressure and velocity. Subsequently, after solving a system of linear equations, exciting forces and wave run-up for the upper and lower cylinders are calculated through the evaluated velocity potentials. Various numerical experiments show the effect of different parameters, such as porous coefficients, draft ratio, the ratio of radii of the upper and lower cylinders and the water depth on exciting force and wave run-up. It is also shown that higher porosity value of the upper cylinder results in higher energy loss conforming to the wave dissipation by the structure. The obtained results establish that appropriate values of different parameters may be considered in designing practical structures in ocean. Successful validation of the present model carried out with an available established one confirms the efficiency of the present model. The present system may be considered as a wave energy device in other problems where it can tap and transfer ocean wave energy to be used as non-conventional energy. [ABSTRACT FROM AUTHOR]

The cavitation performance of an oblique flow field is different from that under a pure axial flow field. This study analyzed the hydrodynamic performance, bearing force, and tip clearance flow field under different rotating speeds and different cavitation numbers in an oblique flow field. Furthermore, this study proposed a hybrid deep learning model CNN-Bi-LSTM to quickly and accurately predict the bearing force of a pump-jet propulsor (PJP), which will solve the problem of time-consuming calculation and consumption of considerable computing resources in traditional computational fluid dynamics. The Shear–Stress–Transport model and Reynolds-averaged Navier–Stokes equations were utilized to procure the training and testing datasets. The training and testing datasets were reasonably divided in the ratio of 7:3. The results show that the propulsion efficiency decreased more obviously under higher rotating speed conditions, with a maximum decrease of up to 13.59%. The small cavitation numbers 1.4721 and high oblique angle significantly impacted the efficiency reduction; the maximum efficiency loss exceeded 20%. Thus, a small cavitation number 1.4721 is extremely detrimental to the propulsion efficiency of the PJP due to the large cavitation area. Moreover, the intensity of the tip clearance vortex continuously increased with the rotating speed. The CNN-Bi-LSTM deep model successfully predicted the phase difference and trend change of the propulsor bearing force under different conditions. The prediction difference was large at the crest and trough of the bearing force, but it is within the acceptable error range.

A novel method of reducing the electromagnetic exciting force of PMBLDCM (permanent magnet brushless DC motor) by optimising the pole embrace is proposed. Firstly, the expression of the Fourier decomposition coefficient of the permanent magnet's magnetomotive force is derived, and electromagnetic vibration force under no load condition is determined by the classical noise principle. The electromagnetic force in different pole embrace with radial magnetisation and parallel magnetisation is also calculated. Furthermore, a novel approach is brought out to suppress the exciting force which plays an important role in the electromagnetic noise by selecting the pole arc coefficient reasonably. The frequency spectrum of the main order excitation force wave is obtained by space and time Fourier decomposition. The results of finite element calculation proved the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient exciting force of equipment for large full-scale wind turbine blade fatigue testing, the influence of gravity on the performance of excitation equipment and fatigue damage evaluation of the different positions of wind turbine blades are analyzed. With the multi-excitation loading in the horizontal direction, the actuator force of the excitation equipment does not need to overcome the gravity of the dynamic mass, w'hich directly outputs the exciting force of the system vibration. The excitation efficiency of the equipment is 77% higher than that of the vertical load. The gravity moment of the horizontal loading mode is perpendicular to the loading direction. That is, the mean load in the flapwise direction is zero. The weight of excitation equipment could replace the tuning mass on the condition that the self-weight of equipment is reduced by the multi-excitation mode, which helps the excitation equipment play the comprehensive function of excitation equipment and tuning mass. At the same time, the gravity moment in the edgewise direction will be decreased by 17.0%-22.5% under the multi-excitation horizontal loading mode. In the vertical loading mode, the gravity moment is the mean load, which only increases fatigue damage accumulation by 15.6%. By comparing the role of gravity in the excitation equipment and fatigue damage evaluation, the multi-excitation horizontal loading mode has more advantage to performance the exciting force than the contribution of gravity to the fatigue damage accumulation in the vertical loading mode. Through the fatigue testing of multi-excitation horizontal loading, the potential of excitation equipment is explored, and the problem of insufficient exciting force in large fullscale wind turbine blade fatigue testing will be solved. [ABSTRACT FROM AUTHOR]

Ａｉｍｉｎｇ ａｔ ｔｈｅ ｄｉｆｆｉｃｕｌｔｙ ｉｎ ｃａｌｃｕｌａｔｉｎｇ ｔｈｅ ｓｔｒｅｎｇｔｈ ｏｆ ｃｏｍｐｏｎｅｎｔｓ ａｎｄ ａｄｊｕｓｔｉｎｇ ｔｈｅ ｐｒｏｄｕｃｔｉｏｎ ｐａｒａｍｅｔｅｒｓ ｏｆ ｄｉｆｆｅｒｅｎｔｉａｌ ｄｒｙ ｓｅｐａｒａ￣ ｔｏｒꎬ ｔｈｅ ｋｉｎｅｍａｔｉｃ ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ｏｆ ｔｈｅ ｓｏｒｔｉｎｇ ｂｅｄ ｏｆ ｄｉｆｆｅｒｅｎｔｉａｌ ｄｒｙ ｓｅｐａｒａｔｏｒ ｗａｓ ｓｔｕｄｉｅｄ. Ｔｈｅ ｍｅｃｈａｎｉｃａｌ ｍｏｄｅｌ ａｎｄ ｄｉｆｆｅｒｅｎｔｉａｌ ｅｑｕａｔｉｏｎ ｏｆ ｍｏｔｉｏｎ ｏｆ ｔｈｅ ｓｅｐａｒａｔｉｎｇ ｂｅｄ ｗｅｒｅ ｅｓｔａｂｌｉｓｈｅｄ ｂｙ ｕｓｉｎｇ ｔｈｅ ｔｈｅｏｒｙ ｏｆ ｍｅｃｈａｎｉｃａｌ ｄｙｎａｍｉｃｓ. Ｔｈｅ ｉｎｆｌｕｅｎｃｅ ｏｆ ｐｈａｓｅ ａｎｇｌｅꎬ ａｎｇｕｌａｒ ｆｒｅｑｕｅｎｃｙ ｒａｔｉｏ ａｎｄ ｅｃｃｅｎｔｒｉｃ ｍａｓｓ ｍｏｍｅｎｔ ｒａｔｉｏ ｏｎ ｄｉｆｆｅｒｅｎｔｉａｌ ｃｏｅｆｆｉｃｉｅｎｔ ｗｅｒｅ ｓｔｕｄｉｅｄ ｂｙ ｎｕｍｅｒｉｃａｌ ｓｉｍｕｌａｔｉｏｎ. Ｔｈｅ ｒｅｓｕｌｔｓ ｓｈｏｗ ｔｈａｔ ｔｈｅ ｅｘｃｉｔａｔｉｏｎ ｆｏｒｃｅ ｏｎ ｔｈｅ ｃｏｍｐｏｎｅｎｔｓ ｏｆ ｔｈｅ ｄｒｙ ｓｅｐａｒａｔｏｒ ｉｓ ａ ｃｏｍｐｏｓｉｔｅ ｈａｒｍｏｎｉｃ ｌａｗ ｄｒｉｖｅｎ ｂｙ ｔｗｏ ｓｉｍｐｌｅ ｈａｒｍｏｎｉｃ ｆｏｒｃｅｓ. Ｗｈｅｎ ｔｈｅ ｉｎｉｔｉａｌ ｐｈａｓｅ ａｎｇｌｅ ｏｆ ｔｈｅ ｅｘｃｉｔｅｒ ｉｓ １８０ ｄｅｇｒｅｅｓꎬ ｔｈｅ ｒａｔｉｏ ｏｆ ａｎｇｕｌａｒ ｆｒｅｑｕｅｎｃｙ ｏｆ ｈｉｇｈ ｓｐｅｅｄ ｓｈａｆｔ ｔｏ ｌｏｗ ｓｐｅｅｄ ｓｈａｆｔ ｉｓ ２ꎬ ａｎｄ ｔｈｅ ｒａｔｉｏ ｏｆ ｅｃｃｅｎｔｒｉｃ ｍａｓｓ ｍｏｍｅｎｔ ｉｓ ａｂｏｕｔ １/４ꎬ ｔｈｅ ｄｉｆｆｅｒｅｎｔｉａｌ ｃｏｅｆｆｉｃｉｅｎｔ ｉｓ ｔｈｅ ｌａｒｇｅｓｔꎬ ｗｈｉｃｈ ｉｓ ｍｏｓｔ ｃｏｎｄｕｃｉｖｅ ｔｏ ｉｍｐｒｏｖｉｎｇ ｔｈｅ ｓｏｒｔｉｎｇ ｅｆｆｉｃｉｅｎｃｙ ｏｆ ｔｈｅ ｄｒｙ ｓｅｐａｒａｔｏｒ. Ｔｈｅ ｒｅｓｅａｒｃｈ ｒｅｓｕｌｔｓ ｈａｖｅ ｃｅｒｔａｉｎ ｇｕｉｄｉｎｇ ｓｉｇｎｉｆｉｃａｎｃｅ ｆｏｒ ｔｈｅ ｄｅｓｉｇｎ ｏｆ ｄｉｆｆｅｒｅｎｔｉａｌ ｄｒｙ ｓｅｐａｒａｔｏｒ ａｎｄ ｔｈｅ ａｄｊｕｓｔｍｅｎｔ ｏｆ ｐｒｏｄｕｃｔｉｏｎ ｐａｒａｍｅｔｅｒｓ. [ABSTRACT FROM AUTHOR]

Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface. To popularize this technique, it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage. For this purpose, an electric vibrator was developed. With this vibrator, electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit. The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source, which produces an axial-rotating exciting force at the bottom of the casing string. Then, the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method, and the response model of casing string to an electric vibrator was developed. Finally, the effects of casing string length, exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program. It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string, and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string. These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.

This article describes the simulation and experimental determination of the oscillation modes of a Coriolis Mass Flowmeter (CMF). The authors use the SolidWorks software to create a suitable model which is a double U-type of CMF. Based on SolidWorks software, the authors established the double-U tube model for CMF, adopted ANSYS-Workbench simulation software to make the modal analysis, and the exciting mode and Coriolis force mode of CMF are obtained by simulation. According to the results of modal analysis, the authors made the harmonic response analysis of the Flowmeter, got the displacement amplitude of the U-shaped tube excited by different frequency loads under the exciting force, and the maximum displacement amplitude at the resonant frequency was determined. Next, the authors use a laser vibrometer to perform an experimental modal test on the flowmeter. The result of the simulation of the finite element model was verified by modal test of the flowmeter. Provides an effective reference for CMF modelling and simulation in the future.

This article describes the simulation and experimental determination of the oscillation modes of a Coriolis Mass Flowmeter (CMF). The authors use the SolidWorks software to create a suitable model which is a double U-type of CMF. Based on SolidWorks software, the authors established the double-U tube model for CMF, adopted ANSYS-Workbench simulation software to make the modal analysis, and the exciting mode and Coriolis force mode of CMF are obtained by simulation. According to the results of modal analysis, the authors made the harmonic response analysis of the Flowmeter, got the displacement amplitude of the U-shaped tube excited by different frequency loads under the exciting force, and the maximum displacement amplitude at the resonant frequency was determined. Next, the authors use a laser vibrometer to perform an experimental modal test on the flowmeter. The result of the simulation of the finite element model was verified by modal test of the flowmeter. Provides an effective reference for CMF modelling and simulation in the future. [ABSTRACT FROM AUTHOR]

The acting forces between soil and potatoes in the process of harvesting by vibration loads are complicated. In order to study the effect of the exciting forces for the dynamic characteristics of potato conveying and vibration separation system, taking potatoes with soil on them and equivalent viscoelastic material as a whole, a mechanic model was establish for the potato conveying and separation system considering the sectional material forces between the potatoes, the soil and the shaker chain in the conveying, separating, crushing and screening process, and then analysis of the model was conducted by asymptotic method numerical integration. The results show that the dynamic characteristic of the conveying and separation system is more complicated under specific conditions, and the system motion is chaotic. The test further shows that the rational use of vibration can improve the separation rate of potato and soil, and improve the harvest quality. [ABSTRACT FROM AUTHOR]

Within the framework of linear water wave theory, the diffraction of water waves by a hollow circular cylinder in an infinite ocean depth is considered. The whole fluid domain is divided into two regions: interior and exterior regions. Using separation of variables technique, Fourier sine transform and Havelock's expansion theorem, the diffracted potentials in each region are obtained, and consequently the exciting forces and their phase angles are evaluated for different draft and different radius of the cylinder. It is observed that the forces attain higher values in the lower frequency range for higher draft and also for higher radius values. The free surface elevation for both exterior and interior regions is also discussed. As the distance from the cylinder surface increases, the elevation of waves reduces. All the observations are validated through suitable graphs. [ABSTRACT FROM AUTHOR]

A time-domain numerical algorithm based on the higher-order boundary element method and the iterative time-marching scheme is proposed for seakeeping analysis. The ship waves generated by a hull advancing at a constant forward speed in incident waves and the resultant diffraction forces acting on the hull are computed to investigate the hull-form effects on the hydrodynamic forces. A rectangular computational domain travelling at ship's speed is considered. An artificial damping beach for satisfying the radiation condition is installed at the outer portion of the free surface except the downstream side. An iterative time-marching scheme is employed for updating both kinematic and dynamic free-surface boundary conditions for numerical accuracy and stability. The boundary integral equation is solved by distributing higher-order boundary elements over the wetted body surface and the free surface. The hull-form effects on the naval hydrodynamics are investigated by comparing three different Wigley models. Finally, the corresponding unsteady wave patterns and the wave profiles around the hulls are illustrated and discussed. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (SCO2) is a vital working fluid in the application of power units and its high density helps to achieve a compact mechanical structure. Centrifugal compressors are of vital use in various kinds of equipment. In this paper, a SCO2 centrifugal compressor of large input power and mass flow rate is designed and numerically investigated. A thorough numerical analysis of the unsteady flow field in the centrifugal compressor is performed in ANSYS-CFX. The computation adopts hexahedral mesh, finite volume method, and the RNG k-ε two-equation turbulence model. Streamlines, temperature, pressure, and Mach number distributions at different time steps in one revolution period are covered to present the unsteady effect of turbomachinery. Meanwhile, the force on a single rotor blade is monitored to investigate the frequency components of exciting force, thus providing the foundation for vibration analysis. Moreover, the torque, output power, pressure ratio, and isentropic efficiency in the steady and the unsteady time-averaged condition are calculated and compared with the design condition to measure the validity of the design. In summary, the unsteady computation result reveals that the unsteady flow characteristics are prominent in the designed compressor and the design of impeller and diffuser meet the requirement. [ABSTRACT FROM AUTHOR]