Effect of an Inclined Slots on the Power Consumption and Vortices Size in a Rushton Turbine Agitated Tank

Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and flow dynamics is essential to enhance operational performance and eliminate flow perturbations.Hence,the present research focuses on a numerical investigation of the impact of inclined slots with different angles installed at the side-wall of a cylindrical vessel equipped with a Rushton turbine.This study explores power consumption and vortex size while considering various rotation directions of the impeller with different rotation speeds.The numerical simulations are conducted for Reynolds numbers ranging from 104 to 105,using the RANS k-εturbulence model to govern the flow inside the stirred vessel,accounting for mass and momentum balances.The results have shown that the installation of slots reduces power consumption and vortex size compared to conventional vessel configu-rations.Moreover,increasing the slot angle from 0 to 32.5°further reduces energy consumption and vortex size,especially with negative rotation speeds.On the other hand,increasing the Reynolds numbers leads to a decrease in power consumption and an increase in vortex size.The present research therefore proposes a design for con-structing Rushton-turbine stirred vessels offering optimal operation,characterized by reduced energy consumption and minimized vortex size.

Five-phase Synchronous Reluctance Machines Equipped with a Novel Type of Fractional Slot Winding

Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are well known because of short end winding length,simple structure,field weakening sufficiency,fault tolerant capability and higher slot fill factor.The five-phase machines equipped with FSCW,are very good candidates for the purpose of designing motors for high reliable applications,like electric cars,major transporting buses,high speed trains and massive trucks.But,in comparison to the general distributed windings,the FSCWs contain high magnetomotive force(MMF)space harmonic contents,which cause unwanted effects on the machine ability,such as localized iron saturation and core losses.This manuscript introduces several new five-phase fractional slot winding layouts,by the means of slot shifting concept in order to design the new types of synchronous reluctance motors(SynRels).In order to examine the proposed winding’s performances,three sample machines are designed as case studies,and analytical study and finite element analysis(FEA)is used for validation.

Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China

To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China.Therefore,a vertical slot fishway(VSF)and a nature-like fishway(NLF)were built near the backwater area of the reservoir to connect the upstream and downstream habitats.Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways.The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species.During the survey,149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF,respectively,while 1263 fish from 27 species were found in the downstream area.Some species captured in the VSF were not found in the NLF,and vice versa,which implied the different preferences of fish.Meanwhile,3789 signals including 2099 upward ones and 1690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF.These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSFandNLF.

Shielding Effectiveness of Rural Concealed Communication Cable of Asymmetric/Symmetric Slots with Different Shapes

With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results showed that for twocore shielded cable, the coupling capacitance of trapezoid slots （asymmetric and symmetric） changed the most, followed by rectangular slots （asymmetric and symmetric）, and the changes of wedge slots were the smallest, but the change tenden- cies were consistent. In addition, with the increase of slot width of different slots, the coupling capacitance of tow-cored shielded cable showed small change.

Numerical Simulation of Residual Circulation due to Bottom Roughness Variability Under Tidal Flows in A Semi-Enclosed Bay

Nowadays there are some chronic serious environmental problems, such as eutrophication, blue tide and so on, in a complicated coastal zone or a semi-enclosed bay, because the water exchanges between an inner bay and an outer sea is weak compared with the supply of contaminant. Under this situation, a method to improve the water quality by 3-dimensional small unsymmetrical structures has been proposed by Komatsu et al. In this paper, several numerical simulations of the tidal current and concentration for various arrangements of bottom roughness in a semi-enclosed model bay are carfled out with a depth-averaged 2-D numerical model. The model is solved by the hybrid finite analytic method with nonstaggered grid. And the SIMPLES algorithm with Rhie and Chow＇ s momentum interpolation technique is used for the simulation. The effect of Komatsu＇ s method for water purification is examined by numerical simulation. The result of numerical experiment indicates that it is possible to generate a new tidal residual current and to activate a tidal exchange by bottom roughness arrangement only.

Influence of Reclamation Works on the Marine Environment in a Semi-Enclosed Bay

The flow and seawater exchange rates have been predicted using a two-dimensional numerical model and a Lagrangian method for a semi-enclosed shallow bay where reclaiming and dredging works are scheduled. The wind effect on the flow and material transport has been emphasized, and a thirty-year mean value of wind has been considered in the numerical simulation. As a whole, even after the reclaiming and dredging are conducted, the flow pattern looks similar to the original state. However, velocity variations up to 20% to 100% appear in the vicinity of the construction area. In the case of summcr wind forcing, the seawater exchange rate increases from 71.6% to 82.9% after the reclaiming and dredging, as indicated by a particle-tracking method. On the contrary, in the case of winter wind forcing, thc seawater cxchange rate appears to be 97.2% under natural conditions but decrcases slightly to 93.2% aftcr the rcclaiming and dredging. Thus, the wind forcing plays an important role in controlling the seawater exchangc rates. The seawater cxchange rate is further improved by 15% if the dredging is simultaneously carried out with the reclaiming. This suggests that the dredging can be an effective means to mitigate the variation of flow.

Numerical Simulation of Aerodynamic Characteristics of Helicopter Rotor with Tip Slots

Effects of tip slots on the aerodynamic characteristics of helicopter rotor were investigated numerically by solving three-dimensional Navier-Stokes equations based on unstructured overset grids algorithm.Improved delayed detached eddy simulation (IDDES) based on the Spalart-Allmaras turbulence model and adaptive grid refinement technique were employed.Several slots in the rotor blade tip were designed on the base of Caradonna-Tung rotor to study the effect of tip slots.Numerical results show that tip slots are able to introduce the airflow from the leading edge and turn it in the spanwise direction to be ejected out of the face at the rotor blade tip,which can reduce the strength of the rotor blade tip vortex and accelerate the dissipation process.Although tip slots may lead to the decrease of airfoils' lift coefficient at the root of the rotor blade,it can increase the lift coefficient of airfoils at the rotor blade tip,so the lift of the rotor with tip slots is almost the same as that of the rotor without tip slots.In addition,tip slots can also reduce the intensity of the tip shock wave,which is beneficial to reduce the wave drag of the rotor.

Semi-enclosed experimental system for coal spontaneous combustion for determining regional distribution of high-temperature zone of coal fire

Temperature variation and gas generation at diferent depths and positions in the coal combustion process were studied to determine the propagation and evolution of high temperature regions in the process of coal spontaneous combustion.This study selected coal samples from Mengcun,Shaanxi Province,People’s Republic of China,and developed a semi-enclosed experimental system(furnace)for simulating coal combustion.The thermal mass loss of coal samples under various heating rates(5,10,and 15℃/min)was analyzed through thermogravimetric analysis,and the dynamic characteristics of the coal samples were analyzed;the reliability of the semi-enclosed experimental system was verifed through the equal proportional method of fuzzy response.The results reveal that the high-temperature zone is distributed nonlinearly from the middle to the front end of the furnace,and the temperatures of points in this zone decreased gradually as the layer depth increased.The apparent activation energy of the coal samples during combustion frst increased and then decreased as the conversion degree increased.Furthermore,the proportion of mass loss and the mass loss rate in the coal samples observed in the thermogravimetric experiment is consistent with that observed in the frst and second stages of the experiment conducted using the semi-enclosed system.The research fndings can provide a theoretical basis for the prevention and control of hightemperature zones in coal combustion.

The Equivalent Parameters of an Inclined Slot in Two Crossed Waveguides with Radiating Slots

The effect of longitudinal-offset radiating slots on a centered-inclined feeding slot in the common broad wall of the two crossed rectangular waveguides is analysed quantitatively. The corresponding equivalent parameters are computed by employing the moment method. The numerical results of resonant length of the feeding slot, VSWR and coupling parameter are showed and compared with the case of no radiating slots and short-end. The agreement between theory and experiment is good.

NUMERICAL INVESTIGATION OF THE LIMIT LOADS FOR PRESSURE VESSELS WITH PART-THROUGH SLOTS

A numerical investigation of the limit loads is carried out for pressure vessels with part-through slots using a general computational method for the limit analysis of 3-D structures. The limit pressures are given for a comprehensive range of geometric parameters. Some of the calculated results are compared with the results of 3-D elastic-plastic finite element analysis and existing numerical solutions. The effects of various shapes and sizes of part-through slots on the load carrying capacity of cylindrical shells are investigated and evaluated. Two kinds of typical failure modes corresponding to different dimensions of slots are studied. Based on the numerical results, a geometric parameter G which combines the slot dimensions and the cylinder geometry is presented. It reasonably reflects the overall effect of slots on the limit loads of cylinders. An empirical formula for estimating the limit pressures of cylindrical shells with part-through slots is obtained.

Optimization design of wide face water slots for medium-thick slab casting mold

A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.

NUMERICAL ANALYSIS OF CENTERED-INCLINED COUPLING SLOTS IN RECTANGULAR WAVEGUIDES

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides, taking into account the transverse distribution of the electric field across the slot aperture. Integral equations are formulated based on dyadic Green's function theories and solved using the method of moments. Trigonometric basis functions are adopted. It is found that the method will converge with up to ten basis functions. The characteristic parameters can be easily obtained for different slot sizes. Resonant length and resonant resistance of the coupling slots are calculated. It is shown that the calculated results have very high accuracy, compared with simulated results obtained from commercial software. Therefore, it can be effectively applied in the synthesis of antenna arrays. Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed. The results show that if the transverse distribution of the electric field is neglected, the calculated error tends to become larger when the slot gets wider or thinner.

Increasing Microstrip Patch Antenna Bandwidth by Inserting Ground Slots

Microstrip patch antenna (MPA) is widely implemented in different communication systems. One of the main disadvantages of MPA which limits its applications is its narrow bandwidth. In this paper I enhanced the bandwidth of MPA by inserting multiple slots in its ground plane. I used FR-4 substrate to design this antenna. The dimensions of this antenna are 59 mm and 79 mm. The dielectric constant is 4.4 and the height is 1.6 mm. I inserted up to 15 slots in ground plane with 1mm width. The spacing between slots is 3 mm. I investigated two designs. In the first design, slots were arranged in parallel to the feeding line. In the second one, slots were arranged horizontally to the feeding line. The main objective of this paper is to design and simulate MPA suitable for wide number of applications. Antenna bandwidth improvement is 18%. All the simulations were obtained by using HFSS simulator.

Computing of Mutual Admittance between Two Circumferential Slots on Cylindrical Waveguide

This paper studies radiation from circumferential slots on cylindrical waveguide by Poynting’s vector method. It can help us to find mutual admittance between two circumferential slots in an antenna array. The main advantage of Poynting’s vector method is its accurate convergence to compute mutual admittance between two circumferential slots. The importance of this matter will be more salient while we want to compare it with other mutual admittances and also use it to optimize an antenna array.

Radiations from an Eccentric Coated Cylinder with N Slots

The transverse magnetic (TM) radiation characteristics are investigated for a cylinder with N infinite axial slots of arbitrary opening size and location. The cylinder is a thin circular conductor and coated by an eccentric material. Fields are found by applying the boundary conditions to the cylindrical wave functions. The addition theorem of Bessel functions is used to obtain an infinite series solution in Fourier–Bessel series form. Results are computed by shrinking the generated infinite series to a finite number of terms and compared to other available data. Numerical results in graphical forms for different values are also developed and discussed for small eccentricities.

Investigation of wave characteristics in a semi-enclosed bay based on SWAN model validated with buoys and ADP-observed currents

In this study, the simulating waves nearshore (SWAN) model with a locally refined curvilinear grid system was constructed to simulate waves in Jervis Bay and the neighbouring ocean of Australia, with the aim of examining the wave characteristics in an area with special topography and practical importance. This model was verified by field observations from buoys and acoustic Doppler profilers (ADPs). The model precisions were validated for both wind-generated waves and open-ocean swells. We present an approach with which to convert ADP-observed current data from near the bottom into the significant wave height. Our approach is deduced from the Fourier transform technique and the linear wave theory. The results illustrate that the location of the bay entrance is important because it allows the swells in the dominant direction to propagate into the bay despite the narrowness of the bay entrance. The wave period T p is also strongly related to the wave direction in the semi-enclosed bay. The Tp is great enough along the entire propagating direction from the bay entrance to the top of the bay, and the largest Tp appears along the north-west coast, which is the end tip of the swells’ propagation.

Radial tidal current field in a semi-enclosed rectangular basin: formation and evolution

The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morphodynamic features in the area. A semi-enclosed rectangular basin with and without a coastal barrier was schematized from the topography of the Bohai Sea and Yellow Sea. The 2D tidal current field in this basin was simulated using the DELFT3D-FLOW model. The concept of tidal wave refraction, which highlights the effect of the sloped or stepped submarine topography on the propagation of the tidal waves, was introduced to explain the formation of the radial tidal current field. Under the effect of tidal wave refraction, co-phase lines of the counterclockwise rotating tidal wave and incident tidal wave are transformed into clockwise and counterclockwise deflections, respectively, leading to the convergence and divergence of the flow field. Regardless of whether a coastal barrier exists or not, the outer radial tidal current field might emerge over certain topography. The responses of the radial tidal current field in this basin to the environmental variations such as coastline changes and bottom erosions were discussed. Results show that local protrusion near the focal point of the radial tidal current field will have limited effects on the location of the tidal system. However, a remarkable shift of the amphidromic point toward the entrance and central axis of this basin and a movement of the focal point of the radial tidal current field toward the entrance could be caused by the significant seaward coastline advance and submarine slope erosion.

Double U-Shaped Slots Loaded Stacked Patch Antenna for Multiband Operation

The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.

Triple Notched Band Characteristics UWB Antenna Using C-Shaped Slots and Slot-Type Capacitively-Loaded Loop (CLL)

Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.

Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.