On calculation of seiche oscillations of the middle part of the Peter the Great gulf

Characteristics of barotropic seiche oscillations of the middle part of the Peter the Great gulf are considered with the use of a spectral-finite difference model. The model is based on a linearized system of shallow water equations. Difference approximation is carried out on an irregular triangular spatial grid. The numerical method involves solving the eigenvalue problem and is able to directly obtain a set of frequencies and the corresponding shapes of seiche oscillations. The grid computational domain covers the Amurskiy bay and the Ussuriyskiy bay. The Zolotoy Rog bay and the Alekseeva bay are described in more detail on the grid. The spatial-temporal characteristics of a number of seiche oscillations corresponding to well-defined peaks of the energy spectrum of the sea level data from the “Vladivostok” station of the Russian tsunami warning service are calculated and presented. The results of calculations for the Alekseeva bay are compared to the data of natural measurements and to the solution to the Cauchy problem.     

Numerical three-dimensional free surface circulation model for the South Biscayne Bay,Florida

A three– dimensional, time dependent free surface model has been developed for predicting circulation and surface height variations in a tidal bay. An explicit finite difference numerical solution is obtained by transforming the vertical coordinate in the governing model equations. The transformed geometry consists of a fixed, flat free surface and a constant depth basin for easy computation. The ocean–bay interface open boundary condition is incorporated into this hydrodynamic model without approximation, and yields rather accurate results for the bay circulation and tide level variations. The numerical method employs a staggered grid Richardson lattice, which has the inherent property of not requiring calculation of the tangential velocity components on solid surfaces. The momentum equations ignore horizontal diffusion which is small for the South Biscayne Bay, for which vertical diffusion and advection dominate.     

Numeric modeling of thermal pollution in Plomin bay area

In order to analyze the thermal pollution of the Plomin bay induced by the used cooling water released from Plomin 1 and Plomin 2 thermal power plants, flow simulations and temperature field analysis were conducted. The measurements of the bay surface temperature field were carried out as well as the corresponding 3D water flow simulations on the realistically modeled bay. The accuracy of the simulation results was evaluated by the comparison of computed and measured surface temperatures. Furthermore, numerical meshes of different density were used in order to determine model sensitivity where the results showed a significant effect of the mesh density on the simulation results. Although the simulations obtained with a denser mesh yield more accurate results and allow for the reconstruction of heated water surface flow with better reliability, the sparser mesh provided sufficiently accurate results as well. The overall temperature field obtained with the numerical model agrees well with the measured temperature values, which demonstrates the successful application of the 3D flow numerical model on the Plomin bay thermal pollution problem.      

A simulation study of despatch bay performance in the steel processing industry

The despatch bay is a critical interface within an organisation, linking the warehousing and transport operations. However, delays here have wider supply chain implications given that the flow of materials through the supply chain is disrupted. Despite this, there has been little research on improvement activities to this process. This paper uses a case study of a steel processor to develop a simulation model to test strategies for increasing despatch bay productivity. From the simulation results, it was found that a combination of improvements were needed, to both reduce process times and ensure the earlier receipt of orders. The research approach presented in this paper can be used in other business environments having similar operating conditions.     

A Constraint Programming model for fast optimal stowage of container vessel bays

Container vessel stowage planning is a hard combinatorial optimization problem with both high economic and environmental impact. We have developed an approach that often is able to generate near-optimal plans for large container vessels within a few minutes. It decomposes the problem into a master planning phase that distributes the containers to bay sections and a slot planning phase that assigns containers of each bay section to slots. In this paper, we focus on the slot planning phase of this approach and present a Constraint Programming and Integer Programming model for stowing a set of containers in a single bay section. This so-called slot planning problem is NP-hard and often involves stowing several hundred containers. Using state-of-the-art constraint solvers and modeling techniques, however, we were able to solve 90% of 236 real instances from our industrial collaborator to optimality within 1 second. Thus, somewhat to our surprise, it is possible to solve most of these problems optimally within the time required for practical application.     

Application of Smoothed Particle Hydrodynamics for modelling gated spillway flows

Computational models of spillways are important for evaluating and improving dam safety, optimising spillway design and updating operating conditions. Traditionally, scaled down physical models have been used for validation and to collect hydraulic data. Computational fluid dynamics (CFD) models however provide advantages in time, cost and resource reduction. CFD models also provide greater efficiency when evaluating a range of spillway designs or operating conditions. Within the present literature, most studies of computational spillway models utilise a mesh-based method. In this work we use the particle based method of Smoothed Particle Hydrodynamics (SPH) to model weir flow through a four bay, gated, spillway system. Advantages of SPH for such modelling include automatic representation of the free surface flow behaviour due to the Lagrangian nature of the method, and the ability to incorporate complex and dynamic boundary objects such as gate structures or debris. To validate the SPH model, the reservoir water depth simulated is compared with a related physical study. The effect of SPH resolution on the predicted water depth is evaluated. The change in reservoir water level with discharge rates for weir flow conditions is also investigated, with the difference in simulated and experimental water depths found to range from 0.16% to 11.48%. These results are the first quantitative validation of the SPH method to capture spillway flow in three dimensions. The agreement achieved demonstrates the capability of the SPH method for modelling spillway flows.     

Optimal location and capacity of emergency cleanup equipment for oil spill response

Myopic planning and tactical decision-making with regards to oil spill events result in severely inefficient cleanup efforts with high fixed, operating and cleanup/damage costs. We propose an integrated framework that addresses some important strategic issues such as determining the optimal location and capacity of cleanup equipment, taking into account their post event implications. We develop a linear integer programming model, exhibit its complexity and propose a solution method by solving a relaxation of the original problem. Realistic examples applied to the Florida peninsula are presented.     

Multibody system model of a cargo airship to study the load exchange process

Projected cargo airships for the transport of large loads exceed the dimensions of existing aircrafts and gave rise to various technical problems. One important task in an airship mission is the loading and unloading of the heavy and spacious load from the payload bay of the airship. In order to study the dynamics of the load exchange process, mathematical models of the airship including the oscillating load frame are developed. The hull together with the load frame represent a multibody system. Crucial aspects contributing to the dynamics of the system are the floatation of the flying crane and nonlinear couplings between hull and load frame. Furthermore, added masses of the surrounding air are considered. Oscillations of the load frame are excited by wind loads, airship maneuvers and winding up the cables.     

Modeling the field of a cable in a two-dimensional nonhomogeneous medium

In this article we model the electromagnetic field of a cable on the surface of a two-dimensional nonhomogeneous medium used for electromagnetic sounding. The model of the medium represents the sea. Calculations are reported describing the coast effect on the electromagnetic field. An iterative field calculation method is proposed, which reduces the computing effort. The effect of sub-seafloor nonhomogeneities on the electromagnetic field measured at the seafloor is investigated numerically.     

A linear programming embedded probabilistic tabu search for the unequal-area facility layout problem with flexible bays

In this paper, a probabilistic tabu search (PTS) approach is proposed to solve the facility layout problem (FLP) with unequal area departments. For the representation, the flexible bay structure (FBS), which is a very common layout in many manufacturing and retail facilities, is used. In this paper, the FBS is relaxed by allowing empty spaces within bays, which results in more flexibility in assigning departments into bays. In addition, departments are allowed to be located more freely within the bays, and they can have different side lengths as long as they are within the bay boundaries and do not overlap. To achieve these goals, department shapes and their locations within bays are determined LP. A PTS approach is developed to search an overall layout structure that describes relative positions of departments for the relaxed-FBS (RFBS). The proposed LP embedded PTS–RFBS approach is used to solve thirteen FLP instances from the literature with varying sizes. The comparative results show that this approach is very promising and able to find new best solutions for several test problems.     

Determination of the stress state of a circular disk with a crack

With the use of complex potentials from the solution of a contact problem for slits in a multiply-connected region, a solution is found for a problem of the theory of elasticity for an isotropic circular disk with an arbitrary radial crack. The case of an edge crack is among the cases for which a solution is found. The types of loading examined are uniform tension on an outside edge, internal pressure on the edges of cracks, and concentrated forces at arbitrary points of a disk. The unknown coefficients in the complex potentials are found from the boundary conditions on the outside edge of the disk by the series method, the colocation method, or the least squares method. Detailed numerical studies are conducted to determine the effect of the geometric characteristics and the points of application of concentrated forces on the character of the stress distribution and the stress intensity factor. A comparative characteristic of the methods used to find the coefficients is presented.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19 pp. 50–61, 1988.     

FLUSHING TIME IN THE CIENFUEGOS BAY,CUBA

We use a high‐resolution numerical model to analyze the hydrodynamical exchange processes of the Cienfuegos Bay with the Caribbean Sea. Results show that freshwater inputs and wind are the main factors controlling the water exchange in the bay. Nine simulation case studies with three wind conditions and three freshwater inputs were carried out. The main conclusion is that the Cienfuegos Bay system has a slow exchange rate, with an average flushing time of 39 days during the rainy period and 50 days during the dry one, for the most probable wind direction. Two new temporary scales for Cienfuegos Bay are discussed: the local e‐flushing time and the flushing lag. The results obtained for these new variables validate the slow exchange capacity of the bay.     

Effect of rotation on the onset of double diffusive convection in a Darcy porous medium saturated with a couple stress fluid

The effect of rotation on the onset of double diffusive convection in a horizontal couple stress fluid-saturated porous layer, which is heated and salted from below, is studied analytically using both linear and weak nonlinear stability analyses. The extended Darcy model, which includes the time derivative and Coriolis terms, has been employed in the momentum equation. The onset criterion for stationary, oscillatory and finite amplitude convection is derived analytically. The effect of Taylor number, couple stress parameter, solute Rayleigh number, Lewis number, Darcy–Prandtl number, and normalized porosity on the stationary, oscillatory, and finite amplitude convection is shown graphically. It is found that the rotation, couple stress parameter and solute Rayleigh number have stabilizing effect on the stationary, oscillatory, and finite amplitude convection. The Lewis number has a stabilizing effect in the case of stationary and finite amplitude modes, with a destabilizing effect in the case of oscillatory convection. The Darcy–Prandtl number and normalized porosity advances the onset of oscillatory convection. A weak nonlinear theory based on the truncated representation of Fourier series method is used to find the finite amplitude Rayleigh number and heat and mass transfer. The transient behavior of the Nusselt number and Sherwood number is investigated by solving the finite amplitude equations using Runge–Kutta method.     

基于弹性区带架构的多目标设施布局问题研究

为解决设施面积不等的连续型设施布局问题,建立了基于弹性区带架构布置形式,以物料搬运成本最小、邻近关系最大、距离要求满足度最大的多目标设施布局模型。模型中考虑了区域内的横向、纵向过道,对设施的长宽比进行了限制,使得结果更符合实际情况。为克服传统多目标单一化方法需要人为设置子目标函数权重、主观性过强的缺陷,采用基于带有精英保留策略的非支配排序遗传算法(NSGA Ⅱ)的多目标优化算法求解模型,设计了相应的编码方式、交叉算子、变异算子、罚函数。最后通过某物流园区的实例分析证明了模型与方法的有效性。     

A coupled mixed problem for a system of electrodes on the surface of a prestressed electroelastic structurally inhomogeneous half-space

The features of the interaction of a system of electrodes with a prestressed structurally inhomogeneous piezoactive half-space are investigated. The problem is reduced to a convolution equation on a system of sections, to solve which, a generalization of a previously proposed method is used, which enables the dynamic properties of the medium to be taken into account with high accuracy. Using the example of the problem of the excitation of shear oscillations of a weakly inhomogeneous piezoactive half-space, it is shown that the effect of the initial mechanical stresses on the electric-induction distribution in the contact zone for a homogeneous and bipolar system of five and nine electrodes is independent of the number of electrodes, but depends considerably on the form of the initial stress state. A triaxial stress state has the strongest effect on the electric-induction distribution.     

圆形孔口裂纹的反平面剪切问题的解析解

利用复变函数方法,通过构造保角映射,研究了带裂纹的圆形孔口的反平面剪切问题,给出了Ⅲ型裂纹问题的应力强度因子.在极限情形下,求得Griffith裂纹在裂纹尖端处应力强度因子,这与已有的结果完全一致.最后数值算例给出了半经和裂纹长度对应力强度因子的影响.     

Limiting state of a multilayered nonlinearly elastic long cylindrical shell under the action of nonuniform external pressure

The buckling of a long multilayered nonlinearly elastic shell made of different materials and subject to the action of external pressure is investigated. The load is not hydrostatic and greatly varies in value and direction. Neglecting the effect of end fastening of the shell, the problem is reduced to an analysis of the loss of load-carrying ability of a ring of unit width separated from the shell. The solution is based on a variational method of mixed type formulated for heterogeneous nonlinearly elastic bodies, taking into account the geometrical nonlinearity, in a combination with the Rayleigh–Ritz method. The initial analysis is reduced to solving the Cauchy problem for a nonlinear ordinary differential equation resolved for the derivative. Numerically, using the Runge–Kutta method, the effect of the number of layers and of the parameter of nonuniformity of the external pressure on the critical buckling force is revealed. The urgency and importance of the problem are connected with the research of reserves in the saving of materials with a simultaneous possibility of increasing the load-carrying ability of a structure.     

Three-dimensional numerical simulation of the plasma plume from a stationary plasma thruster

A numerical method is proposed for simulating the low-density plasma plume exhausted from a stationary plasma thruster in a three-dimensional setting. In contrast to the axisymmetric approximation, the problem is formulated so as to determine the effect of the backflow on the upstream region and the thruster walls, which are of finite size. The numerical method is a generalization of rarefied gas numerical methods to the case when the force field is not specified analytically. The method takes into account the delta-function character of the boundary ion distribution function and the considerable difference between the velocity scales of ions and neutral atoms, which transform into each other. Numerical results are presented that demonstrate the effect of some factors on the plasma plume.     

On the oil-whipping of a rotor-bearing system by a continuum model

The nonlinear dynamic behavior of a rotor-bearing system is analyzed based on a continuum model. The finite element method is adopted in the analysis. Emphasis is placed on the so-called “oil-whip phenomena” which might lead to the failure of the rotor system. The dynamic response of the system in unbalanced conditions is approached by a direct integration method. It is found that a typical “oil-whip phenomenon” is successfully simulated, and the effect of the refinement of the finite element mesh is also checked. Furthermore, the bifurcation behavior of the oil-whip phenomenon that is of much concern in recent nonlinear dynamics research is analyzed. The rotor-bearing system is also examined by a simple discrete model. Significant differences are found between these two models. It is suggested that a careful examination should be made in modeling the nonlinear dynamic behavior of a rotor system.     

The Spatial Analysis of Community Health Services on Wirral Using Geographic Information Systems

This paper discusses the development of a geographical information system (GIS) for analysing the spatial distribution of community-based health services and the patients who use them on the Wirral peninsula in North West England. Information, with full geographical coding, has been obtained about General Practitioners (GPs) on the Wirral and the services they provide, together with the location, age and sex of the patients registered with them. Data have also been assembled on the services provided at local clinics. This is augmented with information on administrative boundaries and the street network held in digital form, and with statistical information for small areas covering demographic structure, social conditions and deprivation. The GIS is being used to identify catchment areas for different services and to produce demographic, social and residential profiles for the patients who use them.