Shape Identification for Fluid-Structure Interaction Problem Using Improved Bubble Element

Numerical solutions for identification of the shape of a circular cylinder are addressed in this paper. The Sakawa-Shindo method is used to minimize the algorithm. A unified computational approach for simulation of flow and shape identification is presented. As a numerical approach for spatial discretization, mixed interpolation by the bubble and linear elements is used for the velocity and pressure fields, respectively.     

Optimal Control in Navier-Stokes Equations

This paper presents a formulation for optimal control of a forced convection flow. The state equation that governs the forced convection flow can be expressed as the incompressible Navier-Stokes equations and energy equation. The optimal control can be formulated as finding a control force to minimize a performance function that is defined to evaluate a control object. The stabilized finite element method is used for the spatial discretization, while the Crank-Nicolson scheme is used for the temporal discretization. The Sakawa-Shindo method, which is an iterative procedure, is applied for minimizing the performance function.     

The Finite Element Analysis of Interaction Problem Through Water,Soil, Balloon and Pile

This paper presents the finite element analysis of an interaction problem involving water, soil, balloon and pile. A building with friction piles is considered, and balloons are introduced to the top of piles. To control the vertical displacement of the building, water is injected into or removed from the balloons. The two-dimensional incompressible Navier-Stokes equation is introduced, and the ALE (Arbitrary Lagrangian Eulerian) method is applied to the water flow analysis. The FS (Fractional Step) method is also applied in the finite element formulation. The soil, which is assumed as a linear elastic body, is subjected to the deformation analysis. The balloon and pile are assumed as a linear elastic truss and a rigid frame, and the deformation analysis is also performed. All the components are discretized by the finite element method in space and are interactively solved by taking into account continuity conditions of traction and displacement.     

Finite Element Analysis of Two- and Three-dimensional Flows Around Box-type Bridge Sections

Multilayer seepage model is proposed instead of three dimensional model. Optimum theory based on multilayer finite element formulation is applied to planning the efficient flow rate and pumping well layout. The Sakawa-Shindo method is used for the optimum control calculation. As a numerical example, calculations are carried out to determine an optimum pumping flow for use where a cut-off wall and pumping wells are combined.     

A PREDICTIVE CONTROL METHOD TO OPERATE WATER GATE OF DAM

A new predictive control method for operating water regulating gate of dams is presented based on a hydraulic model. To consider the hydrodynamic behavior of surface waves through a reservoir, the shallow water equation is used with the discretization by the finite element method. This method provides the appropriate solution of outflow discharge which prevents the overflow of dam by the operation of water gate assuming that the inflow discharge is known as a function of some moment in the future. To show the applicability of this method, one dimensional channels with single and with multiple dams and Moriyoshizan dam reservoir have been computed as the numerical examples. It is shown that the water surface elevation of a reservoir is sufficiently controlled by the present method.     

MODEL VERIFICATION ON 3D TIDAL CURRENT ANALYSIS IN TOKYO BAY

The results of a research project to verify the newly improved multiple- level model for 3D tidal current analysis in Tokyo Bay are presented. The improved multiple-level model includes additional effects due to Coriolis force, river inflows and wind shear stresses. Furthermore, a new numerical treatment of the open boundary condition was applied which effectively eliminated the spurious reflective waves often generated by various numerical methods simulating free surface flows. The mean (time-averaged or residual) and tidal currents in Tokyo Bay were simulated as examples to demonstrate the validity and capability of the newly improved multiple-level model. A series of numerical experiments was conducted to carefully examine the tidal circulations affected by the forcing factors of Coriolis force, river inflows and wind shears, both individually and combined. The numerical results demonstrated that the effects of each forcing term are physically reasonable, with the wind shear effect being the most significant and the case including all forcing terms being in best overall agreement with the field data collected in Tokyo Bay by the Ministry of Transportation. This study has contributed not only to the verification of the newly improved multiple-level model but also to the enhancement of the accuracy of numerical simulations of three-dimensional flow in coastal waters by this model.     

Estimation of Wave Propagation using a Kalman Filter

An estimation method for gravity water wave propagation combining the finite element method and the Kalman filtering technique is presented. The method is further simplified to reduce the computational effort. According to the results obtained with this method, it is possible to estimate the water surface profile by taking into account the measured data, and to filter out the noise included in the measured data and the finite element approximation.     

Parameter Identification and Control of Ground Temperature

A numerical thermal management system for the ground structure is presented. The system consists of two parts, i.e. the identification analysis of thermal conductivity and the thermal control analysis for the ground. The former is carried out by using the nonlinear least squares method and the latter is based on the optimal control theory. The formulations of these methods are presented and they are applied to an actual putting green in a golf course. Reasonable thermal conductivity of the ground is identified by parameter estimation and the ground temperature is theoretically controlled as illustrated by numerical examples.     

Secondary Instabilities of Wakes of a Circular Cylinder Using a Finite Element Method

This study investigates secondary instabilities of periodic wakes of a circular cylinder with infinitely long span. It has been known that after the wake undergoes a supercritical Hopf bifurcation (the primary instability) that leads to two-dimensional von Kantian vorlex street, the secondary instability occurs sequentially, which results in the onset of three-dimensional flow. Williamson (1996) has reviewed that the periodic wakes over a range of moderate Reynolds number from 140 to 300 are characterized by two critical modes. Mode A and Mode B, which are respectively associated with large-scale and fine-scale structures in span. In order to understand a sequence of bifurcation in transitional wake, in this paper, the stability of periodic Row governed by the linearized Navier-Stokes equations is analyzed by using the Floquet stability theory. By employing the finite elemental discretization with a fine mesh, the numerical results for both simulation and stability analysis have high spatio-resolution. The obtained stability results are in good agreement with experimental data and some relevant numerical results. By means of visualizations of the three-dimensionally critical flow structures. the existence of Mode A and Mode B is verified from the spatial structures in both the two modes.