STUDY OF THE ATOMIZED FLOW IN HYDRAULIC ENGINEERING

Atomized flow widely exists in hydraulic engineering. A mathematical model was suggested for the atomized flow by the overflow flip bucket. The following problems have been considered: the hydraulic characteristics of atomized jet; the quantity of the atomized water; and the lateral diffusion of the atomized flow. By comparing the calculating results by the model with that of the prototype observation of Wujiangdu hydropower station, it is found that the model has fairly good predictive ability.

BASIC EQUATIONS AND WAVE THEORY OF GAS-LIQUID TWO-PHASE TRANSIENT FLOW

This paper systematically discussed the equations for two-phase transient flow and pressure wave and interfacial wave. The behaviour of basic equations was analyzed. The formulas for the wave speed of the pressure wave and the interfacial wave were derived. It was proved that various mathematical models can be uniformed by the integrating model and various wave speed formulas can be uniformed by the universal formula derived. The basic equations for the separated flow model are ill-conditioned because of the unreasonable neglect of the pressure differences between the phases and interfaces. Drift flux model can improve the accuracy if some additional equations are provided. The basic equations for homogeneous flow model are well-conditioned and they can be used in two-phase transient flow, especially in the cases of no velocity slips between various phases fluid.

ON MUSHROOM-CLOUD AND SPREADING LAYER REGIONS OF PLANE BUOYANT JETS

The whole field of buoyant jets in stratified environment is divided into buoyant- jet region,mushroom-cloud region and spreading layer region.In this paper a modelling method is used to predict the behaviors of mushroom-cloud and spreading layer regions.The demarca- tions of these regions are given also.

Application of Finite Element Method to the Analysis and Computation of Gradient current

Salinity difference between river and sea water causes the water stratified in the seaward firth. The type of flow can be treated as gradient current. In this paper the finite element method was used to solve two dimensional gradient current problem. The density difference was determined as a function of space and time, replacing the density difference with gradient current to avoid recalculating repeatedly. Two-step explicit scheme of finite element method was used and the computational domain was divided into trianglar elements. The computational results show that finite element method has superiority in gradient current at seaward firth space with complex boundary conditions. The computational process is effective, accurate and applicable with computer.

UNCONFINED SEEPAGE ANALYSIS OF DISCONTINUOUS ROCK SLOPE

Unconfined seepage field of arch dam abutment slope was studied. This paper is composed of two parts. The first part concerns with the numerical methods used in the analysis, which includes the identification of rock blocky system and the algorithm of the unconfined seepage flow in the discontinuity network with the consideration of the grouting curtain and drainage curtain. In the second part a complicated arch dam abutment slope was studied, for which the seepage flow field characteristics was analyzed and the seepage control system was evaluated.

THREE-DIMENSIONAL NUMERICAL SIMULATION OF MUL-TIPLE JETS IN SHALLOW FLOWING RECEIVING WATERS

Simulation of the mixing mechanism of submerged multiport diffusers used to discharge heated water from thermal-electric power plants and households into shallow receiving waters was described. The three-dimensional turbulence model and hybrid finite analytic method were used to predict the behavior of near field for multiport buoyant jets in rivers. The predicted temperature dilution and velocity prove good by comparison with available laboratory measurements. An empirical formula for temperature dilution and velocity in near field for this kind of flow was given. The effect of parameters on the dilution behavior of multiple jets were also discussed.

NUMERICAL SIMULATION OF 3-D AERATED JET BEHIND FLIP BUCKET OF OVERFLOW DAM

Aerated jets, such as the jet flow behind the flip bucket of an overflow dam, widely exists in hydraulic engineering. Up to now the model test and prototype observation have been two main methods of studying the aerated jet for a special hydraulic project. A three-dimensional mathematical model for the aerated jet was established. It seems that the suggested model has high predictive power in comparison with the original two methods of model test and prototype observation which is very useful in the study of energy dissipation and jet flow atomization.

APPLICATION OF MULTIGRID METHOD IN 2-D MATHE-MATICAL MODEL IN OPEN CHANNELS

In 2-D mathematical model, one of important problems is to improve computational speed. The multigrid method is a new rapid iteration method developed in the recent 20 years, and it has been widely used in many fields, but in sediment mathematical model it has been rarely used, especially in plane mathematical model with large scale computational scope. In this paper, the multigrid method was introduced and expected to be used widely in this field. And it is verified that the more layers are adopted, the higher convergent speed will be reached in computation.

MATHEMATICAL SIMULATION OF NAVIGATION CHANNEL CHANGES IN THE FLUCTUATING BACKWATER REGION OF THE THREE GORGES RESERVOIR

In this paper, an one- and two-dimensional connected mathematical model is developed. The two-dimensional characteristics of flow and sediment transport are considered as much as possible in the model. The model is calibrated with field data and applied to simulate the river process of the fluctuating backwater region of the Three Gorges Reservoir. Some conclusions have been made based on the simulation results.

EXPERIMENTAL STUDIES OF SOLUTE TRANSPORT THROUGH AN UNSATURATED NATURAL SOIL

Salt (NaCl) solution was applied to the surface of a cultivated field with 3 × 6 m2 and then was leached downward by a steady infiltration rate 4 mm/d. Sampling programs were designed under guiding of Dagan's scale concept. Each soil sample had eight replicates. Salt concentration exhibited a much more variability in both vertical and horizontal directions than water content, especially in the zones of peak values of concentration. The volume of immobile water, which might play an important role in the variability of concentration, was in the range of 24-39% of the total water volume in the experimental studies.

STUDY ON THE CHARACTERISTICS OF LONG TERM DISCHARGE OF A CATCHMENT

The characteristics of the catchment discharge vary with land use. The characteristics of the long-term discharge of a terraced paddy field catchment were studied. Two kind of tank models for land use were proposed and used to simulate the discharge of the catchment: one is a forest type model used as the upper part of the catchment; the other is a paddy field type model used as the lower part of the catchment. The results of the model simulation were analyzed and compared with that of a forest catchment.

NUMERICAL SIMULATIONS OF WHOLE FIELD BEHAVIOR FOR ROUND BUOYANT JET

Two-scale k-Ε turbulence model was used to obtain a mathematical model of round buoyant jet in static environment. In this paper the hybrid finite analytic method and staggered grid were applied to calculate the whole field of this flow pattern. The agreement between the calculated results and experimental data for gross behavior is good.

GRID GENERATION IN SPACE AND CALCULATION FOR 3-D TURBULENT FLOW

In this paper we studied three dimensional flow with inlet and outlet. We used nonorthogonal curvilinear body-fitted coordinates for the governing equations and grid generation, and gave the physical components for velocity flow field. We used two scale k-Ε-E model for large and small vortices respectively. The computation gives U, V, W, P, T, K, Ε, seven variables. The numerical results of the velocity and temperature distribution agree with the practical data. This method can calculate the vortex, circulation and secondary flow and may be widely used in river flow and in environmental hydraulic problems.

ANALYTICAL SOLUTION OF LONGITUDINAL DISPERSION IN DOUBLE-LAYER STRATIFIED TURBULENT FLOW

In double-layer stratified turbulent flow, the deviation function of the concentration from the cross-section mean and the dispersion coefficients are studied. The one-dimensional simplified dispersion equation is extended to double-layer turbulent flow. The velocity distribution in the upper flow region is logarithmic, and in the lower region is of the power-law. The paper gives particular forms of the concentration deviation functions and accurate formulae of longitudinal dispersion coefficients.

TRANSIENT FLOW DRAINAGE EQUATIONS CONSIDERING BOTH DELAYED GRAVITY RESPONSE AND EVAPORATION FROM WATER TABLE

The drainable porosity is one of the important parameters in the unsteady drainage formulas. Due to delayed gravity response the drainable porosity is a function of the rate of drawdown and the depth of water table. The evaporation from groundwater plays an important role in lowering water table, in drainage design formulas it should be taken into account. Drainage equations considering evaporation from groundwater varying with water table depth and evaporation from water surface and involving constant drain-able porosity have been proposed by many authors. In this paper new formulas considering both delayed gravity yield and evaporation as a function of water table depth are developed and verified by experimental data.

STOCHASTIC PROCESS OF SEDIMENT IN SEDIMENTATION BASIN

Suspended movement is supported by eddy of river. In this paper the turbulent stochastic regularity of flow and sediment was adopted and the settling model of the suspended movement was established. Then, stochastic regularity of the sediment in sedimentation basin was investigated. The calculating results were compared with measured data. The results are in good agreement and the calculating method is very simple. The divided diameter of washload and bed material load was discussed from the relation of turbulent intensity and sediment settling velocity.

PRELIMINARY STUDY ON CIRCULATION HEIGHT OF CIRCULATION FLOW WITH THE HORIZONTAL AXIS

The relationship among circulation height of circulation flow with horizontal axis and incident flow conditions as well as side slope angles of trenches was analyzed on the basis of the velocity distribution data observed in a series of model tests in a flume, and the related formula for the circulation height was proposed. The variation of circulation flow intensity was described.

NUMERICAL ANALYSIS OF FLOWS OVER A WAVY SURFACE

Potential and laminar flows over a wavy surface were studied in this paper. For the potential flow, theoretical analysis and FA numerical computation were adopted respectively. In the computation of the laminar flow, the body-fitted coordinate transformation were used. The results of two methods agree very well. The results show that the difference of the wall pressure distribution between potential and laminar flows is not significant, when the ratio of wave height to wave length is smaller and there are separated regions in the laminar flow field.

ON THE MECHANISM OF DRAG REDUCTION IN HIGH CONCENTRATION NON-HOMOGENEOUS PIPE FLOW

In this paper, a method for calculating the resistance force of high concentration non-homogeneous pipe flow was presented. The experiments were conducted in the bedstead of a recirculating pipeline. The measurement system is composed of the equipments for measuring the discharge, pressure and concentration. Experimental results show that for the laminar and turbulent high concentration flow there exists flow-core region and non-flow-core region, each of them has different characteristics. The comparisons show that the theoretical results are in good agreement with the experimental results.

ANALYSIS OF LIQUID SLUG MOTION IN A VOIDED LINE

A quasi two-dimensional two-phase flow cylinder model of slug motion in a voided line developed in this paper can predict reasonably the change of flow pattern of the slug, air entrainment, holdup and the distribution of axial velocity. However, if using the theory of transfer momentum to estimate the pressure-time history of slug at the elbow, the result of calculation is not good in agreement with that of experiment. Analysis of the experiment results and the estimations of using the theory of transient two-phase flow indicate that an evident water hammer response occurs in the slug, when the high-speed slug impacts on the elbow, and the peaks and waveform of pressure-time history are dependent mainly on the propagation of transient two-phase flow in the slug.