PRESSURE DISTRIBUTION DETERMINED BY USING MEASURED VELOCITY FIELD DATA AND RANS EQUATIONS

The current paper presents the result of a study on determining the pressure distribution along the surface of a foil section by using measured velocity field data and the Reynolds Averaged Navier-Stokes equations. The results are compared with the measured pressure data and show its satisfaction. It is a try to find a new way to determine pressure by combining the experimental data and CFD method.

RANS Simulation for the Maneuvering and Control of a Suboff Submarine Model

Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show that the numerical simulation of the viscous flow related to a moving submarine based on the RANS equation with a relevant turbulence model can not only provide rich flow field details such as flow separation,but also accurately predict its hydrodynamic performance.The present study indicates that CFD can be used to forecast the submarine’s maneuverability in the initial design stage.The present results will be used in the future as a basis for analyzing methods to reduce the vibration and noise generated by the submarine.

Structural optimization of a settler via CFD simulation in a mixer-settler

This work is aimed at optimizing a settler structure in a mixer-settler.Two different aspects have been considered.Firstly,the flowcharacteristics of a settler have been examined by computational fluid dynamics(CFD)simulation with various agitation speeds of the mixer,as well as organic phase volume fractions ranging from 0.075 to 0.6.The aqueous and organic phase turbulent flow fields were measured by particle image velocimetry(PIV)technique to verify the CFD simulation.Two organic phases with different physical properties were assessed in the CFD simulation to simulate the liquid-liquid systems related to rare earth element extraction,i.e.,0.072 mol·L^-1 P507/kerosene and 1.8 mol·L^-1 P507/kerosene.Secondly,the CFD simulation was carried out in a settler equipped with baffles.The effects of number and location of the baffle in the settler on flow features and entrainments of the aqueous and organic outlet were analyzed.Meanwhile,different settler/mixer volume ratios were also examined.By analyses and comparisons,an optimal design for settler was proposed.CFD can provide a significant guidance to better mixer-settler design.

AERODYNAMIC OPTIMIZATION FOR TURBINE BLADE BASED ON HIERARCHICAL FAIR COMPETITION GENETIC ALGORITHMS WITH DYNAMIC NICHE

A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche （HFCDN-GAs） coupled with Reynolds-averaged Navier-Stokes （RANS） equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points＇ ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.

NUMERICAL SIMULATION OF WING-BODY JUNCTION TURBULENCE FLOW

Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique. Three order differential scheme is used in the computation of convection term and two layers turbulence model are employed in the calculation.

A SEPARATED－LAYER FINITE ANALYTIC METHOD FOR NUMERICAL SIMULATION OF A THREE－DIMENSIONAL VISCOUS FLOW FIELD AROUND A SHIP STERN

A calculation code of numeriCal simulation of complete Reynolds-averaged Navier-Stokes(RANS) equations for three-dimensional viscous flow around a ship is developed in this paper using an improved separated-layer finite analytic(SLFA) method. And the k-εmodel is used to compute the turbulent stress. An improvement is also made for grid generation in the aspectS of saving the run time and controlling the grid density in the near wall region. The SIMPLEM algorithm, superior to the well-known SIMILER algorithm, is adopted for speeding up the iterations of the coupling between the pressure and velocity under the unstaggered gild.Rather satisfied agreements with the experimental results are achieved for the Wigley mathematic hull at the Reynolds number of 1. 0×106.

Construction and Validation of an Urban Area Flow and Dispersion Model on Building Scales

This paper presents a numerical model that simulates the wind fields, turbulence fields, and dispersion of gaseous substances in urban areas on building to city block scales. A Computational Fluid Dynamics（CFD） approach using the steady-state, Reynolds-Averaged Navier-Stokes（RANS） equations with the standard k-ε turbulence model within control volumes of non-uniform cuboid shapes has been employed. Dispersion field is computed by solving an unsteady transport equation of passive scalar. Another approach based on Gaussian plume model is used to correct the turbulent Schmidt number of tracer, in order to improve the dispersion simulation. The experimental data from a wind tunnel under neutral conditions are used to validate the numerical results of velocity, turbulence, and dispersion fields. The numerical results show a reasonable agreement with the wind tunnel data. The deviation of concentration between the simulation with corrected turbulent Schmidt number and the wind tunnel experiments may arise from 1） imperfect point sources, 2） heterogeneous turbulent difusivity, and 3） the constant turbulent Schmidt assumption used in the model.

Numerical Simulation of Focused Wave and Its Uncertainty Analysis

On the basis of the transient water wave(TWW) theory,focused wave is generated in the circulating water channel.Numerical simulation of the focused wave is carried out by solving the Reynolds averaged NavierStokes(RANS) equations.The dynamic grid technique is adopted to simulate the motion of the wave maker,and the volume of fluid(VOF) method is used to capture the free surface of the wave.The simulation results are compared with the measured data,and good agreement is obtained.For quantitative estimation of the numerical simulation error and uncertainty,the uncertainty analysis method recommended by the International Towing Tank Conference(ITTC) procedure is performed for the simulation results of the surface elevations at different positions.Both grid-convergence and time-step-size convergence studies are conducted using three types of grids and time step sizes.The simulation results are all monotonously convergent in the verification procedure,and the validations of the simulated surface elevations with the positions at 3.5,4.0 and 4.5 m are all achieved by comparing with the validation uncertainty.It is found that the numerical simulation errors caused by the grid and time-step-size in the convergence studies have the same order of magnitude.In addition,the numerical errors and uncertainties for the surface elevations at different positions are compared and discussed in detail.This paper presents the first attempt to carry out the uncertainty analysis of the simulation of focused wave,and the effectiveness of the proposed verification and validation procedures in the uncertainty analysis is demonstrated.

NUMERICAL SIMULATION OF SCALE EFFECT ON SHIP STERN FLOW AND HYDRODYNAMIC PERFORMANCE

The variations of ship stern flow field structure and its corresponding hydrodnamic performance under full scale Reynolds numbal (5 109) and model scale Reynolds numbal(5 106) are investigated numerically in this paper. The governing equations for 3-D incompressible turbulent flow which consist of RANS equation and K-ε two equation turbulence model are solved by finite difference scheme. Derailed computational results are presented graphically. The comparisons between present calculation, existing measurement and other calculation are made.