桩柱水流作用力实验测量技术研究

桩柱的绕流水流作用力一直是工程设计中所关注的问题。为了精确地测量模型试验中竖直桩柱在不同来流夹角下的水流作用力,基于力的平衡原理,设计并制作了一种新的桩柱水流作用力试验测量装置,并采用标准砝码模拟水流作用力,验证了该测量装置在不同来流工况下的测量精度。结果表明:桩柱受不同来流夹角的水流作用力时,该装置都具有相当高的测量精度,可满足模型试验要求。因此,该测量方法可用于竖直桩柱在水平或斜向水流作用下模型试验中水流作用力的试验研究。

平面旋转水流中颗粒运动分离特性的研究

本文旨在通过数值和实验方法,研究固体颗粒在旋转水流中发生分离运动的特性;通过4阶龙格—库塔法求解颗粒运动方程,求出不同时刻颗粒运动方向与水流运动方向的分离角度。然后,在一个匀速旋转的圆柱形平台上,对不同颗粒粒径、密度和平台转速,进行了不同参数组合的实验。实验结果与数值解吻合良好。最后,利用多元回归方法,提出了误差在25%左右的预估公式。

一种提高正横布置潜艇发射装置发射安全性的方法

正横布置的潜艇发射装置在发射鱼雷诱饵时,由于受潜艇航行带来的水流作用力的影响,鱼雷诱饵出管后将向潜艇的尾部方向回转,如果潜艇发射鱼雷诱饵时的航速较高,则这种回转将十分严重,有可能与发射艇的尾部相碰撞,这将给发射艇及鱼雷诱饵带来安全性问题.文中提出了一种鱼雷诱饵发射装置在艇上作向前倾斜的斜置式布置结构.数值仿真结果表明:此种布置方式可以削弱鱼雷诱饵出管以后的回转趋势,从而可以避免较高航速时鱼雷诱饵与发射艇的回转碰撞.

南津渡水电厂贯流式水轮机调节系统的优化控制设计

结合南津渡水电厂贯流式水轮机调节系统的技术改造,对若干具有代表性的优化控制措施进行分析介绍。

船舶系水鼓防台受力分析和工艺措施

系水鼓是船舶防台风的常用方法之一,文章对系水鼓防台时的船舶受力情况进行了分析,系水鼓防台时船舶可能同时受到风作用力、水流作用力、波浪作用力的作用,当三者同向同时冲击船首时,即是船舶的最危险状态,对这种状态的受力提出了计算方法,同时提出了船舶系水鼓防台的工艺措施。

Analysis of the wave propagation and the flow char-acteristics around cylinder due to dam break water

Dam breaks are easily triggered by heavy rains due to extreme weather such as typhoons,causing serious economic losses and casualties.Through the investigation of Chaoshan coastal zone,it is found that there have been dam breaks caused by geological disasters.In the design and management of water conservancy project,it is very important to analyze the effect of disastrous flow caused by dam break on the building.In this paper,the effect of the dam break flow on the cylinder is simulated numerically by taking the water body with initial velocity as the dam break flow,and the flow characteristics around the cylinder and the water body are analyzed.Numerical model adopted the Renault Average Navier-Stokes(RANS)model and volume of fluid(VOF)method to analyze the evolution of free water surface.It is found that there are different patterns of water movement in the process of dam break resulting in the creation of several isolated convex hull forms of dam-break waves on the stationary water surface,which causes longer disturbances in the water near the cylinder and makes the cylinder more vulnerable to fatigue damage.The increase of the height of the dam breaking water will lead to the increase of the hydrodynamic force on the pipeline.This study has guiding significance for the study of dam break and dam body design in water conservancy projects.

A CFD Based Investigation of the Unsteady Hydrodynamic Coefficients of 3-D Fins in Viscous Flow

The motion of the fins and control surfaces of underwater vehicles in a fluid is an interesting and challenging research subject.Typically the effect of fin oscillations on the fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure interactions.An understanding of the complexities of such flows is of interest to engineers developing vehicles capable of high dynamic performance in their propulsion and maneuvering.In the present study, a CFD based RANS simulation of a 3-D fin body moving in a viscous fluid was developed.It investigated hydrodynamic performance by evaluating the hydrodynamic coefficients (lift, drag and moment) at two different oscillating frequencies.A parametric analysis of the factors that affect the hydrodynamic performance of the fin body was done, along with a comparison of results from experiments.The results of the simulation were found in close agreement with experimental results and this validated the simulation as an effective tool for evaluation of the unsteady hydrodynamic coefficients of 3-D fins.This work can be further be used for analysis of the stability and maneuverability of fin actuated underwater vehicles.

Coupling model for assessing anti-seepage behavior of curtain under dam foundation

The seepage under a dam foundation is mainly controlled by the performance of the curtain.Its anti-seepage behavior may be weakened by the long term physic-chemical actions from groundwater.According to seepage hydraulics and geochemistry theory,a coupling model for assessing the behavior of the curtain under a dam foundation is set up,which consists of seepage module,solute transport module,geochemistry module and curtain erosion module,solved by FEM.A case study was carried out.The result shows that the curtain efficiency is weakened all the time.Aqueous calcium from the curtain is always in dissolution during the stress period for simulation,which leads to the increasing amount in groundwater reaching 846.35-865.312 g/m3.Within the domain,reaction extent differs in different parts of the curtain.The dissolution of Ca(OH)2 accounts to 877.884 g/m3 near the bottom and is much higher than that of the other parts.The erosion is much more serious near the bottom of the curtain than the other parts,which is the same to the upstream and downstream.Calcium dissolution is mainly controlled by hydraulic condition and dispersion,and it varies in a non-linear way within the domain.

Computational Study on Interaction Between Swimming Fish and Drifting Vortices Behind the Cylinder

To predict the flow evolution of fish swimming problems,a flow solver based on the immersed boundary lattice Boltzmann method is developed.A flexible iterative algorithm based on the framework of implicit boundary force correction is used to save the computational cost and memory,and the momentum forcing is described by a simple direct force formula without complicated integral calculation when the velocity correction at the boundary node is determined.With the presented flow solver,the hydrodynamic interaction between the fish-induced dynamic stall vortices and the incoming vortices in unsteady flow is analyzed.Numerical simulation results unveil the mechanism of fish exploiting vortices to enhance their own hydrodynamic performances.The superior swimming performances originate from the relative movement between the“merged vortex”and the locomotion of the fishtail,which is controlled by the phase difference.Formation conditions of the“merged vortex”become the key factor for fish to exploit vortices to improve their swimming performance.We further discuss the effect of the principal components of locomotion.From the results,we conclude that lateral translation plays a crucial role in propulsion while body undulation in tandem with rotation and head motion reduce the locomotor cost.

Experimental study on hydrodynamic effect of orientation micro-pored surfaces

The orientation of the dimple increases the flow distance in the dimple and produces fluid cumulative effect in the dimple length direction, which leads to obvious hydrodynamic effect as a result. In order to investigate the hydrodynamic effect of orientation dimples, a series of experiments was carried out on a ring-on-ring test. Multi-pored faces were tested with different dimple inclination angles and slender ratios. Film thickness and frictional torque were measured under different conditions of load and rotation speed. Experimental results showed that the orientation dimple could produce obvious dynamic effect by change of the flow direction and the increasing dimple orientation leads to increase of the load capability. The hydrodynamic effect strongly depends on dimple orientation parameters such as inclination angle and slender ratio. A larger load capability can be available by increasing dimple orientation and rotation speed. Experimental results agreed well with the theory that orientation micro-pores can significantly improve hydrodynamic performance of surfaces.