模式分辨率对雾数值模拟的影响

利用中尺度数值预报模式MM5对2009年12月9日至11日发生在山西省的一次雾天气过程进行了数值模拟。在垂直分辨率不变的情况下,数值模式的水平分辨率分别采用45×15km、27×9km、15×5km三种方案及在水平分辨率不变的情况下垂直分辨率分别采用23层、30层、43层三种方案进行了对比模拟试验,模拟结果表明:水平分辨率对模式模拟的结果影响没有垂直分辨率的影响大;水平分辨率达到一定的精度,需要相应的提高数值模式的垂直分辨率来预报的准确率;水平格点数越多,模式运行的时间越长;垂直分层越多,相对而言积分时间越长。文章研究的结果将为山西省高速公路大雾数值预报系统的构建提供研究性基础。

资料同化对雾数值模拟的影响

利用中尺度数值预报模式MM5对2009年发生在山西省的几次雾天气过程进行了数值模拟,研究同化不同的探测资料对雾天气过程模拟的影响,结果表明:(1)不同方案模拟的2m温度均比实际观测温度低;(2)相比于未作资料同化的模式试验,同化了观测资料的试验模拟的结果更加接近实况;(3)地面观测资料同化对模拟的结果改进不是很明显;(4)同化高空资料比同化地面资料更有利于模拟雾天气过程,模拟不同高度的温度更接近实测,且低层液态水含量增加。因此,必须在山西省高速公路大雾数值预报系统中必须同化高空探测资料,以提高预报的准确性。

山西省大雾的中尺度数值模拟

利用中尺度模式MM5（The Fifth—Generation NCAR／Penn State Mesoscale Model）对山西省2009年发生的3场典型雾个例进行了数值模拟，探讨了物理过程参数化方案对雾数值模拟的影响，确定了基于模式模拟数据的雾判别指标，为该地区大雾数值预报系统的研制提供了理论基础。结果表明，综合考虑边界层方案和辐射方案对地表温度、高空温度、2m温度及相对湿度、10m风速、雾的空间分布、雾的生消过程、雾的发展高度等要素数值模拟的影响，边界层方案选用high-resolution planetary boundary layers cheme（HIR）方案、辐射方案选用Cloud方案时，雾数值模拟的结果与实况更为一致。综合分析多个典型雾个例的模拟结果，山西省境内雾的预报指标为：20m液态水含量为0．13～0．6g·kg^（-1），20～1500m高度大气层存在逆温层，10m风速小于4m·s^（-1）。

Numerical Simulation of Atomization due to Flood Discharges of Hydropower Stations

To mitigate the damages produced by flood discharges of hydropower stations, a three-dimensional numerical model of the aerated water jet restricted by gravity, air resistance and air buoyancy is proposed. Based on theoretical analysis and prototype data, a three-dimensional stochastic model is constructed using Monte Carlo method to evaluate the range of atomization and intensity of rainfall in gorges, which are strongly affected by complex terrain and various wind conditions. The prototype data observed from two hydropower stations are selected in the feedback and verification analysis to verify the proposed model. The result shows that the computational solutions fit the prototype data well. This model can be used to forecast the atomization of a hydropower station that is being designed or constructed.

Recent Observations and Modeling Study About Sea Fog over the Yellow Sea and East China Sea

This review presents some of the latest achievements in sea fog research,including fog climatology,fog structure in the marine atmospheric boundary layer,and numerical simulations and forecasting of fog.With the development of atmospheric observational techniques and equipments,new facts about sea fog are revealed.The mechanisms involved in the formation,development and dissipation of sea fog are further explored with the help of advanced atmospheric models.

Analysis of Particle Behavior in High-Velocity Oxy-Fuel Thermal Spraying Process

This paper analyzes the behavior of coating particle as Well as the gas flow both of inside and outside the High-Velocity Oxy-Fuel (HVOF) thermal spraying gun by using quasi-one-dimensional analysis and numerical simulation. The HVOF gun in the present analysis is an axisymmetric convergent-divergent nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. In the present analysis it is assumed that the influence of the particles injected in the gas flow is neglected, and the interaction between the particles is also neglected. The gas flow in the gun is assumed to be quasi-one-dimensional adiabatic flow. The velocity, temperature and density of gas in the jet discharged from the barrel exit are predicted by solving Navier-Stokes equations numerically. The particle equation of motion is numerically integrated using three-step Runge-Kutta method. The drag coefficient of the particle is calculated by linear interpolation of the experimental data obtained in the past. Particle mean temperature is calculated by using Ranz and Marchalls' correlation for spherical particles. From the present analysis, the distributions of velocity and temperature of the coating particles flying inside and outside the HVOF gun are predicted.

Verification on Spray Simulation of a Pintle Injector for Liquid Rocket Engine

The pintle injector used for a liquid rocket engine is a newly re-attracted injection system famous for its wide throttle ability with high efficiency. The pintle injector has many variations with complex inner structures due to its moving parts. In order to study the rotating flow near the injector tip, which was observed from the cold flow experiment using water and air, a numerical simulation was adopted and a verification of the numerical model was later conducted. For the verification process, three types of experimental data including velocity distributions of gas flows, spray angles and liquid distribution were all compared using simulated results. The numerical simulation was performed using a commercial simulation program with the Eulerian multiphase model and axisymmetric two dimensional grids. The maximum and minimum velocities of gas were within the acceptable range of agreement, however, the spray angles experienced up to 25% error when the momentum ratios were increased. The spray density distributions were quantitatively measured and had good agreement. As a result of this study, it was concluded that the simulation method was properly constructed to study specific flow characteristics of the pintle injector despite having the limitations of two dimensional and coarse grids.