海上漂浮式激光雷达运动平台模拟器设计及应用

本文介绍了海上漂浮平台运动模拟器的设计和应用。为了模拟测风激光雷达在海上的工作环境,验证测风激光雷达在非稳定平台的风场计算算法,设计了一套六自由度运动平台模拟器,平台可以按浮标实测数据运动或按固定振幅频率正弦数据运动,搭载激光雷达进行测风实验。本文将两台激光雷达分别处于静止和运动状态进行测风,研究平台运动速度对风场反演的影响。结果显示,平台静止时两台雷达风速平均误差最小,为0.0198 m/s,风向平均误差与最小风向平均误差基本相同,为2.0219°。随着平台运动速度的增加,风速和风向的反演误差也随之增加。该平台能够模拟海上漂浮平台的运动,搭载海上测风激光雷达进行实验,且分析结果能为风场反演算法的优化提供参考。

Observation System Experiments for Typhoon Nida(2004)Using the CNOP Method and DOTSTAR Data

This study investigated the influence of dropwindsonde observations on typhoon forecasts. The study also evaluated the feasibility of the conditional nonlinear optimal perturbation (CNOP) method as a basis for sensitivity analysis of such forecasts. This sensitivity analysis could furnish guidance in the selection of targeted observations. The study was performed by conducting observation system experiments (OSEs). This research used the fifth-generation Mesoscale Model (MM5), the Weather Research and Forecasting (WRF) model, and dropsonde observations of Typhoon Nida at 1200 UTC 17 May 2004. The dropsondes were collected under the operational Dropsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR) program. In this research, five kinds of experiments were designed and conducted:(1) no observations were assimilated; (2) all observations were assimilated;(3) observations in the sensitive area revealed by the CNOP method were assimilated;(4) the same as in (3), but for the region revealed by the first singular vector (FSV) method;and (5) observations within a randomly selected area were assimilated. The OSEs showed that (1) the DOTSTAR data had a positive impact on the forecast of Nida's track;(2) dropsondes in the sensitive areas identified by the MM5 CNOP and FSV remained effective for improving the track forecast for Nida on the WRF platform;and (3) the greatest improvement in the track forecast resulted from the CNOP-based (third) simulation, which indicated that the CNOP method would be useful in decision making about dropsonde deployments.

Updating empirical results of wind loads on cooling towers for turbulence intensity effects

Variations of wind effects on large cooling towers observed at different turbulence intensities for our previous full-scale measurements might be caused by the inherent uncertainties in our physical experiments.Accordingly,the one-way analysis of variance(ANOVA)technique is employed for analyzing the data measured on the prototype Pengcheng cooling tower.Because ANOVA indicates that the variations of full-scale wind effects are basically the effects of turbulence intensity,the empirical results of wind loads on cooling towers obtained by generalizing physical experimental data without considering the turbulence intensity effects are updated using model test results obtained in multiple flow fields.The empirical fluctuating wind pressure distribution is updated based on the fact that the fluctuating wind pressure coefficient linearly increases with the increase in the turbulence intensity,and the empirical formulae of the spectra and the coherences is updated based on conservative assumptions.Comparisons of the empirical results and full-scale measurement data suggest that the original empirical results are either too conservative or unsafe for use.However,economic efficiency and conservativeness will be balanced if the updated empirical results are employed for the wind engineering design.

Experimental Investigation of Reynolds Number Effect on Wind Turbine Profiles in the Cryogenic Wind Tunnel Cologne DNW-KKK

Wind turbine size has increased continuously and correspondingly also its Reynolds numbers. The Reynolds number effect can therefore no longer be ignored in design and optimization of wind turbines. Reliable profile test data should be available. A suitable facility for testing wind turbine profiles at high Reynolds numbers is the Cryogenic Wind Tunnel Cologne DNW-KKK. By means of injecting liquid nitrogen the tunnel can be cooled down to 100 K and the Reynolds number therefore can be raised accordingly. The maximum Reynolds number for 2D profile tests can reach 27x10^6. In this paper the test uncertainty and the flow quality of DNW-KKK were analyzed. Then some test results on the Reynolds number effect of the wind turbine profiles will be presented. The Reynolds number effect is different from model to model. Especially for thick profiles and flow control devices the Reynolds number effect is not always like the description in literature.

Tracking of Flat Belts

When applying fiat belts, correct tracking of the belt through the installation has to be assured. Since flat belts are commonly used for conveying and transmission purposes, tracking systems have been well developed, but the ultimate tracking behaviour of the belt can be greatly enhanced by taking special care in the creation of an adequate tracking mechanism. To obtain long-life operation and full value from the equipment, the correct tracking technique plays an important role. This paper deals with two tracking techniques： The skewed and the angled pulley axis. Numerical simulation results are compared with both measurements and an analytical approach. The advantages of numerical simulation compared to experimental tests are ease, convenience and the absence of any safety risk. Compared to analytical approaches the simulation is used for systems for which simple closed form analytic solutions are not possible.

Evaluation of Cloud Feedback at Local Scale： Warming or Cooling？

Clouds affect the climate by positive and negative feedback. To study these effects at local scale, a radiation station was set up, which used two CM21 Kipp ＆ Zonen pyranometers （one inverted）, and two CG1 Kipp ＆ Zonen pyrgeometers （one inverted） in Logan, Utah, USA. The pyranometers and pyrgeometers were ventilated using four CV2 Kipp ＆ Zonen ventilation systems. Ventilation of pyranometers and pyrgeometers prevent dew, frost and snow accumulation, which otherwise would disturb the measurement. Knowing that available energy （Rn） as Rn = Rsi - Rso ＋ Rli - Rio where Rsi and Rso are downward and upward solar radiation, respectively, and Rli and Rio as atmospheric and terrestrial, respectively, the effects of cloudiness were evaluated on a daily and annual basis. The results indicate that for the partly cloudy days of 4 and 5 September, 2007, cloudiness caused less available energy （Rn） in the amounts of-1.83 MJ·m^-2·d^-1 and -3.83 MJ·m^-2·d^-1 on these days, respectively. As shown, due to cloudiness at the experimental site, the net radiation loss was 2,804 - 4,055 = -1,251 MJ·m^-2·d^-1, which indicates a negative feedback due to cloudiness.

Transition prediction of the supersonic boundary layer on a cone under the consideration of receptivity to slow acoustic waves

Transition prediction of the supersonic boundary layer on a cone with small angle of attack and Mach number 3.5 is investi-gated under the consideration of receptivity to slow acoustic waves, as the acoustic waves are the main environmental distur-bances in a conventional, i.e. non-quiet, wind tunnel. It is shown that the e-N method can still yield fairly satisfactory results incomparison with those obtained in wind tunnel experiments, provided that the boundary layer receptivity to slow acousticwaves is properly taken into account, including the dependence of the amplitude of disturbances on the frequency andstream-wise location. Neither the conventional e-N method nor the improved e-N method can yield correct result of transitionprediction, because the receptivity mechanisms considered there are not in accord with the real situation in the wind tunnel.

Performance research and optimization on the fan test system based on experiment

To investigate the fan performance of air conditioning system, two different configuration fan test systems are designed. All scale simulation of the two systems provide the basis for design and improvement of air conditioning system fans to improve the internal flow, increase air volume, and reduce the noise. The conclusion that disturbance on flow of nuzzle outlet is the main sources of measurement error about 5% can be proved by the comparative analysis of the results between computation and experiment. Through Optimization Design of Partial Structure they all meet the industry standard, measurement error less than 1.5%.

Numerical and Experimental Study on Aerodynamic Performance of Small Axial Flow Fan with Splitter Blades

To improve the aerodynamic performance of small axial flow fan, in this paper the design of a small axial flow fan with splitter blades is studied. The RNG k-e turbulence model and SIMPLE algorithm were applied to the steady simulation calculation of the flow field, and its result was used as the initial field of the large eddy simulation to calculate the unsteady pressure field. The FW-H noise model was adopted to predict aerodynamic noise in the six monitoring points. Fast Fourier transform algorithm was applied to process the pressure signal. Experiment of noise testing was done to further investigate the aerodynamic noise of fans. And then the results obtained from the numerical simulation and experiment were described and analyzed. The results show that the static characteristics of small axial fan with splitter blades are similar with the prototype fan, and the static characteristics are improved within a certain range of flux. The power spectral density at the six monitoring points of small axial flow fan with splitter blades have decreased to some extent. The experimental results show sound pressure level of new fan has reduced in most frequency bands by comparing with prototype fan. The research results will provide a proof for parameter optimization and noise prediction of small axial flow fans with high performance.