自制立轴式风向标风速器组合仪

风向标、风速器是学校建立小气象站,进行气象观测活动必不可少的仪器,但一般的风标式风速器需要较复杂的电子仪器,不能直接读出风级。为了解决这一问题,我通过反复摸索,设计制作了立轴式风向标、风速器组合仪,本仪器取材方便,使用简易,可直接观察风向和读出风级。现介绍如下:

Ultrasonic wind velocity measurement based on DSP

Ultrasonic transmitting, receiving and amplifying circuits are designed. Thereceived signals are sampled with the high speed ADC (analog-to-digital converter), and dealt withthe DSP (digital signal processing). A forward-backward IIR (infinitive impulse response) filterwith no delay is designed to filter the sampled data, and series A and B are achieved by narrow andwide band filtering, respectively. In series A, the start point of the cycle first exceeding thethreshold is calculated accuratelyby interpolation, and the start cycle is detected by fittingcycles in series A and its inversion A' to cycles in B with variance analysis. Therefore, the startpoint of the start cycle is calculated precisely. By deriving the relationships between the traveltime in the opposite directions of three axes and the airflow velocities, the wind velocity anddirection are calculated. Experiments show that the reliability and the precision are improved, andthe circuits are simplified.

Study of measurements of air velocity transducer deriving average air velocity of roadway based on one-dimensional linear regression

One-dimensional linear regression equation between measured value of air velocity transducer and the average air velocity was established by experimental data. The effect is to be evaluated. Through judging the parameters, one-dimensional linear equation established is valid. Regression equation can approximately put the measurements of air velocity transducer into the value of average air velocity. The distribution of air velocity field is simulated using Comsol in the conditions of the same length of roadway, the same air velocity and different sections.

Installation position determination of wind speed sensors on steel pole along a high-speed railway

In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Based on the three-dimensional steady Reynolds-averaged Navier-Stokes equations and k-ε double equations turbulent model, the field flow around the wind speed sensor and the steel pole along a high-speed railway was simulated on an unstructured grid. The grid-independent validation was conducted and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. Results show that the steel pole has a significant influence on the measurement results of wind speed sensors. As the distance between two wind speed sensors is varied from 0.3 to 1.0 m, the impact angles are less than ±20°, it is proposed that the distance between two wind speed sensors is 0.8 m at least, and the interval between wind speed sensors and the steel pole is more than 1.0 m with the sensors located on the upstream side.

Trends in Significant Wave Height and Surface Wind Speed in the China Seas Between 1988 and 2011

Wind and waves are key components of the climate system as they drive air-sea interactions and influence weather systems and atmospheric circulation. In marine environments, understanding surface wind and wave fields and their evolution over time is important for conducting safe and efficient human activities, such as navigation and engineering. This study considers long-term trends in the sea surface wind speed(WS) and significant wave height(SWH) in the China Seas over the period 1988–2011 using the Cross-Calibrated Multi-Platform(CCMP) ocean surface wind product and a 24-year hindcast wave dataset obtained from the WAVEWATCH-III(WW3) wave model forced with CCMP winds. The long-term trends in WS and SWH in the China Seas are analyzed over the past 24 years to provide a reference point from which to assess future climate change and offshore wind and wave energy resource development in the region. Results demonstrate that over the period 1988–2011 in the China Seas: 1) WS and SWH showed a significant increasing trend of 3.38 cm s^(-1)yr^(-1) and 1.52 cm yr^(-1), respectively; 2) there were notable regional differences in the long-term trends of WS and SWH; 3) areas with strong increasing trends were located mainly in the middle of the Tsushima Strait, the northern and southern areas of the Taiwan Strait, and in nearshore regions of the northern South China Sea; and 4) the long-term trend in WS was closely associated with El Ni?o and a significant increase in the occurrence of gale force winds in the region.

A Mathematical Model for the Velocity Profile Internally to a Conical Diffuser

The use of diffusers around the horizontal-axis wind turbines has been widely studied since the diffuser improves the power coefficient of the turbine and it is often called DAWTs （diffuser augmented wind turbines）.Turbines using diffuser are called DWATs （Diffuser Augmented Turbines）,and have efficiency bigger than the Betz limit （maximum energy flow extracted = 59.26%）. Thus, this study presents a mathematical model describing the behavior of the velocity profile internally to a diffuser according to the characteristics of flow and geometry of a conical diffuser. The results are compared with experimental data and show good agreement.

A New Calculation Method of the Axial and Radial Velocity and Grade──Efficiency for High──Efficiency Cyclones

At present in China, the cyclones are widely used in the dust removal ventilation system of boilers, industry furnaces or pits etc., because of their simple structure, long life and cost efficiency. In order to improve efficiency of the cyclones, new theoretical calculation method is very important. In this paper, the concept of down-flow quantity is introduced and new formula is deducted based on Kilven law and the work has done by Zhao Weizhong[1]. The formula is not only of advantage theoretically but also fit with experimental results quite well. On the basis, the effect of three-dimensional velocity distribution in the flow field within cyclones and other parameters on the grade-efficiency calculation are analyzed and a new equation for grade-efficiency estimation is introduced. The calculating accuracy of the equation is better than the others theoretically and experimentally.

Estimations of the Maximum Tangential Velocity V_(θm) in the Vortex Core Region and also the Mean Rotational Velocity V_(oi) near the Concave Wall Surface in the Returned Flow Type Cyclone Dust Collector

There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity V0m in the vortex core region in the cyclone body. In order to determine V0~ by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity Voi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities V~ and Voi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.

Contributions of the Secondary Jet to the Tangential Velocity Distribution and to the Collection Efficiency of the Fixed Guide Vane Type Axial Flow Cyclone Dust Collector

In order to control the maximum tangential velocity V?m(m/s)of the turbulent rotational air flow and the collection efficiencyηc(%)using the fly ash of the mean diameter X R50=5.57?m,two secondary jet nozzles were installed to the body of the axial flow cyclone dust collector with the body diameter D1=99mm.Then in order to estimate V?m(m/s),the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied.The comparisons of the estimated results of V?m(m/s)with the measured results by the cylindrical Pitot-tube were shown in good agreement.And also the estimated collection efficienciesηcth(%)basing upon the cut-size Xc(?m)which was calculated by using the estimated V?m(m/s)and also the particle size distribution R(Xp)were shown a little higher values than the experimental results due to the re-entrainment of the collected dust.The best method for adjustment ofηc(%)related to the contribution of the secondary jet flow is principally to apply the centrifugal effect?c(1).Above stated results are described in detail.

Wind speed prediction by chaotic operator network based on Kalman Filter

A novel prediction network composed of some chaotic operators is proposed to predict the wind speed series.Training samples are constructed by the theory of phase space reconstruction.Genetic algorithm is adopted to optimize the control parameters of chaotic operators to change the dynamic characteristic of the network to approach to the predicted system.In this way,the dynamic prediction of wind speed series can be completed.The wind acceleration series can also be predicted by the same network.And the prediction results of both series can be fused by Kalman Filter to get the optimal estimation prediction result of the wind speed series,which is superior to the result obtained by each single method.Simulation results show that the prediction network has less computation cost than BP neural network,and it has better prediction performance than BP neural network and autoregressive integrated moving average model.Kalman Filter can improve the prediction performance further.