Newsletter nº 2 May 2015 Measurement system setup Ajdovščina Fig. 1: The measurement system in Ajdovščina 1
Wind Risk project is being implemented with the contribution of the Civil Protection Financial Instrument of the European Union. Within the Wind Risk prevention project we planned to set up a system to measure wind characteristics in different regions and get information about different types of wind. The measurements of wind speed and direction will be shown on an internet page with live stream that will display the information in real time. The readings will also be used as an alarm system for local civil protection service and will alert them immediately after average wind speed or wind gusts exceed specific limits. To gain this knowledge we have set up the first wind measurement system in Ajdovščina. The area around the city of Ajdovščina is exposed to high winds and wind gusts. The most common phenomena in the area is so called Burja or Bora. Bora is observed in the countries from Italy to Turkey to Russia. The root of the word is found in the Greek word borea, which means north. Bora is a cold wind coming from the north. The wind blows with high average wind speeds and additional violent bursts of wind gusts. In the area the average presence of bora is 42 days per year. The highest wind gust speeds exceed 200 km/h. The high wind causes damage to trees, buildings, affects traffic and people. Location The first measurement system has been set up in the city of Ajdovščina on the roof of the stadium of their football team next to the Ajdovščina sport plane airport. The measurement system is orientated towards the north from where the bora winds generate from the neighboring hills. The roof is approximately 12 meters high and slender on the side of the wind direction, therefore the wind is blows with minimal turbulence and measurements should be realistic. Fig. 2: The location of the first measurement system in Ajdovščina 2
Fig. 3: The map of the first measurement system in Ajdovščina 45 Fig. 4: The plywood orientation from the top The orientation in not important for the sole wind measurement, but more for the plywood board beneeth the anemometer where actual forces will be measured. The purpose of force measurements is to observe the relationship between wind speed and wind direction and the forces it generates. 3
Allthough this might seem trivial, it isn't. Especialy when we talk about wind gusts, since they are very short and the actual forces are not the same as when compared to forces at steady wind. Anemometer The WindMaster Pro anemometer from GILL Instruments is on top of a stiff steel construction that is mounted on one of the roof beams. It is approximately two meters above the roof top. The WindMaster Pro is constructed from stainless steel and has a maximum operating wind speed of 65 m/s. With a fast maximum data output rate of 32Hz as standard, improved vertical (W) resolution and Speed of Sound accuracy and less distortion due to wind loading, this 3 axis anemometer is particularly suitable for precision wind measurement applications requiring 3 axis data. Anemometer records speed in three directions U, V and W. U is defined as towards the direction in line with the north spar as indicated in the diagram. V is defined as towards the direction of 90 anti clockwise from N / the Reference spar. W is defined as vertically up the mounting shaft. Temperature is also recorded. An example of the record is shown below. The M sign in the record stands for metric units. U V W Temperature Fig. 5: The plywood orientation from the side 4
Data acquisition The data from the anemometer is in digital form and is passed through an RS422 cable that is connected to a National Instrument RS422 to Ethernet Interface unit called ENET 485/2. The signal than goes over the Ethernet to the computer. The software used for recording and controlling the output format of the instrument is a program called Wind. Fig. 6: National Instrument RS422 Fig. 7: The window of the program called Wind 5
Live stream A live stream web page will be set up on a remote server in Split that will display the measurements in real time. An alarm system for local civil response units will be integrated in the design of the page that will send out an alert when the wind speed values become critical. Force measurements Further steps include a force measuring system that will used for scientific purposes to study the pressure forces due to wind. AST KAP S force sensors will be mounted behind a square meter plywood board, that will be screwed to the construction beneath the anemometer. The maximum force of the sensors is 2kN. Fig. 8: AST KAP S force sensor The sensors will be connected to the ethernet via a National Instruments Bridge module NI 9237 and a Data acquisition unit NI cdaq 9188. Fig. 9: A Bridge module NI 9237 (left) and a Data acquisition unit NI cdaq 9188 6