Rüzgar Kırıcı Elemanlarda Boşluk Oranının Hız Dağılımı Üzerindeki Etkilerinin İncelenmesi : Deneysel Yollarla

Abstract

Günümüzdeki teknolojik gelişmeler sayesinde, her türlü yapma çevre önceden hazırlanarak, gerek sayısal, gerekse deneysel çalışmalarla performans araştırması yapılabilmektedir. Bu çalışmanın amacı, herhangi bir rüzgar kırıcı elemanın, boşluk oranlarına göre hız dağılımları üzerindeki etkilerinin deneysel yollarla araştırılmasıdır. Bilindiği gibi, rüzgarın insanlar üzerinde doğrudan veya dolaylı etkisi, herzaman hissedilmiştir. Bu etkiyi, iklimsel konfor koşullarına uygun bir şekilde kullanabilmek için, çalışmanın ana fikrini " rüzgar kırıcılar " oluşturmuştur. Çalışmanın birinci bölümünü oluşturan giriş bölümünde, yapısal etkileri nedeni ile mimari aerodinamiğin vazgeçilmez bir parçası olan rüzgarın, genel bir tanımı yapılarak, çeşitli bölgelerde oluşturduğu farklı etkilerden söz edilmiştir. Hava hareketlerinin oluşumu, rüzgar etkileri sonucu ortaya çıkar. Rüzgar, hava kütlesi içinde yeralır ve şiddetine göre yer değiştirerek hava hareketlerini yönlendirir. İnsanoğlu, varolduğu çağlardan günümüze kadar rüzgar ve etkilerini araştırmış, fiziksel konfor koşullarına uygun ortamlar oluşturmaya çalışmıştır ve mimari aerodinamiğin gelişmesinde birtakım kabullerden yola çıkarak, yeni teknikler geliştirmiştir. Hava hareketlerinin incelenmesinde anemometrelerden ve rüzgar tünellerinden yararlanıldığı, tezin ikinci bölümünde anlatılmaktadır. Rüzgar hızını ölçmeye yarayan aletlere "anemometre" adı verilir. Rüzgar tünelleri ise, iklimsel parametrelere uygun yerleşmeler oluşturabilmek ve hava hareketlerinde oluşan hız dağılımlarını inceleyerek, kontrol altında tutabilmek için yapılan deneysel çalışmalar sırasında kullanılırlar. Rüzgar tüneli testleri, hava akımına dayanıklı bina tasarımının geliştirilmesi veya bina modelleri etrafında oluşan hava hareketlerinin etkilerinin incelenmesi amacı ile yapılır. Çalışmanın üçüncü bölümünde, deneysel çalışmanın gerçekleştirildiği İ.T.Ü. Mimarlık Fakültesi Fiziksel Çevre Laboratuarı' nda bulunan mevcut rüzgar tünelinin özellikleri ile, kullanılan araç ve gereçler tanıtılarak, deney düzeneği çeşitli çizim ve fotoğraflarla anlatılmıştır. Ayrıca, " Elde Edilen Deneysel Veriler " başlığı altında % 0, % 5, % 10 ve % 15 boşluk oranlarında elde edilen deney sonuçları karşılaştırılarak, farklı boşluk oranlarının ortalama hız ve turbülans üzerindeki etkileri incelenmiştir. Elde edilen ölçüm sonuçlarından, oluşturulan boşluk oranlarının engelin arkasında farklı mesafelerde, ayrı hava hareketleri oluşturması nedeni ile, farklı ortalama hız değerlerine ulaşılabileceği anlaşılmaktadır. Yani, boşluk oranları, belirli mesafelerde farklı etkiler göstermektedir. Bunun nedeni de, daha önce anlatılmış olan hava hareketleridir.

Owing to the technological development in recent years, performance research can be done with quantitative and experimental workings preparing artificial environment in advance. Our aim is to examine the effects of the emptiness ratios on velocity distribution of wind breaking elements with an experimental methods. The wind, indispensable element of architectural aerodinamics, has been explained in the first chapter of this research and different effects of the wind in various regions have been noted. Generally, the air movement, from high pressure area to low pressure area, is called the wind. The wind is one of the most important parameters which effects the occurence of the air movements on the earth and it effects differently in various regions because of geomorphological structure. For this reason, the effects of the emptiness ratios on velocity distributions have been examined by considering buildings, plants, topographical properties which hindered the wind. To examine the effects of the emptiness ratios on velocity distributions, firstly air movements should be examined. Therefore, in the second chapter, the structure of the wind and wind types has been explained. After some explanations were done about " How does the climateness differences take place? ", the development of the architectural aerodinamics in different cultures has been explained by giving some examples about the opinion of the famous thinkers, in this chapter. Air measurement tools which is used to obtain numerical results, explained in the further part of this chapter. After working principle of the anemometers, which is helped us to measure the velocity of the wind, was examined; some definitions has been done about the wind tunnel types. Then the main criterions, which is used to analyse the results of the experiment of the wind tunnels and how the results will interpret by using mathematical and statistical methods, have been explained. At the end of the second chapter, parameters which effect the characteristic of the wind and the current types explained. The formation of the air movements takes place as the result of the wind effects. The wind takes part in air mass and it directs air movements by moving according to its violence. Because of the heatness privileges which vu is being in atmosphere, low or high pressure centers take place according to the regional differences. Pressure differences between these two centers supplies the formation of the air movements and determines its direction. So, climateness differences take place. Mankind has researched the wind and its effects until these days, and developed new techniques to constitute environment which is suitable for physical comfort conditions. Anemometers and wind tunnels are used being examined the air movements. The tools which are used to measure the velocity of the wind are called as " Anemometer ". The wind tunnel tests are done to develop the design of the buildings or to examine the effects of the air movements which is around the building models. " What kind of effects do air movements in ground cote of the buildings create in artificial environment? " or " How do soot atoms flying from chimney move around the buildings ? " The answer of the questions like these, can be learned owing to the experimental workings doing in tunnels. The design of the buildings are done by examining the results of these experimental workings. Criterions which is used to compare the measurement results obtained from experimental workings doing in the wind tunnels are examined in three groups; Similarity, Section - Model Connection and doing Atmospherical Border Layer. Working to supply the harmony between the model which is used in the experimental working and the actual building is called as the "Similarity ". But, it is impossible to supply the similarity perfectly. Because, material used for the model, shows differences in the physical and chemical properties, density and its composition. Especially, supplying the similarity in workings of the high coated buildings, bridges, transmitter antenna towers effects performance of the design, too much. When doing model in the wind tunnels, there are some rules to be attended. Surface roughness of the inside of the tunnel, effects the current model directly. So, not to create different dinamic effects, the empty measurement must be done before doing actual measurement. After the model was inserted in the tunnel, current model supplying as uniform may breakdown because of the change of the pressure distribution in the tunnel. Especially, if the ceiling of the tunnel is not suitable for the experiment, there will additional pressures on the model in the observation room. This will effect the results of the observation and cause the deviation on the current speed. If one of the apperance techniques is applied, there will be different deviations in the current traces. The deviations must be V1U maximum % 5 in the tunnel observations. If deviations is greater than % 5, new arrangements in the tunnel must be done. The atmospherical boundary layer is the last criteria which is used to compare the results of the experiment obtaining in wind tunnels. In the experiments done for the building designs, which has the scale between 1/200 and 1/1000, the boundary layer may be applied. This expression can be defined by Reynolds number which is the most important criteria in the tunnel observations. Current apperance techniques except the wind tunnels have been developed to understand the experiment results visually. The change in the wind speed and current types in the observation room may be established by the help of these techniques. These techniques are examined in four groups as Smoke tecnique, Sand technique, Liquid technique and Computer supported apperance techniques. The importance of the smoke tecnique is, not to change the prob temperature because of the cold smoke when hot wire anemometer is used. This helps to supply the measurement value much more healthy. It must be take into consideration to control the current apperance time by extending the smoke exit time. Sand technique is not a practical method to be used in the wind tunnel. It is impossible to use this technique in many laboratories. Because, special precautions must be taken not to effect human health and the calibration of the tools that are used. Liquid technique is used to view the currents that are in the horizantal plane. This system helps to view the current apperance by using liquid mixture which depends on chemical spoilt time. Chemical properties of used liquids, effects the formation time of the current lines and the view time of the current lines. Generally, the mixture of chemical materials of yellow pigment and kerosene with white alchol is used in the experiments. The developing technology, helped us to speed up the workings about the computer supported apperance. Software producers, first studied about 2D drawings and then progressed 3D drawings. Among the devoloping technology, the studies about the computurized visiuality, became faster. At the beginning soft - ware produces, basicly studied on two dimensional drawing programs, but today they were able to produce programs which could give three dimensional visiuality. In two dimensional drawings, the measured values recorded in the computer or they measured by the help of visuality program. In this method, the calculation made by excepting the velocity values on the tie point were constant. The occurring vectoral lines, decreased by IX the inverse ratio of the air velocity and then visuality could be made according to the boundary of velocity. These measurements could be revaluated for some instant. Especially, recognizing the three dimensional visiuality which are made by computurized equipments that are supported by laser optic systems give very effective results. As well as technological development the studies on wind tunnel can warn the engineers and architects the missing points about the projects so they could get much more correct results. The results of the wind tunnel experiments, could be idendified by mathematical and statistical methods. And so the physical and statistical behaves of the wind could be explained as turbulance, heaviness and velocity spills. With same reasons the momentarily changes in the velocity, efficiency and the direction of the wind is called as turbulance. These momentarily changes could be seen as surface roughness and vertical unstability. As a function of the surface visuality, the heaviness is occured as topografic speciality and it is a general name which identifies the turbulance. As usual while the air flow passing through a surface, a laminer border surface occured and then this surface became turbulance. Concerning this turbulance surface changes, the velocity rates increased by Reynolds tension. Since everything in the builded environment effected by air motions, the type and character of the wind could be changed. So the air motion on the smooth surface could be so different then the motion on the rough surface. For this reason, at the and of the second chapter, all the parameters that effect the wind character and flow type were inspected seperately. In the third chapter of the study, the characteristics of the wind tunnel which is placed at the I.T.U. Architecture Faculty, Physical Nature Labrotory, has been described. All the equipments were introduced and also experiment systems were described. Under the topic of "Calculated Experimental Values", the experiment results were compared that are calculated at % 0, % 5, % 10, and % 15 emptiness ratios, and also the effects of the different emptiness ratios on the velocity and turbulance which were searched. The transforming vacuum wind tunnel that is placed in I.T.Ü. Architecture Faculty has a collector, a searching room, a difusser and a fan. All the wind tunnel experiments were made by the tecnological developments and computer supporting configurations. The soft-ware that has been used during the experiments is "ACQWIRE". By the help of this soft-ware we were able to calculate the values of the turbulance density and the average velocity and to keep and to interpret them by the help of the graphs. By the help of this experimental study, the effects of the emptiness ratios on the velocity profiles and the relation between human-nature comfort conditions were tried to be calculated. At the end of the measurements, the results were same as the results that were measurement of velocity and turbalance values at the points of 3h, 5h, and 7h behind the barrier at % 0, % 5, % 1 0 and % 1 5 emptiness ratios. The graphs are drawn by the help of EXCEL 5.0. The calculated experiment results, show us that, form emptiness ratios beyond the barrier at the different distances, form different average ratios because of the seperate air motions. It means that, emptiness ratios show different effects at the different distances. It is because of of the air motion that have been written previously.