Toprak Erozyon Çalışmaları İçin Bir Yapay Yağmurlama Aletinin Tasarım Prensipleri ve Yapay Yağış Karakteristikleri

Bu araşt ı rman ı n amac ı , Ankara Üniversitesi Ziraat Fakültesi Toprak Bölümü Ara ştı rma Laboratuvar ı nda kurulan bir yapay yağmurlama aletinin tasar ı m prensipleri ve teknik özelliklerini tan ı mlamak ve oluşturulan yapay yağışları n karakteristiklerini incelemektir. Yapay yağ murlama aletinin ana parçalar ı aç ı klanm ış olup damla oluşturucuları n detay ı ve uniform bir ya ğış elde edebilmek amac ı yla damla oluşturucular ı n uygulama tank ı içerisindeki yerleşim plan ı verilmiştir. Yağış karakteristikleri olarak intensite, damla büyüklüğü, damla düşme h ızı ve kinetik enerji incelenmi ştir. Yağ murlama havzası ndaki yağış intensitesinin dağı l ı mı uniformite katsay ı sı Cv ile değerlendirilmiştir. Cv değerleri çoğunlukla %80'nin üzerinde bulunmuş ve yağmurlama havzas ı nda yağış dağı l ı mı n ı n uniform olduğu saptanm ışt ı r. Farkl ı su yüklerinde, 3 mm ve 5 mm'lik uç çap ı na sahip damla oluşturucularla damla büyüklükleri ölçülmüştür. 5 mm'lik damla olu şturucularla daha büyük damlalar elde edilmi ştir ve su yükünün art ı rı lmas ı yla her iki uç çap ı nda damlaları n büyüklüklerinde azalma olmuştur. Bu koşullar alt ı nda yapay yağmurlama aletinin damla büyüklükleri 4.38 mm ile 5.25 mm aras ı nda değişmektedir. Damla çap ı ve düşme yüksekliğinden yararlan ı larak damla düşme h ı zları hesaplanm ışt ı r. Damla büyüklükleri ve ili şkili damla dü şme h ı zları çok fazla bir değişim aral ığı göstermediği için, yağış kinetik enerjisindeki de ğ işimlerin doğrudan yağış intensitesine bağ l ı olduğ u görülmüştür. Yağış intensitesi ve kinetik enerjisi aras ı nda doğrusal bir bağlant ı kurulmuşt

Anahtar Kelimeler:

Yapay yağ murlama aleti, damla olu şturucu, intensite, damla büyüklüğ ü ve düşme h ı z ı , kinetik enerji

Design Principles of a Rainfall Simulator and Characteristics of Simulated Rainfalls for Soil Erosion Studies

The objectives of this research are both to describe design principles and technical properties of a rainfall simulator constructed at the Research Laboratory of Soil Science Department, Agricultural Faculty of Ankara University, and to examine characteristics of simulated rainfalls. Main elements of the simulator were explained. Details of drop formers and a plan of drop formers within the application tank at which a uniform distribution of simulated rainfall was well attained were giyen. As rainfall characteristics, intensity, drop size, drop fall velocity and kinetic energy were investigated. Uniform intensity distributions of rainfalls in the catchment basin were evaluated by the uniformity coefficient Cv . Cv values were mostly found more than 80%, and uniform rainfall distribution was determined in the catchment basin. At different water height in the application tank, drop sizes were measured with drop formers having 3 mm and 5 mm tip diameter. Bigger drops were obtained with 5 mm drop formers, and drop sizes at either tip diameters were getting smaller with increasing water height. Under these conditions, drop sizes of the simulator were between 4.38 mm and 5.25 mm. Using drop diameters and fall heights of drops, drop fall velocities were estimated. Since drop sizes and related fall velocities did not signifı cantly change, it is observed that changes in kinetic energies of rainfalls were directly dependent upon the changes in rainfall intensities. A linear relationship was established between rainfall intensity and kinetic energy.

Keywords:

Rainfall simulator, drop former, intensity, drop size and fall velocity, kinetic energy,

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