Hazen-Williamz Research Papers - Academia.edu (original) (raw)

Hazen-Williams equation is used widely by irrigation systems’ designers due to its simplicity.However, Darcy-Weisbach equation is more accurate and reliable. The accuracy of the latter is due to its friction coefficient, which depends on both flow characteristics and pipe surface state. On the other hand, Hazen-Williams’ coefficient (C) depends only on pipe substance and age. A comparative analysis of both models was performed through a simple iterative model. The analysis was based on the real state design procedure of drip laterals. More accurate values of coefficient C were suggested to be used in designing drip laterals. A straightforward equation was developed to compute C depending on emitter flowrate, emitter flow exponent, and pipe diameter.The results reveal that C ranges from 132 to 138 for drip laterals, while it was proved that using C=150 is reasonable for manifolds design.

- by Mohammad ElNesr
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- Hydraulics, Friction Models, Irrigation Systems Design, Drip / trickle irrigation

Friction head loss equations and friction correction factors were evaluated and compared to field observations collected from thirty center‐pivots with laterals made of PVCs. The friction head loss equations include Darcy‐Weisbach (D‐W), Hazen‐Williams (H‐W), and Scobey, in addition to a proposed equation valid for smooth and rough pipe types and for all turbulent flow types. The proposed equation was developed by combing the equations of D‐W and H‐W, along with the multiple non‐linear regression technique. The friction correction factors were computed using the typical Christiansen, modified Christiansen, Anwar, and Alazba formulae. The evaluation has been based on statistical error techniques with observed values as a reference. With the combination of modified Christiansen, Anwar, and Alazba formulae, the results revealed that the magnitudes of friction head loss calculated using D‐W equation, H‐W equation, and proposed equation were in agreement with field observations. The root mean square deviation (RMSD) values were found to be ranging from 1.6 to 1.7 m. As expected and when the typical Christiansen friction correction factor was used with the D‐W equation, with the H‐W equation, and with the proposed equation, the results showed poor agreement between observed and computed friction head loss values. This was clearly reflected by the high RMSD values that were ranging from 5.4 to 5.8 m. On the other hand, there was agreement between observed friction head loss values and those calculated using Scobey equation, invalid for PVC pipe type, when combined with the typical Christiansen formula. This interesting finding led to improved results of Scobey equation through a developed Cs coefficient suitably valid for PVC pipe type via analytically mathematical derivation. And accordingly, the RMSD value dropped from about 8.6 to 1.6 m.

- by Mohammad ElNesr and +1
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- Friction head loss equations, Friction Correction Factor, Center-Pivot irrigation system, Hazen-Williamz

Explicacion objetiva y ejercicios prácticos de hidráulica de los libros de MECÁNICA DE FLUIDOS E HIDRÁULICA DE SCHAWN e HIDRÁULICA DE KING.

1925 yılında kurulan Atatürk Orman Çiftliği (AOÇ) arazisinde tarımsal sulama ve çeşitli tesislerin su gereksinimi için çok çeşitli su kaynaklarından yararlanılmıştır. Çiftlik arazisindeki Marmara ve Karadeniz havuzlarının su ihtiyacı için günümüzde Çankaya Alacaatlı Mahallesi sınırları içinde bulunan Kırkgöz Kaptajı'ndan, 1935 ile 1936 yılları arasında Sular Umum Müdürlüğü tarafından 15 kilometrelik bir iletim hattı ile su getirilmiştir. Getirilen su daha sonra Ankara Bira Fabrikası için tahsis edilmiştir. 1939 yılında TEKEL Genel Müdürlüğü mülkiyetine geçen kaptaj sahası 2010 yılında TEKEL'in özelleştirilmesi ile bir ortak girişim grubuna satılmıştır. Su kaynağı varlığını hâlen korusa da iletim hattının en azından yarısının varlığı tartışmalıdır. Makalede varlığını çok az kişinin bildiği Kırkgöz Kaptajı'na ilişkin bulunabilen tarihî belgeler ile kaptaj sahasında yapılan güncel gözlemler bir araya getirilmiştir. Ayrıca 15 kilometrelik iletim hattının güzergâhı çeşitli veri kaynakları kullanılarak tahmin edilmeye çalışılmıştır. Sonuç olarak Ankara tarihinde önemli bir yeri olduğu düşünülen bu yeraltı suyunun yeniden şehre kazandırılması tartışmaya açılmıştır.

- by Onur Bektaş
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- Water resources, Groundwater, Water Privatization, Limestone