Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
An Innovative Preston Tube for Determination of Shear Stress on Smooth and Rough Beds
Abstract Preston tube is a shear stress measuring technique which is widely used due to its simple operation and construction. Although application of this technique in smooth bed is convenient and reliable, such application in rough bed is problematic due to the appearance of additional parameters such as roughness length scale and zero-plane displacement. In present study, a different sort of Preston tube technique is developed which is suitable for bed shear stress measurement in both smooth and rough bed open channel flows. The new instrument works according to an equation derived from wall-similarity approach and double averaging method. Unlike the conventional Preston tube, this instrument consisted of three Pitot tubes and one Prandtl static tube. Other available methods for shear stress estimation [i.e. logarithmic law, Reynolds shear stress profile, energy slope and conventional Preston tube (the later just in the case of smooth bed)] were used for to control the accuracy of the data collected by new instrument. The results comparison shows that this instrument is capable of measuring bed shear stress with accuracy up to ±15.0 and ±24% respectively in smooth and rough bed conditions. These accuracy ranges assure applicability of this device in future open-channel flow studies.
An Innovative Preston Tube for Determination of Shear Stress on Smooth and Rough Beds
Abstract Preston tube is a shear stress measuring technique which is widely used due to its simple operation and construction. Although application of this technique in smooth bed is convenient and reliable, such application in rough bed is problematic due to the appearance of additional parameters such as roughness length scale and zero-plane displacement. In present study, a different sort of Preston tube technique is developed which is suitable for bed shear stress measurement in both smooth and rough bed open channel flows. The new instrument works according to an equation derived from wall-similarity approach and double averaging method. Unlike the conventional Preston tube, this instrument consisted of three Pitot tubes and one Prandtl static tube. Other available methods for shear stress estimation [i.e. logarithmic law, Reynolds shear stress profile, energy slope and conventional Preston tube (the later just in the case of smooth bed)] were used for to control the accuracy of the data collected by new instrument. The results comparison shows that this instrument is capable of measuring bed shear stress with accuracy up to ±15.0 and ±24% respectively in smooth and rough bed conditions. These accuracy ranges assure applicability of this device in future open-channel flow studies.
An Innovative Preston Tube for Determination of Shear Stress on Smooth and Rough Beds
Mohajeri, Seyed Hossein (Autor:in) / Safarzadeh, Akbar (Autor:in) / Neyshabouri, Seyed Ali Akbar Salehi (Autor:in)
02.02.2017
9 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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