Friction factor cause by internally grooved pipe has been investigated experimentally. The result indicates that grooves reduce friction factor. However, in a certain groove numbers, it increases friction due to a series of fluid cycling near the pipe wall.
This paper shows the experimental results of the flutter speed of thin-flat plates with free leading edge in axial flow as a function of plates' geometry, fluid densities, and viscosities, as well as natural frequencies of the plates. The experiment was developed based on similitude theory using dimensional analysis and Buckingham Pi Theorem. Dimensional analysis generates four dimensionless numbers. Experiment was conducted by placing the thin-flat plates in a laminar flow wind tunnel in order to obtain the relationship among those dimensionless numbers. The flutter speed was measured by varying the flow velocity until the instability occurred. The dimensional analysis gives a map of the flutter Reynolds number as a function of a new type of dimensionless number that is hereby called flutter fluid structure interaction number, thickness-to-length, and aspect ratios as the correcting factors. This map is a very useful tool for predicting the flutter speed of thin-flat plates in general. This investigation found that the flutter Reynolds number is very high at the region of high flutter fluid structure and thickness-to-length ratios numbers; however, it is very sensitive to the change of those two dimensionless numbers. The sensitivity is higher at lower aspect ratio.
Introduction of Mn2+ions into ZnO in the form of Zn(1-x)MnxO (0.00≤x≤0.25) has been done by means of coprecipitation method at low temperature using Zn(CH3COO)2·2H2O, Mn(CH3COO)2·4H2O, HCl, and NH4OH as starting materials. The XRD analysis showed that the produced Zn(1-x)MnxO (0.00≤x≤0.09) samples were crystallized in single phase of wurtzite with hexagonal structures. Besides the wurtzite, the presence of the secondary phase of hetaerolite ZnMn2O4with tetragonal structures was detected in the samples having 0.10≤x≤0.25. The nanometer-sized Zn(1-x)MnxO crystals obtained from XRD analysis were well confirmed by SEM and TEM images. The electron diffraction data showed that the secondary phase formed even for 0.01 and 0.10 Mn-doping samples were ZnMn2O4and MnO2. The VSM data indicate that the paramagnetic properties of Mn doping occurred at 0.00≤x≤0.06 and 0.10≤x≤0.25 as well as superparamagnetic properties occur in Mn doping 0.07≤x≤0.09. The most interesting fact in this study was the formation of secondary phases in all Mn-doped ZnO samples, even for the smallest x of 0.01.
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