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Showing 3 results for Type of Study: Research

Mahmoud Salari, Mohammad Mohammadtabar,
Volume 1, Issue 1 (4-2019)

ABSTRACT: the empirical correlation for prediction of the onset of boundary layer transition, presented previously by Taghavi et al., was extended by taking into account both the effects of the streamwise pressure gradients and the freestream turbulence intensity. The correlation was derived based on experimental data of transitional boundary layers subjected to different freestream turbulence intensities and streamwise pressure gradients, obtained by authors and other researchers. The author’s experiments were carried out in two different free stream turbulence levels and four different pressure gradients. A single hot-wire probe was used for measurements of instantaneous flow velocities within the boundary layer. Experiments were conducted in an open circuit wind tunnel of suction type. For each pressure gradient in a distinct free stream turbulence level, the mean longitudinal velocity and root mean square, RMS, of the velocity fluctuations were obtained at several streamwise locations. Experimental results were used to determine variations of streamwise skin friction coefficient and boundary layer shape factor versus the local Reynolds number. Based on the available measurements and mathematical models, an improved empirical correlation was developed. Comparisons with other existing empirical correlations show that the new correlation was more consistent with experimental data.
Amir Reza Askari,
Volume 1, Issue 1 (4-2019)

The objective of the present paper is to investigate the size-dependent response of a fully clamped rectangular micro-plate under random base excitation. The size-dependent Kirchhoff's plate model based on the modified couple stress theory is utilized in the theoretical formulation. The equations of motion which account for the packaging effect and axial residual stresses are derived using Hamilton's principle. To find the spectral density and mean square value of the micro-plate deflection, the standard modal summation method is employed where the micro-plate mode-shapes are extracted using the extended Kantorovich method. A convergence study is conducted to find the number of modes which must be included in the response. It is found that using the first six symmetric mode-shapes for the present micro-plate leads to very accurate results, while single-mode solution gives the mean square value of the response with a maximum error of 10%. Furthermore, the results reveal that the size effect on the mean square value of the mid-point deflection is usually negligible when the ratio of the plate thickness to its material length scale parameter becomes larger than 15.
Yadolah Alinia, Saeed Adib,
Volume 1, Issue 1 (4-2019)

In this paper, the contact problem between a dissimilar wedge and an elastic half-plane is studied. The investigated problem considers the convective effect which resembles a non-Hertzian contact problem. Unlike the previous studies, which focused to find the solutions of the singular integral equations, here, the contact problem is formulated based on the Muskhelishvili complex potential method for the two-dimensional elasticity. The problem formulation is converted into a Riemann-Hilbert problem. Finally, we derive a closed-form solution for the Riemann-Hilbert problem in terms of the Muskhelishvili complex potential. According to the results, the convective effect increases the contact half-length by factor of 35% for the case of maximum material dissimilarity. Moreover, the complex potential for the similar materials condition is extracted in accordance with the previous studies.

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پیشرفت ها در مکانیک جامدات و سیالات Advances in Solid and Fluid Mechanics.
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