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Experimental study of the flow around two finite square cylinders

Sohankar A., Abbasi M., Nili-Ahmadabadi M., Alam M. M., Zafar F.

Archives of Mechanics

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2018

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Vol. 70, nr 5

457--480

EN

An experimental investigation is conducted on the air flow past two wallmounted finite length side-by-side square cylinders, each of the aspect ratio AR = 7. The cylinder center-to-center spacing ratio T/d is varied from 2 to 6, where d is the side-width of the cylinder. The cylinders are placed at three incidence angles with respect to the freestream velocity, i.e. both cylinders at zero incidence angle (case I), both cylinders at 45° incidence angle (case II), and one cylinder at zero incidence angle with the other at 45° incidence angle (case III). The pressure distributions on the surfaces of the cylinders are measured at Reynolds numbers of 5.9 × 104–8.1 × 104. In addition, the flow structures are visualized in a smoke wind tunnel at the Reynolds number of 2 × 103. Depending on the flow characteristics, four flow structures are identified at the mid-height of the cylinders, namely the asymmetric flow, antiphase shedding flow, leading-edge separated flow and wedge flow. The sectional drag near the bottom is more sensitive to T/d than that near the top. The sectional drag coefficient measured at 0.5d below the mid-span can represent the surface-averaged drag coefficient on the entire cylinder.

2

Coupling of subcritical methanol with acidic ionic liquids for the acidity reduction of naphthenic acids

Zafar F., Mandal P. C., Shaari K. Z. K., Ullah Z.

Polish Journal of Chemical Technology

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2017

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Vol. 19, nr 3

68--74

EN

The presence of naphthenic acids (NAs) in crude oil is the major cause of corrosion in the refineries and its processing equipment. The goal of this study is to reduce the total acid number (TAN) of NAs by treating them with subcritical methanol in the presence of acidic ionic liquid (AIL) catalysts. Experiments were carried out in an autoclave batch reactor and the effect of different reaction parameters was investigated. It was observed that TAN reduction was positively dependent on the temperature and concentration of the AIL whereas excess of methanol has a negative effect. Approximately 90% TAN reduction was achieved under the optimized reaction conditions using [BMIM]HSO4 as catalyst. It was also perceived from the experimental results that the AILs with longer alkyl chain exhibited higher catalytic activity. The activity and stability of AIL showed that they can be promising catalyst to esterify NAs under subcritical methanol.

3

A generalized Ostrowski type inequality for a random variable whose probability density function belongs to L-infinity[a,b].

Rafiq A., Mir N., Zafar F.

Demonstratio Mathematica

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2008

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Vol. 41, nr 3

723-732

EN

We establish here an inequality of Ostrowski type for a random variable whose probability density function belongs to L-infinity[a, b], in terms of the cumulative distribution function and expectation. The inequality is then applied to generalized beta random variable.