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RISS 인기검색어
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- 저자 : Zaka Muhammad (검색결과 3 건)
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Investigation of different aspects of laminar horseshoe vortex system using PIV
Muhammad Yamin Younis,Hua Zhang,Bo Hu,Zaka Muhammad,Saqib Mehmood 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2
Juncture flow is a classical fluid mechanics problem having wide applications in both aero and hydro dynamics. The flow separatesupstream of the obstacle due to the adverse pressure gradient generated by it, with the formation of the vortical structure called “horseshoevortex.” The current study is carried out for an elliptical leading edge obstacle placed on a flat plate to investigate the horseshoevortex for a range of Reynolds number (ReW) based on maximum width (W) for which the incoming boundary layer is laminar. Fourdifferent types of horseshoe vortex systems were found: the steady, amalgamation, transition and breakaway. The transition vortex systemis one after which the vortex system changes from amalgamation to breakaway. In this phase the vortex system alternatively undergoesboth amalgamation and breakaway vortex cycles. The effect of variation in the chord wise shape of the obstacle is investigated. Thequantitative measurements of PIV show that the vortex system does not undergo any significant change for different chord lengths of themodel with the fixed aspect ratio and maximum width. The most upstream saddle point is also studied for steady horseshoe vortex regionand found that it is the “saddle of attachment” where flow attaches to the plate surface instead of separating from it.
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Feeding ethogram of Antilochus coquebertii F. preying on Dysdercus koenigii
Mukhtar Adeel,Usama Altaf Muhammad,Ikhlaq Muhammad,Jaleel Waqar,Muhammad Zaka Syed,Ali Asad,Hanif Zahid 한국응용곤충학회 2023 Journal of Asia-Pacific Entomology Vol.26 No.4
Antilochus coquebertii F. (Hemiptera: Pyrrhocoridae) is one of the most important and voracious feeders of Dysdercus spp. First time, this study explained the feeding ethogram of both male and female A. coquebertii on Dysdercus koenigii adults (both male and female). Female adults of A. coquebertii consumed maximum prey (97.78 %) with respect to male (90.91%). The pre-feeding time was recorded maximum in male adults (12.22 min) as compared to female adults (4.1 min). In case of paralysis time, female adults take more time (0.47 min) as compared to male adults (0.46 min). Both male and female adults of A. coquebertii exhibited different preferences towards different body parts of D. koenigii with variable feeding time and number of feedings. Feeding ethogram showed that both of male and female A. coquebertii adults use their antennae in olfactory and gustatory sense. Based on feeding time, abdomen was more favored by male adults and thorax by female adults. While, in case of number of feedings, male adults of A. coquebertii preferred to feed on head and female on thorax of D. koenigii. Increase in body weight of female adults of A. coquebertii after feeding on its prey was found maximum (0.92 g) as compared to male adult (0.66 g). According to these findings, antennae of A. coquebertii have olfactory and gustatory sense while proboscis kept gustatory sense. Female adults of A. coquebertii is more efficient feeder of D. koenigii than male. Abdomen of D. koenigii was more preferred by male adults, while thorax by female adults of A. coquebertii.
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Wakes of two inline cylinders at a low Reynolds number
Farhan Zafar,Md. Mahbub Alam,Zaka Muhammad,Md. Islam 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.1
The effect of vortex impingement on the fluid dynamics around a cylinder submerged in the wake of another of different diameters is numerically investigated at a Reynolds number Re = 200. While the diameter (D) of the downstream cylinder is fixed, impinging vortices are produced from the upstream cylinder diameter (d) varied as d/D = 0.24, 0.4, 0.6, 0.8 and 1.0, with a spacing ratio L = 5.5d, where L is the distance between the center of the upstream cylinder to the front stagnation point of the downstream cylinder. Two-dimensional simulations are carried out using the finite volume method. Fluid forces acting on the two cylinders are correlated with impinging vortices, vortex shedding, and wake structure. Different facets of wake formation, wake structure, and flow separation and their connections to fluid forces are discussed.
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