Unsteady Boundary Layer Flow of A Micropolar Fluid Near A Stagnation Point With Uniform Suction Or Injection

Kertas kerja ini mengkaji kesan sedutan dan suntikan ke atas aliran lapisan sempadan tak mantap di titik genangan depan dinding boleh telap bagi bendalir mikropolar. Halaju aliran luar serta halaju sedutan dan suntikan diandaikan bermula secara dedunyut, seterusnya manjadi malar selepas aliran mula bergerak. Masalah ini dimodelkan oleh persamaan terbitan separa yang perlu diselesaiakn secara berangka untuk beberapa nilai sedutan, suntikan dan parameter bahan. Taburan halaju, mikroputaran dan pekali geseran permukaan dipersembahkan dalam bentuk jadual dan gambar rajah. Hasil kajian menunjukkan kesan sedutan dapat meningkatkan nilai sedutan dan suntikan, kesan mikroputaran berdekatan dinding dapat diperlambatkan. Di samping itu, suntikan didapati memerlukan lebih banyak masa untuk mencapai aliran mantap berbanding sedutan. Kata kunci: Aliran lapisan sempadan tak mantap, bendalir mikropolar, titik genangan depan, sedutan, suntikan This paper studies the effect of suction or injection on unsteady boundary layer flow of micropolar fluid near the forward stagnation point of a permeable wall. The velocity of the external flow as well as that of suction or injection are assumed to start impulsively from rest and are maintained thereafter. The model is governed by a set of coupled partial different equations that is solved numerically for some values of the suction, injection and material parameters. Profiles for the velocity, microrotation and skin friction coenfficient are determined and presented in tables and graphical forms. The results show that suction increases the skin friction while the opposite behaviour is observed for the case of injection. It is also found that an increase in the material parameter will enchance the flow near the wall. On the other hand, it can be seen that in the case of injection, longer time is required to approach the steady flow than in the case of suction. Key words: Unsteady boundary layer flow, micropolar fluid, forward stagnation point, suction, injection