Plane Wall Effect of Flow around Two Circular Cylinders in Tandem Arrangement

Abstract

1 AbstractThe flow characteristic around two circular cylinders in tandem arrangement located near a plane wall were investigated experimentally in a uniform flow at a Reynolds Number of 5.3 x 10 4 . The center to center spacing between the two cylinders relative to the cylinder diameter was constantly maintained at P/D = 1.5. The pressure distributions along the surface of the cylinder and the plane wall were measured by varying the gap-to-diameter of cylinder ratio (G/D) in the range of 0 < G/D < 0.467. Surface oil-film techniques were used to investigate the flow patterns on the cylinder. The result showed that for upstream cylinder, in the gap-to-diameter ratio G/D < /D, there is no stagnation point at front side of the upstream cylinder; it is gradually raised as the gap increase. For the downstream cylinder, a peak on the lower side of the front side of the cylinder is apparent in each of the pressure distributions. This peak represents the reattachment of shear layer that separates from lower side of the upstream cylinder. The reattachment point tends to move forward close to the angular position of  = 0 o as the gap ratio increase. The shear layer bifurcates into two shear layers. One shear layer continues in the downstream direction, and the other shear layer flows in the upstream direction.Keywordscircular cylinders, gap-to-diameter of cylinder ratio, plane wall, tandem arrangement AbstrakDalam penelitian ini telah diamati secara eksperimen karakteristik aliran melintasi silinder ganda yang tersusun secara tandem di dekat dinding datar, untuk aliran seragam (uniform flow) dengan bilangan Reynolds, Re = 5,3 x 10 4 . Untuk jarak antar titik pusat kedua silinder ditetapkan konstan sebesar P/D = 1,5, distribusi tekanan sepanjang permukaan kedua silinder dan dinding datar diukur dengan memvariasikan rasio antara gap dinding dengan silinder dan diameter silinder (G/D) dalam rentang 0 < G/D < 0,467. Metode surface oil-film digunakan untuk memvisualisasikan bentuk aliran pada silinder. Hasil eksperimental menunjukan bila rasio jarak gap G/D < rasio antara tebal lapis batas dan diameter (/D) tidak terjadi titik stagnasi di bagian depan dari silinder upstream; namun stagnasi berangsur-angsur muncul sejalan dengan meningkatnya jarak gap. Sedangkan untuk silinder downstream, pada setiap distribusi tekanan yang diukur terdapat puncak tekanan pada sisi bawah dari bagian depan silinder. Puncak ini menunjukkan posisi reattachment dari shear layer yang terseparasi dari bagian bawah silinder upstream. Sejalan dengan meningkatnya rasio gap, titik reattachment cenderung bergerak maju mendekati posisi  = 0 o . Shear layer terbagi menjadi dua di mana salah satu shear layer menuju ke arah downstream sedangkan shear layer yang lain menuju ke arah upstream.Kata Kuncisilinder sirkular, rasio gap antara dinding dengan silinder, dinding datar, susunan tandem

Simulasi Numerik Karakteristik Aliran Melintasi Dua Silinder Sirkular Tersusun Tandem Dekat Dinding Miring

“…Penelitian secara numerik mengenai aliran melintasi dua silinder sirkular disusun tandem dekat dinding datar telah dilakukan oleh [2]. Data eksperimen yang digunakan sebagai pembanding dari hasil simulasi adalah data hasil eksperimen oleh [3]. Kedua penelitian ini dilakukan pada Bilangan Reynolds 5,3x10 4 .…”

Numerical simulation of cross-flow around four circular cylinders in-line square configuration near a plane wall at supercritical Reynolds number

“…The scale of recirculation eddies was larger as a position of the cylinder closer to the plane wall. Author [18] which researched two circular cylinders in tandem arrangement near a plane wall, at G/D ≤ 0.2, also found there was not stagnation point with Cp = 1 in a front-side of upstream cylinder. This was caused of blockage effect of flow on a gap that a large part of fluid flows to upper-side of the cylinder.…”