摘要：The flow within the tube bundles experiencescomplex unsteady behaviour. Random excitation forcescan cause low-amplitude tube motion that will result in-long-term-fretting-wear or fatigue. All these problems at-tract the attention of researchers in the whole world.Pierson [1] and Huge [2] systematically studiedheat transfer and pressure drop both in staggered and in-line tube bundle arrangements of various configurations incross flow of gases. Ishigai et al. [3] investigate the flowpattern for a wide range of gap ratios. It is reported that forin-line tube bundle five distinct regions are formed. Howe-ver, in case of square tube bundles only three distinct flowpatterns are observed. For very narrow gap ratios the freeshear layer of the front of the cylinder attaches to thedownstream cylinder thus stopping the Karman vortices todevelop. For moderate gap ratio the Karman vortices areshed but are distorted and deflected due to downstreamsuppression. For very wide gap ratios regular Karman vor-tices are shed much like in the case of a single cylinder.Aiba et al. [4] perform experimental study on square in-line tube banks for gap ratio of 1.2 and 1.6. It is observedthat the tube response of the downstream cylinders is quitedifferent from the upstream ones.
