http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
A PIV study of the near wake flow features of a square cylinder: influence of corner radius
R. Ajith Kumar,손창현,B. H. Lakshmana Gowda 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2
In this study, the near wake characteristics of transversely oscillating square-section cylinders with different corner radii were investigatedusing the particle image velocimetry (PIV) technique in a water channel with turbulence intensity of 6.5%. Five models with r/B =0, 0.1, 0.2, 0.3, and 0.5, respectively (where r and B represent the corner radius and the characteristic dimension of the body, respectively),were studied, with the body oscillation limited to that under the lock-in condition. Corner radius was found to significantly influence thecharacteristics of the flow around the bodies, both under stationary and oscillating conditions. The results indicate that the Strouhal numberand vortex strength of the flow increase and decrease, respectively, with an increase in the r/B ratio. The spacing between two rows ofvortices (b) as well as that between consecutive vortices in a row (a) was also found to decrease with the increase in the corner radius. The b/a ratio was found to be nearly independent of the r/B ratio and body oscillation.
Influence of corner radius on the near wake structure of a transversely oscillating square cylinder
R. Ajith Kumar,손창현,B. H. Lakshmana Gowda 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9
The near wake flow field features of transversely oscillating square section cylinders with different corner radii were studied in an attempt to assess the influence of corner radius. The investigation was performed by using particle image velocimetry (PIV) technique in a water channel with a turbulence intensity of 6.5%. Five models were studied with r/B=0, 0.1, 0.2, 0.3 and 0.5 (r is the corner radius and B is the characteristic dimension of the body), and the body oscillation was limited to lock-in condition (at fe/fo=1.0; fe is the excitation frequency and fo is the vortex shedding frequency from a stationary cylinder at the same Re). The corner radius was found to significantly influence the flow features around the bodies. Except for r/B=0.5, for all the other cases of r/B ratios, cycle-to cycle variation in the mode of vortex shedding was observed in the case of oscillating cylinders inducing highly non-linear wake characteristics. Apart from variation in the shedding mode, changes in shedding cycle timing were also observed for sharp and rounded square cylinders. The hgher the r/B ratio, shedding in the near wake was found to be more uniform (lesser variation in shedding cycle timings). Another admissible shedding mechanism is newly identified to operate in the near wake of oscillating cylinders now being called as the ‘passive shedding’ mechanism. Results indicate that increasing the corner radius suppresses the possible instabilities of the cylinder.
Reverse flow in a square duct with an obstruction at the entry
손창현,B. H. Lakshmana Gowda,Myong-Gun Ju 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9
In this paper, the reverse flow in a square duct with an obstruction at the front (which is a square plate), is investigated using particle image velocimetry (PIV). The gap g between the obstruction and the entry to the duct was systematically varied, and it was found that maximum reverse flow occurs around a g/w value of 0.75. The velocity vectors, vorticity plots, and other details described indicate that the flow field is different compared with the two-dimensional channel case.
Experimental and Numerical Studies in a Vortex Tube
Sohn Chang-Hyun,Kim Chang-Soo,Jung Ui-Hyun,Lakshmana Gowda B.H.L The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.3
The present investigation deals with the study of the internal flow phenomena of the counterflow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1MPa to 0.3MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.
Experimental and Numerical Studies in a Vortex Tube
Chang-Hyun Sohn,Chang-Soo Kim,Ui-Hyun Jung,B. H. L Lakshmana Gowda 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.3
The present investigation deals with the study of the internal flow phenomena of the counterflow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1㎪ to 0.3㎪. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.