A numerical study on the flow performance inside the straight pipe with perforated plates

정명희,SELVA KUMAR KUMARESH,김만영,김종민 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

A conventional car silencer is incorporated with several plates containing perforations for the deduction of sound waves from a car exhaust gases. Perforations in tubes or plates facilitate in developing a large variety of comprehensive models for sound attenuation. Exhaust gases passing through unimpeded straight perforated pipe forces the sound waves to dissipate the energy, thereby optimizing the performance and minimizing the back pressure exerted on the engine. On the other hand, the poorly designed perforation can deteriorate the engine performance by increasing the flow back pressure. Owing to the fact, in this work, the numerical model is based on the installation of the perforated plate with distinguishable hole sizes in a uniform circular pipe oriented normally to the mean gas flow direction. The essential function of the perforated plate is to route the gas flow in a non-uniform distribution of holes with various diameters and consequently, establishing the fully developed flow regime inside the pipe. The comprehensive description of flow performance according to the various perforated plate shapes are presented and compared to situations with no perforated plate. This work aims in demonstrating the importance of perforated plate by numerically investigating three different models, namely flat, convex and concave framed plates accomplished with pressure drop. Further, the study shows various flow characteristics associated with the velocity and turbulent intensity profiles as well as the flow uniformity depending on the perforated plates adopted. These results offer a practical guide to the best design of pipe with perforated plates.

Perforated Plate 형상에 따른 촉매 삽입형 머플러 내부의 유동특성 연구

정명희(Myeong Hee Jeong),김만영(Man Young Kim) 한국자동차공학회 2014 한국자동차공학회 학술대회 및 전시회 Vol.2014 No.11

The use of perforated plate and tubes is common in applications such as vehicle exhaust silencers. Also, perforated plate flow conditioners designed to improve flow distribution upstream of an orifice plate flow meter typically have 50 -60% free area but these generally employ a non-uniform distribution of holes of several sizes to encourage the formation of a fully developed pipe flow velocity distribution. In this study, numerical investigations on the flow characteristics according to various perforated plate shapes and then comparing to case without perforated plate. Three different models are flat perforated plate and a convex perforated plate in the direction of inlet, and a convex perforated plate in the direction of outlet. Simulation results show that, pressure drop without reference to perforated plate shape is similar. However, it is different that velocity, turbulence kinetic energy contour, fully developed velocity location and so on. These results offer a practical guide to the best design of catalytic muffler with perforated plate.

Buckling behavior of strengthened perforated plates under shear loading

Bin Cheng,Chun Li 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.13 No.4

This paper is dedicated to the buckling behaviors of strengthened perforated plates under edge shear loading, which is a typical load pattern of steel plates in civil engineering, especially in plate and box girders. The square plates considered each has a centric circular hole and is simply supported on four edges in the out-of-plane direction. Three types of strengthening stiffeners named ringed stiffener (RS), flat stiffener (FSA and FSB) and strip stiffener (SSA, SSB and SSC) are mainly discussed. The finite element method (FEM) has been employed to analyse the elastic and elasto-plastic buckling behavior of unstrengthened and strengthened perforated plates. Results show that most of the strengthened perforated plates behave higher buckling strengths than the unstrengthened ones, while the enhancements in elastic buckling stress and elastoplastic ultimate strength are closely related to stiffener types as well as plate geometric parameters including plate slenderness ratio and hole diameter to plate width ratio. The critical slenderness ratios of shear loaded strengthened perforated plates, which determine the practical buckling pattern (i.e., elastic or elasto-plastic buckling) of the plates, are also studied. Based on the contrastive analyses of strengthening efficiency considering the influence of stiffener consumption, the most efficient cutout-strengthening methods for shear loaded perforated square plates with different slenderness ratios and circular hole diameter to plate width ratios are preliminarily identified.

한국산(韓國産) 활엽수재(闊葉樹材) 천공판(穿孔板)의 미세형태(微細形態)에 관(關)한 연구(硏究) (II) - 천공판(穿孔板)의 구조(構造) -

김대영,이원용,Kim, Dae-Young,Lee, Won-Yong 강원대학교 산림과학연구소 1997 Journal of Forest Science Vol.13 No.-

우리나라산(産) 활엽수재 25과(科)45속(屬)78종(種)의 수종에 대하여 천공을 이루고 있는 구조를 주사전자현미경(SEM)을 사용하여 3차원적(次元的) 형태를 관찰하고, 이들의 미세한 천공구조의 본질을 조사하여 과(科), 속(屬), 종별(種別)로 고유의 특징을 구명하기 위하여 본 연구를 실시 하였으며 천공의 분류는 단천공(單穿孔), 계단천공(階段穿孔) 및 다공천공(多孔穿孔)(계단천공(階段穿孔) 이외의 다공천공(多孔穿孔))의 3가지로 구분하고 이것을 기초로하여 (1) 단천공(單穿孔)만을 갖는 수종(60종), (2) 계단천공(階段穿孔)만을 갖는 수종(5종), (3) 단천공(單穿孔)과 계단천공(階段穿孔)을 갖는 수종(4종), (4) 단천공(單穿孔)과 다공천공(多孔穿孔)을 갖는 수종(2종), (5) 계단천공(階段穿孔)과 다공천공(多孔穿孔)을 갖는 수종(5종), (6) 단천공(單穿孔), 계단천공(階段穿孔) 및 다공천공(多孔穿孔)을 갖는 수종(2종)의 6개의 그룹으로 분류 하였다. 그 결과 Betulaceae에 속하는 수종은 대부분이 계단천공(階段穿孔)을 나타내고 있으나 개서어나무에서는 단천공(單穿孔)이 출현하는 특징이 있으며, Fagaceae의 갈참나무에서는 단천공(單穿孔)의 천공연(穿孔緣)의 주연에 돌기물이 발생된 vesture천공이 관찰 되었다. 또한 계단천공(階段穿孔)의 상하의 bar가 서로 일치되고 있지않은 mismatching perforation plate가 물갬나무와 물오리나무에서 관찰되었으며 또한 계단천공의 bar사이에 벽물질이 남아 일부 또는 전부가 막혀 있거나 microfibrillar 모양의 substructure가 물박달나무와 계수나무에서 발견되었다. Perforation plate was observed in 78 species(45 genera, 25 families) of Korean native hardwoods using SEM and it was divided into three types, i.e., simple, scalariform and multiple perforation plates, Based on occurance of these types, the species examined were classfied into the following six groups : (1) 60species(35 genera, 21 families) having exclusively simple perforation, (2) 5 species(2 genera, 1 families) having exclusively scalariform perforation plates, (3) 4 species(4 genera, 3 families) having simple and scalariform perforation plates, (4) 2 species(2 genera, 1 families) having simple and multiple perforation plates, (5) 5 species(3 genera, 3 families) having scalariform and multiple perforation plates and (6) 2 species(2 genera, 2 families) having simple, scalariform and multiple perforation plates. Mismatching perforation plates were found in two species of Betulaceae, Alnus hirsuta var. sibirica and Alnus hirsuta and peculiar substructure between the bars of the scalariform perforation plate was observed in Betulaceae, Betula davurica and Cercidiphyllaceae, Cerdiphyllum japonicum and the vestured perforation plate was found in Quercus aliena.

Unsteady 2-D flow field characteristics for perforated plates with a splitter

Yaragal, Subhash C. Techno-Press 2004 Wind and Structures, An International Journal (WAS Vol.7 No.5

Wind tunnel experiments were conducted under highly turbulent and disturbed flow conditions over a solid/perforated plate with a long splitter plate in its plane of symmetry. The effect of varied level of perforation of the normal plate on fluctuating velocities and fluctuating pressures measured across and along the separation bubble was studied. The different perforation levels of the normal plate; that is 0%, 10%, 20%, 30%, 40% and 50% are studied. The Reynolds number based on step height was varied from $4{\times}10^3$ to $1.2{\times}10^4$. The shape and size of the bubble vary with different perforation level of the normal plate that is to say the bubble is reduced both in height and length up to 30% perforation level. For higher perforation of the normal plate, bubble is completely swept out. The peak turbulence value occurs around 0.7 to 0.8 times the reattachment length. The turbulence intensity values are highest for the case of solid normal plate (bleed air is absent) and are lowest for the case of 50% perforation of the normal plate (bleed air is maximum in the present study). From the analysis of data it is observed that $\sqrt{\overline{u^{{\prime}2}}}/(\sqrt{\overline{u^{{\prime}2}}})_{max}$, (the ratio of RMS velocity fluctuation to maximum RMS velocity fluctuation), is uniquely related with dimensionless distance y/Y', (the ratio of distance normal to splitter plate to the distance where RMS velocity fluctuation is half its maximum value) for all the perforated normal plates. It is interesting to note that for 50% perforation of the normal plate, the RMS pressure fluctuation in the flow field gets reduced to around 60% as compared to that for solid normal plate. Analysis of the results show that the ratio [$C^{\prime}_p$ max/$-C_{pb}(1-{\eta})$], where $C^{\prime}_p$ max is the maximum coefficient of fluctuating pressure, $C_{pb}$ is the coefficient of base pressure and ${\eta}$ is the perforation level (ratio of open to total area), for surface RMS pressure fluctuation levels seems to be constant and has value of about 0.22. Similar analysis show that the ratio $[C^{\prime}_p$ max/$-C_{pb}(1-{\eta})]$ for flow field RMS pressure fluctuation levels seems to be constant and has a value of about 0.32.

Topology optimization of steel plate shear walls in the moment frames

Mohammad Hadi Bagherinejad,Abbas Haghollahi 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.6

In this paper, topology optimization (TO) is applied to find a new configuration for the perforated steel plate shear wall (PSPSW) based on the maximization of reaction forces as the objective function. An infill steel plate is introduced based on an experimental model for TO. The TO is conducted using the sensitivity analysis, the method of moving asymptotes and SIMP method. TO is done using a nonlinear analysis (geometry and material) considering the buckling. The final area of the optimized plate is equal to 50% of the infill plate. Three plate thicknesses and three length-to-height ratios are defined and their effects are investigated in the TO. It indicates the plate thickness has no significant impact on the optimization results. The nonlinear behavior of optimized plates under cyclic loading is studied and the strength, energy and fracture tendency of them are investigated. Also, four steel plates including infill plate, a plate with a central circle and two types of the multi-circle plate are introduced with equal plate volume for comparing with the results of the optimized plate.

Strengthening of perforated walls in cable-stayed bridge pylons with double cable planes

Bin Cheng,Jie Wu,Jianlei Wang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.4

This paper focuses on the strengthening methods used for improving the compression behaviors of perforated box-section walls as provided in the anchorage zones of steel pylons. Rectangular plates containing double-row continuous elliptical holes are investigated by employing the boundary condition of simple supporting on four edges in the out-of-plane direction of plate. Two types of strengthening stiffeners, named flat stiffener (FS) and longitudinal stiffener (LS), are considered. Uniaxial compression tests are first conducted for 18 specimens, of which 5 are unstrengthened plates and 13 are strengthened plates. The mechanical behaviors such as stress concentration, out-of-plane deformation, failure pattern, and elasto-plastic ultimate strength are experimentally investigated. Finite element (FE) models are also developed to predict the ultimate strengths of plates with various dimensions. The results of FE analysis are validated by test data. The influences of non-dimensional parameters including plate aspect ratio, hole spacing, hole width, stiffener slenderness ratio, as well as stiffener thickness on the ultimate strengths are illustrated on the basis of numerous parametric studies. Comparison of strengthening efficiency shows that the continuous longitudinal stiffener is the best strengthening method for such perforated plates. The simplified formulas used for estimating the compression strengths of strengthened plates are finally proposed.

New form of perforated steel plate shear wall in simple frames using topology optimization

Mohammad Hadi Bagherinejad,Abbas Haghollahi 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.3

This study presents a practical application of topology optimization (TO) technique to seek the best form of perforated steel plate shear walls (PSPSW) in simple frames. For the numerical investigation, a finite element model is proposed based on the recent particular form of PSPSW that is called the ring-shaped steel plate shear wall. The TO is applied based on the sensitivity analysis to maximize the reaction forces as the objective function considering the fracture tendency. For this purpose, TO is conducted under a monotonic and cyclic loading considering the nonlinear behavior (material and geometry) and buckling. Also, the effect of plate thickness is studied on the TO results. The final material volume of the optimized plate is limited to the material volume of the ring-shaped plate. Finally, an optimized plate is introduced and its nonlinear behavior is investigated under a cyclic and monotonic loading. For a more comprehensive view, the results are compared to the ring-shaped and four usual forms of SPSWs. The material volume of the plate for all the models is the same. The results indicate the strength, load-carrying, and energy dissipation in the optimized plate are increased while the fracture tendency is reduced without changing the material volume.

유공형 도로표지의 항력계수에 대한 실험적 연구

성홍기(Hongki Sung),정규수(Kyusoo Chong) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.2

최근 도로시설물에 작용되는 하중을 저감시키기 위하여 다양한 기술이 개발되고 있으며, 그 중 풍하중 저감을 위한 유공판을 사용하는 기술이 일부 적용 중에 있다. 현재 국내 도로시설물 설계기준에서는 유공판의 항력계수에 대한 규정은 마련되어 있지 않다. 미국의 구조물 설계기준 ‘Minimum design loads for buildings and other structures’에서는 Letchford(2001)와 Giannoulis(2012)의 연구 내용을 바탕으로 건축물과 도로시설물의 유공판 항력계수 내용이 개정되었다. 본 연구에서는 유공판 항력계수 규정에 대한 준용 가능성을 분석하고자 관련 풍동실험을 수행하였다. 더불어 풍동실험 결과 값과 미국 설계기준의 항력계수 값을 비교 분석하였으며, 미국 설계기준 항력계수를 적용한 도로표지 지주 및 가로재의 부재 단면적 감소효과를 비교 분석하였다. 본 연구의 풍동 실험 결과 값과 미국 설계기준 값이 매우 유사한 수준으로 도출되었으며, 이에 따라 유공판 항력계수에 대한 준용이 가능할 것으로 판단된다. 항력계수 설계기준의 준용에 따른 유공형 도로표지 구조물의 단면적 감소효과 분석 결과, 지주는 약 9.45%, 가로재는 6.45%의 단면적이 감소하였다. 지주와 가로재를 합친 유공형 도로표지의 전체 구조물은 약 6.45%의 단면적 감소효과가 있는 것으로 나타났다. Recently, various technologies have been developed for road facilities to reduce the load, some of which use technologies employing perforated plates for wind load reduction. Currently, there are no regulations concerning the drag coefficient of perforated plates for domestic road facilities. In the United States, the regulations regarding the drag coefficient of perforated plates in the `Minimum design loads for buildings and other structures` were revised based on the studies of Letchford (2001) and Giannoulis (2012). In this study, a wind tunnel test was carried out to analyze the feasibility of applying regulations involving the perforated plates` drag coefficient. The results of the wind tunnel test and the drag coefficient used in the regulation were compared and analyzed. In addition, the reduction effect of the cross area of road signs calculated by applying the drag coefficient was analyzed. The results of the wind tunnel test and the value of the drag coefficient used in the regulation in the US were found to be very similar. Therefore, it was found that it is possible to apply the formula involving the drag coefficient of the perforated plate to the regulation and that the cross area of the perforated plate used for the post of the road sign is reduced by about 9.45% and that of the horizontal post by about 6.45%.

Vibration of circular plate with multiple eccentric circular perforations by the Rayleigh-Ritz method

Khodabakhsh Saeedi,Alfin Leo,Rama B. Bhat,Ion Stiharu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.5

"The free vibration of a circular plate with multiple perforations is analyzed by using the Rayleigh-Ritz method. Admissible functions are assumed to be separable functions of radial and tangential coordinates. Trigonometric functions are assumed in the circumferential direction. The radial shape functions are the boundary characteristic orthogonal polynomials generated following the Gram-Schmidt recurrence scheme. The assumed functions are used to estimate the kinetic and the potential energies of the plate depending on the number and the position of the perforations. The eigenvalues, representing the dimensionless natural frequencies, are compared with the results obtained using Bessel functions, where the exact solution is available. Moreover, the eigenvectors, which are the unknown coefficients of the Rayleigh-Ritz method, are used to present the mode shapes of the plate. To validate the analytical results of the plates with multiple perforations, experimental investigations are also performed. Two unique case studies that are not addressed in the existing literature are considered. The results of the Rayleigh-Ritz method are found to be in good agreement with those from the experiments. Although the method presented can be employed in the vibration analysis of plates with different boundary conditions and shapes of the perforations, circular perforations that are free on the edges are studied in this paper. The results are presented in terms of dimensionless frequencies and mode shapes."