Numerical Performance of Energy Dissipation Slotted Plate for Bridge Unseating Prevention

Recently, the bridge unseating prevention devices are widely used in active seismic zones. These devices are stiffness dependant, velocity dependant and energy dissipation devices. The energy dissipation devices are designed to overcome the energy that transfers from bridge substructure to superstructure. However, the current devices are not controlled to function with different ground motion intensities and should be replaced after yielding. Therefore, this research introduced a slotted plate energy dissipation device with three parts, each part function in known deformation range. The slotted plate behavior has been evaluated numerically by finite element method. Displacement control and load control analysis has been done, and then the effect of steel grade is studied to predict the suitable steel properties for designing the plate. Moreover, the slotted plate behavior is applied in 3D bridge seismic analysis to assess the multi-level performance and the ability to overcome the seismic effect on the bridge in longitudinal direction. The results approved the capability of the plate to dissipate energy in multi-stage of deformation. The lower steel grade is suitable for low to moderate earthquake zone and the high grade can be used in severe ground motion areas. Furthermore, the bridge longitudinal behavior has enhanced with different steel grades of the slotted plate.

Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

Fluidized bed gasification has proven to be an appropriate technique for converting various biomass feedstocks into helpful energy. Air distributor plate design is one of the critical factors affecting the thermochemical conversion performance of fluidized bed gasifiers. The present study is proposed to investigate the mixing pattern and pressure drop across different configurations of air distributors using a two-fluid model (TFM) of finite volume method-based solver ANSYS FLUENT. The pressure drop across the bed and mixing pattern have been investigated through qualitative and quantitative analysis of CFD results using three diverse distributor plate designs: perforated plate, 90° slotted plate, and 45° swirling slotted plate. The pressure drop by employing the perforated distributor plate reveals the highest pressure drop due to the smallest open area ratio. However, the pressure drop in the case of 90° slotted plate is found to be 7% and 4% lesser than perforated and 45° slotted plate respectively due to a smaller velocity head developed through the wider open area of the straight slotted plates. The distributor design configuration having a 45° slotted plate exhibits considerable pressure drop compared to the 90° slotted plate due to the longer path length of the slot. Numerical pressure drop results across the bed with different types of distributor plates prove reasonable agreement with the experimental results available in the literature. Mixing behavior in perforated distributor plates exhibits lower portion solid volume fraction of around 0.58. However, it falls rapidly as go up the riser (7.7% of column height); 90° slotted plate shows bottom region solid volume fraction of around 0.5. In addition, it exhibits an even broader range of sand volume fraction and column height (13.46% of column height). Finally, the 45° distributor plate reveals the highest range of volume fraction through the riser height (17.3% of column height), indicating the better mixing characteristics of the fluidized zone.

Turbulent kinetic energy and self-sustaining tones: Experimental study of a rectangular impinging jet using high Speed 3D tomographic Particle Image Velocimetry

Impinging jets are widely used in ventilation systems to improve the mixing and diffusion of airflows. When a rectangular jet hits a slotted plate, an acoustic disturbance can be generated and self-sustained tones produced. Few studies have looked at the Turbulent Kinetic Energy (TKE) produced by the aerodynamic field in such configurations and in the presence of self-sustaining tones. The aim of this work is to investigate the energy transfer between the aerodynamic and acoustic fields generated in a rectangular jet impinging on a slotted plate. The present paper methodology is based on experimental data measurements using 3D tomographic Particle Image Velocimetry (PIV) technique and microphones. It was found that the spectrum of the TKE for Re=5294 (configuration of self-sustained tones) is which is smaller than that of the acoustic signal . A negative peak of correlation is obtained between the acoustic signal and TKE for These results may lead to conclude that the acoustic cycle should be covered by the TKE period and the two signals of both fields are in opposition of phase in order to obtain an optimal configuration for energy transfer.

Tomographic and Time-Resolved PIV measurement of an Impinging Jet on a Slotted Plate

In order to reveal the complete topology of unsteady coherent flow structures the instantaneous measurement of the 3D velocity field is being of the great interest in fluid mechanic. Several different methods were proposed to achieve a 3D version of the technique (scanning light sheet, holography, 3D PTV). We aimed in our study to develop a 3D technique than enables to obtain the 3D kinematic field of an impinging jet by using 2D measurements. In this study and in order to validate the proposed technique [1], the tomographic particle image velocimetry technique has been applied to time resolved PIV recordings. The first step before the validation was to study the vortex shedding phenomena between the jet exit and the slotted plate. The experiments were performed at a Re = 4458 with an initial velocity U0=7m/s using three cameras Phantom V711 and a Nd: YLF LDY 300 Litron laser. In the present study, we analyzed the coherent structures organization by a 3D-velocity visualization. Both mean and fluctuating part of velocity were analyzed for several positions in z. The results has shown that a couple of vortex rolls are created downstream the flow at y/H=2.