The effects of splitter plate as a passive turbulence control on the transverse vibration characteristics of a cantilevered rectangular prism with the different finite length (aspect ratio L/H) and depth ratios (side ratio D/H of 0.2 and 0.5) was investigated in a water tunnel. A splitter plate was installed behind the prism with a small gap and sufficient length to prevent vortex shedding intrusion. It enhances the response amplitude ascended linearly with respect to non-dimensional velocity. In the case of the prisms with critical points, interferences of amplitude signal spectra for the period of displacement vanished, yielding a uniform waveform on the response amplitude. Inserting a splitter plate improves the increment rate of the dynamic response of the test models. A brief numerical calculation was performed to find the quantities of flow features around a plain and rectangular prism with a detached splitter plate. The alteration of flow wake characteristics is found by diminishing unsymmetrical vortices shedding and reduce flow entrainment at the trailing edge. The essential findings of the prism with a detached splitter plate are the base pressure improvement, reducing drag force, and vanishing sharp peaks of wake FFT spectra.

This study explores the effect of preheating on the toughness of dissimilar welded joints between AISI 1037 and AISI 304 steels, using Shielded Metal Arc Welding (SMAW) and E309-16 electrodes. The innovation of this approach lies in assessing how preheating temperatures influence the mechanical properties of such welds. Preheating temperatures ranged from 150 °C to 300 °C, with impact testing revealing a notable increase in toughness, from 6.01 Joules at 150 °C to 19.57 Joules at 300 °C. Hardness tests indicated a maximum hardness of 313 VHN in the fusion zone and a minimum of 185 VHN in the AISI 304 area. Compared to non-preheated joints, preheating significantly enhanced impact strength and altered the fracture mode from brittle to ductile. Macrostructural and microstructural analyses with optical microscopy and SEM showcased changes in fracture surfaces and microstructural evolution, highlighting the improvement in mechanical properties due to preheating. These findings demonstrate that preheating critically enhances the toughness and overall performance of dissimilar metal welds, making it a valuable technique in industrial applications where enhanced joint toughness is crucial.

Three-dimensional flow features of the slender rectangular prism with cross-section height (H) to streamwise depth (D) ratio or side ratio (D/H = 0.5) were investigated numerically using the Large-eddy simulations (LES) turbulence model with Reynolds number Re = 22000. Four different aspect ratios (L/H = 2.5 – 10) were employed in this research to study the effect of the spanwise variation of the prism model on the flow pattern around the prism. Moreover, the instability-induced motion of the prism was modeled to predict the alteration of flow characteristics of stationary to vibrating states of the test model. The global quantities such as drag force, pressure coefficient, and Strouhal frequency characteristics are presented, which suggests that the structure end tip effect plays an essential role in the dependency of flow features variation. The velocity vector variations at streamwise and spanwise positions are also demonstrated. The prism model with a small aspect ratio (L/H = 2.5) exhibited Karman vortex suppression at the prism's vicinity, and the streamwise vortices region shrank. The flow features of the vibrating prism show different behaviors from the stationary prism model

Experimental Investigation of Bladeless Power Generator from Wind-induced Vibration

Flow control over a square cylinder using an attached double splitter plate was numerically investigated at a Reynolds number of 104. This study aimed to investigate the effects of the splitter plate and angle of incidence on fluid forces, pressure distributions, and vortex-shedding. The two plates were positioned ¾ H apart, with various inclination angles. The vortex shedding frequency was typically obtained from lift fluctuation measurements, while the aerodynamic force coefficients acting on the model were determined from pressure distributions. This investigation explored characteristics of the vortex formation region, the location of flow separation, and reattachment points. The process also included the gradient pressure recovery corresponding to a minimum drag coefficient reduction. Suppressing lift fluctuation by tilting the plate a ³ 10° negated drag reduction. It was attributed to the pressure gradient effect rather than solely to lift fluctuation frequency. At zero angle of incidence (a), the drag coefficient of a square cylinder decreased by approximately 39.3%. Drag reduction was maximum at about a £ 5° and reached the peak reduction at a = 2.5°, with a 43.8% reduction compared to the bare square cylinder. Additionally, drag reduction achieved with the double splitter plate was twice that of the single splitter, achieving about 20.3%. This study recommended an optimal drag reduction by tilting the plate at an angle of 5 ° or less. Drag reduction provides a means to reduce the energy required to move objects.

In order to investigate the effects of terminal existence of a rectangular prism with side ratio D/H = 0.2 and 0.5 (where D: depth of a prism in the flow direction, H: height of a prism normal to the flow direction) on the flow-induced transverse-galloping vibration, we performed the free-vibration test of a cantilevered prism with a tip in the water tunnel, and 2.5-dimensional (without tip) and 3-dimensional (with a tip) rectangular prisms in the numerical simulation by LES. Numerical result of the response amplitude of 3-dimensional prism agrees well with experimental result of 3-dimensional prism than 2.5-dimensional prism. Numerical result of the response amplitude of 2.5-dimensional prism with a side ratio D/H = 0.2 agrees with experimental results of 3-dimensional prisms. The flow structure around 2.5-dimensional prism with a side ratio D/H = 0.2 is similar to that around 3-dimensional prisms. However, the flow structure around 2.5-dimensional prism with a side ratio D/H = 0.5 is not similar to that around 3-dimensional prism. Therefore, the numerical result of the response amplitude of 2.5-dimensional prism with a side ratio D/H=0.5 does not agree well with the experimental result of 3-dimensional prisms.