Slit Angle Research Articles

Experimental study on the change of the orientation of high aspect ratio nozzle slit relative to the airflow

An experimental study to investigate the flow of liquid jet issued from a high aspect ratio nozzle slit into an incoming airflow by changing the orientation angle from the incoming free-stream was performed. A two-dimensional liquid sheet emerged from the narrow slit into the subsonic air crossflow. Different orientation angles between 0 and 90 degrees were studied. High-speed photography and shadowgraphy techniques were utilized to visualize the flow physics. The influence of the slit orientation angle on the flow morphology and the flow regimes of liquid sheets was investigated. Some fluid flow parameters were obtained by analyzing the images. The changes in breakup height of different orientations were measured. A model was offered for the breakup height of the liquid sheet based on the liquid-to-gas momentum ratio, gas Weber number, and a new non-dimensional parameter as a representation of the angle of slit orientation. Also, the defined sheet trajectory for each orientation angle was obtained, and the variations were examined. Empirical correlations for the defined trajectory of the sheet in terms of liquid to gas momentum ratio and gas Weber number for each orientation angle were proposed.

Fluid-acoustic monolithic simulation based on spectral element method to solve flows past a slotted circular cylinder at low Reynolds numbers

Aerodynamic noise resulting from the flow around cylinders is a significant engineering challenge in aviation and wind engineering. The phenomenon of alternating vortex shedding in the flow leads to vibration and noise generation. However, accurately describing both the flow field and the sound field is challenging due to the significant difference in magnitude between them. To tackle this issue, this work introduces the application of the spectral element method (SEM) and flow-acoustic monolithic simulation for solving the two-dimensional compressible Navier–Stokes equations at low Reynolds numbers. This study is to investigate the reduction of flow-induced noise through the implementation of slotting technology on a circular cylinder. This study focuses on examining two different slit width ratios, s/d = 0.15 and 0.25, with a slit angle of attack of 0°. A comparative analysis is conducted between a complete circular cylinder and a slotted circular cylinder. The findings indicate that the slotted cylinder exhibits reduced intensity of vortex shedding and an extended region of downstream vortex generation compared to the complete cylinder. Notably, when s/d = 0.25, the slotted cylinder demonstrates minimal noise generation. Even at s/d = 0.15, a significant reduction in flow-induced noise is observed. These results highlight the potential of utilizing slotting technology on cylinders to effectively mitigate aerodynamic noise. The application of SEM and flow-acoustic monolithic simulation shows their relevance in analyzing and designing noise mitigation techniques in aerodynamics. This work can develop innovative solutions to reduce noise and improve the performance of various applications in aviation and wind engineering.

P‐179: Design of the Pixel Electrode to Improve the image sticking in FFS‐LCD

In this paper, a series of slit angle designs are designed to achieve the improvement of long‐term image sticking properties. The excellent image sticking of high slit angle design are attributed to the small flexo‐electric effect which is explained by using simulation and theory mode analysis, where the flexo‐electric maintains a lower level and the electric field provides a minor deformation. This novel pixel electrode design which optimizes the performance of image sticking, provides a new paradigm for the high picture quality of liquid crystal display.

Multi-spectral compatible metasurface with low infrared emissivity, independent microwave complex-amplitude control, and high visible transparency.

With the rapid development of communication technology and detection technology, it is difficult for devices operating in a single spectrum to meet the application requirements of device integration and miniaturization, resulting in the exploration of multi-spectrum compatible devices. However, the functional design of different spectra is often contradictory and difficult to be compatible. In this work, a transparent slit circular metasurface with a high filling ratio is proposed to achieve the compatibility of microwave, infrared and visible light. In the microwave, based on the Pancharatnam-Berry phase theory, the continuous amplitude and binary phase can be customized only by rotating the slit angle to achieve an Airy beam function at 8-12 GHz. In the infrared, the mean infrared emissivity is reduced to 0.3 at 3-14 µm by maintaining high conductive filling ratio, and in visible light, based on the transparency of materials, the mean transmittance can achieve 50% at 400-800 nm. All the results can verify the multi-spectral compatibility performance, which can also verify the validity of our design method. Importantly, the multi-spectral compatible metasurface contributes an option for multifunctional integration, which can be further applied in communication, camouflage, and other fields.

Notch strength evaluation for highly ductile Al/Cu bi-metal fabricated by the roll-bonding technique under pure mode I and pure mode II loading conditions

In this work, the aluminum alloy AA1050 and copper sheets are cladded together using the roll-bonding technique to make rectangular bi-metallic joints. To examine the notch strength of this bi-metal under quasi-static loading, central slits with two U-shaped ends are introduced into the bi-metal. The slit orientation angle is adopted such that for horizontal slit, the notched rectangular specimen experiences pure mode I loading. However, when the slit orientation angle changes to about 67 degrees, which is obtained by the finite element (FE) analysis, the U-ends of the slit are subjected to pure mode II loading. Considering three different notch tip radii, two loading conditions, and three replicates for each test configuration, totally 18 U-notched specimens are produced and tested with the goal to measure the notch strength of bi-metal experimentally. According to the experimental observations, the bi-metal joint is perfect such that crack initiates from the notch in the whole thickness, proposing that the whole bi-metal joint can be considered as a single bulk material. Based on these observations and thanks to the virtual isotropic material concept (VIMC), the AA1050/Cu bi-metal is firstly equated with a virtual bulk material having homogeneous and isotropic behavior. Secondly, due to highly ductile behavior of the bi-metal joint proven by the associated tensile stress–strain curve, the fictitious material concept (FMC) is used to equate the virtual isotropic material obtained from the previous step having elastoplastic behavior with a fictitious material having perfectly linear elastic behavior. Finally, the VIMC and FMC are linked to the U-notch maximum tangential stress (UMTS), U-notch mean stress (UMS), and U-notch strain energy density (USED) criteria to predict the notch strengths of the bi-metal joint experimentally measured. With always higher than 92% accuracy for all VIMC-FMC-UMTS, VIMC-FMC-UMS, and VIMC-FMC-USED combined criteria, it is shown that the two-level strategy of material simplification, i.e., VIMC-FMC, is quite successful to be combined with different brittle fracture criteria for predicting the notch strength of AA1050-Cu bimetals under both pure tensile and pure in-plane shear modes of loading.

Study on the influence of slit structure on safe and efficient directional fracture blasting effect

In order to study the influence of slit structure on the blasting effect of slit charge, the super dynamic strain test system and photographic equipment were used to study the dynamic response of slit charge blasting and the distribution of blasting cracks under different slit shapes and slit angles. The results show that changing the shape of the slit does not make the energy-gathering and damage-reducing blasting effect of the slit cartridge disappear, but it will affect its effect. Compared with the round hole slit, the peak strain in the slit direction of the strip slit cartridge blast is larger, the directional crack forming is more obvious, and the blasting effect is better. The energy accumulation and loss reduction effect of the blasting of the strip slotted cartridge increase first and then decrease with the increase of the slit angle. When the slit angle is 20°, the energy accumulation and loss reduction effect of strip slit charge blasting are the largest, the distribution of blasting cracks is the best, and the directional fracture blasting effect of slit charge is the best. Finally, based on the research results of model test, combined with the actual situation of the construction site, the slotted cartridge is applied to the pre-splitting blasting of open-pit slope. Compared with the ordinary cartridge pre-splitting blasting, the slope roughness after blasting is reduced by 46.2%, the half-hole rate of blast hole is increased by 20.5%, the blasting vibration intensity is reduced by 60.3%, and the directional fracture control blasting effect is good.

56‐1: Invited Paper: Ultra‐high Frame Rate ADS LCDs

In recent years, LCD end‐users are putting forward higher and higher requirements for dynamic picture display realism. With the increase of display panel refresh rate, dynamic picture fidelity has a significant improvement. The extremely high refresh rate has become one of the most important indicators of high‐end display panels, especially for video game usage scenarios. However, the increase in refresh rate is a challenge to the drive capability of LCD semiconductor TFTs (Thin Film Transistor), the response time of liquid crystal, and the transmission of high‐frequency signals, resulting in the maximum refresh rate of high‐refresh‐rate displays currently on the market still at 240 ~ 300 Hz. In this paper, we solve the display distortion due to low charging ratio at ultra‐high refresh rate by improving GOA（Gate Driver on Array） driver circuit and applying high stability and high mobility bilayer oxide semiconductor technology. At the same time, the 1ms GTG (Gray to Gray) response time is achieved by testing and optimizing the pixel slit angle and cell gap of ADS (Advanced Super Dimension Switch) LCD, ensuring no image trailing at refresh rates up to 600 Hz. Then the anti‐electromagnetic interference ability of high‐speed signal is improved by high‐speed signal transmission quality enhancement technology. Through the application of the above technologies, we have developed the ultra‐high refresh rate IT display panel products such as 600Hz frame rate FHD NB LCD and 500 Hz FHD MNT LCD. And the 16.0” WUXGA 600Hz ADS LCD achieves the highest CMR 9000 rating in VESA latest dynamic picture CMR certification.

Numerical investigation on the effect of slit thickness and outlet angle of the bladeless fan for flow optimization using CFD techniques

The effect of outlet thickness and outlet angle of the bladeless fan have been an alysed numerically on the aerodynamic performance of the bladeless fan. Five different aerofoil profiles have been considered for the present work is Eppler 479, Eppler169, Eppler 473, S1046 and S1048. The bladeless fan arrangement has been achieved by converting the aerodynamic models listed above. The ANSYS ICEM CFD 16.0 have been used to discretize the enclosure and bladeless fan through finite volume approach. The mesh model is then imported into ANSYS CFX 16.0 pre-processor for applying the required boundary conditions. The governing equations namely continuity and momentum are used to solve the flow physics through and across the bladeless fan and SST k-? turbulence model has been used to predict the turbulence in the bladeless fan. The effect of outlet thicknesses and outlet angles have been varied for all the five aerofoil configurations mentioned and the volumetric flow at inlet have been adjusted from 5 LPS to 80 LPS. Outlet thickness is varied from 0.8, 1.0, 1.3, 1.5 and 2 mm and the slit angle is varied from 20 degrees to 80 degrees in step of 10 degrees. The results predicted that Eppler 473 aerofoil profile showed better performance when the thickness of slit and outlet angle has been fixed constant as 1 mm and 70 degree respectively. Also, the maximum discharge flow ratio is recorded for an inlet volumetric flow rate of 80 LPS and it is found to be 34.37. The present numerical study substantiated that outlet thickness plays a dominant role on the bladeless fan’s aerodynamic performance compared to outlet angle and aerodynamic shape considered in this numerical analysis. The contours of velocity, streamline and pressure of the bladeless fan have been discussed.

Numerical investigation on the effect of slit thickness and outlet angle of the bladeless fan for flow optimization using CFD techniques

The effect of outlet thickness and outlet angle of the bladeless fan have been an alysed numerically on the aerodynamic performance of the bladeless fan. Five different aerofoil profiles have been considered for the present work is Eppler 479, Eppler169, Eppler 473, S1046 and S1048. The bladeless fan arrangement has been achieved by converting the aerodynamic models listed above. The ANSYS ICEM CFD 16.0 have been used to discretize the enclosure and bladeless fan through finite volume approach. The mesh model is then imported into ANSYS CFX 16.0 pre-processor for applying the required boundary conditions. The governing equations namely continuity and momentum are used to solve the flow physics through and across the bladeless fan and SST k-? turbulence model has been used to predict the turbulence in the bladeless fan. The effect of outlet thicknesses and outlet angles have been varied for all the five aerofoil configurations mentioned and the volumetric flow at inlet have been adjusted from 5 LPS to 80 LPS. Outlet thickness is varied from 0.8, 1.0, 1.3, 1.5 and 2 mm and the slit angle is varied from 20 degrees to 80 degrees in step of 10 degrees. The results predicted that Eppler 473 aerofoil profile showed better performance when the thickness of slit and outlet angle has been fixed constant as 1 mm and 70 degree respectively. Also, the maximum discharge flow ratio is recorded for an inlet volumetric flow rate of 80 LPS and it is found to be 34.37. The present numerical study substantiated that outlet thickness plays a dominant role on the bladeless fan’s aerodynamic performance compared to outlet angle and aerodynamic shape considered in this numerical analysis. The contours of velocity, streamline and pressure of the bladeless fan have been discussed.

Heat transfer performance prediction of Taylor–Couette flow with longitudinal slits using artificial neural networks

A numerical analysis is performed to examine the heat transfer performance of turbulence inside coaxial cylinders with complex slit surfaces. The comparison is conducted for various number, width, and angle of slits. The synergistic relationship between the fluid temperature and velocity fields is explored following the field synergy principle. The back-propagation neural network (BPNN) coupled with a genetic algorithm (GA) is developed to predict the thermal performance of Taylor-Couette flow. Lastly, the slit structures are optimized by the particle swarm optimization (PSO) algorithm. Results indicate that the modification of slit structure leads to a remarkable difference in heat transfer performance of Taylor-Couette flow. The Nusselt number increases and then decreases with increasing the slit width, while a smaller slit angle strengthens the heat transfer properties. This principle remains applicable when the slit number changes as well. The smaller synergy angle is observed in the annular gap of the high heat transfer performance model which is owed to the excellent synergistic relationship between the temperature and flow fields. The proposed GA-BPNN model makes a remarkably accurate prediction of the Taylor-Couette flow heat transfer performance. Compared with linear regression, the correlation coefficient (R2) has increased by 24.55 %. According to the PSO algorithm and GA-BPNN model, optimal heat transfer performance is achieved with a slit structure of N = 12, w = 11.33 mm, and β = 60°. The maximum improvement in heat transfer capacity for a given range of Reynolds numbers is 16.35 %.

Numerical Investigation on the Effect of Geometric Shape and Outlet Angle of a Bladeless Fan for Flow Optimization using CFD Techniques

A three dimensional numerical study has been carried out to investigate the effect of various geometric shapes and slit angle on performance of the bladeless fan for various aerodynamic profiles. Aerofoils considered for the present study are E169, E473 and E479 which are then reformed into a typical bladeless fan arrangement. The numerical model of bladeless fan encompassing the outer domain is discretized tetrahedrally through finite volume approach using ANSYS ICEMCFD 20.0 and the necessary boundary conditions are specified in the ANSYS Fluent 20.0 pre-processor. The three dimensional fluid flow variations through and across the aerofoil have been simulated by solving the appropriate governing equations namely continuity and Reynolds Averaged Navier-Stokes equations (RANS). The turbulence induced in the fluid is modelled using SST k-ωmode of closure. Numerically predicted results of lift, drag and streamwise velocity decay along the jet centreline of a cylindrical channel are compared with literature and a very close agreement exists between the two. Upon validation, geometric shapes - circular and square cross section with aspect ratios of 1, 1,5 and 2 and slit angles of 20, 40, 60 and 80 degree for all the above three aerofoil configurations are analysed numerically for various inlet Reynolds number. Pressure, velocity contours and stream line across the bladeless fan are presented and discussed. From the study it is observed that Eppler 473 aerofoil profile with slit thickness of 1 mm and slit angle of 80° provided the maximum discharge ratio of 34.17 for an inlet mass flow rate of 80 LPS.

The peculiar galaxy HRG 705: A possible on-going merging?

ABSTRACT We report the results of the first spectroscopic study of the galaxy HRG 705, which belongs to the Solitaire class of peculiar (collisional) Ring Galaxies, which, in turn, are little studied. The nuclear emission-line spectrum resembles that of a star-forming galaxy (H ii galaxy), with $\boldsymbol z = 0.0305$ and heliocentric velocity of $v = 9\, 144\, \pm \, 36~ {\rm km\, s}^{-1}$. The nuclear region is dominated by intermediate and old stellar populations, in addition to a contribution of 8 per cent of young stars. Based on the complex velocity profile along the slit position angle of 59°, we suggest that the nuclear region is composed by two bodies in gravitational interaction (a possible on-going merging). Analysis of the surface brightness distribution confirmed the existence of the second body, a probable intruder, which lies inside a central pseudo-bulge/disc. HRG 705 does not appear to be oxygen-rich, but it is slightly more (O/H)-enriched than the galaxies of our nearby Universe.

Aerothermal Characteristics of Surface-Mounted Round-Edged Slit Ribs With Performance Optimization Using Response Surface Methodology

Abstract The author has investigated the aerothermal characteristics of round-edged ribs with a continuous slit. The experiments have been performed by mounting an array of ribs on the bottom wall inside a rectangular duct. Heat transfer characteristics have been measured using liquid crystal thermography (LCT), whereas flow characteristics have been measured using two-dimensional particle image velocimetry (2D-PIV) technique. Experiments have been performed for flow over a rib having ∼20% blockage ratio and 10% open area ratio. Geometrical parameters considered for the study are slit angle (α) and rib pitch-to-height ratio (p/e). Experiments have been performed for three distinct rib configurations having α values, i.e., 0 deg, 5 deg, and 10 deg with different arrangements having p/e values of 5, 10, and 15, at four Reynolds number ranges from 6200 to 12200. The heat transfer results are evaluated by examining the surface and spanwise-averaged distribution of augmented Nusselt number (Nu/Nu0, and Nux¯/Nuo,x¯ respectively). Flow field results are explained within the inter-rib region by examining the time-averaged normalized velocity fields, streamlines, fluctuation statistics, and vorticity distribution. The results show that the flow coming out from the rib geometry significantly affects the heat transfer and flow behavior. Further, the impact of geometrical design parameters (α and p/e) on different performance parameters, i.e., overall averaged augmented Nusselt number (Nu/Nu0¯), friction factor ratio (f/f0), and thermal performance factor (TPF) has been analyzed at all four Reynolds numbers using Response Surface Methodology (RSM). Finally, the desired correlations for the performance parameters have been documented and found in accord with an uncertainty range of ±10%.

Conceptual design of a radial collimator for MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source

A parametrized conceptual design for a radial collimator in a neutron backscattering instrument is presented, with application to the characteristic geometry of the MIRACLES spectrometer, that will be constructed at the European Spallation Source (ESS). The analytic development of this design has considered both the forward scattering (sample-analyzer) and backscattering (analyzer-detectors) pathways. All the characteristic dimensions (internal and external radii, slit angle) and figures of merit (such as transmission and estimated background reduction) of the device are calculated as a function of the focal points. Finally, the estimated performance of the final concept has been validated by Monte Carlo simulations.

Development and testing of skin grafts models with varying slit orientations

The ability to expand skin grafts is essential in treating severe burn injuries that require donor skin for transplantation. While most graft mesh manufacturers claim high expansions, the practical expansions observed to date with skin grafts are much lower. To investigate this gap, we studied the biomechanics of skin grafts, considering the common graft pattern orientation, and varied the slit angle to evaluate the mesh expansion and induced stresses. Seven skin graft patterns were designed and modeled for this study, ranging from 0° to 90° with a gap of 15° between the two-consecutive models. A detailed mesh convergence study was carried out to estimate an optimal mesh for accurate and time-efficient results. The results of the finite element modeling were analyzed in terms of deformation, induced stresses up to the ultimate tensile stress (UTS), and meshing or expansion ratio. The expansion ratio was reported to be below 1 for low stretching and increased significantly up to 2.8 at the UTS. High applied strains were associated with high localized induced stresses, which varied with the graft orientation. With varying slit patterning in skin grafts, it was observed that expansions higher than that of traditional grafts could be achieved without overstretching. These findings will aid in the development of novel graft designs with high expansion in the future.

Flow characteristics of elastically mounted slit cylinder at sub-critical Reynolds number

The present work numerically investigates vortex-induced vibrations (VIV) of a two-dimensional circular cylinder with an axisymmetric slit at Reynolds number 500. The study examines the effects of slit shape (i.e., converging, diverging, and parallel slits), the effect of slit-area ratios, slit width, and its angle with the freestream velocity on aerodynamic forces, vibration response, and associated flow characteristics. The results demonstrate that the addition of the slit assists the VIV suppression by adding an extra amount of flow to the main flow. It results in the stabilized wake with the pressure recovery downstream of the cylinder and causes a reduction in the lift force over the cylinder. Also, there exist different shedding patterns associated with different slit shapes. A proper orthogonal decomposition of the flow field suggests that among all the three slits, the parallel slit heavily modifies the flow behind the cylinder by distributing the amount of energy to a large number of modes as compared to other slits (converging slit and diverging slit), where the most of the energy is contained in a couple of modes. Further, increasing the slit angle (for parallel slit) with respect to the freestream increases the slit effectiveness up to a specific value of slit-angle and beyond that starts to affect the VIV suppression adversely. Observations for the effect of slit width are also reported from the perspective of suppression of VIV.

52‐4: Late‐News‐Paper: Development of 240Hz Refresh Rate ADS Mode Gaming Product

The ADS display mode shows significant advantages of high transmittance, wide viewing angle, small color shift at large view angle, etc., and thus has been widely used in all kinds of display product such as mobile phone, tablet, notebook, monitor and television. However, ADS mode shows shortcomings of slow response speed. In this work, we made extreme optimization research and breakthroughs in improving ADS mode response speed from the aspects of LC material, cell gap, and pixel ITO slit angle. Based on the research, 27 inch FHD 240Hz refresh rate gaming product was successfully developed. It has been achieved gray to gray average response time 1.9ms with over driving as well as contrast ratio 1214:1 fulfilling static CR requirements of VESA HDR standard.

Heat Transfer and Entropy Generation Analysis of Slit Pillar Array in Microchannels

Abstract The slit pillar allows a small fraction of the mainstream flow through pillar to disturb the pillar wake zone fluid and eventually enhance the local and global heat transfer performances in microchannels. In this study, three-dimensional full-domain numerical simulations on the hydrodynamic and thermal characteristics of slit pillar array in microchannels are performed. Effects of slit angle and height over diameter (H/D) ratio on the fluid flow and heat transfer are studied. Comparisons with the nonslit pillar array are conducted on pressure drop, surface temperature, Nusselt number, and thermal performance index (TPI). Furthermore, the results are analyzed by using the entropy generation. As a result of secondary flows and enhanced convective heat transfer area, all cases at H/D ratio of 0.3 demonstrate enhanced heat transfer performance at an increase of 18.0–34.7% on Nusselt number, while a reduction of 3.4–12.9% on pressure drop in comparison to the criterion case at the same conditions. Among them, slit 15–15 deg shows the best comprehensive heat transfer performance. Due to the improved uniformities of velocity and temperature distributions, all slit pillar array microchannels show decreased entropy generation. The maximum entropy generation reduction can reach up to 15.8%, as compared with the criterion case at the same conditions. The above results fully demonstrate that the novel slit pillar array microchannel heat sink can be used as an effective approach for heat transfer enhancement.

Physical Modeling Evaluation on Refining Effects of Ladle with Different Purging Plug Designs

Circular slits are introduced in purging plugs for alleviating the stress concentration to prolong their service life. Herein, the effects of slits with different geometries on the mixing time, inclusion removal rate, and slag eye area are studied by water model method. Experimental results show that the inclusion removal rate decreases with increasing slit angle for the gas flow rate of less than 6.02 NL min−1. Moreover, with slit diameter increases, the mixing time and inclusion removal rate decrease when a gas flow rate is less than 5.26 NL min−1. The slag eye area increases with increasing slit diameter, and the slit angle has a positive influence on the formation of the slag eye. Finally, the optimization of the mixing time and inclusion removal rate for less consumption of stirring energy and less slag entrapment indicates that the smaller the slag eye area is, the better the refining effect is.

The drag and lift characteristics of flow around a circular cylinder with a slit

Flow past a circular cylinder with a slit results in local perturbation, which affects the flow pattern, vortex shedding and the aerodynamic forces. This study uses spectral element method to simulate flow past a cylinder with a normal slit or an inclined slit at Reynolds numbers of Re=100 to 500. For a cylinder with a normal slit, the drag and amplitude of the oscillating lift both increase as the width of the slit increases. There are two modes for a cylinder with an inclined slit: an injection mode and a blowing/suction mode. The drag also increases as the angle of inclination of the slit increases and is greater than that for a cylinder that has no slit for flow in the blowing/suction mode, except at low Reynolds numbers, such as Re=100. Increasing the width of slit or the angle of inclination of the slit increases the frequency of vortex shedding. However, a wider slit or larger angle of inclination also results in additional drag. There is a similarity between the external surface and the slit in that the aerodynamic forces due to pressure or shear stress vary with the angle of inclination of the slit.