Tab Configurations Research Articles

Numerical investigation of force over the horizontal jet tab of various sector angle fixed to the convergent-divergent nozzle exit

Abstract In this study, a CFD computational model has been established to properly simulate complex correctly expanded supersonic flow generated by a three-dimensional C–D nozzle for the purpose of Thrust Vector Control (TVC) simulations. Jet tabs affixed to the perimeter of the nozzle exit are used to achieve thrust vectoring. This study focuses on the estimation of the force on the tabs due to the jet issued from the C–D nozzle using Ansys 19.2 three-dimensional density based solver, implicit formulation with SST K–ω turbulence model. The force is calculated for different tab configurations based on tab sector angles of 60°, 90°& 120° for the designed Mach number and X/D ratio of 0.7. The nozzles with Mach 1.6, Mach 1.8 and Mach 2.0 designed using SolidWorks are compared. It has been observed that with an increase in sector angle, tab force increased by an average of 70 % for sector angle of 60° to 90° and 36 % for sector angle of 90° to 120°.

Study of jet tabs in 2D convergent–divergent nozzle for thrust vectoring in aerial vehicles

PurposeIn this study, 2D density-based SST K-turbulence model with compressibility effect is used to observe the flow separation and shock wave interactions of the flow. The wall static pressure and Mach number differences are also evaluated. This study aims to discuss the aforementioned objectivesDesign/methodology/approachThis study outlines the evaluation of the performance of a 2D convergent–divergent nozzle with various triangular jet tab configurations that can be used for effective thrust vectoring of aerial vehicles.FindingsFrom the study, it is seen that the shadow effect induced by the tab with a height of 30% produces higher oblique wave deflection and higher thrust deflection at the exit nozzle. The numerical calculation concluded that thrust vector efficiency of 30% jet tab is, 0.46%. In the case of 10% jet tab height the thrust vector efficiency is higher, i.e. 1.647%.Research limitations/implications2D study.Practical implicationsThe optimization will open up a new focus in TVC that can be implemented for effective attitude control in aircrafts.Social implicationsUsed in future aircrafts.Originality/valueThe influence of shadowing ratio with different tab heights at different Mach numbers has not been reported in the previous studies. Few of the studies on jet tab are focused on the acoustic studies and not pertaining to the aerodynamic aspects. The multi jet configuration, the combination of location, shapes and other parametric analysis have not been covered in the previous studied.

Influence of slot profiles on the characteristics of jets

PurposeThe purpose of this research is to study and investigate the flow control of 0.8 Mach jet using three tab configurations. The tabs with the slots will eventually lead to generation of vortices and thus enhances the mixing characteristics.Design/methodology/approachThe jet flow control is achieved by the usage of three tabs, namely, Tab A, Tab B and Tab C that are placed at the exit plane of the convergent nozzle at 180 degrees apart. Three tabs with different slot profile are designed with the same constant blockage ratio of 7.3%. The tabs produce vortices of varying sizes that directly influence and modify the jet structure, thereby enhancing the efficiency in mass entrainment and mixing. The tabs are studied numerically first and then are compared with the results of the experiments.FindingsThe results are compared with that of the results of the uncontrolled jet. For Mach 0.8 jet, Tab C is found to reduce the core length and gives reduction of 90.23%, in comparison to Tab A and Tab B, which provides 84.1% and 87.79%, respectively. The results of numerical are then compared with the centerline results obtained via experiments. With the engagement of Tabs A, B and C, the jet structure is seen to have been modified at Mach 0.8 with Tab C performing better.Practical implicationsThe tabs are a passive control device that can be practically enabled in the aircraft nozzles to control the flow and even suppress the noise emanated by the jet. Tabs can be effectively used for better thrust vector control and assist in jet noise suppression. Thus, this study on tabs and its uses are important and essential in aerospace technology.Originality/valueThis particular study on mechanical slotted tabs is innovatively carried out by designing the tabs in such a way that one such has not been designed before. The slots run through the adjacent sides of the tabs which is a novelty in itself, whereas perforations made only through the opposite sides of the tabs are studied by various researchers till now. The slots in the adjacent faces modify the flow physics in such a way that it enhances mixing by the creation of turbulence because of the interaction between the main stream and the secondary jet exactly at the core. So far, such slots and profiles are not investigated. By the usage of such tabs, the flow to mix faster is much closer to the core of the jet by creating mixed size vortices and thus has higher efficiency.

A Direct Comparison of Pilot-Scale Li-Ion Cells in the Formats PHEV1, Pouch, and 21700

Li-ion cells of the industrially-relevant formats PHEV1 (prismatic), multi-layer pouch, and 21700 (cylindrical) are directly compared by experiments for the first time. All three cell formats were reproducibly built on pilot-scale with the same anode (graphite), cathode (NMC622), separator, and electrolyte allowing a direct comparison. The main differences between these formats are their capacities (24.6 Ah, 2.2 Ah, 2.3 Ah), volume/surface ratios, as well as tab and the jellyroll/stack configurations (flat-wound, stacked, wound). The comparison involves voltage curves during formation (0.1 C), discharge rate capability (0.5 C−3 C), heating behaviour, cell impedances, geometrical properties such as electrode curvatures and tab configurations, as well as comparison with coin half cells with anode and cathode vs Li counter electrode. The data are put into context with commercial and pilot-line built cells from other studies.

Control of vortex shedding around a circular cylinder using bubble tabs in the laminar flow regime

Vortex induced vibration (VIV) is the major cause of several catastrophic disasters due to fatigue failures induced by drag and lift forces in aerodynamic systems. This study investigates the control of VIV phenomenon through passive bubble tab(s) having a small diameter (d) relative to the main circular cylinder (D) in a two-dimensional (2-D) flow domain. Using ANSYS Fluent computational software, flow analysis was conducted at a Reynolds number (Re) of 80 for various bubble tab configurations at different spacing ratios (x/D) and diameter ratios (d/D). The drag coefficient, the velocity and pressure contours, along with the flow streamlines in eachcase were studied. The results indicated the optimized tab(s) positions for different spacing ratios, diameter ratios, and configurations. The study effectively established that passive bubble tabs can potentially control VIV associated with flows around a circular cylinder.
 Keywords: Vortex Shedding; Drag Coefficient; Circular Cylinder; Bubble Tab(S); Spacing Ratio; Diameter Ratio.

Passive control of coaxial jet with supersonic primary jet and sonic secondary jet

The mixing enhancement of a coaxial jet with a Mach 1.4 primary jet and sonic secondary jet, at different convective Mach numbers, is presented in this study. Rectangular tabs of aspect ratios (AR = h/w, where h and w are the tab height and width, respectively) 2.0 and 0.75 were employed to manipulate the primary and secondary jets, respectively. The primary jet (C0) and coaxial jet without control or manipulation (C1) are studied in order to decouple the effects of rectangular tabs on jet mixing. Four different tab configurations were studied, viz., tabs placed in the primary jet (C2), tabs placed in the secondary jet (C3), and tabs placed in both primary and secondary jets with the relative orientation between them of 0° (C4) and 90° (C5), to document the effect of tabs on mixing. The supersonic core length Lc* of the manipulated jet was used as a measure to quantify the mixing performance of the manipulated jet. The secondary flow reduces the growth rate of the primary shear layer and elongates the supersonic core length. This study reveals that the manipulated jet emulates the characteristic of a non-circular jet. Primary tabs are highly effective in reducing the supersonic core length of the coaxial jet than secondary tabs, and hence, the jet mixing increases. Two different flow categories of the manipulated jet have been identified. The physical reason behind the observed jet mixing and flow categories have been presented based on arguments related to changes in the flow field and shock structure.

Axisymmetric numerical investigation of the heat transfer enhancement from a heated plate to an impinging turbulent axial jet via small vortex generators

The consequences of installing one or two vortex generators on a flat plate under axisymmetric conditions are presented in this work in order to analyse if heat transfer from the plate can be enhanced. Two different configurations have been considered to optimise the radial location of the vortex generators which can improve the heat transfer in comparison with a flat plate without them. To that end, we have conducted several numerical simulations of a turbulent jet impinging against a plate with one or two small tabs and the heat transfer from the plate quantified in terms of the Nusselt number. A jet Reynolds number of 23,000 and a nozzle-to-plate distance of 2 nozzle diameters were used throughout the study. Thanks to a parametric study, with the tab positions as parameters, we obtain different response surfaces which will help us to identify the optimal tab configurations. After that optimization process, we shall show that, for certain radial locations of the tabs, the averaged heat transfer on the tabbed plate can be improved up to around 4.5% with just a 2% of more pumping power due to pressure losses on the tabs. Furthermore, it is even more remarkable the fact that the averaged heat transfer can even be enhanced with around 25% of less pumping power requirements than when the plate is completely flat. We shall show that this effect is due to the fact that the tabs reduce the friction losses on the tabbed plate and, consequently, the pumping power needs. On the contrary, the heat transfer at the stagnation point cannot be ever increased.

Study on the thermal behaviors of power lithium iron phosphate (LFP) aluminum-laminated battery with different tab configurations

The thermal response of the battery is one of the key factors affecting the performance and life span of lithium iron phosphate (LFP) batteries. A 3.2 V/10 Ah LFP aluminum-laminated batteries are chosen as the target of the present study. A three-dimensional thermal simulation model is established based on finite element theory and proceeding from the internal heat generation of the battery. The study illustrates a three-dimensional relationship among the total internal heat generation rate of the battery, the discharge rate of the battery, and the depth of discharge. The effects on the heat distribution of the battery cells by different types of tab distributions are also explored. Results show that the thermal behavior of the discharge process can be effectively simulated with the Bernardi equation, by coupling the dynamic changes of the battery temperature, internal resistance and voltage temperature coefficient. The interior chemical reversible heat of the battery is manifested by the endothermic process when DOD (Depth of Discharge) is smaller than 0.7 and by the exothermic process when DOD is larger than 0.7. The irreversible heat takes an increasingly dominant role with the increase of discharge rate; under the condition of high-rate discharge, batteries with a single-side tab distribution are generally found to have a non-uniform cell temperature distribution, while those with a double-side tab distribution have improved cell temperature distributions. Widening the tabs can also greatly reduce the maximum temperature of the cell.

Analytic theory for foil impedance in spiral wound cell geometries

The analytic theory for 1D foil currents and potentials in spiral wound cells with arbitrary tab configurations is derived. The theory is extended to account for state of charge gradients along the length of the foils revealing how tab geometry can affect the slope of constant current voltage curves. Analytic expressions for cell level properties are derived for common tab configurations. The quality of many tab configurations is compared. A straight forward method is described for the common, previously unsolved problem of disentangling the foil and stack contributions of a measured cell impedance. Many other examples of practical problems and solutions are presented. The analytic theory shows how to directly calculate the foil geometry factor introduced in a previous article [1]. Simple methods are presented for adding corrections for foil effects to a stack centric cell model. The analytic results provide a lot of insight and ease of use that numerical solutions cannot easily deliver.

Accurate and Efficient Treatment of Foil Currents in a Spiral Wound Li-Ion Cell

A coupled multi-physics cell model is presented which takes into account the full physics stack model, a 1D foil model and a 1D thermal model. Procedures are described for calculating the stack impedance and solving the foil and stack models self consistently. A foil impedance Biot number is used to decide if the stack or the foils are dominating the cell impedance, and whether a 1D foil model is required for accurate simulations. When a 0D foil model is deemed sufficient an empirical procedure is described for calibrating this model to yield accurate results. The fully coupled model is used to explore the effects of cell size and internal tab configurations on the simulated high current voltage profiles.

Three-Dimensional Analysis of Coupled Vibrations of Rectangular AT-Cut Quartz Plates with Tab Electrodes

We numerically analyzed the influence of strip tab electrodes on the coupled vibrations of the fundamental thickness-shear (TS) and flexural modes in a rectangular AT-cut quartz plate with rectangular central electrodes. It was assumed that the tabs were extended along the x1 (X) axis and softly supported at two points on a single x1-edge of the plate. We calculated the frequency spectra near the main TS response for three types of tab configurations that possessed a twofold rotational symmetry about the crystal X-axis of quartz as well as the rectangular plate and central electrodes. These results verified that the tabs affect the characteristics of coupling between the TS and spurious modes, and demonstrated that the coupling strength depended on both tab width and tab arrangement. We also clarified each property for the three types of tab configurations.

Mixing enhancement behind a backward-facing step using tabs

Mixing enhancement behind a backward-facing step is experimentally investigated using multiple tabs located at the edge of the backward-facing step. The Reynolds number is 24000 based on the free-stream velocity and step height with a turbulent boundary layer flow at the inlet. A parametric study is performed to find the optimal tab configuration of minimizing the reattachment length. The parameters of the tab are its height and spanwise width, and the spanwise spacing between two adjacent tabs. For each tab configuration, we measure the reattachment length and wall pressure, and for the optimal configuration the streamwise velocity behind the step. For most tab configurations considered, the reattachment length decreases and turbulence intensity increases at almost all spanwise locations. The reattachment length and wall pressure show significant variations along the spanwise direction. It is found that the tabs introduce strong three-dimensional disturbances to the separating shear layer by producing a pair of counter-rotating streamwise vortices and entrain high momentum fluids into the recirculation region, which greatly enhances mixing behind the backward-facing step.

Impact of short-span strip on oscillating-wing tip vortex

The impact of 12 spoiler–tab configurations, of different heights and widths, on the tip vortex generated by an oscillating NACA 0015 wing was investigated experimentally. For an oscillating wing equipped with a spoiler, the peak tangential velocity and core and total circulation were greatly reduced compared to a tab, regardless of its width, while the core radius remained largely unaffected with its center displaced vertically above the baseline wing. The most noticeable impact of a spoiler with a reduced height was its potential in alleviating the blade–vortex interaction (BVI) strength. Meanwhile, the largest favorable impact on the critical vortex flow parameters was achieved via a 25%-span spoiler–tab combination with a height of 5 and 2.5% chord, respectively. A contrary effect on the BVI suppression, especially during pitch-up, was, however, observed. The impact on the BVI can be improved by reducing the height of the spoiler at the expense of unfavorable change in the vortex strength and displacement.

Simple beam connections in combined shear and tension

An investigation into the behaviour of simple beam-to-column connections subjected to combined shear and tension was carried out by testing 108 full-scale specimens, including header angle, knife angle, single angle, and shear tab configurations. Specimens were rotated 0.03 rad, and a prescribed shear between zero and the design shear resistance was held constant while the specimens were loaded in tension to failure. Results showed significant differences in serviceability, ductility, interactions, and ultimate tension strength. Ductility was provided through yielding in bearing at bolt holes, bending of angle legs, and shear yielding of the gross section of connection elements. Tension and shear load versus displacement plots were acquired for all tests because of ductility and serviceability considerations in design. Existing methods of determining connection resistance, including bolt shear, net section shear, and bearing resistance, were used to compare predicted capacity with test results. The findings of the test program indicate that most simple connections can sustain significant amounts of tension in combination with design shear capacity.Key words: beam, connections, shear, tension, experimental, design, steel.

Sub-Boundary-Layer Disturbance Effects on Supersonic Base-Pressure Fluctuations

Fluctuating base pressures were measured for an axisymmetric blunt afterbody modified with two different sub-boundary-layer disturbance tabs, a triangle-tab configuration, and a strip-tab configuration, in a Mach 2.46 flowfield. Normalized rms levels indicate that base-pressure fluctuations increase with addition of the triangle tabs and decrease with the addition of the strip tab. Power-spectral-density (PSD) estimates recorded at the two outermost radial locations for the triangle-tab configuration demonstrated that the fluctuation energy increased when compared to the no-tab case at nearly all frequencies, particularly at frequencies above 1 kHz. This suggests that the triangular tabs energize turbulent structures in the free shear layer because of the introduction of streamwise vorticity. It was also found that a prominent peak in the PSD estimate at the outer two radial locations, found in the no-tab case, is absent for the triangle-tab configuration. Dual-transducer measurements for both tab configurations suggest that correlated pressure fluctuations are realized at most locations across the base simultaneously, lending credence to the idea that a global mechanism acts as a source of the base-pressure fluctuations.

Simple beam connections in combined shear and tension

An investigation into the behaviour of simple beam-to-column connections subjected to combined shear and tension was carried out by testing 108 full-scale specimens, including header angle, knife angle, single angle, and shear tab configurations. Specimens were rotated 0.03 rad, and a prescribed shear between zero and the design shear resistance was held constant while the specimens were loaded in tension to failure. Results showed significant differences in serviceability, ductility, interactions, and ultimate tension strength. Ductility was provided through yielding in bearing at bolt holes, bending of angle legs, and shear yielding of the gross section of connection elements. Tension and shear load versus displacement plots were acquired for all tests because of ductility and serviceability considerations in design. Existing methods of determining connection resistance, including bolt shear, net section shear, and bearing resistance, were used to compare predicted capacity with test results. The findin...

Effect of Specimen Tab Configuration on Compression Testing of Composite Materials

Standard Test Method for Compressive Properties of Unidirectional or Cross-Ply Fiber-Resin Composites (ASTM D 3410) for compression testing of composite materials recommends that low-carbon steel or a glass/epoxy composite be used as the tab material, and that the tabs be tapered. However, many details remain unspecified. An analytical study of tab configurations was performed in the present study to determine the effect of type of tabbing material and tab-taper angle on the stress distributions within a unidirectional composite specimen in compression. More compliant tab materials and shallower tab-taper angles yielded less stress concentration in the tab-tip region of the specimen. Therefore, specimens with these tab configurations should yield higher measured compressive strengths since premature failure at the tab tip is less likely to occur. Although there are relatively few experimental data available for different tab materials and tab-taper angles, those that are available show the same trends as predicted by the present analytical study.

Effects of Specimen Length and Stress Concentration on the Compressive Strength of Unidirectional CFRP.

There are various compression test methods for a unidirectional composite material, but they use different specimen lengths without cosidering the effect of specimen length in detail. In this paper, the effects of specimen length and stress concentration on the compressive strength of unidirectionally carbon-fiber-reinforced plastics were investigated. Compression tests for the CFRP were carried out for a wide range of specimen lengths, three different end tab configurations and two different end tab materials under the condition of constant specimen thickness. This was performed using the Celanese compression test method. The apparent compressive strength measured by the Celanese test method is lower than the true compressive strength because of the stress concentrations near the tab tip of the specimen. However, the apparent compressive strength of the specimen with a circular profile (R25) between the chucking part and the testing part (CFRP) which has slight stress concentration at the tab tip is higher than those of the Celanese specimen configurations. The true compressive strength was obtained using the specimen with the end tab of stainless steel and lengths of 3.2 mm and 6.4 mm.

Stress and Deflection Analysis of Partially Routed Panels for Depanelization

Deflection and stress in partially routed panels have been studied by the finite element method. Emphasis is placed on the effects of partial routing on the assembly processes for surface mount printed circuit boards. To test the validity of the finite element results, the overall deflection profile of a partially routed panel was measured. The calculated deflection profile agreed with the experimental results. Two different tab configurations have been designed and for each design four connecting tab widths have been analyzed.

An investigation of the tabbed vortex flap

Subsonic wind tunnel investigations were conducted on delta wings with tabbed vortex flaps. The tab comprises an up-deflected leading-edge portion of the flap intended to augment the vortex-induced thrust on the down-deflected flap. Balance and pressure measurements on a 74-deg delta model compared plane and tabbed vortex flaps of equal total area; tab modifications intended to improve the L/D over plane flaps were evaluated. In a parallel investigation, detailed spanwise pressures were measured on a 65-deg delta wing model from which sectional lift and drag contributions of the individual wing, flap, and tab surfaces were obtained by integration. Theoretical solutions using the free vortex sheet code with several flap/tab deflections on the 65-deg delta were compared with experimental pressures and vortex core positions. The results of this exploratory study showed that while the tab can augment the flap vortex thrust considerably, an excessive tab drag component may cancel this benefit. Preliminary guidelines toward more efficient tab configurations have been suggested.