Effect Of Gap Width Research Articles

Effect of partitions on flow mechanism and heat transfer in thermal convection

The effect of gap width and partition thickness on the flow mechanism and heat transfer of partitioned thermal convection is investigated using a thermal lattice Boltzmann method from Ra = 8 × 106 to Ra = 1 × 108. Partitioning effects on the heat transfer and the physical mechanism of flow are analyzed using the velocity field and temperature field of the convection. Numerical simulation results show that the optimal gap width decreases and that the optimal partition thickness increases with increasing Rayleigh number (Ra). Gap width and partition thickness have a joint effect on the heat transfer. We have counted the comprehensive influence of dimensionless gap width (D*) and dimensionless partition thickness (S*) on diaphragm heat on Nu under Ra = 108. The results show that the global maximum of Nu appears in the regions of 0.004<D*<0.006 and 0.02<S*<0.035. Two important factors affecting the partitioned thermal convection have been found. In addition, an interesting relationship between the average Nusselt number and the presence of leakage vortices is also discussed in this study.

Effect of Gap Width on the Distance between Bright Patterns in Yellow

This research aims to determine the effect of gap width on the distance between bright patterns in the yellow color experiment. This research was carried out in a virtual laboratory, with the method used is a quantitative method with an experimental method, namely the method used to determine the effect of the independent variable on the dependent variable. Data collection was taken during the practicum using the PhET website in the Wave Interference – Slits section, with yellow light which has a wavelength of around 670-690 nm. The distance between two slits is 1500 nm and three different slit widths are used, namely 500 nm, 600 nm, and 700 nm. This research shows that the smaller the value of the gap width, the greater the value of the dark light pattern. Where, the wider the gap, the denser the light-dark pattern on the screen, and the smaller the gap width, the more sparse the light-dark pattern on the screen. Keywords: Gap Width; PhET; Dark Light Pattern.

Effect of embedded periodic fiber placement gap defects on the microstructure and bistable behavior of thermoplastic composite laminates

AbstractBy inducing periodic gaps, conventional automated fiber placement avoids overlap defects, which are generally prohibited in composite component manufacturing. However, bistable laminates are highly sensitive to imperfections, and it is critical to explore the effect of periodic gaps on the performance of bistable laminates. The principal curvatures and load–displacement curves of thermoplastic composite laminates with manually embedded periodic gaps was studied using experimental and numerical methods in this paper. SEM microscopy was used to observe the gap areas of the cross section of laminates to assess the microstructure of gaps with width variations after curing. In addition, a numerical method was proposed based on the experimentally determined evolution of gap widths and thicknesses of laminate. Subsequently, the effects of gap width, single‐layer thickness, and total thickness on the principal curvature were investigated. Gaps embedded in the 0° and 90° layers of bistable laminates demonstrated a substantial decrease in the snap load of the laminates. Interestingly, by embedding different gap widths in the 0° layers of the laminates, the snap load discrepancy between the snap‐through and snap‐back processes increased as the gap width widened, and the same trend was also found in the curvatures in the two stable states.Highlights Bistable characteristics of laminates with periodic gap defects. Utilizing gaps embedding in 0° layer to tailor the mechanical properties.

Laser-MIG hybrid welding of aluminium alloy extrusions for high-speed trains: effects of gap width on microstructure and properties

6A01-T5 aluminum alloy extrusions with a thickness of 4.5 mm were welded by laser-MIG hybrid welding, and the effects of gap width on the microstructure and properties were studied in details. The results indicated that the priorities of the welding parameters on the tensile strength of joints were laser power, defocusing amount and arc current when the welding speed was constant. The gap tolerance of the optimal welding parameters could reach up to 1.1 mm. The morphology and size of the microstructures were similar when the gap width was no larger than 1.1 mm. The grain boundaries became obvious and even cracks appeared near the fusion line when the gap width increased to 1.5 mm. The microhardness distributions almost the same with the different gap widths: highest in the base materials zone, secondly in the heat-affected zone, then in the weld zone, and lowest near the fusion line. The microhardness values reduced in each zone except base materials when the gap width increased to 1.5 mm. The tensile strength reduced as the gap width increased, the specimens all fractured near the fusion line due to where had the lowest microhardness and the fracture showed ductile failure mode.

Tip Leakage Flow Structures and Its Influence on Cavitation Inception for a NACA0009 Hydrofoil

AbstractCavitation inception in tip leakage flows remains a challenging topic in the engineering field, as the effect of tip gap width on inception is unclear. The present study is devoted to an analysis of the effect of gap width on tip leakage cavitation inception by using full-wetted numerical simulations. Numerical results show that the cavitation inception number is strongly related to the dimensionless gap width τ, which is defined as the ratio of tip gap width to the maximum hydrofoil thickness, and the reason behind it is explained by the specific flow structures. The cavitation inception number of suction side (SS) sheet cavitation decreases gradually with the increase of dimensionless gap. The cavitation inception numbers of tip leakage vortex (TLV) and tip separation vortex (TSV) increase first and then decrease with the increase of the gap, reaching the maximum at τ=0.2 and τ=0.3, respectively. The main reason is that in the gap range of 0.2−0.3, TLV and TSV cores have the highest vorticity and the lowest pressure.

Effect of Hele–Shaw cell gap on radial viscous fingering

The flow through a Hele–Shaw cell is an experimental prototype to study the flow through a porous medium as well as the flow in microfluidic devices. In context with porous medium flows, it is used to visualize and understand hydrodynamic instabilities like viscous fingering (VF). The gap between the plates of the cell is an important parameter affecting the flow dynamics. However, the effect of the gap on the Hele–Shaw cell flows has been minimally explored. We perform experiments to understand the effect of the gap on VF dynamics. It is observed that a minimum gap is required to observe rigorous fingering instability. The onset time of instability, as well as the width of the fingers, increases with an increment in the gap due to a decrease in the convection. The instability increases with an increase in Péclet number, but the effect of gap width on fingering patterns is evident with broader fingers observed for larger b. The results are validated by performing numerical simulations. It is further shown that the gap-averaged three-dimensional simulations using the Stokes law approach and the two-dimensional Darcy’s law result in a small gap Hele–Shaw cell.

Gap effects on the aerodynamic characteristics around three rectangular boxes in tandem arrangement

Multiple-box structures have become increasingly important in practical engineering; for example, some recent large-span bridges were creatively designed using triple-box decks. The flow characteristics and flow-induced responses of multiple-box structures are notably complex due to the existence of gaps. Herein, we conducted a detailed investigation on the effects of gap width on the aerodynamics and flow characteristics of three boxes in a tandem arrangement, that is, a triple-box model. The test model comprised three rectangular cylinders with a side ratio of 3.7 (i.e., SR = 3.7), and it was arranged in line with the incoming airflow. The gap ratio (L/D = the ratio of the gap width L to the height of the box D) was varied from 0 to 10.260. Surface pressure measurement and smoke-wire flow visualization were conducted in the wind tunnel tests. For the pressure measurements, the Reynolds number (Re) was varied from 1.01 × 104 to 2.20 × 104. The smoke-wire flow visualization was performed at a relatively low Re of 6767. The results showed that the gap ratio significantly influenced the pressure distributions, aerodynamic forces, and surrounding flow patterns. A “dual-frequency” phenomenon was observed at low and moderate gap ratios; that is, a dominant frequency and secondary frequency were found. Moreover, the secondary frequency was closely related to the secondary vortices. Furthermore, the dual-frequency phenomenon disappeared at large gap ratios, which was different from the tandem circular cylinders. Based on the experimental results, the flow patterns around the triple-box model were categorized into four basic types, depending on the gap ratio.

DNS analysis of flow and heat transfer of SCO2 in a square subchannel–Effect of gap width

The heat transfer and flow characteristics of supercritical carbon dioxide (SCO2) in a tight lattice are problematic in the thermal-hydraulic design of reactor fuel assemblies. Herein, direct numerical simulation (DNS) was performed to investigate the heat transfer and flow behavior of SCO2 in a vertically upward square subchannel. Emphasis was placed on clarifying the effect of the pitch-to-diameter (p/d) ratio, defined as the subchannel pitch over the rod diameter, on the time-averaged heat transfer and instantaneous velocity/temperature fluctuation. It was found that the wall temperature exhibits a “V-shaped” profile along the rod circumference, which is caused by the combined effects of buoyancy and an uneven flow area. The wall temperature is lower for subchannels with smaller p/d ratios; meanwhile, the circumferential non-uniform heat transfer becomes stronger, which also requires to be considered. The time-averaged streamwise velocity and fluid temperature have similar distributions on the subchannel cross-section, that is, high velocity and temperature occur near the rod gap, while regions with low velocity and temperature are identified in the subchannel interior. With an increase in the p/d ratio, both the temperature and velocity gradients are enlarged. Large-scale flow pulsations were identified in the subchannels. The instantaneous velocity fluctuation is weakened with increasing gap width; however, the fluctuation in the wall temperature exhibits an opposite trend. The effects of the p/d ratio on the dominant frequency of velocity/temperature fluctuation are not universal. Among the three selected cases, a subchannel with a small p/d ratio had a higher dominant frequency of instantaneous fluctuations. The turbulence structure was studied using a quadrant and anisotropy analysis. It was found that the outward and inward interactions included the main turbulence structures in the subchannel interior. In addition, with an increase in the p/d ratio, the transformation from disk-like turbulence to rod-like turbulence can be identified.

Dns Analysis of Flow and Heat Transfer of Sco2 in a Square Subchannel – Effect of Gap Width

Dns Analysis of Flow and Heat Transfer of Sco2 in a Square Subchannel – Effect of Gap Width

The Effect of Gap Width on Premixed Flame Propagation in Non-adiabatic Closed Hele–Shaw Cells

ABSTRACT The premixed flame propagation with conductive heat loss in millimeter-scale narrow closed cells of different gap widths is investigated experimentally and numerically. The flame evolution is observed in a disc-shaped cell of which the width is varied from 2.0 mm to 5.0 mm. A non-monotonic relation between the flame propagation velocity and the gap width is found. Time-dependent numerical results exhibit good agreement with the experimental data and indicate that the flame behaviors are highly sensitive to the gap width. Since gap downsizing leads to significant heat loss and viscous friction from the wall, the propagation velocity will drop to almost laminar flame speed halfway for 2.0 mm width. For larger gaps, the flame propagation velocity is determined by the combined effect of the flame straining and the conductive heat loss. The former increases the flame front area while the latter strongly weakens the flame distortion. The trade-off of them yields the non-monotonic relation and an optimal width of 3.0 mm.

Influence of gap width on buffeting force spatial correlation and aerodynamic admittance of twin-box bridge deck

Wind tunnel tests, including pressure measurement and Particle Image Velocimetry (PIV) test, have been carried out on twin-box bridge decks with four different gap widths (two small gap widths and two large gap widths). The effect of gap width on the buffeting force coherence and aerodynamic admittance of twin-box bridge deck are presented and discussed. The mechanisms of related experimental result are discussed in detail based on the pressure distributions and flow structures obtained in the tests. The measurements reveal that under the influence of vortices shed from the rear edge of the upstream box, the spanwise coherence of buffeting force on the downstream box decrease significantly with the increase of gap width, leading a sudden reduction in total buffeting force coherence on the twin-box bridge deck. While the aerodynamic admittance of twin-box girder increases conspicuously with the increase of gap width due to the generation of the local flow separation at the leading edge of downstream box for large gap width cases.

Investigation of the magnetic flux density dispersion Bd on the gaps of the FeSiBNbCu magnetically soft nanocrystalline block core

This paper focuses on the phenomenon of the magnetic flux density dispersion Bd on the gaps of the Fe73.5Cu1Nb3Si13.5B9 multi-gap nanocrystalline block core. Present state-of-the-art shows, that there is no comprehensive knowledge about the value of the magnetic flux density dispersion Bd on the gaps of nanocrystalline block core and the possibilities of its minimisation. The magnetic flux density dispersion Bd is the source of local eddy currents, which are the cause of increase of power loss and temperature in the chokes’ core. To discuss the effect of gap width and the method of its filling on the power losses in the core, the comparison between inserts of Teflon and magnetic mat composed of 70% Fe53.9Co29.1B13Nb1Si2Cu1 powder with a fraction of 20–36 µm and 30% Ultimeg epoxy resin 2004L was performed.

Effect of gap width on thermal performance of solar air heater having arc-shaped ribs with symmetrical gaps: an experimental investigation

In this paper, thermal performance of a solar air heater (SAH) having arc-shaped ribs with symmetrical gaps has been investigated experimentally and compared with that of smooth SAH. An experimental investigation has been carried out to observe the effect of various gap widths on heat transfer and friction characteristics. The investigation includes the roughness parameter; relative gap width (g/e) ranging from 2 to 5 and flow parameter; and Reynolds number ranging from 3000 to 18,000. The fixed parameters for this study were relative roughness height (e/D) of 0.047, arc angle (α) of 60° and relative roughness pitch (P/e) of 12. Results of the present work have also been compared with previously published work. Nusselt number and friction factor for roughened absorber surface is found to be 3.66 and 2.77 times higher than that obtained for smooth plate, respectively. Maximum value of thermo-hydraulic performance parameter is found to be 2.66 at g/e = 4. Heat transfer and friction factor correlations for proposed roughness have also been developed.

Characterization of designed directional polylactic acid 3D scaffolds for neural differentiation of human dental pulp stem cells

In recent years, 3D printing technology has flourished and applied to tissue engineering regeneration. The purpose of this study is to investigate the effects of gap width between struts (GWbS) of three-dimensional-printed polylactic acid scaffolds (3DP-PLASs) on neural differentiation of human dental pulp stem cells (hDPSCs). Both the 3DP-PLASs with the GWbS of 150μm and 200μm were experimental groups and the 3DP-PLAS without microfilament struts was the control group. Properties of 3DP-PLASs were observed by water contact angles (WCA), atomic force microscope (AFM), and differential scanning calorimeter (DSC). The cell culture of hDPSCs on 3DP-PLASs was performed, and cytotoxicities were measured with Alamar Blue assay. The neural differentiation of hDPSCs on different 3DP-PLASs was compared after neural induction. Expressions of neural markers Nestin, MAP2, beta III tubulin, and GFAP were evaluated with immunocytochemical staining. Our results demonstrated no cytotoxicities among scaffolds, whereas they may differ in crystal sizes and directions resulting from different orders of cooling time, contact surface, and temperature distribution during the building process. In addition, hDPSCs could successfully adhere to 3DP-PLAS modified by alcohol or poly-l-Lysine and demonstrate morphological change and related protein performance. We conclude that 3DP-PLASs with 150μm gaps can induce cellular orientations more easily than those with 200μm gaps. In addition, 3DP-PLASs seem to improve cell adhesion after being coated with poly-l-lysine or soaked with alcohol.

Effect of gap width on electron transport through quantum point contact in hBN/graphene/hBN in the quantum Hall regime

This study investigates quantized electron transport in high-mobility quantum point contact (QPC) devices in hBN/graphene/hBN in the quantum Hall regime. This study primarily focuses on the effect of the gap width of split gates on edge-channel manipulations, which defines the QPC structure and its electrostatic potential distribution. The quantized conductance is governed by the dynamics of edge channels passing through or backscattered at the QPC, which is controlled by both the top-gate and back-gate biases. The effects of the split-gate gap width and the filling in the QPC on the edge-channel manipulations are experimentally verified. The experimental results are consistent with the theoretical predictions of open/closed configurations of the edge channels around QPC with different gate gap widths.

Behavior of three-tube buckling-restrained brace with circumference pre-stress in core tube

The behavior of a new Three-Tube Buckling-Restrained Brace (TTBRB) with circumference pre-stress (σθ,pre) in core tube are investigated through a verified finite element model. The TTBRB is composed of one core tube and two restraining tubes. The core tube is in the middle to provide the axial stiffness, to carry the axial load and to dissipate the earthquake energy. The two restraining tubes are at inside and outside of the core tube, respectively, to restrain the global and local buckling of the core tube. Based on the yield criteria of fringe fiber, a design method for restraining tubes is proposed. The applicability of the proposed design equations are verified by TTBRBs with different radius-thickness ratios, with different gap widths between core tube and restraining tubs, and with different levels of σθ,pre. The outer and inner tubes will restrain the deformation of the core tube in radius direction, which causes circumference stress (σθ) in the core tube. Together with the σθ,pre in the core tube that is applied through interference fit of the three tubes, the yield strength of the core tube in the axial direction is improved from 160 MPa to 235 MPa. Effects of gap width between the core tube and restraining tubes, and σθ,pre on hysteretic behavior of TTBRBs are presented. Analysis results showed that the gap width and the

Experimental investigation on the interaction of a nanopulsed plasma jet with a liquid target

Although the majority of atmospheric pressure plasma jet (APPJ) applications involve the interaction between the plasma and a surface, up to now the number of published papers focusing on this subject is limited, even though the nature of the target may strongly influence the plasma characteristics, the discharge structure, the generated reactive species, and consequently, the overall process. Under this framework, we investigated an APPJ impinging on a liquid surface and the effects of changing the stand-off distance, the applied peak voltage, and the pulse repetition frequency, looking at them as variable parameters often used to optimize plasma surface processes. Intensified charge-coupled device (iCCD) and Schlieren acquisitions suggest a key effect of gap width and peak voltage on the discharge morphology, velocity of the ionization front, and effluent fluid-dynamic behavior. The presence of a grounded liquid substrate enhances the electric field downstream of the source outlet: the smaller the gap the faster the ionization wave and the shorter the time for it to reach the surface. Consequently, a small gap favors the charging of the surface capacitance and the formation of surface ionization waves over the liquid target. Schlieren acquisitions highlight the formation of a transient turbulent structure propagating downstream of the gas flow, starting hundreds of microseconds after the initiation of the plasma discharge. The achieved results support the hypothesis that the formation of the turbulence is caused by a heating effect of the high-voltage electrode on the He gas flow. Another observed effect is the variation of the dimple caused by the He flow on the liquid surface as a consequence of the turbulence generated by the plasma discharge. The results presented here confirm how the gas dynamics and the discharge behavior are strongly affected by the presence of the liquid substrate and by its position with respect to the APPJ.

Experimental Study on Cellular Premixed Propane Flames in a Narrow Gap between Parallel Plates

ABSTRACTExperimental results on laminar propane flames propagating in a narrow gap between parallel glass plates are presented. Development and evolution of cellular flame structure is demonstrated by video and long-exposure photo recordings for stoichiometric and fuel-rich mixtures with equivalence ratio of 1.0:1.25. It is shown that in narrow gaps the lateral cell sizes by far exceed the gap width. Average flame propagation speed obtained for gap widths between 2.5 and 4.4 mm is shown to depend significantly on the gap width due to the effect of heat losses on the normal flame speed, as well as due to cooling of products behind the flame. Effect of gap width on the cellular structure is demonstrated, and statistical characteristics of the cells are obtained for two gap widths. Flame propagation patterns are also obtained for non-central ignition performed at one or simultaneously at two points.

Drag reduction in a class 8 truck - scaled down model

Trucks are heavy load vehicles used mainly for commercial transport operations. There are several classes of heavy duty commercial vehicles classified based on the weight loaded. More than 50% of the engine output power in such trucks is utilized to overcome the drag. Drag force in automobiles is the resistance offered by air on vehicles at higher speeds. Class 8 trucks suffer higher drag when compared to other classes. In the present work, a numerical model is developed using a commercial code ANSYS FLUENT to predict the drag coefficient value. The effects of gap width and cab front radius with a constant fairing is analysed using the numerical model developed. A Class 8 model truck with minimal drag coefficient having constant fairing and optimized gap width between the trailer and cab is proposed.

Modeling and Analysis of Composite Steel Plate Shear Wall with Assembled Multi-concrete Slab

This paper presents numerical investigation of composite steel plate shear wall with vertical assembling mode (V-CSPSW) affecting cyclic loading. Three-dimensional finite element models are developed using ABAQUS emphasizing constitutive material modeling and element type to represent the real behavior of V-CSPSW. Validation of the FE model against the experimental results has shown a good agreement. The numerical studies were focused on the effects of gap width, bolt spacing-to-steel thickness ratio and concrete slab thickness on the V-CSPSW’s behavior. Results indicate that the gap width should less than 48mm and 72mm if the bolt spacing-to-steel thickness ratio is 100 and 125, respectively; meanwhile, the bolt spacing-to-steel thickness ratio of the V-CSPSW should less than 125 if the concrete slab possesses enough restraint stiffness.