Experimental investigation on the effects of convex surface curvature on the aerodynamics and wake characteristics of a square cylinder

The Effects of Surface Curvature on Cartilage Behaviour in Indentation Test: A Finite Element Study

This paper presents a three-dimensional numerical study of water jet impingement cooling on a hot moving/rotating surface. The main objective of this paper is to analyze the effect of surface curvature (convex surface) on heat transfer characteristics. The conjugate heat transfer phenomenon occurring between surfaces with varying curvatures is investigated. The flow parameters, boundary conditions, and computation domain are chosen the same for all the geometries, to have a detailed insight. Two different sets of conditions are considered in this study. In the first set, the effect of curvature on heat transfer is analyzed considering a stationary flat plate (130 mm × 65 mm) and a stationary cylinder (ϕ 41.4 mm). Further we compared the effect of surface curvature between two cylinders of a different radius of curvature (ϕ 41.4 mm & ϕ 20.7 mm). The Reynolds number, Red as defined based on the diameter of the circular nozzle is taken to be 56,000. The surface of the flat plate and the circular cylinder is maintained at a constant temperature condition. The simulation results obtained from this study establish a notable impact of surface curvature and motivates the use of such a non-conventional set-up in a lab-scale facility.

Numerical and experimental investigation on the effect of surface curvature and slope angle on the material removal characteristics in fluid jet polishing

Results of a study of the effects of longitudinal surface curvature on incompressible laminar boundary-layer flows are presented. They were obtained by numerical solution of a generalized Falkner-Skan equation governing similar solutions for flows over curved surfaces. These solutions form a two-parameter family; that is, they depend on a surface curvature parameter in addition to the well-known pressure gradient parameter. The curvature parameter is essentially the inverse square root of the Reynolds number based on freestream conditions and a characteristic radius of curvature. Effects of curvature on skin friction are linear in the curvature parameter. Convex surface curvature produces a decrease in skin friction compared to the zero curvature solution, whereas concave curvature increases skin friction. The magnitude of the correction to skin friction introduced by surface curvature depends on the value of pressure gradient parameter, being smaller for adverse longitudinal pressure gradients than for favorable pressure gradients. It is found, in addition, that concave curvature produces a reduction and convex curvature an increase in the value of momentum and displacement thickness compared to zero curvature solutions. The results also indicate that, for equal flow conditions, boundary-layer thickness is greater for flows with convex surface curvature than for flows with concave curvature.

In this study, computer modeling of the contact fill process with chemical vapor deposition, (CVD) of tungsten is used to show the importance of several details on the quality of the fill process. The effect of surface curvature on the step coverage of CVD‐W has been investigated. It is shown that for contacts with an aspect ratio smaller than one, the effect of surface curvature is substantial and actually improves step coverage. Therefore, surface curvature for features with aspect ratios smaller than one, should be accounted for in computer simulations of the fill process. For contacts with aspect ratios larger than one the effect of surface curvature is negligible. It is shown that the size of the void (which will be formed in cases of step coverage less than 100%) is a better way to describe the quality of the deposition and the repercussions of the void on subsequent process steps such as tungsten etch back. In addition, the size of the void depends for a given set of deposition conditions solely on the depth of the contact rather than the contact diameter (for aspect ratios larger than 1.0).

We analyse the effect of gate surface curvature on the nonlinear behaviour of an array of gates in a semi-infinite channel. Using a perturbation-harmonic expansion, we show the occurrence of new detuning and damping terms in the Ginzburg–Landau evolution equation, which are not present in the case of flat gates. Unlike the case of linearised theories, synchronous excitation of trapped modes is now possible because of interactions between the wave field and the curved boundaries at higher orders. Finally, we apply the theory to the case of surging wave energy converters (WECs) with curved geometry and show that the effects of nonlinear synchronous resonance are substantial for design purposes. Conversely, in the case of subharmonic resonance we show that the effects of surface curvature are not always beneficial as previously thought.

The paper addresses the prediction of disturbance amplitudes and profiles due to localized surface roughness and wall-suction in incompressibl e swept-wing boundary layers subject to cross flow (CF) instability. An accurate and efficient numerical approach for solving the receptivity problem of disturbance generation is presented. The solution method developed models correctly the far-field effects of surface roughness and suction through holes on the disturbances generated. This is shown by studying Swept Hiemenz and Falkner-Skan-Cooke (FSC) boundary layer flows as well as a swept-wing experiment. The numerical results for these flows are compared with local receptivity (residue) theory, with data from Direct Numerical Simulation (DNS) and from measurements, respectively. It turns out that local theory strongly overpredicts both receptivity and effects of surface curvature. Due to the account for effects of surface curvature and weak nonlinearity as well as the potential of coupling the results with NOLOT/PSE-methods, the approach presented is a useful numerical tool for designing active and passive transition control systems for swept wings.

Effects of surface curvature on residual stress field of 316L stainless steel subjected to laser shock peening

Extended reality (XR) systems now use everyday physical surfaces as touch input spaces. However, existing systems rely primarily on flat surfaces due to the given device form factor and sensing capabilities. Despite advancements in sensing technologies that allow touch input across surfaces with diverse curvatures, the effects of surface curvature on user behavior and performance in indirect XR touch interaction remain underexplored. To this end, we present CurvedTouch, a study that investigates the effects of surface curvature and cursor mapping methods on XR indirect touch interaction. We evaluated 4 surface curvatures (flat, R = 75mm, 60mm, and 45mm) and two cursor mapping methods (Projection-based and Distance-based) in a within-subject study by measuring task performance, behavioral pattern, workload, and usability. 16 participants performed the indirect Tap, Drag, and Trace task under certain conditions. Our results reveal that the task performance and usability significantly dropped for a curvature between R = 45mm and R = 60mm. As curvature increases, users change their input strategy from finger-level motion to whole-hand movement. Unlike prior findings in direct touch interaction, we found that minimum button size increases on a high curvature surface in an indirect touch scenario. For the cursor mapping method, distance-based mapping showed higher usability under high curvature. Based on these findings, we came up with design guidelines for interaction type, button size, interaction area, and cursor mapping method for the XR indirect touch interface on a curved surface.

The effect of the surface curvature on the magnetic moment and persistent\ncurrents in two-dimensional (2D) quantum rings and dots is investigated. It is\nshown that the surface curvature decreases the spacing between neighboring\nmaxima of de Haas -- van Alphen (dHvA) type oscillations of the magnetic moment\nof a ring and decreases the amplitude and period of Aharonov -- Bohm (AB) type\noscillations. In the case of a quantum dot, the surface curvature reduces the\nlevel degeneracy at zero magnetic fields. This leads to a suppression of the\nmagnetic moment at low magnetic fields. The relation between the persistent\ncurrent and the magnetic moment is studied. We show that the surface curvature\ndecreases the amplitude and the period of persistent current oscillations.\n

An experimental investigation was performed on the mass transfer by sublimation from the outer surfaces of hollow naphthalene cylinders, 0.75 and 1.00 in. in diam., in parallel air streams at velocities between 20 and 120 ft./sec. Local mass transfer rates on the cylinders were obtained by a profilometric technique consisting of accurate determinations of changes in radii of the subliming surfaces at points along elements of the cylinders.Local coefficients of mass transfer obtained with laminar boundary layers for Reynolds numbers (based on axial length) between 12,000 and 100,000 were found to be up to 8% greater, because of surface curvature, than corresponding values for flat surfaces. Moreover comparison of the mass‐transfer data with a theoretical prediction for laminar skin friction on circular cylinders indicates an effect of surface curvature on the Chilton‐Colburn anology between momentum and mass transfer amounting to as much as 6% in the range of air velocity employed. For turbulent boundary layers obtained by artificial triggering of turbulence at the leading edges of the cylinders no effect of surface curvature was found. The results obtained for Reynolds numbers of 40,000 to 1,000,000 are lower than previously published correlations of turbulent heat, mass, and momentum transfer, when compared by the Boelter, Martinelli, and Jonassen form of the analogy.

Effect of Convex Surface Curvature on the Onset of Nucleate Boiling of Subcooled Fluid Flow in Vertical Concentric Annuli An experimental study has been carried out to investigate the effect of the transverse convex surface curvature of core tubes on heat transfer in concentric annular tubes. Water is used as the working fluid. Three annuli having a different radius of the inner cores, Ri

The effect of surface curvature on the low-wavenumber-frequency spectrum of turbulence-induced surface pressure fluctuations is considered and an estimate for the associated flow noise is obtained. The form of the low-wavenumber cross-spectral density of pressure on the surface of an infinitely long, rigid circular cylinder of radius a due to a statistically stationary turbulent boundary-layer flow at a low Mach number is determined. Viscous effects are ignored. It is shown that, in contrast to the case of an infinite plane surface, the pressure spectrum is finite everywhere in the wavenumber plane (k, n/a) except for a logarithmic, integrable, singularity at the acoustic wavenumber corresponding to the axisymmetric mode (n/a = 0); k and n/a being, respectively, the downstream and circumferential wavenumber. For non-axisymmetric modes (|n/a| > 0), the spectrum has two finite peaks in the radiative domain |k| < ω/c; ω being the frequency and c being the sound speed. For ωa/c large, the peaks occur in the vicinity of the total acoustic surface wavenumbers κ = ± ω/c (κ = (k2 + n2 / a2)½) and the principal contribution which determines the peak characteristics can be identified as being due to creeping rays emanating from turbulent sources on the cylinder out of the line of sight of the associated receiver point. For large value of ωa/c, the point pressure spectrum and the associated radiated sound vary logarithmically with $(\omega a/c)^{\frac{2}{3}}$; corresponding estimates for cylinders of moderate and small radius are also obtained. For an almost plane cylinder, it is shown that the effect of curvature may be included by a suitable simple modification of the form of the pressure spectrum for an infinite plane surface.

The effect of surface curvature on the spontaneous movement of cholesterol between membranes was investigated by measuring the rates of cholesterol transfer from donor vesicles of various sizes to a common acceptor vesicle. Donor vesicles of size in the range 40-240 nm were prepared by extruding multilamellar dispersions through polycarbonate filters of different pore sizes under pressure. The smallest donor vesicle and the acceptor vesicles were obtained by the normal sonication procedures. The rate of cholesterol transfer, as measured by the movement of [3H]cholesterol, decreases with increasing size of the donor vesicle in an almost linear fashion. The extrapolation of the results gave a half-time (t1/2) of 16-20 h of the desorption of cholesterol from a planar bilayer, and this can be considered as a reference value for most cellular membranes which are characterized by very low curvatures. Our earlier studies have shown that the t1/2 for cholesterol efflux is influenced by the presence of gangliosides and phosphatidylethanolamine, and the asymmetric distribution of these lipids in the plasma membrane could partially account for the large difference in the rates of cholesterol movement from the two sides of the plasma membrane. The small differences in rates arising from asymmetric distribution will be magnified by the longer t1/2 obtained here for membranes of low curvatures, so that the large difference in rates might be a coupled effect of lipid asymmetry and low curvature of the plasma membrane. This, in turn, may have a role in maintaining the large differences in cholesterol/phospholipid molar ratios observed between plasma membrane and intracellular membranes.

Surface curvature effects on the tonal noise performance of a low Reynolds number aerofoil