Wedge Opening Angle Research Articles

Biomechanical lower limb model to predict patellar position alteration after medial open wedge high tibial osteotomy

Medial open-wedge high tibial osteotomy is a surgical treatment for patients with a varus deformity and early-stage medial knee osteoarthritis. Observations suggest that this surgery can negatively affect the patellofemoral joint and change the patellofemoral kinematics. However, what causes these effects and how the correction angle can change the surgery’s impact on the patellofemoral joint has not been investigated before. The objective of this study was to develop a biomechanical model that can predict the surgery’s impact on the patellar position and find the correlation between the opening angles and the patellar position after the surgery. A combined finite element and multibody model of the lower limb was developed. The model’s capabilities for predicting the patellofemoral kinematics were evaluated by performing a passive deep flexion simulation of the native knee and comparing the outcomes with magnetic resonance images of the study subject at various flexion angles. The model at a fixed knee flexion angle was then used to simulate the high tibial osteotomy surgery virtually. The results showed a correlation between the wedge opening angles and the patellar position in various degrees of freedom. These results indicate that larger wedge openings result in increased values of patellar distalization, lateral patellar shift, patellar rotation, and patellar internal tilt. The developed model in this study can be used in future studies to monitor the stress distribution on the patellar cartilage and connecting tissues to investigate their relationship with observations of pain and cartilage injury due to post-operative altered patellar kinematics.

Heat Transfer From a Concentrated Tip Source in Falkner–Skan Flow

Abstract The Falkner–Skan flow over a wedge is classic in boundary layer theory. We consider the heat or mass transfer from a source at the vertex of the wedge. The interactions of the thermal boundary layer and momentum boundary layer lead to nonlinear similarity equations which are integrated numerically. There exists a mixing index that depends on the Prandtl number and the wedge opening angle. Attention is paid to special cases such as forced convection in Blasius flow past a semi-infinite plate and the Hiemenz stagnation flow normal to a plate.

Dynamics of water entry

Diving induces large pressure during water entry accompanied by the creation of cavity and water splash ejected from the free water surface. To minimize impact forces, divers streamline their shape at impact. Here, we investigate the impact forces and splash evolution of wedges entering water as a function of the wedge opening angle. A gradual transition from impactful to smooth entry is observed as the wedge angle decreases. After submersion, the wedge experiences significantly smaller drag forces (two-fold smaller) than immersed wedges. Our experimental findings compare favourably with existing force models upon the introduction of empirically based corrections. We experimentally characterize the shapes of the cavity and splash created by the wedge and find that they are independent of the entry velocity at short times, but that the splash exhibits distinct variations in shape at later times. We propose a one-dimensional model of the splash that takes into account gravity, surface tension and aerodynamic forces. The model shows, in conjunction with experimental data, that the splash shape is dominated by the interplay between a destabilizing Venturi-suction force due to air rushing between the splash and the water surface and a stabilizing force due to surface tension. Taken together, these findings could direct future research aimed at understanding and combining the mechanisms underlying all stages of water entry in application to engineering and bio-related problems, including naval engineering, disease spreading or platform diving.

Confinement Induced Splay-to-Bend Transition of Colloidal Rods

We study the nematic phase of rodlike f d-virus particles confined to channels with wedge-structured walls. Using laser scanning confocal microscopy we observe a splay-to-bend transition at the single particle level as a function of the wedge opening angle. Lattice Boltzmann simulations reveal the underlying origin of the transition and its dependence on nematic elasticity and wedge geometry. Our combined work provides a simple method to estimate the splay-to-bend elasticity ratios of the virus and offers a way to control the position of defects through the confining boundary conditions.

Computer simulation of Lennard-Jones fluid adsorption in wedge-shaped pores with smooth walls

The adsorption isotherms and local density distributions in wedge-shaped pores with smooth solid walls are obtained for a molecular fluid by the grand canonical Monte Carlo and multiple histogram reweighting methods. The effect of wedge opening angle on the phase behavior of the fluid is considered, and the peculiarities of the mechanism of wedge-shaped pore filling are established.

High-intensity laser-plasma interaction with wedge-shaped-cavity targets

High-intensity, short-pulse laser-interaction experiments with small-mass, wedge-shaped-cavity Cu targets are presented. The diagnostics provided spatially and spectrally resolved measurements of the Cu Kα line emission at 8 keV. The conversion efficiency of short-pulse laser energy into fast electrons was inferred from the x-ray yield for wedge opening angles between 30° and 60° and for s- and p-polarized laser irradiation. Up to 36±7% conversion efficiency was measured for the narrowest wedge with p-polarization. The results are compared with predictions from two-dimensional particle-in-cell simulations.

Effect of changes of complex surface impedance for acoustic scattering from a wedge

A code written earlier for the calculation of acoustic scattering from a submerged wedge has been employed in order to study the dependence of the scattering amplitude on various assumed surface impedances of the wedge. Typical wedge opening angles are 10°. Plane waves are assumed incident with source and observation points coinciding in the far field along the bisector of the wedge. The target strength for an impedance-coated wedge is found to lie in between those of a rigid and a pressure release wedge. A frequency region up to 20 kHz was considered. Various numerical impedances and angles of incidence are assumed.

Adsorption in a nonsymmetric wedge.

We study adsorption in a nonsymmetric wedge consisting of two chemically different, homogeneous planes. First, we macroscopically analyze configurations of nonvolatile liquid drop placed in such a two-dimensional wedge and construct phase diagrams describing transitions between various interfacial shapes. Then adsorption is discussed within MFT based on the effective interfacial Hamiltonian. Two regimes for the system parameters--the wedge opening angle (2phi) and the critical wetting temperatures of each of the planar walls (T(W1) and T(W2), T(W2)<T(W1))--are identified. In one of them we find the critical filling transition at T(F)<T(W2) and the corresponding critical indices which are equal to those found for a symmetric wedge. In the other regime (T(W2)<T(F)<T(W1)) interfacial configurations are similar to those exhibited in the case of a planar substrate consisting of two chemically different parts. In the borderline case (T(F)=T(W2)), the interface profile above the wall with the lower wetting temperature becomes parallel to it. The line tensions corresponding to T(F)<T(W2) and T(F)=T(W2) cases are evaluated and the critical exponents - different in each case - are identified. An effective one-dimensional Hamiltonian describing fluctuations along the wedge is constructed for the T(F)<T(W2) case.

Three-dimensional asymptotic stress field at the front of an unsymmetric bimaterial pie-shaped wedge under antiplane shear loading

Three-dimensional asymptotic stress field in the vicinity of the front of a bimaterial pie-shaped wedge of general (unsymmetric) geometry is obtained by a recently developed eigenfunction expansion method. The bimaterial pie-shaped wedge is subjected to four combinations of wedge-side boundary conditions – free–free, clamped–clamped, free–clamped and clamped–free. Each material is isotropic and elastic, but with different material properties. Additionally, numerical results pertaining to the variation of the lowest eigenvalues (or stress singularities) with respect to the wedge opening angle of the bimaterial wedge, subjected to the aforementioned wedge-side boundary conditions, are also presented. Dependence of the same on the material properties of the component material phases is also an important part of the present investigation.

Exact surface and wedge exponents for polymers in two dimensions.

Using conformal-invariance arguments in two dimensions, we identify the exact infinite series of basic surface conformal dimensions for polymers, checked by transfer-matrix calculations for the n=0 vector model on a strip. For a self-avoiding branched polymer of arbitrary and fixed topology, near a surface or a wedge, we give the exponent \ensuremath{\gamma} in two dimensions as a function of the topology and of the wedge opening angle.

The Pointless Wedge

The classical solution for an elastic wedge under a concentrated tip moment displays a curious behavior that has been studied and clarified by Sternberg and Koiter. In the present paper the problem is reexamined from another point of view in order to answer some puzzling questions that remain. The wedge is truncated along an arc near its tip, and attention is directed toward the calculation of the twisting stiffness corresponding to the application of a couple to an infinitely stiff reinforcement at the truncated boundary. Good approximate results are found over the full range of wedge opening angles.