Oblique Wedge Research Articles

Characterization on the impact load of a local corner region of a liquid tank entering water

This study conducts a detailed examination of the characteristics of impact loads in complex triangular areas within liquid tanks via the volume of fluids (VOF) method, with a general understanding of impact loads. By comparing the numerical results with previous experimental data of oblique wedge impacts on water surfaces, the effectiveness of the VOF method was confirmed. Complex dynamic phenomena such as fluid climbing, jet impact, and air cavity effects in corner areas were analyzed through 3D flow characteristics. By examining two types of impacts (a structure impacting fluid and a fluid impacting structure), the equivalence between them is verified. An in-depth exploration of the load characteristics in different areas is conducted by combining the free surface evolution. The multipeak characteristics of the load and synchronicity of the peak loads at different parts are closely related to the phenomenon of the climbing fluid being obstructed. Bubble flow also plays a crucial role in affecting the load characteristics. Further exploration of the effects of structural motion on load characteristics reveals complex load variability. These findings provide a valuable reference for understanding the impact loads in complex corner areas of liquid tanks.

Study of Direct-link Test of Oblique Detonation Engine

Based on the shock tube wind tunnel driven by detonation, simulating the flight altitude of 30km and the incoming flow conditions of flight Mach number 9, this paper conducts a study of direct-link test of the oblique detonation engine with an oblique wedge angle of 30 degrees. The detonation process and stationing characteristics of the oblique detonation wave are analysed in detail by the engine wall pressure measurement combined with the high-speed camera for simultaneous shooting. During the test, the oblique detonation wave successfully detonates on the oblique wedge and is validly stationed. Under the collision effect of the shock waves system downstream the oblique wedge, the oblique detonation wave successfully detonates, and the oblique detonation wave spreads and develops upstream direction after the detonation, and finally, the oblique detonation wave is successfully stationed. Using shadow-graph method to observe the wave system in the combustion chamber, the typical flow field structure such as non-reactive shock wave, oblique detonation wave, transverse wave and triple point is clearly observed, and the angle of oblique detonation wave in the oblique detonation engine tested in this paper is greater than 80 degrees. The successful detonation and stationarity of oblique detonation wave in direct-link test proves the feasibility of oblique detonation wave to be applied to hypersonic propulsion.

Initiation characteristics of oblique detonation waves from a finite wedge under argon dilution

In this paper, the flow field characteristics of Oblique Detonation Waves (ODWs) induced by a finite wedge under argon dilution are studied by solving the Euler equations with a detailed chemical model of hydrogen and air. First, the effects of the expansion waves, argon concentration, geometric parameters, and Mach number on the ODW are discussed. The results show that the changes of these parameters may make the oblique detonation not be initiated. Then, the ODW initiation criterion of the finite wedge is summarized, as the characteristic length of the induction zone LC and the characteristic length of the oblique wedge LW meet the condition LC/LW < 1, the initiation of the ODW occurs; otherwise, it does not occur. What’s more, the Constant Volume Combustion (CVC) theory is applied to study the characteristic length of induction zone. It is found that CVC theory is more suitable for the “smooth transition” type of ODW flow field, the theoretical and numerical characteristic length in induction regions are in good agreement. This work is of great significance for the design of oblique detonation engines for hypersonic vehicles.

Study of the features of oblique detonation induced by a finite wedge in hydrogen-air mixtures with varying equivalence ratios

This paper provides a numerical investigation of the features of an oblique detonation process induced by a finite wedge in hydrogen-air mixtures with varying equivalence ratios. The reactive N-S equations with a detailed chemical model are solved to simulate the flow field characteristic of ODW (oblique detonation wave). This paper focuses on the effects of the equivalence ratios and expansion waves, including the initiation characteristics, wave structures, density, and temperature distributions on the ODW. Numerical results demonstrate that the mixtures near the stoichiometric condition have a better performance on the initiation of detonation, both the conditions of lean combustion and rich combustion will result in the no-initiation of oblique detonation. The increasing length of the oblique wedge Lw increases the scope of detonation initiation. It means a decrease in the lower initiation limits and an increase in the upper initiation limits of ODW for different equivalence ratios. The effects of expansion wave on ODW are significant in that the decreased Lw increases the characteristic length in the induction zone at the low and high equivalence ratios.

Investigations on oblique detonations induced by a finite wedge in high altitude

In this paper, the characteristics of two-dimensional (2D) oblique detonation waves (ODWs) induced by finite wedges in high altitude are investigated numerically. The reactive Euler equations with a detailed chemical model are solved. This paper focuses on the effects of expansion waves and altitudes on ODW, including the initiation, wave structures, pressure and temperature distributions. Numerical results demonstrate that both the location of turning point from oblique wedge to horizontal wedge and the altitude influence the initiation characteristics of ODW. Then, the initiation criterion of ODW for finite wedges is proposed in this paper. As the characteristic length of induction zone LC (the length from the front point of oblique wedge to the front point of deflagration wave) and the characteristic length of oblique wedge LW satisfy the relationship LC/LW>1, the initiation of ODW occurs. When LC/LW<1, the initiation of ODW doesn't occur. This work would be significant to the designing of oblique detonation engines (ODE) in air-breathing hypersonic vehicle.

Dorsiflexory Wedge First Metatarsal Osteotomy: Does an Oblique Cut Increase Surface Area?

Category:AnkleIntroduction/Purpose:A plantarflexed first metatarsal can contribute to a forefoot driven cavus foot deformity or result in plantar ulcerations from forefoot pressure overload in a neuropathic patient. Often, this deformity is managed via a dorsiflexon first metatarsal base osteotomy. This osteotomy is often described as a vertical wedge, with a dorsal base, in the proximal metatarsal. Alternatively we propose an oblique wedge, which may also allow for increased surface area for osseous healing to occur, in addition to being more theoretically stable to weightbearing with greater fixation options.Methods:Ten cadaveric below-knee specimens were randomized into an oblique wedge (5 specimens) and vertical wedge (5 specimens) groups. The osteotomies were performed by a single surgeon on the same date. Digital calipers were utilized to obtain measurements to calculate surface area for each osteotomy. Demographic data including patient age at death, height, weight, BMI, sex, and laterality were obtained.Results:The mean surface area of the proximal metatarsal for the vertical group was 298.2±76.5 mm2, whereas the oblique group was significantly larger at 538.6 ± 200.4 mm2 (CI 95%, p=0.0255). Similarily, but not to significance the distal side of the osteotomy demonstrated increased surface area for the oblique group with 397.8±191.4 mm2 compared to the vertical group with 265.8±75.3 mm2 (CI 95%, p=0.13. The groups were demographically similar, including height (CI 95%, p=0.62) and BMI (CI 95%, p=0.19).Conclusion:Our results demonstrate significantly greater surface area for the oblique dorsiflexory wedge first metatarsal osteotomy, compared to the vertical dorsiflexory wedge first metatarsal osteotomy. Further analysis is recommended for large cohort head-to-head clinical comparison of these techniques with consideration for cost effectiveness of fixation constructs, procedural complications and patient reported clinical outcome measures.

Analysis of Ventilation Regimes of the Oblique Wedge-Shaped Surface Piercing Hydrofoil During Initial Water Entry Process

Abstract The suction side of a surface piercing hydrofoil, as a section of a Surface Piercing Propeller (SPP), is usually exposed to three phases of flow consisting air, water, and vapour. Hence, ventilation and cavitation pattern of such section during the initial phase of water entry plays an essential role for the propeller’s operational curves. Accordingly, in the current paper a numerical simulation of a simple surface piercing hydrofoil in the form of an oblique wedge is conducted in three-phase environment by using the coupled URANS and VOF equations. The obtained results are validated against water entry experiments and super-cavitation tunnel test data. The resulting pressure curves and free surface profiles of the wedge water entry are presented for different velocity ratios ranging from 0.12 to 0.64. Non-dimensional forces and efficiency relations are defined in order to present the wedge water entry characteristics. Congruent patterns are observed between the performance curves of the propeller and the wedge in different fully ventilated or partially cavitated operation modes. The transition trend from fully ventilated to partially cavitated operation of the surface piercing section of a SPP is studied and analyzed through wedge’s performance during the transitional period.

Force and Strength Analysis of the Reel with Jaw of Torsion-bar Spring

Structure characteristics and working principle of the reel with jaw of torsion-bar spring are introduced. The reel can not only eliminate the leakage risks of hydraulic jaw, but also reduce the investment cost of enterprises and improve the surface quality of the products. The static analysis of mandrel, sector plate and oblique wedge were conducted, and the main data of stress distribution and deformation were obtained, which provide a reliable theoretical basis for the design and optimization of the reel. The research results show that the external support has a great effect on the stress and deformation of the mandrel. With the increase of the weight of steel stress increases, the drum deformation increases, but the analysis of the position of maximum stress, can be obtained to drum stress and deformation is the main reason of excessive bending moment caused by heavy steel rolls. The bending moment and deformation can be reduced significantly at the end of the steel coil, which can effectively improve the service life of the drum.

LATE TRIASSIC OBLIQUE EXTRUSION OF UHP/HP COMPLEXES IN THE ATBASHI ACCRETIONARY COMPLEX OF SOUTH TIANSHAN, KYRGYZSTAN

The exhumation and tectonic emplacement of eclogites and blueschists take place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan.

Oblique wedge extrusion of UHP/HP complexes in the Late Triassic: structural analysis and zircon ages of the Atbashi Complex, South Tianshan, Kyrgyzstan

ABSTRACTThe exhumation and tectonic emplacement of eclogites and blueschists takes place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan. Our field mapping and structural analysis demonstrate that the Atbashi Eclogite–Blueschist Complex is situated in a complicated duplex formed by a northerly dextral transpression system and a southerly sinistral transtension system. The two major shear systems suggest that the Atbashi Complex was extruded obliquely southwestwards during eastward penetration of the southern tip of the Yili–Central Tianshan Arc of the Kazakhstan Orocline during the Late Triassic. Also, we report new zircon U–Pb metamorphic ages of four eclogites and one garnet-bearing quartz-schist from the Atbashi complex of 217–221 Ma and 223.9 Ma, respectively, suggesting that the main extrusion was later than previously proposed and that the final orogenesis was not completed until the Late Triassic. The HP/UHP rocks have an oblique plunge to the NE and extrusion took place southwestwards during escape tectonics along the South Tianshan accretionary wedge in the Late Triassic. Our work shows that the movement of HP/UHP rocks had a 3D style with an arc-parallel structure, and sheds light on earlier 2D models with either forearc- or backarc-directed extrusions, which indicates that more systematic structural and geochronological work is needed to characterize the accretionary tectonics of many orogens around the world. Our data on the timing of extrusion and emplacement of the Atbashi Eclogite–Blueschist Complex also help to resolve the long-standing controversy about the time of terminal orogeny of the Central Asian Orogenic Belt.

The use of sternal wedge osteotomy in pectus surgery: when is it necessary?

The Ravitch procedure is a well-established surgical procedure for correction of chest wall deformities. Sternal wedge osteotomy is an important part of this procedure. We studied the incidence of wedge osteotomy with respect to the type of chest wall deformity in patients undergoing surgical correction with the use of a recently developed chest wall stabilization system. A total of 47 patients, 39 (83%) male and 8 (17%) female with a mean age of 14.9 ± 2.1 years, underwent the Ravitch procedure. Twenty-four (51.1%) had pectus carinatum, 19 (40.4%) had pectus excavatum, and 4 (8.5%) had pectus arcuatum. A conventional or oblique sternal wedge osteotomy was performed as indicated, followed by chest wall stabilization using the MedXpert system. Of the 47 patients, 27 (57.4%) had a sternal wedge osteotomy. All cases of pectus arcuatum and redo cases underwent sternal wedge osteotomy. Pectus excavatum cases tended to have a greater incidence of wedge osteotomy compared to pectus carinatum cases (68.4% vs. 41.7%, p = 0.052). Patients with more resected ribs had a greater rate of wedge osteotomy (63.4%) compared to those with fewer resected ribs (16.7%, p = 0.043). A sternal wedge osteotomy is more commonly performed in patients with pectus excavatum compared to those with pectus carinatum. All redo and pectus arcuatum cases need a wedge osteotomy for proper correction. Wedge osteotomy is very likely in more aggressive corrections with more rib resections.

Computational and experimental studies of rapid free-surface granular flows around obstacles

The study of the rapid free-surface granular flows that are driven under gravitational acceleration has attracted much attention in recent years. This is not only because such flows occur in many industrial and natural examples, but also because their transport mechanisms can be observed through small-scale lab experiments, modeled with continuum theories, and simulated by computers. When granular particles rapidly propagate around obstacles, the resulting phenomena – shock waves, particle free regions or granular vacua, expansion fans and stagnation zones – are of particular theoretical and practical importance. In this paper we develop a computational method for a hydraulic-type avalanche model that is able to simulate such phenomena. It numerically solves the avalanche model over a structured grid by including the topography of the obstacles. Different finite-difference TVD methods based on the non-oscillatory central (NOC) scheme are tested in computation to compare the resolution of the shock waves when granular flows propagate against an oblique wedge. This is also involved in the choice of the limiters, but which are shown rather insensitive in such computations. A level set formulation is coupled into the governing equations to follow the evolution of the boundaries of the granular vacua. It is tested in a situation when granular particles flow around a circular cylinder, where bow shock waves, granular vacua, expansion fans and stationary zones are all captured in the computation. These results agree well and consistently with the laboratory experiments.

The anatomical safe zone for medial opening oblique wedge high tibial osteotomy

The end of medial opening oblique wedge high tibial osteotomy (HTO) points into a narrow area between the articular cartilage of the posterolateral proximal tibia and proximal tibiofibular joint (PTFJ) at the tibial site, which is an anatomical safe zone (ASZ) for osteotomy. We studied the ASZ and its relation to the fibular tip, including the level of posterior cruciate ligament (PCL) insertion, to avoid penetration into the knee and PTFJ, and PCL injury by osteotomy. Ten pairs of embalmed cadaveric legs were disarticulated at the knee joint and then examined. Soft tissues at the proximal tibia were removed. The posterior capsule of the PTFJ was incised to identify the articular cartilage of the PTFJ at the tibial site. The height of the fibular tip and the thickness of the ASZ were measured and calculated to determine the relationship between the ASZ and fibular tip. The level of PCL insertion was measured from the posterior articular surface of the proximal tibia to the distal attachment of the PCL. The average height of the fibular tip and the thickness of the ASZ were 5.43 ± 1.53 mm and 4.12 ± 1.60 mm, respectively. On average, the fibular tip was 1.31 ± 1.28 mm higher than the ASZ, and the level of PCL insertion was 10.10 ± 1.88 mm. To ensure safety during medial opening oblique wedge HTO, the end of osteotomy should point accurately into the ASZ at a level just below the fibular tip as reference. Proximal osteotomy thickness should not be less than 10 mm at the level of PCL insertion.

The effect of convergence angle on the kinematic evolution of strain partitioning in transpressional brittle wedges: Insight from analog modeling and high‐resolution digital image analysis

Using analog modeling aided by digital image analysis (DPIV), we constrained the long‐term kinematic evolution of strain partitioning in transpressional brittle wedges as a function of convergence angle. We ran a series of dry quartz sand experiments representing highly oblique continent‐continent collision (convergence angles of 4° to 30°). The digital image analysis provided high‐resolution constraints on the long‐term kinematic evolution of these wedges, which could be subdivided in distinct kinematic stages, comprising (1) an initial “distributed strain” stage and (2) an “oblique wedge” stage before (3) the stage of strain partitioning is reached. Thus, we document the evolution of different deformation stages from a single plate tectonic boundary condition. In addition, the relationship between convergence angle, kinematic stages, and wedge geometry (including fault dips and fault hierarchy) was established. The modeling results show that smaller convergence angles lead to steeper faults. Besides, for a constant convergence angle, the proshears that evolved during the strain partitioning stage were less steep than those formed during the oblique wedge stage. The fault slip vector on individual fault segments was derived from the DPIV data set for each time increment, quantifying the magnitude and orientation of slip on fault segments during the different kinematic stages. In addition, in the 7.5° and 15° models, rotation of the slip vector by up to 40° was observed on a single proshear during the strain partitioning stage. These observations allow to some degree a validation of existing analytical models of strain partitioning, in particular the assumption of steady state.

The oblique wedge osteotomy of the metacarpal condyle for reconstructing wassel type IV thumb duplication in older children and adults

In reconstructing the Wassel type IV thumb duplication in infants, a deviation deformity of the retained thumb may be corrected by a closing transverse wedge osteotomy of the metacarpal neck. In older children and adults, this technique may cause avascular necrosis of the retained metacarpal condyle. We have addressed this problem by using an oblique wedge osteotomy of the metacarpal condyle. Ten patients (mean age, 18.9 years) underwent this procedure between 1993 and 2007. Patients with deviation angles of 30° or less had a closing wedge osteotomy, while those with deviation angles exceeding 30° had a rotational bone graft osteotomy. Deviation angles were corrected from a mean of 32° (range, 16° to 55°) to 0° in eight thumbs and 10° in two thumbs. There were no cases of avascular necrosis. All patients achieved good results by Tada's criteria. This technique effectively restores bony alignment of the thumb and preserves vascularity of the retained condyle.

Open wedge valgus tibial osteotomies: affecting the distinct ACL bundles

Valgus alignment affects the biomechanical behavior of the ACL, resulting in an increase of the in situ forces in the posterolateral (PL) bundle of the graft. The amount of valgus alignment creating such effects on the force remains unclear. Furthermore, the mechanistic rational for the increase in situ forces on the PL bundle when compared with the AM during the valgus osteotomy remained unclear. We hypothesized that increasing valgisation of the knee results in significantly increased obliquity and a resulting increasing elongation pattern and apparent strain of the PL bundle compared to the AM bundle. Six cadaver legs were used utilizing two commercial navigation systems including navigated high tibial osteotomy (HTO) and ACL measurements simultaneously. ACL footprints were registered for the central and identified AM and PL bundle. A stepwise oblique open wedge osteotomy was performed for 7.5° and 15° valgisation. Length changes and coronal plane obliquity were determined at 0° and 30° flexion. The apparent strain for each fiber was calculated. Valgisation significantly affects the length and obliquity of the PL portion of ACL. Valgisation of 7.5° appears to be a threshold for affecting PL length and obliquity without significant changes compared to 15°. The mean apparent strain for the PL bundle increases up to 14% with a 15° osteotomy in full extension, compared to 4% for the central and 2% for the AM bundle. HTO should be done prior to fixation the ACL graft in combined procedures as valgisation does affect graft length. Relative alignment influence on obliquity and length of the PL bundle should be considered in valgus knees.

Avoidance of Medial Cortical Fracture in High Tibial Osteotomy: Improved Technique

A new technique in oblique incomplete high tibial osteotomy that permits an increase of valgus correction while preventing fracture of the medial cortex was investigated. Closing wedge or opening wedge osteotomy was done on 23 tibias from cadavers before loading in an Instron testing machine. In seven specimens (Group 1), lateral oblique wedge osteotomy was done. In seven other specimens (Group 2), one medial oblique cut was made. In both groups, the osteotomy terminated 10 mm from the cortex and approximately 2 cm below the plateau. In nine specimens (Group 3), the osteotomy terminated in a 5-mm diameter hole, drilled in an anteroposterior direction, with its center positioned 10 mm from the medial cortex and 2 cm below the articular surface. The maximum angle of opening or closing before fracture of the cortex took place was recorded. In Groups 1 and 2, similar maximum correction angles were observed, 6.7 degrees versus 6.5 degrees, respectively. In Group 3, the stress relieving hole allowed the correction angle to be increased to 10 degrees. An oblique high tibial valgus closing wedge osteotomy with an apical drill hole allows a significant increase of the correction angle compared with the same osteotomy without a drill hole. Medial open wedge osteotomy offers no advantage over lateral closed wedge osteotomy in the maximum obtainable correction angle without failure of the cortex.

長管骨変形に対するoblique wedge osteotomyの経験

長管骨変形に対するoblique wedge osteotomyの経験

Inherent stability of proximal first metatarsal osteotomies: A comparative analysis

Proximal first metatarsal osteotomies have been criticized for their instability leading to the dorsal displacement of the first metatarsal head. The purpose of this study was to compare inherent stability of fixated proximal oblique wedge and crescentic first metatarsal osteotomies against simulated vertical ground reactive forces. The authors evaluated four groups of 10 models each with various proximal osteotomy and fixation configurations. Group I was a control group of bone models without osteotomies; group II had oblique closing wedge osteotomies with one 2.7-mm, fully threaded, cortical screw fixation; group III had oblique closing wedge osteotomies with two 2.7-mm, fully threaded, cortical screw fixation; and group IV had proximal crescentic osteotomies with one 4.0-mm, partially threaded, cancellous screw fixation. All 40 bone models were stressed with simulated vertical ground reactive forces. Maximum load to achieve catastrophic failure was higher in the crescentic group (67.7 N, SD 15.1 N, p < or = .005), but the energy required to displace the osteotomy during the stressing sequence was higher in the two-screw oblique closing wedge osteotomy (390.6 N.mm, SD 153.4 N.mm, p < or = .01). The single-screw oblique closing wedge osteotomies showed the least ability to resist simulated vertical ground reactive forces (39.6 N, SD 19.1 N, p < or = .005).

Treatment planning of oblique wedge fields comparing enhanced dynamic wedge and standard 60 degree wedge for parotid type treatments

The “standard” treatment planning for a parotid or similar treatment volume utilizes wedge field technique. This technique can be accomplished by using two beams on the same side of the patient with the heels of the wedges adjacent. This technique can also be accomplished by using standard or enhanced dynamic wedges. Advantages vs. disadvantages of enhanced dynamic wedged fields will be discussed in this paper.