Influence of Cross-Sectional Shape on the Flow in a Highly Bent Research Intake Duct for Jet Engines

2017 ◽  
Author(s):  
Jakob P. Haug ◽  
Rudolf P. M. Rademakers ◽  
Marcel Stößel ◽  
Reinhard Niehuis
Keyword(s):  
Cross Sections ◽  
Test Facility ◽  
Flow Distortion ◽  
Cross Sectional ◽  
Engine Operation ◽  
Fully Integrated ◽  
Safety Margins ◽  
Duct Geometry ◽  
The Cross ◽  
Sectional Shape

In many modern aircraft concepts, civil as well as military ones, the engine is fully integrated into the fuselage. This integration often requires a highly bent intake duct. Due to the high degree of curvature and also the diffusive character of the intake duct, the inflow at the engine’s fan is non-uniform and may feature severe flow distortions. The size, strength, and pattern of these flow distortions may affect the engine’s compressor system and its safety margins. In this paper five highly bent intake duct geometries are analyzed by means of CFD. They evolve from the same baseline geometry but are defined by different crosssectional shapes. With this variation of the cross-sections, the influence of the cross-sectional shape on the aerodynamics of the intake duct is investigated qualitatively. Based on these analyses a sixth intake duct geometry was created as test vehicle for experimental investigation of intake-compressor interaction within the engine test facility. The defining cross-sectional shapes were selected in order to achieve a flow distortion at the duct outlet plane, that is small enough to ensure a safe engine operation, but is still strong enough to provoke interaction of the distorted flow and the compressor flow. The setup for these fully numerical investigations is based on previous studies of the aerodynamics of intake ducts at the Institute of Jet Propulsion. It is shown that the entrance cross-section has a strong influence on the flow throughout the whole intake duct. Additionally, it could be determined that the flow distortion caused by the strong curvature of the intake duct can be reduced in size and strength by a proper combination of cross-sectional shapes.

scholarly journals Twist-to-bend ratio: an important selective factor for many rod-shaped biological structures

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Steve Wolff-Vorbeck ◽  
Max Langer ◽  
Olga Speck ◽  
Thomas Speck ◽  
Patrick Dondl
Keyword(s):  
Cross Sections ◽  
Phase Field ◽  
Material Properties ◽  
Flexural Rigidity ◽  
Torsional Rigidity ◽  
Cross Sectional ◽  
Deep Groove ◽  
Biological Structures ◽  
The Cross ◽  
Sectional Shape

AbstractMechanical optimisation plays a key role in living beings either as an immediate response of individuals or as an evolutionary adaptation of populations to changing environmental conditions. Since biological structures are the result of multifunctional evolutionary constraints, the dimensionless twist-to-bend ratio is particularly meaningful because it provides information about the ratio of flexural rigidity to torsional rigidity determined by both material properties (bending and shear modulus) and morphometric parameters (axial and polar second moment of area). The determination of the mutual contributions of material properties and structural arrangements (geometry) or their ontogenetic alteration to the overall mechanical functionality of biological structures is difficult. Numerical methods in the form of gradient flows of phase field functionals offer a means of addressing this question and of analysing the influence of the cross-sectional shape of the main load-bearing structures on the mechanical functionality. Three phase field simulations were carried out showing good agreement with the cross-sections found in selected plants: (i) U-shaped cross-sections comparable with those of Musa sp. petioles, (ii) star-shaped cross-sections with deep grooves as can be found in the lianoid wood of Condylocarpon guianense stems, and (iii) flat elliptic cross-sections with one deep groove comparable with the cross-sections of the climbing ribbon-shaped stems of Bauhinia guianensis.

Bounds on the Maximum Thermoelastic Stress and Deflection in a Beam and Plate

1966 ◽  
Vol 33 (4) ◽  
pp. 881-887 ◽  
Author(s):  
Bruno A. Boley
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Practical Interest ◽  
Thermoelastic Stress ◽  
Cross Sectional ◽  
Special Cases ◽  
End Conditions ◽  
Instantaneous Temperature ◽  
The Cross ◽  
Sectional Shape

It is shown in this paper that the thermal stress in a beam or plate cannot exceed the value kαEΔT, where ΔT is the maximum instantaneous temperature excursion in a cross section, and k is a coefficient dependent on the shape of the cross section. A simple general formula for k is found, and results for several special cases of practical interest are given. For rectangular beams (suitably oriented) and for plates, for example, k = 4/3. For any section, k = 1 if the thermal moment is zero; simplifications also occur if the thermal force is zero. The corresponding results for beam deflections are also carried out: The maximum deflection cannot exceed the value kδ kδ′αLΔT, where kδ and kδ′ are coefficients depending respectively on the cross-sectional shape and on the end conditions. For example, for rectangular cross sections, kδ = 3/4; and for a simply supported beam, kδ′ = 1/8.

Design of C-Frames Using Real-Coded Genetic Optimization Algorithms and NURBS

1999 ◽  
Author(s):  
Ashraf O. Nassef ◽  
Hesham A. Hegazi ◽  
Sayed M. Metwalli
Keyword(s):  
Genetic Algorithms ◽  
Cross Section ◽  
Cross Sections ◽  
Design Parameters ◽  
Binary Representation ◽  
Cross Sectional ◽  
Search Spaces ◽  
The Cross ◽  
Sectional Shape ◽  
Real Coded Genetic Algorithms

Abstract C-frames constitute a large portion of machine tools that are currently used in industry. Examples of these frames include drilling machines, presses, punching and stamping machines, clamps, hooks, etc. The design parameters of these frames include the dimensions of their cross-sections, which should be chosen to withstand the applied loads and minimize the element’s overall weight. Traditionally, the cross-section of C-frame belonged to a set of primitive shapes, which included I, T, trapezoidal and rectangular sections. This paper introduces a new methodology for designing the frame’s cross-section. The cross-sectional shape is represented using non-uniform rational B-Spline (NURBS) in order to give it a form of shape flexibility. A special form of genetic algorithms known as real-coded genetic algorithms is used to conduct the search for the design objectives. Real-coded genetic algorithms are known to outperform the simple binary representation genetic algorithms when dealing with continuous search spaces. The results showed that the optimal shape was a semi I/T-section with the material bulk related to the applied load.

Numerical Flow Field Analysis in a Highly Bent Intake Duct

2018 ◽  
Author(s):  
Jakob P. Haug ◽  
Rudolf P. M. Rademakers ◽  
Marcel Stößel ◽  
Reinhard Niehuis
Keyword(s):  
Flow Field ◽  
Cross Sections ◽  
Flow Separation ◽  
Direct Interaction ◽  
Field Analysis ◽  
Test Facility ◽  
Interface Plane ◽  
Flow Distortion ◽  
Safety Margins ◽  
Flow Features

In many modern aircraft concepts, civil as well as military ones, the engine is fully integrated into the fuselage. This integration often requires a highly bent intake duct. Due to the high degree of curvature and also the diffusive character of the intake duct, the inflow at the engine’s fan is non-uniform and may feature severe flow distortions. The size, strength, and pattern of these flow distortions may affect the engine’s compressor system and its safety margins. In this paper the flow through a short highly bent intake duct geometry is analysed by means of CFD. The numerical simulations are validated against experimental data, which are obtained in extensive investigations at the institute’s engine test facility. The setup for the numerical investigations is based on previous studies of the aerodynamics of intake ducts at the Institute of Jet Propulsion, where it is shown that the shape of the entrance cross-section of the intake duct has a strong influence on the flow field throughout the entire intake duct. In this paper the flow throughout the duct is analysed in order to gain information on the flow features which cause the flow distortion at the aerodynamic interface plane (AIP) and how these flow features interact. Two main flow distortion patterns exist at the AIP, one of them is a system of two twin vortices, one on each side in the lower part of the AIP. These are caused by the particular shapes of the cross-sections in the front part of the duct. The dominating flow distortion in the AIP is caused by a large flow separation in the rear part of the duct, which resides in the upper half of the AIP and results in a large total pressure loss and axial velocity deficit, combined with a twin swirl. Although no direct interaction between these two flow patterns is present, it was found that the small vortices in the lower part are influenced by the flow separation at the upper wall in the rear section of the intake duct.

scholarly journals Cross-Sectional Performance of Hollow Square Prisms with Rounded Edges

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 996
Author(s):  
Hiroyuki Shima ◽  
Nao Furukawa ◽  
Yuhei Kameyama ◽  
Akio Inoue ◽  
Motohiro Sato
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Cross Sections ◽  
Cross Sectional ◽  
Hollow Section ◽  
Buckling Resistance ◽  
The Cross ◽  
The Stability ◽  
External Forces ◽  
Sectional Shape

Hollow-section columns are one of the mechanically superior structures with high buckling resistance and high bending stiffness. The mechanical properties of the column are strongly influenced by the cross-sectional shape. Therefore, when evaluating the stability of a column against external forces, it is necessary to reproduce the cross-sectional shape accurately. In this study, we propose a mathematical method to describe a polygonal section with rounded edges and vertices. This mathematical model would be quite useful for analyzing the mechanical properties of plants and designing plant-mimicking functional structures, since the cross-sections of the actual plant culms and stems often show rounded polygons.

Effects of Velocity and Current on Temperature Distribution Within Crossflow (Blown) Electric Arcs

1970 ◽  
Vol 92 (2) ◽  
pp. 276-284 ◽  
Author(s):  
D. M. Benenson ◽  
A. A. Cenkner
Keyword(s):  
Temperature Distribution ◽  
Forced Convection ◽  
Cross Sections ◽  
Constant Velocity ◽  
Constant Current ◽  
Cross Sectional ◽  
Profound Influence ◽  
Arc Current ◽  
The Cross ◽  
Sectional Shape

The effects of both velocity and current upon the temperature distribution within, and the cross-sectional shape of, steady-state 1.1 atm argon crossflow arcs have been determined experimentally. The tests were conducted over one range at constant current (I = 60.3 amp), U = 0, 41.8 ≤ Ucm/sec ≤ 127.0 and another range at constant velocity (U = 41.8 cm/sec), 42.5 ≤ Iamp ≤ 80.8. Forced convection (at constant arc current) exerts a profound influence upon the crossflow arc. At higher velocities, forced convection appears to completely penetrate the plasma. The effect of increasing current (at constant velocity) is to shield a central core region from the flow field. As a result of the effects of velocity, electrode design, interactions of the electrode jets, and slight misalignment of the jets, neither the isotherms nor the cross sections can be considered to be generally circular, even at the higher currents.

On the cross-sectional shape of the cellulose crystallites in the tunicate Halocynthia papillosa

1990 ◽  
Vol 48 (3) ◽  
pp. 566-567
Author(s):  
J.-F. Revol ◽  
Y. Van Daele ◽  
F. Gaill
Keyword(s):  
Contrast Imaging ◽  
Animal Kingdom ◽  
Bright Field ◽  
Field Mode ◽  
Cross Sectional ◽  
Ultrathin Sections ◽  
The Cross ◽  
Sectional Shape ◽  
Valonia Ventricosa ◽  
C Nmr

The only form of cellulose which could unequivocally be ascribed to the animal kingdom is the tunicin that occurs in the tests of the tunicates. Recently, high-resolution solid-state l3C NMR revealed that tunicin belongs to the Iβ form of cellulose as opposed to the Iα form found in Valonia and bacterial celluloses. The high perfection of the tunicin crystallites led us to study its crosssectional shape and to compare it with the shape of those in Valonia ventricosa (V.v.), the goal being to relate the cross-section of cellulose crystallites with the two allomorphs Iα and Iβ.In the present work the source of tunicin was the test of the ascidian Halocvnthia papillosa (H.p.). Diffraction contrast imaging in the bright field mode was applied on ultrathin sections of the V.v. cell wall and H.p. test with cellulose crystallites perpendicular to the plane of the sections. The electron microscope, a Philips 400T, was operated at 120 kV in a low intensity beam condition.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Comparison of the Cross Sectional Area, the Loss in Volume and the Mechanical Properties of LAE442 and MgCa0.8 as Resorbable Magnesium Alloy Implants after 12 Months Implantation Duration

2010 ◽  
Vol 638-642 ◽  
pp. 675-680 ◽  
Author(s):  
Martina Thomann ◽  
Nina von der Höh ◽  
Dirk Bormann ◽  
Dina Rittershaus ◽  
C. Krause ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Degradation Process ◽  
Cross Sectional Area ◽  
Bending Test ◽  
Sectional Area ◽  
Cross Sectional ◽  
Initial Strength ◽  
Three Point Bending ◽  
The Cross

Current research focuses on magnesium based alloys in the course of searching a resorbable osteosynthetic material which provides sufficient mechanical properties besides a good biocompatibility. Previous studies reported on a favorable biocompatibility of the alloys LAE442 and MgCa0.8. The present study compared the degradation process of cylindrical LAE442 and MgCa0.8 implants after 12 months implantation duration. Therefore, 10 extruded implants (2.5 x 25 mm, cross sectional area 4.9 mm²) of both alloys were implanted into the medullary cavity of both tibiae of rabbits for 12 months. After euthanization, the right bone-implant-compound was scanned in a µ-computed tomograph (µCT80, ScancoMedical) and nine uniformly distributed cross-sections of each implant were used to determine the residual implants´ cross sectional area (Software AxioVisionRelease 4.5, Zeiss). Left implants were taken out of the bone carefully. After weighing, a three-point bending test was carried out. LAE442 implants degraded obviously slower and more homogeneously than MgCa0.8. The mean residual cross sectional area of LAE442 implants was 4.7 ± 0.07 mm². MgCa0.8 showed an area of only 2.18 ± 1.03 mm². In contrast, the loss in volume of LAE442 pins was more obvious. They lost 64 % of their initial weight. The volume of MgCa0.8 reduced clearly to 54.4 % which corresponds to the cross sectional area results. Three point bending tests revealed that LAE442 showed a loss in strength of 71.2 % while MgCa0.8 lost 85.6 % of its initial strength. All results indicated that LAE442 implants degraded slowly, probably due to the formation of a very obvious degradation layer. Degradation of MgCa0.8 implants was far advanced.

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