Ring Ribs Research Articles

Influence of Geometrical Parameters on Heat Transfer of Transversely Corrugated Helically Coiled Tube for Deicing Fluid

In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

Research on the influence of ring rib arrangement on vibration and acoustic radiation of cylindrical shell

Based on the thin shell theory and the three-dimensional Sono-elasticity theory, the finite element method is used to study the transmission and variation characteristics of the cylindrical shell, in the case of non-ribs, single ring ribs and multi-ring ribs. The influence of different ribbed forms on the acoustic radiation is also analyzed. The result shows that the ring rib structure can suppress the transmission of medium and high frequency vibration, and the maximum attenuation frequency of the cylindrical shell is changed. The maximum attenuation frequency increases as the number of ring ribs increases. The vibration attenuation of the structure under multi-ribbed is higher than the single-ribbed at the middle frequency band, but lower than the single-ribbed at the high frequency band. The multi- ribbed structure can reduce the low-frequency radiated acoustic power of the structure, but it will affect the high-frequency acoustic radiation characteristics of the structure.

Analysis of the Stresses of the Wall of a Steel Water Tower

We consider the calculation of the wall of a water tower in the form of a welded sheet structure, structurally consisting of a cylindrical vessel with a conical bottom and a roof and a cylindrical support. The creation of the finite element calculation model and determination of the stresses in the tower elements taking into account various features of design, installation and operation of the structure are performed. The questions of local stability of the wall in the joints of cylindrical and conical parts are considered. The necessity of arranging ribs in the conical part along the meridional directions and in the junction points - ring ribs is substantiated.

Free Oscillations of a Composite Structurally Orthotropic Cylindrical Shell Stiffened by Discretely Positioned Ring Ribs

A method for calculating the natural oscillations of a cylindrical shell of an orthotropic material is proposed. The shell is stiffened by a set of sufficiently densely positioned transverse-longitudinal ribs, the arrangement of which allows “smearing” and contains sparsely positioned discrete stiffening rings. The shell may have a closed or open cross section; it is considered to be loaded by external pressure and axial forces. The problem is reduced to a set of homogeneous algebraic equations the number of which is equal to twice the number of discrete ribs; the equation was obtained in explicit form. The comparison of the calculated and experimental data is provided.

Modeling method on acoustic scattering from penetrable objects using a hybrid Kirchhoff/ray approach

A method is put forward to investigate the acoustic scattering from double-sided water loaded targets which is penetrable even in high frequency. The present approach is an extension of the TriKirch method which was elaborated for non-penetrable targets [J. Acoust. Soc. Am. 140(3), 1878-1886 (2016)] and complex targets are dispersed into many triangular planar facets. Reflection coefficient of plane facet is introduced to calculate the scattering amplitude of each non-rigid triangular facets combined with TirKirch method, and the total scattering amplitude of target is obtained by superposing the amplitude of all facets’ contributions coherently. Double bounce (DB) contributions to the scattering is calculating by ray-tracing method. Computations are made for a double-sided water loaded finite cylindrical shell with perforated ring ribs, and are compared with the experimental results，and both results show good agreement.

Analysis of the influence of stiffness reduction on the load carrying capacity of ring-stiffened cylindrical shell

Load carrying capacity is of importance in the evaluation of the stability of submarine pressure shell structure. During the buckling process of cylindrical shell under hydrostatic pressure, the total potential energy of ring-stiffened cylindrical shell can be divided into constant component, linear component and square nonlinear component. Based on the derivations of buckling loads of smooth cylindrical shell and ring-stiffened cylindrical shell, the reduced stiffness method (RSM) is applied to assess the role of different stiffness reductions in the evaluation of stable load carrying capacity of cylindrical shell. This study shows: (1) the circumferential membrane stiffness is influence the stability of cylindrical shell largest; (2) the ring ribs have a significant effect on the overall stability of ring-stiffened cylindrical shells under hydrostatic pressure; (3) the circumferential buckling wave number of ring-stiffened cylindrical shell may not depend on the membrane stiffness reduction of shell, but it increases with the bending stiffness reduction of ring ribs.

Dynamics of a Discretely Reinforced Cylindrical Shell Under a Local Impulsive Load

A procedure and software for studying the dynamics of a reinforced cylindrical shell on an elastic foundation are developed. The shell is under local loads distributed over small areas and varying linearly during a short time. The stringers are described by a structurally orthotropic model and the ring ribs by a discrete model. The candidate solution is expanded into series of natural modes. The influence of a local load on the deformation parameters of the shell is studied using a test example. Conclusions on the effect of the pulse shape, the time of action of the external forces, and the reinforcement on the strain state of the shell are drawn

Design and Test Rig Experiments of a High Speed Tapered Roller Bearing for Main Spindle Applications

A new design of tapered roller bearings (TRB) for main spindles for high-performance cutting (HPC) or heavy roughing applications is presented. The bearing's key features to increase the speed rating are an outer ring rib, additional means of lubrication and ceramic rollers. First results of test rig experiments show that its speed rating is considerably higher than that of standard TRBs while calculations indicate that its stiffness and load rating are superior to conventional spindle bearings (SPB). Measured runout values of the new TRB and a reference SPB indicate that regarding accuracy the new TRB concept can be applicable for main spindles.

The Backing Design in the Free Damping Cylindrical Shell Damping Test

The ANSYS harmonic response results are post-processed with the energy method to obtain the damping loss factor (DLF) of different types of free damping structures. Firstly, the DLF of free damping cylindrical shell in air is compared with DLF of free damping plate in air. Secondly, the DLF of free damping cylindrical shell with stiffened ribs in air is compared with that without stiffened ribs in air. Thirdly, the DLF of free damping cylindrical shell in water is compared with the DLF of free damping plate in water. Fourthly, the DLF of free damping cylindrical shell with stiffened ribs in water is compared with that without stiffened ribs in water. In the end, based on the above analysis, the backing design problem in air and water are discussed. Studies have shown that: DLF of free damping cylindrical shell is close to that of free damping plate in air; DLF of free damping cylindrical shell with stiffened ring ribs is close to that without stiffened ring ribs in air; When testing free damping cylindrical shells DLF in air, plate with the same thickness can be used as the backing; DLF of free damping plate is close to that of free damping cylindrical shell in water; DLF of free damping cylindrical shell with stiffened ring ribs is close to that without stiffened ring ribs in water; When testing free damping cylindrical shells DLF in water, plate with the same thickness can be used as the backing.

Vibro-Acoustics Characteristics of Non-Uniform Ring Stiffened Cylindrical Shells Using Wave Propagation Approach

Based on Donnell’s thin shell theory and basic equations, the wave propagation method is discussed here in detail, which is used to investigate the vibration and sound radiation characteristics of non-uniform ring stiffened cylindrical shells under various boundary conditions. The structure damp effects of cylindrical shells are investigated and the ring ribs were considered very narrow, and the rib forces are considered in radial direction. The conclusion are drawn that with the structural loss factor changing large, the whole pressure level are changed little, but the peak of resonance are slacking down obviously; The shell’s resonance frequency can be changed with irregular ring stiffened cylindrical shell .The work will give some guidelines for noise reduction of this kind of shell.

Coupling Analysis for a Submerged Ring-Stiffened Cylindrical Shell Treated with Active Constrained Layer Damping

Based on the previous study, the coupling analysis for a submerged active constrained layer damping (i.e. ACLD) cylindrical shell with ring ribs is developed in this paper. Firstly, the governing equation for this kind of shell is proposed. Then, a multi-virtual-point-sound-source wave function superposition method combing the transfer matrix method is proposed to obtain the acoustic pressure level. Later, numerical results are given to verify the developed method. Finally, the damping effect for the ACLD treatment on the ring-stiffened cylindrical shell is discussed.

An Equivalent Method to Evaluate the Vibration Control Effect due to Blocking Mass Added to Complicated Structures

The vibration control effect due to blocking mass on vibration transmission of single force excited structure is analyzed by adopting mechanical impedance method. Take the ring ribs cylindrical shell as research object, and simplify it as a mass-spring-damping system. The mechanical impedance of the whole structure is calculated by general commercial software MSC/NASTRAN, and then the vibration control effective and ineffective frequency band of any given mass was discussed. By comparing the vibration control effect calculated by general commercial software (finite element method) and mechanical impedance method, it is proved that mechanical impedance method is effective in analyzing the vibration control effect due to blocking mass.

Stability and vibrations of cylindrical shells discretely reinforced with rings

The linearized system of homogeneous equations of motion of cylindrical shells discretely reinforced with quasiregular sets of ring ribs is solved. Approximate formulas for the critical stresses and natural frequencies are presented

Natural Vibrations of a Cylindrical Shell Reinforced with Two-Layer Rings

The vibrations of a cylindrical shell reinforced with ring ribs attached to the shell by means of elastic elements are studied. The problem is solved by the finite-element method. The shell and ribs are modelled by a plane four-node finite element, which is a combination of a four-node plane stress element and a four-node flexural element. The effect of the stiffness of the elastic elements on the natural frequencies and modes is examined

AN IMPROVEMENT OF THE TECHNOLOGY OF CONTINUOUS MOLDING OF CERAMIC INSULATORS WITH SPIRAL RIBS

New technical solutions in the technology of molding rod insulators with spiral ribs extruded from a vacuum press are considered. Positive results are obtained in a comparative trial of the insulators with spiral and ring ribs.

Vortex dynamics, transition to turbulence, and aeroacoustics in rectangular free jets

An overview of recent studies of compressible, rectangular, free jets is presented, with special focus on understanding the dynamics and topology of coherent vortical structures controlling the jet development, and identifying major near-jet noise generation mechanisms. Relevant issues of subgrid and supergrid modeling in free-jet numerical simulations are addressed in this context. The vortex dynamics underlying axis-switching and vortex bifurcation phenomena are examined, including: the roles of self-induced vortex-ring deformation, reconnection, braid vortices, aspect ratio (AR), and the transition to turbulence from laminar initial jet conditions. Qualitatively different vorticity geometries characterizing the near field of low-AR, M<2, ideally expanded, rectangular jets are demonstrated, involving: (i) self-deforming and (ii) bifurcating vortex rings; interacting ring and rib (braid) vortices—including, (iii) single ribs aligned with corner regions (AR>1), and (iv) rib pairs aligned with the corners (AR=1); (v) smaller-scale, elongated, ‘‘worm’’ vortices in the turbulent jet regime. The near-field entrainment of low-AR rectangular jets is shown to be largely determined by the characteristic geometry of the ring–rib interactions; progress in the study of noise-generation mechanisms in low-AR jets is discussed. [Work sponsored by AFOSR, ONR, and the DoD HPC-MP.]

Stability of an orthotropic cylindrical shell reinforced by ring ribs with allowance for transverse shear

A detailed discussion is given on the stability of a freely supported orthotropic cylindrical shell reinforced by similar ring ribs (frames) placed at equal distances under the action of a uniform external pressure. The shear is taken into account both in the shell itself and in the frames. The solution obtained is illustrated by examples.

The dynamic behaviour of cylindrical shells reinforced by ring ribs—II. Shells of finite length

A circular cylindrical shell reinforced by ribs of limited rigidity and equidistant from each other, clamped by the edges, is under the action of an impulsive load. The basic assumptions are identical to those of part I [1].When the ribs are placed rather frequently the solution to the problem is obtained from those obtained in part I [1] by a change of notation, so we consider below that the ribs are placed “sparsely”. The cases of “small”, “medium” and “large” loads are investigated; the differential equations of motion are listed in a form suitable for numerical integration by an electronic computer for every case. As the distance of the spans from the shell's edges varies the dynamical behaviour of the spans is generally different. It is shown by numerical calculation of some concrete examples that cetera paribus with sufficient accuracy we may consider the dynamic behaviour of all spans, except extreme ones, identical to that of an infinitely long shell, and the extreme spans moment can be analysed by means of the example of a shell clamped by the edges with one ring in the middle. For the values of the parameter μ satisfying μ ≥ μ1 ≤ √6 this is confirmed analytically.

Dynamic behaviour of cylindrical shells strengthened with ring ribs—Part I. Infinitely long shell

The paper considers the dynamic behaviour of infinitely long cylindrical shells made of ideally rigid-plastic material and strengthened with ring ribs of limited rigidity. The principal assumptions are identical with those made in the work [1] where shells with absolutely rigid rings were considered. Distribution of moments and displacements is determined. The values of residual displacements are found as well as of motion stopping times for various loads and parameters of the shell and its strengthening ribs. The maximal residual displacement accumulated in the shell for the entire period of motion under the conditions of “local” collapse is shown to be practically independent of the ring rigidity and to coincide rather accurately with the maximal residual displacement of the shell having absolutely rigid ribs. It is shown that all the results obtained can be applied, after suitable redefinitions, to the case of shells strengthened in the span between the supporting rings, by longitudinal and ring-like ribs of “small” rigidity. The results obtained are also valid for cylindrical shells of finite length with moving supports.