Analysis of Melting Heat Transport in a Cross Flow Direction: A Comparative Study

Abstract The scope of this paper is to provide a method implemented in an application for assessment of dynamic response of free spanning pipelines subjected to combined wave and current loading. The premises for the paper are based on application development within pipeline free span evaluation in a software development project. A brief introduction is provided to the basic hydrodynamic phenomena, principles and parameters for dynamic response of pipeline free spans. The choice of method for static and dynamic span modelling has an influence on calculated modal frequencies and associated stresses. Due to the importance of frequencies and stresses for fatigue and environmental loading calculations, the choice of analysis approach influences the partial safety factor format. The aim of the structural analysis is to provide the necessary input to the calculations of VIV and force model response, and to provide realistic estimations of static loading from functional loads. Environmental flow conditions are implemented in the application, such as steady flow due to current, oscillatory flow due to waves and combined flow due to current and waves. Combined wave and current loading include the long-term current velocity distribution, short-term and long-term description of wave-induced flow velocity amplitude and period of oscillating flow at the pipe level and return period values. Inline and cross-flow vibrations are considered in separate response models. For pipelines and risers, modes are categorized in in-line or cross-flow direction. A force model is also considered for the short-term fatigue damage due to combined current and direct wave actions. Design criteria can be specified for ultimate limit state (ULS) and fatigue limit state (FLS) due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.

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Some Remarks on the Behaviour of Surface Source Distributions near the Edge of a Body

Aeronautical Quarterly ◽

10.1017/s0001925900006387 ◽

1973 ◽

Vol 24 (1) ◽

pp. 25-33

Author(s):

J W Craggs ◽

K W Mangler ◽

M Zamir

Keyword(s):

Flow Direction ◽

Three Dimensional ◽

Cross Flow ◽

Symmetric Case ◽

The Body ◽

Dimensional Problem ◽

Surface Source ◽

Asymmetric Case ◽

Main Flow Direction ◽

Flow Plane

SummaryWhen the incompressible potential flow past a three-dimensional body is represented by source distributions on the body surface, these source distributions have singularities near an edge or corner, for example á trailing edge of a wing or the (unfaired) intersection of a body and a wing. The nature of these singularities is discussed. When assuming slow variations of the geometry in the main flow direction we can consider a two-dimensional problem in the cross-flow plane. Here the tangential velocities and source distributions are proportional to certain powers of the distance from the corner. For example at a convex right-angled corner these powers are − ⅓ in the asymmetric case (the bisector is a potential line) and ⅓ in the symmetric case (the bisector is a streamline) for both sources and tangential velocities. At a concave right-angled corner the corresponding values for the source distributions are ⅓ (asymmetric case) and − ⅓ (symmetric case) whereas they are 1 and 3 respectively for the tangential velocities.

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Investigation of In-Flow Fluidelastic Instability of Square Tube Arrays Subjected to Air Cross Flow

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2015-45091 ◽

2015 ◽

Cited By ~ 1

Author(s):

Tomomichi Nakamura ◽

Shinichiro Hagiwara ◽

Joji Yamada ◽

Kenji Usuki

Keyword(s):

Nuclear Power ◽

Flow Instability ◽

Flow Direction ◽

Cross Flow ◽

Diameter Ratio ◽

Nuclear Industry ◽

Flexible Cylinder ◽

Triangular Arrays ◽

Tube Arrays ◽

Fluidelastic Instability

In-flow instability of tube arrays is a recent major issue in heat exchanger design since the event at a nuclear power plant in California [1]. In our previous tests [2], the effect of the pitch-to-diameter ratio on fluidelastic instability in triangular arrays is reported. This is one of the present major issues in the nuclear industry. However, tube arrays in some heat exchangers are arranged as a square array configuration. Then, it is important to study the in-flow instability on the case of square arrays. The in-flow fluidelastic instability of square arrays is investigated in this report. It was easy to observe the in-flow instability of triangular arrays, but not for square arrays. The pitch-to-diameter ratio, P/D, is changed from 1.2 to 1.5. In-flow fluidelastic instability was not observed in the in-flow direction. Contrarily, the transverse instability is observed in all cases including the case of a single flexible cylinder. The test results are finally reported including the comparison with the triangular arrays.

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Estimation of Hydrodynamic Coefficients for VIV of Slender Beam at High Mode Orders

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 6 ◽

10.1115/omae2010-20327 ◽

2010 ◽

Cited By ~ 3

Author(s):

Jie Wu ◽

Carl M. Larsen ◽

Halvor Lie

Keyword(s):

Modal Analysis ◽

Traveling Waves ◽

Flow Direction ◽

Research Effort ◽

Cross Flow ◽

Bending Moment ◽

Hydrodynamic Forces ◽

High Mode ◽

Excitation Region ◽

Inverse Force

The Hano̸ytangen test program was caried out by MARINTEK for Norsk Hydro in 1997. One purpose of this research effort was to investigate VIV response of deep sea risers subjected to sheared current. A densely instrumented 90 meter long riser model was tested in shear current, and bending strains along the riser was measured. Oscillatory part of both in-line (IL) and cross-flow (CF) displacements can be obtained by applying modal analysis on the bending moment measurements. The primary results from the analysis are that the riser is vibrating at high modes in cross-flow direction (10th–30th mode). The response is dominated standing waves for the lowest speed cases and gradually is influenced by traveling waves for increasing speed. For highest speed cases, it is dominated by traveling waves. The vibration amplitude is significantly smaller than for a rigid cylinder under equivalent conditions. Inverse force analysis estimates hydrodynamic forces from measured response of a slender beam. The method has previously been applied to rotating rig test data. The response was for these cases dominated by relatively low mode orders and standing wave responses. To understand the stochastic behaviour of high mode VIV response, the method is applied to Hano̸ytangen test in the present study to provide valuable insights by estimating CF hydrodynamic forces and coefficients from displacement time series found from modal analysis of measured strains. The results from this work are presented in terms of CF hydrodynamic force coefficients, excitation region and their variations in time and space. New excitation database is extracted based on the analysis results. They are used in VIVANA to predict the displacement and stress against experiment results.

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VIV Response and Drag Measurements of Circular Cylinders Fitted With Permeable Meshes

Volume 2: CFD and VIV ◽

10.1115/omae2015-42278 ◽

2015 ◽

Cited By ~ 1

Author(s):

Murilo M. Cicolin ◽

Gustavo R. S. Assi

Keyword(s):

Reynolds Number ◽

Long Range ◽

Flow Direction ◽

Cross Flow ◽

Circular Cylinders ◽

Peak Response ◽

Vortex Induced Vibrations ◽

Different Types ◽

Cylindrical Tubes ◽

Low Mass

Experiments have been carried out on models of rigid circular cylinders fitted with three different types of permeable meshes to investigate their effectiveness in the suppression of vortex-induced vibrations (VIV). Measurements of amplitude of vibration and drag force are presented for models with low mass and damping which are free to respond in the cross-flow direction. Results for two meshes made of ropes and cylindrical tubes are compared with the VIV response of a bare cylinder and that of a known suppressor called the “ventilated trousers” (VT). All three meshes achieved an average 50% reduction of the peak response when compared with that of the bare cylinder. The sparse mesh configuration presented a similar behaviour to the VT, while the dense mesh produced considerable VIV response for an indefinitely long range of reduced velocity. All the three meshes have increased drag when compared with that of the bare cylinder. Reynolds number ranged from 5,000 to 25,000 and reduced velocity was varied between 2 and 15.

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Performance characteristics of a chilled water spirally coiled finned tube in cross flow for air conditioning applications

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406212447480 ◽

2012 ◽

Vol 227 (2) ◽

pp. 320-331 ◽

Cited By ~ 3

Author(s):

Abdalla Gomaa ◽

Wael IA Aly ◽

Ashraf Mimi Elsaid ◽

Eldesuki I Eid

Keyword(s):

Reynolds Number ◽

Nusselt Number ◽

Friction Factor ◽

Flow Direction ◽

Cross Flow ◽

Finned Tube ◽

Performance Characteristics ◽

Curvature Ratio ◽

Coiled Tube ◽

Chilled Water

In the present study, the thermo-fluid characteristics of a spirally coiled finned tube in cross flow were experimentally investigated. This investigation covered different design parameters such as curvature ratio, air velocity, flow direction, fin pitch and flow rate of chilled water on performance characteristics of the spirally coiled finned tube. The purpose was to evaluate this kind of the spirally finned-tube cooling coils with particular reference to bare coiled tube. Six test specimens were designed and manufactured with curvature ratios of 0.027, 0.03, 0.04, tube pitches of 18, 20, 30 mm and fin pitches of (33, 22, 11 mm). Experiments were carried out in a pilot wind tunnel with air Reynolds number ranging from 35,500 to 245,000. Two types of chilled water flow directions entering the spiral coil were tested at Reynolds number ranging from 5700 to 25,300, the first was inward flow direction and the other was to outward flow direction. The results revealed that the inward flow direction has significant enhancement effect on the Nusselt number compared with outward flow direction by 37.0% for tube pitch of 18 mm and curvature ratio of 0.027. The decrease of fin pitch enhances the Nusselt number by 21.92% on expense of friction factor by 10.9%. In the case of spirally coiled bare tube, the decreasing of the curvature ratio increases air side Nusselt number by 33.69% on expense of friction factor by 18.36%. General correlations of Nusselt number and air friction factor for bare and finned spirally coiled tube were correlated based on reported experimental data.

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The Importance of Mode Number on In-Line Amplitude of Vortex-Induced Vibration of Flexible Cylinders

Volume 5: Materials Technology; CFD and VIV ◽

10.1115/omae2008-57531 ◽

2008 ◽

Author(s):

Susan B. Swithenbank ◽

Carl Martin Larsen

Keyword(s):

Natural Frequencies ◽

Flow Direction ◽

Empirical Relationship ◽

Cross Flow ◽

Bending Stiffness ◽

Mode Number ◽

Flow Mode ◽

Physical Parameters ◽

Complex Data ◽

The Cross

Most empirical codes for prediction of vortex-induced vibrations (VIV) has so far been limited to cross-flow response. The reason for this is that cross-flow amplitudes are normally larger that in-line amplitudes. Additionally the in-line response is considered to be driven by the cross-flow vibrations. However since the in-line frequency is twice the cross-flow frequency, fatigue damage from in-line vibrations may become as important and even exceed the damage from cross-flow vibrations. A way to predict in-line vibrations is to apply traditional methods that are used for cross-flow VIV and establish an empirical relationship between the cross-flow and in-line response. Previous work suggests that the ratio between the in-line and cross-flow amplitudes depends on the cross-flow mode number, Baarhom et al. (2004), but the empirical basis for this hypothesis is not strong. The motivation for the present work has been to verify or modify this hypothesis by extensive analysis of observed response. The present analysis uses complex data from experiments with wide variations in the physical parameters of the system, including length-to-diameter ratios from 82 to 4236, tension dominated natural frequencies and bending stiffness dominated natural frequencies, sub-critical and critical Reynolds numbers, different damping coefficients, uniform and sheared flows, standing wave and traveling wave vibrations, mode numbers from 1–25th, and different mass ratios. The conclusion from this work is that the cross-flow mode number is not the important parameter, but whether the frequency of vibration in the cross-flow direction is dominated by bending stiffness of tension.

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