Numerical Assessment of Similitude Parameters and Dimensional Analysis for Water Entry Problems

The prediction of impulsive loads deriving from the sudden impact of a solid body on the water surface is of fundamental importance for a wide range of engineering applications. The study of hull-slamming phenomena largely relies on laboratory scale experimental investigations and on simplified analytical models. The aim of this paper is to quantitatively assess the interplay between the relevant nondimensional parameters for the water entry of a two-dimensional body, evidencing the similitude conditions that allow the transition from scaled experiments to real size applications. This assessment is performed through the numerical study of the hydrodynamics induced by the water impact of a two-dimensional wedge. The fluid flow is considered incompressible. First of all numerical simulations are validated by comparison with experimental data from the literature and with the Wagner seminal theory. Afterwards, a thorough computational study is performed by systematically varying all the relevant parameters, such as the nondimensional entry velocity and acceleration. We conclude by evidencing some design prescriptions that should be adopted in order to facilitate the transition of laboratory scale experiments to real scale applications.

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A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽

10.3390/s21134459 ◽

2021 ◽

Vol 21 (13) ◽

pp. 4459

Author(s):

José R. González ◽

Charbel Damião ◽

Maira Moran ◽

Cristina A. Pantaleão ◽

Rubens A. Cruz ◽

...

Keyword(s):

Heat Transfer ◽

Thyroid Nodules ◽

Numerical Study ◽

Computational Study ◽

Internal Heat ◽

Heat Transfer Process ◽

The Body ◽

Physical Parameters ◽

Infrared Sensors ◽

Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

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Free Fall Water Entry of a Two-Dimensional Asymmetric Wedge in Oblique Slamming: A Numerical Study

Volume 8: CFD and FSI ◽

10.1115/omae2020-18645 ◽

2020 ◽

Author(s):

Saeed Hosseinzadeh ◽

Mohammad Izadi ◽

Kristjan Tabri

Keyword(s):

Numerical Study ◽

Experimental Studies ◽

Free Fall ◽

Water Entry ◽

Vertical Acceleration ◽

Two Dimensional ◽

Pile Up ◽

Real Phenomenon ◽

Precise Simulation ◽

Good Agreement

Abstract This paper examines the hydrodynamic problem of a two-dimensional symmetric and asymmetric wedge water entry through freefall motion. The gravity effect on the flow is considered and because of precise simulation close to the real phenomenon, the oblique slamming is analyzed. The defined problem is numerically studied using SIMPLE and HRIC schemes and by implementing an overset mesh approach. In order to evaluate the accuracy of the numerical model, the present results are compared and validated with previous experimental studies and showed good agreement. The results are presented and compared for each symmetry and asymmetry in different deadrise angles, drop heights and heel angles. Based on a comparison of the measured vertical acceleration of the experimental wedge data, it is determined that the proposed numerical method has relatively good accuracy in predicting the slamming phenomenon and wedge response. The influence of viscous regime on water entry simulations is investigated, in according to results, effect of viscosity is negligible. Results show that the heel angle dramatically affects the wedge dynamics, pile-up evolution, and pressure distribution. These results suggest evidence for a complex interaction between geometric parameters on the water entry of rigid wedges, which could finally develop our understanding of planing vessels operating in real sea conditions.

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Free Fall Water Entry of a Two-Dimensional Asymmetric Wedge in Oblique Slamming: A Numerical Study

10.1115/1.0000874v ◽

2021 ◽

Author(s):

Saeed Hosseinzadeh ◽

Mohammad Izadi ◽

Kristjan Tabri

Keyword(s):

Numerical Study ◽

Free Fall ◽

Water Entry ◽

Two Dimensional

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Hydrodynamics Loads on Two Degree-of-Freedom Cylinder With Uncertain Natural Frequencies Subject to VIV

Volume 5: Polar and Arctic Sciences and Technology; CFD and VIV ◽

10.1115/omae2009-79323 ◽

2009 ◽

Author(s):

Didier Lucor

Keyword(s):

Natural Frequencies ◽

Numerical Study ◽

Spectral Element ◽

Numerical Approach ◽

Response Surfaces ◽

Degree Of Freedom ◽

Two Dimensional ◽

Wide Range ◽

Two Dimensional Flow ◽

Two Degree Of Freedom

In this numerical study, we build response surfaces of two degree-of-freedom vortex-induced vibrations (VIV) of flexibly mounted cylinders for a wide range of transverse and in-line natural frequencies. We consider both the structure and the flow to be two-dimensional and the structure has a low mass damping. The emphasis is put on the representation of the hydrodynamic loads acting on the cylinder in response to the change in the natural frequencies of the structure. The system is sampled for a wide range of natural frequencies within the synchronization region, totaling 149 two-dimensional flow-structure simulations. The parametric range of the in-line frequency is chosen to be larger than the one of the transverse frequency in order to favor multi-modal responses. No preferred frequencies are emphasized within the intervals of study. The fully spectral numerical approach relies on a stochastic collocation method coupled to a spectral element-based deterministic solver.

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Analytical models to predict structural behaviour of reinforced concrete beams bonded with prestressed fibre-reinforced polymer laminates

Advances in Structural Engineering ◽

10.1177/1369433217732666 ◽

2017 ◽

Vol 21 (4) ◽

pp. 532-544

Author(s):

MS Mohamed Ali

Keyword(s):

Reinforced Concrete ◽

Concrete Beams ◽

Reinforced Concrete Beams ◽

Analytical Models ◽

Experimental Investigations ◽

Poor Correlation ◽

Reinforced Polymer ◽

Wide Range ◽

Fibre Reinforced Polymer ◽

Polymer Laminates

The strengthening of reinforced concrete members with prestressed fibre-reinforced polymer laminates has been investigated by researchers due to major improvements in member serviceability characteristics. Currently, analytical models generally employ mostly empirical procedures in predicting member behaviour, and as a result, the analytical results exhibit poor correlation to experimental investigations. In this article, an analytical model is developed using new and existing theoretical techniques to critically analyse strengthened reinforced concrete beams for a range of loading scenarios to generate moment–rotation and load–deflection relationships. The prestress level and the intermediate crack debonding strain of the prestressed fibre-reinforced polymer laminate with the inclusion of mechanical end anchorage were highlighted as key parameters within the model. The proposed model adopts closed-form solutions to allow for a wide range of beams with varying steel and fibre-reinforced polymer reinforcement ratios and dimensions. The model incorporates calibrated crack spacing theory to predict the crack width and spacing as well as the length of the cracked region in the beam. The models have good correlation with collected experimental data and thus can be used for the analysis of reinforced concrete beams strengthened with prestressed fibre-reinforced polymer, throughout all stages of loading from serviceability to failure.

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Two-Dimensional Unsteady Planing

Journal of Ship Research ◽

10.5957/jsr.1996.40.3.200 ◽

1996 ◽

Vol 40 (03) ◽

pp. 200-210 ◽

Cited By ~ 1

Author(s):

Tore Ulstein ◽

Odd M. Faltinsen

Keyword(s):

Numerical Study ◽

Leading Edge ◽

Length Change ◽

Present Theory ◽

Water Entry ◽

Time Varying ◽

Two Dimensional ◽

Hydrodynamic Problem ◽

Square Root Singularity ◽

The Time Domain

An analytical and numerical study of two-dimensional unsteady planing of a flat plate is presented. The immersion of the plate is assumed small; hence, the spray at the leading edge is represented by a square root singularity. The analogy to airfoil theory is used and the hydrodynamic problem is solved in the time domain. The time-varying wetted-length change due to the water flow is accounted for by a generalized Wagner approach. The present theory is verified by comparison with an analytical solution by Sedov (1940) for water entry of a planing plate and with the linear frequency domain solution by Bessho & Komatsu (1984) for a heaving planing plate.

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Effect of Compressibility on Peak Impact Pressure and Pressure Distribution During Water Entry of a Wedge

Volume 11: Prof. Robert F. Beck Honoring Symposium on Marine Hydrodynamics ◽

10.1115/omae2015-41702 ◽

2015 ◽

Cited By ~ 1

Author(s):

Yi Zhang ◽

Ali Mohtat ◽

Solomon C. Yim

Keyword(s):

Mach Number ◽

Sound Speed ◽

Numerical Study ◽

Pressure Coefficient ◽

Water Entry ◽

Impact Pressure ◽

Speed Ratio ◽

Wave Impact ◽

Entry Velocity ◽

Fluid Compressibility

Ship hull slamming and wave impact on wave energy converters (WEC) are an important problem in naval architecture and marine hydrokinetic for the survivability of vessels and WECs in adverse environmental conditions. An idealized canonical model for these problems can be traced back to the water entry of a wedge–shaped rigid object. Common asymptotic and empirical models are often based on the assumption that the fluid is incompressible and the initial wedge entry velocity to sound speed ratio (defined as the characterized Mach number) is low. In this paper, we present some initial results of a numerical study of the effect of fluid compressibility on the peak slamming impact pressure. The deadrise angle and entry velocity of the model are varied to examine the sensitivity of the peak and distribution of the pressure response with respect to these parameters. The fluid compressibility is controlled through the bulk modulus and manifested as various sound speeds. The normalization using this sound speed shows that the pressure coefficient changes consistently for a certain deadrise angle. The results indicates that despite a low Mach number, the fluid compressibility in the numerical model affects the peak pressure significantly, implying an overestimation in engineering application by the classical asymptotic incompressible theory.

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Analytical and Experimental Investigation of Entrainment in Capillary Pumped Wicking Structures

Journal of Energy Resources Technology ◽

10.1115/1.2906433 ◽

1993 ◽

Vol 115 (4) ◽

pp. 278-286 ◽

Cited By ~ 8

Author(s):

B. H. Kim ◽

G. P. Peterson ◽

K. D. Kihm

Keyword(s):

Flow Visualization ◽

Critical Velocity ◽

High Velocity ◽

Analytical Models ◽

Experimental Investigations ◽

Pumping Rate ◽

Pore Sizes ◽

Wide Range ◽

Small Pore ◽

Capillary Pore

Analytical and experimental investigations were conducted to identify and better understand the parameters that govern the entrainment of liquid droplets in high-velocity gas streams flowing over capillary wicking structures. Using a flow visualization technique, two modes of entrainment were identified and described for high-velocity gas flows over an intermittently interrupted liquid surface. These two modes, roll-wave entrainment and stripping entrainment, were found to correspond to the lower and upper critical gas velocities, respectively. Measurements of the critical gas velocities and the droplet size distribution (Sauter mean diameter) of the entrained sprays were made as a function of the capillary pore size for three different mesh sizes and were compared with several analytical models developed in previous investigations. The flow visualization results indicate that the upper critical velocity is insensitive to variations in the capillary pumping rate provided the capillary pores are properly primed. The experimental results also indicate that the critical velocity for a given mesh is strongly influenced by the mesh dimensions, but that the previously developed criteria for estimating the critical velocity results in an underestimation of the upper critical velocity for all but very small pore sizes. Finally, to resolve this problem a new analytical model for predicting the critical velocity was developed and shown to be accurate for a wide range of capillary pore sizes.

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