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T I Khabakhpasheva - One of the best experts on this subject based on the ideXlab platform.
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fluid impact onto a corrugated panel with trapped gas cavity
Applied Ocean Research, 2013Co-Authors: T I Khabakhpasheva, A. A. Korobkin, Šime MalenicaAbstract:Initial stage of incompressible Liquid impact onto a corrugated elastic panel with account for compressible gas trapping between the corrugations is studied. The Liquid Free Surface is flat and parallel to the panel before impact. The impact velocity is constant in this study. The corrugations are modelled as identical rigid short structures on the Surface of the flat panel. The panel is either of infinite or finite length. There are only two corrugations which are placed symmetrically on the panel. Only a part of the panel between these two corrugations is elastic. The Liquid Free Surface closes the gas cavity between the two corrugations at the initial instant of impact and compresses the gas before the fluid comes in contact with the elastic part of the panel. The elastic deflections of the panel are caused by gas pressure in the cavity. The elastic deflections modify both the pressure in the cavity and the hydrodynamic pressure distribution along the wetted part of the panel. The hydroelastic problem is solved within the Wagner approach. The effect of gas compressibility on the elastic behaviour of the corrugated elastic panel is investigated. It is shown that the pressure in the gas cavity and elastic deflections grow beyond all bounds for the panel of infinite length and are finite if the panel is of finite length. The present model is relevant for the strength assessment of the cargo containment system (CCS) in the tanks of LNG carriers.
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fluid structure interaction during the impact of a cylindrical shell on a thin layer of water
Journal of Fluids and Structures, 2009Co-Authors: T I KhabakhpashevaAbstract:Abstract A two-dimensional unsteady analysis of an elastic circular cylindrical shell that enters a thin layer of an ideal incompressible Liquid is considered. The cylinder initially touches the Liquid Free Surface at a single point and then penetrates the Liquid layer at a constant vertical velocity. The problem is coupled because the Liquid flow, the shape of the elastic shell and the geometry of the contact region between the body and the Liquid must be determined simultaneously. The flow region is subdivided into four complementary regions that exhibit different properties: the region beneath the entering body Surface, the jet root, the spray jet, and the outer region. A complete solution is obtained by matching the solutions within these four subdomains. The structural analysis is based on the normal-mode method. Strain-time histories of the inner Surface of the cylinder are of particular interest. In the case of a very flexible shell three distinct regimes of the impact process were found. For a high impact velocity the lower part of the shell flattens and the shell does not enter the water. For a moderate impact velocity the shell reaches the bottom and an effect of “fluid capture” may occur. For a low impact velocity the shell penetrates the Liquid, but the size of the contact region decreases before the shell reaches the bottom. This behaviour corresponds to exit or “reflection” of the shell from the water layer.
Dominique Toye - One of the best experts on this subject based on the ideXlab platform.
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investigating the effects of hydrodynamics and mixing on mass transfer through the Free Surface in stirred tank bioreactors
Chemical Engineering Science, 2017Co-Authors: Anne De Lamotte, Angelique Delafosse, Sebastien Calvo, Frank Delvigne, Dominique ToyeAbstract:Abstract In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the Liquid Free-Surface and their homogenization in the bulk. A proper understanding of the underlying mechanisms, i.e. hydrodynamics, mixing and mass transfer, and of their interactions is required to design and develop reliable and efficient production-scale bioprocesses. The objective of the present work is to experimentally investigate the coupling between gas-Liquid mass transfer of oxygen with mixing efficiency and circulation patterns inside an arbitrarily chosen stirred-tank configuration aerated through the Liquid Free-Surface, a baffled 20 L-vessel agitated by two Rushton turbines. Based on global parameter values, the most appropriate rotating speed, N = 300 rpm, is selected in order to further study local hydrodynamic quantities using Particle Image Velocimetry (PIV), as well as mixing and mass transfer dynamics using Planar Laser-Induced Fluorescence (PLIF). The results obtained with these local experimental methods are analyzed in detail. Their averages are first successfully compared to global data. Statistical analysis of their spatial distributions show that large-scale flow patterns significantly influence mass transfer through the Free-Surface of the stirred tank. Even if global measurements show that global characteristic times for mixing and mass transfer differ by two orders of magnitude, local experimental characterization shows persistent vertical gradients of dissolved gas concentrations. So the dissolved gas concentration is not as perfectly uniform as one might expect.
A. A. Korobkin - One of the best experts on this subject based on the ideXlab platform.
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fluid impact onto a corrugated panel with trapped gas cavity
Applied Ocean Research, 2013Co-Authors: T I Khabakhpasheva, A. A. Korobkin, Šime MalenicaAbstract:Initial stage of incompressible Liquid impact onto a corrugated elastic panel with account for compressible gas trapping between the corrugations is studied. The Liquid Free Surface is flat and parallel to the panel before impact. The impact velocity is constant in this study. The corrugations are modelled as identical rigid short structures on the Surface of the flat panel. The panel is either of infinite or finite length. There are only two corrugations which are placed symmetrically on the panel. Only a part of the panel between these two corrugations is elastic. The Liquid Free Surface closes the gas cavity between the two corrugations at the initial instant of impact and compresses the gas before the fluid comes in contact with the elastic part of the panel. The elastic deflections of the panel are caused by gas pressure in the cavity. The elastic deflections modify both the pressure in the cavity and the hydrodynamic pressure distribution along the wetted part of the panel. The hydroelastic problem is solved within the Wagner approach. The effect of gas compressibility on the elastic behaviour of the corrugated elastic panel is investigated. It is shown that the pressure in the gas cavity and elastic deflections grow beyond all bounds for the panel of infinite length and are finite if the panel is of finite length. The present model is relevant for the strength assessment of the cargo containment system (CCS) in the tanks of LNG carriers.
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the motion of the Free Surface separation point during the initial stage of horizontal impulsive displacement of a floating circular cylinder
Journal of Engineering Mathematics, 2011Co-Authors: Michail Norkin, A. A. KorobkinAbstract:The initial stage of unsteady two-dimensional flow caused by the impulsive horizontal motion of a floating circular cylinder is investigated by using methods of asymptotic analysis. Initially the cylinder is half-submerged and the Liquid Free Surface is flat and horizontal. The Liquid is of infinite depth. Then the cylinder suddenly starts to move horizontally with a speed given as a function of time. The Liquid is assumed ideal and incompressible and its flow potential. The initial flow is provided by pressure-impulse theory, with an account of a possible separation of the Liquid Free Surface from the trailing face of the rigid Surface of the cylinder. The initial position of the separation point on the Surface of the moving body is determined by using the condition that the fluid velocity is finite at the separation point (Kutta condition). The motion of the separation point along the Surface of the cylinder is numerically determined with the help of the second-order outer solution of the problem and the Kutta condition at the moving separation point. It is shown that the length of the wetted part of the cylinder Surface increases at a rate proportional to the speed of the cylinder. The speed of the separation point depends on the Froude number. The pressure on the wetted part of the cylinder can be below the atmospheric pressure for relatively high speed.
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three dimensional theory of water impact part 1 inverse wagner problem
Journal of Fluid Mechanics, 2001Co-Authors: Yvesmarie Scolan, A. A. KorobkinAbstract:The three-dimensional problem of blunt-body impact onto the Free Surface of an ideal incompressible Liquid is considered within the Wagner theory. The theory is formally valid during an initial stage of the impact. The problem has been extensively studied in both two-dimensional and axisymmetric cases. However, there are no exact truly three-dimensional solutions of the problem even within the Wagner theory. At present, three-dimensional effects in impact problems are mainly handled approximately by using a sequence of two-dimensional solutions and/or aspect-ratio correction factor. In this paper we present exact analytical rather than approximate solutions to the three-dimensional Wagner problem. The solutions are obtained by the inverse method. In this method the body velocity and the projection on the horizontal plane of the contact line between the Liquid Free Surface and the Surface of the entering body are assumed to be given at any time instant. The shape of the impacting body is determined from the Wagner condition. It is proved that an elliptic paraboloid entering calm water at a constant velocity has an elliptic contact line with the Free Surface. Most of the results are presented for elliptic contact lines, for which analytical solutions of the inverse Wagner problem are available. The results obtained can be helpful in testing other numerical approaches and studying the influence of three-dimensional effects on the Liquid flow and the hydrodynamic loads.
S M Dehghan - One of the best experts on this subject based on the ideXlab platform.
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Free vibration analysis of fgm cylindrical shells surrounded by pasternak elastic foundation in thermal environment considering fluid structure interaction
Applied Mathematical Modelling, 2020Co-Authors: Abdolhossein Baghlani, Majid Khayat, S M DehghanAbstract:Abstract This paper presents an investigation on partially fluid-filled cylindrical shells made of functionally graded materials (FGM) surrounded by elastic foundations (Pasternak elastic foundation) in thermal environment. Material properties are assumed to be temperature dependent and radially variable in terms of volume fraction of ceramic and metal according to a simple power law distribution. The shells are reinforced by stiffeners attached to their inside and outside in which the material properties of shell and the stiffeners are assumed to be continuously graded in the thickness direction. The formulations are derived based on smeared stiffeners technique and classical shell theory using higher-order shear deformation theory which accounts for shear flexibility through shell's thickness. Displacements and rotations of the shell middle Surface are approximated by combining polynomial functions in the meridian direction and truncated Fourier series with an appropriate number of harmonic terms in the circumferential direction. The governing equations of Liquid motion are derived using a finite strip element formulation of incompressible inviscid potential flow. The dynamic pressure of the fluid is expanded as a power series in the radial direction. Moreover, the quiescent Liquid Free Surface is modeled by concentric annular rings. A detailed numerical study is carried out to investigate the effects of power-law index of functional graded material, fluid depth, stiffeners, boundary conditions, temperature and geometry of the shell on the natural frequency of eccentrically stiffened functionally graded shell surrounded by Pasternak foundations.
Marco A Ramirezargaez - One of the best experts on this subject based on the ideXlab platform.
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mathematical and physical simulation of the interaction between a gas jet and a Liquid Free Surface
Applied Mathematical Modelling, 2011Co-Authors: J Solorzanolopez, Roberto Zenit, Marco A RamirezargaezAbstract:Abstract In this work a two phase 3D mathematical model was developed using the volume of fluid (VOF) algorithm, which is able to accurately describe the cavity geometry and size as well as the Liquid flow patterns created when a gas jet that impinges on a Liquid Free Surface. These phenomena are commonly found in steelmaking operations such as in the Electric Arc Furnace (EAF) and the Basic Oxygen Furnace (BOF) where oxygen jets impinge on a steel bath and they control heat, momentum and mass transfer. The model was successfully validated with measurements made on a physical model through velocity fields obtained by Particle Image Velocimetry (PIV) and high speed camera images of the cavity. Agreement between model predictions and experimental measurements is excellent in both x -velocity component of the Liquid and cavity sizes. The cavity formed in the Liquid by the impinging jet depends on a force balance at the Free Surface where the inertial force of the jet governs this phenomena, while the Liquid circulation depends on also the jet inertial force of the jet, but its angle plays an important role, being the lowest angle the best choice to shear the bath and promote stronger circulation and better mixing in the Liquid.