Spray Cloud Formation Over Marine Vessels by a Water Breakup Model

2017 ◽  
Author(s):  
Saeed R. Dehghani ◽  
Greg F. Naterer ◽  
Yuri S. Muzychka
Keyword(s):  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Cloud Formation ◽  
Sea Spray ◽  
Governing Equations ◽  
Fishing Vessel ◽  
Wave Impact ◽  
Droplet Sizes ◽  
Marine Vessels ◽  
Breakup Model

Water breakup affects the variety of droplet sizes and velocities in a cloud of spray resulting from a sea wave striking a vessel bow. The Weber and Reynolds numbers of droplets are the main parameters for water breakup phenomena. “Stripping breakup” is a faster phenomenon than “bag breakup” and occurs at higher velocities and with larger diameters of droplets. A water breakup model employs droplet trajectories to develop a predictive model for the extent of spray cloud. The governing equations of breakup and trajectories of droplets are solved numerically. Stripping breakup is found as the major phenomenon in the process of the formation of wave-impact sea spray. Bag breakup acts as a complementary phenomenon to the stripping breakup. The extent of the spray as well as wet heights, for a Mediumsized Fishing Vessel (MFV), are obtained by numerical solutions. The results show that bag breakup occurs at higher heights. In addition, there is no breakup when droplets move over the deck.

Thermal Post-Buckling Analysis of Functionally Graded Composite Plates with Nonlinear Aerodynamic Forces

2010 ◽  
Vol 123-125 ◽  
pp. 280-283
Author(s):  
Chang Yull Lee ◽  
Ji Hwan Kim
Keyword(s):  
Material Properties ◽  
Numerical Solutions ◽  
Virtual Work ◽  
Shear Deformation Theory ◽  
Composite Plates ◽  
Buckling Analysis ◽  
Functionally Graded ◽  
Governing Equations ◽  
Functionally Graded Composite ◽  
Post Buckling

The post-buckling of the functionally graded composite plate under thermal environment with aerodynamic loading is studied. The structural model has three layers with ceramic, FGM and metal, respectively. The outer layers of the sandwich plate are different homogeneous and isotropic material properties for ceramic and metal. Whereas the core is FGM layer, material properties vary continuously from one interface to the other in the thickness direction according to a simple power law distribution in terms of the volume fractions. Governing equations are derived by using the principle of virtual work and numerical solutions are solved through a finite element method. The first-order shear deformation theory and von-Karman strain-displacement relations are based to derive governing equations of the plate. Aerodynamic effects are dealt by adopting nonlinear third-order piston theory for structural and aerodynamic nonlinearity. The Newton-Raphson iterative method applied for solving the nonlinear equations of the thermal post-buckling analysis

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

Electrohydrodynamic rotation of drops at large electric Reynolds numbers

2016 ◽  
Vol 788 ◽  
Author(s):  
Ehud Yariv ◽  
Itzchak Frankel
Keyword(s):  
Electric Fields ◽  
Numerical Solutions ◽  
Fluid Velocity ◽  
Reynolds Numbers ◽  
Mirror Image ◽  
Liquid Drops ◽  
Weakly Conducting ◽  
Strong Electric Fields ◽  
Quincke Rotation ◽  
Asymmetric Solution

When subject to sufficiently strong electric fields, particles and drops suspended in a weakly conducting liquid exhibit spontaneous rotary motion. This so-called Quincke rotation is a fascinating example of nonlinear symmetry-breaking phenomena. To illuminate the rotation of liquid drops we here analyse the asymptotic limit of large electric Reynolds numbers, $\mathit{Re}\gg 1$, within the framework of a two-dimensional Taylor–Melcher electrohydrodynamic model. A non-trivial dominant balance in this singular limit results in both the fluid velocity and surface-charge density scaling as $\mathit{Re}^{-1/2}$. The flow is governed by a self-contained nonlinear boundary-value problem that does not admit a continuous fore–aft symmetric solution, thus necessitating drop rotation. Furthermore, thermodynamic arguments reveal that a fore–aft asymmetric solution exists only when charge relaxation within the suspending liquid is faster than that in the drop. The flow problem possesses both mirror-image (with respect to the direction of the external field) and flow-reversal symmetries; it is transformed into a universal one, independent of the ratios of electric conductivities and dielectric permittivities in the respective drop phase and suspending liquid phase. The rescaled angular velocity is found to depend weakly upon the viscosity ratio. The corresponding numerical solutions of the exact equations indeed collapse at large $\mathit{Re}$ upon the asymptotically calculated universal solution.

The ice nucleating ability of macromolecules in immersion freezing decreases in the presence of salts: Implications for freezing point depression calculations

2021 ◽  
Author(s):  
Jon F. Went ◽  
Jeanette D. Wheeler ◽  
François J. Peaudecerf ◽  
Nadine Borduas-Dedekind
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Pure Water ◽  
Salt Content ◽  
Mixed Phase ◽  
Cloud Formation ◽  
Sea Spray ◽  
Freezing Point Depression ◽  
Immersion Freezing ◽  
Mixed Phase Clouds

<p>Cloud formation represents a large uncertainty in current climate predictions. In particular, ice in mixed-phase clouds requires the presence of ice nucleating particles (INPs) or ice nucleating macromolecules (INMs). An influential population of INPs has been proposed to be organic sea spray aerosols in otherwise pristine ocean air. However, the interactions between INMs present in sea water and their freezing behavior under atmospheric immersion freezing conditions warrants further research to constrain the role of sea spray aerosols on cloud formation. Indeed, salt is known to lower the freezing temperature of water, through a process called freezing point depression (FPD). Yet, current FPD corrections are solely based on the salt content and assume that the INMs’ ice nucleation abilities are identical with and without salt. Thus, we measured the effect of salt content on the ice nucleating ability of INMs, known to be associated with marine phytoplankton, in immersion freezing experiments in the Freezing Ice Nuclei Counter (FINC) (Miller et al., AMTD, 2020). We measured eight INMs, namely taurine, isethionate, xylose, mannitol, dextran, laminarin, and xanthan as INMs in pure water at temperatures relevant for mixed-phase clouds (e.g. 50% activated fraction at temperatures above –23 °C at 10 mM concentration). Subsequently, INMs were analyzed in artificial sea water containing 36 g salt L<sup>-1</sup>. Most INMs, except laminarin and xanthan, showed a loss of ice activity in artificial sea water compared to pure water, even after FPD correction. Based on our results, we hypothesize sea salt has an inhibitory effect on the ice activity of INMs. This effect influences our understanding of how INMs nucleate ice as well as challenges our use of FPD correction and subsequent extrapolation to ice activity under mixed-phase cloud conditions.</p>

scholarly journals The drag-adjoint field of a circular cylinder wake at Reynolds numbers 20, 100 and 500

2013 ◽  
Vol 730 ◽  
pp. 145-161 ◽  
Author(s):  
Qiqi Wang ◽  
Jun-Hui Gao
Keyword(s):  
Circular Cylinder ◽  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Adjoint Equations ◽  
Cylinder Wake ◽  
Near Wake ◽  
Navier Stokes Equation ◽  
D 20

AbstractThis paper analyses the adjoint solution of the Navier–Stokes equation. We focus on flow across a circular cylinder at three Reynolds numbers, ${\mathit{Re}}_{D} = 20, 100$ and $500$. The quantity of interest in the adjoint formulation is the drag on the cylinder. We use classical fluid mechanics approaches to analyse the adjoint solution, which is a vector field similar to a flow field. Production and dissipation of kinetic energy of the adjoint field is discussed. We also derive the evolution of circulation of the adjoint field along a closed material contour. These analytical results are used to explain three numerical solutions of the adjoint equations presented in this paper. The adjoint solution at ${\mathit{Re}}_{D} = 20$, a viscous steady state flow, exhibits a downstream suction and an upstream jet, the opposite of the expected behaviour of a flow field. The adjoint solution at ${\mathit{Re}}_{D} = 100$, a periodic two-dimensional unsteady flow, exhibits periodic, bean-shaped circulation in the near-wake region. The adjoint solution at ${\mathit{Re}}_{D} = 500$, a turbulent three-dimensional unsteady flow, has complex dynamics created by the shear layer in the near wake. The magnitude of the adjoint solution increases exponentially at the rate of the first Lyapunov exponent. These numerical results correlate well with the theoretical analysis presented in this paper.

scholarly journals Global distribution of the effective aerosol hygroscopicity parameter for CCN activation

2010 ◽  
Vol 10 (3) ◽  
pp. 6301-6339 ◽  
Author(s):  
K. J. Pringle ◽  
H. Tost ◽  
A. Pozzer ◽  
U. Pöschl ◽  
J. Lelieveld
Keyword(s):  
Boundary Layer ◽  
Standard Deviation ◽  
Planetary Boundary Layer ◽  
Atmospheric Chemistry ◽  
Regional Distribution ◽  
Cloud Condensation Nucleus ◽  
Cloud Formation ◽  
Sea Spray ◽  
Mean Values ◽  
Aerosol Hygroscopicity

Abstract. In this study we use the ECHAM/MESSy Atmospheric Chemistry (EMAC) model to simulate global fields of the effective hygroscopicity parameter κ which approximately describes the influence of chemical composition on the cloud condensation nucleus (CCN) activity of aerosol particles. The obtained global mean values of κ at the Earth's surface are 0.27±0.21 for continental and 0.72±0.24 for marine regions (arithmetic mean ± standard deviation). The mean κ values are in good agreement with previous estimates based on observational data, but the model standard deviation for continental regions is higher. Over the continents, the regional distribution appears fairly uniform, with κ values mostly in the range of 0.1–0.4. Lower values over large arid regions and regions of high organic loading lead to reduced continental average values for Africa and South America (0.15–0.17) compared to the other continents (0.21–0.36). Marine regions show greater variability with κ values ranging from 0.9–1.0 in remote regions to 0.4–0.6 in continental outflow regions where the highly hygroscopic sea spray aerosol mixes with less hygroscopic continental aerosol. Marine κ values as low as 0.2–0.3 are simulated in the outflow from the Sahara desert. At the top of the planetary boundary layer the κ values can deviate substantially from those at the surface (up to 30%) – especially in marine and coastal regions. In moving from the surface to the height of the planetary boundary layer, the global average marine κ value reduces by 20%. Thus, surface observations may not always be representative for the altitudes where cloud formation mostly occurs. In a pre-industrial model scenario, the κ values tend to be higher over marine regions and lower over the continents, because the anthropogenic particulate matter is on average less hygroscopic than sea-spray but more hygroscopic than the natural continental background aerosol (dust and organic matter). The influence of industrialisation on aerosol hygroscopicity appears to be less pronounced than the influence on the atmospheric aerosol burden. However, in regions influenced by desert dust the particle hygroscopicity has increased strongly as the mixing of air pollutants with mineral particles typically enhances the Kappa values by a factor of 2–3.

scholarly journals Towards theoretical modeling of the sand dunes motion

2017 ◽  
pp. 17-23
Author(s):  
O.I. Gerasymov ◽  
I.S. Andrianova
Keyword(s):  
Sand Dunes ◽  
Reynolds Numbers ◽  
Short Review ◽  
Governing Equations ◽  
Viscous Forces ◽  
Robust Model ◽  
Fold Reduction ◽  
Frictional Dissipation ◽  
Suspended Dust ◽  
Simple Product

The transport of sand by wind is a potent erosion force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This article presents a short review of the physics of wind-driven sand. Specifically, we review the physics of saltation, the formation and development of sand dunes and ripples. We also discuss some classes of the governing equations which describe the physics of wind-driven sand and dune formation. We describe selected types of dunes and conditions under which they occur, and also some features of dunes as well as processes that they are involved in. We show that the normalized dunes height collapses using a simple product of the Froude and Reynolds numbers. This would obscure the effects of frictional dissipation, which clearly plays an important role in all mentioned upper process. Ignoring friction, one can construct a simple energy balance between the kinetic energy of the impacting and the potential energy of the dunes, where we assume the dunes thickness is proportional to ds. This produces the following scaling. In other words, was one to increase the grain diameter ds by a factor of 10 ~ i.e., reduce Re by 100! for the same impact conditions, then the frictionless flow would predict a 10-fold reduction in , whereas the experiments suggest a 100-fold reduction. This shows clearly that viscous forces play a role in the granular dunes formation (and their relevant dynamics), as well as gravity and inertia. These circumstances move us to conclude   the vide range of (non-dissipative) hydrodynamic approaches to describe dunes formation and their dynamics just as a robust model approaches.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

Correlated Compressible and Incompressible Channel Flows

1997 ◽  
Vol 119 (4) ◽  
pp. 911-915 ◽  
Author(s):  
C. Crnojevic´ ◽  
V. D. Djordjevic´
Keyword(s):  
Cross Section ◽  
High Reynolds Number ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Isothermal Flow ◽  
Governing Equations ◽  
Adiabatic Flow ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Reynolds Number Flows

Compressible flow in channels of slowly varying cross section at moderately high Reynolds numbers is treated in the paper by employing some Stewartson-type transformations that convert the problem into an incompressible one. Both adiabatic flow and isothermal flow are considered, and a Poiseuille-type incompressible solution is mapped onto compressible plane in order to generate some exact solutions of the compressible governing equations. The results show striking effects that viscosity may have upon the flow characteristics in this case, in comparison with more conventional high Reynolds number flows.

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