Kelvin-Helmholtz instability by SPH

In this paper, we have modeled the Kelvin-Helmholtz Instability (KHI) problem of an incompressible two-phase immiscible fluid in a stratified inviscid shear flow with interfacial tension using Smoothed Particle Hydrodynamics (SPH) method. The time dependent evolution of the two-fluid interface over a wide range of Richardson number (Ri) and for three different density ratios is numerically investigated. The simulation results are compared with analytical solutions in the linear regime. It was observed that the SPH method requires a Richardson number lower than unity (i.e.,Ri ∼ = 0.8) for the onset of KHI, and that the artificial viscosity plays a significant role in obtaining physically correct simulation results that are in agreement with analytical solutions. The numerical algorithm presented in this work can easily handle a two-phase fluid flow with various density ratios

Kelvin-Helmholtz instability by SPH

In this paper, we have modeled the Kelvin-Helmholtz Instability (KHI) problem of an incompressible two-phase immiscible fluid in a stratified inviscid shear flow with interfacial tension using Smoothed Particle Hydrodynamics (SPH) method. The time dependent evolution of the two-fluid interface over a wide range of Richardson number (Ri) and for three different density ratios is numerically investigated. The simulation results are compared with analytical solutions in the linear regime. It was observed that the SPH method requires a Richardson number lower than unity (i.e.,Ri ∼ = 0.8) for the onset of KHI, and that the artificial viscosity plays a significant role in obtaining physically correct simulation results that are in agreement with analytical solutions. The numerical algorithm presented in this work can easily handle a two-phase fluid flow with various density ratios

Age-Related Activity Changes in Arginine Phosphokinase in the House Fly, Musca Domestica L

The activity of ATP:L-arginine phosphotransferase (E.C.2.7.3.3.). Was shown to exhibit agedependent changes in both male and female house fly. Enzyme activity demonstrated more marked changes in the male than in the female, increasing 44-fold from emergence to a peak at 2 days of age and thereafter declining, at first sharply then gradually to a value at 14 days of age, representing a third of the activity found at the peak. Activity in the female fly also showed a peak at 2 days of age, which thereafter declined, although more gradually than was observed in the male. Activity changes expressed on a per fly or wet weight basis were nearly identical. Agerelated activity changes on a milligram protein basis demonstrated similar increases; however, the percentage decrease from the 2-day peaks were less striking, although highly significant. No kinetic or physical changes in the enzyme were detected, nor could any soluble inhibitors or activators of the enzyme be identified. The changes in arginine phosphokinase activity fall into a sequential pattern of enzyme changes, reflecting an apparently ordered mechanism underlying a decline in flight ability in this specie

Kelvin-helmholtz instability by SPH

cited By 0; Conference of 2nd International Conference on Particle-Based Methods, PARTICLES 2011 ; Conference Date: 26 October 2011 Through 28 October 2011; Conference Code:89485International audienceIn this paper, we have modeled the Kelvin-Helmholtz Instability (KHI) problem of an incompressible two-phase immiscible fluid in a stratified inviscid shear flow with interfacial tension using Smoothed Particle Hydrodynamics (SPH) method. The time dependent evolution of the two-fluid interface over a wide range of Richardson number (Ri) and for three different density ratios is numerically investigated. The simulation results are compared with analytical solutions in the linear regime. It was observed that the SPH method requires a Richardson number lower than unity (i.e., Ri ≅ 0.8) for the onset of KHI, and that the artificial viscosity plays a significant role in obtaining physically correct simulation results that are in agreement with analytical solutions. The numerical algorithm presented in this work can easily handle a two-phase fluid flow with various density ratios

Statistical behavior of supersonic turbulent boundary layers with heat transfer at M_inf=2

International audienceDirect numerical simulations (DNS) of supersonic turbulent boundary layers (STBL) over adiabatic and isothermal walls are performed to investigate the effects of wall heat transfer on turbulent statistics and near wall behaviors. Four different cases of adiabatic, quasi-adiabatic, and uniform hot and cold wall temperatures are considered. Based on the analysis of the current database, it is observed that even though the turbulent Mach number is below 0.3, the wall heat transfer modifies the behavior of near-wall turbulence. These modifications are investigated and identified using both instantaneous fields (i.e. scatter plots) and mean quantities. Morkovin’s hypothesis for compressible turbulent flows is found to be valid for neither heated nor cooled case. It is further uncovered that although some near-wall asymptotic behaviors change upon using weak or strong adiabatic walls, respectively denote the isothermal and iso-flux walls, basic turbulent statistics are not affected by the thermal boundary condition itself. We also show that among different definition of Reynolds number used in STBL, the Reynolds number based on the friction velocity has some advantages data comparison regarding the first and second order statistical moments. More in depth analyses are also performed using the balance equation for turbulent kinetic energy (TKE) budget, as well as the dissipation rate. It is found that the dilatational to solenoidal dissipation ratio increases/decreases when heating/cooling the walls. The DNS of the current STBLs are available online for the community

Fluid-Structure Interaction simulation by smoothed particle hydrodynamics

cited By 1; Conference of ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting, FEDSM 2010 - ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise, FSI2 and FIV+N ; Conference Date: 1 August 2010 Through 5 August 2010; Conference Code:87047International audienceIn this article, a modified SPH algorithm is proposed to solve Fluid-Structure Interaction (FSI) problems including fluid flow in interaction with compatible structures under a large deformation. To validate the current algorithm against available data in literature, we consider two important benchmark cases; namely, an oscillating elastic beam and dam breaking problems. The proposed algorithm is based on the elimination of the intermediate data transfer steps between the fluid and the solid structures, whereby resulting in an easy and time-saving simulation method. With the test application studied, we were able to prove the ability of the modified SPH method for solving of fluid and solid domains monolithically without the need to define an interfacial boundary condition or any additional steps to simulate the deformation of an elastic dam. Numerical results suggest that upon choosing correct SPH parameters such as smoothing function, and lengths, as well as coefficients for artificial viscosity and artificial stress, one can obtain results in satisfactorily agreement with numerical findings of earlier works. Copyright © 2010 by ASME

Bluff-body simulation by SPH method with relatively high Reynolds number in laminar flow regime

cited By 1; Conference of ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting, FEDSM 2010 - ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise, FSI2 and FIV+N ; Conference Date: 1 August 2010 Through 5 August 2010; Conference Code:87047International audienceIn this work, we present solutions for flow over an airfoil and square obstacle using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. For the solution of these two problems, we present an improved WCSPH algorithm that can handle complex geometries with the usage of multiple tangent solid boundary method, and eliminate particle clustering induced instabilities with the implementation of particle fracture repair procedure as well as the corrected SPH discretization scheme. We have shown that the improved WCSPH method can be effectively used for flow simulations over bluff-bodies with Reynolds numbers as high as 1400, which is not achievable with standard WCSPH formulations. Our simulation results are validated with a Finite Element mesh-dependent Method (FEM), and excellent agreements among the results were observed. We illustrated that the improved WCSPH method is able to capture the complex physics of bluff-body flows naturally such as flow separation, detachment of separated flow, wake formation at the trailing edge, and vortex shedding without any extra effort to increase the particle resolution in some specific areas of interest. Copyright © 2010 by ASME

Series solution for heat transfer of continuous stretching sheet immersed in a micropolar fluid in the existence of radiation

cited By 10Purpose - The purpose of this paper is to study a two-dimensional steady convective flow of a micropolar fluid over a stretching sheet in the presence of radiation with constant temperature. Design/methodology/approach - The corresponding momentum, microrotation and energy equations are analytically solved using homotopy analysis method (HAM). Findings - To validate the method, investigate the accuracy and convergence of the results, a comparison with existing numerical and experimental results is done for several cases. Finally, by using the obtained analytical solution, for the skin-friction coefficient and the local Nusselt number as well as the temperature, velocity and angular velocity, profiles are obtained for different values of the constant parameters, such as Prandtl number, material, boundary and radiation parameter. Originality/value - In this paper, a series solution is presented for the first time. © Emerald Group Publishing Limited

A Smoothed Particle Hydrodynamics approach for thermo-capillary flows

cited By 1Interfacial-driven flows are important phenomena in many processes. In this article, we present a Smoothed Particle Hydrodynamics (SPH) model for thermo-capillary flow driven by gradients of the surface tension. The model is based on the continuum surface force (CSF) approach including Marangoni forces. An incompressible SPH approach using (i) density-invariant divergence-free (DIDF), (ii) corrected SPH and (iii) particle shifting approaches for multi-phase systems is used for accurate results. We carefully validate the proposed model using several test cases. First, we demonstrate the effects of corrected SPH and particle shifting approaches using Taylor-Green vortex. Then, we study single-phase flow problems to validate correct implementation of boundary conditions, momentum and energy balance using lid-driven cavity, diffusive transport problem, and buoyancy-driven cavity test cases. Afterward, we investigate different multi-phase flow problems to validate normal and tangential component of the surface tension. Finally, we apply the model to thermo-capillary rise of a droplet due to a temperature gradient. We present a convergence study and compare the results with their counterparts obtained from OpenFoam software as well as Finite Volume method (FVM) reference from literature. We demonstrate that the proposed model is very accurate for thermo-capillary flow. The simulation results of the current SPH approach will be available online for the community. © 2018 Elsevier Lt