scholarly journals A Comparative Numerical Study on the Performances and Vortical Patterns of Two Bioinspired Oscillatory Mechanisms: Undulating and Pure Heaving

2015 ◽  
Vol 2015 ◽  
pp. 1-25 ◽  
Author(s):  
Mohsen Ebrahimi ◽  
Madjid Abbaspour
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Leading Edge ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
And Performance ◽  
Volume Method ◽  
Thrust Production ◽  
High Thrust

The hydrodynamics and energetics of bioinspired oscillating mechanisms have received significant attentions by engineers and biologists to develop the underwater and air vehicles. Undulating and pure heaving (or plunging) motions are two significant mechanisms which are utilized in nature to provide propulsive, maneuvering, and stabilization forces. This study aims to elucidate and compare the propulsive vortical signature and performance of these two important natural mechanisms through a systematic numerical study. Navier-Stokes equations are solved, by a pressure-based finite volume method solver, in an arbitrary Lagrangian-Eulerian (ALE) framework domain containing a2D NACA0012foil moving with prescribed kinematics. Some of the important findings are (1) the thrust production of the heaving foil begins at lower St and has a greater growing slope with respect to the St; (2) the undulating mechanism has some limitations to produce high thrust forces; (3) the undulating foil shows a lower power consumption and higher efficiency; (4) changing the Reynolds number (Re) in a constant St affects the performance of the oscillations; and (5) there is a distinguishable appearance of leading edge vortices in the wake of the heaving foil without observable ones in the wake of the undulating foil, especially at higher St.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

Iterative method for solving fully-coupled fluid solid systems

2010 ◽  
pp. 653-670
Author(s):  
Elisabeth Longatte
Keyword(s):  
Stokes Equations ◽  
Cross Flow ◽  
Elastic Cylinder ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
Ale Formulation ◽  
Volume Method ◽  
Fully Coupled ◽  
Solid System

This work is concerned with the modelling of the interaction of a fluid with a rigid or a flexible elastic cylinder in the presence of axial or cross-flow. A partitioned procedure is involved to perform the computation of the fully-coupled fluid solid system. The fluid flow is governed by the incompressible Navier-Stokes equations and modeled by using a fractional step scheme combined with a co-located finite volume method for space discretisation. The motion of the fluid domain is accounted for by a moving mesh strategy through an Arbitrary Lagrangian-Eulerian (ALE) formulation. Solid dyncamics is modeled by a finite element method in the linear elasticity framework and a fixed point method is used for the fluid solid system computation. In the present work two examples are presented to show the method robustness and efficiency.

CUDA Based Numerical Simulation of Cavity Flow and Performance Analysis

2013 ◽  
Vol 291-294 ◽  
pp. 1954-1957
Author(s):  
Xiao Ping Li ◽  
Hong Ming Zhang
Keyword(s):  
Stokes Equations ◽  
Cavity Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Floating Point Arithmetic ◽  
Upwind Discretization ◽  
C Program ◽  
And Performance ◽  
Volume Method ◽  
Point Arithmetic

Cuda has been widely used in computational fluid dynamics due to the powerful abilities of floating point arithmetic on gpu.This paper solved the Navier-Stokes equations of two dimensional incompressible flow using parallel programming on cuda. The finite volume method and the second-order upwind discretization scheme were used in the simulation.The speed of serial c program and the cuda based program were compared and we also compared the two programs on different hardware.The simulations got high precision results,which showed that the cuda based parallel computing is much more efficiency,and the parallel algorithm could get a more than 10 times the acceleration.

Numerical Study of Wave Slamming on an Oscillating Flap

2014 ◽  
Author(s):  
Yanji Wei ◽  
Alan Henry ◽  
Olivier Kimmoun ◽  
Frederic Dias
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Studies ◽  
Wave Slamming ◽  
Volume Method

Bottom hinged Oscillating Wave Surge Converters (OWSCs) are efficient devices for extracting power from ocean waves. There is limited knowledge about wave slamming on such devices. This paper deals with numerical studies of wave slamming on an oscillating flap to investigate the mechanism of slamming events. In our model, the Navier–Stokes equations are discretized using the Finite Volume method with the Volume of Fluid (VOF) approach for interface capturing. Waves are generated by a flap-type wave maker in the numerical wave tank, and the dynamic mesh method is applied to model the motion of the oscillating flap. Basic mesh and time step refinement studies are performed. The flow characteristics in a slamming event are analysed based on numerical results. Various simulations with different flap densities, water depths and wave amplitudes are performed for a better understanding of the slamming.

Numerical Study of Wing Aerodynamics in Ground Proximity

2008 ◽  
Author(s):  
Alex E. Ockfen ◽  
Konstantin I. Matveev
Keyword(s):  
Iterative Process ◽  
Stokes Equations ◽  
Numerical Study ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Design And Optimization ◽  
Volume Method ◽  
Experimental Design And Optimization

Experimental design and optimization of innovative ground-effect transportation means is an iterative process which requires a large amount of time and resources. To avoid the large experimental expense, numerical modeling can be used to investigate Wing-in-Ground (WIG) vehicle flight. In this paper, modeling technique is applied for a two dimensional NACA 4412 airfoil in viscous flow in and out of ground effect. The numerical method consists of a steady state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using FLUENT 6.3. The modeling procedures are first validated against published experimental data for unbounded flow around an airfoil. Wing section aerodynamic characteristics are then studied for varying ground heights and two separate boundary conditions: fixed ground and moving ground. Ground effect calculations are compared to several previous studies, and our results are found to correlate with published aerodynamic trends in ground effect, although all studies appear to predict different magnitudes of aerodynamic forces.

A Numerical Study of Vortex Shedding From a Square Cylinder With Ground Effect

1997 ◽  
Vol 119 (3) ◽  
pp. 512-518 ◽  
Author(s):  
Robert R. Hwang ◽  
Chia-Chi Yao
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Subsequent Development ◽  
Ground Effect ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Navier Stokes Equations ◽  
Layer Flow ◽  
Volume Method

A numerical study has been conducted to investigate the behavior of the vortical wake created by a square cylinder placed in a laminar boundary-layer flow. The calculations are performed by solving the unsteady 2D Navier-Stokes equations with a finite-volume method. The Reynolds-number regime investigated is from 500 to 1500. Another parameter that is varied is the distance of the cylinder from the wall. The initial and subsequent development of the vortex shedding phenomenon are investigated. The presence of the wall is found to have strong effects on the properties of these vortices, as well as lift, drag, and Strouhal number.

scholarly journals Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1125
Author(s):  
Chemseddine Maatki
Keyword(s):  
Rayleigh Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vorticity Vector ◽  
Volume Method ◽  
The Impact ◽  
Buoyancy Ratio

The finite volume method and potential-vorticity vector formalism in their three-dimensional form were used to numerically study the impact of an adiabatic and impermeable vertical barrier on the dispersion of a local aero-contaminant due to the double-diffusive Rayleigh–Benard convection inside a cubic container. Different governing parameters such as the Rayleigh number, buoyancy ratio and barrier height were analyzed for Le = 1.2 and Pr = 0.7, representing an air-contaminant mixture. The potential-vector-vorticity formalism in the three-dimensional form allowed the elimination of the pressure terms appearing in the Navier–Stokes equations. It was found that the heat and mass transfer as well as the effectiveness of the barrier in reducing contaminant dispersion are strongly influenced by the buoyancy ratio, the barrier size and the Rayleigh number. In addition, the barrier effectiveness is more than 70% for a height of half the building height.

Computed Effects of Rotor-Induced Swirl on Brush Seal Performance—Part 1: Leakage Analysis

1996 ◽  
Vol 118 (4) ◽  
pp. 912-919 ◽  
Author(s):  
M. C. Sharatchandra ◽  
D. L. Rhode
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Brush Seal ◽  
Leakage Resistance ◽  
Flow Features ◽  
Tube Banks ◽  
Volume Method ◽  
Relationship Of

This paper presents a numerical study of the effects of rotor induced swirl velocity on the performance of brush seals. Such effects have been studied experimentally by Ferguson (1988), but this paper is apparently the first to obtain an enhanced understanding from the detailed flowfield distributions. The analysis involves the solution of the full Navier-Stokes equations in a two-dimensional, idealized configuration using a strongly conservative finite volume method developed by the authors in conjunction with the QUICK differencing scheme. The present computations have demonstrated excellent agreement with measurements for the similar flow across tube banks. An enhanced understanding of decreasing leakage with increasing shaft speed was obtained in terms of the various flow features. Specifically, the cause and effect relationship of certain interactions between the axial and tangential flows was identified. Computer-drawn pathlines show how increased leakage resistance results from large rotor-induced lateral motion of leakage fluid particles. In addition, a first-order streamwise periodic boundary condition treatment which facilitates numerical convergence has been proposed for essentially any flow which is streamwise periodic in two orthogonal directions.

scholarly journals Numerical Simulation of Unsteady Compressible Flow in Convergent Channel: Pressure Spectral Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Petra Pořízková ◽  
Karel Kozel ◽  
Jaromír Horáček
Keyword(s):  
Numerical Solution ◽  
Stokes Equations ◽  
Laminar Flows ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Airflow Velocity ◽  
Navier Stokes Equations ◽  
Convergent Channel ◽  
Volume Method ◽  
Predictor Corrector

This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor-corrector Mac-Cormack scheme with Jameson artificial viscosity using a grid of quadrilateral cells. Due to the motion of the grid, the basic system of conservation laws is considered in the arbitrary Lagrangian-Eulerian (ALE) form. The numerical results of unsteady flows in the channel are presented for inlet Mach numberM∞=0.012, Reynolds numberRe∞=4481,and the wall motion frequency 100 Hz.

Leading-Edge Film-Cooling Physics—Part III: Diffused Hole Effectiveness

2003 ◽  
Vol 125 (2) ◽  
pp. 252-259 ◽  
Author(s):  
William D. York ◽  
James H. Leylek
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Density Ratio ◽  
Leading Edge ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Stagnation Line ◽  
Half Angle ◽  
Edge Surface ◽  
And Performance

A proven computational methodology was applied to investigate film cooling from diffused holes on the simulated leading edge of a turbine airfoil. The short film-hole diffuser section was conical in shape with a shallow half-angle, and was joined to a plenum by a cylindrical metering section. The diffusion resulted in a film-hole breakout area of 2.5 times that of a cylindrical hole. In the present paper, predictions of adiabatic effectiveness for the cases with diffused holes are compared to results for standard cylindrical holes, and performance is analyzed in the context of extensive flowfield data. The leading edge surface was elliptic in shape to accurately model a turbine airfoil. The geometry consisted of one row of holes centered on the stagnation line, and two additional rows located 3.5 hole (metering section) diameters downstream on either side of the stagnation line. Film holes in the downstream rows were centered laterally between holes in the stagnation row. All holes were angled at 20 deg with the leading edge surface, and were turned 90 deg with respect to the streamwise direction (radial injection). The average blowing ratio was varied from 1.0 to 2.5, and the coolant-to-mainstream density ratio was equal to 1.8. The steady Reynolds-averaged Navier-Stokes equations were solved with a pressure-correction algorithm on an unstructured, multi-block grid containing 4.6 million finite-volumes. A realizable k-ε turbulence model was employed to close the equations. Convergence and grid-independence was verified using strict criteria. Based on the laterally averaged effectiveness over the leading edge, the diffused holes showed a marked advantage over standard holes through the range of blowing ratios. However, ingestion of hot crossflow and thermal diffusion into the second row of film holes was observed to cause significant, and potentially detrimental, heating of the film-hole walls.

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