scholarly journals Propulsion Performance of the Full-Active Flapping Foil in Time-Varying Freestream

2020 ◽  
Vol 10 (18) ◽  
pp. 6226
Author(s):  
Zhanfeng Qi ◽  
Lishuang Jia ◽  
Yufeng Qin ◽  
Jian Shi ◽  
Jingsheng Zhai
Keyword(s):  
Flow Velocity ◽  
Steady Flow ◽  
Navier Stokes ◽  
Time Varying ◽  
Flapping Foil ◽  
Propulsion Performance ◽  
Reduced Frequency ◽  
Motion Parameters ◽  
Volume Method ◽  
The Impact

A numerical investigation of the propulsion performance and hydrodynamic characters of the full-active flapping foil under time-varying freestream is conducted. The finite volume method is used to calculate the unsteady Reynolds averaged Navier–Stokes by commercial Computational Fluid Dynamics (CFD) software Fluent. A mesh of two-dimensional (2D) NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first investigate the propulsion performance of the flapping foil in the parameter space of reduced frequency and pitching amplitude at a uniform flow velocity. We define the time-varying freestream as a superposition of steady flow and sinusoidal pulsating flow. Then, we study the influence of time-varying flow velocity on the propulsion performance of flapping foil and note that the influence of the time-varying flow is time dependent. For one period, we find that the oscillating amplitude and the oscillating frequency coefficient of the time-varying flow have a significant influence on the propulsion performance of the flapping foil. The influence of the time-varying flow is related to the motion parameters (reduced frequency and pitching amplitude) of the flapping foil. The larger the motion parameters, the more significant the impact of propulsion performance of the flapping foil. For multiple periods, we note that the time-varying freestream has little effect on the propulsion performance of the full-active flapping foil at different pitching amplitudes and reduced frequency. In summary, we conclude that the time-varying incoming flow has little effect on the flapping propulsion performance for multiple periods. We can simplify the time-varying flow to a steady flow field to a certain extent for numerical simulation.

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

scholarly journals Numerical Analysis of Thermal and Aerodynamic Fields in a Channel with Cascaded Baffles

2017 ◽  
Vol 62 (1) ◽  
pp. 16 ◽  
Author(s):  
Younes Menni ◽  
Ahmed Azzi
Keyword(s):  
Fluid Dynamic ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Computational Fluid Dynamic Analysis ◽  
Heat Transfer Coefficients ◽  
Discretization Algorithm ◽  
Volume Method ◽  
The Impact

A computational fluid dynamic analysis of thermal and aerodynamic fields for an incompressible steady-state flow of a Newtonian fluid through a two-dimensional horizontal rectangular section channel with upper and lower wall-attached, vertical, staggered, transverse, cascaded rectangular-triangular (CRT), solid-type baffles is carried out in the present paper using the Commercial, Computational Fluid Dynamics, software FLUENT. The flow model is governed by the Reynolds averaged Navier-Stokes (RANS) equations with the SST k-ω turbulence model and the energy equation. The finite volume method (FVM) with the SIMPLE-discretization algorithm is applied for the solution of the problem. The computations are carried out in the turbulent regime for different Reynolds numbers. In this study, thermo-aeraulic fields, dimensionless axial profiles of velocity, skin friction coefficients, local and average heat transfer coefficients, and thermal enhancement factor were investigated, at constant surface temperature condition along the heated upper wall of the channel, for all the geometry under investigation and chosen for various stations. The impact of the cascaded rectangular-triangular geometry of the baffle on the thermal and dynamic behavior of air is shown and this in comparing the data of this obstacle type with those of the simple flat rectangular-shaped baffle. This CFD analysis can be a real application in the field of heat exchangers, solar air collectors, and electronic equipments.

scholarly journals Navier-Stokes Simulation of the MIT Flapping Foil Experiment Using an Unstructured Finite Volume Method

1999 ◽  
Author(s):  
Dong Jin Kang ◽  
Sang Soo Bae ◽  
Jae Won Kim
Keyword(s):  
Boundary Layer ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Local Minimum ◽  
Free Stream ◽  
Navier Stokes ◽  
Unsteady Boundary Layer ◽  
Flapping Foil ◽  
Volume Method ◽  
Unstructured Finite Volume Method

A Navier-Stokes simulation of the MIT flapping foil experiment is presented. The MIT experiment was designed to provide a good quality database for unsteady boundary layer flows. The unsteady boundary layer around a hydrofoil was generated by flapping two airfoils upstream of the hydrofoil. Present Navier-Stokes simulation is carried out on the entire experimental domain, including the flapping airfoils as well as the downstream fixed hydrofoil. Present Navier-Stokes code uses an unstructured finite volume method based on the SIMPLE algorithm. It uses QUICK scheme for the convective terms and the second order Euler backward differencing for time derivatives to keep second order accuracy spatially and temporally. All other spatial derivatives are approximated by using central difference scheme. All comparisons of present time averaged and unsteady solutions with the corresponding experimental data are satisfactory: all unsteady solutions are compared in terms of time mean and first harmonic. The first harmonic of the velocity shows a peak inside the boundary layer along the surfaces of the hydrofoil and has a local minimum near the edge of the boundary layer. The local minimum becomes manifest as the boundary layer grows. The unsteadiness in the free stream is transferred inside the boundary layer when an unsteady vortex impinges on the surface. The entrained unsteadiness travels with a local velocity slower than that in the free stream. This causes phase lag of the first harmonic between the free stream and the boundary layer and local minimum of the first harmonic near the edge of the boundary layer.

Numerical study of the melting and resolidification of the substrate during the impact of a ceramic droplet in a plasma spraying process

2019 ◽  
Vol 88 (2) ◽  
pp. 20901 ◽  
Author(s):  
Mouloud Driouche ◽  
Tahar Rezoug ◽  
Mohammed El Ganaoui
Keyword(s):  
Numerical Model ◽  
Phase Change ◽  
Solid Phase ◽  
Numerical Study ◽  
Solid Substrate ◽  
Navier Stokes ◽  
Droplet Spreading ◽  
Substrate Melting ◽  
Volume Method ◽  
The Impact

The substrate melting can significantly improve the properties of plasma spray coatings. Indeed the adhesion of the projected particles to the substrate can be ameliorated by the substrate melting. In this article, a numerical model is developed to study the dynamics of fluids and heat transfer with liquid/solid phase change during impact of a fully melted alumina particle on an aluminum solid substrate, taking into account of the substrate melting. The model is based on solving the Navier-Stokes and energy equations with liquid / solid phase change. These equations are coupled with the fluid of volume method (VOF), to follow the free surface of the particle during its spreading and solidification. The finite volume method is used to discretize the equations in a 2D axisymmetric domain. A comparison with the published experimental results was carried out to validate this numerical model. Simulations were performed for different initial droplet diameters to study its effect on droplet spreading as well as on substrate melting. It has been observed that the substrate melting begins before the droplet spreads completely; the substrate melting reaches its maximum when the droplet is close to its total solidification. Droplet spreading and substrate melting are more important for large sizes droplets.

scholarly journals Modelling and assessment of 137-Cs and of heavy metals impact on marine ecosystems

2020 ◽  
Vol 19 ◽  
pp. 119
Author(s):  
M. Psaltaki ◽  
N. C. Markatos
Keyword(s):  
Stokes Equations ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Aegean Sea ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Heat ◽  
Local Ecosystem ◽  
Volume Method ◽  
The Impact

Modelling is an important and useful tool for predicting the behaviour and the impact of pollutants on the local ecosystem parameters. More specifically, simulation and computational methods can be used for estimating the environmental impact on marine ecosystems.The paper presents a three-dimensional general deterministic model, developed to simulate and study the time-dependent behaviour of 137Cs in marine environments. The model capabilities are demonstrated by applying it at the northeast region of the island of Lemnos, in the NE Aegean Sea, Greece. Full Navier-Stokes equations for transient, three-dimensional turbulent flow, heat and mass transfer are solved numerically. The solution method is the finite-volume method and the general CFD code in which the present model is implemented is Phoenics.

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.

scholarly journals A Time-Varying Distributed Unit Hydrograph considering soil moisture content

2021 ◽  
Author(s):  
Bin Yi ◽  
Lu Chen ◽  
Hansong Zhang ◽  
Ping Jiang ◽  
Yizhuo Liu ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Flow Velocity ◽  
Soil Moisture Content ◽  
Surface Characteristics ◽  
Flood Routing ◽  
Time Varying ◽  
Unit Hydrograph ◽  
Water Storage Capacity ◽  
The Impact

Abstract. The distributed unit hydrograph (DUH) method has been widely used for flood routing simulation, because it can well characterize the underlying surface characteristics and various rainfall intensities. The core of the DUH is the calculation of flow velocity. However, the current velocity formula assumed a global equilibrium of the watershed and ignored the impact of time-varying soil moisture content on flow velocity, which leads to a larger flow velocity value. The goal of this study is to identify a soil moisture content factor, which was derived based on the water storage capacity curve, to explore the responses of DUH to soil moisture content in unsaturated areas. Thus, an improved distributed unit hydrograph based on time-varying soil moisture content was proposed in this paper. The proposed method considered the impact of both the time-varying rainfall intensity and soil moisture content on the flow velocity, and the watershed is assumed not to be equilibrium but vary with the soil moisture. The Qin River Basin was selected as a case study, and results of the time-varying distributed unit hydrograph (TDUH) and current DUH methods were used as comparisons with that of proposed method. Influence mechanism of time-varying soil moisture content on the flow velocity and flood forecasts were explored. Results show that the proposed method performs the best among the three methods. The shape and duration of the unit hydrograph can be mainly related to the soil moisture content at initial stage of a storm. When the watershed is approximately saturated, the grid flow velocity is majorly dominated by the excess rainfall.

Experimental and Numerical Study of a Pitching Blade

2010 ◽  
Author(s):  
M. R. Amiralaei ◽  
H. Alighanbari
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Hysteresis Loops ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Qualitative Behavior ◽  
Reduced Frequency ◽  
Lift Curve ◽  
High Turbulence ◽  
Volume Method

The objective of the present study is to investigate the effects of the reduced frequency on the aerodynamic characteristics of a three dimensional pitching blade. Experimental data are recorded at three sections of the blade model; tip, middle, and root sections at low and high turbulence intensities. A 2D numerical simulation is also conducted based on the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations and Finite Volume Method (FVM) and the results are compared with those of the experimental observations. The results show that 2D numerical simulations are useful in obtaining the qualitative behavior of the flow field. Moreover, it is shown experimentally that the reduced frequency is of great importance to the flow physics. It affects the maximum lift coefficients, hysteresis loops, lift curve slopes, and angles at which stall occurs.

scholarly journals Effects of time-varying flexibility on the propulsion performance of a flapping foil

2020 ◽  
Vol 32 (12) ◽  
pp. 121904
Author(s):  
Guangyu Shi ◽  
Qing Xiao ◽  
Qiang Zhu
Keyword(s):  
Time Varying ◽  
Flapping Foil ◽  
Propulsion Performance

scholarly journals A Study of 3D Flexible Caudal Fin for Fish Propulsion

2017 ◽  
Author(s):  
Guangyu Shi ◽  
Qing Xiao ◽  
Qiang Zhu
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Navier Stokes ◽  
Flexible Plate ◽  
Caudal Fin ◽  
Flapping Motion ◽  
Pectoral Fins ◽  
Propulsion Performance ◽  
Soft Membrane ◽  
Volume Method

This paper is inspired by a recent numerical study (Shoele and Zhu, 2012, “Leading edge strengthening and the propulsion performance of flexible ray fins,” Journal of Fluid Mechanics, Vol. 693, pp. 402–432), which shows that, for a 2D flexible ray replicating the pectoral fins of live fish, undergoing a flapping motion in a viscous fluid, the performance can be significantly improved via the flexibility distribution on the rays. In present study, we investigate the propulsion capability of a 3D caudal fin undergoing a flapping motion. The embedded rays are modeled as linear springs and the soft membrane is modeled as a flexible plate being able to deform in span-wise direction. A finite-volume method based Navier-Stokes solver is used to solve the fluid-structure interaction problem. The present paper focuses on the effects of various distributions of the ray and the ray flexibilities, which can lead to different fin deformations. It is shown that the detailed ray distribution has significant influence on the propulsion performance. By distributing fin rays at the tips rather than the middle of fin, a less power expenditure is observed, leading to higher propulsion efficiency. However, larger thrust force is obtained through distributing the rays at the middle, which is attributed to larger effective flapping amplitude. Additionally, ray flexibilities also play a pivotal role in the thrust generation of the fin.

Sign in / Sign up

Export Citation Format

Share Document