A numerical study on controlling flow separation via surface morphing in the form of backward traveling waves

2019 ◽  
Author(s):  
Amir Akbarzadeh ◽  
Iman Borazjani
Keyword(s):  
Traveling Waves ◽  
Flow Separation ◽  
Numerical Study

scholarly journals Flow Separation Control of Backward-Facing Step Airfoil NACA0015 by Blowing Technique

2019 ◽  
Vol 12 (1) ◽  
pp. 99-119
Author(s):  
Khuder N. Abed
Keyword(s):  
Flow Separation ◽  
Numerical Study ◽  
Leading Edge ◽  
Distribution Coefficients ◽  
Open Circuit ◽  
Experimental Investigations ◽  
Backward Facing Step ◽  
Ansys Fluent ◽  
Flow Separation Control ◽  
Naca 0015

The aim of this paper is to control the flow separation above backward-facing step (BFS) airfoil type NACA 0015 by blowing method. The flow field over airfoil has been studied both experimentally and computationally. The study was divided into two parts: a practical study through which NACA 0015 type with a backward -facing step (located at 44.4% c from leading edge) on the upper surface containing blowing holes parallel to the airfoil chord was used. The tests were done over two-dimensional airfoil in an open circuit suction subsonic wind tunnel with flow velocity 25m/s to obtain the pressure distribution coefficients. A numerical study was done by using ANSYS Fluent software version 16.0 on three models of NACA 0015, the first one has backward-facing step without blowing, the second with single blowing holes and the third have multi blowing holes technique. Both studies (experimental and numerical) were done at low Reynolds number (Re=4.4x105) and all models have chord length 0.27m.The experimental investigations and CFD simulations have been performed on the same geometry dimensions, it has been observed that the flow separation on the airfoil can be delayed by using  velocity blowing (30m/s) on the upper surface. The multi blowing holes with velocity improved the aerodynamics properties.The multi blowing holes and single blowing hole thesame effect onpressure distribution coefficients

scholarly journals Numerical Study of Flow Separation and Pressure Drop for Flow Past Staggered Tube Bundles

2015 ◽  
Vol 773-774 ◽  
pp. 363-367
Author(s):  
Azmahani Sadikin ◽  
Norasikin Mat Isa
Keyword(s):  
Flow Separation ◽  
Single Phase ◽  
Numerical Study ◽  
Tube Bundle ◽  
Horizontal Tube ◽  
Diameter Ratio ◽  
Published Data ◽  
Single Phase Flow ◽  
Shell Side ◽  
Tube Bundles

The vertical single-phase flow was studied on the shell side of a horizontal tube bundle. In the present study, CFX version 14.0 from ANSYS was used to predict the flow regimes in the 19 mm diameter in staggered configuration with a pitch to diameter ratio of 1.32. The simulations were undertaken to inform on how the fluid flowed within the tube passages. The results show that the tube bundle arrangement in a heat exchanger does effect to the flow separation and re-attachment points. This is consistent with other published data.

Numerical study of magnetohydrodynamic laminar flow separation in a channel with smooth expansion

2009 ◽  
Vol 59 (5) ◽  
pp. 495-518 ◽  
Author(s):  
T. K. Maikap ◽  
T. R. Mahapatra ◽  
P. Niyogi ◽  
A. K. Ghosh
Keyword(s):  
Laminar Flow ◽  
Flow Separation ◽  
Numerical Study

Numerical Study on the Pulsatile Flow Characteristics of Proximal Anastomotic Models

2005 ◽  
Vol 219 (5) ◽  
pp. 361-379 ◽  
Author(s):  
L P Chua ◽  
J-M Zhang ◽  
S C M Yu ◽  
D N Ghista ◽  
Y S Tan
Keyword(s):  
Flow Separation ◽  
Patency Rate ◽  
Numerical Study ◽  
Flow Characteristics ◽  
High Time ◽  
Shear Stresses ◽  
Proximal Anastomosis ◽  
Haemodynamic Parameters ◽  
Simulation Results ◽  
Wall Shear

Haemodynamics was widely believed to correlate with anastomosis restenosis. Utilizing the haemodynamic parameters as indicator functions, distal anastomosis was redesigned by some researchers so as to improve the long-term graft patency rate. However, there were few studies upon the proximal anastomosis. Therefore, in this study, flow characteristics and distributions of the haemodynamic parameters in proximal anastomosis under physiological flow condition have been investigated numerically for three different grafting angles: namely, 45° forward facing, 45° backward facing, and 90° anastomotic joints. The simulation results showed a flow separation region along the graft inner wall immediately after the heel at peak flow phase and it decreased in size with the grafting angle shifting from 45° forward facing to 45° backward facing. At the same time, a pair of vortex was found in the cross-sectional planes of the 45° backward facing and 90° grafts. In addition, stagnation point was found along the graft outer wall with small shifting during the physiological cycle. High spatial and temporal wall shear stresses gradients (WSSG) were observed around the anastomotic joint. Low time-averaged wall shear stress (WSS) with elevated oscillation shear index (OSI) was found near the middle of anastomosis at the aorta wall and along the graft inner wall respectively, while high time-averaged WSS with low OSI was found at the heel, the toe, and the region downstream of the toe. These regions correlated to early lesion growth. Elevated time-averaged WSSG was found at the same region, where the elevated low-density lipoprotein (LDL) permeability was observed as reported in the literature. The existence of nearly fixed stagnating location, flow separation, vortex, high time-averaged WSS with low OSI, low time-averaged WSS with elevated OSI, and high time-averaged WSSG may lead to graft stenosis. Moreover, the simulation results obtained were consistent with those of experimental measurements. Based on the validated simulation results, the 45° backward-facing graft was found to have the lowest variation range of time-averaged WSS and the lowest segmental average of WSSG among the three models investigated. The 45° backward-facing graft is thus recommended for the bypass operation with expected higher patency rate.

Numerical study of turbulent flow over an S-shaped hydrofoil

2008 ◽  
Vol 222 (9) ◽  
pp. 1717-1734 ◽  
Author(s):  
T Micha Prem Kumar ◽  
Dhiman Chatterjee
Keyword(s):  
Shear Stress ◽  
Turbulent Flow ◽  
Flow Separation ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Pressure Gradients ◽  
Convex Surfaces ◽  
Shear Stress Transport ◽  
Formidable Challenge

In this paper, a numerical study of turbulent flow over the S-shaped hydrofoil at 0° angle of attack has been reported. Here, the flow takes place over concave and convex surfaces and is accompanied by the favourable and adverse pressure gradients and flow separation. Modelling such a flow poses a formidable challenge. In the present work four turbulence models, namely, k–∊ realizable, k–ω shear stress transport

Numerical study of passive and active flow separation control over a NACA0012 airfoil

2008 ◽  
Vol 37 (8) ◽  
pp. 975-992 ◽  
Author(s):  
Hua Shan ◽  
Li Jiang ◽  
Chaoqun Liu ◽  
Michael Love ◽  
Brant Maines
Keyword(s):  
Flow Separation ◽  
Numerical Study ◽  
Separation Control ◽  
Flow Separation Control ◽  
Naca0012 Airfoil ◽  
Active Flow
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