Reynolds Number Effects on Flow Topology Above Blunt-edged Delta Wing VFE-2 Configurations

2015 ◽  
Author(s):  
Mazuriah Said ◽  
Shabudin B. Mat ◽  
Shuhaimi Mansor ◽  
Ainullotfi Abdul-Latif ◽  
Tholudin Mat Lazim
Keyword(s):  
Reynolds Number ◽  
Delta Wing ◽  
Flow Topology ◽  
Reynolds Number Effects

scholarly journals Time-resolved flow dynamics and Reynolds number effects at a wall–cylinder junction

2015 ◽  
Vol 776 ◽  
pp. 475-511 ◽  
Author(s):  
Nikolaos Apsilidis ◽  
Panayiotis Diplas ◽  
Clinton L. Dancey ◽  
Polydefkis Bouratsis
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Large Scale ◽  
Adverse Pressure Gradient ◽  
Horseshoe Vortex ◽  
Flow Patterns ◽  
Flow Dynamics ◽  
Flow Topology ◽  
Time Resolved ◽  
Reynolds Number Effects

This study investigated the physics of separated turbulent flows near the vertical intersection of a flat wall with a cylindrical obstacle. The geometry imposes an adverse pressure gradient on the incoming boundary layer. As a result, flow separates from the wall and reorganizes to a system of characteristic flow patterns known as the horseshoe vortex. We studied the time-averaged and instantaneous behaviour of the turbulent horseshoe vortex using planar time-resolved particle image velocimetry (TRPIV). In particular, we focused on the effect of Reynolds number based on the diameter of the obstacle and the bulk approach velocity, $\mathit{Re}_{D}$. Experiments were carried out at $\mathit{Re}_{D}$: $2.9\times 10^{4}$, $4.7\times 10^{4}$ and $12.3\times 10^{4}$. Data analysis emphasized time-averaged and turbulence quantities, time-resolved flow dynamics and the statistics of coherent flow patterns. It is demonstrated that two large-scale vortical structures dominate the junction flow topology in a time-averaged sense. The number of additional vortices with intermittent presence does not vary substantially with $\mathit{Re}_{D}$. In addition, the increase of turbulence kinetic energy (TKE), momentum and vorticity content of the flow at higher $\mathit{Re}_{D}$ is documented. The distinctive behaviour of the primary horseshoe vortex for the $\mathit{Re}_{D}=12.3\times 10^{4}$ case is manifested by episodes of rapid advection of the vortex to the upstream, higher spatio-temporal variability of its trajectory, and violent eruptions of near-wall fluid. Differences between this experimental run and those at lower Reynolds numbers were also identified with respect to the spatial extents of the bimodal behaviour of the horseshoe vortex, which is a well-known characteristic of turbulent junction flows. Our findings suggest a modified mechanism for the aperiodic switching between the dominant flow modes. Without disregarding the limitations of this work, we argue that Reynolds number effects need to be considered in any effort to control the dynamics of junction flows characterized by the same (or reasonably similar) configurations.

Analysis and direct numerical simulation of the flow at a gravity-current head. Part 1. Flow topology and front speed for slip and no-slip boundaries

2000 ◽  
Vol 418 ◽  
pp. 189-212 ◽  
Author(s):  
CARLOS HÄRTEL ◽  
ECKART MEIBURG ◽  
FRIEDER NECKER
Keyword(s):  
Reynolds Number ◽  
Stagnation Point ◽  
Flow Structure ◽  
Gravity Current ◽  
Three Dimensional ◽  
Head Part ◽  
Two Dimensional ◽  
Flow Topology ◽  
Reynolds Number Effects ◽  
Dimensional Simulation

Direct numerical simulations are performed of gravity-current fronts in the lock-exchange configuration. The case of small density differences is considered, where the Boussinesq approximations can be adopted. The key objective of the investigation is a detailed analysis of the flow structure at the foremost part of the front, where no previous high-resolution data were available. For the simulations, high-order numerical methods are used, based on spectral and spectral-element discretizations and compact finite differences. A three-dimensional simulation is conducted of a front spreading along a no-slip boundary at a Reynolds number of about 750. The simulation exhibits all features typically observed in experimental flows near the gravity-current head, including the lobe-and-cleft structure at the leading edge. The results reveal that the flow topology at the head differs from what has been assumed previously, in that the foremost point is not a stagnation point in a translating system. Rather, the stagnation point is located below and slightly behind the foremost point in the vicinity of the wall. The relevance of this finding for the mechanism behind the lobe-and-cleft instability is discussed. In order to explore the high-Reynolds-number regime, and to assess potential Reynolds-number effects, two-dimensional simulations are conducted for Reynolds numbers up to about 30 000, for both no-slip and slip (i.e. shear-stress free) boundaries. It is shown that although quantitative Reynolds-number effects persist over the whole range examined, no qualitative changes in the flow structure at the head can be observed. A comparison of the two-dimensional results with laboratory data and the three-dimensional simulation provides evidence that a two-dimensional model is able to capture essential features of the flow at the head. The simulations also show that for the free-slip case the shape of the head agrees closely with the classical inviscid theory of Benjamin.

Influence of Active Flow Control on Blunt-Edged VFE-2 Delta Wing model

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
I. Madan ◽  
N. Tajudin ◽  
M. Said ◽  
S. Mat ◽  
N. Othman ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Delta Wing ◽  
Active Flow Control ◽  
Leading Edge ◽  
Control Technique ◽  
Primary Vortex ◽  
Flow Topology ◽  
Main Observation ◽  
Active Flow

This paper highlights the flow topology above blunt-edged delta wing of VFE-2 configuration when an active flow control technique called ‘blower’ is applied in the leading edge of the wing. The flow topology above blunt-edged delta wing is very complex, disorganised and unresolved compared to sharp-edged wing. For the sharp leading-edged wing, the onset of the primary vortex is fixed at the apex of the wing and develops along the entire wing towards the trailing edge. However, the onset of the primary vortex is no longer fixed at the apex of the wing for the blunt-edged case. The onset of the primary vortex develops at a certain chord-wise position and it moved upstream or downstream depending on Reynolds number, angle of attack, Mach number and the leading-edge bluntness. An active flow control namely ‘blower’ technique has been applied in the leading edge of the wing in order to investigate the upstream/downstream progression of the primary vortex. This research has been carried out in order to determine either the flow on blunt-edged delta wing would behave as the flow above sharp-edged delta wing if any active flow control is applied. The experiments were performed at Reynolds number of 0.5×106, 1.0×106 and 2.0×106 corresponding to 9 m/s, 18 m/s and 36 m/s in UTM Low Speed wind Tunnel based on the mean aerodynamic chord of the wing. The results obtained from this research have shown that the blower technique has significant effects on the flow topology above blunt-edged delta wing. The main observation from this study was that the primary vortex has been shifted 20% upstream when the blower technique is applied. Another main observation was the ability of this flow control to delay the formation of the vortex breakdown.

Low-Reynolds-Number Effects on Delta-Wing Aerodynamics

1998 ◽  
Vol 35 (4) ◽  
pp. 653-656 ◽  
Author(s):  
Lance W. Traub ◽  
Brian Moeller ◽  
Othon Rediniotis
Keyword(s):  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Reynolds Number Effects ◽  
Low Reynolds ◽  
Wing Aerodynamics

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds

Reynolds Number Effects on Shock-Wave Turbulent Boundary-Layer Interactions

AIAA Journal ◽  
1977 ◽  
Vol 15 (8) ◽  
pp. 1152-1158 ◽  
Author(s):  
C. C. Horstman ◽  
G. S. Settles ◽  
I. E. Vas ◽  
S. M. Bogdonoff ◽  
C.M. Hung
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Reynolds Number Effects
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