Reynolds number effects on separated flow structure

2002 ◽  
Author(s):  
S. Song ◽  
C. Aubertine ◽  
J. Eaton
Keyword(s):  
Reynolds Number ◽  
Flow Structure ◽  
Separated Flow ◽  
Reynolds Number Effects

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.

Reynolds number effects on the flow structure behind two side-by-side cylinders

2003 ◽  
Vol 15 (5) ◽  
pp. 1214-1219 ◽  
Author(s):  
S. J. Xu ◽  
Y. Zhou ◽  
R. M. C. So
Keyword(s):  
Reynolds Number ◽  
Flow Structure ◽  
Reynolds Number Effects

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.

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

scholarly journals High-Reynolds-number effects on turbulent scalings in compressible channel flow

PAMM ◽  
2015 ◽  
Vol 15 (1) ◽  
pp. 489-490
Author(s):  
Davide Modesti ◽  
Matteo Bernardini ◽  
Sergio Pirozzoli
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
High Reynolds Number ◽  
Reynolds Number Effects ◽  
High Reynolds
Sign in / Sign up

Export Citation Format

Share Document