Spectral and instantaneous flow field characteristics of the laminar to turbulent transition in a cone and plate apparatus

2000 ◽  
Vol 28 (4) ◽  
pp. 336-343 ◽  
Author(s):  
Y. Grad ◽  
S. Einav
Keyword(s):  
Flow Field ◽  
Instantaneous Flow ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Instantaneous Flow Field ◽  
Flow Field Characteristics ◽  
Plate Apparatus

Coherent structure in the turbulent planar jet. Part 2. Structural topology via POD eigenmode projection

2002 ◽  
Vol 460 ◽  
pp. 349-380 ◽  
Author(s):  
S. V. GORDEYEV ◽  
F. O. THOMAS
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Structural Topology ◽  
Instantaneous Flow ◽  
Planar Jet ◽  
Instantaneous Flow Field ◽  
Spanwise Vortex ◽  
Planar Component

The topology of the large-scale structure in the similarity region of a turbulent planar jet is investigated experimentally. The large-scale structure is reconstructed in physical space by projection of measured proper orthogonal decomposition eigenmodes onto instantaneous flow-field realizations. The instantaneous flow-field realizations are obtained by a spanwise aligned triple X-wire rake arrangement which is used in conjunction with the linear stochastic estimation technique. Instantaneous realizations are also acquired via a second triple rake arrangement which provides an assessment of the effect of spatial aliasing on the resulting structural topology. Results indicate that the self-similar large-scale structure in the planar jet consists of a dominant planar component consisting of two lines of large-scale spanwise vortices arranged approximately asymmetrically with respect to the jet centreline. This planar component of the structure resembles the classic Kármán vortex street. There is a strong interaction between structures on opposite sides of the jet in the form of nearly two-dimensional lateral streaming motions that extend well across the flow. In addition, results indicate that the effect of the nonplanar spanwise modes is to both tilt and bend the primary spanwise vortex tubes and thereby redistribute large-scale vorticity. The bending occurs primarily in the streamwise direction. The degree to which the spanwise vortices are distorted varies greatly; in some cases they are nearly streamwise oriented and in others only slight distortion of a spanwise vortex is noted. Based upon the experimental results, prospects for low-order modelling of the jet large-scale structure are discussed.

Instantaneous Flow Field Measurements for Propeller Aircraft and Rotorcraft Research

2000 ◽  
pp. 277-296
Author(s):  
M. Raffel ◽  
F. de Gregorio ◽  
K. Pengel ◽  
C. E. Willert ◽  
C. Kähler ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Instantaneous Flow ◽  
Instantaneous Flow Field

Visualization of Flow Field and Wake over Clean and Under-Loaded Wings

2014 ◽  
Vol 629 ◽  
pp. 24-29
Author(s):  
Hussain H. Al-Kayiem
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
Visualization Technique ◽  
High Lift ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Wake Interaction ◽  
Airfoil Flow ◽  
External Body

Experimental details of the flow field and wake over airfoils and 2-D wings are time and cost consumption. In this study, the flow visualization technique was adopted to investigate the flow field surrounding NACA4412 airfoil. The investigations were carried out in smoke tunnel, operating at low Reynolds number in a range of 105. The airfoil was tested in two operational cases: first as clean wing and the second as under-loaded wing by attached missile model. The experiments were conducted at various angles of attack as 00, 50,100, 150and 200. It was found that the under-load of external body under the wing is influencing the flow structure over the wing. Also, the wake after the external body is swirling, leading to very complicated wake interaction. The results from the work can support the numerical simulation and the prediction of the laminar to turbulent transition and the separation and wake interaction of high lift airfoil flow fields.

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