Water Tunnel Visualizations of Dynamic Stall

1979 ◽  
Vol 101 (3) ◽  
pp. 376-380 ◽  
Author(s):  
K. W. McAlister ◽  
L. W. Carr
Keyword(s):  
Steady Flow ◽  
Dynamic Stall ◽  
Water Tunnel ◽  
Bubble Flow ◽  
Hydrogen Bubble ◽  
Two Dimensional ◽  
Airfoil Surface ◽  
Flow Visualizations ◽  
Stall Angle ◽  
Naca 0012

A two-dimensional experiment was conducted in a water tunnel using hydrogen bubble flow visualizations for the purpose of exposing, independently, the behavior of the viscous and inviscid domains during unsteady airfoil stall. By imposing a large amplitude pitch oscillation about the static-stall angle of a modified NACA 0012 airfoil, an unsteady environment was created that not only altered considerably the progression of flow reversal along the airfoil surface from what was observed in steady flow, but also caused a unique succession of vortical developments to appear that is unparalleled in steady flow.

Unsteady Flow Phenomena in Rotating Centrifugal Impeller Passages

1970 ◽  
Vol 92 (1) ◽  
pp. 65-71 ◽  
Author(s):  
E. Lennemann ◽  
J. H. G. Howard
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Centrifugal Impeller ◽  
Bubble Flow ◽  
Hydrogen Bubble ◽  
Visualization Technique ◽  
Rotating Systems ◽  
Flow Phenomena ◽  
Relative Flow ◽  
Zero Flow

The phenomena of unsteady relative flow observed in a centrifugal impeller passage running at part capacity and zero flow are discussed. The mechanisms of passage stall for a shrouded and unshrouded impeller are investigated and a qualitative correlation is developed for the influence of secondary flow and inducer flow on the passage stall. The hydrogen bubble flow visualization technique is extended to higher velocities and rotating systems and provides the method for obtaining the experimental results.

Dynamic Stall Simulation of Flow Over NACA0012 Airfoil at 1 Million Reynolds Number

2015 ◽  
Author(s):  
Venkata Ravishankar Kasibhotla ◽  
Danesh Tafti
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Dynamic Stall ◽  
Sharp Drop ◽  
Airfoil Surface ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Edge Vortex

The paper is concerned with the prediction and analysis of dynamic stall of flow past a pitching NACA0012 airfoil at 1 million Reynolds number based on the chord length of the airfoil and at reduced frequency of 0.25 in a three dimensional flow field. The turbulence in the flow field is resolved using large eddy simulations with the dynamic Smagorinsky model at the sub grid scale. The development of dynamic stall vortex, shedding and reattachment as predicted by the present study are discussed in detail. This study has shown that the downstroke phase of the pitching motion is strongly three dimensional and is highly complex, whereas the flow is practically two dimensional during the upstroke. The lift coefficient agrees well with the measurements during the upstroke. However, there are differences during the downstroke. The computed lift coefficient undergoes a sharp drop during the start of the downstroke as the convected leading edge vortex moves away from the airfoil surface. This is followed by a recovery of the lift coefficient with the formation of a secondary trailing edge vortex. While these dynamics are clearly reflected in the predicted lift coefficient, the experimental evolution of lift during the downstroke maintains a fairly smooth and monotonic decrease in the lift coefficient with no lift recovery. The simulations also show that the reattachment process of the stalled airfoil is completed before the start of the upstroke in the subsequent cycle due to the high reduced frequency of the pitching cycle.

A modified tangent-gas approximation for two-dimensional steady flow

1958 ◽  
Vol 4 (6) ◽  
pp. 600-606 ◽  
Author(s):  
G. Power ◽  
P. Smith
Keyword(s):  
Least Squares ◽  
Steady Flow ◽  
Variational Approach ◽  
Least Squares Method ◽  
Two Dimensional ◽  
Subsonic Flows ◽  
Von Karman ◽  
Straight Line ◽  
Volume Relationship ◽  
Pressure Volume Relationship

A set of two-dimensional subsonic flows past certain cylinders is obtained using hodograph methods, in which the true pressure-volume relationship is replaced by various straight-line approximations. It is found that the approximation obtained by a least-squares method possibly gives best results. Comparison is made with values obtained by using the von Kármán-Tsien approximation and also with results obtained by the variational approach of Lush & Cherry (1956).

An extended use of the hydrogen bubble flow visualization method

AIAA Journal ◽  
1965 ◽  
Vol 3 (6) ◽  
pp. 1203-1203 ◽  
Author(s):  
WILLIAM O. CRIMINALE ◽  
R. W. NOWELL
Keyword(s):  
Flow Visualization ◽  
Bubble Flow ◽  
Visualization Method ◽  
Hydrogen Bubble

Flow Fields in a Two-Dimensional Diffuser With Extraction of Fluid on the Diverging Walls

1972 ◽  
Vol 94 (3) ◽  
pp. 226-232
Author(s):  
D. O. Rockwell
Keyword(s):  
Experimental Verification ◽  
Static Pressure ◽  
Flow Fields ◽  
Hydrogen Bubble ◽  
Two Dimensional ◽  
Stagnation Region ◽  
Pressure Distributions

A theory is developed to describe the inviscid core in two-dimensional unstalled diffusers with suction (extraction) on the diverging walls. Experimental wall static pressure distributions and streamline patterns agree well with those predicted theoretically. Under appropriate extraction conditions, a stagnation region is located downstream of the diverging wall extraction station. Experimental verification of the streamline patterns and of the location of this stagnation region was achieved via hydrogen bubble visualization. In addition, the possible stall conditions, which result if improper extraction is employed, are described qualitatively.

scholarly journals Asymptotic behavior of a steady flow in a two-dimensional pipe

2003 ◽  
Vol 158 (1) ◽  
pp. 39-58 ◽  
Author(s):  
Piotr Bogusław Mucha
Keyword(s):  
Asymptotic Behavior ◽  
Steady Flow ◽  
Two Dimensional
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