Steady and Unsteady Characteristics of Two Corner Separations in a Decelerating Square Channel Flow

2006 ◽  
Author(s):  
Yoichi Kinoue ◽  
Toshiaki Setoguchi ◽  
Norimasa Shiomi ◽  
Kenji Kaneko
Keyword(s):  
Channel Flow ◽  
Cross Correlation ◽  
Static Pressure ◽  
Three Dimensional ◽  
Side Wall ◽  
Turbulence Level ◽  
Square Channel ◽  
Unsteady Characteristics ◽  
Decelerating Channel Flow ◽  
Peak Value

The three-dimensional separation in a decelerating channel flow generated by the suction through a porous side wall had been investigated experimentally. Unsteady characteristics of two corner separations were especially focused on. The profiles of time averaged static pressure are two-dimensional in the height direction even in the case with large regions of corner separation. The contour of the turbulence level of the mainstream velocity shows two peak values which correspond to two corner separations. The value of cross-correlation gets large negative values without any lag and the value of coherence gets peak value at around 0.5–2 Hz. The corner separations near the top wall and near the bottom wall are not independent and keep coherent structure both with negative value of cross correlation function and with the frequency of around 0.5–2 Hz.

On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study

2000 ◽  
Author(s):  
R. V. Chima ◽  
E. R. McFarland ◽  
J. R. Wood ◽  
J. Lepicovsky
Keyword(s):  
Static Pressure ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wave Structure ◽  
Experimental Measurements ◽  
Flow Conditions ◽  
Pressure Sensitive ◽  
Transonic Flutter ◽  
Probe Measurements

The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, side-wall interference was minimized and excellent periodicity was obtained.

Vortices within the Speparation in a Decelerating Square Channel Flow : Profiles of the Time-Averaged Velocity and Turbulence Level

2004 ◽  
Vol 2004 (0) ◽  
pp. 193
Author(s):  
Yoichi KINOUE ◽  
Toshiaki SETOGUCHI ◽  
Mohammad MAUMUN ◽  
Norimasa SHIOMI ◽  
Kenji KANEKO
Keyword(s):  
Channel Flow ◽  
Turbulence Level ◽  
Square Channel ◽  
Flow Profiles

Vortices Within the Flow Separation in a Decelerating Channel Flow: Time-Averaged Characteristics

2002 ◽  
Author(s):  
Y. Kinoue ◽  
T. Setoguchi ◽  
K. Kaneko ◽  
T. Murasaki ◽  
M. Inoue
Keyword(s):  
Channel Flow ◽  
Flow Separation ◽  
Velocity Gradient ◽  
Side Wall ◽  
Comprehensive Understanding ◽  
3D Flow ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Side Walls ◽  
Decelerating Channel Flow

An experimental equipment for studying the vortex behavior in 3D flow separation was constructed to have a comprehensive understanding of a separated channel flow. The separation occurs on three side walls of the straight channel by the suction from a porous side wall. Several types of separation can be generated by changing the sucked flow rate and providing the inlet flow with velocity gradient. For a strong decelerating-flow without the inlet velocity gradient, an alternate flow pattern with an opposite vortex occurs at considerably irregular intervals. With the inlet velocity gradient, a vortex appears and disappears along an inclined separation line for a moderate decelerating-flow, and a large stable vortex exists in the separation region for a strong decelerating-flow. The behavior of these vortices was examined and discussed in relation to the vortices including in the inlet flow.

2417 Unsteady Characteristics of Two Corner Separations in a Decelerating Square Channel Flow

2006 ◽  
Vol 2006.2 (0) ◽  
pp. 153-154
Author(s):  
Yoichi KINOUE ◽  
Toshiaki SETOGUCHI ◽  
Norimasa SHIOMI ◽  
Kenji KANEKO
Keyword(s):  
Channel Flow ◽  
Square Channel ◽  
Unsteady Characteristics

The Flow Around Surface-Mounted, Prismatic Obstacles Placed in a Fully Developed Channel Flow (Data Bank Contribution)

1993 ◽  
Vol 115 (1) ◽  
pp. 85-92 ◽  
Author(s):  
R. Martinuzzi ◽  
C. Tropea
Keyword(s):  
Channel Flow ◽  
Static Pressure ◽  
Laser Sheet ◽  
Three Dimensional ◽  
Data Bank ◽  
Pressure Measurements ◽  
Two Dimensional ◽  
Middle Region ◽  
Visualization Techniques ◽  
Separating Flows

The flow field around surface-mounted, prismatic obstacles with different spanwise dimensions was investigated using the crystal violet, oil-film and laser-sheet visualization techniques as well as by static pressure measurements. The aim of this study is to highlight the fundamental differences between nominally two-dimensional and fully three-dimensional obstacle flows. All experiments were performed in a fully developed channel flow. The Reynolds number, based on the height of the channel, lay between 8 × 104 and 1.2 × 105. Results show that the middle region of the wake is nominally two-dimensional for width-to-height ratios (W/H) greater than 6. The separated region in front of wider obstacles is characterized by the appearance of a quasi-regular distribution of saddle and nodal points on the forward face of the obstacles. These three-dimensional effects are considered to be inherent to such separating flows with stagnation.

Active Control of the Corner Separation on a Highly Loaded Compressor Cascade With Periodic Non-Steady Boundary Conditions by Means of Fluidic Actuators

2015 ◽  
Author(s):  
Marcel Staats ◽  
Wolfgang Nitsche
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Active Flow Control ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Side Wall ◽  
Compressor Cascade ◽  
Detonation Engine ◽  
The Impact ◽  
Highly Loaded

This contribution discusses the impact of a non-steady outflow condition on the compressor stator flow that is forced through a mimic in the wake of a linear low speed cascade to simulate the conditions that would be expected in a pulsed detonation engine. 2D/3C-PIV measurements were made to describe the flow field in the passage. Detailed wake measurements provide information about static pressure rise as well as total pressure loss. The stator profile used for the investigations is highly loaded and operates with three-dimensional flow separations under design conditions and without active flow control. It is shown that side wall actuation helps to stabilize the flow field at every phase angle and extends the operating range of the compressor stator. Furthermore, the static pressure gain can be increased by 6% with a 4% loss reduction in time averaged data.

Wake Flow of Single and Multiple Yawed Cylinders

2004 ◽  
Vol 126 (5) ◽  
pp. 861-870 ◽  
Author(s):  
A. Thakur ◽  
X. Liu ◽  
J. S. Marshall
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wake Flow ◽  
Upstream Region ◽  
Two Dimensional ◽  
Cylinder Wake ◽  
Dimensional Approximation ◽  
The Face ◽  
Drag And Lift

An experimental and computational study is performed of the wake flow behind a single yawed cylinder and a pair of parallel yawed cylinders placed in tandem. The experiments are performed for a yawed cylinder and a pair of yawed cylinders towed in a tank. Laser-induced fluorescence is used for flow visualization and particle-image velocimetry is used for quantitative velocity and vorticity measurement. Computations are performed using a second-order accurate block-structured finite-volume method with periodic boundary conditions along the cylinder axis. Results are applied to assess the applicability of a quasi-two-dimensional approximation, which assumes that the flow field is the same for any slice of the flow over the cylinder cross section. For a single cylinder, it is found that the cylinder wake vortices approach a quasi-two-dimensional state away from the cylinder upstream end for all cases examined (in which the cylinder yaw angle covers the range 0⩽ϕ⩽60°). Within the upstream region, the vortex orientation is found to be influenced by the tank side-wall boundary condition relative to the cylinder. For the case of two parallel yawed cylinders, vortices shed from the upstream cylinder are found to remain nearly quasi-two-dimensional as they are advected back and reach within about a cylinder diameter from the face of the downstream cylinder. As the vortices advect closer to the cylinder, the vortex cores become highly deformed and wrap around the downstream cylinder face. Three-dimensional perturbations of the upstream vortices are amplified as the vortices impact upon the downstream cylinder, such that during the final stages of vortex impact the quasi-two-dimensional nature of the flow breaks down and the vorticity field for the impacting vortices acquire significant three-dimensional perturbations. Quasi-two-dimensional and fully three-dimensional computational results are compared to assess the accuracy of the quasi-two-dimensional approximation in prediction of drag and lift coefficients of the cylinders.

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