A Note on the Transition Observations on an Axisymmetric Body and Some Related Fluctuating Wall Pressure Measurements

1975 ◽  
Vol 97 (1) ◽  
pp. 82-86 ◽  
Author(s):  
V. H. Arakeri
Keyword(s):  
Pressure Transducer ◽  
Critical Frequency ◽  
Dominant Frequency ◽  
Axisymmetric Body ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Pressure Measurements ◽  
Schlieren Method ◽  
Layer Transition ◽  
Transducer Signal

Boundary layer transition on an axisymmetric body up to Reynolds number of 1.26 × 106 was observed by schlieren method of flow visualization developed for water tunnel use. The spectrum of the flush mounted pressure transducer signal showed a dominant frequency to exist at transition and further, this frequency was in close agreement with the predicted critical frequency by Smith’s approximate method of transition calculation based on linear stability theory.

Velocity and Pressure Measurements Along a Row of Confined Cylinders

2006 ◽  
Author(s):  
Barton L. Smith ◽  
Jack J. Stepan ◽  
Donald M. McEligot
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Symmetry Plane ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Recirculation Region ◽  
Pressure Measurements ◽  
Layer Transition ◽  
Flow Experiments

The results of flow experiments performed in a cylinder array designed to mimic a VHTR Nuclear Plant lower plenum design are presented. Pressure drop and velocity field measurements were made. Based on these measurements, five regimes of behavior are identified that are found to depend on Reynolds number. It is found that the recirculation region behind the cylinders is shorter than that of half cylinders placed on the wall representing the symmetry plane. Unlike a single cylinder, the separation point is found to always be on the rear of the cylinders, even at very low Reynolds number. Boundary layer transition is found to occur at much lower Reynolds numbers than previously reported.

Smoke Visualization of Boundary-Layer Transition on a Spinning Axisymmetric Body

AIAA Journal ◽  
1981 ◽  
Vol 19 (12) ◽  
pp. 1607-1608 ◽  
Author(s):  
T. J. Mueller ◽  
R. C. Nelson ◽  
J. T. Kegelman ◽  
M. V. Morkovin
Keyword(s):  
Boundary Layer ◽  
Axisymmetric Body ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Smoke Visualization

scholarly journals A CFD-Compatible Amplification Factor Transport Equation for Oblique Tollmien-Schlichting Waves in Supersonic Boundary Layers

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
JiaKuan Xu ◽  
Lei Qiao ◽  
Junqiang Bai
Keyword(s):  
Transport Equation ◽  
Amplification Factor ◽  
Flow Instability ◽  
Supersonic Flows ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Two Dimensional ◽  
Layer Transition ◽  
Low Speed ◽  
Tollmien Schlichting

Boundary layer transition is a hot research topic in fluid mechanics and aerospace engineering. In low-speed flows, two-dimensional Tollmien-Schlichting (T-S) waves always dominate the flow instability, which has been modeled by Coder and Maughmer from 2013. However, in supersonic flows, three-dimensional oblique Tollmien-Schlichting waves become dominant in flow instability. Inspired by Coder and Maughmer’s NTS amplification factor transport equation for two-dimensional Tollmien-Schlichting waves in low-speed flows and Kroo and Sturdza’s linear stability theory (LST) analysis results for oblique Tollmien-Schlichting waves in supersonic flows, a new amplification factor transport equation for oblique Tollmien-Schlichting waves has been developed based on LST. The compressible Falkner-Skan similarity equations are introduced to build the relationships between nonlocal variables and local variables so that all the variables used in the present model can be calculated using local variables. Applications of this new transport equation to the flows over supersonic flat plate, 3% thick biconvex airfoil, and one modified supersonic laminar airfoil show promising results compared with the standard LST analysis results.

Behaviour of a natural laminar flow aerofoil in flight through atmospheric turbulence

2015 ◽  
Vol 767 ◽  
pp. 394-429 ◽  
Author(s):  
Andreas D. Reeh ◽  
C. Tropea
Keyword(s):  
Atmospheric Turbulence ◽  
Base Flow ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Oncoming Flow ◽  
Layer Transition ◽  
Weakly Nonlinear ◽  
Free Stream Turbulence ◽  
Wing Section ◽  
Insight Into

AbstractAtmospheric turbulence is encountered frequently in flight and it creates oncoming flow disturbances of varying direction and magnitude for aircraft passing through turbulent zones. The unique measurement set-up on a motorised glider enables the investigation of the flow processes acting on a laminar wing section in flight through atmospheric turbulence. The expected quasi-steady aerofoil characteristics are deduced from an investigation of boundary-layer transition under calm flight conditions. Spanwise frequency–wavenumber spectra and comparisons with linear stability theory (LST) yield insight into the linear and weakly nonlinear stages of transition. Simultaneous measurement of the oncoming flow, characteristic flow quantities on the wing section and the motion of the aerofoil enables correlations between these quantities and provides insight into the unsteady flight physics. Emphasis is placed on the response of laminar–turbulent transition to moderate free-stream turbulence on both sides of the wing section. On the lower side of the aerofoil significant and rapid upstream fluctuations of transition are observed, which correspond closely to variations in the pressure distribution. Wavelet analysis is applied to gain insight into the composition of these streamwise excursions of the transition front in the time-pseudo-frequency domain. It is shown that they are driven by rapid transient base-flow changes and that transition is initiated by a short growth stage of Tollmien–Schlichting (TS) waves.

Unsteady Boundary-Layer Transition in Flow Periodically Disturbed by Wakes

1992 ◽  
Author(s):  
U. Orth
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Pressure Gradients ◽  
Unsteady Boundary Layer ◽  
Velocity Measurements ◽  
Ensemble Averaging ◽  
Layer Transition ◽  
Wake Turbulence ◽  
Turbomachinery Blades

Boundary layers on turbomachinery blades develop in a flow which is periodically disturbed by the wakes of upstream blade cascades. These wakes have a significant effect upon laminar-turbulent boundary-layer transition. In order to study these effects, detailed velocity measurements using hot-wire probes were performed within the boundary-layer of a plate in flow periodically disturbed by wakes produced by bars moving transversal to the flow. The measurements were evaluated using the ensemble-averaging technique. The results show how the wake disturbance enters the boundary-layer and leads to a turbulent patch, which grows and is carried downstream. In favorable pressure gradients, transition due to wake turbulence occured much earlier than predicted by linear stability theory. Between two wakes, laminar becalmed regions were observed far beyond the point at which the undisturbed boundary-layer was already turbulent.

Boundary-Layer Transition on an Axisymmetric Body at Incidence at Mach 1.2

AIAA Journal ◽  
2006 ◽  
Vol 44 (5) ◽  
pp. 973-980 ◽  
Author(s):  
Hiroki Sugiura ◽  
Naoko Tokugawa ◽  
Yoshine Ueda
Keyword(s):  
Boundary Layer ◽  
Axisymmetric Body ◽  
Boundary Layer Transition ◽  
Layer Transition

scholarly journals Blind disturbance separation and identification in a transitional boundary layer using minimal sensing

2021 ◽  
Vol 927 ◽  
Author(s):  
I. Gluzman ◽  
J. Cohen ◽  
Y. Oshman
Keyword(s):  
Boundary Layer ◽  
Numerical Study ◽  
A Priori ◽  
Boundary Layer Transition ◽  
Linear Stability Theory ◽  
Plasma Actuators ◽  
Flow State ◽  
Layer Transition ◽  
Novel Approach ◽  
Tollmien Schlichting

A novel approach is presented for identifying disturbance sources in wall-bounded shear flows. The underlying approach models the flow state, as measured by sensors embedded in the flow, as a mixture of disturbance sources. The degenerate unmixing estimation technique is adopted as a blind source separation technique to recover the separate sources and their unknown mixing process. The efficiency of this approach stems from its ability to isolate any, a priori unknown, number of sources, using two sensors only. Furthermore, by adding a single additional sensor, the method is expanded to also determine the propagation velocity vector of each of the isolated sources, based on sensor readings from three sensors appropriately located in the flow field. Theoretical guidelines for locating the sensors are provided. The power of the method is demonstrated via computer simulations and wind-tunnel experiments. The numerical study considers disturbances comprising discrete Tollmien–Schlichting waves and wave packets. Linear stability theory is used to model source mixtures acquired by sensors placed in a Blasius boundary layer. The experimental study investigates the flow over a flat plate, with hot wires as sensors, and a loudspeaker and plasma actuators as source generators. Based on numerical and experimental demonstrations, it is believed that the new approach should prove useful in various applications, including active control of boundary layer transition from laminar to turbulent flow.

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