A PIV Study of a Plasma Discharge Flow-Control Actuator on a Flat Plate in an Aggressive Pressure Induced Separation

2006 ◽  
Author(s):  
I. G. Boxx ◽  
J. M. Newcamp ◽  
M. E. Franke ◽  
N. M. Woods ◽  
R. B. Rivir
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Pressure Distribution ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Suction Side ◽  
Separation Point ◽  
Initial Separation ◽  
Static Pressure Distribution

An experimental study was performed to examine the effect of a dielectric barrier discharge plasma flow control actuator. The actuator was applied to a flat plate boundary layer in a pressure distribution approximating that of the suction side of an aft-loaded low-pressure turbine blade. Particle image velocimetry was used to obtain two-dimensional velocity field data on four boundary layers with velocity profiles that included fully attached laminar, turbulent, nominally separated and high-separated. Values of Rec ranged from 4500 to 75,000. For the separated boundary-layers the actuator was located downstream of the separation point. Four E-fields were characterized for each case. The actuator was able to induce boundary layer reattachment even when located downstream of the initial separation point. The length scale over which this re-attachment occurs was strongly dependent upon the applied E-field. The actuators also caused significant reduction in the overall boundary layer thickness as a result of the modification of the near-wall static pressure distribution.

Large-Eddy Simulation of Corner Separation in a Compressor Cascade

2018 ◽  
Author(s):  
Byung-Young Min ◽  
Jongwook Joo ◽  
Jomar Mendoza ◽  
Jin Lee ◽  
Guoping Xia ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Boundary Layers ◽  
Best Practice ◽  
Plate Boundary ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Compressor Cascade ◽  
Corner Separation ◽  
Institute Of Technology

In this paper, wall-resolved LES computations for a compressor cascade from Ecole Centrale de Lyon [1] are presented. A computational grid containing about 600 million computational cells was used in these simulations. This grid resolves the details of tripping strips used in the experiments, located near the leading edge of the blade on both suction and pressure sides. Endwall turbulent boundary layer at cascade inlet was measured to be at a momentum thickness based Reynolds number of about 7000 to 8000, with quite a bit of variation in the pitchwise direction. In order to avoid the cost of simulating the entire duct upstream of the cascade, and any auxiliary flat plate boundary layer simulations, the inlet fluctuations for LES computations were generated using digital filtering method for synthetic turbulence generation [27]. Turbulence statistics from a database of high fidelity eddy simulations of flat plate boundary layers (at similar Reynolds numbers) from KTH Royal Institute of Technology in Stockholm [28] were used to fully define the properties of the cascade inlet boundary layer. In this paper, time-averaged results from three LES computations for this configuration are presented — one with no inlet fluctuations at the cascade endwall at the domain inlet, and then two computations with inlet fluctuations and boundary layers at Reθ of 7000 and 8183. These provide a sensitivity of LES predictions of corner separation in the cascade to the boundary layer thickness at cascade inlet. A comparison of these simulations with prior DDES (and RANS) simulations from UTRC [26], as well as existing LES results from Ecole Centrale de Lyon [12], allows to further the understanding of critical elements of the endwall flow physics. More specifically, it provides more insight into which phenomena need to be sufficiently resolved (e.g. horseshoe vortex) in order to capture both the average behavior of the corner separation, as well as its unsteady dynamics. In addition, it provides new information which will help define best practice guidelines for the use of eddy simulations to resolve endwall features in compressors at off-design conditions.

scholarly journals A class of exact Navier–Stokes solutions for homogeneous flat-plate boundary layers and their linear stability

2014 ◽  
Vol 752 ◽  
pp. 462-484 ◽  
Author(s):  
Michael O. John ◽  
Dominik Obrist ◽  
Leonhard Kleiser
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Linear Stability ◽  
Boundary Layers ◽  
Stokes Equations ◽  
Plate Boundary ◽  
Navier Stokes ◽  
Transition Prediction ◽  
Neutral Curves ◽  
Tollmien Schlichting

AbstractWe introduce a new boundary layer formalism on the basis of which a class of exact solutions to the Navier–Stokes equations is derived. These solutions describe laminar boundary layer flows past a flat plate under the assumption of one homogeneous direction, such as the classical swept Hiemenz boundary layer (SHBL), the asymptotic suction boundary layer (ASBL) and the oblique impingement boundary layer. The linear stability of these new solutions is investigated, uncovering new results for the SHBL and the ASBL. Previously, each of these flows had been described with its own formalism and coordinate system, such that the solutions could not be transformed into each other. Using a new compound formalism, we are able to show that the ASBL is the physical limit of the SHBL with wall suction when the chordwise velocity component vanishes while the homogeneous sweep velocity is maintained. A corresponding non-dimensionalization is proposed, which allows conversion of the new Reynolds number definition to the classical ones. Linear stability analysis for the new class of solutions reveals a compound neutral surface which contains the classical neutral curves of the SHBL and the ASBL. It is shown that the linearly most unstable Görtler–Hämmerlin modes of the SHBL smoothly transform into Tollmien–Schlichting modes as the chordwise velocity vanishes. These results are useful for transition prediction of the attachment-line instability, especially concerning the use of suction to stabilize boundary layers of swept-wing aircraft.

scholarly journals Oblique route to turbulence

2011 ◽  
Vol 674 ◽  
pp. 1-4
Author(s):  
MUJEEB R. MALIK
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Direct Numerical Simulations ◽  
Two Dimensional ◽  
Mach 3 ◽  
Transition Scenario ◽  
Flat Plate Boundary Layer

Direct numerical simulations have been performed by Mayer, Von Terzi & Fasel (J. Fluid Mech., this issue, vol. 674, 2011, pp. 5–42) to demonstrate that oblique-mode breakdown leads to fully turbulent flow for a Mach 3 flat-plate boundary layer. Since very low level of initial disturbances is required for this transition scenario, oblique-mode breakdown is the most potent mechanism for transition in two-dimensional supersonic boundary layers in low-disturbance environments relevant to flight.

scholarly journals Evolution of localized artificial disturbance in 2D and 3D supersonic boundary layers

2018 ◽  
Vol 234 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Aleksey Yatskikh ◽  
Yury Yermolaev ◽  
Alexander Kosinov ◽  
Nikolai Semionov ◽  
Alexander Semenov
Keyword(s):  
Boundary Layer ◽  
Wave Packet ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Hot Wire ◽  
Swept Wing ◽  
Artificial Disturbance ◽  
2D And 3D ◽  
Symmetric Shape

The evolution of a controlled broadband wave packet in flat-plate and swept-wing supersonic boundary layers was experimentally investigated at Mach number M = 2. The wave packet was introduced into the boundary layer by a localized pulse electrical discharge. The structure and evolution downstream of the wave packet were studied by hot-wire measurements. It was found that the wave packet has a symmetric shape in a flat-plate boundary layer, whereas there is asymmetry in case of a swept-wing one. The spectral analysis of the development of different modes of the wave packet was provided.

Transition in the Infinite Swept Attachment Line Boundary Layer

1979 ◽  
Vol 30 (4) ◽  
pp. 607-629 ◽  
Author(s):  
D.I.A. Poll
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Flat Plate ◽  
Boundary Layers ◽  
Free Stream ◽  
Plate Boundary ◽  
Swept Wing ◽  
Civil Aircraft ◽  
Transition Behaviour ◽  
Attachment Line

SummaryThe transition behaviour of the boundary layer which is formed along an infinite swept attachment line has been studied experimentally. Circular trip wires and turbulent flat plate boundary layers have been used as sources of disturbance and the range of parameters covered has been such that the results are directly applicable to full scale flight conditions. Simple criteria have been deduced which allow the state of the boundary layer to be determined for given geometric and free stream properties. Sample calculations for typical swept wing configurations suggest that the majority of civil aircraft will have turbulent attachment lines in the cruise and that subsequent relaminarisation in regions of favourable pressure gradient is unlikely.

Flat-Plate Boundary Layers in Accelerated Flow

2016 ◽  
Author(s):  
Pascal Bader ◽  
Manuel Pschernig ◽  
Wolfgang Sanz ◽  
Jakob Woisetschläger ◽  
Franz Heitmeir ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Skin Friction ◽  
Boundary Layers ◽  
Laser Doppler Anemometry ◽  
Plate Boundary ◽  
Boundary Layer Transition ◽  
Test Case ◽  
Transitional Region ◽  
Layer Transition

Flow in turbomachines is generally highly turbulent. The boundary layers, however, often exhibit laminar-to-turbulent transition. But also relaminarization of the turbulent flow may occur. The state of the boundary layer is important, since it strongly influences transport phenomena like skin friction and heat transfer. It is therefore vitally important for the designer to understand the process of boundary layer transition and to determine the position of transition onset and the length of the transitional region. In order to get into the details of transition and relaminarization it is helpful to study simplified test cases first. Therefore, in this paper a relaminarization test case for a simple geometry is investigated: The boundary layer flow along a flat plate is exposed to acceleration with three different acceleration parameters, which is known as a crucial parameter for relaminarization. Measurements were performed for the inlet free-stream velocities of 5 m/s and 9 m/s. Several experimental techniques for detecting transition were tested at the institute before their application. In this work, Laser-Doppler anemometry (LDA) measurements were performed, since this optical technique is non-intrusive and does not disturb the flow. Therefore it can also be used in narrow flow passages where probe blockage can be crucial. As an outcome of this study, an insight into the process of relaminarization is presented. Although the key onset values for relaminarization stated in literature are fulfilled with the test setup, full relaminarization over the whole boundary layer has not been achieved. It seems, that using only the skin friction as indicator for relaminarization is not sufficient.

Tip Leakage in a Centrifugal Impeller

1989 ◽  
Vol 111 (3) ◽  
pp. 244-249 ◽  
Author(s):  
T. Z. Farge ◽  
M. W. Johnson ◽  
T. M. A. Maksoud
Keyword(s):  
Boundary Layer ◽  
Pressure Distribution ◽  
Static Pressure ◽  
Suction Side ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Static Pressure Distribution ◽  
Impeller Outlet

The effects of tip leakage have been studied using a 1-m-dia shrouded impeller where a leakage gap is left between the inside of the shroud and the impeller blades. A comparison is made with results for the same impeller where the leakage gap is closed. The static pressure distribution is found to be almost unaltered by the tip leakage, but significant changes in the secondary velocities alter the size and position of the passage wake. Low-momentum fluid from the suction-side boundary layer of the measurement passage and tip leakage fluid from the neighboring passage contribute to the formation of a wake in the suction-side shroud corner region. The inertia of the tip leakage flow then moves this wake to a position close to the center of the shroud at the impeller outlet.

Large-Eddy Simulation of Supersonic Flat-Plate Boundary Layers Using the Monotonically Integrated Large-Eddy Simulation (MILES) Technique

2002 ◽  
Vol 124 (4) ◽  
pp. 868-875 ◽  
Author(s):  
H. Yan ◽  
D. Knight ◽  
A. A. Zheltovodov
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Large Eddy Simulation ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy

A supersonic flat-plate boundary layer at a Reynolds number of 2×104 based on the inflow boundary layer thickness is investigated at different Mach numbers (M=2.88 and 4) using the monotonically integrated large-eddy simulation (MILES) technique. The inherent numerical dissipation is taken as an implicit subgrid scales (SGS) model to close the Favre-filtered compressible Navier-Stokes (NS) equations. A finite volume method with second-order accuracy in time and space is implemented for the solution of the Navier-Stokes equations on an unstructured grid of tetrahedra. The heat transfer coefficient is predicted by simulating both adiabatic and isothermal cases. The mean flowfield and turbulent stresses are in good agreement with experiment. The relationship between the predicted skin friction coefficient and heat transfer coefficient is in close agreement with the Reynolds analogy factor. The variation of turbulent Prandtl number cross the boundary layer falls within the experimental envelope. These are the first LES predictions of adiabatic and isothermal supersonic flat plate boundary layers using the MILES technique.

The Linear Stability of a Flat Plate Boundary-Layer Approaching a Cylindrical Obstacle

1992 ◽  
Vol 114 (3) ◽  
pp. 306-312 ◽  
Author(s):  
R. E. Spall ◽  
M. R. Malik
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Linear Stability ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Region Of Interest ◽  
Transition Process ◽  
Low Frequencies ◽  
Initial Separation ◽  
Tollmien Schlichting

The linear stability of the low-speed three-dimensional flow over a flat plate with an attached cylinder is studied. The region of interest is upstream of the initial separation point and includes the effects of both adverse and favorable pressure gradients, as well as crossflow. The resulting boundary-layer is subject to both the Tollmien-Schlichting (TS) and crossflow instabilities. Linear stability calculations, using N-factor correlations, indicate that the transition process would be dominated by TS instabilities, although for low frequencies crossflow-type disturbances are important.

Sign in / Sign up

Export Citation Format

Share Document