Boundary interactions with vortical disturbance in an acoustofluidic channel

2017 ◽  
Vol 141 (5) ◽  
pp. 3505-3505
Author(s):  
Kavitha Chandra ◽  
Charles Thompson ◽  
Vineet Mehta
Keyword(s):  
Vortical Disturbance

scholarly journals Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

1998 ◽  
Vol 120 (4) ◽  
pp. 705-713 ◽  
Author(s):  
S. T. Hsu ◽  
A. M. Wo
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Forced Response ◽  
Suction Surface ◽  
Blade Loading ◽  
Beneficial Use ◽  
Unsteady Loading ◽  
Vortical Disturbance ◽  
First Time

This paper demonstrates reduction of stator unsteady loading due to forced response in a large-scale, low-speed, rotor/stator/rotor axial compressor rig by clocking the downstream rotor. Data from the rotor/stator configuration showed that the stator response due to the upstream vortical disturbance reaches a maximum when the wake impinges against the suction surface immediately downstream of the leading edge. Results from the stator/rotor configuration revealed that the stator response due to the downstream potential disturbance reaches a minimum with a slight time delay after the rotor sweeps pass the stator trailing edge. For the rotor/stator/rotor configuration, with Gap1 = 10 percent chord and Gap2 = 30 percent chord, results showed a 60 percent reduction in the stator force amplitude by clocking the downstream rotor so that the time occurrence of the maximum force due to the upstream vortical disturbance coincides with that of the minimum force due to the downstream potential disturbance. This is the first time, the authors believe, that beneficial use of flow unsteadiness is definitively demonstrated to reduce the blade unsteady loading.

scholarly journals Navier-Stokes and Potential Calculations of Axial Spacing Effect on Vortical and Potential Disturbances and Gust Response in an Axial Compressor

1995 ◽  
Author(s):  
Meng-Hsuan Chung ◽  
Andrew M. Wo
Keyword(s):  
Lower Order ◽  
Spacing Effect ◽  
Axial Compressor ◽  
Interaction Effects ◽  
Moving Frame ◽  
Navier Stokes ◽  
Blade Row ◽  
Vortical Disturbance ◽  
Blade Row Interaction ◽  
Gust Response

The effect of blade row axial spacing on vortical and potential disturbances and gust response is studied for a compressor stator/rotor configuration near design and at high loadings using 2D incompressible Navier-Stokes and potential codes, both written for multistage calculations. First, vortical and potential disturbances downstream of the isolated stator in the moving frame are defined; these disturbances exclude blade row interaction effects. Then, vortical and potential disturbances for the stator/rotor configuration are calculated for axial gaps of 10%, 20%, and 30% chord. Results show that the potential disturbance is uncoupled; the potential disturbance calculated from the isolated stator configuration is a good approximation for that from the stator/rotor configuration for all three axial gaps. The vortical disturbance depends strongly on blade row interactions. Low order modes of vortical disturbance are of substantial magnitude and decay much more slowly downstream than do those of potential disturbance. Vortical disturbance decays linearly with increasing mode except very close to the stator trailing edge. For a small axial gap, lower order modes of both vortical and potential disturbances must be included to determine the rotor gust response.

High-Lift Airfoil Interacting with a Vortical Disturbance: Wind-Tunnel Measurements

AIAA Journal ◽  
2015 ◽  
Vol 53 (6) ◽  
pp. 1681-1692 ◽  
Author(s):  
S. Klein ◽  
D. Hoppmann ◽  
P. Scholz ◽  
R. Radespiel
Keyword(s):  
Wind Tunnel ◽  
High Lift ◽  
Wind Tunnel Measurements ◽  
Vortical Disturbance

scholarly journals Navier–Stokes and Potential Calculations of Axial Spacing Effect on Vortical and Potential Disturbances and Gust Response in an Axial Compressor

1997 ◽  
Vol 119 (3) ◽  
pp. 472-481 ◽  
Author(s):  
M.-H. Chung ◽  
A. M. Wo
Keyword(s):  
Spacing Effect ◽  
Axial Compressor ◽  
Leading Edge ◽  
Moving Frame ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Blade Row ◽  
Vortical Disturbance ◽  
Blade Row Interaction ◽  
Gust Response

The effect of blade row axial spacing on vortical and potential disturbances and gust response is studied for a compressor stator/rotor configuration near design and at high loadings using two-dimensional incompressible Navier–Stokes and potential codes, both written for multistage calculations. First, vortical and potential disturbances downstream of the isolated stator in the moving frame are defined; these disturbances exclude blade row interaction effects. Then, vortical and potential disturbances for the stator/rotor configuration are calculated for axial gaps of 10, 20, and 30 percent chord. Results show that the potential disturbance is uncoupled locally; the potential disturbance calculated from the isolated stator configuration is a good approximation for that from the stator/rotor configuration upstream of the rotor leading edge at the locations studied. The vortical disturbance depends strongly on blade row interactions. Low-order modes of vortical disturbance are of substantial magnitude and decay much more slowly downstream than do those of potential disturbance. Vortical disturbance decays linearly with increasing mode except very close to the stator trailing edge. For a small axial gap, e.g., 10 percent chord, both vortical and potential disturbances must be included to determine the rotor gust response.

Receptivity to freestream vortical disturbance of 2D and 3D airfoils

1996 ◽  
Author(s):  
Zhining Liu ◽  
Guohua Xiong ◽  
Chaoqun Liu ◽  
R. Joslin
Keyword(s):  
Vortical Disturbance ◽  
2D And 3D

Leading-edge effects in bypass transition

2007 ◽  
Vol 572 ◽  
pp. 471-504 ◽  
Author(s):  
S. NAGARAJAN ◽  
S. K. LELE ◽  
J. H. FERZIGER
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Bypass Transition ◽  
Turbulent Spot ◽  
Eddy Simulation ◽  
Turbulence Transition ◽  
Large Eddy ◽  
Low Speed Streaks ◽  
Vortical Disturbance ◽  
Blunt Leading Edge

The effect of a blunt leading edge on bypass transition is studied by numerical simulation. A mixed direct and large-eddy simulation of a flat plate with a super-ellipse leading edge is carried out at various conditions. Onset and completion of transition is seen to move upstream with increasing bluntness. For sharper leading edges, at lower levels of turbulence, transition usually occurs through instabilities on low-speed streaks as observed by Jacobs & Durbin (2001) and Brandt et al. (2004) whereas increasing either the turbulence intensity or the leading-edge bluntness brings into play another mechanism. Free-stream vortices are amplified at the leading edge because of stretching. In the case of particularly strong vortices, this interaction induces a localized streamwise vortical disturbance in the boundary layer which then grows as it convects downstream and eventually breaks down to form a turbulent spot. These disturbances, which are localized and hence wavepacket-like, move at speeds in the range 0.55 U∞–0.65 U∞ and occur in the lower portion of the boundary layer. Simulations conducted with isolated vortices confirm such a response of the boundary layer.

scholarly journals Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

1997 ◽  
Author(s):  
S. T. Hsu ◽  
Andrew M. Wo
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Forced Response ◽  
Suction Surface ◽  
Blade Loading ◽  
Beneficial Use ◽  
Unsteady Loading ◽  
Vortical Disturbance ◽  
First Time

This paper demonstrates reduction of stator unsteady loading due to forced response in a large-scale, low-speed, rotor/stator/rotor axial compressor rig by clocking the downstream rotor. Data from the rotor/stator configuration showed that the stator response due to the upstream vortical disturbance reaches a maximum when the wake impinges against the suction surface immediately downstream of the leading edge. Results from the stator/rotor configuration revealed that the stator response due to the downstream potential disturbance reaches a minimum with a slight time delay after the rotor sweeps pass the stator trailing edge. For the rotor/stator/rotor configuration, with Gap1= 10% chord and Gap2= 30% chord, results showed a 60% reduction in the stator force amplitude by clocking the downstream rotor so that the time occurrence of the maximum force due to the upstream vortical disturbance coincides with that of the minimum force due to the downstream potential disturbance. This is the first time, the authors believe, that beneficial use of flow unsteadiness is definitively demonstrated to reduce the blade unsteady loading.

scholarly journals Finescale Doppler Radar Observation of a Tornado and Low-Level Misocyclones within a Winter Storm in the Japan Sea Coastal Region

2011 ◽  
Vol 139 (2) ◽  
pp. 351-369 ◽  
Author(s):  
Hanako Y. Inoue ◽  
Kenichi Kusunoki ◽  
Wataru Kato ◽  
Hiroto Suzuki ◽  
Toshiaki Imai ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Temporal Evolution ◽  
Surface Wind ◽  
Coastal Region ◽  
Japan Sea ◽  
Winter Storm ◽  
Low Level ◽  
Convergence Line ◽  
The Japan Sea ◽  
Vortical Disturbance

Abstract Life histories of low-level misocyclones, one of which corresponded to a tornado vortex within a winter storm in the Japan Sea coastal region on 1 December 2007, were observed from close range by X-band Doppler radar of the East Japan Railway Company. Continuous plan position indicator (PPI) observations at 30-s intervals at the low-elevation angle revealed at least four cyclonic misocyclones within the head of the comma-shaped echo of the vortical disturbance under winter monsoon conditions. The meso-β-scale vortical disturbance developed within the weak frontal zone at the leading edge of cold-air outbreaks. High-resolution observation of misocyclones revealed the detailed structures of these misocyclones and their temporal evolution. As the parent storm evolved, a low-level convergence line was observed at the edge of the easternmost misocyclone. This convergence line was considered to be important for the initiation and development of the misocyclones and the tornado through vortex stretching. The strongest misocyclone gradually intensified as its diameter contracted until landfall, and then began to dissipate soon after landfall. The temporal evolution of the misocyclones through landfall is discussed. Surface wind and pressure variations suggested a cyclonic vortex passage, which was consistent with the passage of the radar-derived misocyclone. The observed pressure drop was also consistent with that computed from the cyclostrophic equation for the modified Rankine vortex. The observed behavior of two adjacent misocyclones was primarily consistent with the rotational flow associated with the other misocyclone. The generation and development processes of the tornado and misocyclones are discussed.

Distortion of the stagnation-point flow due to cross-stream vorticity in the external flow

1995 ◽  
Vol 352 (1700) ◽  
pp. 443-452 ◽  
Keyword(s):  
Boundary Layer ◽  
Stagnation Point ◽  
Three Dimensional ◽  
External Flow ◽  
Stagnation Point Flow ◽  
Spanwise Direction ◽  
Two Dimensional ◽  
Streamwise Vorticity ◽  
Flow Reynolds Number ◽  
Vortical Disturbance

The structure of the stagnation-point flow in the presence of weak steady cross-stream vorticity in the external flow is investigated. A specific case of the two-dimensional basic forward stagnation-point flow past a circular cylinder is considered with the external three-dimensional vortical disturbance taken to be periodic in the spanwise direction with a wavelength λ*≤λ* N =π D /( Re D ) 1/2 , where D is the diameter of the cylinder and Re D is the flow Reynolds number. It is shown that the presence of weak but finite streamwise vorticity, with λ*≤λ* N in the external flow, can be supported by the flow in the stagnation zone, leading to a substructure of counterrotating streamwise eddies in the boundary layer. The magnitude of the streamwise vorticity in the boundary layer is found to match with that in the external flow for A* ^ X*N; it is of much smaller order for λ* > λ* N , which corresponds to a disturbance of the type considered by Hammerlin (1955).

Quantification of Energy Transformation Processes Between Acoustic and Hydrodynamic Modes in Non-Compact Thermoacoustic Systems via a Helmholtz-Hodge Decomposition Approach

2019 ◽  
Author(s):  
Thomas Hofmeister ◽  
Tobias Hummel ◽  
Bruno Schuermans ◽  
Thomas Sattelmayer
Keyword(s):  
Vortex Shedding ◽  
Hodge Decomposition ◽  
Mean Flow ◽  
Hydrodynamic Modes ◽  
Flow Shear ◽  
Decomposition Approach ◽  
Acoustic Damping ◽  
Linearized Euler Equations ◽  
Eigen Solutions ◽  
Vortical Disturbance

Abstract Solutions of the Linearized Euler Equations (LEE) are composed of acoustic, entropy and vortical perturbation types. The excitation of the latter can be provoked by a transformation of acoustic into rotational energy, which originates from the interaction between acoustics and a mean flow shear-layer. This is known as acoustically induced vortex shedding and represents the phenomenon of interest in this study. In the field of thermoacoustics, numerical eigenfrequency simulations with the LEE have moved into focus to determine the acoustic damping rates associated with vortex shedding to complete thermoacoustic stability analyses of gas turbine combustors. However, there is yet no fundamental investigation existent, which establishes the legitimation to consider these LEE damping rates for this purpose. This question arises due to the implicit presence of vortical disturbances caused by vortex shedding next to the acoustic ones in LEE eigensolutions. In conclusion, the corresponding damping rates are not expected to represent the pure acoustic damping rates, which are exclusively required for a thermoacoustic stability analysis. The main objective of this work comprises the clarification, whether damping rates obtained by straightforwardly performed LEE eigenfrequency simulations can be used for a thermoacoustic stability assessment, although their eigen-solutions are “polluted” by further disturbance types, i.e. the vortical one in this study. Therefore, a Helmholtz-Hodge decomposition approach is applied to LEE eigenmode shapes, which allows to explicitly access acoustic and vortical disturbance fields. These are used to extract the unambiguous, pure acoustic damping rates from LEE eigensolutions via evaluations of appropriate energy terms. The resulting damping rates are finally compared to the corresponding, original LEE damping rates and their experimental counterparts.

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