Transpiration Induced Shock Boundary-Layer Interactions

2006 ◽  
Vol 128 (5) ◽  
pp. 976-986 ◽  
Author(s):  
B. Wasistho
Keyword(s):  
Boundary Layer ◽  
Numerical Method ◽  
Vortex Shedding ◽  
Compressible Flows ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Boundary Layer Interaction ◽  
Suction And Blowing

Steady and unsteady shock boundary-layer interactions are studied numerically by solving the two-dimensional time-dependent Navier-Stokes equations. To validate the numerical method, the steady interaction is compared with measurements and other numerical results reported in the literature. The numerical study of the steady interaction leads to a suitable method for transpiration boundary conditions. The method applies to unsteady flows as well. Using the validated numerical method, we show that an unsteady shock boundary-layer interaction can occur in a supersonic flow over a flat plate subjected to suction and blowing from the opposite side of the plate, even though the imposed transpiration is steady. Depending on the Mach number, the Reynolds number, the distance of the transpiration boundary to the lower wall, and the transpiration profile, the unsteadiness can be inviscid or viscous dominated. The viscous effect is characterized by the occurrence of self-excited vortex shedding. A criterion for the onset of vortex shedding for internal compressible flows is also proposed.

scholarly journals Some Modelling Issues on Trailing Edge Vortex Shedding

1999 ◽  
Author(s):  
Wei Ning ◽  
Li He
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Independent Solution ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Navier Stokes Equations ◽  
Averaged Equations ◽  
Edge Vortex

A numerical study has been carried out to investigate modelling issues on trailing edge vortex shedding. The vortex shedding from a circular cylinder and a VKI turbine blade is calculated using a 2-D unsteady multi-block Navier-Stokes solver. The unsteady stresses are calculated from the unsteady solutions. The distributions of the unsteady stresses are analysed and compared for the cylinder case and the cascade case, respectively. The time-averaged equations are then solved and the effectiveness of the “unsteady stresses” in suppressing trailing edge vortex shedding is checked. Finally, the time-independent solution produced by solving the time-averaged equations is compared with the time-averaged solution obtained by integrating the unsteady solutions. The numerical results have demonstrated that a time-independent vortex shedding solution can be achieved by solving the Navier-Stokes equations with the unsteady stresses and the time-averaged effects of the vortex shedding can be included.

A numerical study of vortex shedding from flat plates with square leading and trailing edges

1992 ◽  
Vol 236 ◽  
pp. 445-460 ◽  
Author(s):  
Yuji Ohya ◽  
Yasuharu Nakamura ◽  
Shigehira Ozono ◽  
Hideki Tsuruta ◽  
Ryuzo Nakayama
Keyword(s):  
Shear Layer ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Shear Layer Instability ◽  
Flat Plates ◽  
Navier Stokes Equations ◽  
Trailing Edges

This paper describes a numerical study of the flow around flat plates with square leading and trailing edges on the basis of a finite-difference analysis of the two-dimensional Navier—Stokes equations. The chord-to-thickness ratio of a plate, d/h, ranges from 3 to 9 and the value of the Reynolds number based on the plate's thickness is constant and equal to 103. The numerical computation confirms the finding obtained in our previous experiments that vortex shedding from flat plates with square leading and trailing edges is caused by the impinging-shear-layer instability. In particular, the Strouhal number based on the plate's chord increases stepwise with increasing d/h in agreement with the experiment. Numerical analyses also provide some crucial information on the complicated vortical flow occurring near the trailing edge in conjunction with the vortex shedding mechanism. Finally, the mechanism of the impinging-shear-layer instability is discussed in the light of the experimental and numerical findings.

Interaction of a Steady Approach Flow and a Circular Cylinder Undergoing Forced Oscillation

1997 ◽  
Vol 119 (4) ◽  
pp. 808-813 ◽  
Author(s):  
Jianfeng Zhang ◽  
Charles Dalton
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Large Eddy Simulation Model ◽  
Drag And Lift Coefficients ◽  
Eddy Simulation ◽  
Drag And Lift

This paper presents a numerical study on the interaction of a steady approach flow and the forced transverse oscillation of a circular cylinder. The two-dimensional stream-function/vorticity formulation of the Navier-Stokes equations is solved by a semi-implicit finite-difference scheme. Calculations for flows with different amplitude (a) and frequency (fc) of the oscillation of the cylinder show a strong effect of the oscillation when fc is close to fso, the vortex shedding frequency, of the stationary cylinder. Lock-on of vortex shedding, distinct flow patterns, and increase in both drag and lift coefficients from those of a stationary cylinder are observed for Reynolds number Re = 200, a/R (R is the radius of the cylinder) from 1.0 to 2.0, fc/fso from 0.85 to 1.7. For Re = 855, a/R = 0.26, a large eddy simulation model for turbulent flow is used. The results at Re = 855 and a/R = 0.26 show that lock-on has occurred for fc/fso ≥ 0.85. The behavior of the drag and lift coefficients is seen to be influenced by the lock-on phenomenon.

Effect of Turbulence Modeling on VIV Numerical Simulation

2005 ◽  
Author(s):  
Juan B. V. Wanderley ◽  
Gisele H. B. Souza ◽  
Carlos Levi
Keyword(s):  
Numerical Method ◽  
Compressible Flows ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Reynolds Average

Author’s previous work Wanderley [1] presented an efficient numerical method to investigate VIV phenomenon on circular cylinders. The numerical model solves the unsteady Reynolds Average Navier–Stokes equations for slightly compressible flows using the Beam–Warming implicit factored scheme. In the present work, the effect of the turbulence model on the results is evaluated for both Baldwin Lomax and k-ε models. To demonstrate the quality of the numerical method, results for the transversal oscillation of a cylinder laterally supported by spring and damper are compared with experimental data. The application of the turbulence models showed the much better agreement of the k-ε model with the experimental results.

A Numerical Study of Vortex Shedding From a Square Cylinder With Ground Effect

1997 ◽  
Vol 119 (3) ◽  
pp. 512-518 ◽  
Author(s):  
Robert R. Hwang ◽  
Chia-Chi Yao
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Subsequent Development ◽  
Ground Effect ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Navier Stokes Equations ◽  
Layer Flow ◽  
Volume Method

A numerical study has been conducted to investigate the behavior of the vortical wake created by a square cylinder placed in a laminar boundary-layer flow. The calculations are performed by solving the unsteady 2D Navier-Stokes equations with a finite-volume method. The Reynolds-number regime investigated is from 500 to 1500. Another parameter that is varied is the distance of the cylinder from the wall. The initial and subsequent development of the vortex shedding phenomenon are investigated. The presence of the wall is found to have strong effects on the properties of these vortices, as well as lift, drag, and Strouhal number.

Vortex Shedding From a Square Cylinder With Ground Effect

2003 ◽  
Author(s):  
S. Bhattacharyya ◽  
D. K. Maiti
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Ground Effect ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Navier Stokes Equations ◽  
Cylinder Length

Numerical study on the wake behind a square cylinder placed parallel to a wall has been made. Flow has been investigated in the laminar Reynolds number (based on the cylinder length) range. We have studied the flow field for different values of the non-dimensional gap length between cylinder and the wall. The case when the cylinder is placed on the wall has also been considered. The governing unsteady Navier-Stokes equations are discretised through the finite volume method on staggered grid system. A SIMPLER type of algorithm has been used to compute the discretised equations iteratively. Vortex shedding has been found to be influenced by the wall. Vortex shedding suppression occurs beyond a critical value of the gap length. Due to the shear, the drag experienced by the cylinder is found to increase with the reduction of gap length. The flow is found to be steady when the cylinder is placed on the wall at a range of Reynolds number.

scholarly journals Numerical Investigation of Jet Angle Effect on Airfoil Stall Control

2019 ◽  
Vol 9 (15) ◽  
pp. 2960 ◽  
Author(s):  
Junkyu Kim ◽  
Young Min Park ◽  
Junseong Lee ◽  
Taesoon Kim ◽  
Minwoo Kim ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Separation Control ◽  
Angle Effect ◽  
Stall Control ◽  
The Impact

Numerical study on flow separation control is conducted for a stalled airfoil with steady-blowing jet. Stall conditions relevant to a rotorcraft are of interest here. Both static and dynamic stalls are simulated with solving compressible Reynolds-averaged Navier-Stokes equations. It is expected that a jet flow, if it is applied properly, provides additional momentum in the boundary layer which is susceptible to flow separation at high angles of attack. The jet angle can influence on the augmentation of the flow momentum in the boundary layer which helps to delay or suppress the stall. Two distinct jet angles are selected to investigate the impact of the jet angle on the control authority. A tangential jet with a shallow jet angle to the surface is able to provide the additional momentum to the flow, whereas a chord-normal jet with a large jet angle simply averts the external flow. The tangential jet reduces the shape factor of the boundary layer, lowering the susceptibility to the flow separation and delaying both the static and dynamic stalls.

scholarly journals Numerical simulation on the development of periodic three-dimensional disturbances in a supersonic boundary layer

2019 ◽  
Vol 196 ◽  
pp. 00016
Author(s):  
Gleb Kolosov ◽  
Alexander Semenov ◽  
Alexey Yatskikh
Keyword(s):  
Boundary Layer ◽  
Mass Flow ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Small Diameter ◽  
Supersonic Boundary Layer ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Software Complex

The results of a numerical study of the development of periodic pulsations in a supersonic boundary layer on a flat plate are presented at a Mach number of 2.5 and a unit Reynolds number of 8×106 m–1. Using the software complex ANSYS, the complete Navier-Stokes equations were solved. Periodic mass flow disturbances with a frequency of 20 kHz were introduced into the boundary layer through a small-diameter hole on the surface of the model. Downstream the profiles of the longitudinal mass flow pulsations were recorded, and spectral analysis of the data was carried out. The main characteristics of the development of unstable disturbances in both physical and wave spaces are obtained.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

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