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.

A Numerical Study of the Impact of Wavy Walls on Steady Fluid Flow Through a Curved Tube

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Chekema Prince ◽  
Mingyao Gu ◽  
Sean D. Peterson
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Perturbation Expansion ◽  
Analytical Investigation ◽  
Navier Stokes ◽  
Radius Of Curvature ◽  
Navier Stokes Equations ◽  
Curved Tube ◽  
Small Tube ◽  
The Impact

In this paper, we discuss the impact of a wavy-walled pipe cross-section on steady flow in a curved tube at moderate Dean numbers and small tube radius-to-radius-of-curvature ratios. Parameters investigated include the protrusion height, the number of protrusions around the tube circumference, and the pipe curvature. This work extends a previous analytical investigation that employed a double perturbation expansion to elucidate the flow field as a function of these parameters. Due to the rapid growth in the solution complexity as the number of terms in each expansion increases, the analytical work is relegated to small wall perturbations and low Dean numbers. These barriers are removed in the present study by numerically solving the Navier–Stokes equations at Dean numbers up to 2500. The impact on the axial and secondary flow structures are emphasized, along with the resulting wall shear stress distributions.

scholarly journals Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1125
Author(s):  
Chemseddine Maatki
Keyword(s):  
Rayleigh Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vorticity Vector ◽  
Volume Method ◽  
The Impact ◽  
Buoyancy Ratio

The finite volume method and potential-vorticity vector formalism in their three-dimensional form were used to numerically study the impact of an adiabatic and impermeable vertical barrier on the dispersion of a local aero-contaminant due to the double-diffusive Rayleigh–Benard convection inside a cubic container. Different governing parameters such as the Rayleigh number, buoyancy ratio and barrier height were analyzed for Le = 1.2 and Pr = 0.7, representing an air-contaminant mixture. The potential-vector-vorticity formalism in the three-dimensional form allowed the elimination of the pressure terms appearing in the Navier–Stokes equations. It was found that the heat and mass transfer as well as the effectiveness of the barrier in reducing contaminant dispersion are strongly influenced by the buoyancy ratio, the barrier size and the Rayleigh number. In addition, the barrier effectiveness is more than 70% for a height of half the building height.

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.

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 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.

Numerical Integration of the Navier-Stokes Equations for a Disk Rotating in a Housing

1985 ◽  
Vol 40 (8) ◽  
pp. 789-799 ◽  
Author(s):  
A. F. Borghesani
Keyword(s):  
Boundary Layer ◽  
Cylindrical Cavity ◽  
Boundary Layer Thickness ◽  
Stokes Equations ◽  
Fluid Motion ◽  
Rotating Disk ◽  
Infinite Medium ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Viscous Torque

The Navier-Stokes equations for the fluid motion induced by a disk rotating inside a cylindrical cavity have been integrated for several values of the boundary layer thickness d. The equivalence of such a device to a rotating disk immersed in an infinite medium has been shown in the limit as d → 0. From that solution and taking into account edge effect corrections an equation for the viscous torque acting on the disk has been derived, which depends only on d. Moreover, these results justify the use of a rotating disk to perform accurate viscosity measurements.

Direct simulation of transition in an oscillatory boundary layer

1998 ◽  
Vol 371 ◽  
pp. 207-232 ◽  
Author(s):  
G. VITTORI ◽  
R. VERZICCO
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Two Dimensional ◽  
Temporal Development ◽  
Direct Simulation ◽  
Navier Stokes Equations ◽  
Oscillatory Boundary Layer

Numerical simulations of Navier–Stokes equations are performed to study the flow originated by an oscillating pressure gradient close to a wall characterized by small imperfections. The scenario of transition from the laminar to the turbulent regime is investigated and the results are interpreted in the light of existing analytical theories. The ‘disturbed-laminar’ and the ‘intermittently turbulent’ regimes detected experimentally are reproduced by the present simulations. Moreover it is found that imperfections of the wall are of fundamental importance in causing the growth of two-dimensional disturbances which in turn trigger turbulence in the Stokes boundary layer. Finally, in the intermittently turbulent regime, a description is given of the temporal development of turbulence characteristics.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

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