scholarly journals Quasi-streamwise vortices and enhanced dissipation for the incompressible 3D Navier-Stokes equations

2021 ◽  
Author(s):  
In-Jee Jeong ◽  
Tsuyoshi Yoneda
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Streamwise Vortices ◽  
Navier Stokes Equations

On reduction of turbulent wall friction through spanwise wall oscillations

1999 ◽  
Vol 383 ◽  
pp. 175-195 ◽  
Author(s):  
M. R. DHANAK ◽  
C. SI
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Stokes Equations ◽  
Direct Numerical Simulations ◽  
Wall Friction ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Streamwise Vortices ◽  
Navier Stokes Equations ◽  
Turbulent Wall

A model for turbulent skin friction, proposed by Orlandi & Jimenez, involving consideration of quasi-streamwise vortices in the cross-stream plane, is used to study the effect on the skin friction of oscillating the surface beneath the boundary layer in the spanwise direction. Using an exact solution of the Navier–Stokes equations, it is shown that the interaction between evolving, axially stretched, streamwise vortices and a modified Stokes layer on the oscillating surface beneath, leads to reduction in the skin friction, the Reynolds stress and the rate of production of kinetic energy, consistent with predictions based on experiments and direct numerical simulations.

Enhanced Heat Transfer for Microturbine Recuperators

2001 ◽  
Author(s):  
Brian E. Thompson ◽  
J. M. Floryan ◽  
Richard E. Nolan ◽  
Sarah J. Osgood
Keyword(s):  
Surface Waves ◽  
Stokes Equations ◽  
Narrow Range ◽  
Streamwise Vortex ◽  
Spatial Modulation ◽  
Navier Stokes ◽  
Streamwise Vortices ◽  
Navier Stokes Equations ◽  
Flow Through ◽  
Corrugated Wall

Calculated and measured results are presented to quantify the effects of surface waves in laminar flow through high-aspect ratio channels typical of many in microturbine recuperators. Flow structures were calculated with spectral methods that solve incompressible Navier-Stokes equations and use Fourier expansions to represent the corrugated-wall boundary condition. Stability analysis with a generalized Floquet formulation that accounts for spatial modulation of the flow was used with the spectral flow field to predict the shape of streamlines that lead to streamwise vortices. Results indicate that vortices are produced in a very narrow range of streamline wavelengths and amplitudes. Streamlines were also calculated using a RANS method for the purpose of finding a surface that would produce the necessary streamline patterns. Hot-wire measurements show the frequency and amplitude of streamwise vortex structures increases in the flow over a sinusoidal wall with the predicted surface waves.

Velocity and Turbulence Characteristics of Isothermal Lobed Mixer Flows

1995 ◽  
Vol 117 (4) ◽  
pp. 633-638 ◽  
Author(s):  
P. Koutmos ◽  
J. J. McGuirk
Keyword(s):  
Stokes Equations ◽  
Computational Study ◽  
Cell Formation ◽  
Navier Stokes ◽  
Vortex Cell ◽  
Duct Flow ◽  
Streamwise Vortices ◽  
Computational Investigation ◽  
Navier Stokes Equations ◽  
Flow Development

This work describes an experimental and computational study of flows in model multilobed mixers. Laser Velocimetry was used to obtain the velocity and turbulence fields in the downstream mixing duct. Flow development was quantified by examination of the large cross-plane velocities whose direction implied the formation of two streamwise vortices per lobe. A change from coplanar to scarfed geometry increased vortex strength by 25 percent. Vortex cell formation, roll-up and breakdown to fine scale mixing was attained within a distance of 5 lobe heights. The computational investigation of the coplanar configuration adopted a non-aligned mesh to solve the 3-D Reynolds averaged Navier-Stokes equations. The calculations of the lobe and mixing duct flows were coupled to predict the complete mixer. Comparisons between measurements and calculations using a standard k-ε model suggested good qualitative agreement with maximum disagreement of about 20 percent in peak radial velocities.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Sensitivity analysis for Navier-Stokes equations on unstructured meshes using complex variables

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 56-63
Author(s):  
W. Kyle Anderson ◽  
James C. Newman ◽  
David L. Whitfield ◽  
Eric J. Nielsen
Keyword(s):  
Sensitivity Analysis ◽  
Stokes Equations ◽  
Unstructured Meshes ◽  
Complex Variables ◽  
Navier Stokes ◽  
Navier Stokes Equations

Numerical solution of the reduced Navier-Stokes equations for internal incompressible flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1603-1614
Author(s):  
Martin Scholtysik ◽  
Bernhard Mueller ◽  
Torstein K. Fannelop
Keyword(s):  
Numerical Solution ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations

Development of O(Nm2) preconditioned multigrid solvers for Euler and Navier-Stokes equations

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 717-720
Author(s):  
Jack R. Edwards ◽  
James L. Thomas
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Multigrid Solvers
Sign in / Sign up

Export Citation Format

Share Document