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.

scholarly journals Thermochemical Nonequilibrium in Rapidly Expanding Flows of High-Temperature Air

1997 ◽  
Vol 52 (4) ◽  
pp. 358-368 ◽  
Author(s):  
Michio Nishida ◽  
Masashi Matsumotob
Keyword(s):  
High Temperature ◽  
Vibrational Energy ◽  
Stokes Equations ◽  
Computational Study ◽  
Mass Conservation ◽  
Navier Stokes ◽  
Tvd Scheme ◽  
Governing Equations ◽  
Navier Stokes Equations ◽  
Free Jet

Abstract • This paper describes a computational study of the thermal and chemical nonequilibrium occuring in a rapidly expanding flow of high-temperature air transported as a free jet from an orifice into low-density stationary air. Translational, rotational, vibrational and electron temperatures are treated separately, and in particular the vibrational temperatures are individually treated; a multi-vibrational temperature model is adopted. The governing equations are axisymmetric Navier-Stokes equations coupled with species vibrational energy, electron energy and species mass conservation equations. These equations are numerically solved, using the second order upwind TVD scheme of the Harten-Yee type. The calculations were carried out for two different orifice temperatures and also two different orifice diameters to investigate the effects of such parameters on the structure of a nonequilibrium free jet.

scholarly journals Dynamic Behaviour of the Loads of Podded Propellers in Waves: Experimental and Numerical Simulations

2014 ◽  
Author(s):  
Patrick Queutey ◽  
Jeroen Wackers ◽  
Alban Leroyer ◽  
GanBo Deng ◽  
Emmanuel Guilmineau ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Stokes Equations ◽  
Scale Effects ◽  
Computational Study ◽  
Essential Feature ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Wave Basin

The paper focuses on the hydrodynamic flow around a ship with pods in waves and compares the results of an experimental campaign with numerical simulations conducted during the EU-funded STREAMLINE project. It was the first project for which the effect of waves on cavitation and ventilation was explored in both experimental and numerical ways for a ship with pods. The measurements were carried out in MARIN’s Depressurized Wave Basin (DWB) with a fully instrumented podded ship model, in sailing condition, in waves and depressurised conditions. In this way, the correct representation of cavitation and possible ventilation bubbles and vortices is ensured, resulting in a correct physical behaviour. The discretisation of the Reynolds-Averaged Navier-Stokes Equations (RANSE) is based on the unstructured finite-volume flow solver ISIS-CFD developed by ECN-CNRS. An essential feature for full RANSE simulations with this code is the use of a sliding grid technique to simulate the real propeller rotating behind a ship hull. The computational study in operational service conditions considered here has been conducted to evaluate the instantaneous flow distribution around the podded propellers and to analyse and to compare the unsteady behaviour of the forces induced by the rotating propeller in waves with the measurements from omnidirectional propeller loads as well as the blade forces and moments. The computational study has been done in model and full scale to evaluate the scale effects.

scholarly journals A Computational Study of a Data Assimilation Algorithm for the Two-dimensional Navier-Stokes Equations

2016 ◽  
Vol 19 (4) ◽  
pp. 1094-1110 ◽  
Author(s):  
Masakazu Gesho ◽  
Eric Olson ◽  
Edriss S. Titi
Keyword(s):  
Data Assimilation ◽  
Stokes Equations ◽  
Computational Study ◽  
Nodal Point ◽  
Navier Stokes ◽  
Reference Solution ◽  
Two Dimensional ◽  
Computationally Efficient ◽  
Navier Stokes Equations ◽  
Feedback Control Theory

AbstractWe study the numerical performance of a continuous data assimilation (downscaling) algorithm, based on ideas from feedback control theory, in the context of the two-dimensional incompressible Navier-Stokes equations. Our model problem is to recover an unknown reference solution, asymptotically in time, by using continuous-in-time coarse-mesh nodal-point observational measurements of the velocity field of this reference solution (subsampling), as might be measured by an array of weather vane anemometers. Our calculations show that the required nodal observation density is remarkably less than what is suggested by the analytical study; and is in fact comparable to the number of numerically determining Fourier modes, which was reported in an earlier computational study by the authors. Thus, this method is computationally efficient and performs far better than the analytical estimates suggest.

Understanding subsonic and transonic cavity flows

2001 ◽  
Vol 105 (1044) ◽  
pp. 77-84 ◽  
Author(s):  
J. Henderson ◽  
K. J. Badcock ◽  
B. E. Richards
Keyword(s):  
Acoustic Pressure ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Cavity Flows ◽  
Computational Investigation ◽  
Oscillatory Flows ◽  
Navier Stokes Equations ◽  
Open Flow ◽  
Pressure Distributions ◽  
Cavity Floor

AbstractA computational investigation of the subsonic and transonic turbulent open flow over cavities was conducted. Simulations of these oscillatory flows were generated through time-accurate solutions of the Reynolds-averaged form of the Navier-Stokes equations. The effect of turbulence was included through the k–ω model. The results presented include calculations of the acoustic pressure distributions along the cavity floor, which compare well with experiment. The results are then used to describe the behaviour of the flow.

A computational study of the topology of vortex breakdown

1991 ◽  
Vol 435 (1894) ◽  
pp. 321-337 ◽  
Keyword(s):  
Topological Structure ◽  
Stokes Equations ◽  
Vortex Breakdown ◽  
Computational Study ◽  
Double Helix ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Streamwise Direction ◽  
Navier Stokes Equations ◽  
Axial Velocity Distribution

A fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier–Stokes equations has been performed. Solutions to four distinct types of breakdown are identified and compared with experimental results. The computed solutions include weak helical, double helix, spiral, and bubble-type breakdowns. The topological structure of the various breakdowns as well as their interrelationship are studied. The data reveal that the asymmetric modes of breakdown may be subject to additional breakdowns as the vortex core evolves in the streamwise direction. The solutions also show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown.

Simulation of Three-Dimensional Shear Flow Around a Nozzle-Afterbody at High Speeds

1992 ◽  
Vol 114 (2) ◽  
pp. 178-185 ◽  
Author(s):  
Oktay Baysal ◽  
Wendy B. Hoffman
Keyword(s):  
Shear Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Surface Flow ◽  
Navier Stokes ◽  
Turbulent Shear ◽  
Duct Flow ◽  
Navier Stokes Equations ◽  
Eddy Viscosity Model ◽  
Pressure Distributions

Turbulent shear flows at supersonic and hypersonic speeds around a nozzle-afterbody are simulated. The three-dimensional, Reynolds-averaged Navier-Stokes equations are solved by a finite-volume and implicit method. The convective and the pressure terms are differenced by an upwind-biased algorithm. The effect of turbulence is incorporated by a modified Baldwin-Lomax eddy viscosity model. The success of the standard Baldwin-Lomax model for this flow type is shown by comparing it to a laminar case. These modifications made to the model are also shown to improve flow prediction when compared to the standard Baldwin-Lomax model. These modifications to the model reflect the effects of high compressibility, multiple walls, vortices near walls, and turbulent memory effects in the shear layer. This numerically simulated complex flowfield includes a supersonic duct flow, a hypersonic flow over an external double corner, a flow through a non-axisymmetric, internal-external nozzle, and a three-dimensional shear layer. The specific application is for the flow around the nozzle-afterbody of a generic hypersonic vehicle powered by a scramjet engine. The computed pressure distributions compared favorably with the experimentally obtained surface and off-surface flow surveys.

scholarly journals Numerical Study of Variable Camber Continuous Trailing Edge Flap at Off-Design Conditions

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3185 ◽  
Author(s):  
Mohammed Abdul Raheem ◽  
Prasetyo Edi ◽  
Amjad A. Pasha ◽  
Mustafa M. Rahman ◽  
Khalid A. Juhany
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Computational Study ◽  
Advanced Technology ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Navier Stokes Equations ◽  
Parabolic Profile ◽  
Trailing Edge Flap ◽  
Laminar Flow Control

Numerical simulations are performed to study the outboard airfoil of advanced technology regional aircraft (ATRA) wings with five different variable camber continuous trailing edge flap (VCCTEF) configurations. The computational study aims to improve the aerodynamic efficiency of the airfoil under cruise conditions. The design of outboard airfoil complies with the hybrid laminar flow control design criteria. This work is unique in terms of analysis of the effects of VCCTEF on the ATRA wing’s outboard airfoil during the off-design condition. The Reynolds–Averaged Navier–Stokes equations coupled with the Spalart-Allmaras turbulence model are employed to perform the simulations for the baseline case and VCCTEF configurations. The current computational study is performed at an altitude of 10 km with a cruise Mach number of 0.77 and a Reynolds number of 2.16 × 107. Amongst all five configurations of VCCTEF airfoils studied, a flap having a parabolic profile (VCCTEF 123) configuration shows the maximum airfoil efficiency and resulted in an increase of 6.3% as compared to the baseline airfoil.

Computational Investigation of Inlet Baffle Height on the Flow in a Rectangular Oil/Water Separator Tanks

2015 ◽  
Vol 802 ◽  
pp. 587-592
Author(s):  
Haitham A. Hussein ◽  
Rozi Abdullah ◽  
Md Azlin Md Said
Keyword(s):  
Stokes Equations ◽  
Experimental Tests ◽  
Navier Stokes ◽  
Computational Investigation ◽  
Navier Stokes Equations ◽  
Flow Equations ◽  
Water Separator ◽  
Oil Water ◽  
Volume Method ◽  
Maximum Removal

Gravity Separator Tanks are Used to Separate Oil from Water in Treatment Units. Achieving the Best Flow Uniformity in a Separator Tank will Improve the Maximum Removal Efficiency of Oil Globules from Water. in this Study, the Effect on Hydraulic Performance of Different Inlet Baffle Height inside a Tank was Investigated. some Experimental Tests were Done for Verification the Velocity Profile with Numerical Results Using ADV (Acoustic Doppler Velocimeter). A CFD Programme, Flow 3D Ver.10 was Used in which Finite Volume Method is Used for Solution of Water Flow Equations and RNG Turbulent Model with the Navier-Stokes Equations. the Volume of Fluid (VOF) Method was Used for Tracking of Free Surface in Simulation Program. the Results of the Numerical Simulation Show that the Separation Tank Performance can Be Improved by Altering the Geometry of the Tank and the Effects of Inlet Baffle Height on the Efficiency of the Separation Tank are Investigated via Assessment of the Circulation Zone Volume Variations, and the Uniformity of Flow Values in each Case.

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.

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