The Numerical Prediction of Developing Turbulent Flow in Rectangular Ducts

1981 ◽  
Vol 103 (3) ◽  
pp. 445-453 ◽  
Author(s):  
F. B. Gessner ◽  
A. F. Emery
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Computational Procedure ◽  
Momentum Equation ◽  
Scale Model ◽  
Length Scale ◽  
Basic Technique ◽  
Numerical Predictions ◽  
Iterative Procedures

Comparisons are made between experimental data and numerical predictions based on a three-dimensional length-scale model applicable to developing turbulent flow in rectangular ducts of arbitrary aspect ratio. The numerical method utilizes an explicit (Dufort-Frankel) differencing scheme for the axial momentum equation and involves no iterative procedures. Although the basic technique has been applied previously to another class of three-dimensional flows, it has not been applied until now to slender shear flows dominated by secondary flow of the second kind. The merits of the length-scale model and the computational procedure are assessed by means of comparisons with results referred to both k–ε and full Reynolds stress closure models which have been applied in recent years.

Shallow Turbulent Flow Simulation Using Two-Length-Scale Model

1999 ◽  
Vol 125 (7) ◽  
pp. 780-788 ◽  
Author(s):  
Wihel Altai ◽  
Jian-bo Zhang ◽  
Vincent H. Chu
Keyword(s):  
Turbulent Flow ◽  
Flow Simulation ◽  
Scale Model ◽  
Length Scale

Numerical simulations of the flow through the inlet and isolator of a Mach 4 dual mode scramjet

2012 ◽  
Vol 116 (1182) ◽  
pp. 833-846 ◽  
Author(s):  
S. Janarthanam ◽  
V. Babu
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Dual Mode ◽  
Flow Distortion ◽  
Capture Ratio ◽  
Boundary Interaction ◽  
Numerical Predictions ◽  
Mass Capture

Abstract Results from numerical simulations of the three dimensional flow in the intake-isolator of a dual mode scramjet are presented. The FANS calculations have utilised the SST k -ω turbulence model. The effect of cowl length and cowl convergence angle on the inlet mass capture ratio, flow distortion, shock strength and pressure rise are studied in detail. Three cowl lengths and four or five cowl convergence angles for each cowl length are considered. The predicted values of the dimensionless wall static pressure and inlet mass capture ratio are compared with experimental data reported in the literature. The numerical predictions are shown to agree well with the experimental data. In addition, details of the flow field such as shocks, expansion fans and shock boundary interaction are also captured accurately. Inlet unstart is also demonstrated for one case.

scholarly journals EFFECT OF THE SPANWISE DISCRETISATION ON TURBULENT FLOW PAST A CIRCULAR CYLINDER

2021 ◽  
Vol 158 (A1) ◽  
Author(s):  
S Kim ◽  
P A Wilson ◽  
Z Chen
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Scale Model ◽  
Spatial Density ◽  
Eddy Simulation ◽  
Large Eddy

The effect of the spanwise discretisation on numerical calculations of the turbulent flow around a circular cylinder is systematically assessed at a subcritical Reynolds number of 10000 in the frame of three-dimensional large-eddy simulation. The eddy-viscosity k-equation subgrid scale model is implemented to evaluate unsteady turbulent flow field. Large-eddy simulation is known to be a reliable method to resolve such a challenging flow field, however, the high computational efforts restrict to low Reynolds number flow or two-dimensional calculations. Therefore, minimum spatial density in the spanwise direction or cylinder axis direction needs to be carefully evaluated in order to reduce high computational resources. In the present study, the influence of the spanwise resolutions to satisfactorily represent three- dimensional complex flow features is discussed in detail and minimum spatial density for high Reynolds flow is suggested.

Vertical Buoyant Jet Analysis in an Enclosure Using ITM and LES

2004 ◽  
Author(s):  
Allen E. Badeau ◽  
Ismail B. Celik
Keyword(s):  
Experimental Data ◽  
Boundary Condition ◽  
Control Volume ◽  
Three Dimensional ◽  
Grid Resolution ◽  
Scale Model ◽  
Subgrid Scale ◽  
Buoyant Jet ◽  
Subgrid Scale Model ◽  
Inlet Boundary Condition

The objective of this study is to investigate vertical buoyant jets in an enclosure using Large Eddy Simulation (LES) methods with no sub-grid scale model. This type of methodology is called Implicit Turbulent Modeling (ITM). Two different boundary conditions are applied at the inlet, being a uniform and periodic forcing velocity distribution. To accomplish this goal, a numerical solver was written, named DREAM®, which is capable of solving three dimensional, transient flows using an accurate monotonic upwinding scheme. The three-dimensional Navier-Stokes equations are solved in Cartesian coordinates, with the control volume approach being implemented on a staggered grid. The numerical scheme uses a fractional time step method, Crank-Nicolson, with the overall spatial and temporal accuracy being second order. In ITM simulations, there is no explicit subgrid-scale model (SGS) used for the modeling of the small scale vortical structures. ITM simulations assume that through strict conservation of the fluxing quantities in and out of the cell, the grid resolution is fully capable of capturing the important scales of the flow. The control volume averaging techniques used in the ITM methods acts as an implicit subgrid-scale model, and the resolvable scales of the flow are only dependent on the grid resolution within the domain. The available experimental data, as well as simulations that used SGS models, compare favorably to the ITM simulations from DREAM® in most cases as long as an “adequate” grid resolution is maintained. Results show that the density stratification tends to accelerate the jet and increase the amount of turbulence present within the flow. Perturbation of the inlet boundary condition ensures a sooner onset of turbulence, which is faster than the non-perturbed inlet boundary condition. A similarity solution is achieved at approximately 8 and 13 inlet diameters downstream of the inlet for the perturbed and uniform inlet boundary condition. Comparison between the vertical buoyant jet simulations to the available experimental data shows good agreement for the jet width and buoyant path centerline locations based on the internal densimetric Froude number. The application of these methods to immiscible fluids shows a new dimension to ITM and allows for a high resolution of the resulting flow field without the need for an explicit SGS model.

Secondary Flow Development In A Cascade Like Passage Of A Turbomachine

1983 ◽  
pp. 11-23
Author(s):  
Amer Nordin Darus
Keyword(s):  
Experimental Data ◽  
Numerical Solution ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Rotational Flow ◽  
Simultaneous Solution ◽  
Analytical Formulation ◽  
Curved Duct ◽  
Flow Development ◽  
Vorticity Equations

Makalah ini memaparkan formulasi analitik dan penyelesaian numerik aliran dimensi tiga yang rotasional di dalam sebuah saluran yang melengkung. Formulasi ini berdasarkan perhitungan halaju aliran dan komponen vortisiti selari axis saluran tersebut. Halaju sekunder ditentukan melalui penyelesaian serentak persamaan-persamaan ke terusan dan vortisiti melalui penggunaan fungsi seperti fungsi arus. Hasil-hasil numerik diberikan dan dibandingkan dengan data-data eksperimen yang ada. This article presents the analytical formulation and numerical solution of the three-dimensional rotational flow in curved duct. The formulation is based on calculating the flow - wise velocity and vorticity. components from the momentum equation. The secondary velocities are determined from the simultaneous solution of the continuity and vorticity equations through the use of a streamlike function. The results presented arc compared with the existing experimental data.

The Experimental Study and Numerical Simulation of Turbulent Flow in Pumping Forebay

2009 ◽  
Author(s):  
Chao Liu ◽  
Jiren Zhou ◽  
Li Cheng
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Computational Results ◽  
Experiment Study ◽  
Study Results ◽  
Measurement Results ◽  
Good Agreement ◽  
Made In

The experiment study was made to optimize the design of a pumping forebay. The Combined-sills were made in the forebay to eliminate the circulation and vortices of the diffusing flow successfully. The Numerical simulation of three-dimensional turbulent flow is applied on the complicate fore-and-aft flow of sills. The computational results are compared with the measurement results of physical model. The calculated results are in good agreement with the experimental data. The flow pattern is obviously improved. The study results have been applied in the project which gives a uniform approach flow to the pumping sump.

An experimental investigation of the relative diffusion of particle pairs in three-dimensional turbulent flow

2000 ◽  
Vol 422 ◽  
pp. 207-223 ◽  
Author(s):  
SØREN OTT ◽  
JAKOB MANN
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Turbulent Flow ◽  
Particle Tracking ◽  
Three Dimensional ◽  
Direct Interaction ◽  
General Shape ◽  
Particle Pairs ◽  
Oscillating Grids ◽  
A Minor

The particle tracking (PT) technique is used to study turbulent diffusion of particle pairs in a three-dimensional turbulent flow generated by two oscillating grids. The experimental data show a range where the Richardson–Obukhov law 〈r2〉 = Cεt3 is satisfied, and the Richardson–Obukhov constant is found to be C = 0.5. A number of models predict much larger values. Furthermore, the distance–neighbour function is studied in detail in order to determine its general shape. The results are compared with the predictions of three models: Richardson (1926), Batchelor (1952) and Kraichnan (1966a). These three models predict different behaviours of the distance–neighbour function, and of the three, only Richardson's model is found to be consistent with the measurements. We have corrected a minor error in Kraichnan's (1996a) Lagrangian history direct interaction calculations with the result that we had to increase his theoretical value from C = 2.42 to C = 5.5.

A Length-Scale Model For Developing Turbulent Flow in a Rectangular Duct

1977 ◽  
Vol 99 (2) ◽  
pp. 347-356 ◽  
Author(s):  
F. B. Gessner ◽  
A. F. Emery
Keyword(s):  
Reynolds Stress ◽  
Three Dimensional ◽  
Scale Model ◽  
Length Scale ◽  
Pressure Gradients ◽  
Mixing Length ◽  
Two Dimensional ◽  
Rectangular Duct ◽  
Corner Flows ◽  
Theory And Experiment

A three-dimensional mixing length model is proposed for modeling local Reynolds stress behavior in rectangular ducts of arbitrary aspect ratio. The model is applicable to both developing and fully-developed flows, and can be applied to other 90-degree corner flows with mild streamwise pressure gradients. Comparisons between theory and experiment show that all components of the Reynolds stress tensor are modeled reasonably well, both in the vicinity of a corner and in two-dimensional regions away from the corner.

scholarly journals Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence–aerofoil interaction noise

2017 ◽  
Vol 818 ◽  
pp. 435-464 ◽  
Author(s):  
P. Chaitanya ◽  
P. Joseph ◽  
S. Narayanan ◽  
C. Vanderwel ◽  
J. Turner ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Three Dimensional ◽  
Leading Edge ◽  
Flow Speed ◽  
Integral Length Scale ◽  
Length Scale ◽  
Flat Plates ◽  
Image Velocimetry ◽  
Lift And Drag ◽  
Power Radiation

This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto three-dimensional aerofoils. The influence on the noise reduction of the turbulence integral length scale is also studied. An optimum serration wavelength is identified whereby maximum noise reductions are obtained, corresponding to when the transverse integral length scale is approximately one-fourth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number $St_{h}=fh/U$, where $f$, $h$ and $U$ are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil self-noise dominates the interaction noise. Leading edge serrations are also shown to reduce aerofoil self-noise. The mechanism for this phenomenon is explored through particle image velocimetry measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.

scholarly journals NUMERICAL SIMULATIONS OF BREAKING SOLITARY WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 59 ◽  
Author(s):  
Pierre Lubin ◽  
Stéphane Glockner
Keyword(s):  
Experimental Data ◽  
Solitary Waves ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Point Of View ◽  
Numerical Code ◽  
Scale Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Surface Description

This paper presents the application of a parallel numerical code to breaking solitary waves impacting a seawall structure. The three-dimensional Navier-Stokes equations are solved in air and water, coupled with a subgrid-scale model to take turbulence into account. We compared three numerical methods for the free-surface description, using the classical VOF-PLIC and VOF-TVD methods, and an original VOF-SM method recently developed in our numerical tool (Vincent et al., 2010). Some experimental data for solitary waves impinging and overtopping coastal structures are available in literature (Hsiao et al., 2010). Solitary waves are often used to model tsunami behaviors because of their hydrodynamic similarities. From a numerical point of view, it allows shorter CPU time simulations, as only one wave breaks. Here we apply the model to simulate three-dimensional solitary waves and compare qualitatively our results with the experimental data. We investigate three configurations of solitary waves impinging and overtopping an impermeable seawall on a 1:20 sloping beach.

Sign in / Sign up

Export Citation Format

Share Document