Error Estimation for Three Turbulence Models: Incompressible Flow

2008 ◽  
Author(s):  
Jr Vaughn ◽  
Milton F.
Keyword(s):  
Error Estimation ◽  
Incompressible Flow ◽  
Turbulence Models

POSITIVITY OF k-EPSILON TURBULENCE MODELS FOR INCOMPRESSIBLE FLOW

2002 ◽  
Vol 12 (03) ◽  
pp. 393-406 ◽  
Author(s):  
ZI-NIU WU ◽  
SONG FU
Keyword(s):  
Reynolds Number ◽  
Point Source ◽  
Incompressible Flow ◽  
Iterative Procedure ◽  
High Reynolds Number ◽  
Operator Splitting ◽  
Turbulence Models ◽  
Diffusion Equations ◽  
Advection Diffusion ◽  
High Reynolds

The k-epsilon turbulence model for incompressible flow involves two advection–diffusion equations plus point-source terms. We propose a new method for positivity analysis. This method uses an iterative procedure combined with an operator splitting. With this method we recover the well-known positivity result for the standard high Reynolds number model. Most importantly, we are able to prove the positivity result for general low Reynolds number k-epsilon models.

A Numerical 3-D Model of a Trapezoidal Three-Hole Pneumatic Pressure Probe for Incompressible Flow

2010 ◽  
Author(s):  
Katia Mari´a Argu¨elles Di´az ◽  
Jesu´s Manuel Ferna´ndez Oro ◽  
Eduardo Blanco Marigorta ◽  
Rau´l Barrio Perotti
Keyword(s):  
Incompressible Flow ◽  
Turbulence Models ◽  
Pressure Probe ◽  
Flow Conditions ◽  
Pneumatic Pressure ◽  
Stagnation Points ◽  
Commercial Code ◽  
Reliable Model ◽  
Definition Of ◽  
D Model

Pneumatic pressure probes are well-mature measuring devices to characterize both pressure and velocity fields for external and internal flows. The measuring range of a particular probe is significantly influenced by important factors, like its geometry, the separation angle between the holes, the holes tapping or even flow conditions like separation and stagnation points or the local Reynolds number. Ideally, every pressure probe must be specifically designed for the particular application where it is needed. However, this procedure requires a detailed calibration of the probe for the whole expected range of velocities and incidences. This implies an important cost in both economic terms and operating times. Thus, the definition of an accurate numerical model for the design and calibration of pressure probes at different flow conditions is particularly desirable for these purposes. The first step towards the establishment of this useful methodology is the development of a reliable model to predict numerically the probe measuring characteristics. Thus, in this paper a numerical 3-D model is presented to characterize the calibration of a three-hole pneumatic pressure probe. In particular, a trapezoidal geometry with a 60 degree angle between the holes is considered here. The simulation of the flow incidence is carried out using the commercial code FLUENT, analyzing the influence of different mesh densities and turbulence models. The complete set of numerical cases includes different flow velocities and several yaw angles. The numerical results have been validated using experimental results obtained in a calibration facility, focusing on the definition of a numerical tool for the design and calibration of three-hole pneumatic probes under incompressible flow conditions.

scholarly journals Direct numerical simulation of backward-facing step flow at and expansion ratio 2

2019 ◽  
Vol 863 ◽  
pp. 341-363 ◽  
Author(s):  
A. Pont-Vílchez ◽  
F. X. Trias ◽  
A. Gorobets ◽  
A. Oliva
Keyword(s):  
Incompressible Flow ◽  
Experimental Studies ◽  
Turbulence Models ◽  
Separated Flow ◽  
Numerical Data ◽  
Expansion Ratio ◽  
Backward Facing Step ◽  
Recirculation Bubble ◽  
Practical Applications ◽  
Recirculation Flow

Backward-facing step (BFS) constitutes a canonical configuration to study wall-bounded flows subject to massive expansions produced by abrupt changes in geometry. Recirculation flow regions are common in this type of flow, driving the separated flow to its downstream reattachment. Consequently, strong adverse pressure gradients arise through this process, feeding flow instabilities. Therefore, both phenomena are strongly correlated as the recirculation bubble shape defines how the flow is expanded, and how the pressure rises. In an incompressible flow, this shape depends on the Reynolds value and the expansion ratio. The influence of these two variables on the bubble length is widely studied, presenting an asymptotic behaviour when both parameters are beyond a certain threshold. This is the usual operating point of many practical applications, such as in aeronautical and environmental engineering. Several numerical and experimental studies have been carried out regarding this topic. The existing simulations considering cases beyond the above-mentioned threshold have only been achieved through turbulence modelling, whereas direct numerical simulations (DNS) have been performed only at low Reynolds numbers. Hence, despite the great importance of achieving this threshold, there is a lack of reliable numerical data to assess the accuracy of turbulence models. In this context, a DNS of an incompressible flow over a BFS is presented in this paper, considering a friction Reynolds number ($Re_{\unicode[STIX]{x1D70F}}$) of 395 at the inflow and an expansion ratio 2. Finally, the elongation of the Kelvin–Helmholtz instabilities along the shear layer is also studied.

COMPUTATIONAL STUDY OF DIFFERENT TURBULENCE MODELS FOR AIR IMPINGEMENT JET INTO MAIN AIR CROSS STREAM

2019 ◽  
Vol 46 (5) ◽  
pp. 459-475
Author(s):  
Abd Elnaby Kabeel ◽  
Medhat Elkelawy ◽  
Hagar Alm El-Din ◽  
Ahmed Mohammed El-Banna ◽  
Ravishankar Sathyamurthy ◽  
...  
Keyword(s):  
Computational Study ◽  
Turbulence Models ◽  
Impingement Jet ◽  
Air Impingement
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