|
[Sponsors] |
![]() |
![]() |
#1 |
Guest
Posts: n/a
|
I feel very puzzled about the turbulent K-e models , ..and the SIMPLE method. If SIMPLE method can solve the flow problem, why we need that different turbulence models. Could I just use the SIMPLE method to solve the turbulence flow?
|
|
![]() |
![]() |
![]() |
#2 |
Guest
Posts: n/a
|
The problem with solving turbulence method using simple algorithm is the difficulty in resolving all the time scales in your problem. The method used is often referred as DNS when you do a direct simulation of turbulence.The process is time consuming and needs memory.So people resolve only the larger time scales and use a model for the smaller time scale.
|
|
![]() |
![]() |
![]() |
#3 |
Guest
Posts: n/a
|
If you want to capture the flow physics accurately you need to capture all the scales of motion in time and space. This is a DNS. A RANS set of equations tries to surmount this by treating the fluctuations as a seperate entity and in doing so you end up needing a turbulence closure. This is what the K-e model tries to do. In short, what you see in these books igonores the reality of the flow scales.
The problem lies in the unclosed terms, the Reynolds stress, which arises from the RANS averaging of the Navier Stokes equations. The SIMPLE algoithm as you see applied in many books (Versteeg and Malasekera for example) on unsteady flows is applied to instantaneous equations and does not accouunt for all the scales. In otherwords, it is of no use for real turbulent flows unless you do a DNS and since this is not practically possible for most engineering flows, we use RANS of LES techniques. |
|
![]() |
![]() |
![]() |
#4 |
New Member
pradeep srinivasan
Join Date: Dec 2016
Posts: 2
Rep Power: 0 ![]() |
i am doing simulation of the water container using the tutorial .but the image of the flow pattern is getting disappeared after some time .what might be the problem
|
|
![]() |
![]() |
![]() |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Simple Outlet Question | m.nichols19 | OpenFOAM | 3 | June 25, 2010 01:44 |
Simple Question Regarding Symmetry Planes | Atella | CFX | 3 | April 11, 2010 06:44 |
Simple Question Regarding Symmetry Planes | Atella | Main CFD Forum | 0 | April 9, 2010 10:58 |
Question of Anil Date's SIMPLE method | universez | Main CFD Forum | 0 | November 18, 2009 20:12 |
Simple Question Regarding Continuity Closure | RC | FLUENT | 2 | March 25, 2004 05:30 |