Please give someone give some insights and how it affects our calculation results?
Please give someone give some insights and how it affects our calculation results?
Thank You Julien
So basically for transient analysis, physical time is the actual time taken for a problem to reach the final solution from the initial condition in actual practice.
What is travel exactly?
I know with Ansys CFX they use "residuals" to calculate convergents.
Travel is exactly as explained in the definition I quoted from the Online Help. What is it that you do not understand?
So travel is a way to calculate the time?
A travel a is a measure of the calculation duration. For instance, if you compare the travels in the same project a regular mesh and with finer mesh, you will typically see that a Travel with a finer mesh corresponds to a larger number of iterations than a Travel with a regular mesh. So not only do you have more cells with a finer mesh (and the calculation of each iteration takes more time), but also convergence will be slower in terms of the number of iterations.
So is travel a good way to control convergence?
I am doing a CFD parametric study of a wing.
In Ansys convergence is controlled with the residual. How about with Solidworks?
How to determine if a mesh is good or not?
In my experience it is generally considered to be the number of iterations it takes for disturbance in the flow to traverse the domain.
So how is it use for convergence control?
Use goals. You can set any criteria you want. Might as well set it on what you are interested in.
If travels are the iterations it takes to traverse the domain, what does it mean if the initial iterations per travel are given as 47 and the final solution is given as after 1.5 travels, but there were refinements at 60, 120, and 180 iterations and a goals convergence at ~240 iterations? Is that 1.5 travels of the last refinement or what? Thanks.
It means you refined the mesh. If it takes 1 5 travels to converge it propbably means you had some other physics turned on other that just low speed aero or maybe low speed aero with unsteadiness is my guess. But other than that not a lot.
Bill, what I was getting at is the seeming discrepancy between the iterations per travel number (47), the total travels (~1.5), and the total iterations(~250).
I still do not see your issue. The iterations per travel varies with the mesh density. So when you have auto mesh refinement turned on it is not going to line up as when you dont.
From the Online Help:
Iterations.
Flow Simulation solves the time-dependent Navier-Stokes equations through iterations. If the analysis is unsteady (time-dependent) the each iteration is the time step, which is the same for the whole computational domain. If the analysis is not time-dependent the solution is obtained as steady-state, so to obtain the steady-state solution faster, the time step at the each iteration can be different in the different regions of the computational domain, so the iterations are not connected with the time steps.
CPU time
The CPU time elapsed from the beginning of the calculation to the current moment.
Physical time
Physical time for time-dependent analysis.
For unsteady (Transient, or Time-dependent) problems Flow Simulation "time marches" the solution from initial conditions for the problem’s physical time that you specify.
Travel
The term travel, used together with iterations, is a unit characterizing the calculation duration. It is the calculation period (which can be measured in iterations or some other unit) required for a flow disturbance to cross the computational domain’s fluid region. Therefore, N travels denote the calculation period required for a flow disturbance to cross the computational domain N times. The travel equivalent in iterations is determined as a function of the number of cells just after the calculation starts and can be seen in the Info box when monitoring the calculation (see Information and warnings).