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peterKim August 13, 1999 06:35

(Fluent4.5)Deforming mesh
Thanks for interesting in this.

I study physiolosical blood flow related moiving wall. I have some trouble for a error in Fluent 4.5.; "Coudn't determine grid file format "

How can I solve this error? What case do this error happen to? Please, help me... finally, as followed figure

------------------------- wall(z-wall) inflow -->

------------------------- symmetric

Setting the z-wall of the boundary condition In fluent panel. It is reasonable to set v-velocity be harmonic condition if z-wall is moiving from up to down with pusalting wall.

Thanks for reading.... Have a great day..

John C. Chien August 13, 1999 09:43

Re: (Fluent4.5)Deforming mesh
(1). "do not understand." I have tried to figure out your problem, but I could not put the picture together. (2). You are trying to feed something into this code, and the code said I don't understand. It is very simple. (3). This code problbly can only understand very simple English. So, tell us exactly what you are trying to do. Is the problem 2-D, or 3-D? What is a harmonic condition? What is this z_wall? Where is this pusalting wall? Can you talk to the code, when the wall is not moving?

A.A. August 14, 1999 05:44

Re: (Fluent4.5)Deforming mesh
Make sure that your original grid (a t=0) has a .grd format. If you are reading different grids all the grids you read must have a .grd format.

If you follow Fluent User's manual (moving mesh option) you won't have any problem at all.

Phil Greenfield August 20, 1999 23:41

Re: (Fluent4.5)Deforming mesh
1st) I'd agree with A.A. ; make sure that when entering the grid file names that they include both the path and extension " filename.grd ".

2nd) I believe the temporal variation in reading the grid's determines the characteristic wall velocity's and you don't have to add the additional parameter's in the bc's.

I'm working with squeeze flows using a set of 5 sequential grids to simulate a reduction in cavity volume. I started out giving it both a wall velocity under bc's and a translational velocity based on the time step btwn reading the new grid structures. In my experience and based on a comparison with an analytical solution, it appears that the bc's should be kept at zero and let the timing btwn grid's determine the overall wall velocity. This combination appeared to agree fairly well with my analytical solution based on the scaling parameters in the lubrication approximation. Probably a couple ways to do it, but this worked for me.

I'd be interested in hearing how you eventually work out this problem. I know of a similar modeling scenario to yours which involve's an oscillating wall and may indeed require using both approach's.

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