[Leoma]

Hello everyone,


In an effort to understand Openfoam better I tried to simulate a 3D flow arond cylinder to simulate vortex shedding. Unfortunately, I did not get any turbulence and it looks like a potentialFoam laminar result without a single vortex.


I am aware that there are dozen of tutorials/threads of this problem but they seem to deal with

• laminar flow (no turbulence)
• 2D Simulation
• pimpleFoam but with the turbulence turned of

Here on a quick glance my main parameters:

• U=0.5
• d=0.3
• v= 1,5 * 10^-5
• (Re=10^4)
• endTime=0.48
• deltaT=0.012

I would be very grateful for every help/advice I get and thanks in advance!

[piu58]

I don't have your turbulenceProperties file. But it seems you run a RAS simulation with k-ε model. This model is a steady state one. Turbulence will be covered by the model, and not by the flow itself.
I recommend using LES. I am sure you get decent results with Strouhal numbers which coincide with experimental data, at least for non extreme Re numbers.

[Leoma]

Originally Posted by piu58

I don't have your turbulenceProperties file. But it seems you run a RAS simulation with k-ε model. This model is a steady state one. Turbulence will be covered by the model, and not by the flow itself.
I recommend using LES. I am sure you get decent results with Strouhal numbers which coincide with experimental data, at least for non extreme Re numbers.

Thank you!
You are right. I will try LES and will keep you updated.

[Leoma]

I am currently struggling on the LES simulation because it seems the terminology has changed over the years.

• The oneEqEddy term was replaced
• there are new files needed and old ones not anymore

In Addition, I have no experience with LES simulation, so I believe I chose the wrong boundary conditions for the additional files.


I tried to run my simulation but after one timestep it aborts and a backtrace is generated, which reinforces my theory of ill chosen BCs.


I have again attached my main files, including turbulenceProperties. (without my Mesh, because it is too big)


Thanks again in advance!

[piu58]

Until now I did not look at your files.

But if your mesh is large something seems to be wrong. Flow past cylinders can be meshed easily with blockmesh. Probably there exists a tutorial. In any case you find an example somewhere. (If not than I look after it).

Take such an example. Let it run. Place your b.c. and see what happens. Play with the b.c. until you understand what is adequate. Then, if necessary, you may go back to your mesh.

[Leoma]

Thank you for your help!



I have tried now various 2D cylinder cases and they seem to work. In Addition, I used the pitzDaily case for LES simulation as a base case for my 3D simulation. However, my simulation still aborts after one timestep.

I have checked my Mesh (which was created with Ansys) and it should be suitable for the simulation.


The only difference between the pitzDaily case and mine is, that mine is a 3d case with the walls as noSlip and that there is a obstacle.



I have posted a link to download my full case inclusive my mesh. My guess is that I have missed something crucial for 3D setups but I cannot seem to find it.


I would be very grateful if you could help me again. Thanks in advance!


https://file.re/2021/07/23/pitzdailyles/

[piu58]

Your mesh looks slightly strange. Why do you use such a complicated and twisted mesh? It is not possible to reduce element number in a straightforward way, which would be easy with a structured mesh.

Again, I recommend using a structured mesh. Here you have one. It is 2d, but adding the third dimension is easy. It is also easy to make a finer mesh from that. Comments are in German, sorry.

FoamFile {
 version 2.0;
 format ascii;
 class dictionary;
 object blockMeshDict;
}


convertToMeters 1;

vertices (
	(0.5 0 -0.5)               // 0
	(2 0 -0.5)                 // 1
	(14.0 0 -0.5)             // 2
	(14.0 1.414214 -0.5)      // 3 
	(1.414214 1.414214 -0.5)   // 4
	(0.353553 0.353553 -0.5)   // 5
	(14.0 4.0 -0.5)         // 6o
	(1.414214 4.0 -0.5)      // 7o
	(0 4.0 -0.5)             // 8o
	(0 2 -0.5)                 // 9
	(0 0.5 -0.5)               //10
	(-0.5 0 -0.5)              //11
	(-2 0 -0.5)                //12
	(-4.0 0 -0.5)             //13 linke Kante
	(-4.0 1.414214 -0.5)      //14 linke Kante
	(-1.414214 1.414214 -0.5)  //15
	(-0.353553 0.353553 -0.5)  //16
	(-4.0 4.0 -0.5)         //17o linke Kante, obere Kante
	(-1.414214 4.0 -0.5)     //18o = Ende oberer linker Teil
	(0.5 0 0.5)              //19
	(2 0 0.5)                //20
	(14.0 0 0.5)            //21
	(14.0 1.414214 0.5)     //22
	(1.414214 1.414214 0.5)  //23
	(0.353553 0.353553 0.5)  //24
	(14.0 4.0 0.5)        //25o
	(1.414214 4.0 0.5)     //26o
	(0 4.0 0.5)            //27o
	(0 2 0.5)                //28
	(0 0.5 0.5)              //29
	(-0.5 0 0.5)             //30
	(-2 0 0.5)               //31
	(-4.0 0 0.5)            //32 linke Kante
	(-4.0 1.414214 0.5)     //33 linke Kante
	(-1.414214 1.414214 0.5) //34 
	(-0.353553 0.353553 0.5) //35
	(-4.0 4.0 0.5)        //36o linke Kante
	(-1.414214 4.0 0.5)    //37o = Ende oberer rechter Teil
	
	(14.0 -1.414214 -0.5)     //38
	(1.414214 -1.414214 -0.5)  //39
	(0.353553 -0.353553 -0.5)  //40
	(14.0 -4.0 -0.5)        //41u
	(1.414214 -4.0 -0.5)     //42u
	(0 -4.0 -0.5)            //43u
	(0 -2 -0.5)                //44
	(0 -0.5 -0.5)              //45
	(-4.0 -1.414214 -0.5)     //46
	(-1.414214 -1.414214 -0.5) //47
	(-0.353553 -0.353553 -0.5) //48
	(-4.0 -4.0 -0.5)        //49u
	(-1.414214 -4.0 -0.5)    //50u
	(14.0 -1.414214 0.5)      //51
	(1.414214 -1.414214 0.5)   //52
	(0.353553 -0.353553 0.5)   //53
	(14.0 -4.0 0.5)         //54u
	(1.414214 -4.0 0.5)      //55u
	(0 -4.0 0.5)             //56u
	(0 -2 0.5)                 //57
	(0 -0.5 0.5)               //58
	(-4.0 -1.414214 0.5)      //59
	(-1.414214 -1.414214 0.5)  //60
	(-0.353553 -0.353553 0.5)  //61
	(-4.0  -4.0 0.5)        //62u
	(-1.414214 -4.0 0.5)     //63u
);

/* wirkliche Blöcke */
blocks (
	hex ( 5  4  9 10 24 23 28 29) (106 60 1)   simpleGrading (4.0 1     1) //0
	hex ( 0  1  4  5 19 20 23 24) (106 60 1)   simpleGrading (4.0 1     1) //1
	hex ( 1  2  3  4 20 21 22 23) (65  60 1)   simpleGrading (25.0  1     1) //2
	hex ( 4  3  6  7 23 22 25 26) (65  32 1)  simpleGrading (25.0 5.0  1) //3 o
	hex ( 9  4  7  8 28 23 26 27) (60   32 1)  simpleGrading ( 1    5.0  1) //4 o
	hex (16 10  9 15 35 29 28 34) (60   106 1) simpleGrading ( 1    4.0 1) //5
	hex (11 16 15 12 30 35 34 31) (60   106 1) simpleGrading ( 1    4.0 1) //6
	hex (12 15 14 13 31 34 33 32) (60   32 1)  simpleGrading ( 1    5.0  1) //7    Elemente nach vorn
	hex (15 18 17 14 34 37 36 33) (32  32 1)  simpleGrading (5.0 5.0  1) //8 o  Elemente nach vorn
	hex ( 9  8 18 15 28 27 37 34) (32  60 1)   simpleGrading (5.0  1     1) //9 o
	 
	hex (40 45 44 39 53 58 57 52) (60   106 1) simpleGrading ( 1    4.0 1) //10
	hex ( 0 40 39  1 19 53 52 20) (60   106 1) simpleGrading ( 1    4.0 1) //11
	hex ( 1 39 38  2 20 52 51 21) (60   65 1)  simpleGrading ( 1    25.0  1) //12
	hex (39 42 41 38 52 55 54 51) (32  65 1)  simpleGrading (5.0 25.0  1) //13u
	hex (44 43 42 39 57 56 55 52) (32  60 1)   simpleGrading (5.0  1     1) //14u
	hex (48 47 44 45 61 60 57 58) (106 60 1)   simpleGrading (4.0 1     1) //15
	hex (11 12 47 48 30 31 60 61) (106 60 1)   simpleGrading (4.0 1     1) //16
	hex (12 13 46 47 31 32 59 60) (32  60 1)   simpleGrading (5.0  1     1) //17 Elemente nach vorn
	hex (47 46 49 50 60 59 62 63) (32  32 1)  simpleGrading (5.0 5.0  1) //18u Elemente nach vorn
	hex (44 47 50 43 57 60 63 56) (60 32 1)   simpleGrading ( 1    5.0  1) //19u
);




edges (
	// innerer Ring, darf nicht verändert werden
	arc 0 5   ( 0.469846   	0.17101 -0.5)
	arc 5 10  ( 0.17101 		0.469846 -0.5)
	arc 19 24 ( 0.469846 	0.17101 0.5)
	arc 24 29 ( 0.17101 		0.469846 0.5)
	arc 11 16 ( -0.469846 	0.17101 -0.5)
	arc 16 10 ( -0.17101 	0.469846 -0.5)
	arc 30 35 ( -0.469846 	0.17101 0.5)
	arc 35 29 ( -0.17101 	0.469846 0.5)
	arc 0 40  ( 0.469846 	-0.17101 -0.5)
	arc 40 45 ( 0.17101 		-0.469846 -0.5)
	arc 19 53 ( 0.469846 	-0.17101 0.5)
	arc 53 58 ( 0.17101 		-0.469846 0.5)
	arc 11 48 ( -0.469846 	-0.17101 -0.5)
	arc 48 45 ( -0.17101 	-0.469846 -0.5)
	arc 30 61 ( -0.469846 	-0.17101 0.5)
	arc 61 58 ( -0.17101 	-0.469846 0.5)

	// äußerer Ring mit Radius 1
	/*
	arc 1 4   ( 0.939693 	0.34202 -0.5)
	arc 4 9   ( 0.34202 		0.939693 -0.5)
	arc 20 23 ( 0.939693 	0.34202 0.5)
	arc 23 28 ( 0.34202 		0.939693 0.5)
	arc 12 15 ( -0.939693 	0.34202 -0.5)
	arc 15 9  ( -0.34202 	0.939693 -0.5)
	arc 31 34 ( -0.939693 	0.34202 0.5)
	arc 34 28 ( -0.34202 	0.939693 0.5)
	arc 1 39  ( 0.939693 	-0.34202 -0.5)
	arc 39 44 ( 0.34202 		-0.939693 -0.5)
	arc 20 52 ( 0.939693 	-0.34202 0.5)
	arc 52 57 ( 0.34202 		-0.939693 0.5)
	arc 12 47 ( -0.939693 	-0.34202 -0.5)
	arc 47 44 ( -0.34202 	-0.939693 -0.5)
	arc 31 60 ( -0.939693 	-0.34202 0.5)
	arc 60 57 ( -0.34202 	-0.939693 0.5)
	*/

	// äußerer Radius mit Radius 2
	arc 1 4   ( 1.87939		0.68404	-0.5)
	arc 4 9   ( 0.68404		1.87939	-0.5)
	arc 20 23 ( 1.87939		0.68404	0.5)
	arc 23 28 ( 0.68404		1.87939	0.5)
	arc 12 15 ( -1.87939 	0.68404	-0.5)
	arc 15 9  ( -0.68404	1.87939	-0.5)
	arc 31 34 ( -1.87939 	0.68404	0.5)
	arc 34 28 ( -0.68404	1.87939	0.5)
	arc 1 39  ( 1.87939		-0.68404	-0.5)
	arc 39 44 ( 0.68404		-1.87939 	-0.5)
	arc 20 52 ( 1.87939		-0.68404	0.5)
	arc 52 57 ( 0.68404		-1.87939 	0.5)
	arc 12 47 ( -1.87939 	-0.68404	-0.5)
	arc 47 44 ( -0.68404	-1.87939 	-0.5)
	arc 31 60 ( -1.87939 	-0.68404	0.5)
	arc 60 57 ( -0.68404	-1.87939 	0.5)
);

boundary  (
	top	{
		type symmetryPlane;
		faces	(
			(7 8 27 26)
			(6 7 26 25)
			(8 18 37 27)
			(18 17 36 37)
		);
	}
	
	bottom	{
		type symmetryPlane;
		faces (
			(49 50 63 62)
			(50 43 56 63)
			(43 42 55 56)
			(42 41 54 55)
		);
	}

	inlet {
		type wall;
		faces (
			(14 13 32 33)
			(17 14 33 36)
			(46 13 32 59)
			(46 49 62 59)
		);
	}
	
	outlet	{
		type wall;
		faces (
			(2 3 22 21)
			(3 6 25 22)
			(38 51 21 2)
			(41 54 51 38)
		);
	}

	cylinder {
		type wall;
			faces (
				(10 5 24 29)
				(5 0 19 24)
				(16 10 29 35)
				(11 16 35 30)
				(48 11 30 61)
				(45 48 61 58)
				(40 45 58 53)
				(0 40 53 19)
			);
	}

	frontAndBack {
		type empty;
		faces (
			(5 10 9 4)
			(24 23 28 29)
			(0 5 4 1)
			(19 20 23 24)
			(1 4 3 2)
			(20 21 22 23)
			(4 7 6 3)
			(23 22 25 26)
			(4 9 8 7)
			(28 23 26 27)
			(16 15 9 10)
			(35 29 28 34)
			(12 15 16 11)
			(31 30 35 34)
			(13 14 15 12)
			(32 31 34 33)
			(14 17 18 15)
			(33 34 37 36)
			(15 18 8 9)
			(34 28 27 37)
			(45 40 39 44)
			(58 57 52 53)
			(40 0 1 39)
			(53 52 20 19)
			(39 1 2 38)
			(52 51 21 20)
			(39 38 41 42)
			(52 55 54 51)
			(44 39 42 43)
			(57 56 55 52)
			(47 48 45 44)
			(60 57 58 61)
			(12 11 48 47)
			(31 60 61 30)
			(13 12 47 46)
			(32 59 60 31)
			(49 46 47 50)
			(62 63 60 59)
			(50 47 44 43)
			(63 56 57 60)
		);
	}
);

mergePatchPairs();