# DAMIR88

Members

45

• Rank

## Contact Methods

• Skype
Damir Maleskic

## Profile Information

• Gender
Male
• Are you University user?
Yes

## Recent Profile Visitors

1247 profile views

1. ## Interface type 7: how to calculate STFAC if ISTF=1?

Great!!! But if i had not experimental data witch to refer and compare qualitative or quantitative data, i cannot procede with trial and error method. I'm i wrong?
2. ## Interface type 7: how to calculate STFAC if ISTF=1?

Yes, we are almost there... So if i use ISTF=1, i need a low stifness interface (STFAC), for low down the dumping coefficient and increase the time step. But is there a way to calculate this stifness interface? How can i decide between 1MPa, 40000Pa or 400Pa...? May i refer to a characteristic quantity, like sphere water entering velocity, to calculate the stifness, and if is so, is there a formula to use? thanks
3. ## Interface type 7: how to calculate STFAC if ISTF=1?

Hi Prakash Yes, with ISTF=1 i input a STFAC of 40000Pa and the simulation is large faster than ISTF=0 and STFAC=0.1. In Fact Nodal time step can be seriously affected if penetration is large as the online help says. It says also that "Moreover, there is a viscous damping acting on the rate of penetration. The contact force is then computed as: " so incrasing stifness interface we increase the viscous damping acting on slave nodes, and it results in the viscous behaviour of water. Could it be the reason? thanks
4. ## Interface type 7: how to calculate STFAC if ISTF=1?

Hi everybody i'm simulating a quarter sphere entering in a tank with water; i modelled the water using SPH elements. between the surface of sphere and particles of water i use a type7 interface. i have tryed two ways: with ISTF=1 i set a STFAC=40000Pa with ISTF=0 i set STFAC=0.1 (it is a scale factor to be multiplied by the young modulus of the sphere material, i have wood with E=14500MPa so by 0.1 it is 1450MPa as interface stifness) it comes out a more larger stifness interface respect the previous one. All the rest of model is the same between the two simulations the simulation with lower STFAC seems to be less viscous than the one with bigger STFAC. I'm i wrong? Dose some know why this is the behaviour of water? What does interest the interface stifness with this kind of behaviour? Thank you to all
5. ## Rigid Body Mesh

ok, i understand...but with ISTF=1 and setting a high STFAC , the interface time step jumps too low...i'm wrong?
6. ## Rigid Body Mesh

ok...and this is an idea... what if i use rigid mesh in automesh panel and instead of ISTF=0 i use ISTF=1 so defining a precise STFAC in Pascal? in conclusion i need a sphere (shell elemnts) that behaves as rigid body, so no stresses and strains calculated and output, but with the need to define a type7 contact with a interface stifness... whitch could be the easiest way to do this? thanks
7. ## Rigid Body Mesh

Hi Prakash no, i do not see any stress strain data... to be explicit i'm on the sphere ditching in SPH (water); but my doubt is this: if rigid mesh defines elements just for a topological reppresentation, how can i use these elements as master surfaces in type 7 interface, if don't define a young modulus for sphere material (supposing type7 interface vith ISTF=0 and STFAC= %of young modulus if the material of master surface)
8. ## Rigid Body Mesh

Thanks NSKRTLUS and Prakash I have a body that i mesh 2D with shell elements; for that body i define i rigid with a master node in the centre and the mesh nodes as slave nodes. In the master i apply a initial velocity. But if i mesh it with "rigid body mesh" in Automesh panel, the software will not calculate straind and stresses? Why should not behave like rigid mesh if i define i propery and material? Foe example in any ditching problems i wolud like to treat the ditching object like rigid, but i need a mesh to define interfaces between the object and the fluid. Supposing that the body will float, if i do not define a thikness and density for that rigid ditching body, how can software compute the Arichimedes Principle?
9. ## Rigid Body Mesh

Hi everybody I would like to create a rigid mesh on the surface of a body, because i need a rigid body, for which are not calculated stresses neither strains. Could i mesh this surface using "rigid body mesh" panel in automesh panel? if it is the way, the mesh created will be used just to compute other things like interfaces reactions or others, and the mesh created will be completely rigid ... i'm i wrong? thanks
10. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

Hi Prakash yes, now is clear. i was occuped for an exam, i'm going to continue the work with SPH. Damir
11. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

So the question is: is there a relation to take in account to understand whitch values of Qa and Qb to use, to get a natural behaviour of water? referring to the previous two models, for me, the real behaviour of water was that described by Qa and Qb both 1e-20, and not with the default values 2 and 1 what do you think?
12. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

Hi Prakash I have run my model with Qa=1e-20 and Qb=1e-20 and it behaves very naturally I have run, also the model with Qa=2 and Qa=1 and it behaves strongly viscous The modes are the sames and i used an ORDER=-1 and Alpha_cs=0.001 in both of them. They were the sames, a part of Qa and Qb. i send you two small video in dropbox thanks
13. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

Hi Prakash The units in the model i sent you yesterday in dropbox are: meters, kilograms and seconds
14. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

Prakash Now i'm trying with these Properties, do you think they are right? Mat/LAW6 Water: Kinematic Viscosity=1e-6 Pa and C1=2,2 GPa and Pmin -1e-30Pa and all others parameters set to zero Sph Property: Qa=2 Qb=1 Alpha_cs=none Order=0
15. ## How choose the artificial sound of speed to use an artificial bulk modulus for water?

ok, but i have a simulation with Qa and Qb set to 2e-3 and 1e-30 , but the water continue to behave too viscous; and the sphere remains trapped in water, seems it behaves like an oil. The material used is MAT/LAW6; in this simulation i use the real bulk modulus. Could it be too low values of parameters?
×
×
• Create New...