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Found 16 results

1. Coupled Thermo-Mechanical SPH Solution

Is it possible for Radioss to solve a transient coupled thermo-mechanical problem using smooth particle hydrodynamics? For an example, My fluid's viscosity is strongly a function of temperature, where temperature is strongly a function of strain and time, where strain is a function of temperature, viscosity, and power input. Can anyone tell me if Radioss is an appropriate solver for this type of problem?
2. SPH meshing problem

Hi,I am trying to simulate a bird impact on a plate with RADIOSS. So I am creating my model on hypermesh now, i chose to consider the bird as a fluid with a density of 438 kg/m3. I would like to work with SI units and the dimensions of the bird are : 0.1325m long cylinder with two hemisphere ends having a radius of 0.075m. I am now trying to mesh this geometry with the SPH module in hypermesh. So i entered a pitch of 1e-3m and a density of 438kg/m3 as i said before. But when i create the mesh, nothing happen and i only get this message "0 mass elements created". I attached my file with the topic. I don't know what could be my error, more of that I tried to do it using mm instead of m and it worked... But I really want to use SI units. Thank you in advance for your help, Gaspard. BirdStrikeSI.hm
3. SPH meshing problem

Hi, I am trying to simulate a bird impact on a plate with RADIOSS. So I am creating my model on hypermesh now, i chose to consider the bird as a fluid with a density of 438 kg/m3. I would like to work with SI units and the dimensions of the bird are : 0.1325m long cylinder with two hemisphere ends having a radius of 0.075m. I am now trying to mesh this geometry with the SPH module in hypermesh. So i entered a pitch of 1e-3m and a density of 438kg/m3 as i said before. But when i create the mesh, nothing happen and i only get this message "0 mass elements created". I attached my file with the topic. I don't know what could be my error, more of that I tried to do it using mm instead of m and it worked... But I really want to use SI units. Thank you in advance for your help, Gaspard. BirdStrikeSI.hm
4. SPH+Material

Hi everyone, could anyone tall my if it is possible to use SPH and material law 51? I have to simulate a bottle filled for 97% with fluid and 0.3% with air and I'd like to use SPH method. Could someone help me? Thanks in advance! Marta
5. Modeling wave generation and absorption

Hi, I'd like to model a box floating in open water, that means that wave generation and especially wave absorption should be modelised. I've modeled this on Hypermesh with the solver Radioss In this model, there are 2 sorts of interaction : - fluid/fluid : air with water - fluid/structure : both fluids with the box. First, I've used an ALE model for the fluids. I've tried to use both MAT/LAW51 (multimaterial) and MAT/LAW37 (biphasic material) in order to model this, but everytime there is a leakage and the computation can't run until the end (negative rho error). I've also tried to use MAT/LAW11 (bound) because it doesn't work properly with a biphasic material (negative rho error). Then, I've tried with an SPH model with IN and OUT condition, so that the computaiton doesn't take into account the air/water interaction, the computation also stops because of a leakage. For the fluid/structure interaction, I've used INTER/TYPE18 and INTER/TYPE7 respectively for ALE and SPH model. I have to set a STfval value for the stiffness. I use the formula of the Help page : stfval=rho*v²*A_el/GAP = 66.667avec - rho=rho_water = 0.001g/mm3; - v=10 mm/ms , initial velocity of the box when it is dropped in the water; - A_el = lagragien element surface =500 * 500 mm² ; - GAP= 1.5 * E_el = 1.5 * 250 = 375mm With this value, the box is floating in the air, the only way i've found a value that models reality was by dichotomy.. That's not convenient for further simulation with different initial data.... Should you have any suggestion to model an infinite water volume (so wave absorption) and for the stiffness value, please contact me. Sincerly yours, Emmanuelle
6. SPH Setup Error

@George P Johnson I tried simulating simple SPH model with gravity load and Simple BC with two different pitch for SPH in a single component. But not getting the proper behavior. I assumes it to be maintain the pitch as in its location, because in my main simulation I want to refine the area of focus with small pitch value. Attaching the deck file along with animation. 11aa.avi sph_bc_0000.rad sph bc_0001.rad
7. ERROR with SPH

Hi, I'm doing an analysis of sloshing with a fuel tank. The total event time is 0.7 seconds. On time around 0.4 seconds, the run did stop and this follow message appears to me: MESSAGE ID : 174 ** ERROR : NULL DIAMETER FOR SPH PARTICLE ID=21643 ERROR TERMINATION I'm using a controller of time-step do run this model. Would somebody help me? Best regards, 4_0001.rad 4_0000.out 4_0000.rad 4_0001.out
8. SPH formulation - box deformation

Hello Everybody, I'm trying to use SPH Method with Radioss. I would like to determinate the deformation of a box full of water. I've modeled SPH Particles of water as simple cubic and I've used interface type 7 between water and box. Loads: lock of the base of box and gravity load to water particles. The simulation run without error but results are different than expected: pressure is not uniformly distributed becuase particles don't mantain the initial pitch. What is the error? In attach the .hm file. Could someone help me, please? Thanks in advance. prova_acqua.hm
9. SPH formulation

Hello, I am trying to simulate a tube (ex. toothpaste tube) packing operation. I have to check product behaviour while tube is packing. I used SPH particle. But I dont get appropriate results. i shared rad file. tube_0000.rad

Hi, I want to create a Lump Mass of a stack of Iron Ore over an area (the stack is in the form of a cone). Thought of creating that stack with SPH elements. Is it right approach to this problem? If Yes, what should be the PROP of the SPH (such as: qa, qb, order etc.) and what should be the MAT (Material law and respective parameters) If No, what other alternative available for this. Thanking You. rgrds, Pritam
11. SPH-INOUT Condition

Hi there, I am trying SPH INOUT Collector for simulating water flow at a certain speed in a tank and a pole at middle of the tank. My aim is to capture the vortex formation around the pole. But first of all I'am unable to define properly the INOUT condition (SPH is moving away from the inlet boundary). A set of SHP Particles moving and collides with other (as shown below) At outlet I defined atm. pressure function. I am attaching the deck with the simulation HV video to represent my problem. Kindly request to consider my problem and suggest some solution for it. Thanking You. rgrds, Pritam Inout_0000.rad Inout_0001.rad
12. Introduction of Nanofluidx - SPH solver

Hi All, Click here to view a webinar on Nanofluidx capabilities Regards, Kamlesh
13. Bird Strike experiment reproduction by RADIOSS

Hi I'm now working on BirdStrike Analysis using RADIOSS140. Like many paper on birdstrike analysis reports, I've done a reproduction of birdstrike experiment carried out by Wilbeck in 1977 [1]. The resultant pressure PH(*1) and PS(*2) meets with theoretical value very well. Except that,if you look at the pressure curve, there is a "ZERO Pressure" period just after the first contact. Taking closer look into the animation, the SPH bounce back just after the contact. Such blank period doesn't appear in the experiment result,or analysis results of other researchers report. [Question] : Is there a way to correct this ? Model setting is follows. -bird is using SPH. Material law is MLAW6 (Equation of State). -Using contact TYPE7. Istf = 1 StFac = 550 … recommended value by Altair Support Igap = 0 gapmin = h/2 (h = SPH radius) … recommended value by Altair Support I've varied the value of these parameters which didn't make any difference on "ZERO Pressure" period. ******************* *1 … PH: the peek pressure just after the contact(Hugoniot Pressure) *2 … PS: the constant pressure when bird deformation can be seen as constant flow.(Stagnation Point Pressure) [1]:J. Wilbeck,AFML-TR-77-134 1977 161121_Bird Strike experiment reproduction by RADIOSS.pdf
14. 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
15. SPH ditching IMPVEL or INVEL?

Hi everybody I'm working on a simple model, a water entry of a sphere, of which i have a rudimental experiment; a woody sphere 40 mm diameter dropped from 60 cm above water surface in a glass tank 600x300x330 mm. I model the sphere with shell elements, and a rigidbody linkening all sphere's nodes with the master node in the centre of sphere; my problem is this: If i apply an initial velocity, in the master node of RBody, of 3 m/s that is approx the velocity of sphere just before water entry, the behaviour of sphere is not absolutely the same of my experiment; the sphere just enter for some cm and comes to the water surface, in addition the behaviour of water is far from the experiment. If i apply a Imposed velocity of 3m/s for 0.015 s to the master node the general behaviour is completly different and is more more near the experiment behaviour; the sphere goes down in water, not until the bottom like in experiment, but much more respect the initial velocity load model; the water splash is much more realistic and almost equal the experiment (considering that i don't model the air, that is incorporated in a small part into the water during the sphere motion, and no atmospheric pressure is applied) I would know why such difference between initial velocity and imposed velocity? regards to all Damir
16. SPH- Smoothed Particle Hydrodynamics and Type7 interface

Good morning to everybody I'm working on ditching bodies in water, modelling it with SPH elements, and the bodies like rigid bodies. I use interface type7, as master i take the body surface, and slave nodes i take the sph elements (nodes); In interface edit panel, i use Istf=1 (just 0 and 1 avaible for sph formulation) and here we came to my need: i have to calculate the interface stifness (with istf=1 STFAC=costant interface sifness), between water and body, because from this depends in a large part the time step, but i don't know how. Should i consider a simple average value between bulk modulus of water and young modulus of body material, or a average weighted value, by a characteristic of entry in water, like entry speed or water height... thanks to all Damir
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