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Found 16 results

  1. Hi everybody i would perform a simulation of a lifeboat ditching, like in the tutorials where is used an ALE approximation, but using the SPH approximation, smoothed particle hydrodynamics. Does anyone know how build a sph model in hypermesh and solve it with radioss? Are any kind of tutorial about SPH simulation online? i was not able find it anywhere... Thank you!!!
  2. Emmanuelle Fergon

    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
  3. Pritam K

    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
  4. Rickson Thiago Fernandes

    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
  5. 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
  6. Harsh2610

    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
  7. Pritam K

    Lump Mass in Radioss

    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
  8. Pritam K

    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
  9. Hi All, Click here to view a webinar on Nanofluidx capabilities Regards, Kamlesh
  10. 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
  11. 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
  12. Good evening to every body i'm working on sph modelling of water; to obtain reasonable time step i have to use an artificial bulk modulus in the MAT LAW 6. I have found in the Monagham teory that it should be chosen using an artificial (lower of the real one) sound of speed that should be at least 10 times the maximum phenomena speed. I'm testing a water entry of a wedge, and the water surface imapact speed is 3 m/s. The water tank is in complete rest situatuion. Is this speed that i should use as "maximum speed of phenomena"? Thanks
  13. LBG

    Pressure Captor into SPH

    Hello I actually work in SPH and I would like to create pressure graphs with Hypergraph. Usually, in hyperwork, to have this kind of data, you put pressure sensor into element, which is logic since you make pressure calculation in a volume. But, when you visualize results with HyperView, you can see the pressure evolution, so it should be possible. But, in SPH, there is no element, only nodes. So how can I input pressure sensor into hypermesh, to be able to view them with hyperGraph, after a radioss calculus ? So how or which sensor do I need, where to get it, or which modification should I change in the 0000.rad to be able to have those graph under hyperGraph2D in SPH model Sorry for any poor english, I am french, thank you very much in advance Regards
  14. DAMIR88

    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
  15. 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
  16. DAMIR88

    What is ERROR ID: 400?

    Hi guys I'm trying set up a model of a ditching body in water, modelling Water by Smoothed Particle Hydrodynamics. And i would like to model just an half of entire model applying symmetry conditions. By using /SPHBCS card for the sph symmetry conditions, i select a frame i have previously created, that defines the symmetry plane by the /DIR value. But running radioss it gives me this error ERROR ID : 400 ** ERROR IN SPH CONDITIONS (FRAME) DESCRIPTION : UNDEFINED REFERENCE FRAME ID=1 What could be the reason? maybe i mistake something creating the system or imposing symmetries for SPH elements? Thanks to All D.M