Science method

# Numerical Modeling - Science method

Explore the latest questions and answers in Numerical Modeling, and find Numerical Modeling experts.

Questions related to Numerical Modeling

I'm doing a research on numerical investigation of behavior of steel concrete composite beams. I'm using the Abaqus software in my analysis. In my model, I'm using shell element to model the Steel beam and solid element to model the concrete slab where the reinforcement has embedded in it. The steel beam and the concrete slab is connected using the shear studs which were modelled using solid elements.
My question is,
If we use a tie constrain in between the steel beam top flange (modelled with shell) and shear studs (modelled with solid element) what would happen to degree of freedom in rotation of the steel beam? Here I have used a tie constrain to simulate the welded connection between the steel beam top flange to the shear studs.
Will ABAQUS automatically constrain the degree of freedom in rotation if I use this interaction? If so will it cause any inaccuracy in the final results?

Also, is there any possibility to use shell to solid coupling to simulate the same interaction?

I modeled a earth dam

I want to Simulation Rapid Drawdown of the earth dam at different rates with FLAC 2D software.

Who knows the FISH function or a way to do this simulation in FLAC2D software?

I am attempting a numerical modeling of a pullout test for reinforced concrete. I have calculated the stiffness parameters following the FIB 2010 standard. I used cohesive contact interaction property for modeling ineraction between embedded length of rebar and concrete. However, for some reason, my bond stress vs. slip curve is not declining as expected. I also tried randomly increasing the stiffness parameters (Knn, Kss, Ktt), but the curve still does not behave as it should. Can you suggest what I should do?"

I have written a numerical model for calculating the elastic deformation of two elastic bodies in 3D static contact. The code takes the applied laod, Young's Modulus, Poisson ratio, and surface profile of each body. Calculates influence coefficients based on the equation provided by Love [1]. The problem is solved by conjugate gradient descent and elastic deformation is calculated by Discrete Fourier Transform- Discrete Convolution method.

I tested the model on ball-on-flat and ball-on-ball geometries with the same material properties of each body. I am facing the problem that the elastic deformation contour is diagonal instead of concentric in these cases. The pressure distribution normalized at Hertz Contact pressure and contact width is correct, but the deformation is not. I have double-checked by Kernal/influence coefficient matrix but can not seem to understand this behavior. I have attached the 3D plots of the example (ball-on-ball), the 3D plot of the influence coefficient at 1 point, and the contour of calculated deformation.

Any help, guidance to solve, or help in understanding the problem would be greatly appreciated.

Thanks.

A.E.H. Love. Stress produced in a semi-innite solid by pressure on part of the boundary. Philosophical Transactions of the Royal Society of London, 377:54{59, 1929.

I have modeled a two-dimensional plane strain embankment in Abaqus. I did not apply any forces, boundary conditions, or displacement to the infinite element, and I defined it as CINPE4. I defined two steps for the model: the first step is static to apply gravity load, and the second step is dynamic implicit. In the second step, I applied the time history of the Loma Prieta earthquake horizontally on the base of the model. Ultimately, I observe a concentration of shear strain at the boundary between the infinite and finite elements, as shown in the image below.

In addition, I have attached my model's .inp file to this question for reference.

I want to simulate a discrete random media with FDTD method.

the simulation environment is air that is filled with random spherical particles (that are small to the wavelength) with defined size distribution.

what is an efficient and simple way to create random scatterers in large numbers in FDTD code?

i have put some random scatterers in small area but i have problem producing scatterers in large numbers.

any tips, experiences and suggestions would be appreciated.

thanks in advance.

I am working on Numerical modelling to simulate tribological interactions while marble cutting. If anyone familiar please guide me little bit on this.

Thanks and Regards,

Bhargav Prajwal

How to use matlab to model permafrost priority flow and predict permafrost degradation using the dual permeability model, lattice Boltzmann model or other numerical models of priority flow

I require few tips regarding matching the numerical model of drop weight test with the experimentally obtained data.

I will briefly discuss the drop weight model here. I have modeled a drop weight test on ANSYS workbench. The impact velocity is 2.653 m/s. The impact is happening on a rubber/jute epoxy composite which consists of 2 layers. The upper layer is rubber with modulus of 10 MPa. The lower layer is Jute epoxy composite.

The experimental drop weight curve is already obtained. The material properties of jute epoxy composite are obtained using U20MM software. Some of the stress limits of jute composite (Tensile strength, compressive and shear strength) are obtained using literature. The jute epoxy composite and rubber is modeled as solid plate. The current mesh is coarse. Please note rubber is not modeled using hyperelastic model to avoid complexity. Please see the attached file to see the force vs time curve and the difference in experimental and numerical data. Blue curve is obtained numerically.

Can anyone provide few tips in tuning the material properties/model to match the numerical data with experimental curve.

The application of numerical models in the simulation of rock/soil cutting process and at the same time the wear on the cutting tool.

Dear colleagues,

I am currently conducting a non-linear Pushover Analysis using a Finite Element Method (FEM) software. To ensure the accuracy of my numerical model, I am seeking to validate it against experimental results. Specifically, I am interested in calculating the error between the obtained numerical results and the experimental data and what is the limit error value.

I kindly request your guidance on the most appropriate metrics for calculating the error in my Pushover Analysis. Any advice, references, or past experiences you can share with me would be greatly appreciated.

Thank you in advance for your assistance.

Best regards,

Ismail

Using Abaqus how to analyze diffusion rate in resistance spot welding

For comparison study of experiment and numerical work, I have to create rough surface structure modeling. which implies my numerical model would be more accurate equal to the experimental work.

But I don't know how to create a rough surface on all the inner walls of the channels (see the attachment).

Approximate dimension details:

Channel width 0.5 mm and height: 1mm

Ra: 300 micrometer

Please help me with how to do that.

Hi, i am trying to run HD and ST model with MIKE 3/21 Integrated Model for a coastal area for 1 year with 600 sec timestep interval but there is an abnormal error in the middle of the year. It's 'Blow-up elevation too large'. When I examine the result, there is an anormal elevation values (about 30000 meter) in some nearshore cells. So I changed the timestep interval, resolution but didnt worked. Also, when I runned only HD model, model worked without a problem. But when HD and ST run coupled, there was an error.

So if there is anyone who experience or knowlegde about this issue, can you help me?

Thank you.

Hi All

I am participating in research on numerical simulation of tall buildings' behaviour under different levels of wind speeds (in terms of magnitude). My team need secondary experimental data on the behaviour of tall buildings under wind loads. We need raw data that has just been obtained from the lab/wind tunnel without being processed. We need it to validate the numerical model on the same. Kindly good people, come to our aid. We need it as soon as possible. We can buy if it is for sale. You can contact me on +254 113 957414 or email: deenturayosman@gmail.com.

Thanks, and best regards.

I am student , I have to show the impact of urbanization on groundwater using a numerical model ( feflow) or if someone can help me with another software.

please

thank you

I am using the accelerometer (7264D-2KTZ-2-360) to measure the value of acceleration and multiply with mass to get impact force.

For a mass of 4 kg (timber), dropped at the velocity of 4 m/sec on an aluminum panel, I am getting the contact force of 80kN from my numerical model. And when I take acceleration as field output, it's around

**1200 m/sec2**. However, I am getting the value of the acceleration of around**17 gs (170 m/sec2) from the experiment.**Back calculating my

**gs from the numerical model gives around 130 gs**. I was wondering if such a high value of g is possible for such a low velocity of impact.I need the .for file for numerical analysis

In order to represent our observations or sight of a physical process and to further investigate it by conducting experiments or Numerically models? What are basics one need to focus ? Technically, how one should think? First, thing is understanding, you should be there! If we are modeling a flow we have to be the flow, if representing a let's say a ball, you have to be the ball! To better understand it! What are others?

Hi,

I am working on numerical modeling of a two-phase model for the sediment transport problem
based on the SPH method.

According to previous research and works, none of them mentioned the calibrasion of numerical models and only the validation of the models were done by comparing the numerical results with the laboratory results of common samples such as dam break test cases.

Is calibrasion required for such numerical model?

What is the best option for the calibrasion of results from this numerical modelling?

The 'set large' model has been invoked in the Flac, the calculation step always stop when a failure zone occurs. In this case, I want to use the command of rezone to remesh the grid, but I do not know how to write the Fish function. Can anyone please tell me how to write it?

Pls refer to my command and calculation result in the attachment. Thanks!

Hi

I'm working on a research for developing a nonlinear model (e.g. exponential, polynomial and...) between a dependent variable (Y) and 30 independent variables ( X1, X2, ... , X30).

As you know I need to choose the best variables that have most impacts on estimating (Y).

But the question is that can I use Pearson Correlation coefficient matrix to choose the best variables?

I know that Pearson Correlation coefficient calculates the linear correlation between two variables but I want to use the variables for a nonlinear modeling ,and I don't know the other way to choose my best variables.

I used PCA (Principle Component Analysis) for reduce my variables but acceptable results were not obtained.

I used HeuristicLab software to develop Genetic Programming - based regression model and R to develop Support Vector Regression model as well.

Thanks

My model is a 2D axi-symmetric numerical model, with a needle electrode in the middle and a quartz capillary at the periphery, helium is ejected to the outside from the annular gap formed by the previous two. What conditions should be set for the boundary（red logo）of the needle electrode and the capillary at z=0, can anyone tell me?

Experimental results of the Sound absorption coefficient of material have mostly been found to be in good terms with the Theoretical models. But the calculations look confusing. With imaginary terms and differential equations.

Are there any simplified calculations and methods for theoretical modeling in acoustics?

I made a numerical model of a reinforced concrete frame in ANSYS APDL software in order to perform a PUSHOVER analysis, but the only experiment results that I got from the literature are obtained from a cyclic load experiment. However, the results are illustrated in terms of Base reaction versus roof displacement.

My question is, can I validate my numerical model with the envelope of the experimental cyclic results?

Hello,

I am using macro modelling to model using a solid element masonry triplet. When using the CDP model in ABAQUS the model runs completely and gives me satisfying results compared to the experimental data. However, I am trying to compare the CDP with the Concrete Smeared Cracking model, but the analyses terminate quite early (Probably before cracking).

The material model is defined using density, Elastic and Concrete Smeared Cracking model including Failure Ratios (as default) and Tension Stiffening, did not add Shear retention.

Has anyone from the community came across such situations? and how did you make your model work?

I was thinking that maybe besides the aforementioned parameters other damage criteria has been introduced when using the Concrete Smeared Cracking model.

Many thanks in advance and I would be please if anyone could share their similar experience with me.

I'd like to draw a simple model on Plaxis LE designer but I did not find any guideline video that could help me to design it.

The model sample I attached. Please I hope any one can help me as fast as you can

Thanks

Dear All,

Has a numerical model of the six-DOF seismic shake table been developed to predict the effect of changes in specimen characteristics on the actuator force and shaking table performance?

Has the foundation of the shake tables ever been built using isolators?

Any comments is appreciated.

Dear all,

What are the factors to be taken into consideration when modeling stone columns in FLAC 3D? Are there differences between the modeling of stone columns and piles?

I'm trying to run Mike 21 FM HD model for a river with two boundaries. For upstream I got constant value of discharge and for downstream I set a Water Level time series which relate to the open boundary.

I wanted to test and run the model for 2 days with 30 sec time-step interval but I get an abnormal run completion in the first time step. And there is "Blow Up - Elevation too large". It shows very large water depth. Any suggestions are appreciated.

Thank you.

I am doing numerical model for FSW, I want to know which Equation of State is more compatible for FSW. EOS Polynomial or EOS Gruneisen?

The seismic pounding in adjacent buildings is an important topic in PBSD. Suggestions are requested to numerically model the interaction between the two structures: With Contact Elements? With structural interface elements? With Springs? Thanks in advance for the suggestions.

Dear all,

I am working on analytical and numerical modelling of the energy harvester. what should be the maximum percentage error difference between analytical and numerical results (voltage and deformation)?

Any help would be highly appreciated.

Regards.

Hi

I'm using three different performance criteria for evaluating my model:

1.Nash–Sutcliffe (NSE)

2.Percent bias (PBIAS)

3.Root mean square error (RMSE)

You can suppose that I used a regression model to estimate a time series data such as river mean daily discharge or something like that.

But for a single model and a single dataset, we saw difference performances for each criteria.

Is this possible? I expected that all of these three criteria have same results.

You can see the variation's diagram of these criteria in appendix pic.

Thanks

Hi all

Im modeling interaction of soil and reinforcement in abaqus. As you know there are two obtaining parameters for soil-reinforcement interface from direct shear test of soil and reinforcement:

1. Friction coefficient between these surfaces

2. Apparent cohesion (adhesion)

for simulating mentioned interaction in abaqus I used surface to surface contact algorithm.

Friction coefficient can be defined in Tangential behavior >> Penalty method, However I can not find any way to insert apparent cohesion of interface.

It should be mentioned that Intrinsic cohesion of soil inserted as a plastic property of soil in mohr - coulomb plasticity. But apparent cohesion between these two surfaces cannot be defined in mentioned part, because this property is related in both surfaces.(its not the plastic property of one material).

Im wondering to hear any suggestion.

Thanks for your attention beforehand.

Alireza Akbari

Dear researchers.

I would like please to get your opinion and expertise on this issue.

If we have a paper that deals only with a numerical results obtained from simulation.

Is there any journals could publish that paper since the experimental results can not be obtained?

I would appreciate any recommendation, expertise , advice... as I am posting that to learn from your wide knowledge.

Hi

I wanna model interaction between two different material(soil and reinforcement)in abaqus.

As I know when there is no penetration between these two parts, hard contact must be defined in normal behavior however in my simulation reinforcement penetrates in soil due to loading in normal direction so I think soft contact is required in normal behavior. right??

for this purpose linear relation must be defined but I don't have stiffness (coefficient between stress and over closure).

It should be noted I tried some different value for stiffness just to see effect of that, however the analysis didn't convergence at all.

I'm willing to hear your suggestions.

Best Regards

What is the best statistical index using to evaluate numerical modelling results (R2, MSE, RMSE, MAE, ... etc).

I want to use climatological ocean circulation data into my numerical model as open boundary condition. I found that HYCOM, SODA or CMEMS do not seem to provide climatological circulation data, and WOA only contains climatological temperature and salinity. Previous method I used is that calculated the mean current velocity by many years Reanalysis data, which is complex and need to download many daily or monthly data. So I wonder is anyone use a climatological ocean current data product? Where can I found? Or why many Reanalysis dataset don't have this?

Thank you!

Hello everyone, I would like to select specific areas to apply my model by using APDL, I want to automate as much as possible the numerical simulation and therefore I would like to work with a loop to select the surfaces and then apply the numerical model.

you can give me ideas and proposals please, you will find the geometry in image

I want to model a moving concentrated force to simulate the moving wheel load on the pavement in a simplified way as shown in the attachment. So, is there any way to model the moving concentrated force in Abaqus (without modeling the wheel).

Hi dear researchers

Im trying to model polymeric material, but the elastic module of that is not constant and varies with change in strain, this polymeric strip(membrane element) is embedded in soil as a reinforcement and tensile load will be applied to that, so I wanna know if for my purpose using property >> mechanical >> elastic >>Hyper elastic is suitable or not, because as I know entering stress -strain test data is possible in hyper elastic.

Im wondering if using hyper elastic requires any special conditions or not or any alternative( better) way for my purpose.

Hi

I know the procedure of modeling modal analysis to obtain natural frequencies(I mean using Linear perturbation step>>frequency and without defining any other loading....) but the problem is all examples I have seen is just for model made of just one material(most examples for cantilever beam) but my model is consist of two or more material( 2layer soil and layer of polymer between these soil layers), for obtaining natural frequencies in this case, my exact question is: I have to run modal analysis for each material separately or all together?!

I should mention that the polymeric membrane part does not have any type of support and its just in interaction with soil( normal and tangential behaviour), and if I run the modal analysis for this part alone natural frequencies for polymeric membrane is zero. while the soil is fixed at bottom and sides and by running modal analysis once for soil alone and another time soil with polymer,the natural frequencies are the same for both conditions. so i'm willing to know any advise and special point to obtain natural frequencies procedure for model consist of two or more materials in abaqus.

FLOW 3D is a one-phase numerical model with empirical equations for bedload transport, but OpenFOAM is a physics-based code.

Hi researchers

Im trying to model dense sand which has peak friction angle and constant volume friction angle . As you k now if we plot shear stress - shear displacement(strain) of dense sand till reaching specific displacement curve ascends to the peak point(peak friction angle)and after that with slight reduction becomes constant(constant volume or residual friction angle). I wanna model the behaviour of soil accurately so my purpose is to define friction angle as a function of shear displacement. I searched and understood using SUBROUTINE (specially USDFLD) may help me but I have not work with subroutines at all and this is my first time however I linked vs code and intel R with abaqus and its completely ready for working.

I will be thankful to hear your helps and advises.

Hello everyone,

I have a very naive question. I am working with inhouse code and adapting it for combustion studies ( with flow dynamics ). However, I am unable to find any simple test case to validate the code.

Most of the studies I have come across are multistep. I thought to validate them first with premix or non-premix analytical results but have not been successful to find test case with appropriate reaction mechanism. ( I am looking for single step finite rate chemistry to be simplify things ) .

May some one suggest or recommend some means to do that.

Thanks

Hi,

How the sound absorption coefficient of an acoustic absorber can be calculated using the thermo-viscous module in Comsol? When I tried to calculate the sound absorption of the Helmholtz resonator, it shows lower absorption values than the study done using the narrow region acoustics model. Compared to the thermo viscous model, the narrow region model gives better matching with the analytical model. Can anyone please help in this regard? What are the boundary conditions we have to take care of when we using the thermo-viscous module?

The numerical model and results are attaching here. Thanks in advance.

Howdy!

I am in the process of modeling a very complex manufacturing process that involves a mixture (solid & liquid) with mechanical, thermal, optical and chemical reactions happening simultaneously. In top of that, I also need to take into account stick-slip boundary conditions and a free boundary that evolves and eventually encounters an obstacle (a mold).

I already derived a highly nonlinear system of PDEs that models its behavior and I am about to finish the numerical simulations of a linearized version of the aforementioned problem using Matlab only. Trying to solve the general problem with Matlab would be extremely difficult thus I am now in the search of the best software package that can take into account all the previous phenomena. Any suggestions would be greatly appreciated.

Thank you!

I am working on concrete materials, as part of my Ph.D. work, I need to carry out my thesis work with theoretical and numerical models. Please suggest me.

Thank You

Hi

I am planning to do numerical modeling to know the best shape of a handheld mixer with baffle plates to mix water with a gel homogeneously at the least possible time. However, I am new to numerical modeling.

Could someone guide me in the below questions?

1. What characteristics of the mix should I consider to determine the mixture is homogeneous?

2. What are some of the free tools available to do the modeling in this case?

Any input in this regard would be invaluable.

Thanks and Regards

Karthika

Looking for some reference to understand or learn numerical modeling for compressible fluids (such as crude oil) - flow through the fracture or space between parallel plates. Thank you.

i want to do numerical modeling of masonry but i am confused to select the best software for masonry modeling and which is free as well.

1)autodesk robot

2) opensees

3) seismostruct

4) any other?

I would like to know if the SUPG method has any advantages over the least squares finite element method?

Thank you for your reply.

The concrete damage plasticity (CDP) model can predict the hysteresis behaviour of RCC structure and it is mostly used in Abaqus FEM software. This CDP model is good for the visualization of plastic deformation/localized crack pattern. It is also good for confirming the peak value of each hysteretic cycle but the basic bond-slip behaviour is not noticeable in the output of the result when the CDP is used. This is why the actual energy dissipation area/boundary is not identifiable in the present state of the CDP model. So considering this issue, a new model like CDP is needed to be adapted where it is applicable.

I have a case, which is about internal flow with constant heat flux. Although the inlet boundary condition is laminar, the flow is passing transition and turbulent regime along the tube. As known, the intermittency term is 1 (so, admitted as turbulent inlet BC) for freestream velocity for external flow, I would like to learn that whether using the transitional SST model by laminar inlet boundary condition in the pipe is the corrects way or not.

Best regards,

What differential equation is the source of this numerical approximation

The basic numerical model is each patch has a vertical (Z) and a Zvelocity. Every time step it updates its ZVelocity based on the difference of its current Z and the mean Z of its neighbors. Using Von Neumann neighborhood of 4 neighbors (North South East and West) with non-periodic boundary conditions (cells on edges of the space will have 3 neighbors and corner cells with only have 2)
📷

and where can I find an explanation of why the approximation is a discretization of that.

Hi All

I want to simulate an ambient vibration to be used as an input to a Numerical Model. I want this to represent the vibrations occurred to the building through the wind, vehicle/human movement, etc.

The sole purpose of simulating this ambient vibration is to input it to the numerical model in order to find out the natural frequencies, mode shapes and damping ratios of the building through Operational Modal Analysis

Thank you

I am trying to simulate the deposition of a single extruded path using element birth and death technique. In each load step one element is activated. The initial temperature of the activated element (in the current load step) is to be the nozzle temperature. The initial temperatures of the previously activated elements is obtained from the results (temperature field) of the previous load step. The steps adopted in the model are as follows:

- Creating & meshing the 3D model (of a single extruded strand of length=50mm)
- Deactivating all elements (using EKILL)
- Setting up the solution
- Activating one element
- Specifying initial condition on nodes
- Specifying boundary conditions (Convection load on exterior node)
- Specifying the necessary load step options and solving.
- Repeating steps 4 to 7 for each activated element (using *DO loop).

I am facing the following issues:

- The analysis runs properly only for the first load step, in that the decrease in temperature of the element is in accordance with the convective loading applied on it. But from the second and subsequent load steps onwards, the temperature distribution obtained is not proper. When the second element is activated, the face of the element exposed to ambient air has a constant temperature = nozzle temperature even though convective load is applied on this element. Element numbers 3 and beyond, remain entirely at the constant temperature = nozzle temperature.
**Note:**If however, each load step is run in a separate file (with all other parameters constant and by reading in the solution of the previous load step as the initial condition), the results of each load step are in accordance with the boundary conditions and loads assigned to them. I am unable to identify what's causing these improper nodal solutions when solving all the load steps in a single file.**Am I missing out on any crucial step in my code? Why is there a difference in nodal solution between these two approaches (solving all load steps in one file v/s solving each load step in a separate file)?** - When assigning initial conditions, the temperature distribution from the previous load steps can be read (using LDREAD) for the previously activated elements. However, I am unable to separately provide the initial temperature to the element activated in the current load step. The following warning message gets generated : Initial Conditions not allowed after first Load Step. Currently I have managed to avoid this issue by assigning a uniform temperature (equal to the nozzle temperature) at the beginning of solution for all the nodes (of activated as well as deactivated elements), but I am not sure of it.
**Is there a proper way to separately provide the initial condition for element activated in the current step?** - Also,
**is LDREAD command the proper method for using the results of the previous load step as the initial condition for the current step?**

Since I am new to ANSYS, any suggestions w.r.t these two issues and help in identifying the mistakes in my code/approach will be greatly appreciated.

The relevant screenshots from APDL as well as the code have been attached for reference.

I know that external factors or errors in the construction of a laboratory model influence the experimental results. I modeled a dam with a numerical model (with FLAC-3D). There is a good agreement between this analysis and the experimental results. What is the compelling reason for the small differences? Also, the results are different for two different numerical models. Does only the difference in the governing equations affect this difference or is there another reason?

Hi dear researchers

I connected a rigid body into the part of my structure by tie constraint and then I added displacement to rigid body, in static general step every thing is fine and these two part are connected during displacement but when i run this model in dynamic explicit step , tie constraint does not work properly and rigid body and structure become separate from each other during displacement at the beginning time of this step,could anyone help?

hello,

I hope that you are doing well and that the beginning of March is excellent. First of all, I would like to thank the researchers who responded to my last discussion on terrestrial albedo.

Today's discussion is about a problem I found in the numerical modeling of the convection phenomenon (heat transfer)

the goal is to dimension the prototype to be able to dimension it, so I used the finite difference method to discretize the equations of order 1 (I discretized time by a forward scheme and space by a backward scheme).

Despite this and after I wrote a program on python to be able to extract the results, I found values that are not logical for example the water temperature by heating with a radiation value of the order 500 W/m^2 -10 °C.

someone will give me an idea on what I should do or change ... ? the scheme? .........

thank you in advance

cordially

Firyal LATRACHE

What is the meaning of (A.A.D.%) for reflecting the accuracy of the numerical model as compared with experimental data?

To date, I have had the opportunity to explore several open source and private software like MFiX, Fluent, Sim-flow, Barracuda VR, PHOENICS, etc. I want to investigate 3D, hydrodynamics (include particle behavior), chemicals and radiation heat transfer maybe.

But I saw different problems when I tried to importing geometry as STL on each software.

Which software are you using when you solve this type of analysis?

I am modeling a double pipe (concentric tube) in Ansys Fluent. The center tube contains nanofluid, and the region between the pipes is a vacuum zone. The outer tube is used for reducing convection effects. A DO radiation boundary condition is applied to the outer surface of the outer tube. I am having difficulty in modeling the vacuum region since I don't know how to specify "vacuum" in Fluent.

What is the best way to model this specific region? I just want the rays to pass through the vacuum region and reach the inner tube, the vacuum itself is not important for me.

Thank you in advance.

Which software do you suggest for doing the numerical modeling of scour depth estimation in the cohesive soils?

Which software do you suggest for doing the numerical modeling of scour depth estimation in the cohesive soils?

I am trying simulate an infinite domain so I need to use non-reflective boundary conditions. While searching, I came across PML method, but I have certain doubts.

1) How to decide the dimensions of the PML layer?

2) What effect does PML mesh size have on the reflected waves?

I am using TNO DIANA and I simulated a block of soil of 50 m subjected to an impulse load and tried to see the wave travel. I used PML lengths of 10 to 50 m . However, I can still see waves reflecting back. I also tried to increase the function values assigned at the PML boundaries, but after one point I see that the PML behaves like a clamped or fixed boundary. Can someone point me to a source where PML is explained clearly?

Thank you very much.