I'm doing a natural convection simulation around a house like below image.

However, i have some questions about the boundary condition for my model.

Please help if you know.

1. The green surfaces are virtual surfaces of outer ambient. The bottom surface is the ground so i will set it as Wall.

But what about the **top and side surfaces**?

Should it be **Outflow** with the "**back flow condition = on**"?

2. The **house wall (white color) is very thin**, because they are actually some sheets metal.

So it is **not suitable to create volume mesh** for this wall. I planned to use surfaces for them with **Zero thickness**.

Is it acceptable?

I also see that AcuSolve has a feature named** Thermal Shell**, could i apply this feature for my house wall?

3. Round holes on the house walls are windows and ventilation holes. i want to simulate the hot air inside the house go up and get out to the ambient.

Meanwhile, the cool air will come inside the house through the side window.

Thank in advance.

Have a nice weekend!

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Normally, we usually use "**simple boundary condition**" such as inflow, outflow, wall to assign for the surfaces on our model.

When we want to impose some thing more advance, we will use "**nodal boundary condition**" or "**element boundary condition**".

I have read in AcuSolve help that "**simple BC**" will be converted into "**nodal BC**" and "**element BC**" in by acuprep.

However, i found another kind of BC named "**integrated BC**" in AcuConsole. What is this exactly?

Is there any relationship between "**integrated BC** " and 3 others?

When should we use this type?

Thank you!

]]>I followed the procedures for 5.13 ACU-T: 5403 Piezoelectric Flow Energy Harvester: A Fluid-Structure Interaction in AcuSolve tutorial to do a DC-FSI analysis.

However, I had errors "ERROR: Undefined external node" for all the nodes in the coupling surfaces in OptiStruct model.

I attach the log file and inp file here.

Does any one know why this happen?

Thanks a lot!

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I have a solar panel consisting of five layers, where two dimensions are much larger than the third dimension (by a factor of about 200-300:1). I have already meshed the component very fine in the plane and get the following statistics from AcuMeshSim:

As a setting I tried the following options to minimize the skewness of the elements:

Additionally I tried the option *Surface Mesh Proximity Size Level* with values of 1-3, but my PC does not seem to have the necessary computing capability for this.

I have already read that AcuSolve is very generous in terms of element quality and focuses more on the distribution of the nodes.

If no big temperature gradients are expected, one could estimate if the existing element quality is sufficient or not?

If not, which options could I try?

Thanks in advance!

]]>I have some questions about choosing the turbulence models & density model for a simulation of natural convection of a bulb.

I have gone through several tutorials of AcuSolve regarding natural convection.

They all using "laminar" as turbulence model & boussinegq density model.

So my questions are:

1. does choosing the turbulence model depend on the temperature difference?

since a filament inside a bulb can reach 2000 K and i'm not sure that laminar is suitable for this case or not?

2. if we just need to use laminar, but some how i chose Spalart Allmaras as turbulence model.

will this affect the result? take more time for convergence or reduce the accuracy?

3. Regarding to the conditions of the boussinegq density model, it seems not suitable for gas inside a bulb, because the temperature reach 2000K on the filament.

what should i choose for the density model of gas? maybe ideal gas?

Thanks in advance!

]]>I want to do flexible riser simulation. riser pinned at two end (constrain at xyz translation, free xyx rotation) + upward force (top tension) define as load. The loadsteps in optistruct are:

1. Linear static:

spc: defined

load: defined

2. modal Analysis:

spc: defined

method (struct): defined

statsub (preload): linear static

I get an error during importing op2 file into acuconsole-eigenmode manager.

**The error only occur when there are two subcase (linear static + modal analysis). If i only do modal analysis without linear static, i can import the op2 file without any error.**

**attached is the optistruct and acusolve file. **

I'm looking to import the pressure data I have gotten from Star CCM+ into Hypermesh so that I can get an accurate pressure profile on my airfoils. I have heard I needed a .out file but found that Star only exports as a .csv file. Any advice on how to do get this to work?

Thanks.

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I would like to export these pressure values from AcuFieldView or AcuSolve to FEA solver, how can i do that..? Please help me regarding the same.

Regards,

Sandeep P

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This is the example command for single surface output

**acuLiftDrag -osis airfoil -aoa 5 -ref_vel 14.54 -chord 1 -rho 1.225
-span 50**

This is the example command for all surface output

**acuLiftDrag -osis _all -aoa 5 -ref_vel 14.54 -chord 1 -rho 1.225
-span 50**

Please tell me command for multiple surface output (not all) as shown in below attached figure.

]]>I need to do a thermal cooling simulation for a transformer.

The simple model is shown as below image:

Normally, we run the simulation with water/air.

However, the fluid used in this case is OIL.

So can AcuSolve make the simulation with Oil?

If yes, Is there any special setting has to be made?

Furthermore, how should i define the interface b/w air and Oil (or water) in this case?

Should i use multi-phase (level set/ Euler) or free surface or any other treatment?

Thank you very much!

]]>I have a solar panel, which consists of different layers (solids). The panel is exposed to a irradiance of 800 W/m^2 from straight above:

I have a question regarding the definition of the surfaces under **Solar Radiation Surface** (*Default, Inward, Outward, Both Sides*) for the case shown above.

If I define all surfaces (side-, top & bottom surfaces and also surfaces between different layers) as *DEFAULT*, I get the following results in Hyperview for the solar flux:

If I define all surfaces as *BOTH SIDES*, I get the following results in Hyperview for the solar flux:

How can I decide which option is the right for my usecase to model the physics correctly.

Furthermore, what exactly is designated with *solar_heat_flux* in Hyperview? Is it the radiation intensity or another quantity?

And what are the "best" options for *Solar Radiation Parameters *for num.rays, num. diffuse sub rays, max. ray reflections, min.ray energy?

Thanks in advance!

]]>I've been trying to run a CFD simulation using the Hypermesh solver, however, I always get the same error (ERROR: error occurred executing acuPrep) and I don´t know what it means. Can anyone tell me why this happens and how to fix it? Thanks.

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I want to mesh the geometry with AcuConsole according to the picture below (4 different layers):

The size in the x and y direction is several times larger than that in the z direction, lets say 1 m * 1 m * 0.003 m (x * y * z). I defined the absolute mesh size as 10 mm. Abviously, this leads to only one element per volume in z-direction.

Now to my questions: Which is the best setting to get at least 3 elements per height in z direction in the entire volume of one part (i.e. via different *Volume Mesh Attributes* for different volumes or by appliying a value for the *Surface Mesh Proximity Level*)?

Thanks in advance!

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I have faced an error when doing AcuSolve tutorial Acu-T-5403 DCFSI.

I have completely followed the tutorial step by step.

The AcuSolve and OptiStruct solver started and coupled together.

However, after a few time steps, the acuTail displayed below error:

Did anyone face this issue before?

What is the reason and is there any solution for this?

Thanks in advance!

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I am currrently carrying out thermal analysis in AcuConsole on a photovoltaic panel composed of five different layers (Glass cover, encapsulant, silicium cell, encapsulant, Backsheet). I want to consider thermal radiation on the front& back surface of my PV panel according to the following equations for the front and back surface, respectively:

.

I read in the AcuConsole training manual that calculation of radiation is only possible from surfaces of fluid mediums but I have no fluid in my simulation setup. Therefore my questions are:

1.) Is there any other possibility to implement radiation without a fluid volume (i.e. setting heat flux (boundary condition) to -100 W/m^2 on the corresponding surface)?

2.) The equations above are dependent on a value which has to be calculated by the processor (Trear and Tfront). Is it possible to formulate such boundary conditions that depend on values that will be calculated later by the processor (AcuSolve)?

Thanks in advance!

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What are the proper system requirements for the PC running AcuSolve to optimize the speed?

For example: my model have 1mil nodes and running steady state, so how many cpu should i use for the run?

I couldn't find any document about this in AcuSolve help.

Thanks in advance!

I am on my self paced meshing training using HM desktop. I would like to do 2D cfd simulation. How to do mesh extrusion in HM and reorganize the element to the respective surface (inflow, outflow etc)? In AcuConsole, there is mesh extrusion, is the extrusion feature available in HM as well?

I mesh the top first (as shown below) then want to extrude -0.2 m in z direction. then it become volume element. i not sure how reorganize element for surface boundary condition such as inflow, outflow etc which required 2D element.

Btw, is mesh extrusion available in HM CFD?

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My problem is; I can't calibrate the program. In the attachment you can find a work i prepared. Using a smooth sphere, which is big as a golf ball (d=0.042 m) I analysed over and over with the conditions you can see. After that i prepared a chart and compared it with the literature. According to literature, it should decrease after turbulence zone. However my values always increased. They are even not equal to ampirical values in laminar zone for sphere.

After this I changed my analysis type to transient (when I learned transient analysis option of VWT runs with DES instead of Spalart-Allmaras)

And re run some specific values to see the general characteristic of the curvature (Reynolds number to Cd)

I can't catch the characteristic, which I see in the literature.

For some values like Re= 4e5, 6e5, 1e6... I can't even reach closer to the ampirical values.

Also It happens on another geometries like Ahmed Body, I analyse and I always get different values from literature.

1. I wonder if I am able to change the turbulence model of VWT.

2. How can I use k-omega and k-epsilon turbulence models ( I get error: kinetic energy and dissimilation must be non-zero) (Even I enter values, I get the same error)

3. Why my values have high error ratio, even i prepare my problem with high quality ( Blockage ratio, element value, refinement zones etc...)

Thank you.

vwtAnalysis_transient_ahmedbody.pdf vwtAnalysis_steady_ahmedbody.pdf vwtAnalysis_velocity25_ahmedbody.pdf

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i am doing a CFD simulation using HyperMesh-AcuSolve.

When the solve is running, about step-40. the AcuTail display a message error as below:

acuSolve: *** ASSERTION in Function <lesGmres> File <lesGmres.c> Line <1379>

acuSolve: *** Error from fLesGetHbrgEig <10>

acuRun: *** ERROR: error occurred executing acuProbe".bat

The model file is attached

please help me to fix it.

Thank in advandce!

P/s: when i change the eddy viscosity to a larger number, the solver ran completely at time-step 100.

but the result seems not right.

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I am working on a problem of MCCB and I have received the losses information from flux user. As I am trying to perform a co-simulation , I faced the issue for the transformation. I tried using shift option in the transformation but entire mesh models do not transform.

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I have run an aerodynamic CFD simulation on a racecar using Virtual Wind Tunnel. I would like to be able to open the results in AcuConsole to perform a subsequent heat transfer analysis of a box inside the cockpit of the vehicle. When opening the file in AcuConsole, the volumes, surfaces, and boundary conditions are preset because of the simulation conducted in Virtual Wind Tunnel. The box in the cockpit, which I would like to model as a heat generating volume has been preset as a surface in AcuConsole. Does anyone know of any way to model this box as an object that generates heat?

Thanks for your help

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My objective is to make a thermal analysis of a photovoltaic panel like in the paper I have attached. This panel shall be exposed to a irradiance of 1000 W/m^2 (in negative z-Direction) for 60 seconds at an ambient temperature of 25°C. The target values are the cell reaching solar flux (solar irradiance) and the temperature at the solar cell.

I work with Hypermesh 2019 and the AcuSolve user profile. My procedure was similar to the tutorial ACU-T 3201 (Greenhouse Daytime Simulation): I have already defined the problem description and auto solution strategy, model propoerties and solar radiation models, applied volume parameters and meshed the panel with 1 mm tetra-volume elements.

When I run the Acu Solve Job Lauchner and open the results in Hyperview afterwards, no results are displayed.

Now to my questions:

Is it possible to run a simulation with Acusolve without fluid (only solids) in the system?

How do I define contact conditions like free convection with the environment or conduction?

Do I need an emissivity model like in ACU-T 3200?

Do I need to determine surface groups?

I have also attached the Hypermesh file so to give you an idea of my simulation model.

Thanks in advance! I would be extremely grateful about a help.

2015_Temperature distribution of photovoltaic module based on finite element simulation_Zhou.pdf Validation_2015_Zhou.hm

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Currently I am doing P-FSI with VWT 2017.2. For this purpose I have looked at the instructions on this topic by Ratzel and Nainani. I have two questions regarding the generation of stiffness information about eigenmodes.

1. Is it pointless to carry out the eigenvalue analysis for a single component without spatial fixation (with the consequence that one would have six rigid body modes)? Or can VWT via AccuSolve handle it?

2. Suppose I have an assembly that is made up of several components. Only one component from this assembly is to be exposed to a flow in the VWT. However, in order to map the correct deformation of this component due to the flow, one would have to know the stiffness information of the whole assembly (the components are mechanically coupled in the assembly).

Is it possible to generate the eigenmodes for the whole assembly and assign them to the one component (via OP2 in OptiStruct) that is considered in the VWT so that this one component combines the stiffness information of all components?

]]>How do I fix this? ]]>

I want to simulate a transient flow for indoor in two stages. First stage is heating up process and second stage is cooling down process . My plan is to begin the second stage simulation (cooling down) using the first stage data as the initial data forthe second stage simulation, onced air speed at a point in the domain has reached cerrtain value.

Is there a way to do this in AcuSolve?

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