The physical co-ordinates (x,y,z) are known of specified certain points, I want to write/ print 'cell centroid' and corresponding 'cell id' using DEFINE_ADJUDT macro.

Printing cell centroid for entire domain is straight forward, I wish to centrod location and cell ID for particluar few points only.

Thanks in advanced.

]]>I am using the species transport model together with UDF to simulate the diffusion of charged nanoparticles in a channel.

The UDF is used to add the electric flux due to the external electric field. I printed the resulting electric flux to the console and it gives a huge value as shown in the attached snap below. Also, the resulting contour of species fraction is attached.

Can you please help to solve this? Does the UDF I'm using calculate the electric flux correctly?

Or have I done something wrong with the UDF?

#include "udf.h"

#include "mem.h"

DEFINE_SOURCE(electrostatic_flux,c,t,dS,eqn)

{

real source,x,d,v,con;

x = C_YI(c,t,0); /* Species mass fraction */

d = C_R(c,t); /* density*/

con = x*(d/104);

v = 17.6131*pow(10,(-10)); /* veocity of particles*/

source = con*v; /* resulting electric flux*/

printf("molar flux = %d\n",source);

dS[eqn]=0.0;

return source;

}

I am currently working on a cold spray analysis which is a process to make coatings on a substrate with low porosity, high strength and at low temperature conditions. Compressed air and particles(that will form coating) are bombarded through a nozzle to the substrate. The spray parameters are an important factor in making coating effective and optimized. Hence, ihave started my analysis with nozzle. In ansys fluent, I am getting the floating point errors in calculation part. Dont know the reason.

The complete analysis including geometry, meshing , fluent analysis done till now is shown below:

GEOMETRY

1.Considered an axisymmetric convergent-divergent nozzle.

2.Inlet dia-40mm

Throat dia-2mm

Outlet dia- 4mm

Horizontal distance from y-axis to outlet-280mm

Horizontal distance from y-axis to inlet-70mm

Horizontal distance from y-axis to throat-50mm

3.Generated the surface modal from line modal.

4.Change analysis type to 2D.

MESHING

- I have used 4 edge sizings here. For edge sizing number of divisions given is 7.For edge sizing 2 and 3 number of divisions given as 5.For edge sizing 4 number of divisions=2.And face meshing also done.

2.The qualities are given below:

-Aspect ratio-13.346

-Skewness-0.23

-Orthogonal quality-1

-Element quality-0.95

(All are max values)

3.Assign the named selections for all the parts of nozzle.

FLUENT ANALYSIS

- The parameters i used for general are shown above. Also checked the mesh and it doesnt give any error.

I mean i dont give a value to the rpm before run calculation because the value of rpm what i want to find from the turbine.

Thank you.

*Edit @Rob Title changed for clarity. *

I want to ask you,

How to set fluid flow in ANSYS for incompressible or compressible flow?

Thank you

]]>I am simulating melting behaviour of glass substrate with laser as heatsource.can anyone please explain How can I simulate melting and solidification of glass in Ansys fluent.

]]>thank you for your time to read my question,

I am trying to simulate a flow of steam ejector as a 2d Axisymetric based on this paper https://www.sciencedirect.com/science/article/pii/S1290072912002098, but I have an error "divergence in AMG solver" in the begining of calculation

currently, I am using Ansys R19.1

I read about this error in ansys forum (https://forum.ansys.com/discussion/23920/problem-with-tutorial-in-fluent-divergence-amg-epsilon-for-ic-engine-cold-flow-simulation/p1) but still doesn't work

I checked my model,

the average orthogonal quality ,skewness quality, and aspect ratio is pretty nice, but I have problem with the small curvature of nozzle throat, so the max point of skewness occur in that area

let me describe my set up, I might be has a mistake due to my poor knowledge in ansys

I use Double-precision, pararel, 8 CPU solver for my i5 9300H processor

***Solver type***

Density Based, Steady, Axisymmetric

***Models***

Energy equation (On)

default K epsilon Realizable, standard wall function , compressibility factor (On)

****Materials****

Water vapor Density (ideal gas), CP (Piecewise polynomial),Thermal Conductivity (default, constant),viscosity(default,constant), moleqular weight (default,constant)

***Cell zone***

Water vapor

Boundary condition

Axis

inlet 1(smaller one)>>pressure inlet>> Gauge total pressure 270000Pa, Initial Pressure 135000, Temp 403K

inlet 2(larger one)>>pressure inlet>>Gauge total pressure 1000Pa, Initial Pressure 3000, Temp 280.5K

Outlet>>pressure outlet>> pressure 3000Pa Temp 298K

wall>default>>heatflux 0

operating condition >>0

****Methods****

Formulation Implicit

Gradient Least Squares Cell Based

Flow- second order upwind

turbulenn kinetic energy - second order upwind

turbulent dissipation rate - second order upwind

****Control****

Default

***monitor***

all convergence criteria 1e-06

***initialization**

Hybrid

thank you so much

guys in this forum has told us to make sure out cordinate point for Axisymmerict in X axis,https://www.researchgate.net/post/Anyone-knows-how-to-get-rid-of-Divergence-detected-in-AMG-SolverTEMPERATURE-in-Ansys-Fluent

I have checked my model and it is correct

I tried to reduce the corvergence criteria to 0.001, but it still doesn't works

I tried to reduce the URF, but it still doesnt work too

I tried FMG Initialization but there is an error of invalid CP Value, should I change the CP of piecewise polynomial to constant value?

Hopefully you are guys could give me a suggestion to solve this kind of problem

thank yoi so much

]]>Does anyone know how to simulate Ionic wind? I need recommendations on how to start and which analysis would be perfect for that topic.

Thanks

]]>This is my geometry

Here is my mesh

Some of the options I have selected

This is the error that I'm receiving.

Not sure why I'm receiving this error. I have been breaking my head on this for days now. Any kind of help will be appreciated.

]]>Im using FENSAP - ICE to simulating ice accretion on wind turbine airfoil for my Master thesis.

I read the FENSAP - ICE manual but i dont know how FENSAP - ICE calculates Collection Efficiency and Ice Thickness.

The manual didnot show the detail of Collection Efficiency and Ice Thickness equation.

I really need those equation for my thesis ( because i need to write those equation in my thesis, if not, the thesis maybe will not be accept by professor )

Can anyone explain for me the Equation of Collection Efficiency and Ice Thickness in FENSAP - ICE ?

I will be really appreciate that !

Thank you guys so much !

Best regard !

Sir ive been doing a cfd analysis of a bus body for drag force and drag coeffiecient

i did it for a model and the results came corret but now for my second improved model the values are coming very very high

its for the exact same conditions as my previous model

i am using k-e standard model for analsys and have created a wind tunnel

can someone please help me with this ive been trying it for days now

i have attached the photos of both

please help me out

]]>I have a question and I'm dying to know the answer. Pls, how should one calculate the torque acting on a pipe in which water flows? When selecting the wall of the pipe, should one also include the inlet and outlet of the pipe?

]]>So, I wanted to know if there would be any general reasons to fix if my 1st 10-15 iterations take a lot of time to come, and then my simulation diverges at 100-200 iterations later. The ones from lets say 30 to 100 are quick enough on a 6 core pc with 300k cells (small size), although it diverges anyways.

The question is why would iterations 1 to 10 take so much time, compared to others, where ideally, the solver runs quickly.

I have mass-flow-inlet at the blue region, attached to the 4 tubes and a symmetric design at the other end.

All the grey regions are walls, where the square part has zero temperature in thermal BC, while the tubes have some temperature defined onto them. Air is passed as inlet at a high tempearture through the blue region, while the other side has pressure outlet BC with the design symmetric to the above.

]]>Bottom plate hot, top plate cold, side walls adiabatic.

In the reference values section can i use, bulk mean temperature as a reference temperature.

]]>I dont know how to define Liquid fraction in the udf. Thermal conductivity is dependent on liquid fraction. Can u please check whether the udf code correct or not.

P.S The f in the thermal conductivity section is liquid fraction and ktc is thermal conductivity

that really important for me ! long time working with this

the whole process that i've carry out is lost!

thanks

]]>I am simulating particle trajectories along a pipe. The particles are affected by the drag force and an external force that is applied through the DPM_BODY_FORCE macro, which works fine.

I am trying to make the particles reflect/be trapped if they reach certain positions in the pipe (which are not boundaries). This is done by evaluating the particle position and if the criteria is met then the particle would reflect. The portion that evaluates the particle position works fine. The reflection portion of my UDF is adapted from the example in the manual for the DPM_BC (see below).

Which DPM macro is best suited to do this (evaluate the particle position and then changing their direction/stopping them)? I was using the DPM_BODY_FORCE, but was not successful in making the particles reflect. Is correct to change the particle velocity inside this macro ? Or this is overridden by FLUENT's calculations after the DPM_BODY_FORCE returns an acceleration?

Thanks

UDF used

real save_vn = 0;

DEFINE_DPM_BODY_FORCE(f_ext,p,k)

{

Domain *domain;

Thread *t, *f_thread, *f_thread0;

face_t f0,f;

real dist0, dist, x[ND_ND], dx, dy;

real alpha, A[ND_ND], A_mag, radius, vn;

real force = 0;

real nor_coeff = 1.;

real tan_coeff = 1;

int i;

domain = Get_Domain(1);

t = TP_CELL_THREAD(p); /* particle thread */

dist0 = 999; /* variable that holds the minimum distance calculated by dist */

dist = 0; /* variable for distance between cell centroid and face centroid */

radius = TP_DIAM(p)/2;

/* PORTION THAT CALCULATES MINIMUM PARTICLE DISTANCE TO WALL */

/* RETURNS dist0 - the distance to the wall, f0 - the wall face and f_thread0 - the thread of the wall face*/

if(dist0<=radius)

{

F_AREA(A,f0,f_thread0); /* normal vector to f0 with magnitude = area of cell */

A_mag = NV_MAG(A); /* magnitude of vector A */

A[k]=A[k]/A_mag; /* unity normal vector */

alpha = M_PI/2. - acos(MAX(-1.,MIN(1.,NV_DOT(A,TP_VEL(p))/MAX(NV_MAG(TP_VEL(p)),DPM_SMALL))));

/* Compute normal velocity. */

if(k==0){

for(i=0; i<ND_ND; i++){

vn += TP_VEL(p)[i]*A[i];

}

save_vn = vn;

}else{

vn = save_vn;

}

/* Subtract off normal velocity. */

TP_VEL(p)[k] -= vn*A[k];

/* Apply tangential coefficient of restitution. */

TP_VEL(p)[k] *= tan_coeff;

/* Add reflected normal velocity. */

TP_VEL(p)[k] -= nor_coeff*vn*A[k];

/* Store new velocity in TP_VEL0 of particle */

TP_VEL0(p)[k] = TP_VEL(p)[k];

return(0);

}

/* PORTION THAT CALCULATES EXTERNAL FORCE */

return (force/P_MASS(p));

}

]]>I am currently trying to make simulation of evaporator with muliphase water change. Here is small model of my case.

Hope you will understand what I drawn. I need to inlet water under preasue 30000Pa. Inflict temperature 280C on heaters to make water change to steam and go out of evaporator.

I made multiphase value of fluid, I dont know if i am right with in. In materials i added water and water vapour.

Next I defined viscous model as standard k-epsilon:

During making boundary conditions I cant demand that water will go inside of evaporator with preasure of 30000Pa. I can only choose preasure when i pick "phase" as "mixture". I would like to choose here water liquid.

Another boundary conditions works fine. I defined temperature and preasure outlet.

Next steps was initialize and making calculation. But after making calculations I dont have resultst that I need. I am making this simulation as explicit.

Is there any way to define water on preasure inlet boundary condition? If you see any mistakes please note them. I will be greatfull for help.

Thanks in advance

Matthew

]]>I'm simulating a 2D multiphase phase change problem of water vapour condensing ontop of a pipe wall. I'm currently following a paper to validate my simulation. However in the paper they use OpenFoam to simulate the problem in which the boundary conditions they state are slightly different.

For example on the figure below at boundary b), they use a pressure inlet/outlet boundary condition where the boundary condition switches between being a zerograident condition when outflow occurs and a fixedvalue when inflow occurs.

In my case I will have outflow and inflow since the water vapour will be coming into the domain as the wall temperature is below the saturation temperature of the fluid domain (50 K difference) and outflow will occur as the condensate will drip off the pipe and exit the domain.

The problem is, is that how can I implement a pressure inlet/outlet boundary condition in fluent? As I know that this can be done in Openfoam. I've tried using various outlet conditions in fluent such as pressure outlet, pressure inlet and outflow but they do not give me good results as I notice vortices and swirling starts to form in domain which ruins the liquid-gas interface of the condensate.

Regards

Navdeep

]]>I would like to know that is it possible to do two simulations in one run because it will reduce my computational time, if other boundary conditions except one (here temperature) remains same and geometry and mesh is also remain unchanged.

Please see the image.

I'm a student studying Ansys.

I'm working on a gas - solid flow in a cyclone separator analysis.

I confirmed tangential velocity as the result.

As a result, there was a positive velocity at the inlet and a negative velocity at the opposite side.

I want to obtain the result of velocity for rotation direction in clockwise or non-clockwise, not the above result.

For example, when vortex occurs in a clockwise direcition, a negative velocity.

Please tell me how to set it up.

Thank you.

]]>I simulate air flow around wing within a box fluid domain.

How can I check the momentum concervation or momentum balance for the system with Ansys?

]]>(Picture 1: velocity magnitude contour plot, with streamlines and point of interest. Picture 2: y-velocity data plot in point of interest. Picture 3: comparison of y-velocity from ANSYS FLUENT and LS-DYNA ICFD solver. Picture 4: y-velocity contour plot, comparison between colour in plot on point of interest and legend).

I am currently running a "benchmark" iCFD problem (flow around a cylinder) using LS-DYNA, for Re = 0.5. I am interested in the y-velocity at a point 8 diameters from the cylinder (see pictures below).

When I extract the dataplot from this point, you can see that the velocity is 6e-4 m/s. When I compare this result to the contourplot, however, you can see that the color where the point is situated belongs more to the 2.5e-4 m/s y-velocity.

When comparing the LS-DYNA answer to the FLUENT answer, it is clear that indeed the y-velocity should be much lower than 6e-4 m/s. So why does the dataplot give me a different result, and how can I get the right result?

Kind regards,

Why the guy in this video (look at 4.35) have suppressed for physics solid body?

I think that deactivating the solid body is sufficient for CFD

Thank you

Best regards

So my question is, if I am designing an airfoil, or a body of an airplane and want to run some CFD's on it , how do I figure out the fluid volume ? I am not sure how far the Fairfield must be ? any idea on how I can determine that or guide me to look somewhere?

]]>I will simulate the icing of this plane (fuselage, wings, etc.) with Fensap-Ice. I will do the mesh using Fluent Meshing.

I have created a little fluid domain around the plane ( blue color) in the order to refine the mesh in this zone; and a big fluid domain around the blue one.

The zone of influence (the blue one) and the big fluid domain (the white one) are two separate solids. I have put them under one component and merged topology.

My problem is :

Must I suppress for physics the two solids or not ( as a final step before removing geometry to Ansys fluent Meshing)?

If I deactivate the two solid bodies, I will remove geometry from visibility because these two solids are pure fluid domains.

Thank you

Kind regards

]]>

Thank you so much for reading this post. I am new to Ansys. I am trying to simulate an airfoil. So initially I was looking at tutorials on how to mesh using the Ansys workbench meshing. However I came across meshing in Fluent.

Now I am confused on which one to be used as well as if I should use 2D or 3D. Or both. What would be the difference.

Also for the domain, how do I know I have the correct domain size? What is the best way to figure out the domain size for fluent ?

]]>I am trying to simulate melting PCM in pipe and i create a UDF that it must be dependent on temperature and liquid fraction but when i start calculation in fluent i see Temperature limited error.

what should i do?

my UDF:

#include "udf.h"

DEFINE_PROPERTY(k_npcm,c,t)

{

real E;

real temp = C_T(c,t);

real THE;

if(temp<=350.)

{E=0.;}

else if(350.<=temp<=358.)

{E=(temp-350.)/(358.-350.);}

else

{E=1.;}

THE = 0.2120+(-27852587.84*E*sqrt((1.381*pow(10,-23)*temp)/(3600*53*pow(10,-9))));

return THE;

}

will be very appreciated by your help. Thank you in advance

]]>I have a question related to outlet boundary condition for supersonic flow.

**What I have a read is in supersonic flow static pressure can't propogate back Upstream faster then wave speed **so, I didn't understand this statement can anyone explain me this thing in brief? TIA

when I modeled solar thermal convention using the discrete ordinates radiation method with wavelenght-independent absorption coefficient (gray model), it accounted for emission but when I change to wavelength-dependent absorption coefficient, i.e., spectral bands (non-gray), it gives zero volumetric emission. .. is this by default or maybe I've done somethings wrong .. thank you ..

regarding

Hussein,

]]>I have a simulation which is running fine but without considering the friction of the elements. I would like to introduce the friction coefficients of the deep grove ball bearings (0.0015) to obtain a more realistic results, however I am not sure how to introduce this element into fluent. I believe it should be introduced in the dynamic mesh (along the inertia and the mass) however I cant seem to find where. Hope someone is able to throw some light here! Many thanks in advance

]]>The assumed calculation was in time domain transient based, Second-order implicit and boundary conditions are velocity inlet and pressure outlet.

Currently, I am conducting couple analysis with fluid and structural analysis of the viscoelastic tube. And I plan to create an non-reflecting boundary condition in the couple analysis of ANSYS Workbench under the same boundary condition.

From conservation of mass and conservation of momentum, the boundary condition of numerical solution at the end of tube with iteration of time and space steps is as follows

P is pressure, Q is volume flow rate, Zc is

characteristic impedance of the flow ,G is reflection factor (the ratio of forward and backward pressure waves).

I have short of knowing how to apply the boundary condition at the outlet of the vessel.

I am learning UDF in ANSYS Fluent, but I am not sure how to apply UDF as the boundary equation at the outlet.

In Boundary Conditions, I would like to apply a reflection-free boundary condition at the outlet of the vessel so that the sine wave can propagate.

Therefore, I would like to apply UDF in ANSYS Fluent, but I am not sure how to insert a boundary equation at the outlet.

In the above equation, I understand we need to use UDMI but I need to create new zone ID before the end of the tube and we need to use the variable data from the previous space step and time step. so, I need to extract data and use it in UDF as well. and I am not sure where to interpret the UDF as well.

Will there be any tutorial or course regarding on it?

Thank you very much for the help.

]]>Mathematically, the Convective boundary condition is given as

So can anyone help me?

Should I write a UDF or UDS?

How does the UDF or UDS will work while I am running the simulation?

]]>I am modelling a simple duct in CFX, and i am trying to set the element order in the mesh as Program Controlled or Quadratic. However, every time when i check the number of nodes in CFX-Post or CFX-Solver the number always remains the same, equal to the one that corresponds to Linear Element order. How can i maintain the Element order i chose in the meshing step ?

]]>