I'm modelling water flow in a cylindrical rock core under transient conditions. There, constant 'P' pressure is maintained at upstream and pressure built-up at downstream has to be investigated. Can anybody help me with this? How can I apply newly developed equation to simulate the flow into the software?
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Fluid flow in porous media
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How to add inertial lift force and Dean force
Hi everybody,
I m doing simulation for inertial focusing. I need to see the effect of inertial lift force and dean force on particle. I m just wanted to know where these forces can be defined. I tried to add them in particle tracing-> forces. still no use.
Appreciate help from someone.
Thanks in Advance.
I m doing simulation for inertial focusing. I need to see the effect of inertial lift force and dean force on particle. I m just wanted to know where these forces can be defined. I tried to add them in particle tracing-> forces. still no use.
Appreciate help from someone.
Thanks in Advance.
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Modelling of phase change
Dear Comsol user,
I have one conceptual question...
I would like to model phase change of solid due to heat transfer from fluid above. Intuitively i should model the melting of solid using " heat transfer with phase change". But in different examples it is modeled differently. I found three examples till now "Cooling and Solidification of Metal" , "Tin Melting Front" and one with phase change of ice.
Use of either deformed geometry or phase change should give me the same result.
What is the difference between both of the approaches?
I have one conceptual question...
I would like to model phase change of solid due to heat transfer from fluid above. Intuitively i should model the melting of solid using " heat transfer with phase change". But in different examples it is modeled differently. I found three examples till now "Cooling and Solidification of Metal" , "Tin Melting Front" and one with phase change of ice.
Use of either deformed geometry or phase change should give me the same result.
What is the difference between both of the approaches?
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Coupling Pressure with EOF
I am modeling electroosmotic flow (EOF) in a microfluidic chip. The chip has 2 inlets and 1 outlet. The EOF part seems to be working well. I am using Electric Currents (ec) and Laminar Flow (spf) physics.
On top of the chip are fluid reservoirs. As fluid flows from inlet to outlet the fluid height in the inlet reservoirs decreases and the fluid height at the outlet reservoir increases. This should cause a change in pressure that I would like to model. I have attached a simplified sketch (not to scale) with one inlet and outlet that should clarify my problem.
I am new to fluid dynamics so I may be approaching this problem in the wrong way but here is what I have so far.
The initial pressure (P0) at each reservoir is the same. Once the problem starts (t=0) an electric field is applied between one of the inlets and the outlet. The second inlet is unbiased for now. At any time t>0 there will now be a pressure difference between the inlets and outlet.
I have derived an equation for the pressure in the reservoirs based on the equation P=rho*g*h, where P is pressure, rho is the fluid density, g is gravity, and h is the fluid height in a reservoir.
At a reservoir the pressure will be P = P0 + Pt, where Pt is the pressure change as a function of time. Which is to say the pressure change due to fluid emptying from the inlet or collecting at the outlet.
Therefore, Pt = rho*g*ht, where ht is the change in fluid height in a reservoir. Now volume (V) in the cylindrical reservoirs is given as V=pi*r^2*h, therefore, h = V/(pi*r^2). The change in volume in the reservoirs is equal to the volume flow rate Q multiplied by time. Q = A*v where A is the cross sectional area of the microfluidic channel and v is the flow velocity.
So Pt = rho*g*ht = rho*g*V/(pi*r^2) = rho*g*(Q*t)/(pi*r^2) = rho*g*(A*v*t)/(pi*r^2)
Therefore, at the inlet P = P0 - rho*g*(A*v*t)/(pi*r^2),
and at the outlet P = P0 + rho*g*(A*v*t)/(pi*r^2)
In Comsol for inlet 1, I am using the pressure boundary condition, suppress backflow is unchecked, and flow direction is normal flow. Under pressure condition the units are Pa and I have written the following:
101325-rho*g*((A*spf.U)*t)/(pi*rR^2)
where rR is the reservoir radius, and I have already identified the other variables.
I am leaving the second inlet electrically floating for the moment. The conditions are otherwise the same, so under the pressure condition I have simply left it as
101325
For the outlet, I am using the pressure boundary condition, suppress backflow and normal flow are unchecked. Under pressure condition the units are Pa and I have written the following:
101325+rho*g*((A*spf.U)*t)/(pi*rR^2)
I have tried solving the problem as segregated and as fully coupled, but either way I get the following error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.spf.U@VDN$comp1.u
- Defined as: (0.5*(((comp1.w^2)+((comp1.v^2)+(comp1.u^2)))^(-0.5)))*(2*comp1.u)
Failed to evaluate expression.
- Expression: (0.5*(((comp1.w^2)+((comp1.v^2)+(comp1.u^2)))^(-0.5)))*(2*comp1.u)
Failed to evaluate Jacobian of expression.
- Expression: comp1.spf.U
Failed to evaluate Jacobian of operator.
- Operator: mean
- Geometry: geom1
- Boundary: 6
Failed to evaluate Jacobian of variable.
- Variable: comp1.spf.U
- Geometry: geom1
- Boundary: 6
Failed to evaluate Jacobian of expression.
- Expression: ((-comp1.spf.f0)*comp1.spf.nzmesh)*dvol
Failed to evaluate Jacobian of expression.
- Expression: (-comp1.spf.f0*(test(comp1.u)*comp1.spf.nxmesh+test(comp1.v)*comp1.spf.nymesh+test(comp1.w)*comp1.spf.nzmesh))*(dvol)
- Feature: Time-Dependent Solver 1 (sol1/t1)
I get no errors and the model seems to be working as expected when I set the pressure condition for the inlets and outlet to 101325 Pa. Therefore the problem seems to be with my equation/implementation.
Any help with how I can address this error or approach the problem differently is welcome.
Thanks.
On top of the chip are fluid reservoirs. As fluid flows from inlet to outlet the fluid height in the inlet reservoirs decreases and the fluid height at the outlet reservoir increases. This should cause a change in pressure that I would like to model. I have attached a simplified sketch (not to scale) with one inlet and outlet that should clarify my problem.
I am new to fluid dynamics so I may be approaching this problem in the wrong way but here is what I have so far.
The initial pressure (P0) at each reservoir is the same. Once the problem starts (t=0) an electric field is applied between one of the inlets and the outlet. The second inlet is unbiased for now. At any time t>0 there will now be a pressure difference between the inlets and outlet.
I have derived an equation for the pressure in the reservoirs based on the equation P=rho*g*h, where P is pressure, rho is the fluid density, g is gravity, and h is the fluid height in a reservoir.
At a reservoir the pressure will be P = P0 + Pt, where Pt is the pressure change as a function of time. Which is to say the pressure change due to fluid emptying from the inlet or collecting at the outlet.
Therefore, Pt = rho*g*ht, where ht is the change in fluid height in a reservoir. Now volume (V) in the cylindrical reservoirs is given as V=pi*r^2*h, therefore, h = V/(pi*r^2). The change in volume in the reservoirs is equal to the volume flow rate Q multiplied by time. Q = A*v where A is the cross sectional area of the microfluidic channel and v is the flow velocity.
So Pt = rho*g*ht = rho*g*V/(pi*r^2) = rho*g*(Q*t)/(pi*r^2) = rho*g*(A*v*t)/(pi*r^2)
Therefore, at the inlet P = P0 - rho*g*(A*v*t)/(pi*r^2),
and at the outlet P = P0 + rho*g*(A*v*t)/(pi*r^2)
In Comsol for inlet 1, I am using the pressure boundary condition, suppress backflow is unchecked, and flow direction is normal flow. Under pressure condition the units are Pa and I have written the following:
101325-rho*g*((A*spf.U)*t)/(pi*rR^2)
where rR is the reservoir radius, and I have already identified the other variables.
I am leaving the second inlet electrically floating for the moment. The conditions are otherwise the same, so under the pressure condition I have simply left it as
101325
For the outlet, I am using the pressure boundary condition, suppress backflow and normal flow are unchecked. Under pressure condition the units are Pa and I have written the following:
101325+rho*g*((A*spf.U)*t)/(pi*rR^2)
I have tried solving the problem as segregated and as fully coupled, but either way I get the following error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.spf.U@VDN$comp1.u
- Defined as: (0.5*(((comp1.w^2)+((comp1.v^2)+(comp1.u^2)))^(-0.5)))*(2*comp1.u)
Failed to evaluate expression.
- Expression: (0.5*(((comp1.w^2)+((comp1.v^2)+(comp1.u^2)))^(-0.5)))*(2*comp1.u)
Failed to evaluate Jacobian of expression.
- Expression: comp1.spf.U
Failed to evaluate Jacobian of operator.
- Operator: mean
- Geometry: geom1
- Boundary: 6
Failed to evaluate Jacobian of variable.
- Variable: comp1.spf.U
- Geometry: geom1
- Boundary: 6
Failed to evaluate Jacobian of expression.
- Expression: ((-comp1.spf.f0)*comp1.spf.nzmesh)*dvol
Failed to evaluate Jacobian of expression.
- Expression: (-comp1.spf.f0*(test(comp1.u)*comp1.spf.nxmesh+test(comp1.v)*comp1.spf.nymesh+test(comp1.w)*comp1.spf.nzmesh))*(dvol)
- Feature: Time-Dependent Solver 1 (sol1/t1)
I get no errors and the model seems to be working as expected when I set the pressure condition for the inlets and outlet to 101325 Pa. Therefore the problem seems to be with my equation/implementation.
Any help with how I can address this error or approach the problem differently is welcome.
Thanks.
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Wall condition (no slip or sliding), fluid outlet condition
Hi all,
I am modeling a sphere moving in a moving laminar fluid domain (2D). The sphere is moved by the motion of the fluid, through boundary load on the sphere surface. I am wondering what kind of wall condition should I apply to the sphere surface, 'no slip' or 'sliding'.
Also, what kind of outlet condition should I apply to the outlet? Currently I am using 'pressure, no viscous stress', with pressure '0'. However, in the pressure plot, the pressure close to the outlet is larger than the pressure far away, which seems strange. How can the sphere move if the pressure ahead is smaller than the pressure behind?
I have attached the model and the pressure plot.
Thanks in advance for your help!
I am modeling a sphere moving in a moving laminar fluid domain (2D). The sphere is moved by the motion of the fluid, through boundary load on the sphere surface. I am wondering what kind of wall condition should I apply to the sphere surface, 'no slip' or 'sliding'.
Also, what kind of outlet condition should I apply to the outlet? Currently I am using 'pressure, no viscous stress', with pressure '0'. However, in the pressure plot, the pressure close to the outlet is larger than the pressure far away, which seems strange. How can the sphere move if the pressure ahead is smaller than the pressure behind?
I have attached the model and the pressure plot.
Thanks in advance for your help!
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Frequency dependent pressure waves
Hi,
I am trying to apply pressure waves to a mass contained in a closed volume in order to make it vibrate. So far I got it to vibrate, but I can't seem to find a way to set the frequency of the waves. Is there any way to set the frequency of the applied waves?
Thanks in advance
I am trying to apply pressure waves to a mass contained in a closed volume in order to make it vibrate. So far I got it to vibrate, but I can't seem to find a way to set the frequency of the waves. Is there any way to set the frequency of the applied waves?
Thanks in advance
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(Two phase)Bubble shrink in a two phase flow
I want to simulate a bubble dynamics in the water.
I initialize a bubble in the water, and use phase-field model.
I give the water a velocity in a channel, the bubble moves with the water.
After a few time steps, the bubble become smaller and smaller, than disappear!!!
It is very odd, as I set incompressible flow and a uniform mesh.
Other parameters are default.
What is the reason for this phenomenon.
Thanks.
I initialize a bubble in the water, and use phase-field model.
I give the water a velocity in a channel, the bubble moves with the water.
After a few time steps, the bubble become smaller and smaller, than disappear!!!
It is very odd, as I set incompressible flow and a uniform mesh.
Other parameters are default.
What is the reason for this phenomenon.
Thanks.
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Modelling seperation of ice and salt
Hello,
I am a begginer at CFD modelling, with only basic experience in MATLAB with Euler Methods.
My objective is to model the seperation of ice and salt from seawater. This occurs when a liquid is brought to the eutectic point ( a temperature ranging from -10 to -30 celsius). I am aware of how to model the heat exchange of the problem, my issue is with the phase change that occurs.
If anyone could suggest a general pathway on solving this I would be very grateful.
Kind Regards,
Argyris
I am a begginer at CFD modelling, with only basic experience in MATLAB with Euler Methods.
My objective is to model the seperation of ice and salt from seawater. This occurs when a liquid is brought to the eutectic point ( a temperature ranging from -10 to -30 celsius). I am aware of how to model the heat exchange of the problem, my issue is with the phase change that occurs.
If anyone could suggest a general pathway on solving this I would be very grateful.
Kind Regards,
Argyris
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Undefined value found in the equation residual vector.
I'm solving for lid driven cavity with stratified flow.
My error message looks:
Undefined value found.
- Detail: Undefined value found in the equation residual vector.
There are 3 degrees of freedom giving NaN/Inf in the vector for the variable comp1.T.
at coordinates: (0.080597,0.2), (0.0835821,0.2), (0.0820896,0.202422), .
Thus the error would belong to the heat transfer domain. As I understand, residual vector is the vector that is formed to solve my equation, which in this case would be the temperature equation. It would consist of my thermal properties, Temperature and velocity as a variable along with boundary conditions. But I’m unable to figure what is actually missing.
According to manual I followed “Check for undefined numerical values after each operation” in the assembly settings. After that it display this error :
Function evaluation returns undefined numerical value.
- Function: ^2
- Expression: (comp1.spf.xi_m*comp1.spf.res_v)^2
Failed to evaluate variable.
- Variable: comp1.spf.vhNS_lin
Failed to evaluate expression.
- Expression: nojac((1.4142135623730951^(1-shapeorder(comp1.u)))*max(comp1.spf.vhNS_lin-comp1.spf.vhNS_quad,0))
Failed to evaluate variable.
- Variable: comp1.spf.vhNS
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.spf.crosswindns@VDN${test@85}
Failed to evaluate expression.
- Expression: d((comp1.spf.crosswindns)*(dvol),{test@85})
Failed to evaluate Jacobian of expression.
- Expression: (comp1.spf.crosswindns)*(dvol)
But here it seems that it is referring to components of velocities. My guess would be that it is unable to resolve velocities at the boundary or getting division by zero there.. I’m lost on how to fix this.
I don't think it is due boundary conditions or material properties are the culprits, due to fact that there are 200 iterations. Although the error plot looks really bad i.e no convergence is achieved. My initial guess is good enough since it gives an error of magnitude ~ 10^0 .
Kindly help!!
Regards
Parth Swaroop
My error message looks:
Undefined value found.
- Detail: Undefined value found in the equation residual vector.
There are 3 degrees of freedom giving NaN/Inf in the vector for the variable comp1.T.
at coordinates: (0.080597,0.2), (0.0835821,0.2), (0.0820896,0.202422), .
Thus the error would belong to the heat transfer domain. As I understand, residual vector is the vector that is formed to solve my equation, which in this case would be the temperature equation. It would consist of my thermal properties, Temperature and velocity as a variable along with boundary conditions. But I’m unable to figure what is actually missing.
According to manual I followed “Check for undefined numerical values after each operation” in the assembly settings. After that it display this error :
Function evaluation returns undefined numerical value.
- Function: ^2
- Expression: (comp1.spf.xi_m*comp1.spf.res_v)^2
Failed to evaluate variable.
- Variable: comp1.spf.vhNS_lin
Failed to evaluate expression.
- Expression: nojac((1.4142135623730951^(1-shapeorder(comp1.u)))*max(comp1.spf.vhNS_lin-comp1.spf.vhNS_quad,0))
Failed to evaluate variable.
- Variable: comp1.spf.vhNS
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.spf.crosswindns@VDN${test@85}
Failed to evaluate expression.
- Expression: d((comp1.spf.crosswindns)*(dvol),{test@85})
Failed to evaluate Jacobian of expression.
- Expression: (comp1.spf.crosswindns)*(dvol)
But here it seems that it is referring to components of velocities. My guess would be that it is unable to resolve velocities at the boundary or getting division by zero there.. I’m lost on how to fix this.
I don't think it is due boundary conditions or material properties are the culprits, due to fact that there are 200 iterations. Although the error plot looks really bad i.e no convergence is achieved. My initial guess is good enough since it gives an error of magnitude ~ 10^0 .
Kindly help!!
Regards
Parth Swaroop
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Creeping flow through a hydrogel
Hi everyone,
I am trying to model the diffusion (creeping flow) of molecules through a collagen type I hydrogel. Does anyone have any idea on how to model a portion of a microfluidic device that contains this hydrogel?
Best,
Kevin
I am trying to model the diffusion (creeping flow) of molecules through a collagen type I hydrogel. Does anyone have any idea on how to model a portion of a microfluidic device that contains this hydrogel?
Best,
Kevin
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Error in Two Phase Flow
I am using the Level Set Method in Comsol. When I am using the Time dependent solvers I get the following error-
Failed to find consistent initial values.
Last time step is not converged.
The same problem using Stationary Solver I am getting the following error-\
Wrong number of dofs in initial value.
Can anyone please tell the error in the model
Failed to find consistent initial values.
Last time step is not converged.
The same problem using Stationary Solver I am getting the following error-\
Wrong number of dofs in initial value.
Can anyone please tell the error in the model
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Calculate Drag Coefficient
Background: simulate the drag coefficient for a truck model
I have read the following post
www.comsol.de/blogs/how-do-i-compute-lift-and-drag/
and looked at the flow over an Ahmed body example
which shows that the total drag force in the Y direction is: spf.T_stressy
To calculate c_d i need to calculate
c_d = \frac{ 2F_d}{ \rho u^2 A} (en.wikipedia.org/wiki/Drag_coefficient)
where (please correct if wrong):
F_d = spf.T_stressy
/rho = spf.rho
u = spf.u
Is the above correct? How do I calculate Area? The area should only be the surface exposed in the Y direction (spf.nymesh?)?
thanks in advance!
Jess
I have read the following post
www.comsol.de/blogs/how-do-i-compute-lift-and-drag/
and looked at the flow over an Ahmed body example
which shows that the total drag force in the Y direction is: spf.T_stressy
To calculate c_d i need to calculate
c_d = \frac{ 2F_d}{ \rho u^2 A} (en.wikipedia.org/wiki/Drag_coefficient)
where (please correct if wrong):
F_d = spf.T_stressy
/rho = spf.rho
u = spf.u
Is the above correct? How do I calculate Area? The area should only be the surface exposed in the Y direction (spf.nymesh?)?
thanks in advance!
Jess
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A Vortex Pair Impinging on a Solid Boundary
I am trying to model the Problem of 9.13 from Plawsky Transport Phenomena 3rd ed (below). Any ideas for how to set this up better? Thanks
The method of images uses precisely oriented collections of sources, sinks, and vortices
to establish artificial walls and so simulate more complicated flow fields. One such flow
field is formed by positioning two counter-rotating vortices a distance, d, from the
location of the hypothetical wall. The stream function for this flow is given by:
ψ = qo / 4π{ −ln [(x − d)^2 + y^2] + ln[ (x + d)^2 + y^2]}
a) Demonstrate that there is no flow through the wall.
b) How does the velocity vary along the length of the wall?
c) What is the pressure distribution along the wall?
The method of images uses precisely oriented collections of sources, sinks, and vortices
to establish artificial walls and so simulate more complicated flow fields. One such flow
field is formed by positioning two counter-rotating vortices a distance, d, from the
location of the hypothetical wall. The stream function for this flow is given by:
ψ = qo / 4π{ −ln [(x − d)^2 + y^2] + ln[ (x + d)^2 + y^2]}
a) Demonstrate that there is no flow through the wall.
b) How does the velocity vary along the length of the wall?
c) What is the pressure distribution along the wall?
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Issues with Pipe Flow and Surface Radiation interaction
Hello Comsolers!
I am very new to the program, and I am having some issues regarding Non Isothermal Pipe Flow, Heat Transfer in Solids, and Heat Transfer with Surface to Surface Radiation.
I have a 1D pipe circuit, where the the inlet and outlet (plus 1 meter pipe for each of them) sections are resting on top of a block of soil, and the rest is buried underground. There is a flow of water in the pipe.
The main idea is to simulate the pipes being heated by the Sun's radiation, observe an increase in temperature in the pipe, and observe how the ground is being heated by the thermal transfer between the fluid-pipe-ground.
For some reason, I am not observing a Radiation - Thermal transfer interaction, and I do not know what am I doing wrong.
Here's the boundaries that I have:
For Surface to Surface Radiation: Defined an external radiation source by solar position, a diffuse surface and heat flux (both of these only on the side of the block that is illuminated by the Sun), defined a constant temperature at the base of the block of soil (which is not illuminated).
For Non Isothermal Pipe Flow: Defined an Inlet with a volumetric flow rate, a Heat Outflow at the outlet, and a wall heat transfer with internal film resistance.
For the Heat Transfer in Solid, I have defined a Heat Flux in all applicable domains.
Any help is greatly appreciated! I can provide more details if needed.
Thank you all,
Aaron
I am very new to the program, and I am having some issues regarding Non Isothermal Pipe Flow, Heat Transfer in Solids, and Heat Transfer with Surface to Surface Radiation.
I have a 1D pipe circuit, where the the inlet and outlet (plus 1 meter pipe for each of them) sections are resting on top of a block of soil, and the rest is buried underground. There is a flow of water in the pipe.
The main idea is to simulate the pipes being heated by the Sun's radiation, observe an increase in temperature in the pipe, and observe how the ground is being heated by the thermal transfer between the fluid-pipe-ground.
For some reason, I am not observing a Radiation - Thermal transfer interaction, and I do not know what am I doing wrong.
Here's the boundaries that I have:
For Surface to Surface Radiation: Defined an external radiation source by solar position, a diffuse surface and heat flux (both of these only on the side of the block that is illuminated by the Sun), defined a constant temperature at the base of the block of soil (which is not illuminated).
For Non Isothermal Pipe Flow: Defined an Inlet with a volumetric flow rate, a Heat Outflow at the outlet, and a wall heat transfer with internal film resistance.
For the Heat Transfer in Solid, I have defined a Heat Flux in all applicable domains.
Any help is greatly appreciated! I can provide more details if needed.
Thank you all,
Aaron
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List of function in Comsol 5.2
Dear All,
Can anybody help me with finding the list of inbuilt functions of comsol 5.2. I want to equate my equation in the expression box of 1D plot group.
I am using heat transfer module for conjugate analysis. Have already been through all the reference manual available with the program document.
Regards
Can anybody help me with finding the list of inbuilt functions of comsol 5.2. I want to equate my equation in the expression box of 1D plot group.
I am using heat transfer module for conjugate analysis. Have already been through all the reference manual available with the program document.
Regards
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Variable boundary conditions
Hi all, I'm using the API to run my COMSOL model multiple times in a loop in MATLAB with different initial and boundary conditions.
I was just wondering if it would be possible to set the initial conditions from the last time step of the previous solution, and the boundary conditions as the time varying value of one of the independent variables at the last node point in my mesh.
The problem is one dimensional, and writing the conditions in as a polynomial function using polyval isn't ideal as this seems to produce ill conditioned polynomials with the data I have.
Basically, can you specify the initial and boundary conditions as arrays of values corresponding to either time steps or locations?
I was just wondering if it would be possible to set the initial conditions from the last time step of the previous solution, and the boundary conditions as the time varying value of one of the independent variables at the last node point in my mesh.
The problem is one dimensional, and writing the conditions in as a polynomial function using polyval isn't ideal as this seems to produce ill conditioned polynomials with the data I have.
Basically, can you specify the initial and boundary conditions as arrays of values corresponding to either time steps or locations?
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Heat Source in Turbulent High mach number flow !
Dear COMSOLERS ;
I am trying to simulate an electric arc in a flowing gas through a nozzle. as you can see in the attached model, the arc heat is been added as a heat source in the hmnf interface. also i created a ramp parameter to sweep the heat source value in the auxiliary sweep.
Now , as the ramp value goes higher , the solver gives the following error :
Failed to find a solution for all parameters,
even when using the minimum parameter step.
In Segregated Step 2:
Segregated iteration leads to undefined function value.
There was an error message from the linear solver.
The relative residual (1.2e+003) is greater than the relative tolerance.
Returned solution is not converged.
I tried different type of meshes , ramping the materiel properties and it didn't work out.
it would be great if any could help me solve this problem.
Best Regards ;
I am trying to simulate an electric arc in a flowing gas through a nozzle. as you can see in the attached model, the arc heat is been added as a heat source in the hmnf interface. also i created a ramp parameter to sweep the heat source value in the auxiliary sweep.
Now , as the ramp value goes higher , the solver gives the following error :
Failed to find a solution for all parameters,
even when using the minimum parameter step.
In Segregated Step 2:
Segregated iteration leads to undefined function value.
There was an error message from the linear solver.
The relative residual (1.2e+003) is greater than the relative tolerance.
Returned solution is not converged.
I tried different type of meshes , ramping the materiel properties and it didn't work out.
it would be great if any could help me solve this problem.
Best Regards ;
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Moving Mesh issue at the inlet/outlet
Hello,
I am working on a 2D model on a channel with some obstacles.
The study is time-dependent and I have used the Moving Mesh (ALE).
The lower boundary of my model is moving down. The inlet and the outlet are moving too in order to increase the height of the channel.
I have some issue because the geometry is moving but all the results (especially the velocity) are given as if the geometry doesn't change. So I can see that the geometry is moving in the player but the results keep the first geometry.
I tried to change a lot of options to fix that but I can't find out the problem.
Please, anyone can help me? I attached pictures of the inlet options, the moving boundary options and the results.
Thank you for your time.
Berenice
I am working on a 2D model on a channel with some obstacles.
The study is time-dependent and I have used the Moving Mesh (ALE).
The lower boundary of my model is moving down. The inlet and the outlet are moving too in order to increase the height of the channel.
I have some issue because the geometry is moving but all the results (especially the velocity) are given as if the geometry doesn't change. So I can see that the geometry is moving in the player but the results keep the first geometry.
I tried to change a lot of options to fix that but I can't find out the problem.
Please, anyone can help me? I attached pictures of the inlet options, the moving boundary options and the results.
Thank you for your time.
Berenice
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Plasma plume expansion induced during laser ablation
Hello,
We are trying are to set up a model to study plasma plume expansion induced during pulsed laser deposition. Model is based on compressible Navier stokes equations consisting of mass, momentum and energy conservation. We are using equation based module of COMSOL (PDEs interface). We have implemented these equations of plasma plume into COMSOL and due to some reason it is not converging.
Can anyone assistance in this regards. Thank you.
Saba
We are trying are to set up a model to study plasma plume expansion induced during pulsed laser deposition. Model is based on compressible Navier stokes equations consisting of mass, momentum and energy conservation. We are using equation based module of COMSOL (PDEs interface). We have implemented these equations of plasma plume into COMSOL and due to some reason it is not converging.
Can anyone assistance in this regards. Thank you.
Saba
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how to use two boundary conditions at same boundary
I have been solving darcy's module in which i am supposed to add BCS of inlet pressure as well as mass flux which is at same boundary. But when i add 1 boundary condition it gets overridden by another one. Since i want to use both data in my model iss there any method to add both bcs at same place?
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