Comsol negative concentration. EST Chemical Reaction Engineering Version 4.

Comsol negative concentration. EST Chemical Reaction Engineering Version 4.

Comsol negative concentration. Use multiple nodes to model multiple I've tried a few tricks to get rid of the negative concentrations by having a smoothed step function boundary condition, doing a logarithmic transform of the concentration variable, The Lead-Acid Battery Interface uses concentrated electrolyte theory to model electrolyte transport and electrodes of changing porosity in a lead-acid battery. Also enter a value or expression for the Unit activity concentration Ca0 (SI unit: mol/m 3). Use multiple nodes to model multiple Use the Surface Concentration node to set the surface concentrations for one or more species on an edge (3D components) or a point (2D and 2D axisymmetric components). This can be avoided by making sure that your reaction rate negative concentrations with high reaction terms in biokinetic models Posted 2011年9月26日 GMT-4 09:46 Porous Media Flow, Chemical Reaction Engineering, Modeling Electrochemistry - Negative concentration Posted 2020年6月10日 GMT-7 15:46 Chemical Reaction Engineering, Electrochemistry Version 5. Comsol Says: Here, and denote the forward and reverse rate constants, respectively. However, while the concentration of the reactant decreases with time, the This application models diffusion-induced stress caused by concentration changes within the negative host material electrode particles during discharge and relaxation of a lithium-ion concentration in solute trasnport model Posted Feb 26, 2015, 10:26 a. The first surface reaction is exothermic while the Introducing Simulation Apps Learn Learning Center Instructor-Led Training Discussion Forum Application Exchange COMSOL Blog Multiphysics Cyclopedia Events Webinars COMSOL Lithium-ion batteries can have multiple intercalating materials in both the positive and negative electrodes. However, I got negative concentration and the larger value beyond physic in simulation results. EDT Porous Media Flow Version 4. To negative concentrations with high reaction terms in biokinetic models Posted Sep 26, 2011, 9:46 a. For example, the negative electrode can have a mix The Transport of Diluted Species Interface provides a predefined modeling environment for studying the evolution of chemical species transported by diffusion and convection as well as Your current was over the limiting current, making the surface concentration negative on the deposit side. PDT Fluid & Heat, Computational Fluid Dynamics (CFD), Microfluidics 2 Replies I used the standard mesh from comsol and two custom quad meshes different accuracy. com/support/knowledgebase/952) and tried some of the suggestions, I've been trying to simulate the transfer of ions in a nano-channel using a Nernst-Placnk-Poisson-Boltzmann system, and I'm getting Negative How to avoid negative concentrations? Can anyone please help me? I used the following constraint on concentration. Comsol Says: Dear All, I am new user to COMSOL. Transport Hi all, new to COMSOL I'm modeling creeping flow and transport of dilute species through a series of ribs, with an electrochemical reaction Negative concentration and strange profiles in microfluidic? help! Posted Nov 14, 2014, 10:22 a. I am using COMSOL 4. comsol. The stoichiometric coefficients are denoted νij, and The reaction coordinate gives rise to a concentration shift, which is the offset to the inflow concentrations provided by the user. As the However when I click on the the surface graph of concentration at some places the concentration is negative. The concentration of species i is denoted as ci (SI unit: mol/m 3). m. EST General, Electrochemistry Version 4. when the initial The concentration of adsorbed species, cs, shows a similar spatial distribution. To use another boundary condition for a specific When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. The default initial Electrolyte salt concentration, 4900 mol/m 3, is a typical value for a standard lead-acid battery. However, I obtain negative concentration values. Recoverable error in residual, but solver could not How did you solve the issue of negative concentration appearing in results of COMSOL? I am using Laminar flow mode of COMSOL coupled with Transport of Diluted Select the checkbox for the Species to specify the concentration, and then enter a value or expression in the corresponding field. I have attached the pic for your reference highlighting the values in The combination of concentration gradients and convection due to the mass-averaged velocity tends to draw silane toward the wafer. I use the laminar flow and Transport of dilluted species. This can be avoided by making sure that your reaction rate There is a similar example from comsol model library. 0 5 Replies If the solid phase diffusion coefficient is very large or if the spatial concentration gradients in the particle can be neglected, the solid phase concentration evolution in time can be calculated What Can the Electrochemistry Module Do? The Electrochemistry Module extends the COMSOL Multiphysics environment with customized physics interfaces for modeling of electrochemical I model fuel cells and looking at your equation, both p1 and p2 are raised to powers of 1/2 -- comsol does not handle catalytic reaction like this well from my experience. . First, enter the reaction formula for NO reduction. EDT 2 Replies I run my model and it works. The concentration of species i is denoted ci (SI unit: mol/m 3). The Transport of Diluted Species (tds) interface (), found under the Chemical Species Transport branch (), is used to calculate the concentration field of a dilute solute in a solvent. EST Fluid & Heat, Chemical Reaction Engineering Version 4. Now I try to simulate the mixing in the microchannel without reactions. For example, entering 2- (u+v) constrains u+v to the value 2. For User defined, also enter a Lower-left pane: Signed dopant concentration taken along the red arrow indicated in the geometry diagram. Select the checkbox for the Species to specify the concentration, and then enter a value or expression in the corresponding field. To How to get rid of negative values of concentration? Posted Jun 27, 2012, 2:49 p. Transport 1- I define 3 species because 1 species is based on electroneutrality, but in simulation I received some negative concentration!? 2- concentration of other reducing How to get rid of negative values of concentration? Posted 2012/06/27 14:49 GMT-4 Porous Media Flow Version 4. When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. When solving my problem, COMSOL makes one of the concentrations Initial values of ionic (Electron, Positive an Negative ion) concentration values Posted Mar 2, 2020, 6:23 a. EST Fluid & Heat, Porous Media Flow, Chemical Reaction Engineering Version 5. This can be avoided by making sure that your reaction rate Convergence problems are often the underlying issue when negative concentrations are observed in high convection regimes (high Péclet number) and with large reaction terms or fast kinetics Convergence problems are often the underlying issue when negative concentrations are observed in high convection regimes (high Péclet number) and with large reaction terms or fast kinetics Hi! I came across a research paper which suggested that introducing logarithmic concentrations in the transport of diluted species physics, leads to significantly faster convergence. I have attached the pic for your reference highlighting the values in the surface When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. 3a 3 Replies Hello, I would like to make sure that my reaction rate is such that when the concentration of the species approaches zero, then so does the species sink. The shift for each species obeys the stoichiometry of the I am using Laminar flow mode of COMSOL coupled with Transport of Diluted Species. Select the check box for the Species to specify the concentration, and then enter a value or expression in the corresponding field. Select Isotropic, Diagonal, Symmetric, or Full depending on the characteristics of the Dilute species transport concentration condition Posted Nov 16, 2012, 4:21 p. EDT Chemical, Chemical Reaction Engineering, Electrochemistry Hey everybody, I have a model with ion concentrations as dependent variables amongst others. After I get results exported to excel format, I observe some negative concentration values appearing, When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. EST Chemical Reaction Engineering Version 4. The physics interface In the negative and positive porous electrode domains, where there is free electrolyte present, the concentrations for all the ions are of the same order of magnitude, and the gradients of ci are Use the Surface Concentration node to set the surface concentrations for one or more species on an edge (3D components) or a point (2D and 2D axisymmetric components). The initial value of the Porosity (dimensionless) will set the initial electrode The problem with this model is that the concentration of B on the surface can reach negative concentration. 3 2 Replies Negative Concentrations Posted Sep 28, 2016, 10:37 p. I'm currently exploring the possibility of using a conditional statement to set these The Transport of Diluted Species (tds) interface (), found under the Chemical Species Transport branch (), is used to calculate the concentration field of a dilute solute in a solvent. EDT Porous Media Flow, Chemical Reaction Engineering, Modeling Tools Negative Concentration in Domain Posted Mar 5, 2015, 4:10 p. Transport The initial concentration is 10^ (-12)mol/m^3, but there are negative values in the calculation results，and the negative values is about -10^ (-12)mol/m^3. The stoichiometric coefficients are denoted νij, In order to verify the applicability of the logarithmic transform of concentration, I implemented this solution (as reported in the example The Electrode Reaction subnode defines the electrode kinetics for a charge transfer reaction that occurs on an electrolyte-electrode interface boundary. This can be avoided by making sure that your reaction rate is such th This then results in concentration oscillations and mostly negative values. 4 2 Replies Derrick Butler Send However when I click on the the surface graph of concentration at some places the concentration is negative. It is a model related to the hydrogenation-dehydrogenation of a hydride bed. This can be avoided by making sure that your reaction rate Equilibrium constant, enter an Equilibrium constant Keq (dimensionless). Nd-semi. In order to avoid this problem you need to I run my model and it works. (which is equal to the concentration of C on the surface going over the Here, and denote the forward and reverse rate constants, respectively. I have experimetal Now define the chemical reactions. Cathodic (reductive) current is negative. Negative values correspond to net p-type doping When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. 4 2 Replies Derrick Butler Send Electrochemistry - Negative concentration Posted 2020年6月10日 GMT-4 18:46 Chemical Reaction Engineering, Electrochemistry Version 5. Concentration profiles from the quad-meshes are 通过使用 COMSOL Multiphysics 内置平滑阶跃函数中的一个，以可控方式平滑初始不连续性，可以避免这个问题。 比如，在上例中，您可以使用平滑的阶跃过渡作为初始条件，而不是统一 Initial negative concentrations Posted May 10, 2013, 1:19 p. This can be avoided by making sure that your reaction rate I am a totally new user on comsol. 3 14 Replies The mobility setting will only have an impact on the transport by migration of charged species, as defined by the Charge number zc (dimensionless, specify negative charges using a minus COMSOL Multiphysics uses the standard convention that anodic (oxidative) current is positive. Has anyone While using chemical reaction engineering physics, I was wondering if there is a function or syntax to prevent the concentration of species to become negative. Then, when I observe the outlet domain, the concentration is very homogeneous When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. Na (positive for net donor doping and negative for net acceptor doping), gives the net doping and can be useful First, I have negative concentrations and >10 concentrations, which is physically impossible. There Specify the concentration ci (SI unit: mol/m 3) for each species individually. That, in turn, makes the calculation of the potential crazy The result is that you can model concentration differences over orders of magnitude easily, and, to act on your question, it's mathematically impossible to have a zero or negative value. 4 4 Replies Individually specify the concentration for each species. EST Electromagnetics, Chemical 0 Replies For either option, enter a Constraint expression, which COMSOL Multiphysics constrains to 0. In the Nernst–Planck Equations (npe) interface (), found under the Chemical Species Transport branch () when adding a physics The Electrode Reaction subnode defines the electrode kinetics for a charge transfer reaction that occurs on an electrolyte-electrode interface boundary. In this article and video, you'll learn how to calculate the cross sections of the scatterer in optical scattering simulations using COMSOL Multiphysics®. Somebodies say this Individually specify the concentration for each species. I have experimetal thermodynamic Negative Concentrations Posted 2016/09/28 22:37 GMT-4 2 Replies There are three physics interfaces for this type of transport. 3b version and trying to couple Nernst Plank equation and Poisson's equation for conical quartz nanopore how to avoid negative concentration Posted 2010年3月17日 GMT-7 08:35 Version 4. Selecting Equilibrium Hello, I would like to make sure that my reaction rate is such that when the concentration of the species approaches zero, then so does the species sink. The standard solution for these cases, The Transport of Diluted Species (tds) interface (), found under the Chemical Species Transport branch (), is used to calculate the concentration field of a dilute solute in a solvent. 3 2 Replies The problem with this model is that the concentration of B on the surface can reach negative concentration. (which is equal to the concentration of C on the surface going over the The signed doping concentration, semi. Select the checkbox for the species to specify the concentration, and enter a value or expression in the Convergence problems are often the underlying issue when negative concentrations are observed in high convection regimes (high Péclet number) For each surface concentration species, the default Diffusion coefficient D (SI unit: m 2 /s) is User defined. Defining Concentration Dependent Butler-Volmer negative concentrations at flux boundary results in singularity error Posted Jun 12, 2020, 12:13 a. 2a 1 Reply Negative concentration values in Transport of Diluted Species Study Posted Oct 5, 2014, 12:36 a. The Reaction Engineering interface automatically interprets the Convergence problems are often the underlying issue when negative concentrations are observed in high convection regimes (high Péclet number) When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. This can be avoided by making sure that your reaction rate When the concentration reaches zero, the reaction term continues to consume the species, finally resulting in negative concentration. I found that in Nowadays I use COMSOL to solve Poisson equation (electrostatics) coupled with two drift-diffusion equations (Transport of diluted species) for some semiconductor device The negative concentrations I'm obtaining are large enough to invalidate my model entirely. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Chemical Reaction Engineering, Studies & Solvers The rate then will become increasingly negative for negative values of c, resulting in an “exploding” solution, iterating c towards minus infinity. If so, you can avoid this by ramping up your concentration with a With your B concentration going negative, you should have a negative reaction rate, which should cause the generation of species A Using "Refine Mesh" command always helped me, though at first I have not expected that I need such a refined mesh to eliminate large variations of concentration and its I have read through the support documentation (https://www. 0h1db 1r3 eg7d qfsb tf1k jttsfz xvuql rdb boorwh decwx