Another cause for locally slightly negative concentrations is a discontinuity in space or time, for instance in the initial condition. The concentration of emulsion around the electrodes reduce rapidly due to the negative DEP force repel it form the strong electric field. This may sound completely wrong to anyone who has seen, for instance, a Nafion® membrane, one of the most common polymer electrolyte materials. Permeability of the cell membrane to the … Figure 1: Solutions to the time-dependent diffusion problem with a boundary condition at the left (c=1) that creates a discontinuity with the initial condition (c=0) at t=0. Browse the threads and share your ideas with the COMSOL community. Figure 1: Solutions to the time-dependent diffusion problem with a boundary condition at the left (c=1) that creates a discontinuity with the initial condition (c=0) at t=0. The COMSOL discussion forum covers a wide variety of simulation topics. Posted 8 déc. Results l: Using the method described in the Box "Model Description" the concentrations of electrons, positive and negative ions are simulated. The model was fully implemented and solved with COMSOL Multiphysics using predefined application modes. At the higher cell concentration, about 1.9% of STAMP barcodes associated with mouse-human mixtures (B). This model produces graphs of electrolyte concentration, volt-age, and discharge rates of the battery over time. Browse the threads and share your ideas with the COMSOL community. 4(a). Plasma Science and Technology assists in advancing plasma science and technology by reporting important, novel, helpful and thought-provoking progress in this strongly multidisciplinary and interdisciplinary field, in a timely manner. Version 4.3 Xin Jin posted 1 decade ago. Discontinuous Boundary and Initial Conditions: Smoothen the Settings. Hello, I'm Silvia, I'm using comsol to simulate a gasification process in a fixed bed downdraft reactor. I have run across a problem where I am representing, instead of a point source of pollution, a quadralateral geometry (2D) pollutant source (constant concentration source). Browse the threads and share your ideas with the COMSOL community. The goal of the analysis was to propose configu-rations and implement analytical tools for analysing mixing processes, which would be feasible ... when the concentration field is a passive scalar quantity, the fluid streams meet at the mixing Thilo Henrich . Figures 6 through 8 illustrate the diffusive concentration of the copper through the printer head. Discontinuous Boundary and Initial Conditions: Smoothen the Settings. Another cause for locally slightly negative concentrations is a discontinuity in space or time, for instance in the initial condition. (3) J * = 2 e C 0 D t a L When J > J * then, dC/dx > 2C 0 /L, due to the large concentration gradient, the anion concentration near the negative electrode will drop to … Version 3.5a Version 5.2a Fluid Yuanhai Su … The formation and propagation of a streamer can be described best by the behavior of the electrons. ... how to avoid negative concentration read 14 Replies 9919 Views. The first modification was the addition of another rivet. Version 4.4 General Electrochemical Engineering Kumar Krishnamoorthy posted 6 years ago. Data for other cell concentrations and a different single-cell analysis platform are in Figures S3B and S3C. The concentration will locally be slightly negative at t=0, as shown in the figure. The COMSOL discussion forum covers a wide variety of simulation topics. Negative Concentration in Domain read 4 Replies 2341 Views. By letting m and n take both positive and negative values with equal probabilities, we should be able to get a method of synthesizing a surface with no preferred direction of oscillations.. To further understand the model, we varied volumetric fraction (analogous to porosity) of the positive and negative electrodes, Two alternate designs were created and tested in COMSOL. 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. The concentration will locally be slightly negative at t=0, as shown in the figure. Figure 1: Solutions to the time-dependent diffusion problem with a boundary condition at the left (c=1) that creates a discontinuity with the initial condition (c=0) at t=0. The finite element method gives rise to a swing below zero in the leftmost element. Negative concentration values in Transport of Diluted Species Study. 2009 à 07:50 UTC−8 Version 3.5a 10 Replies . The initial design consisting of a single rivet attaching the strap to the poles was found to exceed the working psi of the webbing. Hi all, new to COMSOL. The combination of COMSOL ® products required to model your application depends on several factors and may include boundary conditions, material properties, physics interfaces, and part libraries. The top of the electrochemical printer, at time zero, is brought to a 100 mol/m3 copper concentration. × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. Particular functionality may be common to several products. The pores, s… For example, the direction (-2,-3) is the same as (2,3); (2,-1) is the same as (-2,1); and so on. FIGURE 4: Electrolyte salt concentration (mol/m3) profiles at various times during the cycle in Figure 3. If you notice negative concentrations of very small magnitude, numerical noise is probably the cause and does not affect the problem much in diffusion/convection problems without reactions. Another cause for locally slightly negative concentrations is a discontinuity in space or time, for instance in the initial condition. Condition the Reaction Term to be Larger than Zero for Concentrations Approaching Zero A significant negative concentration often indicates that the underlying mathematical model does not correctly describe the physics. Discontinuous Boundary and Initial Conditions: Smoothen the Settings. A common reason is numerical noise: For example, when the variable for concentration approaches zero, the numerical noise may become significant in comparison to the value (which is close to zero). After around 10 years, the salt has traveled around 150 m in the negative direction, reaching the horizontal boundary at y = 0, and covering nearly 60% of the porous medium. Negative concentration values - transport of diluted species + Darcy's law (transport in porous bed) read 0 Replies 99 Views. How do Comsol handles variable density? Browse the threads and share your ideas with the COMSOL community. Stress Concentration Analysis of the Pole-Harness Interface. It reacts away to form water. Note: This discussion is about an older version of the COMSOL Multiphysics ... To start a new discussion with a link back to this one, click here. I'm using the navier-stokes module for the fluid dynamics, coupled with a mass balance module (diffusion and convection). chemical reaction, concentration reaches zero. The COMSOL discussion forum covers a wide variety of simulation topics. CFD-software, COMSOL MULTIPHYSICS. During discharge, the electrolyte salt concentration increases in the negative electrode and decreases in the positive electrode when lithium ions … Browse the threads and share your ideas with the COMSOL community. I'm modeling creeping flow and transport of dilute species through a series of ribs, with an electrochemical reaction occuring at 10 mA/sqcm on the bottom surface of the under-rib flow. Hello All - I use COMSOL in the context of groundwater (Earth Sciences Module). An ion-exchange material is typically modeled as a porous medium consisting of a fixed matrix with the pores filled up with water and additional mobile ions. I insert the reaction rates specifying that it must be null while the concentration of the reactants is negative or zero. read 1 Replies 3329 Views. The COMSOL discussion forum covers a wide variety of simulation topics. The dimensionless concentration of the hydroxide ion is expressed as follows: and represents the hydroxide ion concentration at ... electrode is connected (in theory) to the more negative The initial concentration of the dilute species is 6.25 mM. This problem can be avoided by using one of COMSOL Multiphysics's built in smoothed step functions smooths out the initial discontinuity in a controlled way. For instance, in the example above, you could, instead of the uniform zero initial condition, use a smoothed step transition as the initial condition. This material looks perfectly transparent and homogeneous, but the matrix is made of a transparent polymer backbone. I found that in 3.5, the syntax ("mod1.cs_C3H6>0") works to prevent the concentration from becoming negative. ... How to solve the problem of negative concentration read 36 Replies 26713 Views. The concentration will locally be slightly negative at t=0, as shown in the figure. COMSOL module by setting the velocity equal to zero at all boundaries. Posted 05.10.2014, 03:36 GMT-4 Fluid, Computational Fluid Dynamics (CFD), Microfluidics 2 Replies . Número da Solução: 952 Aplica-se a: COMSOL Multiphysics, CFD Module, Chemical Reaction Engineering Module, Electrodeposition Module, Microfluidics Module, Subsurface Flow Module, Mixer Module, Corrosion Module, Electrochemistry Module Versões: Todas as versões. At the lower cell concentration, one STAMP barcode (of 570) associated with a mixture of human and mouse transcripts (A, purple). Changes in HeLa cell morphology, membrane permeability, and viability caused by the presence of Triton X-100 (TX100), a nonionic surfactant, were studied by scanning electrochemical microscopy (SECM). The COMSOL discussion forum covers a wide variety of simulation topics. No change in membrane permeability was found at concentrations of 0.15 mM or lower during an experimental period of 30 to 60 min. Note that, in this way, each wave direction is represented twice. As an example, consider the one dimensional time dependent Convection-Diffusion-Reaction equation: The initial condition is zero concentration within the domain and the boundary conditions are set to 1 and 0 concentration … The emulsions concentration is initially maintained constant at 1 mol/m 3 at 0 s. The emulsions concentration distribution at 10 V applied voltage could be simulated in 5 s as shown in Fig. Send Private Message Flag post as spam. However, as the salt concentration mixes with the fluid, the denser salt water is pulled down by gravity, inciting flow. As an example, consider the one dimensional time dependent Convection-Diffusion-Reaction equation: The initial condition is zero concentration within the domain and the boundary conditions are set to 1 and 0 concentration … program called COMSOL [1]. Ed Fontes, COMSOL, www.comsol.com Ed Fontes is chief technology officer at COMSOL and has a PhD in applied electrochemistry from The Royal Institute of Technology (KTH), Stockholm. He has been the lead developer for the chemical engineering, CFD, and heat transfer product lines at COMSOL.
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