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1. DEFINE FORCE FLUID IN COMSOL 5.1 FOR FREE
2. DEFINE FORCE FLUID IN COMSOL 5.1 SOFTWARE
3. DEFINE FORCE FLUID IN COMSOL 5.1 WINDOWS

Settings window for the fluid flow interface showing the Weakly compressible flow option and gravity feature. Selecting the Weakly compressible flow option removes the dependency between pressure and density, while selecting gravity automatically adds the volume force of buoyancy in the momentum equation. Selecting the Fluid Flow interface node in the Model Builder shows the settings window below. We can find the settings for the Weakly compressible flow option by selecting the Nonisothermal Flow interface or the Conjugate Heat Transfer interface. Where density, ρ, is a function of temperature.įor an ideal gas, density is inversely proportional to temperature. The continuity equation for a compressible fluid looks as follows: In natural convection, there is usually very little influence of pressure waves, which means that we lose very little fidelity in the model’s description of reality by making this simplification. This option also eliminates the description of pressure waves, which requires a dense mesh and small time steps to resolve, thus also a relatively long computation time.

The Nonisothermal Flow interface includes the Weakly compressible flow option, which simplifies flow problems by neglecting density variations with respect to pressure. Solving Natural Convection Problems with Weakly Compressible Flow Let’s learn more about these new features and how you can apply them in your natural convection modeling problems. The Gravity feature makes it easy to define a reference point for hydrostatic pressure and also automatically accounts for hydrostatic pressure variations at vertical boundaries.

DEFINE FORCE FLUID IN COMSOL 5.1 FOR FREE

This simplification is almost always valid for free convection in water subjected to small temperature differences. This implies an even larger simplification compared to the Weakly compressible flow option, but it still gives an excellent and efficient description for systems with small density variations. This option includes the density variation only as a volume force in the momentum equations. The Incompressible flow option with the Boussinesq approximation for buoyancy-driven flow linearizes density using a coefficient of thermal expansion. It allows for larger time steps and shorter solution times for natural convection problems. The Weakly compressible flow option for the fluid flow interfaces neglects the influence of pressure waves, which are seldom important in natural convection. We have introduced a number of new capabilities for this purpose. In the latest version of COMSOL Multiphysics, it is easier to define and solve problems involving natural convection. In this context, mathematical modeling is the perfect tool. In all of the cases mentioned above, it is important for engineers and scientists to understand and design systems to control natural convection.

Environmental sciences and meteorology also involve natural convection problems, as scientists and engineers try to predict and understand transport in air and water. Less obvious natural convection problems are found in industries such as chemical and food processing. The animation shows the value of the velocity in the air around the heat sink. Electronic devices that need to operate in quiet environments often rely on natural convection to circulate air over their built-in heat sinks.įree convection around a splayed pin fin heat sink that is heated from below. For example, we do not want to use noisy fans to cool the amplifiers and TVs in home cinema systems.

DEFINE FORCE FLUID IN COMSOL 5.1 WINDOWS

In this scenario, hot air rises to the ceiling close to heat sources and cool air sinks to the floor close to cold surfaces, such as the windows during winter.Įlectronics cooling is another type of process that often depends on natural convection in order to work. You may be familiar with the concept of natural convection in indoor climate systems. This buoyancy is in turn caused by the fluid’s variations in density with temperature or composition. Natural convection is a type of transport that is induced by buoyancy in a fluid. In this blog post, we give an overview of natural convection, the new functionality, and some of the difficulties that we may stumble upon when modeling natural convection.

DEFINE FORCE FLUID IN COMSOL 5.1 SOFTWARE

The CFD and Heat Transfer modules in version 5.2a of the COMSOL Multiphysics® software include functionality that makes it easier to set up and solve natural convection problems. Natural convection is a phenomenon found in many science and engineering applications, such as electronics cooling, indoor climate systems, and environmental transport problems.