Significance
is incompressible flow density fluid movement does not change. It refers to the unsteady fluid and time-independent. Rather, the fluid is large after a certain time period of a state or stable state. For practical purposes, the fluid is assumed incompressible fluid is flowing. At low speeds, which is substantially the; however, even the liquid velocity will produce an abrupt change in compression or expansion. Typically, the liquid to flow under gravity, and therefore in an open container which occupies the lower part. This property is unique characteristics of the liquid. Conversely, compressible gas flow, regardless of the initial volume of the gas and how much space it occupies its entire limitation any enclosed space. This property is specific to the gas. As in the case of the same liquid, slow flow of the gas employed for incompressible assumptions you can obtain a good approximation. In particular, it is essential to study turbulence awareness and control. Such equations described mainly incompressible fluid Navier-Stokes equations, and the incompressible Stokes equation and Stokes Eigenvalue problem.
incompressible fluid itself does not mean that the flow is incompressible. In the following derivation shows that even a compressible fluid (under the right conditions) - good approximation can be modeled as an incompressible flow. Incompressible flow means that the fluid density is kept constant in a batch with a flow rate of movement.
research tools
because people have limited understanding of nonlinear phenomena in nature, and therefore numerical simulation has become a very important research tool. But direct numerical simulation Navier-Stokes equations have a great difficulty is the contradiction between the huge scale of the problem-solving with limited computing resources and algorithm stability. This is mainly due to the fluid flow regions and more complicated calculation format having different physical nature, there is a small viscosity coefficient due to increased instability that mesh node, resulting in large-scale computing. Therefore, the study of structure and has good stability and convergence efficient algorithm is very important. Numerical methods for solving incompressible flow there are many, such as a finite difference method, finite element method, a finite volume method, boundary element method, and the spectral method. Finite difference method is simple, of arbitrarily complex partial differential equations can write its corresponding differential format. It expresses a simple and intuitive mathematical concept, is the older and mature numerical methods. Finite element method comprises mixing element, and conforming element nonconforming element, like element intermittently. It is possible to more accurately solve complex boundaries and treatment of various boundary conditions, and the less stringent requirements of the grid subdivision. Is a finite volume method, finite difference numerical method between the method and the finite element method is interposed. It is also known as the control volume method, a finite volume method, or a method combining unit generalized difference method. The basic idea is simple, can be derived directly from the physical interpretation. Spectral is a relatively new method for calculation, including the configuration point method, Galerkin spectral method and pseudo spectral method. The method to expand the solution with orthogonal polynomials. It has arbitrary order convergence precision and fast algorithm can be used. Boundary element method is a numerical method for interpolation and split on a boundary based on boundary reduction, it can be easily handled more complex problems, such as fracture, and the like infinite domain.
incompressible flow analysis often tack-free or "complete" Additional effects on the viscosity of the fluid solution method to analyze the effect of fluid
Analysis. Like uniform flow, source, sink, and such simple vortex flow, can be represented by a mathematical expression to determine the flow rate. These solutions can be stacked together in order to express the movement of the wing as the air or some of such actual complex inviscid flow of water in the ship movement. The results obtained in all the mathematical expressions flow field magnitude and direction of the velocity at the point. Then the Bernoulli equation, the pressure can flow on a point (P) and speed (v) link. Where p is a constant fluid density. Thus, the pressure-induced force acting on the boundary can be calculated. Then, the remaining problem is how to determine the influence viscous flow and pressure distribution, as well as fluid friction caused by an additional force parallel to the boundary. In this area incompressible flow, viscosity plays an important role, because it determines the behavior of the fluid (the boundary layer) near the boundary of the flow, and the fluid does not flow behavior (separation region) of the region along the boundary of the flow. Reynolds number, i.e., the inertial and viscous forces in the fluid of the dimensionless ratio gives a measure of the flow characteristics, it is useful for the theoretical and experimental data linking. May refer to the concept of "tack" (Viscosity) of. There are many practical problems can be applied by using a non-tacky, incompressible flow theory and experimental data estimates. First thought is slow moving aircraft through the atmosphere, air-cushion vehicles, helicopters and balloons in the atmosphere, through a variety of ships waters (just below the surface flow is suitable for this area), ground vehicles on the car, train, etc. , and an abnormality of structural loads and vibrations caused by the wind. Other important applications similar incompressible flow theory heating and air-conditioning air flow design of an industrial process, the fixed particles and droplets of liquid transport, steel, etc. and the like. Can refer to "compressible flow, (compressible flow)," aerodynamic "(gas dynamic)," Mach number, (Mach number), "Reynolds number, (Reynolds number) to be understood that such concepts.
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